Recent Trends In Mechanical Engineering National Conference by srikanth hannabeprakash

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

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EFFECT OF PRE-LOAD ON IMPACT DAMAGE IN COMPOSITE STIFFENED PANELS Gururaj Tandel1, G.S.Mahesh2 1

Student, Dept of Mechanical Engineering, DSCE, Bangalore Associate Professor, Research Center, Dept. of Mechanical Engineering, DSCE, Bangalore 1 gururajtandel@gmail.com

Abstract

This paper reports some new development in finite element modeling for numerical solution of impact loading on laminates and structures. The focus is on hard body impact and on impact damage resistance of composite laminates. Finite element modeling here is defined as the analyst's choice of material models finite elements (of different types/shapes/orders), meshes, constraints, governing matrix equations, solution procedure, pre and post processing options in user chosen commercial Finite Element Analysis (FEA) software for the intended analysis namely impact analysis. A critical assessment of available software has lead to the choice of LS-DYNA. In this study influence of compressive preload on low velocity impact behavior of carbon fiber-reinforced composite plates is investigated. This paper primarily describes the finite element modeling strategy of this preloaded composite material. Keywords: composite material, impact, preloading, Ls-Dyna

1. Introduction In recent years the use of composite materials has become increasingly common in a wide range of structural components, engineering applications, aerospace, automotive, defense, and sports industries. Composite materials have numerous advantages over more conventional materials because of their superior specific properties; such as high strength stiffness to weight ratio, improved corrosion, environmental resistance, design flexibility, improved fatigue life, potential reduction of processing, fabrication and life cycle cost. Despite these advantages, laminated composites can be susceptible to damages under transverse impacts. The various damages, such as matrix cracks, delaminations, fiber fracture, and fiber-matrix deboning and fiber pull-out can occur during impact event. These damages cause considerable reduction in structural stiffness, leading to growth of the damage and final fracture. Therefore, the impact response of fiber reinforced laminated composites has been an important area of research for a long time. A number of studies in this field have already been reported in literature. Only very few studies in the literature cover this topic. 2. Numerical study The impact problem can be described as shown in Figure 1. An impactor that has a mass ‘m’ and radius of ‘r’ with the velocity of ‘V’ drops on the center of the composite plate that is fixed longitudinal ends and simply supported at lateral sides.

Figure 1: FE model for impact analysis

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

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2.1 Material and specimen The material used in this study is a carbon fiber-reinforced epoxy (CF/EP) laminate with a symmetric, quasi-isotropic lay-up of 24 plies [-45°/0°/45°/90°] 3s. The plate thickness was 2.7 mm. A final test specimen with a size of 400 mm x 150 mm.

Figure 2: Construction details of (CF/EP) laminate

3. Methods and procedures Numerical results for this study were generated using LS-DYNA a general purpose finite element code with emphasis on nonlinear applications. This program is capable of modeling multilayered anisotropic materials. It provides elements suitable for dynamic analysis of composite plates and shell, taking into account bending membrane coupling and transverse shear deformation effect. Belytschko-Lin-Tsay shell element was implemented in LS-DYNA for twenty four through thickness integration points. Because of its computational efficiency, the Belytschko-Lin-Tsay shell element formulation of choice. 3.1. F E model development The development of the FE model for the low velocity impact simulations in LSDYNA involves the modeling of the composite material, modeling of preload and modeling of the impactor. 3.2. Composite material modeling In this paper all the plates are made from 24 plies of carbon fiber-reinforced composite with stacking sequence of [−45/0/45/90]3s. The carbon fiber-reinforced material properties are shown in Table.1.The linear elastic model MAT54AT_ENHANCED_COMPOSITE_DAMAGE was used. Table 1: Material properties of CE/EP Material

CFRP laminate

p g/cm3

E11 GPa

E22 GPa

G12 GPa

Xt MPa

Xc MPa

Yt MPa

Yc MPa

SC MPa

1.62

153

10.3

5.2

2540

1500

236

DF A LT

DF A ILC

DF A ILM

DF A ILS

v12

0.017

0.0135

0.1

0.03

0.3

3.3. Preload modeling In this study, the explicit solver without dynamic relaxation was used for both preloading and impact loading. The compressive pre-stress was applied within 10 ms (without provoking any noticeable oscillations), with the impact event lasting approximately 6 ms until spring back.

Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

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3.4. Impactor modeling The impactor was modeled as a spherical rigid body with conventional shell elements and the LSDYNA material model MAT20 (MAT_RIGID) and the impactor has a mass of 1.85 Kg .The impactor velocity was 6.5 m/s corresponding to 40 J. 4. Result and Discussion 4.1. Impact contact force The results for the unloaded and preloaded case are shown in Figure 3 and Figure 4 for the composite plate without stiffener.

Figure 3: Unloaded condition without stiffener

Figure 4: Preloaded condition without stiffener

Figure 5: Unloaded condition with stiffener

Figure 6: Preloaded condition with stiffener

Figure 5 and Figure 6 show the contact force for the composite plate with stiffened panel. 4.2. Energy absorbed Table 2: Energy absorbed for the composite plate without stiffener Load condition

Preload kN

Impact Energy [J]

Absorbed Energy [J]

unloaded

preloaded

0.23

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

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Table 3: Energy Absorbed for the composite plate with stiffener Load condition

Preload kN

Impact Energy [J]

Absorbed Energy [J]

unloaded

preloaded

0.23

4.2

4.3. Impact response Table 4: Deflection in composite plate without stiffener Load condition

Preload kN

Max Deflection[mm]

unloaded

preloaded

0.23

Table 5: Deflection in composite plate with stiffener Load condition unloaded preloaded

Preload kN 0 0.23

Max Deflection[mm] 6.5 7

4.4. Impact damage The intralaminar fibre and matrix damage could be analysed in the LS-DYNA simulation result by plotting the MAT54 history variables. The simulation result showed that the only intralaminar failure occurs in matrix tensile mode. Damage starts from the bottom plies on the opposite side of the impact .This is the tensile side under plate bending and since the matrix tensile strength has the lowest value failure occur in matrix tensile mode. The Extent of intralaminar damage for the preloaded model is slightly higher than for the unloaded plate

(a)

(b)

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5. Conclusion The contact force v/s time obtained from the simulation was close to the benchmark results. Impact force is the sole parameter to characterize impact damage resistance for large mass with low velocities. There is a real need to further extend this study to composite structure and components used in practice. References [1] Heimbs S., Heller S., Middendorf P., Hähnel F., Weiße J., “Low velocity impact on CFRP plates with compressive preload: Test and modeling”, International Journal of Impact Engineering, 2009, 36(10–11), 1182– 1193. [2] Fatih Dogan, Homayoun Hadavinia, Todor Donchev, Prasannakumar S. Bhonge “ Delamination of impacted composite structures by cohesive zone interface elements and tiebreak contact”. [3] Abrate,s “impact on composite structures”. Cambridge university press, 1998. [4] LS-DYNA Theory Manual, Livermore Software Technology Corporation, California, USA, LSDYNA 971 R6; 2006. [5] Wolf.Elber"Deformation and Failure Mechanics in Low Velocity Impact in Thin Composite Laminates” (1983) NASA TP#2152.

Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

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PREPARATION AND EVALUATION OF MECHANICAL PROPERTIES OF Al-6061 REINFORCED WITH GRAPHITE AND FLY ASH OF SEED HUSK PARTICULATE METAL MATRIX COMPOSITE Charles Edrard1, N.Kapilan2, Mervin Heribet3 1

Student, 2Assistant Professor & HoD, Dept of Mechanical Engg, NCET, Bangalore 3 Associate Professor, Dept of Mechanical Engineering, NIT, Surathkal, Karnataka. charlese29@gmail.com

Abstract The aim of this work is to study the mechanical properties of aluminum alloy Metal Matrix Composites (MMC) as they are gaining wide spread acceptance for automobile, industrial, and aerospace applications because of their low density, high strength and good structural rigidity. In the present work an attempt has been made to synthesize Al-6061 with graphite and fly ash of seed husk (Hongge seeds) particulate metal matrix composites by using stir casting technique. The addition level of reinforcement is being varied from 0, 4, 6 & 8 wt%. Preheated particle reinforcements are added to Al 6061 alloy to improve wettability and distribution. Micro-structural analysis is carried out for the above prepared composites by taking specimens from central portion of the casting to ensure homogeneous distribution of particles. Micro-hardness, tensile properties of the composites were prepared as per the ASTM E8M standards. Micro-structural characterization revealed fairly uniform distribution in the matrix. The Micro-Vickers hardness of the composite is found to decrease with increase in filler content in the composite. The tensile strength of the composites was found to increase confirming the dispersed graphite and fly-ash in Al-6061 alloy contributed in enhancing the tensile strength and wear resistance too of the composites. Key words: Al-6061 MMC’s, graphite particulates, fly-ash, husk, stir-casting, microstructure.

1. Introduction Metal matrix composites (MMCs) are increasingly becoming an attractive materials in advanced aerospace applications because of their properties, can be tailored through the addition of selected reinforcements [1]. Metal matrix composites have a market potential for various applications, particularly in the automotive industry, where the pressure is to use light weight materials & has increased because of environmental issues. Examples of components that have been manufactured using metal matrix composites include pistons for diesel engines and connecting rods [2]. These materials have also been shown to possess great potential for applications in the brake disks for railway brake equipment [3]. Aluminium-based Metal Matrix Composites (MMCs) have received increasing attention in recent decades as engineering materials. The introduction of a ceramic material into a metal matrix to produces a composite material that results in an attractive combination of physical and mechanical properties which cannot be obtained with monolithic alloys [4]. The various reinforcements that have been tried out to develop aluminium matrix composites(AMCs) such as graphite, silicon carbide, titanium carbide, tungsten, boron, Al203, fly-ash, Zr, TiB2, etc. Addition of hard reinforcements such as silicon carbide, alumina, and titanium carbide improves hardness, strength and wear Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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resistance of the composites [1, 2-4]. Aluminium alloys are still the subjects of intense studies, as their low density gives additional advantages in several applications. These alloys have started to replace cast iron and bronze, to manufacture wear resistant parts. Previous studies have shown that mechanical properties of Al-matrix composites would be enhanced with particulate reinforcement [5]. The particulate reinforced MMCs is mainly used due to easy availability of particles and economic processing technique adopted for producing the particulate reinforced MMCs. Al alloy has been commonly used as a base metal for MMCs reinforced with a variety of fibres, particles and whiskers [6-7]. Amongst different kinds of the recently developed composites, particle-reinforced metal matrix composites and in particular aluminum base materials have already emerged as candidates for industrial applications. Investigation of mechanical behavior of aluminum alloys reinforced by micro hard particles such as Graphite is an interesting area of research. Therefore, the aim of this study is to investigate the effects of different factors such as: (i) weight percentage of the particles (ii) Fabrication process on the microstructure, mechanical properties of the composites. Mechanical properties were evaluated as per ASTM standards using computerized universal testing machine. 2. Experimental details The following section highlights the materials used, their properties, and method of composite preparation and evaluation of microstructural and mechanical properties. 2.1. Materials used The matrix material used for the present study is Al-6061. Table.1 gives the chemical composition of 6061Al. The reinforcing material selected was graphite of particle size 125 µm. Table.2 gives the properties of matrix and reinforcing materials used. Table 1: Chemical composition of Al 6061 Si 0.43 Zn 0.25

Fe 0.7 Ti 0.15

Cu 0.24 Sn 0.001

Mn 0.139 Mg 0.802

Ni 1.05 Cr 0.25

Pb 0.24 Al Balance

Table 2: Properties of matrix and reinforcing materials used in the study Material/ Properties

Density gm/cc

Hardness (HB500)

Matrix Al 6061

2.7

Reinforcement Gr. Particle

2.25

1.7mohs scale

Strength(Tensile/ Compression) (MPa) 115(T)

Elastic Modulus (GPa) 70-80

89.63(C)

8-15

2.2. Preparation of composites Aluminium 6061 alloy is used as the matrix and graphite of 125 µm as reinforcement. The liquid metallurgy route has been adopted to prepare the cast of composites Al-6061+Gr. Preheated graphite powder of laboratory grade purity of particle size 125 µm was introduced into the vortex of the molten alloy after effective degassing using solid hexachloroethane (C2Cl6). Before introducing reinforcement particles into the melt they were preheated to a temperature of 2500C. The extent of incorporation of graphite particles in the matrix alloy was achieved in three steps. That is total amount of reinforcement required was calculated and is being introduced into melt 3 times rather Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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than introducing all at once. At every stage of before and after introduction of reinforcement particles, mechanical stirring of the molten alloy for a period of 10 min was achieved by using Zirconia-coated steel impeller. The stirrer was immersed into the melt, located approximately to a depth of 2/3 rd height of the molten metal from the bottom and run at a speed of 200 rpm. A pouring temperature of 750°C was adopted and the molten composite was poured into cast iron mould. The extent of incorporation of graphite in the matrix alloy was varied from 0, 4, 6 & 8 wt%. Thus composites containing particles were obtained in the form of cylinders of diameter 12.5 mm and length 125 mm. 2.3. Testing of composites To study the microstructure of the specimens the central portion of the casting was cut by an automatic cutter device. The specimen surfaces were prepared by grinding through 200, 400, 600, 800 and 1000 grit papers and then by polishing with 3 µm diamond paste and then etched by Keller’s reagent to obtain better contrast. Microscopic examination of the composites was carried out by optical microscopy. To investigate the mechanical behavior of the composites the tensile tests was carried out using computerized uni-axial tensile testing machine as per ASTM standards. Figure 1 & 2 show the dimensions of the mould and specimen used for tensile studies. For tensile results, test was repeated three times to obtain a precise average value.

Figure 1: Permanent mould for producing composite

Figure 2: Dimensions of the tensile specimen

3. Results and Discussion 3.1. Microstructural studies Fabrication of metal–matrix composites with graphite particles by casting processes is usually difficult because of the very low wettability of graphite particles and agglomeration phenomena which results in non-uniform distribution and weak mechanical properties. In the current work, 6061Al aluminum alloy matrix composites with micro size graphite particles were produced by stir casting method. The magnitude of graphite powder used in the composites was 0, 4, 6 and 8 wt%. The optical micrographs of the 6061Al alloy with 0, 4, 6, and 8wt. % Graphite particulates were shown in Figure 3(a-h). Figure. 3 (a-h) shows microstructure of as cast 6061Al (Figure.3a-b) and 6061Al with 4 wt% (Figure 3c-d), 6wt% (Figure 3e-f) and 8wt% (Figure 3g-h) Graphite particulates. The stirring of melt before and after introducing particles has resulted in breaking of dendrite shaped structure into equiaxed form, it improves the wettability and incorporation of Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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particles within the melt and also it causes to disperse the particles more uniformly in the matrix. Figure 3c-h reveals the distribution of graphite particles in different specimens and it can be observed that there is fairly uniform distribution of particles and also agglomeration of particles at few places were observed in the composite reinforced with 0 wt.%, 4wt%, 6wt% and 8wt% graphite. Further, these figures reveal the homogeneity of the cast composites. The microphotograph also clearly reveals the increased filler contents in the composites at 20 different locations.

Figure 3(a)

Figure 3(e)

Figure 3(b)

Figure 3(c)

Figure 3(f)

Figure 3(g)

Figure 3(d)

Figure 3(h)

Figure 3 (a-h):Showing the Optical Microphotographs of 6061Al with and without Graphite Particulates (a-b) As cast (c) with 0wt% of Graphite at 50X (d) with 4wt% of Graphite at 100X (e) with 6wt% of Graphite at 50X (f) with 6wt% of Graphite at 100X (g) with 8 wt% of graphite at 50X (h) with 8wt% of Graphite at 100X

3.2. Tensile properties In any design work, it is important to consider practically realizable values of strength of the materials used in design. The tensile test is one of the basic tests to determine these practical values. The range of values obtained from the tests forms the basis for the size of the material in the products for the factor of safety. The tensile tests were carried out using computerized uni-axial tensile testing machine as per ASTM standards. Three test specimens were used for each test and average value is reported. Table 3: Showing the tensile test results of cast 6061Al, with addition of 0, 4, 6 and 8wt% of graphite particulates to 6061Al Sl.No

Weight percentage of Gr particles(%)

1 2 3 4

0 4 6 8

Ultimate tensile strength (MPa) 141 183.42 192.33 196

Yield strength (MPa) 125 145.66 157.22 163

Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

250

200

160

150 100 50 0 0

Gr. Weight %

Figure 4: Tensile strength Vs graphite weight

Yield Strength(MPa)

Tensile Strength (MPa)

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120 80 40 0 0

4 6 Gr.Weight%

Figure 5: Yield strength Vs graphite weight

4. Conclusion The present work on synthesis and characterization of Al6061-Graphite composites led to the following conclusions The composites containing Al-6061 with 0, 4, 6 and 8wt% of Graphite particulates were successfully synthesized by melt stirring method using three stages mixing combined with preheating of the reinforcing particles. The optical micrographs of composites produced by stir casting method shows fairly uniform distribution of graphite particulates in the Al-6061 metal matrix. The experimental densities were found to be lower than theoretical densities due to the presence of porosities in all the composites. The addition of graphite has resulted in increase in tensile strength. The tensile strength is a function of volume fraction of reinforcement. As volume fraction increases tensile strength of composite increases. However, addition of graphite has resulted more improvement in tensile properties. References [1] Baradeswaran “Effect of Graphite Content on Tribological behavior of Aluminium alloy Graphite Composite”, European Journal of Scientific Research, Vol.53 No.2 (2011), pp.163170. [2] K. R. Suresh, H.B. Niranjan, P. Martin Jabraj, M.P. Chowdaiah.. “Tensile and wear properties of aluminium composites”, Wear. 255: 638-642, 2003 [3] D.M. Aylor. 1982. Metals Hand Book V-13 & Vol. 19. ASM Metals Park, OH. pp. 859-863. [4] T.V.Christy, N.Murugan and S.Kumar, “A Comparative Study on the Microstructures and Mechanical Properties of Al 6061 Alloy and the MMC Al 6061/TiB2/12P”, Journal of Minerals & Materials Characterization & Engineering, 2010 Vol. 9, No.1, pp.57-65. [5] Rakesh Kumar Yadav, Nabi Hasan, Ashu Yadav “Studies on Mechanical Properties of Al Based Cast Composites”, IJCSMS International Journal of Computer Science and Management Studies, Vol. 11, Aug 2011, Issue 02. [6] Jinfeng Leng,a*Gaohui Wu,a Qingbo Zhou,b Zuoyong Doua and XiaoLi Huanga, “Mechanical properties of SiC/Gr/Al composites fabricated by squeeze casting technology”, sciencedirect Received 11 January 2008; revised 24 April 2008; accepted 14 May 2008. [7] A.R. K. Swamy, A. Ramesha, G.B. Veeresh Kumar*, J. N. Prakash “Effect of Particulate Reinforcements on the Mechanical Properties of Al6061-WC and Al6061-Gr MMCs”, Journal of Minerals & Materials Characterization & Engineering, Vol. 10, No.12,(2011), pp.11411152.

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STUDY ON MECHANICAL PROPERTIES OF GRAPHENE BASED UNSATURATED POLYESTER RESIN COMPOSITES G.Manjunatha 1, Raji George2 1

Assistant Professor, 2Professor, Dept of Mechanical Engineering, MSRIT, Bangalore gmanjumsrit@gmail.com

Abstract Graphene is a material comprising a single layer of carbon atoms, yet particles can have linear dimensions potentially in the millimeter range. It has a remarkable set of properties that offer potential benefits when added to polymer materials. The overall aim of the investigation is to show how graphene can be used in a composite engineering context, to improve the properties of current polymer-based materials. The key challenges are the dispersion and functionalisation of well-defined graphene material, and the development of processing routes to combine it with the selected polymer systems. Graphene-based polymer nano-composites are very promising candidates for new high-performance materials that offer improved mechanical, barrier, thermal and electrical properties. Herein, an approach is presented to improve the mechanical properties of unsaturated polyester resin by using graphene. Polymer nano-composites are constructed by uniformly dispersing a nano-material into the polymer matrix. The mechanical properties such as compression, hardness, and wear properties of graphene reinforced polyester composite were studied. The results showed that the graphene reinforced polyester composite tend to exhibit a significant enhancement in mechanical properties as compared to the pure polyester. Keywords: Nano-composites, polyester, resin, graphene

1. Introduction Nano-composites material has significantly to encompass a large variety of systems such as one-dimensional, two-dimensional, three-dimensional and amorphous materials, made of distinctly dissimilar components and mixed at the nanometer scale. The general class of nanocomposites are organic/inorganic materials is a fast growing area of research. The properties of nano-composite materials depend not only on the properties of their individual parents but also on their morphology and interfacial characteristics [1]. In the present age, the main focus area is in identifying a nanocomposites material which is lighter in weight, eco-friendly, bio-degradable, cost-effective, performanceoriented as well as suited for diverse applications. Unsaturated polyester resin is used for a wide variety of industrial and consumer applications. This consumption can be split into two major categories of applications: reinforced and nonreinforced. In reinforced applications, resin and reinforcement, such as fiberglass, are used together to produce a composite with improved physical properties. Typical reinforced applications are boats, cars, shower stalls, building panels, and corrosion- resistant tanks and pipes. Nonfiber reinforced applications generally have a mineral "filler" incorporated into the composite for property modification. Some typical nonfiber reinforced applications are sinks, bowling balls, and coatings. Polyester resin composites are cost effective because they require minimal setup costs and the physical properties can be tailored to specific applications. Another advantage of polyester resin composites is that they can be cured in a variety of ways without altering the physical properties of the finished part. Consequently, polyester resin composites compete favorably in custom markets [2]. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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2. EXPERIMENTAL 2.1 Materials and Methods The resins used in this study was Unsaturated Polyester with 2% cobalt naphthanate as accelerator, 2% Methyl ethyl ketone peroxide (MEKP) as catalyst in 10% Dimethylaniline (DMA) solution as promoter, in the ratio of the resin/accelerator/catalyst/promoter:100/2/2/2. In addition, graphene was used as filler material. 2.2 Fabrication of nanocomposites Firstly, the precalculated amount of graphene and polyester were weighed and then mixed together in a suitable beaker. Graphene was mixed in stipulated quantity to the polyester thoroughly using the glass stirrer at ambient temperature conditions. Then the mixture was placed in a high intensity ultra-sonicator for 20 minutes at 150Hz pulse mode. External cooling system was employed by submerging the beaker containing the mixture in an ice bath to avoid temperature rise during the sonication process. Once the process was completed, hardener/accelerator/catalyst/promoter (100:10/2/2/2) parts by weight was added to the modified graphene and polyester mixture [1]. A metallic mould with required dimensions was used for making samples on par with ASTM standards. The metallic mould was coated with mould releasing agent to enable easy removal of the sample. The nanocomposites mixture was poured over the metallic mould. The closed mould was kept in the petridish for 3 to 6 hrs at room temperature. The test specimens of required sizes were cut out from the sample. 2.3 Evaluation of mechanical properties Compressive testing samples were prepared with dimensions as per ASTM D 695 standards. In each case, three samples were tested and the average value was tabulated. Compressive strength test were carried out using universal testing machine. Hardness testing samples were prepared with dimensions as per ASTM D 785 standards. In each case, three samples were tested and the average value was tabulated. Hardness test were carried out using Brinell hardness testing machine. Wear testing samples were prepared with dimensions as per ASTM G99 standards. In each case, three samples were tested and the average value was tabulated. The wear testing were carried out using pin-on-disc wear testing machine. 3. Results and discussion 3.1 Mechanical properties The nanocomposites material as a product is to withstand the applied mechanical forces. It is achieved by load transfer between the matrix and the reinforcements. Compression test was carried out on a Universal Testing Machine. Both the pure polyester along with the graphene reinforced polyester samples was tested. The ultimate tensile strength and the young’s modulus of the samples were determined. Figure 1, shows the effect of the ratio of the graphene reinforcement in the polyester sample on compression strength. A study of this figure indicates that for pure polyester the compression strength is low as compared to the reinforced specimens. The compression strength increases with increase in the graphene composition in the sample. Figure 2, shows the Young’s modulus versus Polyester + Graphene percentage The Young’s modulus for the pure polyester sample was 1230 MPa. The ‘E’ increased to approximately 160% with the addition of 0.25% graphene. With further addition of graphene it is noticed that there is good improvement in the mechanical properties of the reinforced specimens.

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Figure 1: Compression strength Vs polyester + graphene percentage

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Figure 2: Young’s modulus Vs polyester+ graphene percentage

Brinell hardness measurements were done on the pure polyester specimen along with the different graphene reinforced specimens. Hardness measurements were carried out at 3 different locations in each case and an average value of the hardness was considered. Figure 3 shows the effect of the ratio of graphene to polyester on the hardness of the specimens when the weight ratio of graphene in the composite was 0.25%, 0.50%, 0.75% and 1.00%.A study of this figure indicates that the hardness of the pure polyester specimen is low when compared to the graphene reinforced polyester composite

Figure 3: Hardness versus polyester + graphene percentage

The wear test was carried out on a pin on disk wear testing machine. Both the pure polyester along with the graphene reinforced polyester samples were tested, the wear rate of the samples with constant speed and varying load were determined. Figure 4 shows the effect of the ratio of the graphene reinforcement in the polyester sample on wear rate. A study of this figure indicates that for pure polyester the wear rate is high as compared to the reinforced specimens. The wear rate decreases with increase in the graphene composition in the sample.

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Figure 4: Wear rate versus load

4. Conclusion 1. Nano-composites are prepared for studying the mechanical properties such as hardness, compression strength and the wear rate. 2. An increase in the percentage composition of the graphene reinforcement in the polyester increases the compression strength. 3. In pure polyester specimen hardness is low in comparison to the one reinforced with graphene. 4. The wear rate decreases with increase in percentage composition of the graphene reinforcement in the polyester. 5. Polymer nano-composites represent a radical alternative to the conventional polymer composites with a wide range of applications. References [1] K.V.P.Chakradhar et al., “Epoxy/Polyester Blend Nanocomposites: Effect of Nanoclay on Mechanical, Thermal and Morphological Properties”,Malaysian Polymer Journal, Vol. 6, No. 2, p 109-118, 2011. [2] Tim Pepper, Polyester Resins, Ashland Chemical Company p 91-96, 2006. [3] Jin Young Kim et al., Effect of modified carbon nanotube on the properties of aromatic polyester nanocomposites, Elsevier Ltd Polymer Journal 49(2008) 3335-3345. [4] Ton-That et al., Polymeric nanocomposites comprising epoxy functionalized graft polymer, United state patent, May 22, 2007. [5] Urszula Kosidlo et al., Production methods of graphene and resulting material properties, Fraunhofer, 2010.

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STUDIES ON WEAR AND CORROSION BEHAVIOR OF SHORT E-GLASS FIBER AND FLY ASH REINFORCED WITH HYBRID COMPOSITE ALUMINUM -7075 M.C.Nandini1, Shivanand2, Pradeep Kumar R3 1

Assistant Professor., Yellamma Dasappa college of Engg, 2Professor ,UVCE Bangalore 3 Engineer-Mechanical design & Engineering, HDO Technologies limited nandini.mc1@gmail.com

Abstract

Composite materials have been increasingly used in aerospace and automotive applications over the last two decades and have seen a dramatic increase in usage in non-aerospace products in the few years. The use of hybrid composites materials is over attractive because of their outstanding strength, stiffness and light-weight properties. An additional advantage of using hybrid composite is the ability to tailor the stiffness and strength to specific design loads. Nowadays these materials are widely used in space shuttle, commercial airlines, electronic substrates, bicycles, automobiles, sports goods and so on. This paper deals with a new form of composites like Al-7075 alloy reinforced with E-glass fiber and fly ash particulates to form MMC’s using stir casting method. The MMC is obtained from different composition of E-glass and fly ash particulates varying the E-glass with constant fly ash and varying fly ash with constant E-glass percentage. The test specimens are prepared as per ASTM standard size by turning and facing operations to conduct hardness, wear and corrosion tests. The test specimens are tested for wear as per ASTM standards G99 by using dry sliding pin on disc machine. It is observed that the MMC obtained has got better wear and corrosion behavior when compared to Al-7075 alone. Keywords: Al 7075, fly ash, E-glass, mechanical properties, wear and corrosion behavior, SEM

1. Introduction Traditional materials do not always provide the necessary properties under all service conditions. Metal matrix composites (MMC’s) are advanced materials resulting from a combination of two or more materials (one of which is metal and the other a non-metal) in which tailored properties are realized. In recent years there has been a considerable interest in the use of metal matrix composites (MMC’s) due to their superior properties. Though many desirable mechanical properties are generally obtained with the fiber reinforcement, these composites exhibit an isotropic behavior and are not easily producible by conventional techniques. MMCs reinforced with E Glass and fly ash particulates tend to offer modest enhancement of properties. Among the MMCs the most metal used is aluminum reinforced with E Glass and fly ash. Generally aluminum is light weight, which is fore most requirement application and is less expensive than other light metals such as titanium and magnesium. Moreover, when a reinforcement material is added to Aluminum matrix, the properties will further enhance, thereby making it a prospective material for many light weight applications. Metal-matrix composites are either in use or prototyping for the space shuttle, commercial airliners, electronic substrates, bicycles, automobiles and a variety of other applications. In this paper the different combination of fly ash and E glass fiber as reinforcement and matrix in Al 7075 was used with the help of simple casting technique called stir casting. Other reinforcement are also used in place of fly ash (2%,4%) and glass fiber(1%,3%,5%) in Al alloy 7075 and studied the effect of all these combination on Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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microscopic and microscopic behavior such as wear rate ,wear loss,hardness,corrosion microstructure and SEM analysis etc. 2. Experimental details A brief description of the matrix material as well as reinforcement material used in synthesis of composites as follows: Matrix Alloy: Aluminium alloy 7075 was used as matrix synthesis of composites. The composition of the matrix alloy was analyzed and the chemical composition and properties of the matrix alloy as given below: Table 1: Chemical composition of Al-7075 Component Si Fe Cu Mn Cr Zn Weight (%)

0.4

0.5

1.22

0.3

0.180.28

Table 2: Properties of aluminum 7075 Density (×1000 kg/m3) 2.810 Elastic Modulus (GPa) 69 9-10 Elongation (%)

5.16.1

87.291.5

Melting point 0c

660.1

2.1. Reinforcements: The role of the reinforcement in a composite material is to increase the mechanical properties of the neat resin system. 2.2. Fly Ash: Fly ash is one of the residues generated in the combustion of coal. The fly ash particulates in reinforcement to form metal matrix composites is therefore very desirable from an environment standpoint. The chemical composition of fly ash is given below: Table 3: Chemical Composition Of fly ash Component Bituminous Sub bituminous

SiO2 (%) 20-60

Al2O3 (%) 5-35

Fe2O 3 (%) 10-40

CaO (%) 1-12

LOI (%) 0-15

40-60

20-30

4-10

5-30

0-3

Lignite

15-45

20-25

4-15

15-40

0-5

E-glass fiber: E-glass or electrical grade glass was originally developed for standoff insulators for electrical wiring. E-glass is a low alkali glass with a typical nominal composition as follows: Table 4: Chemical composition of E-glass fiber

Component Quantity in %

SiO2

Al2O3

CaO

MgO

B2O3

Na2O

K2 O

Fe2O3

55.2

14.8

18.7

3.3

7.3

0.2

0.1

3. Al based MMC preparation by stir casting Stir casting setup as shown in Figures Consisted of a resistance Muffle Furnace and a stirrer assembly, was used to synthesize the composite.

(a)

(b)

(c)

(d)

(e)

(f)

Figure 1: (a) Loading Al 7075 in to furnaces with crucible ,(b) Molten metal,(c) Adding reinforcent Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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material,(d) Stirring after adding reinforcements, (e) Pouring molten metal (f) Removing casting after cooling.

An electric resistance furnace was used for melting the alloy for casting purpose, 7075 aluminum was cut into small pieces and were put into the crucible which is preheated and then it was kept for melting in the furnace. Molten metal was super heated to 1000 0C. Flux was sprinkled on the surface of the liquid metal; to prevent oxidation degassing was carried out by adding chloro ethane to remove hydrogen from the molten metal. In order to avoid void formation during solidification the pre heated E-Glass and fly ashes were then added into the crucible and by using a mechanical stirrer it was thoroughly mixed. The temperature of the molten metal was measured (above 7000C) and then poured into the die preheated to 2500C. 4. Wear testing measurements Wear is a process of removal of material from one or both of two solid surfaces in solid contact. Dry sliding wear tests number of specimen was conducted by using a pin on disc machine supplied by DUCOM. In this experiment test was conducted the fallowing parameters  Load  Speed  Time In the present experimental, the parameters such as speed, time and Track Diameters kept constant throughout for all the experiments. These Parameters are given in Table 5: Table 5: Parameters of wear test Time 15 min Speed 600 rpm Track diameter 80 mm

5. Corrosion Test The corrosion test carried out using static immersion weight loss method as per standards

Figure 2: Corrosion models

6. Results and discussion Effect of different reinforcements on weight loss of MMCs under dry sliding condition. 6.1 Effect of load on wear rate Wear rate and wear resistance for the MMCs were obtained by: Wear Rate: It is defined as wear volume per unit distance travelled. Wear rate (10-3 mm3/N-m) =wt loss X 10-3 π X d2/4 X load X S.D X time (1) Sliding distance = Sliding speed X time = (π D N / 60) t (2) Wear Resistance: - wear resistance is a reciprocal of wear rate. Wear resistance = 1 / wear rate (3)

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wear rate vs load

wear rate

Wear rate

wear rate vs time 5%EG

3% EG 0 2

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1%EG

15 10 5 0

5%EG 3%EG 2

1%EG

Figure 3: Wear rate vs load and time for constant flyash 2% & 4%.

From the above figure it was concluded that, as the load increases the wear rate decreases with increasing the percentage of E glass fiber. 6.2 Scanning Electron Microscopy (SEM) analysis for worn samples at 4 kg load The cleaned, dried and etched specimens is prepared and subsequently mounted on specially designed aluminum stubs using holder.

(a)

(b)

(c)

(a)

(b)

(c)

Figure 5: SEM of MMC with 4 wt. % fly ash and1 wt % E –glass fiber at (a) 250X, (b) 500X, (c) 1000X

Scanning electron micrographs at lower magnification shows that the distribution of fly ash and Glass fiber throughout the MMCs. Scanning electron micrographs at higher magnification shows the particle-matrix interfaces. Figure 4 & 5 shows the surface morphology of aluminium alloy 7075 with fly ash (2%, 4%) and E glass fiber (1%) composite, tested under ambient temperature with load and speed. The structures of the worn surfaces are greatly dependent on sliding speed, load and hardness of particles (reinforcement). Comparing these figures it can be visualized that one of the common features observed in all three MMCs, i.e. the formation of grooves and ridges running parallel to the sliding direction. These wear scars are the primarily characteristic of abrasive wear. On further analyzing, it has been found that grooves are fine on the Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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worn pin surface of Al alloy 7075 with fly ash (2%, 4%) wt. fraction as compared to others. From the micrographs (Figure 4 and 5) some cracks have appeared and these cracks are propagated in different directions. This might be due to strain hardening of aluminum based metal matrix composites with applied load and due to pulling up of hard phase particle. From the figure 3 clearly indicated wear vs time, here we concluded the as the fly ash increases the wear also increases. 6.3 Effect of different reinforcements MMC on corrosion test

24 Hrs

48 hrs B1 B3 B5

72 hrs

1N corrosion… CORROSION RATE

corrsion rate x10-4

0.5N corrosion…

5 0

24 hrs B1 B4

48 hrs

Figure 6: Corrosion rate vs samples number for 0.5 N and 1 N

From the above graph we can conclude that as the time for corrosion increases corrosion rate decreases and as also increase in normality, corrosion rate also increases Scanning Electron Microscopy (SEM) analysis on corroded specimen.

(a) (b) (c) Figure 8: SEM of MMC with 4 wt.% Fly ash and1wt % E –glass fiber on corrosion specimen at (a) 100X, (b) 500X, (c) 1000X, (d) 2000X for 1Normality

Scanning electron micrographs at lower magnification shows that the distribution of fly ash and glass fiber throughout the MMCs. Scanning electron micrographs at higher magnification show the particle-matrix interfaces for the corrosion specimen as shown in the above Figures. As the fly ash content increases the corrosion increases and the corrosion rate decreases with the time and it clearly indicated by the SEM picture of different magnification as shown in Figures. 7. Conclusion

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Aluminium based metal matrix composites have been successfully fabricated by stir casting technique with fairly uniform distribution of fly ash and E-glass fiber. For synthesizing of composite by stir casting process, stirrer design and stirrer position, stirring speed and time, particles preheating temperature, particles incorporation rate etc are the important process parameters. The wear rate showed the two stages of wear for all the applied loads. At the initial stage run-in wear occurred up to 1 km sliding distance and in later stage wear approaches to steady state. The effect of wear rate vs. load, as the fly ash composition increases, the wear rate also increases and decreases with the load.SEM images revealed that fly ash (2%, 4%) and glass fiber (1%) particulates are fairly distributed in aluminium alloy matrix of worn specimen at 4 kg load of different magnification as shown in the figures. Test conducted to determine the corrosion rate revealed that as the time for corrosion increases, corrosion rate decreases and as also increase in normality, corrosion rate also increases. And also SEM images are revealed.

References [1] G. B. Veeresh Kumar, C. S. P. Rao, N. Selvaraj, M. S. Bhagyashekar, “Studies on Al6061-SiC andAl7075-Al2O3 Metal Matrix Composites”, Journal of Minerals & Materials Characterization & Engineering, pp.43-55, Volume 9, 2010. [2] M. Sreenivasa Reddy, #Dr. Soma V. Chetty, $Dr. Sudheer Premkumar “ Evaluation Of Hardness And Tensile Properties Of Al 7075 Based Composite” International Journal of Advances in Engineering Research http://www.ijaer.com/(IJAER) 2012, Vol. No. 3, Issue No. I, January [3] M.K. Surappa, R.K. Uyyuru, S. Brusethaug, “ Tribological behavior of Al-Si-SiCp composites/automobile brake pad system under dry sliding conditions”, Tribology.International 40 (2007), pp. 365- 373, April 2006] [4] Sanjeev kumar and Bikramjit Sharma, “Effects of Thermal Cyclic loading on Cast Aluminium Composite Reinforced with Silicon Carbide and Fly Ash Particles”, M.E. Thesis, Thapar University, Patiala, India, July 2010. [5] R. L. Deuis; C. Subramanian” & J. M. Yellupb, Dry Sliding Wear Of Aluminium Composites- Review Ian Wark Research Institute, University of South Australia, SA 5095, Australia CSIRO, Division of Manufacturing Technology, Adelaide Laboratory, SA 5012, Australia [6] K. Ravi Kumar,’’ Influence of Particle Size on Dry Sliding Friction and Wear Behavior Of Fly Ash Particle – Reinforced A 380 Al Matrix Composites’’ European Journal of Scientific Research,ISSN 1450-216X Vol.60 No.3 (2011), pp.410-420 © Euro Journals Publishing, Inc. 2011 [7] Vishal Sharma and Sanjeev Das, “Synthesis and Interfacial Characterization of Al- 4.5wt%Cu/ Zircon Sand/ Silicon Carbide Hybrid Composite”, Department of Physics and Materials Sciences, M.E. Thesis, Thapar University, Patiala, India, June 2007 [8] W Q.Song, P kraal, A.P.Mourrtz, wear Vol.85, 1995 pp.125-130 [9] G.Straffelini, M.Pellizzare, wear vol.256, 2004 pp 754-763 [10] V.C.UVARAJA a*, N. Natarajan’’ Comparision on Al6061 and Al7075 Alloy With Sic and B4c Reinforcement Hybrid Metal Matrix Composites [11] ZHU Min-hao’’ Friction and wear of 7075 aluminum alloy induced by torsional fretting’’ Tribology Research Institute, Traction Power State Key Laboratory, Southwest Jiaotong University, Chengdu 610031, China Received 17 February 2009; accepted 26 May 2009

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STUDY ON CHARACTERIZATION AND WEAR TEST OF CARBON NANO TUBES REINFORCED COPPER COMPOSITE N.Srinuvasu1, P.A.Udayakumar2, R.N.Rangaswamy3, Ashwin C Gowda4 1,3,4

Production Engg. Dept., 2Mechanical Engg. Dept., GSSIT, Bangalore srinuvas.n@gmail.com

Carbon nano tubes (CNTs) are gaining wide spread applications in several high technological areas owing to its remarkable mechanical and electronic properties. CNTs were discovered to be the fourth form of carbon by the classic experiments of Ijima in 1991. The properties, both electrical and mechanical of the CNTs are studied extensively all over the world by several researchers. It is reported that the CNTs do processes a very high modulus of one Terra Pascal and electrical conductivity (1013 A/cm2). Because of these superior properties CNTs is a potential candidate as reinforcement material to produce composites. Copper and its alloys are used commercially because of its high electrical and thermal conductivity coupled with strength. The hard and refractory ceramic reinforcements such as silicon carbide, Alumina, titanium oxide have commonly used as reinforcements in the ductile copper matrix. Although they posses higher strength, better wear resistance they exhibit lower ductility and thermal conductivity when compared with copper. Further the enhancement in the elasticity modulus of copper based particulate composites is not significant. This project focuses on study of Microstructure, Wear properties and hardness of Cu/CNT (MW CNTs) and to enhance its wear and friction behaviour. Friction and wear tests have been conducted on both sintered pure copper and the developed composites.

Keywords: CNT, MWCNT, SEM, wear test, hardness

1. Introduction Composite materials have gained popularity in high-performance products that need to be lightweight, yet strong enough to take harsh loading conditions such as aerospace components (tails, wings, fuselages, propellers) boat and scull hulls, bicycle frames and racing car bodies. Other uses include fishing rods, storage tanks, base ball bats. The new Boeing 787 structure including the wings and fuselage is composed largely of composites. Composite materials are also becoming more common in the realm of orthopedic surgery. Carbon nanotubes are most certainly among the strongest, stiffest, toughest molecule that can ever be produced, the best possible molecular conductor of both heat and electricity. In one sense the carbon (fullerene) nanotubes is a new man-made polymer to follow on from nylon, polypropylene, and kevlar. In another, it is a new “graphite” fiber, but now with the ultimate possible strength. In yet another, it is a new species in organic chemistry, and potentially in molecular biology as well, a carbon molecule with the almost alien property of electrical conductivity, and super-steel strength. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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The most important application of nanotubes based on their mechanical properties will be as reinforcements in composite materials. Although nanotube filled composites are an obvious materials applications area, there have not been many successful experiments, which show the advantage of using nanotubes as fillers over traditional carbon fibers. The main problem is in creating a good interface between the CNT and the matrix and attaining good load transfer from the matrix to the nanotubes. One of the reasons for this is that the nanotubes are almost always organized into aggregates which behave differently in response to a load, as compared to individual nanotubes. In some cases, fragmentation of the tubes has been observed, which an indication of a strong interface bonding is. In some cases, the effect of sliding of layers of MWNTs and easy pull-out are seen, suggesting poor interface bonding. Micro-Raman spectroscopy has validated the latter, suggesting that sliding of individual layers in MWNTs and shearing of individual tubes in SWNT ropes could be limiting factors for good load transfer, which is essential for making high strength composites. To maximize the advantage of nanotubes as reinforcing structures in high strength composites, the aggregates needs to be broken up and dispersed or cross- linked to prevent slippage. CNT when used as reinforcing phase in MMC can help enhance the properties of conventional metals. We can observe an increase in the value of Young’s modulus, specific modulus, tensile strength, shear strength. The material also shows better damping properties, and hence is capable of reducing vibration mode amplitudes and noise levels. 2. Experimental procedures and materials 2.1 Blending

Figure 1: Blending process of powder metallurgy

The first step in powder metallurgy that is blending produces uniform distribution of the dispersiod in the matrix. The Figure 1 shows that the order of increasing homogeneity which is very much desired in the process. There should be even distribution of the dispersiod in the matrix. Agglomeration might cause uneven distribution of load within the matrix which is not desired for the composite. Basically to check for the homogeneity the bended powder is characterized with the aid of SEM which would show the distribution of the dispersiod in the matrix. 2.2 Compaction

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Figure 2: Compaction process of powder metallurgy

Powders are compacted under high pressure by various methods where the application of pressure packs the powders and reduces porosity. Unlike shaping methods, compaction techniques cause particle deformation. Many compaction methods are used, but the most prevalent method for P/M parts production is uniaxial compaction in a rigid die. This method is cost effective with relatively straightforward tooling. Cold pressing in rigid dies is the most commonly used compaction process, and the concept of die pressing is straightforward. Powder is poured into a die cavity, a movable punch seals the die cavity, and a load is then applied via the advancing punch. In the most simple case there is only one moving punch, and the die is stationary. However, a density gradient in the compact occurs as a consequence of die wall friction, with the highest density being next to the punch face, A floating die table reduces the density gradient by moving the die to offset the friction effect. The powder is densified from both top and bottom planes, and the middle plane has the lowest density. As more features are added to the compact, additional punches are required to produce an acceptable green compact. 2.3 Sintering During sintering, compacted metal powders are bonded or sintered by heating in a furnace to a temperature that is usually below the melting point of the major constituent. Sintering occurs in a series of overlapping but balanced phases, all of which depend on temperature, time, and atmospheric composition, flow, circulation, and direction. 2.3.1.Stages of sintering (A) Point contact of dispersoid with the matrix phase (wetting) (B) Initial stage of dispersing phase (C) Intermediate stage of dispersoid in Metal matrix (D) Final stage of metal powders (particles) fusion. 2.4 Metallography The other major examination tool in metallography is the scanning electron microscope (SEM). Compared to the light microscope, the SEM expands the resolution range by more than two orders of magnitude to approximately 4 nm in routine instruments, with ultimate values below 1 nm. Useful magnification covers the range from the stereomicroscope, the entire range of the light microscope, too much of the range of the transmission electron microscope (TEM) for possible viewing from 1,000x to >100,000x. The SEM also provides a greater depth of field than the light microscope, with depth of focus ranging from 1 µm at 10,000x to 2 mm at l0x, which is larger by more than two orders of magnitude compared to the light microscope. This higher depth of field allows better discernment of topology features during a microscopic investigation, such as the examination of fracture surface during failure analysis.

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The objective of these tools is to accurately reveal material structure at the surface of a sample and/or from a cross-section specimen. Examination may be at the macroscopic, mesoscopic, and/or microscopic levels. For example, cross sections cut from a component or sample may be macroscopically examined by light illumination in order to reveal various important macrostructural features (on the order of 1 mm to 1 m) such as: (a) Flow lines in wrought products (b) Solidification structures in cast products (c) Weld characteristics, including depth of penetration, fusion-zone size and number of passes, size of heat-affected zone, and type and density of weld imperfection (d) General size and distribution of large inclusions and stringer (e) Fabrication imperfections, such as laps, cold welds, folds, and seams, in wrought products (f) Gas and shrinkage porosity in cast products

3. Geometry of die

Figure 3: Punch

Figure 4: Centre body

Figure 5: Bottom plate

4. Preparation of Sample 4.1 Mixing/blending of copper and CNT powders Copper was mixed in constant Weight fractions with 1%, 3% and 5% CNT. Both the powders were initially mixed with hand and the hand-mixed powder was then mixed using the Ball mill to ensure even distribution of CNT in the copper matrix. The powders were ball milled for about 8 mm for each percentage of copper and CNT.

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4.2 Compaction This is the second step in this process in which the ball milled powders were compacted to obtain consolidated green compact. The process involved compaction in rigid die. The die material used was EN19, the tooling standards were obtained from. First Electrolytic copper (purity 99.7%) was taken and inserted into the die. With the aid of an UTM (Universal Testing Machine) pressure was applied to the copper powder. The powder was compacted with varying compaction pressures and the apparent density was noted at each trial. Hence using the trial and error approach the ideal compaction pressure was found out. With this value as the benchmark the rest of the mixtures were compacted and the consolidated green compacts were prepared. 4.3 Sintering The compacted sample has good green strength but is incapable of taking heavy loads which is required in the secondary powder metallurgy operations. Sintering aids in the grain boundary diffusion where the metal atoms move along crystal boundaries to the walls of internal pores, redistributing mass from the internal bulk of the object and smoothing pore walls. The sintering temperature standards for copper as obtained from (ASM Metals Handbook Vol.7 Powder Metal Technologies and applications) was around 750-1000°C, but the sintering operation was carried out at 650°C to make sure that the CNT do not disintegrate as the destruction temperature of CNT’s, used was 750°C.Sintering was carried out for about 1 hour in a nitrogen atmosphere. The nitrogen atmosphere was provided to avoid the oxidation of copper. 5. Material characterization

5.1 Wear test Table 1 shows the wear test results obtained under varying load and speed conditions. 1. Copper: 99% 2. Sintering: 750 0C and 1 hour 3. Specimen: Dia. = 08 mm and Length = 35 mm

Figure 6: Pin on disc Table 1: wear test results Load ( Kg)

Speed (rpm)

100

200

Time (min) 5 10 15 20 5 10 15 20

Wear (µm) 14 20 25 30 16 23 29 24

Frictional force (N) 6.6 8.8 9.5 11.1 6.3 8.5 9.2 10.8

Weight Loss (g) 13.6314 13.6174 00.0140 13.6174 13.5879 00.0295

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300

100

200

300

100

200

300

5 10 15 20

18 26 32 39

6.1 8.2 8.8 10.4 8.1

13.6314 13.6039

10.9

13.6039

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00.0412 13.6314

12.5 13.8

00.0275

7.7

13.6039

10.2

13.5526

11.8 13.2

00.0513

7.4

13.5526

9..9

13.4712

11.2 12.1

00.0814

8.6

13.6314

10.9

13.6003

12.5 14.7

00.0311

8.2

13.6003

10.7

13.5549

12.3 13.9

00.0454

7.7

13.5549

10.6

13.4698

11.7 13.3

00.0851

6. Morphological study 6.1 Scanning Electron Microscopy (SEM) For conventional imaging in the SEM, specimens must be electrically conductive, at least at the surface, and electrically grounded to prevent the accumulation of electrostatic charge at the surface. Nonconductive specimens tend to charge when scanned by the electron beam which causes scanning faults and other image artifacts. Therefore, Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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they are coated with an ultrathin coating of electrically conducting material, commonly gold, deposited on the sample either by low vacuum sputter coating or by high vacuum evaporation. The dispersion of nanofillers in epoxy was studied using SEM (JEOL JSM 840A, Japan). The samples were examined with gold– sputtering for SEM characterization.

Figure 7: Pure Copper SEM Image

Figure 9: 3%CNT/Cu Composite SEM Image

Figure 8: 1% CNT/Cu Composite SEM Image

Figure 10: 5% CNT/Cu Composite SEM Image

7. Results and Discussion Coefficient of friction for pure copper and multi walled carbon nanotubes reinforced copper composite with varying weight percentages under constant load condition is listed in the following table. Table 2: Coefficient of friction for different wt% of CNT’s Constant load=5kg, Speed=200 rpm, Duration=20 min Composition of Coefficient of Friction CNT wt%) Cu+MW Pure copper (Cu) CNT 0 0.22 0.22 1 NA 0.082 3 NA 0.073 5 NA 0.065 Figure 11: CNT Composite Vs Coefficient of Friction of Cu/MWCNT

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Figure 11 indicates that with the increase in the weight percentage of CNT reinforced in copper matrix the wear rate (mm3 / Nm) reduces. Weight loss in grams for 1% multi walled carbon nanotubes reinforced copper composite under variable load condition is listed in the following table

Table 3: Load Vs Weight Loss at 1 wt% of MWCNT CNT = 1 wt%, Speed = 200 rpm Load (N)

Weight Loss (gms) Cu+MWCNT

0.0018

0.0022

120

0.0028 Figure 12: Weight loss Vs load

8. Conclusions The compaction die has been successfully designed and manufactured. To accomplish required density of the compacted specimen of size 20 mm diameter and 20 mm length, a load of 386 kN has been applied for compaction (86% of theoretical density) for 2 minutes. It can be concluded that the homogeneous distribution of CNTs with sound interface in Cu matrix is an important technological issue to enhance the mechanical behaviour and wear resistance of CNT/Cu nano composite. Oxidation wear is the main wear mechanism for the CNT/Cu composite under dry sliding conditions. The formation of carbon film can reduce the friction and wear rate. Compared with pure Cu composite, the CNT/Cu nano composite has a lower coefficient of friction and reduced weight loss. Increasing the nanotube weight fraction can significantly decrease both the coefficient of friction and wear rate of the composite. The optimum nanotubes content is 3 wt %. References [1] Ijima “ Helical microtubules of graphitic carbon”. Nature, Vol 354, P 51-58. [2] S R Dong “An Investigation of the sliding wear behavior of Cu-Matrix composite reinforced by Carbon Nanotubes”. Materials Science and Engg. A 313(2001) P 83-87. [3] Kashyap “Strengthening in carbon nanotube/aluminium (CNT/Al) composites”. Scripta Materialia, USA 53, 10, P 1105 – 1212. [4] W J Harris (2000), “Carbon Nanotubes and related structures”. Cambridge University Press [5] Lau KT, Hui D “Effectiveness of using carbon nanotubes as nano-reinforcements for advanced composite structures”. Carbon 2002;40:1605–6. [6] V.E. Vaganov and V.Yu. Orlov “Processing, Characterization Of Carbon Nanotube-Reinforced Multiscale Composite”. [7] Tatyana S. Koltsova, Larisa I. Nasibulina, Ilya V. Anoshkin, Vasily V. Mishin, Esko I. Kauppinen, Oleg V. Tolochko and Albert G. Nasibulin “New Hybrid Copper Composite Materials Based on Carbon Nanostructures”. Journal of Materials Science and Engineering B 2 (4) (2012) 240-246

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[8] Ch. Guiderdoni, C. Estourne `s, A. Peigney, A. Weibel, V. Turq, Ch. Laurent “The preparation of double-walled carbon nanotube/Cu composites by spark plasma sintering, and their hardness and friction properties”. doi:10.1016/j.carbon.2011.06.063. [9] A. S. Parab, S. K. Gade, G. V. Lavate, Dr. K. N. Patil “Fabrication of Copper (Cu)-Carbon Nanotubes (CNTs) Composite by powder injection route”. Institute Of Technology, Nirma University, Ahmedabad – 382 481, 08-10 December, 2011. [10] Pham Quang, Young Gi Jeong2, Seung Chae Yoon1, Sun Ig Hong1, Soon Hyung Hong and Hyoung Seop Kim “Carbon Nanotube Reinforced Metal Matrix Nanocomposites Via Equal Channel Angular Pressing”. Materials Science Forum Vols. 534-536 (2007) pp. 245-248 online at http://www.scientific.net © (2007) Trans Tech Publications, Switzerland. [11] Gwi-Nam Kim, Hyun-Ji Kim,Joun-Sung Park, Boo-Young Choi and Sun-Chul Huh “A Study on Characteristic Evaluation and Fabrication of Sintered Cu-CNT Composite”. 9th International Conference on Fracture & Strength of Solids June 9-13, 2013, Jeju, Korea [12] Mina Park, Byung-Hyun Kim, Sanghak Kim, Do-Suck Han, Gunn Kim, Kwang-Ryeol Lee “Improved binding between copper and carbon nanotubes in a composite using oxygen-containing functional groups”. CARBON 4 9 ( 2 0 1 1 ) 8 1 1– 818. journal homepage: www.elsevier.com/locate/carbon [13] Yang Chai, Philip C. H. Chan and Yunyi Fu “Copper/Carbon Nanotube Composite Interconnect for Enhanced Electromigration Resistance”. [14] J.P. Tu, Y.Z. Yang, L.Y. Wang, X.C. Ma and X.B. Zhang “Tribological properties of carbon-nanotubereinforced copper composites”. J.P. Tu et al. / Tribological properties of carbon nanotube composites. 1023-8883/01/0500-0225$19.50/0 2001 Plenum Publishing Corporation. [15] A.H.Javadi , Sh.Mirdamadi , M.A.Faghisani , S.Shakhes “Investigation of New Method to Achieve Well Dispersed Multiwall Carbon Nanotubes Reinforced Al Matrix Composites”. World Academy of Science, Engineering and Technology 59 2011

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TRENDS IN NANO-TECHNOLOGY AND ATOMIC FORCE MICROSCOPY PIEZOS-A REVIEW ON THE INSTRUMENTATION AND MATERIALS Srikanth Hannabe Prakash1, J.Subramanyam2 1

Student, Kuvempu University,Shankaraghatta, Assistant Professor., Dept.of Mechanical Engg.,Vemana IT hannabeprakash@gmail.com

Abstract In the context of nanotechnology, products on-the-shelf today which includes advanced materials such as graphene, photonic crystals, battery devices, terahertz devices are brought under limelight. A means of applications development from the materials in nanotechnology mostly involves thin films. The Atomic Force Measurement (AFM) cantilever, a micro fabricated cantilever with an integrated tip mounted on a cantilever holder chip is the investigation of interest of modern scientific community. The prolong endurance of lead-based piezo is inevitable choice for there were evidences of pivoting ideological uptakes for energy harvesters to an extent of recent discoveries owing to the piezoscopic nanoscale phenomena. These thin films are analyzed for the various properties of which topography studies is critical. In this context, surface analysis by AFM has a role. With this microscopy, the data acquisition is primarily done through the effect called piezoelectricity, achieved with piezoelectric materials such as Lead Zirconate Titanate (PZT). The technique of popular usage is the hydrothermal method. The heat treatment of the titanium substrate is used in order to help the growth of PZT, since Ti is oxidized in PZT, and to increase the adherence of the PZT films, precursors reacting with the thin titanium oxide film. PZT are widely studied and used in many industrial applications such as acoustic transducers, sensors, actuators, filters.

Keywords—Nanotechnology; Atomic Force Microscopy; Piezoelectricity 1. Introduction Nanotechnology is the work frame for materials in the size range of 1 to 100 nano meters. It is foretold as the technology of the future1. They are believed to be more sustainable than naturally occurring materials2.Currently the research areas of nano regime spans widely into the scope of material science3. We wish to emphasis on these selected materials in some depth while at the same time, we will be also involving some lithographical aspects revolving around the fundamentals of Atomic Force Microscopy. Graphene Graphene has a single layer of carbon atoms. It is peeled off the Scotch tape. There were other methods used for their discovery as stated by the Noble Prize winners Andre Gein and Konstantin Novoselov. Scientists wanted to use diffraction of electrons to make faster, thinner and efficient current carriers4. It has been proposed to replace ITO5. Plasmonics Nano particles as have the characteristics of changing colours as the sizes of the particles are varied. Using this phenomena, there are researches in areas of optical communication, imaging etc. This class of6 materials is believed to solve some of the limitations of present modes of communications . Display Devices The contribution to display devices cannot be undermined as they are making inroads in developing our entertainment products7. Quantum dots have prevailed over OLEDs with their capability to offer greater brightness in LCDs8. Semiconductor Technology Carbon Nanotube has paved way for logic gate fabrication replacing the conventional gateoxides. They are foretold to be perfect match to speeds and revolutions of microelectronics with Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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the Moore’s 10Law9. But it’s not merely shrinking semiconductors that make up nanoelectronics . There is also a lithography-free fabrication techniques for silicon and germanium substrates11. Even the IC packaging is replaceable by nanomaterials12. Battery Technology Lithium-ion battery is promising to fulfill the expectations of an ideal battery13. Solar Energy There are currently great deals of work happening in this area. But analysts have doubts over the return on investment on this technology14. Terahertz Wave Propagation This area has seen immense activity especially in the aerospace domain. The implications on the ecological and animal health effects have to be considered before there are applications15.

2 Piezo Materials In AFM Principle of AFM The Atomic Force Microscopy (AFM) was developed by Gerd Binnig, Calvin Quate and Christoph Gerber. It allows the analysis of conducting and insulating materials. It does not have optical focusing element. Here, a sharp probing tip is scanned very closely across the sample surface. The distance between the tip and the sample surface is very tiny to an extent that atomic-range forces act between them. In an AFM, the tip is attached to the end of a cantilever in order to measure these forces.The measurement of the cantilever deflection can then be used to maneuver the tip surface distance on an atomic scale. This huge resolution can be achieved, so that even the atomic arrangement of the surfaces can be probed. This measurement is a so-called static operating mode, in which the static deflection of the cantilever is employed. Usually, the forces acting of the tip will cause it to snap onto the sample, which results in an effective, nanometer range flattening of the tip, and friction and stiction between the tip and the sample. To circumvent the above problem, the socalled dynamic force microscopy modes can be used, as was pointed out by the AFM inventors. In these modes, the cantilever vibrates during the operation in those operating modes. In the dynamic modes, Figure 1: A typical AFM probe with a sharp tip on the sample. changes in the free resonance frequency and the damping of the cantilever vibration caused by the forces between the tip and the cantilever can be measured and used to regulate the tipsample distance. To achieve atomic resolution, ultra-clean and flat surfaces prepared in highly sophisticated vacuum systems are needed. But we have used the AFM from Easyscan as shown

Figure 2: Forces on the AFM cantilever and. Figure 3: Easyscan 2 FlexAFM used by the authors. the sample holder substrate

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above which uses dynamic mode in air that yielded pretty good results. Under ambient conditions, sample surfaces are covered by a layer of adsorbed gases consisting primarily of water vapour and nitrogen that is 10-30 monolayers thick. When the probe touches this contaminant layer, a meniscus forms and the cantilever is pulled by surface tension toward the sample surface. The magnitude of the force depends on the details of the probe geometry, but is typically on the order of 100 nN. T This meniscus force and other attractive forces may be neutralized by operating with the probe and part of the sample or the entire sample fully immersed in liquid. There are many advantages in operating an AFM with the sample and the cantilever immersed in a fluid. These advantages include the elimination of capillary forces, the reduction of van der Waals forces, and the ability to study technologically or biologically important processes at liquid-solid interfaces. However, there are also some disadvantages involved in working in liquids. These range from such nuisances as leaks to more fundamental problems, for example, sample dame on hydrated and vulnerable biological samples. In addition, a large class of samples, including semiconductors and insulators, can trap electrostatic charge (partially dissipated and screened in liquid).This charge can contribute to additional substantial attractive force between the probe and the sample. This normal force creates a substantial frictional force as the probe scans over the sample. In practice, it appears that these frictional forces are far more destructive than the normal force and can damage the sample, dull the cantilever probe, and distort the resulting data. Also, many samples such as semiconductor wafers cannot be practically immersed in liquid. An attempt to avoid these problems is the non-contact mode of AFM16. The AFM cantilever is a micro fabricated cantilever with an integrated tip mounted on a cantilever holder chip. Research for fabricating silicon nanotip array has undergone recently17. But Hyo-Jin Nam et al. have proposed to use PZT cantilevers for high-speed AFM18. The movement of electrons in the nanowires and rods is leading to the conductivity of piezo materials19. We suggest even there, a PZT has a place20. Chung-Hao Yi et al.21 have undertaken such a fabrication. Nevertheless, structural instabilities looms large22. Mark James Jackson23 describes the following steps for the fabrication of a cantilever probe: 

Anisotropic etching is used to carve a pyramidal pit into the surface of a Si (100) wafer.  A Si3N4 film is deposited over the surface and fills in the pyramidal pit. The film is patterned into the shape of a cantilever.  A glass plate is prepared with a saw cut and a Cr bond inhibiting region. The glass is anodically bonded to the annealed nitride surface.  A second cut removes the bond-inhibited part of the glass and exposes the cantilever.  Silicon is etched away leaving the Si3N4 microcantilever attached to the edge of the glass block. The reverse side of the cantilever is coated with a reflective metal coating for the deflection detector. When the sensor tip encounters the sample, a repulsive force that increases with decreasing tip-sample distance acts on it. In the static force-operating mode, the bend of the cantilever, due to the force acting on its tip, is measured using a cantilever deflection detection system.

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In dynamic operating modes, the cantilever is excited using a piezo element. This piezo is oscillated with fixed amplitude at an operating frequency close to the free resonance frequency of the cantilever. The repulsive force acting on the tip will increase the resonance frequency of the cantilever; This will cause the vibration amplitude of the cantilever to decrease. The vibration of the cantilever is also detected using the cantilever deflection detection system.The measured laser beam deflection or cantilever vibration amplitude can now be used as an input for a feedback loop that keeps the tip-sample interaction constant by changing the tip height. The output of this feedback loop thus corresponds to the local sample height. An image of the surface is made by scanning over the sample surface in the X and Y Direction. The sample structure image is now obtained by recording the output of the height control loop as a function of the tip position.

Figure 4: AFM system internal block diagram.

Figure 5: Piezo elements in the AFM detection system.

Figure 6: Feedback loop with the AFM detection System

There are interferences in the output frequency because of the delicate nature of probing which are   

Mechanical vibration from machines or heavy transformers in direct vicinity (e.g. pumps) Electrical interference (in the electronics, or in electrical forces of the tip-sample interaction). Infrared or other light sources (light bulbs, sample illumination in an inverted microscope)24.

3. Piezoelectric materials Ferroelectric ceramics are widely used as capacitors25, transducers and thermistors. Walter Cady was the first to make a piezoelectric resonator26. W. F. G. Swann studied the Piezoelectric properties of Rochelle salt27.These piezo materials include the potassium dihydrogen phosphate groups, LiNbO3 family, LiTlC4H4O6. H2O, Cd2Nb2O7 pyrochlore family, PbNb2O6 tungsten bronze family, G.A.S.H family, Sn(NH2)2 thiourea, TGS family, (NH4)2SO4 family, Colemanite, (NH4)2Cd2(SO4)3 family, Alums, Dicalcium Strontium Propionate, Boracite family, (NH4)HSO4, NaNO2 family, KNO3, LiH3(SeO3)2 family, (NH4)NaSO4, N(CH3)4.HgCl3 family, K4Fe(CN)6. 3H2O family, SbSl family, YMnO3 family, Sodium Potassium Niobates, Pb(Zr, Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Ti)O3 etc. Jaffe et al. formulated the optimization conditions for PZT systems for piezoelectric responses far superior than anything known in their time28.Reference 29 will provide detailed background on the historical perspective regarding ferroelectric ceramics. Ferroelectric Random Access Memory (FeRAM) is catching fire like forests in the new alley of semiconductor devices30. Yet the issue of lead-free materials for substitution looms large. Also stacking plays a major role in terms of capacitance it can offer in addition to the incredible memory retention due to hysteresis31.

Figure 7: Tracing the topography of a sample in AFM.

Characteristics of Piezoelectric materials Piezoelectric materials utilize electrical energy to mechanical deform and vice versa. The former effect called the motor effect is attributed to the domain redistribution32. Ferroelectric materials are a subset of piezoelectric materials. These piezoelectric materials are in turn a subset of pyroelectric33 class of materials34. All these materials belong to dielectric family of ceramics. Ferroelectric materials have something similar to ferromagnetic materials. They possess electric hysteresis and have domain walls, which align on applying electric field. In an electric field, the crystal structure of the ferroelectric changes from the cubic to tetragonal to rhombohedral. On heating, the dielectric constant keeps increasing until a point is reached after which it starts decreasing. This critical temperature point is called the Curie temperature, named after the Noble Prize winner Pierre Curie who discovered this phenomenon. More details regarding the piezoelectric hysteresis effects and influence of dielectric constants along with the thermodynamic equations involving piezoelectric coefficients are referred to 35 and 36. Methods of preparation Many have used hydrothermal method for the synthesis of Pb (Zr, Ti)O3 with many modifications like [37, 38, 39 and 40]. A couple of works on synthesis of PZT by mechanical activation from amorphous precursors41 and calcinates42 were also reported. A work reported that a sol-gel and mixed-oxide method improves densification43. Reference 44 tells about the two-stages of a solid-state reaction done separately. A. L Ding et al. did work on PZT fine powders for their applications45. In research unexpected methods also evolve46.Thin films of PZT are often reported to be formed by reactive sputtering47. Thermal annealing is carried out to control nucleation and growth48. Properties of Lead Zirconate Titanate T-I Cheng et al. did sintering at 1000 0C, 1100 0C and 1200 0C and concluded that the PZT sintered at 1100 0C for 2 hr possess high relative density, high dielectric constant, low dielectric loss, and superior piezoelectric properties49. Z. Surowiak et al. investigated nano crystalline properties of PZT50.Also, a special investigation on electrical properties were carried out by Lu Ran et al.51.Computer simulations on the fracture feature52 and poling behaviour53 were some of studies of researchers were our findings. Meanwhile Wang Yi et al. 54 experimented on the stress corrosion cracking as well. Poling process is known to have a frequency dependent behaviour as per the work of 55. T Malysh and J. Erhart56 studied the electric field applicability limits for hard and soft PZT ceramics. G. Yang et.al. 57 should be attributed with the study on the uniaxial stress and DC bias fields. Then, Xiaoyan Wang et al. 58 Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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studied the obvious dielectric properties. A peculiar type of low-temperature and high pressure class of PZTs was studied by V. Bornand et al.59. R. A Dorey and R.W. What more determined the reduction in the value of d 33 piezoelectric co-efficient from various factors in thick films60. C. S. Lynch61 performed large field electromechanical measurements and calibrated their home brew instruments. Processing of Lead Zirconate Titanate If solid materials are used, it should be a tapping mode of AFM. The material to be replace as a piezo itself is first analyzed with AFM because its dielectric property has to be studied62. Usually, thin films are analyzed with AFM. Their properties at nanoscale are influenced by thickness63. To adapt a process for fabricating devices from piezo ceramics, we follow some steps64. He in turn attributes the observations to the domains. 5. Piezomaterial in afm Piezoelements are an integral part of the instrumentation and analysis of detection systems for cantilever deflections and in scanning and control systems of a generic AFM. Piezoresistive detection An alternative detection system which is not as widely used as the optical detection schemes are piezoresistive cantilevers [65, 66, 67]. These cantilevers are based on the fact that the resistivity of certain materials, in particular of Si, changes with applied stress. Four resistances are integrated on the chip, forming a Wheatstone bridge. Two of the resistors are in unstrained parts of the cantilever; the other two are measuring the bending at the point of the minimal deflection. For instance when an AC voltage is applied between terminals a and c one can measure the detuning of the bridge between the terminals b and d. With such a connection, the output signal varies only due to bending, but not due to changing of the ambient temperature and thus the coefficient of the piezoresistance. Piezo Tubes Almost all Scanning Probe Microscopies (SPMs) use piezo translators to scan the tip or the sample. A popular solution is the tube scanner. They are now widely used in SPMs due to their simplicity and their small size [68, 69]. The outer electrode is segmented in four equal sectors of 90 deg. Opposite sectors are driven by signals of the same magnitude but opposite sign. This gives, through bending, a two-dimensional movement on, approximately, a sphere. The inner electrode is normally driven by the z-signal. It is possible, however, to use only the outer electrodes for scanning and for the z-movement. The main drawback of amplifying the zsignal to the outer electrodes is, that the applied voltage is the sum of both the x- or y-movement and the z-movement. Hence a larger scan size effectively reduces the available range for the zcontrol. Piezo Effect An electric field applied across a piezoelectric material causes a change in the crystal structure, with expansion in some directions and contraction in others. Also, a net volume change occurs66. Many SPMs use the transverse piezoelectric effect, where the applied electric field E is perpendicular to the expansion/contraction direction. ∆ = ( . ) = , (1) Where d31 is the transverse piezoelectric constant, V is the applied voltage, t is the thickness of the piezo slab or the distance between the electrodes where the voltage is applied, L is the free length of the piezo slab, and n is the direction of polarization. Piezo translators based on the transverse piezoelectric effect have a wide range of sensitivities, limited mainly by mechanical stability and breakdown voltage70. 5 Conclusion This paper has reviewed on the key elements connected with the nanotechnology to an introductory stage and provides a springboard for thorough investigations. AFM working and critical elements and arguments revolving around the mechanisms is explained. Notable works

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to be taken up for study in design, manufacture and testing of piezoelements is discussed. Emphasis is laid on the piezo material lead zirconate titanate. Acknowledgment We thank the Dept. of Science and Technology and the Nano Mission commission for initiating the Nanotechnology Masters of Technology programme at Kuvempu University. References [1]. Vandana Sharma and Janani Gopalakrishnan, “Nanotechnology: The lord of small things”,Electronics For you, vol. 43, no. 7, July 2011, pp. 26. [2]. Rosemarie Szostak and Michael Kapralos, “Eco-metamaterials,” SPIE Professional, July 2012, pp. 2426. [3]. Advertisement of Jain University, “Jain university is a renowned University in Karnataka and a leader in Teaching and Research”, Nano Digest, vol. 4, no. 5, November 2012, pp. 55. [4]. Kathy Sheehan(ed), “Many Uses for graphene nanoribbons”, SPIE Professional, July 2012, pp. 12. [5]. Dr. S.S.verma, “Can graphene electronics take over”,Electronics For you,vol. 43, no. 2,February 2011, pp. 66. [6]. Jagmeet Singh and Dr. S. S. verma, “Plasminics promises faster communication”,Electronics For you, vol. 43, no. 3, March 2011, pp. 48. [7]. Janani Gopalakrishnan Vikram, “Display innovations”,Electronics For you, vol. 43, no. 6, June 2011, pp. 28. [8]. Prachi Patel, “Quantum dots are behind new displays,” IEEE Spectrum, August 2012, pp. 11-12. [9]. Janani Gopalakrishnan, “Semiconductor fabrication”, Electronics For you, vol. 43, no. 5, May 2011, pp. 28. [10]. Jack Mason, “Nanoelectronics means more than simply shrinking semiconductors,”, 2002. [11]. Huatao Wang and Tom Wu, “A general lithography-free method of microscale/nanoscale fabrication and patterning on Si and Ge surfaces,” Nanoscale Research Letters, vol. 7, no. 110, 2012. [12]. Cher Ming Tan, Charles Baudot, Yongdian Han and Hongyang Jing, “Applications of multi-walled carbon nanotube in electronic packaging,” Nanoscale Research Letters, vol. 7, no. 183, 2012. [13]. Shweta Dhadiwal Baid, “Lithium-ion batteries: Portable power source for portable devices,” Electronics For you, vol. 43, no. 5, June 2011, pp.76. [14]. Peter Fairley, “Argument over the value of solar focusses on Spain,” IEEE Spectrum, September 2012, pp. 11-12. [15]. Carter M. Armstrong, “The truth about terahertz,” IEEE Spectrum, September 2012, pp. 28-33. [16]. Sam Zhang, Lin Li and Ashok Kumar, Materials Characterization Tecchniques, CRC Press, 2009, pp. 107. [17]. Chi-Chang Wu, Keng-Liang Ou and Ching-Li Tseng, “Fabrication and characterization of well-aligned and ultra-sharp silicon nanotip array,” Nano Research Letter, vol. 7, no. 120, 2012. [18]. Hyo-Jin Nam, Seong-Moon Cho, Youngjoo Yee, Heon-Min Lee, Dong-Chun Kim, Jong-Uk Bu and Jaewan Hong, “Fabrication and characteristics of piezoelectric PZT cantilever for high speed Atomic Force Microscopy,” Integrated Ferroelectrics, vol. 35, pp. 185-197, 2001. [19]. Colm Durkan, “Electromigration:How currents move atoms, and implications for nanoelectronics,” in Current at the Nanoscale, Imperial College Press, 2007. [20]. Licien Eyraud, Laurent Lebrun, David Audigier, Benoit Guiffard and Daniel Guyomar, “Electron transfer between ionized vacancies in lead zirconate titanate and its effects on piezoelectric properties and squeeze behaviour,” Ferroelectrics, vol. 413, pp. 371-380, 2011. [21]. Chung-Hao Yi, Chia-Hsin Lin, Yi-Hui Wang, Syh-Yuh Cheng and Horng-Yi Chang, “Fabrication and characterization of flexible PZT fibre and composite,” Ferroelectrics, vol. 434, no. 1, pp. 91-99, 2012. [22]. S. Teslic, T. Egami and D. Viehland, “Structural instabilities in PZT,” Ferroelectrics, vol. 194, no. 1, pp. 271-285, 1997. [23]. Mark James Jackson, Microfabrication and Nanomanufacturing, Springer. [24]. Operating Instructions : easyScan 2 FlexAFM, Version 2.1. [25]. Emilien Bouyssou, Guillaume Guegan and Robert Jerisian, “Lifetime Extrapolation of PZT capacitors,” Integrated Ferroelectrics, vol. 73, pp. 49-56, 2005. [26]. Walter Cady, Piezoelectricity,1946. [27]. L. E. Cross and R. E. Newnham, “History of Ferroelectrics,” in Ceramics and Civilization, vol. 3, The American Ceramic Society Inc., 1987. [28]. B. Jaffe, R.S. Roth and S. Marzullo, “Piezoelectric properties of lead zirconate-lead titanate solid solution ceramics,” Journal of Applied Physics, vol. 25, no. 6, pp. 809-810, 1954. [29]. Gene H. Haertling, “Ferroelectric Ceramics: History and Technology,” Journal of Americal Ceramic Society, vol. 82, no. 4, pp. 797-818, 1999. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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[56]. T. Malysh and J. Erhart, “Electric field applicability limis for PZT ceramics,” Ferroelectrics, vol. 319, no. 1, pp. 45-56, 2005. [57]. G. Yang, W. Ren, S. –F. Liu, A. J. Masys and B. K. Mukherjee, “Effects of unixial stress and DC bias field on the piezoelectric, dielectric and elastic properties of piezoelectric ceramics,” Proceedings of IEEE Ultrasonics Symposium, 2000. [58]. Xiaoyan Wang, Zhaoquan Gong, Yanxue Tang, Xiyun He, Qizhuang He, Zifei Peng and Dazhi Sun, “Dielectric properties of functionally graded ferroelectric PZT ceramics,” Ferroelectrics, vol. 403, no. 1, pp. 191-195, 2010. [59]. V. Bornand, J. Rouquette, J. Haines, M. Pintard and P.H. Papet, “Structure and behaviour of low temperature high-pressure perovskite compounds in the PZT system.,” Integrated Ferroelectrics, vol. 62, pp. 43-47, 2004. [60]. R. A. Dorey and R. W. Whatmore, “Apparent reduction in the value of the d33 piezoelectric coefficients in PZT thick films,” Integrated Ferroelectrics, vol. 50, pp. 111-119, 2002. [61]. C. S. Lynch, “Large field electro-mechanical measuement technique for ferroelectric materials,” Integrated Ferroelectrics, vol. 111, pp. 59-67, 2009. [62]. E. B. Araujo, E. C. Lima, I. K. Bdikin and A. L. Kholkin, “Thickness dependence of structure and piezoelectric properties at nanoscale of polycrystalline PZT films,” Proceedings of ISAF, Aveiro, 2012. [63]. A. Goswami, Thin Film Fundamentals, New Age International LTD., 2008, pp. 349-409. [64]. Jyh-Cheng Yu, Jun-Xiang Wu, Tsung Her Yeh and Chen-Chia Chou, “Compatibility of material processing and fabrication of sol-gel derived PZT based devices,” Ferroelectrics, vol. 383, pp. 127-132. [65]. U. Stahl, C. W. Yuan, A. L. Delozanne and M. Tortonese, “Atomic force microscope using piezoresistive cantilevers and combined with a scanning electron microscope ,” Applied physics Letters, vol. 65, pp. 2878-2880, 1994. [66]. R. Kassing and E. Oesterschulze, Sensors for Scanning Probe Microscopy, pp. 35-54, Kluwer, 1997. [67]. N. W. Ashcroft and N. D. Mermin, Solid State Physics, Holt Reinhart and Winston, 1976. [68]. G. Binnig and D. P. E Smith, “Single-tube three dimensional scanner for scanning tunneling microscopy,” Review of Scientific Instruments, vol. 57, no. 1688, 1986. [69]. C. J. Chen, “In-situ testing and calibration of tube piezoelectric scanners,” Ultramicroscopy, vol. 42-44, pp. 1653-1658, 1992. [70]. Bharath Bhushan, Nanotribology and Nanomechanics, Springer, 2005, pp. 41-110.

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CHARACTERIZATION OF PULTRUDED FIBER REINFORCED HIGH PERFORMANCEPOLYMER MATRIX COMPOSITE WITH CARBON NANO TUBES (CNT) H.S.Kumaraswamy1, M.K.Venkatesh2 1

Student, Department of Mechanical Engineering, DSCE, Bangalore Assistant Professor, Department of Mechanical Engineering, DSCE, Bangalore kumarhs89@gmail.com

Abstract Polymer matrix composites (PMC) have established themselves as engineering structural materials, not just as laboratory curiosities or cheap stuff for making chairs and tables. Glass fiber reinforced polymers represent the largest class of PMC. Introducing Carbon Nano Tubes (CNT) into matrix material enhances the mechanical properties of the composite materials. Pultrusion process suites our requirements when compare to other processes. Material such as glass fibers with epoxy resin and cynate ester are used in this process because of their light weight and good mechanical properties. To improve the strength and conductivity of the polymer composite, CNT is used. In the present work, pultrution of 3 mm diameter wire is carried out for glass fiber with epoxy and cynate ester respectively. So volume fraction test is conducted using crucible furnace. CNT is introduced in two different compositions to verify the rate of increase of the mechanical strength and glass transition temperature. To avoid agglomeration of CNT, ultrasonicator is used for proper mixing. Tensile test is carried out using dynamic testing machine and glass transition temperature (Tg) is carried out by using Differential Scanning Calorimeter (DSC) test results indicate that increase in percentage of CNT shows increase in tensile strength of glass fiber reinforced polymer (GFRP).

Keywords: glass fibers, epoxy resin, pultrusion process, cynate ester,

1. Introduction Composites are one of the most advanced and adaptable engineering materials known to men. Progresses in the field of materials science and technology have given birth to these fascinating and wonderful materials. Composites are heterogeneous in nature, created by the assembly of two or more components with fillers or reinforcing fibers and a compactable matrix. The matrix may be metallic, ceramic or polymeric in origin. It gives the composites their shape, surface appearance, environmental tolerance and overall durability while the fibrous reinforcement carries most of the structural loads thus giving macroscopic stiffness and strength. Pultrusion is a composite fabrication process designed for structural shapes. The investment cost is very high and therefore only feasible for mass production parts. Fibers are drawn through a resin bath and then through a forming block. Heaters are used to insure fast curing through steel dies and then the part is cut to proper length. Pultruded parts are strongest in the longitudinal direction because of their fiber orientation. Fiber orientation can be changed to increase strength in other directions. Solid, open sided and hollow shapes can be produced at almost any length. Cores such as foam and wood can be built inside of the pultruded shapes. Due to the pressure and designs of production, protruded production can be up to 95% effective in material utilization.

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Figure1: pultrusion process

2. Glass fibers Glass fibers (GF) are the most common reinforcement for polymeric matrix composites. Their principal advantages are the relationship between their low cost, high tensile strength, high chemical resistance, and insulating properties. The disadvantages are low tensile modulus, relatively high specific gravity, sensitivity to abrasion during handling, low fatigue resistance, and high hardness. E-glass and S-glass are the types of fibers more commonly used in the fiber-reinforced plastic industry-glass fibers have the lowest cost of all commercially available reinforcing GFs, which is the reason for their widespread use in the fiber-reinforced plastic industry. Table1: Properties of Glass Fiber as per the Manufacturer

Fiber type

Tensile strength(MPa)

Young’s modulus (GPa)

E-glass

1250

Density (kg/m3) Coefficient of thermal expansion (K-1) 2550 4.7X 10-6

Figure 2: Glass Fiber Reinforcement of having 1200 Tex

3. Epoxy resin Epoxy resin has been used in a wide range of fields, such as paints, electricity, civil engineering, and bonds. This is because epoxy resin has excellent bonding property, and also after curing, it has excellent properties on mechanical strength, chemical resistance, and electrical insulation. In addition, epoxy resin is able to have various different properties as it is combined and cured together with various curing agents. This issue describes the types of curing agents for epoxy resin and characteristics comparing to Three Bond products. The epoxy resin compositions of three bond currently on the market are the three bond 2000 series (base agent for epoxy resin), the three bond 2100 series (curing agent for epoxy resin), and the three bond 2200 series (one-part thermal cure epoxy compound resins).

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Table 2: Properties of epoxy resin given by manufacturer

Test Colour on gardener scale Epoxy value viscosity@250c Martens value

Result unit GS

Requirement 0 to 1

Result 0.08

Eq/kg MPas 0 C

5.25 to 5.4 1000 to 12000 145 to 175

5.38 11250 152

Figure 3: Epoxy resin with suitable hardener

4. Cynate ester Traditional epoxy resin systems have long been used for vacuum impregnation of large electro-magnets. However, the mechanical strength of these systems is disappointingly low when operated at temperatures above about 70°C where the failure mechanism is more often by adhesion at the copper interface than by cohesion within the resin. A range of resin systems based on cyanate ester are currently being developed by CTD Inc. which are suitable for vacuum impregnation and may offer advantages over the epoxy resin systems. Table 4: Properties of Cynate ester given by the supplier

Resin

RS-14

Density

1.200

Tensile properties Ultimate Strength Young’s modulus MPa GPa 80 2.8

Percentage elongation 5.1

DMA (Tg) °c 253

Figure 4: Cynate ester

Figure 5: GFRP samples are produced by using pultrusion machine

5. Volume fraction Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Volume fraction of the pultruded composite wire is determined by using crucible furnace and the procedure for glass fiber with epoxy resin is as follows 0

1. A crucible is heated to 600 C for 10 min or more. It was then cooled to room temperature and its mass was determined to the nearest 1.0 mg. This was recorded in the data sheet. 2. The laboratory exhaust fan or ventilation system was turned on. 3. The mass of the specimen and the crucible together was determined to the nearest 1.0 mg. 4. The crucible and the specimen were placed in the furnace. The heating element 0 was turned on to 565 C. The specimen is allowed to remain in the furnace for a minimum of one hour or until the entire matrix has disappeared (extra time is required for thicker laminates). 5. The crucible and the remains were removed from the furnace and cooled to room temperature. Then they were carefully placed on a gram scale and the post burnout mass was determined. The same procedure is carried for glass fiber with cynate ester resin but the temperature of 0 the heating element should be 700 C 6. Tensile test The tensile test of the prepared samples is conducted by dynamic tensile testing machine.

Figure 5: Dynamic tensile testing machine

7. Glass Transition Temperature (Tg) The glass transition temperature (Tg) is one of the most important properties of any epoxy and is the temperature region where the polymer transitions from a hard, glassy material to a soft, rubbery material. As epoxies are thermosetting materials and chemically cross-link during the curing process, the final cured epoxy material does not melt or reflow when heated (unlike thermoplastic materials), but undergoes a slight softening (phase change) at elevated temperatures. The glass transition temperature (Tg), not to be confused with melting point (Tm), is the temperature range where a thermosetting polymer changes from a hard, rigid or “glassy” state to a more pliable, compliant or “rubbery” state. In actuality Tg is not a discrete thermodynamic transition, but a temperature range over which the mobility of the polymer chains increase significantly.

Figure 6: Differential scanning calorimetry (DSC)

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8. Result’s and discussions The results from the crucible furnace for glass fiber with epoxy resin and cynate ester resin are as follows

VOLUME… EPOXY RESI…

VOLUME… CYNAT E…

GLASS FIBE…

GLASS FIBER…

Figure 7: Volume fraction of GFRF with epoxy resin and cynate ester resin

9. The theoretical stress for GFRP samples with epoxy Theoretical stress can be calculated by using formula σ = σ f *ff + σ m (1-ff) σ f = tensile strength of fiber σ m = tensile strength of matrix Table 5: Theoretical stress for GFRP samples with epoxy resin

Specimen description

Diameter(mm)

Tensile strength N/mm2

1 – GFRP without CNT 2 - GFRP with 0.5% CNT 3- GFRP with 0.75% CNT

2.96

780

2.96

1056

2.96

1194

Table 6: Theoretical stress for GFRP samples with cynate ester

Specimen description 1 –GFRP without CNT

Diameter(mm) 2.96

Tensile strength N/mm2 782

10. Tensile test results Table 7: Tensile test results

Specimen description 1 –GFRP without CNT 2- GFRP with 0.5%CNT 3- GFRP with 0.75% CNT

Diameter(mm) 2.96 2.96 2.96

Tensile strength N/mm2 529 659 964

Table 8: Tensile test results obtained from the dynamic testing machine for GFRP samples with cynate ester

Specimen description 1 –GFRP without CNT

Diameter(mm) 2.96

Tensile strength N/mm2 430N/mm2

11. Glass transition temperature (Tg) of GFRP samples Glass transition temperature of the GFRP sample with epoxy resin is as follows On set peek temperature = 174.93 °C Peek temperature = 177.31 °C

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= 180.33 °C

The peek temperature is the glass transition temperature of the GFRP sample with epoxy resin which is equal to 177.31 °C The glass transition temperature of the GFRP samples with cynate ester resin is as follows On set peek temperature = 208.35 °C Peek temperature = 220.36 °C End set peek temperature = 223.60°C The peek temperature is the glass transition temperature of the GFRP sample with cynate ester resin which is equal to 220.36°C 12. Results and discussion Increase in tensile strength of the GFRP samples with epoxy resin and cynate ester resin while percentage of CNT increases. Sample 1= GFRP without CNT Sample 2=GFRP with 0.5% CNT Sample 3=GFRP with 0.75% CNT As the percentage of CNT increases tensile strength also increases in the pultruded samples.

600 400

1.EPOXY RESIN

200

2 CYNATE ESTER

0 1

Figure 8: comparison of tensile strength of the GFRP samples with epoxy resin 2500 2000 1500 1000 500 0

EXPERIMENT AL THEORITICAL 1

Figure 9: Comparison of experimental and theoretical result of tensile strength for GFRP sample with epoxy resin

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20 15 10

EXPERIMENT AL

THEORITICAL

0 1

Figure 10: Comparison of Experimental and Theoretical result load for GFRP sample with epoxy resin

13. Conclusion Polymer composites wires were pultruded by glass fibers. here epoxy and cynate ester resin used as a matrix material.Multi-walled carbon Nano tubes were introduced in two composition to the matrix material and then pultruded again based on mechanical test conducted, following conclusions are made.  Tensile strength of the GFRP samples with 0.5% CNT IS 16% more than the GFRP without CNT. And GFRP with 0.75% have tensile strength 25% more than GFRP without CNT and GFRP with 0.75% CNT have tensile strength 9% more than the GFRP with 0.5% CNT.  Tensile strength of the GFRP sample with epoxy resin is 18.7% more than the GFRP sample with cynate ester resins both without CNT.  Glass transition temperature (Tg) of GFRP sample with cynate ester resin is too higher than theGlass transition temperature (Tg) of GFRP samples with epoxy resin.so the cynate ester resin have more thermal conductivity than epoxy resin.  Pultrusion process is very economical compared to other process because of less wastage and also having high production rate. References [1]. Lubin, Hand book of composites, Van Nostarnd, New York, 1982. [2]. R.E. Horton and J.E. McCarty, Damage Tolerance of Composites, Engineered Materials Handbook, Vol 1, Composites, ASM International, 1987. [3]. Reinhart, T. J., ed. Engineered Materials Handbook Volume 1, Composites. Materials Park, OH: ASM International, 1987. [4]. Josmin P. Jose, Sant Kumar Malhotra, Sabu Thomas, Kuruvilla Joseph, Koichi Goda, and Meyyarappallil Sadasivan Sreekala (2010) “Advances in Polymer Composites: Macro- and Micro composites – State of the Art, New Challenges, and Opportunities” 41, 446–453. [5]. Mel M. Schwartz, “Composite Materials, Vol. II: Processing, Fabrication, and Applications:, 1/e, ISBN: 0-13-300039-7, 1997, Figure: 2.1,2.2,2.3,2.4and2.5 Net Composites Tapton Park Innovation Centre Brimington Road, Chesterfield S41 OTZ, UK. [6]. S.M.Moschiar, M.M.Reboredo, A. VazquezI nstitute of Materials Science and Technology (INTEMA) Mar de1 Plata, Argentina, “PULTRUSION PROCESS” 25, 1632, (1991). [7]. Raymond Wolff, Stratikore, Inc. “Thermoplastic Pultrusion Process using Commingled Glass/Polypropylene Roving” Composites 2011 American Composites Manufacturers Association February 2-4, 2011 Ft. Lauderdale, Florida USA. [8]. F.J.G. Silva , F. Ferreira , C. Costa , M.C.S. Ribeiro, A.C. Meira Castro “Comparative study about heating systems for pultrusion process” Composites: Part B 43 (2012) 1823–1829. [9]. Professor Hongjie Dai “An introduction to carbon nanotubes” Eighth Edition (Prentice Hall, 2002). [10]. Paul Holister, Paul Holister, Cristina Román Vas “NANO TUBES” CMP Científica January 2003.

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AN EXPERIMENTAL INVESTIGATION ON THE EFFECT OF MECHANICAL PROPERTIES OF ALUMINUM ALLOY EXPOSED TO DIFFERENT COMBINATION OF CHEMICAL SOLUTION B. Satheesh kumar1, V.D.Ragupathy2, Satish Chandra kumar3, G.Narayanan4 1,2,3,4

Liquid Propulson Systems Centre, Bangalore, ISRO, Bangalore satheeshb1978@gmail.com

Abstract AA-6351 is a 6-XXX series aluminum alloy contains Si and Mg as a major alloying element and heat treatable medium high strength wrought alloy. Due to its excellent general corrosive resistance coupled with excellent mechanical properties and cost, it is being widely used in aerospace applications. However to withstand critical and severe exposure to different environments, various type of surface treatments are provided on aluminum alloy components like chromic acid anodizing, sulphuric acid anodizing, alocrom treatment, cadmium plating and dichromate golden yellow coating etc. In launch vehicle, some of the brackets are fixed by bonding process using araldite and hardener rather than normal welding processes. During chemical bonding of brackets, components are also exposed to different kind of chemical environments as a part of the process. However the complexity of component geometry coupled with facility constraint and higher number of components in a single batch are prime reasons for non-complete removal of left out chemicals from the surface of components. Keeping this uncertainty and to investigate the effect of the left out chemicals on the intended performance of the components, a detailed investigation study is carried out with emphasis on mechanical properties. A series of experiments are carried out to study the effect of mechanical properties of aluminum alloy of AA-6351-T6 material exposed to different chemical exposure like combination of (1) HCl & DeMineral (DM) water (2) NaCl & DM water (3) Chromic acid & DM water and (4) H2S04 , DM water and Na2Cr2O7. Rectangular Tensile test coupons (as per ASTM E8 Standards) are dipped into different chemical solutions for one hour duration and tensile tested to assess the effects on mechanical properties like yield strength, UTS, % of elongation and % reduction of area. The various results observed are discussed in this paper. Keywords: Aluminum alloy, yield strength, ultimate tensile strength, AA6351-T6, % reduction of area, % of elongation

1. INTRODUCTION Aluminum alloy has a unique combination of properties such as high strength to weight ratio, excellent corrosive resistance, availability and cost. These unique properties make aluminum most versatile engineering and structural material particularly in Aerospace and transportation industries. Aluminum is well known for light weight characteristic having an average density of 2.7 gm/cc. (appx. one third of steel). To improve corrosive resistance characteristic of Aluminum alloy components and for chemical bonding processes, the components are exposed to different kind of chemical environments. Hence an experiment investigation is carried out to assess the effect of mechanical properties of components, when exposed to chemical environments. Aluminum Alloy AA 6351 is a medium strength heat treatable aluminium alloy with good mechanical properties coupled with good correction resistance and weldability which is widely used in Aerospace application. Plates of 12.5 mm thickness aluminium alloy (AA 6351 in T6 condition Solution heat treated and artificially aged) were used in this investigation. The various international designations of AA 6351 is as shown in table “1” and the chemical composition of AA 6351 is presented in Table 2 and mechanical properties of the material is presented in Table 3. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Table – 1 Designations of AA 6351

Aluminum Association AA 6351

UNS No. A 96351

ISO Al –Si 1 Mg

IS 64430

Table – 2 Chemical compositions (wt %) of AA 6351:

Si 1.0 %

Mg 0.9 %

Mn 0.7 %

Cu 0.1 %

Zn 0.1 %

Fe 0.5 %

Ti 0.2 %

Al Remaining

Table 3 Mechanical properties of AA 635-T6:

UTS (MPa)

0.2 % Proof stress (MPa)

295 (min.)

250 (min.)

% of elongation (50 mm GL) 11% (Min.)

2. EXPERIMENTAL PROCEDURE In this experiment, tensile test coupon itself was taken as a specimen for investigation. Rectangular tension test specimens were prepared as per ASTM-E8 standard. Refer Figure-1 for the dimension details of specimen. Specimens were designed as A, B, C, D & E. All specimens except “E” is exposed to different chemical environments for the period of one hour and detailed presented in the table 4.

Figure –1 Rectangular tension test specimens (ASTM-E8 STD) Table – 4 Specimen Vs Chemical solutions (Exposure time – one Hour)

IDN. NO. CHEMICAL SOLUTION Specimen “A” 700 g of DM water, 270g sulphuric acid and 30g Sodium di-chromate. Specimen “B” 400g of DM water, 100g Chromic acid Specimen “C” 850g of DM water, 150g Hydro chloric acid Specimen “D” 1000g of DM water, 53g Sodium Chloride Specimen “E” NOT EXPOSED TO ANY CHEMICAL ENVIRONMENT To study the effect of mechanical properties of specimen exposed to different chemical environment, tensile test was carried out using Universal Testing Machine and Mechanical properties Ultimate Tensile strength, 0.2 % proof strength, Percentage of elongation and Percentage reduction of area were measured. MTS 810 Universal Testing Machine (UTM) is used to evaluate the mechanical properties of the material at room temperature; standard dog bone specimens as per ASTM E8 were utilized. The engineering tension test is widely used to provide basic design information on the strength of materials and as an acceptance test for specification of materials. In tension test, a specimen is subjected to a continuously increasing tensile force while simultaneous observations are made on the elongation of the specimen. The shape and magnitude of stress – strain curve of a metal will depend on generally its composition, heat treatment, prior history of plastic deformation and the strain rate, temperature and the state of stress. The parameters used to describe stress – strain curve of metal are the tensile strength, yield Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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strength, percent elongation. The first two are strength parameters and the last parameter indicates ductility. Tensile strength or ultimate tensile strength (UTS) is the ratio of maximum load to the original cross section area of the specimen. Yield strength or yield point of aluminium is not seen on stress – strain curve. So it is taken as the % elongation or strain of the gauge length. It is generally taken as 0.2% of original gauge length. 3. RESULTS OF EXPERIMENTS The tensile test result is directly obtained from UTM and presented in table 5 and percentage of elongation is presented in table 6, percentage reduction of area is presented in table 7 and breaking strength is presented in table 8. Table -5 Specimen test results (UTM)

Idn. No. 0.2 % P.S.(MPa) UTS (MPa)

E 289.7 326.7

A 284.7 322.3

B 286.2 324.6

C 281.2 316.3

D 286.5 324.1

A 9.4

B 8.9

C 7.7

D 8.8

18.8

17.8

15.4

17.6

Table – 6 Percentage of elongation

Idn. No. E Change in length ∆L 9.0 (mm) % of elongation 18.0 (GL 50mm) Table -7 Percentage reduction of area

Idn. No. E A B C 2 Ao (mm ) 156.75 157.25 157.87 157.37 Af (mm2) 115.54 110.25 108.6 118.81 % reduction of area 26.3 29.9 31.2 24.5 Note: Ao – Initial area of cross section Af – Final area of cross section

D 158.12 112.35 28.9

Table 8 Breaking strength

Idn. No. E A B C Breaking load (Kgs) 4380.5 4298.4 4405.2 4441.5 Breaking strength (MPa) 274.1 268.2 273.7 276.9 Note: Breaking strength - Breaking load / Ao The stress- strain for different specimens is presented in Figure – 2 SPECIMEN –“A”

D 4350.0 269.9

SPECIMEN –“B” Stress (MPa)

Stress (MPa)

Strain (mm/mm)

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SPECIMEN –“D”

Stress (MPa)

Strain (mm/mm)

SPECIMEN –“E”

Stress (MPa)

SPECIMENS AFTER TENSILE TEST

Strain (mm/mm) Figure -2 Stress strain curve

TENSILE TEST RESULTS Idn. No.

Thickness (mm)

0.2 % Proof stress (Mpa)

UTS (Mpa)

%age of elongation (50mm GL)

% reduction of area

Breaking Strength (Mpa)

E A B C D

12.54 12.58 12.63 12.59 12.65

289.7 284.7 286.2 281.2 286.5

326.7 322.3 324.6 316.3 324.1

18.0 18.8 17.8 15.4 17.6

26.3 29.9 31.2 24.5 28.9

274.1 268.2 273.7 276.9 269.9

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4. DISCUSSION 0.2 % PROOF STRESS (MPa)

4.1 Variation of 0.2% proof stress: 292 290 288 286 284 282 280 278 276 A

SPECIMEN IDN. NO.

1. Reduction in 0.2 % proof stress is noticed for all specimen A, B, C & D compare to raw specimen “E”. Hence minor degradation of material is confirmed by dipping into the chemical solution. 2. Specimen “C” (HCl + DM water solution) has more degradation around 9 MPa 0.2 proof strength is less than specimen “E”. Hence HCl is more prone to degrade the material. 3. The effect of chromic acid and sodium chloride (Specimen B & D) is less compare to HCl (Specimen ‘C’) 4.2 Variation of UTS UTS (MPa)

330 325 320 315 310 A

SPECIMEN IDN. NO.

1. Reduction in UTS is noticed for all specimen A, B, C & D compare to raw specimen “E”. Hence minor degradation of material is confirmed by dipping into the chemical solution. 2. Specimen “C” (HCl + DM water solution) has more degradation around 10 MPa UTS is less than specimen “E”. Hence HCl is more prone to degrade the material. 3. The effect of chromic acid and sodium chloride (Specimen B & D) is less compare to HCl (Specimen ‘C’).

% of elongation

4.3 Variation of % of elongation 20 15 10 5 0 A

SPECIEMN IDN. NO.

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1. Percentage of elongation for Specimen “A” is around 0.8 % more than Specimen “E”. 2. Specimen “C” (HCl + DM water solution) has reduced percentage of elongation by 3.6 % than specimen “E”. Hence HCl is more prone to reduce the ductility of material. 3. The effect of chromic acid and sodium chloride (Specimen B & D) is very less compare to HCl (Specimen ‘C’).

% REDUCTION OF AREA

4.4 Variation of % reduction of area 40 30 20 10 0 A

SPECIMEN IDN. NO.

Breakign strength (Mpa)

1. Percentage reduction of area for Specimen “A”, “B”, “C” is more than Specimen “E”. 2. Specimen “C” (HCl + DM water solution) has reduced % reduction of area by 1.8 % than specimen “E”. Hence HCl is more prone to reduce the ductility of material. 4.5 Variation of breaking strength 280 275 270 265 260 A

SPECIEM IDN. NO.

1. Breaking strength of specimen “C” is more than specimen “E” (appx. 2.8 Mpa). Effect on hydro chloric acid on breaking strength is almost nil. 2. Breaking strength for Specimen “A”, “B”, “D” is less than Specimen “E”. 5. CONCLUSION

Based on the results obtained from the above investigation, it is concluded that, (1) Marginal degradation of 0.2 % PS, UTS & % of elongation, exposed to different chemical solutions. (2) Effect of degradation is more when specimen is exposed to HCl solution compared to other chemical solution. (3) Marginal increase in % reduction of area is observed other than HCl solution. At the outset, the effect of mechanical properties of Aluminum Alloy 6351-T6 Material is very minor, exposed to above combination of chemical solutions. References

[1] Metallurgy for the Non-Metallurgist (Edited by Arthur C.Reardon) [2] Aircraft production technology and Management (By S.C.Keshu & K.K.Ganapathy) [3] Light alloy (By I.J.Polmear) [4] Mechanical Metallurgy (By Gerorge E.Dieter) [5] Standard guide for preparation of metal surfaces for adhesive bonding (ASTM D2651-01) [6] American Society for Metals hand book (Volume 05) Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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MODELING OF BAMBOO AS A FUNCTIONALLY GRADED MATERIAL G. Lokesha1, M. Venkatarama Reddy2, T. Yella Reddy3 1

Associate Professor, Department of Mechanical Engineering, Vemana I.T, Bangalore. 2 Principal, Sri Krishna College of Engineering, Bangalore. 3 Formerly of Department of Mechanical Engineering, UMIST, UK. lokeshgreddy.vit@gmail.com

Abstract Bamboo is an optimized natural composite that exploits the concept of Functionally Graded Material (FGM). Biological structures such as bamboo have complicated micro-structural shapes and material distribution, and thus the use of numerical methods such as finite element method can be a useful tool for understanding the mechanical behavior of these materials. This paper explores techniques such as finite element method to investigate the structural behavior of bamboo. Two-dimensional models of bamboo cells are built and simulated under tensile load, compression load and bending load cases, using ANSYS 12.1 version with two material options, one with isotropic material properties (averaged Young’s modulus) and the second with Functionally Graded Material (FGM) properties (spatially varying Young’s modulus). To estimate the local features, such as stresses near supports, pin connections or holes, it is necessary to employ a numerical procedure that accurately models material gradients through the cell wall. In this study the stress obtained from FGM model are much higher than those obtained from isotropic material model and the maximum stresses are noted at the outer diameter. This is due to the fact that the higher stiffness of that fiberdense region and also the stress redistribution through the bamboo wall.

Keywords: Bamboo, functionally graded material / structure, finite element analysis 1. INTRODUCTION Bamboo (Latin: Bambusa) is a group of perennial evergreens that belong to the true grass family Poaceae (subfamily Bambusoideae, tribe Bambuseae). There exist 75 genera and about 1250 species. These tall grasses only produce a primary shoot without secondary growth, contrarily to most woods. Among plants, bamboo has a unique structure which resembles that of a unidirectional fiber reinforced composite with many nodes along its length. Furthermore, bamboo’s growth is very fast producing an adult tree in one year. From the analysis of the microstructure of bamboo[1], it was found that bamboo is a biological natural composite that can be regarded as Functionally Graded Material. Bamboo mainly consists of two materials, a fiber material surrounded by a matrix material. The volume fraction of fibers shows a gradient over the thickness of the stem, which can be characterized mathematically. Besides that, also the shape and size of the individual fibers change in the radial direction. This leads to a highly anisotropic structure, in which the fiber volume concentration, Young’s modulus, tensile strength and fracture toughness are functionally graded. On average the distribution of the volume concentration of fibers is found to be 60% at the outer side of the stem and 20% at the most inner side of the wall. The overall volume concentration is 40%. Most work in the literature that characterizes bamboo is experimental, dedicated to estimating strength and stiffness properties. Few works treating the modeling of natural

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fibers have been found in the literature and these deals primarily with simplified analytical model. Considering that biological structures, such as bamboo, have complicated shapes and material distribution inside their domain. The use of numerical methods such as finite element method (FEM)and multiscale methods, such as homogenization can be useful tools for understanding the mechanical behavior of these materials. The objective of this work is to explore computational technique, including FEM to investigate the structural behavior of bamboo. The elastic properties considered in this study employ the Young’s moduli obtained by Nogata and Takahashi [7] through detailed experiments. They tested several small specimens cut from different locations through thickness of the wall of the culm. These tests allowed them to determine the variation of Young’s modulus that occurs through the wall thickness due to the graded distribution of longitudinal bamboo fibers. Rule of mixtures was employed to estimate a Young’s modulus of the composite material with fiber having Ef = 55 GPa, and the matrix of Em=15 GPa. Here the Poisson’s ratio of 0.35 is used. The estimated variation of Young’s modulus through the bamboo thickness is given by expression [6] E(r) =3.75℮(2.2r/t) GPa (1) where ‘r’ denotes the position through thickness of the cell wall starting at the inner surface and ‘t’ denotes the thickness of the cell wall. The modulus at the inner surface is 3.75 GPa. The variation expressed by this equation corresponds to a common bamboo species known as Moso bamboo. For the 13 mm cell wall thickness of the model used in this study, the equation gives a maximum modulus of 33.84 GPa at the outer edge of the wall.

2. Material models 2.1 Isotropic material The first model considers a homogeneous isotropic material model with average Young’s modulus determined from the following expression. (2) The average modulus is obtained by integrating Eq.2 between r = 0 to r = 13. Which yields E = 13.67 GPa. This is close to the value of E=15 GPa for bulk material reported by Nogata and Takahashi [7], which was obtained through the rule of mixtures. 2.2. Functionally graded material The second material model considers the continuous gradation of the young’s modulus through thickness of the cell wall as described by eq.1. Fig. 1 below shows the variation of young’s modulus through the thickness from inner to outer edge of the bamboo wall. The objective of comparing these material models is to find differences in displacements and stresses computed by numerical method. This is necessary to investigate under what circumstances bamboo can be modelled as simplified homogeneous structure using average or effective properties, and when it may be beneficial or necessary to incorporate material variation in the model to capture actual gradients thought cell wall.

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Figure 1. Layered

approximation of Young's modulus through thickness of wall. The of each tread represents the E value for the elements of the layer

level

3. Bamboo geometry for analysis The bamboo geometry is a hallow cylinder with periodic stiffeners called diaphragms, located at positions called nodes. A bamboo cell is the section of culm between two diaphragms. The diameter of the culm is lightly tapered, being largest near the ground. As illustrated in Fig 2, the internal and external diameter of the cell modelled in this study is 70 mm and 96 mm, respectively. The wall thickness is 13 mm, internal nodal distance is 340 mm and the light taper is neglected. Figure 2 shows the geometry of the modelled cell. A fillet was created to transition the diaphragm into the cell wall. This simulates actual bamboo structure and eliminates the stress concentrations that would be created by the presence of sharp corners. The fillet radius in the present model is 13 mm. One bamboo cell was modelled for the study under tension and bending loads. For compression a node is considered at the centre. The maximum specimen height was taken 96 mm (equal to the outer diameter [31]).

Fig. 2. view of half

Section one-

(lengthwise) of cell showing dimensions (mm) adopted for FEM

4 FEM descritization of bamboo A full cell from node to node and of circular cross-section was descritized. Fig. 3 and 4 shows the FEM descritization of the bamboo cell used for tension and compression load cases for the two models (isotropic and FGM) respectively. The mesh consists of 34,248 first order solid brick elements (type SOLID 45). With six layers through the thickness, the model has 35,150 nodes with 105450 degrees of freedom. As the element size used is very small a linear 1 st order elements will capture the response of the structure Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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to the required accuracy. Using higher order elements like quadratic will make the solution more expensive in terms of computing time and space requirements. Single material property is used for homogeneous isotropic analysis, mesh in Fig. 3 and a graded (in 6 steps) material model is used for the mesh in Fig.4.

Fig.3. Finite element descritization of bamboo cross-section for Isotropic material

Fig. 4. Layered finite element approximation of bamboo cross section for FGM.

5. Loads and boundary conditions For tension loading all the nodes at one end of the bamboo were constrained in axial (X-Axis) direction. To avoid the rigid body motion in other two directions (Y-Axis and Z-Axis), few nodes that is nodes lying in the center line were constrained in Y and Z axis at the left most end of the bamboo cell. The load is applied to other end of the bamboo using ANSYS CERIG element in X-direction. This element will make sure that all the nodes on the loaded plane are displaced by the same amount there by distributing loads as per the stiffness of the concentric circular elements. As per the stiffness of the structure the outermost layer of the nodes will take the maximum load and the innermost will take lesser load keeping the displacements of the end nodes same in Xdirection. Loaded element faces included the five outer-most layers of elements, lying D = 67.85 mm and exterior diameter, De = 90 mm. Applied tension is limited to these elements in order to confine loading to the cell walls, thus avoiding artificially loading the diaphragm. A schematic illustrating tension loading of the bamboo model is shown in Figure.5a. For compression load case, loading and boundary conditions were same as that of tensile case. Compression load was applied to the faces of all elements on the opposite end. Figure 5b shows a schematic of the bamboo cell model compression boundary conditions For bending load case the cell was assumed to be a cantilever with one end fixed and a concentrated load applied at the free end in transverse direction. Figure 5c shows the details of constraints and loads.

(a)

(b)

(c)

Figure 5. (a)Bamboo discretization boundary conditions and applied load for tension load (b) For compression load & (c) For bending load case

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6. Results and discussion This section presents the results of finite element analysis and their comparison with available analytical solutions. The displacement and the stress results are presented for tension and compression cases. These are compared with analytical solutions for an isotropic case and the effect of different material models are studied. Fig. 6a & Fig.6b shows the stresses for tension case for isotropic and functionally graded material models respectively. In isotropic case same stresses are obtained throughout the thickness, as it is true because of constant E value throughout. In functionally graded material model maximum stress is obtained at the outer layer, because of high E value,

Fig. 6a Tension case: Axial stress plot (Isotropic material model)

Fig.6b Tension case: Axial stress plot (Functionally graded material model)

Figure 7a & Fig.7b shows the stresses for compression case for isotropic and functionally graded material models respectively. In isotropic case same stresses are obtained throughout the thickness, as it is true because of constant E value throughout. In functionally graded material model maximum stress is obtained at the outer layer, because of high E value,

Fig. 7a Compression case: Axial stress plot (Isotropic material model)

Fig.7b Compression case: Axial stress plot (Functionally graded material model)

Similarly Figure 8a & 8b, shows the stresses for Isotropic and functionally graded material models respectively for bending. The stresses near interior of the bamboo wall are very less. The stresses near the outside of the cell are much higher in functionally graded material compared to the isotropic material model. Therefore the stress distribution in the functionally graded material differs greatly with isotropic material properties and leads to remarkable stress redistribution in the bamboo cell. This is due to the fact that the fibre density from inner diameter to outer diameter increases exponentially and hence the stiffness of the bamboo cell. The stress plots also demonstrate that the material gradient through cell wall has greater influence on the local cell wall stresses.

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Fig. 8a Stress plot: Isotropic material model

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Fig. 8b Stress plot: Functionally graded material

Table 1 shows that in all cases, the model that incorporates material variation through the thickness of the cell wall is stiffer than the model that employs a homogeneous Young’s modulus obtained from averaging the expression for material variation in eq.2. The close agreement between axial deformation in the FGM and homogeneous isotropic model indicates the use of averaged (or bulk) properties is consistent for estimating elongation. The stresses near the outside of the cell are much higher in functionally graded material compared to the isotropic material model. Therefore the stress distribution in the functionally graded material differs greatly with isotropic material properties and leads to remarkable stress redistribution in the bamboo cell. This is due to the fact that the fibre density from inner diameter to outer diameter increases exponentially and hence the stiffness of the bamboo cell. The stress plots also demonstrate that the material gradient through cell wall has greater influence on the local cell wall stresses. Table 1, shows the comparison of Finite Element Analysis results with analytical calculations.. Table 2, shows the displacements and stresses normalized with analytical solutions for better understanding of the results. Table 1 Comparison of FEM results with analytical solutions Deflections (mm)

Stress (MPa)

Case Name

Analytical Isotropic FGM

Tension 0.0598 Compression 0.0169 Bending 2.923

0.0598 0.0171 2.903

0.071 0.0193 3.114

Analytical Isotropic FGM

Tension 2.95 Compression 2.95 Bending 54.57

2.96 2.97 55.3

5.84 6.09 101.95

Table 2 Normalized displacements and stresses Normalized displacements (mm) Case Name Isotropic FGM Tension 1.00 1.19 Compression 1.01 1.14 Bending 0.99 1.07

Normalized stress (MPa) Case Name Isotropic Tension 1.00 Compression 1.01 Bending 1.01

FGM 1.98 2.06 1.87

7. Conclusions Finite element simulation of bamboo structure using two material models and three loading conditions are preformed. Functionally graded material model is used to approximate the continuously varying material properties of the bamboo across the cell wall thickness and its influence in the mechanical behaviour of the bamboo was studied.

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Average material properties are derived to simulate the Isotropic material model. The finite element results are compared with the actual closed form solutions. As can be seen from the displacement results for isotropic and functionally graded material models are closely matching. It should be sufficient to model the bamboo with simple elastic modulus obtained by rule of mixtures or an average modulus obtained from FGM variation. This simple approximation will provide suitable numerical accuracy for capturing the “global” deflection response of a bamboo structure. To estimate the local features, such as stresses near supports, pin connections or holes etc., it is necessary to employ a numerical procedure that accurately models material gradients through the cell wall. In this study the stress obtained from FGM model are much higher than those obtained from Isotropic material model and the maximum stresses are noted at the outer diameter. This is due to the fact that the higher stiffness of that fiberdense region and also the stress redistribution through the bamboo wall. The analytical calculations and FEM (isotropic material model) computations agree well for all the loading cases but are between 10 % to 20 % less than those computed using FEM for a FGM model. Keeping this in view analytical calculations can be performed with an appropriate margin for each of the loading case. Acknowledgement: The author is thankful to the Principal and Head of the Mechanical Engineering of Vemana Institute of Technology for their kind encouragement. The laboratory facilities provided by the parent body are gratefully acknowledged.

References [1] Y. Xu, Y. Zhang, and W. Wang. “Study on the manufacturing technology on medium density fiberboard from bamboo”. Symposium on Utilization of Agricultural and Forestry Residues. Nanjing, China, (2001), 117-123. [2] Liese., W. “Anatomy and properties of bamboo”, Recent research on bamboos. Proceedings of the International Bamboo Workshop. October 6-14, 1985, Hangzhou, China. (1985). [3] Ulrike G.K. Wegst, The mechanical performance of natural materials, PhD thesis, (1996), University of Cambridge, UK. [4] Amada, S., Munekata, T., Nagase, Y., Ichikawa, Y., Kirigai, A. and Yang, Z., The Mechanical structures of bamboo in viewpoint of functionally gradient composite materials, J. Composite Materials, 30 (7), (1996), 800-819. [5] Emilio Carlos Nelli Silva, Matthew C, Walters and Glaucio H. Paulino, Modeling bamboo as a functionally graded material, J. Mater. Sci. 754-759(2006) [6] ‘Methods of tests for bamboo’. Bureau of Indian Standards, Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002 (2008). [7] Nogata F, Takahashi H, compos Eng 5:743 (1995).

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TRIBOLOGICAL PROPERTIES OF ALUMINIUM SICLICON CARBIDE METAL MATRIX COMPOSITES Ashokkumar C.N., Vijayasihmareddy B.G., Mujeeb Pasha Department of mechanical Engineering, Vemana I.T., Bangalore Abstract The modern development in the field of science and technology demands the development of advanced materials for various engineering applications especially in the field of transportation, aerospace and military related areas. This paper concerns with the development of aluminium based silicon Carbide (SiC) particulate Metal Matrix Composite (MMCs) using conventional low cost method to attain homogeneous distribution of the reinforcement particles. The reinforcement content was varied from 0-15% in steps of 5%. The wear behavior examination was carried out using pin-on disc apparatus. The tests were conducted at different loading conditions at constant time. Results showed that the wear rate decreases with increase in SiC content but increases with increase of load. The microstructures of cast samples were examined. Keywords: aluminium, Silicon carbide, MMCs, wearrate

1. Introduction Monolithic materials have limitations in achieving good combination of strength, stiffness, toughness and density. To overcome these shortcomings and to meet the ever increasing demand of modern day technology, composites are most promising materials of recent interest. Now a days the particulate reinforced aluminium matrix composite are gaining importance because of their low cost with advantages like isotropic properties and possibility of secondary processing components. The most commonly employed metal matrix composite system consists of an aluminium alloy reinforced with hard ceramic particles, the latter usually being silicon carbide or soft particles such as graphite or talc. The composite material shows different strengthening mechanisms in comparison to conventional materials. Thus much research, both experimental and analytical, have been done to gain a better understanding of their wear behavior and mechanical behavior. The fact is that the tribological properties are the one that define possible application of the material more than their mechanical properties, since they have better co-relation with behaviour in practice. Numerous experiments have been conducted, friction and wear properties of aluminium matrix composites .For certain applications, the use of composites rather than metals has in fact resulted in savings of both cost and weight. Some examples are cascades for engines, curved fairing and fillets, replacements for welded metallic parts, cylinders, tubes, ducts, blade containment bands etc. 2. Experimental procedure 2.1 Materials The metal matrix material selected for the present investigation was Al2014.This matrix alloy is commonly used in the manufacture of aircrafts structures and truck frames. It has good surface finish, high corrosion resistance and can be easily anodized. The reinforcement material was Silicon carbide (SiC) with an average grain size of 50 microns. It is highly wear resistant and has good mechanical properties with low density.

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2.2 Processing method Melting of matrix and reinforcement was carried out in Electric Induction furnace‖. The matrix alloy Al 2014 was taken in a graphite crucible and placed in the induction furnace for melting. While the reinforcement was taken in an aluminium foil and placed in muffle furnace maintained at 500oC in order to oxidise the reinforcement. The matrix phase was found to melt in the range of 700-750oC. Then the reinforcement packed in pure aluminium foil is dropped in the molten aluminium metal and when the aluminium foil melts and the reinforcement is dispersed in the matrix, the mixture is stirred in order to obtain uniform distribution of the reinforcement particles. The melt with the reinforced particles was poured into the preheated metalic die of size 60 mm diameter and150mm height. 2.3 Wear resistance evaluation Abrasive wear behaviour of the composites were examined under dry conditions in accordance with ASTM standards using computerized pin-on-disc sliding wear testing machine. The apparatus consists of an EN31 steel disc of 165mm diameter with hardness 60HRc, grounded to surface roughness 1.6Ra. The standard test procedure was employed. Wear specimen 10 mm in diameter and 30 mm in height were cut from cast samples, machined and then polished. Disc was cleaned each time before and after the test with acetone to remove any possible traces of particles on the surface. The specimen which was cleaned with acetone was weighted before and after the tests using an electronic balance accurate to 0.001 g. The surfaces of the worn specimens are not studied in the present examination. 3. Results and discussion Experiments have been conducted by varying weight fraction of SiC (5%, 10% and 15%).Hardness test has been conducted on each specimen at 8 different locations by applying a load of 200N using Vickers hardness testing machine. The corresponding values of hardness were calculated using standard formula.

Figure 1: Comparative bar chart (Hardness)

The results as indicated in Figure 1 shows the increasing of hardness with increase in weight percentage of SiC. The best value of hardness comes out to be of sample containing 15% SiC.

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Wear tests were carried out at different conditions and tabulated in Table 1 Table 1: Comparative results for different compositions with varying load and speed.

5% of SiC Speed (rpm)

Sl.No.

10% of SiC

15% of SiC Load (N)

Wear rate (Micrometer)

107

100

133

105

150

115

100

118

150

100

127

100

150

1 300

400

500

Wear rate (micrometer)

140 120 100 80 5% SiCp

10% SiCp

15% SiCp

20 0 0

100

150

200

Load N

Figure 2: Variation in wear rate with the applied load for various composites for a constant speed of 300rpm

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Wear rate (micrometer)

140 120 100 80

5% SiCp

10% SiCp

15% SiCp

20 0 0

100

150

200

Load N

Figure 3: Variation in wear rate with the applied load for various composites for a constant speed of 400rpm

Wear rate (micrometer)

140 120 100 80 5% SiCp

10% SiCp 40

15% SiCp

20 0 0

100

150

200

Load N

Figure 4: Variation in wear rate with the applied load for various composites for a constant speed of 500rpm

Figures 2, 3 and 4 represent the wear rate for different loads at constant speeds of 300rpm, 400rpm and 500rpm respectively. Mild wear was observed for a small applied load, but as load increases wear rate also increases. Also it is observed that as percentage of SiC particales increases the wear rate decreases considerably with load. After casting, microstructure of the Aluminium silicon carbide metal matrix composite prepared in the present study is analysed.

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Figure 5: Microstructure of (95%Al 5%SiC) at 100x magnification

Figure 6: Microstructure of (90%Al 10%SiC) at 100x magnification

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Figure 7: Microstructure of (85%Al 15%SiC) at 100x magnification

The microstructures of the aluminium silicon carbide metal matrix for different composition of SiC particles is as shown in Figures 5, 6 and 7. It was understood from Figure 7 that density of silicon carbide particles decreases inspite of an increase in concentration as compared to figure 1 and figure 2. This may be attributed to the fact that the SiC particles greatly interact with each other leading to clustering of particles and consequently settling down. 4. CONCLUSIONS The experimental study revels following conclusions Metal matrix composite was synthesized successfully. The result of study suggests that hardness of MMC increases with increase of percentage SiC particles. The reinforcement of Al-2014 alloy with SiC particulates up to a volume fraction of 15% has a marked effect on the wear rate. At various loads and speeds the wear loss of aluminium reinforced with 15% silicon carbide is less than the wear loss for Aluminium reinforced with 5% SiC. That is abrasive wear resistance of MMC increases with increase of SiC particles. But wear rate increases with increase in load for the same composition. References [1]. J Ramadan ,Mustafa “Abrasive Wear of continuous fibre reinforced Al and Al-alloy Metal Matrix Composites” JJMIE Vol. 4,No.2, 2010, pp 246-255 [2]. Manoj Singla, Deepak Dwivedi, Lakhvir Singh, Vikas Chawala.”Development of aluminium based silicon carbide particulate Metal Matrix composite”. Journal of Minerals & Materials Characterization & Engineering. Vol.8,No.6,2009, pp 455-467 [3]. M.Prasannakumar,K.Sadashivappa,G.P.Prabhukumar,S.Basavarajappa,”Dry sliding wear behaviour of garnet particles reinforced zinc-aluminium alloy Metal Matrix Composites”. Materials science.Vol.12, No.3, 2006,pp209-213 [4]. F.Bonollo,L.Ceschini,G.L.Garanani,G.Palombarini,I.Tangerini,A.Zambon. “ Early stages of sliding wear behaviour of Al2O3 and SiC reinforced aluminium” Journal de Physique III, Vol.3, 1993, pp1845-1848 [5]. J.P.Pathak,J.KSingh,S.Mohan “Saynthesis and characterization of aluminium-silicon-silicon carbide composite” Indian Journal of Engineering and Materials sciences. Vol.13, 2006, pp238246. [6]. G B Veeresh Kumar, C S P Rao and N Selvaraj, “Mechanical and Tribological Behavior of Particulate Reinforced Aluminium Metal Matrix Composite”s, Journal of Minerals and Materials Characterisation & Engineering, Vol. 10, No. 1, 2011, pp 59-91,

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QUASI-STATIC AND LOW VELOCITY IMPACT ENERGY ABSORPTION CHARACTERISTICS OF ALUMINIUM HONEYCOMB B.G.Vijayasimha Reddy1 , K.V.Sharma2, T.Y.Reddy3 1

Professor & HoD, Dept. of Mechanical Engineering, Vemana IT, Bangalore 2 Professor, Dept. of Mechanical Engineering, UVCE, Bangalore 3 Formerly of Department of Mechanical Engineering, UMIST, UK. bgvsreddy@gmail.com

Abstract Sandwich panels are commonly used as structural members because of their superior structural and energy absorbing capabilities combined with low weight. Specifically, the use of aluminum honeycomb in lightweight sandwich structures continues to increase rapidly due to the wide fields of applications, such as aircraft, ships, and automobiles. The lateral and axial crushing of honeycombs has received a great deal of attention in the context of energy absorption. In particular, as core material in sandwich panels for crash barriers for high and medium velocity impact situations. This paper presents the experimental data on aluminum honeycomb specimens tested under the quasi-static compressive and low velocity impact loading conditions. The quasi-static study focuses on the load-deformation response and energy absorbing characteristics of honeycomb in the in-plane and out-of-plane orientations. The macro-deformation behaviors under such loading conditions are studied and reported. Low velocity impact tests are conducted on aluminum honeycomb specimens to quantify the energy absorption capacity. A comparison of the results of quasi-static and low velocity impact tests is made. The observations and the results from these tests are used to employ the aluminum honeycomb as a core material in the sandwich panels subjected to low velocity impact. Keywords:

1.0 Introduction The word ‘honeycomb’ is used here in a broader sense to describe any array of identical prismatic cells which nest together to fill a plane. The cells are usually hexagonal in section, as they are in a beehive, but can also be triangular, or square, or rhombic. Human made polymer, metal and ceramic honeycombs are now available [1]. Polymer honeycombs are used as core material in the manufacture of sandwich panels from doors to advanced aerospace components. The ceramic honeycombs are used for high temperature processing (as catalyst carrier and heat exchangers). Metal honeycombs are widely used for energy absorbing applications (for example, the feet of the Apollo-II landing module used crushable aluminum honeycomb as shock absorbers) [2]. Specifically, the use of aluminum honeycomb in lightweight sandwich structures continues to increase rapidly due to the wide fields of applications, such as aircraft, ships, automobiles etc. The lateral and axial crushing of honeycombs has received a great deal of attention in the context of energy absorption. In particular, it as en used as a protective material for high and medium velocity impact situations and is often used as core material in sandwich panels for crash barriers. There is a second good reason for studying honeycombs. They have regular geometry and hence their deformation behavior under loads can be analyzed more or less exactly. Large scale models can be made from rubber, metals or ceramic and their deformation modes can be observed and analyzed. Mc Farland [2] is responsible for Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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pioneering investigations on the plastic crushing of honeycombs under axial compressive loads. These were first studied in the context of moon landing. Wierzbicki et al. [3], Killingworth and Stronge [4] and others [5-11] have carried out experimental studies to understand the behavior of honeycombs under different loading conditions. 2.1 Specimens and Loading Conditions 2.1.1Specimens Specimens of (100x100x50) mm size made of aluminum honeycomb supplied by Honeycomb India Private Ltd, were used in the present study. The densities of the specimens tested were in the range of 85-100 kg/m3. The cells of the honeycomb were of regular hexagonal shape with side length (l) of 4 mm and wall thickness (t) of 0.068 mm. Each specimen prepared consisted of 88 cells with 8 rows and 11columns and the thickness to length ratio was 0.017. These specimens were carefully prepared so that the edges and cell faces were clean. 2.1.2 Loading Conditions and Test Method Uni-directional compression tests were conducted using an electronic universal testing machine at a constant deformation rate of 10 mm/min. The tests were conducted as per the ASTM standard test method for static energy absorption properties for honeycomb sandwich core materials, D7336/D7336M-07. The deformation mechanisms and the load-compression response data of the specimens were recorded. Figures [2.1(a), (b) and (c)] shows the two principal loading directions namely out-of-plane compression (along the direction of cell axis) and in-plane compressions (transverse to the direction of cell axis) respectively.

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(b)

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(c)

Figure 2.1(a), (b) and (c) Showing the out-of-plane and in-plane loading directions

3.1 Load-Displacement Characteristics and Deformation Behavior of Aluminum Honeycomb The honeycomb samples described in the section 2.1 were compressed between two rigid platens of the universal testing machine in each of the directions refer Figures [2.1(a), (b), and (c)]. The macro-deformation patterns which were observed and a comparison of the load-deformation characteristics of honeycomb in the three principal directions are discussed. 3.1.1Out-of-Plane Compression (Along the direction of cell axis) Figure 3.1 shows a typical load-displacement curve for aluminum honeycomb specimen under uni-directional compression. The photographs of the undeformed specimen and the specimen undergoing various stages of deformation are shown Figure (3.2). This curve shows three distinct phases of deformation namely elastic, plateau (perfectly plastic) and densification (or locking) respectively.

Figure 3.1 Typical load-displacement curve for aluminum honeycomb compressed in the out-of-plane direction

These are shown as zone 1 to 3 Figure (3.1) and are explained below. Zone 1: This represents the initial, stiff and elastic part of the specimen behavior Figure (3.1). In this zone, the deformation of cells was apparently uniform throughout the length of the specimen. No local folds or kinks were seen and a slight barreling of the specimen was observed. The initial plastic crushing of cells occurred at top end of the specimen at

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an average load of about 30 kN. During this stage, both axial buckling and bending of cell walls of the specimen took place in a progressive manner. The form of the specimen in elastic compression (δ = 1mm), Figure [3.2(iii)]. Zone 2: This progressive crushing of cells of the honeycomb was characterized by the load fluctuations which were small in amplitude. This phase of deformation is called as plateau zone. Amplitude of the fluctuations was higher initially and then gradually decreases refer Figure (3.1). The deformation front continued progressing until the plastic (folding) deformation reached the bottom end of the specimen. This was accompanied with a reduction of about 80% of the length of the specimen at a nearly steady load of 17 kN. The pattern of fold formed in this zone is similar to concertina type of foldings observed during compression of metal tubes under similar loading conditions by Reddy et al [3].This progressive crushing load was nearly half the initial crushing load. Photograph of the deforming specimen at the start of the plateau zone can be seen in Figure [3.2(iv)]. Photographs [3.2(v-viii)] show the various deformation stages of the specimen. Zone 3: After a deformation under compression of about 39 mm, the load required to cause further crushing increases steeply Figure (3.1). This is the compaction or densification zone. At the beginning of this phase the specimen looked like a perforated plate. Further compression causes compaction of the plate. The final thickness of the compressed perforated plate is about 10 mm. The densified specimen can be seen in Figure [3.2 (viii)].

i) Undeformed honeycomb

ii) Specimen between flat platens (δ=0)

iii) Plastic fold formation at the top (δ=1 mm)

iv) Beginning of the plateau (δ=2.5 mm)

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v) Continued plastic folding of rows of cells (δ=10 mm)

vi) Continued crushing in plateau (δ=15 mm)

vii) Progress of gross deformation (δ= 30 mm)

viii) Densified core into hexagonal perforated plate (δ= 41mm)

Figure 3.2 Photographic views of progressive deformation stages of honeycomb compressed along the cell axis (out-of plane)

4.1 Results and Discussion 4.1.1 Quasi-static tests The energy absorbing characteristics of the aluminum honeycomb for the three loading orientations which were deduced from the load-displacement data are presented in Table 4.1 and discussed. Table 4.1 Summary of results of quasi-static tests on aluminum honeycomb

Mass of the Specimen (gm)

Nominal Density (kg/m3)

Initial Crush Load (kN)

Plateau Load (kN)

Max. Crush Length (mm)

Energy Absorbed EA (kJ)

Specific Energy Absorbed SEA (kJ/kg)

0.74

32.06

Out-of-Plane Compression 23.28

46.57

33.80

18.10

38.30

In-Plane Compression (across the cell faces) 22.57

45.14

1.56

1.77

93.50

0.15

6.78

In-Plane Compression (across the cell corners) 23.56

46.13

2.15

2.55

79.00

0.31

13.56

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Figure 4.1 Comparison of initial crush load and plateau load for the honeycomb specimens

Figure 4.2 Comparison of specific energy absorbed for the honeycomb specimens

Figure (4.1) shows the comparison of initial crush load and plateau loads for the out-of-plane and two cases of in-plane loading orientations. The average initial crushing load for the five honeycomb specimens tested is about 33 kN. The variation in the crush load among the five specimens tested is about 6%. The average plateau load is about 18 kN and the variation is about10 %. Initial collapse occurs at a load, which is nearly twice the mean steady load causing progressive crushing. The amplitudes of the little peaks represent progressive foldings. These peaks are initially higher and then decrease gradually. The plastic collapse was always initiated at the top end and the deformation front then gradually progresses with the continued crushing until all the plastic foldings reaches the lower end of the specimen. After all the folds were formed throughout the length of the specimen, the load increases very rapidly indicating densification of the folds. The average specific energy absorbed in this mode of deformation is about 32 kJ/kg, Figure (4.2).

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4.1.2 Dynamic tests The comparative load-displacement curves for the specimens tested are shown in Figure (4.3). The observations from a crushed honeycomb specimen under low velocity impact loading shows that, the collapse pattern was similar to that under quasi-static loading for out-of plane orientation. However, under impact loading conditions the load acts on specimen for a very short interval of time (milli seconds). This causes the local compaction of cells in the top rows of the honeycomb structure. Therefore the degree of compaction is higher under impact loading. The locally compacted rows of cells act as stiffeners which causes a small increase in the plateau load. Figure (4.4) shows the variations of plateau load with the impact velocity. When the impact velocity increase from 3.8 m/s to 5.4 m/s, the corresponding plateau load increase from 23.5 kN to 24.7 kN. It is also observed that the crush length of the specimen increases with the impact velocity. The average crush lengths were 21.5 mm, 34.5 mm and 44 mm for the corresponding impact velocities of 3.8 m/s, 4.5 m/s and 5.4 m/s. For a constant mass of the impactor and at a constant crush length of the specimens, the energy absorption capacity of the honeycomb increases with the increase in the impact velocity. For a crush length of 20.5 mm the energy absorption increases from 454 J to 513 J for an increase in impact velocity from 3.8 m/s, to 5.4 m/s. Figure (4.5) shows the variations of energy absorption with the impact velocity. Figure 4.6 shows the comparative quasi-static and dynamic load-displacement curves for honeycomb

compressed at out-of plane orientation Figure 4.3 Comparative load-displacement curves for honeycomb specimens crushed at different impact velocities

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Figure 4.4 Variation of plateau load with impact velocity for honeycomb specimens.

Figure 4.5 Variation of energy absorption with impact velocity for honeycomb specimens.

Figure 4.6 Comparative quasi-static and dynamic load-displacement curves for honeycomb

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5 Conclusions 1. Honeycombs deform by different mechanisms that depends on the direction of loading. The stiffness and strength in the case of out-of-plane compression is higher when compared with the stiffness and strength values obtained in the case of in-plane compression. 2. The plateau load in the out-of-plane compression is about 10 times higher when compared with that of the in-plane loading across the cell faces. The average plateau load for the honeycomb across the cell corner is nearly twice when compared with that of the cases of across the cell faces. This makes the aluminum honeycomb suitable for use in energy absorption situations. 3. The specific energy absorption in the case of out-of-plane compression is about twice when compared with that of compression across the cell corners and also 4.5 times more than that of compression across the cell faces. Therefore out-of plane orientation is more suitable position to be placed in sandwich panels as core material. 4. Dynamic crushing tests conducted on aluminum honeycomb at different impact velocities indicates that, the energy absorption capacity increases with an increase in the impact velocity. 5. Energy absorption capacity of aluminum honeycomb increases under dynamic loading condition when compared with the quasi-static loading conditions. This increase in energy absorption capacity is 25%.

References [1] Gibson L J and Ashby M F., “Cellular Solids-structure and properties”-2nd edition, Cambridge University Press, UK, ISBN 0-521-49911-9 (1997). [2] Mc Farland R K., “The development of metal honeycomb energy absorbing elements”. J. P. L, Technical Report No.32-639 (1964). [3] Wierzbicki

T.,

“Crushing

analysis

metal

honeycombs”.

Int

Impact Engineering Vol.2, pp 157-174 (1983). [4] Papka S D and Kyriakides S., “In-plane biaxial crushing of honeycombs”, Part-2: Analysis. Int J of Solids and Structures Vol.36. pp 4397-4423 (1999). [5] Triantafyllidis N and Schraad M W., “Onset of failure in aluminum honeycombs under general in-plane loading”, J Mech Phys Solid, 46(6) pp.1089 (1998). [6] Kilnworth J W and Stronge W J., “Plane punch indentation of a ductile honeycomb”, Int J Mech Sci., Vol.31 pp359-378 (1989). Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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[7] Wu E and Jiang W S., “Axial crush of honeycombs”, Int J of Impact Engineering Vol.2, pp 157-174 (1985). [8] Said M R and Reddy T Y., ‘‘The energy absorption of aluminum honeycomb under quasi-static loading”, Proceedings of 4th Int Con On Mechanical Engineering-2, pp37-42 (2001). [9] Hong S T, Pan J, Tyan T and Prasad P, “Effects of impact velocity on crush behavior of honeycomb specimens”, SAE technical paper series, 2004-01-0245, SAE World congress, Michigan (2004). [10] Tan Chee-Fai and Said M R., “Aluminum honeycomb under quasi-static compressive loading: an experimental investigation”, Suranaree J of Sc Technology, Vol.16 (1) pp1-8 (2008). [11] Zou Z, Reid S R, Tan P J and Harrigan J J., “Dynamic crushing of honeycombs and features of shock fronts”, Int J of Impact Engineering Vol.36, pp 165-176 (2009).

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STUDY OF EFFECT OF CUTTING PARAMETERS ON POWER CONSUMPTION IN TURNING OF MILD STEEL USING TAGUCHI DESIGN AND ANOVA Akshay Kumar1 , Shanmukha Nagaraj2 1

Student, M.Tech, Computer Integrated Manufacturing, 2Professor and Associate Dean Department of Mechanical Engineering, R. V. College of Engineering, Mysore Road, Bangalore kumarraiakshay@gmail.com

1,2

Abstract Energy savings one among the few important features in machine tool and industrial equipment and this demands for improved energy efficient manufacturing techniques. The purpose of this paper is to study the effect of cutting speed, feed and depth of cut on power consumption in turning of mild steel using high speed steel cutting tool. Experiments were conducted on a precision centre lathe equipped with a multi component cutting force measuring dynamometer. Full factorial Taguchi design in design of experiments was adopted in order to plan the experimental runs. Analysis of variance (ANOVA) was used to study the influence of cutting parameters on power consumption. Among the speed and feed rate combination available on the lathe, three levels of cutting parameters are chosen and numbers of trials are carried out. The results showed a significant effect of cutting speed and depth of cut on power consumption but as per feed rate results has not substantially affected the response. Among the interactions, cutting speed and depth of cut interaction are found to be influencing. Keywords: Metal cutting, Power consumption, Taguchi parametric design, ANOVA.

1. Introduction Energy savings is increasingly recognized as one of the most important features in consumer products and industrial equipment. This same trend applies in the machine tool industry. Intensive energy consumption in industry has drawn increasing attention due to its adverse environmental impact and the exhaustion of natural resources. The energy consumed by manufacturing industries accounts for 30% of the total world energy and 36% of the global CO2 emission. In addition, recently rising costs for energy and natural resources heavily burden a large amount of manufacturing companies all over the world. Hence from both environmental and economic perspectives, improved energy efficient manufacturing is urgently required. Modern machine tools rely on electricity as their main power source. One major component of machine tool power consumption is spindle rotation. The power usage is highly dependent on cutting resistance. Spindle motors expend power to provide the cutting force necessary to overcome cutting resistance. Turning is a very important machining process in which a single point cutting tool removes unwanted material from the surface of a rotating cylindrical work piece. The cutting tool is fed linearly in a direction parallel to the axis of rotation. Turning is carried on lathe that provides the power to turn the work piece at a given rotational speed and feed to the cutting tool at specified rate and depth of cut. Therefore three cutting parameters namely cutting speed, feed rate and depth of cut need to be optimized in a turning operation. Turning operation is one of the most important operations used for machine elements construction in manufacturing industries i.e. aerospace, automotive and shipping. Turning produces three cutting force components as shown in fig.1,(the main cutting force Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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i.e. thrust force, (FY), which acts in the cutting speed direction, feed force, (FX), which acts in the feed rate direction and the radial force, (FZ), which acts in radial direction and which is normal to the cutting speed). Out of three force components the cutting force (main force) constitutes about 70% to 80% of the total force ‘F’ and is used to calculate the power ‘P’ required to perform the machining operation. Power is the product of main cutting force and the cutting velocity. (1) Where P is the power in watt, V is the cutting speed in m/ min and Fc is the main cutting force in N.

Figure : 1 Cutting forces acting on tool

Based on the literature survey it was found that many researchers have used design of experiments (DOE) techniques like Taguchi design, response surface methodology(RSM) and ANOVA to study the effect of various cutting parameters, tool geometries on different characteristics like material removal rate (MRR), surface finish, power consumption etc. After conducting experimental analysis process parameters were optimised. M. Mori., et al (2011) measured power consumption while changing cutting conditions (cutting speed, feed rate, and axial and radial cutting depth) during drilling, end milling and face milling. They found that power consumption can be reduced by setting the cutting conditions high yet within a value range which does not compromise tool life, surface finish, thereby shortening of machining time [1]. L. B. Abhang and M. Hameedullah (2010) experimentally investigated power consumption in turning EN-31 Steel under different cutting conditions. The experimental runs were planned according factorial DOE. The data collected was statistically analysed using ANOVA. They developed power consumption prediction models by using RSM. They concluded that, the smallest the values of the cutting speed, feed rate, depth of cut and tool nose radius, the lowest is the metal cutting power consumption [2]. Anirban Bhattacharya., et al (2009) carried out an experimental study investigating the effects of cutting parameters on surface roughness and power consumption during high speed machining of AISI 1045 steel. The ANOVA results showed a significant effect of cutting speed on the surface roughness and power consumption [3]. Aman Aggarwal., et al (2008) experimentally investigated the effects of cutting speed, feed rate, depth of cut, nose radius and cutting environment in CNC turning of AISI P-20 tool steel. Taguchi technique as well as 3D surface plots of RSM revealed that cryogenic environment is the most significant factor in minimising power consumption followed by cutting speed and depth of cut [4]. In the present work, effect of cutting speed, feed and depth of cut on power consumption in turning of mild steel using high speed steel cutting tool has been found. Taguchi’s parametric design is an effective tool for robust design. It offers a simple and qualitative optimal design at a relatively low cost. The greatest advantage of this approach is to save the experimental time as well as the cost by finding out the significant factors. One important step involved in Taguchi’s technique is selection of orthogonal array (OA). An OA is a small set from all possibilities which helps to determine least no. of experiments, which will further help to conduct experiments to determine the optimal level for each process parameter and establish the relative importance of individual process parameters. To obtain process

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parameter setting, Taguchi proposed a statistical measure of performance called signal to noise ratio (S/N ratio). In addition to S/N ratio, ANOVA is used to indicate the influence of process parameters on performance measure. Taguchi proposed three categories of performance characteristics in the analysis of S/N ratio, i.e, the smaller the better, the higher the better, and the nominal the better[6]. ANOVA is a statistical method used to interpret experimental data and make necessary decisions regarding which parameters affect the performance of a product or process. ANOVA breaks total variation down into accountable sources; total variation is decomposed into its appropriate components [5]. 2. Experimental details 2.1 Work material, cutting tool and machine. The work material selected for the study was mild steel owing to its lower cost, ready availability, and a wide range of applications from automotives to domestic goods to constructional steel and many other machine elements such as keys, rings, fence posts etc. the work specimen diameter was 40 mm and length approximately 500 mm. HSS V-tool was used as the cutting tool. The experiment was carried out on a precision centre lathe (PSG 124). Technical specifications are: centre height: 210 mm, length of bed: 2500 m, main motor power: 3.7 kW, spindle speed range: 63-1250 rpm. The lathe tool dynamometer was used for measuring the cutting forces.

Figure 2: Experimental setup

2.2 Cutting conditions and Experimental procedure. Among the speed and feed rate combinations available on the Lathe, three levels of cutting parameters were selected. It is given in table-1. Table 1: Factors and their Levels

Factors

Process parameters

Level 1

Level 2

Level 3

Cutting speed(m/min)

12.57

27.65

45.24

Feed rate(mm/rev)

0.14

0.16

0.19

Depth of cut(mm)

0.5

1.0

1.5

As per Taguchi’s method the total DOF of the selected OA must be greater than or equal to the total DOF required for the experiment. So, an L27 OA (a standard three-level orthogonal array) having 26 DOF was selected for the present work. The non-linear relationship among the process parameters, if it exists, can only be revealed if more than two levels of the parameters are considered. Thus each selected parameter was analyzed at Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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three levels. It was also decided to study the two-factor interaction effects of process parameters on power consumption. Interactions considered were between cutting speed and feed rate (A × B), feed rate and depth of cut (B × C), and cutting speed and depth of cut (A × C). Power consumption being a ‘lower the better’ type of machining quality characteristic, the S/N ratio for this type of response was used and is given below: = −10 log [ ( + + ⋯+ )] (2) where y1, y2, ........ yn are the responses of the machining characteristic, for a trial condition repeated n times. The S/N ratios were computed using Eq. (2) for each of the 27 trials and the values are reported in Table-2. Table 2:L27 OA and calculated values of power consumption and S/N ratio

Trial

Cutting

Feed

Depth of

Main cutting

Power

S/N ratio

no.

speed

F(mm/rev)

cut(mm)

force FC (N)

consumption(W)

(dB)

V(m/min) 1

12.57

0.14

0.5

147.15

30.83

-29.7795

12.57

0.14

1.0

245.25

51.38

-34.2159

12.57

0.14

1.5

313.92

65.77

-36.3606

12.57

0.16

0.5

156.96

32.88

-30.3386

12.57

0.16

1.0

274.68

57.55

-35.2009

12.57

0.16

1.5

392.40

82.21

-38.2985

12.57

0.19

0.5

196.20

41.10

-32.2768

12.57

0.19

1.0

284.49

59.60

-35.5049

12.57

0.19

1.5

421.83

88.37

-38.9261

27.65

0.14

0.5

156.96

72.33

-37.1864

27.65

0.14

1.0

215.82

99.46

-39.9530

27.65

0.14

1.5

304.11

140.14

-42.9312

27.65

0.16

0.5

156.96

72.33

-37.1864

27.65

0.16

1.0

235.44

108.50

-40.7086

27.65

0.16

1.5

333.54

153.71

-43.7340

27.65

0.19

0.5

264.87

122.06

-41.7315

27.65

0.19

1.0

294.30

135.62

-42.6465

27.65

0.19

1.5

362.97

167.27

-44.4684

45.24

0.14

0.5

225.63

170.13

-44.6156

45.24

0.14

1.0

235.44

177.52

-44.9849

45.24

0.14

1.5

323.73

244.09

-47.7510

45.24

0.16

0.5

166.77

125.74

-41.9895

45.24

0.16

1.0

225.63

170.13

-44.6156

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45.24

0.16

1.5

353.16

266.28

-48.5068

45.24

0.19

0.5

186.39

140.54

-42.9560

45.24

0.19

1.0

284.49

214.51

-46.6290

45.24

0.19

1.5

441.45

332.85

-50.4450

3. Results and Discussion Table 3 presents the results of ANOVA and indicate that cutting speed (A) and the depth of cut(C) are the most significant factors. In addition the most significant interaction between machining parameters on power consumption was between cutting speed and depth of cut (A*C). Statistically F-test decides whether the parameters are significantly different. A larger F value shows the greater impact on the performance characteristic. Larger F values are observed for cutting speed (141.84) and depth of cut (43.63). Table-3Analysis of Variance for power

Source

DF Seq SS

Adj SS

Adj MS F

Cutting Speed

99388.9

99388.9 49694.5 141.84 4.46 0.000

Feed rate

4335.0

Depth of cut

30570.4

30570.4 15285.2 43.63

4.46 0.000

Cutting Speed*Feed rate

1216.1

304.0

0.87

3.84 0.523

Cutting Speed*Depth of cut 4

7627.2

1906.8

5.44

3.84 0.020

Feed rate*Depth of cut

1159.7

289.9

0.83

3.84 0.543

Error

2802.8

350.3

Total

147100.2

2167.5

6.19

Ftab

4.46 0.024

S = 18.7176, R-Sq = 98.09%, R-Sq (adj) = 93.81%, 95% confidence level The analysis is made with the help of a software package MINITAB 16. The main effects plots are shown in the Figure 3. In the plots, the x-axis indicates the value of each process parameters at 3 levels and y-axis the response value. Horizontal line indicates the mean value of the response. According to the main effect plot, the optimal conditions for minimum power consumption are: cutting speed at level 1 (12.57 m/min), feed rate at level 1 (0.14 mm/rev) and depth of cut at level 1 (0.5 mm). Figure 4 shows the interaction plot for power consumption. It indicates a slight interaction between cutting speed and depth of cut affecting the response. M a in E f f e c ts P l o t f o r p o w e r F itte d M e a ns C u t t in g S p e e d

F e e d ra t e

2 00 1 50

Mean

1 00 50 1 2 .5 7

2 7 .6 5 Dept h of cu t

4 5 .2 4

0 .5

1 .0

1 .5

0 .1 4

0 .1 6

0 .1 9

2 00 1 50 1 00 50

Figure 3: Main effects plot for power

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Interaction Plot for power Fitted Means 0.14

0.16

0.19

0.5

1.0

1.5

200 C utting Spe e d 100

200 F e e d r a te 100

C utting Speed 12.57 27.65 45.24 C utting Speed F eed 12.57 rate 27.65 0.14 45.24 0.16 0.19

De pth of cut

Figure 4: Interaction plot for power

4. Conclusion This research was mainly focused towards the identification of most significantly influencing factors. The F-values obtained from MINITAB software are in reasonable agreement with the values obtained from the numerical methods. A larger F value shows the greater impact on the performance characteristic. Accordingly the cutting speed and depth of cut have significant influence on the power consumption during turning of mild steel. Also there is a slight interaction between cutting speed and depth of cut which affects the power consumption. Acknowledgements We acknowledge with thanks the HOD, Foreman and lab assistants of workshop, Industrial Engineering & Management department, RVCE Bangalore for providing the necessary guidance, equipment and work materials to carry out the experiment. References [1]. Mori, M. Fujishima, Y. Inamasu, Y. Oda, “A study on energy efficiency improvement for machine tools,” CIRP Annals - Manufacturing Technology 60 (2011) 145–148. [2]. L. B. Abhang and M. Hameedullah, “Power Prediction Model for Turning EN-31 Steel Using Response Surface Methodology,” Journal of Engineering Science and Technology Review 3 (1) (2010) 116-122. [3]. Anirban Bhattacharya, Santanu Das, P. Majumder, Ajay Batish, “ Estimating the effect of cutting parameters on surface finish and power consumption during high speed machining of AISI 1045 steel using Taguchi design and ANOVA,” Prod. Eng.Res.Devel. (2009) 3:31-40, DOI 10.1007/s11740-008-0132-2. [4]. Aman Aggarwal, Hari Singh, Pradeep Kumar, Manmohan Singh, “Optimizing power consumption for CNC turned parts using response surface methodology and Taguchi’s technique—A comparative analysis,” Journal of materials processing technology 200 (2008), 373–384. [5]. Douglas C. Montgomery, Design and Analysis of Experiments, eighth edition, John Wiley and Sons, 2013. [6]. Philip J. Ross, Taguchi techniques for quality engineering, 2nd edition, Tata McGraw Hill.

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DESIGN AND ANALYSIS OF MODULAR FIXTURE FOR VOLUTE LINER ON VERTICAL TURRET LATHE FOR SIDE MACHINING R.Praveena1, T.N.Manjunath2, K.M.Veerasekhara3 1,2

Dept. of Mechanical Engineering, RVCE, Bangalore, 3Weir Minerals (India) Pvt. Ltd Bangalore praveenarvce711@gmail.com

Abstract

In manufacturing industries fixtures play vital role for increasing productivity by reducing the production time and efforts. In industry, heavy, tough slurry pumps are produced. Volute liners are integrated part of slurry pumps, which are manufactured in the company. For volute liners, totally three set ups of machining were carried out on Vertical Turret Lathe (VTL). The existing method is suitable for machining the two set ups and this method doesn’t give much problem in machining, but third set up is quite difficult to machine, so the third setup of machining was carried out from external contract basis. For complete machining of one volute liner may takes around 5 to 7 days. The main objective of this paper is to design and analyse the fixture, thereby reduce the lead time and to increase the productivity. Based on the study of the components and machine availability, fixture design is made. Two concept designs were put out and one best concept design is taken for fixture design. Detail design and 3-D modelling were made by using CATIA V5. Analysis of fixture was made by ANSYS. The stress and deformation values are 45.86 MPa (max) and 0.23 mm (max), which are well within the safe working limits. Balancing test for fixture is made by manual calculation and probable counter weight is calculated with respect to the fixture. Two Single Minute Exchange of Dies (SMED) plates are used. This helps in reducing the time consumption during loading. Keywords: Modular fixture design, counter weight, VTL (Vertical turret lathe), Ansys, SMED (Single Minute Exchange Die).

1. Introduction In manufacturing industries fixtures are very important. They are used to hold the workpiece firmly during machining process. Fixtures are the main contributors in reducing the total manufacturing cost of the product. The main problems in manual planning of fixture are almost impossible for the designer to analyse all the alternatives of fixture planning which makes it extremely hard to find out the optimal fixture planning. One way to solve these problems is by using the computer assist in designing and planning of fixture. In recent years, the research on automated modular fixture planning has been paid more and more importance. The fixture designing and manufacturing is considered as complex process that demands the knowledge of different areas, such as geometry, tolerances, dimensions, procedures and manufacturing processes. Yuguang Wu, Shuming Gao and Zichen Chen [1] described the automated modular fixture planninh based on linkage mechanism theory. Fixture planning was developed based on concept like IRC triangle and locator visible cone. This approach identifies all the locating plan candidates of a work piece. R. Hunter, J. Rios, J.M. Perez, A. Vizan [2] describes functional approach for the formalization of the fixture design process. The high level fixture Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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function involves Part orientation, Part support, Part location, Part information, Part machining, Constraints and Fixture functional elements are discussed. Yon-Chun Chou, R. A. Srinivas and Sujit Saraf [3] proposed the automatic design of machining fixtures. The general strategy for all fixture development is developed. A three stage design process has been proposed for automatic design of fixture includes conceptual design, configuration design and detail design. N. P. Maniar, D. P. Vakharai [4] proposed Design and Development of Rotary Fixture for CNC. Fixture is developed using the 3D software and balancing of the fixture is made using Quadrant Computer Aided Mass Balancing Method. The mass to be added for balancing the fixture is determined and also its position. V.Sivaraman, S.Sankaran, L.Vijayaraghavan [5], Dr R. R. Malagi, Rajesh. B. C [6] describes The Effect of Cutting Parameters on Cutting Force during Turning. They described if the cutting speed increase then the cutting force will decreases. For both increase in feed and depth of cut the cutting force will decreases. J. D. Lee, L. S. Haynes [7] proposed finite-element analysis of flexible fixturing system. In flexible manufacturing positioning and constraints are the important factors. Computer software, Ansys is used for the analysis and design of fixture. In this paper, we present a new approach to design modular fixture with the great flexibility for the machining of volute liner. Volute liners are the integrated part of the Slurry pumps used in the chemical and slurry extraction fields. The concept of fixture drawing is made which is suitable for a group of volute liner, which comes under same Family. Then the detailed drawing is made by using CATIA CAD tool and the analysis is made by using ANSYS software. Due to eccentricity, fixture is balance by using the concept proposed by N. P. Maniar, D. P. Vakharai [4]. The cutting forces included in the machining process for the analysis are calculated by using the formulas in Fundamentals of Metal Cutting and Machine tool by B. L. Juneja. G. S. Sekhon and Nitin Seth [8]. The obtained values are compared with the online calculator from Kennametal PVT Ltd [9]. 2. Fixture Design 2.1 Concept drawing The study of component is made and depending on the machine availability, Concept drawing is made. The Figure 1.1 shows the concept drawing. Cylindrical locating principle is used for location purpose. Four locating blocks are used as shown in the figure. For balancing the component the supporting screw jack structure is used. Clamping is done by M24 stud. By these arrangements all degrees of freedom will be arrested except the rotational motion which can be restricted by vertical support or restrictor. From the study of the component, it needs three sets of machining. This paper specifies the fixture design for the third set up. For that previously machined surfaces are taken as reference for the design.Third set up is little difficult and the machining surface is in critical location of the component. For that the vertical plate is used and gussets are provided to with stand the deflections.

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Figure 1.1:Concept drawing

2.2 3-D Design of Fixture CATIA is used to build the 3D model from the concept design. Figure 2.1 shows the isometric view of the 3D-Design of fixture. Two SMED plates are used to reduce the time consumption during the loading of the component to the machine.

Figure 2.1: 3D-Isometric view of Turning Fixture.

2.3 Detail drawing 2.3.1 Locating Blocks Locating blocks are the primary components of the fixture which are used to locate the component. Cylindrical surface of the component is used for location. The detail drawing of locating blocks are shown in the Figure 2.2. The material used is hardened steel to with stand the wear resistance.

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Front View

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Side view

Figure 2.2: Front View and Side Views of Locating Block

2.3.2Fixture Plate Vertical plate and horizontal plates are welded each other. Two gussets are used to with stand the bending moments. Material used is Mild steel. For the locating of blocks M16 holes are drilled. And central tapped hole is provided for fixing the block to the fixture plate. To restrict the Rotational degree of freedom, Side supporting Bolts are provided. To balance the component the supporting structure is provided. Figure 2.3 shows the fixture plate dimensions in two views.

Figure 2.3: Fixture Base Plate side Sectional view

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Figure 2.3: Front view of Fixture plate.

3. Balancing of Fixture Fixture balancing is most important aspect in the eccentric components. The designed fixture consisting of more eccentric structures, so the fixture balancing is done by using the principles stated by N. P. Maniar, D. P. Vakharai [4]. Balancing is made by using some assumptions. The C G of each component in each quadrant is taken and the mass of the component in each quadrant is calculated to find the un-balanced weigh. Table 3.1 shows the mass and moment of inertia in each quadrant. Table 3.2 shows the horizontal and vertical forces in each quadrant. Table 3.3 shows the resultant moment of inertia. Table 3.4 shows the Resultant load and the angle in which the balancing weigh to be added. During calculation the 2D view is used for balancing of fixture. Table 3.1 Mass and Moment of inertia in each quadrant

Quadrants

Mass mi (kg)

xi (mm)

yi (mm)

mi xi2 (kg mm2 )

mi yi2 (kg mm2 )

81.086

168.7

107.8

2307682.4

942287.4

20.41

31.9

108.2

20769.4

238944.8

III

11.8

39.5

103.8

18410.95

127138.4

54.2

104.4

108.3

590745.3

635705.8

Σmixi2 =2937608.05

Σmi yi2=1944076.4

Total

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Table 3.2 Horizontal and vertical forces in each quadrant

Quadrants

Mass mi (kg)

FH=mi cosθ i (kg)

FV= mi sinθi (kg)

81.086

68.311

17.19

20.41

-5.76

19.58

III

11.8

-4.19

-11.03

54.2

45.24

-29.84

Σ FH = 103.599

Σ FV = 4.093

Total

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Table 3.3 Resultant moment of inertia

Ixx = Σ mixi2 Iyy = Σ mi yi2 Izz = Ixx + Iyy M = Σ mixi2 + Σ mi yi2

2937608.05 mm4 1944076.4 mm4 2937608.05 mm4

Table 3.4 Resulting unbalanced weight

ΣFH2 ΣFV2 R = √ (ΣFH2 + ΣFV2) tan θi θi

10732.75 Kg 16.75 Kg 103.67 Kg -0.0395 -2.26 Deg

To find the distance at which the balancing weight to be added is, M=U/r2 r2=M/R r = 168.33 mm. Where, Iyy or M= Resultant moment of inertia. (Kg mm2) r = distance at which the unbalancing mass to be kept. (mm) R= Total unbalanced weight. (Kg) θi = Angle between the axis of balancing line and X axis FH= Horizontal force Fv= Vertical Force Ixx= Moment of inertia along xx axis Iyy= Moment of inertia along yy axis

Fig ure 3.1 shows the coordinates in which balancing weigh is added. X axis and Y axis shows the Distance from the axis of machining. From the analysis of fixture balancing using quadrant computer aided mass balancing method, it was found that the balancing weight of 103.67 kg and should add with 168.33 mm from centre and at an angle of -2.2 o. But in practical, the machine capacity is 8 tones, and the SMED plate weight is found to be 700 kg. The weight of unbalancing is 14% of total weight. Since the cutting speed is low. There is no need for the counter weight for this fixture

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Figure 3.1: Moment of inertia in each quadrant and the balancing mass for the fixture.

4. Analysis of fixture base plate For the validation of fixture, the fixture base plate is taken in to account for the analysis. The cutting forces are calculated using the basic formulas and the theoretical values have been compared with the online calculator from Kennametal PVT Ltd. The vertical down ward forces and horizontal forces are found to be 4145.73 N and 3459.38 N. And the material properties are taken with standards of mild steel. Analysis shows that the obtained values are well within the working condition, so the design is safe. Figure 4.1 to Figure 4.4 shows the ANSYS results of stress and the deformation values.

Figure 4.1: Von- Mises stress distribution for locating blocks.

Figure 4.2 Deformation values for locating blocks.

Figure 4.3: Stress distribution for Fixture base plate

Figure 4.4: Deformation values for

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Fixture base plate

The induced stress in the fixture base plate for loading condition is 45.86 MPa which is less than the allowable stress 125 MPa. And also deformation values are low. Therefore the design is safe. 5. Bill of materials Table 5.1 List of Bill of materials with the raw material dimensions and the required quantities

1 2 3 4

Component Description Base Plate Vertical Plate Gussets Side supporting plate

Locating Blocks

Item

6 7 8 9 10 11 12 13 14 15 16 17

Supporting Structure (Tapped) Supporting Structure (Threaded) Component Clamp Component Bolt Screw Washer Side Bolt Locating pins Fixture Clamp Squire Bolt Screw Counter weight

Material Mild steel Mild steel Mild steel Mild steel Hardened steel

Raw Material size (mm) 550X450X35 400X450X30 250X150X30 200X200X30

Qty. 1 1 1 1

150X50X40

Mild steel

φ50, H= 100

Mild steel

φ50, H= 50

Mild steel Standard Standard Standard Standard Standard Standard Standard Standard Mild steel

200X100X20 M24X350 M24 φ30X4 M16X70 M16X90 150X50X15 38X38X100 M14 φ100X100

1 1 1 1 3 6 4 4 4 1

6. Conclusion This paper describes the new design for the volute liner, which are used in slurry pumps. The side machining is the difficult setup in machining of volute liners. This paper present the easy way of design of fixture for volute liner on vertical turret lathe. The unbalanced weight is calculated by taking the centre of gravity and the weight in each quadrant [4] and it is found to be in safer limit. This shows that the design is good and optimal. The induced stress in the fixture base plate for loading condition is 45.86 MPa which is less than the allowable stress 125 MPa. and also deformation values are low. Therefore the design is safe. The future works are the design should be manufactured and the balancing is to be determined using suitable instruments. And also use of automated fixture needs to be developed for the component.

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7.Acknowledgement The authors would like to thank JIT Technologies, Jitendra Kumar K E and G.R. Rajkumar, Department of mechanical engineering, RVCE for the support. References [1]. Yuguang Wu, Shuming Gao and Zichen Chen, “Automation modular fixture planning based on linking mechanism theory”, Robotics and Computer-Integrated Manufacturing. 27 June 2006, volume 24 (2008),PP 38-49 [2]. R. Hunter, J. Rios, J.M. Perez, A. Vizan, “A functional approach for the formalization of the fixture design process”, International Journal of Machine Tools & Manufacture. April 2005, 46 (2006), PP 683–697. [3]. Yon-Chun Chou, R. A. Srinivas and Sujit Saraf, “Automatic Design of Machining Fixtures: Concept”, Int J Adv Manuf Technol (1994). PP 9:3-12. [4]. N. P. Maniar, D. P. Vakharai, “Design and Development of Rotary Fixture for CNC”, International Journals of Engineering Science Invention, December 2012 Volume 1, Issue 1,PP 32-43. [5]. Dr R. R. Malagi, Rajesh. B. C, “Factors Influencing Cutting Forces in Turning And Development of Software to Estimate Cutting Forces in Turning”, International Journal of Engineering and Innovative Technology (IJEIT) Volume 2, Issue 1, July 2012. PP 37-43. [6]. J. D. Lee, L. S. Haynes, “Finite-Element Analysis of Flexible Fixturing System”, Transactions of the ASME, MAY 1987, Vol.109, PP 134-139.

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INVESTIGATIONS ON MACHINING CHARACTERISTIC OF HARDEN STEELS USING MULTI-LAYER COATED CARBIDE TOOLS (INSERTS) R.Naveen kumar1, Vidhya Shankar2, Uday Kumar3, C.Ashwin Gowda4 1

Student, 1,2,3,4Department of Mechanical Engineering, GSSIT, Kengeri Satellite town, Bangalore, naveenreddy.kr @gmail.com

Abstract

The objective of this work is to investigate machining characteristic conditions under which multi-layer coated carbide tool can promote optimal results in the turning of EN8 and EN31 steel with continuous and interrupted surfaces. The tool is used in the radial turning of EN8 and EN31 with two types of surfaces under consideration namely continuous surface and Interrupted surface, with four interruptions. In this study number of turning experiments is carried on the continuous surfaces and interrupted surfaces applying different parameters such as cutting speed, feed rate and depth of cut. Here, Taguchi method is applied to find optimum process parameters for turning of EN8 and EN31. Orthogonal array, signal to noise ratio, cutting forces and Analysis of variance (ANOVA) are applied to study the performance characteristics of machining parameters with consideration of surface finish and tool life. Multiple regression equations are formulated for estimating predicted values of surface roughness and tool wear. Scanning Electron Microscope (SEM) images are obtained for the desired optimum cutting combinations. Keywords: Hard material turning, taguchi method, surface roughness test, sem analysis .

1. Introduction Turning of hardened steels have been increasingly used to replace grinding operations, due to the development of very hard tool materials and very rigid machine tools, which can ensure the same accurate geometrical and dimensional tolerances. Within the last years, hard turning operations have become more and more capable with respect to surface roughness and IT standards. Additionally, these processes offer a high flexibility; increased material removal rates and even the possibility of dry machining .However, there are some restrictions to its use in the machining of hardened steels with interrupted surfaces, because tools generally used for this purpose are brittle and, have little resistance against the typical shocks of interrupted cutting. On the other hand, interrupted surfaces are typical for turned parts, lending importance to the study of the turning of such surfaces in hardened steel parts. The main goal of this work is to contribute to the studies about this problem. Turning experiments were carried out on different work piece surfaces using multilayer coated carbide tool. The final purpose was to find the best cutting parameters in continuous as well as interrupt turning, in terms of tool wear, surface roughness and tool life. The machining of hardened steel components with multilayer coated carbide tool having a geometrically defined cutting edge has gained substantially in importance due to improvements in the performance of such modern cutting tool materials. Hard turning is increasingly a profitable alternative to finish grinding. The objective is to remove work piece material in a single cut rather than a lengthy grinding operation, thus reducing processing time and production costs. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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In terms of surface finish the roughness parameters taken into consideration are generally the average roughness Ra. Results come mostly from studies of continuous hard turning. According to some authors the main factors that have a direct influence on surface quality are the corner radius of the cutting edge and the feed rate. Generally speaking, the greater the feed, the greater the value of Ra; however, this is still influenced by the occurrence of tool nose chipping or surface cratering. When analyzing surface quality in hard turning, special attention was paid to metallurgical alterations in the superficial layer. Most common for hard turning is the occurrence of a white layer. White layer is a result of microstructure alteration. It is called “white” layer because it resists standard etchants and appears white under an optical microscope (or featureless in a scanning electron microscope). In addition the white layer has high hardness, often higher than the bulk. Authors claim that the white layer has a mixed martensite and austenite structure. The objective of this paper is to take the study of Diniz and Oliveira a step further by comparing the performance of alumina-based ceramics reinforced with silicon carbide (Al2O3 + SiC) against that of low PCBN content grade (with an added ceramic phase–TiN) in interrupted\ turning. In addition to continuous cutting, two forms of interrupted turning were used, i.e., 4 surface interruptions. Moreover, analysis of the work piece surface roughness and of the tool wear lands using scanning electron microscopy (SEM) were carried out. 2.Experimental set up Preparation of work piece was carried out by milling machine. Initially work pieces (EN8 and EN31) marked to cut the slots outer dia of work piece after marking it has been machined by milling machine according to dimensions 65 mm ×200 mm.

Figure 2.1: Slots preparation for interrupt turning (outer dia)

Figure 2.2: Work piece for continuous turning

After preparation of work piece material, it has been heat treated to increase hardness number of the material up to 45 hrc. The steps followed in heat treatment a) stress relive b) Hardening c) tempering d) oil quenched. Compositions of materials are: EN8 0.439% C, 0.81% Mn, 0.014% P, 0.016% Su, 0.218% Si, and 0% Ch. EN31 1.091% C, 0.525% Mn, 0.029% P, 0.036% Su, 0.219% Si, and 1.067% Ch. From Taguchi method selected orthogonal array was L 9 which has 9 rows corresponding to the number of tests with three columns at three levels. The outputs studied were temperature, surface roughness (Ra) and tool wear. For the purpose of observing the effect of cutting conditions say cutting speed, feed rate on the finished product in, two factors, each at three levels, are taken into account, as shown in Table. Table 2.1: Factor and level used in experiment Sl. No. Cutting Speed in m/min Feed rate in mm/rev Depth of cut in mm

1level 80 0.1

2 level 140 0.2

3 level 200 0.3

0.1

0.2

0.3

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3. Experimental work 3.1 CNC Turning. Experiment is conducted to measure the surface roughness and tool wear. Two cylindrical bars ( One regular surface and other with four slots to promote interrupt cutting), of the material EN8 and EN31 were received. The cylindrical bar of dimensions 200 mm length and 65mm diameter were used for machining.Then the CNC turning operation was carried out at a commercial engineering works shop (Manjunath engg work) at different cutting parameters and chips for each cutting parameters were collected.The length of cut for each test was 20 mm in the axial direction. All tests were performed under dry cutting conditions. Figure shows work pieces after turning under different parameters.

Figure 3.1: Work set up for continuous and interrupt turning

Figure 3.2: Tally Surf (Surface roughness measuring instrument).

Surface roughness test was carried out to determine the surface roughness values, set as shown in figure3.2 3.2 Tool wear test. Tool wear test were carried out by scanning electron microscope (SEM). Before conducting Sem analysis test multi layer coated carbide tools cleaned in etchants and placed in sem machine. In which flank wear, crater wear and micro structure can be determined. 4. Results and discussion 4.1Experimental results. The experimental data have been optimized with Taguchi’s design of experiment. For the analysis of these data ANNOVA has been used. Table 4.1: EN 31 material continuous turning Doc Vc in

F in

Sl.No..

Ra in

Tool wear

in m/min

mm/rev

Mean of

Cutting

means

forces

SNRA1 microns

in mm

0.1

3.91

0.01642

-11.8435

3.91

112

0.2

4.05

0.02682

-12.1491

4.05

118

0.3

7.20

0.03722

-17.1466

7.20

140

0.1

0.3

3.38

0.02506

-10.5783

3.38

151

140

0.2

3.75

0.03546

-11.4806

3.75

175

140

0.3

0.1

4.48

0.04586

-13.0256

4.48

222

200

0.1

0.3

2.57

0.0337

-8.19866

2.57

180

200

0.2

0.1

3.91

0.0441

-11.8435

3.91

210

200

0.3

0.2

4.04

0.0545

-12.1276

4.04

244

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Table 4.2: EN 31 materials interrupt turning Mean Vc in

F in

Doc in

Ra in

Tool wear

Cutting

Sl.No.

SNRA1 m/min

mm/rev

microns

in mm

forces means

0.1

3.89

0.00091

-11.7990

3.89

125

0.2

4.79

0.02488

-13.6067

4.79

138

0.3

5.15

0.03985

-14.2361

5.15

158

140

0.1

0.3

2.76

0.02629

-8.81818

2.76

162

140

0.2

3.60

0.04126

-11.1261

3.60

184

140

0.3

0.1

3.85

0.05623

-11.7092

3.85

242

200

0.1

0.3

1.60

0.04267

-4.08240

1.60

206

200

0.2

0.1

1.89

0.05764

-5.52924

1.89

233

200

0.3

0.2

2.67

0.07261

-8.53023

2.67

270

Table 4.3 EN 8 continuous turning Vc in

F in

Doc in

Ra in

Tool wear

m/min

mm/rev

microns

in mm

Sl.No..

Mean of SNRA1

Cutting forces means

0.1

3.43

0.01642

-10.7059

3.43

0.2

3.56

0.02682

-11.0290

3.56

104

0.3

8.36

0.03722

-18.4441

8.36

118

140

0.1

0.3

2.55

0.02406

-8.13080

2.55

106

140

0.2

4.18

0.03546

-12.4235

4.18

124

140

0.3

0.1

4.70

0.04586

-13.4420

4.70

136

200

0.1

0.3

1.83

0.0337

-5.24902

1.83

112

200

0.2

0.1

2.55

0.0441

-8.13080

2.55

128

200

0.3

0.2

4.34

0.0545

-12.7498

4.34

148

Table 4.4: EN 8 interrupt turning Vc in

F in

Doc in

Ra in

Tool wear in

Sl.No..

Mean of

Cutting

means

forces

SNRA1 m/min

mm/rev

microns

0.1

4.09

0.00091

-12.2345

4.09

105

0.2

6.68

0.02488

-16.4955

6.68

116

0.3

7.63

0.03985

-17.8752

7.83

132

140

0.1

0.3

2.87

0.02629

-9.15764

2.87

124

140

0.2

3.63

0.04126

-11.1981

3.63

138

140

0.3

0.1

4.83

0.05623

-13.6789

4.83

150

200

0.1

0.3

1.41

0.04267

-2.98438

1.41

138

200

0.2

0.1

2.80

0.05764

-8.94316

2.80

154

200

0.3

0.2

3.62

0.07261

-11.1742

3.62

176

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Main Effects Plot for SN ratios

Data Means vc in m/mi

f in mm/rev

-11

-8

-12

-10

-13 -14 80

140

200

0.1

0.2

0.3

doc in mm

-10

f in mm/re v

-6

-11

Mean of SN ratios

Data Means

vc in m/min

-10

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-12

-12 -14 80

140 doc in mm

200

0.1

0.2

0.3

0.1

0.2

0.3

-6 -8 -10

-13

-12

-14

-14 0.1

0.2

0.3

Signal-to-noise: S maller is better

Figure 4.1: EN 31 continuous turning

Figure4.2: EN 31 interrupt turning

It is very clear that the surface roughness is minimum when cutting speed is 200 m/min, feed rate is 0.1 mm/min and depth of cut is 0.2 mm. The S/N ratio analysis also suggests the same level of parameter. Main Effects Plot for SN ratios

Main Effects Plot for SN ratios

Data Means

Data Means f in mm/re v

vc in m/min -8

-10

-12

-14 80

140 doc in mm

200

0.1

0.2

0.3

-8 -10

Mean of SN ratios

vc in m/min -8

f in mm/re v

-14 -16 80

140 doc in mm

200

0.1

0.2

0.3

0.1

0.2

0.3

-8 -10 -12

-12

-14

-16 0.1

0.2

0.3

Signal-to-noise: Smaller is better

Signal-to-noise: S maller is better

Figure 4.3: EN 8 continuous turning

Figure4.4: EN 8 interrupt turning

Figure 4.4: EN 31 work piece material (continuous and interrupt turning) Vc = 200 m/min, F= 0.1 mm/rev, DOC= 0.3 mm

Figure 4.5: EN 8 work piece material (continuous and interrupt turning) Vc = 200 m/min, F= 0.1 mm/rev, DOC= 0.3 mm

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5. Conclusions Based on the results of this work in the radial turning of EN 8 and EN 31, 50 HRC with coated carbide tools with different cutting conditions, it can be concluded that: In both, continuous and interrupted cutting, the coated carbide tool flank wear rate was much high wear rate at higher cutting speeds used. In continuous cutting, the main wear mechanism of the coated tool was abrasion for the lowest cutting speed and diffusion for the highest cutting speed. In interrupted cutting, the main wear mechanism of the coated carbide tool was abrasion at high cutting speeds. At low cutting speeds, abrasion was stimulated by slow destruction (attrition). In both cases, sudden chipping of the cutting edge occurred in response to mechanical shocks. The work piece roughness values obtained with the ceramic tools during their lives were considered high for an operation intended to replace grinding, because the type of wear these tools underwent caused considerable variations in the tool nose shape. Based on the results of this work, it can be concluded, in terms of tool life and surface roughness that coated carbide performs better in both interrupted and continuous surface. It was also concluded in these works that, in spite of the higher price of the tools like CBN and ceramic compared with multilayer coated carbide tool, it is the only tool material that is able to turn hardened steels, achieving very long tool lives and obtaining levels of surface roughness suitable for an operation aiming to replace grinding. The results of analysis show that feed rate have present significant contribution on the surface roughness whereas depth of cut and cutting speed have less significant contribution on the surface roughness. But depths of cut and cutting speed have higher significant contribution on the tool life whereas feed rate have lesser significant contribution on the tool life in case of both continuous and interrupt turning. The best combinations obtained in both continuous and interrupt turning are same and are reported for EN8 and En31work piece material Finally we concluded that first combination ( i.e., Vc = 200m/min, F= 0.1 mm/rev, DOC= 0.3 mm) is the best one to get good surface finish and also minimize the tool wear both in case of continuous and interrupt turning. References [1]. Diniz, A.E., Oliveira, A.J., 2008. Hard turning of interrupted surfaces using CBN tools. Journal of Materials Processing Technology 195, 275–281. [2]. Farhat, Z.N., 2003.Wear Mechanisms of CBN cutting tool during high-speed machining of mold steel. Materials Science and Engineering A361, 100–110. [3]. Ferraresi, D., 1977. Fundamentals of Metal Cutting (Fundamentos da Usinagem dos Materiais), second ed. Editora Edgard Blucher, São Paulo (in Portuguese). [4]. Grzesik,W., 2008. Influence of toolwear on surface roughness in hard turning using differently shaped ceramic tools.Wear 265, 327–335. [5]. Grzesik, W., Zalisz, Z., 2008. Wear phenomenon in the hard steel machining using ceramic tools. Tribology International 41, 802–812. [6]. Huang, Y., Dawson, T.G., 2005. Tool craterwear depth modeling in CBN hard turning.Wear 258, 1455–1461. [7]. Juvinall, R.C., Marshek, K.M., 1999. Fundamentals of Machine Component Design, third ed. John Wiley & Sons, Hoboken. [8]. Klocke, F., Brinksmeier, E., Weinert, K., 2005. Capability profile of hard cutting and a. grinding processes. Annals of the CIRP 54, 557–580. [9]. Ko, T.J., Him, H.S., 2001. Surface integrity and machinability in intermittent hard turning. The International Journal of Advanced Manufacturing Technology 18, 168– 175. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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EXPERIMENTAL STUDY ON WORK PIECE TEMPERATURE WHEN DRILLING HARDENED STEELWITH COATED CARBIDE TOOL USING WITH AND WITHOUT COOLING SYSTEM S.Rajesh.S1, Vidhya Shankar2, Uday Kumar3, Ashwin C Gowda4 1

Student, 2,3,4Department of, Mechanical Engineering, GSSIT, Bangalore, India rajeshreddy402@gmail.com

Abstract The aim of this project is to determine the temperature of hardened EN8 and EN31 steel, during drilling by Taguchi technique for optimize the cutting parameters, also surface finish, and tool wear. First work piece is prepared to exact dimension and to place the thermocouples holes were drilled by conventional drilling machine. Simple thermocouple setup is prepared with digital electronic display. The work piece is hardened by heat treatment to 45HRC and then the drilling is carried out in CNC drilling machine with coated carbide drill (TiCN-Titanium Carbon Nitride) for different cutting parameters, through dry machining and one cooling/lubrication systems were used. Thermocouples were fixed at distances very close to the drilling hole by CNC machine of the work piece. The temperature from different cutting parameters at different depth of length is note downed during machining. Then the surface roughness of drilled hole is finding out by surface roughness tester. Then the microstructure and tool wear was found out using Scanning Electron Microscope (SEM). Then we can predict the lower temperature, high degree of surface finish with less tool wear from different cutting parameters for both dry machining and cooling/lubrication system. The experimental data have been optimized with Taguchi’s design of experiment. For the analysis of these data Analysis of variance (ANOVA) has been used. Key words: hardened steel; coated carbide drill; Temperature; surface roughness; tool wear

1.INTRODUCTION The aim of this work is to determine the heat flux and the coefficient of convection in drilling using the inverse heat conduction method. The machining of hardened steels has alwaysbeen a great challenge in metal cutting. Drilling is the machining process in which most difficult to cool the temperature due to the tool’s geometry. The importance of temperature prediction for machining processes has been well recognized in the machining research community due to its effects on tool wear and its constraints on productivity, chip formation and also surface finish of the work piece. Many researchers have developed analytical models to study the thermal aspects in machining, and their results are fundamental for calculating the temperature in many practical processes such as grinding, milling, drilling, turning and so on. Heat conduction studies in machining are interesting and necessary, because they allow define coatings for tools more efficient in function of the degrading effect that the heat provoke on tool performance in worked material by machining. Intense local heat may affect the heat treatment or provoke artificial aging and residual stress.The experimental approaches in the machining studies are usually expensive and require a lot of time. The alternatives used by modern researchers are the mathematical and computational models, in particular computational routines developed in Finite Elements Analysis using Abaqusand ANSYS. The values found for both experiments showed that the Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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finite element methodology has good agreement between the measured and predicted temperature. Optimize the cutting parameters during drilling of hardened steel, by Statistical technique called Taguchi method.L9 orthogonal array, signal to noise ratio and ANOVA are applied to study the performance characteristics of machining parameters with consideration of surface finish and tool life.The embedded thermocouple technique is used to measure the cutting temperatures at the interface between the tool and the work piece. This technique was used because it is easy to apply, but it only measures the maximum temperature in the contact area of thermocouple with work piece. The material used is EN8 is unalloyed medium carbon steel with good tensile strength and EN31 is a high carbon alloy steel which achieves a high degree of hardness with compressive strength and abrasion resistance, which are hardened to 45 HRC before CNC machining. TiCN (Titanium Carbon Nitride) coated drill bit is used to machining in CNC machine which have the improved hardness and wear and corrosion resistant, operating life and productivity.The drill coated with TiCN coating has great tool life compared with other coated-drills life and uncoated drill. 2.EXPERIMENTAL SET UP The first step is preparation of work piece to exact dimension which is required for CNC drilling operation. In these 18pieces solid blocks of both EN8 and EN31 where prepared to a dimension of 40mmX40mmX50mm. Then holes are drilled to theworkpiece toplace the thermocouples. The four holes are drilled in the work piece at 10mm distance between each hole of 6.3mm Diameter and 13mm depth. These holes are drilled in conventional drilling machine shown in figure 2.1. Then after the heat treatment process is carried out to the prepared blocks to 45HRC. The steps followed in heat treatment a) stress relive b) Hardening c) tempering d) oil quenched. Compositions of materials are: EN8 0.439% C, 0.81% Mn, 0.014% P, 0.016% Su, 0.218% Si, and 0% Ch. EN31 1.091% C, 0.525% Mn, 0.029% P, 0.036% Su, 0.219% Si, and 1.067% Ch. To measure the temperature thermocouples is used. These thermocouples are placed on a small setup box. This is shown in the figure 2.2. It consists a) four thermocouples (0oC to 1200o C) made by Chromel-Alumel, b)Digital temperature indicator, c)Thermoelectric converter d)Channel selector. The four thermocouples are connected through wires to Channel selector, with four different channels respectively. Then connect channelselector to thermoelectric converter. Then from this thermoelectric converter to digital temperature indicator. This digital temperature indicator indicates only the temperature of the selected channel.

Figure 2.1: Work piece ready for. heat treatment

Figure 2.2: Thermocouples with full setup.

From Taguchi methodselected orthogonal array was L 9which has 9 rows corresponding to the number of tests with three columns at three levels. The outputs studied were temperature, surface roughness (Ra) and tool wear. For the purpose of observing the Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

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effect of cutting conditions say cutting speed, feed rate on the finished product in, two factors, each at three levels, are taken into account, as shown in Table 2.1 Table 2.1: Factor and level used in experiment

Sl. No. Cutting Speed in m/min (Vc) Feed rate in mm/min (Vf)

1level 60 20

2 level 80 30

3 level 100 40

3. EXPERIMENTAL WORK 3.1 CNC Drilling Experiment is conducted to measure the temperature, surface roughness of work piece and tool wear. 18 blocks of hardened EN8 steel and 18 blocks of hardened EN31 steel (9 blocks of each for dry machining and other 9 for coolant machining) were used. The rectangular blocks of each 40mmX40mmX50mm were used for machining. The block is placed in a vice of VMC (vertical machining centre) machine. The block is firmly fixed in the vice of VMC so that it should not vibrate and come out of it during machining. Then the thermocouples are placed in the work piece holes which had been drilled previously in conventional drilling machine before hardening as shown in figure 3.1. Now the temperature indicator is switched on which is placed on the machine. The machining process starts, the CNC program is prepared for drilling. First small punch is done on the work piece by a center bit, and then on the same punched place drilling is carried out. During drilling is carrying the temperature is note down for different depth from top surface of work piece. The process is carried out for both using coolant machining shown in figure 3.2 and dry machining shown in figure 3.3. The CNC drilling operation was carried out at a commercial engineering works shop for different cutting parameters, and chips for each cutting parameters were collected.

Figure 3.1:The thermocouples are placed inPreviouslydrilled holes

Figure 3.3: Dry machining.

Figure 3.2:using coolant machining.

Figure 3.4: Drilled block with TallySurf and set up.

3.2 Surface roughness set up: The drilled block is brought and adjusted at flat surface to probe of Surface roughness measuring instrument called Tally Surf, so that it can easily pass through the hole. As the probe moves in the hole the reading Ra = arithmetic mean deviation of profile is note down showed in the display. This will continue for all the blocks. The figure 3.4 shows the setup. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

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3.3 Tool wear test: Tool wear test were carried out by scanning electron microscope (SEM). Before conducting SEM analysis test the drill bits are cut to 10mm length from tip. It consist chisel edge, flank, face, lip. So that it is easy to place in SEM. 4. RESULTS AND DISCUSSION 4.1 Experimental Results: Temperature, surface roughness under different parameters for drilling and also signal to noise ratio from the ANNOVA software is shown in the table 4.1 for EN8 with coolant, table 4.2 EN8 without coolant, table 4.3 for EN31 with coolant, and EN31 without coolant. Some of the abbreviations are Vc = CuttingSpeed inRPM(Mt/min). Vf= feed in mm/min. Temperature in deg C = At depth from top surface in mm. Ra = Surface roughnessin microns. SNRA1 = signal to noise ratio. 4.2 SEM images of drill bit at 250X:

Figure 4.1

Figure 4.2

Figure 4.1 = drill bit ofEN8 with coolant. Figure 4.3 = drill bit of EN31 with coolant.

Figure 4.3

Figures 4.4

Figure 4.3 = drill bit of EN8 with out coolant. Figure 4.4 = drill bit of EN31 without coolant.

Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering” Table 4.1: EN8 with coolant machining

Temperature in deg C S.N

1851 (60) 1851 (60) 1851 (60)

(Ra)

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Table 4.2: EN8 without coolant machining

SNRA1

Temperature in deg C

(Ra)

SNRA1

Vf 10

9.37042

110

131

0.34

9.37042

113

134

1.55

-3.80663

0.53

5.51448

104

121

144

1.73

-4.76092

0.21

13.5556

114

130

1.42

-3.04577

0.37

8.63597

109

129

1.37

-2.73441

0.43

7.33063

117

141

1.68

-4.50619

0.36

8.87395

116

135

1.49

-3.46373

0.38

8.40433

100

119

138

1.58

-3.97314

0.47

6.55804

107

123

148

1.88

-5.48316

0.32

1.45

-3.22736

2547 4

(80) 2547

(80) 3184

(100) 3184 (100) 3184 (100)

Table 4.3: S.N

EN31 with coolant machining

Table 4.2 : EN31 without coolant machining

Temperature in deg C

1851 (60) 1851 (60) 1851 (60) 2547 (80) 2547 (80) 2547 (80) 3184 (100) 3184 (100) 3184 (100)

SNRA1

(Ra)

SNRA1

Vf 10

(Ra)

0.26

11.7005

117

137

1.40

-2.92256

11.3727

108

124

155

1.53

-3.69383

117

139

168

1.71

-4.65992

0.27

0.29

0.21

13.5556

115

135

1.37

-2.73441

0.31

10.1728

120

140

1.49

-3.46373

0.36

8.87395

112

130

165

1.64

-4.29688

0.10

112

130

1.28

-2.14420

0.32

9.89700

120

158

1.58

-3.97314

0.45

6.93575

105

137

167

1.68

-4.50619

10.7520

Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

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4.2 ANNOVA Results: Graphs with respect to signal to noise ratio:

Main Effects Plot for SN ratios

Data Means

Data Means vc in m/min

fc in mm/min

Mean of SN ratios

10 Mean of SN ratios

vc m/min

-3.0

f in mm/min

-3.5

-4.0

-4.5 7

-5.0

6 60

100

Figure4.2.1: En 8 with coolant

Main Effects Plot for SN ratios

Data Means

vc in m/min

fc in mm/min

vc in m/min

-2.5

Mean of SN ratios

Figure 4.2.2: En 8 without coolant

Main Effects Plot for SN ratios

100

Signal-to-noise: Smaller is better

f in mm/min

-3.0

-3.5

-4.0 7 -4.5

6 60

100

Signal-to-noise: Smaller is better

Figure4.2.3:En 31 with coolant

100

Signal-to-noise: Smaller is better

Figure4.2.4:En31 without coolant

From this graphs we can observe that as the speed increases with less in feed good surface finish will be obtained. Sometimes the result various depending on type of materials. 5. Conclusion The results of analysis show that feed rate and cutting speed have present significant contribution on the temperature and surface roughness. But feed rate have higher significant contribution on the tool life. When drilling using coolant system tool life can be increase 3 times without coolant drilling, and surface roughness values lesser when compare to with and without coolant. When cutting speed increases and lower feed rate which results less temperature and good surface finish. The best combinations obtained for en8 and en31 work piece materials by using with coolant and without coolant are EN8: Vc =80m/min, fc = 20mm/min. EN31: Vc =100m/min, fc = 40mm/min. Depending upon material, the cutting parameters varies. From the SEM image we can observe that the wear in chisel wear of tool is more in without coolant machined drill bit. References [1]. S.A. Jalali, W.J. Kolarik, Tool life andmachinability models for drilling steels, Int. J. Mach. Tools Manuf. 31 (3) (1991) 273–282. [2]. Chen W C, Tsao CC. Cutting performance of different coated twist drills. J Mater Process Technol. (1999) 88 : 203-207 [3]. Chryssolouris G, Guillot M.,”A comparison of statistical and AI approaches to the selection of process parameters in intelligent machining”, ASME J EngInd 1990; 112:122–31. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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[4]. Chua MS, Rahman M, Wong YS, LohHT.”Determination of optimal cutting conditions using design of experiments and optimization techniques”, Int J Mach Tools Manuf 1993; 33(2): 297–305. [5]. Yang H, Tarng YS,” Design optimization of cutting parameters for turning operations a. based on the Taguchi method”, J Mater Process Technol 1998; 84:122–9. [6]. Paulo davim.J,”Study of metal-matrix composites based on the Taguchi techniques”,Journal of material processing technology 132 (2003) 250- 254 [7]. Graham T. Smith,” Cutting Tool Technology”, Springer-Verlag London Limited 2008. [8]. Han-Ming Chow, Shin-Min Lee, Lieh-Dai Yang, “Machining characteristic study of friction drilling on AISI 304 stainless steel”. Journal of materials processing technology 207 (2008) 180–186. [9]. Routio. M and. Saynatjoki.M, Tool wear and failure in the drilling of stainless steel J. Mater.Process. Technol. 52 (1995), pp. 35–43 [10]. Philip J Ross (1996) Taguchi techniques for quality engineering, McGraw-Hill [11]. Phadke M S (1989) Quality engineering usingrobust design, Prentice Hall, Englewood Cliffs, NJ. [12]. Mustafa Kurt,EyupBagei, Yusuf Kaynak(2009) Application of taguchi method in the optimization of cutting parameters for surface finish and hole diameter accuracy in dry drilling process. Int. J. AdvManufTechnol 40: 458 – 469. [13]. PauloDavim.J (2003) Study of drilling metal – matrix composites based on the taguchi techniques. Journal of Materials Processing Technology, 132,250-254 [14]. Tsao.C.C., H. Hocheng (2004) Taguchi analysis of delamination associated with various drill bits in drilling of composite material,44, 1085-1090. [15]. S. Basavarajappa, G. Chnadramohoan, J. Paulo Davim (2008), Some studies on drilling of hybrid metal matrix composites based on taguchitechniques, Journal of Materials Processing Technology, 196, 332-338 [16]. Mustafa Kurt, EyupBagei, Yusuf Kaynak (2009), Application of taguchi methods in the optimization of cutting parameters for surface finish and hole diameter accuracy in dry drilling process.,

Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

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OPTIMAL MACHINING CONDITIONS FOR TURNING OF AL-SIC METAL MATRIX COMPOSITES USING ANOVA M.S.Nezami1, Naved Imam2, Sourabh Kumar3, Rajeev Kumar4 1,2,3,4

Department of Mechanical Engineering, SJB Institute of Technology, Bangalore. nezami.saquib@gmail.com

Abstract Metal Matrix Composite (MMC) is an advanced engineering material possessing numerous favorable characteristics like light weight, high strength, high stiffness, ability to be operated at elevated temperatures etc. However, it is very difficult to machine these materials as they contain very hard abrasive ceramic as a dispersed phase in a ductile material matrix phase. Our study aims at casting of AlSiC composite rods with Al 75% and 25% SiC as a composition. The study employs CNC turning operation and Taguchi's L8 orthogonal array is used for experimental design. An attempt is made to optimize the effects of the three parameters such as cutting velocity, feed rate and depth of cut on the surface roughness values (Ra and Rz). Analysis of Variance (ANOVA) has been performed to know the effects of these three factors on the responses using statistical software MINTAB 16. Based on the number of trials conducted it is concluded that moderated cutting velocity, lower feed rate and higher depth of cut are the ideal machining conditioning for the considered metal matrix composite. Measured surface roughness values (Ra & Rz) using zeiss surface roughness measuring equipment is the deciding criteria for this conclusion Keywords: Metal matrix composite, orthogonal array, ANOVA

1. Introduction Metal matrix composites are widely used composite materials in aerospace, automobile, electronics and medical industries. This is because of their superior mechanical properties like strength to weight ratio and high thermal conductivity. The desired properties are mainly manipulated by matrix, the reinforcement element and the interface. These composites are manufactured by introducing hard ceramic reinforcements such as zirconia, alumina, silicon carbide (SiC) into a base matrix elements like aluminium, magnesium or titanium alloy in the form of particulates, fibres or whiskers. There are several methods to manufacture MMCs but the stir casting is very popular method. The properties of the particle reinforced metal matrix composites produced by this way are influenced to a large extent by type, size and weight of fraction of the reinforcing particles and their distribution in the cast matrix. An enduring problem with MMCs is that they are difficult to machine due to high hardness and abrasive nature of reinforcing particles which in many cases are significantly harder than the commonly used high speed steel (HSS) tools and carbide tools. These results in rapid tool wear and poor quality of the machined surface. Most of the researchers reported that Poly-Crystalline Diamond (PCD) tools and CVD (Chemical Vapour Deposition) are the most preferred one to machine (either turning or milling) MMCs. The difficulties associated with the machining of MMCs need to be minimised if these materials are to be used more extensively. In the present investigation an attempt is made is made to study the effects of cutting variables on surface roughness in CNC turning of AlSiC by performing analysis of performance. Cutting Velocity, Feed Rate and Depth of Cut are chosen as the influencing parameters and a 23 full factorial (Taguchi's L8 orthogonal array) design of experiments was carried out to collect the experimental data and to analyse the effect of these parameters on surface roughness values. The statistical software MINITAB 16 is used to perform ANOVA. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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2. Experimental Details 2.1 Work Material The master material with composition of Al as 75% and SiC 25% is selected. The eight test specimens are cast into Ø21x230mm sizes. Specimens are rough machined to get the shaft. The diameter is maintained at 19.3mm to ensure rigidity in the chuck. The specimens are machined with three different input parameters for 60mm length on each piece.

Figure 2.1: Al - 25% SiCp work pieces

2.2 Experimental Plan and Procedure The experiments were carried out on a CNC turning centre machine (MAZAK Quickturn 15N) at Government Tool room and Training centre (GT&TC), Mysore, India. Specimens of Ø19.3x230mm size were used for the experimentation. The test specimen was mounted in a chuck.

Figure 2.2.1: MAZA K Quickturn 15N

Figure 2.2.2: Experimental Setup

The required cutting velocity, feed rate and depth of cut were incorporated in CNC part programming to perform the operations as per Taguchi's L8 orthogonal array. Each sample was marked with corresponding trial number to identify the conditions used. The steps were repeated until the whole experiment was complete. The two levels of the process parameters/factors are given below. Table 2.2.1: Process Parameters and their levels

Sl. No. 1 2 3

Parameter A B C

Level 1 140 0.05 0.5

Level 2 240 0.1 1

where A is cutting velocity (m/min), B is feed rate(mm/rev) and C is depth of cut (mm).

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Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

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The process parameters for eight different specimens were based on Taguchi's L8 orthogonal array which can be tabulated as follows. Table 2.2.2: Taguchi's L8 orthogonal array Exp. Run 1 2 3 4 5 6 7 8

A 1 1 1 1 2 2 2 2

Process Parameters B 1 1 2 2 1 1 2 2

C 1 2 1 2 1 2 1 2

The instrument used for measuring the surface was surface tester. Zeiss Surfcom 130A was used to measure the roughness of each trial sample. The test was conducted for 40mm length of the specimen. The surface roughness values (Ra and Rz) for all the eight specimen can be tabulated as follows. Table 2.2.3: Ra and Rz values Exp. 1 2 3 4

Ra 0.402 0.948 1.179 1.215

Rz 2.354 4.059 5.363 6.475

Exp. 5 6 7 8

Ra 0.741 0.607 1.057 1.084

Rz 3.696 3.084 4.824 5.209

3. Statistical Analysis The mathematical relationships between responses and machining parameters was established using multiple regression analysis. In the present study, the correlation between the process parameters cutting velocity, feed rate, depth of cut and surface roughness are established. The multiple linear regression models were obtained using MINITAB 16. Ra = - 1.57387 + 0.0064125 A + 19.189 B + 2.0701 C - 0.0251 AB - 6.98 BC - 0.00689 CA Rz = - 6.13775 + 0.035525 A + 78.598 B + 6.4726 C - 0.2172 AB + 8.08 BC - 0.03044 CA

4. Analysis of Variance (ANOVA) Analysis of Variance (ANOVA) is a method of apportioning variability of an output to various inputs. Below table shows the results of ANOVA analysis. The purpose of the analysis of variance is to investigate which machining parameters significantly affects the performance characteristics. The following tables were obtained after performing ANOVA for Ra and Rz.

Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

Table 3.1: ANOVA table for Ra

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Table 3.2: ANOVA table for Rz D Seq F SS 1 0.258

Adj SS 0.258

0.769

Sourc e A

0.82

0.532

7.50

.223

9.413

29.79

0.115

0.028

0.50

0.608

0.838

2.65

0.351

0.007

0.14

0.772

0.589

1.87

0.402

0.015

0.27

0.695

0.020

0.06

0.842

0.059

1.05

0.492

1.158

3.67

0.306

Error

0.056

Error

0.316

Total

0.596

Total

12.59

Sourc e A

D F 1

Seq. SS 0.008

Adj. SS 0.008

Adj. MS 0.008

0.14

0.421

0.028

0.007

5. Optimisation and Analysis Results Based on the mathematical model given by equations for Ra and RZ, the study on the effects of various machining parameters on Ra and Rz have been made so as to analyze the suitable parametric combinations that can be made for achieving controlled surface roughness. The plots were obtained for various combinations of cutting velocity versus surface roughness (both Ra and Rz), feed rate versus surface roughness and depth of cut versus surface roughness. These plots are as follows.

Main Effects Plot for Means

Main Effects Plot for SN ratios

Data Means

Data Means A A

3.2

0.65

2.8

0.55 0.50 140

240

0.05

0.10

C 0.65

Mean of Means

Mean of SN ratios

0.60

2.4 2.0 140

240

0.05

0.10

C 3.2

0.60

2.8

0.55

2.4 2.0

0.50 0.5

1.0

0.5

1.0

Signal-to-noise: Nominal is best (10*Log10(Ybar**2/s**2))

Figure 5.1: Main Effects Plot for Means

Figure 5.2 :Main Effects Plot S/N Ratios

6. Conclusion The paper examines the influence of cutting velocity, feed rate and depth of cut on surface roughness in CNC turning of Al/SiC metal matrix composites. A functional relationship between the surface roughness and cutting parameters is established using the principles of Regression Analysis. The goodness of fit between the developed model and the experimental results is further evaluated through Analysis of Variance (ANOVA) and F-ratio test. In the light of the above analysis, the following conclusions are established.

Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

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 

   

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The use of ANOVA to analyze the influence of process parameters like cutting speed, feed rate, depth of cut is a useful tool for achieving the best surface finish in the Aluminum silicon carbide composite. Results of Analysis of Variance (ANIOVA) for Ra and Rz values as obtained in tables 3.1 and 3.2 respectively indicate that the feed rate is the most significant machining parameter for affecting the performance characteristics followed by cutting velocity and depth of cut. From Fig 5.1, it is observed that the feed rate has a minimum influence on surface roughness values at 0.05 mm/rev and increasing thereafter. It can also be concluded from the same figure that Feed Rate is the most influential factor and directly proportional for increase in surface roughness i.e. as feed rate increases the surface roughness also increases. Hence reduced feed is desirable for minimum surface roughness. From the main effects plot, it can also be inferred that the surface roughness also improves with increase in cutting velocity. Moderate cutting velocity, lower feed rate and higher depth of cut are the ideal machining conditions for machining Aluminum Silicon Carbide Composite. Moderate cutting velocity, lower feed rate and higher depth of cut are the ideal machining conditions for machining Aluminum Silicon Carbide Composite. From our experimental values, it can be noticed that the best surface roughness values are obtained as 0.402µm and 2.354µm for Ra and Rz values respectively at Cutting Velocity 140m/min, Feed Rate 0.05mm/rev and Depth of Cut 0.5mm.

Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

RTME’13

AUTOMATION OF BEARING BUSH ASSEMBLY STATION WITH PLC INTEGRATION M.K.Srinivas1, Dodda Hanamesha2, K.M. Ravi Kumar3 1, 2

Dept. of Mechanical Engg.,1, 2Government Engineering College, Dairy Circle, Hassan 3 Department of PG Studies, VTU Regional Office, Mysore, srigowda043@gmail.com

Abstract In manual bush bearing assembly, assembly operation is performed manually by hammering to the bush to the bush block or work piece. Assembly operation depends on operator that is productivity depends on operator efficiency. In manual assembly station, operator perform operations like loading work piece to work holder, selecting the tool bit, checking whether bush is in coaxial alignment, hammering, unloading of work piece and counting of finished work piece. Thus the loading of workpiece, to assemble the bush and unloading of workpiece takes more cycle time. This leads to increase in Manufacturing Lead Time (MLT) and Work in Process (WIP). The main limitation of manual operations is it is tedious and less productivity. Current industries seeks for the mass production and requires continuous operation, manual assembly of the component does not suits hence innovation requires for continuous mass production. To overcome this problem in manual assembly station, the concept of automation is used. This project involves design and fabrication of pneumatically operated assembly station with Programmable Logic Controller (PLC) integration. In this loading the work piece to assembly station, feeding the bush, assembly of the same and unloading of work piece are performed automatically. Keywords: Plc, automation, proximity sensor, solenoid valve

1. INTRODUCTION The main aim of Automation is to increase productivity and quality of products, reduce the cost of production and to over come the problem associated with the labor shortage. Even the lower level technologies can be made highly productive by automation in simple form. The automated assembly systems are designed to perform the assembly operations in a fixed sequence to assemble the parts. Four types of system/operational planning issues are significant which are: delivery of parts at workstations, assembly of the components to the main body, design of the conveyor system and the controlling the motion of the actuators by using programmable logic circuits. The key operations has to be performed by the assembly line are  Transfer of bearing block  Feeding the bush to the assembly line  Assembly of bush to the component The bearing bush is feeded by the bush feeder mechanism and is delivered to assembly station. This bush is assembled to the main body after it has been ensured that there is a coaxial alignment between the bearing blobk and the bearing bush with the help of sensors integrated in the system and the process is completed. Sensitivity analysis is carried out to observe the impact of process parameters on the performance of system. A comparison of these functions with the manual assembly station to identify sensitive process parameters affecting the system. The Pneumatic system will be developed in this project aiming at Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

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achieving low cost automation to automate the process as it is cheaply available in nature and of low maintenance. 2. PROBLEM DEFINITION The operating characteristics of a system can be drastically affected by variations in the handling and mounting of bearings. Substandard performance can result when a bearing is damaged by excessive force or shock loading during assembly, or by a fit which is too tight or too loose. The below figure shows how the bush is assembled manually, here the component is initially placed on the component and gently hit by the hammer. Once the race way of bush fits into component, a bit is placed on the bush and again it is hit by the hammer until the bush is completely fits into base body.

Figure 1: Manual assembly of bush

The most common cause of bearing failure is excessive force applied during assembly and unskilled technicians, which usually results in adverse effects on bearing performance. The associated problems are,  Brinelling (raceway damage)  Cracks in the bush  Overloading  Shape deformation of bush  Reduced lifetime

Excessive forces during assembly of bearings are generated by poor handling techniques or incorrect/uncontrolled interference due to poor design or tolerance stack up. Improper assembly of bearing not only damages the bearing but can also damage the whole system. In most of the cases the bearing assembly is done manually by a technician, above said problems are expected. 3. Aim of the Project Project aims at providing a low-cost PLC based automated bearing assembly station to increase productivity and quality of products, reduce the cost of production and to over come the problem associated with the labor shortage. 4. Objective The main objective of the project is to Design and Develop an automated assembly station to perform the assembly process with PLC Integration. Programming the System in PLC ladder logic/diagram. To develop an assembly machine which can automatically feed the bearing bush to the assembly station by using the pick and place arm. The assembly will Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

RTME’13

be carried out, if once the co axial alignment between the bearing bush and the bearing block is achieved. The testing will carried out by using a strain gauge. 5. Literature Survey Literature survey is the first phase of the project work where importance is given for understanding the present scenario in the industry related to the work. This section gives the works that have been carried out in the area under consideration and also books, articles, different websites, related to automation, and pneumatics. Robert B.van Varseveld et al, describes the Accurate Position Control of a Pneumatic Actuator Using On/Off Solenoid Valves have described the development of an inexpensive, fast acting and modulation in place of rather costly servo valves. Also the overall efficiency of the actuators is compared with servo valves accurate position controlled pneumatic actuator. The paper describes to use On/Off valve using Pulse width efficiency which is obtained by various other researchers. Jiing-Yih Lai et al, in their paper on - Accurate Position Control of a Pneumatic Actuator have experimentally proven that their proposed control system of single open valve was far better than the conventional off control valve strategy which proved that it was better to obtain the desired accuracy in position without having any mechanical stops in the actuator. Nabil Shaukat briefly describes the design and development of a low cost plc based fully automated assembly station, which can replace old manual operations. They use PLC as the control, which can increase their production with a greater economy. Kelvin Erickson, in this paper discussion is made on writing PLC program, history of PLC, how to write PLC ladder logic. Why should we select ladder logic to write PLC program. Steps in writing ladder diagram. 6. Scope of the Work To provide a low-cost PLC based automatic liquid filling and sorting system. This will give an error free mechanism, which can increase the production with greater economy. The control system can not only applied to bush assembly machine, but also can be applied to various have similar requirement of the industrialization of the automatic production line 7. LAYOUT OF ASSEMBLY STATION AND THEIR COMPONENTS

Assembly Station Layout. The below figure shows the layout of bush bearing assembly station and its working principle with different components including its bush feeder mechanism, conveyor and pallet fixture, pneumatic drive and control system of which is explained below.

Figure 3: Layout of bush bearing assembly station

 Pneumatic cylinders  Sensors  PLC board Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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 Direction and pressure valves  Regulated power supply system  Transformer  Relay  Aluminum manifold  Bush feeder system  Chain conveyor Aluminum pneumatic cylinder MA series: MA series is made of the higher lever steel material. It is thermos table and endurable. The bore size of 40 mm.

Figure 4: Pneumatic cylinders

Figure 5: Inductive proximity sensors

Characteristics: Working medium:Air FixedType:LB.FA.SDB Ensured Pressure Resisance:13.5MPa Operating Speed Range:50~800mm/s Operating Temperature Range:0~70°C Inductive Proximity Sensor Inductive proximity sensors operate under the electrical principle of inductance. Inductance is the phenomenon where a fluctuating current, which by definition has a magnetic component, induces an electromotive force (emf) in a target object. To amplify a device’s inductance effect, a sensor manufacturer twists wire into a tight coil and runs a current through it. An inductive proximity sensor has four components. The coil, oscillator, detection circuit and output circuit. The oscillator generates a fluctuating magnetic field the shape of a doughnut around the winding of the coil that locates in the device’s sensing face. When a metal object moves into the inductive proximity sensor’s field of detection, Eddy circuits build up in the metallic object, magnetically push back, and finally reduce the Inductive sensor’s own oscillation field. The sensor’s detection circuit monitors the oscillator’s strength and triggers an output from the output circuitry shown in Figure 5.

Figure 6: Sensor construction

Figure 7: PLC board

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PLC Board Logic Control Board details  AC Power plug-in jack for 230VAC with Transformer and Line Filter is Status LED  8 POT Inputs for ADC - General Purpose  8 optocoupler isolated inputs with screw terminals  Input status LEDs  8 relay outputs with 10A/250VAC contacts with screw terminals  Output status LEDs Programming the PLC Ladder Logic Ladder logic is the main programming method used for PLCs. The ladder logic has been developed to mimic relay logic. Modern control systems still include relays, but these are rarely used for logic. A relay is a simple device that uses a magnetic field to control a switch, as pictured in Figure 3.2. When a voltage is applied to the input coil, the resulting current creates a magnetic field. The magnetic field pulls a metal switch (or reed) towards it and the contacts touch, closing the switch. The contact that closes when the coil is energized is called normally open. The normally closed contacts touch when the input coil is not energized. Relays are normally drawn in schematic form using a circle to represent the input coil. The output contacts are shown with two parallel lines. Normally open contacts are shown as two lines, and will be open (non-conducting) when the input is not energized. Normally closed contacts are shown with two lines with a diagonal line through them. When the input coil is not energized the normally closed contacts will be closed (conducting).

Figure 8: Simple Relay Layouts and Schematics

Programming The first PLCs were programmed with a technique that was based on relay logic wiring schematics. This eliminated the need to teach the electricians, technicians and engineers how to program a computer but, this method has stuck and it is the most common technique for programming PLCs today. An example of ladder logic can be seen in Figure 3.3. To interpret this imagines that the power is on the vertical line on the left hand side, we call this the hot rail. On the right hand side is the neutral rail. In the figure there are two rungs, and on each rung there are combinations of inputs (two vertical lines) and outputs (circles). If the inputs are opened or closed in the right combination the power can flow from the hot rail, through the inputs, to power the outputs, and finally to the neutral rail. An input can come from a sensor, switch, or any other type of sensor. The power needs to flow through some combination of the inputs (A, B, C, D, E, F, G, H) to turn on outputs (X, Y). An output will be some device outside the PLC that is switched on or off, such as lights or motors. In the top rung the contacts are normally open and normally closed. This means if input A is on and input B is off, then power will flow through the output and activate it. Any other combination of input values will result in the output X being off.

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Figure 9: Simple Ladder Logic Diagram

PLC Circuit Connection

Figure 10: Circuit connection

PU-tube Tube made up of polyurethane are widely used in pneumatic systems. It is the indispensible part. Without the tubes, the system can not work. AEROFLEX can provide the high quality tubes and the exact sizes, the different colors.

Figure 11: PU tubes

Figure 12: Solenoid valve

Series Solenoid Valve Features Model Position and way no Working media working pressure Max pressure resistance Operating temperature Electrical entry Highest action frequency

4V110 2 position, 5 way 40 micron filtered air 0.15-0.8 Mpa 1.2MPa 10-50` c lead wire or connector type 5 cycles/ second

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Response time

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0.05 seconds

5V and 12V Regulated power supply

Figure 13: Regulated power supply system

Features of regulated power supply system Input 5-0-5 VAC to 12-0-12 VAC Output : Dual output ± 5 V@1 A regulated low ripple DC voltage Heat sink for regulator ICs Onboard bridge rectifier to convert AC to DC LED indication for both the outputs Thermal overload/short circuit protection (provided by IC feature) Screw terminal connector for easy input and output connection Transformer 220VAC TO 12V (1A) A transformer is a static electrical device that transfers energy by inductive coupling between its winding circuits. A varying current in the primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic flux through the secondary winding. This varying magnetic flux induces a varying electromotive force (emf) or voltage in the secondary winding.

Figure 14: Transformer

Figure 15: Relay

12 VDC SPDT Relay Miniature sealed relay. 12Vdc, 320 Ohm coil. S.P.D.T., 3A contacts. 0.90" x 0.70" x 0.55" high. PC leads, UL.12VDC 40A SPDT Automotive Relay - Plastic Tab Single Pole Double Throw Relay with a plastic mounting tab Automotive type relay 5 Terminals Ratings: NO: 40A/14VDC NC: 30A/14VDC

Figure 16: working of relay Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Aluminum Pneumatic Manifolds Aluminum pneumatic manifolds are a convenient junction point for the distribution of media in fluid handling applications. Quickly create an organized method of supplying multiple lines from a single source by threading pneumatic fittings into the ports. Our standard aluminum manifold offering can easily accommodate the plumbing and installation requirements of your pneumatic control systems.

Figure 17: Pneumatic manifold

Features  Two to 10-stations  Black anodized for corrosion resistance  Mounting versatility  Two sets of mounting holes for convenience Fittings Standard plastic fitting series is of all the specification, including PT metric thread and G thread, inch size and America size. The structure is various, including from straightfittings, angle fittings, tee fitting, flow control fittings.

Figure 18 Angle fitting

Figure19 Flow control fitting Figure 21 Silencer fitting Figure 20 T fitting

8. Conclusion Low cost automated assembly station is achieved. In this machine operation like loading and unloading of work piece, assembly operation and cycle time of the process is measured by using a timer. All these operations are performed automatically. References [1]. A. Che Soh, S.A. Ahmad, A.J. Ishak and K. N. Abdul Latif. ” Development Of An Adjustable Gripper For Robotic Picking And Placing Operation”, Department Electrical and Electronic of Engineering, Universiti Putra Malaysia, 43400 Serdang [2]. Jiing-Yih Lai, Graduate Associate, Chia-Hsiang Menq, “Accurate Position Control of a Pneumatic Actuator”, ASME Fluid Power Laboratory, Department of Mechanical Engineering, The Ohio State University, Columbus, Ohio. [3]. Robert B. van Varseveld and Gary M. Bone, “Accurate Position Control of a Pneumatic Actuator Using On/Off Solenoid Valves”. [4]. Nabil Shaukat, “A PLC Based Automatic Liquid Filling Process”, IEEE, publication page No. 226-233, 2002 [5]. Ali K Gunal,VShigeru Sadakane, “Modeling Of Chain Conveyors And Their Equipment Interfaces” , Production Modeling Corporation,Three Parklane Boulevard, Suite 910 West Dearborn, Michigan 48126, U.S.A [6]. Mirza Jahanzaib, Syed Athar Masood, Khalid Akhtar, “Performance Analysis of Process Parameters Effecting the Automated Assembly System”, College of Electrical and Mechanical Engineering, National University of Science & Technology, Islamabad Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34 41

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[7]. Avvaru Ravi Kiran, B.Venkat Sundeep, Ch. Sree Vardhan , Neel Mathews, “The Principle of Programmable Logic Controller and its role in Automation”. Electronics and Communications, KL University, Guntur. [8]. BOSCH REXROTH Pneumatics Practical Manual. [9]. Kelvin T Erickson, “A Programmable logic controllers”, IEEE potentials, pp.14-17, march-1996. [10]. Nabil Shaukat, “A PLC Based Automated Assembly Process”, IEEE, publication page No. 226-233, 2002.

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MULTI OBJECTIVE OPTIMISATION OF LASER MICRO DRILLING OF SILICON CARBIDE PLATES U.M.Madhu Patel1, A.Bharatish2, H.N.Narasimha Murthy3 1

Student, Product Design and Manufacturing 2 ,3Department of Mechanical Engineering, 1,2,3 RV College of Engineering, Bangalore, India, maddyzizou@gmail.com

Abstract

Laser machining is an advanced manufacturing technique in which the material is removed in three steps namely melting, vaporization and chemical degradation. The capability of laser to transfer high energy to the focused point for melting of material has made laser to be used in micro drilling of ceramics and materials. Taper, heat affected zone, entrance circularity and surface roughness of drilled hole are important attributes which influence the quality of a drilled hole in laser drilling. This paper examines the effect of laser parameters on the quality of drilled holes in Silicon carbide ceramics which are used in microelectronic devices, based on the orthogonal array experimentation and response surface methodology. Extensive trials were conducted on SiC plates and major factors influencing the particular quality parameter is arrived at. Taper is significantly influenced by laser power and assist gas pressure. Heat affected zone is influenced by laser power. Entrance circularity is significantly influenced by laser power and assists gas pressure. Surface roughness is influenced by laser power. The objective of this paper is to optimize various factors influencing the quality of micro drills using Analysis of variance (ANOVA) method. Multi objective optimization achieved using response surface model indicated that, all the four quality parameters are optimized at 200W laser power, 5000Hz frequency and 5 bar assist gas pressure. Keywords: Laser drilling, Silicon carbide, Response surface methodology.

1. Introduction Development in laser technology has led the usage of laser in many industrial processes such as drilling, cutting, micro machining, welding, marking, sintering and surface treatment of different materials. Laser machining is an advanced technique in which the material is removed in three steps namely melting, vaporization, and chemical degradation. The capability of laser to transfer high energy to the focused point for melting of materials has made laser to be used in micro drilling of ceramics and metals [1]. Some of the important applications include drilling of nozzle guide vanes, printed circuit boards and turbine blades [2]. Silicon carbide is a good corrosive resistant, not attacked by any acids or alkalis or molten salts up to 800°C. The high thermal conductivity coupled with low thermal expansion and high strength gives this material exceptional thermal shock resistant qualities. Hence it is used in abrasives, refractories and numerous high-performance applications [3]. CO2-laser is one of the most popular lasers for material processing because they are electrically more efficient, produce higher powers than other lasers in the continuous mode [4]. The qualities of the drilled holes are mainly judged by circularity, taper, HAZ and spatter. Most of the researchers have concentrated on the laser drilling of ceramics, metals and plastics [6]. From the review of literature, it has been found that most of the researchers have concentrated on development of statistical models for taper angle, HAZ and Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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circularity. But, no comprehensive research has been reported on laser micro drilling of silicon carbide ceramic samples using design of experiments approach. Hence, this paper focuses on investigating the influences of laser parameters such as laser power, pulse frequency and assist gas pressure on taper, HAZ and entrance circularity by drilling 3 mm thick silicon carbide ceramic using 12 kW CO2 laser. The laser parameters are co-related with responses using regression models and the optimised parameters were obtained using Response Surface Methodology (RSM). 2. Experimental 12kW Trumph Laser Cell 1005 emitting CO2 laser in continuous mode was used to drill the holes on 3 mm thick SiC ceramic whose properties are presented in the Table 1. The technical specifications of the laser system are as shown in the Table 2. In this study, three controllable factors namely laser power frequency and assist gas pressure were considered to study their influence on Entrance circularity, HAZ and taper. Based on the preliminary experiments, the range of laser power, frequency and assist gas pressure were selected as 200-1000 W, 5000-10000 Hz and 2-5 bars respectively. When laser drilling was attempted on silicon carbide samples, at the laser power lesser than 200 W, through holes were not achieved whereas at the power greater than 1000W, micro cracks were observed leading to failure of the specimens. The frequency and assist gas pressure were accommodated under the maximum range. L9 (33) Orthogonal array layout was selected for the investigation which is shown in the Table 3. Two replicates were used to ensure the repeatability of the responses. The experimental responses are presented in Table 4. Figure.1 shows the SiC specimens used for experimentation. Figure.2-3 shows the HAZ and entrance hole diameter of the drilled holes, which is captured using Vision Measurement Machine (VMM). Table 1: Properties of silicon carbide ceramic used for drilling 3)

Density (g/cm Thermal expansion coefficient (10-6J/°C) Thermal conductivity (W/mK) Young’s modulus (GPa) Poisson’s ratio Heat capacity at constant pressure (J/kg.K)

3.1 4.0 120 410 0.14 750

Table 2: Technical specifications of laser system Machine model Wavelength Frequency Power Working distance Maximum field size

Trumpf Lasercell 1005 CO2 laser 10.6µm 10Hz – 10kHz 1800 W – 12000 W 500 mm 2000 mm X 1500 mm

Beam diameter Mode of operation

0.25 mm Continuous type

Table 3: L9 Orthogonal array experimental layout Expt. No.

Laser power, Lp (W)

Experimental factors Frequency, Fr (Hz)

1 2 3 4 5 6 7 8 9

200 200 200 600 600 600 1000 1000 1000

5000 7500 10000 5000 7500 10000 5000 7500 10000

Assist gas pressure, Agp (bars) 2 3.5 5 3.5 5 2 5 2 3.5

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Proceedings of National Conference on “Recent Trends in Mechanical Engineering” Table4: Experimental responses

Specimen-1

Specimen-2

Figure 1: Laser drilled specimens

Figure 2 (a) : Scheme of HAZ Figure 2(b) : Entrance hole diameter Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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2. Scheme for measuring the responses Vision Measurement Machine (VMM) was used to measure the responses such as entrance diameters, exit diameters and HAZ of the specimen. The hole entrance circularity was determined by using the Eqs. (1) Cent = Dmin/Dmax (1) where Dmin and Dmax are the minimum and maximum diameters of the entrance hole respectively. Entrance, exit and HAZ hole diameter was measured by taking the average value of the minimum and maximum readings of the diameters.

(

) ∗

(2)

Taper was measured using the Eqs.(2) where Dent is the entrance diameter, Dext is the exit diameter and t is the thickness of the specimen. The measured experimental responses are shown in Table 4. The laser parameters were fed to the MINITAB software as inputs to analyze the parameters to obtain nominal circularity, HAZ and minimum taper. Surface roughness was measured using the Mitutoyo surface roughness tester. 3. ANOVA of Experimental Responses ANOVA was performed on the experimental responses as shown in Tables (5)-(8), considering 95% confidence level to assess the significance of the experimental parameters. The assessment was made using F and p distributions. 4. Response Surface Methodology (RSM) models The relationship between the laser drilling parameters and the responses was modelled using RSM. The general first order RSM model used to predict the influence of laser parameters on the response factor is given by Eq. (3). Yi= β0 + β1Xi1 + β2Xi2 +………………….. βj Xij+ ε (i= 1, 2……………N) (3) where yi is the response factor and xij are the values of ith observation and jth level of the drilling parameters. The terms βi are the regression coefficients. For the modeling, the higher order linear effects are considered and the interactive effects are not considered. The Response Surface representing the taper (T) as a function of laser drilling parameters such as laser peak power(P), frequency(Fr) and assist gas pressure (Agp) can be represented by Eq. (4) Taper (T) = β0 + β1(P) + β2(Fr) + β3(Agp)

(4)

Based on the experimental results of laser drilling, the mathematical relationship established for correlating entrance circularity (Cent) and the laser parameters is presented as Eq. (5) Taper (T) = 0.475833 - 0.0001477 P(W) + 1.95751E-005 Fr(Hz) - 0.061935 Agp(bars) (5) R2 value for model was 87.00 %Similarly, RSM models developed for HAZ, entrance circularity and surface roughness are presented as Eqs. (6)–(8) HAZ = 0.500876 + 0.00032225 P(W) - 4.83733E-006 Fr(Hz) -0.0123117 Agp (bars) (6) R2 value for model was 91.96 % Ent cir = 0.925995 - 1.042E-005 P(W) - 6.671E-007Fr(Hz) + 0.0050206 Agp(bars) (7) 2 R value for model was 88.20 % Surface roughness = 4.1434 + 0.001026 P(W) - 1.28E-005Fr(Hz) + 0.1056 Agp (bars) (8) R2 value for model was 91.47 % The adequacy of the model was further analyzed by using R2 values. These values represent the confidence level of regression. The R2 values obtained for the RSM models for all the Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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responses indicated that the experimental and the predicted values were in good agreement. The experimental and predicted responses along with error in the prediction are shown in Table.9. The errors indicated that the RSM models can predict the responses with very good accuracy, in all the cases. Factors Laser Power (W) Frequency (Hz) Assist gas pressure(bars) Error Total

Factors Laser Power (W) Frequency (Hz) Assist gas pressure(bars) Error Total

Table 5: ANOVA table for Taper D.O.F Sum of Mean Fcal squares squares 2 0.0325 0.0162 29.648 2 0.0144 0.0072 13.190 2 0.0519 0.0259 47.333 2 4.98E-06 2.49E-06 8 0.0005 Table 6: ANOVA table for HAZ D.O.F Sum of Mean squares squares 2 0.1067 0.0533 2 0.0009 0.0004 2 0.0035 0.0017 2 0.0002 0.0001 8 0.1115

Ftab

32.518 14.467 51.917

19.51 19.51 19.51

Fcal

Ftab

365.84 3.336 12.163

95.684 0.872 3.181

19.51 19.51 19.51

Table 7: ANOVA table for Entrance circularity Sum of Mean Factors D.O.F Fcal squares squares Laser Power (W) 2 0.0001 6.87E-05 27.593 Frequency (Hz) 2 1.74E-05 8.72E-06 3.500 Assist gas pressure(bars) 2 0.0003 0.000181 72.799 Error 2 4.98E-06 2.49E-06 Total 8 0.0005 Table 8: ANOVA table for Surface roughness D.O.F Sum of Mean Fcal squares squares Laser Power (W) 2 1.0106 0.5053 24.672 Frequency (Hz) 2 0.0629 0.0314 1.536 Assist gas pressure(bars) 2 0.1616 0.0808 3.944 Error 2 0.0409 0.0204 Total 8 1.2761 Factors

Expt. No. 1 2 3 4 5 6 7 8 9

Ftab

26.306 3.336 69.403

19.51 19.51 19.51

Ftab

79.196 4.930 12.662

19.51 19.51 19.51

Table 9: Experimental and predicted values along with % error of the responses. Taper HAZ Entrance circularity Surface roughness Exp Pre Error Exp Pre Error Exp Pre Error Exp Pre Error % % % % 0.381 0.420 10.034 0.540 0.516 4.481 0.930 0.930 0.063 4.554 4.495 1.277 0.362 0.376 3.709 0.500 0.485 2.808 0.940 0.936 0.411 4.663 4.622 0.873 0.307 0.332 7.923 0.476 0.455 4.454 0.943 0.942 0.085 4.645 4.748 2.220 0.310 0.268 13.546 0.561 0.626 11.705 0.934 0.933 0.010 4.891 5.064 3.540 0.269 0.224 16.837 0.568 0.596 4.988 0.934 0.939 0.566 5.422 5.191 4.258 0.524 0.459 12.388 0.596 0.621 4.189 0.920 0.923 0.322 4.793 4.842 1.027 0.105 0.116 10.734 0.771 0.737 4.473 0.938 0.937 0.118 5.58 5.633 0.958 0.334 0.351 5.038 0.790 0.762 3.563 0.920 0.920 0.020 5.356 5.284 1.331 0.259 0.307 18.559 0.728 0.731 0.437 0.929 0.926 0.298 5.37 5.411 0.764

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6. Results and discussion 6.1 Analysis of parametric influences of taper The taper decreases with the increase in laser power and assist gas pressure as reflected in the surface plot as shown in Figure 3. This is mainly because at higher assist gas pressures, the effect of pressure on the hole exit diameter is greater than that on the hole entrance which causes the reduction in hole taper. Also higher peak power produces larger hole exit diameter because after the laser beam breaks through the material the effect of the peak power which results in greater energy pulse, has more effect on the hole exit than the hole entrance[7]. 6.2 Analysis of parametric influences of HAZ The surface plot shown in Figure 4 reflects the increase in HAZ with increase in laser power whereas the assist gas pressure and frequency showed no effect on HAZ. This is mainly because at higher laser power, the amount of heat flux entering the work piece increases thus imparting higher thermal energy to the surface of the workpiece. Due to slower temperature decay caused by lower thermal conductivity of silicon carbide, structural changes takes place thus increasing the extent of HAZ[8]. 6.3 Analysis of parametric influences of entrance circularity The entrance circularity increases with increase in the assist gas pressure and decreases with the increase in the laser power as shown in Figure 5. This is mainly because increase in assist gas pressure instantly ejects the material from the top surface and hence entrance circularity increases. As the laser power increases, high thermal energy causes the material to melt and vaporise resulting in higher disorder thus decreasing the entrance circularity [9]. 6.4 Analysis of parametric influences of Surface roughness The surface roughness increases with increase in the laser power where as the assist gas pressure and frequency has no effect on it as shown in the Figure 6. This is mainly because the peripheral high fluence region continues to interact with the material causing larger material ablation which led to the increase in surface roughness. Therefore lower levels of laser power is preferred to minimise the surface roughness [10].

Figure 3: Response surface plot for Taper

Figure 4: Response surface plot for HAZ

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Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

Figure 5: Response surface plot for Entrance circularity

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Figure 6: Response surface plot for surface roughness

7. Conclusions 12 kW CO2 laser drilling of 3mm thick silicon carbide specimens was carried out to study the effects of laser parameters such as laser power, frequency and assist gas pressure on Taper, HAZ, Entrance circularity and Surface roughness.  Both taper and entrance circularity was influenced by assist gas pressure and power. HAZ and surface roughness was influenced by laser power.  The generated regression models indicated the perfect correlation between laser parameters and experimental responses.  Multi objective optimisation of experimental responses carried out using grey relational analysis suggested that lower laser power, frequency and higher assist gas pressure are required to obtain nominal entrance circularity, minimum taper, HAZ and surface roughness. References [1]. Avanish Kr. Dubey, Vinod Yadava. “Experimental study of Nd:YAG laser beam machining-An overview”. Journal of Materials processing technology 195(2008) 15-26. [2]. S. Bandyopadhyay, J.K. Sarin Sundar, G. Sundararajan, S.V. Joshi. “Geometrical features and metallurgical characteristics of Nd:YAG laser drilled holes in thick IN718 and Ti-6Al-4v sheets”. Journal of materials processing technology 127 (2002) 83-95. [3]. Anoop N. Samant & Claus Daniel & Ron H. Chand &Craig A. Blue & Narendra B. Dahotre. “Computational approach to photonic drilling of silicon carbide”. Int J Adv Manuf Technol (2009) 45:704–713. [4]. Dubey Avanish Kumar, Yadav Vinod. “Laser beam machining-a review”. International Journal of Machine Tools and Manufacture 2008;48(6):609-28. [5]. Yilbas BS. “Parametric study for laser hole drilling of Inconel 617 alloy”. Lasers in engineering 2002;12(1):1-16. [6]. E. Kacar, M. Mutlu, E. Akman, A. Demir, L. Candan,T. Canel, V. Gunay, T. Sınmazcelik. “Characterization of the drilling alumina ceramic using Nd:YAG pulsed laser”. Journal of materials processing technology 209 (2009); pp- 2008–2014. [7]. M. Ghoreishi, D.K.Y. Low, L. Li, “Comparative statistical analysis of hole taper and circularity in laser percussion drilling”. International Journal of Machine Tools & Manufacture 42 (2002); pp-985– 995. [8]. Sanjay Mishra, Vinod Yadava, “Modeling and optimization of laser beam percussion drilling of thin aluminium sheet”. Optics and Laser technology 48(2013) 461-474. [9]. R. Biswas, A.S.Kuar, S.Sarkar, S.Mitra. “A parametric study of pulsed Nd:YAG laser micro-drilling of gamma-titanium aluminide” . Optics & Laser Technology 42 (2010); pp- 23–31. [10]. Dipak K.Das, Tresa M.Pollock. “Femtosecond laser maching of cooling holes in thermal barrier coated CMSX4 superalloy”. Journal of Materials Processing Technology 209 (2009) 5661-5668.

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STUDY ON CUTTING TOOL LIFE B.H.Chandrashekar1, Ashwin C Gowda2, P.A.Udayakumar3 1

Student, 2 Assistant Professor, Dept. of Mechanical Engg, GSS Institute of Technology, Bangalore, 3 Assistant. Professor & HoD, Dept. of Mechanical Engg, GSS Institute of Technology, Bangalore chandrumech@gmail.com

Abstract In the metal removal process, as tool wear increase causes tool failure and contribute to increased machining cost. To reduce the machining cost, improve production rate and to achieve better efficiency it is essential to study the tool failure modes and optimize every possibility. Three major factors that play a significant role in effective tool life are i) Tool material ii) Tool construction iii) Tool geometry and selection of these depend upon the end use requirements. The ultimate failure is understood to have taken place when the tool has worn out and can machine no more and could break under the cutting forces enhanced due to the blunt cutting edge. The gradual wear that leads to this ultimate failure is unavoidable but controllable. On the other hand a tool could fail due to many causes which we would call as premature failure. In this paper, the probable failure modes, reasons for such failures and corrective measures to be undertaken to minimize such failures are discussed. Keywords: Tool wear, tool failure, modes of tool failure, tool failure prediction, cutting tools

1. Introduction Recent developments in technology have put tremendous pressure on manufacturing industries to decrease the cutting cost, increase the quality of machined components. Cutting tools are subjected to wear and fails, we need to consider the optimum utilisation of tool by enhancing the tool life by best practices to reduce the production cost. The following aspects of a cutting tool play significant role in determining the productivity of a machining operation: 1) Tool material 2) Tool construction 3) Tool geometry 2. Cutting tool materials The cutting tool materials that are commonly used are: Plain carbon and low alloy steels High-speed steels Cemented carbides, cermet and coated carbides Ceramics Synthetic diamond (Poly Crystalline Diamond-PCD) and Cubic Boron Nitride (CBN) 2.1 Tool material properties 1) Red hot hardness 2) Toughness 3) Wear resistant 4) Low co-efficient of friction and 5) Good thermal conductivity and specific heat 2.2 Tool material selection Factors to be considered in selection of cutting tool material are a) Heat, pressure, wear, Interrupted cuts. 3. Mechanism of Metal Cutting (Geometry) The Metal Cutting is controlled by three main elements. 1) Rake Angles 2) Lead Angles 3) Clearance Angles Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Rake angle -controls the cutting forces Cutting Forces change approximately 1% per degree of Rake change (mild steel)

Figure 1: Cutting forces acting on positive and negative rake angle.

Lead Angles Increasing the Lead Angle places the forces more into the Radial Plane. The greater the angle, the greater is the rigidity. Lead angle depends on the type of work piece, machine rigidity and fixture rigidity.

Figure 2: Lead angle in turning tool

Figure 3: Clearance angle in turning tool

Clearance angles The clearance is provided to avoid rubbing action between tool and work piece Figure 3 4. Categories of tool failure are Abrasive Wear 1) Flank wear Mechanical Failure 1) Chipping 1a. flank chipping, 1b. Rake face chipping 2) Depth of cut notching and 3) Fracture Heat Failure 1) Built up edge 1a) Rake surface, 1b) Flank surface 2) Thermal cracking, 3) Crater wear and 4) Thermal deformation 4.1 Abrasive wear Abrasive wear occurs as a result of the interaction between the work piece and the cutting edge. This interaction results in the abrading away of relief on the flank of the tool. This loss of relief is referred to as a wear land. It’s influenced by hardness, elastic properties and geometry of the two mating surface. The larger the amount of elastic deformation a surface can sustain, the greater will be its resistance to abrasion. A Brittle material like cast iron causes more of abrasion wear than ductile steel. It must also be noted that any material transferred from one surface to another which is highly strain hardened could add to the abrasive wear. The width of the wear land is determined by the amount of contact between the cutting edge and the work piece. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Figure 4: wear land

Figure 5: Flank wear

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Figure 6: Flank wear and crater wear

Flank wear Flank is the Flat Surface of an insert perpendicular to the rake face. The cutting force normal to the direction of velocity keeps the tool pressed against the wok piece. The friction between clearance face and the machined surface progressively flattens the cutting edge. A flat wear land is produced on the clearance face extending from the cutting edge along the clearance face. As the length of the wear land increases friction and heat generated in cutting increased and leads to further wear. Flank wear is mostly caused by abrasion of the flank (shown in fig 5). Flank wear is the desired tool failure mechanism and it is worsened by higher temperatures (speed) and cutting tool pressure. It is Only failure mechanism that is predictable 4.2 Mechanical failures Main Mechanical Failures are 1) Chipping 2) Notching

3) Fracture

Chipping Tool wear results in the loss of small slivers from the cutting edge of the tool. Chipping is also called frittering. There are two Types of Chipping 1) Flank Chipping 2) Rake Face Chipping Flank chipping or mechanical chipping Mechanical Chipping occurs when small particles of the cutting edge are broken away rather than being abraded away in abrasive wear. This happens when the mechanical load exceeds the strength of the cutting edge. Mechanical chipping is common in operations having variable shock loads, such as interrupted cuts. Chipping causes the cutting edge to be ragged altering both the rake face and flank clearance. This ragged edge is less inefficient, causing forces and temperature to increase, resulting in significantly reduced tool life. Mechanical chipping is often the result of an unstable setup. i.e., a tool holder or boring bar extended to far past the ideal length/diameter ratio, unsupported work pieces etc..,

Figure 7: Rake face and flank face Chipping

Figure 8: Rake Face Chipping due to thermal expansion

Mechanical chipping is best identified by observing the size of the chip on both the rake surface and the flank surface. The forces are normally exerted down onto the rake surface producing a smaller chip on the rake surface and a larger chip on the flank surface Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Rake face chipping due to thermal expansion and radial cutting forces figure 8. Chipping occurs when work pieces/cutting edge interface does not have adequate clearance to facilitate an effective cut. This may be result of misapplication of a cutting tool with inadequate clearance for the work pieces material being cut. Depth of cutting notching

Figure 9: Depth of cut notching

It was described that the hardness of the chip and a thin layer of the machined surface were significantly harder than the bulk material. It may be visualized that in turning, the tool will have its tip in the bulk of the material; but at the distance equaling the depth of cut, the tool will be cutting through some significantly harder material (the work hardened layer) causing a notch to appear on the flank face, called the depth of cut notch. Depending on the shape and geometry of the tool, the notch wear can be highly influential on tool life or be completely insignificant compared with other modes of wear. Effect • Localized failure at the depth of cut line. – Localized Chipping and Localized Cratering • Typical with SS, high temperature alloys & all work-hardening materials • Typical when the work pieces have scale or a hardened surface. Depth-of-cut notching can be minimized by following methods • by CVD coatings with cobalt enriched grades. • Increased lead angle (thins the chip reducing forces) • Use tapered cuts Fracture

Figure 10: Failure due to fracture

Tool fracture occurs when the tool is unable to support the cutting force over the toolchip contact area and results in loss of only a small part of tool. It is called as chipping or breakage. It is common in interrupted cuts and in non-rigid setups. Chipping and breakage can be minimized by using  Tougher cutting tool material: Cobalt enriched grades Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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TiC, & TaC grades Stronger geometry by using negative rake rather and increase tool nose radius Maximize rigidity and reduced metal removal rate

4.3 Heat related failure Below are Heat related Failures occurring in Cutting tool. 1) Built Up Edge 2) Thermal Cracking 3) Cratering 4) Thermal Deformation Built-up edge

Figure 11: Built-up edge

Built-up Edge is also called as Adhesion. This occurs due to welding between the tool and chip (i.e. work material is deposited on the rake and flank face of the tool) at the asperities and the subsequent breakage of the welds. When weld breaks it plucks away material from the tool. We can expect that this wear will be inversely proportional to the hardness of the work material and directly proportional to the normal stress on the sliding surface. It is the product of the localized high temperature and extreme pressure at the tool and chip interface. It depends on the Normal face between the sliding surfaces and the apparent area of contact. It is dependent upon the Relative hardness of the chip and tool. Built-up edge is not stable and will slough off periodically, adhering to the chip or passing through the tool and adhering to the machined surface. Rake Face on Rake face

Figure 12: Built up edge in Rake face

 

Welding of work pieces material to the rake face of the cutting tool Loss of effective geometry causes increases in cutting forces and eventual tool breakage

Minimizing “built up edge” • Using higher cutting speed- At high speeds, that is at high tool-chip interface temperatures, the welds between tool and chip would be predominantly temperature welds. There is insufficient time for pressure welds to occur. Temperature welds Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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being soft will separate easily. No built up edge is formed. However there is small amount of material plucked off from tool surface. PVD coating by using materials like TiC, TiN: TiC and tin have lesser affinity to steel to form built-up edge. Moreover low wettability of these materials by ferrous material reduces built-up edge formation. The edges are uniformly coated hence there is less chance of adherence property Polished edges: Adherence property is weaker at polished surfaces. Using Coolant: Coolant washes away built up material at earlier stages. by using positive rake : Area of contact is minimum. by Minimizing the flank wear

Built up Edge on Flank Face This is normally associated with inadequate clearance angles under the cutting edge. Soft Springy materials tend to “spring-back” after being cut and rub the flank of the tool.

Fig 13 Built up edge in flank face

Thermal-mechanical cracking Thermal cracking This thermal cracking is evenly-spaced cracks perpendicular to the cutting edge  It is commonly observed in milling and interrupted cutting.  Caused by variations in temperature in milling induce cyclic thermal shock as the surface layer of tool repeatedly expands and contracts due to heating and cooling of the edge Minimizing thermal cracking Thermal Cracking can be minimized by following method: • Using tougher, more thermal-shock-resistant tool material • Use a grade with more TaC content and higher cobalt content carbide grade • Avoid coolant if possible or assure a steady supply • By reduced cutting speed. Cratering

Figure 14: Crater wear

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Cratering is tool wear characterized by a concave depression in the rake face of the cutting tool. Cratering is also called crater wear.  Cratering is typical in machining carbon steels at elevated speeds.  This are Caused by extreme heat & pressure of chip and it involves diffusion or dissolution of tool material into the chip Minimizing crater wear  By reduce cutting speed (by reduced spindle speed)  By using higher TiC content grade and lower cobalt grade  By Use of CVD coated grades - Al2O3 & TiC Thermal deformation

Figure 15: Thermal deformation

It is also called as plastic deformation and takes place as a result of combination of high temperature and high pressures on the cutting edge. When the cutting edge loses its hot hardness the forces created by the feed rate cause the cutting edge to deform. The amount of thermal deformation is in direct proportion to the depth of cut and feed rate.  It is typical in machining alloy steels at elevated speeds.  Results in Bulging or blunting of the tool edge. Minimizing thermal deformation  By using higher TiC Content grade and lower cobalt grade  By Using CVD coated grades - Al2O3 & TiC

4.4 Tool life Tool life is defined as the length of time that a cutting tool can function properly before it begins to fail Taylors tool life equation VTn = Ct Where, T is time in minutes, Ct is constant and varies with tool and work material, tool geometry n determines the slope of the tool life curve and depends primarily on the tool material V is cutting speed in m/min

Some of the more common criteria for judging the end point of tool life are Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Width of wear land i.e. occurrence of a certain width of wear land. Depth of crater wear i.e. occurrence of a certain depth of crater wear. Increase of cutting force, or power consumption, by a certain amount. Increase of radial force on the tool by a certain amount. Increase of feed force by a certain amount. Sudden change in finish and dimension of work piece.

5. Conclusion As discussed above higher tool life can be achieved by following below suggestions.  Selecting the machining parameters from manufacturers catalog.  Selecting right tool for right applications from cutting tool manufacturers catalog.  Mechanical failures like chipping can be minimized by using selection of tougher cutting tool material with higher cobalt content and choosing TiC and TaC grades.  Select the positive rake angle for soft materials and negative rake angle for hard materials.  Heat related failures can be minimized by Thermal shock resistant tool materials, tools with higher cobalt content, TaC grade and reduced cutting speed.  Using CVD coated grades with lower cobalt content and higher TaC content can overcome thermal deformation. References [1] Tsao Chung-Chen, Hocheng Hong, “Comparison of the tool life of tungsten carbides coated by multi-layer for End mills using the Taguchi method Journal of Materials Processing Technology 123 (2002) [2] Caldeirani Filho Universidad Federal de Uberlandia. A.E.Diniz, Unicamp, Influence of Cutting Conditions on Tool Life, Tool Wear and Surface Finish in the Face Milling Process, Universidad Estadual de Campinas, 13083-970 Campinas, SP, Brazil, Journal of the Brazilian Society of Mechanical Sciences, J.Braz.Soc. Mech. Sci. Vol.24 no.1 Rio de Janeiro Mar. [3] MC Shaw - Theory of Metal Cutting [4] Catalogs of cutting tool manufacturing industries like Kennametal, Sandvik, Iscar, Guhring, etc. [5] Ashish Bhateja, Jyoti Bhardwaj, Maninder Sing and Sandeep kumar pal, Gulzar institute of Engineering and technology, Punjab, Optimisation of Different performance parameters, International Journal of Engineering and Science (IJES) vol. 2, ISSN: 2319-1813, ISBN 2319-1805

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EXPERIMENTAL INVESTIGATION OF THE SEED METERING MECHANISM OF A LOW COST SEED AND FERTILIZER SOWING MACHINE K.S.Meenalochani1, G.Sudheendra2 1

Assistant Professor, Department of Mechanical Engg, Vemana I.T, Bangalore 2 Professor, BMS College of Engineering, Bangalore meena_sreenivas@yahoo.com

Abstract Planting seeds is an important activity in farming. Machines available for this purpose are expensive which an average landholding Indian farmer cannot afford to buy. So, low cost seed sowing machines are needed in Indian scenario. Metering mechanism is the heart of sowing machine and its function is to distribute seeds uniformly at the desired rates. A simple seed metering mechanism is designed and tested for the concept. The mechanism is simple in construction and thus reduces the total cost of the machine. It has a cam wheel with cam pins which operates a follower. The follower in turn rotates a disc which pulls the seed plate and seeds fall into the delivery tube through the hole in the seed plate. It can be used for different types of seeds by replacing the seed plates with the ones that are designed for the required seed size. The mechanism can also discharge the required fertilizer along with the seeds which is essential for better growth of plants. During backward motion of the machine, the follower slips off the cam pins and the seeds are prevented from dropping into the soil. Since the mechanism involved is simple, it does not require any special skills to operate it. The machine can greatly reduce the farmers’ dependency on laborers. Key words: Seed sowing, metering mechanism, Cam wheel, Follower.

1. Introduction Most of the Indian population lives in its villages and thus the contribution of agriculture to Indian economy becomes very important. Farming work is arduous and physically straining. Seed sowing is the one of the major farming activities, the objective of which is to sow the seeds at the required depth and spacing. 1.1 Traditional sowing method In traditional methods of sowing, a field is initially prepared with a plough to expose and break up the topsoil. This produces a series of linear cuts known as furrows. The field is then seeded by throwing the seeds over the field, a method known as manual broadcasting. Seeds that landed in the furrows had better protection from the elements, and natural erosion or manual raking would preferentially cover them while leaving some exposed. The result was a field planted roughly in rows, but having a large number of plants outside the furrow lanes. There are several downsides to this approach. In manual seeding, it is not possible to achieve uniformity in distribution of seeds. A farmer may sow at desired seed rate but inter-row and intra-row distribution of seeds is likely to be uneven resulting in bunching and gaps in field. It is necessary to sow at high seed rates and bring the plant population to desired level by thinning. Depth of seed placement would also be not uniform. Labour requirement is high because two persons are required for dropping seed and fertilizer. A further important consideration was weed control. Broadcast of seeding results in a Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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random array of growing crops, making it difficult to control weeds using any method other than hand weeding. 1.2 Seed drill There are machines that help to sow new seeds into the ground. A seeding machine removes a layer of the topsoil and mixes that soil with the seeds. It takes the same amount of topsoil off every time, ensuring that all the seeds are planted at the same depth. Uniformity of spacing is also important from the view point of securing effective mechanical harvesting in crops [1]. To achieve optimum yields, an efficient sowing machine should attempt to fulfil these requirements. In addition, saving in cost of operation, time, labour and energy are other advantages to be derived from use of improved machinery for such operations. The main components of a seed drill are seed and fertilizer boxes, metering mechanism, furrow openers, covering devices, frame, ground drive system and controls for variation of seed and fertilizer rates. In operation, the seed drill is dragged forward to allow the coulters or furrow opener to cut open the soil, with a metering mechanism on the hopper periodically allowing a number of seeds to fall into the tubes, and through them into the freshly cut soil. The result is a set of spaced seeding locations, which can then be covered by a built-in rake. The major difference in different designs of seed drills/planters is in type of seed and fertilizer metering mechanism. The cost of the machine available in the market is around Rs35, 000/ 1.2.1 Seed metering devices Metering mechanism is the heart of sowing machine and its function is to distribute seeds uniformly at the desired application rates. A seed drill or planter may be required to drop the seeds at rates varying across wide range. The two main types of seedmetering components are mass flow seed meters and precision seed meters. While both of these release seeds at regular intervals along the row planting process, mass flow meters release a number of seeds at a time while precision seed meters release only one or two seeds per interval[2].

Figure 1: Fluted roller and plate metering mechanisms Fluted roller metering mechanism consists of a roller which has axial or helical flutes machined on it. Rotation of fluted roller in housing, filled with seeds, causes the seeds to flow out from roller housing in a continuous stream. Seed rate is controlled by changing exposed length of fluted roller in contact with seeds. Horizontal, inclined or vertical plate with cell type metering mechanism picks and drops individual seed or a hill of seeds depending on design of cell on the plate. Spacing between seeds/hills is controlled Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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by drive ratio and number of cells on plate. Separate plates are required for sowing different crops. Many machines have been patented in the past few decades for their different mechanisms of sowing the seeds. Machines available in the market and the patented machines are very expensive and many are sophisticated. These machines are meant for large landholding farmers. Most of the Indian farmers cannot afford to buy these machines. So, a simple and low cost machine is the need of time for Indian farmers. This machine should be able to plant the seeds along with fertilizer at the required spacing, which would in turn increase the yield. 2. Description and working principle of the metering mechanism developed The main objective is to select the optimum number of seeds depending upon the type of grain and to sow them at required distance. Fertilizer should also be placed nearer to the seeds sown so that seeds get the required fertilizer for better growth. Before dropping the seeds and fertilizers, a furrow opener makes a groove on the soil. The leveller or closer closes these grooves after seeds and fertilizers are placed. The line diagram of the machine structure and the metering mechanism is shown in the figure 2.The wheels 2 are mounted on the journals of the body 1. A cam wheel 3 is mounted on the axis of the wheel on one of the sides only. The pins are clamped on to the cam wheel by means of screws. So, the number of pins can be changed according to the requirement. As the cam wheel rotates, the pin hit the follower 4 which in turn rotates a pulley 5 which is mounted on the spindle 6.The follower is pulled back to its original position by means of a spring. A stopper prevents the follower from over oscillating. The spindle 6 is mounted on two housings 7 which are clamped on to a platform 8. A disc 9 mounted on the spindle 6 pulls the string14 which operates closing and opening mechanism. The seeds and fertilizers are stored in a box 10 and they fall on the soil through the delivery tube 12.The closer 13 closes the groove made by the furrow opener 11. In the present work, the provision has been made for only one box. However the design is a modular construction and we can mount atleast 3 boxes.

Figure 2: Schematic diagram of the seed metering mechanism Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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1-Body structure; 2-Ground wheel; 3- Cam wheel; 4- follower; 5- pulley; 6- Spindle; 7- Housing ; 8Platform ; 9- Disc ; 10 – Seed & Fertilizer box ; 11- Furrow opener ; 12 – Seed (fertilizer) delivery tube; 13- Leveller; 14- String

2.1 Reverse motion of the machine When the machine has to be moved in the backward direction due to some unavoidable reasons during sowing, the follower smoothly slips off the cam pins and the seeds are prevented from falling into the soil.

Figure 3(a): Follower during the forward motion of the machine

Figure 3(b): Follower during the backward motion of the machine

2.2 Construction of seed plates Figure 3 shows the arrangement of seed & fertilizer box and the seed plates. The construction of plates is in such a way that the seed damage is minimum during metering and the machine can be used for sowing other types of seeds with minimum changes. There are three plates 15, 16 &17. The top plate 15 is welded onto the seed box 10. Bottom plate 17 is clamped on to the top one. In between these two plates, another plate 16 slides against a spring force 18. The seeds and fertilizer get collected in the holes provided in the moving plate from the seed and fertilizer box, through the holes in the top plate. When the string is pulled by the cam action, the plate 16 slides in the groove made in the bottom plate. The collected seeds and fertilizers reach the holes provided in the bottom fixed plate. The delivery tube connected to these holes carries them to the soil [figure 3]. The spring 18 pulls back the plate to its original position.

Figure 3: Seed plates Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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3. Results and Discussion The mechanism was tested with ragi seeds and fertilizer. The seed spacing and the number of seeds dropped for each cam action are found to meet the requirements and are 125mm and 10 to12 seeds respectively. The same mechanism can be used to sow other types of seeds by changing the seed plates and providing the required number of pins on the cam wheel. Cost of the machine is worked out to be Rs 8000/- which is easily affordable by the small landholding farmers. Number of pins required: The linear distance travelled by the wheel for one revolution (D) = π×diameter of the wheel = π×300 = 1000mm Let the required seed spacing = ‘d’ mm ⁄ Then number of pins required = Required seed spacing for ragi seeds = 125mm Number of pins to be fixed for ragi seed = 1000⁄125 = 8 Pins 4. Conclusion The broadcasting method of seed sowing has many disadvantages and the machine developed complements this traditional method. The mechanism involved is simple in construction and it does not need special skills to use the machine. It is manually operated so, fuel or other running costs are saved. The machine is portable due to its compactness and even women folk can operate it with ease. It would greatly reduce the dependence of farmers on labourers. The yield of the crops can be increased enormously as the required seed spacing is maintained throughout the field. The seeds also get the required fertilizer which also plays a part in increasing the productivity. There are possibilities to improve the machine by incorporating few changes. The machine can be powered by a motor. The mechanism can be extended to sow more number of rows at a time.

References [1] Claude Culpin, Farm machinery, Granada publishing Limited, 10th Edition, 1981. [2] Donnell hunt, Farm Power and Machinery Management, 9th Ed., Iowa State University Press, AMES, 1995, 263-269. [3] Nigel Cross, Engineering Design Methods, John Wiley & Sons Ltd,UK,2000 [4] Dieter, Engineering design, McGraw-Hill, 3rd Edition, 2000

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NON DESTRUCTIVE TESTING FOR AEROSPACE APPLICATIONS – AN OVERVIEW Prof. S. Mohan1 1

Professor, Department of Mechanical Engineering, Vemana I T, Bangalore

Abstract Aerospace components and systems are generally designed with low factor of safety as compared to that of components for ground applications. The materials involved are of high strength materials both at room and operating environmental conditions and must be able to withstand and sustain the loads which include fatigue and cyclic loads, vibrations and shock loads etc. Special manufacturing techniques are adopted and the processes involved in realization of these components called for rigorous qualification aspects. The products designed with optimized design protocols, during the process of manufacturing, assembly and testing should have least defects or even zero defects. The operating conditions and environments play a key role in failure propagation during the life cycle of the components/assemblies. While extra care and attention is needed during the realization, special monitoring techniques during the service are required so that defects present if any, do not grow further and lead to a catastrophic failure. In such a scenario, NDT techniques is indispensable part of aerospace certifying process. The various NDT techniques utilized in aerospace systems evaluation are discussed with their associated limitations, applications and advantages. Some of the advanced NDT techniques are also elaborated. Keywords: vibration and shock loads, NDT,

1. Introduction Aerospace vehicles primarily includes all that machines that travels through the air and beyond and include aircrafts, helicopters, rockets, missiles, etc..While the fundamental principle involved in their flight is different for various categories of aerospace vehicles, the principle requirement is light weight and high strength which is common for all categories. In order to achieve the principle and functional requirements all vehicles are designed with low factor of safety compared to their ground equivalent and thereby safety margin is drastically reduced with these systems. In order to meet the flight requirements all the aerospace vehicles should have very optimized designed with very minimal defects or even zero defects. The performance of these systems are very much governed by the operating environment and equally important is the defects present or growing in the system. The design of aerospace systems are adequate and meets the requirements provided the systems are free from defects or in certain cases, the defects are acceptable from design and performance point of view. It is also that discontinuities are always present in any material and aerospace materials are no exception to the same. While extra care and attention is made during the fabrication of aerospace material, it is very obvious that discontinuities do exist but in controlled size, which later on may become harmful to the system. In such a scenario, it is essential to carry out detailed study on the defects present in the material before fabrication, during fabrication and after fabrication. It is much more important that the defects are to be monitored during service frequently to ensure the systems are fit for flight Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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use as and when required. The evaluation of defects present in a system is widely assessed by non-destructive testing and evaluation compared to destructive testing considering the cost of material and value added status of the hardware. It is imperative that the non-destructive testing and evaluation is indispensable part of the aerospace system certifying process. The various non-destructive methods utilized in aerospace system evaluation are discussed to give an insight to the applicability of the process versus improved defect detection activity along with advancement in their respective methods. 2. Visual Testing An important and most insignificant testing method which gives vital information on the surface and sub-surface defects. Several information on the shape and size of the product are derived from this test. Surface deformities, corrosion inspection and mapping are done using this test. In order to carry out the tests, several advanced microscopes which can give 2D information and 3D information are used to access and provide clues for decision making. Microscopes with magnification ranging from 40X to 175X are commonly used for this inspection, while scanning electron microscopes with magnification of 3,00,000X are used for grain level analysis which provide a vital input on the strength of material. Endoscopes are used for internal inspection of engine components, feed systems and inaccessible areas. Fibrescopes are used for inspection of non-rigid portion of the vehicle , while boroscopes are widely used for inspecting the tubes . The latest advancement in the area of visual testing is videoscope , which carries the optic fibre system along with laser measuring system and the display is obtained on the computer display system with provisions of depth and area measurement on the area of inspection. The different systems that are used are given in Figure 1 & 2

Figure 1: Stereo microscope

Figure 2: Videoscope

3. Penetrant testing An important surface defect detection techniques which helps in finding out the surface defects such as tight cracks, pores opened to surface, crevices, grooves, etc…The surface inspection is carried out before fabrication and after finishing the products. Sometimes intermediate inspection are also resorted during fabrication. All types of welds, which are prone for surface discontinuities are subjected to this testing. All machined components are subjected to penetrant testing as the sharp corners and machining stress can generate surface defects on the material surface. Generally Red coloured die based penetrant Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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are used for the inspection, but to improve the sensitivity fluroscence based penetrant are used. To further improve upon the sensitivity UV lamp inspection in a dark background are resorted. Extreme caution is being followed for the selection of penetrant and associated chemicals but advancement in chemical technology helped in overcoming the constraints of using them. A typical fluorescent penetrant inspection system is given in Figure 3.

Figure3: Typical fluorescent penetrant inspection system

4. Radiography Testing Radiography are widely carried out using X-ray and Gamma rays as sources of energy for testing the material. This test generally gives an indication of the volumetric defects inside the raw materials, finished goods and weldments. Interpretation of X-rays carried out on weldments are difficult compared to other articles being inspected. One important method is fine focus x-ray inspection wherein finer defects are inspected, which is not normally seen by regular focus. Fine focus X-rays are the technique for the day for inspecting aerospace components and weldments so that defect detection capability is improved. Added to this digital radiography and flat panel detectors are used in the industry to have better imaging analytical ability. The contrast and definition could be improved with these advanced methods to avoid repeat radiography to achieve better results. Digital radiography has helped to improve the tomography studies so that three dimensional analysis could be carried out and thus helps in fixing the defects in all directions. The digital radiography system is seen in Figure 4.

Figure 4: Digital radiography system

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5. Ultrasonic Testing The mechanical waves generated by the peizo electric crystals are used in this method. With the application of composites in aerospace, ultrasonic testing has acquired significant prominence with the detection of debonding or commonly refered to as delamination a most significant and harmful defect. The technique used is pulse echo whereas in certain cases through transmission techniques are also followed. The pulse echo techniques is useful in fixing the depth of detect, whereas through transmission technique is useful in the mapping the defective location. Conventional welding techniques used in aerospace application such as Tungstun Inert gas welding and special welding process such as electron beam welding are inspected using pulse echo technique with angle beam probes to detect defects oriented in the fusion zone. One of the latest addition to the aerospace welding process is friction stir welding, which is commercially picking up. The nature of the defect associated with this welding process has called for the advanced ultrasonic inspection process such as phased array ultrasonic testing which involves multiple element in a single probe. The firing sequence of the individual elements are electronically controlled to generate in the mechanical waves in the desired fashion so that volume inspection is possible with single scan. There are also Time of Flight Diffraction (TOFD) technique in practice using mechanical waves for sizing the defect.

Figure 5: Conventional UT equipment

Figure 6:Phased Array UT equipment

6. Eddy current Testing This is widely used for inservice inspection of aircrafts, space shuttles and reusable aerospace vehicles. Eddy currents are generated in the material to be inspected, and change in the eddy current parameters due to the presence of the defect are sensed in through the sensing coil , which gives an indication of the presence of defect. While direct visualization of defect is not possible, the defects located shall raise an alarm to the inspector, and the defect portion could be identified. Generally used in tube inspection, rivet hole inspection and other areas not accessible for other methods. The limitation is that the technique shall be used for inspecting surface and sub-surface defects. However this technique is also used for conductivity testing, positive material identification, coating thickness measurements which are all very much essential for aerospace applications. The coils used for this inspection shall be made in any form as suited to our requirement and donot contaminate the area of inspection. Multiple eddy current coils placed in a single probe is being developed for wide area inspection such as aircraft wings, bodies of aircraft, bulkhead areas, etc… Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Figure 7: Eddy current testing

7. Acoustic Emission testing This does not form a part of the non-destructive method but of late this is also considered to be a part of it. Basically mechanical waves in the acoustic range are generated in the material during the growth of defects and this principle is used for this testing. The only method to detect the active defects and growth of defects during the material testing, shall give a meaningful intuition of the defects and shall prevent catastrophic failure of the value added hardware in service. Latest data acquisition system and software shall guide for the operator , provides necessary alarm at the time of failure. This method is generally adopted during the qualification phase of the system development, but are also regularly used for the acceptance testing to avoid losing the value added components. 8. Other methods Holography and shearography are generally used in acceptance of the spacecraft tanks. In these methods, the components are slightly stressed and change in stress fields prior to stress and during stress are studied. This gives an indication of the defects present in the system. Both are optics based methods and gives an true indication of the surface and subsurface defects.Leak testing is another method that is used to detect the leaks in various aerospace systems that contain fluids in ambient or pressurized condition. The most common technique followed is bubble technique for rough inspection and mass spectrometer leak detector is finer detection and quantification of leak. There are several techniques such as vaccum testing, acquarium methods to fix the leakage in the aerospace systems. 8.1 Solid propulsion

The solid propulsion is achieved through solid rocket motors (SRM). The SRM consists of an end inhibited solid propellant grain having a central hollow port, a convergentdivergent type nozzle at one end and an igniter system at other end. [1] A typical solid rocket motor is as shown in figure 1. The SRM are used for the launch and/ boost phase either in the main engine or as strap-on boosters. They are also used for critical tasks such as ignition, spin, separation and assistance (Retro and Ullage rockets). The solid propellant is a homogenous mixture of ammonium per chlorate as oxidizer, aluminum powder as fuel, in polymeric binders such as Hydroxyl Terminated Poly-Butadiene Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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(HTPB), Carboxyl Terminated Poly-Butadiene (CTPB), or Poly-Butadiene Acrylonitrile (PBAN), etc. The propellant slurry as mixed, is cast and cured to solidify in an insulated cylindrical chamber with a central mandrel. After solidification, the mandrel is removed and propellant grain ends are trimmed and inhibited at ends. The igniter is assembled inside the port at head end side and the nozzle at the aft end of SRM. Upon ignition, the ignition system spreads the flame through out the propellant port. The propellant grain, deflagrate uniformly, radial from its port towards its outer diameter at a pre-determined burning rate. The exhaust propels out through nozzle providing necessary thrust to the vehicle. Solid rocket motors of size 40 mm to 2800 mm in diameter and length 150 mm to 17000 mm are used in our programs. Pyrotechnic devices help in starting ignition and also enable destruction of a motor, in case of erratic performance. Typical specific impulse of solid propellant systems is 210 to 230 sec. 8.2 Time of Flight Diffraction (TOFD) ultrasonic technique for solid rocket motor cases

All the butt welds of high pressure vessels manufactured in accordance with ASME Sect. VIII.DIV.2 should be inspected by using RT for quality assurance. But recent ASME Code Case 2235 permits automatic UT in lieu of RT. The new automatic UT technique using TOFD (Time of Flight Diffraction) method can be used for inspection of welds of heavy wall pressure vessels in lieu of RT. Advantages of TOFD technique are as follows. 1. 2. 3. 4. 5.

High Probability of Flaw Detection High Accuracy of Flaw Location Measurement High Accuracy of Flaw Sizing in Length Weld Integrity can be observed in Real Time as probes scan the welds All inspection data can be digitised and stored so that the data can be recalled and processed as and when required again.

The TOFD configuration consists of separate ultrasonic transmitter and receiver as shown in figure. After emission of a compressional wave from a transmitter, the first signal to arrive at the receiver is lateral wave through upper surface. In the absence of defects the second signal to arrive at the receiver is the backwall echo. The diffracted signal generated at the upper tip of a defect will arrive before the signal generated at the lower tip of a defect. With a time of flight of each flight path, the ultrasonic velocity and the spatial relationships of the two probes, location and height of defects can be very accurately calculated.

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Figure 8: TOFD principle and echo patterns of defects

TOFD system consists of computerized UT detector, transmitter, receiver, preamplifier, encoder and cables. TOFD system is small and light and is portable and accessible to inspection position. Typical data presentation is in D-scan which is parallel scanning by placing weld at the center of the two probes. Signals from the upper and lower tips of a defect are displayed on gray scale. Gray scale imaging techniques are applied to the RF (AC) signal phases and enable weld integrity to be observed in real time. The defects are shown like as shell pattern on CRT. A-scan signals are stored in the memory together with location signals. D-scan and length and height of a defect can be accurately measured. D-scan is the most popular scanning procedure for welds See figure. This technique is used for NDE of thick solid rocket motor cases made of Maraging steel.

Figure 9: TOFD System, scanning method and D-scan display

8.3 NDE techniques for Solid Rocket Motors

The solid rocket motors have a solid propellant grain web with a hollow port, bonded to an insulated case, a nozzle and ignition system. The density of propellant is about 1.6 g/cm3. The propellant must be free from cracks, voids, porosity, inhomogeneous mix, etc. The propellant web must be free from defects and its bonding with insulated case must be free from debonds. To ensure this structural integrity, following advanced NDE techniques are used.  High energy X-ray radiography of propellant grains using 15 MeV Linear accelerator and Tangential X ray radiography for checking Propellant to insulation bond integrity.  Modified triangulation techniques tpo characterize the defects in propellant grains Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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 Low frequency Swept frequency ultrasonic inspection, to study bond between case/ insulation/propellant interfaces.  Infrared Thermography to study bonding in SRM nozzles  Microwave testing of propellant grains for study of propellant curing  Acoustic emission testing during proof pressure testing of motor cases.

Figure 10:

Delamination image as in x ray radiograph and after image processing

8.4 Defects in propellant grain

Figure 11: Density ratio method

Solid rocket motor propellant grain defects are detected by normal grain radiography. Note the position of the film. Due to large web thickness triangulation technique needs modification to characterize the defects like porosities and cracks. Above figure illustrates the technique. From tangential radiography of nozzles and some rocket motors, it is possible to identify whether a given caseto insulation interface is just a 'Kissing bond 'or a 'strong real bond' using an advanced quantitative NDE technique called Density ratio method. In this method, ratio between optical density at interface and that at a fixed distance from interface is obtained and compared with calculated value. 8.5 Infrared Thermography

In some of the solid rocket motors, there is need to inspect Kevlar composite case to Rocasin rubber insulation interface to ensure good bonding. Infrared thermography was proved as an excellent NDE tool for this requirement when compared with high-energy and Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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conventional X-ray or Ultrasonic testing In this technique, IR heating is carried out from Rocasin rubber side and transient thermal images are analysed to detect the debonds. 8.6 Neutron Radiography of Pyrotechnic Devices.

Pyrotechnic devices are used in launch vehicles for variety of applications such as ignition, stage separation, stage destruction, closing and opening of valves, deployment of solar panels in satellite, etc. They typically contain explosive charge in metallic casing. The density of charge is very low compared with that of case material. Hence, conventional radiography cannot image the charge well since, the image of the charge is masked by that of the case. Resorting to neutron radiography has solved this problem. Unlike X-rays, neutron attenuation characteristics are related to the nuclei and not to atomic number. Hence some of the low atomic number materials like hydrogen, boron which are abundant in pyro charge, offer more attenuation to neutrons than the metals do. This means we get better image of pyro charges while images of the outer case are masked. A typical 'Through bulkhead initiator is a pyro device to safe guard against inadvertent electrical actuation. In this, detonation shock from a donor charge is transmitted across a metallic bulkhead to the acceptor charge retaining bulkhead integrity. The acceptor charge, which is in contact with detonating charge, actuates the main charge system. A confined explosive stimulus transfer unit normally triggers the donor charge. Neutron radiography is used to ensure presence of charge, absence of pores and proper contacts in the assembly. In accelerator based neutron radiography facility, the gamma content in neutron beam is quite high. Hence in order to get pure neutron images, transfer-imaging technique is used successfully to image various pyrotechnic devices 8.7 Advanced NDE of Spacecraft Propellant Tanks

The propellant tanks are used in spacecraft to store corrosive liquid propellants under pressure and supply gas free propellants to thrusters during its operating life. The tanks are fabricated out of Ti6Al4V material in all welded condition. The welding methods used are electron beam welding, astro arc welding and manual TIG. The propellant tank has a propellant management device (PMD) working on the principle of surface tension, to ensure bubble free propellant under zero "g" environment. Following advanced NDE techniques are adopted.  X ray radiography to detect internal discontinuities like porosity, lack of penetration, lack of fusion etc. Tangential radiography using VIDISCO Flat panel X ray system  Automatic ultrasonic immersion testing as a complementary technique to x-ray for detecting mapping, and characterizing the LOF/LOP. Eddy current inspection to detect cracks in the bolt holes. Acoustic emission testing during proof pressure tests  Holographic inspection of complete tank shell excluding the ports and area covered by the suspension ring. The acceptance criterion is no indication of a disturbed interference pattern when compared with allowable defect size. Synthetic Aperture focusing technique. The Synthetic Aperture Focusing Technique (SAFT) is used to restore ultrasonic images obtained either from B or C scans with focusing distortion. With the use of this technique an improvement of the image resolution can be obtained, without the use of the traditional ultrasonic lenses. It is possible through software algorithm to implement SAFT to work properlyand restore distortions in B scan images., it is necessary to know accurately the Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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path traveled by the ultrasound from the transducer to target and back again. Therefore a geometrical model of ultrasonic signal and its correlation to adjacent scan A lines are used to restore the image. In order to minimize the execution time of this algorithm, the correlation is calculated only between few lines adjacent to the analyzed line, in a correlation window. The results obtained with algorithm implemented in C language, is quick and efficient in improving the lateral resolution to the images submitted to it. 8.8 NDE Techniques in near future

Growth of space technology in future demand accurate, reliable, efficient and faster NDE systems. Following NDE techniques will provide solutions to our future requirements: Expert NDT systems: will help in repetitive activities. They are rule based activities, which removes monotony; are amenable to automation and provides perfect documentation.Computed Tomography system: Tomography gives cross sectional image of the object. While medical tomography systems are in the market, Industrial tomography systems have not yet gained popularity due to the requirement of very high investment. Compton Scatter tomography has unique applications sensitive to material density. This NDE technique help in checking the integrity of hardware and alloy structure in metals which are accessible from one side only. Machine vision equipment: will be used for imaging and carrying out accurate dimensional measurements of components at inaccessible zones. Image analysis, image processing and pattern recognition systems will be highly useful for efficient NDE. Advances in ultrasonic testing specially, low frequency type, Swept frequency type and ultra high frequency type, acoustical microscopy, Synthetic aperture focusing techniques and laser techniques will find their applications. 9. Conclusion Non-destructive methods are widely used in all industries ranging from aerospace to petroleum from the design phase inspection to the inservice inspection. Several post failure analysis are also carried out using the methods described above to fix the probable cause of failure. For reusable aerospace vehicles such as aircrafts, helicopters, there are certain periodic inspections using these methods depending on the service life. All the methods have made certain advancements which are described in brief shall make the inspections more meaningful and interesting in detection of defects. REFERENCES [1] Advances in NDE Science and technologies Ed: Baldev raj 2009 [2] Sutton, G.P., Rocket Propulsion elements, Ed.7 John Wiley, N.Y. 2001 [3] EVS Namboodiry, Proc. Vikram Sarabhai Space Safety Symposium July14-15, 1999 VSSC Thiruvanathapuram pp 49-56. [4] V Gnanagandhi ibid. 1. pp 56-74 [5] V N Misale et al. ISRO-Technical Note 1982. [6] C Subbaiah et al. Neutron Radiography of Pyro devices “NERAG ’94 SHAR Centre, Sriharikota 1994. [7] Aerospace Recommended Practice ARP 1317. Society of Automotive Engineers, Inc. 400 Commonwealth Drive Warrendale PA14096.

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FATIGUE FAILURE PREDICTION AND PREVENTION OF AN ELEVATOR DRIVE SHAFT A.Shiva kumar1, N.G.S.Udupa2, M.L.J.Suman3 1

Student, Dept. of Mechanical Engineering-PG Machine Design, NCET, Bangalore 2 Professor & HoD, Dept. of Mechanical Engineering, NCET, Bangalore 3 Assitant Professor, MME Department, M.S. Ramaiah School of Advance Studies, Bangalore shivakumarannaiappa@gmail.com

Abstract In this paper the failure of an elevator drive shaft is analyzed. The failure in most of the elevator drive shaft occurs at the keyway region. The reason for such a failure in the drive shaft is due to faulty design of the failure prone areas, improper maintenance and fatigue loading. The stress analysis and fatigue life analysis of the shaft is carried out by using Finite Element Method (FEM) using ANSYS software and it is compared with the theoretically calculated values. Also some of the probable methods to prevent such failure are discussed and associated finite element analysis is also carried out. It has been observed that a reasonably closed agreement exist between the values obtained by FEM and theoretical analysis. The fatigue endurance limit and the cycles for the failure are calculated and the new methods of assembly are deployed to enhance the life of shaft Key words: Fatigue, drive shaft, keyway region.

1. Introduction A shaft is a rotating circular member used to transfer the power. It is supported by bearings and supports gear, sprockets, wheels and rotors. Generally transmission shafts are subjected to axial and transverse loads or the combination of both. Generally shafts are not of uniform diameter but are stepped to provide shoulders for locating gears, pulleys and bearings. The stress on the shaft at a particular point varies with rotational speed of shaft, there by introducing fatigue. The first scientific investigation on fatigue failure was by August Wohler on railway axles. Even a perfect component when repeatedly subjected to loads of sufficient magnitude, will eventually propagate a fatigue crack in some highly stressed region, normally at the surface, until final fracture occurs. Extensive work has been carried out by failure analysis research community investigating the nature of fatigue failures using analytical, semi-empirical and experimental methods. [2]. Keyways are the more failure prone regions due to discontinuity in the geometry. Even a small indentation at the keyway of the gear wheel hub leads to crack propagation and finally to failure. Even though the keyways are manufactured as per the design standards the failure may occur due to over loading. [5] Fatigue failure of the shafts at keyway may occur due to improper fillet radius under the torsional – bending loads. [1]. Figure 1 shows an elevator system used in this work. A shrink-fit is a semi-permanent assembly system that can resist the relative movement or transmit torque between two components through the creation of high radial pressures at the interface of its constituent parts. It provides a low cost joining method and is widely used in industry, with applications to cutting tool holders, wheels and bands for railway stock, turbine disks, rotors for electric motors and for locating ball and roller bearings. Shrink-fits are also an effective way of assembling machine elements such as a gear to a shaft to transmit torque. The underlying principle involves establishing a pressure between the inside diameter of the gear hub and the outside diameter of a shaft through interference in dimensions at their radial interface. Commonly, expansion of the external part by heating, or cooling of the shaft is employed, the part located and then the whole assembly returned to operating

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temperature where upon the pressure maintains part location to allow transmission of a torque.

2. Analysis of elevator drive system: The elevator drive system used in this work consists of an electric engine, which produces 6.5 HP, rotating at 1500 rpm and reduction ratio of the worm gear is 28.6.The shaft is assembled to the pulley by key. The four main ropes of the elevator are placed on the pulley and by revolving in both direction of the drive shaft and pulley, the elevator moves up and down. Service speed of the elevator is 0.6 m/s. The shaft is supported in three points in form of journal bearings as shown in figure 2.

Figure 1: Elevator system inside the building

Figure 2: Elevator drive system

2.1 Mechanical and chemical properties of the shaft: Table 2.1 and the table 2.2 show the details of mechanical and chemical properties of the shaft analyzed. [1] Table 2.1 Mechanical properties of the elevator drive shaft (St 52.0)

Yield strength(MPa) 339

Tensile

Rapture elongation

strength(MPa)

(%)

569

Hardness (BHN)

165

Table 2.2 chemical properties of the elevator drive shaft

0.22

0.4

0.012

0.13

0.031

0.29

3. Stress analysis 3.1 Stress analysis of conventionally keyed shaft At the minimum load (weight of the empty cabin (420 kg) and balance weight (580 kg) is considered) the reaction forces causes a bending moment of 437.4 N m at the fracture surface resulting as normal stress value of 20.6 MPa. Shear forces, caused due to the loads of empty cabin, ropes and balance weights, forms a shear stress of 3.5 MPa. By analyzing maximum stress value, balance weight, cabin weight with four persons inside (each person is 80 kg and the total weight of the cabin is 740 kg), torsion moment and impact ratio is considered. In this case bending moment of 571 N m occurs at the fracture surface causing a normal stress value of 27 MPa. Shear stress value, due to shear force, is Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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4.7 MPa. The 6.5 HP electric engine rotates at 1500 rpm, conversion ratio of the worm gear is 28.6 and drive system efficiency (due to worm gear mechanism) is 0.7. Considering these parameters, torsion moment is calculated as 887.7 N m. Total shear stress is calculated under these circumstances as 25.7 MPa. Since the failure of the shaft has occurred at keyway the shear fatigue notch effect ( = 2.64) and bending fatigue notch effect ( = 2.46) and the impact ratio ( ) is obtained by considering the geometry and material of the shaft [5]. Next, the equivalent stresses causing failure of shaft (fig 5) at maximum load is obtained as 162Mpa [1] by ‘‘Shape Deformation Energy Hypothesis” =

. [6]

(1)

3.2 Fatigue life analysis The stress life method is used to calculate the fatigue life of the drive shaft. The SN curve for the shaft material (St 52.0-Steel tube Magvant) is estimated. To draw the S–N curve of the shaft, according to Juvinall and Shigley [8, 9], stress value ( ) where fatigue failure cycle at 10E3 cycles occur, can be calculated as = 0.9*569 =512MPa. (2) Fatigue strength (endurance limit ) of the shaft material was calculated as =0.5*UTS = 0.5*569 = 284MPa. [7] (3) Considering size factor (ka) for 60 mm diameter shaft as ka = 0.77 and surface factor (fine polished) kb= 0.95, the new endurance limit ( is calculated as = 284 *0.77 * 0.95 = 208MPa. [7] (4) Since we have obtained the maximum and minimum stress values the effect of mean stress on the endurance limit cannot be zero. The mean stress is to be estimated considering the change stress value at fracture surface with time which is bit tedious. By our calculations done before we calculated maximum and minimum stress values. Minimum stress value occurred at empty cabin in stationary position with no acceleration, whereas the maximum stress value occurred at acceleration of the elevator and four persons (each person is assumed to be 80 kg) inside the cabin. But in real, number of persons transported inside the cabin is not always the maximum transportation number of person (four). Therefore a ‘‘variable-amplitude stress” occurs at the fracture surface depending on the number of persons inside the cabin as shown in the fig 3, in which the maximum peak indicates the stress value at the fracture surface when the elevator is moving, the minimum peak indicates the stress value at the fracture surface when the elevator is in stationary condition. So to calculate mean stress the variable stress acting must be transformed into constant stress amplitude(fig 4) by assuming that always maximum stress occurs at the fracture surface (always four persons are transported). In this case the average stress value obtained is 108Mpa. Therefore the modified endurance limit ( is calculated by using criterion of Goodman as = 208 *(1- (108/569)) =170.[7] Where,

(5)

is modified endurance limit in MPa

is mean stress in MPa UTS is ultimate tensile strength in Mpa Thus the 1st 2nd points of the S-N curve are obtained and it is plotted as shown in figure 6.

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Figure 3: Variable amplitude load acting on the fracture surface [1]

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Figure 4: Constant amplitude load acting on the fracture surface. [1]

Figure 5: Failed shaft [1]

Figure 6: Estimated stress – cycle curve for a material St52.0

3.3 Finite Element Method The Finite Element Method is carried out to examine the stress distribution in the keyway. In this analysis the shaft is modeled and analyzed by utilizing ANSYS. Figure 7 shows the meshing arrangement of an elevator drive shaft here, the shaft is subjected to both bending and twisting loads. The maximum stress obtained at the high stress concentration region due to its low radius of curvature (keyway region) can be seen from the fig 7. FEM yielded a maximum stress of 161MPa at the keyway region which is in close agreement with theoretically calculated values.

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Maximum stress (161 Mpa) generated in the keyway slot.

Fig 7 Stress contours of a shaft of keyway radius 0.5mm under combined load

4. Failure prevention methods Since the failure of the elevator drive shaft has occurred at the keyway region due to low radius of curvature of the keyway slot the failure can be prevented by eradicating the faulty, design of the keyway. The following methods are adopted to prevent failure are 4.1 Increasing the radius of curvature of keyway In this method the radius of curvature of the keyway slot is increased from 0.5mm to 1, 1.5,2 and3mm, so that the high stress concentration is reduced at the keyway slot. Fig 8 shows the VonMises stresses generated for a drive shaft with a keyway radius of curvature, 2mm from which it is evident that by increasing the radius of curvature the stress concentration is reduced at the keyway slot. 4.2 Adopting shrink fit method Shrink fit is one of the fastening methods of shaft and hub. In this work the elevator driveshaft and the pulley is assembled by shrink fit method in which the geometrical discontinuity in the shaft and pulley is eradicated (keyway is eliminated). Here, a shrink allowance is one of the important parameter which has to be taken care to obtain a proper shrink fit joint without slip of shaft and pulley. The contact stresses generated in the interface of shaft and pulley acts as the holding aid of the shaft and pulley, which varies with the shrink allowance and the geometrical dimensions of shaft and hub. The contact pressure is calculated as P= - ) ]/2 ( )[3] Where, P is contact pressure (Mpa) is outer diameter of the internal cylinder (mm), is Inner diameter of the internal cylinder (mm), is outer diameter of the external cylinder (mm), is shrink allowance in µm, =is young’s modulus in Mpa. By using the contact pressure generated the circumferential stresses and the tangential stresses generated acting on the shaft and pulley is obtained as, circumferential stress induced on pulley: = [(p / ( - )]/ (1+ ),[3] where, is circumferential stress in Mpa, P is contact pressure in Mpa, a= inner diameter of inner cylinder in mm, c = external radius of inner cylinder, b = outer radius of outer cylinder. Tangential stress induced on pulley: = [(p / ( - )]/ (1- ), where, is tangential stress in Mpa.

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Circumferential and tangential stress induced on shaft:

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= -P. next, VonMises

stresses acting on the shaft and pulley is calculated as where, is the VonMises stresses generated, is the radial stresses (Mpa), is the circumferential stress (Mpa).[3] Thus the stresses generated in the interface of the shaft and pulley is obtained which has to be overcome by the load acting on the shaft to cause failure.

Figure 9: Contact stresses induced between the interface of shaft and the pulley for an interference of 50µm under no load condition

Figure 8: Vonmises stresses generated in the keyway for a radius of curvature of 2 mm

4.3 FE analysis of shrink fitted shaft and pulley The FE analysis of the shrink fitted shaft and pulley is carried out for a shrink allowance of 50, 75,100 and 125µm. The load acting on the shaft is increased to 10, 15 and 20 times the maximum load (total weight of 740 kg) acting on conventionally keyed shaft to study the load bearing capability of the shrink fitted shaft. The contact stress induced in the interface of the shaft and pulley for an interference of 50µm under no load condition is shown in the figure 4.2, CONTAC 174 and TARGE 170 elements are used to carry out the contact analysis, from the figure 9 it is evident that the contact stresses generated is maximum at the interface of shaft and pulley and the stresses reduces as it moves away from the interface. Figure 10 shows the stress contours of the shrink fitted shaft and pulley for an interference of 50 µm subjected to maximum load (total weight of 740 kg).

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Figure 10: Stress contours of a shrink fitted shaft for an interference of 50µm under combined load

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Figure 11: Effect of radius of curvature

5. Results and Discussions By increasing radius of curvature of the keyway slot, high stress concentration in the keyway is reduced. Figure 11 shows the effect of radius of curvature on the stress distribution in the keyway slot, it is observed that when the radius of curvature is increased from 0.5mm to 1, 1.5, and 2 mm the stress reduces gradually and becomes constant for the further increase in radius of curvature. Figure 12 shows the comparison of the contact stresses generated by theoretical method (Lame’s equation) and FE method, for an interference of 50, 75,100 and 125µm from which we can observe that the stresses values obtained by both the methods are in close agreement with minimum deviation. From Figure 13 it evident that for a maximum load(740kg) the stresses generated in the shrink fitted shaft is low compared to the stresses generated than the conventionally keyed shaft, since the maximum load(740kg) does not able to overcome the contact stresses induced between the shaft and pulley interface .

Figure 12: Comparison of the stress variation for an increasing interference

Figure 13: Stresses reduced for an increasing interference.

6. Conclusions Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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The faulty design of the keyway is the reason for the high stress concentration at the slot which leads to failure of the shaft. By increasing the radius of curvature of the keyway from 0.5mm to 1, 1.5,2 and 3mm, the sharp corners in the keyway is avoided. Hence, the stresses induced in the keyway are reduced and finally failure of shaft is prevented. By adopting the shrink fit method the dis-continuity in the geometry (in shaft and pulley) is eradicated. Hence, the stresses induced in the interface of shaft and pulley must be overcome by the load acting on the shaft to cause failure. The load bearing capacity of the shrink fitted shaft is 10 times greater than the load bearing capacity of conventionally keyed shaft. (Figure 13). References [1] A.Goksenli, I.B. Eryurek “Failure analysis of an elevator drive shaft”. Engineering failure analysis, Vol.16, 2009, PP 1011-1019 [2] Deepan Marudachalam M.G, K.Kanthavel, R.Krishnaraj ‘‘Optimization of shaft design under fatigue loading using Goodman method’’ International Journal of Scientific & Engineering Research Volume 2, Issue 8, 2011, PP 75-80 [3] Bahattin Kanber ‘‘Boundary Element Analysis of Interference Fits’’ Turkish J. Eng. Env. Sci. Vol 30, 2006, PP 323-330 [4] Borut Zorc, Ale’s Nagode, Borut Kosec, Ladislav Kosec ‘‘Elevator chain wheel shaft break analysis’’ Engineering failure analysis, 2013. [5] Frost NE, Marsh KJ, Pook LP. Metal fatigue, New York: Dover Publisher; 1999. [6] John C. Strength of materials and structures. New York: Arnold Publisher; 1999. [7] Buch A. Fatigue data handbook. Trans Tech, Publisher, 1998. [8] Juyinall RC, Marshek KM. Fundamentals of machine component design. 2nd ed. New York: Wiley and Sons; 1991. [9] Shigley JE, Mischke CR. Mechanical engineering design. 5th ed. New York: McGraw-Hill; 1989. [10] A.H.V. Pavan K.S.N. Vikrant M. Swamy G. Jayaraman, Root cause analysis of bowl-mill, pinion shaft failures. Engineering failure analysis, 2013.

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ANALYSIS OF FUEL ACCESS CUTOUT IN THE WING STRUCTURE FOR FATIGUE LIFE ESTIMATION AND DAMAGE TOLERANCE EVALUATION Venkanna.Balulad1, S.Sourabha Havaldar2, P.K.Dash3 1

Student, Dept. of Mechanical Engineering-PG Machine Design, RVCE Bangalore 2 Assistant Professor, Dept. of Mechanical Engineering-PG, RVCE Bangalore 3 Chairman, Bangalore Aircraft Industries Limited, R.T.Nagar, Bangalore vsbalulad.bec@gmail.com

Abstract A stiffened panel consisting of a fuel access cutout and stiffening members is considered for analysis. Fatigue cracks get initiated from high tensile stress locations. Wing bottom skin experiences tensile stress field during flight. Cutouts required for fuel access and landing gear opening and retraction in the bottom skin introduces stress concentration. Stress analysis is carried out to identify the maximum tensile stress location in the panel. In a metallic structure, fatigue manifests itself in the form of a crack which propagates. If the crack in a critical location goes unnoticed it could lead to a catastrophic failure of the airframe. Stress intensity factor calculations are carried out for crack initiation with incremental crack lengths using Modified Virtual Crack Closure Integral (MVCCI) method. Analytical evaluation of the crack arrest capability of the stiffening members ahead of the crack tip is carried out. Damage tolerance capability of the stiffened panel has been demonstrated using residual strength diagram for the panel. Keywords: Transport aircraft, Stress analysis, Fatigue crack, Tensile stress, Airworthiness, Catastrophic failure, crack arrest, damage tolerance.

1. Introduction Airframe is the basic structure of the aircraft which carries the load. Aircraft is symbol of a high performance mechanical structure, which has the ability to fly with a very high structural safety record. Aircraft experiences variable loading in service. Rarely an aircraft will fail due to a static overload during its service life. For the continued airworthiness of an aircraft during its entire economic service life, fatigue and damage tolerance design, analysis, testing and service experience correlation play a pivotal role. As a part of this exercise, various structural features are being evaluated for damage tolerance qualities. The first phase of damage evaluation of an integrally stiffened panel with two large cut outs of the wing bottom skin is described here. Figure 1 shows the drafting of panel. It has variable thickness built in on the inside so that the outer surface remains smooth from aerodynamic point of consideration. The edges of the large cutouts are thickened and auxiliary holes are provided all around the cutouts to fasten cover plates. These auxiliary holes are fatigue critical locations in the panel. This analysis does not include the cover plate in position. 2. Literature Review Boris G. Nesterenko [1], explains the results of the research on some actual problems on ensuring damage tolerance of the airplanes. He considered the fatigue crack growth under random spectra in his first problem. The experimental study of fatigue crack growth in specimens was conducted at a regular and random spectrum of loading. Generalized Wallenberg model was used for the calculations of crack growth under the spectrum of transport airplane wing loading. He considered the residual strength of the Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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stiffened structure such as skin with stringers in his second problem. An effective engineering method using the R- curve of the material was proposed for analysis of the residual strength. In that case the experimental investigation was conducted on the Rcurve of the material of a passenger airplane fuselage skin. The results of the analysis were compared to the experimental results, published in the literature. Also the experimental research of the residual strength in case of multiple site fatigue damages was carried out and the residual strength criterion in such case was proposed. Grigory I. Nesterenko [2], explains the test analytical results of investigating into the fail-safety, fatigue and damage tolerance of Russian aircraft. Stresses in wide body aircraft structures are given. Fatigue life curves generated for wing and fuselage structures. Residual strength data are presented for these structures having a skin crack under the broken stiffener. Generalized curves for skin crack duration under the broken stiffener are presented. And the values of tolerable stresses in the wing and fuselage structures of aircraft are determined. The residual strengths for the wing and fuselage structures with two-bay skin crack under the broken stiffener are outlined to estimate fail-safe parameters of these airplane structures. The generalized average curves of skin crack growth duration from visually detectable till tolerable lengths under broken stiffener are plotted for damage tolerance estimation. Rama Chandra Murthy [3], presents the methodologies for damage tolerant evaluation of stiffened panels under fatigue loading. The two major objectives of damage tolerant evaluation, namely, the remaining life prediction and residual strength evaluation of stiffened panels have been discussed. Eccentric and concentric stiffeners have been considered. Stress intensity factor (SIF) for a stiffened panel has been computed by using parametric equations of numerically integrated modified virtual crack closure integral technique. The percentage increase in life is relatively less in the case of eccentric stiffener compared to that of concentric stiffener case for the same stiffener size and moment of inertia. From the studies, it has also been observed that the predicted residual strength using remaining life approach is lower compared to other methods, namely, plastic collapse condition and fracture toughness criterion and hence remaining life approach will govern the design. It is noted that residual strength increases with the increase of stiffener size. 3. Load on Aircraft Wing Box The all-up weight of the aircraft (12-seater) is 5000 kg. Design load factor considered = 3, Total load acting on the aircraft = 5000×3= 15,000 kg-f Factor of safety considered = 1.5, the design load = 15,000×1.5 = 22,500 kg-f Lift load on the wing = 80% of total load= 0.8×22,500 = 18,000 kg-f Load acting on each wing = .5×18,000= 9,000 kg-f, Total span of the wing = 5500 mm Resultant load is acting at a distance of 2200 mm from the root of the wing The wing box considered is 1800 mm away from the root of the wing Bending moment at the section A-A = 9,000×400= 3600×10³ kg-mm Load to be applied at the edge of the box= (3600×10³ / 1510) = 2384 kg-f

4. Geometrical Configuration of the Wing Box Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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A stiffened panel consisting of a fuel access cutout and stiffening members is considered for the analysis.

Figure 1: Detailed Drafting of the model

Figure 2: Model representing fuel access cutout

Figure 3: Model representing bottom skin

Figure 4: Model representing the assembly of bottom skin, cutout, ribs, spars, top skin

5. Methodology The Finite Element Analysis mainly includes three parts 1.Pre-Processing 2.Processing and 3.Post-Processing. The pre-processing stage involves the preparation of nodal co-ordinates & its connectivity, meshing the model, load & boundary conditions and material information for finite element models carried in MSC PATRAN. The processing stage involves stiffness generation, modification and solution of equations resulting in the evaluation of nodal variables, run in MSC NASTRAN. The post-processing stage deals with the presentation of results, typically the deformed configurations, elemental stresses and forces etc. Two important features of the FEM are 1. Piece-wise approximation of physical fields on finite elements provides good precision even with simple approximating functions (increasing the number of elements we can achieve any precision). 2. Locality of approximation leads to sparse equation systems for a discretized problem. This helps to solve problems with very large number of nodal unknowns. 6. Materials used for the Analysis Relevant material properties for fatigue and damage tolerance are fairly well documented in the literature. The key material properties that are pertinent to maintenance cost and structural performance are Density, Young’s modulus, Ultimate and Yield strengths, Fatigue strength etc. Mechanical properties of the skin, stiffening members and rivets are required for finite element models. Aluminum 2024-T351 is used as a material for wing box.

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Table 1: Properties of AL-2024T351 Properties

Value

Poisons ratio

0.3

Yield strength

360 MPa

Density

27.21 N /mm3

Ultimate strength

483 MPa

Young’s modulus

70000 MPa

ultimate strength

483 MPa

The Al 2024-T351 is an aluminum alloy with copper as the primary alloying element 2024 aluminum alloys composition roughly includes 4.3-4.5 % of Copper, 0.5-0.6 % of Manganese, 1.3-1.5% of Magnesium and less than half a percentage of Silicon, Zinc, Nickel, Chromium, Lead and Bismuth.. It is used in applications requiring high strength to weight ratio, as well as good fatigue resistance. It has an average machinability. Due to poor corrosion resistance, it is often clad with aluminum or Al-Zn for protection; this may reduce the fatigue strength. 7. Results and Discussions Finite element modeling of the structure which consists of Skin, cutout, ribs, and spars is as shown in the fig. which mainly includes QUAD and TRIA elements meshing for skin cutout, spars, ribs. A typical load of 2384 kg-f (Loading Condition) is applied at the tip of the wing box which is 2580mm from the root of an wing box. The bending stresses are developed in the wing box structure. As a result of which the maximum tensile stress acting on the wing box will be 30.5 kg/mm2 (FEA) which will be acting at the rivet hole location of fuel access cutout provided in the wing box.

Figure 5: Finite Element Model and load acting on the structure.

Figure 6: Maximum stress location in structure

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Figure 7: Maximum stress observed at the cutout

7.1 Damage tolerance evaluation It is expected that fatigue crack[4] will initiate at an auxiliary hole where the tensile stress is maximum. This location is indicated in figure. The fatigue crack will initiate at point of maximum stress and propagate to the cutout free surface. As the crack propagates, the stress at the opposite end of the hole increases. A fatigue crack will initiate that point and propagate towards the integral stiffener. The objective of this phase of study is to assess the crack arrest capability of the integral stiffener when the ligament from the hole to the cutout free surface is broken and the crack from the other end of the hole propagates towards the stiffener. It is further assumed that another symmetrical crack is not present at the other side of the cutout. Figure shows the local finite element model of a narrow strip encompassing the crack path. The boundary displacements for this strip are obtained from the previous ‘global model’ of the panel and the loading fixture. The strip is analyzed under this imposed boundary displacements. Crack lengths from the hole towards the stringer are modeled for the estimation of the stress intensity factor by separating elements at the nodal points along the crack line. Figure shows the stress intensity factor variation with crack length for a remotely applied load. Under the integral stiffener, it is assumed that the crack is propagating in the skin and the remaining depth of the stiffener is uncracked. It can be seen from this figure that ‘K’ increases with crack length up to a certain point and then begins to drop as more and more skin loads get pumped into the stringer. As expected, ‘K’ reaches a minimum value just after the stringer location and then begins to increase again with crack length. A simplified edge crack ‘K’ expression comparison is also shown in this figure. This compares reasonably well with the FEA. K-expression till the influence of the stiffener begins to dominate [5]. The corresponding residual strength of the skin is shown in the figure. This exhibits the typical stiffened panel response. Point 1 in this figure indicates the residual strength of the panel. If the stringer remains intact when the crack tip reaches it, then the stiffener can arrest the crack up to a design limit load stress of 30.5 kg/mm2. In our continuing investigation, this theoretical estimation is planned to be assessed through fatigue crack growth and residual strength tests.

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8. Conclusions 1. The static stress analysis of an integrally stiffened panel has been validated by MVCCI method by taking a simple problem of plate with a crack. Qualitatively, the stress and deformation patterns have been captured in the FEA. Small load line eccentricities have dominant on the out of the plane deformation of the panel. This has been accounted for through a nonlinear analysis. The location of maximum tensile stress and its magnitude have been obtained. 2. The stress intensity factor variation of a crack emanating from the maximum stress auxiliary hole has been obtained analytically. 3. The residual strength of the panel and the crack arrest capability of the integral stiffener have been analytically evaluated. References [1] Boris G. Nesterenko, “Analytically experimental study of damage tolerance of aircraft structures”, Moscow Institute of Physics and Technology (State University), Department of Aerodynamics and Flight Engineering, Russia, 2002. [2] G.I. Nesterenko and B.G. Nesterenko, “Ensuring Structural Damage Tolerance of Russian Aircraft” International Journal of Fatigue 31, 1054–1061, 2009. [3] Rama Chandra Murthy, G S Palani and Nagesh R Iyer “Damage tolerant evaluation of cracked stiffened panels under fatigue loading”. Sadhana Vol. 37, Part 1, pp. 171–186._c February 2012. [4] . S. M. Beden et al “Review of Fatigue Crack Propagation Models for Metallic Components” European Journal of Scientific Research, ISSN 1450-216X Vol.28 No.3 (2009), pp.364-397. [5] Jarkko Tikka and Patria, “Fatigue life evaluation of critical locations in aircraft structures using virtual fatigue test”, 2002.

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LINEAR STATIC ANALYSIS OF THE WING BOX AND EVALUATION OF TOP SKIN PANELS FOR BUCKLING LOAD CARRYING CAPABILITY Veeresh Gachchinamath1, N.G.S.Udupa2, K.E.Girish3 1

Student, Dept. of Mechanical Engineering-PG Machine Design, NCET, Bangalore 2 Professor & HoD, Dept. of Mechanical Engineering-PG, NCET, Bangalore 3 Director, Bangalore Aircraft Industries Limited, R. T. Nagar, Bangalore v_gmath@yahoo.com

Abstract An aircraft is a complex structure with flying capability. Major components of an aircraft such as wing, fuselage and tail surfaces are of semi-monocoque construction. A thin skin which is seen from outside is reinforced by stiffeners in two orthogonal directions which carries the major distributed load on the aircraft. Under the action of flight loads the airframe is subjected to bending, torsional and shear loads. In the aircraft wing the top cover is subjected to axial compressive stress due to bending and shear stresses due to shear force and torsional moment. The principal failure mode of the wing is buckling under static loading. The wing skin panels between ribs and stringers starts buckling under small bending loads which eventually leads to failure of the wing as the applied bending moment reaches the design ultimate value. Current study is on a wing with two spars and multiple ribs. The present study investigates a simple box-beam wing structure subjected to bending loads. A buckling analysis of the wing top skin panels has been carried out under the action of axial compression. An appropriate interaction equation is employed to estimate the margin of safety against buckling. A finite element analysis is carried out using MSC NASTRAN/PATRAN to study the same problem and validate using theoretical calculations. Keywords: Wing, Semi-monocoque construction, stiffeners, Flight loads, Bending stress, Shear stress, Ribs, Stringers and Buckling.

1. Introduction Modern aircraft wings are thin-walled structures composed of ribs, spars and stiffened panels, where the top skin is subject to compressive forces in flight that can cause buckling instability. For civil aircraft, the top skin is, under aerodynamic loading, subject to axial compressive forces that can cause buckling instability. Typically these stiffened panels can have a considerable post buckling reserve of strength, enabling them to remain in stable equilibrium under loads in excess of their critical buckling load, provided the initial buckling mode is a local one. Aircraft wing components and fuselage components are joined, in metallic structure, by means of riveting (and more recently welding) to form complete wing and fuselage structure. For stiffened panel construction components can be machined integrally. Single piece stiffened panels have several potential advantages that include cost savings through reductions in assembly, labour, tooling, part count and manufacturing time. An aircraft wing-box is composed mainly of skin-stringer panels, spars, spar caps and wing ribs. The design of skin-stringer panels forms an important and major portion of the wing-box design. Depending on their location, stiffened panels are mainly loaded in compression and in tension. Upper panels are subjected to compressive load while Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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the lower panels are subjected to tensile load.The Finite Element method synthesizes complicated structural systems as a connected collection of objects, called finite elements that embody local physical laws. The use of finite element analysis have made its way to a stage where they are widely used in various engineering applications and are improving steadily over the past decade. Engineers are able to predict the behavior of these elements as it would be in the form of mathematical models which will then be solved, resulting in a set of linear algebraic equations. There are many references that can be found to better understand the concept of using finite element as an analysis tool [2]. It is a form of numerical analysis which can be used for stress prediction and structural optimization. The objectives of the present study are, to investigate an aircraft wing box-beam structure subjected to bending loads using wing with two spars and multiple ribs, buckling analysis of the wing top skin panels under the action of axial compression and employing an appropriate interaction equation to estimate the margin of safety against buckling 2. Geometrical Configuration

Figure 1: Wing box dimensions

Figure 2: Alignment of ribs in wing box and dimensions of one rib

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Figure 3: Dimensions of stringers

Figure 4: Complete solid model of wing box

Figure 5: Complete wire frame model of wing ` box

The wing box consists of five ribs, three Z-sections and two L-sections stiffeners, two C-section spars, top and bottom skin, all connected together as an integrated model. The geometric dimensions of the parts are shown in the figures1 to 3. A three dimensional view of the wing box is shown in the figure 4. The wing box considered for the study is shown in figure 5. 3. Material Specification Selection of aircraft materials depends on any considerations, which can in general be categorized as cost and structural performance. Cost includes initial material cost, manufacturing cost and maintenance cost. The key material properties that are pertinent to maintenance cost and structural performance are  Density (weight)  Stiffness (elastic modulus)  Strength (ultimate and yield strengths)  Durability (fatigue)  Damage tolerance (facture toughness and crack growth)  Corrosion A single material is used with desired properties in all components of the aircraft structure for analysis. 3.1 Aluminum Alloy – 2024-T351 The material considered for the wing box structure is aluminum alloy-2024T351, having the following properties: 1) Elastic Modulus, E=70000N/mm2 2) Poisson’s Ratio, =0.3 Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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3) Yield strength, σu=280 N/mm2 4) Ultimate strength, σu=470 N/mm2 5) Elongation, =19% 4. Loads on the Wing Box Structure Most of the wings buckling loads are carried by the spars in the wing structure. The maximum bending moment occurs at the root of the spar where wing and fuselage components will be attached to each other. The load calculation for the wing box section is described in the next section. 4.1 Load Calculation for the Wing Box  Weight of the aircraft considered = 34335N  Design load factor = 3’g’  Factor of safety considered in design of aircraft = 1.5  Therefore Total design load on the aircraft = 154507.5N  Total lift load on the aircraft is distributed as 80% and 20% on wing and fuselage respectively.  Total load action on the wings = 123606N  The load acting on each wing = 61803N  The resultant load is acting at a distance 1150mm form the wing root  The bending moment about a section at the root = 71.07345 x 10 6N-mm  The load required at the tip of the wing box to simulate the same bending moment at the root of the wing is 71.07345 x 10 6/1100 = 64608.66N  This 64608.66N of load is converted into uniformly distributed load (UDL) and applied at the tip of the wing box. 5. Finite Element Analysis 5.1 Introduction to FEA Approach The Finite Element Method (FEM) is a numerical technique for solving problems which are described by partial differential equations or can be formulated as functional minimization. A domain of interest is represented as an assembly of finite elements. Approximating functions in finite elements are determined in terms of nodal values of a physical field which is sought. A continuous physical problem is transformed into a discretised finite element problem with unknown nodal values. For a linear problem, a system of linear algebraic equations should be solved. Values inside finite elements can be recovered using nodal values.The software used for the analysis of the wing box is MSC PATRAN & MSC NASTRAN. 6. Finite Element Model of the Wing Box All the dimensions of the complete assembly of the structure are as per the description provided in the previous section in the problem definition chapter. A finite element model is the complete idealization of the entire structural problem including the node location, the element, physical and material properties, loads and boundary conditions. The purpose the finite element model is to make a model that behaves mathematically as being modeled and creates appropriate input files for the different finite element solvers. Finite element model of the wing box is as shown in Figure7. Meshing is carried out by using CQUAD4 and CTRIA3 shell elements. Triangular elements are used for the transition between the coarser mesh to finer mesh. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Fine meshing is carried out at the locations where there is stress concentration. Coarser meshing is carried out at rest of the regions in the structure. At three locations of the rib webs are simulated by using beam elements to arrest buckling.Verification for the boundary, duplicates is carried out. Normal for each element is assigned. The material properties are assigned to every element in the model. 6.1 Finite Element Model Details Table 1: Details of FEM

Type of Finite Element

No. of Elements

CQUAD4 26312 CTRIA3 113 BAR 277 6.2 Different Structural Members of the Wing Box and Boundary Conditions  Top and Bottom plate/skin.  Ribs  Stringers/stiffeners  Spars The corresponding mesh generated for each of the above mentioned members are shown in the figure below

Figure 7: View of Meshed Model

Figure 8: Region of application of Loads and Boundary conditions

The loads and boundary conditions along with the finite element model are shown in the figure 8. A load of 6586kg is introduced at one end of the wing box. This load will essentially create the required bending moment at the fixed end. The larger side of wing box is constrained with all six degrees of freedom at larger portion of skin, spar and stringer region as shown in figure 8. 7. Finite Element Modeling and Stress Analysis in Wing Box 7.1 Linear Stress Analysis of the Wing Box: The average stress by FEM is obtained by averaging two rows of elements at the edge of the panel. The analytical calculation is carried out as follows:  Bending Moment is calculated as the product of calculated load and the distance at critical section.  Compressive load is calculated with the help of Bending Moment by considering the ratio of Moment and the Depth at the critical section of the top plate.  Theoretical average stress is obtained by taking the ratio of compressive load and the cross sectional area at critical section of the top plate considered. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Table 2: Comparative results of average stress between Analytical method and FEM

Average Stress by Analytical method 4.5 kg/mm2

Figure 9: FEM Results for Linear static analysis of wing box of wing box

Average Stress by FEM 3.721 kg/mm2

Figure 10: FEM Results for Linear static analysis showing region of max stress

7.2 Buckling Analysis of the Wing Box Buckling is observed due to the applied load. Hence to avoid the failure of the wing due to buckling three stiffeners for each web portion of the ribs is added. Sixteen panels of the top plate of the wing box are evaluated for failure due to buckling. The investigation shows no buckling after the addition of the stiffeners at the rib webs. The analytical buckling factor is calculated for each of the top plate panels for comparison with the FEM results obtained as follows: 1) Elastic buckling strength of each the panels in compression is evaluated by using the equation: σcr = π2 x Kc x E x [t/b]2 12[1-(γe) 2] (1) Where, σcr = Buckling strength Kc = Buckling coefficient which depends of edge conditions and sheet aspect ratio (a/b), where, a =long dimension of plate or unloaded side. E= Modulus of Elasticity γe = Elastic Poisson’s ratio t = Sheet thickness b = Short dimension of plate of loaded edge. 2) Crippling load is calculated as: Pcr = σcr x Area (2) Where, Pcr = Crippling load 3) Buckling factor is calculated as: Buckling = Pcrippling/ Papplied (3) Where, Papplied =Applied load

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Figure 11: FEM Results for buckling analysis of wing box showing region of max buckling

8. Results and Discussion Table 3: Comparative results of buckling factor between analytical method and FEM Panel

Average Stress (N/mm²)

a/b ratio

Buckling coeff

Buckling strength (N/mm²)

Crippling load (N)

30.5375

199.6225 6094.46

1.41

4.2

255.521

51008.66

8.36

8.9

14.3824

199.6225 2870.99

1.41

4.3

261.53

52223.1426

18.18

18.9

12.3743

199.6225 2470.25

1.41

4.3

261.53

52223.1426

21.14

21.96

163.889

199.6225 32716.2

1.41

4.3

261.53

52223.1426

1.59

1.65

23.0476

277.62

6398.67

125.8191

34930.46

5.45

5.44

5.2248

277.62

1450.6

125.8191

34930.46

24.07

24.01

12.4822

277.62

3465.38

125.8191

34930.46

10.07

10.05

152.4474

277.62

42323.5

125.8191

34930.46

3.57

3.6

22.7311

277.62

6310.77

125.8191

34930.46

5.53

5.5191

2.37

277.62

657.95

125.8191

34930.46

53.08

22.6103

277.62

6277.12

125.8191

34930.46

5.56

5.54

175.01

270.12

48602.5

125.8191

34930.46

3.11

31.9708

270.12

8636.13

132.8274

35899.98

7.45

7.44

17.8208

270.12

4813.96

132.8274

35899.98

4.15

15.7352

270.12

4252.73

132.8274

35899.98

8.44

8.42

96.7089

270.12

26123.8

132.8274

35899.98

1.37

Area (mm²)

Load (N)

Buckling Buckling factor factor (FEM) (Analytical)

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9. Conclusions A segment of wing box was considered for evaluation of its static load and buckling load carrying capability.FEM was adopted for carrying out linear stress analysis and buckling analysis. One of the critical load cases from the normal flight condition was considered for the analysis. Maximum stress developed in the wing box is 82.9 N/mm2.Linear static buckling analysis was carried out for segment of wing box. One of the root panels of the top skin showed the max buckling deformation and the buckling load factor is 24.01.Compressive stressed developed on the top skin panel were obtained from the linear static analysis result. Critical buckling stress for each panel was calculated theoretically. Theoretical calculation is verified with the FEM results. There is a good correlation between hand calculation and FEM predictions. References [1] Ahmadian, M.T., Movahhedy, M.R., Rezaei, M.M. ”Design and Application of a New Tapered Superelement for Analysis of Revolving Geometries, Finite Element in Analysis and Design, Vol. 47 Issue 11, pp. 1242- 1252,2011 [2] Taylor R. The role of optimization in component structural design: application to the F-35 joint strike fighter, 25th International Congress of the Aeronautical Sciences; 2006. [3] Kuntjoro, W, Wing Structure Static Analysis using Superelement, International Symposium on Robotics and Intelligent Sensors-2012, Procedia Engineering 41 (2012 ) p.1600 – 1606, (IRIS 2012) [4] Sridhar Chintapalli, The development of a preliminary structural design optimization method of an aircraft wing-box skin-stringer panels Aerospace Science and Technology 14p.188– 198, 2010 [5] E F Bruhn, B S, M S, C E, Professor(Emeritus) of Aeronautics and Astronautics Purdue University, “Analysis and design of flight vehicle structure”, chapter C5 p.670–672, 1973

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FATIGUE ANALYSIS OF A DIESEL ENGINE CONNECTING ROD N.G.Ramesh1 1

Assistant Professor, Dept. of Mechanical engineering, Sapthagiri College of Engineering, Bangalore

Abstract The connecting rod forms an integral part of an internal combustion engine. It acts as a linkage between piston and crank shaft. The main function of connecting rod is to transmit the translational motion of piston to rotational motion of crank shaft and it also transmits the thrust load of the piston to the connecting rod. The connecting rod is a high volume production from automobile side. Connecting rod used in automotive engines is a critical component which comes under the influence of different types of loads in operation. Fatigue loading is one of the prime causes contributing to its failure. Failure and damage are also more in connecting rod, so stress analysis in connecting rod is very important. In this study, a detailed load analysis is performed on connecting rod, followed by Finite Element Method (FEM) using ANSYS . In order to calculate stress in different part of connecting rod, the total forces exerted by the connecting rod were calculated and then it is modeled, meshed and loaded in ANSYS software. The maximum stresses in different parts of connecting rod were determined by analysis. . Keywords: Connecting rod, FEA, Fatigue analysis, Stress concentration factor, ANSYS

. 1. Introduction The internal combustion engine [1] is an engine in which the combustion of a fuel (normally a fossil fuel) occurs with an oxidizer (usually air) in a combustion that is an Integral part of the working fluid flow circuit. In an internal combustion engine (ICE) the expansion of the high-temperature and high-pressure gases produced by combustion apply direct force to some component of the engine. The force is applied typically to pistons, turbine blades, or a nozzle. This force moves the component over a distance, transforming chemical energy into useful mechanical energy. Some of the important components of the internal combustion engine are cylinder, piston, piston rings, connecting rod, crankshaft etc. Conversion of the piston’s reciprocating motion into the rotational motion of the crankshaft is the major function of the connecting rod. Since the connecting rod has two ends, one of its ends is connected to the piston by the piston pin, and the other end revolves with the crankshaft and is separated in a way that it allows it to get clamped around the crankshaft as shown in figure 1.

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Figure 1: Connecting rod of an I.C. Engine

2. Materials used for Connecting Rod There are some materials that are commonly used for connecting rods. They are usually drop forged out of a steel alloy. Connecting rods manufactured under this method are capable of bearing very heavy loads without twisting, snapping or bending. Aluminum and titanium are the materials used in performance vehicles. Connecting rods for automotive applications need to be lightweight but strong enough to withstand and transmit the thrust from the piston to an engine's crankshaft. Holes on both ends of a connecting rod are machined to a high precision to perfectly connect to piston. Even construction equipment like bulldozers, backhoes uses internal combustion engines, thus requiring connecting rods. 3. Different type of loads acting on connecting rod 3.1. Inertia load: The inertial force of the reciprocating mass generates a tensile load which is proportional to the product of the piston assembly weight, and reciprocating mass of the connecting rod axial loading (Fay) is due to gas pressure and rotational mass forces. 3.2. Axial compression load: connecting rod receives a large compressive load during the combustion stroke. Connecting rod is in compression as the piston is accelerated down the cylinder bore. 3.3. Bending Load: Bending moments originate due to eccentricities, crankshaft, case wall deformation, and rotational mass force. The connecting rod experiences inertia forces plus direct forces that produce bending in a plane perpendicular to the crankshaft longitudinal axis. The connecting rod undergoes a complex motion, which is characterized by inertia loads that induce bending stresses. 4. Problem definition and methodology The diesel engine connecting rod is a high volume production critical component. It connects reciprocating piston to rotating crankshaft, transmitting the thrust of piston to the crankshaft. Every diesel engine requires at least one connecting rod depending upon the number of cylinders in the engine. For the analysis of I.C. engine connecting rod the most critical area is considered and accordingly the two dimensional model of connecting rod is formed. The different dimensions of the connecting rod are shown in the table 1 and figure 2 below.

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Figure 2: AUTOCAD model of connecting rod Table 1: Major parameters in connecting assembly

Table 2: The major specifications of constantrod speed single cylinder 4 stroke diesel engines

5. Material Properties The material used in the connecting rod is alloy steel and it has the following properties as shown in Table 3. Table 3: Material properties

6. Finite Element Model of the Connecting Rod [2] Figure 3 shows the meshed model of connecting rod considering the tetrahedral elements throughout the rod and without any hexahedron elements. The Connecting Rod consists of pin end, crank end, and rod. All these features are considered for the development of the finite element model.

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Figure 3: Meshed model of the connecting rod.

7. Analytical load calculations of the connecting rod [3,4,5] During the operation of the engine, the connecting rod undergoes a combination of axial and bending stresses acting on the rod in operation. The axial stresses are produced due to cylinder gas pressure (compressive only) and the inertia force arising in account of reciprocating action (both tensile as well as compressive), where as bending stresses are caused due to the centrifugal effects. The force acting on the small end of connecting rod is a combination of gas forces and inertia forces. Forces on connecting rod small end = Gas forces - Inertial Forces of piston 7.1 Gas Forces Gas forces are calculated using maximum gas pressure values taken from Table 2. The peak firing pressure for the engine is 80.44 bars and the same value is used for calculating the peak firing pressure acting on the piston surface. This peak firing pressure gets added up to the force acting on piston pin end. Gas force acting on the piston surface = Peak firing pressure × π/4×D2 From Table 2 we have ‘D’ is the diameter of the piston =114.3mm Peak firing pressure 80.44 bar = 8.044 MPa Gas force =   114.32 ×8.044=82538.08 N 4

7.2 Inertia Forces on the Piston This inertia forces due to reciprocating parts can be calculated by multiplying the mass of the reciprocating parts and the acceleration of the reciprocating parts. Mass of the reciprocating parts includes mass of piston, piston rings, gudgeon pin and small end of the connecting rod. Inertia forces of piston = mp × ap Where, mp is the mass of reciprocating parts. ap is the acceleration of reciprocating parts. Acceleration of reciprocating parts = rω2 (cos θ + cos (2θ/n)) r is the crank length=56.5mm n is the ratio of connecting rod length to crank length. The maximum acceleration occurs corresponds to TDC position where the angle is 0° or 360°. The second term in acceleration equation is neglected considering the length of the connecting rod as infinite and in that case the motion will approach to simple harmonic type. The aim of calculating these forces is to find the maximum force with respect to fatigue. The magnitude of angular velocity used for calculating acceleration of reciprocating parts is taken with respect to top engine speed which is 1500 rpm = 157.07 rad/s. Hence, Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Acceleration of reciprocating parts = 0.0565 × (157.07)2= 1394.08 m/s2 Total mass of the reciprocating parts = 0.502 + mass of the piston assembly and the Gudgeon = 0.502+ 1.71 Total mass of the reciprocating parts = 2.212 kg Inertia forces of piston =1394.08×2.212 =3083.70 N Therefore, Forces on connecting rod small end =82538.08-3083.70= 79454.37 N The net force considered for performing the static analysis was 79.454 kN. This was applied as axial force at the small end center of connecting rod. Calculating forces exerted on pin end Maximum Inertia force is considered: Fj = - (mj) rω2 (Cosθ +Cos (2θ/n)) Where, mj = 2.212 kg ; R = 0.0565 m ; Fj= -2.212×0.0565×157.07 2= - 3102.84 N Calculating forces exerted on crank end The combustion pressure force doesn’t have effect on crank end, but it is affected by inertia force. Fjr max is the maximum inertia force exerted on crank end of connecting rods. The inertia force exerted on crank end was calculated as Fjr = - rω2 [(mp+ mcr,p) + ( mcr,c - mc )] Where mp = Mass of the piston assembly(kg), mcr, c =concentrated mass of connecting rods on the crank end, mcr,c = 0.725  mcr = 0.725  1.875 = 1.3594 kg mcr,p= concentrated mass of connecting rods on the pin end. mcr,p = 0.275  mcr= 0.275  1.875 = 0.515 kg mc = concentrated mass of crankshaft on crank end. mc = 0.25  mcr = 0.25  1.875 = 0.4687 kg Fjr = - 0.0565×157.072[ (1.71+0.515) +(1.3594- 0.4687) ] Fjr = -4343.00 N Table 4: Forces on connecting rod body from calculation

8. Load and boundary conditions The boundary conditions are applied after creating the Finite Element Model. Axial loading was considered for all the analyses, since this is the primary service loading. Tension loads were applied on the bearing surfaces of the connecting rod. In actual service condition the pin end experiences tension by the piston pin causing distribution of load along the upper half of the inner diameter, which is approximated by the cosine function. The connecting rod was constrained in all six degrees of freedom from the bearing surfaces on one end and load was applied at the other end.

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Figure 4: Boundary conditions

9. Results and Discussion Geometric locations were identified on the connecting rod at which stresses were traced over the entire load cycle to obtain the stress at various locations. High stressed regions of the crank end, the pin end at the oil hole, the shank and at transitions to the shank at the crank and piston pin ends regions are shown in figure 4. Static analysis of connecting rod was conducted in order to understand the fatigue locations. The constraints used for performing the static analysis were as shown in Figure 5.

Figure 5: Geometric locations of the connecting rod

9.1. Compression loading condition The compression loading for the crank end and piston end is assumed to have a loading over the 180 0 contact arc. A force of 79.454 KN was also used in compression. The compression pressure applied on crank end while for the pin end is constrained for compression loading in the crank end, the piston pin end is constrained in all six directions (three for translational and three for rotational) through 180 0 contact arc. Uniform loading was applied at crank end through 1800 contact arc. For compression loading in the pin end the crank end is constrained in all six directions through 180 0 contact arc.

Figure 6: Displacement contours for crank end compression and pin end restrained.

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Figure 7: Von Mises stress contours for crank end compression and pin end restrained.

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Figure 8: Von Mises stress at I section

10. Fatigue life prediction of connecting rod Fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. A mechanical component loaded with a periodic stress that oscillates between some limits is subjected to stresses called repeated, alternating, or fluctuating stresses. Often the machine members fail under the action of repeated or fluctuating stresses. The most distinguishing characteristic of these failures is that the stresses have been repeated a very large number of times. Hence, the failure is called a fatigue failure. A fatigue failure [6] begins with a small crack. Once the crack is initiated, the stress concentration effect becomes greater and the crack progress more rapidly. As the stressed area decreases in size, the stress increases in magnitude until, and the remaining area finally fails suddenly. 10.1. Fatigue life prediction The Stress Life (S -N) theory was employed to evaluate the connecting rod fatigue life. In order to perform the fatigue study[7], the finite element results should be combined to obtain the alternate stress(σa) and mean stress (σm) for each operating condition.

Figure 9: Nomenclature for constant amplitude cyclic loading.

From stress analysis, we have σcompressive= 300.06 MPa and σtensile = 25.925 MPa. The alternating and mean stresses are 137.33 MPa and 163.26 MPa respectively. After calculating the alternate and mean stresses, we can plot the Modified Goodman diagram. From Table 3, we have, σu= Ultimate strength =850 N/mm2, σy = Yield strength = 570 N/mm2, σe = Endurance limit = 0.5 σu = 425 N/mm2 10.2. Goodman diagram With the alternate and mean stresses, and using the Modified Goodman diagram [8] for the connecting rod material, it is possible to evaluate the fatigue factors. A straight line connecting the endurance limit and the ultimate strength is shown in a line AB in figure 10. A Goodman line is used when the design is based on ultimate strength and may be used for ductile or brittle materials.

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Figure 10: Goodman diagram

Line AB connecting endurance limit and ultimate strength is called Goodman’s failure stress line. If a suitable factor safety applied to endurance and ultimate strength, a safe stress line CD may be drawn parallel to the line AB. The value of notch sensitivity factor (q) can be calculated using the notch root radius 13 mm. Notch sensitivity factor is 0.8.[9] Fatigue concentration factor Kf can be calculated by equation

Where, Kb: load factor for reversed bending load = 1 Ksur : Surface finish factor =0.8 Ksz :size factor =0.87,Kf :18 1 / F.S = (163.26/850) + [(137.33*1.24) / (425*1*0.8*0.897)] Factor of safety = 1.34 From the Goodman diagram, the factor of safety obtained was 1.34. The fatigue factor acceptable criterion is 1.34. By analyzing the numerical results and established acceptable criteria, we can conclude that no connecting rod fatigue failures are expected for these load levels. 10.3. Predicting the life of the connecting rod material from the S-N curve The standard S- N [10] curve as shown in figure 11 is used for calculating fatigue life of the component. By using alternate stresses we can expect the life cycles of the component.

Figure 11: Standard S N curve

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With the alternate and mean stresses, and using the S-N diagram for the connecting rod material, it is possible to evaluate the fatigue cycles. From result alternating stress is 137.33 N/mm2. Stress ratio is -1 for reversed load i.e. maximum compressive stress to the maximum tensile stress. From S-N diagram using the alternate stress and stress ratio, we can predict the life of the component. Table 5: Results of fatigue study on the connecting rod material

By analyzing the results and established acceptable criteria, we can conclude that no connecting rod fatigue failures are expected for these life cycles of the component. 11. Conclusions The maximum compressive stress was obtained between small end and shank of connecting rod. Validation of ANSYS results with that of experimental revealed deviation of ±10% testifying the considerations of numerical analysis. Fatigue life of the connecting rod was determined to be around 107 cycles, with a factor of safety of 1.34, which is satisfactory for mechanical components. The software also reveals the importance of the varying I - cross section which is provided for uniform stress distribution over the entire web of the connecting rod. 12. Scope for Future Work In this project linear static FEA of the connecting rod was performed using ANSYS. The research work can be extended to study the effect of loads on the connecting rod under dynamic conditions. The connecting rod may be analyzed for vibrations, which is important from the

design point of view. References [1] Charles F Taylor ,“The internal combustion engine in theory and practice, edition 10 M.M. Noor, M.N. Shuhaizal, K. Kadirgama, Julie J. Mohamed, M. R. M. Rejab, A. N. M. [2] Rose, “Analysis of Connecting Rod based On Finite Element Approach, Malaysian Technical Universities Conference on Engineering and Technology”, Proceedings of MUCET 2008, pp. 1-4 [3] Christy V Vazhappilly, P.Sathiamurthi, “Stress Analysis of Connecting Rod for Weight Reduction-A Review”, International Journal of Scientific and Research Publications, Volume 3, Issue 2, February 2013, pp. [4] Vivek.C.Pathade, Bhumeshwar Patle, Ajay N. Ingale, “Stress Analysis of I.C. Engine Connecting Rod by FEM, International Journal of Engineering and Innovative Technology” , Volume 1, Issue 3, March 2012.pp. 12-15 [5] N.P.Doshi, N.K.Ingole, “Analysis of Connecting Rod Using Analytical and Finite Element method”, International Journal of Modern Engineering Research Vol.3, Issue.1, Jan-Feb. 2013 pp-65-68 [6] M.N. Mohammed, M.Z. Omar, Zainuddin Sajuri, A. Salah, M.A. Abdelgnei, “Failure Analysis of a Fractured Connecting Rod”, Journal of Asian Scientific Research Volume 1 issue March 2004.pp. 737-741 [7] H.B.Ramani, Neeraj Kumar,P.M. Kasundra, “Analysis of Connecting Rod under different Loading Conditions Using Ansys Software”, International Journal of Engineering Research & Technology Volume. 1 Issue 9, November- 2012, pp

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[8] Prof. Pushpendra Kumar Sharma, Borse Rajendra, “Fatigue Analysis and Optimization of Connecting Rod Using Finite Element Analysis”, International Journal Of advance research in Science and Engineering, Vol. No.1, Issue No. 1. 2012. [9] “Machine Design data hand book, by Dr K Lingaiah volume 1 edition 12. [10] Tony George Thomas, S. Srikari, M. L. J Suman, “Design of Connecting Rod for Heavy Duty Applications Produced By different Processes For enhanced Fatigue Life”, Sas tech Journal Volume 10, Issue 1, May 2011.

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DESIGN AND TOLERANCE STACK UP ANALYSIS FOR CAR SIDE DOOR LATCH 1

H.Chethan, 2Naveen Udupa, 3Ramakrishna Hegde

Student, Dept. of Mechanical Engineering, RVCE, Bangalore 2 Deputy Manager, IFB Automotive Private Ltd. Bangalore 3 Assistant Professor, Dept. of Mechanical Engineering, RVCE, Bangalore chethanhh17@gmail.com

Abstract Side door latch is one of the major components of a car that the driver and passengers never see. It protects the vehicle occupants from being ejected through the doors which have known to be opened during motion or accidents. In addition to meshing the latching requirements, the latch manufactures have to meet the government safety standards. The intent of this work is to redesign an existing passenger car side door latch to improve the manufacturability using Design for Manufacture (DFM) guidelines and tear down analysis. Tolerance analysis used to estimate the effects of manufacturing variation on the finished products. Tolerance stack up analysis is used to find the clearance or interference between two features on a part and their assembly variations. Concept development involves different analysis techniques, design verification aspects for the parts of the assembly and associated tolerance analysis. The variation aspect in assembly level are elaborated and presented. Keywords: Side door latch (SDL), DFM&A, tear down analysis, tolerance stack up analysis

1. Introduction A car door latch refers to the mechanical device used to align the door in a closed position relative to the vehicle body framework. The major role of a latch is to perform lock/unlock and latch/unlatch functions. A latch unit consists of several components. The number of components varies according to the complexity and the mechanical/electromechanical features specified by the customer [1] Generally the side door latches of a car contain the following components: Striker, catch, pawl, detent lever, inside release lever, outside operating lever, intermittent lever, inside locking lever. Maintaining government safety standards and satisfying the different OEM design specifications in a cost-effective, timely manner is a major challenge for a automobile latch manufacturer. Latch manufacturers have to meet the standards set by governments. At the same time each manufacture has its own testing requirements. Tolerance analysis is used to estimate the effects of manufacturing variation on the finished products. Either design tolerances or manufacturing process data may be used to define the any variation. Conventional methods used for tolerance stack up analysis are worst-case and statistical analysis [2]. Manual construction of tolerance check sheet is commonly used tools for tolerance analysis. Tolerance check list is used in the industry by draftsmen and designers to calculate the maximum or minimum distances (clearance or interference) between two features on a part or assembly. The tolerance analysis is different from tolerance allocation. In tolerance analysis the component tolerances are known and the resulting assembly variation is calculated by summing the component tolerances. In tolerance allocation, the assembly tolerance is known from the design requirements, whereas the available assembly tolerance must be distributed or allocated among the components in some rational way.

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Figure 1(a): Tolerance allocation

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Figure 1(b): Tolerance analysis

2. Concept development The concept development consists of the following steps,  Tear down analysis  Component analysis  CAD models of the SDL  DFM&A of SDL 2.1 Tear down and Component analysis Tear-down analysis and component analysis are the pre-stages of the concept development which helps to understand the importance of the functional parts, interaction between the parts, functional features, etc., 2.2 Cad models of the SDL The SDL was modelled using CATIA V5 R20 software. The models were created from the customer requirements and the existing side door and back door latch drawings. It provided the complete data of the SDL and other profiles. All other dimensions were measured by Vernier calliper. 2.3 DFM & assembly of SDL The design for manufacturability and assembly guidelines were directly and indirectly applied to redesign the SDL. The following objectives were established for the redesign of SDL,  Fastening process was eliminated.  Stopper feature on the top plate was eliminated.  Double side riveting process was designed.  Functional improvement was achieved. 3. Concept selection The SDL has selected based on the five important parameters (refer figure 3.15) that are listed below,  Functionality  Manufacturability  Assembly  Package  Cost 3.1 Functionality The functionality was captured from the existing SDL and it has been implemented in the new SDL. All the concepts have been worked on without any functional loss.

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3.2 Manufacturability The requirements for load conditions vary from one car manufacturer to another. So the new SDL has been designed with a special attention given on the load improvement. 3.3 Assembly The assembly process was improved by eliminating the housing part and fastening process. 3.4 Package The package size is maintained the same as the existing SDL, and some of the nonfunctional profiles has been modified. Hence, the new SDL has been packaged in the existing door module. 3.5 Cost The cost of the new SDL will be reduced, as the fastening assembly process is eliminated. Bending feature in the top plate has been eliminated along with three screws and a housing part. 4

Design verification In general terms, Verification is a quality control process that is used to evaluate the product that complies with the specifications and conditions imposed at the start of a development phase. Design verification is a process to examine design outputs and to use objective evidence to confirm that output meets input requirements. Verification activities are conducted at all the stages and levels of product design. The verification can be determined by inspection, demonstration, test and analysis [3]. Feature comparison analysis of existing SDL with new SDL has been carried out for the design verification process.

Figure 2. Shows the comparison analysis of existing SDL with new SDL

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Figure 3 : Comparison Analysis for existing SDL with new SDL.

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Figure 4(a): Existing SDL

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Figure 4(b) : Modified SDL

5. Tolerance stack up Analysis 5.1 Tolerance check sheet Manual construction of tolerance check sheet is a popular technique for analyzing tolerance accumulation in parts. For SDL assembly, tolerance check sheets were developed for all parts listed below  Base plate vs. Catch / Pawl rivet  Catch vs. Catch rivet  Pawl vs. Pawl rivet  Top plate vs. Catch / Pawl rivet  Top plate vs. Inside release lever rivet  Inside release lever vs. Inside release lever rivet  Outside operating lever vs. Outside release lever rivet  Top plate vs. Outside release lever rivet  Outside operating lever vs. Outside operating lever rivet  ALH release lever vs. Outside operating lever rivet The manual construction of tolerance check list only deals with the worst-case analysis and it considers variation in only one direction at a time, i.e. length or diameter. In Table 1 the length was considered for the first direction. The catch and catch rivet is indicated by A and B respectively. The basic dimensions and its tolerances as per drawing are added in the check list. The values of all the clearance fits are calculated and the same is tabulated. (Table1) Tolerance check sheet for Catch vs. Catch rivet is illustrated in Table 1

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Table 1: Tolerance stack up check sheet- Catch vs. Catch rivet

5.1.1 Calculations Minimum condition: Bmin – Amax = 5.6 – 5.7 = 0.1 = Clearance Nominal condition: B – A= 5.6 – 5.4 = 0.2= Clearance Maximum condition: Bmax - Amin = 5.75 – 5.3 = 0.45 = Clearance For the second direction, diameter was considered. Here the catch and catch rivet diameter is identified by C and D respectively. Minimum condition: Cmin – Dmax =7– 6.9 = 0.1 = Clearance Nominal condition: C – D= 7 – 6.9 = 0.1= Clearance Maximum condition: Cmax – Dmin = 7.15 – 6.8 = 0.25= Clearance 5.2 Tolerance analysis Tolerance analysis is a method of predicting and analysing assembly variation due to tolerance of individual components and assembly operations. Tolerance analysis is carried out when the tolerances of individual parts are known and the designer intends to find out or allocate the dimensions for assembly. This involves:  Gathering data on the individual component variations.  Creating an assembly model to identify which dimensions contribute to the final assembly dimensions.  Applying the manufactured component variations to the model to predict the variations in assembly dimension.

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5.2.1 Assembly variation for inner release of the side door latch 2.1.1 Nominal assembly variation Figure 5(a) shows the free, operating and full length for inside release of the latch.

Figure 5 (a). Inner release basic dimensions for nominal conditions

Figure 5 (b) : Inner release variation for maximum condition

5.2.1.2 Maximum assembly variation The contributing dimensions for maximum variation condition was identified and applied to the model to find the variations for inner release of the latch. Figure 5(b) shows the maximum variation. 5.2.1.3 Minimum Assembly Variation The contributing dimensions for minimum variation condition was identified and applied to the model to find the variations for inner release of the latch. Figure 6 shows the minimum variation.

Figure 6: Inner release variation for minimum condition

5.2.2 Assembly variation for outer release of the side door latch 5.2.2.1 Nominal variation The free, operating and full length for outer release of the latch is showed in Figure 7 (a)

Figure 7 (a): Outer release basic dimensions for nominal conditions

Figure 7(b): Outer release variation for maximum condition

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5.2.2.2 Maximum variation The contributing dimensions for maximum variation condition was identified and applied to the model to find the variations for outer release of the latch. Figure 7(b) shows the minimum variation. 5.2.2.3 Minimum variation The contributing dimensions for minimum variation condition was identified and applied to the model to find the minimum variations for outer release of the latch. Figure 8 shows the minimum variation.

Figure 8: Outer release variation for minimum condition

6. Conclusion A redesign of an existing passenger car side door latch has been carried out to improve manufacturability using design for manufacture (DFM) guidelines and tear down analysis. This helped in improving the design as double side riveting is achieved compared to the single side riveting in the older design. This eliminates the fastening process in the assembly which previously consisted of inserting three screws and a housing part. In order to determine the clearance or interference between two features on a part and their assembly variation, tolerance stack up analysis was done. The check sheet clearly indicated that there was no interference fit present between any features of assembled parts which naturally simplifies the assembly process. The assembly variation for inside release of the latch was found to be ± 1.5mm compared to that of outside release of the latch which was determined to be ±1mm.

References [1] Portillo, Oscar, Dobson and Kimberly, “60g Inertia Load Analysis of Automotive Door Latches” – F2008-SC-033. [2] Suyash Y. Pawar, Harshal A. Chavan and Santhosh P. Chavan, “Tolerance Stack Up Analysis And Simulation Using Visualization VSA”, International Journal of Advanced Engineering Technology, Volume 2, Issue 1, pp.169-175, 2011 [3] Maropoulos P.G. and Ceglarek D “Design Verification and Validation in Product Lifecycle”, CIRP Annals – Manufacturing Technology, Volume 54, Issue 2, pp.607-622, 2010 [4] Rosan Lal Virdi, Kushdeep Goyal and Jatinder Madan, “Concept and Guidelines of Design for Manufacturability: A Shift from Traditional Design Concept”, National Conference on Advancements and Futuristic Trends in Mechanical and Materials Engineering, pp. 162 -164, 2010 [5] Ajith V Gokhale and Vithoba Saravate, “Design of Door Latching and Locking Systems for Crashworthiness”, Technical Paper, SAE 2008-28-0058, 2008 [6] Daniel I. Udriste and Eugen M. Negrus, “Construction and Kinematics of Automotive Side door Latch Mechanisms”, Technical Paper, SAE 2005-01-0881, 2005 [7] Kenneth W. Chase, “Tolerance Allocation Methods for Designers”, ADCATS Report No. 99-6, 1999 [8] Hussain T., Ali Z. And Larik J, “A Study On Tolerance Representation, Variation Propagation Analysis and Control In Mechanical Assemblies”, Sindh University Research Journal (Science Series), Volume 44, Issue 3, pp.427 – 432, 2012 Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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DETERMINATION OF STRESS CONCENTRATION FOR PLATE WITH AN OBLIQUE ANGLE WITH DIFFERENT CUT-OUTS BY USING FINITE ELEMENT AND ANALYTICAL METHOD Amaresh Gunge1, Biradar Mallikarjun2 1

Student, Dept. of Mechanical Engineering-PG Machine Design, NCET, Bangalore 2 Assistant Professor, Dept. of Mechanical Engineering, NCET, Bangalore amargunge93@gmail.com

Abstract Determining stress concentration factors is of practical importance for many engineered structures because geometric discontinuities are frequently the site of failure. Localized stresses around geometric discontinuities such as holes, shoulders, and grooves cannot be predicted using elementary stress formulae. The concentration of stress resulting from these abrupt transitions is frequently too high to be attributed solely to the decrease in net cross sectional area. Stress concentration factors, often determined experimentally or computationally. The present study is to analyze the stresses in a series of thick, wide, flat plates with oblique holes subjected to bending using the Finite Element Method (FEM), for different angles of hole obliquity and orientation are considered to provide stress concentration factors at such holes. The work also covers, hole obliquity angles from 0 to 60°. The results for bending are compared with those determined using mathematical calculations in order to verify the finite element results. FEM is used for obtained analysis and results were validated by analytical method. Key words: finite plate, infinite plate, cutouts, stress concentration

1. Introduction In practice, as per the engineering applications all components have changes in section, shape or micro structural discontinuities. Any discontinuity will change the stress distribution in the vicinity of the component. The holes in plates assuming homogenous, isotropic, and elastic material, the cause of this highly localized or accumulation of stress near the change of cross section or clustering of stress lines at the point of discontinuity is termed as stress concentration using a factor known as stress concentration factor (SCF’s). The stress concentration factor (kt) can be designated by using ratio of the maximum stress (σMax.) to the nominal stress (σnom). The principal cause of stress raisers are some sort of discontinuities, they are geometric discontinuities such as holes, notches and internal defects such as cracks, voids. Thus the discontinuities cause’s areas of stress concentration within the component. When any component is statically loaded and the force is evenly distributed over its area, then a reduction in area due to a stress raiser increases the local stress. A material can fail, via a propagating crack because the concentrated stress exceeds the material’s theoretical cohesive strength. The strength of the material is always lower than the theoretical value because stresses will be more in small cracks that concentrate stress. In any ideally elastic component, the maximum stresses can be determined by multiplying the nominal stress by the appropriate geometrical stress concentration factor. The nominal stress is calculated using particular loading by net cross sectional area. Determining stress concentration factors is of practical importance for many components, because geometric discontinuities are frequently the site of failure. When compared to the expected stress concentration in a homogeneous isotropic component, the effect of the geometry and obliquity of the hole can be quantitative. The stress concentration factor is solely depending on the system of loading, geometry and

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material. There are various components in gas turbine engine, nozzle- guide vanes having oblique holes. These holes are done in such a way so that components temperature can be kept as low as possible. In certain situations these holes are required to allow cool air to pass through these holes so that hot components of gas turbine engine can be cooled down to the allowable limit. Geometrical shapes of these holes can be, elliptical, circular and square depending on design requirements. Also, these holes are drilled either normal to plane of the components or making certain angle with the normal. The oblique holes are done for cooling component to avoid thermal load and increase component life. The localized stress around geometric discontinuities such as holes, shoulders and grooves cannot be predicted using elementary stress formulas. The concentration of stress resulting from these abrupt transitions is frequently too high to be attributed solely to the decrease in net cross sectional area. Stress concentration factors, often determined experimentally or computationally, are used to scale the nominal stress in a continuous structure to account the effect of the discontinuity In this project work, The Stress concentration factor around circular and oblique holes will be determined which can be utilized as a multiplication factor to estimate stress distribution around the oblique hole for different oblique angles. Methods used for stress analysis is Finite element technique (FEM), Uniaxial tensile test has been used to study stress concentration factor around oblique hole. The main purpose of the work is to study and understand the stress concentration factors in finite and infinite plate with hole different cut-outs, to determination of stress concentration factor; by FEA, experimental/ theoretical methods. The various normal holes have been considered to evaluate stress concentration factor (SCF) and the obtained results are compared with R.E Peterson’s Design for Stress concentration factor, for better solution. 2. Stress Concentration Factor It is convenient to express stresses in non-dimensional form. However, there is usually more than one reference stress which may be used for this purpose and the resulting stress-concentration factors (SCF) may be seen to have merit for particular purposes. Since more than one definition is used here, the matter will be considered before the results are presented.

3. Materials Table: 4.1 Material properties Name of the Material Alluminium 2014 Titanium (Ti-5% Al2.5%) Nickel(5Ni steel)

Young’s modulus(Gpa)

Yield strength (MPa)

Poison’s ratio

290

0.33

110

795

0.34

207

530

0.31

Steel 0.2%C

200

250

0.30

4. Plate Dimension (Isotropic Plates) 4.1. Finite Plate details 1) Length of plate=400mm 2) Width of plate=100mm 3) Thickness of plate=5, 7,9,11 and 13mm. 4.2. In-finite plate details Condition for selecting in-finite plate W/d ≥ 10 Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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1) Length of plate=500mm 2) Width of plate=100mm 3) Thickness of plate=5, 7,9,11 and 13mm. 4.3. Cut-out dimension 1) Circular cut-out=Dia10mm 2) Elliptical cut-out…=.10mm major and 5mm minor axis

Model converged 600 400

MAX VONMISES STRESS

200 0 0

5000

10000

Figure :4 (a) Graph shows that Number of elements Vs Max. Von-misses stress

Thickness (t) mm

FEM result (SCF)

Analytical results (SCF)

Max. Stress (FEM)

Max. stress (analytical)

Sl. No.

Thickness (t) mm

FEM result (SCF)

Analytical results (SCF)

Max. Stress (FEM)

Max. stress (analytical)

Table 5(b):Circular cut-out (Nickel)

Sl. No.

5. Results and discussions Table 5(a):Circular cut-out (Al-2014)

1 2 3 4 5

5 7 9 11 13

2.63 2.4 2.3 2.2 2.2

2.72 2.72 2.72 2.72 2.72

490 486 454 440 448

492.53 518 533 544 548

1 2 3 4 5

5 7 9 11 13

2.64 2.4 2.3 2.2 2.2

2.72 2.72 2.72 2.72 2.72

893 884 832 825 820

900 948 974 991 1003

Analytical result (SCF)

Max. stress (FEM)

Max. Stress (analytical)

l. No.

Thickness (t) mm

FEM result (SCF)

5 7 9 11 13

2.64 2.4 2.3 2.2 2.27

2.7 2.7 2.7 2.7 2.7

1350 1330 1250 1250 1230

1340 1411 1451 1476 1493

1 2 3 4 5

5 7 9 11 13

2.64 2.4 2.3 2.2 2.27

2.7 2.7 2.7 2.7 2.7

420 410 392 389 387

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Max. stress (analytical)

FEM result SCF)

1 2 3 4 5

Analytical results (SCF) Max. Stress (FEM)

Thickness (t) mm

Table 5(d): Circular cut-out (steel)

Sl. No

Table 5(c): Circular cut-out (Ti-5%AL2.5%)

421 443 456 464 469

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Thickness (t) mm

FEM result (SCF)

Analytical results (SCF)

Max. Stress (FEM)

Max. stress (analytical)

Sl. No.

Thickness (t) mm

FEM result (SCF)

Analytical results (SCF)

Max. Stress (FEM)

Max. stress (analytical)

Table 5(f): Elliptical cut-out (nickel)

Sl. No.

Table 5(e): Elliptical cut-out (Al- 2014)

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1 2 3 4 5

5 7 9 11 13

2.9 2.5 2.39 2.29 2.23

2 2 2 2 2

378 375 372 364 328

294 333 354 368 376

1 2 3 4 5

5 7 9 11 13

2.9 2.5 2.39 2.29 2.23

2 2 2 2 2

673 685 680 666 601

538 610 648 672 690

Thickness (t) mm

FEM result (SCF)

Analytical results (SCF)

Max. Stress (FEM)

Max. stress (analytical)

Sl. No

Thickness (t) mm

FEM result (SCF)

Analytical results (SCF)

Max. Stress (FEM)

Max. stress (analytical)

Table 5(i): Elliptical cut-out (steel)

Sl. No

Table 5(g): Elliptical cut-out (Ti-5% AL2.5%)

1 2 3 4 5

5 7 9 11 13

2.9 2.5 2.39 2.29 2.23

2 2 2 2 2

1004 1003 1002 1001 899

806 913 972 1009 1035

1 2 3 4 5

5 7 9 11 13

2.9 2.5 2.39 2.29 2.23

2 2 2 2 2

325 323 320 319 284

254 287 305 317 325

6. Geometric Model

Figure 7.1: Geometric Modeling of the component Using CATIA

Figure 7.2: Geometric Modeling of the component Using CATIA.

7. FEM Results

Figure 8(a): FEA Results for plate with oblique with 5mm hole thickness for Al material. (300). (300).

Figure 8(b): FEA Results for plate with oblique hole with 7 mm thickness for Al material.

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Figure 8(c): FEA Results for plate with oblique hole with 9 mm thickness for Al material. (300).

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Figure 8(d): FEA Results for plate with oblique hole with 5mm thickness for Al material. (300).

Figure 8(e): FEA Results for plate with oblique hole Figure 8(f): FEA Results for Plate with oblique hole with 7 mm thickness for Al material. (300). with 9 mm thickness for Al material. (300).

4 3.5 S C F

3 2.5 Circular

Square

1.5

Triangular

1 0.5

Ellipitical

0 0.05 0.07 0.09 0.11 0.13 t/w Figure 8.1: Graph of stress concentration (kσ) V/s (t /w).

8. Conclusion This study provides a detailed discussion of SCF’s in plats with either normal or oblique holes in uniform tensile load and I plane bending load. The obtained results demonstrate a strong relationship between maximum stress concentration factor and the angle of obliquity. For the loading scheme studied as the obliquity increases the maximum stress concentration decreases. For an obliquity angle of 600 there is an approximately 11% increase in the maximum SCF as the hole diameter ration increases from 0.1 to 0.2.In normal cylindrical hole with its axis normal to the plane of the plate, the maximum stress concentration occurs in the mid plane region but gradually moves along the hole towards acute angles tip and obtuse angle tip s the obliquity is increases. As the experimental stress concentration factors found considerably lower than finite elemental results. The experimental results obtained apply to plates with a ratio of hole diameter d to plate width w of 0.11. It would be valuable to extend this work for same

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obliquity angle by prediction stress concentration factors for other d/w ratios like 0.2 0.3 0.4.As obliquity angle increases the maximum stress concentration decreases. References [1]. Jinho Woo and Won-Bae Na, “Effect of Cutout Orientation on Stress Concentration of Perforated plates with Various Cutout and Bluntness”, International Journal of Ocean system engineering 1(2) (2011) 95-101,2011 [2]. Mckenzie d. J. White “Stress concentration caused by an oblique round hole in a flat plate under uniaxial tension.” Journal of Strain Analysis, Vol 3, No 2 ,1968. [3]. Mohammed.M, Dryden J. R., and. Jiang L, “Stress Concentration around a hole in a radially inhomogeneous plate,” International Journal of Solids and Structures, vol. 48, pp. 483-491, 2011. [4]. Boljanović,S., Maksimovi,S., Posavljak,S., Fatigue life estimation of cracked structural components, In: Proceedings of the 10th International Conference DEMI 2011, Banja Luka, 26-28 May 2011, Republic of Srpska, pp. 165-172. [5]. Carpinteri,A., Brighenti,R., Vantadori,S., Notched shells with surface cracks under complex loading, International Journal of Mechanical Sciences, vol.48, 2006, pp.638-649. [6]. Stanley.P and Starr .A.G have find out “Stress concentration at an oblique hole in a thick plate”. Journal of Strain Analysis, Vol 35, No 2, 2000. [7]. Troyani.N, C. Gomes, and G. Sterlacci, “Theoretical stress concentration factors for short rectangular plates with centered circular holes,” Journal of Mechanical Design, vol. 124, March, 2002. [8]. Zirka A. I.,. Malezhik M. P, and. Chernyshenko I. S, “Stress distribution in an orthotropic plate with circular holes under impulsive loading,” International Applied Mechanics, vol. 40, no. 2, 2004. [9]. Yang .Z,. Kim C. B, Cho C., and Beom H. G., “The concentration of stress and strain infinite thickness elastic plate containing a circular hole,” International Journal of Solids & Structures, vol. 45, 2008 [10]. Mittal N. D. and Jain N. K., “Finite element analysis for stress concentration and deflection in isotropic and orthotropic rectangular plates with central circular hole under transverse static loading,” Material Science and Engineering A, vol. 498, pp. 115-124, 2008. [11]. Hasan T., Das A., Rahman T., Chowdhury S. C., and Alam M. T. , “Stress analysis of steel plate having holes of various shapes, sizes and orientations using finite element method,” Proceedings of the International Conference on Mechanical Engineering 2009 (ICME2009) Dhaka, Bangladesh, December 2009.

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EVALUATION OF FAILURE MECHANISMS BETWEEN IDENTICALSTRESS MAGNITUDES IN A FUSELAGE SPLICE JOINT A.Nanjunda Reddy1, C.Venkate Gowda2, S.Rajanna3 1

Student, Dept. of Mechanical Engineering-PG Machine Design, NCET, Bangalore 2 Assistant Professor, Dept. of Mechanical Engineering, NCET, Bangalore 3 Associate Professor, Govt. Engineering College, Kushalnagar nanjreddy@gmail.com

Abstract Today's highly competitive environment in the commercial air transportation business instigates airline companies to re-qualify their fleets, without compromising on safety of the structure. Hence more attention is given to the Multi Site Damage (MSD) type of structure failure. This type of structure failure occurs in aging aircraft in the longitudinal splice joint. A fuselage of a commercial aircraft typically undergoes a cycle of pressurization for every single flight operation. These pressurization cycles creates identical stress magnitudes at the riveted locations and leads small fatigue cracks. These small cracks may coalesce to form a large crack, which may then progress fast and lead to ultimate failure. Such failure takes place in two ways; one is due to fracture and other is due to net section yielding. These failure mechanisms are studied by using MSC NASTRAN/PATRAN software. The stress intensity factor calculations are carried out by using Modified Virtual Crack Closure Integral (MVCCI) method. Keywords: fuselage, MSD, fatigue, damage tolerance, pressurization

1. Introduction Multi-site damage is defined as simultaneous occurrence of small fatigue cracks along the row of fastening holes in the same membrane. The MSD problem is related to fuselage having longitudinal splice joints involves fatigue cracks along the row of rivets in the outside skin of the joint. Fatigue loading of the joint is due to cycles of pressurization and MSD has been most apparent in fuselage lap joint structures, and can result in unexpected catastrophic failure of aircraft, as it is difficult to detect. Since in the initial stage the crack is difficult to detect because it is hidden by the rivet head or it is hidden by paint. The presence of a single crack in the joint is not dangerous damage in the riveted lap joint due to its presence it does not mean that the service life of the aircraft should be terminated. According to fracture mechanics, the crack would propagate at some finite speed for some time unless the crack length reaches some critical value. The figure.1 shows the MSD type of structure failure. Aloha accident is one of best example for MSD type of structure failure. The aircraft fuselage suffered fracture and separation of the top of the fuselage while cruising at 24,000 feet, resulting in sudden decompression and severe structural damage. The investigation concluded that the crack did not arrest at the fuselage frames because of the multiple sites where cracking had initiated.

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Figure 1: MSD structure failure in Aloha aircraft.

The literature survey reveals that MSD reduces residual strength and fatigue strength and hence overall structural integrity. Consequently, the residual strength of a panel with a leading crack and MSD cracks is known to be lower than that of a panel with the same leading crack without MSD [2]. Hence detailed failure investigation is carried for butt splice joint with doubler plate and loaded rivets. 1.1 Material data The metallic material AL 2024-T3 is widely used in the aircraft industry. Since it has good agreement with fatigue strength corrosion resistance, and tensile strengthproperties. Hence AL 2024 -T3 is used for the analysis and some of its properties are shown in the table 1 and 2 Table1: Chemical properties of Al2024-T3

Component Al Chromium Cu Ferrous Magnesium Manganese Titanium Zinc Other

% of composition 90.7-94.7 % Max 0.1 % 3.8-4.9 % Max 0.5 % 1.2-1.8 % 0.3-0.9 % Max 0.15 % Max 0.25 % Max 0.15 %

Table2: Mechanical properties of Al2024-T3

Properties

AL 2024-T3

density Youngs modulus

27.21 N /mm3 70000 Mpa

fracture toughness poisons ratio yield strength ultimate strength

80 Mpa√m 0.3 360 Mpa 483 Mpa

2. Geometrical Model The geometrical model of fuselage having different parts is shown in the fig 2 Fuselage is modeled with the skin of 2000 mm diameter, length 2000 mm and 2 mm thickness. The fuselage is separated by a gap of 2mm along the longitudinal direction which is shown in the fig 2.The two splice joints are joined by doubler plate having size of 200 x 103 x 2 mm thickness. Skin and doubler plate is fastened by rivets having 6mm diameter. The fuselage is subjected to an internal pressure of 10 psi.

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Figure 2: Fuselage model

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Figure 3: Standard rivet arrangement in a fuselage joint

The rivet configuration of the model is as shown in the figure 3. The first row of rivets from the joint is at a distance of 15mm. The first row and the second row are separated by a distance of 20mm, and the distance between the two adjacent rivets in a row (pitch distance) is 40 mm. There are 298 holes on one side of the fuselage joint. 3. Finite Element Analysis In this project Nastran/patran is utilized to carry out the FE analysis, the analysis consists of two steps as explained below 3.1 Global Analysis: The whole component is analyzed to determine the stress distribution during internal pressurization. FEA of the Fuselage is carried out with quad 4 type of elements and rivets are considered as 1D element. The table 3 gives the details of no of elements and nodes used in FE analysis. For this panel, all the six degrees of freedom are arrested on either sides of the panel and internal pressure is applied as a uniformly distributed normal outward load on the shell. Due to internal pressurization fuselage deforms outwards and induces both hoop and longitudinal stresses. Hoop stresses are perpendicular to the direction of crack propagation. Hence hoop stress will have significant influence on the crack growth. Table 3: No of elements and nodes used in FE model

Sl. No

Type

No's

1D Bar Elements

596

Quad Elements

11212

Nodes

15351

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Figure 4 shows stress distribution in the fuselage structure under constant amplitude load. The maximum stress concentration is at the failure prone areas (riveted locations) and panel experiences remote stress away from the riveted locations. The color pattern in the figure indicates stress distribution in the structure.

Figure 4: Stress contour in the fuselage

Analytical method: In this method the hoop stresses are obtained by using following formula (

) =

Where, σc – Hoop stress in Mpa P – Internal pressure in N d – Diameter of fuselage in mm t – Thickness of fuselage in mm The hoop stresses obtained by analytical method is 34.33Mpa which is in close agreement with the FE values. 3.2. Local Panel Analysis: From the global analysis it is proved that the maximum stress concentration is at the riveted location which may lead to fatigue crack initiation and failure of the structure. Hence detailed analysis is carried out at the failure prone region by considering small segment of length 600 mm and width 200 mm (figure 5) to acquire more précised values. Here, the loads for the local analysis are calculated to obtain the stresses which will be in agreement with that the stresses obtained in the global analysis.

Figure 5: Flat panel geometry for local analysis

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A quad 4 element which is having 4 nodes, six degrees of freedom is used for panel and 1D element is used for rivets. Around the riveted holes fine mesh is maintained with an element length of 1mm and the aspect ratio is kept within 1.5.One end of the plate is constrained in all directions (all degrees of freedom are arrested) and the deformation along the Z- axis is constrained. Next, on the other end of the plate a uniaxial tensile load of 68.67 N is applied.The table 4 provides information about, no of elements and nodes used in theflat panel. Table 4: Shows no. of elements and nodes Used in flat panel model

Sl. No

Type

No's

1D Bar element

Quad element

42738

Nodes

108421

MPC

Figure 6: Stress distribution at the tip crack in the flat panel

Stress contour in an MPC plate. Multi point constraints are used for transmitting loads and displacements from rivets to structure. Since in real structure, for the same boundary conditions the rivets will make contacts with upper skin of the holes in the direction opposite to applied load. The lower skin (doubler plate) makes contacts with rivets in the direction of load. Figure 6 gives stress distribution in the panel in presence of crack at riveted hole. 3.3. Failure Mechanisms Generally failure of the MSD structure takes place by two ways 3.3.1 Fracture: According to fracture mechanics whenever SIF exceeds the fracture toughness of material, failure takes place. i.e. ≥ Where, KI – stress intensity factor. KIC –critical stress intensity factor The SIF is evaluated through the estimation of Strain Energy release rate. The SERR is estimated using the well-known Modified Virtual Crack Closure Integral (MVCCI) technique. Thisprocedure involves, K=√ × Where, G-Energy release rate in N/mm E- Modulus of elasticity in Mpa Strain energy release rate

∆ ×∆ ×∆ ×

Where, ∆f-Grid point force in N ∆v-crack opening displacement in mm ∆a-element length at the crack tip in mm t - Thickness of the panel plate in mm

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3.3.2. Plastic collapse condition: This type of failure condition exists when the average stresses between two adjacent cracks exceeds the yields strength of the material which is called as net section yielding.Net section yielding will be calculated between two advancing crack tips by taking an average value of the elemental stresses obtained between the two crack tips and compared with yield strength of material. i.e. σavg≤ σy. 4 .Results And Discussions The stress intensity factor value is calculated for different incremental crack length by using MVCCI method. For each crack length, the stress intensity factor value is compared with the fracture toughness of the material 80 √ . And also averages stresses is compared with tensile yield strength of the material. Table 5: Comparison Of KI & Σ avg With KIC&Σy Respectively fora 2 mm Plate

sl no 1

Half crack length KI KIC σ avg σy (mm) (Mpa√m) (Mpa√m) (Mpa) (Mpa) 2

6.55

42.236

360

Table 6: Comparison of KI&σavg with KIC & σy respectively fora 1.8 mm plate.

sl no

KIC Half crack length KI (mm) (Mpa√m) (Mpa√m)

σ avg (Mpa)

σy (Mpa)

7.19

51.345

360

4.5

7.37

56.858

360

6.66

49.834

360

7.62

63.117

360

7.15

57.43

360

7.5

7.77

71.2696

360

9.032

82.629

360

7.49

68.12

360

10.5

9.925

97.748

360

8.9

84.786

360

11.5

10.67

111.67

360

10.1

118.34

360

12.5

11.55

129.492

360

13.5

12.41

158.186

360

12.4

167.84

360

14.5

14.31

197.828

360

15.82

228.63

360

15.5

16.78

277.132

360

18.69

349.92

360

18.91

376.05

360

16.5

21.22

461.07

360

Parametric study is carried out for different thickness of the skin and doubler plate to 1.8mm and 3mm respectively. Rivet hole size is changed to 5 mm .Same type of analysis is carried out as like previous flat plate analysis.The table 6 provides the data regarding SIF and net section stresses for each incremental crack length. Figure 7& 8 shows the graph of KI v/s half crack length. It is evident that the when the crack length is increased gradually from 2 to 16 mm for a 2 mm skin plate the SIF considerably increases(fig 7) but does not account for the failure. Where is in the 1.8mm skin plate when the crack length is increased from 3 mm to 16.5 mm the SIF considerably increases(Figure 8).

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20 18 16 14 12 10 8 6 4 2 0

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SIF Mpa√m

SIF in Mpa√m

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20 15 10 5 0

crack length in mm

crack length in mm Figure 7: variation of SIF Vs. half crack length for 2 mm skin plate

Figure 8: variation of SIF Vs. half crack length for 1.8 mm skin plate.

400 350 300 250 200 150 100 50 0

σ avg in MPa

In the net section yielding mechanism, when the crack length is increased from 2 to 16 mm in a 2 mm plate the average also increases gradually, at the crack length of 16 mm the stresses exceeds the yield strength of the material. Whereas in the 1.8mm plate the stress exceeds at the crack length of 16.5 mm which are shown in the figures 9 & 10 respectively.

crack length in mm Figure 9: variation of σσavg v/s half crack length for a 1.8 mm plate

400 350 300 250 200 150 100 50 0 0

crack length in mm Figure 10: variation of σσavg v/s half crack length for a 2 mm plate.

Conclusions The hoop stress (34.33MPa) obtained by both analytical and FE analysis are in close agreement and at the rivet holes the stress concentration is maximum in the global model. Increase of crack length in the plates (both 1.8 & 2 mm) leads to increase in SIF but lies within the fracture toughness value & hence, it does not account to the catastrophic failure. The net section stresses generated exceeds the yield strength for a crack length of 16 and 16.5 mm for 2 & 1.8 mm plate respectively, and leads to failure of the plates. It is observed that by varying geometrical specification of the doubler and skin the failure can be controlled to have either net section yielding or fracture. Even though skin

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thickness is reduced from 2 mm to 1.8 mm, it is observed that the net section stress at 16 mm is reduced because of the increased in the doubler plate thickness. Finally it is evident that even though the crack is present in the plate it does not leads to the catastrophic failure but it can account for a net section yielding failure. References [1] Elangovan.R “Analytical determination of residual strength and linkup strength for curved panels, with multiple site damage’’ International Journal of Engineering Science and Technology (IJEST), ISSN: 0975-5462, Vol. 3 No. 5 May 2011. [2] Furukawa.C.H et al, “On the finite element modeling offatigue crack growth in pressurized cylindrical shells”, International journal of fatigue, vol 31, pp 629-635, 2009 [3] Brown.A.Metal“Simulatingfretting contact in single lapsplices” ,International journal of fatigue, vol 31, pp 375-384, 2009 [4] AndrzejLeski, “Implementation of the virtual crack closuretechnique in engineering FE Calculations”, finite elementsin analysis and design, vol 43, pp 261-268, 2007 [5] Ahmed et al., ‘’ Evolution of Multiple-Site Damage in the Riveted Lap Joint of a Fuselage Panel’’ Proceedings of the 8th Joint NASA/FAA/DoD Conference on Aging Aircraft, January 31 – February 3, 2005, Palm Springs, CA. [6] Jones R., L. Molent, S. Pitt, ‘’Study of multi-site damage of fuselage lap joints”, theoretical and applied fracture mechanics, volume 32. issue2, pages 81-100, September-October 1999.

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DESIGN AND STRUCTURAL ANALYSIS OF HIGH PRESSURE CASING OF A STEAM TURBINE K.Laxminarayan1 , K.Kumar2, M.Venkatarama Reddy3 1

Senior Technical Support Engineer,Design Tech,2Manager, Infosys, Bangalore 3 Principal, Sri Krishna College of Engineering, Bangalore laxminarayan.krishnappa@designtechsys.com

Abstract Contact pressure analysis of turbine casing is very important in steam turbine which needs to be addressed for structural integrity. During operating condition steam turbine casings are subjected to very high pressure and temperature which results in stress and strain distribution. If the contact pressure is not achieved as per the standards then it leads to leakage of steam and explosion of casing. If these effects needs to be validated it is very costly. This can be studied using finite element analysis by using simulating techniques. In this work contact pressure analysis of steam turbine is validated by comparing hand calculation and Finite Element (FE) analysis results. Pretension in bolts is considered to achieve a firm contact between the casings. Hypermesh software is used for FE analysis of 3D and CAD model and contact pressure is determined using RADIOSS software. Optimization details of design and operating parameters to get improved overall efficiency of the steam are elaborated in detail. During the last several years the primary changes to the design of steam turbines have focused on improving their efficiency, reliability and reducing operating costs. Key words: Pretension Bolts, boiler, reheater, steam turbine

1. Introduction The casing of a turbine is a pressure vessel where high temperature and high pressure steam from the boiler passes through nozzles to rotate turbine discs. The casing withstands the steam pressure and supports internal components, i.e. turbine shaft with blades A turbine casing is a massive cast structure with a large wall thickness. A casing is subjected to thermal stress across a wall, and to cyclic and sustained pressure/stress in service. Frequent start-ups and shutdowns generate cyclic compressive and tensile stresses in the casing walls. Increased efficiency requires higher steam pressures and temperatures. It requires materials with improved thermal fatigue resistance, greater toughness and higher strength. Materials used for casings are usually low alloy Cr-Mo, and Cr-Mo-V cast steels, with ferrite, ferrite-bainite, or tempered martensite microstructure. The strength of these steels at elevated temperature is obtained by solid solution strengthening and precipitation hardening. High pressure turbine casings are liable to damages caused by distortion and cracking. Distortion occurs due to thermal gradient, rapid start-ups and shutdowns cycles, or load shifts. Casing distortion can cause damage by allowing contact between stationary and rotating parts.[1]. Holmberg and Axelson [2] presented an analysis of stresses in circular plates and rings, with applications to rigidly attached flat plates and flanges, considering the loading at bolt force point as well as gasket compression. The ASME Code contains extensive rules for the design of pressure vessel components, including rules for noncircular pressure vessels of unreinforced and reinforced construction. These rules cover the sides, reinforcing ribs, and end plates of such vessels. Russian scientists P.Shlyakhin [14], A.Kostyuk and V.Frolov [3] have proposed methods to design flanges and bolts of a Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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steam turbine casing. The method proposed by Shlyakhin stands out since it incorporates the bolt design along with flange design. The theory of elasticity has been extensively employed in analysis and design of bolted flanged connections. Waters and Taylor [4] developed an analytical method, based on the theory of elasticity, for ring and hub flanges with straight hubs. The deflection results calculated were compared with test results to demonstrate good agreement. Based on the theory of beam on elastic foundation, Timoshenko [5] proposed a simplified method for the analysis of bending of circular rings. The maximum circumferential stresses for ring flanges and longitudinal stresses for hub flanges can be calculated by using this method. Holmberg and Axelson [6] presented an analysis of stresses in circular plates and rings, with applications to rigidly attached flat plates and flanges, considering the loading at bolt force point as well as gasket compression. A wide variety of machines with rotating components incorporate blades for imparting energy to, or extracting it from [12], various fluid streams. Examples include turbines, pumps, compressors, fans, propellers, etc. In all of these applications, the blade design is critical for achieving optimal overall performance. Srinath and Nayak [7] have carried out a study of the effects of elastic constants in contact stress problems through analytical and experimental (photo elastic) approaches by considering a point contact problem (i.e. sphere pressing against a plane surface under the action of normal force) and have also developed transitional formulae for considerations which translating a model to prototype.

Figure 1 Typical steam turbine

2. Geometric Modelling In an ideal scenario, CAD and FEA activities are coordinated to minimize the duplication of effort as analysis is made an integral part of the design process. The geometry built by the design team will ideally be usable FEA and all downstream applications. It is the responsibility of both the analyst and the designer, or geometry provider, to plan projects such that the optimal level of coordination between CAD and Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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FEA is achieved. Before attempting to consider the merits of using the design model as the analysis model, the conditions listed below must be met.  Design models are built in 3D solids or surfaces that fully enclosed volumes.  The part can and should be meshed with tetrahedrons, or is simple enough to provide the foundation for solid mapped brick meshing or mid-plane surface extraction for building shell models.  The CAD model exists at the time the analysis is to be performed.  The solid modelling CAD systems use either a Boundary Representation (B-Rep) or Constructive Solid Geometry (CSG) method to represent a physical solid object .The B-Rep and CSG representations provide a complete mathematical definition of a solid object. In contrast, to traditional surface modeling software, solid modeling software has automated the process of creating solid model topology. The modelling software UG is used to model the blade and disc of the steam turbine first stage.

UG introduces a comprehensive set of products for integration of product development processes for engineering and manufacturing industry organizations either large or small. It provides a combination of tools to cater for varying levels of usage and required capability with in an organization. UG provides advanced 3D product life cycle management solutions for collaborative product development. Some of the features are mechanical design, assembly, drafting, and mould tooling design; weld design, aerospace sheet metal design, wire frame & surface design, ergonomics design & analysis enovia, and smart team etc.

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Figure 2 Cad Model of Steam Turbine Casing

3. Finite element modeling and analysis In this part the modelled casing is taken up for contact pressure and structural analysis. By carrying out the contact pressure analysis it will be taken care that required contact pressure is maintained at the parting plane and thus no steam leaks out of the casing [11].By carrying out the structural analysis the stresses and deflections in the casing can be determined. Finite element analysis is a numerical technique by which the solution of a set of differential equations may be performed. The finite element method is probably the most widely used form of computer-based engineering analysis. Most engineers, from all disciplines, will touch on the method at some point in their careers. The method can be used for analysis of a broad range of engineering problems. Finite element methods are predominantly used to perform analysis of structural, thermal, and fluid flow situations. They are used mainly when hand calculations cannot provide accurate results. Finite element modelling involves the processes of feature suppression, model idealization and meshing of the solid model. The bottleneck of the whole process is model idealization, which is the process of generating a geometric model into an analysis model of suitable quality and reduced size so that it may be analysed efficiently using FEA. The purpose of a finite element analysis is to re-create mathematically the behaviour of an actual engineering system. In other words, the analysis must be an accurate mathematical model of a physical prototype. In the broadest sense, this model comprises all the nodes, elements, material properties, real constants, boundary conditions, and other features that are used to represent the physical system Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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In FEA General purpose programming terminology, the term model generation/finite element modelling usually takes on the narrower meaning of generating the nodes and elements that represent the spatial volume and connectivity of the actual physical prototype. Therefore finite element modelling can be broadly described as process of defining geometric configuration of the models nodes and elements. ALTAIR HYPERWORKS used for the present work offers the following approaches for model generation/finite element modelling. Default mesh control in ALTAIR HYPERMESH produces an adequate mesh for any analysis, however several mesh controls have been provided in order to achieve mesh of desired quality depending upon the requirement.

Figure 3: Finite Element mode

l Figure 4: Applied boundary condition, pressure load & preload

4. Results and Discussions The main objective of this analysis is to find the contact pressure developed at the high pressure casing parting plane for peak load condition. Figure 5 clearly shows that contact pressure achieved is 46Mpa which is greater than 3 times the operating pressure applied. Since contact pressure achieved 46Mpa is greater than 15Mpa i.e 3 times operating pressure, this ensures that there will be no leak and the casing is safe. This analysis is used to find stresses and deflections developed in the casing and bolts at the peak load condition.

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Figure 5: Contact Pressure

Figure 7: Stress contour on bolts

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Figure 6 : Displacement Contour

Figure 8: Stress contour on casing

Analytical calculation [11] Operating Pressure = 5 MPa For safe Condition Contact pressure = 3 times operating pressure =3*5 = 15 MPa From the above relation it is clear that contact pressure at the parting plane should be greater than 15 MPa. Figure 5 clearly shows contact pressure achieved is 46MPa which is greater than 15MPa. This validates that the casing is safe and there is no leakage at the parting plane region. 5. Conclusion The required contact pressure (such as 3 times the pressure at respective stage) is achieved in the high pressure as well as in the intermediate pressure stages. The analysis results along with the results shown for validation of the procedure show that this design procedure has been successful in generating an optimum design solution and thus can be easily implemented. It is clear from the results that the stress in the casing is well within the allowable stress of 210 MPa. The peak stresses are found at supports i.e. where boundary condition has been applied and at the bolt locations. These peak stresses are just surface stresses and do not pose any problems to the implemented design. The finite element analysis gives a complete picture of mechanical behavior of the flange structures, and design guidelines without costly experiments. The analysis results show that this design procedure has been successful in generating an optimum design solution and thus can be easily implemented. References Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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[1]. “ASME Boiler and Pressure Vessel Code, Section 8, division 1,Pressure Vessels,” The American Society of Mechanical Engineering, New York, NY, 1986 Edition. [2]. Bach, C.,”Versuche Uber die Widerstansfahigkeit ebener Platten”,Springer Variag, Berlin, Germany,1891 104 pages. [3]. Westphal, M.,”Berchnung der Festigkeit loser und fester Flansche”,VDIZ,Vol.41,No.36,Sept.,1897,pp.1036-1042. [4]. Waters, E.O and J.H Taylor, “The Strength of Pipe Flanges”, Mech.Eng. Vol.49, No.5a, May1927, pp.531-542. [5]. Timoshenko, S.,”Flat Ring and Hubbed Flanges”, Contribution to discussion of (6).Mech Engg, Vol.49, No.12, Dec,1927, pp.1343-1345. [6]. Holmberg, E.O and K.Axelson,”Analysis of Stresses in Circular Plates and Rings”(With Application to rigidly Attached Flat Heads and Flanges),ASME Trans J.Appl.mech.Vol.54,No.2,Jan.,1932,pp.13-32. [7]. Waters E.O., D.B.Wesstrom and F.S.G.Williams + others, ”Formulas for Stresses in Bolted Flanged Connections”,ASME Trans Vol.59,1937,pp.161-169.Discussion: Vol.60,Apr 1938, pp.267-278. [8]. Waters E.O., D.B.Wesstrom and F.S.G.Williams+ others,” Formulas for Stresses in Bolted Flanged Connections”, Taylor Forge and Pipe Works, Chicago, 1937(printed 1949). [9]. Mckenzie.H.W, D.J.White and C.Snell,”Design of Steam-Turbine Flanges: A Two-Dimensional Photoelastic Study”, Jour, Strain Anal., Vol.5, No.1, Jan., 1970, pp.1-13. [10]. Blach A.E. and A.Bazergul, “Methods of Analysis of Bolted Flanged Connections- a Review”, WRC Bulletin, No.271, Oct., 1981, pp.1-15. [11]. P.Shlyakhin, Steam Turbines: Theory and Design, Foreign Language Publishing House, Moscow (translated from Russian by A.Jaganmohan. [12]. A.Kostyuk, V.Frolov, first published1981, Steam and Gas Turbines.

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PIN SHEAR STUDY DURING BLADE OFF USING ANSYS B.S.Kiran Kumar1, M.Venkatarama Reddy2 1

Regional Technical Manager, ANSYS Software Pvt., Ltd, Koramangala, Bangalore 2 Principal, Sri Krishna School of Engineering and Management, Bangalore kiran.kumar@ansys.com

Abstract A blade off testing is a specific aero engine testing required by the Federal Aviation Administration (FDA) and other safety agencies to certify safety and performance of jet engines. The tests require engine manufacturers to carry out tests of the engine, to make sure that the engine can survive a compressor fan blade or turbine blade breaking off within the engine, without fragments being thrown out through the casing of the engine. The testing usually requires a specially prepared compressor or turbine blade with an embedded small explosive charge, to separate it on command during the test. In the present study, design of closing blade pin is carried out to study the shear strength of the pin material during blade off situations. Experimental testing of pin shear was carried out, finite element model of pin shear was built using ANSYS 14.5 version. The analysis is carried out for full loading conditions for various materials such as stainless steel, aluminum and titanium. Results obtained from ANSYS are validated against experimental data and comparative details are presented. Key words—Blade off, Pin Shear, Failure

1. Introduction Blade off testing is a specific form of air safety testing required by the Federal Aviation Administration and other safety agencies to certify safety performance of jet engines. The testing usually requires a specially prepared compressor or turbine blade with an embedded small explosive charge, to separate it on command during the test. The tests and standard do not require that the engines continue to operate after the blade failures, only that no fragments penetrate the engine outer casing and that it not vibrate badly enough during its shutdown that it will tear loose from the aircraft, barring other failures. Passing the Fan Blade Off containment test is a major milestone in the aero engine development cycle. The fan blades (not rotating) are visible in Figure 1. When an engine is running there is a risk that the fan blade may break off. This event is known in the turbine industry as fan blade out or fan blade off (or FBO for short).To fly, an engine must be certified by the Federal Aviation Administration (FAA). One milestone of the certification process is the fan blade off test. The basic idea is that the blade release should: 1. Not cause an engine fire (usually from cut fuel/oil supply lines) 2. Not fracture the cases / mounts. The current environment for designing aircraft engine and engine-frame structural systems requires extensive levels of efforts to prepare and integrate models, generate analysis results and post-process data. Additionally, the accuracy of the simulations is less than desired, leading to less than optimal designs, costly testing and re-designs and most important, uncertainties in factor of safety. One of the primary concerns of aircraft structure designers is the accurate simulation of the blade out event. The loss of a first stage fan blade in a high bypass turbine engine can be initiated by material failure due to fatigue, crack, a bird strike or some other foreign object damage. During operation of the engine the area around the pin holes is loaded by very high stresses, this is due to the centrifugal forces coming from the rotating structures. It is very important to understand these stresses Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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during design stage itself to ensure that they are well within the safe limit. If the stresses generated are high (above yield, ultimate strength) then the pin can fail in shear causing the blade failure and heavy damage can happen for the entire engine casing itself. In the present work the pin failure in the closing blade has been studied using Material testing as well numerically simulated the same using Finite element analysis using ANSYS commercial program.

Figure. 1: Fan Blade-Out test Rig

Figure 2: Engine Failure seen during blade-off event The main objectives of this work are: 1. Material testing for finding the load which causes failure. 2. Verification of material testing through finite element analysis. 3. Study of Pin shear for various materials. The shear stress acts parallel to the plane where the tensile and compressive stress acts parallel to the shear plane there are two main shear forces acting, one is the direct or transverse shear stress and corresponding to the type of stress observed in pin, rivets, bolts etc. The other type of shear stress is called the pure or torsional shear observed in shafts and rods. The method of applying load to shear is shown in figure. Here a cylindrical specimen is placed in the central holes of the fixed block and the load is applied to the block thereby producing a single shear. If the specimen is extended to the gap between the two fixed blocks as shown in the figure 3. It is called double shear.

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Figure 3: Schematic of single and double shear test MATERIAL TESTING Testing was carried out at Material testing laboratory in department of mechanical engineering Bangalore Institute of Technology, Bangalore.

Figure 4: Mild steel specimen used for testing Universal testing machine was used for testing the specimen as shown in the below picture

Fig. 5. Universal testing machine with shackles and specimen fitted

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Table 1: Summary of the material testing results

Sl. No

Material used

Type of shear

Mild steel

Single shear

Aluminium

Single shear

Observation: Material used Diameter of Specimen d Area of C/S, A = π d2/4

Average Value

Ultimate shear strength (MPa)

Mode of fracture

38095

337.09

Ductile

18312

162.038

Ductile

Fracture load (f) kg f

3,750 4,000 3,900 1,700 1,900 2,000

36,787 39,240 38,259 16,677 18,639 19,620

= Mild steel = 12 mm = 113.01 mm2

Specimen calculation: Single shear: Maximum shear stress τmax = F/A MPa = 38,095 / 113.01 = 337.09 MPa Where F = Fracture load in N and A = Area of C/S of Specimen in mm2 Here the specimen calculations are shown for Mild Steel component and the same is repeated for Aluminium also.

Figure 6: Fractured component pictures

STRUCTURAL ANALYSIS Finite Element Idealization The material testing is a three dimensional structure by construction and hence which requires three dimensional finite element model. The complete modeling of the geometry is carried out using ANSYS Design Modeler program.

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Figure 7: Assembled components There are three components model one is the pin and two shackles. One of the shackles is fixed and other is free to move in the axial direction. 20 Node hex element (higher order) is used for generating mesh. Mapped mesh is generated for all the three components as shown in the figure 8.

Figure 8: Finite element model Since the area of interest in this study is pin, we have discretized pin with fine mesh and shackle with relatively coarse mesh. Twenty noded brick element is used to develop this FE model. This element is available in finite element software ANSYS Workbench 14.5 is being used in the model. This element is having three degrees of freedom per node, viz translation in x, y & z directions. The finite element model of the shear test is shown in Fig.9 B. Boundary conditions and loading Frictionless contact is defined between the pin and shackles for full load transfer from shackles to pin during application of loading.

Fig.ure 9: Frictionless contact between pin and shackles Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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 The bottom of one of the shackle is completely fixed as shown in below picture.  The pin is fixed in X and Z direction at ends and is allowed move in Y direction ONLY.  The second shackle is fixed in X and Z direction and is allowed move in Y direction ONLY as shown in the below picture.  The value of force required to fracture the component is converted into pressure and applied to the following face of the shackle as shown in the Figure.11

Figure 10: Loads and boundary condition definitions The problem was solved using ANSYS workbench Mechanical interface using nonlinear methods, here the loads are applied gradually and in the increments. The problem was solved for three different materials and the results are presented in the next section Fig.11 shows the total deformation of the entire assembly. Since the area of interest is pin the results are plotted specific to pin component

Figure 11: Deformation plot

Figure 12: Equivalent Von-mises stress

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Figure 13: Principal stress plot The above Figure 13. Clearly shows that one side of pin (loaded side) is in compression state and the other side of the pin is in tension state. Since the entire area of cross section of the pin experiences the load, we need to find the average shear stresses at the point where the specimen gets sheared. ANSYS does not do this calculation automatically; to do this a small macro is developed using ANSYS commands for extracting the results in ANSYS postprocessor.

Figure 14: Average shear stress calculations for mild steel The procedure described here was carried out for mild steel and Aluminium materials. Since the Titanium material was not available for testing, hand calculations were performed for this material for calculating the Average shear stress value.

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Table 2: Summary of the material testing and FEA results

Conclusions:



 FEA methodology has been well established for shear testing using ANSYS Program. Results obtained from ANSYS were matching very well with the experimental results as tabulated above in Table 2.  The above procedure can be extended for predicting the ultimate Shear Strength of the metallic Structures using ANSYS program.

The authors would like to sincerely thank staff members of Mechanical department, Bangalore Institute of technology for all support and cooperation for conducting the experiments at material testing laboratory. We also would like to extend our sincere thanks to Dr. Kumar Kenchegowda for all guidance and insights for validating the results. Last but not least, we would like to thank our family members for all support extended during this work. REFERENCES [1] Dynamic Loads in the Fan Containment Structure of a Turbofan Engine J. Aerosp. Engrg. Volume 22, Issue 3, pp. 260-269 (July 2009) [2] Penetration of disk fragments following impact on thin plate: Juan-juan Li, Hai-jun Xuan, Lian-fang Liao, Wei-rong Hong and Rong-ren Wu. Publisher Zhejiang University Press, co-published with Springer-Verlag GmbH:ISSN 1673565X (Print) 1862-1775 (Online): Issue Volume 10, Number 5 / May, 2009 [3] Aeroengine turbine blade containment tests using high-speed rotor spin testing facility: XUAN Hai-Jun; WU RongRen; 2006, vol. 10, no6, pp. 501-508 [8 page(s) (article)] (11 ref.) [4] Aircraft Engine Blade-Out Dynamics: Kelly S. Carney, Charles Lawrence and Dorothy V. Carney, NASA Glenn Research Center, 2002 [5] The Use of LS-DYNA Models to Predict Containment of Disk Burst Fragments Eric Stamper and Steven Hale, CAE Associates Inc, 2002 [6] Containment and penetration simulation in case of blade loss in low pressure turbine: Astrid Kraus, Jorg Frischbier, MTU Aero Engines GMBH, Munich, Germany, 2002 [7] Simulation of aircraft engine blade-out structural dynamics: Charles Lawrence and kelly carney, Glenn Research Center, Cleveland, Ohio,2001 [8] Penetration simulation for uncontained engine debris impact on fuselage-like panels using LS-DYNA: Norman F. Knight Jr, Navin Jaunkyb, Robin E. Lawsonc and Damodar R. Ambur, 2000 [9] Developing an Efficient FEM Structural Simulation of a Fan Blade Off test in a Turbofan jet engine, Jason Burkley Husband, 2007, etd-10292007-111221 [10] Effects of multiple blade interaction on the containment of blade fragments during a rotor failure: S. Sarkar and S. N. Atluri, Volume 23 , Issue 2-4, Year of Publication: 1996, ISSN:0168-874X [11] Mechanical Metallurgy – Dieter G.E. – Mc Graw Hill Publications New York 1986. XXIII + 751 p., DM 138.50, ISBN 0–07–016893–8. [12] Mechanical Testing and ASTM Standards: [13]http://www.astm.org/Standards/physical-and-mechanical-testing-standards.html

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Application of Topology Optimization for LED Monitor Screen Bracket Analysis M.Saradha Sr.Lecturer, Dept. of Mechanical Engineering. Vemana IT, Bangalore

Abstract From the industry manufacturing point of view, saving of materials and reducing the cost of a product is a challenging task for a design engineer. Therefore, design engineer has to think various methods to solve the above mentioned problems and implement some of the optimization methods to solve several problems. Topology Optimization is used to scoop out the excess material of LED Screen Bracket thereby minimizing weight. Linear analysis is carried out to find the displacement of the bracket. Keywords:

1. Introduction Optimization can be defined as the automatic process to make a system or component as good as possible based on an objective function and subject to certain design constraints. Structural optimization yields a result which exhibits “optimal” structural performance of a given design space under a set of loads and boundary conditions. There are four types of structural optimization, namely topography, size, shape, and topology. These types of optimization consist of algorithms which are fed a variety of constraints and objectives to converge onto a solution. A feasible design is one which satisfies all constraints and an infeasible design is one which does not satisfy one or more of the constraints. The optimum design is one which minimizes/maximizes the objective function while satisfying all constraints. 1.1 Overview of Topology Optimization Topology optimization is a mathematical approach that optimizes material layout within a given design space, for a given set of loads and boundary conditions such that the resulting layout meets a prescribed set of performance targets. Using topology optimization, engineers can find the best concept design that meets the design requirements. Topology optimization is used at the concept level of the design process to arrive at a conceptual design proposal that is then fine tuned for performance and manufacturability. This replaces time consuming and costly design iterations and hence reduces design development time and overall cost while improving design performance. Another problem is that the solution of a topology optimization problem can be mesh dependent, if no appropriate measure is taken. Topology optimization aims at providing the best possible arrangement of material over a given design space, or spatial domain, to minimize/maximize an objective.

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1.2 Problem Statement The LED Monitor Screen Bracket analysis has two objectives to perform. The first objective of the analysis is to determine the deflection of the bracket due to a mounted TV screen of 400N. The second objective is to determine a Light Weight Design of the bracket and to redesign the suitable bracket. 2. Linear Static Analysis The deflection of the bracket due to mounted Monitor Screen is found out by Linear Static Analysis using RADIOSS Solver. Material of the bracket is chosen as steel and properties are assigned to the model. FE model with boundary conditions is shown below. Results of Linear Analysis of the bracket with displacement of 0.174 mm at node 33645 and mass of 2.88 Kg are obtained.

Figure 1: Solid Model of the Bracket

Figure 2: Displacement Results

3. Topology Optimization Analysis Topology Optimization is carried out using OptiStruct Solver. It is implemented to determine the Light Weight Design of the Bracket. The design space/variable (part of the model which will be re-designed) is defined by means of a property collector. There are two new properties: Design Flange Property - Topology Optimization is performed. Design Variables, Responses, dconstraints and Min Objective is given. Non Design Flange Property- Design is not altered/optimized.

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Figure 3: Design Variable for Design Flange

In line with the objective of this optimization study (i.e. minimize the compliance and keep only 30% of the initial mass/volume of the bracket), two responses are needed: Response about volume or mass (same material everywhere) and Response regarding the compliance. The objective of this optimization, the response “compliance” must be “minimized”. 4. Visualizing the topology optimization results

Figure 4: Optimization result

Red color indicates elements with a (standardized) density of 1 (load bearing elements; needed), blue refers to elements with a density of 0. The latter do not carry loads and hence, can be “neglected” or removed. Displacement of the Topology Optimized Model is 0.263 mm and mass is 1.77 Kg. 5. Redesigning the product After two to three trial of Topological Optimization, we obtain a Redesigned Model. Final design will be subjected to a linear static analysis to evaluate its overall performance. Displacement of the Redesigned Model is 0.257 mm and mass is 1.87 Kg. 6. Comparison of results Table 1: Comparison of final results

Linear Static Bracket Analysis Topology Optimized Linear Static Analysis Redesign Static Analysis

Displacement 0.174mm 0.263mm

Mass 2.88Kg 1.77Kg

0.257mm

1.87 Kg

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7. Conclusion Linear static Analysis of bracket is carried out using Radioss Solver to obtain the displacement values. Topology optimization (Weight Optimization) is carried out using optistruct solver to scoop out the excess material of the Bracket and to obtain the suitable displacement and weight of the product. Finally Redesign of the optimized bracket is done for aesthetic look of the bracket and Linear Static Analysis is carried out to verify the displacement results. By comparing the results it is clear that almost 1kg of material is saved. References [1]. [2]. [3]. [4]. [5].

Enhancing Topology Optimization to industry by Chang Liu, JCM, Vol 2, Jun 2010 Practical Finite Element Analysis by Nitin S. Gokhale, Sanjay S. Despande, Anand N Building Better Products with Finite Element Analysis by Vince Adams Operations Research by S D Sharma Engineering Optimization- Theory and Practice by S S Rao.

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FEA AND EXPERIMENTAL QUASI-STATIC CRUSHING OF ALUMINIUM EMPTY TUBE 1

1,3

Mujeeb Pasha, 2Vijayasimha Reddy B.G., 3Ashok Kumar C.N.

Assistant Professor, 2Professor & HoD, 1,2,3Dept. of Mechanical Engg, Vemana I T Bangalore mujeebpasha2002@yahoo.co.in Abstract The technology of energy absorption of vehicular structures colliding with another object has advanced rapidly during the past few decades, largely because of the need to avoid or reduce injury and damage, hence improving the crashworthiness of the systems. Considerable attention has been directed towards designing frontal structures which collapse in a stable manner at a controlled rate. During this collapse, the energy is absorbed in a predictable manner and thus negates the force of impact. One of the most interesting energy absorbing components used in this trade is a cylindrical tube. In this report axial compression of such tubes compressed between flat plates has been examined. Experiments to understand the energy absorbing capacity of unconstrained tubes of Aluminum were conducted under quasi-static axial loading conditions. Failure modes and load displacement characteristics of such tubes were studied in order to assess their mean crushing load and energy absorbing capacities. Both the energy absorbing capacity and specific energy absorption capacities of the tubes are studied. The specific energy absorption capacity and mean crushing loads obtained during investigation can be used as data in designing the energy absorbers for various engineering applications like impact energy absorbers, crash pads, etc. In both the cases, load-displacement characteristics and the deformation mechanisms were studied in order to assess energy absorbing capacities. The study also focuses on the crushing behavior of aluminium tubes under the above loading configuration. Finite element simulation using Ls-Dyna is carried out on aluminium tube. A comparison of energy absorption capacities of this material obtained from the experiment and simulation is made. The results obtained from the simulation of aluminium tube are in good agreement with experimental results.

Keywords: Energy absorb, Ls-Dyna, Hypermesh

1. Introduction Engineers and designers in many industries require information on the maximum amount of energy that can be absorbed for a specific deformation. For example the deformation of passenger cars is designed in a range of accident scenarios to maintain survivable volume with acceleration levels, which avoid human injury. In other practical situations, the maximum amount of energy, which can be absorbed prior to a material failure, is required.

Collisions between objects giving rise to suddenly acting loads are common in everyday life. Collisions are either accidental or intentional-whether they are desirable or not. Such impacts and collisions can and will result in loss of limb, life and property as well as undesirable short and long term effects on environment. It is possible to try and reduce the possibility of unwanted collisions but impossible to prevent them. Impact energy absorbers Impact energy absorbers are expandable mechanical structural elements which are brought into action to dissipate the kinetic energy in the event of unwanted collisions. As such they are single shot devices and have to replace once they have ‘blown’ after serving the Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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purpose. Examples in the extreme are sand or gravel beds in air fields for the emergency landing of aircrafts and bumpers in cars. In some cases, the structural element of the main structures may serve a secondary purpose as energy absorbers and be pressed into service in case of more severe collisions. Similarly those elements whose principal purpose is energy absorption may serve a secondary purpose as less important structural members. In some situations when the passive safety device or the energy absorber is stationary-as in road side construction, at the end of railway lines bottom of lift shafts-the mass of IEA is not a critical design parameter. If the IEA is to be fitted onto the moving structure it is safeguarding, as in cars-the mass of the energy absorber has to be kept as low as possible because the energy absorber mass increases the total mass of moving structure and hence the kinetic energy to be absorbed. In such cases it is very important to make the IEA as light as possible. Applications of IEAs include the bottom of lift shafts or nuclear fuel funnels, roadside crash barriers, civilian and military vehicles, aircraft and ships. The rapid advancement of technology in the recent years has called for renewed emphasis to be placed on safety in transportation and industrial areas. IEAs come in many different shapes and sizes, ranging from simple plates and shells to specially manufacture cellular solids and fluid filled devices, each with a unique collapse characteristic. The selection of an appropriate energy absorber depends very much on its application and the desired response upon impact. However, for an IEA to be effective it should possess the following qualities: 1. A high specific energy absorbing capacity (energy absorbed per unit mass) is essential for IEAs in moving structures like automobiles and aircraft. 2. A high energy-dissipation density, or energy absorbed per unit volume, is necessary in cases where an IEA of compact size is required. Most importantly, an IEA must be able to perform its purpose of mitigating the effects of an impact without any chance of failure.

Figure 2.1(a): Alexander’s model for the collapse of a tube subjected to axial loading

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2. Experimental FLow Chart

Figure 2.1 (b): Flow chart indicates the step wise procedure during the test

Vickers Hardness The Vickers hardness-testing machineVM-50 was used to determine the hardness of the specimens. Hardness is defined as a measure of material resistance to localized plastic deformation (e.g. a small dent or a scratch). Table:…………….

Material Aluminium

Aluminium Aluminium

Specimen code

Dimensions mm OD T

Yield strength ‘ y ’

CA-A1-1

1.60

150

91.54

CA-A1-2

1.60

150

91.58

CA-A2-1

1.60

200

91.53

1.60

200

91.54

1.60

250

91.56

1.60

250

91.57

N/mm2

AVG ‘ y ’ N/mm2 91.56

CA-A2-2 CA-A3-1 CA-A3-2

91.535

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91.565

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Axial Compression Of Empty Metal Tubes Under Quasi-Static Loading Conditions: 

The tubes were tested under uni-axial compressive load in a 50kN electronic version UTM at elongation rate of 1mm per min.  The crushing behavior was observed, the load- displacement and stress-strain curves were plotted.  The energy absorbing characteristics like crushing load, energy absorbed during the plastic deformation were recorded.  Theoretical values of the initial crushing load, energy absorbed, specific energy absorbed were calculated.  The theoretical and experimental values are compared results are tabulated.  The axial compression tests were carried out to obtain the energy absorption capacity of different materials using electronic universal testing machine.

Deformation mechanism of aluminium tube:

Figure 4.3 Load-Displacement Curve of CA-A1-1

PHOTOGRAPHIC VIEWS:

Figure 4.4 The photographs of progressive deformation of axially compressed aluminium tubes in experiment.

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Figure 4.5 (f) Comparative Load-Displacement curves of quasi-static experimental results.

Table 4.2 Comparison of the quasi-static experimental results crushed up to length of 90 mm

Dimensions Specimen CA-A1-1

Diameter (mm) 50

Length (mm) 150

Thickness (mm) 1.6

Energy Absorption (kJ)

Specific Energy Absorption (kJ/kg)

1.047

10.5

CA-A2-1

200

1.6

1.044

7.9

CA-A3-1

250

1.6

1.013

6.1

Discussion Result obtained from quasi-static test on specimens of different length of comparative loaddisplacement curves for the specimens of different length are shown in the figure 4.4 (a-g) respectively. The specimens of different length after crushing reveals that the deformation pattern of Aluminium tubes was identical through the observed under the quasi-static loading conditions.

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3 Finite Element Analysis

Figure 5.1 (f) Tube meshed with impactor and base.

Figure 5.1 (k) Exported file to Ls-Dyna.

Figure 5.2 The photographs of progressive deformation of axially compressed aluminium tubes in FEA.

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Figur e 5.3 (d) Comparative Load-Displacement curves of quasi-static FEA results

Simulation of Aluminium tube The geometry of aluminium tube was constructed for 150 mm length, diameter of 50 mm and thickness of 1.6 mm with hyper mesh pre-processor. The quasi-static test properties of aluminium tube are input to material model.

4 Results and Discussions Axial Compression tests were conducted and the load displacement curves were obtained for each of the test material. From these curves the energy absorbing capacities are determined by tracing the area under the average load line. The energy absorbing capacity of aluminium is found to be appropriate when compared to FEA. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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It has been observed that, it is not possible to predict the beginning of deformation of tubes, whether it occurs from bottom or top side of the specimen Figure 6.3 Comparative Load-Displacement curves of the quasi-static experimental and analysis results.

Table 6.1 Comparison of Experimental and FEA results up to 90mm Energy Absorbed (kJ)

Energy Absorbed (kJ)

Experimental

FEA

CA-A1-1

1.047

1.009

CA-A2-1

1.044

1.006

CA-A3-1

1.013

0.997

Specimen Code

5 Conclusion Experiments were conducted to understand the behavior of metal tubes under quasi-static axial compression load conditions. The Aluminium tubes are tested for empty conditions. The plastic crushing of thin tubes resulted in Euler type of buckling. From this it can be concluded that the deformation modes depends on geometric and material properties of materials. A comparison is made on the specific energy absorbing capacity and means crushing loads for both experimental and FE analysis of Aluminium tubes. The specific energy absorption capacity and mean crushing loads obtained during investigation can be used as data in designing the energy absorbers for various engineering applications like impact energy absorbers, crash pads. These Quasi-static test results can be taken to predict quasi-static behavior of the metal tubes under impact loading conditions. The energy absorption of aluminium tube of different length is tested under quasi-static loading condition about 5% more compare with the LS Dyna simulation.

References [1]. S. R. Reid., and C. Peng., “Dynamic uniaxial crushing of wood”, Int. J. Impact engineering.Vol.19, pp 531-570 (1997 [2]. S. R. Reid, C. Peng and T.Y. Reddy., “Dynamic uniaxial crushing and penetration of wood”, In: Mechanical properties of materials at high rates of strain. J. Harding, edition, Inst. phys. conf. series no 102: Bristol, pp 535-542 (1989). [3]. W. J. Stronge and V. P. W. Shim., “Micro-dynamics of crushing in cellular solids”, J. of Engineering materials and technology. Vol.110, pp185-190, Transctions of the ASME (1988). [4]. T. Y. Reddy., “Impact energy absorption using laterally compressed metal tubes”. Ph. D thesis, Cambridge University, U.K (1978). [5]. W. Johnson., “Impact strength of materials”, Eward Arnol Limited, ISBN0-7131-3266-3 (1972). [6]. T.Y.REDDY and R.J.WALL, Axial compression of foam-filled thin- walled circular tubes, Int. j. impact engng vol. 7, No.2, pp. 151-166, 1988. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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[7]. ABRAMOWICZ, W and JONES, N, Dynamic axial crushing of circular tubes, Int .j. impact engng. , 2, pp. 263-281 (1984). [8]. AL-HASSANI, S. T.S, JOHNSON, W and LOWE, W. T, characteristic of inversion tubes under axial loading, j. Mech .sci. ,25 , pp 370-381 (1972) . [9]. W. JOHNSON and S.R REID, Metallic energy dissipating systems. , Appl. Mech .Rev, 31, 277-288 (1978).

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CRITICAL SPEED DETERMINATION OF A SINGLE STAGE IMPULSE TYPE STEAM TURBINE BLADED ROTOR DISC V.G. Bharath 1, Vikram Krishna2 1

Lecturer, Dept. of Mechanical Engineering, VIT, Bangalore Design Engineer, Ramaiah Institute of Advanced Studies, Bangalore 1 bharathvg@gmail.com

Abstract Dynamic phenomena are some of the predominant criteria effectuating the failure of rotating turbo machinery. The ambient interaction of these turbo machines is of cardinal importance, since operating them at certain speed ranges may lead to either long term dynamic fatigue due to induced alternating stresses or resonant failure. Dynamically sound design of machinery in aerospace applications is not only crucial from the monetary standpoint, but also from the safety perspective. The potential consequences of “ambient interaction” are referenced to highlight the common outcomes of the structural interaction of the turbo machine rotor with a host of detrimental ambient factors. Resonant vibrations incited by the running speed harmonic excitations, steam impinging frequency, engine order excitations are fundamental causes for failure of turbine components. The mainstream discipline that is encompassed by this study is the modal analysis. Modal analysis is performed to estimate the critical speeds and study the mode shapes of the bladed rotor disc under prestressed condition. Finite Element (FE) analyses were adopted to execute the work, and were implemented in ANSYS. Keywords: ANSYS, Dynamic, Modal analysis, resonant failure, rotor disc, turbo machinery.

1. Introduction Steam turbines are mainly used to drive machines, pumps, compressors and electrical generators of various capacities. In an impulse type steam turbine, the blades are set on the rim of the revolving wheel mounted on a central shaft. Steam passing through a fixed nozzle passes over the curved blades and absorbs the kinetic energy of the expanded steam thereby turning the wheel and shaft (turbine rotor) on which they are mounted. The literature survey indicates that steam turbines are among the most suitable and viable prime movers for power generation. With phenomenal increase in power consumption and consequently enormous demand for power generation, plants with smaller capacities are going to be most commonly used sources in the coming years. In spite of several advantages, these turbine rotors [1] seem to fail mainly due to resonant stresses developed at the critical speeds of the rotor. Also, blade failures are caused by resonant conditions triggered by the coincidence of the blade natural frequencies with the nozzle excitations. In this context, modal analysis on turbine rotors during its operation has acquired significance with the main objective of preventing failure of turbines due to resonant stresses. Modal analysis on turbine rotor assembly may help in a reliable design. Further, this may reduce high factor of safety employed in the industry and contribute to reduction in weight and enhanced performance. In this context, in the present investigation an attempt has been made to carryout systematically a detailed modal analysis on a bladed turbine rotor for various speeds in order to study the critical speeds and mode shapes of the bladed rotor disc.

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2. Vibrations 2.1 Bladed Vibration The Motion of a body about its equilibrium position which repeats itself after a certain interval of time is known as vibration. Vibration is a physical phenomenon occurring in bodies due to their over-elastic properties or due to various external sources, which cause them to continuously oscillate about their mean position. Blade failures due to fatigue are predominantly due to vibrations, caused by resonant conditions triggered by the coincidence of the blade natural frequencies with the nozzle excitations. The causes of blade vibrations are loose fittings, misalignment, bent shaft, eccentric journals, insufficient vibration isolation, and defective Bearing and the factors affecting blade vibrations are blade taper, asymmetry of blade cross section, centrifugal forces and blade setting angle. 2.2 Disc Vibration Various periodically varying forces are conducive to exciting the some of the natural frequencies of the disc causing resonant vibrations in the disc. Causes of disc vibrations are force transmission from blade to the disc, non-uniformity of steam flow around the disc, inertia forces of unbalanced residual masses, running the turbine close to critical speeds and steam pressure pulsation. 3. Finite Element Techniques Finite Element Analysis (FEA) is a numerical technique that can be used to approximate the structural dynamic characteristics of vibrating mechanical systems. This technique can be used for structural dynamic studies of existing equipment or to evaluate the dynamic characteristics of machines and structures prior to fabrication. It is important to realize that the finite element method [2] is an approximate numerical technique. The accuracy of a solution obtained by finite element analysis depends on several factors, the most important of which are: • Degree of refinement of the finite element mesh. • Appropriateness of the finite element types used to model a machine/structure. • Boundary conditions used at the limits of the finite element model. Because a finite element model provides a more detailed mathematical description of a mechanical system than an experimental model, it is well suited for structural dynamic modification studies. An experimental model is usually sufficient to serve as a valuable root-cause analysis tool. However, the finite element model [3] is required to propose and incorporate design modifications directed at removing resonance excitation problems. The finite element method provides the vibration analyst with a numerical technique to evaluate  Natural frequencies and mode shapes to ensure that equipment does not operate at or near any resonant frequencies.  The stiffness of supporting structures/foundations.  Areas of structural weakness or probable resonances which can be addressed during the design stage. The finite element method [4] can also be used to estimate stress levels in rotating equipment during operation, which includes both centrifugal stresses and stresses due to the application of dynamic loading, such as unbalanced forces.

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4. Methodology 4.1 Modal analysis Modal analysis basically determines the natural frequencies and the corresponding mode shapes of a structure or a machine component while it is being designed. Modal Analysis is essential in anticipating the vibration levels or determining what actions to be taken if the vibration is to be controlled. The primary objective of modal analysis is to assist the designer to design [5], [6] the structure and determine its weight, stiffness and frequency of operation in such a manner as to minimize any vibrations by precluding resonant vibration. 4.2 Prestressed Modal Analysis A prestressed modal analysis is where the modal response of a structure is analyzed when a mechanical stress is applied to the structure. This can be performed to calculate the frequencies and mode shapes of a prestresssed structure, such as spinning turbine disc. 4.3 Model considered for analysis This is an impact type steam turbine. The disc has 72 shrouded blades arrayed around its periphery as shown in figure 1. The turbine casing has 10 nozzles, from which steam impinges on the blade surfaces tangentially, and torque is developed.

Figure 1: The bladed disc of the steam turbine rotor

Figure 2: 10 deg sector bladed disc of steam turbine rotor

4.4 Geometric Modeling A 100 cyclic symmetry model is used for the analyses instead of the entire model, in order to save time, memory requirements and ANSYS computational resources. This model enshrouds 2 blades, and is as shown in figure 2. This model comprises all the nodes, elements, material properties, real constants, boundary conditions, and other features that are used to represent the physical system.

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4.5 Finite element modeling The sector shown in figure 2 was meshed using tetrahedron brick elements, and due to the complexity of geometry, the component was free meshed as shown in figure 3. Then, the cyclic symmetry model option was activated to expand the 100 sector 36 times about the z – axis, to obtain a meshed 3600 model. A cyclic symmetry analysis requires that a single sector be modeled, called the basic sector. A proper basic sector represents one part of a pattern that, if repeated N times in cylindrical coordinate space, yields the complete model.

Figure 3: Meshed 10º Sector of bladed disc of steam turbine rotor

The detailed procedure of carrying out prestressed modal analysis in ANSYS has been shown in figure 4. Import 10 deg Sector Model

Define Cyclic Symmetry

Define Static Analysis

Turn "Prestress" Flag "On"

Impose Inertia Boundry Condition

Solve Static Analysis

Define Modal Analysis

Set Modal Options

Turn "Prestress" Flag "ON"

Solve Modal Analysis

Review Mode Shapes and frequencies

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Figure 4: Prestressed model analysis procedures in ANSYS

4.6 Campbell diagram A common way to identify forced response regions of a bladed disc is the Campbell diagram, which is a key plot in the dynamic design process [7]. It is a plot of Frequency – vs – Rotational speed. It is essential in eliminating the critical speeds that could be encountered during operation, for different vibration modes of the component. Resonance is caused when the nozzle passing frequency coincides with one of the natural frequencies of the bladed disc. Nozzle passing frequency is defined as the number of times steam from the nozzles impinges on a blade per second. It is a function of the rotor running speed and the number of nozzles. NPF = t N/60 where t is the number of nozzles =10, N is the rotor running speed. Engine order excitations [8] are caused by non –uniformities on the stator blade row .The excitations can induce vibrations in fundamental blade modes. These excitation frequencies are computed at different disc speeds (N) using a generalized empirical formula EOF = nN/60 Hz where n = 1, 2, 3, etc. The critical speeds for the bladed disc can be evaluated by extrapolating the points of intersection of the nozzle passing frequency and the engine order excitations lines with the Eigen frequency lines onto the speed axis. When the frequency of external excitation (Engine order and nozzle passing) coincides with any of the natural frequencies, the amplitude of vibration increases excessively, and this condition of the structure is called resonance. A typical Campbell diagram [9], showing Eigen frequency lines of the bladed disc along with engine order and nozzle passing excitation lines is shown in figure 5. The black spots in the figure represent resonance due to coincidence of the nozzle passing and engine order frequencies with the natural frequencies of the bladed disc. Table 1: Prestressed modal analysis results

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Campbell Diagram - Prestressed Case 9000 8000

Natural Frequency (Hz)

7000 Mode 1 Mode 2

6000

Mode 3 Mode 4

5000

Noz zle P ass ing Frequency Engine Order E x citation [E .O.1]

4000

Engine Order E x citation [E .O.2] Engine Order E x citation [E .O.3]

3000

Engine Order E x citation [E .O.4] Engine Order E x citation [E .O.5]

2000 1000 0 0

10000

20000

30000

40000

50000

Rotational Speed (rpm)

Figure 6: Campbell diagram of prestressed modal analysis

Figure 7: A typical Campbell diagram showing points of resonance

5. Results and Discussions 5.1 Prestressed modal analysis As explained in the previous chapter, a detailed analysis has been carried out on a steam turbine rotor assembly to study the critical speeds and mode shapes of the bladed rotor disc, under prestressed condition. In table 1 has been presented the variation of natural frequency with different rotational speeds of the rotor from 0 to 50000 rpm in steps of 5000 rpm. Also, listed are the nozzle passing frequency (npf) extracted from the rotational speeds (rpm x 10 / 60) and first five engine order excitations extracted from nozzle passing frequency (npf x 1/10, npf x 2 / 10, npf x 3 / 10 etc). Figure 6 has been presented the Campbell diagram of natural frequency (Hz) with rotational speed for the first four modes of Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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natural frequencies, Nozzle passing frequency, and the first five engine order excitations. Figure 7 has been presented the displacement contour plot of disc at mode 1. 5.2 Inference and Interpretation of Results Since the nozzle passing frequency excites only the first four modes of the bladed disc in the speed range of 0-50000 rpm, only the first four modes were considered for analysis. Also, since the blade geometry is such that it is not only shrouded along its full length by the disc but also substantially inferior in size in comparison with the disc, blade resonances occur at very high frequencies. These are very unlikely to be excited by either nozzle passing frequency or engine order frequencies, as the rotor is never run at such high speeds. From figure 6 and Table 2, it can be seen that the first critical speed i.e., the excitation of the first mode can occur at any of these speeds due to their respective sources of excitation. The second critical speed, i.e., the excitation of the second mode can occur at any of these speeds due to their respective sources of excitation and is shown in table 3. The third critical speed, i.e., the excitation of the third mode occurs at 32500 rpm due to nozzle passing frequency excitation. The fourth critical speed, i.e., the excitation of the fourth mode occurs at 35000 rpm due to nozzle passing frequency excitation. It is observed from the Campbell diagram [10] for the prestressed modal analysis of figure 6, that a spin stiffening behavior is exhibited by the rotor disc. As the rotational speed is increased from 0 to 50000 rpm, the natural frequencies are observed to augment (increase) significantly for all the modes. This is the result of the structure being stiffened due to static prestressing as the spinning speed is increased. Table 2: List of first critical speed with respective excitation source First Critical Speed (rpm)

Excitation Source

4500

Nozzle Passing

10000

Engine Order 5

13000

Engine Order 4

20000

Engine Order 3

45000

Engine Order 2

Table 3: List of second critical speed respective excitation source Second Critical Speed (rpm)

Excitation Source

17500

Nozzle Passing

41500

Engine Order 5

Figure 7: Displacement contour plot of disc at mode 1 Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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6. Conclusions Novel method that is based on ANSYS Modal analysis procedures has been developed for estimating resonant speeds that could be encountered during operation of turbine rotors for different vibration modes. It is found to be very effective in finding forced response regions of the bladed disc of small and medium capacity steam turbine rotors. References [1] Donald Andrew Phillips.-Finite Element Analysis of a Shaft-Rotor System, Virginia Polytechnic Institute and State University, January 23, 2001. [2] Klaus Jurgen Bathe-Finite element procedures, Prentice Hall of India publications [3] Tirupathi R Chandrupatla - Introduction to Finite Elements in Engineering, Prentice Hall of India Publications [4] ANSYS Help files. [5] Mahadevan and Balaveer Reddy - Design data hand book, CSB Publishers and Distributors [6] Prof H.G.Patil -Design data hand book [7] John c Nicholas, “Operating turbo machinery at or near the second critical speed in accordance with API specifications” Rotor Bearing Dynamics ,Wellsville,NY.USA. [8] Markus Jocker, Alexandros kessar, Torsten H. Fransson, “Comparison of models to predict low engine order excitations in a high pressure turbine stage”, kungliga teknisha Hogskolan (KTH), S-10044, Stockholm, Swedan. [9] Murali P Singh, John J. Vargo, Donald M. Schiffer, james D.dello, “SAFE Diagram – Adesign and reliability tool for turbine blading”, Dresser-Rand, Wellsville, NY,USA. [10] J.S.Rao, “Turbomachine Blade Vibration”, Published by ‘JohnWiley & Sons’, New Delhi, India, 1991.

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HEAT TRANSFER ANALYSIS OF RECUPERATIVE AIR PREHEATER H.H.Vishwanath1, Thammaiah Gowda 2, S.D.Ravi3 1

Student, 2Professor and Head, 3 Senior Engineer Adichunchanagiri Institute of Technology, Chikmagalur, 3 Ingersoll Rand, Bangalore vishwanath1hh@gmail.com

1,2

Abstract Steam generators are very complex class of pressure vessels. It contains many accessories for the generation of required steam quality. The prime motto of industrial steam generator is to generate steam at Medium Pressure (MP), Low Pressure (LP) steam at required temperature and quantity for the process industries like sugar, paper, jute and chemical plants. Air preheaters make a considerable contribution for the improvement of the overall efficiency of fossil-fuel-fired power plants. In this study, a theoretical design of recuperative primary air preheater with in-line tube arrangement and a combination of fluid dynamics analysis with theoretical value is attempted. The model enables heat transfer of the fluegas flow through the air preheater and the resulting temperature distribution in the matrix of the preheater.The present work is carried in Mysore Paper Mills (MPM) Bhadravathi, Computational Fluid Dynamics (CFD) analysis of recuperative air preheater is carried out using ANSYS CFX-12.1.The analysis of flue gas flow phenomenon and air flow phenomenon are discussed using Laminar model, k-ε model, k-ω model and SST model. The parameters like temperature distribution, heat flux, pressure drop, velocity, are also discussed. An increase of 2.7% in boiler efficiency was found out with incorporation of this design, thereby an increase in the air inlet temperature of about 600C is observed. Keywords: Recuperative Air preheater, k-ε model, k-ω model, SST model.

1. Introduction The Mysore Paper Mills Limited, (MPM) founded by Sri.Krishnaraja Wodeyar bhadur in 1937 the Maharaja of erstwhile Mysore State was incorporated on 20th May 1936 under the then Mysore Companies Regulation, VIII of 1917. Later it became a Government Company in 1977 under Section 617 of the Companies Act, 1956. The Company has Its Registered office at Bangalore and its Plant Located at Bhadravathi. In India 65 percent of energy consumption due to coal fired power generation is dependent on non-coking coal as high ash coal in pulverized form. The total coal consumed for power generation accounts 50% of the coal produced in India including middling’s and sinks available from more than 17 Washeries. The quality of Indian coals available for power generation is progressively detoriating with growing emphasis on open cast mining. The high ash content along with highly abrasive nature of the ash causes forced outage of thermal power plants. The average national availability of thermal power plant is between 52 – 53 percent. The existing coal based power plants have reached 36% efficiency. In future program degradation in quality of coal will cause further reduction of the efficiency of power generation as well as inherent creation of pollution problems. Besides pollution caused by the thermal power station is expected to increase its planned addition of power generation capacity. A primary air heater is a tubular, In-line tube arranged air heater. This is arranged in the form of cross-flow heat exchanger. Many primary air heaters are used in coal-fired power plants. In MPM the plant is operating without Air preheater, here the atmospheric Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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air is being fed into the plant. The objective of this work is to investigate the performance of primary air heaters at Mysore Paper Mills Ltd, design & analysis of Recuperative air preheater using CFD. 2. Methodology Theoretical Tubular Primary air preheater Design In this design, hot gas flows outside the tube bank, transfers heat to the inside tube. The heat transfer rate can be calculated as Q = W × C (T − T ) = W × C (t − t ) ) The density of Flue gas is calculated as by using density, velocity, of flue gas and inside tube diameter, number of tubes can be calculated as below equation W N = 0.05 d ×ρ ×v According to the space requirement the width and depth of the air preheater is calculated as follows. N ×S W= 12 N ×S H= 12 Heat transfer coefficient of both flue gas side and air side can be calculated using below equations respectively. W . C h = 2.44 N d. F h = 0.9G . d . Where, C and F are temperature factors evaluated at average flue gas temperature and film temperature respectively from table of D Q Kern W G = FGA L FGA = (S − d )N 12 The overall heat transfer coefficient U is calculated by using flue gas and air side heat transfer coefficient from below equation. 1 d 1 = + U hd h Heat transfer is also given by from below equation Q = UA∆T After finding out the area of heat transfer, one can calculate the actual length of the tube as mentioned below π×d ×N ×L A= 12 To check the metal temperature at the exit portion using below equation G (T − t ) (T − t ) = (G + a ) Where, d G = dh 1 a = h The Gas side and Air side pressure drop is given by following equation respectively. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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∆P = 93 × 10

× 0.02

W N

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L + 5d ρ d ∆P

= 0.038 × N

Table 1: Theoretical design in SI units

Parameter

Symbol

Unit

Quantity

Gas quantity

W W t t °T Q T ρ

Kg/hr

85000

Kg/hr

104000

°C

120

°C

200

2016.84

Air quantity Air inlet temperature Air outlet temperature Flue gas inlet temperature Heat transfer Flue gas outlet temperature Density of flue gas Number of tubes Width of Air preheater Depth of Air preheater Length of Air preheater Gas side heat transfer coefficient Air side heat transfer coefficient Overall heat transfer coefficient Flue gas side pressure drop Air side pressure drop

°C

134 3

Kg/m

0.833

N W D L h

W/m k

48.612

W/m2k

51.872

W/m2k

23.96

∆P ∆P

mmwc

967.83

mmwc

961.5

1332 m

2.82

2.286

5.08 2

Figure 1: In line tube arrangement of primary air preheater

3. Geometry modeling and meshing The geometric modeling of heat exchanger was built in ICEM CFD on same grounds as in experimental study. Since flow around heat exchanger and inside the tubes have scaled down from 1332 tubes matrix to the 9 tubes matrix with 3 rows and 3 columns. The HX domain is in rectangular in shape, to reduce the computational domain this scaled down approach is been selected. The simulation done on a scaled down model of the heat exchanger would imply to the whole domain. So scaled down model of heat exchanger was built in ICEM CFD. Heat exchanger model can be seen in Fig.2a. Time tubes and flow rates are scaled down the full model including ducts. The heat exchanger tubes are considered structured mesh and around the tubes have considered unstructured meshes for geometry. It was not possible to create hexahedral volumes in heat exchanger model around the tubes volumes. So an unstructured mesh was Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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generated using robust volume meshing. The Robust Volume Meshing method produces a triangular or quadrilateral volume meshes. The volume mesh is produced interactively and can contain many different element types, including hexahedral and wedge elements. The mesh has been clustered more at wall of the heat exchanger to capture boundary layer growth near the wall. Grid refinement study was carried out in order to see if flow captured is sensitive to grid distribution, it can be seen from fig 2b&c. Refining grids beyond 12.5 lakhs elements does not alter the results by more than 2 % and hence results at this grid resolution are optimum to predict flow in heat exchanger accurately. Boundary conditions Any numerical simulation can consider only a part of the real physical domain or system. Furthermore, walls that are exposed to flow represent natural boundaries of physical domain. The numerical treatment of boundary conditions requires a particular care. Stability and convergence speed of solution scheme can be negatively influenced. Steady state approach with stationary domain, non-buoyant condition, low intensity turbulence and static temperature of 300 K are used as criterion for solution. Air at 250 C and Flue gas are used as domain fluid and reference pressure is taken as 1 ambient. ‘No slip’ conditions are used at the wall. The upwind advection scheme is used and a very small physical timescale is specified. The flow models used is SST. Fig2d shows the boundary representations, white color arrows are inlets and yellow color arrows represents.

4. Results and discussion Numerical analysis is carried out for heat exchanger using counter flow approach. Ansys CFX 12.0 is been used for simulate the HX process in the selected HX domain. Geometrical configurations are shown in the geometry and meshing part. The cold air is entering into the domain with ambient condition at 35 C, and hot flue gas will enter into the tubes bundle domain with hot condition at 200 C. Flue gas is the mixture of CO2 and N2 . Air exit duct

Flue gas exit

HX tubes

Flue gas entrance

Baffles Air entrance duct

Figure 2: Geometry modeling and meshing, a) 3 by 3 matrix HX tubes with flues gas and air flow ducts’ b) Structured meshed computational model view for HX tubes alone with 3 by 3 matrixes’ c) Tetrahedral meshes for flue gas path with baffles are in positions’d) Boundary condition graphical representations.

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CFD modeling is done as like test setup condition and heat transfer is also enabled in the simulation. Heat transfer option is Thermal energy used with omega based SST turbulence model is used to resolve the near wall heat transfer coefficient effectively. In the actual setup there are 1332 HX tubes with big compartment, for simulation simplification 9 HX tubes are selected by 3 × 3 matrix. It is been scaled down by geometrically, dynamically and kinematical. The scaled down ratio is 148 times as compared to the test model. This modeling scaled down model itself called for 12.5 lakhs computational mesh elements. Inner core of the tubes are considered structured meshes and tubes thickness is also structured mesh. The baffles and air manifolds are in the modeling and it is little complex to generate the structured mesh apart from the tubes. So unstructured meshes called tetrahedron elements are generated with fine meshes, in which it can able to capture the boundary layers using by prism layers of the unstructured meshed model around the HX tubes. Flue Gas flow phenomenon Flow gas enters the domain in tubes location, the temperature of the flue gas is at 200 when it enters. One can see the velocity vector in below Fig 3a the gas is entering into the tubes domain and passes over the HX tubes. Baffles are hindering the flue gas path and change the flow path for effective heat transfer can be done in this process. Baffles are designed such way that entire length of the tubes has to exchange the heat information by conduction and convection process.

Figure 3 Flue gas flow phenomenon a) Velocity vector for flue gas flow b) Temperature contours plot c) Static pressure contours plot d) Velocity streamlines for flue gas flow path

Figure 3b shows the temperature variation for flue gas across the fluid domain, when the flue gas enters into the domain the temperature is 200 oC. When the hot gas reached at exit location of the domain temperature brings down to 120 o C. Baffles are the good options for increase the heat transfer rate across the domain. Temperature profile can see that the temperature bring down effectively in half of the length of domain. The temperature reduction is 80oC effectively, the calculations are also shows similar range of the temperature data and it is very much closer to the test data. Temperature comparisons can be seen in summary part of the report. The flue gas is a combination of CO2 and N2. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Figure.5c shows the static pressure variation across the flue gas domain. The system static for the entire domain is offering 800 Pa its almost 0.2 PSI. The estimated pressure drop is not exceeding beyond the limit and these numbers are expected for this type of fluid domains. Also the pressure variation is uniform across two planes. So this indicates the flow behavior inside the fluid domain remain same even though we select the full geometry. Velocity streamline is shown in figure 2d, from which it can be seen that the velocity of flue gas is increasing at the baffles. Air flow phenomenon in the fluid domain Air enters the domain in tubes location, the temperature of the air is at 35 when it enters. One can see the velocity vector in below Fig 4a; the air is entering into the tubes from the entrance duct and leaving domain through exit domain. The velocity distribution across tubes is not varied much. Velocity of air is same at inlet and outlet of the domain. Fig 4b shows the temperature variation for airflow across the fluid domain, when the air enters into the domain the temperature is 35oC. When the hot air reaches the exit location of the domain temperature shoots up to 95 oC. Temperature profile can see that the temperature shoots up in half of the length of domain. The temperature rise is 60 oC effectively, the calculations are also shows similar range of the temperature data and it is very much closer to the test data.

c) d) Figure 4. Air flow phenomenon in the fluid domain, a) Velocity surface streamlines for air flow path, b) Temperature contours plot, c) HX tubes wall temperature contours plot, d) Heat flux contours over HX tubes Table.3. Comparison of flue gas air and HX tube for two in let temperature Air Performance Design

Mass flow rate

Air inlet Temp

Air Exit Temp

Air inlet Pressure

Air Exit Pressure

Pressure drop

kg/s

Air at 35 C

0.195

308

361.84

306.26

Air at 25 C

0.195

298

355.13

306.25

Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

HX Tubes Performance

Flue gas Performance Design

Mass flow rate kg/s

Flue gas inlet Temp K

Flue gas outlet Temp K

Flue gas inlet Pressure Pa

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Flue gas outlet Pressure Pa

Pressure drop

Heat Flux

Wall Temp

W/m2

Air at 35 C

0.16

473

401

1051.13

1419.5

376

Air at 25 C

0.16

473.1

396.7

1045.37

1510.43

370.42

Temperature on HX tubes are shown in below fig 4a) air entrance side of the tubes has low temperature region, it is about 60 C. The flue gas looses the enthalpy when its reach the exit of the domain, due to this reason the low temperature is captured. The high temperature over HX tubes captured where the flue gas enters the domain. And we can see that the baffles are changing the flue gas flow directions, due to the change in direction the temperature profile over HX tubes are changing. Heat flux on HX tubes are shown in below fig 4b) flue gas entrance side of the tubes has low heat flux region is captured. Once enter the flue gas inside, the tendency of hot fluid take a turn towards baffles side and right side has little recirculation flow. Due to the flow turn the heat transfer rate is less in that location. Other places of tubes have better heat transfer. 5. Conclusions The heat transfer, temperature variation, velocity of both flue gas and air and heat flux is reported in this study. From fig 3(a, b) the baffles are providing the hindrance to the flow path of flue gas, so that the maximum heat flux is observed at this point of HX tubes it can be seen from fig 4d So it can be concluded that by providing baffles the rate of heat transfer will be increased. An optimum air side pressure drop is observed, which depicts the installation of medium quantity of air blower, by which energy consumed will be less, from that the overall efficiency of the plant will increase. From incorporating the proposed design in the existing plant, the temperature of the primary air would increase by about 60oC. Then the efficiency of the boiler would increase by 2.7%, their by reducing the coal consumption. References [1]. P.N.Sapkal, P.R.Baviskar, M.J.Sable, S.B.Barve ― “To optimise air preheater design for better performance”. NEW ASPECTS of FLUID MECHANICS, HEAT TRANSFER and ENVIRONMENT. ISSN: 1792-4596, ISBN: 978-960-474-215-8, PP.61-69. [2]. Pipat Juangjandee ― “Performance Analysis of Primary Air Heater Under Particulate Condition in Lignite-Fired Power Plant” Engineering, Computing and Architecture, ” ISSN 1934-7197,vol 1,issue 2,2007 [3]. Bostjan Drobnic, Janez Oman. ― “A numerical model for the analyses of heat transfer and leakages in a rotary air preheater” , International Journal of Heat and Mass Transfer 49, PP.5001–5009, 2006. [4]. Stephen K.Storm,john Guffre, Andrea Zucchelli ”Advancements with Regenerative Airheater Design, Performance and Reliability” POWER-GEN Europe 7-9 June 2011. [5]. P.N.Sapkal, P.R.Baviskar, M.J.Sable, S.B.Barve, “Optimization of Air Preheater Design for the Enhancement of Heat Transfer Coefficient”, International Journal of Applied Research in Mechanical Engineering (IJARME), ISSN: 2231 –5950, Volume-1, Issue-2, 2011. [6]. Melling.A.Tracer “Particles and Seeding for Particle Image Velocimetry Measurement Science and Technology”, vol.8 no .12, PP.1406-1416, 1997. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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INVESTIGATION ON THERMOCHEMICAL HYDROGEN PRODUCTION CYCLE TO UTILIZE WASTE HEAT ENERGY P.Rajeesh1 , T.Mohammad Shekoor2 1

Student, 2Professor, 1,2Dept. of Mechanical Engineering, LBS College of Engineering, Kasaragod, Kerala, rajeesh3003@gmail.com

Abstract This review paper intends to provide an overall vision of hydrogen production by the use of heat energy. Heat recovery method may successfully be used as a source of heat energy. This study is focused on only water splitting cycle where water is the only input & hydrogen and oxygen are the output. At present, more than one hundred of thermo chemical cycles are known for hydrogen splitting process. Our aim is to find out the most suitable cycle on the basis of economy, availability of reactant and simplicity of cycle. Lot of thermo chemical cycles have been studied, from which Cu-Cl cycle is best suitable for low temperature hydrogen production by using solar energy, engine waste heat. This is promising to the alternative method for conventional hydrogen production. In addition to low temperature, it requires very low electricity for completion of a cycle. Intermediate chemical reactions are very safe, chemicals are easily available and efficiency of the cycle reaches almost 50%. Keywords: hydrogen, water splitting, cycle

1. Introduction Hydrogen is an alternative source for fossil fuels. The main attractive feature for hydrogen as fuel is the byproduct of hydrogen combustion is nonpolluting water. The smallest molecule of universe sees highest demand due to its non-polluting end product as well as its remarkable chemical and physical properties. Due to its rising demand researchers have been looking at different possibilities to generate hydrogen by biological and chemical means. Hydrogen considered as an ideal energy storage medium because of the following reasons. (1) It is the most abundant element and it exists in both water and biomass; (2) It has a high energy yield (122 kJ/g)compared to other fuels such as gasoline (40 kJ/g); (3) It is environmentally friendly because its end use will not produce pollutants, greenhouse gases, or any harmful effect on the environment (4) Hydrogen can be stored in gaseous, liquid or metal hydride form [1]. 1.1 Some concern about hydrogen Purpose of hydrogen application has lot of limitations. Main problem is its storage. Hydrogen must be compressed to minimize its storage volume because of its low energy density. Hydrogen with low volumetric energy is generally stored as a compressed gas or liquid, meaning that an advanced compression process is needed. This will increase the cost to the use of hydrogen. The storage of hydrogen in metal hydride form is another alternative to compression. However, metal hydrides are often expensive, heavy, and have a limited lifetime, making the process costly and less practical. Considering the application of hydrogen in road transportation, present efforts are based on two directions. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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One is to make hydrogen-combustion vehicles, and the other is to make hydrogen fuel-cell vehicles. The advantages of hydrogen vehicles include a reduction in the emission of carbon dioxide and other smog-producing pollutants, as well as a great reduction in the release of nitrogen oxides (NOx). Unfortunately, the introduction of hydrogen vehicles into the commercial market has faced the challenges of inadequate hydrogen fueling infrastructure and high production cost in comparison to other petroleum-based vehicles. From this we understand that the main challenge regarding hydrogen is its storage and production. In this paper passed through about hydrogen production. Electrolysis of water is one of the easy and greener route to generate hydrogen, this is the conventional method .But this required electricity. Scientists are looking to go one more step ahead, i.e. to reduce or avoid the requirement of low amount energy in the sense of cost, quantity, quality. The product cost of hydrogen may reduce, if we are using renewable energy for the production of hydrogen. But still renewable energy contributes only about 5% of the commercial hydrogen production primarily via water electrolysis, while other 95% hydrogen is mainly derived from fossil fuels [2]. So far, hydrogen production process featured in environmentally friendly, large scale, low cost and high efficiency is still unavailable for commercialization. 1.2. Hydrogen production Currently, most of the world’s hydrogen is produced by a process called “steam reforming”. In this methane is used as fuel. This has two step, the reformation process in which methane mixed with steam is passed over a catalyst bed at high temperature (700– 900°C) and high pressure (1.5–3 MPa) to form a mixture of hydrogen and carbon monoxide (CO). The second step is the shift reaction in which CO from the first step reacts with additional steam to give CO2 and more hydrogen. Another process used for hydrogen generation that involves fossil fuels is coal gasification. In this process, the coal undergoes partial oxidation at high temperature and pressure (~5 MPa) with the help of oxygen and steam to produce a mixture of hydrogen, CO, CO2, methane and other compounds. At temperatures above 10000C and pressures of 1 bar, mostly hydrogen and CO remain [3]. The process can be represented by the following reactions. Biomass, such as crops, plants, and animal wastes, can also be used to produce hydrogen via thermo chemical and biological processes. Pyrolysis and gasification are feasible thermo chemical routes for hydrogen production, whereas biophotolysis, biological gas shift reaction, and fermentation are promising biological processes. If hydrogen is produced from natural gas, coal, or biomass, it will use a lot of energy, not to mention the substantial amount of CO2 that will be generated as a by-product. Therefore, the best way of producing hydrogen is to utilize an alternative energy, such as wind, geothermal, solar, etc. Solar energy (waste heat) is the most promising source alternate energy. 1.2.1 Hydrogen Production by Solar Energy Hydrogen production via solar water splitting generally can be categorized into three types 1. Photo biological water splitting In this hydrogen production in two different ways, i.e. products generated, and reaction mechanisms involved. Hydrogen production by photosynthetic oxygenic cyanobacteria or green algae under light irradiation and anaerobic condition is referred to as water biophotolysis, while hydrogen production by photosynthetic an oxygenic bacteria under light irradiation and anaerobic condition is referred to as organic biophotolysis. 2. Photo catalytic water splitting Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Photo catalysis is defined as the chemical reaction induced by photo irradiation in the presence of a catalyst, or more specifically, a photo catalyst. Such material will facilitate chemical reactions without being consumed or transformed. Photosynthesis by plants is a well known example of photo catalysis in nature. Titania has been widely used photo catalyst for water splitting. It has very low efficiency. This is due to the reason, the decomposition of water into hydrogen and oxygen reaction requires very large positive Gibbs free energy thus backward reaction easily proceed and most of the catalyst activated by UV light, but UV light in solar energy only 4%. 3. Thermo chemical water splitting This is the most promising method to use for the hydrogen production. In this method temperature range decide the choice of cycle. Main reason for considering thermo chemical reaction is due to availability of heat energy. A large quantity of heat energy wasted day by day through solar energy, engine exhaust etc. in the following section we are trying to find the most suitable, cost effective thermo chemical cycle for hydrogen production. In all the cycles’ water is the input. 2. Thermo chemical water splitting cycles Thermo chemical cycles combine solely heat source (thermo) with chemical reaction split water into its hydrogen & oxygen component. Thermodynamic analysis of thermo chemical water splitting gives the basic idea about the reaction. 2.1. Thermodynamics of water splitting:The energy required for the endothermic reactions is equal to the enthalpy change of the reaction, ∆H and consists of two paths, thermal energy requirement ∆Q and useful work requirement ∆W. In the case of reversible chemical reaction at constant temperature and pressure the following condition hold [4]. ∆W=-∆G (1) T∆S=∆Q (2) Where ∆G & ∆S represent Gibb’s free energy & entropy of reaction respectively, thus we write, -∆H = -∆G-T∆S (3) The equilibrium constant k is related to the Gibb’s free energy change ∆G for the chemical reaction as follows, ∆G=-RTlnK (4) ∆G decreases with increase of K. If the value of ∆G is negative, it is possible that the chemical reaction proceed spontaneously. Exergy is a thermodynamic quantity, which encapsulate the energy and entropy of a flow through a system and can be thought of quantifying the thermodynamics quality of these flow. Exergy can be expressed as, E = H-Ho-To(S-So) (5) The measure of how well heat energy is converted into chemical energy stored in H2 for given process is given by exergy efficiency, defined as η exergy = (-n∆G|H2+O2→H2O)/Qheat (6)

Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

Fig.2. Equilibrium composition of water vapor.[4]

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Fig.1. G-T diagram for water splitting [4]

where n is the molar flow rate of H2 produced & ∆G is the standard Gibbs energy change of the reaction at 298K(23kJ/mol) [9]. 2.1.1 Water splitting via single step:H2O→H2+0.5O2 (7) Because of the endothermic reaction the energy that is equal to ∆H should be provided to split water in H2 & O2, Where ∆G as useful work and T∆S as a thermal energy. The ∆G-T diagram for the water splitting reaction is shown Fig.1. The water decomposition reaction has a large positive free energy change and a small positive entropy change shown in the Fig.1. Thus the equilibrium for the reaction in unfavorable for hydrogen production. The water decomposition process is non spontaneous except at high temperature then turning temperature (4500). Exergy equal to ∆G as well as thermal energy T∆S is required to be supplied to thereactionsystem. 2.1.2. The dissociation of water proceeds in two step:H2O→HO+O and HO→H+O (8) The combination of H and O atom produce molecules of H2 , O2, OH as follows, 2H→ H2 2O→O2 (9) O+H→OH The theoretical mole fraction of 6 component (H2, O2, OH, H2O,H, O) for a total pressure of 1 atm shown in the fig. It is seen that 35%of water vapor dissociate at the temperature of 30000K and that the mole fraction of atom of H2 andO2 are dominant in the reaction system temperature higher than around 3500K. From these two thermodynamic aspects we can conclude that direct thermal decomposition of water is not feasible with present technology

3. Thermo chemical process From the above section, we got the idea that the direct splitting of water requires a very large quantity of heat. Thermochemical cycle will help to reduce the required temperature below 2000K. For maintaining the cyclic operation some chemicals are recycled repeatedly. At present more than 2500 thermochemical cycles have been known for water splitting purpose. These cycles require multiple steps (more than 2) and were suffering inherent inefficiency associated with heat transfer and product separation in each step. In recent years significant progress has been accomplished in hydrogen production using thermo chemical reaction. Mr. James. E. Funk gives the brief review about the progress of thermochemical hydrogen production. Table.1.summary of Ispra chemical cycle [7]

Proceedings of National Conference on “Recent Trends in Mechanical Engineering” No.

Mark

Max. terms elements

Reactions

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Mark 1 Mark 1B Mark 1C Mark 1S Mark 2 Mark 2C Mark 3 Mark 4 Mark 5 Mark 6 Mark 6C Mark 7 Mark 7A Mark 7B Mark 8 Mark 9 Mark 10 Mark 11 Mark 12

Hg,Ca,Br Hg,Ca,Br Cu,Ca,Br Hg,Sr,Br Mn,Na,(K) Mn,Na,(K),C V,Cl,O Fe,Cl,S Hg,Ca,Br,C Cr,Cl,Fe,(V) Cr,Cl,Fe,(V),Cu Fe,Cl Fe,Cl Fe,Cl Mn,Cl Fe,Cl I,S,N S(hybrid) I,S,N,Zn

1050 1050 1070 1070 1070 1120 1070 1070 1120 1070 1070 1070 1070 1120 1120 920 1120 1120 1120

4 5 4 3 3 4 4 4 5 4 5 5 5 5 3 3 6 2 4

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The chemical combinations studied in Ispra, Italy as shown in table.1. Each cycles required very high temperature and number of chemical reaction also high. Lot of other thermochemical cycles also present, another main cycle is metal oxide redox reaction. From the below Table 1 and Table 2, we conclude that most of the cycle required temperature range above 10000C for completing the cycle. These cycles are also difficult to implement in low temperature heat sources such as engine waste heat. But some chlorine related cycle achieves low temperature thermochemical cycle for the production of hydrogen effectively.

Table.2. Metal oxide based reaction [2, 3, 5, 6, 8, 10, 11, and 14] Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering” Redox pairs

Reaction scheme

Advantages

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Disadvantages 1 High temperature required for the reduction step;

Fe3O4/F eO

Activation step: Fe3O4 = 3FeO +0.5O2 (endothermic, above 2500 K under 1 bar) Hydrolysis step: 3FeO +H2O + Fe3O 4+H2 (exothermic, <1000 K)

SnO2/S nO

2 Rapid deactivation of the iron oxide particles during cyclic reaction; 3 Severe sintering and melting during thermal decomposition of Fe2O4 with strong vaporization;

1 Lower activation temperatures;

Iron-based oxide

ZnO/Zn

Relatively high theoretical hydrogen yields; 2 Avoid the recombination reactions and irreversibility associated with quenching needed with volatilemetal oxides such as zinc or cadmium oxides

2 Thermodynamically increase the oxygen partial pressure required, in comparison to pure Fe3O4. 1 Relatively high temperature for the thermal dissociation of ZnO;

Activation step: ZnO =Zn + 0.5O2 (endothermic), 1700e1800C, the temperature for which the free Gibbs energy equals to zero is 2350 K) Hydrolysis step: Zn þ H2O = ZnO + H2 (exothermic, <1000 K)

Activation step: SnO2 = SnO + 0.5O2 (endothemic, 1600 _C; the temperature for which the free Gibbs energy equals to zero is 2056 C) Hydrolysis step: SnO +H2O = SnO2 +H2 (exothermic, 550 _C)

2 Need fast quenching to minimize Zn recombination; 3 Need an effective Zn/O2 separation technique; 4 Limited hydrolysis reaction rate because of the formation of a ZnO(s) layer.

1 Relatively low thermal reduction temperature; 2 High chemical conversion rates 3 Fast reaction kinetics passivation phenomenon occurring at the nanoparticles).

surface

1 Low exothermic heat (_49 kJ/mol at 500 _C) that can lead to weak self-heating;

(no

2 Back reaction begins to inhibit

the hydrolysis process at lower temperature (550 _C).

CeO2/C e2O3

2CeO2 = Ce2O 3+ 0.5O2 (endothermic, above 2000 _C under 100e200 mbar) Hydrolysis step:

1 High temperature required for the reduction of Ce(IV) to Ce(III) oxide;

2 No reduction observed at higher pressures;

(exothermic, 700-800 K)

3 Partial vaporization of CeO2 during reduction.

Ce 2O3+ H 2O = CeO + H2

Hybrid Chlorine Cycle Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

Proceedings of National Conference on “Recent Trends in Mechanical Engineering”

(1) Cl2(g) + H2O(g) 2HCl(g) +1/2O2(g) (2) 2HCl(g) H2(g) + Cl2(g) electrolysis Iron-chlorine cycle (1) 3FeCl2(s) + 4 H2O(g) Fe3 O4(s) + 6HCl(g) + H2(g) (2) Fe3 O4(s) + 8HCl(g) FeCl2(s) + FeCl3(s) + 4 H2O(g) (3) 2FeCl3(s) 2FeCl2(s) +Cl2(g) (4) Cl2(g) + H2O(g) 2HCl2(g) + 1/2O2(g) Vanadium-chlorine cycle (1) 2VCl2(s) + 2HCl(g) 2VCl3(s) + H2(g) (2) 4VCl3(s) 2VCl2(s) + 2VCl4(g) (3) 2VCl4(l) 2VCl3(s) + Cl2(g) (4) Cl2(g) + H2O(g) 2HCl(g) + 1/2O2(g) Cerium-chlorine cycle (1) 2CeO2(s) + 8HCl(g) 2CeCl3(s) + Cl2(g) + 4H2O(g) (2) 2CeCl3 (s) + 4H2O(g) 2Ce O2 (s) +6HCl(g) + H2(g) (3) Cl2(g) + H2O(g) 2HCl(g) + 1/2O2(g) Cerium-chlorine cycle (1) 2CuCl2(s) + H2O (g) 2Cu2OCl2(s) + 2HCl(g) (2) Cu 2OCl2(s) CuCl(l) + 1/2O2(g) (3) CuCl(l) 2CuCl2(aq) + 2Cu(s) electrochemical (4) 2CuCl2(aq) 2CuCl2(s) (5) 2Cu(s) +2 HCl(g) 2CuCl(l) + H2(g)

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850 0C 750C 9250C 1250C 4250C 850-9250C 1200C 7500C 200 0C 850-9250C 1100C 9250C 850-9250C 425 0C 5300C 25-800C >1000C 425-4750C

Table.2. Chlorine based thermochemical cycle [12,13,15] Cycle

Advantages

Challenges

Efficiency

Hybri d Cl2

Simple principle, known technology in HCl electrolysis, two step separation.

Limited equilibrium reaction (60%) at 8500C, new technology required to improve efficiency in reverse Deacon reaction (same challenge for the other cycles except for CuCl cycle).HCl/ H2 and Cl / H2 O separation.

34-35%

Fe-Cl

Low costs, chemistry of iron oxides well known.

Heat management during (3), competition in product formation (dimerization of FeCl3 into Fe2Cl6 ).

18.5%

V-Cl

High projected efficiency.

Unknown thermodynamic data for vanadium oxides, slow kinetic, separation methods.

31-46%

Ce-Cl

The cycle can be partially carried out in the aqueous phase, allowing optimization of operating temperature.

Low efficiency, slow kinetics (if gas-solid reaction).

20.9%

Cu-Cl

Low maximum temperature, all reactions demonstrated at laboratory scale, safe, abundant and inexpensive intermediate chemicals, no catalyst needed for thermal reactions, internal support.

Development of the electrochemical reaction. H2 O/HCl separation in (1), H2 /HCl separation in (5), incomplete reaction (5).

15-43%

Chlorine based thermochemical hydrogen production requires low temperature for a cycle; this temperature range is acceptable for the low temperature reaction.

4. Conclusion Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Lot of thermo chemical cycles have been studied, from which Cu-Cl cycle is best suitable for low temperature hydrogen production by using solar energy, engine waste heat etc. This is promising to the alternative method for conventional hydrogen production. In addition to low temperature, it requires very low electricity for completion of a cycle. Intermediate chemical reactions are very safe, chemicals are easily available and efficiency of the cycle reaches almost 50%. Reference [1]. Chi-Hung Liao, Chao-Wei Huang and Jeffrey C. S. Wu, Hydrogen Production from Semicondu based Photocatalysis via Water Splitting, Catalysts 2012, 2, 490-516. [2]. Lan Xiao, Shuang -Ying Wu , You-Rong Li, Advances in solar hydrogen production via two-step water-splitting thermo chemical cycles based on metal redox reactions, Renewable Energy 41, 2012, 1-12 [3]. 3 Sibieude, F., Ducarroir, M., Tofighi, A., Ambriz, J.: High temperature experiments with a solar furnace: The decomposition of Fe3O4, Mn3 O4, CdO. Int. J. Hydrog. Energy 7(1), 1982, 79–88 [4]. Atsushi Tsutsumi, Thermodynamics of water splitting,Energy carriers and conversion system-Vol.1,1995 [5]. Christopher Perkins, Alan W. Weimer, Likely near-term solar-thermal water splitting technologies, International Journal of Hydrogen Energy 29, 2004, 1587 – 1599. [6]. Tamaura, Y., Steinfeld, A., Kuhn, P., Ehrenberger, K., “Production of Solar Hydrogen by a Novel 2-step, Water Splitting Thermo chemical Cycle”, Energy, Vol. 20, 1995, pp. 325- 330. [7]. James E. Funk, Thermo chemical hydrogen production: past and present, International Journal of Hydrogen Energy 26, 2001, 185-190. [8]. C.Agrafiotis, M. Roeb, A.G. Konstandopoulos, L. Nalbandian, Solar water splitting for hydrogen production with monolithic reactors, Solar Energy 79, 2005, 409–421. [9]. Aldo Steinfeld, Solar thermochemical production of hydrogen, Solar Energy 78, 2005, 603–615. [10]. Steinfeld, Solar hydrogen production via a two-step water-splitting thermochemical cycle based on Zn/ZnO redox reactions, International Journal of Hydrogen Energy 27, 2002, 611 – 619. [11]. Peter G. Loutzenhiser 1, Anton Meier 2 and Aldo Steinfeld, Two-Step H2O/CO2Splitting Solar Thermochemical Cycle Based on Zn/ZnO Redox Reactions, Materials 2010, 3, 4922-4938. [12]. Manuela Serban, Michele A. Lewis and John K. Basco, Kinetic Study of the Hydrogen and Oxygen Production Reactions in the Copper-Chloride Thermochemical Cycle, AIChE 2004 Spring National Meeting New Orleans, LA, 2004, April 25-29. [13]. Stephane Abanades, Patrice Charvin, Gilles Flamant, Screening of water-splitting thermochemical cycles potentially attractive for hydrogen production by concentrated solar energy, Energy 31, 2006, 2805–2822 [14]. Berman, A., Epstein, M. The kinetics of hydrogen production in the oxidation of liquid zinc with water vapor. Int. J. Hydrogen Energy 25, 2000, 957–967. [15]. Michele A. Lewis*, Joseph G. Masin, Patrick A. O’Hare, Evaluation of alternative thermochemicalcycles. Part I: The methodology, international journal of hydrogen energy, 2008, 1 – 1 0

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HEAT TRANSFER ON A PLATE IMPINGED WITH COLD AIR JET V.M.Jeevanlal1, B.C.Anil Kuma2 1 2

Assistant Professor,

Student, Thermal and Fluids Engineering, Department of Mechanical Engineering, LBS College of Engineering, Kasaragod jeevanlalmalayil@gmail.com

1, 2

Abstract This paper reviews the study of heat transfer on a plate impinged with cold air jet. Both theoretical and experimental studies were conducted. Numerous studies of the heat transfer and flow characteristics for jet impingement on surfaces have been reported in this field to enhance the rate of cooling of heat generating devices. Enhancement of heat transfer by mounting porous blocks on hot plate, study of effect of surface curvature and roughness on heat transfer performance, effect of turbulence of jet, effects of multiple jets, and effects of jet plate size and plate spacing on the stagnation Nusselt number are the main works reviewed. Keywords: flow characteristics, heat transfer performance ,stagnation Nusselt Number

1. Introduction The world is progressing towards the modern and sophisticated technologies in the field of mechanical, electrical/electronics, aeronautical and so on. In fact such advanced technologies will lead to large heat emissions. Cooling of such devices has become a challenging for decades. Numerous researches have been carried out in this field to enhance the rate of cooling of heat generating devices. One of the common day to day examples is the cooling of microprocessor chips used in almost all modern electronic devices such as laptops/computers. Some of the industrial appliances also require cooling such at turbine cooling; IC engines cooling, casting industries, the electronics components in rockets during launch and so on. Jet impingement is a good option of cooling in high heat flux regions. This method is found to be most effective in simple and complex geometries. At present thermal management has great importance in engineering and industrial fields. It is mechanical engineer’s duty that improves the performance of existing cooling systems or to design an effective thermal management system. So research in jet impingement cooling/heating has vital importance and the literature discussing the jet impingement techniques is reviewed in the following section.

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Figure.1.flow regions of impinging jet

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Figure.2. impinging jet

2. Experimental studies Jet impingement cooling is mostly used in high heat applications like turbine blade cooling, metal forming and so on. Jet impinging is considered to be more advantageous than ordinary convective methods. Moreover, jet impingement is a good option of cooling in high heat flux regions [1]. This technique can be most effective in simple and complex geometries. Heat characteristics of impinging jets were initially studied by Gauntner[1] at NASA Lewis research center and developed an impingement cooling program to develop the heat transfer correlations for cylindrically shaped leading edge of vanes/blades and for impingement cooling along vane or blade suction and pressure surfaces. Lee [3] ,conducted a study in which the local heat transfer coefficients are measured for an air jet issuing from a long straight pipe and impinging perpendicular on a hemi spherically convex surface. Experiments are made for Re=11,000-50,000, ⁄ =2-10 and ⁄ =0.034-0.089. (L=Nozzle to surface distance, d=pipe nozzle diameter, D=outer diameter of hemisphere, ⁄ = dimensionless nozzle-to-surface distance, ⁄ =surface curvature).The result shows that the stagnation point Nusselt no ( ) increases with increasing value of ⁄ . Maximum Nusselt No at the stagnation point occurs at ⁄ = 6 to 8 for all Reynolds and ⁄ ’s tested. Both the stagnation point and the average Nusselt no over the curved surface are well correlated with Re, ⁄ , and ⁄ . For larger ⁄ , , dependency on Re is stronger because of an increase of turbulence in the approaching jet as a result of the more active exchange of momentum with a surrounding air. They obtained Correlation for Stagnation Nusselt No are as follows . . . 1.68( )( ⁄ )( ⁄ ) For 2 ≤ ⁄ ≤ 6 1.38(

)( ⁄

) For 6 ≤ ⁄ ≤ 10

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These correlations are valid for , 11,000 ≤ Re ≤ 50,000 and 0.034 ≤ ⁄ ≤ 0.089 . For shorter distances that is 2 ≤ ⁄ ≤ 6, varies according to α (Laminar boundary layer flow). For larger distances , the Re number dependence is stronger ( α . for 6 ≤ ⁄ ≤ 10 ) mainly due to an increase of turbulence in the approaching jet as a result of the stronger exchange of momentum with surrounding ambient air. Chakroun et al [5], conducted an experimental investigation of heat transfer from a round air jet impinging normally from below on to a heated square plate .Objective was to study the effect of roughness on both heat transfer and fluid flow characteristics . Smooth and rough plates were used in experiments.Re varied from 6500 to 19000.Nozzle to plate distance varied from 0.05 to 15times nozzle exit diameter to cover both potential core and far regions of the jet flow. The roughness was composed of cubes of 1mm dimension distributed uniformly along the plate. According to author most of the works are carried out on smooth surface. But in most of the applications the surface is rough. Velocity profile as well as the turbulence intensity profiles were measured using LDA technique at radial distances ( ⁄ ) of 1, 2.5,4 and 6 for each ⁄ position. (r=distance along the plate cetreline, H=distance between plate and nozzle exit, D=nozzle exit diameter). The result was, the local and average nusselt values for the rough plate should an increase ranging from 8.9% to 28% over those for the smooth plate. Roughness was found to have a strong effect on the flow characteristics; it affected the mean velocity as well as the turbulent intensity of the flow. Roughness causes the heat transfer to increase from 8.3% to about 28% depending on the jet Reynolds No and ⁄ value. The increase gets higher with increasing Reynolds No. Dong [7] conducted experiments to investigate the heat transfer characteristics of a row of three premixed, laminar butane/air flame jets impinging on water cooled flat plate. They inferred that the maximum local heat flux and the maximum area averaged heat flux occurred at a moderate nozzle to plate distance of 5d. The lowest area averaged heat flux was produced when both the jet to jet spacing and the nozzle to plate distance were small. Comparing with single jet there was an enhancement in heat transfer. From this study they concluded that the between jet interference reduces the heat transfer in the interacting zone. This heat transfer depression effects become stronger when the ⁄ and ⁄ ratios are small. (s=distance between ceters of two nozzles=nozzle exit diameter=distance ⁄ ratios also reduce the area between nozzle and impinging plate). Small ⁄ averaged heat flux. The highest heat transfer is obtained when both the ratios are at a moderate value of 5, at which both the local and maximum heat fluxes are reaching their maximum values. Amy [8], investigated the influence of a protruding pedestal on impinging jet heat transfer. A discretely heated portion of a protruding pedestal is exposed to a single circular impinging air jet with Re=10,000-30,000. Jet exit diameters of 3.5, 9.5, and 21mm are positioned a jet exit to surface distances of 2-5 diameters. The non-dimensional heat transfer over the discretely heated portion of the pedestal is compared to a flat plate design to gauge the effects of Reynolds No, jet diameter and jet exit-surface spacing. In all cases the presence of the protruding pedestal downstream is found to increase heat transfer. Narayanan [9], presented an experimental study of flow field, surface pressure, and heat transfer rates of a submerged, turbulent, slot jet impinging normally on a flat plate. In their study two nozzle-to-surface spacings of 3.5 and 0.5 nozzle exit hydraulic diameters, which correspond to transitional and potential core jet impingement respectively are considered. Study reveals that high heat transfer rates in the impingement region for transitional jet impingement, and a non monotonic decay in heat transfer coefficient for potential- core jet impingement. Guerra [10] studied the near wall behavior of an impinging jet. This work investigates the applicability of scaling log-laws to the turbulent impinging jet. Velocity Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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and temperature fields are studied here. The experiments were conducted for one nozzleto-plate spacing and a Reynolds No.( ⁄ =2 and Re = 35,000) . From this work they confirmed the already known facts that is for large ⁄ , nozzle to plate spacing rates the Nusselt No is maximum at the stagnation point and decreasing with increasing ⁄ . Result reveals that the logarithmic portion of the velocity and the temperature laws of the wall increases with increasing maximum jet velocity and decreasing minimum temperature. San and Wen [10] experimentally studied the effects of jet plate size and plate spacing (jet height) on the heat transfer characteristics of a confined circular air jet impinging vertically on a flat plate. For this purpose a constant heat flux was arranged (1000 ⁄ ). They found that the stagnation Nusselt No is proportional to the 0.638 power of the Re and inversely proportional to the 0.3 power of the ⁄ . The stagnation Nusselt No was also found to be a function of exp [-0.044 ( ⁄ ) - 0.011( ⁄ )] Vadiraj and Prabhu [12] performed experimental study and theoretical analysis of local heat transfer distribution between smooth flat surface and impinging air jet from a circular straight pipe nozzle. Experiments are conducted to measure the wall static pressure distributions at different jet-to-plate spacing. They developed following correlations For ⁄ ≤ 3.0 Nu=0.2636 Re0.6188 ( ⁄ )-0.0898 ( ⁄ )-0.074 For ⁄ ≥ 4.0 Nu=0.198 Re0.6632 ( ⁄ )-0.0826 ( ⁄ )-0.3702 From this experiment they identified as stagnation region ( 0≤ ⁄ ≤1.0), transition region ( 1.0 < ⁄ < 2.5) and wall jet region ( ⁄ > 2.5). Increase in Reynolds number increases the heat transfer at all the radial locations for a given ⁄ . Vadiraj and Prabhu [12] investigated the enhancement of heat transfer on a flat surface with axisymmetric detached ribs by normal impingement of circular air jet. A single jet from a long pipe nozzle which develops fully developed flow is chosen. Different configurations of detached ribs are arranged axiymmetrically on the target plate. The ratio of average Nusselt numbers of ribbed and smooth surface is seen to increase with Reynolds number Attalla and Ahmed [14] conducted experimental study for knowing the effect of nozzle inlet chamfering on the heat transfer distribution over the plate. Reynolds No based on jet inlet diameter varied from 6000 to 40000 and ⁄ is also varied from 1 to 6. Result shows that the chamfered edge has no effect on local Nusselt number distribution along the streamwise direction. 3. Numerical works Shung [2] studied the thermal performances of different shape porous blocks under an impinging jet. A study of the enhancement of the convection heat transfer of a laminar slot jet impinging on a porous block mounted on a heated region was investigated numerically. A numerical method (SIMPLEC) was used to solve the governing equations. Three different shape porous blocks were studied (rectangle, convex and concave). The results indicated that the heat transfer is mainly affected by the fluid flow near the heated region. For a lower porous block, the heat transfer is enhanced by three types of porous block. However for a higher porous block, heat transfer is only enhanced by the concave porous block. Behnia et al. [4] numerically studied the problem of cooling of a heated flat plate by an axisymmetric isothermal fully developed turbulent jet. Computations performed with Normal-velocity relaxation turbulence model (V2F model). Local heat transfer coefficient predictions are compared to the available experimental data. Results showed excellent agreement with experimental data. The axisymmetric, incompressible, Reynolds averaged N-S equations were solved in conjunction with the k-ε and transport equations, and the f elliptic relaxation equation on a finite- difference grid. Several Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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turbulent prandtl Number formulas were examined. (k=turbulent kinetic energy, ε= dissipation rate of turbulence, f= variable related to energy re distribution) For ⁄ =2, near the stagnation region, the flow decelerates in the axial direction and turns as exhibited by the sharp curvature in the stream lines. The entrainment is clearly evident by the curving of the stream lines outside the pipe towards the core of the jet. This leads to the formation of a recirculation region in the vicinity of the pipe wall. For ⁄ =6, the maximum value of k (turbulent KE) predicted by k-ε model is 60% higher than V2F. Simulations have been carried out for a constant Re (Re=23,000) and a wide range of aspect ratios (0.5≤ ⁄ ≤ 14) to determine the dependence of the stagnation nusselt no on ⁄ . This dependence is crucial in many applications of impingement cooling. While comparing it is observed that V2F model predictions are good in agreement with experimental data than k-ε model. Chiriac and Alfonso [6] had found from their literature review that the behavior of the two dimensional impinging jet in the laminar and transitional regime is not at all well known. The objective of this study was to characterize the behavior of the confined laminar impinging jet and the attendant heat transfer removal to the target wall. The jet Reynolds no based on a hydraulic diameter of 2W (W=jet nozzle width) is varied from 250 to 750. The prandtl No is assumed to be 0.72, with air as the cooling fluid. For writing continuity, 2D momentum, and energy equations they assumed 2D, unsteady, nonisothermal, incompressible flow. A numerical finite difference approach was used to compute the steady and unsteady flow and heat transfer due to a confined 2D slot jet impinging on an isothermal plate. A fixed jet- to-plate spacing was used. The flow was found to become unsteady at Re between 585 and 610. In the steady regime, the stagnation Nusselt No increased monotonically with Re, and the distribution of heat transfer in the wall jet region was influenced by flow separation caused by re entrainment of the spent flow back in to the jet. Quan [13] applied pressure and temperature sensitive paints for study of heat transfer to a circular impinging air jet. Experimental and computational studies are performed to study pressure and temperature distributions and flow patterns on impinging target surface subject to a single air jet. The optimal separation distance ( ⁄ ) for stagnation Nu is found to be about 5. CFD comparison is performed using FLUENT commercial code. Kumar [16] numerically studied mixed convection in a 2D laminar incompressible offset jet flow and solved unsteady form of velocity transport equation. The behavior of the jet in Re=300-600 and Grashof number Gr=103-107 was studied. They found that the reattachment length is strongly dependent on both Re and Gr.The velocity distribution in the jet is taken as parabolic and its temperature is same as the ambient temperature. Clustered Cartesian grids are used in computational domain. L.B.Y. [17] performed a three dimensional numerical simulation of impinging jets arrays on a moving plate. They investigated numerically the flow field structure and its effect on heat transfer characteristics of array of jet impinging on moving heated plate. Result revealed the presence of a complex flow field with horseshoe vortices formed around the first column of jets due to the cross flow created by the moving surface. The stream wise Nusselt number profile showed strong periodic oscillations, spatially. 4. Conclusion Impinging jets have been studied over the years for their importance in industrial applications, mainly in cooling, heating or drying. Jet impingement technique provides high levels of convective heat and mass transfer. A lot of experiments can be performed on jet impingement cooling of plates. There is a possibility to conduct experiment by varying nozzle geometries, plate material etc and also by providing surface indentations of various geometries on plate we can investigate the heat transfer performances. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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References [1]. Peter Hrycak, David T. Lee, James,Gauntner and John N. B. Livingood, Experimental Flow Characteristics of a SingleTurbulent Jet Impinging On A Flat Plate” NASA TN D- 5690, JANUARY 1973. [2]. Wu-shung fu and hsin-chien huang, Thermal performances of different shape porous blocks under an impinging jet, International Journal of Heat and Mass Transfer.Vol.40,No 10, pp.22612272,1997. [3]. D.H.Lee, Y.S.Chung,and D.S.Kim , Turbulent flow and heat transfer measurements on a curved surface with a fully developed round impinging jet, International Journal of Heat and Fluid flow. Vol 18. 160-169,February 1997. [4]. M.Behnia, S.Parneix and P.A.Durbin, Prediction of heat transfer in an axisymmetric turbulent jet impinging on a flat plate, , International Journal of Heat and Mass Transfer.Vol.41,No 12, pp.18451855,1998. [5]. W.M.Chakroun,A.A. Abdel-Rahman, S.F. Al-Fahed, Heat transfer augmentation for air jet impinged on a rough surface, Applied Thermal Engineering 18 (1998) 1225-1241. [6]. Victor A. Chiriac, Alfonso Ortega, A numerical study of the unsteady flow and heat transfer in a transitional confined slot jet impinging on an isothermal surface, International Journal of Heat and Mass Transfer.45 (2002) 1237-1248. [7]. L.L.Dong, C.W. Leung, C.S. Cheung, Heat transfer of a row of three butane/air flame jets impinging on a flat plate, International Journal of Heat and Mass Transfer.Vol.46 (2003) 113-125 [8]. 8 Amy S. Fleischer, Sharareh R.Nejad, Jet impingement cooling of a discretely heated portion of a protruding pedestal with a single round air jet, Experimental Thermal and Fluid Science 28 (2004) 893-901. [9]. V.Narayanan, J.Sayed-Yagoobi, R.H. Page, An experimental study of fluid mechanics and heat transfer in an impinging slot jet flow, International Journal of Heat and Mass Transfer.47 (2004) 1827-1845. [10]. Danielle R S Guerra, Jain Su, Atila P. Silva Freire, The near wall behavior of an impinging jet, International Journal of Heat and Mass Transfer.48 (2005) 2829-2840 [11]. Jung-Yang San, Wen –Zheng Shiao, Effects of jet plate size and plate spacing on the stagnation Nusselt Number for a confined circular air jet impinging on a flat surface, International Journal of Heat and Mass Transfer.49 (2006) 3477-3486. [12]. Vadiraj Katti, S. V. Prabhu, Experimental study and theoretical analysis of local heat transfer distribution between smooth flat surface and impinging air jet from a circular straight pipe nozzle, International Journal of Heat and Mass Transfer.51 (2008) 4480-4495. [13]. Quan Liu, A.K.Sleiti, J.S.Kapat, Application of pressure and temperature sensitive paints for study of heat transfer to a circular impinging air jet, International Journal of Thermal Sciences 47 (2008) 749-757. [14]. Vadiraj Katti, S.V. Prabhu, Heat transfer enhancement on a flat surface with axisymmetric detached ribs by normal impingement of circular air jet, International Journal of Heat and Fluid Flow.29 (2008) 1279-1294. [15]. M.Attalla and M.S. Ahmed, Influence the nozzle shape on local heat transfer in impinging jet, International journal of systems applications,engineering and development,Issue6,Volume6,2012. [16]. K.Kumar Raja, Manab Kumar Das, P.Rajesh Kanna, Numerical study of mixed convection in a two-dimensional laminar incompressible offset jet flow, International Journal of Heat and Mass Transfer.52 (2009) 1023-1035. [17]. L.B.Y.Aldabbagh,A.A.mohamad, a three dimensional numerical simulation of impinging jet arrays on a moving plate, International Journal of Heat and Mass Transfer.52 (2009) 4894-4900.

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HYDROGEN FUELED INTERNAL COMBUSTION ENGINE A TECHNICAL REVIEW C.Satheesh Kumar1 , T.Mohammad Shekoor2 1

Student, 2Professor, Dept.of Mechanical Engineering, 1,2LBS College of Engineering, Kasaragod, Kerala, satheeshgreeshmam@rediffmail.com

Abstract Hydrogen as a fuel in Internal Combustion (IC) engines is a solution for the near future to realize zero CO2 emissions for traffic applications. The hydrogen fuelled IC engine is ready for this application. The storage and production of hydrogen, and to build the necessary infrastructure, are the real shortcoming in the general use of hydrogen in IC engines. This is the review that indicates the evolution in the development of hydrogen fuelled engines. By considering the various aspects of fuel, hydrogen is expected as a best option when consider as a gaseous state fuel. It is identified as a best alternate fuel for internal combustion engines as well as power generation application, which can be produced easily by means of various processes. The hydrogen in the form of gas can be used in the both spark ignition and compression ignition engines for propelling the vehicles and other engines. Keywords: Ttraffic applications, alternate fuel, power generation

1.Introduction Also, their combustion products are causing global problems, such as the greenhouse effect, ozone layer depletion, acid rains and pollution, which are posing great danger for our environment, many engineers and scientists agree that the solution to all of these global problems would be to replace the existing fossil fuel system with the clean hydrogen energy system Fossil fuels which meet most of the world’s energy demand today are being depleted rapidly.. Hydrogen is a very efficient and clean fuel. Its combustion will produce no greenhouse gases, no ozone layer depleting chemicals, and little or no acid rain ingredients and pollution. Hydrogen, produced from renewable energy sources, would result in a permanent energy system which would never have to be changed. Unfortunately, fossil fuels are not renewable. In addition, the pollutants emitted by fossil energy systems (e.g. CO, CO2, NOx, radioactivity.) are greater and more damaging than those that might be produced by a renewable based hydrogen energy system.. By accounting the various aspects of hydrogen fuel, considered as one of the suitable alternative source to replace the fossil fuel, its clean burning characteristics of hydrogen provide a strong incentive to study its utilization as a possible alternate fuel. Fuel cell was considered to be the cleanest and most efficient means of using hydrogen. Currently fuel cell technology is expensive and bulky. Hence a low cost technology to produce hydrogen is necessary .Hydrogen can be used in spark ignition (SI) as well as compression ignition (CI) engines. Lowering of worldwide CO2 emission to reduce the risk of climate change (greenhouse effect) requires a major restructuring of the energy system. The use of hydrogen as an energy carrier is a long term option to reduce CO2 emissions. However, at the present time, hydrogen is not competitive with other energy carriers. Global utilization of fossil fuels for energy needs is rapidly resulting in critical environmental problems throughout the world. There is an urgent need of implementing the hydrogen technology. A worldwide conversion from fossil fuels to hydrogen would eliminate many of the problems and their consequences. Many researchers have been directed their studies towards the effect of using hydrogen in internal combustion engines.

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2.Hydrogen as an engine fuel There are a number of unique features associated with hydrogen that make it remarkably well suited in principle, to engine applications. Some of these most notable features are the following Hydrogen, over wide temperature and pressure ranges, has very high flame propagation rates within the engine cylinder in comparison to other fuels. These rates remain sufficiently high even for very lean mixtures that are well away from the stoichiometric mixture region. The associated energy release is also so fast that the combustion duration tends to be short and contributes towards producing high-power output efficiencies and high rates of pressure rise following spark ignition. The lean operational limit mixture in a spark ignition engine when fuelled with hydrogen is very much lower than those for other common fuels. This permits stable lean mixture operation and control in hydrogen fueled engines. The operation on lean mixtures, in combination with the fast combustion energy release rates around top dead center associated with the very rapid burning of hydrogen– air mixtures results in high-output efficiency values. Of course, such lean mixture operation leads simultaneously to a lower power output for any engine size. One of the most important features of hydrogen engine operation is that it is associated with less undesirable exhaust emissions than for operation on other fuels. As far as the contribution of the hydrogen fuel to emissions, there are no unburnt hydrocarbons, carbon monoxide, carbon dioxide, and oxides of sulfur, smoke or particulates. The contribution of the lubricating oil to such emissions in well-maintained engines tends to be rather negligible. Only oxides of nitrogen and water vapor are the main products of combustion emitted. Also, with lean operation the level of NOx tends to be significantly smaller than those encountered with operation on other fuels. The fast burning characteristics of hydrogen permit much more satisfactory high-speed engine operation. This would allow an increase in power output with a reduced penalty for lean mixture operation. Also, the extremely low boiling temperature of hydrogen leads to fewer problems encountered with cold weather operation. Varying the spark timing in hydrogen engine operation represents an unusually effective means for improving engine performance and avoidance of the incidence of knock. Also, the heat transfer characteristics of hydrogen combustion in engines are significantly different from those in engines operating on other fuels. The radiative component of heat transfer tends to be small yet the convective component can be higher especially for lean mixture operation. The sensitivity of the oxidation reactions of hydrogen to catalytic action with proper control can be made to serve positively towards enhancing engine performance. 3. Combustive properties of hydrogen As can be seen the flammability limits (i.e. possible mixture compositions for ignition and flame Propagation) are very wide for hydrogen (between 4 and 75 percentage hydrogen in the mixture) compared to gasoline (between 1 and 7.6 percentage). This means that the load of the engine can be controlled by the air to fuel ratio, as for diesel engines. Nearly all the time the engine can be run with a wide open throttle, resulting in a higher efficiency. Hydrogen has very low ignition energy. The amount of energy needed to ignite hydrogen is about one order of magnitude less than that required for gasoline. This enables hydrogen engines to ignite lean mixtures and ensures prompt ignition. Hydrogen has a small quenching distance, smaller than gasoline. Consequently, hydrogen flames travel closer to the cylinder wall than other fuels before they extinguish. Thus, it is more difficult to quench a hydrogen flame than a gasoline flame. The temperature may not exceed hydrogen’s auto ignition temperature without causing premature ignition. Thus, the absolute final temperature limits the compression ratio. The high auto ignition temperature of hydrogen allows larger compression ratios to be used in a hydrogen engine than in a hydrocarbon engine. Hydrogen has high flame speed at stoichiometric ratios. Under these Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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conditions, the hydrogen flame speed is nearly an order of magnitude higher (faster) than that of gasoline. This means that hydrogen engines can more closely approach the thermodynamically ideal engine cycle. At leaner mixtures, however, the flame velocity decreases significantly. Hydrogen has very high diffusivity. This ability to disperse in air is considerably greater than gasoline and is advantageous for two main reasons. Firstly, it facilitates the formation of a uniform mixture of fuel and air. Secondly, if a hydrogen leak develops, the hydrogen disperses rapidly. Thus, unsafe conditions can either be avoided or minimized. Hydrogen has very low density. This results in two problems when used in an internal combustion engine. Firstly, a very large volume is necessary to store enough hydrogen to give a vehicle an adequate driving range. Secondly, the energy density of a hydrogen-air mixture, and hence the power output is reduced. Advantages of hydrogen for spark ignition engines

. Figure 1: Flammability limits for air with hydrogen (H2), air with natural gas (CH4) and air with gasoline

In 2013 VVN Bhaskar et al [1] studied on Hydrogen fuelled IC engine. Fig.1 [1] gives the flammability limits for different fuels at normal temperature and pressure. As can be seen the flammability limits (possible mixture compositions for ignition and flame propagation) are very wide for hydrogen (between 4and 75% hydrogen in the mixture) compared to gasoline (between 1 and 7.6%). This means that the load of the engine can be controlled by the air to fuel ratio, as for diesel engines. Nearly all the time the engine can be run with a wide open throttle, resulting in a higher efficiency. The second advantage of hydrogen for SI engines is the high burning velocity. For near stoichiometric mixtures the combustion is almost a constant-volume combustion, which increases the (thermodynamic) efficiency. Also the properties of lean hydrogen flames will cause flame acceleration due to cellularity and no turbulence enhancing methods have to be used (swirl ports, etc.).Again this increases the efficiency of the engine. Furthermore, hydrogen has a high octane number and the compression ratio of the engine can be increased. This, of course, increases the efficiency. Finally the emissions of a hydrogen engine are very clean, only the noxious component NOx is emitted.

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4.Performance and emission characteristics of hydrogen fueled engine. The use of the hydrogen as a fuel in the engines has been studied by different authors in the last decade with several degrees of success However; these reports are not necessarily consistent among several researchers. M.A Escalante Soberanis and A.M Fernandez [2] also carried out a technical revision on internal combustion engine run with hydrogen fuel. They reported the thermal efficiency of an engine fueled with hydrogen can overcome to that achieved with a gasoline engine (38.9% with hydrogen and 25% with gasoline). The power output of an engine fueled with hydrogen has reached, in laboratory tests, an 80% of that reached by a gasoline engine Hariganesh R et al [3], in the Madras Institute of Technology, a comparison study between gasoline and hydrogen as fuels was made. For this purpose, a single cylinder spark ignition engine was adapted to be fueled with hydrogen by injection in the intake manifold. The results of UHC emissions showed that, using hydrogen as a fuel, the levels were near zero, while with gasoline it would maintain over the 2500 rpm, at different requirements of power output. The specific fuel consumption, working with hydrogen, is less than the half than that of gasoline, due to the low energy density of hydrogen. For the case of nitric oxides emissions, it was reported higher levels in hydrogen combustion. The emissions of the first mixture were about 8000 ppm at an equivalence ratio of 0.85, while for gasoline it was reported 2000 ppm at an equivalence ratio of 1.03, approximately. The minimum ignition energy and the wide range of flammability of hydrogen allow the presence of combustion at lower equivalence ratios than those with gasoline, and it can obtain a higher power at specific equivalence ratios. The high power output of the engine, running with hydrogen, was about 80% of the power reached with gasoline. Hydrogen engine recorded higher volumetric efficiency, compared with that of gasoline, with a power output between 2 and 7 kW, was observed. In the case of thermal efficiency, it reached a maximum of about 27%, at different speeds, over that with gasoline which is about 25%. Erol Kahraman et al [4] experimentally investigated a conventional four cylinder spark ignition engine operated on hydrogen and gasoline. The compressed hydrogen at 20 MPa has been introduced to the engine adopted to operate on gaseous hydrogen by external mixing. In order to prevent backfire, they were installed the mixer between the carburetor body and inlet manifold at an engine speed above 2600 rpm. Specific features of the use of hydrogen as an engine fuel have been analyzed. The test results have been demonstrated that power loss occurs at low speed hydrogen operation whereas high speed characteristics compete well with the gasoline operation. But, fast burning characteristics of hydrogen permit high speed engine operation. This allows an increase in power output and efficiencies, relatively. NOx emission of hydrogen fueled engine is about 10 times lower than gasoline fueled engine. The slight traces of CO and HC emissions presented at hydrogen fueled engine are due to the evaporating and burning of lubricating oil film on the cylinder walls. Short time of combustion produces a lower exhaust gas temperature for hydrogen. They also suggested that appropriate changes in the combustion chamber together with a better cooling mechanism would increase the possibility of using hydrogen across a wider operating range.

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Figure 2.4: Engine speed Vs NOx emission Figure 3.4: Engine speed Vs CO emission

Figures 2.4 illustrate NOx levels of both engines. Significant decrease in NOx emission is observed with hydrogen operation. Almost 10 times decrease in NOx can be noted, easily. The cooling effect of the water sprayed plays important role in this reduction. Also operating the engine with a lean mixture is kept NOx levels low. Figures 3.4 shows CO emission versus engine speed for both engines. Although excess air for complete combustion is present in the cylinder, the engine is not capable of burning the total fuel. It was expected that hydrogen fuelled engine must have zero CO emission. As it is seen in Figures 3 [4] some amount of CO is still present. This is due to the burning of lubricating oil film inside the engine cylinder. As engine speed increases, CO emission tends to decreases.

Figure 4: Engine speed Vs HC emission

The temperature caused by combustion is very high inside the cylinder. As the piston expands the heat evaporates some amount of oil. In addition to this evaporated oil, incompletely burned oil also contributes to HC emission shown in Figure 4 [4]. 5. Conclusion

The use of hydrogen in internal combustion engines may be part of an integrated solution to the problem of depletion of fossil fuels and pollution of the environment. Today, the infrastructure and technological advances in matters of engines can be useful in the insertion of hydrogen as a fuel. There are good prospects for increased efficiencies, Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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high power density, and reduced emissions with hybridization, multi-mode operating strategies, and advancements in ICE design and materials. The hydrogen infrastructure at the time is not in place to supply hydrogen demands, but with more development using hydrogen as a fuel will motivate the development of the infrastructure. References [1]. VVN Bhaskar, Dr. R. Hari Prakash ,Dr. B. Durga Prasad, Hydrogen fuelled IC engine – an overview, International Journal Of Innovative Technology And Research Volume No. 1 Issue No. 1, December-January 2013, 046-053. [2]. M.A. Escalante Soberanis and A.M. Fernandez, A review on the technical adaptations for internal combustion engines to operate with gas/hydrogen mixtures, International Journal of Hydrogen Energy, 35(21), 2010, 12134–12140. [3]. Hari Ganesh R, Subramanian V, Balasubramanian V, Mallikarjuna J.M, Ramesh A and Sharma R.P, Hydrogen fueled spark ignition engine with electronically controlled manifold injection: an experimental study, Journal of Renewable Energy, 33(6), 2008, 1324- 1333. [4]. Erol Kahramana, S. Cihangir Ozcanlib, Baris Ozerdemb,An experimental study on performance and emission characteristics of a hydrogen fuelled spark ignition engine International Journal of Hydrogen Energy. 32 (2007) 2066 – 2072

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OPTIMIZATION OF HYBRID GREEN LUBRICATION FOR CLEAN AND BETTER PERFORMANCE Bandoli Siddheshwar Iresh1, M.Krishna2 1, 2

Dept. of Mechanical Engineering, R.V. College of Engineering, Banglore, India siddheshbandoli@gmail.com

Abstract This paper presents vegetable oils are being potential source of environmental friendly lubricants, due to a combination of biodegradability, renewability and excellent lubrication performance. But vegetable oil was restricted due to low thermo-oxidative stability and poor cold flow behavior which was improved by chemical modification via esterification process. The aim of this paper was to formulate green lubricant which gives clean and better performance under working condition. In order to satisfy this objective, methyl ester of sunflower oil, methyl ester of soybean oil, methyl ester of palm oil and castor oil were selected and multi response optimization was applied using grey relation analysis. Blending of different oils was done by L27 orthogonal array. Twenty seven experimental runs based on orthogonal array of Taguchi’s experimental method were performed. An optimal parameter combination of blended oils was obtained by grey relation analysis. Various tribological studies of formulated green lubricant were evaluated then it is compared with conventional synthetic lubricant. From the results it is verified that the performance and emission characteristic of green lubricant was better than synthetic lubricant. Keywords: Esterification, Grey Relational Analysis, Transterification.

1. Introduction The two stroke engine oil is ultimately burned along with the fuel as a total loss oiling system. Because of this pollution are increases as exhaust emission also increases. Two stroke engine oil must lower in ash content so that deposit that formed in combustion chamber should be minimum. In order to serve this purpose green lubrication is a best option. The synonyms for green lubrication are biodegability, biobased, eco friendly, renewable and non toxic. Green lubricants are those that degrade quickly and naturally with time. The lubricant must be formulated with renewable/vegetable oil in majority, readily biodegradable and free from heavy metals and other toxic ingradient. The main objective is to form two stroke engine oil which gives clean and better performance under operating condition. To satisfy this objective, blending of different vegetable oil is carried out using Taguchi’s experimental techniques.But vegetable oils has low oxidative stability and poor cold flow properties. Objective: To improve properties of vegetable oil by chemical modification.  To form best combination of two stroke engine oil in order to provide clean and better performance.  To form less expensive engine oil. 2. Selection of Vegetable Oils Table 1: Comparision between four different vegetable oils Sunflower Soyabin Palm Castor oil oil oil oil Density (gm/cc) 0.9180 0.9160 0.8850 0.9650 Kin. viscosity at 40° c (cSt) 34 32 41 5.9(at 100°c) Flash point(°c) 316 324 310 235 Pour point(°c) -17 -16 5 -10 Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Sunflower oil can be used as base oil for formation of green lubricant because of its better chemical and physical property [2]. Limitation of soyabin oil is their highest percentage of unsaturation present in the oil [2]. From Table 1, palm oil has a poor cold flow property and thermal decomposition or burning of castor oil may release oxides of carbon, acid smokes, irritating fumes which are oxides of sulphur and acrolein and also other hazardous gases[ 1,2 ]. Perhaps its limitation, castor oil is used in small amount in formation of green lubricant because of its better lubricating property. 3. Chemical Modification The inherent problem of vegetable oil are poor oxidation and low temperature properties which can be improved by attaching functional group at the sites of unsaturation through chemical modification. Transesterification is the general term used to describe the important class of organic reactions where an ester is transformed into another through interchange of the alkoxy moiety. When the original ester is reacted with an alcohol, the transesterification process is called alcoholysis. Procedure for esterification of vegetable oil  1000ml of vegetable oil is taken in a round bottom flask.  Prepare a solution of potassium methoxide and to the round bottom flask containing vegetable oil.  Continuously stirred the mixture for 60 min with constant heating of nearly 70-80 deg. Celsius.  Mixture is fed it into the separating flask , this allow the separation of ester and glycerine into two different layer.  Figure 1 shows top layer which is separated is a methyl ester of vegetable oil and bottom layer is glycerine which can be used in manufacturing of detergent.

Figure 1: Seperation of methyl ester and glycerine of vegetable oil

Figure 2: Redwood viscometer

4. Apparatus Used Apparatus used for finding the chemical and physical property of vegetables oils. Figure 2 shows the Redwood Viscometer which is used to determine the kinematic viscosity and absolute viscosity of the given lubricating oil at different temperatures. Requirement:- Thermometer 0-100°c (2 Nos) , Stop watch, 50 ml standard narrow necked flask The redwood viscometer consists of vertical cylindrical oil cup with an orifice in the centre of its base. The orifice can be closed by a ball. A hook pointing upward serves as a guide mark for filling the oil. The cylindrical cup is surrounded by the water bath. The water bath maintains the temperature of the oil to be tested at constant temperature. The oil is heated by heating the water bath by means of an immersed electric heater in the water bath, The provision is made for stirring the water , to maintain the uniform temperature in the water bath and to place the thermometer ti record the temperature of oil and water bath. This viscometer is used to determine the kinematic viscosity of the oil. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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From the kinematic viscosity the dynamic viscosity is determined. Filled oil volume of flask= 50 cc Kinematic viscosity = 0.026 T – 179/T Where T = Time taken in sec for collecting 50 cc of given oil at particular temp. Density = (w2 – w1)/50 gm/cc) Where w2 = weight of flask + oil (gm) and w1 = weight of flask (gm) Absolute or dynamic viscosity in centipoise = Density (gm/cc) × kinematic viscosity (cSt)

Figure 3: Cloud and Pour point apparatus

Figure 4: Pensky Martin flash point apparatus

Devices indicate the lowest temperature of utility for petroleum products. Fig.3 shows the cloud and pour point chamber immerses four copper test jackets in suitable freezing mixtures, providing inlet and outlet connections for circulating refrigerated coolant from an external source. Figure 4 shows Pensky Martin flash and fire point apparatus where Pensky– Martens closed cup is sealed with a lid through which the ignition source can be introduced periodically. The vapour above the liquid is assumed to be in reasonable equilibrium with the liquid. Closed cup testers give lower values for the flashpoint (typically 5–10 K) and are a better approximation to the temperature at which the vapour pressure reaches the "lower flammable limit" (LFL). Figure 5 shows Carbon residue apparatus which will give the percentage of carbon present in the oil. This value gives an approximate indication of combustability and deposit forming tendency of the fuel. Procedure for calculating the carbon residue 1) Calculate the weight of empty crucible. 2) Calculate the weight of crucible and 10 gm of oil. 3) After burning the oil, calculate the weight of crucible and substract it from original weight.

Figure 5: Carbon Residue apparatus

Figure 6: PH indicator

Figure 6 shows the PH indicator which is used to measure PH by matching it with the standard chart. It measure PH accurate to the nearest whole number.

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5. Formation of Hybrid Green Lubricant For the formation of hybrid green lubricant Taguchi’s experimental techniques are very useful. 5.1 Taguchi’s Orthogonal Array Blending of methyl esters and vegetable oil is made by using L27 orthogonal array. Twenty seven experimental runs based on an orthogonal array of Taguchi method were performed. The process parameters were ME of sunflower oil, ME of soyabin oil, ME of palm oil and castor oil each at three level and responses were the kinematic viscosity and flash point. The controllable input parameters are ME of sunflower oil: 55%, 60% and 65% ME of soyabin oil: 15%, 20% and 25% ME of palm oil: 5%, 10% and 15% Castor oil: 5%, 10% and 15% The response variables are kinematic viscosity in cSt and flash point in degree Celsius. Table 1 shows Taguchi’s L27 orthogonal array which has twenty seven experimental runs. It has four factors each at three levels. Table 1Taguchi’s L27 Orthogonal Array

5.2 Taguchi’s Grey Relational Analysis Optimal parameter combinations of blended oils were determined by Grey relational analysis. By analyzing the Grey relational grade, the degree of influence for each controllable process factor onto individual quality target can be found. 5.2.1 Data Preprocessing Grey data processing must be performed before Grey correlation coefficient can be calculated. A series of various units must be transformed to be dimensionless. If the target value of the original sequence is “the larger the better”, then the original sequence* is normalized as follows Xi (k) = {xi(0)(k) – min. xi(0) (k)}/{max. xi(0)(k) – min.xi(0)(k)} If the purpose is “the smaller the better”, then the original sequnce is normalized as follows Xi*(k) = {max. xi(0)(k) – xi(0)(k)}/{max. xi(0)(k) – min. xi(0)(k)} However, if there is “a specific target value”, then the original sequence is normalized using, Xi*(k) =1–[│xi(0)(k)-OB│/ max. { max. xi(0)(k)-OB, OB-min.xi(0)(k)}] For the response kinematic viscosity the data is normalized by “a specific target value” citeria. For the response flash point the data is normalized by “larger the better criteria”

Table 2 Grey relational generation data Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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5.2.2 Grey Relational Coefficients and Grey Relational Grade Following the data preprocessing, a Grey relational coefficient can be calculated using the preprocessed sequences. The Grey relational coefficient is defined as follows (x0 *(k), xi*(k) )= (min. + max.)/ (0i(k) +  max.) 0i

0 < (x0*(k), xi*(k) )  1 (k) is the deviation sequence of reference sequence x0*(k) and xi*(k) namely,

0i(k) = │x0*(k) – xi*(k)│ A Grey relational grade is a weighted sum of the Grey Relational Coefficient, and is defined as follows, (x0 *,xi*)=  k (x0*(k), xi*(k) )  k =1 Choose the parameter combination which gives higher Grey relational grade. In table 3 experiment number 19 gives highest Grey Relational Grade, therfore selecting the parameter combination of 65% ME of sunflower oil, 15% ME of soyabin oil, 15% OF ME OF palm oil and 10% of castor oil. Table 3 Grey relational coefficient and Grey relational grade

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6. Performance Calculations The performance calculation for single cylinder two stroke engine is Brake Power, BP = (V× I)/(1000 × ηgen) Kw Where V = dc voltage in volts, I = dc current in amps,η gen= Generator efficiency = 80% Mass of Fuel Consumed, Mfc = (X × 0.72 ×3600)/(1000×t) Kg/hr Where X = burette reading in cc, 0.72 = density of petrol in gm/cc, t = time taken in seconds Specific Fuel Consumption, Sfc = (Mfc/BP) Kg/Kw hr Actual Volume of Air Sucked into the cylinder, Va= Cd × A × √(2Gh) × 3600 in m3/hr Where, H= (h×δw)/(1000×δa) meter of water, A = area of orifice =(∏d2)/4 h=manometer reading in mm, δw=density of water=1000 kg/m3,δa=density of air = 1.193 kg/m3 Cd = coefficient of discharge=0.62 Swept Volume , Vs= (∏d2/4) ×L × N× 60 Where d=diameter of bore=56.7mm, L=length of bore= 56.7 mm, N speed of engine=3000rpm Volumetric Efficiency ηv = (Va × Vs) ×100 % Brake Thermal Efficiency, ηthermal = (BP×3600×100)/(Mfc × Cv) Where Cv= calorific value of petrol=43500KJ/kg, BP = brake power in kw Mechanical Efficiency, ηmech = (BP/IP)×100 Where BP= brake power in KW IP = indicated power FP = friction power in KW IP = FP + BP Friction power is obtained by graph using Willan’s line 7. Performance Testing Set Up Bajaj single cylinder two stroke engine specification Number of Stroke 2, Diameter of bore 56.7mm, Length of bore 56.7mm, Generator Efficiency 80% , Rated Power 2.5HP@3000RPM Table 4: Performance testing of Green engine oil Table 5: Performance charactisics of Green engine oil

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Table 7: Performance Charactristics of Engine oil

8 RESULTS AND DISCUSSION 8.1 Performance Evaluation

Figure 7: Fuel Consumpion Vs Brake Power Power

Figure 9 Specific Fuel Consumption Vs Brake Power

Figure 8: Mechanical Efficiency Vs Brake

Figure 10 Thermal Efficiency Vs Brake Power

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Figure 11 Volumetric Efficiency Vs Brake Power

8.2 EMISSION CHARACTRISTICS 8.2.1 MAK 2T ENGINE OIL

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Figure 12 Kinematic Viscosity Vs Temp. for Green oil

8.2. 2 GREEN ENGINE OIL

Figure 13. Emission charactristics of MAK2T Engine oil

Figure 14. Emission charactristics of Green oil

Carbon monoxide (CO) = 2.479% Carbon dioxide (CO2) = 0.97 % Hydrocarbon (HC) = 1828 ppm

Carbon monoxide (CO) = 0.936% Carbon dioxide (CO2) = 2.11 % Hydrocarbon (HC) = 1013 ppm

8.3 Comparision between Green Engine Oil and Make 2T Engine Oil Table 8: Comparision between Green engine oil and MAK 2T oil MAK 2T GREEN ENGINE OIL ENGINE OIL Density (gm/cc) 0.8797 0.8557 Kinematic 8.4 9.75 Viscosity (cSt) Flash Point(°C) 94 190 Pour Point(°C) -7 -3 CarbonResidue (%) 0.01 0.01 PH 7 7 Price per lit. Rs. 244 Rs.87

9. Conclusions The approach of using chemically synthesized vegetable oil improved the thermo oxidative stability and cold flow properties of bio based lubricant to some extent. This study concentrated on the application of Taguchi’s method coupled with Grey Relational Analysis for solving multi criteria optimization problem in the field of formation of hybrid Green lubricant. Table 1, 2 and 3 shows number of experiment conducted and Grey Relational grade from which best parameter combination was selected. Table 5, 7 shows mechanical and thermal efficiency of green engine oil 48% and 15% respectively greater Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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than the MAK 2T engine oil which is 35% and 13% resp. Fig. 7, 8, 9, 10, 11, 12, 13 and 14 shows the performance and emission characteristics of green engine oil is better than MAK 2T engine oil. Finally table 8 shows comparative study between MAK 2T engine oil and Green engine oil. Table 8 shows Green engine oil has greater advantages than MAK 2T engine oil. References [1] Sevim Z. Erhan and Brajendra K. Sharma “Modification of Vegetable Oil for use as Industrial Lubricants” Food and Industrial Oil research, Department of Chemical Engineering, Pennsylvania State University, USA. [2] Arumugam S, Sriram G and Subadhra L “Synthsis, Chemical Modification and Tribological Evaluation of Plant Oil as Biodegrable Low Tempataure Lubricant” International Conference On Modeling Optimization and Computing, 2012, vol. 38, pp 1508-1517. [3] Aristotelis Xenakis, Vassiliki Papadimitriou and Theodare G. Sothiroudis”Collidal Strcture In Natural Oils”International Conference On Current Opinion in Colloid and Interface Science, Dec. 2010, ISSN:1359-0294, vol. 15, Issue 6, pp 55-60. [4] N.J. Fox and G.W. Stachowiak “Vegetable Oil Based Lubricant-A Review Of Oxidation” Tribology International, Nov. 2007, vol. 40, pp 1035-1045. [5] N.H.Jayadas and K. Prabhakaran Nair “Coconut Oil As Base Oil For Industrial LubricantEvaluation And Modificationof Thermal, Oxidative and Low Temperature Properties” Tribology International, Oct. 2006, vol. 39, pp 873-878. [6] M.Munoz, F.Moreno, C.Monne, J.Morea and J. Terradillos “Biodiesel Improves Lubricity Of New Low Sulphur Diesel Fuels” International Journal Of Renewable Energy, vol. 36, May 2011, pp 2918-2924. [7] S.A.Lawal, I.A.Choudhary and Y. Nukman “ Application Of Vegetable Oil Based Metal Working Fluids in Machining of Ferrous Metal” International Journal Of Machine Tools and Manufacturing, vol. 52, Sept.2011, pp 1-12. [8] George Karavalakis, Stamoulis Stournas and Dimitrios Karonis” Evaluation Of The Oxidation Stability Of Diesel/Biodiesel blends” International Journal Of Fuel, vol. 89, April 2010, pp 24832489. [9] Sukumar Puhan, N. Vedaraman, G. Sankaranarayanan and Boppana V. Bharat Ram “Performance Emission Study Of Mahua Oil(medhaca indica oil) Ethyl Ester In A 4 Stroke Natural Aspirated Direct Injection Diesel Engine”, International Journal Of Reneawable Energy, vol. 30, Nov. 2004, pp 1269-1278. [10] George E.Totten, Steven R.Westbrook and Rajesh J.Shah “Fuels and Lubricant Handbook: Technology, Properties, Performance and Testing” ASTM International, ASTM Manual Series: MNL 37WCD. [11] Vikash Agarwal, Jyoti Vimal and Vedansh Chaturvedi “ Optimization Of Extrusion Blow Molding Process Parameter By Grey Relational Analysis and Taguchi Method” International Journal Of Research in Engineerin and Applied Science, ISSN: 2249-3905,Feb. 2012, vol. 2, Issue 2, pp 407-417.

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BIO-DIESEL PRODUCTION BY ALKALI CATALYZED TRANSESTERIFICATION OF DAIRY WASTE SCUM Satish Hulamani 1, H.Manjunath2 1

PG student, 2 Professor, Department of Mechanical Engineering, SSIT, Tumkur shulamani@yahoo.co.in

Abstract Biodiesel is recognized as a clean alternative fuel or as a fuel additive to reduce pollutant emission from Combustion Ignition (CI) engine and minimum cost so there is need for producing biodiesel other than from seed oil. In this study the diary waste scum were used as the raw material to produce biodiesel. The potential of using dairy waste scum as a feed stock for bio-diesel production was investigated. Scum Oil Methyl Ester (SOME) is produced in laboratory by transestrification followed by esterification process. The present analysis confirms that biodiesel from dairy waste scum is quit suitable as an alternative to petroleum diesel with recommended fuel properties as per ASTM standards. This new way for using dairy waste scum reduces the cost of production of biodiesel and the problem related to the disposal of dairy scum. Key words: Transesterification , scum oil methyl ester

1. Introduction Alternative fuel derived from vegetable oil and animal fat have increasingly important due to decreasing petroleum resources and increase in pollution problems. Biodiesel is a cleaner fuel than petroleum diesel and an exact substitute for existing compression engines [1]. Scarcity of fossil fuel increases the searching of new biomass to trap renewable energy sources more attractive. Currently bio-diesel is prepared from oil like soybean, canola, palm, sunflower etc. through out the world [2,3]. It is now believed that the world food crisis will occur as the result of using food crops for producing bio-diesel [4]. This lead to search for excavation of bio-diesel feed stocks from unconventional, non-edible oil and fats like, waste grease, waste cooking oil, waste tallow, jatropha, seed oil, tobacco seed oil, rubber seed oil, polanga seed oil etc. Bio-diesel is generally reported as being more costly than conventional diesel fuel. The cost of raw materials accounts for 75–85% of the production cost of bio-diesel [5,6]. The higher price of bio-diesel made researchers to look for newer ways to reduce cost to make newer bio-diesel competitive. The present analysis revels that bio-diesel from Dairy Waste Scum Oil is a suitable alternative for petroleum diesel. Annual production of milk in India is 150 million tones per year. Thousands of large dairies are engaged in handling this milk across the country. Raw chilled milk of cows and buffalos are standardized into market milk and milk products such as Butter, Ghee,Cream, Peda, Panner, Cheese, Yoghurt, Ice cream and other products. Large dairies are handling number of equipments for processing, handling, storage, packing and transportation of milk and milkproducts. Enormous quantities of water are used for housekeeping, sterilizing and washing equipments, during this process residual butter and related fat which are washed and get collected in effluent treatment plant as a scum. Scum is a less dense floating solid mass usually formed by a mixture fat, lipids, proteins, packing materials etc. A large dairy, which processes 5 lakh liters of milk per day, will produce approximately 200–350 kgs of effluent scum per day, which makes it difficult to dispose. Most of the dairies dispose this scum in solid waste disposal site or by incinerating. By doing so, it is economically wasteful and generates pollutants. Further, scum causes direct as well as indirect operational difficulties for effluent treatment. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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There are four common methods for the production of bio-diesel, which are studied extensively. They are direct use and blending, micro emulsification, pyrolysis and transesterification [7]. Transesterification is the most commonly used and well established process to improve the fuel property of oils and this is the method of choice for the current study. Transesterification is a well-known process since; in 1864, Rochleder described glycerol preparation through the ethanolysis of castor oil [8], the proportion of reagents affects the process, in terms of conversion efficiency [9], and this factor differs according to the oil. Several researchers have identified the most important variables that influence the transesterification reaction, namely, the reaction temperature, the type and amount of catalyst, the ratio of alcohol to oil, the stirring rate and the reaction time, etc.[10]. In this sense, it is important to characterize the oil and the feasibility to convert the oil into biodiesel [11,12].Biodiesel has several distinct advantages over petro-diesel in that it has higher combustion efficiency, lower sulfur and aromatic content which means it will not emit toxic gases. The major drawback of biodiesel is that it costs much more than petro-diesel when using vegetable oils as feedstock. Therefore, it is necessary to find ways to minimize the production cost of biodiesel. One way is to choose cheaper feed stocks such as dairy waste scum; Transesterification is the displacement of alcohol from an ester by another alcohol [13]. Overall transesterification reaction was given by three consecutive and reversible reactions are believed to occur [14,15]. This reaction is widely used to reduce the viscosity of triglycerides derived from renewable feedstock such as vegetable oil and animal fat for use in compression engine [16]. Catalyst is used to increase the transesterification reaction rate and yield. Excess alcohol used too, make possible to complete the reversiblereaction [17]. When compared to other alcohols, methanol is preferred because of its low-cost and its physical and chemical advantages (polar and shortest chain). It can quickly react with Triglycerides. Alkali catalyst such as Potassium Hydroxide (NaOH) is easily get dissolved in methanol. In methanolysis, formations of emulsion were quick and easily break down to form glycerol rich bottom layer and Methyl ester rich upper layer [9]. Transesterification occurs approximately 4000 times faster in the presence of alkaline catalystthan the same amount of acid catalyst [8]. For alkali catalyst transesterification, the reactant must be anhydrous, large water makes the reaction partially change to saponification [18]. NaOH is used as an alkali catalyst because it is used widely in large industrial scale bio-diesel production. However the optimum conditions for bio-diesel production strongly depend upon the properties of raw oil used [19]. The chemical properties of the esters determine their feasibility as fuel, the intent of this work is to investigate and optimize the parameters involved in the transesterification of Dairy Waste Scum Oil for fuel use, to develop low-cost chemical process and to determine the influence of the chemical properties of the oil in the transesterification. Transesterification tests were conducted in the stirred tank reactor that was equipped with temperature controller and a reflux condenser, to avoid methanol losses 2. Materials and methods Scum oil transesterified to produce Scum oil methyl ester (SOME), which has fuel properties similar to diesel. In the present study, scum oil methyl ester was considered as a potential alternative fuel for an unmodified diesel engine. The scum collected from the KMF, Tumkur (Karnataka milk federation) diary. and processed immediately to avoid increase in free fatty acid further by biological action. Scum is turbid white in colour and semi solid in texture. A known quantity of scum is heated to the temperature of 50–60 0C to melt into liquid condition and allowed to settle for few minutes and lower aqueous phase has to be removed further. The top oil layer is Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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separated, centrifuged to remove the unwanted suspended solids such as film wastes and other solid wastes. It is heated to the temperature of 110 0C until the oil becomes substantially anhydrous for transesterification [18]. It is then filtered through steel micromesh. Now the oil is ready for transesterification. Oil yield per kg of scum is 600 g The other materials used in the study were NaOH and Methanol(99.8% pure). All the chemicals were purchased from Merck whichwere of analytical reagent grade. Diesel was taken from commercial diesel No. 2. The chemical and physical properties of scum oil are given in Table 1. [27] Table 1 Fatty acid composition of dairy scum oil [27] Component Carbon Fatty acid% Butyric 4:0 1.3634 Caproic 8:0 1.4987 Capric 10:0 0.9444 Lauric acid 12:0 2.7176 Myristic acid 14:0 14.3526 Palma tic acid 16:0 42.1390 Steric 18:0 15.7632 Oleic acid 18:1 19.2093 Linoleic acid 18:2 0.4822 Linolenic acid 18:3 0.2509

2.1. Transesterification reaction set up The transesterification reaction was carried out in a system consists of a 1 L double-necked round bottom flask, which was put inside the heat jacket. Thermostat was a part of heat jacket to maintain the temperature of the reactant at a desired value. The reaction was carried at desirable temperature. Methanol has a boiling point of 65 0C, which vaporizes at elevated temperature during the reaction. To prevent the loss of methanol during reaction, a water-cooled condenser was used to condense the vapors and reflux it back into the reactor. The condenser also helps in maintaining atmospheric pressure inside the reactor. The side neck was used for fixing condenser. In order to achieve perfect contact between the reagents and the oil during transesterification, they must be stirred well at constant rate. A stirrer assembly was inserted through the main neck to the round bottom flask for effective stirring through a gas seal.

Figure 2.1: Reactor with condenser

Figure 2.2 : Esterification process

2.2. Transesterification process The reactor was charged with a given amount of Dairy Waste Scum Oil, which was stirred and preheated at different temperatures, mean while a solution of NaOH in methanol (CH3OH) was added. The reaction condition was varied; to obtain a large range of methyl ester yields. Heating and stirring was then stopped, neutralized with acetic acid and the product was allowed to separate into two phases. The optimum of each parameter involved in the process was determined while the rest of them remained constant. After each optimum was obtained, this value was considered to be constant during the

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optimization of the next parameter. Ester yield results (given as percentages) were related to the weight of oil at the start.(Weight of ester/Weight of oil). 2.3. Separation After completion of the reaction the product is transferred into a separating funnel for certain time interval (approximately 12 h) for phase separation. Since the solubility of methyl ester is low, the glycerin tends to collect at the bottom. With excess alcohol the unconverted triglycerides should be essentially zero. How ever some mono-glycerides and di-glycerides must be present [21]. Due to their polarity partially reacted glycerides should be preferentially attracted to the glycerin phase and then removed when phase is separated. 2.4. Washing Washing is a process to remove the entrained glycerol, catalyst, soaps and excess methanol. Free glycerin in the product is from transesterification reaction, when esters are completely washed with water and there should be a trace amount of methanol left since the alcohol is more soluble in water than in bio-diesel. The washing process also removes soaps and residual catalyst. The mixing of ester with water should be gentle to reduce the loss of ester due to formation of emulsion that could increase separation time [21]. To reduce the number of washing cycles the initial washing was done by diluted acetic acid continued by distilled water until the lower layer had a pH of similar to the pH of distilled water indicating the bio-diesel is free from catalyst [9]. 2.5. Drying Water in fuel causes generally two problems; first it can cause corrosion of engine fuel systems. The other major problem contributes microbial growth [22]. Drying suggest the possible separation of water from bio-diesel. Washing with water increases the water content on bio-diesel. Drying helps to remove dispersed and dissolved water in bio-diesel [5,9], which cause poor combustion plugging and smoke in optimal engine performance [23]. Drying was performed in hot air oven at 105 0C as long as the water content reduces below 0.05% as per ASTM. The drying process also removes the traces of methanol as well.

Figure 2.3: Transesterification process

Figure 2.4 :Water washing set

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Figure 2.5: Dairy waste scum

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Figure 2.6: Scum biodiesel

3. Result and discussion 3.1. Catalyst optimization The amount of alkali catalyst NaOH used affects the conversion efficiency of the process. The catalyst amount is varied in the range of 0.4–1.4 wt.% for six different values (0.4, 0.6, 0.8, 1.0, 1.2 and 1.4wt.% NaOH). It is noted that during the present experiments, the excess addition of KOH increased the yield. The Optimum was achieved using 1.2 wt.% of NaOH, which produced an 88.0% yield of transparent ester. NaOH amounts greater than 1.2wt.% produced a smaller ester yield, because of the presence of soaps, which prevents ester layer separation [11,25]. Optimum concentration of NaOH was 1.2 wt.% for 88% yield which is much higher than the findings of Phan [25] (0.75 wt.% NaOH for 90% yield). It can be concluded that the concentration of NaOH strongly dependent on the type of oils used. 3.2. Reaction temperature optimization With increase in temperature the conversion takes place at a faster rate. The optimum temperature for the reaction is found to be in the range of 60 0C. Maximum yield of 95.9% esters occurred at this temperature 60 0C. This result clearly shows that the rate of the reaction was strongly influenced by temperature [17,26]. However there was a slight decrease in yield after 60 0C due to the enhancement of transesterification and saponification reaction [25]. The requirement of higher temperature in yield was due to difference in raw feed stock oil [17]. 3.3. Reaction time optimization It has been observed that the ester yield increases with the increase in reaction time. The dependency of reaction time was studied at different time intervals ranging from 20–60 min. Results obtained from the present experiments with oil revealed that about 60 min of reaction are sufficient for the completion of the esterification. The maximum yield of 95.9% occurs at 60 min. The increase in reaction temperature speeds up the reaction rate and shortens the reaction 4. Conclusion Bio-diesel has become more alternative recently because of its environmental benefits and the fact that it is made from renewable resources. The remaining challenges are its cost and limited availability of fat & oil resources. There are two aspects of cost of biodiesel, the costs of raw material (Fat & Oil) and cost of processing. In terms of production cost, there are also two aspects, the transesterification process and by product (Glycerol) recovery. A continuous transesterification process is one choice to lower the production cost. The recovery of high quality glycerol is another way to lower production cost. The low-cost transesterification process of Dairy Waste Scum Oil has been described. Under optimal conditions, scum oil methyl esters yield of 96.7%, was achieved. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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The cost of the scum bio-diesel is very competitive 60–70% less when compared to other bio-diesel produced from edible and non edible fat and oils. In brief these properties make them a good alternative to petroleum based diesel fuel. One limiting factor is quantity, nevertheless scum oil bio-diesel is justified by ecological disposal of dairy scum and the net energy requirement is positive. Dairy industries can use these kinds of projects to solve their ecological problems in scum disposal and to improve their economy. References [1] Knothe G, Karhl J, Van Gerpen J, editors. The biodiesel hand book. IL(USA): AOCS press Champaign; [2] Lang X, Dalai AK, Bakshi NN, Reaney MJ, Hertz PB. Preparation and characterization of bio-diesels from various bio-oils. Bioresour Technol 2001;80(1):53– 63. [3] Altun S. Fuel properties of biodiesels produced from different feedstocks. Energy Educ Sci Technol Part A 2011;26(2):165–74. [4] Kalam MA, Saifullah MG, Masjuki HH, Husnawan M, Mahlia TMI. PAH and other emissions from coconut oil blended fuels. J Sci Ind Res 2008;67(11):1031–5. [5] Van Gerpen JH, Hammond EG, Yu L, Monyem A. Determining the influence of contaminants on biodiesel properties. Society of Automotive Engineers Technical Paper Series, SAE, Warrendale, PA. 1997;Paper No-971685. [6] Demirbas AH. Inexpensive oil and fats feedstocks for production of biodiesel. Energy Educ Sci Technol Part A 2009;23(1):1–13. [7] Ramadhas AS, Jayaraj S, Muraleedharan C. Use of vegetable oil as I.C engine fuels – a review. Renew Energy 2004;29(5):727–42. [8] Formo MW. Ester reactions of fatty materials. J Am Oil Chem Soc1954;31(11):548– 59. [9] Freedman B, Pryde EH, Mounts TL. Variables affecting the yields of fatty esters from transesterified vegetable oils. J Am oil Chem Soc 1984;61(10):1638–43. [10] Peterson CL, Reece DL, Cruz R, Thompson J. A comparison of ethyl and methyl esters of vegetable oil as diesel fuel substitute. Liquid fuels from renewableresources. In: Proceedings of alternative energy conference of ASAE, 1992. p. 99-110. [11] Coteron A, Vicente G, Martinez M, Aracil J. Biodiesel production from vegetable oils. Influence of catalysts and operating conditions. Recent Res Dev Oil Chem1997;1:109–14. [12] Anggraini AA. Wiederverwertung von gebrauchten speiseolen/-fetten imenergetischtechnischen Bereich-ein Verfahren und dessen Bewertung. In:Dep. Agrartechnik,Universitat Gesamthochschule ,Kassel: Witzenhausen,Germany; 1999. p. 193. [13] Otera J. Transesterification. Chem Rev 1993;93(4):1449–70. [14] Freedman B, Butterfield RO, Pryde EH. Transesterification kinetics of soybeanoil. J Am Oil Chem Soc 1986;63(10):1375–80. [15] Noureddini H, Zhu D. Kinetics of transesterification of soy bean oil. J Am Oil Chem Soc 1997;74(11):1457–63. [16] Krawczyk T. Biodiesel alternative fuel makes inroads but hurdles remain.Inform 1996;7(8):800–15. [17] Ma F, Hanna MA. Biodiesel production: a review. Bioresour Technol1999;70(1):1– 15. [18] Wright HJ, Segur JB, Clark HV, Coburn SK, Langdon EE, DuPuis RN. A report on ester interchange. Oil and Soap 1944;21(5):145–8. [19] Dorado MP, Ballesteros E, Lpez FJ, Mittelbach M. Optimization of alkalicatalyzed transesterification of Brassica carinata oil for biodiesel production.Energy Fuels 2004;18(1):77–83. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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[20] Ma F, Clements LD, Hanna MA. The effects of catalyst, free fatty acids and water on ransesterification of beef tallow. Trans ASAE1998;41(5):1261–4. [21] Sinha S, Agarwal AK, Garg S. Biodiesel development from rice bran oil: transesterification process optimization and fuel characterization. Energy Convers Manage 2008;49(5):1248–57. [22] Demirbas A. Progress and recent trends in bio-diesel fuels. Energy ConversManage 2009;50(1):14–34. [23] Fernando S, Karra P, Hernandez R, Jha SK. Effect of incompletely converted soybean oil on biodiesel quality. Energy 2007;32(5):844–51. [24] Chand P, Reddy CV, Verkade JG, Wang T, Grewell D. Thermogravimetric quantification of biodiesel produced via alkali catalyzed transesterification ofsoybean oil. Energy Fuels 2009;23(2):989–92. [25] Phan AN, Phan TM. Biodiesel production from waste cooking oils. Ful2008;87:3490–6. [26] Antonlin G, Tinaut FV, Briceno Y, Castano V, Perez C, Ramirez AI. Optimisation of biodiesel production by sunflower oil transesterification. Bioresour Technol2002;83(2):111–4. [27] Bio-diesel production by alkali catalyzed transesterification of dairy waste scum P. Sivakumar , K. Anbarasu, S. Renganathan Fuel 90 (2011) 147–151

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HEAT TRANSFER CHARACTERISTICS AND PERFORMANCE OF A CLOSED LOOP PULSATING HEAT PIPE M.Gangadharappa1, E.R.Babu2, G.Mahesh3 1

Student, Alpha college of Engineering and Technology, Department of Mechanical Engineering, Bangalore 2,3 Bangalore Institute of Technology, Bangalore

Abstract Thermal control is a generic need for any heat dissipation system. Heat pipes emerge as the most appropriate technology and most thermal effective solution due to their excellent heat transfer capability, heat transfer efficiency and structural simplicity. This paper attempts to describe the heat transfer characteristics of Closed Loop Pulsating Heat Pipe (CLPHP) which are new entrants in the family of closed passive two phase heat transfer system. It also shows the comparison of thermal efficiency of CLPHP for different filling ratios with two different working fluids, acetone and ethanol. This device is a combination of lot of events and mechanisms like bubble nucleation, collapse and agglomeration, bubble pumping action, pressure and temperature perturbations, flow regime changes, dynamic instabilities, meta-stable non equilibrium conditions, flooding, bridging. The aim of research work presented in this paper is to better understand the heat transfer characteristics on a CLPHP made of capillary tube of 2 mm inner diameter. The performance of the CLPHP are investigated for filling ratios of 30%, 40%, 50%, 60% and 70%. The results indicate that the performance of this device changes with the changing of working fluid, filling ratios and heat input. Keywords: Closed Loop Pulsating Heat Pipe; pressure pulsations; Acetone and Methanol.

1. Introduction Heat pipe is device of very high thermal conductance. The idea of heat pipe was first suggested by Gaugler [1]. It was not, however, until its independent invention by Grover [2], Grover et al. [3] that the remarkable properties of the heat pipe became appreciated and serious development work took place. The main difference between the heat pipe and the thermosiphon is orientation. In thermo-siphon, the evaporator has to be in lower side and the condenser is in upper side so that, after condensation the condensate will go downward due to the gravitational force, but in heat pipe the evaporator can be in any orientation. In this experiment, a thermo-siphon is used for observing its pulsating action under different heat input, filling ratio and different liquid. Here, condenser is placed in upper side, so the gravitational force will assist the liquid to move downward. There are different types of heat pipe. Pulsating or oscillating heat pipe is one of them. The general configuration of pulsating heat pipe is shown in Figure 1.

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Figure 1: Configuration of pulsating heat pipe

The pulsating heat pipe was first introduced by Akachi et al. [4]. Typically it comprises of a tube of capillary dimension, which has been evacuated and partially filled with the working fluid. Surface tension of liquid effects result in the formation of slugs of liquid interspersed with bubbles of vapour. The operation of pulsating heat pipes are outlined as, when one end of the of the capillary tube is heated (the evaporator), the working fluid evaporates and increases the vapour pressure, thus causing the bubbles in the evaporator zone to grow. This pushes the liquid towards the low temperature end (the condenser). Cooling of the condenser results in a reduction of vapour pressure and condensation of bubbles in that section of the heat pipe. The growth and collapse of bubbles in the evaporator and condenser sections, respectively, results in an oscillating motion within the tube. Heat is transferred through latent heat in the vapour and through sensible heat transported by the liquid slugs. The performance of a pulsating heat pipe depends on several parameters. They are (i) working fluid, (ii) internal diameter, (iii) total tube length, (iv) length of condenser, evaporator and adiabatic section, (v) number of turns and loops, and (vi) inclination angle. The present experiment is done by two different working fluids. One is acetone and another is ethanol. The choice of working fluid depends on various properties. A first consideration in the identification of the working fluid is the operating vapour temperature and its inherent thermal conductivity. Within the acceptable temperature range several fluids can show the desired property and a variety of characteristics has to be examined in order to determine the most acceptable of these fluids for the application being considered. The prime requirements are as follows [5-10]: (i) good thermal stability, (ii) moderate vapours pressure on the operating temperature range, (iii) high latent heat, (iv) high thermal conductivity, (v) high surface tension, (vi) acceptable freezing or pour point, (vii) low liquid and vapour viscosity, and (viii) high dP/dT that means the change of pressure is high with the change of temperature. Higher value of this parameter indicates high bubble formation and high heat transfer. 2. Experimental setup In general, the CLPHP operates on the basis of the movement of liquid slugs and vapour plugs, which is governed by surface tension and buoyancy. Therefore, the inner diameter must be small enough so that the working fluid will distribute itself inside the tube length and form the liquid slugs and vapor plugs due to the effect of surface tension. The heoretical maximum inner diameter Dmax for a CLPHP is suggested as =

(

−

)

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Where D is the inner diameter of CLPHP tube, and is the density of liquid and vapor, respectively, σ is the surface tension, and g is the gravity acceleration. In order to study the influence of thermo physical properties on the start-up performance of CLPHP, two working fluids such as acetone and ethanol are used here. WATER TANK

CONDENSOR WATER IN 1

ADIABATIC SECTION

WATER OUT

VOLTAGE

AMPERE

EVAPORATOR

Figure 2: Experimental setup

Figure 2 illustrates the schematic of the experimental setup. The CLPHP with four turns, and the inner radius of each turn is 12.5 mm. The lengths of evaporator, adiabatic section and condenser are 55, 80, and 50 mm respectively. The heat load is applied by mica heater which is placed on the outer wall surface of the evaporator, and it is dissipated from the condenser by cooling water with a constant inlet temperature of 200C. Both the evaporator and adiabatic section are well thermally insulated by glass wool fibers. The PHP is to be filled by different amount of working fluid. In this experiment, the filling ratios are 30%, 40%, 50%, 60% and 70%. for both working fluids. The filling procedure is done by a syringe injector. After filling the tube on their desired filling ratios, the evaporator section has to be heated by the variac. By changing the variac voltage, different voltage and current are supplied to the evaporator. For heating the evaporator a mica heater is used. Water is used for cooling the condenser. The K type thermocouples are used to monitor the temperature of different position of the heat pipe. The temperature is recorded on a regular time interval. Generally, the time interval is 5 minutes. The temperature is recorded when the steady state condition is reached. 3. Results and Discussion 3.1. Effect of Charging Ratio on Thermal Performance of PHP Figure 3.1 (a) and (b) shows the effect of filling ratio on the thermal performance of PHP. The overall thermal resistance of the PHP firstly reduces with the increase of the amount of heat input, but rises when the heat input exceeds the heat transfer limit. While charging 30%, 40%, 50%, 60%, and 70% the heat pipe works in the PHP mode with a steady and continuous flow, more liquid can return to the heating section so that the heat transfer limit is apparently increased. As a result, there is an optimal charging ratio (50%) for which the thermal resistance has a lowest value of 1.071 K/W at the heating power of 22W for Acetone and an optimal charging ratio (40%) for with the thermal resistance has the lowest value of 1.717 K/W W at a heating power of 22W for Ethanol, with the heat transfer limit reaches the highest.

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Thermal Resistance Rth (ºK/Watts)

2.5 2

14 watts

1.5

18wat ts

1 30%40%50%60%70% Filling ratio

10 watts

Thermal Resistance Rth (ºK/W)

10 watts

3.5 3

14 watts

2.5

18wat ts

1.5

22 watts

30%40%50%60%70% Filling ratio

(a) Acetone

(b) Ethanol

Figure 3.1: Variation of Thermal Resistance with Filling Ratio

3 30%

2.5 40% 2

50%

1.5

60% 70%

1 10

Heat input Q ( W) (a) Acetone

Thermal Resistance Rth(ºC/W)

Thermal Resistance Rth ( ºC/W)

3.2 Effect of Heat Input on Thermal Performance of PHP

3 30% 2.5

40%

50%

1.5

60%

70% 10

Heat Input Q (W)

(b) Ethanol

Figure 3.2: Variation of Thermal Resistance with Heat Input

Figure 3.2 (a) and (b) shows the thermal performance in terms of effective thermal resistance which is defined as the ratio of the temperature difference between the evaporator and the condenser to the net heat input in the system. It is clear that the thermal resistance decreases with increase in heat input for both Acetone and Ethanol. Till about 18W input power the thermal performance improvement is quite drastic while thereafter it is mild. Further, it is seen that Acetone exhibits lower values of thermal resistance compared to Ethanol. The lower values of thermal resistance of Acetone indicate that Acetone has better heat transport capability compared Ethanol.

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64.00

EVP. TEMMPERATURE °C

30 % 40 % 50 % 60 % 70 %

62.00 60.00 58.00 56.00 54.00 52.00 50.00

EVP.TEMPERATURE °C

3.3 Effect of Evaporator Temperature on Thermal Performance of PHP 85 80 75 70 65 60 55 50 45 40

30% 40% 50% 60% 70% 0

10 14 18 22 HEAT INPUT Q (W)

(a) Acetone

HEAT INPUT (W)

(b) Ethanol

Figure 3.3: Variation of Evaporator Temperature with Filling Ratio

Figure 3.3 (a) and (b) shows the effect of heat input on evaporator temperature when Acetone and Ethanol used as working fluids in PHP. It is evident from the experiments that, there is a continuous pressure pulsation during the flow in a PHP. Thus the temperature readings are recorded only after the steady and continuous movement of the working fluid. It is also clear that the evaporator temperatures are more at higher heat input of 22 W due to intermittent motion of the working fluid and takes more time to reach the steady State. From this comparison, Acetone could be stated as the best working fluid to be used as it presents the lowest evaporator section temperatures. 4. Conclusion From the investigation of this heat pipe at different heat input, filling ratio and fluid, the following findings are obtained. It could be observed that PHP has better operational performance and self- sustained thermally driven pulsating action for charging ratio of 50% for Acetone and 40% for Ethanol. In both working fluids, Ethanol is having more thermal resistance where as Acetone is having lesser thermal resistance. So Acetone gives best thermal performance in comparisons with Ethanol. Acknowledgment The authors are grateful to the Management and Department of Mechanical Engineering, Bangalore Institute of Technology, Bangalore, India, for extending the facilities to carry out this Investigation. References [1]. Gaugler, R. S US patent 2350348.Appl. 21 Dec, 1972.Published 6 June 1944. [2]. Grover, G. M US patent 3229759.Filed 1963. [3]. Grover, G.M., Cotter, T.P. and Erickson, G.F. Structures of very high thermal conductance. J. App. Phys., Vol. 35, pp.1190-1191,1964. [4]. Akachi, H., Polaassek, F., SStulc, P., “Pulsating heat pipes”, Proceedings of the 5th International Heat Pipe Symposium, Melbourne, Australia, 1996, p. 208–217. [5]. Wallis, G., “One Dimensional Two-Phase Flow”, McGraw Hill Inc., 1969. [6]. Khandekar, S., Schneider, M., Groll, M., “Mathematical modeling of pulsating heat pipes: state-of-the-art and future challenges”, 5th ASME/ISHMT joint

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International Heat and Mass Transfer Conference, Kolkata, India, 2002, pp. 856– 862. [7]. Groll, M., Khandekar, S., “Pulsating heat pipes: a challenge and still unsolved problem in heat pipe science”, Proceedings of the 3rd International Conference on Transport Phenomena in Multiphase Systems, Kielce, Poland, 2002, pp. 35–44. [8]. Duminy, S., “Experimental investigation of pulsating heat pipes”, Diploma thesis, Institute of Nuclear Engineering and Energy Systems (IKE), University of Stuttgart, Germany, 1998. [9]. Khandekar, S., Schneider, M., Schaafer, P., Kulenovic, R., Groll, M., “Thermofluid dynamic study of flat plate closed loop pulsating heat pipes”, Microsc. Thermophys. Eng. 6 (4) (2002) pp. 303–318. [10]. Shafii, M.B., Faghri, A., Zhang, Y., “Thermal modeling of unlooped and looped pulsating heat pipes”, ASME J. Heat Transfer 123 (2001) pp. 1159–1172.

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CFD ANALYSIS OF SUPERSONIC EXHAUST IN A SCRAMJET ENGINE Rudra Murthy1, D.K.Ramesha2, P.Hemanth Kumar3 1,3

Student, 2Associate. Professor, Department of Mechanical Engineering, UVCE, Bangalore. rameshdkuvce@gmail.com

Abstract

When pressures and temperatures become so high in supersonic flight that it is no longer efficient to slow the oncoming flow to subsonic speeds for combustion, a Supersonic Combustion Ramjet (SCRAMJET) is used in place of a ramjet. This paper is aimed at modeling the supersonic flow inside SCRAMJET engine using the Computational Fluid Dynamics (CFD) ANSYS Fluent. The purpose of this test is to validate Fluent's ability to predict reflecting shock waves and their effect on wall pressure distribution and heat transfer. Supersonic flow from a nozzle that represents the exhaust nozzle of a SCRAMJET is modeled. Jet from the nozzle is issued into a domain which is bounded on one side by an after body wall which is parallel to the centerline of the nozzle. Shocks propagating from the nozzle exit reflect from the after body. Measured values of the distribution of wall pressure and heat transfer rate along the after body are used to validate the CFD simulation. In this study, k-ε model has been used to examine supersonic flow in a model scramjet exhaust. The configuration used is similar to the DLR (German Aerospace Center) scramjet model and it is consists of a one-sided divergent channel with wedge-shaped and without wedge shaped. For the purpose of validation, the k-ε results are compared with experimental data for temperature at the bottom wall. In addition, qualitative comparisons are also made between predicted and measured shadowgraph images. The k-ε computations are capable of predicting flow simulations well and good. Keywords: Mach number, scramjet, ansys, fluent, afterbody

1. Introduction Scramjets are engines designed to operate at high speeds usually only associated with rockets and are typically powered by hydrogen fuel. Scramjet is an acronym for Supersonic combustion ramjet. A ramjet has no moving parts. Air entering the intake is compressed using the forward speed of the aircraft. The intake air is then slowed from a high subsonic or supersonic speed to a low subsonic speed by aerodynamic diffusion created by the inlet and diffuser. Fuel is then injected into the combustion chamber where burning takes place. The expansion of hot gases then accelerates the subsonic exhaust air to a supersonic speed. This results in a forward velocity. Scramjets on the other hand do not slow the free stream air down through the combustion chamber rather keeping it at some supersonic speed. This may appear mechanically simple however it is immensely more aerodynamically complex than a jet engine. Keeping the free stream flow supersonic enables the scramjet to fly at much higher speeds. Supersonic flow is needed at higher speeds to maximize efficiency through the combustion process. Scramjet top speeds have been estimated between Mach 15 to Mach 24, however at this early stage Mach 9.6 is the fastest recorded flight achieved during the third and final flight of the X-43A flown by NASA. This is three times the speed of the SR-71, officially the fastest jet-powered aircraft which achieved Mach 3.2.

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2. Geometric Model Supersonic flow from a nozzle that represents the exhaust nozzle of a supersonic combustion ramjet (SCRAMJET) is modeled. Jet from the nozzle is issued into a domain which is bounded on one side by an after body wall which is parallel to the centerline of the nozzle. Shocks propagating from the nozzle exit reflect from the after body. Measured values of the distribution of wall pressure and heat transfer rate along the after body are used to validate the CFD simulation. The flow is considered to be two-dimensional, because the span of the experimental outlet is considerably larger than the height. Both geometries are shown in Fig. 1 and Fig. 2. The flow enters the exhaust section at a Mach number of 1.66. In each case, the cowl wall opposite the after body angles initially upward. This is followed by a wedge, inducing a shock that reflects off of the after body.

Figure 1: Sketch Showing Nozzle Separators and cowl

Figure 2: Problem Description: 20-Degree PAfterbody

3. Input Parameters 3.1 Material Properties Table 1: Material Properties Property

Values 3

Density(kg/m )

Ideal Gas

Molecular Weight

113.2

Viscosity(kg/m-s)

1.7894 X 10-5

Thermal Conductivity (W/m-K)

0.0242 Temperature Dependent

Specific Heat

3.2 Geometric Property Table 2: Geometric Properties Property Nozzle outlet diameter (cm) Length of cowl (cm)

Dimension 1.524 3.5 D

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3.3 Boundary Condition Table 3: Boundary Conditions Boundary Conditions Values Inlet Total Pressure (gauge) 551600 Pa Inlet Static Pressure (gauge)

127100 Pa

Inlet Total Temperature

477.8 K

Inlet Turbulent Intensity

Wall temperature

328 K

Outlet Pressure (gauge)

2780 Pa

A pressure inlet is used such that the inlet Mach number is 1.66. The wall temperature (not given in [1]) is set to 328 K. A constant static pressure of 2780 Pa is used for the pressure outlet condition at the top and right of the geometries shown in Fig 2.The authors of the experimental paper [1] used a substitute gas without combustion. The substitute gas was chosen to give properties as close as possible to combustion gases used in practice. The gas used was a 60% Argon and 40% Freon-12 mixture at a total temperature of 477.8 K. Tables were provided in [1] giving the specific heat at constant pressure for temperatures between 111 K and 533 K. For the flow calculation, Cp was assumed to have a piecewise-linear dependence on temperature. Three points were used to define the curve at 205.6 K, 438.9 K, and 533.3 K. 4. CFD Meshing Two-dimensional grids were made for the test of the 20-degree geometry. The CFD mesh was a 39230-cell mesh made entirely out of quadrilateral cells The Quadrilateral grids are shown in figure below.

Figure 3: Quadrilateral Grid for 20-Degree Afterbody

5. RESULTS AND DISCUSSON Figure 4 displays the contours for the 20 degree afterbody. Notice that, for this case, the shock wave is much more diffuse by the time it reflects off of the afterbody.

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Figure 4: Pressure contours 20-Degree Afterbody with wedge

Figure 5 gives the temperature contours for the 200 afterbody with wedge using an adapted quadrilateral mesh. The shocks were induced at the wedge due to inclination of wedge (shock generator) by 19 0 with respect to the nozzle axis. Shock wave is much more diffuse by the time it reflects off of the afterbody.The thrust generation is maximum due to 20 degree afterbody inclination with respect to the nozzle axis and reflecting shock on the afterbody reflects away from the body.

Figure. 5: Temperature contours 20-Degree Afterbody with wedge

Figure 6: Pressure variation along the centerline 20-Degree Afterbody with wedge

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Figure 6 gives Pressure variation along the centerline 20-Degree Afterbody with wedge, as a function of horizontal distance. Pressure is maximum at the nozzle end as the exhaust gas moves away from the nozzle end pressure gradually decreases and take sudden peak near the wedge due to shock waves that is pressure concentration more. Across the wedge pressure again reduces because of 20 degree afterbody inclination with respect to nozzle axis. 5.1. Comparison of predicted static pressure distribution on the 20- degree afterbody with wedge and experimental data

Figure 7: Comparison of Predicted Static Pressure Distribution on the 20-Degree Afterbody with Experimental Data

Figure 7 describes the Normalized Pressure as a Function of Horizontal Distance for the 20-degree Afterbody with wedge and for the Hopkins et al. [1] Results. 5.2 Comparison of predicted total heat flux along the 20-degree afterbody with wedge and experimental data

Figure 8: Comparison of Predicted Total Heat Flux along the 20-Degree Afterbody with Experimental Data Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Figure 8 describes the Heat Transfer Rate as a Function of Horizontal Distance for 20-degree Afterbody and for the Hopkins et al. [1] Results. 6. Conclusion It is interesting to note that obtaining experimental pressure measurements was a quicker process than CFD modeling in terms of both overall time taken and the time to investigate each configuration. However, CFD generates a much larger number of flow parameters than can be experimentally determined and is significantly less expensive, in terms of both personnel and equipment, than performing experiments in the shock tunnel. Also, once a model has been developed and verified subsequent modeling is significantly quicker and easier than experiments. Supersonic flow from a nozzle that represents the exhaust nozzle of a supersonic combustion ramjet (SCRAMJET) is modeled suing ANSYS Fluent. Jet from the nozzle is issued into a domain which is bounded on one side by an afterbody wall which is parallel to the centerline of the nozzle. Shocks propagating from the nozzle exit reflect from the afterbody. Measured values of the distribution of wall pressure and heat transfer rate along the afterbody are used to validate the CFD simulation. Pressure distributions obtained on a cowl and afterbody model with the flow of simulated combustion products and the flow from a substitute gas mixture of 50 percent Argon and 50 percent Freon 13Bl were in good agreement in the two-dimensional region of the flow. References [1] [2] [3] [4]

[5]

[6]

[7]

[8] [9]

Hopkins, H. B., Konopka, W., and Leng, J. “Validation of scramjet exhaust simulation technique at Mach 6”. NASA Contractor Report 3003, 1979. A. Lyubar and T. Sattelmayer “Numerical investigation of fuel mixing, ignition and flame stabilization by a strut injector in a scramjet combustor.” Gerlinger, P., Möbus, H., Brüggemann, D. “An Implicit Multigrid Method for Turbulent Combustion”, Journal of Computational Physics, 2001, 166. Ro A. Oman K. M, Foreman, Jo Leng, and H. B. Hopkins “Simulation of hypersonic scramjet exhaust” Grumman aerospace corporation for Langley Research Center NASA CR-2494, March 1975. Kristen Nicole Roberts. “Analysis and design of a hypersonic scramjet engine with a starting mach number of 4.0.” University of Texas at Arlington in august 2008. Tohru Mitani, Toshinori Kouch “Flame structures and combustion efficiency computed for a mach 6 scramjet engine” Original Research Article Combustion and Flame, Volume 142, Issue 3, August 2005. K.M.Pandey and T.Sivasakthivel “CFD Analysis of a Hydrogen Fueled Mixture in Scramjet Combustor with a Strut Injector by Using Fluent Software”, IACSIT International Journal of Engineering and Technology, Vol.3, No.2, April 2011. Hopkins, H., Konopka, W., and Leng, J., “Validation of Scramjet Exhaust Simulation Technique”, NASA CR-2688, June 1976. Hopkins, H., Konopka, W., Leng, J., and Oman, R., “Simulation Experiments UsingHydrogen/Oxygen Gas Mixtures in a High-Pressure Detonation Tube,” NASA CR-128955, 1973.

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NUMERICAL SIMULATION OF LATER PART OF SUCTION IN PRODUCER GAS FUELED HIGH COMPRESSION SI ENGINE Kolke Deepak Kumar1, H.N.Vidya Sagar2, D.K.Ramesha 2 1

Student, 2Associate Professor Thermal science and engineering, Dept. of Mechanical Engineering, U.V.C.E, Bangalore rameshdkuvce@gmail.com

Abstract The primary objective of this work is to attempt to operate a Spark Ignition (SI) engine with producer gas at Highest Useful Compression Ratio (HUCR), using Computational Fluid Dynamics (CFD) tools by predicting the compression pressures (motoring curve) and improving the flow behavior inside the engine to enhance turbulence to avoid knocking conditions. Simpler models like flat plate piston and cylinder were used in the simulation instead of actual bowl in piston adopted in the diesel engine to analyze the flow pattern, compression pressures, thermodynamic behavior and identifying key parameters to optimize the SI engine for HUCR. A detailed 3D CFD modeling of the actual engine geometry were simulated to obtain relevant flow parameters under non-firing (cold flow) conditions. This work also attempts to simulate the performance aspects related to high Compression Ratio (CR) SI engine using high octane and low energy density gaseous fuel known as producer gas using CFD tool . It also emphasizes the potential of bio-mass derived producer gas as the future fuel for power generation application. The present work is restricted to only cold flow analysis and hence arriving at peak pressures attained during compression process. This approach is to attribute basically for the degradation of the performance absorbed in considering single independent grid. The variation of P-θ curve (motoring curve) is also plotted. Keywords: Producer Gas, Ansys CFX.11, optimization, Crank Angle, Pressure difference and Temperature difference.

1. Introduction In the recent times, gaseous fuels are gaining prominence as cleaner fuels for power generation via internal combustion engine route, the power generation package including both reciprocating engines and gas turbine machinery. Complete combustion with minimal emission is the key feature of gaseous fuels and this feature is currently being exploited the world over for power generation purposes. Producer gas derived from biomass is one such eco-friendly gaseous fuel. While natural gas is the most used one next one being the land fill gas or biogas, which is diluted natural gas (with 20-30% CO2 ) biomass-based producer gas is perhaps the least used fuel. [1,3]. Internal combustion reciprocating engines have integrated into societal service in the last century. Their use has improved the quality of life substantially, but at the cost of degradation to the environment, certainly in several countries with insufficient environmental consciousness. Therefore, large impetus is being given to improve the efficiency and thereby reduce the emissions by using two approaches namely, improving in engine design and use of alternate fuels in place of fossil fuels. [1, 2]. In the recent times, there is a renewed interest in biomass gasification technology, which has simulated interest in producer gas-operating engines. Whatever work has been attempted in this area has been limited to lower CR (less than 12.0)engine due to perceived limitation of knock at higher CR. A review of some of earlier studies relevant to this work, namely producer gas engines, fluid flow in reciprocating engines are presented now[3,4]. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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1.1 Literature Review Summary of literatures in the field of producer gas based engines reveals modest research work accomplished since the inception of biomass/ charcoal gasification systems. This could be attributed to two reasons, namely non-availability of standard gasification system that could generate consistent quality of producer-gas and the other related to misconception about producer gas fuel. The literature in the area is scant. The literature review is categorized into two sub-topics, namely producer gas engines, fluid flow in reciprocating engines. It is evident from the literature that in-cylinder processes in reciprocating engines are extremely complex in nature. While much is known about these processes, they are not adequately understood at a fundamental level. Therefore at present constructing a model to predict the engine operation from the governing equation is difficult. The present study attempts to analyzing the thermodynamic behaviour and identifying key parameters. A detailed 3D CFD modeling of the actual engine geometry to obtain relevant parameters of turbulence under non-firing (cold flow) analysis is carried out. 2. Problem Description The geometry considered for modeling is identical to the combustion chamber of small power level engine (SPE). The combustion chamber comprises of a flat cylinder head and an eccentricity located hemispherical bowl. The geometry details of the engine are given in Table.1. The piston, which is one of the moving boundaries, simulates the reciprocating movement of an engine. The minimum clearance between the piston and the cylinder head as the piston approaches its uppermost point of travel is about 7.25mm for a CR of 17. The Table 2 shows cylinder dimensions. 2.1 Modelling Parameter Make and Model

Table 1: Engine Details for modeling Specification Kirloskar, RB-33 Coupled to a 25kVA Alternator

Engine Type

In-Line, 3 Cylinder, 4-Stroke, Naturally Aspirated

Rated Output – Diesel

28 kW @ 1500 rev/min

Net Output – Diesel

24 kW (21kWe) @ 1500 rev/min

Type of Cooling

Water Cooled with Radiator

Bore x Stroke

110 x 116 mm

Swept Volume

1.1 Litre

Compression Ratio

17:1

Bumping Clearance

1.5 mm

Combustion Chamber

Flat Cylinder Head and Hemispherical Bowl-in Piston Type Battery Based Distributor Type with Ignition Advance/Retard Facility Cold, Offset from the Axis of Cylinder by 8mm

Ignition System – Gas Spark Plug Type & Location - Gas Mode Intake Port Valve Timing

Firing Order SFC, g/kWh – Diesel

Directed Type Inlet Valve Opening – 26 ° BTC Inlet Valve Closing – 66 ° ABC Exhaust Valve Opening – 64 ° BBC Exhaust Valve Closing – 38 ° ATC 1-2-3 280 – 290

Air-to-Fuel Ratio

20 to 21:1 at 24 kW

Alternator Efficiency

87%

Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Fig 1: Cylinder dimensions

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Fig 2: Geometry details of RB33 engine

Fig 3: Modeling of manifold and valves of IC engine.

The Figure 1, shows the cylinder dimensions and Figure 3, shows the modeling details of IC engine. The dimensions are taken from the engine model RB33, and generated the models in Auto CAD. The only modification done is the bowl in piston is replaced with flat plate piston, and remaining all features are restored, keeping in mind that after the desired result are obtained through simple flat plate piston, high complex IC engine geometry can be tackled. The Figure 2, shows the features of original Kirloskar made RB33 engine. 2.2 Boundary Conditions The flow domain considered for simulation is downstream of the engine intake manifold. Therefore, flow through intake manifold is not modelled. Exhaust Valve is not considered, and hence the exhaust stroke is also not modelled. In the present analysis, air with ideal gas behaviours or cold flow simulation is done, mass flow rate 40g/s is set with flow condition being subsonic. Outlet boundary condition is set to supersonic. Walls are adiabatic and no slip condition is applied. At the start of the computations proper initial conditions are specified for all variables. Secondorder Backward Euler (SBE) method used for discretizing the transient term and high resolution method for discretizing the convection terms.

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Table : 2 Constraints made use in the simulation BASIC SETTINGS MESH MOTION

Cylinder Wall Cylinder Head

Boundary Type Wall Wall

Location Cylinder wall Cylinder head

Piston

Wall

Piston

Inlet Inlet Manifold1 and manifold2

Inlet

Inlet Manifold 1. Manifold 2 Inlet valve bottom, Inlet valve top1, Inlet valve top2, Inlet valve top3

Wall

Inlet Valve Bottom and outlet valve

Wall

Inlet Valve Rod and outlet rod

Wall

Inlet valve rod

Unspecified Stationery Specified Displacement Stationery Stationary Specified Displacement Unspecified

2.3 Grid Generation There are two types of grid generation in Ansys CFD package, namely structured mesh and unstructured mesh. Figure 4, shows the modeled Engine with flat head piston, one inlet and one outlet valve. The number of grid points or nodes plays an important role in arriving at the appropriate accurate results. The spacing ratio between the nodes is maintained as 1 throughout the domain.

Fig 4: Geometry showing manifolds,cylinder, inlet & outlet

Fig 5: Structured mesh geometry with 8.44x105 nodes

Fig 6: Figure showing the quality of mesh

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2.4 Grid study under various strokes

Fig 7: Grid pattern at 90°CA

Fig 9: Grid pattern at 270° CA

Fig 11: Grid pattern at 6300 CA

Fig 8: Grid pattern at 1800 CA

Fig 10: Grid pattern at 360°CA

Fig 12: Grid pattern at720°CA

2.5 Computational Procedure The simulation was carried out for one single cycle comprising of suction, compression expansion and exhaust without combustion. Computations have been made for an operational speed of 1500 rpm, with time step of the order of 1° CA (100 micro seconds). The calculations commence with the piston at TDC, with the intake valve closed. Using the initial and boundary conditions as mentioned earlier, the computation proceeds with the piston descending downwards and the intake valve beginning to open so as to allow fluid to enter the flow domain i.e. cylinder. The closure of the intake valve takes place in accordance with the actual valve timing of the engine. At which time the boundary condition at the intake valve is changed from pressure to wall to prevent fluid escaping from the cylinder. Further, upward movement of the piston results in compression of the fluid till the piston reaches TDC, beyond which fluid expansion occurs.

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3. RESULTS 3.1 P-θ Curve

Absolute Pressure (bars)

The simulated absolute values are plotted against crank angle. The simulated values are superimposed on theoretical values obtained from adiabatic condition as shown in Figure 13. Since our interest is on the later part of suction stroke, the plot shows range from 180° to 540°. The simulated values obtained from CFX and the theoretical values obtained from adiabatic equation [6] (PVγ= Constant) are superimposed in Figure 13, as shown.

P-Ѳ Curve for air 39 bars

36 bars

Theoritical pressure

20 10 0 160

260

360

460

Crank angle (Degrees) Fig.13: Superimposed Graphs of simulated and theoretical values of P-θ Curve

For theoretical values, making use of adiabatic equation (PVγ=Constant). For air (γ = 1.4) P2 

P1 V2     V1 



(1) Sample calculation: 1) for 180° CA let us calculate P2. We have, where, P1 P2 

V 2     V1 

P1=0.82bar(based



output) (2) d= 0.110m, L1=0.116m, L2=0.00725m(comp) V1=A×L= ( Π/4 × d2)×0.116 V2= same as V1@ 180° ∴ P2= 0.82 bar Table 3: Theoretical and CFX simulated Pressure values. Crank angle (CA) in degrees 180

Theoretical Absolute pressure in bars 0.82

CFX Absolute pressure value in bars 0.82331

225 270 315

0.82 1.58 5.71

0.97034 1.73 6.52

360 405

39.77 5.71

36.19 6.32

450

1.58

2.91

suction

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The reason attributed to the difference in pressure rise in between theoretical and simulated values is, the theoretical values obtained are ideal one, which means it represents perfect mixing and filling of gas (air) within the engine cylinder. Coming to the simulated values, the CFX calculates making use of prevailing conditions which are actual existing inside cylinder. One reason for improper mixing is due to rapid movement of piston in during suction, compression, expansion and exhaust strokes which creates vacuum and swirls within the cylinder which are lasting only for few micro seconds. 3.2 Temperature curves The temperatures (T2) at different crank positions are calculated using the adiabatic equation (2) in terms of pressure and temperature ratios. The Table 4 shows the theoretical values simulated values at different crank angles. Sample Calculation: 1) Calculation of T2 at 270° CA P2 = (( T2 / T1 ) γ / γ-1 ) (3) P1 P1= 0.82 bar, T 1= 400K, P2=1.58 bar, γ =1.4 for air. ∴ T2= 482.4 K Table 4: Theoretical and CFX simulated temperature values

Temperature in kelvin

Crank angle (CA) in degrees 270

Theoretical Temperature values ( in K) 482.4

Simulated temperature values in ( in K) 495

315

695.4

726.5

360

1208.5

1194

405

695.4

731

450

482.2

502

Temperature curves

1300 1200 1100 1000 900 800 700 600 500 400

Simulated temperature

160

260

360

460

560

Crank angle in degrees Fig. 15: Graph of temperature values of both theoretical and simulated against CA.

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3.3 Velocity and Streamline Plots: The velocity and streamline flows are very much important when studying fluid flow behavior taking place within the cylinder. This study will help us to understand the turbulence phenomena, through which we can model the engine accordingly specially the gas engine, where the kinetics modeling play an important role. The following pictures show us the nature of fluid behavior at different crank angles during one complete cycle of four stroke engine.

Fig 16: Streamlines at 90° CA

Fig 17: Streamlines at 180° CA

Fig 18: Streamlines at 270°

Fig 19: Streamlines at 360° CA

Fig 20: Streamlines at 540° CA

Fig 21: Streamlines at 630°

Fig 22: Vector plot at 90° CA

Fig. 25 Vector plot at 360° CA

Fig 23: Vector plot at 180° CA

Fig. 26 Vector plot at 540° CA

Fig 24: Vector plot at 270°

Fig. 27 Vector plot at 630°

4. Conclusions In the present work an attempt has been made to apply k-ε model to study in cylinder flow behavior simulating cold or motoring conditions. The simulations have been carried on complex engine geometry with flat face piston along with an intake valve and outlet valve which is located at an offset. The simulations were conducted using Air ideal gas which obeys state equation. The simulations were conducted for one single engine cycle corresponding to an engine speed of 1500 rev/min involving suction, compression,

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and expansion strokes. The challenge has been for establishing a stable grid structure which will with-stand all the four strokes (720°) continuously under dynamic conditions. Experiments have been conducted on 3 Dimensional model and studies have been conducted to simulate the flow in an engine cylinder geometry using turbulence model such as K-ε. Analysis has done so far have been by considering single independent grid for each stroke of a four stroke engine cylinder [Sridhar. G, 2003 Feb]. Hence there is a scope to improve the performance and out come by conducting advance studies on grids structures to capture fluid flow accurately for all the four strokes that is 720° continuously. Therefore the challenge is to come out with stable and sustainable grids under dynamic conditions. Given below are the observations from the present study: 1. CFD simulation study has been carried on combustion chamber geometry using commercially available CFD software, Ansys CFX.11. 2. Optimization of mesh has been carried on different Meshes (blocking approaches). 3. Optimization studies carried out on movement and failure of grids during simulation processes. 4. The pressure difference between CFX simulated and the theoretical values is found to be 8%. 5. The theoretical and simulated P-θ curves for motoring are found to be similar. 6. The temperature difference between CFX simulated and the theoretical values is found to be 2% NOMENCLATURE P : Pressure (bar). V : Volume (m3). T : Temperature (K). n : Polytropic index. ABBREVIATIONS CFD : Computational fluid dynamics. TDC : Top Dead Center. IMEP : Indicated Mean Effective Pressure. CR : Compression Ratio. CA : Crank Shaft Angle. 3D : Three Dimensional. HUCR : Highest Useful Compression Ratio. CGPL : Combustion Gasification Propulsion Laboratory.

References [1]. Sridhar.G Rao (2003): “Experiments and Modelling studies of Producer Gas based SparkIgnited Reciprocating Engines”, Ph.D. Thesis, Indian Institute of Science. [2]. G. Sridhar : “ Experimental and Modelling Aspects of Producer Gas Engines. [3]. G. Sridhar, H.V. Sridhar, S. Dasappa, P.J. Paul, N.K.S. Rajan and H.S. Mukunda (2005): “Development of Producer Gas Engines” from the Journal of Automobile Engineering, Part D, Proc. Instn. Mech Engrs, Vol. 219, pp – 423-438. [4]. G. Sridhar, P.J. Paul and H.S. Mukunda (2004): “Simulation of fluid flow in high compression ratio reciprocating IC engine”, Journal of Power & Energy, Part A, Proc. Instn. Mech Engrs Vol 218, pp-403-416. [5]. G. Sridhar, P.J. Paul and H.S. Mukunda (2006): “Zero-Dimensional Modeling of Producer Gas Based Reciprocating Engine”, paper accepted for publication in the Journal of Power & Energy, Part A, Proc. Instn. Mech Engrs, Vol. 220, No. 8, pp. 923-932. [6]. John B.Heywood (1988): “Internal Combustion Engine Fundamentals”, McGraw- Hill College. [7]. John D Anderson Jr. “Computational fluid mechanics basics with applications,” McGraw-Hill Publications, 1995. [8]. S.V.Patankar, “Numerical heat transfer and fluid flow,” McGraw-Hill publications, New York, 1980.

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EFFECT OF BAFFLE INCLINATION ON SHELL AND TUBE HEAT EXCHAGER USING CFD B.N.Ravikumar1, Praveen Karande2, D.K.Ramesha3 1,2

Student, 3Associate Professor, Thermal science and Engineering, Dept. of Mechanical Engineering, U.V.C.E, rameshdkuvce@gmail.com

Abstract Heat exchangers are devices in which heat is transfer from one fluid to another. Shell-and-tube heat exchangers are used extensively in engineering applications like power generations, refrigeration and air-conditioning, petrochemical industries etc. In this present study, attempts were made on investigating the shell side design of a shell-and-tube heat exchanger; in particular the segmental baffles inclination dependencies of the Heat Transfer Coefficient (HTC) and the pressure drop. The impacts of various segmental baffles inclination angles on fluid flow and the heat transfer characteristics of a shell-and-tube heat exchanger for six different baffle inclination angles namely 0°, 5°, 10°, 15°, 20°, 25°, and 30°. The shell side design has been investigated numerically by modeling a small shell-andtube heat exchanger. The study is concerned with a single shell and single side pass parallel flow heat exchanger. The flow, pressure drop, heat transfer coefficient and temperature fields inside the shell are studied using noncommercial Computational Fluid Dynamics (CFD) software tool ANSYS Fluent 13.0. For a given baffle cut of 36 %, the heat exchanger performance is investigated by varying mass flow rate of 0.5kg/s and 1kg/s with baffle inclination angle. CFD analysis of shell and tube heat exchanger was carried out using k-ε model to predict the economizer feed water outlet temperature. The obtained CFD results are valid with Kern’s method for a mass flow rate 0.5kg/s. Keywords: Baffles, ansys fluent, k-ε model, kern's method

1.Introduction Heat exchangers are devices in which heat is transfer from one fluid to another. The most commonly used type of heat exchanger is a shell-and-tube heat exchanger. Shell-and-tube heat exchangers are used extensively in engineering applications like power generations, refrigeration and air-conditioning, petrochemical industries etc. These heat exchangers can be designed for almost any capacity. The main purpose in the heat exchanger design is given task for heat transfer measurement to govern the overall cost of the heat exchanger.The heat exchanger was introduced in the early 1900s to execute the needs in power plants for large heat exchanger surfaces as condensers and feed water heaters capable of operating under relatively high pressures. Both of these original applications of shell-and-tube heat exchangers continued to be used; but the design have become highly sophisticated and specialized, subject to various specific codes and practices. The broad industrial use of shell-and-tube heat exchangers known today also started in the 1900s to accommodate the demands of emerging oil industry. The steadily increasing use of shell-and-tube heat exchangers and greater demands on accuracy of performance prediction for a growing variety of process conditions resulted in the explosion of research activities. These included not only shell side flow but also, equally important, calculations of true mean temperature difference and strength calculations of construction elements, in particular tube sheets. 2. Geometric Model The model is designed according to TEMA (Tubular Exchanger Manufacturers Association) Standards Gaddis (2007), using ANSYS Design Modeller software. The Design Modeler application is designed to be used as a geometry editor of existing CAD models. The Design Modeler application is a parametric feature-based solid modeller Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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designed so that intuitively and quickly begin drawing 2D sketches, modeling 3D parts, or uploading 3D CAD models for engineering analysis preprocessing. Design parameters and fixed geometric parameters have been taken similar to Ender Ozden and Ilker Tari (2010)[1], as indicated in Table. 2.1 Table 2.1: Geometric dimensions of shell and tube heat exchanger [1] Heat exchanger length, L

600 mm

Shell inner diameter, Di

90 mm

Tube outer diameter, do

20 mm

Tube bundle geometry and pitch

Triangular, 30 mm

Number of tubes, Nt

Number of baffles. Nb

Central baffle spacing, B

86 mm

Baffle inclination angle, θ

0° , 5° 10°,15° ,20°,25° and 30°

Fig.2. 1: Front View Arrangement of Baffles and Tubes for Shell and Tube Heat Exchanger with 0° Baffle Inclination.

3. Boundary Conditions In ANSYS CFX pre-processor, the various fluid and solid domains are defined. The flow in this study is turbulent, hence Shear Stress Transport (SST) K-ω turbulence model is chosen. The boundary conditions are specified in ANSYS Fluent pre-processor and then the file is exported to the ANSYS Fluent. The same procedure is adopted for the other two models. Boundary conditions considered are the working fluid of the shell side is water, the shell inlet temperature is set to 300 K, the constant wall temperature of 450 K is assigned to the tube walls, zero gauge pressure is assigned to the outlet nozzle, the inlet velocity profile is assumed to be uniform, no slip condition is assigned to all surfaces, the zero heat flux boundary condition is assigned to the shell outer wall (excluding the baffle shell interfaces), assuming the shell is perfectly insulated.

Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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4. CFD Modeling and Meshing

Fig.4: Front View of Arrangement of Baffles and Tubes of Shell and Tube Heat Exchanger with 10° Baffle Inclination.

Fig4. Isometric View of Arrangement of Baffles and Tubes of Shell and Tube Heat Exchanger with 10° Baffle Inclination.

4.1 Meshing The three-dimensional model is then discretized in Ansys meshing. In order to capture both the thermal and velocity boundary layers the entire model is discretized using tetrahedral mesh elements with boundary layer prism elements. Fine control on the prism mesh near the wall surface allows capturing the boundary layer gradient accurately. The first cell height in the fluid domain from the tube surface is maintained at 100 microns to capture the velocity and thermal boundary layers. The discretized model is checked for quality and is found to have a minimum angle of 18. Once the meshes are checked for free of errors and minimum required quality it is exported to ANSYS Fluent solver. Total no of elements used in this simulation is approximately 0.8millions.

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Fig.4.1: Sectional meshing view of arrangement of baffles and tubes of shell and tube heat exchanger with 10° baffle inclination.

5.Results And Discusson The Shell side CFD analysis of a small shell-and-tube heat exchanger is modeled with sufficient detail to resolve the flow and temperature fields. From the CFD simulation results, for fixed tube wall and shell inlet temperatures, shell side heat transfer coefficient, pressure drop and heat transfer values are obtained. The sensitivity of the shell side flow and temperature distribution to baffle orientation is observed.Table 5 shows the pressure drop, Outlet Temperature, Heat Flux, HTC along the length of the heat exchanger at both vertical and horizontal plane for different degree baffle orientation. Table 5.: Results of CFD analysis for 0.5kg/s and 1kg/s mass flow rates Angle degree 0 5 10 15 20 25 30

Mass flow rate( kg/s) 0.5 1 0.5 1 0.5 1 0.5 1 0.5 1 0.5 1 0.5 1

Pressure drop(Pa) 1825.57 7263.49 1781.01 7069.18 1728.06 6837.32 1677.98 6612.38 1636.8 6424.18 1600.61 6268.94 1558.25 6086.79

Outlet Temperature K 355.119 340.614 357.621 341.538 358.002 341.54 357.949 341.469 357.494 340.897 357.269 340.648 356.41 340.07

Heat Flux (W/m2) 451703 665418 472211 680543 475451 680688 475491 679855 471891 671208 470464 667796 464176 659219

HTC (W/m2K) 3955.333141 5341.719515 4221.748382 5522.229525 4276.138397 5535.488908 4287.721293 5540.339011 4260.289803 5492.565649 4255.436159 5444.418174 4203.540865 5382.522005

5.1Validation Of Numerical Model In order to validate the numerical model, the Kern method[2,3] is used to calculate the overall heat transfer coefficient and calculate the overall pressure drop in the shell side of Shell and Tube Heat exchanger with segmental baffles. Comparisons of the present Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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results with the prediction of correlations are done. It is found that the average deviation of the overall heat transfer co-efficient between present results and Kern design results is about 1.10 %. On the other hand, the average deviation of the overall pressure drop between present results and Kern method results is about 3.39% for 0.5 kg/s mass flow rate. Considering the error of heat transfer coefficient associated with the Kern design results and the error of pressure drop associated with the Kern method results (both less than 10%), it can be concluded that the present model can give a satisfactory prediction in both heat transfer and pressure drop characteristics. Table.5.1: Validation Results Parameters

CFD Results

Kern’s method results 2

Angle degree

Mass flow rate (kg/s)

Pressure drop(pa)

HTC (w/m k)

Pressure drop(pa)

HTC (w/m2k)

0.5 1

1825.57 7263.49

3955.333141 5341.719515

1887.82 7222.9

3959.97 5462.729

8000

Pressure DRop Pa

7000 6000 5000 4000 m=0.5 kg/s

3000

m=1 kg/s

2000 1000 0 0

Baffle Angle (Degree)

Fig.5.2: Comparison of Pressure Drop with Baffle angle 6000

HTC W/m2 K

5500 5000 4500 4000 3500 3000 0

Baffle Angle (Degree)

Fig. 5.3: Comparison of HTC with Baffle angle

The Figs 5.2 and 5.3 give the graph of Pressure drop v/s baffle angle and HTC v/s baffle inclination for mass flow rates of 0.5 kg/s and 1 kg/s. As we keep on increasing the mass flow rate the HTC increases. The maximum HTC is at 15 degree of baffle inclination is 4287.721293 W/m2K for 0.5 kg/s and 5540.33901 W/m2K for 1 kg/s. 6.Conclusion The study was carried out with shell and tube heat exchanger for two different mass flow rated and for different angle of baffle inclinations. The CFD results were validated with Kern’s results. Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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1. If the inclination angle of baffle is 15° the HTC is increased by 8.39 percent when compared to the segmental baffles perpendicular to fluid flow that is 0°. 2. It is found that the average deviation of the HTC between present results and Kern design results is about 1.10 %. On the other hand, the average deviation of the overall pressure drop between present results and Kern method results is about 3.39% for 0.5 kg/s mass flow rate. 3. The maximum baffle inclination angle can be 15°, if the angle is beyond 20°, the centre row of tubes are not supported. Hence the baffle cannot be used effectively. 7. References [1]. Ender Ozden, Ilker Tari, Shell side CFD analysis of a small shell-and-tube heat exchanger, Energy Conversion and Management 51 (2010), pp. 1004 – 1014. [2]. T. Kuppan, Heat Exchangers Design Handbook, Marcel Dekker Inc., New York,2002. [3]. G. Towler and R. Sinnott Chemical Engineering Design, Elsevier, 2008 [4]. Gaddis D, editor. Standards of the Tubular Exchanger Manufacturers Association. Tarrytown (NY): TEMA Inc.; 2007. [5]. Schlunder, E.V, Heat Exchanger Design Handbook, Hemisphere Publishing Corp., New York,Bureau of Energy Efficiency, 1983. [6]. Mukherjee, R., Practical Thermal Design of Shell-and-Tube Heat Exchangers, Begell House.Inc, New York, 2004. [7]. Kern DQ. Process heat transfer. New York (NY): McGraw-Hill; 1950.

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SIMULATION OF STEEL GRADE CHANGE IN A WATER MODEL TUNDISH Sangamesh M Hosur1, Kishore2, D.K.Ramesh3, 1

Student, Thermal science and engineering, Dept. of Mechanical Engineering, UVCE Assistant. Professor, Department of Mechanical Engineering, Don Bosco Institute of Technology, B-74, 2 Associate Professor, Thermal science and engineering, Dept. of Mechanical Engineering, UVCE rameshdkuvce@gmail.com

Abstract The tundish working as a buffer and distributor of liquid steel between the ladle and Continuous Casting (CC) moulds. It plays a vital role in the performance of CC machine, solidification of liquid steel and quality of productivity. Therefore it is necessary to control the flow pattern, heat transfer and inclusion particle movement of molten steel in the tundish. Hence this paper targets to study the performance of tundish by studying water volume fractions and validated against the Planar Laser Induced Fluorescence (PLIF) results obtained from available literature. The variation of time dependent concentration field is measured by PLIF. Due to special calibration procedure of the PLIF system the optical, geometrical and physical parameters do not have to be determined analytically, thus leading to reliable results. The experiments have shown that the mixing process correlates with the quasi steady state flow patter. Such information is important in steel production because the number of mixed slabs produced during sequence casting with a grade change is closely related to the mixing of the tundish melt. Hence in this paper PLIF measurements are used to validate numerical solutions of the mixing processes in water models of metallurgical reactor. Keywords: Continuous Casting, Tundish, FLIP, water volume fraction

1. Introduction India has emerged as the fourth largest steel producing nation in the world, as per the recent figures release by World Steel Association in April 2011. In 2010, India was the 5th largest producer, after China, Japan, USA and Russia had recorded a growth of 11.3% in steel production as compared to 2009[3]. Steel is more environmentally compatible because it is produced with a minimum energy input and can be recycled without loss of quality.A continuous casting plant primarily consists of the ladle turret, several steel ladles, tundish, and oscillating mould with lower rolls to support the strand. The secondary metallurgy (degassing,de-oxidation, alloying, temperature and cleanliness adjustments) taking place in the ladle is a discontinuous process, whereas the solidification of the steel melt in the mould to a strand is a continuous process. The tundish links the discontinuous secondary metallurgy with the continuous casting. It serves as steel melt buffer during the ladle change, distributes the steel melt to several strands and separates non-metallic particles (i. e. Al2O3, SiO2) into the top slag cover due to buoyancy forces. Due to high temperatures of the steel melt, the flow and thermal phenomena are in a range for which no adequate measurement technique is available. For this reason, physical and numerical simulations have to be done. Water can be used for the physical simulation because the kinematic viscosities of steel melt and water are comparable, thus making the fluidic behavior of both fluids similar (νst,1536°C = 8.26.10-7 m2/s, νw,20°C = 10.0.10-7 m2/s). Considering the similarity laws, the results for water can be transferred to the steel melt. These results are used to provide quantitative information of the concentration fields in water models of metallurgical reactors and using the results as validation criteria for CFD simulations [2].

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2. Literature The modeling and design of the tundish and tundish furniture can be divided into three main categories, i.e., physical modeling, plant trials and mathematical modeling. Physical modelling has great benefits over doing plant trials. Physical modelling has great benefits over doing plant trials [1]. 1. It does not operate under harsh conditions. 2. It does not interfere with the plant production. 3. It has got good control as it is carried out in Laboratory PLIF is one technique among the physical modelling techniques. The principle of PLIF is that Some naturally occurring materials glow under the influence of energy. The emitted radiation in the visible range is called luminescence. It is to be distinguished between fluorescence and phosphorescence. Fluorescence arises spontaneously and stops as soon as the input of energy stops (10-9 s < t < 10-6 s), whereas phosphorescence lasts substantially longer after the input of energy (10-4 s < t < 102 s). In PLIF (Planar Laser Induced Fluorescence) technique, the physical quantity is measured inside a thin laser light sheet plane. The fluorescence signal is recorded by CCD (Charged Couple Device) cameras, which are equipped with monochromatic filters to separate the fluorescence signal from the excitation light. PLIF is a non-intrusive in-situ-measurement technique with a high temporal and/or spatial resolution. The PLIF measurements have been carried out at a water model (scale 1:3) of a 16 tonnes single-strand tundish with flat bottom. In steelworks, the tundish without any flow control devices is used to produce stainless steels (X5CrNi18-9, AISI 304). Figure 3 shows the test rig of the water model tundish with the PLIF system, flexible laser light arm with the CCD-cameras and the piping of the test rig.

Fig. 1. CF Water model tundish (scale 1:3) and PLIF facilities and piping of the test rig

A certain amount of fluorescent dye is gradually added to a known volume of fresh water during the calibration process. Thus, the maximum, known concentration in the water model arises at the end of the calibration. This process is carried out for a thin object and laser light sheet plane, respectively so that optical, geometrical, and physical parameters have not to be determined. This way, one can forego the theoretical determination of the spatially varying intensity IE inside the laser light sheet plane.

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3. Present work From the literature survey it is found water volume fractions determined by PLIF technique can be used as the experimental results to validate numerical simulation done by using commercial package i.e ANSYS. Thus validated numerical model is used to simulate other tundish container designs to improve the molten steel flow pattern that leads in improving the performance of tundish and can produce high quality steel. 3.1 Objective 1. Creating the baseline geometric model[1] of the tundish container using ANSYS design Modeller. 2. Meshing[1] the geometric model of the tundish and checked for free of errors. 3. To study the flow behaviour of the tundish container. 4. To carry out numerical study of tundish container using ANSYS simulator and validating the numerical results to a water model by comparing with water volume fractions 3.2 Methodology 1. Pre Processing: Consists of the construction of geometry, the generation of the mesh on the surfaces or volumes. This stage is done with the software ANSYS Meshing, linked to FLUENT. The geometry is created in ANSYS Design Modeller 2. Definition of boundary conditions and other parameters, initial conditions, before starting a simulation in FLUENT, the mesh has to be checked, scaled and modified if necessary. The physical models have to be tackled. This includes the choice of compressibility, viscosity, heat transfer considerations, laminar or turbulent flow, steady or time dependent flow. The boundary conditions have to be clear because they specify the information of the state of the flow in the determined zones: walls, symmetries, inlet air, outlet air, etc 3. Resolution of the problem, which is done through iteration until the convergence of the variables is obtained. First of all, the variables of the flow have to be initialized and set to be computed from a certain part specified by the user. In this stage the equations of the flow are solved. The values of the pressures are constantly updated and corrected through iterations. The convergence is checked until it reaches the criterion value set by the user. 4. Post Processing or analysis of the results computed. There are lots of choices: water volume fractions are extracted.

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4. Geometric Modelling , Meshing and Boundary Conditions 4.1 Geometric Modelling Table 1: Dimensions of the original 16 tonnes tundish and the water model tundish (scale 1:3) Roger Koitzsch et.al [2]

Volume of tundish at filling level H

V in m3

Original Tundish 2.227

Tundish length

L1 in m

3.140

1.047

Tundish Width

B1 in m

0.780

0.260

7.000

Property

Inclination of side walls

Symbol

γ in

Model Tundish 0.084

Filling level of steady state casting

H in m

0.800

0.266

Distance shroud-bottom of tundish

Zsh in m

0.600

0.200

Position of Shroud

Lsh in m

0.335

0.122

Diameter of Shroud

dsh in m

0.068

0.023

Position of SEN

LSEN in m

2.885

0.962

Diameter of the SEN

dSEN in m

0.070

0.023

Cross section of the tundish

A in m

0.703

0.079

Hydraulic Diameter

dhyd in m

1.175

0.691

Fig. 2. 3D modeling of tundish container.

4.2 Meshing The three-dimensional model is then discretized in ANSYS meshing element type is tetrahedral. Total no of elements used in this simulation is 0.55 millions as shown in fig 3.

Fig. 3. CFD Meshing Details of Tundish container

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4.3 Boundary Conditions 4.4 Table 2: Boundary conditions for a typical steady-state casting sequence of the 16 tones tundish and the water model tundish Roger Koitzsch.et.al [2]. Tundish Parameters

Symbol

Original

Water model Re similarity

Fr similarity

ρ in kg/m3

7038

998

Kinematic viscosity

v in m2/s

8.72X10-7

10.06X10-7

Volumetric flow rate

Ṽ in l/s

5.39

2.08

0.35

Mean velocity through the tundish

ū in m/s

0.0077

0.0267

0.0052

Velocity in the shroud

|Wsh|

1.49

2.42

0.973

Mean residence time

t in s

420

210

Reynolds number

10380

10.38

2110

Froude number

2.26X10-3

1.36X10-3

2.26X10-3

Density

5. Results and Discussion

Fig. 4. Water volume fraction contour at mid plane after 30 sec.

Fig. 5. Water volume fraction contour at mid plane after 85 sec.

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Fig. 6. Water volume fraction contour at mid plane after 125 sec.

Fig. 7. Water volume fraction contour at mid plane after 160 sec.

Fig 7 exemplary shows the results of numerical simulation at different times. The high flow velocities in the inlet region of the tundish cause an intensive mixing. The turbulent character of the shroud jet which impacts on the bottom and is redirected to the side walls of the tundish can be clearly seen. The time-dependent and spatial expansion of the fresh water correlates with the convective mass and momentum transport, characterized by the quasi steady-state flow structure. The fresh water flows along the bottom of the tundish toward the SEN up to x/L1 = 0.5 - 0.6. This bottom-based flow transports fresh water into the recirculating region. Because the mass and momentum exchange between the recirculating region and the ambience takes place very slowly, the concentration inside the recirculating region remains low for a while, Figure 5. For θ = 1.5, Figure 6, the tundish can be roughly separated into three zones. A low concentration of crh ≈ 15 % is to be found in the inlet region of the tundish (0 ≤ x/L1 < 0.33). In the middle region (0.33 ≤ x/L1 < 0.66) the concentration of crh ≈ 25 % is quite high as well. In the outlet region (0.66 ≤ x/L1 < 1), and in particular below the free surface, clearly lower concentrations of crh ≈ 50 % can be found. From the outlet region of the tundish, water is transported inside the counter-rotating vortices back toward the inlet zone. Even for θ > 2, Figure 7, the concentration below the free surface remains noticeably high. 6. Conclusion The continuous casting process is not a very old manufacturing process, but in the last four decades, it became the most common process for producing most basic metals. One of the particular important components in this system is the tundish. Traditionally, the tundish acted as a reservoir between the ladle and the mould but more recently it has been used a grade separator, an inclusion removal device and a metallurgical reactor. A continuous drive to understand the molten metal flow patterns inside the tundish has led to many research papers being published in the modeling of the flow patterns, through either water modeling or numerical modeling. These numerical modeling involves number of Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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steps. The first step is the validation the numerical (CFD) model. By comparing the water volume fraction contours we conclude that the model is in agreement with water model results obtained by PLIF experiment set up. In further step we can modify the geometrical changes like adding swirl chamber, dimensions. This validated model is applied to evaluate results. Hence numerical simulation helps in changing the design parameters and test the performance virtually. Through this we can optimize the tundish design parameters.

PLIF measurement in the centre plane (y/B1 = 0) of the water model tundish

CFD results

Fig. 8. Comparison of Water volume fraction contour at mid plane after

7. REFERENCES [1]. Dr.D K Ramesha, Kishore , Sangamesh.M.Hosur “Numerical Study of Performance of Tundish Container using CFD” National Conference on Emerging Trends in Engineering and Management ISBN: 978-81-926416-0-7 [2]. Roger Koitzsch, Dr.-Ing. Hans-Jurgen Odenthal, Dr.-Ing. Herbert Pfeifer “Simulation of steel grade change in a water model tundish using the combined DPIV/PLIF Technique”Metal(2007) [3]. http://www.indiasteelexpo.in/IndustryOverview.php [4]. Chakraborty S, Sahai Y, “Mathematical Modelling of Transport Phenomena in Continuous Casting Tundishes’ Iron& Steelmaking”, Vol. 19, (6),( 1992) pp. 479. [5]. Kemeny F, Harris DJ, McLean A, Meadowcroft TR, Young JD, ‘Fluid Flow Studies in the Tundish of a Slab Caster’, Proceedings of the 2nd Process Technology Conf., Warrendale, PA, 1981. [6]. Lievenspiel O, Chemical Reaction Engineering – An Introduction to the Design of Chemical Rectors, John Wiley and Sons Inc., New York, 1967. [7]. Mazumdar D, Guthrie RIL, ‘The Physical and Mathematical Modelling of Continuous Casting Tundish Systems’, Iron and Steel Institute of Japan Int. Vol. 39, No. 6,(1999), pp.524-547 [8]. Singh S, Koria SC, “Model Study of the Dynamics of Flow of Steel Melt in the Tundish”, Iron and Steel Institute of Japan Int., Vol. 33, No. 12,( 1993) pp. 1228-1237.

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PRODUCTION OF BIODIESEL FROM A NON-EDIBLE SEED (SIMAROUBA GLAUCA) BY USING CALICUM OXIDE AS A HETEROGENEOUS BASE CATALYST AND EVALUATING FUEL PROPERTIES S.B.Arun1, R.Suresh2, and M.Sharath3 1

Research Scholar, 2Associate Professor,3Student Department of Mechanical Engineering, Siddaganga Institute of Technology, Tumkur arunsb2012@gmail.com

Abstract The present scenario of world fuel consumption is massive and still increasing. Oil import constitutes a major part of our trade deficit and has an enormous impact on our economy. Some day we may be faced with an oil crisis that is not temporary; today oil field discovery and production is on the decline. Initiating from this point of view, various sources were looked at for production of alternate fuels. Biofuels are renewable liquid fuels coming from biological raw materials have been to be good substitute for oil sectors. The purpose of our work is to study biodiesel production by transesterification of non-edible seed oil (Simarouba oil) with methanol in a heterogeneous system, using calcium oxide (CaO) as a solid base catalyst and to study the fuel properties like density, viscosity, flash point, fire point and calorific value with varying blends of simarouba oil and comparing it with natural diesel as per ASTM standards. Key words: Bio-diesel, Simarouba oil, CaO catalyst, Transesterification, Fuel property.

1. Introduction Simarouba belongs to the family Simaroubaceae Quasia. It had also been known as paradise tree, Lakshmi taru, Acetuno, a multipurpose tree that can grow well under a wide range of hostile ecological condition. Its origin is native to North America, now found in different regions of India. It was a medium sized tree generally attains a height about 20 m and trunk diameter approximately 50 – 80 cm and life about 70 years. It could grow under a wide range of agro climatic conditions like warm, humid and tropical regions. Its cultivation depends upon rainfall distribution (around 400 mm), water holding capacity of the soil and sub-soil moisture. It produces bright green leaves 20-50cm length, yellow flowers and oval elongated purple colored fleshy fruits [1].Its seeds contain about 40% kernel and kernels content 50 -55% oil. It was used for industrial purposes in the manufacture of soaps, detergents and lubricants etc. [2]. Simarouba was a rich source of fat having melting point of about 29 0C. The major green energy components and their sources from Simarouba were biodiesel from seeds, ethanol from fruit pulps, biogas from fruit pulp, oil cake, leaf litter and thermal power from leaf litters, shell, unwanted branches etc. Biodiesel (fatty acids methyl esters, FAME) has recently become very attractive, because of its environmental benefits due to its production from renewable sources. Biofuels have become a matter of global importance because of the need for an alternative energy at a cheaper price and with less pollution [3]. Nowadays, most biodiesel is produced by base catalysed transesterification. It is the most popular of all method because of minimum side reactions, conversion in excess of 90% can be achieved in low temperature (150˚F), direct conversion without intermediate step [4]. Homogeneous alkali-catalyzed transesterification is much faster than acid-catalyzed transesterification. A number of studies have been conducted on biodiesel processes, such as acid-catalyzed process, supercritical process, enzymatic process and heterogeneous catalytic process. Due to noncorrosive, 78 Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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environmentally benign and easily separated from the liquid products the heterogeneous base catalysts can be designed to give higher activity, selectivity and longer catalyst lifetimes. The biodiesel obtained by heterogeneous catalyst is of low viscosity and the waste water produced is less during the process when compared to homogeneous catalyst. Hence total cost involved in the process is lees [5]. In this work, we intend to examine a heterogeneous base catalyst in order to develop an effective biodiesel process catalyst with high activity and durability; hence the catalytic efficiency of CaO in the transesterification reaction of Simarouba oil is evaluated with respect to the conversion of Simarouba oil to methyl esters. 2.Material and Methodology All chemicals were Analytical Reagents and bought locally. Methanol was dried and distilled before use. It consists of oil bath, reaction flask with condenser and digital rpm controller with mechanical stirrer. The volume is about 2 L and consists of three necks. A thermometer was used to measure the reaction temperature. Fatty acid methyl ester content in the transesterified oil was determined by Gas Chromatograph (Chemito CERES 800 plus G.C). 2.1. Extraction of oil. Simarouba seeds were obtained from different parts of Odisha, India and decorticated

Soxhletion

Methanol Recovery

manually. The oil was extracted from the kernel by mechanical expeller and Soxhlet extraction. The yields were given in table-1. In the process of mechanical expeller, a screw press oil expeller was used. The oil after mechanical extraction was subjected to filtration and neutralization [6]. For Soxhlet extraction, the kernels were crushed using a mechanical blender and for Soxhlet extraction procedure, 50 g of crushed kernel was packed in a thimble and the oil was extracted with methane for 2 h. In Soxhlet extraction methods, the oil was isolated from methane by rotary evaporator. 2.2. Preparation of solid base catalyst. Calcium oxide (24 gm) was dipped in 200 ml of ammonium carbonate solution (12% by wt) then the mixture was stirred for 30 minutes at room temperature. After filtration and drying the precipitate at 110˚C till constant weight, the dried solid was sieved (48 mesh) then calcined at 900˚C for 1.5 hours. After cooling in desiccators to room temperature the base CaO catalyst is ready to use.

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Weighing

Magnetic Stirrer

Filtration

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Drying

2.3. Transesterification of crude oil of simarouba glauca Transesterification reactions were carried out in a 2000 ml glass reactor with a condenser. The reaction procedure was as follows: First, the catalyst was dispersed in methanol under magnetic stirring followed by the addition of Simarouba oil into the mixture and heated by water circulation. The mixture was vigorously stirred and refluxed for the required reaction time and then the reaction mixture was allowed to settle down to separate into three phases in a separating funnel as shown in figure-1. The upper layer was biodiesel consists of methyl esters and unreacted triglycerides, the middle layer was glycerol and the lower layer was a mixture of solid CaO and a small amount of glycerol. Then the methanol is recovered from biodiesel. After that the biodiesel is subjected to decalcification by adding complexity agent to remove impurities. Then we get the pure biodiesel and for property test like flash point, fire point etc. [7]. The general equation of transesterification process of vegetable oils containing triglycerides as follows:

R1, R2, and R3 are fatty acid alkyl groups (could be different, or the same), and depend on the type of oil. The fatty acids involved determine the final properties of the biodiesel (ketene number, cold flow properties, etc.)

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2.4Transesterification process parameters 1. Methanol to oil molar ratio: 9:1 2. Amount of calcinated CaO catalyst: 1.5% (w/v) 3. Reaction temperature: 70˚C 4. Reaction time:

3 hours

Biodiesel

Glycerin Catalyst

Separating Funnel

3.Results and Discussion The percentage yield of oil from simarouba through different extraction methods are given in table-1. The percentage composition of fatty acids present in Simarouba oil was determined by gas chromatographic analysis (Chemito CERES 800 plus G.C) and is represented in table-2. Simarouba glauca oil consists of 96.11% pure triglyceride esters. Table – 1 Percentage yield of oil from Simarouba Kernel Extraction Method Yield in % Mechanical Expeller 15 Soxhlet Apparatus 50-55

Table – 2 The Fatty acid composition of Simarouba oil determined by Gas Chromatography Fatty acid Percentage (%) Stearic Acid 23.23 Oleic Acid 57.17 Palmitic Acid 12.81 Linoleic Acid 4.01 Arachidonic Acid 1.18

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4.Fuel properties of Diesel, Simarouba oil and Biodiesel: The biodiesel was prepared and the fuel properties are measured following standard procedure. The properties of biodiesel are compared with its oil, natural diesel and ASTM biodiesel standards as shown in table-3.

Pensky martin closed cup apparatus (Flash and fire point)

Hydrometer and measuring tube (Specific gravity)

kinematic viscosity bath instrument With cannon fenske tube (viscosity)

Bomb calorimeter (Calorific value)

4.1The above apparatus are used to determine the following properties. Viscosity: Among the general parameters for biodiesel the viscosity controls the characteristics of the injection from the diesel injector because high viscosity leads to unfavorable pumping; inefficient mixing of fuel with air contributes to incomplete combustion which results in increased carbon deposit formation [8]. The kinematic viscosity of crude Simarouba oil was found to be 17.3 centistokes and it is reduced to 4.8 centistokes after transesterification 82 Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Density: The higher densities of Simarouba oil and biodiesel as compared to diesel may be attributed to the higher molecular weights and triglyceride molecules present. Flash Point: It was the lowest temperature at which the oil gives off enough vapors that ignite for a moment, when a tiny flame is brought near it. Flash point of Simarouba oil and biodiesel were determined 2250C, 1650C respectively and compared it with diesel as shown in figure-4. The flash point of bio diesel was higher than the diesel, which was safe for transport. Fire Point: It is the lowest temperature at which oil vapors ignite and fire persists for about 5 to 6 seconds when a tiny flame is brought near it. Fire point of biodiesel is determined 172˚C. Table -3 Fuel properties of Diesel, Simarouba oil and Biodiesel Diesel Simarouba Fuel properties Biodiesel oil Kinematic Viscosity (at 40˚c) 2.8 17.3 4.8 Density 812 860 830

ASTM D6751 1.9–6.0 -

Flash Point, 0 c Fire Point, 0c Calorific value, MJ kg-1

>130 -15–10 -

53 60 42.50

225 -

165 172 39.8

Comparision of Density (kg/m3) of Simarouba oil, Biodiesel and Diesel 870

860

Comparision of Viscosity (centistoke) of Simarouba oil, Biodiesel and Diesel

860

840

Viscosity (centistoke)

Density (kg/m3)

850 830 830 820

813

810 800 790 780

17.3

15 10 4.8 2.8

5 0

Simarouba oil

Biodiesel

Diesel

Simarouba oil

Biodiesel

Diesel

Viscosity Figure-2

Figure-3

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Comparision of Flash point (˚c) of Simarouba oil, Biodiesel and Diesel 250

225

Flash Point (˚c)

200

165

150

100

53 50

0 Diesel

Simarouba oil

Biodiesel

Flash piont

Figure-4

5.Conclusion Biodiesel has become more attractive to replace the petroleum fuels. As per reputed literature, most of the transesterification studies have been done on edible oils like rapeseed, soybean, and sunflower etc by using CaO catalyst. The tree borne oil like Simarouba glauca is the most potential species to produce biodiesel in India which could offer opportunity the generation of rural employment. The process is based on the heterogeneous base catalyzed transesterification and can be further improved to get high yield and good fuel quality Biodiesel. 6.Acknowledgement The authors are grateful to Department of Biofuel I&D Centre, SIT Tumkur, and Mr.Yatish K.B., Scientific Assistant., for helping and supporting us to do project on Biofuel production and testing. The authors are also grateful to Department of Chemistry, SIT Tumkur, for helping us in preparing catalyst for this project. References [1]. Gilman E.F. and Watson D.G., Simarouba glauca: Paradise-Tree, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611. Fact Sheet ST-590, http://hort.ufl.edu/database/documents/ pdf/tree_fact_sheets/simglaa.pdf [2]. Joshi S. and Hiremath S., Simarouba, oil tree, University of Agricultural Science, Bangalore and National Oil Seeds and Vegetable Oils Development Board, Gurgaon, India, (2001). [3]. Okoro L.N., Belaboh S.V., Edoye N.R. and Makama B.Y., Synthesis, Calorimetric and Viscometric Study of Groundnut oil Biodiesel and Blends, Research Journal of Chemical Sciences, 1(3), 49-57 (2011) [4]. Biodiesel Production by Using Heterogeneous Catalysts, By Rubi Romero, Sandra Luz Martinez and Reyna Natividad. [5]. A review on biodiesel production using catalyzed transesterification by Dennis Y.C. Leung, Xuan Wu, M.K.H. Leung.

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[6]. Mishra S.R., Mohanty M.K., Das S.P. and Pattanaik A.K., and metal catalysts, Appl. Catal. A: Gen., 257, 213–223 Production of Bio-diesel (Methyl Ester) from Simarouba (2004)

[7]. Gerpen J. V., Biodiesel processing and production, Fuel Process Technol, 86, 1097–1107(2005) [8]. Raja S.A., Smart D.S.R. and Lee C.L.R., Biodiesel production from simarouba oil and its characterization, Research Journal of Chemical Sciences, 1(1), 81-87 (2011)

[9]. Gerpen J. V., Biodiesel processing and production, Fuel Process Technol, 86, 1097–1107(2005) [10]. Enciner J.M., Gonzalez J.F., Rodriguez J.J. and Tajedor A., Biodiesel fuel from vegetable oils: Transesteification of Cynara cardunculus L, oil with ethanol, Energy Fuels, 16, 443 – 450 (2002)

[11]. Biodiesel production using solid metal oxide catalysts by A.A Refaat. Phytochemical investigation of nutshell of simarouba glauca, by Meena Rani.

[12]. Abhullah, A.Z., Razali, N., Mootabadi, H., and Salamatinia, B., “Critical Technical areas for future improvement in biodiesel technologies”, Environmental Research Letter, 2, 034001, pp 6, 2007. [13]. Abigor, R.D., Uadia, P.O., Foglia, T.A., Hass, M.J., Jones, K.C., Okpefa, E., OBibuzor J.U., and Bafor., “Lipase-Catalyzed production of biodiesel fuel from some Nigerian lauric oils”, Biotechnological Aspects: Complex Liquids, Biochemical Society, pp979-981,2000. [14]. Agarwal, A.K., “Biofuels (alcohols and biodiesel) applications as fuels for internal combustion engines”, Progress in Energy Combust Science, 33, pp 233-71, 2007. [15]. Ahmet Necati Ozsezen., Mustafa Canakci., Ali Turkcan., Cenk Sayin., Performance and combustion characteristics of a DI diesel engine fueled with waster palm oil and canola oil methyl esters., Fuel 88 (2009) 629-636.

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EXPERIMENTAL INVESTIGATION OF JATROPHA BIO DIESEL AS ALTERNATIVE FUEL IN DIESEL ENGINES K.M.Mrityunjayaswamy1, D.K.Ramesha2, B.G.Vijayasimha Reddy3, Honne Gowda4 1,3

Department of Mechanical Engineering, Vemana I.T, Bangalore 2 Department of Mechanical Engineering, UVCE, Bangalore 4 Department of Mechanical Engineering, BIT, Bangalore swamykmM61@gmail.com

Abstract Vegetable oils are the most suitable alternative fuel for diesel engine operation due to their renewable nature and their fuel properties are close to conventional diesel. The primary problems associated with Straight Vegetable Oils (SVO) as a fuel in diesel engines are caused by high viscosity and low volatility. This causes improper atomization of fuel during injection. These leads to incomplete combustion and results in formation of deposits on injector and cylinder heads, leading to poor performance, higher emission and reduce engine life. This high viscosity of vegetable oils can be reduced by transesterification process. This work has been carried out on Jatropha Straight Vegetable Oil (JSVO) and its transesterified oil that is, bio-diesel with diesel fuel. Experiments were carried out on a single vertical cylinder-water cooled diesel engine using jatropha Bio-Diesel (JBD) with 5%, 10%, 15%, 20% 25%, 30% and 50% blending at various power output. The performance of the engine was evaluated based on brake thermal efficiency, brake specific fuel consumption, brake specific energy consumption. The investigation reveals that B-20 (20% bio-Diesel and 80% diesel) is widely used blend because with balances properly the differences with conventional diesel performance, emission benefits and cost. The results discussed along with necessary data, graphs and tables. It concludes that the bio-diesel is going be the dominant alternative to diesel in coming years, as technologies are still in the experimental stage

Keywords : alternative fuels, bio-fuels, bio-diesel, atomization, emission, transesterification, blending

INTRODUCTION Economic progress of any country will be decided by the amount of the fuel consumption per capita. Presently India imports 70% of its petroleum demand. This will have a negative effect on our economic development and they are depleting in nature. The increasing demand on the petroleum products over the years also have a strong threat to clean environment from harmful emissions like CO2, CO, SOX , NOx etc. Out of petroleum products, diesel is the most widely used from farming to transportation and industries to domestic purposes than petrol. In this context, plant based oils or vegetable oils or bio-fuels which are renewable in nature are the promising alternatives to diesel, since they have properties very close to petroleum diesel and less harmful emissions1 . In the present work, the effect of various performance parameters have been studied in order to arrive at optimum combination of parameters which would result in best possible 86 Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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performance with such bio-fuel i.e., jatropha oil. The comparative properties of rice bran and diesel are given in table-1. Table: 1 Comparison of properties of JSVO, JBD, with conventional Diesel.

Sl. No.

Property

JSVO

JBD

Unit

Diesel

Kg/m3

840

918.6

863.6

0.84

0.918

0.863

Cst.

4.59

49.93

5.8

KJ/Kg

42490

39774

40695

45-55

40-45

52-54

Density at 40 C

Specific gravity at

Kinematic viscosity at 40 C

Calorific value

Cetane number

Flash point

C

252

140

Fire point

C

263

151

Carbon residue

0.1

0.54

0.23

Ash content

< 0.001

0.03

< 0.01

Colour

40 C

Light yellowbluish

Light

Honey

brown

colour

From the Table-1 it is evident that rice bran oil has relatively higher viscosity. The heating value is approximately 90% of diesel oil. The rice bran oil is miscible with diesel oil in all proportions. Hence investigation was also carried out with the use of jatropha and diesel oil blends. Table-2 shows properties of blends. In this investigation jatropha bio-diesel obtained by transesterification are considered.

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Table:2 Properties of JBD Blended With Diesel at Different Proportions.

% of Vegetable oil with Diesel blend

Density kg/m3

Calorific value KJ/Kg

841.1

42400

842.2

42310

843.5

42206

844.2

42112

846.6

42041

847.1

41951

851.1

41592

Transesterification Bio-diesels are manufactured from bio-fuels by transesterification process, where the triglycerides of jatropha oil is transferred in to their corresponding mono esters by the reaction of methanol in the presence of sodium hydroxide catalyst.2 The chemical reaction involved in this process is shown below. O || CH2 – O – C – R O ||

CH2 -OH Heat plus

CH2 – O – C – R + 3CH3 OH

CH – OH + 3R – C – OCH3 Basic or Acid

catalyst

| CH2-OH

|| CH2 – O – C – R ester

(Triglycerides)

(Methanol) (Glycerol) Methyl (Bio-diesel)

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This investigation also involves the experimental analysis of the use of JBD, blends of biodiesel with petroleum diesel fuel for their performance as engine fuels. The engine performance parameters like brake thermal efficiency, brake specific fuel and energy consumption, emissions like carbon monoxide (CO) and unburnt hydro carbons (UBHC) have been evaluated. Finally conclusions based on the findings are made.

EXPERIMENTAL SETUP 4

4 5

1. 2. 3. 4.

Engine Dynamometer Fuel Tank Fuel tank with Preheating Arrangement

5. Burette

6. Valves 7. Fuel Filter 8. Air Filter 9. Silencer 10. CO/HC exhaust gas analyzer

9 8

Results and discussion The experiments were conducted to evaluate the performance and emissions of the diesel engine with neat JBD; Blends of JBD with diesel at 5%, 10%, 15%, 20%, 25%, 30% and 50%. For comparison the experiment was conducted with neat diesel. All these experiments were conducted at constant engine speed 1500rpm. Based on the results of these experiments it is observed that the optimum values are obtained for B20 of JBD. Hence performance and emission analysis for B20 of JBD are considered in this study and compared with neat Diesel

Brake Thermal Efficiency (BTE): Fig 1. Show the variation of BTE with brake power (BP) for B20 blend of jatropha bio-diesel (JBD) and neat diesel. It is observed that BTE of B20 blend of JBD are comparable with petroleum diesel even though the calorific value of this blend is less than petroleum diesel, this is due to more complete combustion of bio-diesel by transesterification process and molecules of bio-diesel and bio-fuels contain some amount of oxygen that also takes part during combustion resulting in almost complete combustion.

Brake specific energy consumption (BSEC):

Fig2. Show the variation of BSEC with BP for B20 blends of JBD and neat diesel. It is also observed that BSEC of B20 blend of JBD is comparable with neat diesel; this is again because of almost complete combustion of bio-diesel

Carbon Monoxide (CO): Fig3. Show the variation of CO with BP for B20 blend of JBD and neat diesel. It is observed that B20 blend of JBD have lower values of CO than neat diesel. This is again because of more complete combustion of bio-diesel compared to diesel due to a presence of oxygen in bio-diesel. 89 Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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Un-Burnt Hydrocarbon (UBHC): Fig4. Show the variation of UBHC with BP for B20 blend of JBD neat diesel. It is observed that the B20 blend of JBD have lower values of UBHC than neat diesel. This is because of the bio-diesel is comprised of vegetable oil, methyl ester i.e., they are hydro carbon chains of the original vegetable oil that have been chemically split off from naturally occurring triglycerides. And its one end of the hydrocarbon chains are oxygenated, this leads to lowering the hydrocarbon emissions. Conclusions The following conclusions are made based on this research work 1. The JSVO is converted in to its Bio diesels i.e. JBD through chemical process called transesterification. During this process the glycerin is separated from the JSVO, which reduces their viscosity and removes impurities present in straight vegetable oils. After this process two products called methyl ester and glycerin are obtained. This methyl ester generally named as “Bio-diesel”. The properties of bio-diesel closely match with diesel and hence can be used directly in diesel engines. The byproduct glycerin can be used for soap production and other cosmetic applications. 2. The 20% blend of JBD with diesel was found to be the best, since the optimum values of BTE, BSEC are obtained. 3. The emissions such as CO and HC to be less than diesel for 20% blend of JBD, because of better atomization and more complete combustion. Hence it is concluded that the bio-diesel of jatropha blended with diesel can be successfully used in Diesel engines without major engine modification, since these results in best performance and minimum harmful emissions. 30 25 20

BTE(%)

Neat Diesel

10 5

JBD-B20

0 0.0

0.5

1.0

1.5

2.0

2.5

BP(Kw)

Figure. 1 Variation of BTE with BP for neat diesel and JBD-20

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70 BSEC (KJ/Kw.hr.)x10 3

60 50 40 30 Neat Diesel

20 10

JBD-B20

0 0.0

0.5

1.0

1.5

2.0

2.5

BP(Kw)

Figure. 2 Variation of BSEC with BP for neat diesel and JBD-20

0.12 0.1

CO(%)

0.08

Neat Diesel

0.06 JBD-B20

0.04 0.02 0 0.0

0.5

1.0

BP(Kw)

1.5

2.0

2.5

UBHC(ppm)

Figure. 3 Variation of CO with BP for neat diesel and JBD-20

80 70 60 50 40 30 20 10 0

Neat Diesel JBD-B20

0.0

0.5

1.0

1.5

2.0

2.5

BP(Kw)

Figure. 4 Variation of UBHC with BP for neat diesel and JBD-20

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References: [1]. Dr.D.M. Hegde “Vegetable oils Scenario in India: past, present and future”. Proceeding of renewable energy science series XII, ministry of non-conventional energy sources, Govt. of India. pp 1-17, Dec 2003. [2]. M Canakci “Perfomance and Emissions characteristics of biodiesel from soybean oil” Proceedings of IMechE Vol. 219 Part D:1. Automobile Engineering pp 915-921 Jan 2005 [3]. Dr.J.G.Suryavanshi and Prof.N.V.Deshpande “A Review of performance and emission characteristics of soyabean methyl ester fueled diesel engine.” [4]. Recep Altin, Selim Cetinkaya, Huseyin Serdar Yucesu. “The potential of using vegetable oil fuels as fuel for diesel engines”. [5]. Mr. T.Alwarsamy, A.Lemin, Mr. N.Dhandapani “Emission control and performance Characteristics of Diesel engine using Fumigation of methanol:. Paper No. GTME 2005- 004, pp 021 -028 [6]. K Murugu Mohan Kumar and J Saranjan “Critical Review on Bio-diesel as substitute fuel for Diesel engines”. [7]. Mrityunjayaswamy K M, Premkumara G and D K Ramesha “Performance and emission Characteristics Of Four Stroke Diesel Engine Using Bio Oils-Diesel Blends as Fuel” IC- AME2008, SVNIT- Surat, Gujarat, India, pp-246-248, Dec2008 [8]. D K Ramesha, Premkumara G, Rashmi H V, “Effect of Methyl Esters of Pongamia as a Fuel on the Performance and Emissions of Four Stroke Diesel Engine” IC- AME2008, SVNIT- Surat, Gujarat, India, pp-128-133, Dec2008

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NATURAL CONVECTION IN A CAVITY WITH POROUS MEDIA - EFFECT OF ASPECT RATIO B.Aparna1, K.N.Seetharamu2 1

Assistant Professor, Dept of Mechanical Engineering, Vemana I.T, Bangalore 2 Chair Professor in Thermal Engg, PESIT, Bangalore aparnab.vit@gmail.com

Abstract Natural convection is a process of heat transfer where energy is transported both by random molecular motion and by bulk fluid motion. Natural convection in porous media has wide applicability in various natural and industrial processes. Examples are fluid flow in geothermal reservoirs, dispersion of chemical contaminants through water saturated soil, petroleum extraction, migration of moisture in grain storage systems, building thermal insulations, catalytic reactions. Thus, the study of natural convection in enclosure cavities is receiving more and more research attention. For this reason, this mode of heat transfer has been extensively studied experimentally as well as analytically and numerically for different flow aspects. In this paper, natural convection in a square cavity is studied using finite element based computational procedure. The enclosure used for flow and heat transfer analysis has been bounded by adiabatic top wall, constant temperature cold vertical walls and a constant temperature hot horizontal bottom wall. The grid independent study has been made with different grids to yield consistent values. Different grid sizes 30x30, 40x40, 50x50 uniform meshes have been studied. Study shows the convergence of average Nusselt number for a grid size of 40x40. Hence a grid size of 40x40 is used in all computations. Nusselt numbers are computed for different Rayleigh’s numbers (Ra) and aspect ratios of 1 and 2. Results are presented in the form of streamlines, isotherm plots and average Nusselt number. The average Nusselt numbers increase with Rayleigh number and with increase in aspect ratio. Key words: Porous media, Average Nusselt number, streamlines, isotherms

1. Introduction Flow in the porous enclosure has a considerable importance in various practical situations like in buildings in which heat is transferred across an insulation filled enclosure. Other examples are in geothermal and oil extraction applications. By a porous medium we mean a material consisting of a solid matrix with an interconnected void. We suppose that the solid matrix is either rigid (which is the usual situation) or it undergoes small deformation. The interconnectedness of the void (the pores) allows the flow of one or more fluids through the material. In the simplest situation (“single phase flow”) the void is saturated by a single fluid1. In a two phase flow gas and a liquid share the same void space. In a natural porous medium the distribution of pores with respect to shape and size is irregular. In porous media there is a buoyancy-driven flow which is entirely enclosed by a solid wall along which differential heating is applied, the resulting temperature difference leading to the generation of buoyancy force which causes the flow. The most widely considered situation involving a porous enclosure is that of a rectangular enclosure completely filled with a saturated porous medium and with one wall heated to a uniform temperature , the opposite wall cooled to a uniform temperature and with the remaining two walls adiabatic. The most studies of this type of flow have assumed that the 93 Department of Mechanical Engineering, Vemana Institute of Technology, Bangalore-34

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enclosure is vertical, i.e. that the heated and cooled walls are vertical and that the adiabatic walls are horizontal. The porosity φ of a porous medium is defined as the fraction of the total volume of the medium that is occupied by void space, thus φ is the fraction that is occupied by solid. For an isotropic medium the “surface porosity” (that is, the fraction of void area to total area of a typical cross section) will normally be equal to φ. For natural media, φ does not normally exceed 0.6. For man-made materials such as metallic foams φ can approach the value 1. Finite element method2 is a numerical technique for finding approximate solutions to boundary value problems. It is based on the discretisation of the domain, structure or continuum into number of elements and obtaining the solution.

2. Numerical Analysis Henry Darcy derived various relations of the momentum equation which is the porous-medium analog to Navier-stokes equation. Darcy’s experiments on steady state unidirectional flow in a uniform medium revealed proportionality between flow rate and the applied pressure difference. In modern notation this is expressed in the refined form as = µ (1) where

is the pressure gradient in the flow direction and

is the dynamic viscosity of

the fluid. The co-efficient K is independent of the nature of the fluid but it depends on the geometry of the medium. K is called intrinsic-permeability or specific permeability. Velocity in vertical direction is = + g (2) µ

The permeability

of porous medium is given by bejan: =

(

(3)

)

The variation of density with respect to temperature is given by Boussinesq approximation as: = ∞ [1 − β ( − ∞ )] (4) Differentiating (1) with respect to y yields: =

(5)

Similarly differentiating equation (2) with respect to x after incorporating Boussinesq‘s approximation yields: =

∞β

(6)

Eliminating pressure term from equation (5) and (6) gives: β − = (7) The energy equation is given as: +

(8)

The continuity equation can be automatically satisfied by introducing stream function as: = =− Equation (7) and (8) are the two governing partial differential equations in dimensional form with many variables. These equations can be non-dimensionalised which reduces the number of variables and thus facilitates the solution. The following non-dimensional parameters are used to convert above said equations into non-dimensional form: Non-dimensional temperature

( − (

−

∞) ∞)

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Non-dimensional stream function

Non-dimensional height

Non-dimensional width

̅=

β Δ

Rayleigh number

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Substitution of above non-dimensional equations into (7) and (8) and gives rise to following non-dimensional equations: + ̅ ̅

– ̅

=− = ̅

(9) +

(10)

Equations (9) and (10) are two coupled partial differential equations as change of a variable in one equation affects the other equation. Galerkin’s method3 is employed to convert the partial differential equation into matrix form of equation for an element. The present study is carried out by using simple 3 noded triangular elements. Natural convection in a square cavity filled with porous media with different boundary conditions is studied by Basak4,5. The square cavity with given thermal boundary conditions (hot bottom wall and cold side walls) and mesh of square cavity are shown in Figures 1 and 2.

Figure 1: Square cavity with given thermal boundary conditions

Figure 2: Mesh grid of size 41*41

Computer code is written in MATLAB for generation of mesh, for analysis and also for post-processing to get required contour plots of streamlines ad isotherms. The heat transfer co-efficient in terms of local Nusselt number is defined by: T Nu = n Where, n denotes the normal direction on a plane. Integrating the local Nusselt number over, average Nusselt number is obtained as = Different grid sizes of 30x30, 40x40, 50x50 uniform meshes have been studied. Study shows the convergence of average Nusselt number for a grid size of 40x40. Hence a grid size of 40x40 is used in all computations. Convergence is shown in the Figure 3.

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Figure 3: Avg Nu vs Mesh density graph

3. Results and Discussions In this numerical study, a cavity with horizontal bottom wall being hot with two vertical cold side walls is being considered with aspect ratios of 1 and 2. As for the validation of the code, average Nu of side wall should be half of average Nu of bottom wall. Where

represents average Nusselt number for bottom wall. represents average Nusselt number for left wall. represents average Nusselt number for right wall.

Nusselt numbers are computed for different Rayleigh’s numbers (Ra) and for aspect ratios of 1 and 2 . Results are tabulated as shown in Table 1 and 2 respectively Table 1: Rayleigh Number values for AR of 1 Ra 100 200 300 400

Table 2: Rayleigh Number values for AR of 2 Ra 100 200 300 400 500

Average Nu 6.275 8.325 9.788 10.968

Average Nu 6.348 8.703 10.318 11.588 12.673

Non dimensional distance

As symmetry of thermal boundary condition is considered (i.e. hot bottom wall and two side cold walls), flow circulation which is represented in streamlines is of two loops one in clockwise and the other in anti-clockwise direction. The positive sign of ψ denotes anticlockwise circulation and clockwise circulation is represented by negative sign of ψ. Figures 4, 5 represent different streamlines for different Ra values for an aspect ratio of 1.

Non dimensional distance

Figure 4: Streamlines for Ra=200

Non dimensional distance

Figure 5: Streamlines for Ra=400

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In general, for uniformly heated bottom wall, fluid rises from the centre of hot bottom wall due to buoyancy and flows down along the cold vertical walls forming two symmetric rolls inside the cavity. At low Ra values, magnitudes of stream functions are small which indicated porous media of low permeability which offers high resistance to fluid flow. At higher Ra values which indicated comparatively less densities in porous bed, flow intensity inside the cavity increases as seen from streamlines of Figure 5. For an aspect ratio of 2, streamlines are shown in Figures 7 and 8 with the mesh generation given in Figure 6. Isotherms break into two symmetric contour lines and start shifting towards side walls as shown in Figures 9 and 10 for aspect ratio of 1 and 2 respectively.

Non dimensional distance

Figure 6 : Mesh of 40*40 size for an aspect ratio of 2

Non dimensional distance

Figure 7: Streamlines for Ra=200

Non dimensional distance

Figure 8: Streamlines for Ra=400

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Non dimensional distance

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Non dimensional distance

Figure 9: Isotherms for Ra=400 with aspect ratio 1

Figure 10: Isotherms for Ra=400 with aspect ratio 2

Sub-routine is written to get local Nusselt numbers for bottom walls. To evaluate average Nusselt number of bottom wall, local Nu values are taken from MATLAB program and fed into hypergraph and graph is obtained as shown in fig 4.29. Area under the graph gives average Nusselt number value of bottom wall.

Ra=100 Ra=200 Ra=300 Ra=400

Non Dimensional Distance

4. Conclusion In the present study, prime objective is to study flow pattern and heat distribution during natural convection in a fluid saturated porous square cavity and varying aspect ratio . Contours of stream functions and isotherms are symmetric about centre of vertical line for uniform temperature. It is concluded that average Nusselt number Nu increases with increase in Rayleigh number and for a given Ra, increase in Nu is obtained with increase in aspect ratio for bottom wall. References [1]. Bejan, A. (1995). Convective Heat Transfer, 2nd edition, New York, John Wiley and Sons. [2]. Segerlind, L.J. Applied Finite Element Analysis, John Wiley and Sons, New York (1982). 98

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[3]. Lewis, R.W., Nithiarasu, P, Seetharaamu, K.N., fundamentals of the finite element Method for Heat and Flow, John Wiley and Sons, Chichester (2004). [4]. Ram Satish Kulari, Tanmay Basak and S.Roy (2009). Bejan Heatlines and numerical visualization of Heat flow and thermal mixing in various differentially heated porous cavities, Numerical Heat Transfer Part A, 55:487-516. [5]. Tanmay Basak, S.Roy and I.Pop (2006). Natural convection in a square cavity filled with a porous medium: Effects of various boundary conditions, International Journal of Heat and Mass transfer, 53: 1430-1441.

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