Mechanics, Materials Science & Engineering journal Vol. 13

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Mechanics, Materials Science & Engineering, December 2017

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Dynamic Behaviour of Pre-Tension Fiber Composite Plate 1

Ali Sadiq Yasir 1

University of Kufa, Engineering Faculty, Mechanical Engineering Department, Iraq

a

alis.alathari@uokufa.edu.iq DOI 10.2412/mmse.91.69.250 provided by Seo4U.link

Keywords: composite plate, fiber pre-tension, natural frequency, modes shape.

ABSTRACT. The fiber pre-tension is one of techniques that used to improve the properties of fibrous composite plate.

In this paper, we study the fiber pre-tension effect on dynamic behavior for composite plate. The natural frequency and mode shapes studied for pre-tensioned fiber composite plate. The pre-stressing ranges (2-20MPa) applied on the fibers during curing process at room temperature. Dynamic model achieved using finite element to get the natural frequencies and modes shape and compare the results with analytical solution by used iteration of JACOBI method that solved by using FORTRAN language. The results show that the Fiber pre-tension will increasing the natural frequency ( n) of cantilever composite plate by (53%) and the modes shape show that the models will deform in three directions (Z, x, and y) for most modes.

Introduction. A Composite material usually defined as a "combination of two or more materials with significantly different properties". Such materials are made for improving the (structural, thermal, or other physical characteristics) of a single material.

A typical composite contains one or two phases that are more discontinuous called (reinforcements).

They are usually stronger than the continuous phase (matrix). Some examples of composite materials used as "concrete, filled plastics, armours, aerospace, automotive, sports", and unidirectional continuous or chopped fiber reinforced composites. Multidirectional reinforced composites, such as laminates and fabric or three dimensionally reinforced materials, which, are widely used. Mechanical, physical, or other properties of composite depend on those of the constituents and their distribution.

[1] Some of the properties are strong functions of the arrangement of the constituents, e.g., "fibers orientation, the shape, the size, size distribution" etc.

The concentration is usually measuring in terms of volume or weight fraction of the constituents and its distribution is a measure of homogeneity of composite.

There are three common types of composite materials: 1)

Fibrous composite: consists of fibers (long, short, or chopped) in matrix.

2)

Laminated Composite: consists of layers of various materials.

3)

Particulate Composite: consist of particles in matrix.

The fibrous composites commonly used in industry for their high specific strength "the ratio of thermal conductivity, increased fatigue life. The endurance limit of toughened composites can be much higher than of steel and aluminium [2].

1

open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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The constituent materials in the fibrous composites are fibres and matrix. Fibers are the major load carrying components while the matrix transfer the loads between the fibres, provide barrier against adverse environments, protect the surface from abrasion and provide lateral supports. The different fibres used are glass, aramid, carbon, or metals fibre [3].

Laws of Composite Materials: Longitudinal Modulus of Elasticity: (E1) To find the modulus of elasticity in fiber direction (E1), form Fig. 1 [4].

Fig. 1. The fiber matrix arrangement for an element of composite loaded in longitudinal direction [4].

E1= Ef Vf + Em Vm= EfVf + Em (1-Vf ) where Vm

( 1)

matrix volume fraction

Vf fiber volume fraction The longitudinal modulus of elasticity is affected by fiber volume fraction as shown in Fig. 2.

Fig. 2. Variation of (E1) with fiber volume fraction [4].

Poisson's ratio (

12).

The Poisson s ratio ( (E1) [4].

12),

can be obtained by an approach similar to the analysis for elastic modulus

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f Vf

m

Vm

f Vf

m

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(1-Vf)

(2)

Figure 3 shows the effect of fiber volume fraction on the poisons ratio for composite materials.

Fig.

12)

with fiber volume fraction [4].

-D Element (Quadrilateral Shell 4-node Element).

A shell element is a surface type element, it is really a 2D element but also called 3D element because it is not restricted to the XY-plane like 2D solid element, it can be located anywhere in the threedimensional space and it can deformed outbecause a geometric surface has no physical thickness. The ANSYS real constant used to assign a thickness to a shell element. Shell elements also called (Plate Elements), and are used to model panel type structure where the thickness is small compared to other dimensions of the part. They can carry in-plane loads (also called membrane load) and out-of plane bending moments and twisting [5].

Shell element type (Shell-63) shown in Fig.(4), is an older type of shell elements but it is still very widely used .It can analyze large deflections but not plasticity .This type of shell elements is used with modeling the dynamic model with ANSYS for the composite plate [6].

Fig. 4. Quadrilateral 4-node shell element [5].

The nodal displacement vector at the i-th nodes written as:

(3)

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The displacement vector

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at any point (x, y) is to be expressed as follows [6]:

(4)

Where

and

are the shape functions and are equal to:

(5)

Hence, it can be shown that:

(6)

and it is required to formulate the shape functions.

(7)

Substituting these values at the four nodes, it can be shown that:

(8)

Or in the matrix form:

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(9)

Similarly:

(10)

Analytical Analysis of Dynamic Model To compare the results of finite element analysis of dynamic model by ANSYS with another type of analysis, used the analytical method by the Fortran program to solve the equations using JACOBI iteration [7].

The JACOBI method produce all eigenvalues (Natural Frequencies) and eigenvector (Modes Shape) of matrix [D] simultaneously, where [D] = [dij] is real symmetric matrix of order (N N). This method is based on the theorem in linear algebra that states that a real symmetric matrix [D] has only real eigenvalues and that there exists a real orthogonal matrix [R] that ([R]T[D] [R]) is diagonal .The diagonal elements are the eigenvalues, and the column of matrix [R] are the eigenvectors.

The governing equation for dynamic eigenvalue (Natural Frequencies) problem with no damping and no external forces [8]:

(11)

where [K]

is symmetrical stiffness matrix and [M] is symmetrical mass matrix.

The pre-stressing of fibers will effect on the stiffness matrix [K] only and the values of pre-stresses will be the same as in ANSYS model.

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where

, Mij=

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V

when the natural mode of vibration is:

(12)

Then:

and (13)

By assuming that

then:

(14) by multiplying by [K]-1 :

(15)

Where:

In general the matrix [D] is non-symmetric, although the matrix [K] and [M] are both symmetric, since JACOBI method is applicable only to symmetric matrices [D], we can derive the standard eigenvalue problem with symmetric matrix [D].

Assuming that the matrix [K] is symmetric and positive definite and can using the Choleski decomposition.

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(16)

where [U] is an upper triangular matrix, and substitutions it in Eq. (13):

(17)

Multiplying this equation by

to obtain :

(18)

The standard eigenvalue:

(19)

The roots a victor

are called the eigenvalues and represent, for each root

, there exist

, which is knowing as the eigenvector can be obtained as ratio of its component.

The effect of pre-stress on the stiffness matrix [K] is done by its effect on the elastic modulus (E), while the mass matrix [M] was not affected by the pre-stress.

The Result and Discussion.

The dynamic analysis used to determine the natural and fundamental frequency for the composite plate with volume fraction of (Vf=30%) and used the finite element method (ANSYS) and (Jacobi iteration by FORTRAN program) to analyze the composite plate model and find the natural frequency for pre-stressed samples. The natural frequency depends on the stiffness and mass according to the relation [9].

(20)

where

n

natural frequency, Hz;

k stiffness of sample, N/m; m Mass of sample, kg.

As the pre-stress will increase the stiffness of the plate, then the natural and fundamental frequency will increase as the pre-stress level increase The higher natural frequency is desired to make the plate farther from resonance for the dynamic plate.

Figure (5) show the natural frequency for the plate at different value of pre-tension on fibers in cantilever composite plate.

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0.9 0.8 1st Mode Frequency (Hz)

0.7 0.6 0.5

Ansys(2)

0.4

Analytical

0.3 0.2 0.1 0 0

5

10

15

20

25

Pre-stress(MPa)

Fig. 5. Relation between pre-

n ).

From this figure can notice the increasing in natural frequency value with increase the pre-stress on the fiber, the increasing ratio reach to (54%) and that occur due to the increasing in composite plate stiffness due to the pre-stressing on fiber.

Figures (6, 7, 8, 9 and 10) show the increasing in frequency of 2nd, 3rd, 4th, 5th, and 6th mode with prestressing level and the increasing ratio reach to (54%) at maximum pre-stressing value.

Fig. 6. Relation between pre-stress levels and 2nd

1).

Fig. 7. Relation between pre-stress levels and 3rd

2).

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4th Mode Frequency(Hz)

120 100 80 60

Ansys(2)

40

Analytical

20 0 0

5

10

15

20

25

Pre-stress(MPa)

Fig. 8. Relation between pre-stress levels and 4th

3).

180

5th Mode Frequency(Hz)

160 140

120

Ansys(2)

100

Analytical

80 60 40 20 0 0

5

10

15

20

25

Pre-stress(MPa)

Fig. 9. Relation between pre-stress levels and 5th

4).

6th Mode Frequency(Hz)

180 160 140 120 Ansys(2)

100

Analytical

80 60 40 20 0 0

5

10

15

20

25

Pre-stress(MPa)

Fig. 10. Relation between pre-stress levels and 6th

5).

Figures 11-16 show the modes shape of pre-stressed cantilever composite plate, from these figures can notice the deflection that happened for pre-stressed composite plate in six degree and that give an idea about the shape of body that deflected due to its own force.

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Mechanics, Materials Science & Engineering, December 2017

Fig. 11. 1 st mode shape.

Fig. 12. 2 nd mode shape.

Fig. 13. 3 rd mode shape.

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Mechanics, Materials Science & Engineering, December 2017

Fig. 14). 4 th mode shape.

Fig. 15. 5 th mode shape.

Fig. 16. 6 th mode shape.

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Mechanics, Materials Science & Engineering, December 2017

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Summary. The pre-tensioned fiber in composite plate give more stiffness for the material and that n) about (54%), and that preferred to been away from resonance. The frequency of composite plate in different modes shape will increase also due to the fiber pre-tension and that make the composite plate more resist to deflect due to its own weight in 6th degree of freedom (D.O.F). The convergence between the analytical solution (using FORTRAN and JACOBI iteration) and numerical analysis (using ANSYS software) reach to (94%).

Appendix: Material Properties: The properties of matrix and glass fiber used in numerical and mathematical analysis are The matrix There are many types of resin that can be used as a matrix like polyester, polyethylene, polystyrene, epoxy, etc. The resin type used in this work is Epoxy resin (LECO-POX103) which is manufactured by (Leyco Chem.) for chemical industries in Germany.

The (LECO-POX103) is a low viscosity component epoxy resin system with formulated amine hardener.This type of epoxy has the following properties: Mixing volume ratio (A/B): 7/3 (A

Epoxy resin, B

The hardener).

Density1050 kg/m3; minimum curing temperature 10 Co, linear shrinkage 0.3 %, volume shrinkage 3.5 %, compression strength 85-100 MPa, tensile strength 40-70 MPa, modulus of elasticity 2.8 GPa The glass fiber.

The aim of using the fibers in composite is to carrying the load that applied to composite while the matrix holding and protecting the fibers that distributing the load between them The type of fibers used is (E-glass) with the commercial name of (Vela Glass 875U).

This type of fibers is dry, unidirectional glass fiber. For most applications, Vela-Glass 875U is a proven cost effective alternative to traditional strengthening techniques.

The general properties of this glass fiber are [10]: Color: white, primary fiber direction: 00 (unidirectional), density: 2285 kg/m3, tensile strength 1350 MPa, modulus of elasticity 60 GPa. Acknowledgment.

I would like to express my Acknowledgment to staff of mechanical engineering lab and staff of computer lab in Faculty of Engineering, University of Kufa, Iraq.

References [1] Z. Hashin, B.W. Rosen, E.A. Humphrey (1997). Fiber Composite Analysis and Design. 1, 20-24, Final report, National Technical Information Service.

[2] H. Garmestany (1997), Mechanical and Microscopy Analysis of Carbon Fiber Reinforced Polymer Matrix Composite Materials, Florid department of transpiration, Report.

[3] A. D. Kelkar (2003), Introduction to Low Cost Manufacturing of Composite Laminate, American Society for Engineering Education, pp. 1-13.

[4] J. Adams, I. Doner (1967), Micromechanics of Composite Materials Journal of composite materials, 7, pp.1-10.

[5] A.T. Nettles (1994), Basic Mechanical of Laminated Composite Plates, NASA Reference Publication, report, pp. 1-23.

[6] Saeed Movaeni (1999), Finite Element Analysis: Theory and Application with ANSYS, Prentice Hall, London.

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[7] Robert D. Cook (1995), Finite Element Modeling for Stress Analysis, John Wiley and Sons, Inc. [8] Paul Dufour (2003), ANSYS Tips : Picking and Element Type for Structural Analysis, Belacan Engineering Group.

[10] Gwo Chung Tsai (2003), Integrated Multi-Media with Experiment for Mechanics of Composite Materials, International conference on engineering education, pp. 12-24.

[11] Muhanad L. AL-Waily (2004), Analysis of Stiffened and Un-Stiffened composite plates subjected to time dependent loading, M.Sc. Thesis. pp. 13-14.

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Laser Welding of Secondary Cell made of Aluminium and Nickel Heeshin Kang1, a, Jiwhan Noh1, Byunghoon Seo1 1

Korea Institute of Machinery and Materials, Daejeon, Korea

a

khs@kimm.re.kr DOI 10.2412/mmse.39.73.113 provided by Seo4U.link

Keywords: laser, welding, metal, aluminium, nickel, process.

ABSTRACT. The purpose of this study is to make the experimental basis for the development of the laser-assisted micro welding technology. The basic experiments are carried out on the melting of the thin aluminium and nickel sheets in order to secure the micro laser welding process technology for manufacturing the secondary cell. The micro laser welding joints are lap joints. The welding specimens are made from the aluminium and nickel foil. The thickness of metal sheet is 0.1 mm and 0.15 mm. The quality of welding specimens is tested by observing the shape of the beads on the plate after the laser welding and the cross-section of the welded parts is observed by using metallography method. The mechanical tensile test is carried out for analyzing the performance of welding strength. The monitoring method by using ultraviolet and infrared light sensors are used for finding the correlation with the results of the mechanical and metallurgical test.

Introduction. Laser welding is one of the important technologies used in the manufacturing of lighter, safer product at a high level of productivity; to that end, the leading manufacturers have replaced spot welding with laser welding in the process of the secondary cell assembly. Korean manufacturers are developing and applying the laser welding technology using the Nd:YAG laser.

The conventional spot resistance welding used in the secondary cell assembly process has been an obstacle to cell design and manufacturing due to the limited applicability and lower welding efficiency resulting from the geometry and welding characteristics of spot welding machines. As such, the industry has been trying to develop new welding and joining technologies. This study was conducted to develop a laser welding technology for the secondary cell, a welding quality inspection technique, and a robot control. In particular, due to the characteristics of laser welding where the laser beams have to be directed perpendicularly to the welding surface - it is very difficult to instruct the robot to direct the laser beam perpendicularly on to a curved surface. Indeed, many studies have been performed to improve the speed of the laser welding process and the quality of welding parts [1-3]. In this study, these problems were addressed by applying the laser welding method and the quality monitoring method [4-7].

Experimental equipment. Figure 1 shows a schematic block diagram and the developed system of the entire remote laser welding control system. The beam from the laser generator is transmitter via an optical fiber to the welding head at the end of the robot's arm. The laser welding can be achieved by manipulating the axes of the robot system. The laser generator used was 1.6 kW fiber laser system and the robot system was the 6 axes Industrial robot of payload 130 kg. To conduct a basic study of the weldability of the remote laser welding system, the lap welding were conducted with the common aluminium and nickel foils. The weld joints were inspected and tested for tensile strength to determine the optimal welding parameters. In order to devise a technique of measuring the quality of the laser welding on a real-time-basis, basic experiments were conducted with a technique capable of deter-mining the quality of welding by monitoring plasma and temperature.

The pattern welding tests were conducted to examine the accuracy of the entire remote laser welding system.

-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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Fig. 1. The laser welding system.

Table 1. Core units of remote laser welding system Laser source

1.6 kW high-power fiber laser

Focusing unit

Collimation, Bean expander, Image transfer optics, F-theta lens

Scanning unit

XY 2 axes scanner

Handling system

6 axes industrial robot (payload: 130kg)

Workpiece device

Jig, Clamping

Position sensing, process monitoring

CCD vision, Optical emission monitoring

Main control

PC-based controller

Figure 2 shows the process sequence of quality monitoring system for the laser welding. During the laser welding on a real-time-basis, the basic tests were conducted to develop a technique which facilitates the evaluation of weld quality by monitoring plasma and temperature. The tests were conducted using the fiber laser. To monitor weld quality using plasma flux intensity, the initial criteria of plasma intensity - which itself determines the critical weld quality - needs to be determined. When the plasma intensity lies between the maximum and minimum values of the standard range as Figure 3 (a), the weld quality can be judged to be acceptable.

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Fig. 2. Process sequence of quality monitoring system.

Fig. 3. The results of fiber laser welding quality monitoring by using reference curves.

Test results. Figure 4 shows the size of laser welding specimens. In the fiber laser tests, dissimilar light metals of the nickel and aluminium foils were welded at a laser powers of 165W and a welding speed of 1 m/min. The diameter of laser beam is about 0.3 mm and the focal length of laser objective MMSE Journal. Open Access www.mmse.xyz

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lens is 490 mm. The fiber laser was tested at from 100 W to 500 W power using an ultraviolet light and infrared light sensors. The results were obtained by scanning the specimens by using the laser scanner of the laser welding system.

Figure 5 shows the results of laser welding plasma monitoring test. An ultraviolet light and infrared light sensors were used in the tests conducted to detect plasma intensity. The plasma and temperature signals could be detected at the appropriate values, confirming that real-time-based quality monitoring can be implemented. Table 2 shows the results of the welding test to find the optimal welding conditions by using a fiber laser. Table 2 show the strength average value after peel test for laser welding specimens. The strength average value of spot welding is about 0.5 kgf in peel test. The strength average value of the laser welding is 2.414 kgf and better than the conventional spot welding.

(a)

(b) Fig. 4. The size of the specimens; (a) nickel, (b) aluminum.

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(a)

(b) Fig. 5. The results of the laser welding test using the fiber laser. (a) welding specimens, (b) the wavelength graph by spectrometer.

Table 2. The strength average value after peel test for laser welding specimens.

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Summary. The laser welding system was built on the basis of the interfacing between the laser system and the industrial robot system. Using the laser welding system, the lap welding of aluminium and nickel foils were conducted and the tensile strength of the samples was tested to determine the optimal welding parameters. The weld joints and defects were analyzed after the laser welding tests. During the laser welding, the plasma intensity signals were measured and analyzed to assist the development of a technique, which enables evaluation of the quality of laser welding in real time. On the basis of the laser welding quality tests, the lap welding of dissimilar metals and the algorithms for evaluating the quality of laser welding will be tested in further studies.

References [1] F. Coste et al., A Rapid Seam Tracking Device for YAG and CO2 High-Speed Laser Welding, Proc. ICALEO 85, 1998, 217-223.

[2] T. Eimermann, Hem Flange Laser Welding, 25th ISATA Symposium, No. 921089, Florence, Italy, June, 1992.

[3] E. Beyer, A. Klotzbach, V. Fleischer, and L. Morgenthal, Nd:YAG-Remote Welding with Robots, Proceedings of Lasers in Manufacturing, 2003, 367-373.

[4] A. Klotzbach, V. Fleischer, L. Morgenthal, and E. Beyer, Sensor guided remote welding system for YAG-laser applications, Proceedings of Lasers in Manufacturing, 2005, 17-19.

[5] M. W. de Graaf, R. G. K. M. Aarts, J. Meijer, and J. B. Jonker, Robot-sensor synchronization for real-time seam-tracking in robotic laser welding, Proc. 23rd Int. Cong. On Applications of Lasers and Electro-Optics, 2004, 1301.

[6] P. Aubry, F. Coste, R. Fabbro, and D. Frechett, 2D YAG welding on non-liner trajectories with 3D camera seam tracker following for automotive applications, Laser Appls. Auto Industry, Section F-ICALEO, 2000, 21.

[7] E. Beyer, P. Abels, Process Monitoring in Laser Materials Processing, Laser Advanced Materials Processing (LAMP92), 1992, 433-438.

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AC Conductivity Studies of MgCuZn Ferrite 1

Madhuri W.1, a, M. Penchal Reddy2, N. Ramamanohar Reddy3, K.V. Siva Kumar4 1

Centre for crystal growth, VIT University, Vellore, India

2

Center for Advanced Materials, Qatar University, Doha, Qatar

3

Department of Materials Science &Nanotechnology, Yogi Vemana University, Kadapa, India

4

Ceramic Composites Materials Laboratory, Sri Krishnadevaraya University, Anantapur, India

a

madhuriw12@gmail.com DOI 10.2412/mmse.12.48.768 provided by Seo4U.link

Keywords: AC conduction, activation energy, critical exponents, ferrites.

ABSTRACT. Mg0.5-xCuxZn0.5Fe2O4 (x = 0 to 0.3) are synthesized by conventional ceramic double sintering technique.

Temperature dependence of AC electrical conductivity is estimated in the temperature range of 30 to 200 oC and frequency dependence up to 1MHz. Room temperature conductivity is of the order of 10 -8 -1m-1 and increases to 10-5 -1m-1 at higher temperatures. Temperature dependence of all the compositions follows Arrhenius law while the frequency dependence follows the double power law. The activation energies and the critical exponents evaluated supports jump relaxation model of conduction mechanism.

Introduction. Electric and magnetic characteristics of ceramic materials are of increasing importance in the fields of radio electronics, optoelectronics, microwave electronics and modern communication devices. Ferrites find vast application in these fields. An important property of these materials is their high electric resistance compared to that of other elemental magnetic materials, which generally possess low eddy current losses at high frequencies. Ferrites have very high resistivity which is one of the considerations for microwave applications. The order of magnitude of the conductivity greatly influences the electric and magnetic behavior of ferrites. This has aroused considerable interest in the study of electrical conductivity and frequency dependent electrical behavior of ferrites [1, 2]. The AC conductivity of a magnetopolarization conductivity is a function of frequency and temperature. It is supposed to follow the power law as [3]:

(1)

where (0) denotes dc conductivity corresponding to frequency independent plateau at low frequency, A and B are the AC coefficient and n1 and n2 are the power exponent.

Materials and methods. Reagent grade MgO, CuO, ZnO and Fe2O3 are weighed according to the stoichiometry [Mg0.5-xCuxZn0.5Fe2O4 (x = 0 to 0.3)] and mixed and grinded. The powders are presintered at 800 oC for 2 hours. The obtained powders are milled in a ball mill for 10 hours at 300 rpm.

Thus, obtained green powders are made into pellets of 1cm diameter using uniaxial press and are sintered at 1250 oC for 2 hours in Zn atmosphere. The polished pellets are given good ohmic contacts o using Du Pont silver paint. The values of Z Z C temperature o intervals in the temperature range 30 to 200 C at different frequencies in the range 100 Hz to 1 MHz -NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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with the help of a low frequency impedance analyzer Hioki LCR Hitester model 3532-50 and a computer interfaced tubular furnace. The conductivity arises as a result of charge hopping from one site to another site. The AC conductivity is obtained from the real part of impedance as:

(2)

where t/A is the geometrical factor of the sample.

Results and discussion. Single phase spinel structure formation is confirmed from X-ray diffraction studies which is published in our earlier work [4]. Fig. 1 shows the compositional variation of AC electrical conductivity of Mg0.5-xCuxZn0.5Fe2O4 samples. Within the experimental error AC conductivity is found to be independent of copper concentration. The temperature dependence of AC electrical conductivity of MgCuZn ferrites is shown in Fig. 2. The AC electrical conductivity has increased with increase in temperature. In the investigated temperature range the conductivity has increased by two orders of magnitude. Rise in temperature of the sample will help the trapped charges to be liberated and to participate in the conduction process, with the result conductivity increases, which is the normal behaviour of semiconducting materials like ferrites. Similar results were reported by, Bellad [5] in LiMg ferrites, by Ahmed [6] in the case of Er substituted MgTi ferrite. In the investigated temperature region AC conductivity exhibited two slope regions indicating mixed conduction mechanism in the series of ferrites. The activation energies (see Table. 1.) in the intrinsic region (high temperature region) i.e., region II are greater than those of region I. High activation energies in region II suggest polaron happing and low activation energies at low temperatures must be due to free charge carriers [7]. Further, all the activation energies are found to be greater than the ionization energies (Ei = 0.1ev) of the donor or acceptors and thus the possibility of band like 3+ conduction is ruled out. The values are even higher than the Fe2+ transition energy (Ee = 0.2ev) supporting the polaron hopping in the intrinsic regions [8]. Examination of compositional dependence of conductivity and activation energies reveal a good correspondence, that is samples having low conductivity have high activation energy and vice versa.

Fig. 1. Variation of AC electrical conductivity with copper.

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Fig. 2. Variation of AC electrical conductivity with reciprocal temperature.

The variation of AC electrical conductivity as function of frequency in the mixed MgCuZn ferrites is shown in Fig. 3. The figure reveals that there are two distinct regions with two different slopes. This suggests that the frequency variation of AC conductivity is fitting to the relation = o + A +B [3].

Fig. 3. Variation of log( ) AC with log(f) at room temperature.

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Table 1. Activation energies and critical exponents from AC conductivity studies of the series.

Copper Content

Region II

Region I

Region I

Region II

n1

n2

x

E1 ev

E2 ev

0.0

0.28

0.5

0.26

0.58

0.05

0.3

0.5

0.5

0.73

0.1

0.26

0.42

0.22

0.53

0.15

0.21

0.41

0.13

1

0.2

0.24

0.63

0.64

0.34

0.25

0.29

0.53

0.16

0.81

0.3

0.39

0.52

0.24

0.86

The values of n1 and n2 evaluated corresponding to the two regions are tabulated in Table 1. If the values of the exponents n1 and n2 is equal to zero then the conduction is independent of frequency or DC conduction. If it is less than or equal to 1 then the conduction is frequency dependent. Physically the n value signifies the strength of carrier-lattice interactions. The n1 and n2 values less than one strongly suggest hopping conduction mechanism. The frequency response of conduction is interpreted in terms of the jump relaxation model [9, 10] where the conduction is due to translational hopping for n1 < 1 and localized rotational hopping for n2 AC electrical conductivity of all the samples is increasing with increasing temperature.

Summary. Mg0.5-xCuxZn0.5Fe2O4 (x = 0 to 0.3) are synthesized conventionally by solid state reaction route. Temperature dependence of AC electrical conductivity confirmed semiconducting behavior of these ferrites. In the temperature range of 30 to 200 oC AC conductivity has increased by two orders.

Activation energy of all the samples supports hopping conduction mechanism. The frequency dependence follows the double power law. The evaluated critical exponents from the frequency dependence also support hopping conduction mechanism.

References [1] Madhuri, W., Reddy, M. P., Kim, I. G., Reddy, N. R. M., Kumar, K. S., Murthy, V. R. K. (2013), Transport properties of microwave sintered pure and glass added MgCuZn ferrites, Materials Science and Engineering: B,178(12), 843-850. DOI 10.1016/j.mseb.2013.03.020.

[2] Reddy, M. P., Balakrishnaiah, G., Madhuri, W., Ramana, M. V., Reddy, N. R., Kumar, K. S., Reddy, R. R. (2010), Structural, magnetic and electrical properties of NiCuZn ferrites prepared by microwave sintering method suitable for MLCI applications, Journal of Physics and Chemistry of Solids,71(9), 1373-1380, DOI 10.1016/j.jpcs.2010.06.007.

[3] Gurusiddappa, J., Madhuri, W., Suvarna, R. P., Dasan, K. P. (2016), Conductivity and dielectric behavior of polyethylene oxide-lithium perchlorate solid polymer electrolyte films, Indian Journal of Advances in Chemical Science, 4(1), 14-19.

[4] Madhuri, W., Reddy, M. P., Reddy, N. R. M., Kumar, K. S. (2014), Thermoelectric Studies of MgCuZn Ferrites, International Journal of ChemTech Research, 6(3), 1771-1774.

[5] Bellad, S. S., Watawe, S. C., Chougule, B. K. (1999), Some AC electrical properties of Li Mg ferrites, Materials Research Bulletin, 34(7), 1099-1106, DOI 10.1016/S0025-5408(99)00107-5.

[6] Ahmed, M. A., Ateia, E., Salem, F. M. (2006), Spectroscopic and electrical properties of Mg Ti ferrite doped with different rare-earth elements, Physica B: Condensed Matter, 381(1), 144-155, DOI 10.1016/j.physb.2005.12.265.

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[7] Ali, I., Islam, M. U., Ashiq, M. N., Iqbal, M. A., Khan, H. M., Karamat, N. (2013), Effect of Tb Mn substitution on DC and AC conductivity of Y-type hexagonal ferrite, Journal of Alloys and Compounds,579, 576-582, DOI 10.1016/j.jallcom.2013.06.182.

[8] Madhuri, W., Reddy, M. P., Kim, I. G., Reddy, N. R. M., Kumar, K. S., Murthy, V. R. K. (2013), Transport properties of microwave sintered pure and glass added MgCuZn ferrites, Materials Science and Engineering: B, 178(12), 843-850, DOI 10.1016/j.mseb.2013.03.020.

[9] Funke, K. (1993), Jump relaxation in solid electrolytes, Progress in Solid State Chemistry, 22(2), 111-195, DOI 10.1016/0079-6786(93)90002-9.

[10] Youssef, A. A. (2002), The Permittivity and AC Conductivity of the Layered perovskite [(CH3)(C6H5) 3P] 2HgI4, , 57(5), 263-269, DOI 10.1515/zna-20020510.

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Conductivity and Modulus Study of Lithium Nickel Titanate 1

C. Pavithra1, W. Madhuri1, a 1 a

Center for Crystal Growth, VIT University, Vellore, Tamilnadu, India madhuriw12@gmail.com DOI 10.2412/mmse.86.65.206 provided by Seo4U.link

Keywords: lithium nickel titanate, sol-gel, ac conductivity, electric modulus.

ABSTRACT. This paper is reported on Ni-doped lithium titanate by sol-gel method and microwave processing. The structural formation of lithium nickel titanate is confirmed by powder X-ray diffraction technique. The AC conductivity and modulus study are discussed. The electrical conduction mechanism of lithium nickel titanate is small polarons.

Introduction. Lithium ceramics have attractive property for fast tritium release, high density, thermal stability, low activation energy, Li-ion battery which is used in portable electronic devices, communication facilities, electronic vehicles and stationary energy storage systems [1-5]. Different techniques are used to produce lithium titanate ceramics such as sol-gel, other wet chemical methods and solution combustion and polymer solution. Among these methods, the sol-gel method is easy to synthesis and yields high homogeneity [6]. Microwave sintering of ceramics is the easiest and cheapest method, offering rapid heating rate, low sintering temperature and uniform sintering [7]. The electrical property of the material depends on structural changes in the material. The structural and electrical conductivity of the lithium nickel titanate (LNT) synthesized by sol-gel method [8] and microwave processing is discussed.

Experimental Procedure. The starting materials are lithium monohydrate (Sigma- Aldrich, 97%, LiOH.H2O), and nickel nitrate (Sigma-Aldrich, 97.0%, Ni(NO3)2. 6H2O) and titanium butoxide (Sigma-Aldrich, 97.0%, Ti(OC4H9)4). The details of sol-gel synthesis are published in our previous article (MMSE). The obtained gel from the sol-gel technique is dried. Further obtained powder is calcinated at and sintered at 5min using microwave furnace. The conductivity measurements are conducted on a pellitized sample using LCR bridge (HIOKI-HI Tester 50-3532).

Results and Discussion Structural Analysis. The structural analysis of LNT is confirmed by powder X-ray diffraction technique (PXRD). The phase formation of LNT is in agreement with the reported and JCPDS file no: 71-2348. A typical PXRD for x=0.5 is shown in Fig. 1 which confirms the monoclinic crystal structure and C2/c space group [4].

Conduction Mechanism. AC electrical conductivity as a function of frequency at different temperatures is shown in Fig 2. From Fig. 2 it is ac increases with frequency suggesting polaron conduction. Conduction by polarons belong to two categories, large polarons and small polarons. (i) Large polarons- the ac conductivity decreases with frequency and the conductivity is by band mechanism at all the temperatures. (ii) Small polarons- The ac conductivity increases with frequency. The present case shows small polarons mechanism. The electrical conductivity depends on hopping of electrons between different valence states of an ion like Ni2+ Ni3+ or Ti3+ i4+. The conductivity of the material is high at high frequency and temperature.

GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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This indicates that the conduction is by thermally driven charge carriers. The conductivity is low at low frequency due to the active grain boundary. [1], [2], [9], [10].

Li3.5Ni 0.5Ti2O6

10

20

30

40

50

60

70

2 (deg)

Fig. 1. PXRD of LNT.

Fig. 2. AC conductivity with frequency at different temperatures of LNT. Electric Modulus study. The electric modulus is used to understand the conduction process by interfacial polarization effect. Electric modulus is calculated using the relation M*= M +jM , M - . are the real and imaginary parts of electric oZ* and o modulus Co oA/d o is permittivity of free space, A is the cross-sectional area of the pelletized are the real and imaginary parts of MMSE Journal. Open Access www.mmse.xyz

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impedance,

The real part of the electric modulus is shown in Fig 3a. The is increasing with increase in frequency and it reaches a maximum value at high and it approaches to zero at all the frequency. Increasing temperature resulted in decrease of recorded temperatures, indicating the suppression of the electrode polarization effect. The

Fig 3b. It explains the charge transport mechanism such as conductivity relaxation and electrical transport behaviour of the materials.

The presence of a peak in the imaginary part indicates the conductivity relaxation behaviour of the samples. At lower temperature, x=0 sample shows prominent relaxation peaks, which disappeared on increasing the tempe tends to zero at lower frequencies justifies that the electrode polarization does not make any contribution to the modulus [11], [12].

a)

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Fig. 3. (a) real electric modulus with frequency at different temperatures,(b) imaginary part of electric modulus with temperature at varies temperatures.

Summary. The nickel doped lithium titanate is prepared by sol-gel technique and microwave sintered. The phase formation of LNT is confirmed by powder X-ray diffraction technique and the electrical conductivity is LNT is proposed to be by small polarons. Modulus studies have confirmed no contribution of electrode polarization in the conduction mechanism.

References [1] Barick, B. K., Choudhary, R. N. P., Pradhan, D. K. (2013), Dielectric and impedance spectroscopy of zirconium modified (Na 0.5 Bi 0.5) TiO 3 ceramics. Ceramics International, 39(5), 5695-5704, DOI 10.1016/j.ceramint.2012.12.087.

[2] Dash, U., Sahoo, S., Chaudhuri, P., Parashar, S. K. S., Parashar, K. (2014), Electrical properties of bulk and nano Li2TiO3 ceramics: A comparative study, Journal of Advanced Ceramics, 3(2), 8997, DOI 10.1007/s40145-014-0094-0.

[3] Fehr, T., Schmidbauer, E. (2007), Electrical conductivity of Li2TiO3 ceramics, Solid State Ionics, 178(1), 35-41, DOI 10.1016/j.ssi.2006.11.002.

[4] Puli, V. S., Picchini, R., Orozco, C., Ramana, C. V. (2016), Controlled and enhanced dielectric properties of high-titanium containing LixTi0.1Ni O via chemical composition-tailoring, Chemical Physics Letters, 649, 115-118, DOI 10.1016/j.cplett.2016.01.054.

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[5] Reddy, M. P., Madhuri, W., Sadhana, K., Kim, I. G., Hui, K. N., Hui, K. S., Reddy, R. R. (2014), Microwave sintering of nickel ferrite nanoparticles processed via sol gel method, Journal of Sol-Gel Science and Technology, 70(3), 400-404, DOI 10.1007/s10971-014-3295-7.

[6] Roy, A. K., Prasad, K., Prasad, A. (2013), Piezoelectric, impedance, electric modulus and AC conductivity studies on (Bi0. 5Na0. 5) 0.95 Ba0. 05TiO3 ceramic, Processing and Application of Ceramics, 7(2), 81-91, DOI 10.2298/PAC1302081R. [7] Sinha, A., Nair, S. R., Sinha, P. K. (2010), Single step synthesis of Li 2 TiO 3 powder, Journal of Nuclear Materials, 399(2), 162-166, DOI 10.1016/j.jnucmat.2010.01.013.

[8] Pavithra, C., Roopaskiran, S., Madhuri, W. (2017). Impedance Analysis of Microwave Processed Lead Nickel Titanate, Mechanics, Materials Science & Engineering MMSE Journal.

Open Access, 9. DOI 10.2412/mmse.18.22.667.

[9] Puli, V. S., Orozco, C., Picchini, R., Ramana, C. V. (2016), Chemical composition-tailored Li x enhanced dielectric properties, Materials Chemistry and Physics, 184, 82-90, DOI 10.1016/j.matchemphys.2016.09.028.

[10] Wu, X., Wen, Z., Lin, B., Xu, X. (2008), Sol gel synthesis and sintering of nano-size Li 2 TiO 3 powder, Materials Letters, 62(6), 837-839, DOI 10.1016/j.matlet.2007.06.073 [11] Wu, X., Wen, Z., Xu, X., Gu, Z., Xu, X. (2008), Optimization of a wet chemistry method for fabrication of Li 2 TiO 3 pebbles, Journal of Nuclear Materials, 373(1), 206-211. DOI 10.1016/j.jnucmat.2007.05.045.

[12] Yu, C. L., Yanagisawa, K., Kamiya, S., Kozawa, T., Ueda, T. (2014), Monoclinic Li 2 TiO 3 nano-particles via hydrothermal reaction: Processing and structure, Ceramics International, 40(1), 1901-1908, DOI 10.1016/j.ceramint.2013.07.097.

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XRD, UV-Vis-NIR and FT-IR Studies of ITO and Cr: ITO Thin Films Prepared

by Electron Beam Evaporation Technique 1

Deepannita Chakraborty1, S. Kaleemulla2,a, N. Madhusudhana Rao3, K. Subbaravamma4, G. Venugopal Rao5 1 – Thin films Laboratory, School of Advanced Sciences, VIT University, Vellore, Tamilnadu, India 2 – Thin films Laboratory, Centre for Crystal Growth, VIT University, Vellore, Tamilnadu, India 3 – Department of Physics, VIT- AP University, Amaravati, Andhra Pradesh, India 4 – Department of Physics, AMET University, Kanathur, Chennai, Tamilnadu, India 5 – Materials Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu, India a – skaleemulla@gmail.com DOI 10.2412/mmse.36.15.807 provided by Seo4U.link

Keywords: Cr and Sn co-doped Indium Oxide, Dilute magnetic semiconductors, wide band gap.

ABSTRACT. The Indium-tin-oxide (ITO) and Cr doped ITO thin films were prepared using electron beam evaporation technique. The prepared thin films were subjected to structural and optical properties. From the XRD it was observed that the films were crystalline in nature with cubic structure. The crystallite size was calculated using Scherer’s relation and found that it was about 25 nm. The optical transmittance and absorbance spectra were recorded using UV-Vis-NIR spectrophotometer. From these, the optical band gap of ITO and Cr:ITO thin films were found to be 4.0 ev and 3.97 eV, respectively. The Fourier transform-Infrared spectroscopy study showed the peaks at 292, 519, 804, 957, 114, 1387 and 2985 cm-1 which are characteristic of In-O bonds.

Introduction. It is known that extensive work is being carried out on optical and electrical properties of wide band gap oxide semiconductors such as ZnO, TiO2, SnO2, In2O3, Cu2O etc. [1-7].

Among the other oxide semiconductors, In2O3 is the one of the best suited materials for many electronic applications. It is a transparent, degenerate n-type wide band gap semiconductor with cubic structure in which the optical and electrical properties can be varied by doping of tin (Sn) or creating off stoichiometry. In In2O3 lattice if 10% of Tin (Sn) is doped the resultant material indium-tin-oxide is called as ITO [8, 9]. Due to its peculiar properties of high electrical conductivity and high optical transmittance in visible region it finds numerous applications such as nano electronics, opto electronics, sensor devices, flat panel displays and energy storage devices [10-18].

However, the studies of magnetic properties of ITO and impurity doped ITO thin films are meager.

Recently continuous efforts are being put on magnetic properties of ITO and doped ITO nanoparticles, thin films and nanostructures. At present, this paper has been focused more on the structural and optical properties of ITO and Cr:ITO thin films and magnetic studies will be carried out in the future.

Experimental Details. The ITO and Cr doped ITO source materials were prepared using solid state reaction and studied their physical properties [12]. The same powder samples were taken here as source materials to prepare the ITO and Cr: ITO thin films on glass substrate. The films were prepared using electron beam evaporation technique [12A4D]. A base pressure of 5x10-6 mbar was created before coating the films. The total set up was kept in coating unit and the substrate temperature was raised to 350 °C and maintained the same temperature till the end of the coating. © 2017 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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The thicknesses of the films were found to be about 250 nm. X-ray diffractometer (D8 Advance, BRUKER) was used to establish structural aspects. The diffused reflectance spectra were recorded on UV-Vis-NIR Spectrophotometer (JASCO V-670). Fourier Transform Infrared (FT-IR) Spectroscopic analysis was carried using FT-IR Spectrophotometer (SHIMADZU).

Results and Discussion.

(b) (In0.90Cr0.05Sn0.05)2O3

(4 4 0)

(6 2 2)

(3 2 1 ) (4 0 0 )

(2 2 2)

(a) (In0.95Sn0.05)2O3

Intensity (a.u)

(2 2 1)

Structural Analysis. Figure 1 shows the XRD profiles of ITO and Cr doped ITO thin films. The Cr doped ITO thin films exhibited two more diffraction peaks in addition to pure ITO thin films. The diffraction peaks such as (2 2 1), (2 2 2), (3 2 1), (4 4 0), (4 0 0) and (6 2 2) were observed for Cr: ITO thin films which are characteristic of cubic structure of indium oxide [JCPCS 06-0416]. No other diffraction peaks other than indium oxide were observed in the XRD patterns. No significant change in the diffraction peak toward higher or lower diffraction angles. The crystallite size was calculated using Scherer’s relation and found to be 25 nm. A slight decrease in lattice parameter was observed by adding Cr into the ITO lattice.

(b) (a)

20

40

60

80

2(degrees)

Fig. 1. XRD profile of ITO and Cr:ITO thin films.

Optical Properties. Figure 2 shows the optical transmittance spectra of ITO and Cr: ITO thin films prepared on glass substrates. From the figure it can be seen that the ITO thin films exhibited good optical transmittance about 70% in the visible region. The transmittance of the films decreased to large extent by doping chromium into the ITO lattice.

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(a) (In0.95Sn0.05)2O3

90

(b) (In0.90Cr0.05Sn0.05)2O3

Transmittance (%)

80

(a)

70 60 50 40

(b)

30 20 10 0

500

1000

1500

Wavelength (nm)

Fig. 2. Optical transmittance spectra for ITO and Cr:ITO thin films.

The optical band gap (Eg) of the films was determined from the optical transmittance data using Taucâ&#x20AC;&#x2122;s relation [19]. đ?&#x203A;źâ&#x201E;&#x17D;đ?&#x153;? = (đ??¸đ?&#x2018;&#x201D; â&#x2C6;&#x2019; â&#x201E;&#x17D;đ?&#x153;?)

đ?&#x2018;&#x203A;

(1)

where n â&#x20AC;&#x201C; depends on the kind of optical transition that prevails.

Here n = 1/2, as In2O3 is directly allowed n-type degenerate semiconductor. The optical bang gap is obtained by plotting (ÎąhĎ&#x2026;)2 versus the photon energy (hĎ&#x2026;) and by extrapolating of the linear region of the plots to zero absorption (ď Ą= 0).The optical bang gap Eg is obtained by plotting (ÎąhĎ&#x2026;)2 versus the photon energy (hĎ&#x2026;) and by extrapolating the linear region of the plots to zero absorption (Îą= 0).

Fig. 3 shows the optical band gaps of ITO and Cr: ITO thin films. The pure ITO thin films exhibited a band gap of 4.0 eV and Cr: ITO thin films exhibited a band gap of 3.95 eV. The observed band gap is almost equal to that of band gap of bulk ITO [20].

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Cr: ITO 680.00G

510.00G

340.00G

170.00G



(h) (eV/cm)

2

3.95 eV ITO

6.60T

4.40T

2.20T

4 eV 0.00 3.0

3.5

4.0

4.5

h(eV)

Fig. 3. Optical band gaps of ITO and Cr:ITO thin films.

110

(Ino.90Cr0.05Sn0.05)2O3

100

Transmittance (%)

90

1143 778

80 70 60

955

487 429

50 40 30 500

1000

1500 -1

Wavenumber (cm )

Fig. 4. FT-IR spectra of Cr: ITO thin films.

Fig. 4 shows the FTIR spectra of Cr: ITO thin films recorded at room temperature. The same trend was observed in pure ITO thin film. In2O3 exhibits intense bands around 419 and 440 cm-1 attributed to In-O lattice stretching vibrations [21].

Summary. ITO and Cr: ITO thin films were prepared using electron beam evaporation technique and studied for their structural and optical properties. Both ITO and Cr: ITO thin films were in cubic structure with crystallite size of 24 nm. No new diffraction peaks related to nickel was found in XRD. A band gap of 4.0 eV was observed for ITO thin films and it decreased to 3.95 eV by doping Cr into the ITO lattice. The FT-IR studies revealed the characteristics of In2O3 lattice.

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Acknowledgements. We are grateful to UGC-DAE-CSR, IGCAR, Kalpakkam 603102, Tamilnadu, India, for providing financial (Grant no. CSR-KN/CRS-72/2015-16/809) support to carry out the present work. We also thank VIT-SIF for providing XRD and UV–Vis–NIR facilities.

References [1] V. Bilovol, C. Herme, S. Jacobo, A.F. Cabrera (2012), Study of magnetic behaviour of Fe-doped SnO2 powders prepared by chemical method, Materials Chemistry and Physics, 135, 334-339, DOI 10.1016/j.matchemphys.2012.04.055.

[2] S.N. Kale, S.B. Ogale, S.R. Shinde, M. Sahasrabuddhe, V.N. Kulkarni, R.L. Greene, T. Venkatesan (2003), Magnetism in cobalt-doped Cu2O thin films without and with Al, V, or Zn codopants, Applied Physics Letters, 82(13), DOI 10.1063/1.1564864.

[3] M.V. Limaye, S.B. Singh, R. Das, P. Poddar, S.K. Kulkarni (2011), Room temperature ferromagnetism in undoped and Fe doped ZnO nanorods: microwave-assisted synthesis, Journal of Solid State Chemistry, 184(2), 391-400, DOI 10.1016/j.jssc.2010.11.008.

[4] Y. Matsumoto, M. Murakami, T. Shono, T. Hasegawa, T. Fukumura, M. Kawasaki, P. Ahmet, T. Chikyow, S.-y. Koshihara, H. Koinuma (2001), Room-Temperature Ferromagnetism in Transparent Transition Metal-Doped Titanium Dioxide, Science, 291(5505) 854-856, DOI 10.1126/science.1056186.

[5] M. Venkatesan, C.B. Fitzgerald, J.G. Lunney, J.M.D. Coey (2004), Anisotropic Ferromagnetism in Substituted Zinc Oxide, Physical review letters, 93, 177206, DOI 10.1103/PhysRevLett.93.177206.

[6] P. Xiaoyan, J. Dongmei, L. Yan, M. Xueming (2006), Structural characterization and ferromagnetic behavior of Fe-doped TiO2 powder by high-energy ball milling, Journal of Magnetism and Magnetic Materials, 305(2), 388, DOI 10.1016/j.jmmm.2006.01.109.

[7] G.Z. Xing, J.B. Yi, D.D. Wang, L. Liao, T. Yu, Z.X. Shen, C.H.A. Huan, T.C. Sum, J. Ding, T. Wu (2009), Strong correlation between ferromagnetism and oxygen deficiency in Cr-doped In2O3-δ nanostructures, Physical Review B, 79, 174406, DOI 10.1103/PhysRevB.79.174406.

[8] A. De, P.K. Biswas, J. Manara (2007), Study of annealing time on sol–gel indium tin oxide films on glass, Materials Characterization, 58(7), 629-636, DOI 10.1016/j.matchar.2006.07.011.

[9] G. Peleckis, X.L. Wang, S.X. Dou (2006), Room-temperature ferromagnetism in Mn and Fe codoped In 2 O 3, Applied physics letters, 88(13), 132507, DOI 10.1063/1.2191093.

[10] Y. Akaltun, M.A. Yıldırım, A. Ateş, M. Yıldırım (2011), The relationship between refractive index-energy gap and the film thickness effect on the characteristic parameters of CdSe thin films, Optics Communications, 284(9), 2307-2311, DOI 10.1016/j.optcom.2010.12.094.

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[12] S.H. Babu, S. Kaleemulla, N.M. Rao, G.V. Rao, C. Krishnamoorthi (2016), Microstructure, ferromagnetic and photoluminescence properties of ITO and Cr doped ITO nanoparticles using solid state reaction, Physica B: Condensed Matter, 500, 126-132, DOI 10.1016/j.physb.2016.07.037.

[13] M. Fang, A. Aristov, K.V. Rao, A.V. Kabashin, L. Belova (2013), Particle-free inkjet printing of nanostructured porous indium tin oxide thin films, RSC Advances, 3(42), 19501-19507, DOI 10.1039/C3RA40487K.

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[14] J. Gao, R. Chen, D.H. Li, L. Jiang, J.C. Ye, X.C. Ma, X.D. Chen, Q.H. Xiong, H.D. Sun, T. Wu (2011), UV light emitting transparent conducting tin-doped indium oxide (ITO) nanowires, Nanotechnology, 22(19), 195706-195716, DOI 10.1088/0957-4484/22/19/195706.

[15] I. Hamberg, C.G. Granqvist (1986), Evaporated Sn‐ doped In2O3 films: Basic optical properties and applications to energy‐ efficient windows, Journal of Applied Physics, 60(11), R123-R160, DOI 10.1063/1.337534.

[16] J.T. McCue, J.Y. Ying (2007), SnO2−In2O3 Nanocomposites as Semiconductor Gas Sensors for CO and NOx Detection, Chemistry of Materials, 19(5), 1009-1015, DOI 10.1021/cm0617283.

[17] H.T. Ng, A. Fang, L. Huang, S.F.Y. Li (2002), Protein microarrays on ITO surfaces by a direct covalent attachment scheme, Langmuir, 18(16), 6324-6329, DOI 10.1021/la0255828.

[18] K. Sreenivas, T. Sudersena Rao, A. Mansingh, S. Chandra (1985), Preparation and characterization of rf sputtered indium tin oxide films, Journal of Applied Physics, 57(2), 384-392, DOI 10.1063/1.335481.

[19] J. Tauc, Amorphous and Liquid Semiconductors, 2 ed., Plenum Press, New York, NY, USA, 1974.

[20] A. El Hichou, A. Kachouane, J.L. Bubendorff, M. Addou, J. Ebothe, M. Troyon, A. Bougrine (2004), Effect of substrate temperature on electrical, structural, optical and cathodoluminescent properties of In2O3-Sn thin films prepared by spray pyrolysis, Thin Solid Films, 458(1-2), 263-268, DOI 10.1016/j.tsf.2003.12.067.

[21] M.M. Gerbier, M.I. Baraton, J. Machet, P. Quintard (1984), Ion plated indium oxide : infrared and optical study, Journal of Molecular Structure, 115(1-2), 103-106, DOI 10.1016/00222860(84)80025-3.

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Numerical Investigation in Piezoresistive Pressure Sensors 1

Hamid Dehghani 1, a 1

Department of Mechanical Engineering, Islamic Azad University, Parand Branch, Tehran, Iran

a

hamid.dehghani.parand@gmail.com DOI 10.2412/mmse.87.47.99 provided by Seo4U.link

Keywords: piezoresistive pressure sensor, Wheatstone bridge, diaphragm shape, holes.

ABSTRACT. In this paper, a Piezoresistive Micro Electro Mechanical System (MEMS) pressure sensor has been optimized. This paper finds an optimal diaphragm shape with optimum hole by numerical method, Finite Element Method (FEM). Circular, square, and rectangular diaphragms are measured in this paper. Additional aim of this study is to find out the effect of holes, temperature, and material in these diaphragms. Regarding to applied stress and sensor output, results were showing that gold-circulate-shape diaphragms are performing much more efficient than other shapes. In addition, rectangular holes have better influence on the function of diaphragms too.

Introduction. Pressure sensors are extensively used in locomotive, medicinal, and various types of industrial applications [1-35]. MEMS devices have very low power consumption. Besides, they require very low space [32-36].

In this paper, it is expected that Wheatstone bridge configuration is used to sense the stress developed in a diaphragm. The stress is sensed by measuring change in piezo resistors which are connected in Wheatstone bridge configuration that are situated on a pressure sensor diaphragm. The pressure is converted into an electrical signal using resistance change phenomena due to the stress or strain of the piezo resistors. The stress or strain causes electrical signal fluctuations in two ways, one way is by structural deformation induced resistance variations, and the other way is by the quantum physical phenomena induced resistivity variations [1-32].

Three different shapes of diaphragms have been compared together. Stress, deflection, sensor output voltage and sensitivity of circular, square, and rectangular shapes of diaphragms have been examined.

The materials are silicon and gold [16-32].

The diaphragm shapes that have been simulated in FEM software are shown in Fig. 1. The dimensions of the diaphragm are such that the area is same in all the three cases [32-36].

1

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a)

b)

c)

Fig. 1. Circular, square and rectangular diaphragms, and their relative dimensions used in simulations [32]. a) Square diaphragm; b) Rectangular diaphragm; c) Circular diaphragm Sensor Diaphragm Design. To model the silicon pressure sensor diaphragm, it is assumed that the diaphragm has a uniform thickness, with perfectly clamped edges. In the steady state, the diaphragm deflection is governed by the Lagrange equation as in eqn. (1) which allows to calculate the out-ofplane membrane deflection w(x,y) as a function of position [3-4, 32]. In this case, Cartesian coordinates are chosen for analysis as the diaphragm is rectangular.

,

where P D

(1)

represents the differential pressure applied on the membrane of thickness h; is a rigidity parameter which depends on material properties given by eqn. (2)

(2)

The anisotropy coefficient depends on the crystallographic orientation. E is the Young modulus wh is the Poisson s ratio [32- 36]. The factor G is called the shear modulus or Coulomb Modulus and it describes the reaction of the material to the shear stress.

Can be calculated using eqn. (3) and eqn. (4).

G=

(3)

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(4)

However, the exact solution of eqn. (1) does not exist and one of the approaches used to analyze the basic shapes is the Polynomial approximation [5-6, 32]. This approach is used to analyze the deflection and stress for the different shapes of diaphragms.

Circular Diaphragm.

Considering the isotropic circular membrane of radius, a as shown in Fig. 1, which is characterized by the axial symmetry. So, to simplify calculations, the out of plane deformation w(r) is dependent only on the distance from its center r and is given by eqn. (5) [7, 32-36].

(5)

Square Diaphragm. The solution to eqn. (1) for a square diagram with side length of as shown in Fig.1(a) is , with appropriate approximations and simplification yields the displacement of a square diaphragm which changes with uniform pressure (P), given by eqn. (5) [7, 32].

The solution to eqn. (1) for a square diaphragm with side length of 2a as shown in Fig. 1 is w(x,y) with appropriate approximations and simplification yields the displacement of a square diaphragm which changes with uniform pressure (P), given by eqn. (6) [7].

(6)

Rectangular Diaphragm. In case of a rectangular diaphragm, the deflection in the diaphragm can be simplified as in eqn. (7) [7, 16-36]. The width of rectangular diaphragm is 0. a and a length is 2a as shown in Fig. 1.

(7)

Sensor Design. A pressure sensor is designed to measure a pressure from 1MPa to 100 MPa. The diaphragm thickness (h) is estimated as 30 the rectangular diaphragm design, a length to width ratio of 1.25 is assumed. Various diaphragm is 0.28 [8, 16-36].

Table 1. Dimensions of various diaphragms in the design.

Diaphragm type

Dimensions

Circular

250 (radius)

Square

443 (side)

Rectangular

396 500(length

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m)

width)

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Sensor Circuit Design. A Wheatstone bridge circuit as shown in fig. 2 is used for sensing the output voltage [9, 15-36]. Four piezo resistors namely R1, R2, R3 and R4 form the bridge circuit.

Fig. 2. Wheatstone bridge configuration to measure output voltage due to change in resistances on the sensors.

The length, width and thickness of the piezo resistors are 200 m, 10 m and 10 m respectively.

The piezo resistors are placed with an offset (dis the longitud -4

sensor is zero. When a pressure is applied, the resistance of the piezo resistors change thus the bridge is not balanced which results in a voltage at the output. As the applied pressure results in more diaphragm deflection, that causes more stress and more output voltage. Thus, the bridge output voltage is a direct indication of the applied pressure [17-36].

Stress concentration region. Another thing that will be considered in this area is the effect of holes on the diaphragms. The main concept for this approach is to increase stress that occurred on diaphragms. SCR (Stress Concentration region) is an approach where defects or holes are made to increase stress. To produce SCR, no extra high tech equipment is needed; because it just involves etching and mask design. Therefore, this approach appears to be the most suitable for enhancing the sensitivity of Piezoresistive MEMS since the Piezoresistive material has good sensitivity to stress and no additional complicated equipment or process are required [9-12].

In this paper, the effect of three different shapes of hole have been studied in all considering diaphragms. Maximum stress, maximum deflection and maximum sensitivity in each case had been calculated.

Application Mode Using ABAQUS. In this paper, we introduce an implementation of the extended -28]. Applied approach in this article enables the use of available ABAQUS capabilities (interactive FEM mesh generation, finite element libraries and so on) to solve the problems presented in previous sections [16-36].

Results and Discussion. In this section, deflection and stress and sensitivity for all the three diaphragms under consideration are compared. Stress contours of each situation are also presenting in this section [30-35].

Effect All the three diaphragms are simulated using ABAQUS and various results are compared. Fig. 3 shows a comparison of Stress, maximum Sensitivity and maximum deflection in various diaphragm shapes while applied pressure is constant [20-36]. It can be observed from Fig. 3 that the deflection is more in circular diaphragm. As observed in Fig. 4 the rate of change of deflection is more in case of Circular diaphragm, while rate of changing of stress in rectangular shape is bigger than the two others [30-32].

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Table 2. Comparison of three diaphragms upon thickness change- units SI. Max. stress with Max. stress with

Imposed

Type of

thickness10mm

thickness30mm

pressure (MPa)

diaphragm

3.95e9

4.31e8

10

Circular

5.14e9

5.69e8

10

Rectangular

4.83e9

5.38e8

10

Square

Table 3. Comparison of deflection in three diaphragms with thickness change- units SI. Max. deflection with thickness 10mm

Max. deflection with thickness 30 mm

Imposed pressure (MPa)

Type of diaphragm

3.41e-5

1.3307e-6

10

Circular

2.55e-5

1.0131e-6

10

Rectangular

2.75e-5

1.0844e-6

10

Square

Table 4. Comparison of sensitivity in three diaphragms with thickness change- units SI. Max. sensitivity with thickness of 10mm

Max. sensitivity with thickness30mm

Imposed pressure (MPa)

Type of diaphragm

3.41e-12

1.3301e-13

10

Circular

2.54e-12

1.0131e-13

10

Rectangular

2.76e-12

1.0842e-13

10

Square

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a)

b)

c) Fig. 3. Stress, Maximum Sensitivity, and maximum deflection in three different shapes of diaphragm. a), Stress in three different shapes of diaphragm; b) Maximum Sensitivity in three different shapes of diaphragm; c) Maximum deflection in three different shapes of diaphragm.

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a)

b) Fig. 4. Maximum Stress and maximum deflection in three different shapes of diaphragm. a) Maximum Stress in three different shapes of diaphragm, b) Maximum deflection in three different shapes of diaphragm.

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a)

b) Fig. 5. Stress and Deflection contours in three shapes of diaphragms. a) Stress contours in three shapes of diaphragms, b) Deflection contours in three shapes of diaphragms.

As observed from the stress counters, The Stress is minimum at the center of the diaphragm and maximum at edges. Table 5 provides a comparison between the maximum deflections, Stress, and sensitivity in all the three different diaphragms at an applied pressure of 10 MPa [27-33].

Table 5. Maximum Stress, Maximum Deflection & Maximum Sensitivity at 10 MPa applied pressure.

Diaphragm Type Circular Rectangular Square

Applied Pressure (MPa) 10 10 10

Maximum Stress (Pa) 4.37E+08 5.65E+08 5.37E+08

Maximum Deflection (m) 1.33E-06 1.01E-06 1.08E-06

Maximum Sensitivity 1.33E-13 1.01E-13 1.08E-13

Fig. 4 shows a comparison of the maximum stress and deflection in various diaphragm shapes as the applied pressure is changed. It can be observed from Fig.4that the stress is more in rectangular shaped diaphragm [30-33].

Table 5 provides a comparison between the maximum deflections in all the three different diaphragms at an applied pressure of 10MPa [32]. It can be noted that in a rectangular diaphragm, the stress is much larger compared to other diaphragm shapes. This is because the diaphragm structure is more asymmetric.

Mechanical Analysis of the effect of holes on diaphragms.

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Table 6 summarizes the analysis result of stress, deflection, and sensitivity difference for different types of SCR holes in each diaphragm type. In Fig. 6-8 stress contours in three shapes of diaphragms with different kinds of hole have been compared together [25-36].

Fig. 6. Stress contours in three shapes of diaphragms with rectangular holes.

Table 6. Maximum Stress, Maximum Deflection & Maximum Sensitivity in three shapes of diaphragms with three kinds of hole and without hole.

Maximum Sensitivity

Maximum Stress

Maximum deflection

Hole Type

1.437e-13

4.854e8

1.437e-6

Rectangular

1.282e-13

4.260e8

1.282e-6

Hexagonal

1.273e-13

4.204e8

1.273e-6

Circular

1.330e-13

4.371e8

1.330e-6

without hole

1.058e-13

5.188e8

1.058e-6

Rectangular

1.007e-13

5.387e8

1.007e-6

Hexagonal

1.002e-13

5.299e8

1.002e-6

Circular

1.013e-13

5.649e8

1.013e-6

without hole

1.361e-13

5.542e8

1.361e-6

Rectangular

1.078e-13

5.136e8

1.078e-6

Hexagonal

1.074e-13

5.064e8

1.074e-6

Circular

1.084e-13

5.367e8

1.084e-6

without hole

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Geometry of Diaphragm

Circular

Rectangular

Square

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Fig. 7. Stress contours in three shapes of diaphragms with hexagonal holes.

Fig. 8. Stress contours in three shapes of diaphragms with circular holes.

Fig. 9. Stress

holes.

According to the figure 9, circular diaphragm has minimum stress.

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Fig. 10. Deflection holes.

According to the figure 10, circular diaphragm has maximum deflection.

Fig. 11. Sensitivity holes.

According to the figure 11, circular diaphragm with rectangular holes has maximum sensitivity.

Other material. In next part, we change sensor type of diaphragm to gold in previous analysis [2033]. Gold properties are as follows: MMSE Journal. Open Access www.mmse.xyz

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Table 7. Gold properties.

Item

Value

unit

Elastic Modulus

7.8e+010

N/m2

0.42

N/A

Shear Modulus

2.6e+010

N/m2

Density

19000

kg/m3

Tensile Strength

103000000

N/m2

Thermal Expansion Coefficient

1.4e-005

k

Thermal Conductivity

300

Specific Heat

130

Results relevant to silicon and gold sensors expansion is ordered in table 8.

Table 8. Maximum deflection.

Total deflection of gold sensors Total deflection of silicon sensors Type of diaphragm 1.2252e-05

0.53228e-5

Circular

4.6994e-06

2.0260e-6

Rectangular

Fig. 12. Deflection material.

Temperature. In this section, we are going to change the temperature.

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Fig. 13. Stress

holes

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temperature.

According to the figure 13, circular and rectangular diaphragms with rectangular holes have maximum stress, and all the diaphragms without the holes have minimum stress. So, stress does not have any change with changing the temperature.

Fig. 14. Deflection holes

temperature.

According to the figure 14, diaphragms with the holes have maximum deflection, and diaphragms without the holes have minimum deflection.

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Fig. 15. Sensitivity holes

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temperature.

According to the figure 15, diaphragms with the rectangular holes and circular diaphragm have maximum sensitivity, and diaphragm without the holes have minimum sensitivity. As a result, diaphragms with circular shape and rectangular holes with minimum thickness have the best performances. Because, these diaphragms have minimum stress, minimum deflection, and maximum sensitivity rather than others.

Summary. In this paper, from numerical results in three different shapes of diaphragm, circular type diaphragm had better function. This result is founded on the contrast among stress and deflection results in these diaphragms. Nevertheless, at what time the stress in the diaphragm is measured, the rectangular diaphragm touches more stress compared to the square diaphragm. Thus, the chance for the sensor breakdown is more in the rectangular diaphragm when compared to the square diaphragm.

To decrease stress, one can increase the diaphragm thickness. In conclusion, circular typed diaphragms are more preferred than the other two shapes, namely square and rectangular diaphragms.

In addition, we added holes in diaphragms, important differences have been observed. The Piezoresistive MEMS with circular diaphragms and rectangular holes had more sensitivity compared to other situations.

In conclusion: Circular diaphragm has minimum stress.

Circular diaphragm has maximum deflection.

Circular diaphragm with rectangular holes has maximum sensitivity.

Circular and rectangular diaphragms with rectangular holes have maximum stress, and all the diaphragms without the holes have minimum stress. So, stress does not have any change with changing the temperature.

Diaphragms with the holes have maximum deflection, and diaphragms without the holes have minimum deflection Diaphragms with the rectangular holes and circular diaphragm have maximum sensitivity, and diaphragm without the holes have minimum sensitivity.

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As a result, diaphragms with circular shape and rectangular holes with minimum thickness have the best performances. Because, these diaphragms have minimum stress, minimum deflection, and maximum sensitivity rather than others.

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[18] Nader Mohammadi, Arash Mohammadz , 23 (1), 54-64. a Solar Domestic Hot Water System by the Use of Imperialist Competitive Algorithm with the Help of Ex78, 2015 [20] Nader Mohammadi, Farahnaz Fallah Tafti, Ahmad Reza Arshi, Arash Mohammadzadeh, Raghad -496, 2014 [21] Amir Mohammadzade Industrial Engineering, Volume 5, Pages 73-85, 2012 [22] Amir Mohammadzadeh, Nasrin Mahdipour, Arash Mohammadzadeh, Mohammad Ghadamyari (2012), Comparison of forecasting the cost of water using statistical and neural network methods: Case study of Isfahan municipality, Vol. 6, 3001 [23] Arash Mohammadzadeh, N. Etemadee (2011), Optimized Positioning of Structure Supports with PSO for Minimizing the Bending Moment, International Review of Mechanical Engineering, 5 (3), 422-425.

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[33] Arash Mohammadzadeh, N. Etemadee (2012), Design of Heater for City Gate Station Assisted

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[34] M. Dehghan, M. Mirzaei, A. Mohammadzadeh (2013), Numerical formulation and simulation of a non-Newtonian magnetic fluid flow in the boundary layer of a stretching sheet, Journal of Modeling in Engineering, 11 (34), 73-82.

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Synthesis and Characterization of L-Alanine Functionalized Nano Hydroxyapatite 1

B.V. Jogiya1,a, A.K. Bhojani1, P.D. Solanki1, H.O. Jethva1, M. J. Joshi1 1

Crystal Growth Laboratory, Department of Physics, Saurashtra University, Rajkot, Gujarat, India

a

bhoomika.cpi@gmail.com DOI 10.2412/mmse.58.20.50 provided by Seo4U.link

Keywords: hydroxyapatite (HAP), L-alanine functionalization, XRD, FTIR, TEM, TGA.

ABSTRACT. Hydroxyapatite (HAP) Ca10(PO4)6(OH)2 is a biomaterial exhibits excellent biocompatibility and finds numerous applications in clinical as well as industrial field. Synthetic HAP is extensively used in bone repair and bone augmentation by acting as fillers in the bone fractured sites. In the present study the synthesis of L-alanine functionalized HAP nanoparticles is carried out using the surfactant mediated approach and characterized by different techniques. The FTIR spectra revealed the presence of amino acid in the sample. The powder XRD study indicated no major change in the crystal structure and alternation of unit cell parameters. The average crystallite size of L-alanine functionalized HAP nanoparticles is smaller than the pure HAP nanoparticles. The TEM images indicated change in the morphology from needle to spherical with reduced size. The slight reduction in the thermal stability after functionalization by L-alanine is observed from the TGA.

Introduction. Hydroxyapatite (HAP or Ca10(PO4)6(OH)2) is a bio-mineral exhibiting bio-compatible and bi-active nature. It finds many clinical applications such as bone and tooth implant materials [1], [2], [3]. The functionalization of the HAP nano-particles by amino acids has synergetic effects on their structural, morphological and surface properties [4]. The functionalizing HAP with amino acids has resulted in to high protein adsorptive capacity [4]. It is possible to extend and fine-tune the bioactivity of nanoparticles like HAP by surface functionalization using water-soluble biomolecules.

In this regard, amino acids are ideal candidates for the production of bio-inorganic HAP nanoparticles and bio-nano-composites due to their relative low cost, intrinsic biocompatibility and ability to interact with HAP surfaces [5].

In the present study the authors have selected L-alanine for the functionalization of HAP and compared it with the pure HAP. Materials and Methods.

The HAP nano-particles were synthesized by the surfactant mediated approach. Calcium nitrate hexahydrate (Ca(No3)26H2O), potassium dihydrogen phosphate (KH2PO4), Triton X-100, aqueous ammonia (all AR grade) were used as precursors. Initially, 2 ml of Triton X-100 was mixed with 100 ml of 0.3 M calcium nitrate hexa-hydrate aqueous solution and, thereafter, the 100 ml of 0.18 M potassium dihydrogen phosphate aqueous solution was added and the mixture was treated with rature. This resulted into milky white solution with precipitates. The precipitates were recovered by filtration (Whatman filter paper No. 1) and washed with the mixture of ethanol and de-ionized water and then dried in air at room temperature. The L-alanine functionalized HAP (Al-HAP) nano-particles were synthesized by adding 100 ml of 0.6 M concentrations of L-alanine aqueous solutions to the solution of calcium nitrate hexa-hydrate before the addition of surfactant and, thereafter, the same experimental procedure was repeated. Here, calcium to phosphate ratio was maintained 1.67 and the synthesized samples 1

This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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were labeled as Al-HAP and the pure sample as HAP. This method is briefly discussed by Jogiya et al. [6].

The Powder X-ray Diffraction (XRD) study was carried out on Bruker AXS D8 Advance setup using Microscope (TEM) analysis was conducted to determine the morphology and size of the synthesized nano-particles using TECNAIKA20 (Philips) setup operating at 200 kV potential. The Fourier Transform Infrared (FTIR) spectra were recorded on Thermo Scientific Nicolet 1510 in KBr media in the range of 400cm-1 to 4000cm-1. The Thermo-Gravimetry Analysis (TGA) was carried out on Result and Discussion. Figure (1) shows the XRD pattern of the pure HAP and Al-HAP, which is in good agreement with reference pattern (JCPDF-76-0694) of pure HAP. The broadening of the peaks confirms the nanocrystalline nature of the sample. Crystallite size is calculated from (002) -alanine markedly reduced the particle size which may be due the adsorption of amino acid on the surface of HAP. The unit cell parameters are calculated using powder-X software which is given in (Table 1). The monoclinic crystal structure has been found for the present nanoparticles.

Table 1. Unit Cell parameter of pure and L-Al-HAP. Sample Name

Pure-HAP Al-HAP

Unit Cell Parameter o

9. 432

o

)

Crystallite Size using formula (nm)

18.843 6.915

33

10.995 17.086 7.806

18

Fig. 1. Powder XRD Pattern.

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Fig. 2. TEM image (a) Pure HAP, (b) Al-HAP. The agglomeration is taking place to minimize the energy. The functionalization affected the morphology of the nano-particles from needle shape to spherical shape. The needle shape morphology of pure HAP is due to growth in {100} direction, the functionalization affects the morphology by reduction in growth in {111} direction [7-8]. The observed particle size is ranging from 10-30 nm.

Fig. 3. FTIR spectra.

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Fig. 4. Thermograms of the samples.

The FTIR spectra of the pure HAP and Al-HAP are shown in figure 3. The absorption peak located at 3370.7 cm-1 and 1641.5 cm-1 are due to the stretching and deformation of (O-H) vibrations. The peak observed at 2896.2 cm-1 and 2776.6 cm-1 correspond to the -CH3& -CH2- in aliphatic compound.

The small hump 3033.2 cm-1 indicates the NH3+ stretching in amino acid. The characteristic of the PO43- group of HAP is clearly observed in the spectrum. The strong absorption peak observed at 1053.2 cm-1 is due to asymmetric mode of PO43- here, the shifting of the peak from 1036.6 cm-1 to 1053.2 cm-1 is due to L-alanine. The medium peak observed at 564.2 cm-1 and 526.6 cm-1 is attributed to the bending modes of PO43-.This suggests successful functionalization of L-alanine with HAP. Figure 4 shows the thermo gram of Al-HAP. The weight loss observed in Al-HAP is slightly more than that of the pure HAP. For the pure HAP nano particles the sample remained stable up to 1000C temperature with only 0.5% weight loss and then it slowly decomposed up to 9000C temperature. At 9000C temperature only 1.7% weight loss was observed. The Al-HAP sample shows more weight loss with comparison to the pure HAP. Being an organic content the L-alanine destabilized earlier and this can be the reason of more weight loss. This further proves the successful functionalization of L-alanine with HAP. Summary. Pure HAP and Al-HAP has been successfully synthesized by using surfactant mediated approach. The functionalization of L-alanine is confirmed by FT-IR. The powder XRD study confirmed the monoclinic crystal structure with reduced average crystallite size due to functionalization of HAP by L-alanine. The TEM images indicated morphological change from needle to spherical and also confirmed that the size is in the range of nm. The TGA suggested less thermal stability of the Al-HAP samples compared to pure HAP due to functionalization.

References [1] V.C. Gshalaev and A.C. Demirchan (2013), Hydroxyapatite: Synthesis, Properties and Applications, Nova Science Publisher, New York, ISBN: 978-1-62081-934-0, p. 490.

[2] Frayssinet P., Bonnevialle P., Autefage J., Sharrock P., Bonel G. (1991) Bioartificial Hydroxyapatite Implants. In: Langlais F., Tomeno B. (eds) Limb Salvage. Springer, Berlin, Heidelberg DOI 10.1007/978-3-642-75879-9_22 [3] A. A. Marino, R. O. Becker, C. H. Bachman (1967), Dielectric determination of bound water of bone. Phys. Med. Biol., 12 (3), 367-378.

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[4] B. Palazzo, D. Walsh, M. Iafisco, E. Foresti, G. Martra, C. L. Bianchi, G. Cappeletti, N. Roveri (2009), Amino acid synergetic effect on structure, morphology and surface properties of biomimetic apatite nanocrystals, Acta Biomater, 5(4) 1241-1252, DOI 10.1016/j.actbio.2008.10.024 [5] R. Gonzalez-McQuire, J.-Y. Chane-Ching, E. Vignaud, A. Lebuglec, S. Mann (2004), Synthesis and characterization of amino acid-functionalized hydroxyapatite nanorods, J. Mater. Chem., 14 (1), 2277 2281, DOI 10.1039/B400317A [6] W.K. Burton, N. Cabrera, F.C. Frank (1951), The growth of crystals and the equilibrium structure of their surfaces, Phil. Trans. R. Soc. London, 243, 299- 358, DOI 10.1098/rsta.1951.0006 [7] F.F.A. Hollander, M. Plomp, C. J. Streek, W. J. P. Enckevort (2001), A two-dimensional Hartman-Perdok analysis of polymorphic fat surfaces observed with atomic force microscopy, Surf. Sci. 471 (1), 101-113.

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Role of Ionization Energies in Tri Hydride Superconductors 1

K. Subbaravamma1,a, S. Kaleemulla2, G. Venugopal Rao3 1

Ranjani, Anupuram, Tamilnadu, India

2

Centre for Crystal Growth, VIT University, Vellore, Tamilnadu, India

3

Materials Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu, India

a

suba2271@gmail.com DOI 10.2412/mmse.45.73.186 provided by Seo4U.link

Keywords: superconductivity, tri hydrides, ionization energies, critical temperature, high pressure.

ABSTRACT. Hydrogen dense materials of the form AH 3 (where A can be Al, Sc, Ga, S, Cr, Se, Y, La, P) are gaining interest with respect to study high temperature superconductivity at pressure with the reach of available techniques. In the present work, we have used first principle calculations to correlate the ionization energies and the superconducting critical temperatures for the metal hydrides. Using a linear regression, a straight line fit of the correlation implies a certain limit for sum of the ionization energy needed for superconductivity to occur. Alkali C 60 superconductors shown similar nature with ionization energy.

Introduction. Superconductivity was first discovered in 1911 by Kamerling Onnes. In a span of 105 years greatest advances, cuprates, C60 compounds, pnictides and other systems were found. Nearly four decades ago hydrogen was suggested to be a superconductor under high pressure. However further calculations showed that highest critical temperatures possible with metallic hydrogen.

Hydrogen being lightest, possess very high vibrational frequencies, a strong electron phonon interaction, hence high transition temperature Tc is expected [1]. Since then many scientists are working on metallization of hydrogen, by doping the heavier elements into hydrogen. Hydrogen rich compounds are considered to metalize at lower pressures than pure hydrogen. In this process number of hydrogen rich materials are predicted. A room temperature superconductor probably is the most needed system in science and technology.

Primary role of pressure application is to modify the energies of the levels in a system, while the effect of a change in temperature is to modify the occupation of the energy levels [2]. Hence the critical temperature of a superconductor depends on both lattice and electronic properties, one expects pressure to have profound effect on transition temperatures Tc. Enhancement of Tc under pressure is experienced already in High Temperature Superconductor (HTSC) materials. Ionization potentials influence band structure, i.e., density of states. Hence ionization energies contribute to transition temperatures (Tc) of superconductors, similar studies for C60 superconductors [3] and for HTSC [4] were published. Role of ionization energies are more important in atomic level superconductors.

Materials undergo structural changes on applied pressures. The pure material gallium is superconducting in four different crystal structures with transition temperature range from 1 K to 8 K. In contrast, with same lattice constant, Niobium and Tantalum have identical crystal structure (bcc), but their transition temperatures differ by a factor of two. Obviously, the structure of the material and the electron configuration are important for the understanding of superconducting phenomenon. Hydrogen, isoelectronic to alkali metal, is insulating under ambient conditions. Since it has high binding energy, high pressure is required to attain metallic phase.

1

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Emergence of high temperature superconducting phases in several pressurized hydrogen dense materials have been predicted [5]. Until now, ionization energies are correlated to C60 compound superconductors. No study has been carried out on how the superconducting critical temperature evolves with ionization energies in tri hydrides and tetra hydrides. Hence we considered the examples of AH3 series of hydrogen dense materials with preliminary calculations.

In this paper, we consider set of tri hydrides under pressure and attempt to identify the role of ionization energies in effecting superconducting transition temperature. Preliminary results are presented here.

Results and discussion. First we discuss, element wise pressure effects, then trihydride compounds taken from literature. The variation of critical temperature (Tc) with pressure for some of the elements is shown in figure 1.

S

18

Sc

15

La

12

P

9 6

Se Y

3

Al 0 0

20

40

60

80

100

120

140

160

Pressure (GPa)

Fig. 1. Pressure dependence of critical temperature for La, Sc, P, S, Se, Y and Al elements.

The transition temperature with respect to pressure has an increasing nature except for Aluminum and Selenium. Phosphorus is having steeper increase where as Sulfur shows slow increase in transition temperature as pressure increases [6].

Many elements show superconductivity under pressure with varying critical temperature, eg., Sc, Y, Se, S and P show superconductivity under high pressure. Ga, Al, Cr and La show superconductivity at ambient pressures. Table 1 gives the data of superconducting transition temperatures, corresponding pressures and ionization energies of above mentioned elements [6].

Table 1 depicts that as the ionization energy increases, increasing trend in transition temperature is observed except for Sc and La. It is to be noted that all these elements exhibit transition temperature at different pressures.

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Table 1. Ionization energy (Eion ), critical temperature (Tc) and pressure of some elements.

Element

Eion (eV)

Tc (K)

Pressure(GPa)

Sc

6.5613

0.34

21

Ga

5.9991

1.08

1 atm

Al

5.9856

1.18

1 atm

Y

6.2171

2.8

15

Cr

6.7663

3

1 atm

La

5.5767

6

1 atm

Se

9.7521

7

13

S

10.3597

17

160

P

10.4864

18

30

The pressure effects of trihydrides are presented here. The variation of critical temperature (Tc) with increasing pressure has been shown in Figure 2 for SH3, ScH3, CrH3, SeH3, YH3, LaH3 and PH3. The data has been collected from the references [5, 7, 8, 9]. All the tri hydrides mentioned in this figure show a decreasing trend of critical temperature with increasing pressure, except for PH3, for which an increase in critical temperature is seen with increasing pressure.

220 200 180 160 140 120 100 80 60 40 20 0

ScH3 YH3 LaH3 SeH3 SH3 CrH3 PH3

0

50

100

150

200

250

300

Pressure (GPa)

Fig. 2. Pressure dependence of critical temperature for AH3 compounds.

Now we study, nature of ionization energies to transition temperature of tri hydrides with preliminary calculations. We considered ionization energies of the isolated atoms. In molecules, calculations of ionization energies are complicated process. Table 2 (Row wise) and Table 3 (Column wise) gives the summary of different tri hydrides with their ionization energy sum ( Eion), pressure and critical temperature (Tc). The data are from Ref. [7 to 14].

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Table 2. Row wise ionization energy sum ( Eion ), pressure and critical temperature (Tc) in AH3 (A = Sc, Cr, Ga, Se, Al, P and S) compounds.

4th Row Material Eion (eV)

3rd Row

ScH3

CrH3

GaH3

SeH3

AlH3

PH3

SH3

44.1168

54.2108

57.2388

61.7611

53.2606

60.4580

68.4860

Pressure (GPa)

18

81

120

120

110

207

150

Tc (K)

19.3

37.1

89.78

110

24

103

203

Table 3. Column wise ionization energy sum ( Eion), pressure and critical temperature (Tc) in AH3 (A = Sc, Y, La, Al, Ga, S and Se) compounds.

3rd Column Material Eion (eV)

13th Column

16th Column

ScH3

YH3

LaH3

AlH3

GaH3

SH3

SeH3

44.1168

38.9601

35.8122

53.2606

57.2388

68.4860

61.7611

Pressure (GPa) 18

17.7

11.0

110

120

150

120

Tc (K)

40

22.5

24

89.78

203

110

19.3

The ionization energy sum ranging from 35.812 eV to 68.486 eV, spanning about 32.674 eV and corresponding critical temperature ranging from 19.3 K to 203 K, spanning about 183.7 K is observed from Table 2 and Table 3.

From Table 2, it is worth mentioning that for the tri hydrides of Sc, Cr, Ga and Se, the transition temperature increases with decreasing ionization energies. Similar trend is observed for the tri hydrides of Al, P and S. A decrease in transition temperature with increasing ionization energy for YH3 and LaH3, except for ScH3 is noticed from Table 3. Similar trend is observed for SH3 and SeH3, where as for AlH3 and GaH3, the transition temperature increases with decreasing ionization energy.

Figure 3 shows the sum of ionization energies Eion for different tri hydrides versus the transition temperature Tc. Using a linear regression, data fits into the range 19 K Tc 203 K. The slope of the correlation has a value of approximately 147.76 10-3 eV/K or 1719 KB and an ordinate intercept value of 42.05 eV. The trend of Tc in YH3 with increasing pressure is different from that in pure Y, while the change of the d state in pure Y is the same as in fcc-YH3, indicating different origins of superconductivity in Y and YH3.

In the present paper, the ordinate intercept demonstrates that there is an absolute value of ionization threshold to obtain superconductivity. Theoretical studies of YH3 and LaH3 show deviation from this threshold value. However, rest of the samples lie within this range. Experimental results may help to resolve this discrepancy.

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0

0

40

Temperature (K) 80 120 160

ISSN 2412-5954

200

-3

-20

ion

147.76 x 10 eV/K . Tc 42.05 eV

ion

1719 . KBTc 6.74 x 10

-18

J

-40 -60 -80 -100

Fig. 3. Relationship between ionization energy sum and critical temperature. Data points are from Table 2. The slope is calculated for all data points.

Summary. An effort is made for correlation between ionization energies and the superconducting critical temperature of metal hydrides, using preliminary calculations. Fitting the data of Eion versus Tc for tri hydrides using linear regression, gives an ordinate intercept value of 42.05 eV, which demonstrates that to obtain superconductivity for the hydrides studied, there is an absolute value of ionization threshold. We continue to do systematic further study. This work may provide piece of advice for future understanding of the superconductivity under pressure with respect to ionization energies, in particular atomic level superconductors.

References [1] N.W. Ashcroft (1968), Metallic Hydrogen: A High-Temperature Superconductor? Phys. Rev. Lett. 21, 1748.

[2] H.G. Drickamer (1961), Optical studies at high pressure, in F.P. Bundy, W.R. Hibbard Jr., H. M. Strong Eds., Progress in very high pressure research, pp. 16, John Wiley & Sons, Inc., New York.

[3] Florian Hetfleisch, Marco Stepper, Hans-Peter Roeser, Artur Bohr, Juan Santiago Lopez, Mojtaba Mashmool and Susanne Roth, Physica C 513 (2015) 1.

[4] H.P. Roeser, D.T. Haslam, J.S. Lopaz, M. Stepper, M.F. von Schoenermark, F.M. Huber, A.S. Nikoghosyan (2011), Electronic Energy Levels in High-Temperature Superconductors, J. Supercond.

Nov. Magn., 24(5), 1443-1451, DOI 10.1007/s10948-010-0850-5 [5] D.Y. Kim, R.H. Scheicher, H. Mao, T.W. Kang, R. Ahuja (2010), General trend for pressurized superconducting hydrogen-dense materials, Proc. Natl. Acad. Sci., 107 (7), 2793-2796, DOI 10.1073/pnas.0914462107 [6] Cristina Buzea and Kevin Robbie, Supercond. Sci. Technol. 18 (2005) R1-R8.

[7] A. Drozdov, M.I. Eremets, I.A. Troyan, arXiv:1508.06224 (2015), Superconductivity above 100 K in PH3 at high pressures.

[8] S. Zhang, Y. Wang, J. Zhang, H. Liu, X. Zhong, H. Song, G. Yang, L. Zhang, Y. Ma (2015), Phase Diagram and High-Temperature Superconductivity of Compressed Selenium Hydrides, Scientific Reports 5, 15433, DOI 10.1038/srep15433

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[9] S. Yu, X. Jia, G. Frapper, D. Li, A.R. Oganov, Q. Zeng, L. Zhang (2015), Pressure-driven formation and stabilization of superconductive chromium hydrides, Scientific Reports 5. 17764, DOI 10.1038/srep17764 [10] A.P. Durajski, R. Szczesniak, Superconducting state above the boiling point of liquid nitrogen in the GaH3 compound, Supercond. Sci. Technol. 27 (2014) 11501, DOI 10.1088/09532048/27/1/015003.

[11] A. Drozdov, M.I. Eremets, I.A. Troyan, V. Ksenofontov, S.I. Shylin (2015), Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system, Nature, 525 73-76, DOI 10.1038/nature14964 [12] D.Y. Kim, R.H. Scheicher, R. Ahuja (2009), Predicted high-temperature superconducting state in the hydrogen-dense transition-metal hydride YH3 at 40 K and 17.7 GPa, Phys. Rev. Lett. 103 (7) 077002, DOI 10.1103/PhysRevLett.103.077002 [13] I. Goncharenko, M.I. Eremets, M. Hanfland, J.S. Tse, M. Amboage, Y. Yao, I.A. Trojan (2008), Pressure-induced hydrogen-dominant metallic state in aluminum hydride, Phys. Rev. Lett.

100 (4), 045504, DOI 10.1103/PhysRevLett.100.045504 [14] A.P. Durajski, R. Szczesniak, Superconducting state above the boiling point of liquid nitrogen in the GaH3, compound, Supercond. Sci. Technol. 27, (2014) 015003, DOI 10.1088/09532048/27/1/015003

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Structural, Spectroscopic, Thermal and SHG Efficiency Studies of LPhenylalanine Doped KDP Crystals 1

D.D. Khunti1, a, b, J.H. Joshi1, H.O. Jethava1, M.J. Joshi1, K.D. Parikh2 1

Department of Physics, Saurashtra University, Rajkot (Gujarat), India

2

Shri M.P.Shah Arts & Science College, Surendranagar (Gujarat), India

a

dhavaldkhunti@gmail.com

b

dhavalinnovations@gmail.com DOI 10.2412/mmse.4.93.354 provided by Seo4U.link

Keywords: NLO, XRD, TGA, SHG efficiency, Kurtz-Perry.

ABSTRACT. Crystal growth is an important branch of solid state physics and material science. The Growth of Nonlinear Optical (NLO) materials crystals receives much importance nowadays because NLO materials have various applications in modern technologies like Laser technology, optoelectronics, and fiber optics, etc. Potassium dihydrogen phosphate (KDP) is a well known nonlinear optical (NLO) material with different applications. Since most of the amino acids exhibit NLO property, it is of interest to dope them in KDP. In the present study, amino acid L-Phenylalanine doped KDP crystals have been grown by slow evaporation solution growth technique. In present study powder XRD analysis was carried out which show that pure and L-Phenylalanine doped KDP crystals have tetragonal symmetry. The doping of L-Phenylalanine was confirmed by FT IR and paper chromatography. Thermal analysis has been performed on the grown crystals.The SHG efficiency of L-Phenylalanine doped KDP crystals was found to be increasing with a doping concentration of LPhenylalanine.

Introduction. The demand for high quality large size KDP single crystal increases due to its application as frequency conversion crystal in inertial confinement fusion [1, 2]. KDP belongs to scalenohedral (twelve faced) class of tetragonal crystal system [3]. With the aim of improving the second harmonic generation (SHG) efficiency of KDP, researchers have attempted to modify KDP crystals by doping different types of impurities. The non-linear optical (NLO) and other properties of the crystal have been improved by doping of organic impurities [4-9]. KDP doped with amino acids like L-glutamine acid, L-gistidine, and L-valine was reported [10]. Kumaresan et al. [11] has reported the thermal dielectric properties of amino acids such as L-glutamic acid, L-histidine and L-valine doped KDP crystals. They found improved NLO properties of the KDP crystal and modifications in the structural, optical, mechanical, and electrical properties, too. Parikh [12] has reported the SHG efficiency of L-arginine doped KDP crystal. Kumaresan et al. [13] has also reported the effect of metal ion and amino acid doping on the optical properties of KDP crystal. Muley et al. [5] has studied thermal, NLO properties of KDP crystal doped with L-arginine and L-alanine. Suresh Kumar and Rajendrababu [6] studied the effects of L-arginine, L-histidine and glycine on the growth of KDP single crystals and observed that addition of amino acid enhances transparency, thermal stability and NLO efficiency of KDP crystals. Amino acid family crystals are playing an important role in the field of non-linear optical organic molecular crystal. Among them L-Phenylalanine (LPA) with chemical formula (C6H5CH2CH(NH2)COOH) is the -amino acid with a non-reactive hydrophobic benzyl side chain. The physical, chemical and non-linear optical properties of KDP are enhanced by adding optically active amino acids as dopants.The growth and characterization of Single crystals of KDP doped with amino acids namely glycine, arginine, alanine, tryptophan, histidine have been reported earlier [5-8]. In the present work, single crystals of Potassium dihydrogen phosphate (KDP) added 1

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with different concentrations (0.4 wt.% and 0.8 wt.%) of amino acid L-Phenylalanine impurities were grown using slow evaporation solution growth (SESG) technique at room temperature. In the present investigation, pure KDP crystals and the L-Phenylalanine doped crystals have been grown and characterized by Powder XRD, FT-IR, TGA and SHG efficiency.

Crystal Growth and Synthesis. The pure and amino acid doped KDP crystals were grown by using slow evaporation solution growth technique at room temperature. All the chemicals used for the study were of analytical grade. 300 mL double distilled water was taken and pure KDP powder was dissolved till saturation occurred. The saturated solution was stirred continuously using a magnetic stirrer for 5 hours and filtered using Whatman filter paper No. 1. The solution was then subdivided into 3 different glass beakers, each of them containing 100 mL of pure solution. One beaker containing a pure solution that transferred into a petri dish, covered with a thick paper with fine pores in order to minimize the rate of evaporation. L-Phenylalanine with different concentrations ( 0.4 wt.% and 0.8 wt.%) were added into the remaining beakers, all the solutions were stirred again for 5 hours to make the solutions homogeneous. All the solutions were then transferred into a petri dish, covered with a thick paper with fine pores in order to minimize the rate of evaporation. Upon complete evaporation of the solvent, single crystals of size 3.5cm 2cm were harvested within eight days as shown in Fig. 1 (a), (b) and (c).

Fig. 1. As grown crystal of (a) Pure KDP, (b) 0.4 wt.% L-Phenylalanine doped KDP, (c) 0.8 wt.% L-Phenylalanine doped KDP. Result & Discussions: Powder XRD Study. The powder XRD study was conducted to verify the single phase nature of the samples. Figures 2 show the powder XRD patterns of pure KDP, 0.4 wt. % and 0.8 wt. % LPhenylalanine doped KDP crystals. The unit cell parameters were calculated by using software Powder-X and listed in table 1. This suggests that the crystals retain almost the single phase structure and exhibit very slight variation in the unit cell parameters on doping of L-Phenylalanine. The variation in the intensities of various diffraction patterns on changing the concentration of doping was observed.

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Fig. 2. Powder XRD patterns of Pure and doped KDP. Table 1. Unit cell parameters of pure and doped KDP. Sample

a

Unit Cell Volume[

Pure KDP

7.457

6.976

387.91

0.4 wt.% L-Phenylalanine doped KDP

7.455

6.980

387.93

0.8 wt.% L-Phenylalanine doped KDP

7.459

6.980

388.34

3

]

FT-IR Spectroscopy study. The FT-IR Spectrum of pure KDP,0.4 wt.% L-phenylalanine doped KDP(LPA) and 0.8 wt.% L-phenylalanine doped KDP (LPA) crystals is shown in Fig.3. In this fig we observed broad envelopes between 2300 cm-1 to 3500 cm-1 are due to NH3+ stretching vibration and O-H stretching at 3560 cm-1 (0.4 wt.% LPA) and 3410 cm-1 (0.8 wt.% LPA). C-H Stretching of CH2 is observed at 2877 cm-1 (0.4 wt.% LPA) and 2982 cm-1 (0.8 wt.% LPA). C=O stretching is revealed by absorption peak at 1494 cm-1 (0.4 wt.% LPA) and 1512 cm-1 (0.8 wt.% LPA). Intense absorptions observed at 520 cm-1 (0.4 wt.% LPA) and 528 cm-1 (0.8 wt.% LPA) due to P-OH deformation. Absorptions observed at 837 cm-1 (0.4 wt.% LPA) and 846 cm-1 (0.8 wt.% LPA) are due to NH3+ rocking, while absorptions observed at 704 cm-1(0.4 wt.% LPA) and 698 cm-1 (0.8 wt.% LPA) are due to the presence of benzene ring. It is easily concluded that L-Phenylalanine doping was MMSE Journal. Open Access www.mmse.xyz

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successfully achieved because the absorptions due to N-H, C=O, C-H remain absent in pure KDP crystals.

Fig. 3. FT-IR spectra of pure KDP AND L-Phenylalanine doped (0.4 wt % and 0.8 wt.%) KDP. Thermal studies. In the present investigation, the effect of L-Phenylalanine doping on thermal stability of KDP crystals is studied by employing the thermogravimetry analysis (TGA). Figures 4 and 5 indicate thermograms for pure KDP and 0.4 wt % and 0.8 wt.% L-Phenylalanine doped KDP respectively. It has been observed that initially the crystal gives up the water of hydration to become anhydrous and remains in that form up to end of the analysis. One can see from the thermogram that on increasing the level of L-Phenylalanine doping the dehydration process starts early and the crystal becomes anhydrous faster than the pure KDP. Since amino acid becomes unstable at lower temperatures, it weakens KDP crystal and as a result, the dehydration process takes place earlier and faster with a comparison to pure KDP. This also proves that the amino acid has entered the KDP crystal in a doped form. The similar nature was obtained for L-arginine, L-threonine and L-lysine doping in KDP [12, 14, 15]. The doped crystals possess slightly less thermal stability than the MMSE Journal. Open Access www.mmse.xyz

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undoped crystals, which is the sacrifice to be given for obtaining higher optical transmission and higher SHG efficiency.

Fig. 4. TGA OF pure KDP crystals.

Fig. 5. TGA of L-Phenylalanine doped (0.4 wt.% and 0.8 wt.%) KDP crystals.

SHG efficiency. The Kurtz powder method was used for the measurements of SHG efficiency [16].

For the Nd:YAG laser, the fundamental beam of 1064 nm generates the second harmonic signal of 532 nm. The SHG efficiency is listed in table 1 for different samples. The second harmonic signal generated in the crystals was confirmed from the emission of green radiation. The NLO SHG efficiency of the crystals was found to be 2.18 times more than pure KDP [17]. The results show that by doping KDP with amino acid, the NLO efficiency of KDP can be enhanced. Due to the substantial number of defects formed as a result of doping one can expect enhancement of SHG signals. The phosphate (PO4) group of KDP makes a significant contribution to the SHG effect and hydrogen bonds help in enhancing the birefringence. The possibility of hydrogen bond formation between oxygen unit of a PO4 group of KDP and the amino group NH3 of the amino acid may have led to an increase in non-linearity of KDP [18], which in turn increases the SHG efficiency.

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Table 2. SHG efficiency of pure KDP and (0.4 wt % & 0.8 wt. %) L-Phenylalanine doped KDP. Sample

SHG efficiency

Pure KDP

1

0.4 wt.% L-Phenylalanine doped KDP

1.25

0.8 wt.% L-Phenylalanine doped KDP

1.39

Summary. The pure and different weight percentages (0.4 wt.%, 0.8 wt.%) L-Phenylalanine doped ADP crystals were successfully grown by using slow solvent evaporation technique at room temperature. The powder XRD study showed single phase nature of the pure and doped crystals. All the crystals belong to tetragonal crystal system. The FT-IR spectroscopy showed the shifting of various vibration modes of functional groups and change in force constant which confirms the presence of a dopant in KDP. Thermograms of pure and L-Phenylalanine doped KDP crystals suggested that as the doping increased the crystals became thermally less stable and dehydrated faster at comparatively lower temperature. The SHG efficiency increased as the doping level of LPhenylalanine increased in KDP crystals.

Acknowledgements. The Authors are thankful to Prof. Hiren H. Joshi (HOD, Physics Department, Saurashtra University, Rajkot) for his kind interest and support and UGC for DRS SAP II and DIST for FIST. Author (DDK) is thankful to Department of Social Justice and and impowerment Government of Gujarat for allowing him to carry out research activity.

References [1] X. Sun, X. Xu, Z. Gao, Y. Fu, S. Wang, H. Zeng, Y. Li, Effect of EDTA on the Light Scatter in KDP Crystals, Journal of Crystal Growth, Vol. 217, 2000, pp. 404-409.

[2] N. Zaitseva, L. Carman, I. Smolsky, Habit Control during Rapid Growth of KDP and DKDP Crystals, Journal of Crystal Growth, Vol. 241, No. 3, 2002, pp. 363- 373. DOI 10.1016/S00220248(02)01244-7 [3] R.W.G. Wyckoff, Crystal Structure, 2-nd Edition, Interscience, New York, 1960.

[4] J. Podder, The Study of Impurities Effect on the Growth and Nucleation Kinetics of Potassium Dihydrogen Phosphate, Journal of Crystal Growth, Vol. 237-239, 2002, pp. 70-75. DOI 10.1016/S0022-0248(01)01854-1 [5] G.G. Muley, M.N. Rode, B.H. Pawar, FT-IR, Thermal and NLO Studies on Amino Acid (LArginine and L-Alanine) Doped KDP Crystals, Acta Physica Polonica A, Vol. 116, 2009, pp. 10331038.

[6] B. Suresh Kumar, K. Rajendra Babu, Effect of L-Arginine, L-Histidine and Glycine on the Growth of KDP Single Crystals and Their Characterization, Indian Journal of Pure and Applied Physics, Vol. 46, No. 2, 2008, pp. 123-126.

-Histidine Doped KDP [7] S. Gunasekaran, G.R. Ramkumaar, Crystals in High Speed Applications, Indian Journal of Physics, Vol. 83, No. 11, 2009, pp. 15491555. DOI 10.1007/s12648-009-0138-4 [8] K.D. Parikh, D.J. Dave, B.B. Parekh, M.J. Joshi, Growth and Characterization of L-Alanine Doped KDP Crystals, Crystal Research and Technology, Vol. 45, No. 6, 2010, pp. 603-610. DOI 10.1002/crat.201000019 [9] M. Priya, C. M. Padma, T. H. Freeda, C. Mahadevan, C. Balasingh, Electrical Conductivity Measurements on Gel Grown KDP Crystals Added with Urea and Thiourea, Bulletin of Material Science, Vol. 24, No. 5, 2001, pp. 511-514. DOI 10.1007/BF02706723 MMSE Journal. Open Access www.mmse.xyz

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[10] P. Kumaresan, S. Moorthy Babu, P.M. Anbarasan, Influence of Dopants (L-Glutamic Acid, LHistidine and L-Valine) on the Performance of KDP Crystals, 4th DAE-BRNS Laser Symposium, Vol. 4, 2005, pp. 521-522.

[11] P. Kumaresan, B.S. Moorthy Babu, P.M. Anbarasan, Thermal Dielectric Studies on Pure and Amino Acid (L-Glutamine, L-Histadine, L-Valine) Doped KDP Single Crystals, Optical Materials, Vol. 30, No. 9, 2001-1368. DOI 10.1016/j.optmat.2007.07.002 [12] K.D. Parikh, D.J. Dave, B.B. Parekh, M.J. Joshi, Thermal, FT-IR and SHG Efficiency Studies of L-Arginine Doped KDP Crystals, Bulletin of Material Science, Vol. 30, No. 2, 2007, pp. 105-112.

DOI 10.1007/s12034-007-0019-4 [13] P. Kumaresan, B.S. Moorthy Babu, P.M. Anbarasan, Effect of Metal Ion and Amino Acid Doping on the Optical Performance of KDP Single Crystals, Journal of Optoelectronics and Advanced Materials, Vol. 1, No. 2, 2007, pp. 65-69.

[14] D.J. Dave, K.D. Parikh, B.B. Parekh, M.J. Joshi, Growth and spectroscopic, thermal, dielectric and SHG studies of L- threonine doped KDP crystals, J. Opt. Adv. Mater. 11, 602-609 (2009). INISTCNRS, Cote INIST: 27497.

[15] K.D. Parikh, D.J. Dave, M.J. Joshi, Crystla Growth, Thermal, Optical and Dielectric Properties of L-Lysine doped KDP Crystals, Modern Phys. Lett. B 23, 1589 (2009). DOI 10.1142/S0217984909019740 [16] S.K. Krutz, T.T. Perry, J. Appl. Phys. A Powder Technique for the Evaluation of Nonlinear Optical Materials, 39, 3798 (1968); DOI 10.1063/1.1656857 [17] Z. Delci. D. Shyamala., S. Karuna, A.Thayumanavan, Optical Characterization Studies on boron doped KDP crystals, Archives of Physics Research, 3(5), 2012, 346-353.

[18] K.G. Rewatkar, V.D. Maske, Harish Khorde, Growth and Characterization of L- alanine doped KDP crystal, International Journal of Computer, Information Technology and Bioinformatics, 1(2), 2012, 33-37.

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Synthesis and Characterization of Iron Oxide-Chitosan Nano Composite 1

A.L. Kavitha1,a 1

Department of Chemistry, Kings College of Engineering, Punalkulam, Thanjavur, India

a

alkavitha82@gmail.com DOI 10.2412/mmse.92.76.971 provided by Seo4U.link

Keywords: nanocomposite, self-assembly, microwave, iron oxide, chitosan.

ABSTRACT. The focal point of this paper, nanocomposite of hybrid materials Chitosan(CH) with -Fe2O3, Chitosan -Fe2O3 -Fe2O3 -Fe2O3 were synthesized by the self-assembly and microwave method and characterized. The average particle size was found to be 27 30nm by XRD and AFM. The synthesized nanoparticles were dispersed into the prepared chitosan (CH) solution. After the dispersion, the CH- -Fe2O3, CH- -Fe2O3 nanocomposite was subjected to characterizations such as UV-Visible, XRD and SEM with EDX. The CH-Fe2O3 nanocomposite to impart good antibacte -Fe2O3 and pristine chitosan.

Electrochemical response studies were carried out using CH- -Fe2O3 nanocomposite with carbon paste modified electrode.

Introduction. Nanoparticles (NPs) are solid particles or particulate dispersions with a size in the range between 1 and 100 nm. Among the various nanomaterials, magnetic nanoparticles have been recently increased interest due to promising applications as; Drug delivery, Hyperthermia treatment, Cell separation, Biosensors and enzymatic assays etc. Pure magnetic nanoparticles themselves may not be very useful in practical applications because they are more likely to aggregate for their large ratio of surface area to volume and strong magnetic dipole-dipole attractions between particles compared with other nanoparticles and have limited functional groups for selective binding [1-9].

In order to improve the stability and biocompatibility, the iron oxide NPs are often modified with biopolymer. Among the various biopolymers, chitosan (CH) along with NPs has been utilized as a stabilizing agent due to its Excellent film forming ability, Mechanical strength, Biocompatibility, Non-toxicity, High permeability towards water, Susceptibility to chemical modifications, Costeffectiveness etc. for enzyme immobilization [10-21]. Iron oxide NPs with polymer are usually composed of the magnetic cores to ensure a strong magnetic response and a polymeric shell to provide favorable functional groups and features. Chitosan with iron oxide composites have recently attracted much attention since surface functionalization of the nanoparticles allow their covalent attachment, self assembly and organization on surface making them promising for the loading of biomolecules in a favorable microenvironment for the development of a biosensor [22-29].

In the present work, the iron oxide particles were synthesized by two different methods such as selfassembly and microwave. The synthesized iron oxide particles were characterized by XRD, FT-IR, SEM and AFM. Chitosan was prepared and characterized by using XRD, FT-IR and SEM techniques.

The synthesized iron oxide particles, chitosan and iron oxide-chitosan composite were used for; Antibacterial activity and Electrochemical response studies.

Chemicals. Chemicals such as ferric chloride (FeCl 3), urea (CH4N2O), tetra-n-butylammonium bromide (C16H36NBr), ethylene glycol (C2H6O2), potassium hydroxide (KOH), sodium hydroxide (NaOH), zinc chloride (ZnCl2), ethanol (C2H5OH), Acetone (C3H6O),

1

he Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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graphite powder and paraffin oil were purchased from Merck and used as such without further purification.

Synthesis of iron oxide Nanoparticles.

Self-assembly method:

Microwave method: 250 mM FeCl3 was initially dissolved in 30 ml of ethylene glycol and 70 ml of water. KOH was added into the solution to maintain the pH 10. In the first process, the solution was stirred with a magnetic stirrer and heated at 200 oC for 1 hour 45 min; while in the second process, the solution was refluxed for 45 min in a microwave oven. A brown colour precipitate of -Fe2O3 settled down was decanted with water and acetone several times and dried in hot oven at 200 oC for 2 hours.

Synthesis of Chitin and Chitosan The shells of crab were obtained from the coastal area of Nagapattinam. The shells were washed well with sea water and again with fresh water before converting to the final product. From this, chitin and chitosan were prepared.

Preparation of chitin: The well dried crab shell was powdered by crushing in a mortar. About 50 g of this powder was taken in a 500 ml beaker. 250 ml of 5% HCl was added to remove calcium carbonate present in the powder. The mixture was then allowed to stand for about 2 h. It was filtered with a muslin cloth and the residue was transferred into a 500 ml beaker. 250 ml of 5% NaOH was added to it slowly to remove protein present in the powder. The mixture was then allowed to stand for about 3 h and filtered through muslin cloth to get chitin.

Preparation of chitosan: 2 grams of chitin was added to 60% anhydrous ZnCl2 solution and heated in a boiling water bath for 30 minutes. The mixture was then dissolved in dilute acetic acid. It was then filtered to remove the unreacted chitin and other impurities. The filtrate was precipitated using 20% sodium hydroxide solution. It was then filtered through muslin cloth and air dried to get chitosan.

Procedure for antibacterial activity. Chitosan (0.25%) solution was prepared by dissolving 25 mg of chitosan in 100 ml of acetate buffer (0.05 M, pH 4.2) solution. The calculated amount of -Fe2O3 was dispersed in the chitosan solution by stirring at room temperature. Then, it was sonicated to get a solution of -Fe2O3-chitosan composite (1:5). The synthesized -Fe2O3-chitosan composite was -Fe2O3, chitos -Fe2O3-chitosan composite solutions were then tested for antibacterial activity against E. coli and S. aureus microorganism by AATCC 147 method (sterile AATCC bacteriostatic agar medium was dispensed in to the sterile petri dishes. Overnight culture was used as an inoculum by using sterile swab. The test organism was inoculated over the surface of the agar plate and gently pressed in the centre of the Mat culture. The plates were then incubated overnight at 37oC).

-Fe2O3, -Fe2O3-chitosan composites were coated separately on both cotton and silk fabrics by dip-Fe2O3 -Fe2O3-chitosan composite (1:5) was taken by diluting it with distilled water. The test fabric was immersed into the solution and kept for 10 minutes. Then the fabric was taken out, washed with water and air dried. tested for antibacterial activity against E. coli and S. aureus by AATCC 147 standard method. against E. coli and S. aureus.

Preparation of -Fe2O3-chitosan (3:1) composite containing carbon paste electrode. The carbon paste electrode (CPE) was prepared in a regular way by mechanically mixing graphite powder and MMSE Journal. Open Access www.mmse.xyz

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paraffin oil in an agate mortar for 30 min. CPE containing chitosan (0.1g)- -Fe2O3(0.3g) nanocomposite (1:3) was prepared in the similar procedure (initially the CH solution was prepared by dissolving CH in acetate buffer (0.05 -Fe2O3 nanoparticles was dispersed in the CH solution by stirring at room temperature, finally, a highly viscous solution of CH with uniformly dispersed -Fe2O3 nanoparticle -Fe2O3chitosan composite and paraffin oil were mixed for 1 min, followed by the incorporation of the graphite powder and mixing continued for additional 30 min. A portion of the paste obtained was packed firmly into a glass tube. The electrical contact was established through a copper wire. The electrode surface was smoothed on a weighing paper before starting every new experiment.

Results and Discussion. Characterization of Iron oxide Nanoparticles Iron oxide particles synthesized by self assembly method. XRD: The X-ray diffraction pattern of iron oxide is shown in Fig. 1. Peaks are observed at -space values of these main peaks are 3.68, 2.69, 2.51, 2.29, 2.07, 1.69, 1.63, 1.48, 1.45, and 1.35 , which are corresponding to h k l planes of 012, 104, 110, 006, 202, 116, 211, 214, 300 -Fe2O3 particles [JCPDS 80-2377]. The average grain size is calculated using Scherrer formula and found to be 27 nm.

(104)

(202)

Counts

(012) (2 (006)

(116)

(110) 2

Fig. 1. XRD pattern of -Fe2O3 particles synthesized by self-assembly method.

AFM: Fig.2. Sh -Fe2O3 particles. The particles are small in size. The average diameter of the particles is found to be 27 nm.

Fig. 2.

-Fe2O3 particles synthesized by self-assembly method.

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Iron oxide particles synthesized by microwave method.

XRD: -Fe2O3 particles. Fig.3. shows its XRD pattern.

This is confirmed with the standard pattern (JCPDS 15-0615) [1]. Diffraction peaks of 2 at are observed. The d-space values of these main peaks are 3.750, 2.950, 2.642, 2.089, 1.822 and 1.638 , which are corresponding to h l planes of 106, 206, 109, 0012, 2112 and 2014 respectively. The average grain size is calculated using Scherrer formula and found to be 28 nm.

Fig. 3.

-Fe2O3 particles synthesized by microwave method.

AFM: -Fe2O3 particles is shown in Fig.4. The surface looks rough because of voids present between the particles. The size of particle is found to be small. The mean size of particles is 22 nm [4, 5].

Fig. 4.

-Fe2 O3 particles synthesized by microwave method.

Antibacterial activity of Synthesized Fe2O3-chitosan composite is characterized using XRD, UV and SEM with EDAX techniques and MMSE Journal. Open Access www.mmse.xyz

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then tested for a against gram positive bacteria (S. aureus) and gram negative bacteria (E.coli) as per AATCC 147 method. Their results are given below; XRD: The XRD pattern of -Fe2O3-chitosan composite is given in Fig. 5. It shows a single peak -Fe2O3 particles are not found.

This indicates that -Fe2O3 particles are fully incorporated within the chitosan matrix. This type of behaviour is considered as advantage for biocompatibility issue [11].

Fig. 5.

-Fe2O3-chitosan composite.

UV-Vis: The UV-

-Fe2O3-chitosan to the chitosan oligomer [12] originating from the degradation of product chitosan (Fig.6). The absorption band observed at 226 nm (curve b) may be due to the absorption and scattering of light by iron oxide particles and its characteristics of the indirect band gap of semiconductors [13]. When the iron oxide is incorporated as composite, the absorbance band at 220 nm has shifted to higher wavelength region with increased intensity. This absorption variation may be due to the association of iron oxide particles by successive loading within chitosan.

Fig. 6. UV-

-Fe2O3-Chitosan composite.

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-Fe2O3, chitosan and -Fe2O3-chitosan composite are depicted in Fig.7.

-Fe2O3 particles is shown in image a, which reveals spheroid shape and the EDAX image confirms the presence of Fe and O (image b). The porous film of chitosan containing pin holes is shown in image c; the Fe2O3 dispersed within the porous network of chitosan as composite is shown (image d) and the EDAX image confirms the presence of Fe and O (image e) in the composite[31, 32].

SEM:

-Fe2O3 Fig. 7. SEM images -Fe2O3 -Fe2O3-chitosan composite.

-Fe2O3-chitosan composite; EDAX of (b)

Antibacterial activity assessment.

-Fe2 O3 Fe2O3-chitosan was performed with Escherichia coli and Staphylococcus aureus organism (Method: AATCC 147). The result of antibacterial assessment by zone of inhibition (Fig. Fe2O3-chitosan composite has tremendous inhibitory effect against E.coli and S.aureus (Table 1) when co -Fe2O3. When the concentration of either chitosan -Fe2O3 is increased, the zone of bacterial inhibition is also increased accordingly.

Fig. 8. Antibacterial assessment against E.Coli and S.aureus organism by zone of inhibition; (1) -Fe2O3, -Fe2O3-Fe2O3-chitosan composite at higher concentration.

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Table 1. Antibacterial assessment by zone of inhibition method.

Test

Chitosan (mg)

-Fe2O3 (mg)

1

25

-

2

-

5

3

25

5

4

50

10

Test Organism

Zone of inhibition (mm)

E.coli

2

S.aureus

0.2

E.coli

0.5

S.aureus

0.2

E.coli

16

S.aureus

10

E.coli

18

S.aureus

12

Antibacterial finishing on Textile fabrics. Chitosan, -Fe2O3, -Fe2O3-chitosan composites were individually coated on textile substrates such as cotton and silk by dip-coat method. The finished fabrics were characterized by different techniques. Antibacterial activity was checked by zone of inhibition method (AATCC 147) against Staphylococcus aureus and Escherichia coli bacteria, then UV-protection activity was analyzed using UV-DRS spectroscopy.

Antibacterial activity of cotton and silk fabrics coated with -Fe2O3-chitosan composite.

-Fe2O3 as well Antibacterial activity test was performed against E.coli and S.aureus -Fe2O3-chitosan composite coated cotton and silk (Fig.9). The result by zone of inhibition shows better inhibitory effect against E.coli and S.aureus for compositeFe2O3 coated fabrics.

-Fe2O3 Fe2O3 chitosan coated silk.

-Fe2O3 -Fe2O3-chitosan coated -Fe2O3-chitosan coated silk; and activity against E. coli -Fe2O3-Fe2O3 -Fe2O3-

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Table 2. Antibacterial activity assessment by zone of inhibition method.

Compound

Fabric

Zone of inhibition (mm)

-Fe2O3 -Fe2O3-chitosan composite

Cotton

-Fe2O3-CH composite -Fe2O3 -Fe2O3-chitosan composite

Silk

-Fe2O3-CH composite

E.coli

S.aureus

17

20

28

24

35

29

12

16

26

28

34

32

-Fe2O3 -Fe2O3-chitosan is increased in coating, the zone of bacterial inhibition is also increased for both coated cotton and coated silk (Fig. 10).

Fig. -Fe2O3-chitosan composite in coating and antibacterial activity; (a) Cotton and (b) Silk tested against E.coli, (c) Cotton and (d) Silk tested against S.aureus.

-Fe2O3 -Fe2O3 Fig. 11 depicts the XRD patterns of bare electrode, and the electrodes modified with chitosan, -Fe2O3, and -Fe2O3-Fe2O3 and chitosan are observed in the composite modified electrode as evinced by comparing the XRD pattern of composite with the JCPDS 025-1402 pattern -Fe2O3 .

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-Fe2O3, (d) -Fe2O3-chitosan composite.

-Fe2O3 -Fe2O3-chitosan modified electrode was investigated using SEM (Fig. 12). The images (a-c) clearly reveal the changes in the morphology of the respective materials. The image -Fe2O3 particles are uniformly embedded in the chitosan network.

-Fe2O3

-Fe2O3-

chitosan composite.

-Fe2O3,

-Fe2O3-CH, composite carbon paste

modified electrode.

Cyclic voltammetric investigation of carbon paste electrode.

-Fe2O3 otassium ferrocyanide (2.5 mM) and aqueous potassium chloride (0.1M) at 1:1 ratio.

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-Fe2O3-chitosan is shown in Fig. 13 (a-Fe2O3 composite on the electrode surface, redox peak was observed.

(a)

-Fe2O3, chitosan and -Fe2O3-chitosan

(b)

(d)

(c)

Fig. 13. Cyclic voltammograms of carbon paste electrode containing at 50mV/s scan rate in -Fe2O3 -Fe2O3-chitosan.

-Fe2O3-chitosan composite and others, Good redox peak behaviour was obtained for the electrode containing the composite, which could be due to the presence of -Fe2O3 -Fe2O3 particles with chitosan has resulted into increased electron mobility at the electrode surface.

-Fe2O3-chitosan composite as a function of scan rate varying from 10 to 500 mV/s (Fig. 14).

The variation of the peak current with scan rate is shown in (Fig. 15). It is observed that the peak current increased linearly with the increase in scan rate (with linear regression coefficient 0.981), indicating improved redox behaviour. The slope value obtained from log ip against log plot is 0.41, which is less than 0.5. Thus, the redox reaction is considered as diffusion controlled process.

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log Current ( A)

-Fe2 O3-chitosan composite at various scan rates (10, 20, 30, 40, 50, 100, 200,300 & 500 mV/s) in KCl medium containing potassium ferrocyanide.

y = 0.4102x + 0.7954

log Scan rate mV/s

Fig. 15. Plot of log ip -Fe2O3-chitosan in carbon paste electrode. The surface parameters like surface coverage ( ), Diffusion coefficient (Do), and rate constant for electron transfer process -Fe2O3-chitosan carbon paste modified electrode was studied extensively. The surface coverage was calculated using the formula [25] is 0.9721 10-6mol-1cm-2, since the area of the 1/2 2 electrode is 0.196 cm2. The plot of ip against 1/2 (ip , r =0.982) gives the value of D0 as -3 2 -1 10 cm s (Fig. 16). The rate constant for the electron transfer process was calculated using Ep against ln 1/2 plot (Fig. 17) (Ep=0.251 ln 1/2 + 0.147, r2=0.936) and the value arrived at is ks=1.3 s- 1.

-Fe2O3-chitosan in carbon paste electrode provides fast electron transfer between the redox center of the surface of electrode.

Electrochemical impedance spectroscopy.

Electrochemical impedance spectroscopy study (EIS) of bare, -Fe2O3, chitosan, -Fe2O3-chitosan in carbon paste electrodes have been investigated in potassium ferrocyanide (2.5 mM)/KCl (0.1M) at 1:1 ratio in the frequency range 0.01-105 Hz. In the EIS, the semicircle part corresponds to the electron transfer limited process its diameter is equal to the electron transfer resistance, RCT, which controls the electron transfer kinetics of the redox probe at the electrode interface.

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Current(A)

y = 4.0911x

y = 4.0911x

1/2

1/2

.

Ep(V)

Fig. 16. Plot of iP v

y = 0.2513x + 0.1471

log Fig. 17. Plot of EP Vs log

1/2

1/2

.

Fig. 20-Fe2O3 -Fe2O3chitosan in carbon paste electrode respectively. Only a depressed semicircle is observed for bare CPE (Fig. 18), indicating a rather slow electron-transfer rate between the couple of potassium ferrocyanide (2.5 mM)/KCl (0.1M) (1:1) and the electrode surface. However, the Nyquist plot of Potassium ferrocyanide (2.5 mM)/KCl (0.1M) -Fe2O3, chitosan (Fig. 19) was quite different, which -Fe2O3-chitosan is formed of a sem composite greatly enhance the electron-transfer rate of potassium ferrocyanide (2.5mM)/KCl (0.1M) (1:1) and the conductivity of the modified electrode. The results are similar to the electrochemical behaviour of potassium ferrocyanide (2.5 mM)\KCl (0.1M) (1:1) by CVs.

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Fig. 18. Electrochemical impedance spectra of Bare carbon paste electrode.

Fig. 19. Electrochemical impedance spectra of carbon paste electrode containing chitosan.

-Fe2O3.

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-Fe2O3-chitosan composite.

Summary. Synthesis and characterization of iron oxide particles and Chitosan: -Fe2O3 Fe2O3 particles were synthesized by two different methods such as self assembled and microwave respectively. The synthesized iron oxide particles were characterized by XRD and AFM. Chitosan was prepared and characterized.

Synthesis and characterization of iron oxide-chitosan composite: -Fe2O3-chitosan composite was prepared and characterized by UV, XRD and SEM analyses.

Antibacterial activity of composite material: -Fe2O3-chitosan composite showed high antibacterial activity against S.aureus and E.coli bacteria. When compared between them, inhibitory effect with E.coli was better than with S.aureus.

Antibacterial activity in composite material coated on cotton and silk: The coated fabrics were then -Fe2O3-Fe2O3chitosan composite coated silk showed improved antibacterial activity against E.coli and S.aureus -Fe2O3 -Fe2O3 coated silk.

The coated fabrics were tested for UV protection capability. UV protection activity results (40% reflectance for uncoated material and 5% reflectance for coated material) obtained are at acceptable levels.

-Fe2O3-CH composite carbon paste modified electrodes: -Fe2O3-CH composite carbon paste modified electrodes were prepared and characterized. The electrochemical responses of this electrode have been studied in potassium ferrocyanide/KCl system using cyclic voltammetry and electrochemical impedance spectroscopy. The results of cyclic -Fe2O3-CH composite (3:1) carbon paste modified electrodes compared to bare, magnetite, chitosan composite electrodes. This type electrode can be used for binding studies and biomedical applications.

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[21] Alejandro L., Carola B., Victoria L.C., et al. (2009). Water dispersible iron oxide nanoparticles coated with covalently linked chitosan. J Mater Chem, 19: 6870 6876.

[22] Na Z., Xia Z., Weiying Y., et al. (2009). Direct electrochemistry and electrocatalysis of hemoglobin immobilized in a magnetic nanoparticles-chitosan film. Talanta; 79: 780 786.

[23] Yue W,, Yujun W,, Guangsheng L,, et al. (2009). In situ preparation of magnetic Fe3O4-chitosan nanoparticles for lipase immobilization by cross-linking and oxidation in aqueous solution. Bioresour Technol, 100: 3459 3464.

[24] Shengfu W., Yumei T., Dongming Z., et al. (2008). Amperometric tyrosinase biosensor based on Fe3O4nanoparticles chitosan nanocomposite. Biosens Bioelectron; 23: 1781 1787.

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[25] Karina D., Marcos D.V.F., Valfredo T., et al. (2008). Synthesis and characterization of the iron oxide magnetic particles coated with chitosan biopolymer. Mater. Sci. Eng., C., 28: 509 514.

[26] Kaushik A., Solankia P.R., Ansaria A., et al. (2009) Iron oxide-chitosan nanobiocomposite for urea sensor. Sens Actuators B; 138: 572 580.

[27] Cheong S.J., Leea C.M., Kim S.L., et al. (2009). Superparamagnetic iron oxide nanoparticles loaded chitosan-linoleic acid nanoparticles as an effective hepatocyte-targeted gene delivery system.

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[28] Kaushik A., Solankia P.R., Ansaria A., et al. (2008). Chitosan iron oxide nanobiocomposite based immunosensor for ochratoxin-A. Electrochem Commun; 10: 1364 1368.

[29] Singh R., Verm R., Kaushik A., et al. (2011). Chitosan iron oxide nano-composite platform for mismatch-discriminating DNA hybridization for Neisseria gonorrhoeae detection causing sexually transmitted disease. Biosens. Bioelectron; 26: 2967 2974.

[30] Liang-Shu Z., Jin-Song H., Han-Pu L., et al. (2006). Self-assembled 3D flowerlike iron oxide nanostructures and their application in water treatment. Adv. Mater.; 18: 2426 2431.

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[32] Rajendran R., Balakumar C., Mohammed Ahammed H.A., et al. (2010). Use of Zinc oxide nanoparticles for production of antimicrobial textiles. Int. J. Eng. Sci. Tech.; 2: 202 208.

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Review: Failure Detection Method of Polymer Composite Gears 1

Hailemariam Nigus 1 1

Federal TVET Institute, Addis Ababa, Ethiopia

a

hailuqua@gmail.com DOI 10.2412/mmse.54.24.7 provided by Seo4U.link

Keywords: polymers, polymer gear, reinforced polymer composite gear, test rigs, test gear.

ABSTRACT. Polymer composite gears widely used these days as substitute material for steel gear in different load conditions and devices. Its failure mode differs from gears made of steel, thus it is important to categorize the failures shown by polymer composite gears. Several previous studies noted that wear detection, surface condition monitoring, weight loss and temperature detection can be used in detecting failure of polymer composite gear. Most pure polymer gears cannot with stand high temperature, the gear simply melts instead of creating crack. This article reviews the failure detection method mentioned above. Other researcher works were studied and their findings were extracted in order to identify the methods they used. The most common method used was wear detection, temperature detection and it was supplemented by other methods such as surface condition monitoring. Failures shown by polymer composite can be concluded to be tooth breakage, tooth deformation, material removal and surface fatigue. The review also concluded that the usage of reinforced polymer materials did a considerable improvement in polymer gears strength and performance.

Introduction. Polymers are giant organic molecules made up of hydrogen and carbon atoms with a series of repeating units connected to each other. The repeating structure molecules are called as monomers. Polymers are used in different devices like gears, Polymers gears are chosen to replace steel gear in low load devices due to the technical advantage and economic gains. The advantages of polymer gear is easy to operate with small amount of lubrication, light in weight material, clean environment and low operating noise [1] compared to metal gear. However, polymer materials suffer from poor mechanical strength and low thermal resistance [2] compared with composite polymer and metal gears.

Thermoplastic Polymer composites gears developed by adding filers like Carbon fibers, glass fiber, silicon carbide and pozzolanic cement (PPC) are combined with polymer materials [5, 7, 19]. And plastic fiber resin and wound or molded it forms carbon fiber, glass fiber and silicon carbide reinforced plastics and Portland as filler material into the polypropylene matrix [7], which is extremely rigid, a very high strength-to weight and with very high heat withstanding and tolerance [3-4] of composite gears. Mao et.al. [20] has also discussed the detail fabrication of polymeric composite gears using various materials such as glass and carbon fiber reinforced Nylon 66 and Acetyl.

A wide variety of different types of polymer materials (PA, POM, etc.), different reinforcements (carbon fibers, glass fibers, nanoparticles, etc.) and internal lubricants (PTFE, MoS2, etc.) can be used to tailor a polymer for a specific application. However, due to the large number of different materials available, it is very difficult to determine the optimal material combination for a specific gear drive, especially when also considering noise and vibration properties [14-18, 28, 31, and 34].

Natural materials also utilized to reinforced polymer composites gears to focus on the ecological recycling. Rice hull is a residual product of rice and it contains natural silica [5] describes by carbonized rice hull it gives Rice- Hull-Silica-Carbon (RHSC) with high strength and low frictional 1

GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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of porous carbon material. The said research have used the RHSC as a reinforcing material in plastic gear.

Nonmetallic gear developed as an alternative to metallic gear because of their superior advantages on wear and fatigue characteristics (Duzcukoglu et al, 2009 [8], Hoskins et al., 2011 [9], Kirupasankar et al., 2012 [10] demonstrated that due to reinforcement, and residual compression stress in the tooth profile is more effectual in increasing the fatigue strength.

The load-carrying capacity, wear and fatigue life of gears are affected by many factors [1-3]. In the case of injection-molded plastic gear, the plastic materials and the bulk temperature are the most important factors [6]. The bulk temperature is easy to come close to the glass transition temperature of the plastic materials. Therefore, the plastic gears are added with reinforcing materials for keeping strength in high bulk temperature by improving heat resistance property.

Research emphasized on the effect of various parameters on the performance of the composite gear such as fiber length, gear tooth fillet radius, topography, fatigue and failure, tooth deflection, friction and wear etc.[11-14]. Few researchers determined the polymeric composite gear wear with respect to metallic gear by either bending strength or surface durability (Chauhan et al., 2010 [11]).

Gears are generally subjected to uni-directional cyclic loads; however, in applications like actuators of satellite launchers, gears experience bi-directional cyclic loads due to its rotation in both clockwise and counter clockwise directions [18]. Bidirectional and uni-directional bending fatigue performance of injection molded unreinforced and carbon fiber reinforced polyamide 66 gears were evaluated using a test rig [16-18, 29].

Composite gears of Acetyl, friction and wear performance were found to be entirely [26] dependent on surface temperature at high loads. The gear surface will wear slowly with a low specific wear rate if the gear is loaded below the critical value.

The composite gear material tested to evaluate its friction and wear characteristics in adhesive and abrasive wear modes. Weight loss due to wear of the composite gear is evaluated through direct measurement under a specific load and running condition. This is because shear strength and surface energy of the composite material changes while toughness and hardness of the material improves due to strengthening by cement fillers [7].

Polymer gear failures are different from steel and polymer composites because of the material properties of polymer are totally different from the two. An example of polymer gear failure is melting of material which does not occur for steel gears and polymer composites. This type of failure can be categorized under thermal damage [6, 7, 13, 23-27].

In this articles review influence of reinforcement on the wear resistance, hardness of polymer gears, surface temperature and tribological property is well discussed.

Experiments Test gear. To determine the strength of polymer based gears using nylon materials of different grades, test gears were developed. Different condition monitoring techniques for polymer-based gears are considered [14] for use in gear tests. The tests gears available uses Nylon (30% glass filled) with 25% Sic, Nylon 6 with 25% Sic, Nylon 66 with 25% Sic. This material were utilized in producing these gears using injection molding, fig 1 shows the injection molding machine. Based on [4] mentioned composition ratios gears of various reinforced materials were made as depicted in fig 2, 3, &4.In the process of testing, test polymer based gear was mated against the hobbled standard metal spur gear [25-27].

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Fig. 1. Injection molding machine [4].

Fig. 3. Nylon 6 + Sic [4].

Fig. 3. Nylon 66 + Sic [4].

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Fig. 4. Nylon (GF) + Sic [4].

Similarly, test gears made from polyacetal copolymer (POM) and the composite materials of POM and RHSC-particle were also developed [15]. These were made in order test the strength of poly acetyl copolymer based gears. The dopant ratio and median grain diameters of RHSC-particle are shown Table 1.

Table 1. Material for test gears [5].

Unreinforced polyamide 66 (PA) and 20 wt. % and long carbon fiber reinforced polyamide 66 (PACF) were utilized prepared by injection molding for the said test gears [18, 21, and 25] as shown in fig. 5.

Fig. 5. View of injection molded unreinforced and reinforced polyamide Gears [18].

Experimental test rig. Test gears were subjected to some experimental test to measure its strength and durability under different parameters such as: rotational speed, torque, and temperature. This MMSE Journal. Open Access www.mmse.xyz

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done with the use of experimental test rig. In gear tooth surface temperature test, temperature test uses non-contact infrared temperature sensors to indicate significant variation in gear temperature depending upon the toque transmitted, operating speed and material properties [13]. The schematic representations of this experimental apparatus as shown in Fig.6 and Fig.7 are used to measure different parameters such as rotational speed, torque and temperature for the test gears types. The synchronous speed of the motor can be set at random within the range from 300 to 1800 rpm and the rotational speed of test gear is monitored by a tachometer. To set up the testing torque, a torque meter and a powder brake were added to this equipment. During the experiment, the bulk temperature of test gear was measured by a radiation thermometer [5].

Fig. 6. Experimental apparatus and measuring system.

Fig. 7. Experimental apparatus and measuring system for spur gear pair and helical gear [5] crossed helical gears [5].

Test rig also used evaluating the bending fatigue performance of polymer composite gears. The entire system consisting of loading system, control panel, thermal camera and data acquisition, is shown in Fig. 8. The picture shown in Fig. 9 is the close-up view of test rig consists of driving and driven shafts which were suitably supported between bearings at a desired center distance.

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Fig. 8. In-house developed gear test rig [18].

Fig. 9. Gear test rig (close-up view) [18].

Polymer composite gears can be tested in much the same way as metal gears, using a back to back test configuration where the gears are loaded by winding in the torque to a prescribed level (Fig. 10) [27]. The main difference in the design of this rig is that the bearing block locating the test gears was made to pivot, with the gears loaded by a moment arm and adjustable weight. The arrangement is shown in Fig 10.

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Fig. 10. Test rig for polymer gears. [27].

The composite test gears are subjected to the dynamic test and wear loss is evaluated by weight loss measurement [7, 16]. The photographs of intact tooth profile and tooth profile after test have been given in the figure 11& figure 12.

Fig. 11. Gear pair meshing at dynamic condition [7].

Fig. 12. Measurement of a tooth temperature [16].

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The Pin on Disc machine can also consider as test rig which is used to evaluate the wear and friction characteristics as depicted in fig 13.The sliding friction test occurs between a stationary pin stylus and a rotating disk. Normal load, rotational speed, and wear track diameter can be varied [13].

Electronic sensors monitor wear and the tangential force of friction as a function of load, speed, lubrication, or environmental condition [5].

Fig. 13. Pin on Disc setup [4].

Result and discussion.

Wear evaluation and surface pitting. The results from pin on disc testing which was done to study the wear behavior and pitting of the polymer composite materials showed that surface hardness is higher and wear was less in Nylon 66 material when compared to other test gears [4] as shown in table 2.

Table 2. Test results of wear and hardness [4].

Bulk temperature. Gear surface temperatures were measured during running using an infra-red video camera [17, 20]. The picture on Fig. 14 shows an image of the running gears and the temperature changes across the face width as well as circumferentially around the gears using this method.

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Fig. 14. Surface temperature measurements [17, 20].

The bulk temperature of RHSC gear discusses in [5] increases over time and reaches equilibrium as shown in fig.15. However, the bulk temperature of POM rapidly increases after the start of rotation, peaks, and then decreases gradually, reaches equilibrium, Fig 16 shows also when the test gear is helical.

Fig. 15. Spur gear pair, Torque 3.0 Nm [5]

Fig. 16. Helical gear pair, Torque 3.5 Nm [5] The surface temperature in reinforced gear is less compared with the unreinforced polymer gear [14] due to high thermal conductivity of the glass filled nylon also contributes to increased heat dissipation as shown in fig 17.

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Fig. 17. Gear tooth surface temperature of unreinforced and glass reinforced gear [14].

The enhancement in mechanical properties of polyamide nano composite gears results in higher power transmission efficiency compared to unreinforced polyamide gears [21]. The surface temperature of reinforced polymers compared with pure polymers discussed in [16, 18, 29] ,Fig. 18 shows the net surface temperature of PA and PACF gears subjected to 8.5 Nm loads, Temperature rise of PACF gears was about 84% lesser than that of PA gears subjected to bi-directional loads [18]. It can also be seen that temperature rise in PA gear under bi-directional load was higher than uni-directional load as shown in figure 19.

Fig. 18. Surface temperatures of PA and PACF gears [18].

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Fig. 19. (a) Hysteresis loops of PA and PACF gears subjected to bidirectional load, (b) Hysteresis loops of PA and PACF gears subjected to uni-directional 8.5 Nm loads [18].

Fatigue life. Gear fail mode can be avoided by using an appropriate material pair. Fatigue can be measured by life span tests and is predictable. However, the melting of pure polymer gears, which is a consequence of high gear temperatures, is not easily predictable. For reliable and optimal gear design, gear testing cannot be avoided because the tribological interaction between gears is specific for each combination of materials [30]. Reinforced gears exhibited longer life compared with unreinforced gears due to their superior mechanical strength and thermal resistance [23]. Mao [27] performed extensive testing of different gear geometries, loads and with different material combinations.

Plastic gears are affected by heat; the average value of the gear bulk temperature during operation was used as an index to evaluate the fatigue life. The average bulk temperature represents the amount of fatigue work to the test gears during operation. Figure 20 and figure 21 represents the fatigue life by temperature index of composite gears and pure polymer gears [5].

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Fig. 20. Bulk temperature and fatigue life (Spur gear pair and helical gear pair) [5].

Fig. 21. Bulk temperature and fatigue life (Crossed helical gears) [5].

Failure mode of composite gears. Several damage mechanisms can occur on polymer gears according to the literature. The main ones are excessive tooth wear, fatigue (tooth cracking) and tooth deformation [27, 23].

The failure mechanism depends on the testing conditions (load, speed and temperature) and material combination [23]. Surface cracks were dominant in unreinforced gears subjected to low stresses. Severe deformation was observed at higher stress levels.

Wear rate also the predominate form of failure for polyacetal (POM) gears, especially above critical loads [27]. Other specific research was performed with the goal of better understanding gear rolling sliding contact [32] and gear durability [16]. The damage forms of composite and pure polymer gears are shown in Fig. 22 and Fig.23. In the case of spur gear pair, POM was melted for the frictional heat.

However, RHSC-gear was breakage [5]. The damage forms differ in existence of the RHSC particle.

Also, the damage forms of helical gear pair are approximately equal to the case of spur gear pair [5, 22-24].

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Fig. 22. Damage forms of spur gear (Torque 3.0 Nm) [5].

Fig. 23. Damage forms of crossed helical gears (Torque 0.5 Nm, Rotational speed 500 rpm) [5].

The failure mode in figure 24 (a-f) shows different loading conditions of pure polymer with different applied loads (uni directional and bi-directional) and angular speeds [18]

Fig. 24. Failure modes of PA gears [18].

Regarding, reinforced fibers are generally orient along the melt flow and boundary of the cavity. Due to the presence of reinforced fibers in the direction of crack growth, tortuous nature of path was observed on PACF gear tooth. (Figs. 25(a-d)) when subjected to both uni-directional and bi-directional loads fiber pull-out and matrix separation. Thus, both bi-directional and unidirectional loads generated similar failure in the PACF gear [18].

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Fig. 25. Failure modes of PACF gears [18].

Tooth surface. The coefficient of friction of composite materials and pure polymer gears were tested [7] in different loading conditions as a result the reinforced polymer shows less coefficient of friction as depicted in fig 26 and 27.

Fig. 26. Coefficient of friction evaluated for an applied load (a) 19.6 and (b) 29.4 N [7].

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Fig. 27. Coefficient of friction on abrasive mode under applied load (a) 9.8 N and (b) 19.6 [7].

The influence of normal load and sliding velocity, coefficient of friction and specific wear rate is plotted against two different applied normal loads during wear test . The coefficient of friction, of all the gear materials for adhesive and abrasive wear properties, decreased with increase in normal load as shown in Figure 28 and Figure29. Further, it is observed that under same loading conditions , PPC reinforced composite gear materials exhibit less specific wear rate than unreinforced polypropylene, comparable to abrasive wear as well. The same trend has also demonstrated in the Figure 29. It is observed that 10% cement filled composite material exhibits less specific wear rate than pure polypropylene.

Fig. 28. Specific wear rate with applied Normal load in adhesive wear.

Fig. 29. Specific wear rate with applied normal load in abrasive wear [7].

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From both intact edge profile and edge profile after test, are taken into account, and the weight loss due to wear and wear volume have been calculated for all the samples for two variable loading conditions i.e. 13.5 N and 8.5 N. The graphical expressions for both the cases are highlighted in the Figures 30-31 and Figures 32-33 respectively. Weight loss due to wear and wear volume of pure polypropylene gear is showing the highest value at elevated rpm. At 2500 rpm, both the parameters, weight loss due to wear and wear volume are highest in comparison with other running speeds. The reason is that the engaged tooth pair comes in contact more frequently when the running speed is 2500 rpm as compared to other variable speeds. Due to repeated contact, more friction takes place between the common tooth pair with less time as compared to other speeds.

Fig. 30. Weight losses due to wear at different rpm with 13.5 N loads [7].

Fig. 31. Weight losses due to wear at different rpm with 8.5 N loads [7].

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Fig. 32. Wear volume at different rpm with 13.5 N loads [7].

Fig. 33. Wear volume at different rpm with 8.5 N load [7].

Influence of reinforcement on gear efficiency. Providing unreinforced materials on gear molding has mattered on its efficiency. Reinforced gears exhibit less tooth deflection than unreinforced ones for the same loading condition due to the superior material modulus [22, 24]. During testing, repeated gear tooth deflection and material hysteresis contribute to an increase in gear temperature. [21] Discussed an increase in torque increases the gear pair efficiency, as shown in Figs. 34 and 35.

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Fig. 34. Efficiency of unreinforced nylon 6/6 gears tested at (a) 1.5 Nm torque and 1000 r/min and (b) 2 Nm toque and 1000 r/min [21].

Fig. 35. Efficiency of carbon-fiber-reinforced nylon 6/6 gears tested at (a) 1.5 Nm torque and 1000 r/min and (b) 2 Nm toque and 1000 r/min [21].

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Summary. Hence, it can be effectively concluded that the usage of polymer material and the addition of reinforced material did considerably improve the polymer gears strength and performance.

The advantage of using composite gears is the inability of gears requirements. The composite which has carbon fiber matrices has better mechanical properties, higher specific strength (strength to density ratio), higher specific modulus, and better fatigue and wear resistance compared to metals. It has also higher specific energy absorption, which is imperative in low load gear design, due to the fact that it will reduce weight, cost, noise and vibrations. Moreover, polymeric matrix composites (PMC) have limited transmission gearing and low loading abilities. The polymer composite gears and pure polymer gear failure mode is different. Polymer composite gear failure can be wear or fatigue. Fatigue can be measured directly by life tests, but wear needs to be continuously recorded by test rigs.

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[15] Yousef S.S., Burns.D.J, Mckinlay W., Techniques for assessing the running temperature and fatigue strength of thermoplastic gear, Mechanism and Machine Theory, 8, 175-85, 1973. lu, PA 66 spur gear durability improvement with tooth width modification, Materials and Design 30 (2009) 1060 1067 [17] K. Mao et al., Polymer gear surface thermal wear and its performance prediction, Tribology International 43 (2010) 433 439 [18] M. Kodeeswaran et.al, Bi-Directional and Uni-Directional Bending Fatigue Performance of Unreinforced and Carbon Fiber Reinforced Polyamide 66 Spur Gears, international journal of precision engineering and manufacturing vol. 17, no. 8, pp. 1025-1033 [19] R. Vigithra, Design and Analysis of Nano Composite Spur Gear, ARPN Journal of Engineering and Applied Sciences, Vol. 10, No. 11, June 2015 [20] K. Mao, A new approach for polymer composite gear design, science direct Wear 262 (2007) 432 441 [21] S. Senthilvelan, R. Gnanamoorthy, Efficiency of injection-moulded polymer composite spur gears, Technical Note 925.

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[26] N.A. Wright, S.N. Kukureka, Wear testing and measurement techniques for polymer composite gears, Wear 251 (2001) 1567 1578 [27] K. Mao, W. Li, C.J. Hookec, D. Walton, Friction and wear behavior of acetal and nylon gears, Wear 267 (2009) 639 645.

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Thermal Load Analysis and Comparison of Total Heat Flux and Temperature Distribution Between Carbon Graphite and Aluminum Alloy 4032 Pistons using FEA Technique (Research) Jatender Datta1, Sahib Sartaj Singh2 1

Research Scholar, PhD (Mechanical Eng.), Desh Bhagat University, Mandi Gobindgarh, India

2

Workshop Suptt., Punjabi University, Patiala, India DOI 10.2412/mmse.48.77.368 provided by Seo4U.link

Keywords: piston analysis, thermal load on piston, cast alloy steel piston, piston properties, finite element method, analysis on piston.

ABSTRACT. This paper describes the results of thermal load applied on the pistons made by aluminum alloy 4032 and carbon graphite by using finite element Analysis (FEA) .The parameters used for the simulation are operating gas temperature and material properties of pistons. The specifications used for the study of these pistons belong to four stroke 100cc hero bike engine. This paper illustrates the procedure for analytical design of aluminum alloy, and carbon graphite pistons using specifications of four stroke 100cc hero bike engine. The results predict the Total Heat Flux, Temperature distribution and critical region on all of these pistons using FEA with Temperature of 200 degree Celsius on the top of piston. It is important to locate the critical area and advantages/disadvantages of both materials. The 3D modelling of piston is done in Solidworks (Feature module) and Simulation module used to mesh the pistons, thermal analysis with temperature applied on the top of piston head.

Introduction. Piston is a cylindrical member which is placed inside cylinder and on the combustion gases exerts pressure. It is made up of cast iron or aluminium alloy. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings.

It absorbs the side thrust resulting from obliquity of the connecting rod. It also dissipates the large amount of heat generated by the combustion gases form the combustion chamber to the cylinder wall.

In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder wall.

FEA (Finite Element Analysis).

Finite element analysis (FEA) is the modelling of products and systems in a virtual environment, for the purpose of finding and solving potential (or existing) structural or performance issues. FEA is the practical application of the finite element method (FEM), which is used by engineers and scientist to mathematically model and numerically solve very complex structural, fluid, and multiphysics problems.

FEA software can be utilized in a wide range of industries, but is most commonly used in the aeronautical, biomechanical and automotive industries.

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Volumetric Properties.

Table 1. Aluminum Alloy 4032.

S. No

Properties

Value

1

Mass

0.072 kg

2

Volume

2.72e-005m3

3

Density

2680 kg/m3

4

Weight

0.71 N

Properties

Value

1

Mass

0.060 kg

2

Volume

2.72e-005m3

3

Density

2240 kg/m3

4

Weight

0.59 N

Table 2. Carbon Graphite.

S. No

Mechanical Properties.

Table 3. Aluminum Alloy 4032.

S. No

Properties

Value

1

Poissons ratio

0.34

2

Thermal expansion coefficient

1.94e-005/K

3

Density

2680 kg/m3

4

Thermal conductivity

138 W/(m-K)

5

Specific heat

850 J (kg-K)

Properties

Value

1

Poissons ratio

0.28

2

Thermal expansion coefficient

1.3e-005/K

3

Density

2240 kg/m3

4

Thermal conductivity

168 W/(m-K)

5

Specific heat

44 J (kg-K)

Table 4. Carbon Graphite S. No

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Table 5. Engine Specifications.

Type

Air cooled, 4 - stroke single cylinder OHC

Displacement

97.2 cc

Max. Power

6.15kW (8.36 Ps) @8000 rpm

Max. Torque

0.82kg - m (8.05 N-m) @5000 rpm

Max. Speed

87 Kph

Bore x Stroke

50.0 mm x 49.5 mm

Carburettor

Side Draft , Variable Venturi Type with TCIS

Compression Ratio

9.9 : 1

Starting

Kick / Self Start

Ignition

DC Digital CDI

Oil Grade

SAE 10 W 30 SJ Grade , JASO MA Grade

Air Filtration

Dry , Pleated Paper Filter

Fuel System

Carburettor

Fuel Metering

Carburetion

Reverse Engineering the Piston.

With the help of measuring instruments like vernier calliper etc. the dimensions of the model piston were measured. By using this measurement 3D model of the piston were drawn using Solidworks 3D modelling software as below:

Fig. 1. Model of Piston.

Boundary Conditions and Loads.

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Applied Temperature value of 200 degree Celsius on the top of piston. Note: Units, boundary conditions and loads will be same in both tests.

Meshing of Piston.

Table 6. Mesh Information.

Mesh type

Solid Mesh

Mesher Used:

Standard mesh

Automatic Transition:

Off

Include Mesh Auto Loops:

Off

Jacobian points

4 Points

Element Size

2.94563 mm

Tolerance

0.147281 mm

Mesh Quality

High

Table 7. Mesh Information Details.

Total Nodes

26221

Total Elements

14224

Maximum Aspect Ratio

90.342

% of elements with Aspect Ratio < 3

84

% of elements with Aspect Ratio > 10

0.443

% of distorted elements (Jacobian)

0

Time to complete mesh (hh;mm;ss):

00:00:07

Fig. 2. Meshed Model.

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Table 7. Properties Study.

Study name

Study 1

Analysis type

Thermal(Transient)

Mesh type

Solid Mesh

Solver type

Direct sparse solver

Solution type

Transient

Total time

1 Seconds

Time increment

0.1 Seconds

Contact resistance defined

No

Result folder

SolidWorks document (C:\Users\JATENDER DATTA\Desktop\desk new)

Table 8. Units.

Unit system:

SI (MKS)

Length/Displacement

mm

Temperature

Kelvin

Angular velocity

Rad/sec

Pressure/Stress

N/m2

Results and Discussions.

Figure (3) Maximum temperature shows on the top of the piston and distribute of temperature shown until slightly down of 3rd piston ring groove due to heat produce by the gases in block.

Figure (4) Maximum temperature 200 deg. elsius shows on the top of the piston and distribute of temperature until last as 108 deg. Celsius due to heat produce by the gases in block.

Fig. 3. Temperature Distribution for Aluminum Alloy 4032.

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Fig. 4. Temperature Distribution for Carbon Graphite.

Fig. 5. Total Heat Flux for Aluminum Alloy 4032.

Fig. 6. Total Heat Flux for Carbon Graphite.

Figure (5) it shows the maximum total heat flux in the piston due to the application of gases is 23.5 MW/m2 which is observed on the 3rd groove of piston ring and heat flow graphics shown till the holes just down the 3rd groove.

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Figure (6) it shows the maximum Total heat flux in the piston due to the application of gases is 4.92 MW/m2 which is observed on the 3rd groove of piston ring and heat flow graphics shown till just down the piston pin hole.

Summary. According to the results maximum heat transfer occurs in the piston made of Carbon Graphite as compared to Aluminum alloy 4032 due to the higher thermal conductivity.Furthermore, according to volumetric properties, Carbon Graphite material is much lighter than aluminium 4032.

Moreover, other advantage of carbon graphite piston is that Carbon shows an excellent resistance to thermal shock and exhibits self -lubricant properties which increase the operational reliability of the engine and result in reduced lubricant consumption.

Carbon graphite has low thermal expansion coefficient as compared to aluminium 4032. At last, Carbon Graphite is much better than aluminium alloy 4032 as Piston material and suitable for IC engine.

References [1] Ekrem Buyukkaya (2008), Thermal Analysis of functionally graded coating AlSi alloy and steel pistons, Surface and Coatings Technology 202(16):3856-3865, DOI 10.1016/j.surfcoat.2008.01.034 [2] P. Carvalheira, P. Goncalves, FEA of Two Engine Pistons Made of Aluminium Cast Alloy A390 and Ductile Iron 65-45-12 Under Service Conditions, 5th International Conference on Mechanics and Materials in Design Porto-Portugal, 24- 26, pp .1-21, 2006.

[3] C.H. Li, Piston thermal deformation and friction considerations, SAE Paper, vol. 820086, 1982, DOI 10.4271/820086 [4] Properties And Selection: Irons, steels and high performance alloy, ASM Handbook, vol. 1, ASM International, 1990.

[5] A.C. Alkidas, Performance and emissions achievements with an uncooled heavy duty, single cylinder diesel engine, SAE, vol. 890141, 1989, DOI 10.4271/890144.

[6] A.C. Alkidas, Experiments with an uncooled single cylinder open chamber diesel, SAE Paper, vol. 870020, 1987, DOI 10.4271/870020 [7] M. Srinadh, K. Rajasekhara Babu (2015), Static and Thermal Analysis of Piston and Piston Rings, International Journal of Engineering Technology, Management and Applied Sciences, 3 (8), 51-58.

[8] Mandeep Singh, and Manish Bhargava - Analysis and Comparison of Different Materials for a Single Cylinder Four Stroke 225cc Piston using FEA Vol.6, No.4 (Dec 2016)

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Jatropha: an Alternate of Diesel Bio-Diesel For Combustion in IC Engine 1

Pravesh Kumar Srivastava 1, a, Nishant Kumar Srivastava1, b, Harsh Srivastava1, c, Suresh Kumar Gigoo1, d 1

Rajarshi Rananjay Sinh Institute of Management & Technology, Amethi, India

a

mechanical.hod@rrsimt.ac.in

b nishantsrivastava@rrsimt.ac.in c

harshsrivastava32@gmail.com

d

director@rrsimt.ac.in DOI 10.2412/mmse.32.88.61 provided by Seo4U.link

Keywords: biodiesel, specific gravity, indicated power generation.

ABSTRACT. With the rapid growth in consumption of petroleum products in last 3 decades it has been a major concern to estimate the uses and also seeking for other alternate fuels, since we have very limited resource of petroleum product and their rapid consumption rate because of technological advancement. The situation arises where it is essential to look ld develop such a fuel which may be environmental friendly and also can be used with the similar specification of transportation industry. In the present paper the sole concern is to introduce a cleaner alternate fuel which will certainly eliminate the dependency of conventional fuel (petrol, diesel etc.) and provides a cleaner environment. Bio-diesel prepared from the seeds of Jatropha has been tested in 4-cylinder engine and the engine performance and results have been analyzed to get the clear specification of an environmental friendly fuel.

Introduction. In the current era, industries and automobile sector solely dependent on the nonrenewable resources. There resources are expected to be exhaust very soon because of their consumption rate and dependency. The enhanced demand of the petroleum product caused a severe threat to the environment thereof essentially it is required to search for alternate fuel to diminish the complete load from petroleum. In the presented paper the bio-diesel prepared from the seeds of Jatropha is considered to the most suitable alternate fuel. Many researches have successfully tested this bio-diesel to be the best alternate fuel. This paper gives the theoretical as well as the experimental demonstration of bio-diesel and engine performance is analyzed. With the growth of industrialization, world needs an alternate of petroleum because the more need of transportation system requires huge quantity of fuel but as we do have limited resources and their day by day depletion causes threatening situation which demanded an alternate fuel which can easily be obtained. Bio- diesel are the best substitute of the petroleum resources, the major advantage is that they are renewable and available at low cost. They are not only affordable but also have low carbon content so produce less CO2 and CO. Having such specification bio-diesel is environmental energy source. It can produce same power as the compared with diesel in conventional diesel engine. Bio-diesel can be prepared from many vegetables like neem, sunflower, coconut, linseed etc., but among all Jatropha is consider to be most suitable because of its low cost and availability. It can be harvested in all agro-climate condition and can also be grown in low and high rainfall region, therefore it ensure the production at very low cost.

Jatropha can be mixed in any ratio with diesel but 5 to 20% blending is the best suited ratio whereas direct use of Jatropha oil in diesel engine can cause some problem because of its high viscosity but chamber. The present paper attempts to review the work performance of diesel engine using Jatropha.

1

-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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Since with the rapid growth in the consumption of fossil fuel in automotive sector is resulting into the climate change which is considered to the most concerning issue of the century, recent studies shows that emission of greenhouse gases to the atmosphere contribute to increase the global mean promoted the use of renewable energy sources. This resources are capable enough to reduce the dependency on crude oil. The present paper is restricted only to the bio-diesel as a substitute, it can be obtained from various non-edible seed plant but Jatropha gives the satisfying results thus analysis and experimentation is carried out with neat bio-diesel prepared with the transesterification process depending upon its FFA content for the production of bio-diesel that can be used to operate CI engine.

A. Material: 1. Bio diesel (Jetropha) 2. Test Rig 3. Tachometer Availability of Fuel. This bio-diesel is derived natural oils like vegetable oils. It can be used as a fuel at varying blended ratio with petroleum based diesel engine or can simply be used as a neat. This biodiesel is prepared from raw vegetable oil extracted from seeds of Jatropha by a chemical process of transesterification which remove glycerol from the oil. Jatropha is a low cost seed which is rich in oil content and have small gestation period which grows on rich or degraded soils and not only this these plants can grow in low and high rainfall region as well. Seed of Jatropha are harvested in the dry season, it can yield up to 10 times the amount oil as other sources of bio-diesel can. The most beneficiary aspect of Jatropha 0 years without replanting. The Jatropha plant bears fruit from the second year of its plantation and economic yield stabilizes from the 4th year or onward. The economic yield can be considered as 0.75-2 kg/plant and 4-6 tons per hectare per year depending upon the agro-climate conditions of the region and agricultural practices.

India has vast stretches of degraded land, mostly in areas with unsuitable climatic conditions where Jatropha can easily be grown with adverse climatic condition. The use of 11 million hectare of waste land can give 12 million jobs by cultivation of Jatropha thereof its commercial cultivation is seeking for the demand.

Characteristics of fuel. Bio-diesel is mono-alkyl ester made from non-edible vegetable oil. The biodiesel is similar in fuel characteristic to conventional diesel oil obtained from crude oil. It is compatible with petroleum diesel and can be blended in any ratio with diesel to obtained suitable blend. It is highly oxygenated fuel which results in better combustion and engine performance and flame temperature as compared to diesel and emit lesser gaseous emission. Higher flash point makes the storing of bio-diesel less risky than diesel.

Table 1. Characteristics of fuel.

Sl. No. 1.

2.

3.

4.

5.

6.

7.

8.

Characteristics Specific gravity Kinematic viscosity at room temp. (m2/sec) Dynamic viscosity (N-sec/m2) Cetane number

Calorific value (kj/kg) -15

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Quantity 0.87 - 0.9 0.14 x 10-4 12.5 x 10-3 46 - 70 150 158 40105 13

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Table 2. Comparison of fuel properties of diesel and bio diesel.

Sr. No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Fuel Properties Fuel standard Fuel composition Lower heating value (MJ/kg) 3

)

Water (by wt.) (ppm) Carbon (wt%) Hydrogen (wt%) Oxygen (wt%) Sulphur (wt%)

Cetane number Stoichiometric air/fuel ratio (w/w)

Diesel

Bio-Diesel

ASTM D 975 C10-21 HC 42.52 1.3-4.1 848 161 87 13 0 0.05(max.)

188 to 343 60 to 80 -15 to 5 -35 to -15 40 to 55 316 15

ASTM D 6751 C12-22 FAME 37.12 1.9-6.0 878 0.50 % (max) 77 12 11 0 182 to 338 100 to 170 -3 to 12 -15 to 16 48 to 60 N.A 13.8

Experimental Procedure Table 3. Experimentation setup: engine specification.

Sl. No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Specification Engine type Capacity Bore x stroke: Bore/stroke ratio Double overheadcamshaft Maximum power Specific outout Maximum torque Specific torque Break mean effective power Engine coolant Unitary capacity Aspiration Intercooler Catalytic convverter Weight to power ratio

Capacity Naturally aspirated engine 1.4 Lit. 1396cc (85.189 cu in) 75x79 mm, 2.95x3.11 in 0.95 4 valve per cylinder ,16 valve in total 54 PS (52.8 bhp) (39 kW) at 5500 rpm 37.5 bhp/litre, 0.62bhp/cu in.

85 N-m(63 ft-lb)(8.7 kgm) at 2500 rpm 60.89 N-m/litre (0.74 ft-lb/cu3) 765.1 kPa (111 psi) Water 349 cc Normal D None Y 25.27Kg/kw, (42.21lb/bhp) 53.8 PS/g , 39.57 kw/g , 53.07 bhp/ton,0.02bhp/lb.

Power to weight ratio

Procedure of Test Rig. The experimental investigation carried out in a 4-cylinder, 4-stroke air aspirated water cooled diesel engine developing power 39 kW at 5500 rpm was used. The engine specification as mentioned above. An eddy current dynamometer was used for loading engine.

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The fuel level and lubrication oil level were checked and a three way cock is opened to allow the flow of fuel into the engine.

The cooling water is supplied to the engine cooling water jackets and to the brake drum.

The electrical power is supplied to the panel instrumentation.

The engine is de-compressed by a decompression lever provided on the engine head.

The engine is unloaded by removing the weight from the hanger and started by cranking.

The experiment is repeated for different loads several times.

Fig. 1. Schematic diagram of test rig.

Parameters to be determined. Indicated power.

Indicated power of an engine, the useful work performed by gases in the cylinder of a piston engine per unit time, it is determined by the analysis of indicator cards made during engine test. The indicated power of a given engine is different under different operating conditions. The relation of indicated power to the frequency of revolution is called the speed characteristics. Indicator cards are read at various frequencies of revolution in order to plot the speed characteristic of the indicated power. The indicated power at given frequency of revolution is determined by measuring the area of the cards.

The indicated power is partially consumed in overcoming the frictional force within the engine and setting the auxiliary mechanisms in motion. The indicated power may be defined as the sum of power produced at crankshaft (actual horsepower) and the power consumed by losses (friction horsepower).

Friction Power.

An engine has moving parts that produce friction. Some of these friction forces remain constant (as long as the applied force is constant), some of these friction losses increase as engine speed increases, such as piston side forces and connecting bearing forces (due to increased inertia forces from the oscillating piston). A few friction forces decrease at higher speed, such as the friction force on the the cam follower away from the cam lobe). Along with friction forces, an operating engine has pumping losses, which is work required to move air into and out of the cylinders. This pumping loss is minimal at low speed, but increase approximately as the square of the speed, until at rated power an engine is about 20% of the total power production to overcome friction and pumping losses.

Break Power.

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Brake power is the power output of the drive shaft of an engine without the power loss caused by gears, transmission, friction, etc., well as other terms.

The power developed by an engine and measured at the output shaft is called the brake power (bp).

An IC engine is used to produce mechanical power by combustion of fuel. Power is referred to as the rate at which work is done. Power is expressed as the product of force and linear velocity or product of torque and angular velocity. In order to measure power one need to measure torque or force and speed. The force or torque is measured by dynamometer and speed by tachometer. Brake power is less than indicated power.

Performance Analysis.

Performance of engine is slightly lesser as compared to diesel. Accordingly to improve the performance, the injection process which ensures the better atomization of fuel in combustion chamber as bring out complete combustion phenomenon with perfect delay period. The major advantage with bio-diesel is that it can be blended in any ratio for better performance and increased lubricity makes better running of vehicle.

Fig. 2. Model Graph

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Calculation. Indicated Power.

(1) (2) (3) (4)

Where Pi Engine indicated power; Imep

Indicated mean effective power (N/m2);

Ac Cylinder area (m2); L

Stroke length (m);

n

Number of cylinders;

N Engine speed (rpm) z = 1 (for 2-stroke engines), 2 (for 4-stroke engine) Vc cylinder swept volume (m3) Ve engine swept volume (m3).

Engine Mechanical Efficiency ( m):

(5)

Where

Engine break power;

Engine Specific Fuel Consumption (SFC): (6) Engine Thermal Efficiency:

(7) Where Pb brake power; FC

fuel consumption (kg/h);

CV

calorific value of fuel.

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Test Readings.

Table 3. Experimentation Setup: Engine Specification.

Sl. No 1 2 3

Trials 1st 2st 3rd

Diesel (N) 935 rpm 890 rpm 930 rpm

Biodiesel (N) 862 rpm 845 rpm 820 rpm

4

Average performance

910 rpm

845 rpm

Indicated Power with normal diesel: 32398.4 w (or 32.39kw or 43.45hp at 910 rpm) Indicated Power with Biodiesel: 30084.24 w (or 30.08kw or 40.45hp at 845 rpm) Result and Discussion: Power using bio-diesel gives 30.8 kW power whereas in the case of normal diesel it is 32.49 kW which is slightly greater than the power developed by the biodiesel which clearly indicates that if we use biodiesel as a replacement of diesel then we will have to face this loss in power whereas the efficiency is same with both of the fuel. Advantages of diesel blend are as follows: As biodiesel is low on cost as compare to normal diesel. Its cost as a fuel 45rupee/litre while in bulk as a crude biodiesel it cost around 6 rupee/litre which is far more less than the gasoline.

As 1% blend of biodiesel improves lubricity 65% so smooth functioning of engine.

Exhaust contain very low amount of harmful gases so it is considered as a green fuel.

Due to high lubricity engine clogging is nearly eliminated which reduces maintenance cost.

Engine life is increased.

In countries where most of the time temperature is above 25 there is no need of any change in engine or any engine modification while in other countries where temperature is low a thermostatic tank is used as a required change for easy cold starting.

It is clean fuel as well as efficient too.

Table 4. Engine efficiency depending on diesel and biodiesel fuel.

Sl. No.

Entity

Diesel

Biodiesel

1

Power

32.48 kW

30.8 kW

2

Cost

60 INR/liter

10 INR/liter

Summary. The use of biodiesel will lead to loss in engine power mainly due to the reduction in heating value of biodiesel compared to diesel and it results in the increases in biodiesel fuel consumption. From the review it can be concluded that the use of biodiesel favors to reduce carbon deposits and wear of the key engine parts, compared with diesel. It is attributed to the lower soot formation, which is consistent to the reduced PM emission of biodiesel, and the inherent lubricity of biodiesel. This increase is mainly due to higher oxygen content for biodiesel. Moreover, the cetane number and different injection characteristics also have an impact of NOX emission for biodiesel. It is accepted commonly that CO emission reduces when using biodiesel due to higher oxygen content and the lower carbon to hydrogen in biodiesel as compared to diesel. It is predominant view point that HC emission reduce when biodiesel is fuelled instead of diesel. This reduction is mainly MMSE Journal. Open Access www.mmse.xyz

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contributed to the higher oxygen content of biodiesel, but the advancement in injection and combustion of biodiesel also favor the lower THC emission. The further improvement in production of biodiesel should be performed in the future to promote.

References [1] Jayant Arbune, Shyam Manatkar, Neha Koparde, Manjiree Hingane, Abhijeet Ghadge (2014), Performance and emission analysis of biodiesel (Jatropha+chicken fat) on diesel engine, International Journal of Research in Engineering & Technology, 2(5), 81-90.

[2] Jinlin Xue, Tony E.Grift, Alan C.Hansen (2011), Effect of biodiesel on engine performance and emission, Renewable and Sustainable Energy Reviews, 15(2), 1098-1116, DOI 10.1016/j.rser.2010.11.016 [3] Dou D., Balland J. (2002), Impact of Alkali Metals on the Performance and Mechanical Properties of NOx Adsorber Catalysts, SAE Technical Paper 2002-01-0734, DOI 10.4271/2002-01-0734.

[4] Lisi L., Lasorella G., Malloggiand S., Russo G (2004). Single and combined Deactivating effect of Alkali Metals and HCL on commercial SCR Catalyst, Applied Catalysis B: Environmental, 50(4), 251-258, DOI 10.1016/j.apcatb.2004.01.007 [5] Cavataio G., Jen H., Dobson D., Warner J. (2009), Laboratory Study to Determine Impact of Na and K Exposure on the Durability of DOC and SCR Catalyst Formulations, SAE Technical Paper 2009-01-2823, , DOI 10.4271/2009-01-2823.

[6] Tatur, M., Nanjundaswamy, H., Tomazic, D., and Thornton, M., Effects of Biodiesel Operation on Light-Duty Tier 2 Engine and Emission Control Systems, SAE Int. J. Fuels Lubr. 1(1):119-131, 2009, DOI 10.4271/2008-01-0080.

[7] Donepudi Jagadish, Puli Ravi Kumar, K. Madhu Murthy (2011), The effect of supercharging on Performance and emission characteristics of C.I engine with Diesel-Ethanol-Ester Blends, Thermal Science, 15 (4), pp. 1165-1174, DOI: 10.2298/TSCI100513042J [8] S. Jindal, B.P. Nandawana, N.S. Rathore, V. Vasistha (2010), Experimental investigation of the effect of compression ratio and injection pressure in a direct injection diesel engine running on Jatropha methyl ester Applied thermal engineering, 30(5), 442-448, DOI 10.1016/j.applthermaleng.2009.10.004 [9] Deepak Agarwal, Avinash Kumar Agarwal et al. (2007), Performance and emissions characteristics of Jatropha oil (preheated and blends) in a direct injection compression ignition engine, Applied Thermal Engineering, 27(13), 2314-2323, DOI 10.1016/j.applthermaleng.2007.01.009 [10] Wang Ying, Zhou Longbao (2008). Experimental study on Exhaust Emissions from a multicylinder DME engine operating with EGR & Oxidation Catalyst. Applied Thermal Eng., 28 (13), 15891595, DOI 10.1016/j.applthermaleng.2007.10.018 [11] P.P. Sonune, H.S. Farkade et al. (2012): Performance and Emissions of CI Engine Fuelled With Preheated Vegetable Oil and its Blends A Review, International Journal of Engineering and Innovative Technology (IJEIT), 2(3), 123-128.

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A Review on Air Preheater Elements Design and Testing 1

Akash Kumar Modi1,a, Azharul Haque1, Bhanu Pratap1, Ish Kumar Bansal1, Prasoon Kumar1,b, S. Saravanan1,c, M. Senthil Kumar1,d, C. Ramesh Kumar1,e 1

VIT University, Vellore, India

a

akashkumar.modi2013@vit.ac.in

b

prasoon.kumar2013@vit.ac.in

c

saravanan.s2015@vit.ac.in

d

msenthilkumar@vit.ac.in

e

crameshkumar@vit.ac.in DOI 10.2412/mmse.86.90.615 provided by Seo4U.link

Keywords: air pre heater, Ljungstrom air-preheater, heating elements, Reynolds number.

ABSTRACT. This review paper is based on theories and complications related to air-preheater & the heat transfer surfaces used in it. Numerous papers and sufficient amount of literature were gone through to understand how an airpreheater is designed and the performance parameters associated with the same. Air-preheaters (APH) are heat exchangers, which are used to pre-heat the air before any other process takes place. APH finds its wide use in power plants, automobiles and all such areas where there is a need to pre-heat the air and save fuel. A thorough survey was also done on the heating elements or surfaces used in air-preheaters for the transfer of heat between cold and hot fluid. Various types of widely used profiles were identified first and a research was then conducted to find out how the experimental investigation of heat transfer plates can be done. Excerpts have also been provided regarding the design of experimental setup for the same and the dependence of various parameters on one another. The paper is concluded with an opinion on the use of plate profiles for air-preheater.

Introduction.

1

-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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APH Design

As shown in Fig.1, RAPH consists of a central rotor which is connected to the element baskets or rotating baskets. Within the element baskets, the heating elements/plates are kept in stacks. As the rotor rotates, the baskets also rotate with the rotor surrounded by a rotor shell. The area of the RAPH MMSE Journal. Open Access www.mmse.xyz

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is divided into two parts as shown in Fig.2 (bi-sector), 3 parts (tri-sector) 4 parts (quad-sector) etc. In case of bi-sector APH, flue gas passes through one sector while the cold gas passes through the other sector. The rotation of baskets ensures that all the plates are subjected to both hot as well as cold air.

The hot flue gas heats up the plates corresponding to its sector; the same heat gets transferred to the cold air by the plates as the basket rotates. Again, the plates get heated up as they come across the sector of flue gas. In case of tri-sector apart from flue gas sector, we have two other sectors for primary air (conveys pulverized coal to the furnace) and secondary air (air for combustion). This type of APH is also known as Ljungstrom air-preheater.

Warren [4] published his studies on Ljungstrom air preheater and based on the experimental results, he confirmed a minimum reduction of 10% in power plants fuel consumption. Heidari et al. [5] investigated RAPH in 3-D and treating it as a porous media with the help of fluent software. They highlighted the effect of factors such as rotational speed of the matrix, mass flow rate of fluid, matrix material and temperature of the incoming air on the performance of the preheater. Wang et al. [3] made use of semi analytical method to examine the 3-dimensional heat transfer of tri-sectional rotary air preheater. In this paper, main focus was on the temperature distribution of the matrix.

Stationary plate regenerative air-pre heater - The plates or heating elements are stationary in this case as compared to a rotating air preheater. Instead, the ducting system of inlet air and outlet air is made rotary so that all the plates are exposed to both hot and cold air. Such an air-pre heater is also known as Rothemuhle Air-pre heater.

Tubular type APH it consists of a nest of straight tubes that are roll expanded or welded into tube sheets and then enclosed in a steel casing. This casing serves as an enclosure for fluid or gas passing outside the tubes and has got both air and gas inlet-outlet openings. An expansion joint between the floating tube sheet and casing provides an air/gas seal. Intermediate baffle plates parallel to the tube sheets are frequently used to separate the flow paths and eliminate tube damaging flow induced vibration [1]. The most common flow arrangement in tubular APH is the counter flow of fluids in which flue gas passes vertically through the tubes and air passes horizontally through one or more passes outside the tubes. Provisions are frequently provided in the design for the bypass of cold air or recirculation of hot air in order to control cold end corrosion and ash fouling.

Pressure drop: in recuperative air-preheaters, frictional loss during flow; inlet and exit shock losses as well as losses during return bends in flow passage contribute towards pressure drop. Pressure drop is directly proportional to the square of the mass flow rate of air.

Leakage: recuperative units may begin operation with essentially zero leakage, but leakage occurs as time and thermal cycles accumulate. With regular maintenance, leakage can be kept below 3%.

Approximate air heater leakage can be determined based on gas inlet and outlet oxygen (O2) analysis (dry basis).

Plugging and Erosion: plugging is referred to as fouling and the closing down of heat transfer flow passage by gas which is enriched with ash particles and corrosion products, whereas erosion is the removal of a material layer because of high velocity dust particles. It usually occurs at the gas inlet where the velocity is high. The consequences of erosion are dangerous such as structural weakening, loss of heat transfer area and perforation of components, which may result in air to gas leakage.

Erosion can be controlled by reducing the velocities, removing the affected material, galvanization or by using a sacrificial material. In an APH, the cold end flue gas temperature is designed for acid due point. Once the coal is burnt completely [6], sufficient alkaline fly ash is available which can absorb the acid (H2SO4) thus preventing fouling, corrosion of air-preheater and ducting [7]. If ash to

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Fig. 2. Rotary APH [47].

The main requirements of an APH are high heat transfer rate, low pressure drop and low sensitivity to fouling. These features mainly depend upon the profile of heating elements used.

APH Performance. The performance of a Ljungstrom air-preheater largely depends upon the geometry or profile of the heating elements used in it. The profiles are designed in such a way that it increases the efficiency of the air-preheater along with decrease in fouling rate and pressure drop.

Sreedhar Vulloju et al. [8] proved that the performance of a Ljungstrom air-preheater gets affected with the profile of the heating elements used. They conducted the experimental study on two different profiles: FNC (Flat Notched Crossed) and DU (Double Undulated) elements using a wind tunnel setup. The performance characteristics of these elements were evaluated and compared at different Reynolds number and finally the better profile of the two was suggested. The Ljungstrom airpreheater is widely used in power industry compared to any other combustion air-preheater because of its compact design proven performance, reliability and fuel flexibility.

Factors contributing towards the deterioration of APH are usually seal leakage, reduction in heat transfer capacity and absorption of heating elements used due to fouling, plugging and corrosion. Ash carry over from economizer hopper can also contribute to degradation of air preheater performance.

The expansion joints and ducting also undergo erosion sometimes upstream and downstream of air pre heaters. This erosion also contributes towards the loss of margin in draught system and poor air pre heater performance. The overhauling of an air-preheater consumes plenty of time in overcoming all these obstructions.

APH Performance Indices. To know whether the performance of an APH is as per the requirements or not, certain performance indicators have been defined which are used to evaluate the performance of the heat exchanger. A discussion on air-preheater by Ray [9] gives a brief idea about these indices.

1) Air-in leakage: this leakage is assumed to occur entirely between air inlet and gas outlet. It is expressed as a percentage of inlet gas flow. Various seals such as radial seals, axial seals, circumferential seals etc are provided to prevent this leakage as leakage reduces the efficiency of airpreheater.

2) GSE (Gas side efficiency): it is defined as the ratio of gas temperature drop across the air-preheater to the temperature head. Where: (1) (2)

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3) X-Ratio: it is defined as the ratio of heat capacity of air passing through the air-preheater to the heat capacity of flue gas passing through the air-preheater. X-Ratio is dependent upon moisture in coal, air infiltration, air and gas mass flow rates; leakage through the APH; specific heats of air and flue gas.

4) Pressure drop: it refers to the change in the pressure of both air and flue gas as these passes through the APH. Low pressure drop is preferred for better performance of an air-preheater.

5) Temperature drop of flue gas: there is a decrease in temperature of flue gas as it transfers the heat to the heating elements of the air-preheater.

6) Temperature rise of air: as the air being transferred to the boiler comes in contact with the heating elements, the temperature rises as the elements are at a high temperature when compared to in coming air.

Shruti et al [10] presented an experimental study on the performance indices of air-preheater. They conducted an experiment based on routine operational data obtained from LANCO-UPCL, Nagarjuna thermal power plant situated in Udupi, Karnataka. The indices were evaluated before and after different adjustments of clearance of radial sector plate and the observations were recorded. The results showed that air leakage gradually decreased after adjusting the radial seal sector plate clearance. It was observed that gas side efficiency gradually increased as the area between air to the gas side between the rotor and the air preheater housing decreases. It was also observed that X-ratio registered an increase with varying adjustments of hot end and cold end radial sector plates. It indicates maximum heat is recovered in the air pre heater.

APH Leakage. Leakage is a major problem as far as rotary regenerative or Ljungstrom air-preheater is concerned [11]. It not only reduces the APH efficiency but also increases the overall heat rate of the power plant. Fig. 3 shows the various paths of leakage in an APH.

Fig. 3. Flow passage of air & flue gas. ; ; tly leaking into APH gas outlet; -heated FD fan air flow surpassing or escaping the air-preheater; n air bypassing the air heater; ;

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Path 1 is the direct transfer of the cold air coming from the FD (forced draught) fan to the APH and then to the boiler. Path 2 shows the path of flue gas coming from the furnace and being transferred to further components via ID (induced draught) fan. Path A shows that the air coming from the FD fan surpasses the APH from the top and moves out via ID fan. Path B shows the air from the FD fan after getting heated up by the APH moves out of ID fan instead of going to the boiler. Path A and B represents circumferential leakage. Path C and D represents bypass leakage in which both cold air as well as flue gas moves to their respective destinations without coming in contact with the APH. In order to prevent this leakage, seals are incorporated into use. Major types of seals used in power plants are [10] are radial seals, bypass seals, axial seals and circumferential seals.

A study conducted by Kumar et al [7] on performance evaluation of air-pre heater at off-design condition provides ample information about air-pre heater leakage and performance improvement of the same. Their paper analyses a simple flow model of the rotary regenerator and classifies fluid leakage into two categories: i) Pressure Leakage: As the highly pressurized flue gas passes through the sealing system [12], a fraction of it gets mixed with low pressurized cold air. So here leakage is by virtue of pressure difference. ii) Carry over leakage: This occurs when a part of gas stream trapped in voids or empty spaces of the rotor element gets carried to the other gas stream during rotation. The carry over leakage can occur in both the direction. Leakage drift [7] - Air-preheaters are designed with a certain percentage or allowance in leakage. Leakage drift refers to the increase in leakage of air to flue gas due to the deteriorating condition of the sealing system used.

Many air-preheaters are provided with additional space which allows them to accommodate extra heating elements in case underperformance is observed. But all air-preheaters are not provided with additional space. In such cases, the old heating elements are replaced with a new set of heating elements.

Heating elements. Heating elements used in air-preheaters are made up of Corten steel i.e. HSLA (High strength low alloy steel). Corten steel is preferred for heating elements as this material offers high resistance to corrosion, erosion and high thermal conductivity [8]. The profile or geometry of heating elements used also greatly affects the performance of an air-preheater. Based on the profile geometry it is classified into seven types and they are: 1) DU (Double undulated). Undulated means having a wavy form. The common characteristic of DU element is the alternate stacking of undulated element sheets with sheets that contain both undulations and notches. Fig. 4 shows the view of the DU type profile.

Fig. 4. DU Profile [48].

2) DN (Double Notched). These plates offer reduced fouling and better clean-ability when compared with the equivalent DU elements, while maintaining similar pressure drop and heat transfer characteristic. Fig. 5 shows the view of the DN/DL type profile.

Fig. 5. DN / DL Profile [48].

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3) DL (Double notched loose packed). This Configuration is same as that of DN element, however the elements are stacked loosely within the baskets, hence the elements can move back and forth upto 1 inch during soot blowing.

4) FNC (Flat notched crossed). Fig. 6 shows the constructional features of FNC type plates. This type of plates offers higher thermal performance and lower pressure drop than standard DU type element.

It is mainly used in low fouling applications such as oil and gas since elements of this profile are extremely difficult to clean.

Fig. 6. FNC Profile [48].

5) NF (Notched flat). As shown in Fig. 7 this consists of a notched flat plate followed by a completely flat plate. Most common configuration of NF element are NF6 which has large, open spaced notches and is ideal for high ash coals and NF3.5 for low fouling fuels with high acid dew points.

Fig. 7. NF Profiles [48].

6) NU (Notched Undulated). Fig. 8 shows NU type profile. These are similar to NF series but carry an undulated sheet instead of a flat sheet.

Fig. 8. NU Profile [48].

7) CU (Corrugated Undulated). This profile is typically used only in natural gas fired units. Most appropriate when used with the low density flue gases produced when firing gaseous fuels like natural gas. Fig. 9 shows the features of CU profile.

Fig. 9. CU Profile [48].

The plates are provided with corrugations so as to increase the heat transfer surface area [13]. There are different geometries available in corrugated plate such as cross corrugated surface, corrugated undulated, cross wavy surfaces etc. The cross wavy (CW) and especially the Cross Corrugated (CC) MMSE Journal. Open Access www.mmse.xyz

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surfaces show superior performance over others thereby giving a small volume and weight of the heat transfer matrix [14]. However, as the CC surface is well documented in the literature and probably it is easier to manufacture with small passage dimensions, this should be the first choice for further studies by recuperator manufacturers [15].

Testing of Heating elements. The testing of heat transfer surfaces of various profiles is done so as to find out the profile which optimizes the heat transfer characteristics and efficiency of an airpreheater. It must be emphasized that regarding the need to determine the heat transfer coefficient the most important parameters are the identification of the geometry of the thermal element and specifically the hydraulic diameter of the flow channels as well as the mass of a single element [16].

Software Analysis. Dilip et al. [17] conducted a software analysis on heating elements on different plate profiles. The profiles were first developed using Pro-E software and were then imported to ANSYS CFX to conduct the CFD analysis. A 70 MW Unit of KLTPS (Kutch Lignite Thermal Power Station) of GSECL (Gujarat state electricity corporation limited) situated in Panadhro, Kutch was under observation to get the operational data for the experiment. The APH of this 70 MW Unit was under observation to collect data such as inlet-outlet temperature of air and flue gas, inlet-outlet pressure of air and flue gas, composition of flue gas and properties of flue gas. The profiles of the heating element used were NF, ACE (Advanced clear element), FNC, NU and CU. The boundary conditions were applied and CFD analysis was conducted on each plate profile so as to obtain the temperature profile of flue gas outlet temperature. The efficiency of APH was then calculated for each plate profile and results were then compared. The results showed the heat transfer was dependent on the type of plate profile used in air-preheater and NF profile was the most efficient among all the profiles studied.

Experimental Testing. In the paper presented by Vulloju et al. [8] two methods have been identified to determine the performance of heat transfer elements namely Residual time test and Cold flow studies which were explained bellow: 1) Residual Time test: It is the time taken by air to travel from one side of the element to another.

Residual time is directly proportional to the length of air travel which in turn is directly proportional to the surface area of the plates. High length of air travel signifies high surface area which means high heat transfer as heat transfer takes place through convection in case of heating elements. Higher the residual time, higher is the heat transfer coefficient of the plates. The study was conducted on FNC and DU plate profiles and concluded that FNC elements have more residual time than DU elements.

(3) Where RT residual time; lT Length of path of air travel; A Contact of air surface area through element.

But h

A, where h

heat transfer co-efficient.

2) Cold flow studies: This involves the construction of an experimental setup on the footsteps of a Wind tunnel. The setup is then used to determine the performance parameters for various plate profiles. Dariusz Butrymowicz et al. [16] suggested a method for the measurement of heat transfer coefficient of matrices or heating elements used in rotating regenerative heat exchangers. The socalled single blow technique is thought to be an efficient method used to experimentally determine the average heat transfer coefficient in regenerative heat exchangers composed of thermal elements.

Heat transfer coefficient is based on the actual surface area of the thermal elements and takes into account convective heat transfer between gas and the thermal element on the wall surface. In the the comparison of the actual temperature, profile of gas (that is heated or cooled in the tested matrix) MMSE Journal. Open Access www.mmse.xyz

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measured at the outlet of the tested matrix with the predicted one on the basis of the theoretical model.

The agreement between the experimental temperature profiles and theoretical prediction depends on CFD is a branch of science which can be helpful for analysing fluid flow, heat transfer, chemical reactions etc by solving complex mathematical equations with the help of numerical analysis. It is potentially helpful in designing a heat exchanger system from scratch as well as in troubleshooting or optimization by suggesting design modifications. Some of the commercial CFD codes frequently used are FLUENT, CFX, STAR, CD, FIDAP, ADINA, CFD2000, PHOENICS and others [15]. The model became the basis for many further modifications and is still being developed by removing the numerous simplifications assumed by the author in order to obtain an analytical solution of the model equations. Shekoor et al [15] did an investigation on the design optimization of corrugated surface heat exchangers using CFD. A quantitative examination of the thermal performance of the corrugated surface heat exchanger [19] was carried out with various modifications in pitch-height ratio and different corrugation angles [20]. Design optimization of cross corrugated surface with different corrugation angles [21] such as 300, 450, 600 and 750 was investigated in this paper.

Experimental Apparatus. Experimental analysis of APH mostly involves test setup which includes a wind tunnel [8]. As shown in Fig. 10, it consists of a converging section, test section in the middle and a diffuser section. A wind tunnel is a tool used for aerodynamic research. The object or specimen is kept in the middle and the fluid is made to pass over it. A wind tunnel reverses the real life situation in which the fluid is stationary and the object moves through it. Inside the tunnel, the object is stationary and the fluid moves over it. The driving unit consists of a Fan, Blower or a Compressor connected to an electric motor. The location of the driving motor depends upon the type of the tunnel.

Compressor or blower or the fan creates a flow of air which gets settled in a large chamber known as the settling chamber, this chamber is equipped with wire gauges and a set of honeycombs so that the flow can be straightened and irregularities be removed. In cases of very low velocities, near stagnation conditions exist in the settling chamber. This chamber supplies the flow to the converging section located downstream. This is carefully designed to accelerate the flow from the settling chamber to the test section velocity with minimum disturbance.

The converging section or the nozzle feeds the test section with a jet of uniform velocity. The model to be tested is fixed here with suitable supports. A transparent window is also provided on the sidewalls of the test section so that the test specimen and the measuring instruments can be monitored properly. The diffuser takes the flow from the test section and discharges it into the atmosphere at a relatively high pressure.

Fig. 10. Wind tunnel setup [8].

The plates or heating elements are kept in the middle test section. The flue gas is made to pass first thus heating the elements. The blower or compressor attached to the diffuser then creates a suction

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effect, which passes cold air through the heating elements. The overall idea is to simulate the condition of a Ljungstrom air-preheater through the use of this wind tunnel. After the heating, cold air passes through, heat gets transferred from the plates to the air hence a temperature rise of cold air is noticed. The velocity of cold air is measured for a range of Reynolds number based on which the fanning friction factor, pressure drop and heat transfer coefficient of the plate profiles are calculated.

In the experiment conducted by Vulloju et al [8], the velocity measurement was done using a TSI Velocity meter. TSI Velocity meter is an advanced electronic model of a Hot Wire Anemometer. A hot wire anemometer consists of a tiny wire (d=0.005 mm) held between two prongs; it is heated (hence the term Hot-wire) to a given temperature by passing an electric current through it. When such a wire is introduced into the flow of a gas it cools down the hot wire to a lower temperature due to convective heat transfer from the wire element to the gas. Higher the heat transfer from the wire, higher is the heat transfer coefficient of the fluid which is directly proportional to the velocity of the fluid and so the velocity can be calculated.

(4) (5) Reynolds number is calculated by using formula:

(6) Density of air in kg/m3;

where

- Viscosity of air in pa/sec.

Friction factor is calculated by the following formula

(7) Where p Pressure difference in mm of water column; L

Length of test, section in wind tunnel in m;

f

friction factor;

Dh hydraulic diameter of the plate profiles.

(8) where Nu Nusselt number; Pr

Prandtl number.

Single blow technique [16] can also be used to find the heat transfer coefficient of the matrices of a rotary regenerative air-preheater.

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Fig. 11. The idea of heat transfer measurement by single-blow technique [16].

The experimental part of the single blow method is carried out in a wind tunnel as shown in Fig.11.

Because of limitations of the test chamber of the tunnel, usually the entire heat exchanger cannot be tested so the test involves only a matrix composed of thermal elements used in a real heat exchanger.

Temperature and pressure measurement points are placed at the inlet and outlet of the tested matrix.

Static pressure difference is measured in order to determine the frictional flow resistance [22]. In addition, the velocity of gas flow through the matrix should be also measured. It may be suggested that the temperature of gas flowing through the matrix should be raised above the ambient temperature by approximately 10 20 K. An electrical heating coil made of resistance wires may be applied for this purpose. Due to the required velocity homogeneity, the heating coil should disturb the flow as little as possible. The structure of the coil also affects the gas temperature profile obtained after switching it on or off which is important from the point of view of the theoretical model applied to draw up the measurement results. Due to the homogeneity of velocity profiles required in theoretical models, it is recommended to place a flow straightener (in the form of a honeycomb matrix) before the test section [23]. In order to eliminate the influence of disturbances generated at the tunnel outlet geometry, a similar flow straightener should be also placed at the outlet of the test section. The following conditions required before the measurement:

The measurement of pressure differences between the inlet and the outlet of the tested matrix, including gas velocity measurement, can be used to determine the frictional resistance as a function of Fanning coefficient f versus Reynolds number, Re.

Fig. 12. The complete measurement apparatus [16]. 1 Packages of investigating elements, 2 pressure measuring point, 3 electrical heater for heating air, 4 flow rectifier 5 fan, 6 pile up elements DEBIMO, 7 diffuser.

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The difference here as shown in Fig.12 is that instead of using flue gas to heat the elements, an electric heater is provided just before the heating elements to heat the incoming air, which later transfers the same to the plates.

Dependence of parameters on Reynolds number. Experimental characteristics such as fanning friction factor, pressure drop and heat transfer coefficient vary with Reynolds number (Re). The below formula shows the relation between the friction factor and Reynolds number.

(9) The experimental graph given by Dariusz Butrymowicz [13] is given below in Fig. 13:

Fig. 13. Graph showing the variation of colburn-j factor with Reynolds no. [16].

Fig. 14. Variation of friction factor with Reynolds no. [16].

From the analytical as well as graphical results, it was found that there was a decrease in friction factor as shown in Fig.14, as well as in colburn-j factor with the increase in Reynolds number.

Summary. After going through numerous study material, research papers and experimental work done in the field of air-preheater and heating elements, the fact got consolidated that the heating elements forms the heart of the air-preheater and the performance of the APH gets significantly affected with the change in geometry of the plates. Although when it comes to the experimental investigation of heat transfer characteristics of heating elements used in air-preheater, less but significant work has been done i is possible to determine the heat transfer characteristics of the plates using a wind tunnel like setup which aims to simulate the conditions of an air-preheater. However, we feel that an appreciable amount of difference in the readings may arise when we compare the simulated readings with the MMSE Journal. Open Access www.mmse.xyz

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readings of experiment done on an actual air-preheater, so we suggest that more work needs to be done on the determination of performance characteristics of the heating elements.

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[35] Ghodsipour N, Sadrameli M. (2003), Experimental and sensitivity analysis of a rotary air preheater for the flue gas heat recovery. Appl. Therm. Eng., 23 (1), 571 80. DOI 10.1016/S13594311(02)00226-0.

[36] Skiepko T., Shah R.K. (2004). A comparison of rotary regenerator theory and experimental results for an air preheater for a thermal power plant. Exp. Therm. Fluid Sci.; 28:257 64. DOI 10.1016/S0894-1777(03)00048-7.

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[37] Stephen K. Storm, John Guffre (2010), Experiences with regenerative air heater performance evaluations and optimization, PowerGen Europe, 1-18 [38] Energetica India Magazine (n.d.). Retrieved from www.energetica-india.net/download.php?seccion=articles&archivo...pdf [39] Donald Q. Kern (2004), Process heat transfer, Tata McGraw-Hill Publication, pp. 701.

[40] Rodney R. Gay (2004), Power Plant Performance Monitoring, pp. 433.

[41] British Electricity International (1991), Modern Power Station Practice, Pergamon Press London, Vol. B, 3rd edition, [42] Howden Power Ltd (2000), Product Information, Air preheater customer manual.

[43] Ramesh K. Shah, Dusan P. Sekulic (2003), Fundamentals of Heat Exchanger Design, ISBN: 978-0-471-32171-2 [44] Yunus A Cengel, Afshin J. Ghajar (2015), Heat and Mass Transfer: Fundamentals and Applications (Fifth Edition), ISBN 0073398187 [45] P.K. Nag (2002), Power Plant Engineering Tata McGraw-Hill Education.

[46] Ljungstrom Air Preheater (n.d.) In Power Magazine Business and Technology for the Global Generation Industry, since 1882. Retrieved from http://cdn.powermag.com/wp- content/uploads/2007/02/520004dd01907-15-03.gif [47] Basketed Elements In Products by Paragon Technology. Retrieved from http://www.paragonairheater.com/products_basketed_elements.

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Numerical Analysis of Clamped Fluid Conveying Pipe 1

Imran Shaik1, a, Shaik Riyaaz Uddien1, A. Krishnaiah1, Shankarachar Sutar2 1

University College of Engineering, Osmania University, Hyderabad, India

2

Scientist, CSIR-Indian Institute of Chemical Technology, Hyderabad, India

a

imranshaik1414@gmail.com DOI 10.2412/mmse.53.64.857 provided by Seo4U.link

Keywords: clamped-clamped, Euler Bernoulli, fluid conveying pipe, weldment, ABAQUS.

ABSTRACT. This paper presents vibration analysis and mathematical model using Euler-Bernoulli and Hamilton's energy expressions for fluid conveying welded Galvanized Iron pipe with clamped-clamped boundary condition. A 3D CAD Model was developed in NX-ideas for empty pipe, pipe with fluid flow and welded pipe with fluid flow. Vibration analysis was performed on developed models for 3 mode shapes to generate frequency data using ABAQUS. The developed models were imported in to ABAQUS for generating frequency data. For the welded pipe, effects of weldment at girth welds on the vibration characteristics and stability of pipe was investigated. Results acquired from ABAQUS were compared with theoretical results of natural frequencies and observed the variation of 3% error.

Introduction. The fluid conveying pipes are widely used in many industrial applications such as chemical plants, fertilizer plants, nuclear plants and pharmaceutical industries etc. The pipes are subjected to different environmental conditions such as wind forces, earthquakes, and Coriolis forces of fluid flow. Over the last sixty years, extensive studies have been carried out on pipeline systems subject to different boundary conditions and loadings. These pipes however frequently transport fluids from initial point to destination. The subject of piping vibration has attracted a lot of attention from various researchers in recent times due to vast applications.

Avinash B. Kokare et.al [1], studied about vibrational characteristics of pipe conveying fluid and FE simulation to evaluate velocity and pressure distribution in a single phase fluid flow. Long Liu and Fuzhen Xuan [2], presented the flow induced vibration analysis of supported pipes conveying pulsating fluid using precise integration method. Gongfa Li et.al [3] investigated natural frequencies using Lagrangian interpolation function, the first order Hermite interpolation function and the Ritz method to obtain the element standard equation. Wentao Xiaoet.al [4] studied finite element analysis of nonlinear vibration response using Lagrangian interpolation function, the first order Hermit interpolation function and the Ritz method to obtain the element standard equation, and then integrated a global matrix equation, obtained the response of conveying fluid pipe with the New mark method and Matlab. Muhsin J. Jweeg et al [5] dynamic Analysis of Pipes Conveying Fluid Using Analytical, Numerical and Experimental Verification with the Aid of Smart Materials and the results presented in this study compared with the results performed by using analytical solution for equation of motion and also, compared with the results performed by using ANSYS Software.

T.G. Ritto et.al [6] studied about dynamic stability of a pipe conveying fluid with an uncertain computational model. Ivan Grant [7] Presented on flow induced vibrations in pipes; a finite element approach methodology is used to determine the critical fluid flow velocity that induces the threshold of pipe instability. B. Mediano-Valienteet al. [8], discussed on stability analysis of a clamped-pinned pipeline conveying fluid by means of the eigenvalues of a Hamiltonian linear system associated. From this analysis, characteristic expressions dependent on material constants have been developed.

1

bH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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Nabeel. K. Abid et.al. [9] Investigated the stability of fluid coveying welded pipe is of practical importance because the welding induced residual stresses which effected on the vibration characteristic and stability of pipe. Singiresu S. Rao [10], Vibrations of Continuous Systems.

Adekunle. O. Adelaja [11] investigated the nonlinear transverse vibration of a flexible pipe conveying hot pressurized fluid in pinned-pinned condition. M.P. Paidoussis and N.T. Issid [12] studied about dynamics and stability of flexible pipe containing flowing fluid, where flow velocity is entirely constant or with a small harmonic component superposed. L.G. Oslon and D. Janison [13] investigated motion of elastic pipes conveying fluid for various idealized cases.

Nomenclature.

S No

Symbols

Description

1

p

Density of pipe in (kg/

2

f

Density of fluid in (kg/

3

U

4

E

5

mf

Fluid mass in (kg)

6

mp

mass of the pipe in (kg)

7

W

Displacement component at any point in the cross section (m)

8

Dx

Small element of the pipe

9

f(x,t)

10

w(x, t)

(N/

External transverse force per unit area Transverse deflection of pipe Ith normal mode shape of a pipe

11 12

Fluid velocity in (m/s)

Z

Axial strain in Z direction Ith mode of vibration

13 14

T

Weld Tension in N

15

K

Spring stiffness

Modelling, Simulation and Analysis of fluid conveying pipe.

Firstly, mathematical model for clamped clamped boundary condition was developed and then fluid motion equation and natural frequency equations were also developed accordingly.

The model of fluid conveying pipe is done by using I-DEAS software and the analysis of the same is done by ABAQUS software which includes standard / CFD modules to analyze fluid structural interaction. Simulation of clamped-clamped pipe performed to get the frequencies of pipe without and with welding conditions.

The FE analysis was carried out to calculate vibration characteristics of a welded pipe conveying fluid with a velocity of 5m/s and boundary conditions using a general-purpose FE package ABAQUS/Standard V6.14. The approach is divided into five parts: thermal analysis, coupled field thermal-structure analysis, computational fluid dynamics (CFD), coupled field fluid-structure analysis, and modal analysis.

The coupled field fluid-structure analysis solved the equations for the fluid and solid domains independently of each other. It transfers fluid forces and solid displacements, velocities across the fluid-solid interface. The algorithm continues to loop through the solid and fluid analyses until MMSE Journal. Open Access www.mmse.xyz

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convergence is reached for the time step (or until the maximum number of stagger iterations is reached). Convergence in the stagger loop is based on the quantities being transferred at the fluidsolid interface.

The modal analysis was used to determine the vibration characteristics (natural frequencies and mode shapes) of a welded pipe conveying fluid. The natural frequencies and mode shapes are important parameters in the design of a structure for dynamic loading conditions. The procedure to do a prestressed modal analysis is essentially the same as a regular modal analysis, except that you first need to pre-stress the structure by doing a static analysis. Build the model and obtain a static solution with pre-stress effects turned on from thermal-structure and fluid-structure analyses A non- linear transient thermal analysis was conducted first to obtain the global temperature history generated during and after welding process (at the weld region). The basis for thermal analysis is a heat balance equation obtained from the principle of conservation of energy. The FE thermal solution employed a nonlinear (material properties depend on temperature) transient thermal analysis using two modes of heat transfer: conduction, and convection, to determine temperatures distributions that vary over time. The applied loads at the region of weld are function of time which described by divided the load-versus-time curve into load steps. For each load step, its need to specify both load and time values, along with other load step options such as stepped or ramped loads, automatic time Results and Discussion.

Mathematical model, simulation and different analyses were done for fluid conveying pipe. Different cases were also considered for analysis.

Mathematical model developed for fluid conveying pipe with fixed ends.

The Fig.1 shows the welded pipe conveying fluid, the welding is done at mid span of 1-inch of pipe material and L is length of the pipe.

Fig. 1. Welded pipe conveying fluid with fixed ends.

The governing equation of motion of a fluid conveying welded pipe by using Eulertheory is given by:

(1)

Where the terms are as followed

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The equation of fluid motion The equation of motion of piping vibration is given below

(2)

The Free vibration solution can be found using the method of separation of variables as (3) Where T (t) is a harmonic function T (t) =

Natural frequency equation for clamped-clamped pipe. In the present study, we use exact method to obtain the natural frequencies of fluid conveying pipe as given below: (4) (5)

(6)

(7)

Substituting in boundary condition, when W =0 at x= 0 From equation (7)

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(8) When W =0 at x= 0 From equation (8) (9) Substituting x=0

(10) As x =0

(11)

Now W (x) =0 at x= l

Similarly,

From equations We get

Stiffness matrix as follows

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By solving above stiffness matrix (12) Similarly,

By solving above stiffness matrix (13) On combining and simplifying: (14) Simulation of clamped-clamped pipe. Fig. 2 (a) shows the finite element structural mesh model consists of 2266 elements and 2277 nodes with first order quadrilateral linear elements. Fig.2 (b) shows the finite element of fluid mesh model consists of 2400 elements and 3417 nodes with first order hexahedral fluid elements.

a)

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b) Fig. 2. (a) Finite element structural mesh model with boundary conditions, (b) finite element fluid mesh model with fixed ends.

Table 2. Material properties of GI pipe.

1 Inch Pipe Span

2 meters (welded at mid span)

Pipe Material

Galvanised Iron

Pipe Outer Diameter (OD)

0.034m

Pipe Inner Diameter (ID)

0.0304m

Pipe Wall Thickness (t)

0.00178m

Density of Steel

7850 kg/m3

Young's modulus (E)

200 Gpa

Poisons Ratio

0.28

Fluid Density ()

1000 kg/m3

Mass of Pipe (mp)

3.61 kg

Mass of Fluid (mf)

1.76kg

Dynamic Viscosity of fluid

0.

Analysis of simulated model. Thermal analysis.

DC3D20 element type is used, which it is 3-D twenty nodes with a single degree of freedom, temperature, at each node. The 20-node elements have compatible temperature shapes and are well suited to model curved boundaries. It is applicable to a 3-D, steady-state or transient thermal analysis; it is applicable to a 3-D, steady-state or transient thermal analysis. Fig.3 & Fig.4 shows the preheating and cooling transformation during welding process.

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Fig. 3. Heat cycle.

Fig. 4. Continuous cooling transformation diagram of Steel B. Coupled field thermal structure. A stress analysis was then developed with the temperatures obtained from the thermal analysis used as loading to the stress model. C3D20 element type was used, which can mesh irregular shape without as much loss of accuracy. C3D20 element has compatible displacement shapes and is well suited to model curved boundaries. It is defined by 20 nodes having six degree of freedom per node. The element may have any spatial orientation. C3D20 has plasticity, creep, stress stiffening, large deflection, and large strain capabilities as shown in Fig. 5. Temperature plot in degree Celsius.

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Fig. 5. FE analysis of clamped-clamped pipe with welding at mid span.

Cases Analysed. Fluid conveying pipe was analyzed by considering different cases and relevant analysis has been done.

(1) Pipe acts as a beam when velocity, (V) =0 and weldment effect, (T) =0 (2) Fluid flow velocity (V) =5.0 m/sec, with weldment effect (T) =0 (3) Fluid flow velocity (V) = 5.0 m/sec, without weldment Effect, (T) =10N Case 1 when there is no velocity and no weldment effect on a pipe it behaves as a beam. The results obtained are shown in table 3. Similarly, for case 2 analysis by considering a fluid velocity 5 m/sec and weldment effect T=0 the natural frequencies were found for 3 mode shapes.

Finally, in Case 3, V=5 m/sec and T=10. Newton is applied to piping system to obtain natural frequencies using FORTRAN program code. The natural frequencies of a clamped-clamped pipe with and without welding, with and without velocity for all 3 cases mentioned above are run by ABAQUS simulation software and results were generated and compared with analytical results.

Table 3. FE analysis of fluid conveying welded pipe with different conditions.

Mode No.

Empty pipe V=0, T=0 Natural Freq. by ABAQUS Software in Hz

Natural Freq.

Theo. in Hz

1

50.82

49.58

2

139.36

3

271.31

Percent age of Error

Pipe without weld V=5m/sec, T=0 Natural Freq. by ABAQUS Software in Hz

Natural Freq.

Theo. in Hz

2.43

36.35

35.76

137.52

1.32

99.54

265.37

2.18

192.66

Percen tage of Error

Perce ntage of Error

Natural Freq. by ABAQUS Software in Hz

Natural Freq.

Theo. in Hz

1.6

31.36

30.71

2.07

98.15

1.39

85.75

83.92

2.13

187.13

2.87

166.22

163.97

1.35

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Pipe with weld V=5m/sec, T=10

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Fig. 6. Vibration analysis of clamped-clamped empty pipe ends without welding first mode shape.

Fig .7. Vibration analysis of clamped-clamped empty pipe ends without welding second mode shape.

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Fig. 8. Acceleration vs. Frequency of an empty pipe with clamped ends without welding.

The Fig. 6 and Fig. 7 show the finite element analysis of clamped ends for empty pipe with Abaqus simulation for first and second mode shapes. The first natural frequency of pipe is excited at 50.82 Hz, 2nd mode it is found to be 139.36 Hz and for 3rd mode shape 271.31Hz. For all the cases observed that the maximum deflection of the pipe is found approximately 2mm.

Similarly, harmonic analysis (sine sweep) was done on the structure by applying harmonic force of 1g acceleration to plot the Acceleration vs. Frequency. To find the frequency Peaks on the pipe as shown in Fig. 8.

Fig. 9. Vibration analysis of clamped-clamped with velocity (V) =5m/sec without welding (T) =0.

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Displacement vs. Time

Fig. 10. FE analysis of clamped pipe with deflection plot at V=5m/sec and T=0.

In case 2 fluid structure interaction is studied for clamped end pipe without welding and with fluid velocity V=5m/sec and T=0 as shown in Fig. 9 and Fig. 10. The piping vibration natural frequencies are obtained for 3 mode shapes by ABAQUS simulation the 1st mode shape is found at frequency 36.355 Hz, 2nd 99.54 Hz and 3rd Mode 192.56 Hz for all the three cases the maximum displacement was found within 0.35mm from the displacement vs. time plot.

Fig. 11. Vibration analysis of clamped-clamped with velocity V =5m/sec without welding T =10N

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Fig. 12. Fluid Structure interaction of clamped pipe with V=5m/sec, T=10 N. The Fig. 11 and 12 shows the weldment effect for fluid velocity at (V) =5m/sec and T=10N. In this case the 1st mode of frequency is 31.36Hz, 2nd 85.75Hz and 3rd mode 166.22Hz the maximum displacement found for all 3 cases is 0.305 mm.

Summary. The fluid-conveying pipes considering c-c boundary condition are used to develop mathematical model.

The theoretical results of empty pipe and fluid flow in a pipe with applied velocities for three mode shapes are analyzed and compared with Abaqus software results of natural frequencies. The generated finite element data using Abaqus software are compared with analytical data. a)

The natural frequency of the pipe increases with increase in fluid flow velocity for c-c ends.

b) The weld deposit on a pipe with c-c ends also play a major role in reduction of natural frequencies with increase in weldment. The percentage error found to be less than 3% and it is in good agreement. c) The frequency of first mode of vibration is computed by varying the fluid flow velocity with and without welding effects, for which critical flow velocities are obtained. d) In the case of c-c condition the instability region lies in the range of 32.0 to 33.56 for magnitude of 10 weld tension.

Acknowledgement: Shaik Imran and Shaik Riyaaz Uddien are students of Department of Mechanical Engineering, University College of Engineering, Osmania University, Hyderabad.

References [1] Avinash B. Kokare et. al. (2015), Vibration Characteristics of Pipe Conveying Fluid, 4, pp. 1095110954 [2] Long Liu, Fuzhen Xuan (2010), Flow-Induced Vibration Analysis of Supported Pipes Conveying Pulsating Fluid Using Precise Integration Method, pp. 1-15.

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[3] Gongfa Li et. al. (2014), The nonlinear vibration analysis of the fluid conveying pipe based on finite element method, pp. 19-24 [4] Wentao Xiao et. Al. (2014), Finite element analysis of fluid conveying pipe line of nonlinear vibration response, pp. 37-41 [5] Dr. Muhsin J. Jweeg et. Al. (2015), Dynamic analysis of pipes conveying fluid using analytical, numerical and experimental verification with the aid of smart materials, 4 (12), pp. 1594-1605 [6] T.G. Ritto et.al (2014), Dynamic stability of a pipe conveying fluid with an uncertain computational model, 49, pp. 412-426 [7] Ivan Grant, Flow induced Vibration in pipes, A Finite Element Approach, Thesis for Bachelor of Science in Mechanical Engineering, Cleveland State University, May 2010 [8] B. Mediano-Valiente et.al (2014), Stability Analysis of a Clamped-Pinned Pipeline Conveying Fluid, 13, pp. 54-64.

[9] Nabeel.K.Abid et.al (2010), Investigation into the vibration characteristics and stability of a welded pipe conveying fluid, 4, pp. 378-387 [10] Singiresu S.Rao, Vibrations of continuous systems, Textbook published by John Wiley & Sons, Inc., New Jersey, USA 2007.

[11] Adekunle O. Adelaja (2013), Temperature modulation of vibration responses of a flexible fluid conveying pipe, 3, pp. 740-749.

[12] M.P. Paidoussis, N.T. Issid (1974), Dynamic and stability of flexible pipe containing flowing fluid, pp. 267-294.

[13] L.G. Oslon, D. Janison (1997), Application of a General purpose Finite Element Method to Elastic Pipes Conveying Fluid, 11, pp. 207-222.

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Analysis and Optimization of the Control System of a Hydraulic Fine-Blanking Press 1

Guodong Yi1, a, Peng Zhang1 1

School of Mechanical Engineering, Zhejiang University, Hangzhou, China

a

ygd@zju.edu.cn DOI 10.2412/mmse.39.87.164 provided by Seo4U.link

Keywords: hydraulic fine-blanking press, open-loop control, closed-loop control, optimization, simulation.

ABSTRACT. Fine-blanking is an efficient and precise machining method. The hydraulic control system of the fineblanking press has an important influence on the forming efficiency and accuracy of the part. The paper puts forward an analysis and optimization methods of the control system for velocity stability. A hydraulic control system model is established and the main parameters of blanking process such as blanking force, blank holder force and counter force were calculated and analyzed. According to the velocity changes of the master cylinder with open-loop control in blanking process, the causes and effects of each change point and the variation characteristics of load, acceleration and displacement of master cylinder are elaborated. The velocity changes with closed-loop control based on velocity and position feedback are described and compared with that of the open-loop control. Based on the comparative analysis, the influences of the system and components on the velocity are studied, and the open-loop control is selected as the control method of the fine-blanking press. The optimal control strategy for the steady velocity of main cylinder is proposed with the automatic optimization algorithm and the simulation results.

Introduction. Fine-blanking is a high efficiency and high-precision machining method, which has been widely used because the blanking parts can be used directly without further processing.

However, the precision of the repeatability of the precision is difficult to guarantee because the sharp blanking load and speed change rapidly in a short time. However, it is difficult to maintain the repeatability precision of the fine-blanking due to the tremendous changes in load and speed in a very short period of time. To solve this problem, it needs not only a high rigidity mechanical structure but also an effective hydraulic control system. The control system regulates and controls the pressure and flow of the hydraulic system to balance the load and stabilize the speed so that the fine blanking working conditions will not fluctuate violently. Therefore, it is conducive to stabilizing the operation of the fine-blanking press and improve the machining quality through the analysis and optimization of the control strategy [1].

A number of optimization methods have been proposed: Shen studied the optimal control variable trajectory under a given circle using the dynamic programming algorithm to reduce the fuel consumption clearly without deteriorating the performance [2]. Baghestan proposed a nonlinear back stepping control algorithm with an energy-saving approach for position tracking to satisfy the tracking and energy-saving objectives [3]. Ding proposed the approximate internal model control integrated with a position feedback control in cascade control design to improve the trajectory-tracking performance of the hydraulic servomechanism [4]. Coelho presented an adaptive cascade controller tuned by using evolutionary algorithms for performance optimization of the trajectory tracking control of a hydraulic actuator with an overlapped proportional valve [5]. Tri introduced a control algorithm, which is the combination of a modified back stepping control with an iterative learning mechanism for the adaptive trajectory tracking control of an electrohydraulic actuator [6].

1

-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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PID (proportional-integral-derivative)-based methods are the most widely researched and applied: Jia established the cerebellar model articulation controller neural network and PID coupling control strategy to enhance the tracking performance of hydraulic roll bending loop [7]. Shen studied a PI controller combined with an offline designed feedback controller and an online adaptive compensator to improve force tracking performance of an electro-hydraulic force servo system [8]. Chalupa proposed an optimal PID and model predictive controllers for both a linearized model and the nonlinear system [9]. Ye presented an improved particle swarm optimization algorithm to search for the optimal PID controller gains for the nonlinear hydraulic system [10]. Li used trial and error to get suitable PID parameters for electro-hydraulic proportional control to ensure the accuracy of conveyor speed control [11]. Du proposed a new load-prediction based method using feed forward control for the servomotor and control valves to supplement conventional PI feedback control [12]. Elbayomy designed a PID controller optimized by the genetic algorithm to improve the performances of the hydraulic servo actuator system[13]. Muhammad presented an optimal hybrid fuzzy proportion integral derivative controller based on combination of PID and fuzzy controllers to acquire precise tracking performances [14]. Cao optimized PID Parameters of hydraulic system with NLPQL algorithm to obtain the global optimal solution effectively [15]. Zheng introduced a fuzzy PID control method based on the relationships between the PID parameters and the response characteristics to improve the overall performance of the electro-hydraulic position servo system [16].

Based on the above research, the paper establishes the hydraulic control system model of a fineblanking machine calculates and analyzes the main blanking process parameters and their mutual relations. Then, the change characteristics of speed, load, acceleration and displacement of the master cylinder under open-loop control and closed-loop control are studied, and the control method suitable for fine blanking system is determined through comparative analysis. Finally, an optimal control strategy is set up based on the characteristics of fine blanking to meet the performance and quality requirements of the blanking process.

Hydraulic Control System Model of the Fine-blanking Press. The following assumptions are proposed in the modelling according to the characteristics of blanking process: (1) The master cylinder, press cylinder and counter cylinder are the main objects, and the stepping cylinder is simplified due to its little influence on the punching.

(2) All solenoid directional valves are considered as logic elements, that is, the valves are opened and closed in full synchronism with the control signal.

(3) The hydraulic components that are not closely related to the blanking process are omitted.

(4) The influence of system oil leakage is not considered to improve the analysis simulation speed.

The hydraulic control system model is shown in Fig. 1.

Calculation of the fine-blanking Load. The fine-blanking forces include the cutting force blank holder force , and the counterforce .

The cutting force the coefficient :

is a function of cutting length , material tensile strength

, the

, thickness , and

(1) where

is determined by the Poisson's ratio; generally,

= 0.9.

The blank holder force is a function of blank holder circumference tensile strength , and the coefficient :

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and height , material

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(2) where

= 1.9 while

The counterforce

= 600 MPa. is a function of compression area

and counterforce intensity

: (3)

where

= 70 MPa in the large area and 20 MPa in the small area.

The typical process parameters were designed based on the working conditions of the fine blanking press as follows: material thickness is 4 mm, cutting length is 1200 mm, material tensile strength is 600 MPa, blank holder height is 0.6 mm. , and were calculated based on the above computational formulas and parameters as follows: ; ; .

Fig. 1. The hydraulic control system model.

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Relationship between the blank holder force and the pressing depth. The process of the blank holder pressing into the material is divided into two stages by the material elastic limit, the first one is elastic deformation, and the second stage is plastic deformation. The curve of blank holder force and pressing depth is shown in Fig. 2. After the blank holder is fully pressed into the material, the load of the master cylinder rises rapidly. At this time, the differential pressure switch 13-S12 is started and the pressure in the press cylinder is partially relieved, and the pressing process is completed.

x: Pressing depth (mm); y: Blank holder force (kN).

Fig. 2. The curve of blank holder force and pressing depth.

The relationship between the blanking force and the blanking thickness. The blanking force rises sharply at the beginning of the punching process. Although the deformation of the sheet decreases the shearing area, but is increasing due to the hardening of the material until the peak is reached. Then, starts to declined gradually due to the effect of the shear area reduction on the blanking force exceeds that of the material hardening, with the change trend similar to the extrusion process, and there is no sharp decline of the blanking force which often occurred in ordinary punching process due to the premature material fracture. In general, the limit of appears at the position where the punching depth is about 1/3 of the plate thickness. The variation of the blanking force with the blanking depth is shown in Fig. 3.

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x: Blanking depth (m); y: Blank force (N).

Fig. 3. Variation of the blanking force with the blanking depth.

Analysis of the open-loop control. The purpose of analyzing the open-loop control process is to illustrate the operating status of the system at each stage of the blanking process and the relevant influencing factors, to clarify the inherent characteristics of the system.

The initial position of the punching start point is set to 0 and the start time is set to 0.2s. According to the hydraulic system model shown in Fig. 1, the action sequence of the main hydraulic elements during blanking process is shown in Fig. 4, and the velocity variation of the master cylinder in blanking process is simulated in Fig. 5.

(a) Master cylinder

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(b) Press cylinder

(c) Counter cylinder Fig. 4. Action of the key valves in blanking process.

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D

B

G

E

F

C

A

H

x: Time (s); y: Velocity of the master cylinder (m/s).

Fig. 5. Velocity variation curve of the master cylinder in open loop control.

The velocity of the master cylinder fluctuated during the blanking process, and the generation and influence of each velocity change point are as follows: Velocity change point A: A small peak of the velocity appears when the master cylinder starts, because the spool of the proportion valve has not yet started at this time, and the oil in the master cylinder is actually supplied by the relief valve on the control cover of the press regulating valve before the proportional valve.

When the cartridge valve on the main oil line just started, the large pressure difference between the two ends leads to the pressure inside the cylinder chamber close to 0 and the import pressure close to 245 bar, so the velocity rises rapidly in a short time. This process has a short duration of about 20 ms then the velocity reduces due to the throttling of the damping port. When the spool of the proportion valve started, the velocity rises again. The flow of the relief valve on the control cover of the pressregulating valve is shown in Fig. 6.

x: Time (s); y: flow of the relief valve on the control cover (L/min).

Fig. 6. The flow of the relief valve on the control cover of the press-regulating valve.

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In Fig. 6, the flow through the relief valve in the first 20 ms is large, and then fluctuates at about 5 L/min according to the change of the master cylinder load to help the pressure relief valve to maintain the pressure stable at both ends of the proportional valve. After the proportional valve main spool started, the flow through the relief valve is relatively small and difficult to cause a large effect on the master cylinder velocity.

In practice, the speed change at point A will be smoother than the simulation results, because the solenoid directional valve that controls the cartridge valve on the main oil line is not started instantaneously, but cannot be eliminated completely in the given control mode.

Velocity change point B: The velocity change point B appears at the end of the blank holder pressing process. Since the pressure cylinder has not yet started to retreat, the cylinder still maintains high pressure, and the master cylinder continues to rise, resulting in a rapid increase of the blank holder force. At the same time, the pressure difference between two ends of the proportional valve of the master cylinder begin to decline due to the response time of the pressure regulating valve, and the flow rate into the master cylinder is reduced with a certain opening width of the main spool of the proportional valve, resulting in a speed decrease after the point B. Velocity change point C: The velocity change point C appears when the mold is closed, at this time the blank holder force reach the maximum, and counterforce is also established, resulting in a peak of the main cylinder load, and a trough of speed, as shown in Fig. 7. The differential switch is started after the point C. The proportional relief valve of the press cylinder system is partially relieved, and the pressure-regulating cartridge raises the pressure of the proportional valve inlet, so the speed starts to rise again. The velocity change point C appears at the position where the master cylinder displacement is 0.605 mm with the set operating parameter, as shown in Fig. 8, the velocity change point 3 appears at the position where the master cylinder displacement is 0.605 mm.

x: Time (s); y: Blank holder force (red) and counter force (green) (N).

Fig. 7. Curves of blank holder force and counter force.

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x: Time (s); y: Master cylinder velocity (red) (m/s), 13-S12 (green) (null), master cylinder displacement (blue) (m).

Fig. 8. Details of the velocity change point C. The pressure variety of the solenoid pilot valve of the proportional relief valve is assumed to be synchronized with the control signal in the simulation, but there will be a delay in practice, resulting in the hysteresis of the pressure regulating of the press cylinder, and the rising cylinder may lead to plastic deformation of the material within the scope of the blank holder, which wastes energy and adversely affects the blanking process.

It is desirable that the pressure of the press cylinder begin to be partially relieved when the blank holder is fully pressed into the material and the press force required for the blanking process is established. The partial relief of the press cylinder pressure is controlled by the differential pressure switch 13-S12 or the position sensor 13-S10, ensuring that the blank holder can be fully pressed into the material.

If the counter force is established after the blank holder force is established, the calculated value of the diameter ratio of the two ends of the differential pressure switch is 1.4:1 according to the principle of force balance, which can be appropriately increased in practice due to the inertia of the system.

Velocity change point D: The speed change point 4 appears at the beginning of the punching, at which point the pressure of the counter cylinder is partially relieved, and the blanking force is still small, so a trough of the master cylinder load appears. The pressure-regulating valve starts to raise the proportional valve inlet pressure according to the rise of the system pressure, but cannot immediately reach the target value due to the response time. The above factors lead to a speed overshoot at the speed change point D, as shown in Fig. 9.

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x: Time (s); y: Master cylinder velocity (red) (m/s), master cylinder load (green) (N), blanking force (blue) (N).

Fig. 9. Details of the speed change point D. Velocity change point E: The speed change at point E is due to a sudden change in the flow caused by the spool of the cartridge valve on the master cylinder oil circuit reaches the limit position. It takes about 160ms for the cartridge valve spool to be fully opened due to the throttling of the control chamber and a stroke of 12mm. During the opening process, a portion of the inlet flow is used to fill the cylinder chamber so that the outlet flow is less than the inlet flow. The inlet and outlet flow is equal after fully opening, resulting in a sudden increase in the speed at point 5, as shown in Fig. 10.

x: Time (s); y: Inlet flow (red) (L/min), outlet flow (green) (L/min), spool displacement (blue) (m).

Fig. 10. The impact of the opening size of the cartridge valve on the flow.

Velocity change point F: MMSE Journal. Open Access www.mmse.xyz

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A speed trough appears at point F, mainly because the peak of the master cylinder load appears at this time, but the speed changes slowly due to the slow change in the master cylinder load. The running state of each valve is stable at this stage, and the main factor affecting the speed change is the responsiveness of the pressure regulating cartridge valve on the system pressure changes, the faster the response speed is, of the master cylinder speed more stable. Due to the stability of the valve running state at this stage, the main factor affecting the speed change is the ability of the pressure regulating cartridge valve responding to the system pressure change, which means that the faster the response speed is, the more stable the master cylinder speed is.

Velocity change point G: The speed change point G appears when the master cylinder reaches the preset vertex, and the spool of each valve of the master cylinder oil circuit is open at this moment. The main reason for the rapid decline in speed is the power off of the 10-Y9, resulting in the oil flowing to the master cylinder flows back to the tank through the cartridge valve controlled by 10-Y9.

At the power-on moment of the 10-Y9, the pressure of the counter cylinder and the pressing cylinder still exist, and the pressure of the master cylinder is large, resulting in a large flow back to the tank through the cartridge valve. Subsequently, the differential pressure between the master cylinder and the tank is reduced due to the pressure relief of the counter cylinder and the press cylinder, and the spool of the master cylinder oil circuit is gradually closed, resulting in a decrease in the flow of the return tank.

Velocity change point H: At the speed change point H, all the valves on the master cylinder main oil circuit are closed, and the pressure of the counter cylinder and the press cylinder are relieved, so the elastic deformation of the material is recovered, resulting in a small displacement of the main cylinder after the speed rises to the highest point, and the speed becomes negative.

During the blanking process, the master cylinder load is the sum of the blank holder force, the counter force and the blanking force, as shown in Fig. 11.

x: Time (s); y: Cutting force (red) (N), counter force (green) (N), blank holder force (blue) (N), total load of the master cylinder (magenta) (N).

Fig. 11. Load variation curve during blanking.

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The peak 1 appears when the mold is closed, the peak 2 appears when the punching force is maximum, which is slightly lower than the peak 2.

The operating curve of the master cylinder in open-loop control mode is shown in Fig. 12.

x: Time (s); y: Master cylinder displacement (red) (m), master cylinder acceleration (green) (m/s2), master cylinder velocity (blue) (m/s).

Fig. 12. Operating curve of the master cylinder in open-loop control mode.

The displacement of the master cylinder during the blanking process is approximately straight, and the acceleration at each speed change point is less than 5 m/s2.

Analysis of closed-loop control. The closed-loop control of the speed and position of the master cylinder is carried out to investigate the performance of the system.

With the slider speed as the control variable, the schematic diagram of the closed-loop control system is shown in Fig. 13 (a).

With the slider displacement as the control variable, the schematic diagram of the closed-loop control system is shown in Fig. 13 (b).

(a) Closed-loop control with speed

(b) Closed-loop control with displacement

Fig. 13. Closed-loop control system.

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The slider speed is simulated in a closed-loop control in the case where the proportional valve responds quickly (bandwidth is nearly 100 Hz), and the results are shown in Fig. 14.

x: Slider displacement (m); y: Slider velocity in open-loop control (green) (m/s), slider velocity in closed-loop control (red) (m/s).

Fig. 14. Simulation of the speed in open loop and closed-loop control.

The speed variation in the open-loop control is suppressed by the closed-loop control of the speed, and the speed waveform of the system during the whole blanking process is also improved.The speed decline reduced by nearly 2/3 at position 1, but a short-time speed overshoot appears at position 2; In particular, the corresponding mold at the A has just closed the position, the speed of the decline reduced by nearly 2/3, but at the same time B appeared a short time speed overshoot; The speed fluctuation due to the fully open of the cartridge valve spool at position 3 is advanced to a displacement of 0.66mm, which is helpful to stabilize the speed in the blanking process; A small bump at position 4 is formed since the speed trough caused by the load crest is suppressed.

The simulation of the slider displacement in a closed-loop control is shown in Fig. 15.

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x: Slider displacement (m); y: Slider velocity in open-loop control (green) (m/s), slider velocity in closed-loop control of the displacement (red) (m/s) , slider velocity in closed-loop control of the speed (blue) (m/s).

Fig. 15. Simulation of the displacement in closed-loop control.

The speed appears a peak at position 1 by the displacement closed-loop control. The control accuracy of the displacement is improved and the slider can be stopped more accurately at position 2, but the fluctuation of the velocity curve is greater than that of the speed closed-loop control.

Comparison of the open/closed loop control. The main factor that affects the performance of the open-loop control is the response of the pressure regulating valve in front of the master cylinder proportional valve to the system pressure variation. The pressure-regulating valve adjusts the pressure difference between the two ends of the proportional valve to stabilize the flow into the master cylinder. The response time of the ideal pressure regulating valve is zero, that is, the outlet pressure of the proportional valve can be adjusted in real time according to the inlet pressure. In the open loop control simulation with the ideal pressure regulating valve, the slider speed is approximately straight, as shown in Fig. 16. Therefore, if the valve performance is better, the system speed can be stabilized by open loop control.

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x: Slider displacement (m); y: Actual velocity of the slider (green) (m/s), ideal velocity of the slider (red) (m/s).

Fig. 16. Comparison of the slider speed.

The simulation results show that there is a risk of system oscillation due to the speed control of the proportional valve with low frequency response. The duration of the punching process is very short, usually less than 0.5 s, and the response time of the proportional valve is close to 0.1 s in the step change from 0.1 to 100 %, so the speed closed-loop control is not necessary. The slider displacement curves of the open loop control and the closed loop control are both close to the straight line due to the short stroke, as shown in Fig. 17.

x: Time (s); y: Slider displacement in closed-loop control of displacement (red) (m), slider displacement in open-loop control (green) (m/s), slider displacement in closed-loop control of velocity (blue) (m/s).

Fig. 17. Displacement curve of the master cylinder in different control modes.

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In summary, according to the variation in load and the configuration of the hydraulic system, the open-loop control mode should be adopted for the system during the blanking stage.

Optimization control strategy of the blanking process. The optimization control strategy is to adjust the system components according to the trend of slider speed and displacement variation in the open-loop control mode described in the previous section to reduce the speed fluctuation of the system.

The improvement of the cutting speed can accelerate the plastic deformation of the metal, which is conducive to the formation of smooth shear section, but will increase the die wear, and reduce its service life quickly. In the shearing process, the work of the punching force is converted into heat energy, most of which occurs in the shear zone of grain deformation. In the shearing process, the work of the punching force is converted into heat mainly in the grain deformation of the shear zone.

The curve of the blanking force variety shows that most of the heat is generated in the first half of the shear process, so the appropriate reduction of the punching speed at this stage is helpful in improving the life of the die edge and stabilizing the quality of the shear section. The punching speed can be appropriately increased in the subsequent intermediate stage of the punching process to improve the punching efficiency.

The master cylinder speed should be reduced when the punching process approaches the end to control the position accuracy of the top dead center of the slider. When the slider is near the top dead center position, the opening of the proportional valve is small or is actually closed, the flow required for the last displacement to the top dead center (tens of microns) is together provided by the relief valve on the cover plate of the press regulating valve and the proportional valve to achieve precise control of the slider.

In order to avoid the occurrence of the speed change point A in the open loop control, the two cartridge valves on the master cylinder oil circuit should be started at the end of the fast forward process to complete the initialization of the proportional valve inlet pressure before the start of the punching stage. The proportional valve should also be started for a certain period of time due to the dead band, so that the main spool is located at the 0 position when punching stage is started.

The master cylinder load continues to increase during the pressing of the blank holder, and a load peak appears at the end of the process due to the die closing. The control current of the proportional valve in this region continues to rise, which is helpful in suppressing the speed trough at point C in the open loop control. The pressure difference between the two ends of the proportional valve becomes smaller and the opening of the main spool becomes larger due to the response time of the pressure regulating cartridge, which keeps the flow through the proportional valve relatively stable.

The master cylinder load changes smoothly after the punching process begins, and the proportional valve control current remains constant to maintain the master cylinder speed stable. The master cylinder speed is slowed down due to the load increase during the punching process, which is consistent with the principle of reducing the speed at the beginning of the blanking to increase the life of the die.

The punching force begin to decrease in the middle of the punching process. The slider punching speed starts to rise when the proportional valve control current is constant. But the speed rise is limited due to the regulation of the pressure regulating valve.

The proportional valve control current begins to be reduced when the slider reaches the deceleration point. The proportional valve is almost or completely closed when there is a slight distance from the top dead center, and the cartridge valve in the main oil circuit begins to close. The cartridge is closed when the slider reaches the top dead center, and the punching process ends. The position of the deceleration point is determined by the slider speed, the ramp time and the response time of the proportional valve.

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The blanking force is related to the amount of the material deformation in the blanking process, and the counter force is basically unchanged. The unloading speed of the blank holder is the only adjustable parameter. The slower speed stabilizes the master cylinder load but causes a waste of energy. The faster speed reduces the energy loss but causes the speed fluctuation of master cylinder.

From the perspective of the optimization of the punching conditions, the unloading of the blank holder force should not be too fast. The ideal situation is that the reduction of the blank holder force is equal to the increase of the blanking force after the die closing, which keeps the load stable from the die closing to the blanking force rising to the maximum, and stabilizes the punching speed. Although some of the energy is consumed, it is worthwhile for the stability of the system speed and accuracy.

The simulation results of the hydraulic control system in the blanking process based on the slider speed control optimization and load optimization are shown in Fig. 18. In the case of the best fit of all the valves, the slider speed is stable and the overshoot of the master cylinder position is less than 0.005 mm.

x: Slider displacement (m); y: Slider velocity (m/s).

Fig. 18. Speed curve of the master cylinder with the open-loop optimal control.

The changes of the corresponding force and master cylinder load are shown in Fig. 19, which is moderate compared with the load without optimization, and is conducive to the stability of the slider speed.

The automatic optimization algorithm is based on the basic control system. The algorithm flow chart is shown in Fig. 20.

Data acquisition: collecting and recording the displacement curve of the master cylinder, the pressure time curve of the counter cylinder and the blank holder, the action time of the control current and the spool position data of each valve.

Data analysis: calculate the positions of the speed change points and the maximum blanking force point through integrating the displacement time curve of the master cylinder.

Optimization strategy generation: building a strategy based on the location and timing of velocity change points using theoretical and practical data through the neural network.

Execution or non-execution: deciding whether to execute the optimization strategy based on the current machine conditions and machined parts quality.

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Local optimum calculation: finding the optimal set of control parameters through multiple iterations.

Stability analysis: analyzing the variation of all working parameters in each blanking to find the trend of parameters changing as soon as possible and adjust them in time.

x: Time (s); y: Cutting force (red) (N), counter force (green) (N), blank holder force (blue) (N), total load of the master cylinder (magenta) (N).

Fig. 19. System load changes after the optimization.

Fig. 20. Flow chart of the automatic optimization algorithm of the control system.

The basic control system is active prior to the optimizing control, and the data is recorded and analyzed to calculate the corresponding optimizing control methods. After starting the optimizing control, the control system determines and corrects the optimal control parameters through multiple MMSE Journal. Open Access www.mmse.xyz

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tests, and the parameters will be continuously monitored during the subsequent processing for processing of anomalies timely.

Summary. In this paper, taking the control strategy of the hydraulic system in the blanking and punching stage as the research object, the guiding principle of the control strategy is studied. The system performance of the open - loop control and the closed - loop control and the factors influencing the change point of the component characteristic curve are analyzed, and the reference indexes of the control mode are put forward. The optimizing control algorithm of the process is studied at last.

(1) According to the change of the load in the fine blanking process and the configuration of the hydraulic system, it is appropriate to adopt the open loop control mode in the blanking phase.

(2) The load of the main cylinder changes smoothly through the load and speed control optimization, which is conducive to the stability of the slider speed.

(3) The controllability of the hydraulic system will be improved if damping is used to mitigate the possible impact according to the characteristics of the system load changes.

Acknowledgements The authors gratefully acknowledge the financial support from the Natural Science Foundation of China (Grant number: 51375438).

References [1] T. Schwarzgruber, T. E. Passenbrunner, L. Re. Control design for a multi input single output hydraulic cylinder system. 19th IFAC World Congress, Cape Town, South Africa, August 24-29, 2014 [2] W. Shen, J. Jiang, X. Su, H. R. Karimi. Control strategy analysis of the hydraulic hybrid excavator.

Journal of the Franklin Institute 352(2015) 541-561 [3] K. Baghestan, S. M. Rezaei, H. A. Talebi, M. Zareinejad. An energy-saving nonlinear position control strategy for electro-hydraulic servo systems. ISA Transactions 59(2015) 268-279 [4] W. Ding, H. Deng, Y. Xia, X. Duan. Tracking control of electro-hydraulic servo multi-closedchain mechanisms with the use of an approximate nonlinear internal model. Control Engineering Practice 58 (2017) 225- 241 [5] L. S. Coelho, M. A. B. Cunha. Adaptive cascade control of a hydraulic actuator with an adaptive dead-zone compensation and optimization based on evolutionary algorithms. Expert Systems with Applications 38 (2011) 12262 12269 [6] N. M. Tri, D. N. C. Nam, H. G. Park, K. K. Ahn. Trajectory control of an electro hydraulic actuator using an iterative backstepping control scheme. Mechatronics 29 (2015) 96 102 [7] C. Jia, X. Shan, Y. Cui, T. Bai, F. Cui. Modeling and simulation of hydraulic roll bending system based on CMAC neural network and PID coupling control strategy. Journal of Iron and Steel Research, International 2013, 20(10): 17-22 [8] G. Shen, Z. Zhu, J. Zhao, W. Zhu, Y. Tang, X. Li. Real-time tracking control of electro-hydraulic force servo systems using offline feed back control and adaptive control. ISA Transactions 67 (2017), 356-370 [9] P. Chalupa, J. Computers and Mathematics with Applications 66 (2013), 155 164 [10] Y. Ye, C. Yin, Y. Gong, J. Zhou. Position control of nonlinear hydraulic system using an improved PSO based PID controller. Mechanical Systems and Signal Processing 83 (2017), 241 259 [11] R. Li, J. Luo, C. Sun, S. Liu. Analysis of Electro-hydraulic Proportional Speed Control System on Conveyer. Procedia Engineering 31 (2012), 1185 1193 MMSE Journal. Open Access www.mmse.xyz

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[12] C. Du, A. R. Plummer, D. N. Johnston. Performance analysis of a new energy-efficient variable supply pressure electro-hydraulic motion control method. Control Engineering Practice 60 (2017), 87 98 [13] K. M. Elbayomy, Z. Jiao, H. Zhang. PID Controller Optimization by GA and Its Performances on the Electro-hydraulic Servo Control System. Chinese Journal of Aeronautics 21(2008), 378-384 [14] B. N. Muhammad, S. Wang. Optimization Based on Convergence Velocity and Reliability for Hydraulic Servo System. Chinese Journal of Aeronautics 22(2009), 407-412 [15] H. Cao, H. Guo. Optimization of PID Parameters of Hydraulic System of Elevating Wheelchair Based on AMESim. Procedia Engineering 15 (2011), 3710 3714 [16] J. Zheng, S. Zhao, S. Wei. Application of self-tuning fuzzy PID controller for a SRM direct drive volume control hydraulic press. Control Engineering Practice 17 (2009), 1398 1404.

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Analysis of Sanitary and Hygienic Labour Conditions of Drivers of Public Transport Buses 1

Deriugin 1

State Higher Educational Institution

a

oleg.kot@meta.ua

b

lenusia3366@gmail.com

c

sihc@yandex.ua

V.1,a, Tretiak

1,b

, Cheberyachko S

1,c

, Ukraine

DOI 10.2412/mmse.45.99.15 provided by Seo4U.link

Keywords: sanitary and hygienic conditions, harmful factors, noise load, vibration load, temperature environment, concentration of harmful substances, public transport bus, maximum permissible level.

ABSTRACT. Sanitary and hygienic labour conditions of the drivers of public transport buses have been analyzed. Three of the most popular brands of public transport buses have been studied. It has been determined that sanitary and hygienic labour Mercedes-Benz Sprinter 411 , 23 , negative indices. Moreover, they are characterized by excess level of noise load (2.9 to 7.7 dBA), vibration load (10 to 20 dB), and such microclimatic indices of working environment which excess in summer achieves inadmissible figures (up to 15-20 0 ). Positive result of the analysis has also been identified, i.e. concentration of harmful substances within working environment is less than the admissible level.

Introduction. Efficiency and safety of passenger transportation by means of motor vehicles depends directly of psychophysical state and health of a driver; the requirements are regulated by the current legislation. Commonly known unfavourable effect of harmful factors upon drivers when they perform transportation work (stressful and often variable conditions of passenger transportation, increased responsibility for passenger safety in the context of time deficit, imperfect design of motor vehicles, effect of harmful substances etc.) results in both progress of occupational diseases and effect on systematic diseases state. Following diseases can be singled out among the basic risks of occupational diseases contraction - blood circulatory system diseases as well as disease connected with overfatigue, fatigue, and depression (Fig. 1 [1, 2]).

Recently, modern medicine has paid more and more attention to the studies dealing with the effect of harmful substances formed in the process of passenger tr of factors of objective evaluation and subjective evaluation are applied to do that.

Group 1 includes functioning of spare capacities of cardiovascular system and respiratory system as well as supporting-motor apparatus while taking into consideration age properties of the people under examination. Group 2 includes subjective evaluation of health according to questionnaire survey. The evaluation reflects partially the characteristics of central nervous system [3-6].

As a result, determination of regularities of the interaction between the effect of harmful working factors upon the level of occupational diseases of drivers is one of the key problems today (Fig. 2).

1

-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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Fig. 1. Structure of risks of occupational diseases contraction of drivers performing passenger transportation by means of public transport buses [1, 2].

That is why analysis of sanitary and hygienic labour conditions being the initial data for various studies (decrease in biological age of drivers, level of occupational risk of various diseases contraction, determination of efficient operating modes etc.) concerning labour conditions and health of drivers of public transport buses is a burning problem.

Fig. 2. Harmful environmental factors effecting upon the health of drivers of public buses Statement of the research task. Despite the fact ,that sanitary and hygienic working conditions of public transport bus drivers in the process of passenger transportation have already been adequately studied and used as the basis for relevant standards to provide rational labour activity of drivers [7], the problem of occupational health maintenance as well as the development of safe labour conditions for drivers remains topical worldwide [8]. Due to the availability of the great number of private carriers, more and more often scheduled requirements for the organization of work-rest regime of drivers have started to be violated. Moreover, considerable relaxation of hold on the health has resulted in the increased number of fatal cases of drivers when they transport passengers as well as in the contraction of occupational diseases. Furthermore, psychological stress of drivers has incremented greatly as well due to more intensive traffic, increased flow of input information for making decisions, responsibility for the safety of transportation process, route complexity etc. Thus, in the city of MMSE Journal. Open Access www.mmse.xyz

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Dnipro, a driver who transported passengers within the route #76 (r Nagornyi Rynok) died of heart attack on 09.02.2017.

In due time, the problems were highlighted by a number of national and foreign scientists. In particular, papers by Yu.O Davidich considered the issues of ergonomic support of transportation process to minimize their effect upon labour activity of drivers. The scientist managed to find dependence of the changes in physiological state of drivers upon the length of the route, its complexity, power of a vehicle and other parameters [9]. However, he paid minor attention to the effect of sanitary and hygienic conditions. This very disadvantage is also observed in a paper by . .

Lobashov [10] where he analyzes labour activity of a driver, his/her possibility to perform both physical and mental work connected with driving process, ability to keep the required rate and struggle against fatigue. Interesting data were published in a paper by T.L. Liebiediev at al. The authors tried to establish relations between the inadequacy of standards concerning driving period and chronic fatigue as well as increased nervous and emotional stress stipulating the changes in vegetative nervous system and increasing the risk of cardiovascular diseases and diseases of digestive system [11]. Consequently, it is required to analyze the effect of harmful factors and labour conditions of public transport bus drivers.

Objective and task of the research. Objective of the research data was to measure harmful factors: level of noise load, level of vibration load, temperature environment of working space, concentration of harmful substances within the working space for the analysis of sanitary and hygienic labour conditions of drivers of the corresponding brands of public transport buses.

To achieve the objective it is required to solve following problems: - to measure the indices of harmful factor: level of noise load, level of vibration load, temperature environment of working space of drivers of different brands of public transport buses; - to make comparative analysis of the obtained results of indices of harmful factors with maximum permissible levels (MPLs) of DSTU determining standards of working environment.

Materials and research methodology. Sanitary and hygienic labour conditions of drivers of public transport buses in terms of indices of basic unfavourable working factors (level of vibration load, level of noise load, concentration of harmful substances within the working space etc.) were estimated Benz Sprinter 411 , 23 , transportation performed with the help of motor vehicles in the city of Dnipro. The experiment involved 12 drivers at the age of 28-45 whose working experience was 5-20 years. Total estimation of labour conditions relied upon the requirements and recommendations stipulated in Hygienic labour classification according to the indices of harmfulness and hazard of working environment, complexity and stressfulness of the labour process (Order # 248 of 08.04.2014 registered in the Ministry of Justice of Ukraine on the 6th of May 2014, #472/25249).

Level of noise load was measures according to the developed methodology and DSN 3.3.6.037-99 place of a driver was measured wit 45-60 km/h.

The least velocity was selected of the velocities. The measurements were performed according to five (at least) values of constant velocities with the value rounding to 5km/h: the least index, the highest index, and intermediate index to provide interval evenness between the velocity values of a public transport bus. No less than three measurements of noise load value were performed within each point ccording to the results of the measurements, averaged arithmetic values rounded to the whole number were taken. If the difference between the greatest and the least values of noise load levels in each point exceeded 2 dBA, then the measurements were repeated.

Sanitary and hygienic analyses of temperature environment parameters of working space of a driver of public transport bus corresponded to following regulatory documents: DSN 3.3.6.042-99, DSN MMSE Journal. Open Access www.mmse.xyz

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3.3.6.096-2002, SN 2152-80, DSN 3.3.6.037-99 dards of microclimate in working . Parameters of temperature environment of working space of a driver of public transport bus Tenzor-41 TESTO 405-V1 The analysis was performed under following conditions: air shade temperature was +32. . . +34 0 the bus was moving southward (deviation of the direction was + 150. . . 200 km/h, the temperature was measured from 1200 to 1400. It has been proved that within the time period solar radiation and temperature indices being measured are the most stable [12]. Temperatures were -thighs, and feet-calves.

The research was performed in such an order. Taking into account the fact that seats of a driver and a passenger are located symmetrically and climatic environment for a driver and passenger is similar, thermometers were mounted on a passenger seat. The measurements were performed three times within each zone with five-minute periodicity.

Sanitary and hygienic analysis of concentration parameters of harmful substances within working space of a driver of a public transportation bus has been carried out in accordance with normative documents: DSN 3.36.042-99 parameters of harmful substances within working space of a driver of a public transport bus were GX benzol, petroleum, xylol, carbon oxide, toluol, chlorine, oxides of nitrogen, hydrogen sulphide, ethyl g within the -10 VLO-200 Similar approach to identify hazardous concentrations of harmful substances was used in paper [13].

The obtained results were processed using methods of variance and correlation analysis involving software application Microsoft Office Excel-2010.

Level of vibration load was measured according to the developed methodology and DSN 3.3.6.039-

Vibration load at the working place of a drive of corresponding brands of public transport buses was measured as follows: in the process of the public transport bus movement at constant velocity while passenger transporting and involving motionless public transport bus during idle period within a driver rest area. Gearbox vibration was analyzed in the process of public transport bus movement in second gear within smooth section of asphalt road when rotation frequency of a crankshaft was 12001300 rot/min.

Results of the research. It has been determined that the level of noise load is among unfavourable factors effecting upon a driver health in a cab of public transport bus (Table 1). It is common knowledge that level of noise load effects considerably psychological state of a driver. There are following consequences of noise load effect upon a driver: irritancy, low level of self-control and attention. That may affect the process of positive decision-making to be important, for instance, for a driver in the context of quick changes in situation while driving a vehicle in terms of urban traffic or deterioration of attention in the process of long-term operation which will increase the risk of road accident.

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Table 1. Levels of noise load at working place of a driver in a cab of a public transport bus.

Bus brand

Benz Sprinter 411 23

Level of sound pressure in octane bands with average geometric frequencies, Hz 63

125

250

500

1000

2000

4000

8000

90.4

86.4

82.3

78.3

76.2

69.2

67.9

63.1

0.56

0.54

0.50

0.46

0.49

0.47

0.44

0.39

91.3

87.3

83.1

79.1

77.0

69.9

68.6

63.8

0.62

0.59

0.55

0.51

0.54

0.52

0.48

0.43

94.9

90.8

86.4

82.2

80.0

72.7

71.3

66.3

0.97

0.95

0.89

0.82

0.87

0.84

0.77

0.69

66

64

Equivalent level of sound, dBA 82.9

84.6 87.7

MPL according to DSN 3.3.6.037-99 Buses

91

83

77

73

70

68

80

According to the studies represented in Table 1 it is possible to conclude that average value of equivalent level of noise load at working place of a driver in Benz Sprinter 411 -78.7 dBA; 23 -78.8 dBA; 80.5 dBA. The indices of noise load level of the corresponding brands of public transport buses are not higher than MPL rate. We consider that there are various reasons for that from poorly fixed panels to required major repair of both engine and passenger compartment. , accuracy, responsivity, and comfort; moreover, it may result in fatigue progress etc. That is why the index should meet the requirements of standards and cannot exceed MPL (Table 2).

The most favourable working conditions for drivers of public transport buses are: 18-23 0 in cold season and 20-23 0 in warm one [14]. transport bus depends on the design features hermiticity of a cab, location of engine, its heat insulation, and efficiency of heating system or conditioning depending upon the season as well as quality of materials used to equip the cab.

Research data represented in Table 2 may help conclude that during a warm season (June-September) drivers work under conditions of increased temperature. Temperature values, starting from 6th successive hour of their work (1000-1100 a.m.) exceeded permissible values and achieved 43-45 0 Moreover, corresponding indices obtained in a cold season also differ considerably from the permissible ones. It means that neither ventilation system not heating one can provide the required air temperature. For instance, in summer sun-heating of cab walls, extra warm from the operating engine and heat emission by passengers play important role as the majority of public transport buses are not equipped with conditioner.

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Table 2. Microclimatic conditions at working places of public transport bus drivers.

Bus brand

Air temperature, 0 C

Relative humidity, %

Air rate, m/s

Cold season and transitional season Benz Sprinter 411 23

0.5-0.8 +2 - +29

16-78

0.5-0.9 0.6-0.9

MPL according to DSN 3.3.6.042-99

17-23

75

0.3

Warm season Benz Sprinter 411 Ruta 23

0.5-0.8 27-30

20-86

0.9 0.9

MPL according to DSN 3.3.6.042-99

18-27

65

0.2-0.4

Availability of harmful substances (dust) within working space of a bus driver as well as within a index may result in a progress of hypersensitivity reactions, deterioration of immune system, feeling unwell by the bus drivers [15]. As data from Table 3 demonstrate, concentration levels of harmful substances are within 7-10 mg/m3. However, the data are averaged indices; in certain cases, dust concentration and wear or design imperfectness of protective tightening components of a public transport bus body as well as road conditions of transportation favour it.

Table 3. Concentration levels of harmful substances (dust) within working space of a public transport bus driver.

Dust level (averaged), mg/m3 Bus brand breathing Benz Sprinter 411 Ruta 23

Near the floor

7.29 0.35

3.11 0.27

7.86 0.43

4.49 0.42

10.43 0.51

5.76 0.48

PCL

6.0

Contamination with toxic chemical substances of thermal destruction products of discharged fuel and oils of the transport means itself as well as harmful substances getting into the public transport bus from the environment are considerable unfavourable factor within cabs of public transport buses. instance, in insignificant amounts, the former may provoke sense of alcoholic intoxication, thus MMSE Journal. Open Access www.mmse.xyz

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resulting in road accident participation. That very time, nitrogen dioxides irritate mucous coats of respiratory tracts which may result in serious intoxication and provoke sensory, functional, and pathological effects. In turn, carbon dioxide causes changes in central nervous system by means of its own effect and hypoxia state. According to the data from Table 4, concentrations of carbon oxide and nitrogen oxide are within the standard rates in a working space of the public transport bus cabs.

However, in the context of the decrease of cab hermiticity indices and incomplete fuel combustion resulting from the deferred maintenance of engine systems, their concentration may experience drastic increase. It should also be noted that the increase in concentration of harmful chemical substances may also be a result of idle time of public transport buses in traffic jams.

Table 4. Concentration levels of harmful chemical substances within the working space of a driver of public transport bus.

Contamination of cabs of public transport buses with harmful chemical substances, mg/m Nitrogen oxides Bus brand

(MPL is 5.0 mg/m Within a breathing zone

Benz Sprinter 411 23

Carbon oxide (MPL is 20.0 mg/m

Near the floor

Within a breathing zone

Near the floor

2.

.5

1.

.2

7.

.4

7.

.1

2.

.4

2.

.2

12.

.4

11.

.1

2.

.3

2.

.4

18.

15.

.9

The obtained data make the authorities of transportation enterprises take corresponding organizational measures to minimize the effect of making it possible for drivers to recover after their working shift.

Level of vibration load upon a driver is one of the most unfavourable working factors affecting the health of public transport bus drivers. Bus movement is accompanied by the oscillations due to the unbalanced force actions within units and aggregates as well as external changing action because of road surface irregularities. The oscillations are transmitted to the body of a public transport bus; they are also transmitted through road surface and ground to the elements of roadside area. Vibration load action may be considered on the analogy of the noise in two aspects: effect upon a driver and passengers of a public transport bus and effect upon the surrounding objects. Vibration load results in the violation of physiological and functional state of a driver s organism, fatigue, and devastating diseases. Stable harmful physiological changes, being a result of long-term action of vibration load, factor into vibration disease [16].

According to the research data (Table 5) one may conclude that the levels of vibration load at the working places of bus drivers exceeded standard rates by 10-20 dB (MPL according to the value of vibration acceleration should be 65 dB). Imperfectness of design or poor condition of a vehicle suspension system is the reasons to consider public transport buses as inappropriate in terms of vibration load.

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Table 5. Levels of vibration load within the cab of a public transport bus.

Bus brand Benz Sprinter 411 Ruta Bohdan

Axels X0, Y0, Z0

Corrected value of vibration, dB

Minimum and maximum values, dB

Z0

75.8

70-80

X0, Y0

71.8

68.5-76.0

Z0

80.5

73-90

X0, Y0

85.0

77-93

Z0

77.0

74-89

X0, Y0

86.3

74-97

MPL according to DSN 3.3.6.039-99 corrected levels, category 1, transportation 65

Z0

vibration acceleration;

107

Buses

62

X0, Y0

vibration velocity

vibration acceleration;

116 - vibration velocity

Summary. According to the results of the analysis of sanitary and hygienic labour conditions of drivers of such public transport buses as Mercedes Benz Sprinter 411 , 23 , being the most popular in the segment of motor passenger transportations in the city of Dnipro, it is possible to draw following conclusions. All the tested public transport buses have excessive levels of noise load (2.9-7.7 dBA), excessive levels of vibration (10-20 dB), and excessive indices of microclimatic conditions at the working places of public transport buses drivers which become inadmissible as temperature indices of the excess are up to 15-20 0 However, the analysis of sanitary and hygienic labour conditions of drivers of public transport buses has positive result as well concentration of harmful substances within a working place of a public transport bus driver is not higher than MPL. In addition to recommendations concerning the decrease in harmful effect of should not last more than 8 hours with obligatory breaks to have rest lasting not less than 45 minutes after each cycle.

References [1] Sukhova, Ya. M., Assessment of occupational health risks of drivers of specialized vehicles [ ], [dissertation]. St. Petersburg; -Western State Medical University named after I.I. , 2009, 189 pp.

[2] , (2013) On formation of kinematical and dynamical parameters of output elements of the mine vehicles in transient motion. Scientific Bulletin of National Mining University, 2013, 4, pp. 65-70.

[3] Demetska, , (2002) Biological age and certain homeostasis indices displayed by workers of of the prime occupations in the context of ferrous-based alloys manufacture [Biolohichnyy vik ta deyaki pokaznyky homeostazu u robitnykiv osnovnykh profesiy vyrobnytstva ferosplaviv].

Environment and Health, 2002, 3, pp. 34-37.

[4] Kashuba, , (2003) On the methodological approaches to the determination of biological age of a human [O metodolohycheskykh podkhodakh k otsenke byolohycheskoho vozrasta cheloveka].

Labour hygiene, 2003, 34, pp. 813-825.

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[5] Ingram, D.K., (2001) Strategy for identifying biomarkers of aging in long-live species.

Exp.Gerontol, 2001, 36, pp. 1025-1034/ [6] Abramovich, S.G., (2001) Biological age of a human, cardiovascular system, and ageing rate [Biologicheskiy vozrast cheloveka, serdechno sosudistaya sistema i skorost' stareniya]. Clinical medicine, 2001, 5, pp. 3-32.

[7] The Ministry of Transport and Communications of Ukraine (2010), On the approval of working time provision and time off for the drivers of wheeled vehicles [Polozhennja pro robochyj chas i chas vidpochynku vodii'v kolisnyh transportnyh zasobiv].

Available at: http:// zakon3.rada.gov.ua/laws/show/z0811-10 [8] Grebenkov, S.V., (2011) Structure of motor-transport sector in Saint Petersburg labour conditions, professional health, and safety, Saint Petersburg [Profil' avtotransportnogo sektora v Sankt-Peterburge - usloviya truda, professional'noye zdorov'ye i bezopasnost']. 2011, 54 pp.

[9] Davidich, , (2011) Ergonomic provision for transport processes [Erhonomichne zabezpechennya transportnykh protsesiv]. Kharkiv National Academy of Municipal Economy named , 2011, 392 pp.

[10] , et al. (2016) Application of models and techniques of ergonomics in terms of transport systems [Zastosuvannya modeley i metodiv erhonomiky i lohistyky v transportnykh systemakh]. Kharkiv National University of Municipal E Publis 2016, 332 pp.

[11] Liebiedeieva, .L., Gurov, S.V., Petrov, Chorny, , (2016) Analysis of health status of taxi drivers according to the results of questionnaire survey [ ]. Actual Problems of Transport Medicine, 2016, 2(44), pp. 67-73.

[12] Vereshchiagin, S.B., (2011) Analysis of temperature conditions and humidity in a vehicle cab under the conditions of heat [Issledovaniye temperaturnogo rezhima i vlazhnosti v kabine transportnogo sredstva v usloviyakh zhary]. Messenger of MSTU named after N.E. Bauman, , 2011, 3, pp. 56-63.

[13] Sidorenko, S.G., (2015) Hygienic assessment of labor conditions of road train drivers and workers of solvent-extraction plants being in contact with fumigated grain cargo [Gigiyenicheskaya otsenka usloviy truda voditeley avtopoyezdov i rabochikh masloekstraktsionnykh zavodov, kontaktiruyushchim s fumigirovannymy zernovymy gruzami]. Actual Problems of Transport Medicine, 2015, 1(39), pp. 59-71. , Galych, V., (2010) Analysis of requirements for microclimate at the [14] Lukianenko, workplace of operator of mobile agricultural machinery [Analiz vymoh do mikroklimatu na ]. Messenger of Kharkiv National Technical Agricultural University named after Petro Vassylenko, 2010, 2, pp. 232-247.

[15] Karakushikova, .S., Toguzbaieva, Niiazbekova, L.S., Seiduanova, L.B., Zhunistaiev, D.D., Nurshabekova, , (2012) Hygienic assessment of technological environment pollution of motor-transport drivers and preventive control [Gigiyenicheskaya otsenka zagazovannosti proizvodstvennoy sredy voditeley avtotransporta i profilakticheskiye meropriyatiya]. Messenger of KAZNMU, 2012, 2, pp. 15-20.

[16] Romanchenko, . ., Syrmolotov, I.V., Karaivan, S.Yu., Novikov, Nikulin, (2011) On the influence of vibration on a human [O vozdeystvyy vybratsyy na cheloveka]. Almanac of Modern Science and Education, Tambov Gramota pp. 56-58.

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Analysis of Cost Efficiency in the Context of a Filling and Charging Station for Hybrid Vehicles 1

Pivnyak G.G.1, Kravets V.V.1, a, Bas K.M.1, Kravets Vl.V.2, b, Zubariev M.S.1, c, Tokar L.A.1 1 2

National University of Railway Transport, Dnipro, Ukraine

a

prof.w.kravets@gmail.com

b

vladkravetsphd@gmail.com

c

mykola.zubariev@gmail.com DOI 10.2412/mmse.95.86.168 provided by Seo4U.link

Keywords: hybrid vehicles, transition probability matrices, transition value matrices, mathematical expectation of Markov process value.

ABSTRACT. A method of the analysis of cost efficiency in the context of filling and charging stations for hybrid vehicles is proposed. Dynamic model of random Markov process for hybrid vehicles maintenance in the form of asymmetric state graph with four nodes is constructed. Relevant mathematical model of random Markov process in the form of recurrent quartic matrix format is being developed. Matrix of transition values to reconstitute and store both mechanical and electrical subsystems of hybrid vehicles, mathematical expectations of values of certain transitions is formed. A matrix of transition values to re-establish and store both mechanical and electrical subsystems of hybrid vehicles; mathematical expectations of values of certain transitions as well as mathematical expectation of a random Markov process value on the whole are introduced.

Introduction. Global environmental problems are closely connected with energy efficiency of vehicles. Basic tendency concerning the improvement of energy efficiency of vehicles is forecasted and implemented in the field of the progress of electromechanical systems [1-3]. More specifically, hybrid cars and their companion infrastructure (i.e. filling and charging stations) are developed.

A wide range of emerging problems are solved wholistically relying on fundamental results represented, for instance, in monographs [4, 5]. In this context, random processes within complicated systems (technical, biological) modeling, their reliability and cost-efficiency estimation are performed on the basis of Markov chains (discrete, continuous) [6-8]. Following the continuity in the material statement, the paper uses symbols and formulas mentioned in [6, 9].

Formulation of the problem. Filling and charging station for the maintenance of hybrid cars is under consideration. Hybrid car is represented as an engineering system consisting of two independent subsystems (i.e. bisystem): 1) Mechanical subsystem involving internal combustion engine and its companion equipment; 2) Electrical subsystem involving power-wheel and its companion equipment.

Maintenance process of a stream of hybrid cars at a filling and charging station is cyclic and random.

For the considered problem, a period of cyclic process is taken to be twenty-four hours. The maintenance process involves activities connected with vehicle health check and recovery (filling, charging) of both mechanical and electrical subsystems. Each of the systems may be in either of the two lumped states: 1

GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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- power capacity recovery state symbolized as

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; and

- power capacity conservation state symbolized as

.

Random transitions (steps) of the subsystems from one state to another are considered in the context of the discrete moments

(1)

separated by pitch (stage). At this point, the pitch distance determines the accuracy of the engineering problem as well as the amount of calculations being made. Substantiation of the pitch distance is the individual problem being solved depending upon specified problem both heuristically and with the help of strict mathematical calculating values [10]. The following is recommended: no more than one transition of the subsystems from one state to another should take place during period. For the periodic random process, the pitch should not excess the period or it should be a multiple of the period. It may turn out to be expedient to select the pitch distance according to . To simplify the process of the engineering problem solving, as a first discrete time k , i. e. approximation, pitch distance of discrete time is set equal to an hour ( ). Then, those discrete moments, during which random transitions of hybrid vehicles from one state to another are recorded, can be identified using the simple formula:

,

where

(2)

; and

.

(3)

Depending upon the formulated conditions of the engineering problem under consideration, it is expedient to analyze dynamics of random process concerning the maintenance of hybrid vehicles as well as cost efficiency of a filling and charging station basing upon a theory of Markov random processes. The analysis involves the development of reasonable scheme of the process, adequate mathematical model as well as computational algorithm to model the process.

Dynamic scheme of random process of hybrid vehicles maintenance. In the process of independent maintenance of each subsystem of hybrid vehicle ( ) following random transitions may take place at discrete moments: - recovery state of

where

th

subsystem continues during following pitch; that is:

is the random event probability; MMSE Journal. Open Access www.mmse.xyz

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- recovery state of th subsystem has been completed during k th pitch; during following pitch, a transition to conservation state takes place; that is:

where

is probability of contrary event. It is obvious that

;

(4)

- conservation state of th subsystem during th pitch has been terminated; during following pitch, a transition to recovery state (recharging, refilling) takes place; that is:

where

is probability of the contrary event;

- conservation state of

where

th

system has been continued during following pitch; that is:

is the probability of opposite event. It is obvious that

;

(5)

Probabilities of random transitions of each of the systems during discrete moments can be determined with the help of statistical methods as a result of processing of experimental data concerning specific filling and charging station functioning. Qualitative estimations of the probabilities are defined according to following approximate formulas:

;

V k

;

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;

(6)

m k , M k

(7)

Mechanics, Materials Science & Engineering, December 2017

where th pitch; th

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is the number of cases corresponding to a transition of type one for

th

system during

is the number of cases corresponding to a transition of type two for

th

system during

pitch; th

during

th

during

is the number of cases corresponding to a transition of type three for

th

system

is the number of cases corresponding to a transition of type four for

th

system

pitch; pitch; is the number of cases corresponding to recovery state of

th

subsystem during

th

pitch; is the number of cases corresponding to observation state of th

th

subsystem during

pitch.

It should be noted that obvious equalities take place:

;

(8) .

(9)

In the process of hybrid cars maintenance at a filling and charging station, every of the two independently operating subsystems (mechanical subsystem and electrical one) can perform random transition from one state to another and back (states of recovery and observation) during discrete moments. On the whole, possible states of any hybrid vehicle can be determined with the help of diagram of states or according to generating function [8] at a rate defined in the form of :

1)

:

2)

:

3)

:

4)

:

A sequence of random events connected with intermittent transitions of hybrid vehicle on the four demonstrated possible discrete states within the determined discrete moments may be a random process taking place in a discrete Markov chain [9]. It is convenient to illustrate dynamics of the process of hybrid vehicle transition at filling and charging station as of possible states using such an asymmetric state graph:

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Fig. 1. Dynamic scheme of a random process concerning hybrid vehicle maintenance at a filling and charging station.

In this context, the number of peaks (states) and arcs (transition possibilities) within the asymmetric graph is determined as follows: , respectively. The asymmetric graph of states as well as corresponding discrete nonuniform Markov chain is the dynamic scheme of random process of hybrid vehicles maintenance at a filling and charging station.

Matrix mathematical model of Markov random process concerning hybrid vehicle maintenance at a filling and charging station. According to the demonstrated graph of discrete states, nonuniform Markov chain, mathematical model of random maintenance process for hybrid vehicles is developed.

The model is reduced to the recurrent matrix form of 4th order [9]: .

In this context, column matrix of possibilities

(10)

of the four states

of a

th hybrid vehicle is determined during following pitch with the use of column matrix of the bisystem probability of states during previous th and square matrix of

the transition probabilities. Components of the square matrix of transition probabilities correspond to arches of the graph of state graph of discrete Markov chain; the components are determined as conditional probabilities with the help of statistically determined probabilities of random transitions of both mechanical and electrical subsystems of hybrid vehicles: , , ,

; that is ,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

.

(11)

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It should be noted that sums of matrix columns discrete time; that is:

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and

are normalized at each pitch of

, , (12) , ,

and

, (13) .

The conditions enable analyzing stability (convergence) of the iteration process and controlling the accuracy of calculation procedures at each pitch (verification).

The problem is to determine probabilities of the four states of a hybrid vehicle at its following stage according to the probabilities of states at the previous pitch in the context of the preset boundary conditions. The boundary conditions are strictly determined initial ( ) and final ( ) conditions of the hybrid vehicle. Initial state is determined as a result of diagnosing of both mechanical and electrical subsystems within the initial pitch. Final condition of hybrid vehicle maintenance is target-oriented; it is the achievement of stable state at certain pitch when both mechanical and electrical subsystems have already been recovered, operating in a standard mode and being conserved, i.e. state .

Maintenance process for hybrid vehicles at a filling and charging station is considered as a finite sequence of probabilities of random states within discrete moments. Nature and duration of random maintenance process of both mechanical and electrical subsystems, limited by the preset boundary conditions, can be determined as a result of calculation experiment according to the developed mathematical model in the form of nonuniform, discrete Markov chain.

Transition values for hybrid vehicles maintenance at a filling and charging station. Random values for the recovery and conservation of certain subsystems within each pitch of staying at a filling and charging station are characterized by following distribution laws: - for a mechanical subsystem: c1 r1 - for an electrical subsystem:

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c2

In this context, and are discrete random values to recover both mechanical and electrical subsystems; and are discrete random values to conserve both mechanical and electrical subsystems; and are cost of time unit within the preset pitch while recovering both mechanical and electrical subsystems; and are time cost within the preset pitch while conserving both mechanical and electrical subsystems.

Depending upon discrete time, random maintenance values for mechanical ( ) and electrical ( ) subsystems of hybrid vehicles at filling and charging station at k th pitch with duration are determined statically according to the formulas:

;

;

;

(14)

.

In this context, is maintenance cost for th subsystem within corresponding to the transition of type one (recovery-recovery);

(15) th

pitch in those cases

is maintenance cost for th subsystem within transition of type two (recovery-conservation);

th

pitch in those cases corresponding to the

is maintenance cost for th subsystem within transition of type three (conservation-recovery);

th

pitch in those cases corresponding to the

is maintenance cost for th subsystem within transition of type four (conservation-conservation).

th

pitch in those cases corresponding to the

Adequate mathematical expectations of values to recover and conserve both mechanical and electrical subsystems are: ; ; (16) ; ,

Thus, they depend on discrete time

being assumed as constants within

interval.

Dimensions of a matrix of transition values of random maintenance process of hybrid vehicles at a filling and charging station depend on the number of arches of the asymmetric state graph, i.e.

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,

(17)

where

;

;

;

;

c23 k

;

r1 k v2 k

;

c1 k

l2 k ; ; (18)

;

;

;

;

;

;

;

.

from every possible state, mathematical expectations of transition values of hybrid vehicles at filling and charging stations are determined according to a matrix of transition values in the form of: ; ; (19) ; ,

or in the equivalent record using mathematical expectations concerning recovery and conservation of both mechanical and electrical subsystems, ; ; (20) ; .

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The obtained mathematical expectations of transition values for every possible state form the row matrix:

.

(21)

Within each pitch, corresponding probabilities of hybrid vehicles states are assumed as those determined with the help of a matrix of transition probabilities in the form of column matrix . The product of row matrix

of mathematical expectations of transition values

possible state by column matrix of the probabilities of the states determines the expected value of random process of hybrid vehicles transition according to the possible states: .

(22)

Total cost of random Markov process of recovery-conservation of hybrid vehicles at a filling and charging station during a day is estimated as follows:

.

(23)

Summary. Method to estimate economic efficiency of filling and charging stations for hybrid vehicles is proposed on the basis of the theory of Markov random processes. Dynamic model of random process of hybrid vehicles maintenance at filling and charging station in the form of asymmetric state graph with four peaks and sixteen arches is developed.

A method to estimate economic efficiency for a filling and charging station for hybrid vehicles maintenance is proposed. The method is based upon a theory of Markov random processes. A dynamic model of random process of hybrid vehicles maintenance at a filling and charging station is developed in the form of asymmetric state graph with four peaks and sixteen arches. Adequate mathematical model of Markov random process for the maintenance of hybrid vehicles is developed in the form of recurrent matrix form of 4th order. Values for recovery and conservation of both mechanical and electrical subsystems of hybrid vehicles are considered as discrete random values; corresponding distribution laws are determined. Matrices of transition values, mathematical expectations of values of certain transitions as well as mathematical expectations of a random Markov process on the whole are introduced to estimate economic efficiency of a filling and charging station for hybrid vehicles.

References [1] Cao, J., & Emadi, A. (2012). A New Battery/UltraCapacitor Hybrid Energy Storage System for Electric, Hybrid, and Plug-In Hybrid Electric Vehicles. IEEE Transactions on Power Electronics, 27(1), 122-132. DOI:10.1109/tpel.2011.2151206.

[2] Electric Vehicle Scenario Simulator Tool for Smart Grid Operators. Energies, 5(12), 1881-1899.

DOI:10.3390/en5061881.

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Mechanics, Materials Science & Engineering, December 2017

ISSN 2412-5954

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Mechanics, Materials Science & Engineering, 7, 85-96. DOI:10.13140/RG.2.2.34948.32643.

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