Mechanics, Materials Science & Engineering Journal (MMSE journal) by MMSE Journal

Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

Sankt Lorenzen 36, 8715, Sankt Lorenzen, Austria

Mechanics, Materials Science & Engineering Journal

September 2017

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

Mechanics, Materials Sciences & Engineering Journal, Austria, Sankt Lorenzen, 2017

Mechanics, Materials Science & Engineering Journal (MMSE Journal) is journal that deals in peer-

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MMSE Journal is dedicated to knowledge-based products and services for the academic, scientific, professional, research and student communities worldwide. Open Access model of the publications promotes research by allowing unrestricted availability of high quality articles.

All authors bear the personal responsibility for the material they published in the Journal. The Journal Policy declares the acceptance of the scientific papers worldwide, if they passed the peer-review procedure. Published by industrial company Magnolithe GmbH

Editor-in-Chief Mr. Peter Zisser Dr. Zheng Li, University of Bridgeport, USA Prof. Kravets Victor, National Mining Univerisity, Ukraine Ph.D., Girish Mukundrao Joshi, VIT University, India Dr. Yang Yu, University of Technology Sydney, Australia Prof. Amelia Carolina Sparavigna, Politecnico di Torino, Italy ISSN 2412-5954 e-ISSN 2414-6935

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

CONTENT I. Materials Science MMSE Journal Vol. 12 ................................................................................ 5 Friction Stir Welding of Aluminium Alloy With a Distinct Material Sandwiched. R Akash Sharma, Prashant K. Pandey, Harpreet Singh, Hitesh Arora........................................................... 6 A Fuzzy Approach to Trim Down the Struggles in Machining of AMMC by Optimizing the Tool Wear and Process Cost. G. Vijaya Kumar, B. Haritha Bai, P. Venkataramaiah .................. 14 The Material of the Working Fluid of the Solar Energy Heat Converter for Space Application. Yu.M. Mar’yinskykh ................................................................................................ 24 Transition Bars and Related Honeycomb and Fingerprint Textures Exhibited by 12OBAC, 16OBAC and a Binary Mixture of Them. Amelia Carolina Sparavigna..................................... 31 II. Mechanical Engineering & Physics MMSE Journal Vol. 12 ............................................... 40 Experimental Study of Circulating Vortex Movement Working Environment in Vibrobunker. V.P. Symonyuk, V.Y. Denysiuk, Y.S. Lapchenko ..................................................... 41 Analyzing the Antecedents and Consequences of Manual Log Bucking in Mechanized Wood Harvesting. Kalle Kärhä, Jyri Änäkkälä, Ollipekka Hakonen, Teijo Palander, Juha-Antti Sorsa, Tapio Räsänen, Tuomo Moilanen .................................................................................................. 55 Evaluation of Low Velocity Impact Response of Composite Plates Embedded with SMA Wires- An Analytical and Numerical Approach. Buddhi Arachchige ........................................ 70 The Effect of Rice Husk Ash on the Strength and Durability of Concrete at High Replacement Ratio. Binyamien I. Rasoul, Friederike K. Gunzel, M. Imran Rafiq ........................ 82 Applied Load on Blade Bearing in Horizontal Axis Wind Turbine Generator. Chen L., Xia X.T., Qiu M. ........................................................................................................................... 93 A Refined Technique for the Automated Determination of Friction Losses in the Toothing of Multithreaded Transmissions with Differential Mechanisms and D. Planetary Volontsevich, Gears. Ie. Veretennikov, I. Kostianyk, S. Pasechnyi ..................................................... 106 The Vehicle Controlling Near the Screening Surface Using Thrust Vector Deflection of the Electric Motor with Gimbal Mounted Propeller. Kravets V.V., Kravets Artemchuk V.V. .......................................................................................................................... 117 Vl.V., III. Electrical Complexes and Systems Vol. 12 ........................................................................ 123 Investigation of the Process Parameters Influence on the Energy Efficiency of an Induction Motor under Model Predictive Control GRAMPC. G.G. Diachenko, O.O. Aziukovskyi ......... 124 VI. Environmental Safety Vol. 12 ............................................................................................ 132 Understanding the Nature of Wet Air Deposition on Rooftops in Uyo Metropolis. Ihom A.P., Uko D.K., Markson I.E. , Eleghasim O.C. ................................................................................. 133 VII. Economics & Management MMSE Journal Vol. 12 ....................................................... 142 Effect of Maintenance Methods and Manufacturing of Track Components on the Profitability Rates in Egyptian National Railways and Comparison with Global Railway Networks. Karim Mohamed Eldash, Ahmed Abdel Moamen Khalil, Lobna Hane Mostafa ......... 143 VIII. Philosophy of Research and Education Vol. 12 .............................................................. 153 About Teaching English Writing and Composition in the Active Technology-Enhanced Environment (on the Material of an Experimental Project). M. S. Staton, S. R. Nedbailik ..... 154

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

I . M a t e r i a l s S c i e n c e M M S E J o u r n a l V o l . 1 2

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

Friction Stir Welding of Aluminium Alloy with a Distinct Material Sandwiched Akash Sharma 1, Prashant K. Pandey1, Harpreet Singh1, Hitesh Arora1, a 1 – Lovely Professional University, Phagwara, Punjab, India a – hitesh.15774@lpu.co.in DOI 10.2412/mmse.43.51.842 provided by Seo4U.link

Keywords: friction stir welding, thin sheets, multi-lap joint, M2 HSS tool, dissimilar material welding, solid state welding process efficiency.

ABSTRACT. The multi-lap joint has been created between the two sheets of the aluminum alloy: Al5052-H32 while a pure copper foil was placed in between, using the process of friction stir welding (FSW). The tool material was selected to be M2 HSS, considering its heat tolerance capacity and high strength. To reduce the number of experiments performed, Taguchi method’s L9 approach was brought into use. The test for ultimate shear strength was carried on for all the samples. In case of AlA-Cu-AlA welds, it was found out that the optimum values of the ultimate tensile strength were obtained for the parameters: tool rotation speed at 800 rpm, traverse speed at 5 mm/min and the plunge depth being 0.2 mm. It was also added to our knowledge that the AlA-AlA joint had greater value of the ultimate shear strength when compared with AlA-Cu-AlA joint while working with the parameters for the optimum ultimate shear strength for the former. It was noticed that the clamping also played a significant role while friction stir welding the thin sheets and foil.

Introduction. The FSW process is a kind of solid state welding process and hence, for the joint to be formed, the material need not reach its melting point [1-2]. Instead, the temperature just enough for plasticizing the material is required to be maintained while the force applied by the tool in downward direction with the simultaneous rotational movement of tool intermixing the base materials creates a joint [3, 4]. The heat is generated by the frictional force between the rotating tool and the surface of the base material in contact with the tool [5]. With significantly lesser heat than the melting points of the base materials, lesser HAZ (heat-affected zone) is created and hence there is a lesser effect on the original material properties [6]. The FSW was invented in 1991 at “The Welding Institute (TWI)” when Wayne Thomas used a tool having a probe with the correct rotational speed and torque [7, 8]. The selected tool had hardness greater, than that of any of the base materials [9]. FSW could be utilized for joining similar as well as dissimilar materials. However, only lap and butt arrangement of sheets is feasible while making a joint [10]. Several samples of the multi-lap joint consisting of two dissimilar materials had been evaluated for their shear strengths. The thickness of the sheets used was relatively lesser (i.e., 1 mm each for Al5052-H32 and 0.1 mm for pure copper) than the thickness of sheets that are usually joined with the FSW process [11, 12, 13]. The scanning electron microscopy was performed on the friction stir welded AlA-Cu-AlA sample having the highest value of the ultimate shear strength by carbon-coating the sample. The copper cladded aluminium tubes, which are excellent heat sinks can be fabricated using the process discussed in this paper, while keeping their weight to the minimum since no extra filler material is used in the discussed joining process [14]. Experimental setup. There were two different base metals used: Al-5052 H32 and pure copper for the sheets and foil to be joined using friction stir welding process. The thickness of each sheet of aluminium alloy was 1 mm while the thickness of the copper foil was 0.1 mm and hence, the total

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

thickness of the multi-lap joint was 2.1 mm. The tool was made up of M2 (Molybdenum) H.S.S. (High Speed Steel). It also goes by the name “tool steel” & is renowned material in tooling standards. (a)

(b)

Fig. 1. (a) Side view of a tool, (b) top view of a tool. The tool material M2 HSS has much higher value of hardness, i.e. 60 HRC (Rockwell C Hardness) than that of Al-5052 H32 that has a Brunel hardness of 60 and pure copper having a Rockwell Hardness (F-scale) of 54, even without the heat treatment. In order to keep the flexibility of the tool during its working while it is prone to shocks, it wasn’t tempered. The chemical composition of the aluminium alloy used in the experimentation is specified in the following Table 1. The physical properties of the aluminium alloy, pure copper, and tool steel used in the experiment are mentioned in the following table 2. Table 1. Chemical composition of Al5052-H32. Element

Mass

2.48%

0.3%

0.23%

0.09%

0.03%

0.02%

Remaining (96.83%)

Table 2. Physical properties of Al5052 - H32, pure copper and M2 HSS. Material

Density

Melting Point

Al5052 - H32

2.68 g/cm3

607 °C - 649 °C

Pure Copper

8.96 g/cm3

1085 °C

M2 HSS

8.16 g/cm3

1427 °C

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

Table 3. Tool specifications. Pin Parameters

Dimensions

Pin Height

1.5 mm

Pin Diameter

5 mm

Shoulder Diameter

18 mm

Collet Size For Tool

18 mm

Total Length Of The Tool

94.5 mm

The Vertical Milling Centre (VMC) was used for the friction stir welding of two sheets of Al-5052 H32 with a copper foil in the middle. Also a work table was mounted over the base of VMC for making the clamping of work-pieces easier. The design of experiment was established by referring Taguchiâ&#x20AC;&#x2122;s L9 approach and the parameters are listed in table 3.

(b)

(a)

Fig. 2. (a) Vertical milling center; (b) Cast iron work table. Table 4. L-9 Orthogonal array used in welding. Rotational Speed (RSM)

Traverse (mm/min)

Plunge Depth (mm)

700

0.1

700

0.2

700

0.3

800

0.2

800

0.3

800

0.1

900

0.3

900

0.1

900

0.2

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

Results and discussions. Fig. 3 shows the morphology of the welded specimens before shear test. The samples are free from defects and very smooth layer of welding was observed.

Fig. 3. Welded joints at different parameters according to L-9 orthogonal array The values of ‘Fracture Load’ along with the visual appearance of joints after the friction stir welding of AlA-Cu-AlA for the parameters obtained by L9 orthogonal array are listed in the Table 4. Table 4. Fracture loads for the FSWed samples. Sample For Shear Testing

Shear Fracture Load (N)

S. No.

Parameters

800 RPM; 5mm/min traverse speed; 0.2 mm plunge depth

3177.459

800 RPM; 15 mm/min traverse speed; 0.1 plunge depth

2823.318

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

900 RPM; 10 mm/min traverse speed; 0.1 mm plunge depth

2819.394

800 RPM; 10 mm/min traverse speed; 0.3 mm plunge depth

2727.18

900 RPM; 15 mm/min traverse speed; 0.2 mm plunge depth

2442.69

700 RPM; 5 mm/min traverse speed; 0.1 mm plunge depth

2159.181

900 RPM; 5mm/min traverse speed; 0.3 mm plunge depth

1799.154

700 RPM; 10 mm/min traverse speed; 0.2 mm plunge depth

1654.947

700 RPM; 15 mm/min traverse speed; .3 mm plunge depth

1617.669

The area of contact between the plates is same as the welded region in prepared sample for shear strength testing. Thus, Area = Diameter of tool shoulder × Width of sample = 0.018 m × 0.04 m = 7.2 × 10-4 Also, ultimate shear strength (MPa) = maximum load of fracture (N) / contact area (m2). Hence, the values for the ultimate shear strength are given in table 5.

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

Table 5. Ultimate shear strength values for the FSWed samples. S. No.

Parameters for AlA-Cu-AlA Joint (Tool Rotation Speed in RPM; Traverse Speed in mm/min; Plunge Depth in mm)

Maximum Shear Load (N)

Ultimate Shear Strength (MPa)

800; 5; 0.2

3177.459

4.413

800;15; 0.1

2823.318

3.921

900; 10; 0.1

2819.394

3.915

800; 10; 0.3

2727.18

3.787

900; 15; 0.2

2442.69

3.392

700; 5; 0.1

2159.18

2.998

900; 5; 0.3

1799.154

2.498

700; 10; 0.2

1654.947

2.298

700; 15; 0.3

1617.669

2.246

The highest ultimate shear strength came out to be 4.413 MPa in the case of AlA-Cu-AlA joint with the parameters: 800 rpm, 5 mm/min traverse and 0.2 mm plunge depth. For the same parameters, the ultimate shear strength came out to be even higher as in the case of AlA-AlA joint having the ultimate shear strength as 5.955 MPa. Moreover, the second highest value of the ultimate shear strength came out to be 3.921 MPa, in case of AlA-Cu-AlA joints at the parameters: 800 rpm, 15 mm/min traverse and 0.1 mm plunge depth. For the same parameters, the ultimate shear strength for the AlA-AlA joint came out to be 4.922 MPa. The SEM (Scanning Electron Microscope) images obtained for the AlA-Cu-AlA sample welded at 800 rpm tool rotation speed, 5 mm/min tool traverse speed and with a plunge depth of 0.2 mm are given below:

Fig. 4. Microstructure of welded joints at different parameters according to L-9 orthogonal array.

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

Summary. Following conclusions are drawn from the present investigation: 1. The friction stir lap welded bond of AlA-AlA always has ultimate shear strength higher than the AlA-Cu-AlA FSWed lap joint for the same parameters. 2. For the thin sheets, clamping is vital because otherwise the sheets may bend under the heavy loads. 3. All the factors: plunge depth, tool rotational speed and the traverse speed play a very significant role in the surface as well as the strength of the joint. 4. In case of thin sheets of AL5052, lower values of tool rotational speed cause the material not to plasticise properly and thus making a weak and irregular joint while the higher values of tool rotational speeds burn the work-piece material and cause tunnelling defects. References [1] Farrokhi H., Heidarzadeh A., Saeid T. (2013) Frictions stir welding of copper under different welding parameters and media. Science and Technology of Welding and Joining, 18, pp. 697-702. [2] Ă&#x2021;am G. Friction stir welded structural materials: beyond Al-alloys (2011). International Materials Reviews, 56, pp. 1-48. [3] Motalleb-nejad P, Saeid T, Heidarzadeh A, Darzi K, Ashjari M. (2017) Effect of tool pin profile on microstructure and mechanical properties of friction stir welded AZ31B magnesium alloy. Materials & Design, 59, pp. 221-6. [4] Mishra RS, Ma ZY. (2005) Friction stir welding and processing. Materials Science and Engineering: R: Reports, 50, pp. 1-78. [5] Wei Zhang, Yifu Shen, Yinfei Yan and Rui Guo, Dissimilar friction stir welding of 6061 Al to T2 pure Cu adopting tooth-shaped joint configuration: microstructure and mechanical properties, Ma-terials Science & Engineering A, DOI 10.1016/j.msea.2017.02.091 [6] Shude Ji, Zhengwei Li, Liguo Zhang, Yue Wang (2017). Eliminating the tearing defect in Ti-6Al- 4V alloy joint by back heating assisted friction stir welding. Materials Letters, 188 (1), pp. 21-24, DOI 10.1016/j.matlet.2016.10.032 [7] Hui Shi, Ke Chen, Zhiyuan Liang, Fengbo Dong, Taiwu Yu, Xianping Dong, Lanting Zhang, Aidang Shan (2017). Intermetallic Compounds in the Banded Structure and Their Effect on Mechan-ical Properties of Al/Mg Dissimilar Friction Stir Welding Joints. Journal of Materials Science & Technology, 33(4), pp. 359-366, DOI 10.1016/j.jmst.2016.05.006 [8] Nan Xu, Qining Song, Yefeng Bao, Yongfeng Jiang, Jun Shen (2017), Achieving good strengthductility synergy of friction stir welded Cu joint by using large load with extremely low welding speed and rotation rate, Materials Science & Engineering A, 687 (1), DOI 10.1016/ j.msea.2017.01.052 [9] H. Dawson, M. Serrano, S. Cater, N. Iqbal, L. Almasy, Q. Tian, E. Jimenez-Melero(2017). Impact of friction stir welding on the microstructure of ODS steel, Journal of Nuclear Materials, 486, pp. 129-137, DOI 10.1016/j.jnucmat.2016.12.033 [10] Ahmed M.M.Z., Ataya Sabbah, El-Sayed Seleman, M.M., Ammar H.R., Ahmed Essam (2017). Friction stir welding of similar and dissimilar AA7075 and AA5083. Journal of Materials Processing Technology, 242(1), pp. 77-91, DOI 10.1016/j.jmatprotec.2016.11.024 [11] Kim K.H., Bang H.S., Bang H.S., Kaplan A.F.H. (2017). Joint properties of ultra-thin 430M2 ferritic stainless steel sheets by friction stir welding using pinless tool. Journal of Materials Processing Technology, Vol. 243, pp. 381-386, DOI 10.1016/j.jmatprotec.2016.12.018 [12] A. Yazdipour, A. Heidarzadeh (2016). Effect of friction stir welding on microstructure and mechanical properties of dissimilar Al 5083-H321 and 316L stainless steel alloy joints, Journal of Alloys and Compounds, 680 (1), pp. 595-603, DOI 10.1016/j.jallcom.2016.03.307 MMSE Journal. Open Access www.mmse.xyz

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[13] V.C. Sinha, S. Kundu, S. Chatterjee (2016). Microstructure and mechanical propertiesof similar and dissimilar joints of aluminiumalloy and pure copper by friction stir welding. Perspectives in Sci-ence 8, pp. 543-546 [14] Q. Zheng, X. Feng, Y. Shen, G. Huang, P. Zhao (2016). Dissimilar friction stir welding of 6061 Al to 316 stainless steel using Zn as a filler metal, Journal of Alloys and Compounds, 686 (1), pp. 693-701, DOI 10.1016/j.jallcom.2016.06.092.

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

A Fuzzy Approach to Trim Down the Struggles in Machining of AMMC by Optimizing the Tool Wear and Process Cost G. Vijaya Kumar1,a, B. Haritha Bai2,b, P. Venkataramaiah1,c 1 – Department of Mechanical Engineering SV University, Tirupati, India 2 – Department of Mechanical Engineering, JNTUA, Anantapur, India a – Vijayluther2003@yahoo.co.in b – Haritha324@gmail.com c – pvramaiah@gmail.com DOI 10.2412/mmse.40.42.927 provided by Seo4U.link

Keywords: AMMC, machining, WEDM, tool wear, process cost, analysis, optimization, fuzzy-logic.

ABSTRACT. Aluminum Metal Matrix Composites (AMMCs) are the precise resources for aerospace, marine and automobile industries, due to their elevated strength to mass ratio. In machining vicinity of these materials, industries are facing lots of troubles, as the existence of abrasive particles such as silicon carbide, aluminium oxide etc., causes the brisk tool wear and hence tool malfunction within a very near to the ground machining time. In other hand, machining the difficult-to-machine electrically conductive components with the high degree of accessible accuracy and the fine surface quality make WEDM priceless. Still, a threat occurred is the ceramic particles resists the current through the composites. Hence this paper focused on trim down these struggles. For this selecting the matrix material among the three series of aluminium materials available with the suppliers by means of the normalization criterion have been done. AMMC samples are produced as per the taguchi experimental design in view of collective material and WEDM parameters and machined to obtain the responses: Tool wear and process cost. These are analyzed and derived an optimal set of parameters with the patronage of fuzzy approach.

Introduction. Aluminium Metal Matrix Composites are vastly developed advanced resources which are fine alternatives to many conventional materials, mostly when high strength and lowweight parts are needed. AMMCs have found many unbeaten engineering applications in recent years by means of their incomparable properties such as high strength-to-weight ratio and high toughness etc. [1, 2]. Conventional machining of AMMCs causes serious tool wear due to the existence of abrasive particles and hence tool malfunction [3]. As a result, researchers are attracted to machine MMCs using various non-conventional machining methods such as abrasive jet machining, laser beam machining and electrical discharge machining (EDM) [4–6]. WEDM is a better substitute As WEDM process provides an effective solution for machining hard materials, it confirms easy control and can machine obscure shapes [7, 8]. The discharge current has most significance on kerf width, among the process parameters: discharge duration, pulse interval time, discharge current and the wire drum speed [9].The pulse on time and peak current are the momentous parameters which affecting the, surface roughness and cutting speed. The wire tension has minor effect on the cutting speed but it has great effect on the surface roughness [10]. Factors like pulse on time, pulse off time, servo voltage, rate of wire feed, tension of wire, servo feed, spark gap voltage and rate of dielectric fluid are playing a momentous role in cutting operations for maximization of MRR, minimization of surface roughness and minimization of spark gap in WEDM [11] Various optimization techniques have been used by the researchers to find the best combination of process parameters [12]. Fuzzy logic is with an immense potential to confine analysis, decision-making and other aspects [13]. A fuzzy logic’s rule base contains three basic units: fuzzifier, inference engine and defuzzifier. The primary task of the 1

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

system is to create a relation between influential parameters and responses [14-16]. Many authors have got assistance of fuzzy logic for optimizing machining parameters and succeed in their research [17-20]. In the present paper an optimum combination of collective, material and machining parameters has been derived using fuzzy logic to trim down the struggles in machining of AMMCs by means of optimizing the Tool wear and process cost. Design of experiments and production of AMMCS. As many numbers of parameters are considered for this research, Taguchi experimental design has been incorporated to reduce the number of experiments and cost. The parameters and their levels considered for this research (table 2) are collected from the past research except the selection of base material is followed a normalization technique. A. Selection of Base Material. Selection of base material is one of the most important activities for preparation of Aluminium Metal Matrix Composite materials and it was paying attention of many researchers from past few decades. An inappropriate selection of materials may result in damage or failure of a system and severely decreases the performances [21]. For selecting the base materials, properties such as Tensile strength, hardness, melting point, density and cost of the material (table 1) of various alloys of 5xxx, 6xxx, 7xxx series, which are available with the suppliers are considered. For the present work, a general normalization procedure is followed to select the base material. The properties whose higher values are desirable, such as strength, hardness and melting point are normalized using equation1 and tabulated in the table1. In addition, properties whose smaller values are always preferable, such as density and cost are normalized using equation2 and tabulated in the table1. Table 1. Properties and cost of various alloys and their normalized values.

Alloy

Normalized values of

Properties of various alloys and cost

Aluminium TS

alloys properties and cost TS

Sum of Normalized values

5XXX Series Al5052

262

625

2.68

270

0.17 0.00 1.00 0.00 1.00

2.17

Al5083

345

615

2.66

450

1.00 1.00 0.60 1.00 0.00

3.60

Al5754

245

600

2.67

450

0.00 0.41 0.00 0.50 0.00

0.91

6XXX Series Al6061

350

651

2.7

350

1.00 1.00 0.40 1.00 0.00

3.40

Al6063

241

654

2.7

250

0.00 0.00 1.00 1.00 1.00

3.00

Al6082

330

650

2.7

280

0.82 0.82 0.20 1.00 0.70

3.53

Al6351

310

649

2.71

300

0.63 1.00 0.00 0.00 0.50

2.13

7XXX Series Al7050

552

147

629

2.83

550

0.00 0.00 0.00 0.00 0.33

0.33

Al7075

572

150

635

2.81

350

0.59 1.00 1.00 1.00 1.00

4.59

Al7475

586

150

635

2.81

650

1.00 1.00 1.00 1.00 0.00

4.00

NB* TS – Tensile Strength, H – Hardness, MP – Melting Point, D – Density, C – Cost From the table 1 it is observed that the sum of Normalized values of 5083 in 5XXX Series is larger, MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

6082 in 6XXX Series is larger and 7075 in 7XXX is larger. Hence, these alloys are selected as Base materials. Table 2. Influential parameters and their levels. Sl. No

Level 1

Level 2

Level 3

Material Parameters Base material (BM) Al5083

Al6082

Al7075

Al2O3

Flyash

Type of reinforcement material (RM) SiC Percentage of reinforcement 2.5 particle (PRFM) WEDM Parameters Pulse on time(Ton) 108

110

112

Pulse off time (Toff)

Water pressure(wp)

Wire feed (Wf)

Servo feed (SF)

1030

1050

1070

1 2 3

Influential parameters

Experimental Design. For the present work, L27 Taguchi experimental design (table 3) have been obtained through mini-tab software by considering various influential parameters related to material and WEDM (table 2). Production of AMMC samples. For the present work nine AMMC samples are produced using stir casting furnace as per Taguchi L27 experimental design (table 2). To produce AMMCs, First the stir casting furnace with graphite crucible is switched on and allow it to raise the temperature up to 500OC then the required amount of base material is poured into the crucible and the temperature is raised up to 850OC and allow it to maintain the same up to complete melting of base material. At this stage, the wetting agent Mg of 1% is added to the base material by reducing its temperature to 100o above the melting point of the alloy. Then the reinforcement particles are added slowly to the molten base material while the stirrer rotating. Before adding the reinforcement particles, they are heated to oxidise their surfaces. After mixing, the temperature of the slurry is raised up to 850OC for getting improved fluidity and stirring is continued up to 5 minuets. Then the mixed slurry was poured in different preheated steel dies to produce the samples. Experimental work and optimization of parameters. The experiments were conducted in ULTRA CUT WEDM Machine (Supplied by Vellore Wire Cut. Pvt. Ltd, Vellore, Tamilnadu) as per the L27 Taguchi experimental design and the experimental data is recorded in the Table 4. For these experiments, brass wire is used as electrode and water as dielectric fluid. Experimental results are optimized using fuzzy logic and analyzed as following Normalization of Experimental Data. Data normalization is required where the range and unit in one data sequence may differ from the others. In data pre-processing, the original sequence is transformed to a comparable sequence. Various methodologies are available for various quality characteristic of a data sequence. For quality characteristic of the “larger – the - better”, the data can be normalized as

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

đ?&#x2018;Ľâ&#x2C6;&#x2014;đ?&#x2018;&#x2013;(k) =

đ?&#x2018;Ľđ?&#x2018;&#x153;đ?&#x2018;&#x2013;(đ?&#x2018;&#x2DC;) â&#x2C6;&#x2019; min đ?&#x2018;Ľđ?&#x2018;&#x153;đ?&#x2018;&#x2013;(đ?&#x2018;&#x2DC;) max đ?&#x2018;Ľđ?&#x2018;&#x153;đ?&#x2018;&#x2013;(đ?&#x2018;&#x2DC;) â&#x2C6;&#x2019; min đ?&#x2018;Ľđ?&#x2018;&#x153;đ?&#x2018;&#x2013;(đ?&#x2018;&#x2DC;)

(1)

Table 3. Taguchi design of experiments. Expt. No

AMMC Sample No.

Material parameters

WEDM parameters

RFM

PRFM Ton Toff

Al5083

SiC

2.5

108

1030

Al5083

SiC

2.5

108

1050

Al5083

SiC

2.5

108

1070

Al5083

Al2O3

5.0

110

1050

Al5083

Al2O3

5.0

110

1070

Al5083

Al2O3

5.0

110

1030

Al5083

Fly ash

10.0

112

1070

Al5083

Fly ash

10.0

112

1030

Al5083

Fly ash

10.0

112

1050

Al6082

SiC

5.0

112

1030

Al6082

SiC

5.0

112

1050

Al6082

SiC

5.0

112

1070

Al6082

Al2O3

10.0

108

1050

Al6082

Al2O3

10.0

108

1070

Al6082

Al2O3

10.0

108

1030

Al6082

Fly ash

2.5

110

1070

Al6082

Fly ash

2.5

110

1030

Al6082

Fly ash

2.5

110

1050

Al7075

SiC

10.0

110

1030

Al7075

SiC

10.0

110

1050

Al7075

SiC

10.0

110

1070

Al7075

Al2O3

2.5

112

1050

Al7075

Al2O3

2.5

112

1070

Al7075

Al2O3

2.5

112

1030

Al7075

Fly ash

5.0

108

1070

Al7075

Fly ash

5.0

108

1030

Al7075

Fly ash

5.0

108

1050

1 2

26 27

For quality characteristic of the â&#x20AC;&#x153;smaller â&#x20AC;&#x201C; the - betterâ&#x20AC;? the data can be normalized as

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đ?&#x2018;Ľâ&#x2C6;&#x2014;đ?&#x2018;&#x2013;(k) =

max đ?&#x2018;Ľđ?&#x2018;&#x153;đ?&#x2018;&#x2013;(đ?&#x2018;&#x2DC;) â&#x2C6;&#x2019; đ?&#x2018;Ľđ?&#x2018;&#x153;đ?&#x2018;&#x2013;(đ?&#x2018;&#x2DC;) max đ?&#x2018;Ľđ?&#x2018;&#x153;đ?&#x2018;&#x2013;(đ?&#x2018;&#x2DC;) â&#x2C6;&#x2019; min đ?&#x2018;Ľđ?&#x2018;&#x153;đ?&#x2018;&#x2013;(đ?&#x2018;&#x2DC;)

(2)

Where i = 1â&#x20AC;Ś, m; k = 1â&#x20AC;Ś, n; m â&#x20AC;&#x201C;is the number of experimental data items; n â&#x20AC;&#x201C; the number of parameters; đ?&#x2018;Ľđ?&#x2018;&#x153;đ?&#x2018;&#x2013;(k) â&#x20AC;&#x201C; denotes the original sequence; đ?&#x2018;Ľâ&#x2C6;&#x2014;đ?&#x2018;&#x2013;(k) â&#x20AC;&#x201C; the sequence after the data pre-processing; max đ?&#x2018;Ľđ?&#x2018;&#x153;đ?&#x2018;&#x2013;(k) â&#x20AC;&#x201C; the largest value of đ?&#x2018;Ľđ?&#x2018;&#x153;đ?&#x2018;&#x2013;(k); min đ?&#x2018;Ľđ?&#x2018;&#x153;đ?&#x2018;&#x2013;(k) â&#x20AC;&#x201C;the smallest value of đ?&#x2018;Ľđ?&#x2018;&#x153;đ?&#x2018;&#x2013;(k); đ?&#x2018;Ľđ?&#x2018;&#x153; â&#x20AC;&#x201C; is the desired value. For the experimental values of, tool wear and process cost, smaller-the-better is applicable. Hence, its experimental values are normalized using Eq. 2 and tabulated the values in table in Table 4. Resolving the Fuzzy Grade. A fuzzy logic unit contains a fuzzifier, defuzzifier, a fuzzy rule base, membership functions and an inference engine. In the fuzzy logic analysis, the fuzzifier uses membership functions to fuzzify the input values and then the inference engine performs a fuzzy reasoning on fuzzy rules to breed a fuzzy value. Finally, the defuzzifier converts the fuzzy value into a Fuzzy grade (table4). The structure built for this study is a Two input- one-output fuzzy logic unit as shown in Fig. 1. The input variables of the fuzzy logic system in this study are the normalized values of experimental data of Tool wear and process cost. They are converted into linguistic fuzzy subsets using membership functions of a triangle form (fig2), and are evenly assigned into three fuzzy subsets: low (L), medium (M), and High (H). Dissimilar with the input variables, the output variable is assigned into relatively nine subsets i.e., very very low (VVL), very low (VL), Low(L) medium low(ML),medium (M), medium high(MH) high(H), very high (VH), very very high(VVH) grade. The fuzzy rule base consists of a group of If - then control rules to express the inference relationship between input and output. For this work 9 fuzzy rules are defined and shown in Figure 3.

Fig. 1. Two input- one-output fuzzy logic unit.

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

Fig. 2. Membership functions of a triangle form. Table 4. Experimental results, normalized values of experimental data and fuzzy grade values. Expt. No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

Experimental Results Tool wear 0.018 0.01 0.014 0.018 0.025 0.018 0.015 0.011 0.018 0.013 0.009 0.012 0.019 0.013 0.013 0.015 0.016 0.009 0.019 0.014 0.016 0.014 0.002 0.014 0.013 0.012 0.015

Process Cost 633 519 533 477 395 569 698 705 1277 567 394 346 781 822 987 408 658 510 569 394 414 352 309 568 470 600 561

Normalized values of experimental resultsProcess Tool wear cost 0.3043 0.6652 0.6521 0.7828 0.4782 0.748 0.3043 0.8271 0 0.9119 0.3043 0.7316 0.4347 0.5988 0.6086 0.5915 0.3043 0 0.5217 0.7336 0.6956 0.9123 0.5652 0.962 0.2608 0.5128 0.5217 0.4698 0.5217 0.2993 0.4347 0.8975 0.3913 0.6394 0.6956 0.7937 0.2608 0.732 0.4782 0.9123 0.3913 0.8194 0.4782 0.9561 1 1 0.4782 0.7328 0.5217 0.8338 0.5652 0.9996 0.4347 0.7394

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Fuzzy Grade 0.3832 0.6692 0.5272 0.4034 0.223 0.3918 0.4462 0.6223 0.2833 0.5799 0.698 0.6578 0.3238 0.5244 0.4815 0.4952 0.4215 0.6881 0.3764 0.5565 0.4485 0.5653 0.9615 0.5244 0.5995 0.6616 0.4745

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

Fig. 3. Nine fuzzy rules. Obtaining the Optimal Combination of Influential Factors After resolving the Fuzzy Grade, the consequence of each parameter is separated based on Fuzzy Grade of various levels. The mean values of Fuzzy Grade for each level of the influential factors and the effect of influential factors on multi responses in rank wise are summarized in Table 6. Mostly, the parameter level with larger Fuzzy Grade is considered as optimized. From the table 5 and fig. 4, the optimal combination of influential factors is Base material at level 3 i.e.. Al7075 reinforcement material at level 1 i.e. SiC, percentage of reinforcement material at level 1 i.e.; 2.5 ton at level 3 i.e.; 112, Toff at level 2 ie; 58, WP at level 1 i.e.; 3, WF at level 2 i.e.; 2, SF at level 3 i.e.; 1070. (“BM3RM1PRFM1TON3TOFF2WP1WF2SF3”) are the optimum influential parameters for optimized tool wear and process cost. Table 5. Fuzzy grade for each level of influential factors. Level

PRFM

Ton

Toff

0.438844

0.544078

0.581733

0.516100

0.463656

0.582200

0.480456

0.493622

0.541133

0.488789

0.521056

0.444933

0.593111

0.484533

0.542567

0.518011

0.574244

0.521356

0.451433

0.593189

0.497456

0.487489

0.531200

0.542589

Delta

0.135400

0.055289

0.130300

0.148256

0.129456

0.097667

0.062111

0.048967

Rank

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Fig. 4. Fuzzy Grade for each level of influential factors. Confirmation experiment. For the obtained optimal combination, confirmation test has been conducted and compared the results (Table 6) with initial set of parameters. These results are satisfactory as the responses for optimal combination shows better performance. Table 6. Comparison of responses between AMMC with initial combination and optimal combination. Influential parameters combination Initial Combination

Combination of Controllable Parameters

Tool Wear

Process Cost

BM 2RM2PRM2TON2TOFF2WF2WP2SF2

0.018

476

Optimal combination

BM3RM1PRFM1TON3TOFF2WP1WF2SF3

0.010

275

Gain

N/A

0.08

201

Summary. For this paper WEDM experiments are conducted by producing AMMC samples as per L27 Taguchi experimental design which is considered the collective material and machining parameters. The Fuzzy approach has been applied effectively for determining the set of optimum influential parameters. After analyzing the data, it is concluded that Ton, RM and Toff are the most significant parameters which influence the multi responses, PRM and BM are the medium influenced parameters on multi responses and WP, WF SF are influenced lastly the multi responses. When compared the conformational experimental results with initial set of parameters combination, the better improvement is noted, and the improvement in tool wear is 0.08mm and in process cost is Rs 201. Hence, it is concluded that this approach provides a systematic and effective methodology for optimizing the collective material and machining parameters which in turn reduces the manufacturing cost and greatly enhances manufacturing efficiency. References [1] Vukcevic M., Delijic K. (2002) Some New Directions in Aluminum Based PM Materials for Au-tomotive Applications, Materials in Technological, 36 (1), pp101-105. [2] M. Rosso, Ceramic and metal matrix composites: Routes and properties, Journal of Materials Processing Technology, 175 (2006), 364â&#x20AC;&#x201C;375, DOI 10.5402/2013/648524

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[3] Sushant Dhar, Rajesh Purohit , Nishant Saini , Akhil Sharma , G. Hemath Kumar (2007), Mathe-matical modeling of electric discharge machining(EDM) of Al-4Cu- 6Si alloy-10%SiC composites, Journal of materials processing technology, 194, pp. 24-29. [4] Hamatami G, Ramulu M (1990), Machinability of high temperature composites by abrasive water jet, ASME J. Eng. Mater. Technol., 112(4):381–386, DOI 10.1115/1.2903346 [5] Muller F, Monahan J (2000), Non-conventional machining of particle reinforced metal matrix composite, Int. J. Mach. Tools Manuf., 40, 1351–1366 DOI 10.1016/ S0890-6955(99)00121-2 [6] Muller F, Monahan J (2001), Non-conventional machining of particle reinforced metal matrix composites, J. Mater. Process Technol., 118, 278–285, DOI 10.1007/s00170-011-3242-5 [7] Garg M. P., Jain A., Bhushan G. (2012), Modeling and multi objective optimization of process parameters of WEDM using non dominated sorting algorithm, Proceedings of Institution of Mechan-ical Engineers, Part B, Journal of Engineering Manufacture, 226 (12), 1986-2001, DOI 10.1177/0954405412462778 [8] Kozak J., Rajurkar K.P., Chandarana N. (2004), Machining of low electrical conductive materials by wire electrical discharge machining (WEDM) process, Journal of Materials Processing Technol-ogy, 149, 266-276, DOI 10.1016/j.jmatprotec.2003.11.055 [9] Shyam Lal, Sudhir Kumar, Z. A. Khan, A. N. Siddiquee (2014), Wire electrical discharge machining of AA7075/SiC/Al2O3 hybrid composite fabricated by inert gasassisted electromagnetic stir-casting process, Journal of the Brazilian Society of Mechanical Sciences and Engineering, 36, 335346 [10] Ibrahem Maher, liew Hui Ling, Improve WEDM performance at different machining parame-ters, IFAC (2015), 105-110. [11] G. Rajyalakshmi, Simulation, Modelling and Optimization of Process parameters of Wire EDM using Taguchi –Grey Relational Analysis, IJAIR, 2012. [12] Bhaskar Chandra Kandpal, Jatinder kumar, Hari Singh, Machining of aluminium metal matrix composites with Electrical discharge machining – A Review, Materials Today: Proceedings 2(2015) 1665 – 1671. [13] Kosko, B. Neural network and fuzzy systems – A dynamic approach to machine intelligence. Prentice Hall of India, New Delhi, 1997. [14] Tozan, H.; Vayvay, Ö.The effects of fuzzy forecasting models on supply chain performance, In Dimitrov D. P. et al (eds.) Proceedings of the 9th WSEAS international conference on fuzzy systems - advanced topics on fuzzy systems Book Series: Artificial Intelligence Series-WSEAS, 112. 107(2008), [15] Tozan, H.; Vayvay, Ö. Fuzzy Forecasting Applications on Supply Chains, WSEAS Transactions on Systems, 7, (2008), 600-609 [16] Tozan, H.; Vayvay, Ö.Hybrid grey and ANFIS approach to bullwhip effect in supply chain networks, WSEAS Transactions on Systems, 8, (2009), 461-470 [17] Sharma, V. et al. Multi response optimization of process parameters based on Taguchi-fuzzy model for coal cutting by water jet technology. // International Journal of Advanced Manufacturing Technology. DOI: 10.1007/s00170-011- 3258-x [18] Tonkovic, Z. et al. Predicting natural gas consumption by neural networks, Tehnicki vjesnikTechnical gazette, 16, 3(2009), 51-61. [19] Galzina, V. et al.Application of fuzzy logic in boiler control, Tehnicki vjesnik-Technical gazette, 15, 4(2008), 15-21.

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[20] Lin, J. L. et al. Optimization of the electrical discharge machining process based on the Taguchi method with fuzzy logics, Journal of Materials Processing Technology, 102(2000), 48-55. [21] Ali Jahan, Faizal Mustapha, Md Yousof Ismail, Saupan, S., M., Marjan Bahraminasab. (2011). A Comprehensive VIKOR method for material selection, Materials and Design, PP 1215-1221, DOI 10.1016/j.matdes.2010.10.015.

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The Material of the Working Fluid of the Solar Energy Heat Converter for Space Application Yu.M. Mar’yinskykh 1, a 1 – Associate Professor at the Shostka Institute of the Sumy State University, Ukraine a – mymih44@gmail.com DOI 10.2412/mmse.90.3.605 provided by Seo4U.link

Keywords: thermal solar energy converter (TSEC), space application, power, construction, parameters, temperature.

ABSTRACT. The research is dedicated to reasoning the need for creation of a functional material as an active medium of conversion of solar energy into mechanical energy with further conversion of it into electric power and using it in power plants and in projects of solar power satellites (SPSs). There have been considered the ways of generating energy from the points of view of the environment and inexhaustibility, which include photoconverting power engineering, methods of heat conversion of solar energy and the problems, restraining creation of large-sale projects. The result of the research is the development of a method of continuous generating useful mechanical energy by using the functional material (working fluid) in the process of heating it with solar radiation in the heat-absorbing zone and cooling it down in the heat-radiating zone within the optimum rated temperature range. The corresponding theoretical researches have been conducted in order to assess quantitatively the capacity of the metal segment as working fluid of the heatconverting panel while the thermal solar energy converter (TSEC) for space application is functioning. The graphic curves of segments capacity in various temperature ranges have been presented herein. The time response of the TSEC metal segment functioning cyclicity has been studied at solar concentration of n = 1.2, for different temperature ranges. A solution has been suggested that allows a significant increase of TSEC efficiency by improving the physical and technical characteristics of the segment material. The promising character of changing one of the series of parameters that define the segment material has been shown; and it leads to an opportunity to compete with photoconverting systems according to their efficiency, provided several parameters are combined in an optimum way. A variant of structure of a TSEC as an electric drive has been shown. It may also be applied on earth if modified correspondingly. The conversion method under consideration enables to construct SPSs and calculate the paths of motion so that the time of a power plant being in the subsolar zone and the shadow zone while moving around the Earth per one rotation could match the time of a TSEC cycle.

Introduction. Nowadays, such world problems of energetics as energy safety, energy efficiency and environmental protection are appended with the factor of energy pricing policy. The significance of the energy problem is worth considering due to the obvious fact that the products manufactured by any industry are purchased for money equivalent to the amount of energy expenditure. The restricted and non-renewable character of energy resources on earth as well as the increasing consumption of them caused by the people’s comfortable living conditions are leading to the produced useful energy becoming more expensive, which makes us search for alternative ways of generating energy by using renewable sources. The Price Factor of Technologies and Materials of the Photoconverting Power Engineering. The most promising among the renewable types of power engineering is the solar power engineering, particularly the photoconverting one, and the concomitant thermal energy, generated by this way of conversion, will make the increase of the environment temperature negligibly small. When getting this energy from earth energy resources, there is a direct risk of increase of the parameter values which are included into the definition of environment entropy.

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In its turn, improving the photoconverting ways of generating energy causes a row of problems that are hard to solve. Thus, with significant reduction of consumption of photoconverting materials accomplished through the concentrated solar radiation method, with application of linear Fresnel lens in the module itself [1] and because of the complexity of its structure, it is difficult to solve the problem of deployment of the system, which is based on them, in space. The 3rd-generation photoconverters using the nano- and microstructures (Vapor-Liguid-Sol: 2-VLS method) that belong to the class of devices of special industrial design with conducting quantum wires are resistant to radiation damage in space conditions, but they possess properties of metallic conductivity, because of which the applicability of the method is limited [2]. Proceeding from the analysis of works [3], it follows that only the silicon photoconverters of a planar design with conducting quantum wires that belong to the 3rd generation are of a certain interest concerning their further development. The class of multijunction (cascade) Đ?3 Đ&#x2019;5 with the structure of such Cu (ZnGa)Se2- elements, the efficiency of which reaches 33%, can be used in space. However, their production requires creating high-technology equipment, which causes their high cost. Thus, let us take the cascade photocells, the efficiency factor of which reaches 28%, and in prospect the prime cost of 1 W of capacity based on them will make USD 1.5 [4]. In this connection, there are many competing companies that possess the complicated technology of epitaxial growth of multijunction photoconverters and production of solar cells using the concentrated solar radiation with the possibility of space application, though the problem of pricing policy remains actual for them. Proceeding from the analysis of full production cycle of photoconverters for space application, starting from extraction of raw materials with creation of high-technology process of their production to their further application in large-scale projects of solar power satellites (SPS), it is obvious that the cost of generated energy after transportation onto the Earth remains sky-high. This makes us search for new ways and methods of improving the cycle. Proceeding from this fact, the method of heat conversion of solar energy into the mechanical energy with the possibility of further converting it into the electric power by using the corresponding TSEC for space application. Due to the possibility of future developing the following method of conversion of solar energy, the need has arisen to define the notion of active medium of conversion as the composition of substance that participates in converting the solar radiation energy into energy of some other type. For a thermodynamic conversion system in SPS projects based on gas or steam turbine converters, the active medium is either liquid metal with phase transformations or gas which is intended for serving as working fluid. At the stage of heating the active medium to the operation temperature and partially at cooling it down , there is no useful effect; in this case the medium is in a passive state. The active medium of the photoelectric conversion system for space application demonstrates a complex architecture based on nanoheterostructure consisting of semiconducting materials and metals. The active medium of thermoelectric systems of direct conversion of heat into electric power through physical phenomena and effects is solid bodies (metals), i.e. each conversion system needs a corresponding active medium. The Dependence of Capacity of the Metal Segment in the Process of Its Performing Work at Heat Absorption and Radiation in Space on Parameters, Characterizing Its Physical Properties. Let us estimate the capacity of the medium of solar energy conversion into the mechanical energy from duraluminum alloy with possible further application of it as an active medium of conversion in TSECs for SPS projects. In order to calculate the capacity of the segment in the form of a plate, which the TSEC panel consists of, the average indices of an alloy, which is not prepared specially for this purpose, are used. The mechanism of performing the continuous effective work by the active medium of the material (elastic metal plate), located in the thermal trap, lies in periodical conversion of the solar radiation, falling onto its surface, which by its thermal properties is close to a black body, as a result of thermal expansion and compression at cooling down in the shadow zone, when released from the thermal trap. The segment material must comply with its main functionality: to perform mechanical work continuously, to have the minimum specific heat capacity and density with the maximum values of the thermal expansion coefficient, the modulus of elasticity at physical loads (compression - tension), and the plates surface emissivity is close to unity with the possibility MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

of placing them in the heat-absorbing zone of the thermal trap and beyond it in the heat-radiating zone in the shadow. The thermal trap consists of low-emission transparent with selective coating on the side of solar radiation of surface, but reflecting the heat radiation from the heated panel and preventing it from coming out in full. Nearby the opposite unlit (shadow) surface of the panel, it is possible to place specular heat-reflective foil, when it goes about the variant without using the concentration of solar radiation. To ensure rigidity, the panel segment may look like a segment of an oval line in the cross-section, so that its opposite extreme longitudinal parts could not re-radiate onto themselves. Here below, there are tabular data on the segment material, its parameters and values of constants, where the changes of values of the modulus of elasticity and the linear thermal expansion coefficient within the studied temperature ranges are negligibly small: Ď&#x192; = 5.67Âˇ10-8W/m2K4â&#x20AC;&#x201C; Boltzmann constant; c = 850 J/kgKâ&#x20AC;&#x201C; specific heat capacity; Ď = 2780kg/m3 â&#x20AC;&#x201C; density; Đ&#x2022; = 7Âˇ1010 Pa â&#x20AC;&#x201C; Young modulus; Îą = 23.8Âˇ10-6K-1 â&#x20AC;&#x201C; linear thermal expansion coefficient; k = 0.95 â&#x20AC;&#x201C; emissivity; Îľ = 0.12 â&#x20AC;&#x201C; reverse radiating capacity; G = 1360W/m2 â&#x20AC;&#x201C; solar constant; d = 3Âˇ10-3m â&#x20AC;&#x201C; segment thickness; m =16kg â&#x20AC;&#x201C; segment mass; Îš = 10m â&#x20AC;&#x201C; segment length; n = 1 and 2 â&#x20AC;&#x201C; solar concentration. Let us estimate the capacity of the panel segment. In the heliostationary orbit of the near-Earth space environment, where the TSEC is going to be placed, the Earth albedo is negligibly small compared to the thermal processes on the converter. The amount of thermal solar energy at irradiation of the panel segment is used for heating it, for reverse heat radiation, for insignificant reflection from the surface of the thermal trap, wherein the panel is situated, and for heat-stretch work of the segment: Î&#x201D;Q = Î&#x201D;Q1+Î&#x201D;Q2+Î&#x201D;Q3 + Î&#x201D;A.

(1)

In our calculations, we shall require increasing the heat radiation from the segment to the outside through the transparent low-emission coating of the thermal trap, which it really is, by the value of the falling radiation, reflected from the upper surface of the thermal trap; then the equation (1) shall assume the following look: â&#x2C6;&#x2020;đ?&#x2018;&#x201E; = â&#x2C6;&#x2020;đ?&#x2018;&#x201E;1 + â&#x2C6;&#x2020;đ?&#x2018;&#x201E;â&#x20AC;˛2 + â&#x2C6;&#x2020;đ??´. â&#x2C6;&#x2020;đ?&#x2018;&#x201E;â&#x20AC;˛2 = đ?&#x153;&#x20AC;đ?&#x203A;ż(đ?&#x2018;&#x2021;04â&#x20AC;&#x201C; đ?&#x2018;&#x2021;4 )đ?&#x2018;&#x2020;â&#x2C6;&#x2020;đ?&#x153;?

where Î&#x201D;Q = GSÎ&#x201D;Ď&#x201E;; Î&#x201D;Q1= Ď VcÎ&#x201D;T. Since the absorbing and the reflecting surface is the same. â&#x2C6;&#x2020;đ?&#x2018;&#x2122; = đ?&#x2018;&#x2122;0đ?&#x203A;źâ&#x2C6;&#x2020;đ?&#x2018;&#x2021; â&#x20AC;&#x201C; segment stretch while heating; MMSE Journal. Open Access www.mmse.xyz

(2)

Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

đ??š = đ??¸đ?&#x2018;&#x2020;đ?&#x2018;&#x203A; đ?&#x203A;źđ?&#x2018;&#x2021; â&#x20AC;&#x201C; force close to terminal, which can suspend the segment stretch within the temperature range, where the modulus of elasticity remains the biggest (SĐż â&#x20AC;&#x201C; sectional area of segment, đ?&#x203A;ź = 0.97đ?&#x203A;źâ&#x20AC;˛). Proceeding from the last correlations, the segment work at heat-stretch may be determined and inserted into the equation along with the previous ones (2). The amount of heat is coming into the thermal trap to the segment within the time dĎ&#x201E;, and the corresponding heating occurs for the value dT. Whence the segment heating time within the temperature range from T0 to T is determined by the following expression: đ?&#x2018;&#x2021; â&#x201E;&#x17D;(đ?&#x2018;?đ?&#x153;&#x152;+2đ??¸đ?&#x203A;ź2đ?&#x2018;&#x2021;) 0 đ?&#x2018;&#x203A;đ??şâ&#x2C6;&#x2019;đ?&#x153;&#x20AC;đ?&#x153;&#x17D;đ?&#x2018;&#x2021;4

đ?&#x153;? = â&#x2C6;Ťđ?&#x2018;&#x2021;

đ?&#x2018;&#x2018;đ?&#x2018;&#x2021;.

(3)

The highest temperature value must be lower or equal to terminal, to which the segment can be heated up, which does not cause any difficulties to determine it at a certain solar concentration. The capacity, determined by the ratio of the work performed by the segment in the process of its heating up to the time spent on this process, is determined through the following expression: đ?&#x2018;&#x2021;

đ?&#x2018;&#x192;=

â&#x2C6;Ť02đ?&#x2018;&#x2030;đ??¸đ?&#x203A;ź2đ?&#x2018;&#x2021;đ?&#x2018;&#x2018;đ?&#x2018;&#x2021; đ?&#x2018;&#x2021; 2 â&#x2C6;Ťđ?&#x2018;&#x2021; â&#x201E;&#x17D;(đ?&#x2018;?đ?&#x153;&#x152;+2đ??¸đ?&#x203A;ź đ?&#x2018;&#x2021;) đ?&#x2018;&#x2018;đ?&#x2018;&#x2021; 0

(4)

đ?&#x2018;&#x203A;đ??şâ&#x2C6;&#x2019;đ?&#x153;&#x20AC;đ?&#x153;&#x17D;đ?&#x2018;&#x2021;4

In figure 1, there are graphs of heated segment capacity in dependence on temperature values from 250K to 430K and in the higher temperature range from 350 K to 530 K at concentrations n = 1 and n= 2 respectively.

Fig. 1. Graphs of heated segment capacity in dependence on temperature values. In the denominator of the expression (5) for determining the time of the panel segment cooling down, the coefficient 2 indicates a two times increase of the area of the heat-radiating surface beyond the thermal trap in the shadow. đ?&#x2018;&#x2021;0

đ?&#x153;?â&#x20AC;˛ = â&#x2C6;Ť đ?&#x2018;&#x2021;

â&#x201E;&#x17D;(đ?&#x2018;?đ?&#x153;&#x152;â&#x2C6;&#x2019;2đ??¸đ?&#x203A;ź2đ?&#x2018;&#x2021;) 2đ?&#x153;&#x20AC;đ?&#x153;&#x17D;đ?&#x2018;&#x2021;4

đ?&#x2018;&#x2018;đ?&#x2018;&#x2021;.

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(5)

Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

The segment capacity in the process of heat-radiating (cooling down), determined by the ratio (6), is shown in figure 2. The expression in the numerator corresponds to the work of the reverse process. It is negative in relation to work at heating, then the expression (6) will be positive, if we change the limits of integration; this method covers the following expressions (7) as well: đ?&#x2018;&#x2021;

đ?&#x2018;&#x192;â&#x20AC;˛ =

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Fig. 2. The segment capacity in the process of heat-radiating. The capacity per one cycle of the process of heat-absorbing and heat-radiating by the segment is determined by the expression (7), and its corresponding curve is shown in figure 3. đ?&#x2018;&#x2021;

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2đ?&#x2018;&#x2021;đ?&#x2018;&#x2018;đ?&#x2018;&#x2021; â&#x2C6;Ťđ?&#x2018;&#x2021;4đ?&#x2018;&#x2030;đ??¸đ?&#x203A;ź 0

đ?&#x2018;&#x2021; đ?&#x2018;&#x2021;0 2 đ?&#x2018;&#x2021; )đ?&#x2018;&#x2018;đ?&#x2018;&#x2021; â&#x2C6;Ťđ?&#x2018;&#x2021; â&#x201E;&#x17D;đ?&#x2018;?đ?&#x153;&#x152;+2đ??¸â&#x201E;&#x17D;đ?&#x203A;ź đ?&#x2018;&#x2021; đ?&#x2018;&#x2021;â&#x201E;&#x17D;đ?&#x2018;?đ?&#x153;&#x152; â&#x2C6;&#x2019; 2â&#x201E;&#x17D; đ??¸ đ?&#x203A;ź 0 4 đ?&#x2018;&#x2018;đ?&#x2018;&#x2021;+â&#x2C6;Ť ( 4 2 đ?&#x153;&#x20AC;đ?&#x203A;ż

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Fig. 3. Capacity per one cycle of the process of heat-absorbing and heat-radiating segments.

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(7)

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The relative curve of the segment capacity along with a value of specific heat capacity of the material decreased by 0.01 per cycle in figure 3 are shown in dotted lines. These indices increase twice, if we consider each of the directions of two-dimensional expansion. This structure variant of TSEC as an electric drive of the power plant is shown in figure 4, where (A) is the general view, (B) is the cross-section; the part of the thermal trap in the horizontal position corresponds to the heatabsorbing state, and the one in the vertical position - to the heat-radiating state in the shadow area.

Fig. 4. Structure variant of electric drive. (1, 5) – rigid framework made of carbon, its sides and diagonals with reflecting coating serve as ways for movement of the side ends (3) of the plane (4) along them from the heat-converting segments of the active material; (2, 6) – the opposite surfaces of the thermal trap in the framework (10); (7) – rigid connection; (8) – biaxial generator; (9) – generator rods; (11) – solar concentrator; (12) – radiation reflector. The Analysis of the Research Results. Based on the suggested method of conversion of solar energy, the dependence of the capacity of the segment as working fluid of TSEC on several variables has been discovered. These variables are the physical characteristics of the material, which the segment is made of. The requirements, made to the optimisation of functioning of TSEC for space application, lie in receiving an active medium of the rigid elastic material of the panel, the functionality of which is directed to obtaining the maximum capacity per heating-cooling cycle as a result of expansion and compression at minimum weight and size parameters in two perpendicular directions. This is indicated by the researches [5] that allow predicting mechanical properties of nanocrystalline materials and the scheme of their production. The possibility of a wide range of combinations of physical and technical parameters of the active medium of the segment material at its production, MMSE Journal. Open Access www.mmse.xyz

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which are included into the analytical expression of capacity, allows choosing an optimum variant for its maximum value, which is going to be an alternative for the existing conversion systems. The advantages of TSEC are its significant service life, the safety and resistance to radiation and meteor showers, and the processability of deployment in space. Summary. During the accomplishment of a TSEC project, there is a problem arising: its conversion of mechanical energy into electric power. In this connection, a superconducting generator without any magnetic conductor will be an integral part of the TSEC. The low temperature value in the shadow area will allow it to function at small energy expenditure on cryostat. This conversion method enables to construct SPSs and calculate the path of motion so that the time of a power plant being in the subsolar zone and the shadow zone while moving around the Earth along the path per one rotation could match the time of a TSEC cycle. Herewith, the dimensions will be reduced, and there is no need to block the full stream of solar radiation, falling onto TSEC, with foil in order to create a heat-radiating zone while shadowing. References [1] Alferov Zh. I., Andreev V.M., Rumiantsev V.D. The Tendency and Prospects of Development of the Solar Power Engineering, Physics and Technology of Semiconductors. 2004. Vol. 38. Edition 8. pp. 946-947. [2] L. Nsakalakos, J.Balh, J.Fronheiser, B. Korevaar, O. Sulima. Silicon nanowire solar cells., J. Rand, Appl. Phys. Lett. Vol. 91. 2007. [3] Yefimov V.P. The New-Generation Photoconverters of Solar Radiation Energy, Physical Surface Engineering. 2010. Vol.8. No.2 pp. 100-113. [4] Andreev V.M. Concentrator Solar Photo Power Engineering, Alternative Power Engineering and Ecology - ISSAEE. 2012. No. 05-06 (109-110). pp. 42-44. [5] Wenwu Xu, Lilian P. Davila. Size dependence of elastic mechanical properties of nanocrystal line aluminum. Mater. Sci. Eng. A 692, 2017, pp. 91- 93, DOI 10. 1016/J.msea.2017.03.06

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Transition Bars and Related Honeycomb and Fingerprint Textures Exhibited by 12OBAC, 16OBAC and a Binary Mixture of Them 1

Amelia Carolina Sparavigna1, a 1 – Department of Applied Science and Technology, Politecnico di Torino, Torino, Italy a – amelia.sparavigna@polito.it DOI 10.2412/mmse.56.32.234 provided by Seo4U.link

Keywords: liquid crystals, phase transitions, Alkyloxybenzoic acids.

ABSTRACT. By means of the polarized light microscopy, at the transitions between the smectic and nematic phase and between the smectic and the isotropic phase of some liquid crystals, we can observe the rising of transition bars and the presence of undulations in them. We can also see “honeycomb” and “fingerprint” textures as the evolution of the transition bars. Here, we will show some of these textures exhibited by compounds of the 4,n-alkyloxybenzoic (nOBAC) acid series. The compounds are 12OBAC, 16OBAC and a binary mixture of them. The binary mixture originates remarkable textures, which seem those of a modern art painting.

Introduction. The thermotropic liquid crystals are materials displaying one or more mesophases between the isotropic liquid and the solid phase. The mesophase sequence is observed when the temperature of the liquid crystal changes, that is, the mesophases are appearing according to a sequential ordering of molecular arrangements, mainly constrained by the molecular shape. For instance, in the case of rod-like molecules in it, the material can achieve a mesophase characterised by an orientational order of the long axes of molecules, passing in this manner from the isotopic to the nematic phase by decreasing the temperature. A further decrease of temperature can produce a smectic phase. In this mesophase, the order increases: besides the orientational order, the molecules are arranged in layered structures, in some cases with tilt (smectic C), or positional order within the layers, as observed in smectic B for instance [1-4]. Since the liquid crystal materials are strongly anisotropic, they possess optical birefringence. For this reason, these materials can be studied by means of a polarized light microscope, inserting the liquid crystal by capillarity in a cell made by two glass slides, with a gap between them ranging from 10 to 100 microns. The cell is placed in a thermostage, where the temperature drives the phase transitions of the material. The transitions are accompanied by beautiful phenomena, with sudden changes of colours and textures and a very rich formation of different patterns. In this paper we show the appearance of transition bars and undulated textures during the observation of two 4,n-alkyloxybenzoic acids (12OBAC, 16OBAC) and a binary mixture of them. These acids are members of the family of compounds, some of which we investigated in [5-11]. The undulated textures, which are different from the well-known transition bars [4], appear at the isotropic-smectic phase transition of 16OBAC and at the nematic-smectic phase transitions of 12OBAC and of the binary mixture. As discussed in [11], these undulated textures look like those observed in the smectic C phase near a smectic C - smectic A transition, by Johnson and Saupe [12]. Similar undulations have also been found in the smectic A phase [13,14]. In this paper we will point out that, in the case of 12OBAC, the transition bars can also evolve in “fingerprint” and “honeycomb” textures, where the focal conic domains seem arranged in a honeycomb structure. For the binary mixture 12OBAC1

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16OBAC, the transition bars rapidly evolve in fingerprints dressed by stripes. Honeycomb textures are also observed. The binary mixture originates remarkable textures, which seem those of a modern art painting. Alkyloxybenzoic compounds. The 4,n-alkyloxybenzoic acid (nOBAC) compounds have mesophases because their molecules are able to form hydrogen-bonded dimers, rigid and long enough to provide mesogenic conditions. The molecular structures of the closed and open dimers have been investigated in the framework of ab-initio calculations in Ref.15. The monomeric units of the 4,n-alkyloxybenzoic acid (nOBAC) compounds are composed of two sterically distinct molecular parts, the oxybenzoic acid residue and the aliphatic chain (n is the number of carbon atoms in the aliphatic tail). The compounds with number n ranging from 3 to 6 have a nematic mesophase but not a smectic phase. From 7 to 18 carbon atoms in the alkyl tails, the smectic phase appears [16]. Some of the 4,n-alkyloxybenzoic acids possess the texture transition in the nematic phase [6-8,17]. Optical investigations in compounds with homologous index n ranging from 6 to 9, show a nematic phase subdivided in two sub-phases, characterized by different textures. The transition from one of the nematic sub-phases into the other, that is the texture transition, is considered as originated by the growth of cybotactic clusters in the nematic phase (the cybotactic clusters are groups of dimers possessing a short-range smectic order [18]). Binary mixtures, approximately 1:1 in weight of 6OBAC with other members of the homologous series (7-, 8-, 9-, 12- and 16OBAC), have also the texture transition in the nematic phase [6]. It is remarkable to note that these binary mixtures exhibit an increase in the temperature ranges of the smectic and nematic phases. In these mixtures, the mesogenic units are dimers of the same acid (homodimers) but also hydrogen bonded pairs of two different acids (heterodimers) [18-21]. In spite of the microscopic disorder introduced by mixing two components, the polarized light microscope analysis of the liquid crystal cells reveals the texture transition [6]. This means a persistence of cybotactic clusters, also in the case of mixed dimers. For the investigation of the transition bars and related textures, here we are using 12OBAC, 16OBAC and a binary mixture of them, approximately 1:1 in weight (52:48). In the Table I we report the characteristic features of these materials. 16OBAC compound does not possess a nematic phase. 12OBAC compound does not possess a texture transition in the nematic phase. In fact, the temperature range of nematic phase is quite narrow and at rather high temperature. The smectic-like nematic phase is suppressed, included in a wide smectic phase. This happens because the compound has rather long dimers. The binary mixture has a narrow temperature range for the nematic phase but a wide smectic range. Table 1. Transition temperatures (in °C) of the two alkyloxybenzoic acid compounds and of their mixture, on heating and on cooling. 12OBAC does not show a texture transition in the nematic phase. 16OBAC exhibits just a smectic phase. The mixture does not exhibit the texture transition. Compound 12OBAC 16OCAC 12OBAC-16OBAC

Transition temperatures (°C) Cr  65  Cr  91  Sm  131  N  138  I I  137  N  130  Sm  88  Cr Cr  93  Sm  133  I I  132  Sm  88  Cr Cr  71  Sm  132  N  138  I I  136  N  130  Sm  66  Cr

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All the compounds were inserted in the cell when the material was in the isotropic phase. The untreated glass surfaces of the cell walls were rubbed with cotton-wool, to favor a planar alignment. As previously told, the liquid crystal cells were heated and cooled in a thermostage and textures observed with a polarized light microscope. 16OBAC. This compound has so long molecules and so high transition temperatures that a nematic phase is not allowed. If we use this material we see a direct transition between isotropic and smectic phases. On cooling, the transition appears as a branched figure growing from the black field of crossed polarizers, as we can see in the Figure 1. In a slow cooling from the isotropic liquid phase, if the temperature is immediately fixed at the instant when the smectic phase starts its formation, undulated textures dressing the Schlieren texture can be observed near defects (Figures 1 and 2).

Fig. 1. 16OBAC compound has a transition directly from the isotropic phase in the smectic C phase. On the left, we can see the transition bars, which evolve in a Schlieren texture (the width of the images on the left is 1 mm). On the right, we are showing the periodic undulation appearing near the defects of 16OBAC smectic phase. The undulation is due to some stresses on the smectic planes (image on the right is 0.25 mm width).

Fig. 2. The sequence shows an evolution of the decorative undulation near defects (16OBAC). From left to right, the temperature is lowered of one degree. The stripes are removed by a further decrease of the temperature. MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

Johnson and Saupe have observed undulation instabilities for the first time, when studying the transition from smectic C to smectic A [5]. As for those observed by Johnson and Saupe, the undulations are dressing the texture of the smectic phase. The undulations are considered as smectic layer undulated deformations, which appear due to the thermal stresses. In the smectic C of 16OBAC, we have observed that undulations are metastable, when the sample is kept at the same temperature for enough time [11]. We can see that they disappear due to the motion of dislocations. The image sequence in the Fig.2 shows the evolution of undulated texture when the temperature is lowered with a rate of 0.5 degree per minute. The period grows, and, when the temperature is further lowered of about two degrees, the undulated texture disappears.

Fig. 3. In the upper panel we can see the transition bars exhibited by 12OBAC, which appear on cooling from the nematic phase. Image width is 1 mm. In the lower two panels, a “honeycomb” texture (on the left) and a “fingerprint” texture (on the right) are shown. These textures are observed in the sample, when the temperature is maintained constant as soon as the transition bars are observed. 12OBAC. In this material, dimers are long enough to maintain the smectic order until a high temperature is reached. On cooling, the nematic phase appears at 137°C. Then we can see the coloured nematic bubbles display themselves in the black field of the microscope. Under a further lowering of temperature, the smectic phase appears at 130°C. Of the undulations in the smectic texture, we have discussed in [11]. Here we concentrate on the transition bars at the nematic-smectic transition. We can see a beautiful example of transition bars growing in the nematic phase in the upper panel of the Figure 3. Actually, on cooling the sample, if the temperature is fixed just 0.5-1 degree below the nematicsmectic transition, the transition bars are observable. We can also observe their evolution into “honeycomb” and “fingerprint” textures. These textures are given in the lower panels of the Figure 3. One of the textures is defined “honeycomb”, because it seems that the boundaries among domains have hexagonal patterns. Two other examples of “honeycomb” textures are given in the Figures 4 and 5.

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Fig. 4. Honeycomb texture. In the left panel, the original image. In the right panel, the same image in grey tones, enhanced by means of the GIMP Retinex filter.

Fig. 5. Another example of the honeycomb texture. In the lower panel, the image in grey tones has been enhanced by means of the GIMP Retinex filter.

Fig. 6. In the upper panel we can see the fingerprint texture at the transition from the nematic to the smectic phase of the binary mixture 12OBAC-16OBAC. Stopping the decrease of the temperature as soon as we see the passage of fingerprints, we can observe the texture in the lower panel (image 0.5 mm width). MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

Fig. 7. In another part of the same sample shown in Figure 6, we can see some focal conic domains surrounded by the transition bars. Binary mixture. The mixture 1:1 in weight of 12OBAC and 16OBAC has a clearing point at 138° C and a transition from smectic to nematic at 132°C. The smectic range, as shown by Table I, is wider, twenty degrees more than that of the single compounds. As previously told, the increase of smectic range in the case of binary mixtures of alkyloxybenzoic acids is an interesting phenomenon, observed for mixtures of 6OBAC with 7-,8-,9-,12- and 16OBAC [13]. Transition bars are very beautiful and with a rapid evolution in a fingerprint patter. If the temperature is stopped when the fingerprint appears, we can observe that periodic instabilities are decorating the texture and the domains (see Figure 6). The behaviour of these instabilities is the same as that of 12OBAC instabilities [11]. We can also observe some focal conic domains surrounded by the transition bars, in the manner shown in the Figure 7.

Fig. 8. It is possible to observe some “honeycomb” domains also in the binary mixture.

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Let us note that, as shown by the Figure 8, it is also possible to observe some “honeycomb” domains. As in the case of 12OBAC, the smectic phase can have focal conic domains. For the binary mixture, these domains are surrounded by period patterns, merged in the fingerprints, as given in the image of Fig.7. The decrease of temperature destroys the periodic pattern and the fingerprints. In the Figure 9, we give two other examples of focal conic domains merged in fingerprints in the smectic phase of the binary mixture. The binary mixture originates remarkable textures, which seem those of a modern art painting. The Figure 10 is also showing a remarkable similarity between 12OBAC and the binary mixture 12OBAC/16OBAC. Both materials have focal conic domains arranged in hexagonal distribution.

Fig. 9. Focal conic domains in the smectic phase of binary mixture 12OBAC-16OBAC, merged in the fingerprints. The width of images is 1 mm. Sometimes we can see defects looking like “eyes” in the domains.

Fig. 10. Focal conic domains with hexagonal arrangement in the smectic phase of 12OBAC (left panel) and of the binary mixture 12OBAC-16OBAC (right panel). Summary. The alkyloxybenzoic compounds that we have here considered have a similar behaviour, that is, they show the appearance of an undulated texture, dressing the smectic texture. The binary mixture has undulations too, decorating a fingerprint texture. In the binary mixture, the fingerprints are substituting the usual transition bar. Let us remember that in this material the molecular disorder is increased, as shown by the wider smectic range given in the Table I. Actually, the melt of the nematic phase is composed of monomers, and open and closed MMSE Journal. Open Access www.mmse.xyz

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homo- and heterodimers. After the transition in the smectic phase, the presence of homo- and heterodimers, with rather different lengths, persists. This intrinsic disorder increases the smectic range. The fact that a cholesteric-like texture (the fingerprint) is observed near the nematic-smectic transition could be due to a chiral-like behaviour of heterodimers, probably of the open ones. The chiral-like behaviour is suppressed by a further decrease of temperature, because open dimers turn into closed dimers. References [1] de Gennes, P. G., & Prost, J. (1993). The Physics of Liquid Crystals. Clarendon Press, Oxford. ISBN-13: 978-0198517856 [2] Chandrasekhar, S. (1992). 10.1017/CBO9780511622496

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[3] Gray, G., & Goodby, J. (1984). Smectic Liquid Crystals. Leonard Hill, Glasgow and London. ISBN-10: 0863440258, ISBN-13: 978-0863440250 [4] Demus, D., & Richter, L. (1978). Texture of Liquid Crystals, VEB Deutscher Verlag fur Grundstoffindustrie, Leipzig. [5] Sparavigna, A., Mello, A., & Montrucchio, B. (2006). Texture transitions in the liquid crystalline alkyloxybenzoic acid 6OBAC. Phase Transitions, 79(4-5), 293-303. DOI 10.1080/01411590600748132 [6] Sparavigna, A., Mello, A., & Montrucchio, B. (2007). Texture transitions in binary mixtures of 6OBAC with compounds of its homologous series. Phase Transitions, 80(3), 191-201. DOI 10.1080/01411590601007603 [7] Frunza, L., Frunza, S., Petrov, M., & Sparavigna, A. C. (1996). Dielectric and DSC investigations of 4-n-substituted benzoic and cyclohexane carboxylic acids. 1. Textural changes in homologous 4-n-alkoxybenzoic acids. Molecular Crystals and Liquid Crystals, 6(3), 215-223. [8] Montrucchio, B., Sparavigna, A., & Strigazzi, A. (1998). A new image processing method for enhancing the detection sensitivity of smooth transitions in liquid crystals. Liquid crystals, 24(6), 841-852. DOI 10.1080/026782998206669 [9] Strigazzi, A., Sparavigna, A. C., Torgova, S. I., Montrucchio, B., & Sanna, A. (1998). Chiral mesoscopic structure of the nonchiral liquid crystal OOBA. National Conference on Physics of – INFMeeting, Rimini, 25-30 Giugno, 1998 Matter [10] Torgova, S.I., Sparavigna, A., & Strigazzi, A. (2000). Chiral Textures Formed by Achiral pSubstituted Biphenylcarboxylic and Benzoic Acids, Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, 352:1, 111-118, DOI 10.1080/10587250008023167 [11] Sparavigna, A., Mello, A., & Massa, G. (2009). Undulation textures at the phase transitions of some alkyloxybenzoic acids. Phase Transitions, 82(5), 398-408. DOI 10.1080/01411590902898874 [12] Johnson, D., & Saupe, A. (1977). Undulation instabilities in smectic C phases. Physical Review A, 15(5), 2079. DOI 10.1103/physreva.15.2079 [13] Delaye, M., Ribotta, R., & Durand, G. (1973). Buckling instability of the layers in a smectic-A liquid crystal. Physics Letters A, 44(2), 139-140. DOI 10.1016/0375-9601(73)90822-0 [14] Clark, N. A., & Meyer, R. B. (1973). Strain‐induced instability of monodomain smectic A and cholesteric liquid crystals. Applied Physics Letters, 22(10), 493-494. DOI 10.1063/1.1654481 [15] Bobadova‐Parvanova, P., Parvanov, V., Petrov, M., & Tsonev, L. (2000). Molecular structure of the nematic liquid crystals made by hydrogen bonded in dimers molecules. Crystal Research and MMSE Journal. Open Access www.mmse.xyz

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Technology, 35(11â&#x20AC;?12), 1321-1330. DOI: 10.1002/1521-4079(200011)35:11/12% 3C1321::aid-crat1321%3E3.3.co;2-3 [16] Bryan, R. F., Hartley, P., Miller, R. W., & Shen, M. S. (1980). An X-Ray Study of the p-nAlkoxybenzoic Acids. Part VI. Isotypic Crystal Structures of Four Smectogenic Acids Having Seven, Eight, Nine, and Ten Alkyl Chain Carbon Atoms. Molecular Crystals and Liquid Crystals, 62(3-4), 281-309. DOI 10.1080/00268948008084027 [17] Petrov, M., Braslau, A., Levelut, A. M., & Durand, G. (1992). Surface induced transitions in the nematic phase of 4-n octyloxybenzoic acid. Journal de Physique II, 2(5), 1159-1193. DOI 10.1051/jp2:1992194 [18] De Vries, A. (1970). X-ray photographic studies of liquid crystals I. A cybotactic nematic phase. Molecular Crystals and Liquid Crystals, 10(1-2), 219-236. DOI 10.1080/15421407008083495 [19] Dhar, R., Pandey, R. S., & Agrawal, V. K. (2002). Optical and thermodynamic studies of binary mixtures of nematic liquid crystals from homologous members of alkyloxybenzoic acid. Indian journal of pure & applied physics, 40(12), 901-907. [20] Kang, S. K., & Samulski, E. T. (2000). Liquid crystals comprising hydrogen-bonded organic acids I. Mixtures of non-mesogenic acids. Liquid Crystals, 27(3), 371-376. DOI 10.1080/026782900202822 [21] Herbert, A. J. (1967). Transition temperatures and transition energies of the p-n-alkoxy benzoic acids, from n-propyl to n-octadecyl. Transactions of the Faraday Society, 63, 555-560. DOI 10.1039/tf9676300555

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I I . Mech ani cal En gin eeri n g & Ph ys i cs M M S E J o u r n a l V o l . 1 2

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Experimental Study of Circulating Vortex Movement Working Environment in Vibrobunker V.P. Symonyuk1,a, V.Y. Denysiuk1,b, Y.S. Lapchenko1,c 1 – Lutsk National Technical University, Lutsk, Ukraine a – v.symonyuk@lntu.edu.ua b – v.denysiuk@lntu.edu.ua c – y.lapchenko@lntu.edu.ua DOI 10.2412/mmse.58.82.178 provided by Seo4U.link

Keywords: vibration, vibrobunker, vibro-treatment, container, micro-hit, piezo-element.

ABSTRACT. In the article the results of experimental research of vibration process of processing of details checked reproducibility experiment and the accuracy of the results. Found that the results of mathematical modelling in the allowable limits coincide with the results of the experiment. Analyzed the technological capabilities of the vibrotreatment of machine in a wide range of frequency and scale. Clearly presented reason of problem the choice of optimum vibro-treatment of machine and possible directions to overcome them.

Introduction. The process of vibration treatment lies in the consistent application of surface machined parts large quantities of micro-hit, as well as applying a large amount of micro-scratch on the surface of the particles of the desktop environment. The basis of the process is mechanical or mechanic-chemical removal of small particles of metal and its oxide with a machined surface, and burnishing micro-roughness surface due to plastic deformation particles working environment, that reproduce in the process of complex movements [1]. Research results. The formation of a surface layer during vibration processing takes place under the influence of multiple micro-hit particles working environment, which cause the formation of trace processing, change the geometrical and physical-mechanical parameters of surface layer (roughness, micro-hardness, residual stress and structure). The shape and dimensions of the traces of processing determined by the parameters of the working environment, modes of processing, properties of the treated material. The combination of such elements as the consistent application of a large number of micro-hits, intensive mixing of the working environment and machined parts at various speed mixing and mutual orientation, accompanied by (depending on the characteristics of the working environment and modes of vibration) clicking the metal and its oxide, surface plastic deformation, and creates the conditions for the implementation of treatment, finishing, grinding and other operations [2]. Formulation of the methodology of experimental installation according to one value from the other is a clear determination of the sequence of actions aimed to get expressed in numeric form value the initial value at a particular value input the magnitude. Any experiment in general consists of the following stages: a clear definition or set of input quantities; carrying out manipulations, resulting in under the influence of the input quantities in a research facility appears or changes original size; fixing the qualitative and quantitative characteristics of the initial value. The experiment is preceded by a preparation for it, and the results of the experiment are amenable to analytical treatment, during which established the validity of information, as well as the qualitative and quantitative characteristics of the dependency of one value from another. With the aim of minimizing the number of repeated measurements in the course of the experiment, the applied mathematical experiment planning, which MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

allows to minimize the complexity of the experiment at given levels of reliability of the information obtained. In this case, the preparation of the experiment involves preparation equipment used in the experiment, check its serviceability and correct functioning. Experiment itself consists of multiple repetition the three specified stages, the number of repeated measurements is determined by mathematical planning of experiments. The first stage-set the level of utilization of vibrobunker working with mixture. This step performed by weighing a given mass of mixture and loading it into the container. In this case, the container slightly collapses on the springs, so the necessary re-adjustment of the magnetic gap. Then you can move on to the next stage. Analysing the results of mathematical modelling and visual observation of the process of vibro-treatment of machine on the experimental setup, it can be argued that setting mode occurs in less than one second, i.e. almost instantly. Therefore, time experimenter is required for the transition from the first phase directly to the third should suffice to vibration machine itself carried out the second phase, that is, to stabilizing fluctuations span voltage after the container. During the third stage is quantitative determination of scale of fluctuations of the container. Given the lack of special equipment for the quantitative determination of this magnitude, developed his own technique. The essence of this methodology is as follows. To a platform mounted spring loaded piezo-element that perceives fluctuations in vibrobunker with the help of a docked bar on vibrobunker. Processing of the results of the experiment carried out to verify the reliability of the data on the results of mathematical modelling of vibro-treatment of machine and the adequacy of the mathematical model. The implementation of this task, closely related to the mathematical planning of experiments. The essence of mathematical experiment planning method is scientific and reasonable choice of the number of necessary measurements and experimental for obtaining the necessary information from a given level of its reliability. Mathematical experiment planning provides for the consistent implementation of the following operations: encoding factors; the assembly plan-matrix experiments; randomization experiments; implementation of the experiment; check mechanical experiments; check the adequacy of the model; evaluation of the significance of the regression Given that the coefficients. experiment was one-factor, you need to encode the levels of only one factor. Taking that approximation according to scale of fluctuations of the container from the workload of working mixture wears the quadratic character, you must select the three levels of the factor (mass loaded mix): the upper (3 kg), bottom (0 kg) and zero (1,5 kg). The encoding of the respective levels of factor will be as follows: the upper +1, bottom – -1, zero – 0. The necessity of drafting a plan matrix for the one-way experiment disappears, because this feature is to define all necessary for a complete evaluation of combinations of the levels of all the factors. In this case, only one factor, i.e. it is impossible in principle to compose combinations; Note that the experiments must be on all three levels one factor: experiment №1 is on the bottom, experiment №2 – on the top, experiment №3 – at ground level. For the randomization of experiment, i.e., determining the sequence of their execution, the most convenient to use random numbers. However, experiments always conducted in a few repetition, mostly in three. Take the number of experimental – three. Therefore, the random number generator has issued the following sequence of conducting experiments: first repetition: 1, 3, 2; second repetition: 3, 1, 2; third repetition: 1, 2, 3. The implementation of the experiment should be carried out according to the methods described above. For the rest of the operations, which involves mathematical experiment planning, they detailed in the next section. During the experiments, it was necessary to examine how the effect on the inten-sity and quality of vibration processing options vibro-drive, namely: – amplitude of the oscillations A and the working body (vibrobunker); – frequency of oscillation f vibrobunker; – duration of treatment (vibro-abrasive grinding) T. MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

Based on the obtained results, formulate requirements to vibro-drive that provided the least optimal correlation between indicators of the intensity and quality of vibro-treatment of machine. Indicator of the intensity of the vibration treatment accepted the value of removing metal shavings Q that was determined by how the difference between the mass of details before and after the vìbro-abrasive of grinding. The quality of the surface roughness of grinding surface determined by the vibro-abrasive of parts according to GOST 2789-89. Therefore, the parameter that characterizes the quality of vibration pro-cessing is the arithmetic average of the absolute deviations of profile within the basic length of the Ra and grade of roughness surface. Also given the task of figuring out the basic laws of vibration processing from the action of a number of factors, which depend on the type and parameters of the vìbro-drive or substantially affect the intensity and quality of processing. Such factors include the impact of stagnant zones; mass and dimensions of machined parts; the influence of electromagnetic field on the process details of magnetic materials; the ratio of the volumes; the ratio of the working volume of the hopper and the loaded volume mixes (details + an abrasive); abrasive grain. According to the recommendations for building graphics patterns enough to 4 points, because they allow you to accurately hold the curve when there is no kinks. It was decide to conduct a study at four levels the values of factors. These levels were set for values of amplitude of vibration A and oscilla-tion frequency f vìbrobunker. Research of influence of parameter T (time) has a specific character, since it does not require prior installation of certain values, because the planning was conducted for two-factor experiment. When planning the study was selected the classic method of conducting experiments, because the number of factors is small, they are not truly independent because the amplitude and frequency of vibration of the body related. The essence of the classic method is the initial value (bottom or top) one of the factors, which then (from the bottom up, or vice versa) changes within the range of variation of the values of this factor in the persistence of values of all the other factors. Interval of variation for each of the factors was taking into account the gained experience of similar research carried out in the past. Were taken following the upper and lower values of variation and the steps: the lower the value of the amplitude of the oscillations vìbrobunker Ан=1 mm; the upper value of the amplitude of the oscillations of vìbrobunkerАВ=4 mm; step variation amplitude of ІА=1 mm; the lower value of the oscillation frequency vìbrobunker fн=17 Hz; top value fluctuations vìbrobunkerafВ=41 Hz; step of variation of frequency Іf=8 Hz. Experimental studies were performed for the following stages. Conducted a series of experiments to determine the dependency indicators of the intensity and quality of vibro-treatment of machine from amplitude oscillation vìbrobunker.The duration of each experi-ment was 3 hours. Mark abrasive 24 (flap). Held one long (6 hours) experiment to determine the dependency indicators of the intensity and quality of vibro-treatment of machine on the duration of treatment, as well as studies of other laws that were discussed above. To install according to the indicators of the intensity and quality of vibro-treatment of machine from relations volumes simulta-neously machined parts and abrasive, working volume of the hopper and loaded the mix was carried out a few additional experiments with variation the specified parameters. As the research, designs used details such as bodies of rotation that have external and internal cylindrical, flat and butt, ob-tained in different ways (milling, grinding) and have a different initial roughness. This will allow you to find out the extent of the handless of each type of surface, assess the rounding of sharp edges. In experiments to determine the dependency indicators of the intensity and quality of vibrotreatment of machine from the amplitude and frequency of oscillations used samples from two different mate-rials: from non-magnetic steel 12Х18Н10Т and brass LS 59-1L. The study of influence of electro-magnetic field on the process of vibration processing was used as prototypes of parts of the ring of cardan bearing after stamping of steel Shkh15. Experiments were conducted in the following order: washing of the samples by a warm soap solution from dirt; drying of the samples; determination of MMSE Journal. Open Access www.mmse.xyz

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the initial mass m1, gram, and roughness Ra1, micron sample processing; relabeling in the samples; conducting the experiment; cleaning and washing of the samples from the residues of abrasive; drying; measuring mass m2, gram, and roughness Ra2, micron sample after treatment; calculate removal wood shavings of metal by the formula:

(1)

Based on the obtained values were graphics chip removal according to metal Q, gram and roughness Ra, µm from the amplitude of A frequency, f for each material (steel 12Х18Н10Т and brass LS 591L). The dependence of the indicators of the intensity and quality of vibro-treatment of machine on the duration of treatment was studied in the following way. In vibrobunker has been downloaded 14 parts of steel 45, vibration modes: amplitude of 1,5 mm, frequency 33 Hz, abrasive material is shredded waste abrasive wheels abrasive 63. During the processing of intervals from the bunker removed 2 parts and parameters was measuring: removing metal shavings Q, and roughness of Ra, µm on the method stated above. Then there arithmetic mean of each parameter. Based on the obtained values were graphics according to the removal of chips and roughness Ra, µm on the duration of treatment (vibro-abrasive grinding), min. As a result of the experiment were obtained the following scale of fluctuations of the container depending on the workload of his working mixture (table 1). Table 1. The results of experimental measurements of scale fluctuations of the container, mm. Level pf charging № of repetition

0 kg

1,5 kg

3 kg

2,0

1,5

2,0

1,5

1,0

2,5

1,5

2,0

1,5

2,0

1,0

1,5

1,0

2,5

2,0

1,5

1,0

2,5

2,0

1,5

2,0

1,5

Arithmetica l mean

2,4

2,0

2,1

1,6

1,4

1,6

1,2

1,1

Quadratic mean

2,4

2,0

2,1

1,6

1,4

1,7

1,3

1,1

Electromagne t number

The table shows that the average and the average quadratic value scale fluctuations not significantly different, i.e. we can conclude about a bit of accidental errors of measurement. When the theoretical development in future experiment everywhere takes the average value of the scale. Based on table one folding table for mathematical processing of results of the experiment (table 2). For these data is calculated criteria Kohren: G=0,722. Table value criterion Kohren Gt=0,977. Because the value criterion Kohren, calculated by the results of the experiment, is smaller than the table, the experimental data can be considered reliable, and the experiment is reproducible.

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Q m m .

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

Table 2. The results of the experiment. Level of charging, kg 0 1,5 3

Swing fluctuations in repetition, mm I II III 2,4 2,0 2,1 1,6 1,4 1,6 1,2 1,2 1,1

Arithmetica l mean, mm 2,17 1,53 1,17

Dispersion, mm2 0,04335 0,01335 0,00335

The experimental data is extrapolated by three-point dependence of scale fluctuations of the container from the workload of working mixture:

(2)

where R – swing vibration of container, m – the mass loading of the container, b0, b1, b2 – coefficients of extrapolation. A method of sequential substitution into equation (2) data of the experiment at each of the three points found coefficients interpolation (up to two significant digits). After that, the equation (2) have the form: (3) The adequacy of this equation is tested by the criterion of Fisher. Is calculated for the equation (3) dispersion of adequacy is S2ad=1,417×10-4. In accordance with the criterion, Fisher F=7,077×10-3. Table value criterion of Fisher for the occasion – F=5,987. Because the value criterion of Fisher, calculated for equation (3) is less than the table value for this case, the description according to scale of fluctuations of the container of his equation (3) can be considered adequate. As a result of mathematical modelling in the same experiment using program "vibro" obtained the following values according to scale of fluctuations of the container from the mass loading of the container (table 3). Table 3. Results of mathematical modeling. Mass of charging, kg Swing fluctuations, mm

0 2,3

1,5 1,5

3 1,0

The accuracy of the mathematical model on the basis of which established the program "vibro", in case according to scale of fluctuations of the container from the level of its busy working mixture tested by Fisher (model (3) this dependence obtained on the basis of experimental data). Dispersion of adequacy in this case is S2ad=0,0133416. In accordance with the criterion, Fisher F=1,885. Table value criterion of Fisher for the occasion – F=5,987. Taking into account that the table values of the Fisher criterion is much more than calculated when determine the reliability of mathematical model, this model can be considered reliable. Circulation of the vortex motion of working environment largely ensures the efficiency of vibration of details. According to the directions and objectives of research conducted by experimental measurements of parameters of a circulating vortex motion. Measurements made at different laws control the electromagnetic drives [3].

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

Experimental measurements carried out directly at vibrobunker. In the measurement of applied optical method with frame-by-frame registration the position of the elements of the work environment. Made frame-by-frame sensing surface of working environment in vibrobunker. Frame rate amounted to 1 s. Observing consistent to the staff position of the elements of the work environment. To simplify the measurement in a working environment added part of the special elements (tokens) that by their parameters a little different from the elements of the work environment. Processing of photos of adjacent frames served as the basis for establishing the coordinates of a set of separate individual elements of the work environment. The coordinates of the item, the working environment and their change on individual frames are defined in rectangular Cartesian, polar in a curvilinear or special coordinates. Adopt a rectangular Cartesian coordinate system XOY with the center in the central part of the vibrobunker (fig. 1). Multiple adjacent frames determine the coordinates of a single abrasive granules or marker. Install the consistent position of the individual granules on the surface of the working environment. Formed by an array of vectors of position of certain individual elements as a set of vectors:

xC 2   xCq   x A1   x A2   x An  xB1  xB 2 x  Br  xC1 ,.. ,.. ,.. ,.. ,.. ,..  .  y  y y y y y y y A B 1 1 A B 1 1 An Br C 1 C 1                  yCq  Vectors define the position of the item in the working environment on the surface in the form of points А1, А2, .. Аn; В1, В2, .. Вr; C1, C2, .. Cq. The number of points was chosen large enough to describe the traffic on the entire surface of the desktop environment. The number of vectors depend on how long the item is located on the surface of the working environment. An array of the selected points describes the trajectory of particles on the entire surface of the desktop environment. Trajectory has the appearance of broken lines (fig. 2). To determine the speed of the slow circulation of movement of the working environment was determined by the increases in the origin of items in nearby positions. Increments the coordinates was shaped in the form of vectors:  x A1   x A2   x An   A ,  A , ...  A ;  y n   y 1   y 2   x B1   x B2   x Bn   B ,  B , ...  B ;  y n   y 1   y 2   xC1   xC2   xCn  , , ...   y C1   y C2   y Cn 

Resulting increments can be submitted in the form of the distances between the individual provisions of points. For example, point A

2 2   yA , ... xA  1

  yA . xAi  2

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;;

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

C1 E1

a A1

D1 y

B2 C2

E1 D2

y B3 C3 A3 х

Fig. 1. Scheme determination of details on individual images of the shooting when using a rectangular Cartesian coordinate system.

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

е1

В3 В2 В1 С3 А3

С2

е4

е2 А2

С1 А1

е3 Fig. 2. Typical experimentally determined the trajectory of the moving granules on the surface of the working environment. The average speed of the circulating movement are defined with the dependencies:

vxA1 

 xA  , ... v yA1  yA . t t 1

Thus, defined the field of velocity on the surface of the working environment. In some cases, the position of the item in the working environment it is advisable to identify in a polar coordinate system. Mainly determine the position of an item that moves directly to the periphery of the vìbrobunker (fig. 3). Moving A point is on a trajectory, close to the arc of the circle. Determined by the radius of the trajectory and angular position of the element. In the case shown in fig. 3, the radius of a trajectory similar to the radius of the container, and the angular position is determined by the angle φ. Linear speed desktop item is calculated by the formula:

vA 

 1

t

 Re ,

where φ2, φ1 – the corner coordinates of the element defined by the neighboring frames; Δt – the time interval between the coordinates; Re – the radius of the circle trajectory of moving the item to the desktop environment.

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

φ1 х

a A2

φ2

Fig. 3. Determine the position of the item to the desktop environment using the polar coordinate system. The center of curvature of the trajectory is not necessarily located in the center of the vibrobunker, and the radius of curvature of the trajectory is established from the analysis of photography. In order to improve the quality of field velocities are introduced a special coordinate system. They allow you to define the features of a local Vortex motion desktop (coordinate system in the form of an arc K1M1 (figure 4) provides an opportunity to identify local moving items in diametric intersection of the desktop environment.

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

D1 Ń&#x2026;

D2 Ń&#x2026;

b H2

Fig. 4. Determination of regularities of vortex circulation movement working environment with the use of specially typed coordinate systems. Coordinate system in the form of an arc or line allows you to install features and limits the current. This system allows you to determine the degree of passing elements into the work environment. Similarly used coordinate system in the form of a closed polygon (polyhedron). Shown in Figure ABCD elements combined in a quadrilateral. His move from frame to frame describes the average speed of the elements of the working environment within the quadrangle. Deformation of the quadrangle characterize the differences of the elements of the working environment. Change the position of the quadrangle, in particular its surface, characterizing local Vortex movement of elements of the work environment. Frame-by-frame survey provides an opportunity to determine the rotational movements of the parts and abrasive granules. For this purpose, apply bullets cylindrical shape with a small value (in the form of disc). On individual frames, registered angular position details and use the normal to its control surface (fig. 5).

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

2b 2а

Fig. 5. The definition of cross-corner position marker in the working environment and forecast the trajectory of movement of an item in the volume of the working environment.



Vectors of normal for neighbouring leaders n2 ,n 3,n 4,n 5 are determined by the position of the disc. On the photo the disc is registering in the form of an ellipse, the difference axes which determines the angles of the drive (fig. 6).

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

2а

Fig. 6. Determination of the angular position of the drive for size values of the axes of an ellipse, which corresponds to the angle of the surface of the disc marker. Angular position of the parts is determined by the angle θ, which is associated with the ratio of axes of an ellipse, respectively:

b .  a 

  arccos

Angular position of the disc in the plane of the coordinate axes xoy is determined by an angleφ between the small axis of an ellipse and the x axis. The analysis of time-lapse shooting you can predict the trajectory of the parts in the volume of work environment. Definition of forecast trajectory of movement simulates scheme (fig. 7). For details (marker) and made frame-by-frame shooting. On frames fixed position details, starting from the point of the A1 and ending point of the AK. Further reorganization frame-by-frame shooting for as long as the piece again appeared on the surface (about point A1). Trajectories of the details shown dotted line. It can be fairly accurately estimated. Exactly determined time finding parts in the volume of work environment.

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

n2 A3

n1 A1

а working environmen t surface Ak

forecast the trajectory of movement detail in volume

b Fig. 7. Determination of the predictive values of the trajectory of motion of the parts in the volume of workenvironment:а– fixed movement parts on the surface; b – the spatial movement of parts (the trajectory shown in dotted line). In the study of the process of vibro-treatment of machine by the time it was found that removing the metal occurs enough evenly over all the time with some increase in the initial period when the withdrawal relatively rough mikro- roughness and rounding sharp edges [8]. With the increase of grit abrasive environment, i.e. the size of the granules abrasive crumbs, removal of the metal increases due to the increase in mass of the grains and increase the depth of their penetration into the metal, causing more extensive workability. Summary. As a result of studies found that shock impulse load on the vìbrobunker lead to slow circulation of movement work environment. This movement intensification in non-symmetrical shock load. Circulation motion is circular or arcuate vortex ring that covers the entire volume of the desktop environment. To determine the nature of the Vortex motion accepted is the application of the law changes the amount of movement in the integral form for the selected control the volume of the working environment. The average speed of a circulating movement depends on the intensity of im-pact, speed vibrobunker to the punch and the mass of the working environment. Angular speed of a MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

vortex movement is proportional to the average velocity of the circulating traffic. In the working environment is a chaotic movement of individual items (blasting media granules) which is caused by shock loads the granules from the neighboring granules. Chaotic movement manifests itself in the form of deviations of the trajectory of a single pellet from the high trajectory of a circulating movement. Devia-tion of the trajectory close to harmonic (sinusoidal). References [1] L. Lubenska, Y. Nechaj, G. Burlakova (2009). Features of spindle processing in the free abrasion environment, Vibration in techniques and technology, №4 (56), P. 97–102. [2] А. Nikolayenko, M. Kalmykov (20 09). Study of vibrational intensity dependency from vibrodrive location, Eastern-Europe journal of advanced technology, № 2/5(38), P. 54–57. [3] V. Strutynskiy, V. Symonyuk, V. Denysiuk (2016). Improvement of equipment and process of hit-pulse processing of parts in vibrobunker: monography, Lutsk: Entrepreneur Gadyak Ganna Volodymirivna, printing house “Volynpolograph»ТМ, 139 pp.

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Analyzing the Antecedents and Consequences of Manual Log Bucking in Mechanized Wood Harvesting Kalle Kärhä1, a, Jyri Änäkkälä1, 2, Ollipekka Hakonen1, 2, Teijo Palander2, Juha-Antti Sorsa3, Tapio Räsänen3, Tuomo Moilanen4 1 – Stora Enso Wood Supply Finland, Helsinki, Finland 2 – University of Eastern Finland, Faculty of Science and Forestry, Joensuu, Finland 3 – Metsäteho Ltd.,Vantaa, Finland 4 – Ponsse Plc., Vieremä, Finland a – kalle.karha@storaenso.com DOI 10.2412/mmse.45.20.957 provided by Seo4U.link

Keywords: forest engineering, cross-cutting, cut-to-length (CTL) method, softwood, value recovery, Big Data, sawmilling industry, Finland.

ABSTRACT. The study focused on the frequency of applying a manual tree-stem bucking to logs in coniferous forests of Finland. The aim of the study was to clarify harvesting conditions where manual log bucking is utilized most and the effects of the utilization of manual bucking on the log bucking outcome. In addition to the stm Big Data of harvesters, in order to investigate the consequences of manual log bucking, data from the enterprise resource production (ERP) systems of wood procurement organization and sawmills was collected, as well as harvester operators were interviewed. The study results illustrated that the share of manual bucking of Norway spruce (Picea abies L. Karst.) logs was, on average, 46% and with Scots pine (Pinus sylvestris L.) logs 67%. The operators used manual bucking more frequently in thinning stands with small-sized and defected log stems. When the utilization degree of manual log bucking was high, the utilization of log sections with spruce and pine log stems was lower, logs were shorter and the volume of logs was smaller. Furthermore, log percentage and apportionment degree were significantly lower when the shares of manual log bucking were higher. The relative production value of spruce logs was lower, and correspondingly the relative production value of pine logs was higher when applying plenty of manual bucking. On the basis of the study results, it can be recommended that now-adays the target for the manual log bucking percentage with spruce must be less than 20– 30% of the total log volume cut. In the future, our aim must be fully automatic or semi-automatic and harvester computer-aided bucking based on the quality grades of the log section zones of log stems with pine and spruce. It will require equipping harvesters with novel mobile laser scanning (MLS) and machine vision (MV) applications.

Introduction. Globally the wood harvesting is becoming increasingly mechanized both in treelength (TL) and cut-to-length (CTL) systems. The main drivers for this trend are the potential for increased productivity and reduced costs, the labour-related issues (i.e. enhancing safety, labour shortages and rising wage costs), and the increased global competition in forest industries [1]. Almost 100% of wood harvesting is currently carried out using mechanical harvesting systems in Finland [2]. In the 2010’s around 1,870–1,990 harvesters and 1,930–2,020 forwarders have annually been used in wood harvesting operations in Finland [3]. The wood harvesting is a crucial element in supply chains of forest industries. There will be a time when a forest owner realizes a return from the investments of decades. As the whole volume of a tree is seldom merchantable and the prices for the different sections of a tree stem vary a lot, the most important issue is cross-cutting (i.e. bucking) the tree stem into sawlogs, veneer logs and pulpwood poles for the mills of forest industries [4]. According to the classical study of the value recovery by Geerts and Twaddle [5], even 40% of the total monetary value of stems can be lost during wood harvesting operation, and the biggest single source of loss comes from log bucking in which up to more than 20% of the potential value can be lost. MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

The CTL method is used for the wood procurement of industrial roundwood in Finland, and also in many other countries in the world. In customer-driven wood procurement process of CTL method, tree stems are bucked into favourable log dimensions at the harvesting site. In this process, the sawmill customers will have information about the demand of the markets of sawn goods, and thus order the target distribution of logs based on the demand of end-product markets. In the forest, harvester computer calculates the optimal bucking proposals for each tree stem by taking into account the bucking instructions of harvesting site. The bucking instructions consist of target distribution, price matrix and the various other bucking parameters and guidelines. The goodness of bucking outcome can be evaluated with several attributes, for instance using the dimensions, value and reject percentage of logs and apportionment degree [e.g. 6–11]. The modern harvesters are equipped with powerful on-board computers, advanced measurement and monitoring technologies, geographical information systems and communication systems, as well as optimization models designed to assist the harvester operator in the log bucking decisionmaking process of the CTL system. These applications of modern harvesters have a significant potential to increase efficiency and value gain from the whole supply chain of the forest industries [1]. When cutting Norway spruce (Picea abies L. Karst.) log stands, the guideline for the harvester oper-ator is to utilize the bucking proposals by the harvester computer (i.e. automatic bucking) as much as possible because there is a belief that, hence, the bucking outcome of log stems can be maximized at the harvesting site [12, 13]. Of course, the harvester operator can utilize manual bucking (i.e. the operator him-/herself decides the cross-cutting points of log, or in other words, no bucking with the suggestions supplied by the harvester’s automatic system) with damaged or defected parts of log stems – for instance butt rot, crookedness, top changing, vertical branch, large branch – or some other reasons in the stand. The quality of Norway spruce does not fluctuate much and the values of different lumber grades are quite small. Correspondingly, the values of Scots pine (Pinus sylvestris L.) lumber are significantly dependent on the quality of pine log [12]. The log sections of Scots pine stem are generally regarded as dividing into three quality zones: 1) a knotless or slightly knotty butt zone, 2) the dead knot zone in the middle of the stem, and 3) the fresh knot zone on the upper part of the log section in the stem. Consequently, when cross-cutting pine log stems, the quality bucking is conducted and the bucking is not necessarily managed by according to the target and price matrices. Hence, it is a target that the harvester operator will utilize a lot of manual bucking on the log section of pine. Several research groups [6–8, 11, 14–18] have compared the bucking options (i.e. manual vs. automatic bucking) and underlined that the gains of automatic or computer-aided bucking are bigger than manual bucking. However, almost all these studies [6–8, 14–18] have been carried out in the context of manually cross-cutting, i.e. there has been automatic, optimal computer-based bucking and manu-ally bucking by a lumberjack with a chain saw in the comparison. That is to say, no mechanized cross-cutting with modern harvesters in these log bucking studies. During the last seven years (2010–2016) in Finland, the annual cuttings of softwood logs have been, on average, 23.3 million solid m3 over the bark (later only: m3) of which the proportion of Norway spruce log cuttings has been 53% and the share of Scots pine log cuttings 43%. Furthermore, the average log consumption of sawmilling industry has been annually 23.9 million m3 in the 2010’s in Finland [19]. Nevertheless, how much softwood logs mechanically harvested are bucked manually and automatically? For successful implementation of mechanical wood harvesting, this information is mandatory. However, it is not yet known in Finland. Therefore, Stora Enso Wood Supply Finland (WSF), the University of Eastern Finland, Metsäteho Ltd. and Ponsse Plc. undertook a study on the frequency of applying a manual tree-stem bucking to logs in coniferous forests of Finland. The aims of the study were to clarify:  Harvesting conditions where manual log bucking is utilized most;  The main reasons for using plenty of manual bucking; MMSE Journal. Open Access www.mmse.xyz

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 The effects of the utilization of manual bucking on the log bucking outcome (Fig. 1). The hypotheses of the study were:  With Norway spruce log stems, the best bucking outcome is achieved when manual bucking is minimized;  In cuttings of Scots pine log stands, the best bucking result is reached when manual bucking is maximized.

Fig. 1. The framework of the study on manual log bucking. Material and methods. For the study, the stm files [20] of 55 harvesters were collected in June and August 2015 from the harvesters of eastern Finland and in December 2015 and January 2016 from the harvesters operating in southern Finland at the harvesting sites of Stora Enso WSF. The starting point of stm data collection was the beginning of 2014. All harvesters of the study were Ponsse (Bea-ver, Ergo 6w, Ergo 8w, Fox, HS16 Ergo and Scorpion) harvesters (Fig. 2).

Fig. 2. Log bucking in the study with the Ponsse Beaver harvester in a spruce-pine-mixed stand. Photo: Jyri Änäkkälä..

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

There were 1–2 operators in each study harvester. When analyzing the stm data and calculating the volumes of manual bucking on the log section of stems, the manual bucking volumes were considered the following cross-cuttings:  Logs with bucking carried out manually by the operator;  Offcut pieces (length of <1.5 m) by sounding log section;  Pulpwood poles cut from the log section of stem. All other buckings on the log section of stems were classified automatic bucking in the study. The manual log bucking percentage was determined by dividing manually bucked log volume by the total log volume. The percentage of the defected timber of log stem was defined by dividing the volume of manually bucked offcuts and pulpwood poles on the log section of stem by the total volume of log section. The spruce and pine log lengths used were mainly 3.7–5.5 m with the increments of 0.3 m. Also, some shorter (3.1 & 3.4 m) and longer (5.8 & 6.1 m) log lengths were applied. The minimum top diameter of spruce logs was 16 cm and 15 cm with pine logs in the study. The total stm data of softwood log stems was 1,296,297 m3 and 1,964,884 log stems. The softwood log removal was more than 20 m3 on each harvesting site. There were totally 5,634 harvesting sites in the study. The stm material varied from 1,848 to 52,897 m3/harvester. In addition to the stm data of harvesters, in order to detect the consequences of manual log bucking, data from the enterprise resource production (ERP) systems of Stora Enso WSF and sawmills was collected. Total data from the ERP system of Stora Enso WSF was 91,496 m3 and from the ERP systems of sawmills 74,803 m3. The goodness of bucking outcome was evaluated with the following attributes:  The utilization of log section (volume, length, top diameter of log section);  Log percentage;  Log dimensions (volume, length, top diameter of logs);  Reject percentage;  Apportionment degree;  The relative production value of logs. Of the attributes of the consequences of manual log bucking, the reject percentage, apportionment degree, and the relative production value of logs were investigated at the batch level of harvesting sites (i.e. the combination of 1…n harvesting sites). The rest of the attributes (i.e. the utilization of log section, log percentage, and log dimensions) were the harvesting site-specific variables based on the stm data of harvesters in the study. Moreover, all harvester operators who worked during 2015 in the harvesters studied (N=81) were aimed at to be interviewed for the study. Total of 74 harvester operators were interviewed by phone by two research scientists in December 2015 – January 2016. Thus, the response rate of interview survey was 91%. When the operators were interviewed, they were asked to estimate how much they had bucked Norway spruce and Scots pine logs with manual bucking of their total log volumes cut during the period of December 2014 – November 2015. In the interview survey, the following questions were also asked:  Which bucking option (i.e. automatic or manual bucking) produces better bucking result in the opinion of an operator;  Which elements does the good bucking outcome consist of;

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 What are the effects of harvesting conditions and the other variables on the utilization degree of manual bucking on the log section of spruce and pine log stems;  What are the most common reasons for the utilization of manual bucking with spruce and pine log stems;  Is the operator willing to take part in bucking education session if the education will be organized. The variables related to manual log bucking in the study were analyzed using distributions, mean values, standard deviations and Spearman’s rank correlations (ρ). The differences between the classified groups of the manual bucking percentages of spruce and pine logs were researched by the Mann-Whitney test (U) and the Kruskal-Wallis one-way ANOVA test (χ2) because the circumstances (i.e. ratio or interval scales in variables and/or normal distribution of samples) for using parametric tests did not exist. Results. Totally 4,051,804 softwood logs of which 2,496,356 spruce logs and 1,555,448 pine logs were bucked in the study. The results illustrated that the manual bucking percentage of spruce logs was, on average, 45.5% and with pine logs 67.4%. There was statistically significant positive correlation (ρ=0.579; p<0.001) between the shares of manual bucking of spruce and pine logs: when the manual bucking percentage with spruce was low, also the manual bucking percentage of pine logs was low at the harvesting site in question, and vice versa (Fig. 3). Fig. 3 presents also that there was a huge variation of the shares of manual bucking on harvesting sites of the study. Moreover, there was a significant correlation (ρ=0.708; p<0.001) between the shares of manual bucking in cross-cutting spruce and pine logs by harvester (Fig. 4). There were statistically significant differences between study harvesters in the manual log bucking percentages with spruce (χ2=2,107; p<0.001) and pine (χ2=1,773; p<0.001).

Share of manual bucking of pine logs (%)

100 90 80 70 60 50 40 30 20 10 0 0

90 100

Share of manual bucking of spruce logs (%)

Fig. 3. The shares of manual bucking of Norway spruce and Scots pine logs by harvesting site (n=4,964) in the study.

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Share of manual bucking of pine logs (%)

100 90 80 70 60 50 40 30 20 10 0 0

90 100

Share of manual bucking of spruce logs (%)

Fig. 4. The average shares of manual bucking of Norway spruce and Scots pine logs by harvester (n=55). The results demonstrated that the operators apply manual bucking with both spruce and pine log stems more frequently in thinning stands with small-sized and defected log stems (Tables 1 and 2, Figs 5 and 6). Respectively, some manual bucking was used when bucking log stems from regeneration fellings with large-diameter and good-quality log stems. On the contrary, forest site class had no significant effect on the utilization of manual bucking in the study (Tables 1 and 2, Figs 5 and 6). Table 1. Harvesting conditions and classified groups related to the shares of manual log bucking with Norway spruce logs. Share of manual log bucking (%) <30 [A] 30â&#x20AC;&#x201C;60 [B] >60 [C] Cutting method (%) Regeneration 75.8 70.4 felling Thinning 14.7 21.1 Other cutting 9.5 8.5 Height of removal of spruce log stems (m) 18.4 18.1 DBH of removal of spruce log stems (cm) 27.6 27.5 Volume of removal of spruce log stems (dm3) 712 694 Share of defected timber on spruce log section (%) 11.9 13.3 Share of spruce of log stem removal (%) 62.0 62.1 Share of pine of log stem removal (%) 32.4 31.0 Share of hardwood of log stem removal (%) 5.6 6.9 Forest site class (%) Upland forest with grass-herb 26.6 28.1 71.8 69.2 vegetation Moist upland forest site Dry upland forest site 1.5 2.7 DBH = Diameter at breast height (d1.3); * p<0.05; ** p<0.01; *** p<0.001.

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56.0 36.2 7.8 17.2 26.5 607 14.8 54.2 36.2 9.6 29.1 65.0 5.9

Statistically significant differences between Groups A, B & C A-C***, B-C***

A-B***, A-C***, B-C*** A-B**, A-C***, B-C*** A-B***, A-C***, B-C*** A-B***, A-C***, B-C*** A-B**, A-C***, B-C*** A-B**, B-C*** A-B**, A-C***, B-C***

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Fig. 5. Spearman’s correlations (ρ) and their statistical significances (*p<0.05;

p<0.01;

***

p<0.001) between the antecedents and manual log bucking percentage, as well as between manual log bucking percentage and the consequences with Norway spruce logs. Table 2. Harvesting conditions and classified groups related to the shares of manual log bucking with Scots pine logs. Share of manual log bucking (%) <60 [A] 60–80 [B] >80 [C] Cutting method (%) Regeneration 75.3 70.0 felling Thinning 17.1 23.6 Other cutting 7.6 6.4 Height of removal of pine log stems (m) 18.4 18.2 DBH of removal of pine log stems (cm) 26.7 26.8 Volume of removal of pine log stems (dm3) 648 643 Share of defected timber on pine log section (%) 12.3 15.0 Share of spruce of log stem removal (%) 60.4 55.2 Share of pine of log stem removal (%) 33.5 37.8 Share of hardwood of log stem removal (%) 6.1 6.9 Forest site class (%) Upland forest with grass-herb 17.5 8.6 vegetation Moist upland forest site 82.5 66.3 Dry upland forest site 0.0 25.1 DBH = Diameter at breast height (d1.3); * p<0.05; ** p<0.01; *** p<0.001.

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60.8 32.9 6.3 18.0 26.3 621 17.4 55.1 35.6 9.3 6.6 78.8 14.6

Statistically significant differences between Groups A, B & C A-C***, B-C***

A-B***, A-C***, B-C*** A-C***, B-C* A-B*, A-C***, B-C*** A-B***, A-C***, B-C*** A-B***, B-C*** A-B***, A-C* A-B***, A-C***, B-C***

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Fig. 6. Spearman’s correlations (ρ) and their statistical significances between the antecedents and manual log bucking percentage, as well as between manual log bucking percentage and the consequences with Scots pine logs. The consequences of the utilization of manual log bucking were significant in the study. When the utilization degree of manual log bucking was high, the utilization of log section with spruce and pine log stems was lower: the length of log section was shorter, the top diameter of log section was thicker, and the volume of log section was smaller (Tables 3 and 4). When using plenty of manual log bucking, the logs cut were also shorter and the volume of logs was smaller. Furthermore, log percentage (i.e. log recovery) was lower on harvesting sites (Figs 5 and 6, Tables 3 and 4). There was no significant connection between the utilization degree of manual bucking and the reject percentage of pine logs (Fig. 6, Table 4). Nonetheless, with spruce and pine log stems, the apportion-ment degrees were significantly lower when the shares of manual log bucking were higher (Figs 5 and 6, Tables 3 and 4). When looking at the production value of logs, the relative production value of spruce logs was significantly lower, when the share of manual bucking was high (Fig. 5, Table 3). In turn, the relative production value of pine logs was significantly higher, when the share of manual bucking was high (Fig. 6, Table 4). Table 3. The consequences of the utilization of manual log bucking with Norway spruce logs. Share of manual log bucking (%) <30 [A] 30–60 [B] >60 [C] Length of spruce log section (m) 10.9 10.2 8.9 Top diameter of spruce log section (cm) 18.1 18.4 18.9 Volume of spruce log section (dm3) 550 523 435 Spruce log length (m) 4.96 4.82 4.66 Spruce log top diameter (cm) 22.3 22.4 22.0 Spruce log volume (dm3) 251 247 229 Spruce log percentage (%) 77.2 75.4 71.7 Reject percentage of spruce logs (%) 2.80 2.33 2.10 Apportionment degree of spruce logs (%) 75.1 69.4 59.0 Relative production value of spruce logs (%) † 100.6 100.3 99.1 * p<0.05; ** p<0.01; *** p<0.001; † Average relative production value of spruce logs = 100%.

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Statistically significant differences between Groups A, B & C A-B***, A-C***, B-C*** A-B***, A-C***, B-C*** A-B***, A-C***, B-C*** A-B***, A-C***, B-C*** B-C* A-B***, A-C***, B-C*** A-B***, A-C***, B-C*** A-B**, A-C*** A-B***, A-C***, B-C*** A-C**, B-C**

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Table 4. The consequences of the utilization of manual log bucking with Scots pine logs. Share of manual log bucking (%) <60 [A] 60–80 [B] >80 [C] Length of pine log section (m) 10.4 9.9 9.2 Top diameter of pine log section (cm) 18.1 18.4 18.7 Volume of pine log section (dm3) 486 467 434 Pine log length (m) 4.84 4.79 4.71 Pine log top diameter (cm) 21.4 21.6 21.5 Pine log volume (dm3) 225 227 221 Pine log percentage (%) 75.0 72.7 69.8 Reject percentage of pine logs (%) 4.01 3.96 3.52 Apportionment degree of pine logs (%) 70.0 63.3 52.5 Relative production value of pine logs (%) † 99.1 100.4 100.9 * p<0.05; ** p<0.01; *** p<0.001; † Average relative production value of pine logs = 100%.

Statistically significant differences between Groups A, B & C A-B***, A-C***, B-C*** A-B***, A-C***, B-C*** A-B***, A-C***, B-C*** A-B***, A-C***, B-C*** A-B*, A-C***, B-C** A-B***, A-C***, B-C*** A-B***, A-C***, B-C*** A-B**, A-C***

More than a half (55%) of the harvester operators interviewed regarded automatic bucking as significantly better or better than manual bucking to produce the highest bucking outcome with spruce log stems (Fig. 7). Only 11% of the operators believed that the manual bucking causes clearly better or better bucking result than automatic bucking in cross-cutting spruce logs. In cross-cutting pine log stems, 40% of the operators considered that automatic log bucking yields significantly better or better bucking outcome than manual bucking. On the contrary, 29% of the harvester operators estimated that manual bucking produces clearly better or better pine bucking result than automatic 7). bucking (Fig.

Share of operators (%)

50 45

Spruce log

Pine log

35 30 25 20 15 10 5 0 1

1 = Automatic bucking significantly better … 5 = Manual bucking significantly better

Fig. 7. The estimates of the harvester operators (n=74) interviewed which bucking option (i.e. auto-matic vs. manual) produces better bucking outcome in cross-cutting spruce and pine log stems. The high log percentage received the highest weight for the good bucking outcome. Its weight was, on average, 29% with both spruce and pine log stems. Nonetheless, the variation was quite large between the statements among the harvester operators interviewed (Fig. 8). In addition to the log percentage, the operators raised the importance of low reject percentage, the high production value of logs, and high apportionment degree as the elements for the good bucking outcome. The weights of these elements were, on average, 20–25% (Fig. 8). With both spruce and pine log stems, the aver-age weights were at very similar levels.

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50 45

Spruce log

Pine log

Weight (%)

35 30 25 20 15 10 5 0 High log percentage

Low reject percentage High production value of logs

High apportionment degree

Fig. 8. In the view of the harvester operators (n=74) concerning the weights of the selected elements for the good bucking outcome in cross-cutting spruce and pine log stands. The bars describe the average and the black lines the standard deviation. The operators told that the most significant reason for using manual log bucking with spruce log stems is rot on log section, mainly on the butt of a stem; then the operator has to sound one offcut piece or several pieces or pulpwood pole(s) from the butt of a stem. With spruce log stems, the second and the third most important reasons for manual log bucking were crook in a stem and defect part on log section, respectively. On the other hand, with pine log stems, the most important reason for utili-zation of manual log bucking was crook on log section. The second and the third most important reasons were defect part on log section and corkscrew in a stem. Besides, the harvester operators were asked when they utilize most frequently manual log bucking. The results showed that the operators use manual log bucking most frequently in poor-quality and relative small-sized thinning stands which locate in vigorous forest sites (Fig. 9). Many harvester operators underlined also that the manual log bucking must be applied if target distributions do not work in the log stand. Correspondingly, a little manual log bucking is utilized in high-quality and large-diameter regeneration fellings which are poor in nutrients, as well as on the middle parts of log stems (Fig. 9).

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954 Regeneration felling Thinning Large-diameter stand Small-diameter stand High-quality stand Poor-quality stand Spruce-dominant stand Pine-dominant stand Mixed-wood stand Fast-grown forest site Oligotropfic fores site On butt of stem On middle part of stem On top of stem Target distributions do not work in stand

Spruce log Pine log

1 = A little manual bucking ...

5 = A lot of manual bucking

Fig. 9. The evaluations of the harvester operators (n=74) where they utilize a little and where they use a lot of manual log bucking when they are cross-cutting spruce and pine logs. The bars describe the average and the black lines the standard deviation. The harvester operators were notably willing to take part in log bucking education. Only less than one tenth (8%) of the operators reported that they are not willing to attend bucking education if it will be arranged in the near future. The rest of the operators interviewed were willing to participate log bucking education sessions. Discussion. The data, particularly the stm data with almost two million softwood log stems and more than four million softwood logs cross-cut for the study was large. Actually, it can be concluded that we had Big Data in the study. On the other hand, the data on the ERP systems was smaller but it can be estimated that also this data gave reliable findings. The manual log bucking percentages for each study operator could not be calculated because the stm data used did not consist of a mark on operator identification information, and there were two operators in many harvesters of the study. Neverthe-less, it can be assumed that there was also a significant difference between the harvester operators in the study because there was a large variation between the percentages of manual log bucking in the harvesters of the study (cf. Fig. 4). The antecedents of manual log bucking were detected in the study. The focus was on the variables of harvesting conditions, i.e. cutting method, the size, defectiveness, tree species of log stem removal, and fertility of forest site class. The results of interview survey displayed also the bucking – among others target distributions – used in the log stand affect the frequency of using manual buckinstructions ing (cf. Fig. 9). Besides, Änäkkälä [21] has highlighted that a lot of manual log bucking is applied when there are only a few log dimensions (lengths and top diameters) in the target distribution, and in particular the proportions of long logs required are relatively high. The results demonstrated that there is a strong correlation between manual bucking percentages with spruce and pine log stems by harvesting site and by harvester. This is not a desirable situation when you have to minimize the share of manual bucking with spruce log stems and to maximize the share of manual bucking with pine log stems. Depending on the issue, with which criterion the goodness of bucking outcome is evaluated, two recommendation sets for the present utilization of manual log bucking can be drawn up:

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

 If the ultimate target for log bucking is to maximize the production value of logs cut, then the study results point out that we have to minimize the manual bucking percentage with spruce log stems and to maximize the manual bucking percentage with pine (Fig. 10).  If your main log bucking target is some other one (i.e. other than the high production value of logs in cross-cutting), hence it is useful to minimize your manual bucking percentage with both spruce and pine log stems, apart from the reject percentage of spruce logs (Fig. 10).

Fig. 10. Summary of the impacts of the manual log bucking percentages of Norway spruce and Scots pine on the selected log bucking results in the study. The green colour illustrates an eligiple log bucking outcome and the red colour an undesirable result. Whatever the bucking target is, it can be estimated that the manual bucking percentage with spruce log stems must be at a lower level than nowadays. The average manual bucking percentage was 46% with spruce logs in the study. Based on the study results, it can be recommended that the target for the manual log bucking percentage with spruce must be less than 20–30% of the total log volume cut (cf. Table 3). In order to achieve this target, the wood harvesting entrepreneurs and their harvester operators, as well as harvesting officers in wood procurement organizations must be offered the buck-ing education sessions. – It was great to notice that almost all harvester operators of the study were very willing to participate bucking education if the education will be organized. Besides, some follow-up studies after bucking education sessions will be needed to clarify what is the progress in the manual log bucking percentages of operators. Likewise, more accurate survey on the reasons (e.g. rot, defected tree section, corkscrew and crook), why the operator utilizes manual log bucking in his/her cross-cutting work, could be carried out in the near future. Namely in the interview survey, the operators was just asked what are the most essential reasons for selecting manual bucking option. The results showed that the production value and value recovery of pine log stems cut can be increased with utilization of manual bucking. It is a huge potential in the future. Lebelle et al. [22] have also researched the effects of manual and automatic bucking on value recovery in a pinedominated stand with 22 study plots in Germany. The study results by Lebelle et al. are in line with our findings because they displayed that the value recovery is higher with large-diameter pine log stems when using manual bucking. On the other hand, in the research by Uusitalo et al. [12], automatic bucking of pine log stems did not markedly lower the amount of good-quality lumber compared to quality (i.e. manual) bucking with the study material of 100 sample pine stems.

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

In addition to the study by Lebelle et al. [22], there is only one other novel bucking research [11] in which the impacts of manual bucking on bucking result have been studied. Holappa Jonsson and Hägglund [11] clarified in Sweden the utilization of manual bucking also in pine stands and noted that there is a significant negative correlation between the utilization degree of manual log bucking and the apportionment degree and that besides there is no significant correlation between manual bucking percentage and the reject percentage of pine logs. Our results are similar with the results by Holappa Jonsson and Hägglund [11] (cf. Fig. 6, Table 4). Nowadays, harvester operators can conduct a quality bucking with pine log stems. It calls, however, extremely close attention in log bucking work for the harvester operator. It can be assumed that the harvester operator can do very precisely quality (i.e. manual) log bucking with pine stems at the beginning of his/her work shift but at the end of his/her work shift with increased fatigue his/her ability to produce high-quality manual log bucking is at the lower level [cf. 23, 24]. Therefore, in the future, our target must be fully automatic or semi-automatic and harvester computer-aided quality bucking based on the quality grades of the log section zones of log stems with pine and spruce. It will require equipping harvesters with novel mobile laser scanning (MLS) and machine vision (MV) ap-plications [25–27]. The connection between manual log bucking percentage and the productivity of cross-cutting work was not detected in this study. It can be presupposed that when the harvester operator utilizes plenty of automatic log bucking, his/her performance of cutting work is higher [cf. 23, 24, 28]. Lebelle et al. [22] sorted out the influence of automatic and manual bucking on harvesting productivity. The results by Lebelle et al. [22] did not, however, endorse the assumption introduced above but the average harvesting productivity was higher – but not statistically significant – in manual bucking compared to automatic bucking. Nonetheless, the Big Data studies on the effects of using manual and automatic log bucking on cutting productivity will be needed in the future. The harvester operators interviewed said that the most significant criterion related to the good bucking outcome is high log percentage (Fig. 8). The view of the operators reflects that the operators regard the forest owner of harvesting site as his/her primary customer. In other words, the operator aims to buck the stems so that the log percentage in the stand is maximized, because the price for logs is much higher than the price for pulpwood. Nevertheless, when surveying the criteria for the goodness of bucking outcome in terms of sawmill, the most significant criterion is not log percentage but high-quality logs supplied with high production value and low reject percentage, as well as the realized log matrix meets well target distribution set, i.e. apportionment degree is high. Consequently, harvester operators could be reminded that a sawmill is also their customer and the criteria for log bucking come from sawmills to harvesters and operators. In other words, we have a need of better communi-cation concerning the targets of log bucking in the supply chain of sawmilling in results the future. Summary. industry The study introduced that the share of manual bucking of Norway spruce logs was, on average, 46% and with Scots pine logs 67%. The harvester operators used manual bucking more frequently in thinning stands with small-sized and defected log stems. On the basis of the study, it can be concluded that if the ultimate target for tree-stem log bucking is to maximize the production value (i.e. value recovery) of logs, then nowadys we have to minimize the manual bucking percentage with Norway spruce log stems and to maximize the manual bucking percentage with Scots pine log stems. In the future, our aim must be fully automatic or semi-automatic and harvester computer-aided bucking based on the quality grades of the log section zones of log stems with Scots pine and Norway spruce. It will require equipping harvesters with novel mobile laser scanning (MLS) and machine vision (MV) applications. References [1] Marshall, H. D. (2005). An Investigation of Factors Affecting the Optimal Log Output Distribution from Mechanical Harvesting and Processing Systems (Doctoral dissertation). Oregon State Uni-versity. Retrieved from http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/9570/ Mar-shall?sequence=1 MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

[2] Strandström, M. (2017). Timber Harvesting and Long-distance Transportation of Roundwood 2016. Metsätehon Tuloskalvosarja 1b/2017. Retrieved from http://www.metsateho.fi/wp-content/ up-loads/Tuloskalvosarja_2017_01b_Timber-Harvesting-and-Long-distance-Transportation-ofRound-wood-2016.pdf [3] Mäki-Simola, E. (2017). The average forest machinery in commercial roundwood production in Finland, 2010–2016. Natural Resources Institute Finland, Unpublished statistics. [4] Marshall, H. (2007). Log merchandizing model used in mechanical harvesting. In A. Weintraub, C. Romero, T. Bjørndal, & R. Epstein (Eds.), Handbook of Operations Research in Natural Resources (pp. 379-389). New York, NY: Springer Science+Business Media. ISBN 978-0-387-718149 [5] Geerts, J. M. P., & Twaddle, A. A. (1984). A method to assess log value loss caused by crosscutting practice on the skidsite. New Zealand Journal of Forestry, 29 (2), 173-184. Retrieved from http://nzjf.org.nz/free_issues/NZJF29_2_1984/D48E7FD6-CF5B-4BDB-A01ED317C7E30D18.pdf [6] Pickens, J. B., Lee, A., & Lyon, G. W. (1992). Optimal Bucking of Northern Hardwoods. Northern Journal of Applied Forestry, 9(4), 149-152. [7] Bowers, S. (1998). Increased Value through Optimal Bucking. Western Journal of Applied For-estry, 13(3), 85-89. [8] Wang, J., LeDoux, C. B., & McNeel, J. (2004). Optimal tree-stem bucking of northeastern species of China. Forest Products Journal, 52(2), 45-52. Retrieved from https://www.nrs.fs.fed.us/ pubs/jrnl/2004/ne_2004_wang_001.pdf [9] Malinen, J., & Palander, T. (2004). Metrics for Distribution Similarity Applied to the Bucking to Demand Procedure. International Journal of Forest Engineering, 15(1), 33-40. Retrieved from https://journals.lib.unb.ca/index.php/IJFE/article/view/9861 [10] Nummi, T., Sinha, B. K., & Koskela, L. (2005). Statistical properties of the apportionment degree and alternative measures in bucking outcome. Revista Investigación Operacional, 26(3), 259-267. Retrieved from https://www.researchgate.net/profile/Tapio_Nummi2/ publication/265254527_STATISTICAL_PROPERTIES_OF_THE_APPORTIONMENT_DEGREE_AND_ALTERNATIVE_MEASURES_IN_BUCKING_OUTCOME/links/5406ce750cf2bba34c1e5f6f.pdf [11] Holappa Jonsson, S., & Hägglund, J. (2016). The Effect of Harvester Drivers on Assortment Yield and Length Distribution of Pine Logs in Final Fellings. Sveriges Lantbruksuniversitet, Institutionen för skogens ekologi och skötsel, Kandidatarbete i skogsvetenskap 2016:04. [12] Uusitalo, J., Kokko, S., & Kivinen, V.-P. (2004). The Effect of Two Bucking Methods on Scots Pine Lumber Quality. Silva Fennica, 38(3), 291-303. DOI 10.14214/sf.417 [13] Kivinen, V.-P. (2007). Design and testing of stand-specific bucking instructions for use on mod-ern cut-to length harvester (Doctoral dissertation). University of Helsinki, Dissertationes 37. ISBN 978-951-651-163-7 Forestales [14] Twaddle, A. A., & Goulding, C. J. (1989). Improving profitability by optimising log-making. New Zealand Journal of Forestry, 34(1), 17-23. Retrieved from http://nzjf.org.nz/free_is-sues/ NZJF34_1_1989/351BD376-E2F0-4A77-97DC-78702A1EE735.pdf [15] Wang, J., Liu, J., & LeDoux, C. B. (2009). A Three-Dimensional Bucking System for Optimal Bucking of Central Appalachian Hardwoods. International Journal of Forest Engineering, 20(2), 2635. Retrieved from https://www.nrs.fs.fed.us/pubs/jrnl/2009/nrs_2009_wang-j_001.pdf [16] Akay, A. E., Sessions, J., Serin, H., Pak, M., & Yenilmez, N. (2010). Applying Optimum Buck-ing Method in Producing Taurus Fir (Abies cilicica) Logs in Mediterranean Region of Turkey. Baltic Forestry, 16(2), 273-279. Retrieved from https://www.balticforestry.mi.lt/bf/ PDF_Arti-cles/201016[2]/Abdulach_etal_2010%2016(2)_273_279.pdf MMSE Journal. Open Access www.mmse.xyz

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[17] Serin, H., Akay, A. E., & Pak, M. (2010). Estimating the effects of optimum bucking on the economic value of Brutian pine (Pinus brutia) logs extracted in Mediterranean region of Turkey. African Journal of Agricultural Research, 5(9), 916-921. Retrieved from http://www.academicjournals.org/article/article1380795030_Serin%20et%20al.pdf [18] Akay, A. E., Serin, H., & Pak, M. (2015). How stem defects affect the capability of optimum bucking method? Journal of the Faculty of Forestry Istanbul University, 65(2), 38-45. DOI 10.17099/jffiu.54455 [19] Ylitalo, E. (2017). Forest industries’ wood consumption in Finland, 1860–2016. Natural Re-sources Institute Finland, Statistics Database. Retrieved from http://stat.luke.fi/en/woodconsumption [20] Skogforsk. (2007). StanForD. Standard for Forest Data and communications. Retrieved from http://www.skogforsk.se/contentassets/b063db555a664ff8b515ce121f4a42d1/stanford_maindoc_070327.pdf [21] Änäkkälä, J. (2017). The frequency of manual bucking on Norway spruce logs in eastern Finland at Stora Enso Wood Supply Finland (Master’s thesis). University of Eastern Finland. [22] Labelle, E. R., Bergen, M., & Windisch, J. (2017). The effect of quality bucking and automatic bucking on harvesting productivity and product recovery in a pine-dominated stand. European Journal of Forest Research, 136(4), 639-652. [23] Gellerstedt, S. (2002). Operation of the Single-Grip Harvester: Motor-Sensory and Cognitive Work. International Journal of Forest Engineering, 13(2), 35-47. Retrieved from https://journals.lib.unb.ca/index.php/IJFE/article/view/9893 [24] Nicholls, A., Bren, L., & Humphreys, N. (2004). Harvester Productivity and Operator Fatigue: Working Extended Hours. International Journal of Forest Engineering, 15(2), 57-65. Retrieved from https://journals.lib.unb.ca/index.php/ijfe/article/view/9850/9989 [25] Marshall, H., & Murphy, G. (2004). Economic evaluation of implementing improved stem scan-ning systems on mechanical harvesters/processors. New Zealand Journal of Forestry Science, 34(2), 158-174. Retrieved from http://www.scionresearch.com/__data/assets/ pdf_file/0020/5375/03_Mar-shall_Murphy.pdf [26] Murphy, G., Wilson, I., & Barr, B. (2006). Developing methods for pre-harvest inventories which use a harvester as the sampling tool. Australian Forestry, 69(1), 9-15. DOI 10.1080/00049158.2006.10674982 [27] Murphy, G. (2008). Determining Stand Value and Log Product Yields Using Terrestrial Lidar and Optimal Bucking: A Case Study. Journal of Forestry, 106(6), 317-324. [28] Häggström, C. (2015). Human Factors in Mechanized Cut-to-Length Forest Operations (Doctoral dissertation). Swedish University of Agricultural Sciences, Acta Universitatis agriculturae Sueciae 2015:59. urn:nbn:se:slu:epsilon-e-2644

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

Evaluation of Low Velocity Impact Response of Composite Plates Embedded with SMA wires- An Analytical and Numerical Approach Buddhi Arachchige1, a 1 – Cranfield University, Bedford, United Kingdom a – B.M.Archchige@cranfield.ac.uk DOI 10.2412/mmse.43.56.827 provided by Seo4U.link

Keywords: impact, shape memory alloys, recovery stress, smart composites, finite element.

ABSTRACT. This paper involves an analytical and numerical study to analyse the effect of SMA wires on the low velocity impact response of composite plates. First order shear deformation theory and a two-degree of freedom springmass system derived functions for the contact force history, which was used to study the impact response of SMA embedded graphite/epoxy flat plates. Numerical modelling in LSDYNA is used to validate the analytical model and studies were performed analytically and numerically to analyse the effect of SMA volume fraction and positioning on the impact performance. Results proved that SMA wires improved impact damage resistance.

Introduction. Composite materials are widely used for various applications in aerospace, automotive, marine industries due to their attractive properties such as been lightweight, high strength and corrosion resistivity [1-4]. However, composites are susceptible to impact damage due to lack of through the thickness reinforcement and weak interfaces. Delaminations and matrix cracking are the dominant failure modes in a low velocity impact event and thus reduces the structural integrity of a composite material [5-7]. Therefore, improving the damage resistance of composites is vital and embedding SMA wires into a composite laminates is considered to be an effective method to increase the damage tolerance of composite structures [8]. The effect of embedding SMA wires into composites on the low velocity impact behaviour have been a widely popular topic among researchers [9-14]. Lei et al. [9] investigated the macroscopic mechanical behaviour of SMA embedded hybrid composites. Results proved that ultimate strength of the composite increased with the number of embedded SMA fibre and reduction in the rupture elongation. Aurrekoetxea et al. [10] studied the effect of super-elastic shape memory alloy wires on the impact behaviour of woven carbon fabric composites. Their results proved that SMA wires improved the energy absorption capability on hybrid composites. Kang and Kim [11] experimentally investigated the effect of SMA wires on low velocity impact damage behaviour of glass/epoxy laminates. The main conclusions drawn from their study were that impact damage was mainly in the form of delaminations and impact response was affected by both the SMA wires and temperature. Raghavan et al. [12] evaluated the capability of shape memory alloy fibres to improve damping capacity and toughness of a thermoset polymer matrix. Reinforcement of the polymer with SMA fibres resulted in an improvement in damping, tensile and impact properties. Lau et al. [13] studied the low velocity impact behaviour of shape memory alloy (SMA) stitched composite plates. The analytical study based on quasi-static energy balance equation derived that the delamination energy for stitched glass/epoxy plates were smaller compared to unstitched composite plates and that the number of matrix cracks were less for the stitched plates. Tensile modulus of the stitched plates were also greater proving that impact resistance could be improved by the use of SMAs in composites. Tsoi et al. [14] experimentally analysed the effect of shape memory alloys on impact 1

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

resistance of glass/epoxy composites. They demonstrated that placement of SMA wires are crucial and positioning them closer to the bottom layer significantly improved resistance to fibre breakage. It was also shown that higher volume fraction of the wires improved impact damage resistance. Paine and Rogers [15] proved that SMA wires were able to reduce composite ply-delamination by 25% by embedding them within graphite/bismaleimide hybridized composite. Khalili and Ardali [16] developed an analytical model to study the low velocity impact response of doubly curved composite plates embedded with SMA wires. They used the first order shear deformation theory and a two-degree of freedom spring-mass model to analyse effect of impact parameters and shape memory wires on the impact response, and proved that structural stiffness is increased through the use of SMAs in composites. This paper focuses on developing an analytical model to analyse the low velocity impact response of flat composite plates embedded with SMA wires. The main highlight of this research is the development of a finite element model in LS-DYNA, which was identified as the research gap. To the authorsâ&#x20AC;&#x2122; present knowledge, this is the first finite element model to evaluate the impact response of SMA embedded composite plates.

Fig. 1. Composite plate embedded with SMA wires. Analytical Modelling. The analytical modelling consists of a square plate 100mmĂ&#x2014;100mm with a total thickness of 0.85 mm. The stacking sequence of the composite plates were [45Â°/-45Â°/90Â°/0Â°] and the SMA wires were aligned along the centre of the plate, covering a 20 mm width. The diameter of SMA wires were 0.2 mm. A spherical steel impactor with diameter 15.35 mm and mass of 2.38 kg was impacted at the centre. First order shear deformation theory presents the displacement field as: đ?&#x2018;˘(đ?&#x153; 1, đ?&#x153; 2, đ?&#x153; , đ?&#x2018;Ą) = đ?&#x2018;˘0(đ?&#x153; 1, đ?&#x153; 2, đ?&#x2018;Ą) + đ?&#x153; đ?&#x153;&#x2018;1(đ?&#x153; 1, đ?&#x153; 2, đ?&#x2018;Ą)

(1)

đ?&#x2018;Ł(đ?&#x153; 1, đ?&#x153; 2, đ?&#x153; , đ?&#x2018;Ą) = đ?&#x2018;Ł0(đ?&#x153; 1, đ?&#x153; 2, đ?&#x2018;Ą) + đ?&#x153; đ?&#x153;&#x2018;2(đ?&#x153; 1, đ?&#x153; 2, đ?&#x2018;Ą)

(2)

đ?&#x2018;¤(đ?&#x153; 1, đ?&#x153; 2, đ?&#x153; , đ?&#x2018;Ą) = đ?&#x2018;¤0(đ?&#x153; 1, đ?&#x153; 2, 0)

(3)

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

where 𝑢0, 𝑣0 and 𝑤0 represents the displacements of a point(𝜁1, 𝜁2, 0) on the mid-surface of the shell; 𝜑1 and 𝜑2 are the rotations. The equations of motion for a symmetric cross-ply composite shell considering in-plane initial stress resultants 𝑁𝑖 𝑦and 𝑁𝑖 are expressed as [16]: 𝑥 2 𝜕 𝑢01

𝐴11 ( 𝜕𝑥+ 2 2 + 𝜕𝑥𝜕 𝜑𝜕𝑥2 ) 1 2

2 𝜕 𝑣0

𝜕𝑤0

2 𝜕 𝑣0

1 𝜕𝑤0

2 0

𝜕 𝑢 ) 𝜕𝑥22 2𝑢 𝜕 0

𝑅1 𝜕𝑥1 ) + 𝐴12 ( 𝜕𝑥1𝜕𝑥2 + 𝑅2 𝜕𝑥1 ) + 𝐴66 ( 𝜕𝑥1𝜕𝑥2 +

𝜑 𝑘𝑠ℎ𝐴55 ( 𝑅11

2𝑢

1 𝜕𝑤0 + 𝑅1 𝜕𝑥1

−

𝑢0 ) 𝑅12

𝑖

𝜕𝑁11 𝜕𝑥1

𝑖

2𝑣

𝜕𝑤

𝑁11 𝜕𝑤0 𝑅1 ( 𝜕𝑥1

−

𝑢0 𝑅1 )

− 𝐼0

2𝑢

𝜕𝑤

𝜕𝑡2

−

2𝜑

𝜕 1 + 𝑐0𝐷66 ( 𝜕𝑥 2 + 2

𝜕 𝜑1 𝐼1 𝜕𝑡=2 0

(4)

𝜕 𝑢0 0 0 𝜕 0 1 𝜕 0 1 𝜕 0 𝜑 𝐴12 (𝜕𝑥1𝜕𝑥2 + 𝑅1 𝜕𝑥2 ) + 𝐴22 ( 𝑥𝜕 2 + 𝑅2 𝜕𝑥2 ) + 𝐴66 ( 𝜕𝑥 2 + 𝜕𝑥1𝜕𝑥2 ) + [𝑘𝑠ℎ𝐴44 ( 2 + 1 𝜕𝑤0 + 𝑅2 𝜕𝑥2

−

𝑣0 )] 𝑅22

𝜕𝜑1

− 𝑐0𝐷66 (𝜕𝑥

1𝜕𝑥2

𝜕𝜑2 ) 𝜕𝑥12

𝑖

𝜕𝑁22 𝜕𝑥2

𝑖

𝑁22 𝜕𝑤0 𝑅2 ( 𝜕𝑥2

−

𝑣0 𝑅2 )

𝜕 𝑣0 𝐼0 𝜕𝑡2

𝑅2

𝜕 𝜑2 𝜕𝑡2

(5)

2 2 𝜕 𝑤0 𝜕𝜑1 1 𝜕𝑢0 𝜕 𝑤0 𝜕𝜑2 1 𝜕𝑣0 1 𝜕𝑢0 + − ) + 𝑘 𝐴 ( 2 𝑠ℎ 44 𝜕𝑥 2 + 𝜕𝑥2 − 𝑅2 𝜕𝑥2 ) − 𝑅1 {𝐴11 ( 𝜕𝑥1 𝜕𝑥1 𝑅1 𝜕𝑥1 𝜕𝑥1 2 𝜕 𝜕𝑣0 𝑤0 1 𝜕𝑢0 𝑤0 𝜕𝑣0 𝑤0 𝜕𝑤 𝑢 𝐴12 ( 𝜕𝑥2 + 𝑅2 )} + 𝑅2 {𝐴12 ( + 𝑅1 ) + 𝐴22 ( 𝜕𝑥2 + 𝑅2 )} + 𝜕𝑥1 [𝑁𝑖11 (𝜕𝑥1 0− 𝑅01)] + 𝜕𝑥1 )] 2 𝜕 𝑤0 𝜕𝑤0 𝑣0 𝜕 + 𝜕𝑥 [𝑁𝑖22 (𝜕𝑥 − + 𝑞 = 𝐼 𝑅2 𝜕𝑡2 0 2 2

𝑘𝑠ℎ𝐴55 (

2 𝜕 𝜑1

+𝐼1

2𝑢

2 𝜕 𝜑2

𝜕 𝜑1 ) 𝜕𝑥22

− [𝑘𝑠ℎ𝐴55 (𝜑1 +

𝜕𝑤0 𝜕𝑥1

(6)

𝑢

− 𝑅01)] = 𝐼2

𝜕 𝜑1 𝜕𝑡2

𝜕 0 𝜕𝑡2

2 𝜕 𝜑1

2𝑣

(7)

𝐷66 (𝜕𝑥1𝜕𝑥2 +

+𝐼1

2 𝜕 𝜑2

𝐷11 ( 𝜕𝑥 2) + 𝐷12 (𝜕𝑥1𝜕𝑥2 ) + 𝐷66 (𝜕𝑥1𝜕𝑥2 +

𝑤

+ 𝑅10) +

𝜕 𝜑2 ) 𝜕𝑥12

2 𝜕 𝜑1

2 𝜕 𝜑2

+ 𝐷12 (𝜕𝑥1𝜕𝑥2 ) + 𝐷22 ( 𝜕𝑥 2) − [𝑘𝑠ℎ𝐴44 (𝜑2 + 2

𝜕𝑤0 𝜕𝑥2

𝑣

− 𝑅02)] = 𝐼2

𝜕 𝜑2 𝜕𝑡2

𝜕 0 𝜕𝑡2

(8)

For a flat rectangular plate 𝑅1 = 𝑅2 = ∞ Stress-strain relationship for a laminate composite embedded with SMA wires are expressed as: 𝜎1 𝑄11 𝑄12 𝜎 { 2} = ( 𝑄12 𝑄22 𝜎3 0 0

𝜀1 0 𝜎𝑟 𝑄11𝑚 𝑄12𝑚 0 𝛼1𝑐 0 ) { 𝜀2 } + { 0 } 𝑘𝑠 − ( 𝑄12𝑚 𝑄𝑚22 0 ) {𝛼2𝑐 } 𝑘𝑐∆𝑇 0 𝑄66 𝛾12 0 0 𝑄𝑚66 0 𝜏23 𝑄 [ ] = ( 44 0 𝜏13

0 𝛾 )[ 𝑄55 𝛾

23 1

]

(10)

𝐴𝑖𝑗 𝐵𝑖𝑗 𝑁 { }=( 𝜀 0 𝑁𝑖 } 𝐵𝑖𝑗 𝐷𝑖𝑗 ) {𝜀 1 } + {𝑀 𝑖 𝑀 MMSE Journal. Open Access www.mmse.xyz

(9)

(11)

Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

đ?&#x2018; đ?&#x2018;&#x2013; = {

đ?&#x2018; đ?&#x2018;&#x2013; } = {đ?&#x2018; đ?&#x2018;&#x; â&#x2C6;&#x2019; đ?&#x2018; đ?&#x2018;&#x2021;} ; đ?&#x2018;&#x2013;, đ?&#x2018;&#x2014; = 1,2,6 {đ?&#x2018;&#x20AC; đ?&#x2018;&#x2013; đ?&#x2018;&#x20AC;đ?&#x2018;&#x; â&#x2C6;&#x2019; đ?&#x2018;&#x20AC; đ?&#x2018;&#x2021;

(12)

{đ?&#x2018;&#x2020;} = [đ?&#x2018;&#x2DC;đ?&#x2018; â&#x201E;&#x17D;đ??´đ?&#x2018;&#x2013;đ?&#x2018;&#x2014;]{đ?&#x153;&#x20AC;0}; đ?&#x2018;&#x2013;, đ?&#x2018;&#x2014; = 4,5

(13)

đ?&#x153;&#x17D;đ?&#x2018;&#x;đ?&#x2018;&#x2DC;đ?&#x2018; đ?&#x2018;Ľâ&#x201E;&#x17D;đ?&#x2018;Ľ â&#x2C6;&#x2019; (đ?&#x2018;&#x201E;11đ?&#x2018;&#x161;đ?&#x203A;ź1đ?&#x2018;? + đ?&#x2018;&#x201E;12đ?&#x2018;&#x161;đ?&#x203A;źđ?&#x2018;Ąđ?&#x2018;?)đ?&#x2018;&#x2DC;đ?&#x2018;?đ?&#x2018;Ľâ&#x201E;&#x17D;đ?&#x2018;Ľâ&#x2C6;&#x2020;đ?&#x2018;&#x2021; đ?&#x153;&#x17D;đ?&#x2018;&#x;đ?&#x2018;&#x2DC;đ?&#x2018; đ?&#x2018;Śâ&#x201E;&#x17D;đ?&#x2018;Ś â&#x2C6;&#x2019; (đ?&#x2018;&#x201E;12đ?&#x2018;&#x161;đ?&#x203A;ź1đ?&#x2018;? + đ?&#x2018;&#x201E;đ?&#x2018;&#x161; 022đ?&#x203A;źđ?&#x2018;Ąđ?&#x2018;?)đ?&#x2018;&#x2DC;đ?&#x2018;?đ?&#x2018;Śâ&#x201E;&#x17D;đ?&#x2018;Śâ&#x2C6;&#x2020;đ?&#x2018;&#x2021;

}

(14)

In this particular problem, the SMA wires are placed in x-direction. Therefore, đ?&#x2018;&#x2DC;đ?&#x2018; đ?&#x2018;Ś â&#x20AC;&#x201C; is zero since no wires are placed in y-direction. Double Fourier series are used to obtain solutions to the dynamic problem based on expansion of loads, displacement and rotation functions. Deflections and rotations of a flat composite plate using Double Fourier series are expressed as [17]: đ?&#x2018;&#x161;đ?&#x153;&#x2039;đ?&#x2018;Ľ1 đ?&#x2018;&#x203A;đ?&#x153;&#x2039;đ?&#x2018;Ľ2 â&#x2C6;&#x17E; â&#x2C6;&#x2018;â&#x2C6;&#x17E; đ?&#x2018;˘0(đ?&#x2018;Ľ1, đ?&#x2018;Ľ2, đ?&#x2018;Ą) = â&#x2C6;&#x2018;đ?&#x2018;&#x203A;=1 đ?&#x2018;&#x161;=1 đ?&#x2018;&#x2C6;đ?&#x2018;&#x161;đ?&#x2018;&#x203A;(đ?&#x2018;Ą)đ?&#x2018;?đ?&#x2018;&#x153;đ?&#x2018; đ?&#x2018;&#x17D; đ?&#x2018; đ?&#x2018;&#x2013;đ?&#x2018;&#x203A; đ?&#x2018;?

đ?&#x2018;Ł0(đ?&#x2018;Ľ1, đ?&#x2018;Ľ2, đ?&#x2018;Ą) = â&#x2C6;&#x2018; â&#x2C6;&#x17E; đ?&#x2018;&#x203A;=1 â&#x2C6;&#x2018;

đ?&#x2018;&#x161;đ?&#x153;&#x2039;đ?&#x2018;Ľ1 đ?&#x2018;&#x203A;đ?&#x153;&#x2039;đ?&#x2018;Ľ2 â&#x2C6;&#x17E; đ?&#x2018;&#x161;=1 đ?&#x2018;&#x2030;đ?&#x2018;&#x161;đ?&#x2018;&#x203A;(đ?&#x2018;Ą)đ?&#x2018; đ?&#x2018;&#x2013;đ?&#x2018;&#x203A; đ?&#x2018;&#x17D; đ?&#x2018; đ?&#x2018;&#x2013;đ?&#x2018;&#x203A; đ?&#x2018;?

(15)

(16)

đ?&#x2018;&#x161;đ?&#x153;&#x2039;đ?&#x2018;Ľ1 đ?&#x2018;&#x203A;đ?&#x153;&#x2039;đ?&#x2018;Ľ2 â&#x2C6;&#x17E; â&#x2C6;&#x2018;â&#x2C6;&#x17E; đ?&#x2018;¤0(đ?&#x2018;Ľ1, đ?&#x2018;Ľ2, đ?&#x2018;Ą) = â&#x2C6;&#x2018;đ?&#x2018;&#x203A;=1 đ?&#x2018;&#x161;=1 đ?&#x2018;&#x160;đ?&#x2018;&#x161;đ?&#x2018;&#x203A;(đ?&#x2018;Ą)đ?&#x2018; đ?&#x2018;&#x2013;đ?&#x2018;&#x203A; đ?&#x2018;&#x17D; đ?&#x2018; đ?&#x2018;&#x2013;đ?&#x2018;&#x203A; đ?&#x2018;?

(17)

đ?&#x2018;&#x161;đ?&#x153;&#x2039;đ?&#x2018;Ľ1 đ?&#x2018;&#x203A;đ?&#x153;&#x2039;đ?&#x2018;Ľ2 â&#x2C6;&#x17E; đ?&#x153;&#x2018;1(đ?&#x2018;Ľ1, đ?&#x2018;Ľ2, đ?&#x2018;Ą) = â&#x2C6;&#x2018;â&#x2C6;&#x17E; đ?&#x2018;&#x203A;=1 â&#x2C6;&#x2018;đ?&#x2018;&#x161;=1 đ?&#x2018;&#x2039;đ?&#x2018;&#x161;đ?&#x2018;&#x203A;(đ?&#x2018;Ą)đ?&#x2018;?đ?&#x2018;&#x153;đ?&#x2018; đ?&#x2018; đ?&#x2018;&#x2013;đ?&#x2018;&#x203A;

(18)

â&#x2C6;&#x17E; â&#x2C6;&#x2018;â&#x2C6;&#x17E; đ?&#x153;&#x2018;2(đ?&#x2018;Ľ1, đ?&#x2018;Ľ2, đ?&#x2018;Ą) = â&#x2C6;&#x2018;đ?&#x2018;&#x203A;=1 đ?&#x2018;&#x161;=1 đ?&#x2018;&#x152;đ?&#x2018;&#x161;đ?&#x2018;&#x203A;(đ?&#x2018;Ą)đ?&#x2018; đ?&#x2018;&#x2013;đ?&#x2018;&#x203A;

đ?&#x2018;&#x17D;

đ?&#x2018;&#x161;đ?&#x153;&#x2039;đ?&#x2018;Ľ1

đ?&#x2018;&#x17D;

đ?&#x2018;?

đ?&#x2018;?đ?&#x2018;&#x153;đ?&#x2018;

đ?&#x2018;&#x203A;đ?&#x153;&#x2039;đ?&#x2018;Ľ2 đ?&#x2018;?

(19)

đ?&#x2018; đ?&#x2018;&#x2013;đ?&#x2018;&#x203A;

đ?&#x2018;&#x203A;đ?&#x153;&#x2039;đ?&#x2018;Ľ2 đ?&#x2018;?

(20)

The terms of the Fourier series can be expressed as: đ?&#x2018;&#x17E;đ?&#x2018;&#x203A;(đ?&#x2018;Ľ1, đ?&#x2018;Ľ2, đ?&#x2018;Ą) = â&#x2C6;&#x2018; â&#x2C6;&#x17E; đ?&#x2018;&#x203A; =1 â&#x2C6;&#x2018;

đ?&#x2018;&#x161;đ?&#x153;&#x2039;đ?&#x2018;Ľ1 â&#x2C6;&#x17E; đ?&#x2018;&#x161;=1 đ?&#x2018;&#x201E;đ?&#x2018;&#x161;đ?&#x2018;&#x203A;(đ?&#x2018;Ą)đ?&#x2018; đ?&#x2018;&#x2013;đ?&#x2018;&#x203A; đ?&#x2018;&#x17D;

Impact Model. A two degree of freedom system consisting of the plate and impactor is considered as shown in Figure 2.

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

Fig. 2. Two degree of freedom spring-mass model. The contact force is related to contact deformation by [17]: đ??šđ?&#x2018;?â&#x2C6;&#x2014;(đ?&#x2018;Ą) = đ??ž2â&#x2C6;&#x2014;đ?&#x153;&#x2022;

(21)

The equations of motion for the two degree of freedom system is: đ?&#x2018;&#x161;1đ?&#x2018;§Ě&#x2C6;1 = â&#x2C6;&#x2019;đ?&#x2018;&#x2DC;1đ?&#x2018;§1 â&#x2C6;&#x2019; đ?&#x2018;&#x2DC;2(đ?&#x2018;§1 â&#x2C6;&#x2019; đ?&#x2018;§2)

(22)

đ?&#x2018;&#x161;2đ?&#x2018;§Ě&#x2C6;2 = â&#x2C6;&#x2019;đ?&#x2018;&#x2DC;2(đ?&#x2018;§2 â&#x2C6;&#x2019; đ?&#x2018;§1)

(23)

The analytical force-function is defined as [17]: đ??šđ?&#x2018;?â&#x2C6;&#x2014;(đ?&#x2018;Ą) = đ??ž2â&#x2C6;&#x2014;[đ??´1(đ??ś1 â&#x2C6;&#x2019; 1)đ?&#x2018; đ?&#x2018;&#x2013;đ?&#x2018;&#x203A;đ?&#x153;&#x201D;1đ?&#x2018;Ą + đ??´2(đ??ś2 â&#x2C6;&#x2019; 1)đ?&#x2018; đ?&#x2018;&#x2013;đ?&#x2018;&#x203A;đ?&#x153;&#x201D;2đ?&#x2018;Ą]

(24)

The natural frequency of the composite plate is expressed as: [16]

đ?&#x153;&#x201D;2đ?&#x2018;&#x161;đ?&#x2018;&#x203A; =

â&#x2C6;&#x2019;(đ?&#x2018;?13đ??žđ?&#x2018;&#x2C6;+đ?&#x2018;?23đ??žđ?&#x2018;&#x2030;+đ?&#x2018;?33+đ?&#x2018;?34đ??žđ?&#x2018;Ľ+đ?&#x2018;?35đ??žđ?&#x2018;&#x152;) đ?&#x153;&#x152;â&#x201E;&#x17D;

(25)

Model validation. The analytical model is validated with available experimental work on impact response of SMA embedded flat composite plates. Material properties of graphite/epoxy CU-125NS are presented in Table 1 and material properties of SE 508 SMA wire in Table 2. Stress strain behaviour is depicted in Figure 3.

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

Table 1. Properties of plate [18]. E1

135.4GPa

9.6GPa

G12

4.8GPa

đ?&#x153;?

0.31

Table 1. Properties of SMA wires [18]. Martensite

Austenite

Transfer coefficient

4.6MPa/Â°C

6.4MPa/Â°C

Elastic modulus

17.0GPa

40.1GPa

Failure stress

1179MPa

1434MPa

Failure strain

14.9%

14.4%

Fig. 3. Stress-strain behaviour of SE508 wire. Numerical modelling. In this section, a finite element model in LS-DYNA is developed. Material Model 54 with Chang-Chang failure criteria in LSDYNA is used to model the composite failure in the plate. Four failure modes; tensile fibre failure, compressive fibre failure, tensile matrix failure and compressive matrix failure are incorporated in this model. The size of the composite plate was 100 Ă&#x2014; 100đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 with a 0.85mm thickness. The composite plates were meshed using 1 Ă&#x2014; đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 shell elements. Integration points were used in defining the layers. Similarly, to the experimental study [14], SMA wires of 0.2mm diameter were spaced equally within a width of 20mm. They were embedded in between the 8 layers (i.e. at 4 layers from the bottom layer) corresponding to a stacking sequence of [45Â°/-45Â°/90Â°/0Â°]s as shown in Figure 4. Material model 30 is used to model the shape memory wires and material model 20 was used for the impactor. The mass of the impactor was 2.38kg with an impact velocity of 4.4m/s. An impact model for a flat plate was also developed to compare the performance of the SMA embedded composite.

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

Fig. 4. Finite element model (SMA Embedded plate) (a) impact model (b) placement of SMA wires.

c) Fig. 5. Finite element models (a) Conventional plate (without SMA) (b) von Misses stress in SMA plate (c) bending of SMA wires. Analysis and Results. Analytical Model. The force function in equation 24 is used to analyse the effect of SMA wires on impact resistance of composites. Results were compared with that of a flat composite plate with the same material and dimensions under same impact loading conditions. Results proved that the impact performance of the composite plate embedded with SMAs are 7% higher than the conventional plate. MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

Fig. 6. Analytical model contact force history. The effect of the fibre volume fraction of SMA wires are also studied. The volume fraction đ?&#x2018;&#x2DC;đ?&#x2018; is varied from 0 to 0.3. The results proves that an increase in SMA volume fraction from 0 to 0.1 causes the maximum contact force to increase by 6%, proving that the volume fraction is a vital factor in improving the impact resistance of SMA embedded plates.

Fig. 7. Effect of SMA volume fraction on contact force history. Validation. The numerical model was validated with the analytical model developed. Contact force history comparison is shown in Figure 8. These results proved that the numerical model closely matched with the analytical model and experimental work done in literature [18]. The difference in maximum contact force of the numerical model was less than 5% when compared to the analytical and experimental models.

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Fig. 8. Contact force history comparison. A comparison is made to analyse the effect of the SMA wires on the impact response and deflection histories. Results of the SMA embedded plate were compared with the conventional plate to compare the performance under impact loading. Until the fracture point at around 3-4ms, there was not any different in the contact force histories between the two plates. This proved that up-to that point, the SMA wires had negligible effect. However, after the composite laminates fractured, it was observed that the contact force of SMA embedded plates were higher than the conventional plate, thus implying that SMA wires resist higher impact loads after fracture and that they prevent damage propagation of the laminates. The deflection history results showed that SMA embedded plates deflected less than the conventional plates. Deflection recovery was also higher and it almost recovered up-to its original shape as shown in Figure 10. This was due to the smaller damage regions of the SMA embedded plate caused by higher impact resistance and recovery stress generated by the SMA wires. FE simulations showed that this stress recovery caused the SMA plate to bounce the impactor.

Fig. 9. Contact force history (Conventional and SMA embedded plate).

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Fig. 10. Deflection history (Conventional and SMA embedded plate). Parametric Study. A parametric study is carried out to analyse the effect of the positions of SMA wires on improving impact damage resistance of composite laminates. Four different locations were analysed at 1/6, 3/6, 4/6, 5/6 positions through the plate thickness, corresponding to 1/6 been SMA placement is on the upper layers, 3/6 been on the mid surface and 5/6 on the bottom surface. FE models developed to study this placement effect are shown in Figure 11. a)

Fig. 11. Positioning of SMA wires (a) 1/6, (b) 3/6, (c) 4/6, (d) 5/6. Contact force history plot is shown in Figure 9 and it is clearly seen that when SMAs are embedded in the bottom layer (5/6), the plate resists a higher impact force. Moving the wires from top layer (1/6) to the bottom layer (5/6) increased the maximum contact force by 13%, thus proving the effectiveness of SMA placement in laminate design to withstand impact loading.

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Fig. 12. Effect of SMA wire placement on contact force history. Summary. This paper presented an analytical and numerical model to analyse the effect of SMA wires on the low velocity impact performance of flat composite laminates. First order shear deformation theory was used in deriving the contact force function, and natural frequency of the plate was determined by incorporating the effect of SMA volume fractions, recovery stresses and thermal expansion coefficients. Contact force history results proved that the SMA embedded plate resisted 7% higher impact loads than the conventional plate. Studying the effect of SMA volume fraction suggested that the plate is able to sustain 6% higher loads than the conventional plate when volume fraction increases from 0 to 0.1. A major highlight of the present paper, which is the development of a finite element model in LSDYNA, validated the analytical model results and experimental work on SMA embedded plates. Finally, an analysis was performed to analyse the effect of SMA wire placement in the laminate, and results proved that placing SMA wires in the bottom layer increases the impact resistance by 13%. References [1] Aktas M, Atas C, Icten BM, Karakuzu R. An experimental investigation of the impact response of composite laminates. Compos. Struct. 2009; 87 (4): 307-13. [2] Atas C, Sayman O. An overall view on impact response of woven fabric composite plates. Compos Struct 2008; 82(3): 336-45, DOI 10.1016/j.compstruct.2013.01.025 [3] Aslan Z, Karakuzu R, Okutan B. The response of laminated composite plates under low-velocity impact loading. Compos. Struct. 2003; 59 (1): 119-27. [4] Palazotto AN, Gummadi LNB, Vaidya UK, Herup EJ. Low velocity impact damage characteristics of Z-fibre reinforced sandwich panels- an experimental study. Compos. Struct. 199l; 43 (4): 275-88. [5] Papadda S, Rametta R, Largo A, Maffezzoli A. Low velocity impact response in composite plates embedding shape memory alloy wires. Polym. Compos. 2012; 33 (5): 655-64, DOI 10.1002/pc.22170 [6] Baucom JN, Zilkry MA. Low-velocity impact damage progression in woven E-glass composite systems. Compos Part A: Applied Science and Manufacturing 2005; 36 (5): 658-64. [7] Sayer M, Bektas NB, Sayman O. An experimental investigation on the impact behaviour of hybrid composite plates. Compos. Struct. 2010; 92 (5): 1256-62. [8] Sun M, Wang Z, Yang B, Sun X. Experimental investigation of GF/epoxy laminates with different SMAs positions subjected to low-velocity impact. Compos. Struct. 2017; 171: 170-184. MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

[9] Lei H, Wang Z, Tong L, Zhou B, Fu J. Experimental and numerical investigation on the macroscopic mechanical behaviour of shape memory alloy hybrid composite with weak interface. Compos. Struct .2013; 101: 301-12. [10] Aurrekoetxea J, Zurbitu J, Mendibil OL, Agirregomezkorta A, Soto SM, Sarrionandia M. Effect of super-elastic shape memory alloys wires on the impact behaviour of carbon fibre reinforced in situ polymerized poly(butylene terephthalate) composites. Materials Letters 2011; 65: 863-65, DOI 10.1016/2Fj.matlet.2010.12.020 [11] Kang WK, Kim KJ. Effect of shape memory alloy on impact damage behaviour and residual properties of glass/epoxy laminates under low temperature. Compos. Struct. 2009; 89: 455-60. [12] Raghavan J, Bartkiewicz T, Boyko S, Kupriyanov M, Rajapakse N, Yu B. Damping, tensile, and impact properties of super-elastic shape memory alloy (SMA) fibre-reinforced polymer composites. Compos. Part B 2010; 41: 214-22. [13] Lau TK, Ling YH, Zhou ML. Low velocity impact on shape memory alloy stitched composite plates. Smart Mater. Struct. 2004; 13: 364-70, DOI 10.1088/0964-1726/13/2/015 [14] Tsoi KA, Stalmans R, Schrooten J, Wevers M, Mai YW. Impact damage behaviour of shape memory alloy composites. Mater. Sci. Eng. A 2003; 342 (1): 207-15. [15] Paine SNJ, Rogers AC. The response of SMA hybrid composite materials to low velocity impact. Journal of Intelligent Material Systems and Structures 1994; 5(4): 530-5, DOI 10.1177/1045389X9400500409 [16] Khalili SMR, Aradali A. Low-velocity impact response of doubly curved symmetric cross-ply laminated panel with embedded SMA wires. Compos. Struct. 2013; 105: 216-26. [17] Gong SW, Toh SL, Shim VPW. The elastic response of orthotropic laminated cylindrical shells to low velocity impact. Compos. Eng. 1994; 4: 241-66. [18] Sun M, Kim HE, Lee HI, Choi I, Ahn MS, Koo NK, Bae SJ, Roh HJ. Low velocity impact characteristics of composite plates with shape memory alloy wires. Journal of theoretical and applied mechanics 2011; 49 (3): 841-857.

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The Effect of Rice Husk Ash on the Strength and Durability of Concrete at High Replacement Ratio 1

Binyamien I. Rasoul1,a, Friederike K. Gunzel1,b, M. Imran Rafiq1,c 1− School of Environment & Technology, University of Brighton, UK a – B.Rasoul@brighton.ac.uk b– f.k.gunzel@brighton.ac.uk c – M.Rafiq@brighton.ac.uk DOI 10.2412/mmse.31.86.30 provided by Seo4U.link

Keywords: concrete strength, durability, chloride ion, non-steady-state migration test, rice husk ash, pozzlanic activity.

ABSTRACT. The objective of this study is to investigate the effects of Rice Husk Ash, with different replacement levels, on the strength and durability of concrete. Three types of rice husk ash with different chemical composition and physical properties were used for this study. Ordinary Portland Cement (OPC) type 52.5 N was replaced with 5%, 10%, 15%, 20%, 30%, 40% and 50% RHA (by weight) for strength test, additional samples with 60% RHA replacement were used for durability experiments. The ratio of water/cementitious material was kept at a constant value of 0.50. Superplasticizer was used to maintain a consistent workability of the fresh concrete. The compressive strength was measured after 7, 28 and 90 days, while splitting tensile strength was obtained at age of 28 and 90 days. The migration coefficient of chloride ion penetration was evaluated using non-steady-state migration tests [1] at 28 days age. The results revealed that the RHA properties (silica form, fineness, silica percentage and loss on ignition) have a direct impact on the development of strength at long-term age [2]. Experiments showed that even with 50% replacement of OPC with RHA, concrete has a higher strength and durability performance compared to OPC concrete. This may be attributed to the fact that increasing replacement ratios of RHA leads to a reduction in porosity, which in turn increases the strength and durability of concrete.

Introduction. Improving the concrete’s performance by utilizing industrial and agricultural waste as supplementary cementitious materials is gaining popularity amongst researchers in recent years [3]. Pozzolanic materials such as fly ash, silica fume, ground granulated blast furnace slag and rice husk ash are by-products of other industries, containing high amounts of amorphous silica. This leads to a pozzolanic reaction the released calcium hydroxide of cement hydration process making these materials a suitable blending material for OPC. Rice husk ash is produce annually in huge quantities [4] by incinerating rice husk in electric power stations or by incinerating the husk at agricultural fields. The annual production of rice according to [5] in 2013 was 730.2 million tons. Rice husk is generally estimated about 20% of the plant weight and the ash is about 20% of the husk weight [6]. This huge amount of rice husk beside of environment dumping problem. Key ingredient of the RHA is reactive amorphous silica that reacts with calcium hydroxide liberated by cement hydration in concrete matrix to produce dense calcium silicate hydrates (CSH) that is mainly responsible for improved concrete performance [7]. Many studies investigated the effect of RHA blended cement in concrete mixtures; some include the effect of RHA on the strength and durability. However, there are many discrepancies in the results. For example, Mehta [6] found higher strength in concrete with up to 50% RHA compared to the OPC control, even as early as 3 days. Similarly, Isaia et al. [8] found that replacing cement by 50% RHA achieved the same strength as the OPC concrete.

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

On the other hand, many authors report only much lower replacement percentages as possible: Ganesan et al. [9] found that only up to 30% of OPC could be replaced with RHA without detrimental effects. Ettu et al. [10] report these as 15% RHA replacement without any reduction in strength. The optimum level of cement replacement with RHA was found to be between 10% and 20% according to Safiuddin [11]. Leong [12] reported that up to 5% of cement replacement by RHA increase the strength compare to OPC concrete. Madandoust et al. [13] and Marthong [14] show reduction in compressive strength for all RHA blended concrete compared to the OPC control. The positive effects of RHA on the concrete performance were attributed to the high content of amorphous silica and the very high surface area of the particles [8] and the particle characteristics such as shapes (spherical to un-regular ratio) [11]. Durability it is another important concrete property, which can be defined as the capability of concrete to resist weathering action and chemical attack. Many studies have investigated the impact of replacement of cement with RHA to enhance the performance of concrete [15]. However, the relationship between the physical and chemical properties of RHA to the level of replacement that can be used to reduce chloride ion penetration, is currently not fully understood. Madandoust et al. [13] concluded that blending Portland cement with RHA prevents the diffusion of Cl¯. The improvement is mainly caused by the reduction of permeability/diffusivity in blended concrete. As with the compressive strength, contradicting results are reported in the literature: some authors found that blending cement with up to 40% RHA increases corrosion resistance [16]. On the other hand, other authors reported a maximum of only 15% [18] to 25% [9], [17] of RHA to have a positive effect on the diffusion coefficient. The objectives of this study are to improve the understanding of the effects of the chemical and physical properties of the RHA on the concrete performance and to investigate the contradiction in literature data on the effect of RHA properties on the strength and chloride ion diffusion with the aim to find the optimum replacement ratio of cement by RHA depending on the properties of the RHA. Research Programme. A. Materials 1) Cement: The compositions of the cement (Rugby CEM I 52.5N) used in concrete blended RHA mixtures provided by the manufacturer (CEMEX UK Cement Ltd) is given in Table 1. Table 1. Physical and Chemical Properties of OPC (CEM i 52.5n). Physical properties Specific Surface area

450m2/kg

Initial setting time

130 minutes

Chemical compounds (% of total cement mass) CaO MgO 63.8 *

SiO2

19.9

3.10

Fe2O3 4.80

Al2O3 1.10

SO3

Na2O

Clˉ

FL*

LOI

3.3

0.70

0.06

3.0

2.70

FL = Free Lime

2) Rice Husk Ash: Three different types of RHA were used as a partial replacement with cement. The rice husk ash was provided by Navdanya Food PVT LTD Odisha, India. X-ray fluorescence was used to determine the chemical composition, while the physical properties (particle size distribution and specific surface area) were obtained with a laser diffractometer Mastersizer 2000 particle size analyzer. The physical properties and chemical composition are given in Tables 2 and 3 respectively. MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

Table 2. Physical Properties of RHA Types. RHA type

Specific surface area (m2/kg)

Mean particle size (µm)

Reactive silica( % of total RHA weight)

Colour

RHA-A

537

23.397

69%

Grey

RHA-B

587

20.948

80%

Dark Grey

RHA-C

691

15.804

84%

Black

Table 3. Chemical Composition of RHA Types (% of Total Mass). RHA type SiO2

Al2O3 Fe2O3 CaO

MgO

Na2O

P2O5

SO3

MnO

LOI*

RHA-A 92.10 K 2O

0.24

0.72

1.37

0.40

0.08

0.11

3.80

RHA-B 89.31

0.39

0.99

1.81

0.75

1.10

0.17

5.10

1.39 RHA-C 84.30

0.18

0.73

1.52

0.68

0.08

0.14

11.35

1.07

1.07 *LOI: Loss on ignition of rice husk ash at 975±25°C for 15 minutes according to EN 196-2:1994 Table 4. Properties of Fine Aggregate (Sand). Sieve aperture

Weight (g)

Percentage (%)

Cumulative passing (%)

4mm

2.2

97.8

2.8mm

8.6

89.2

1.4 mm

19.4

69.9

600μm

140

27.9

41.9

300μm

159

31.7

10.2

150μm

9.0

1.2

75μm

4.0

0.8

0.4

63μm

1.0

0.2

Pan

Table 5. Properties of Coarse Aggregate (Gravel). Sieve aperture

Weight (g)

Percentage (%)

Cumulative passing (%)

9.5 mm

3.0

97.1

8.0 mm

9.6

87.5

4.0 mm

341

68.1

19.4

Pan

19.4

3) Fine Aggregate: The sieve analysis of fine aggregate (sand) according to British Standard BS EN 12620 [19] is presented in Table 4.

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

4) Coarse Aggregate: Uncrushed gravel (maximum size 10 mm) was used as coarse aggregate according to the British Standard BS EN 12620 [19]. The sieve analysis of aggregates is presented in Table 5. 5) Superplasticizer: Fosroc Auracast 200 superplasticizer was used in the experimental work. According to the manufacturer, the Fosroc Auracast 200 has a high range water reducing capabilities and excellent scattering levels with strong performance. The main objective of using superplasticizer is to increase the workability of concrete blended RHA in order to require little vibration during casting. B. Experimental Procedure 1) Strength of Concrete: The mix design for concrete was based on British mix design method (DOE) [20]. The target mean strength was 50 MPa for the OPC control mixture at 28 days. Details of the mix proportion of the concrete mixes are presented in Table 6. The water to binder ratio (w/b) kept constant at 0.50 as well as the portion of fine aggregate (785 kg/m3) and coarse aggregate (800 kg/ m3); superplasticizer was used to keep the workability to a slump of 50-200 mm. The total time of mixing was 5 minutes. Standard 100 mm cubes were cast from each mixture to measure the effect of RHA on the compressive strength at the age of 7, 28, and 90 days. All specimens were kept in the molds for 24 hours and then placed in water for curing until the day of testing. The splitting tensile strength was measured at 28 and 90 days using 100mm diameter and 200mm high cylinders. Table 5. Concrete Mix Proportions. RHA Replacement (%)

Cement (kg/m3)

RHA (kg/m3)

Superplasticizer (%)

460

0.25

437

0.25

414

0.25

391

0.25

368

0.25

322

138

0.50

276

148

1.00

230

2.00

2) Chloride Ion Penetration: Chloride ion penetration was measured by the Nordtest (NT BUILD 492) method [21], which is a non-steady state migration method based on a theoretical relation between diffusion and migration. The method enables the calculation of the apparent chloride diffusion coefficient (Dnssm) from an accelerated test [1]. The samples were prepared from 28 day cured cylinder specimens sized 100mm diameter and 200mm height; these are cut with a saw to 50 mm high cylindrical slices. After the specimen was placed on the plastic support in the catholyte reservoir (10% NaCl solution) the sleeve above the specimen with was filled with 300 ml of 0.3N NaOH as anolyte solution (see Figure 1). A 30V electrical potential was applied and the initial current through each specimen was recorded. Then, after adjusting the voltage depending on the value of the initial current the test was continued for 24 to 96 hours depending on the initial current. The principle of the test is that chloride ions are forced to migrate out of the 10% NaCl catholyte solution subjected to a negative charge at the surface of the specimen, through the concrete into the 0.3N NaOH anolyte solution at the opposite surface of the specimen. After the test, the specimen is axially split and a silver nitrate solution is sprayed on to one of the freshly split surfaces; the chloride MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

penetration depth (xd) is measured by observation of the color change in order to calculate the apparent non steady state diffusion migration coefficient (Dnssm). Figure 1 shows the details of the test setup. đ??ˇđ?&#x2018;&#x203A;đ?&#x2018; đ?&#x2018; đ?&#x2018;&#x161; =

0.0239(273+đ?&#x2018;&#x2021;)đ??ż (đ?&#x2018;&#x2C6;â&#x2C6;&#x2019;2)đ?&#x2018;Ą

(đ?&#x2018;Ľđ?&#x2018;&#x2018; â&#x2C6;&#x2019; 0.0238â&#x2C6;&#x161;

(273+đ?&#x2018;&#x2021;)đ??żđ?&#x2018;Ľđ?&#x2018;&#x2018; đ?&#x2018;&#x2C6;â&#x2C6;&#x2019;2

)

(1)

where Dnssm â&#x20AC;&#x201C; is the non-steady-state migration coefficient (Ă&#x2014;10-12 m2/s); U â&#x20AC;&#x201C;is the absolute value of the applied voltage (V); T â&#x20AC;&#x201C; is the average value of the initial and final temperature in the anodic solution (ÂşC); L â&#x20AC;&#x201C; is the thickness of the specimen, usually 50 mm; xd â&#x20AC;&#x201C; is the average value of measured chloride penetration depth (mm); t â&#x20AC;&#x201C; is the testing period (h).

Fig. 1. The non-steady state migration test set-up: Anolyte (0.3M NaOH), Catholyte (10% NaCl) [1]. Results and Discussion. The results of the compressive strength tests to determine the optimum RHA replacement in concrete are shown in Figure 2; each data point represents the average value of three samples. The RHA blending increases the strength at the early age (7 days) up to 15% replacement ratio, for all RHA types. This early strength increase is unexpected as reactive silica cannot provide significant strength contribution unless hydration is at a progressed state (e.g. [18]). The early strength development may be attributed to the filler effect (physical) of the fine-grained RHA rather than the pozzolanic effect (chemical). However, the strength increase is most pronounced at the age of 28 days as a result of RHA silica reacting with the calcium hydroxide of cement hydration. This means that in RHA blended concrete, the Ca(OH)2 formed during hydration of Portland cement is rapidly consumed due to the high poz-zolanic reactivity of RHA. As time passes the rate of hydration reaction is faster than OPC and thus producing more secondary CSH. The volumes of Ca(OH)2 crystal are reduced and higher volume of CSH than OPC are seen and consequently accelerates and enhances the hydration [22].

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A. Compressive Strength 80

RHA-A 7d RHA-B 7d

RHA-C 7d Compressive strength (MPa)

OPC 7d

RHA-A 28d

RHA-B 28d

RHA-C 28d 30

OPC 28d RHA-A 90d

RHA-B 90d

RHA-C 90d 0 0

OPC 90d

RHA Replacement (%)

Fig. 2. Compressive strength of control and RHA blended concrete.

50 Compressive strength (MPa)

7d [9]

7d [14]

7d[11]

30 28d [9]

28d[11]

28d [14]

10 90d [9]

90d [14]

RHA Replacement (%)

Fig. 3. Compressive strength of RHA blended concrete from [9] [10] [13] [14]. Moreover, the high amount of amorphous RHA silica (RHA-C) consisting of irregular or angular and spherical shaped particles [1], [23], [24] with high fineness of particles improve the particle packing density of the blended cement, leading to a reduced volume of larger pores and a more homogenous microstructure of the cement paste, particularly in the interfacial zone around the aggregate leading to increase the strength. Based on the RHA properties given in Tables 1 and 2 (amorphous silica structure and high surface area) RHA-C blended concrete shows in the highest increase of the MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

compressive strength with increasing replacement ratio up to 15%; the compressive strength increased about 29% compared to the control sample. However, the strength of RHA concrete declines with increasing replacement ratio over 15%; nevertheless, even with 50% replacement the compressive strength of RHA-C (84% amorphous silica) concrete was still 12% higher than the control sample. This result confirms the result obtained by Mehta [6] and Isaia et al., [8]. This phenomenon can be explained by the amorphous siliceous nature and very high fineness that make RHA-C a highly reactive pozzolana. On the other hand, the performance of RHA with partially crystalline silica (RHA-A 25% crystalline; RHA-B 10% crystalline) exhibit higher compressive strength at 50% replacement after 90 days about 6.69% and 1.77% respectively compared to OPC concrete due to the crystalline silica particles behavior as a micro filler justifying better the density of mixture. Comparing the experimental results to the published literature ([8], [9], [10], [11], [13], [14]) it can be seen from Figure 3 hat the results are very inconsistent: the compressive strength increases with RHA content up to 30% [9], while the results from [10] and [13] show compressive strength reduction for RHA blended concrete. Furthermore, the value of compressive strength decreases below that of OPC concrete beyond 35% RHA mixture [9]. Similar results were reported by Zhang and Malhotra [7], where 30% is the optimal limit of replacement without negative impact on the strength of concrete. Moreover, Karim et al. [25] concluded after doing a review on the literature of RHA impact on the strength of mortar and concrete that 30% replacement ratio appears to be the optimal limit. On the other hand, the results obtained by Isaia et al., [8] showing excellent performance of concrete blended RHA even with 50% replacement ratio compared to the OPC concrete. This high performance of concrete blended RHA was due to the amorphous silica structure and the finesses of RHA particle size according to Ganesan et al. [9]. B. Splitting tensile strength The results of the splitting tensile strength at 28 and 90 days are presented in Figure 4. From the observation, the splitting tensile strength at long-term age is higher than the control for all RHA replacement percentages. The increase of splitting tensile strength at 50% RHA replacement is 11.17%, 9.14% and 15.17% for RHA-A, B and C respectively. However, the results from the literature are again inconsistent: Several authors ([26], [26], [26]) report a reduction of splitting tensile strength with increasing RHA content for RHA contents up to 20%. This has been explained by the increased brittleness of RHA concrete [29]. On the other hand, several authors ([29], [23]) reported an increase of splitting tensile strength for maximum RHA replacements up to 25%.

6 RHA-A 28d Splitting tensile strength(MPa)

RHA-B 28d RHA-C 28d

OPC 28d

RHA-A 90d RHA-B 90d

RHA-C 90d

OPC 90d

0 0

RHA Replacement (%)

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

Fig. 4. Splitting tensile strength of control and RHA blended concrete. C. Chloride Permeability The results of the non-steady state migration test are illustrated in Figure 4. The results show that using RHA drastically enhances resistance to chloride ion penetration compared to the control concrete. Resistance to chloride ion penetration in concrete was improved from 11.55×10-12 m2/s to 1.77×10-12 m2/s, 2.19×10-12 m2/s and 0.80×10-12 m/s2 for 50% replacement with RHA-A, B and C respectively. The improved resistance for chloride penetration was also reported by several other authors ([9], [17], [18], [31], [32]); the optimum replacement in these studies was reported to be between 15% and 25% [9]. With increased RHA replacement up to 60%, the chloride penetration of RHA-A concrete reduced further to 2.10×10-12 m2/s, while RHA-B and C showed an increase to 1.64×10-12 m2/s and 0.98×1012

m2/s respectively. The behavior of RHA-A can be attributed to two factors; first, the high amount of silica content (92.10% of total weight), of which about 75% are amorphous. Second, the behavior of crystalline silica (about 25% of silica) as micro filler after all amorphous silica reacted with calcium hydroxide of cement hydration. It can be seen that the diffusion coefficient of RHA blended concrete specimens continuously decreases with increase in RHA content up to 50% of RHA-C and B, while continues decreasing with RHA-A even with 60%; nevertheless, still higher than RHA-C coefficient at 60% replacement ratio.

Dnssm×10-12 m2/s

RHA-A

RHA-B

RHA-C 4

OPC

0 0

RHA Replacement (%)

Fig. 5. Chloride ion diffusion of RHA concrete after 28 days. D. Effect of Superplasticizer Ratio on Strength Results of cubes and cylinders with superplasticizer obtained from experimental analysis shows that by using superplasticiser in RHA concrete the compressive and tensile splitting strength of concrete were increased. Several authors report increase of strength and durability for concrete with superplas-ticizer compared to control samples ([33] [34] [35]). The strength increase may be as large as 30% at 7 days and 50% at 28 days when the author used superplasticizer 1.61% of cement weight [32]. The positive effect has been attributed to improved compaction of concrete and more water being availa-ble to lubricate the mix [38].

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Summary. The results presented in this paper indicate that up to 50 % of rice husk ash (by weight) can be incorporated in concrete without adversely affecting on the strength and durability of the concrete. Based on experimental results, the following conclusions can be drawn: 1. The obtained test results showed that the compressive and splitting tensile strength of concrete have noticeably been improved. These properties are influenced by variations in reactive silica content in the RHA (the higher the amount of silica in amorphous form, the higher the concrete strength and resistivity value became), amount of crystalline to amorphous silica form content, grain size of RHA particles, concrete age, Best results were achieved with the more reactive RHA (RHA-C). The coarser, less reactive RHA-A and B produced lower strength results for the whole range of cement replacement. 2. The increase in compressive and tensile strength of concrete with RHA containing a high amount of crystalline silica (RHA-A and B) is better justified by the filler effect (physical) than by the pozzolanic effect (chemical). After depletion of all amorphous silica by reacting with calcium hydroxide [Ca(OH)2] to produce secondary C-S-H gel, the remaining silica, which is in crystalline form will behaves as a filler. 3. According to the experimental results as much as 60% by weight of OPC can be replaced by all RHA types used in the study improving the durability of concrete (chloride ion resistance); the best results were achieved with RHA-C with a 91% reduction of chloride penetration; this can be attributed to the high reactivity of the amorphous silica and fine grain size of RHA-C. This is a much higher reduction than previously reported in the literature where only a 15% to 40% reduction could be achieved ([16], [18]). 4. Overall RHA-C performed best of all three RHA types used in this study. Both compressive and tensile strength had a maximum at 15% replacement, but were still higher than the control concrete at 50% replacement. The reduction of chloride penetration was at a maximum at 50% replacement with only a slight reduction at 60% replacement. 5. The many discrepancies in published literature on strength and durability of RHA blended concrete can be attributed to the different RHA properties used by various authors. Especially the content of active (amorphous) silica and the grain size have a large influence on its performance as pozzolanic material. Based on the results of the present study the future work will investigate the following points: – Investigations will be undertaken to determine the effect of increasing the RHA content (for up to 70% or more) on the properties of concrete, and investigate the effect of high dosage of superplasticizer on the workability and compressive and splitting tensile strength. – RHA with defined properties will be produced by controlled re-incineration and grinding; this will be used to further investigate the effect of RHA particle grain size and the content of amorphous silica on the strength and durability of the concrete. – Experiments will be carried out using different amounts of superplasticizer to be able to distinguish between the effect of the superplasticizer and RHA on the strength and durability of the concrete. References [1] NT BUILD 492, Concrete, mortar and cement-based repair materials: chloride migration coefficient from non-steady-state migration experiments, Nord test Method 492, Finland, 1999. [2]B. I. Rasoul, F.K. Günzeland M. I. Rafiq. Effect of rice husk ash properties on the early age and long-term strength of mortar. Accepted by fib Symposium, Maastricht 12-14 June 2017. [3] M. S. Imbabi, C. Carrigan and S. McKenna. Trends and developments in green cement and concrete technology. International Journal of Sustainable Built Environment, 1(2), pp. 194-216, 2012, DOI 10.1016/j.ijsbe.2013.05.001 MMSE Journal. Open Access www.mmse.xyz

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[4] V. M. Malhotra. Reducing CO2 emissions. Concrete international 28 (09), pp. 42-45, 2006. [5] F. Fao, 2013. Statistical Yearbook: World Food and Agriculture. FAO Food Agric. Organziation UN Rome Italy, 2013. [6] P.K. Mehta. Siliceous Ashes and Hydraulic Cements Prepared Therefrom, Belgium Patent 802909, July 1973, U.S. Patent 4105459, August 1978. Retrieved from: http://www.patentability.com/US4105459.html. [7] M.H. Zhang and V.M. Malhotra. High-performance concrete incorporating rice husk ash as a supplementary cementing material. ACI Materials Journal, 93(6), pp. 629-636, 1996. [8] G.C. Isaia, A.L.G. Gastaldini and R. Moraes. Physical and pozzolanic action of mineral additions on the mechanical strength of high-performance concrete. Cement and concrete composites, 25(1), pp. 69-76, 2003, DOI 10.1016/S0958-9465(01)00057-9 [9] K. Ganesan, K. Rajagopal and K. Thangavel. Rice husk ash blended cement: assessment of optimal level of replacement for strength and permeability properties of concrete. Construction and Building Materials, 22(8), pp. 1675-1683, 2008, DOI 10.1016/j.conbuildmat.2007.06.011 [10] L.O. Ettu, C.A. Ajoku, K.C. Nwachukwu, C.T.G. Awodiji and U.G. Eziefula. Strength variation of OPC-rice husk ash composites with percentage rice husk ash. Int. J. App. Sci. and Eng. Res., 2, 4, 420-424, 2013, DOI 10.12691/ajmm-2-2-3 [11] M.D. Safiuddin, J.S. West and K.A. Soudki. Hardened properties of self-consolidating high performance concrete including rice husk ash. Cement and Concrete Composites, 32(9), 708-717, 2010, DOI 10.1016/j.cemconcomp.2010.07.006 [12] T.L. Leong. Effects of Rice Husk Ash (RHS) Produced from Different Temperatures on the Performances of Concrete. Doctoral dissertation, UTAR, 2015. [13] R. Madandoust, M.M. Ranjbar, H.A. Moghadam and S.Y. Mousavi. Mechanical properties and durability assessment of rice husk ash concrete. Biosystems engineering, 110(2), pp. 144-152, 2011. as partial replacement of cement on [14] C. Marthong. Effect of Rice Husk Ash (RHA) concrete properties. International Journal of Engineering Research and Technology 1(6), pp 6, 2012. [15] K.E. Hanna and G. Morcous. Effectiveness of Class C fly ash on mitigating alkali-silica reaction in concrete pavement. International Journal of Construction Education and Research, 5(3), pp.167- 181, 2009, DOI 10.1080/15578770903152781 [16] P. Chindaprasirt, S. Rukzon and V. Sirivivatnanon. Resistance to chloride penetration of blended Portland cement mortar containing palm oil fuel ash, rice husk ash and fly ash. Construction and Building Materials, 22(5), pp.932-938, 2008. [17] V. Saraswathy and H. W. Song, H.W. Corrosion performance of rice husk ash blended concrete. Construction and Building Materials, 21(8), pp. 1779-1784, 2007, DOI 10.1016/j.conbuildmat.2006.05.037 [18] G.R. de Sensale, Effect of rice-husk ash on durability of cementitious materials. Cement & Concrete Composites, 32, pp 718 â&#x20AC;&#x201C; 725, 2010. [19] British Standards Institution BS EN 12620. Aggregates for concrete. London, 2002. [20] J. Newman and B.S .Choo. Mix Design of Concrete: British (DOE) Method. Advanced concrete technology 3: processes. Butterworth-Heinemann., pp 31, 2003. [21] NT BUILD-492, NORDTEST METHOD: Concrete, Mortar And Cement-Based Repair Materials: Chloride Migration Coefficient From Non-Steady-State Migration Experiments. 1999.

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[22] G. Sivakumar and R. Ravibaskar, R. Investigation on the hydration properties of the rice husk ash cement using FTIR and SEM. Applied Physics Research, 1(2), pp.71-77, 2009, DOI 10.5539/ apr.v1n2p71 [23] C.L. Hwang and S. Chandra. The Use of Rice Husk Ash in Concrete. Waste Materials Used in Concrete Manufacturing. Edited by Chandra, S., Noyes Publications, USA, pp 184-234, 1997. [24] Bronzeoak Ltd., Rice Husk Ash Market Study - A Feasibility Study Internal Report, UK Companies, EXP 129, DTI/Pub. URN 03/668 United Kingdom, pp 1-53, 2003. [25] M.R. Karim, M.F.M. Zain, M. Jamil, F.C. Lai and M.N. Islam. Strength of mortar and concrete as influenced by rice husk ash: a review. World Applied Sciences Journal, 19(10), pp.1501-1513, 2012, DOI 10.5829/idosi.wasj.2012.19.10.533 [26] S. Tushir, Mohit and G. Kumar. Effect of Rice Husk Ash on Split Tensile Strength of Concrete. International Journal on Emerging Technologies 7(1): pp. 78-82, 2016. [27] R. Kishore, V. Bhikshma and P.J. Prakash. Study on strength characteristics of high strength rice husk ash concrete. Procedia Engineering, 14, pp. 2666-2672, 2011. [28] D.V. Reddy, M. Alvarez and D. Arboleda. Rice Husk Ash as a Sustainable Concrete Material for the Marine Environment. Sixth LACCEI International Latin American and Caribbean Conference for Engineering and Technology (LACCEIâ&#x20AC;&#x2122;2008), 2008. [29] G.A. Habeeb and M.M. Fayyadh. Rice husk ash concrete: the effect of RHA average particle size on mechanical properties and drying shrinkage. Australian Journal of Basic and Applied Sciences, 3(3), pp. 1616-1622, 2009. [30] A.N. Givi, S.A. Rashid, F.N.A. Aziz and M.A.M. Salleh. Contribution of rice husk ash to the properties of mortar and concrete: a review. Journal of American science, 6(3), pp. 157-165, 2010. [31] G.R. De Sensale. Effect of rice-husk ash on durability of cementitious materials. Cement and Concrete Composites, 32(9), pp.718-725, 2010. [32] C.Y. Kawabata, H. Savastano Junior and J. Sousa-Coutinho. Rice husk derived waste materials as partial cement replacement in lightweight concrete. Cencia e Agrotecnologia, 36(5), pp. 567-578, 2012. [33] D.S. Khatri. Impact of admixture and rice husk ash in concrete mix design. IOSR Journal of Mechanical and Civil engineering, 11(1), pp.13-17, 2014. [34] B.D. Reddy, S.A. Jyothy and I.R. Reddy. Effect of rice husk ash on the properties of ordinary Portland cement and Portland slag cement with and without super plasticizers. International journal of civil, structural, environmental and infrastructure engineering research and development (ijcseierd), 1(3), pp.1-8, 2013. [35] C. Yamakawa, K. Kishitani, I. Fukushi and K. Kuroha. Slump control and properties of concrete with a new superplasticizer. ii: high strength in-situ concrete work at hikariga-oka housing project. In Admixtures for Concrete-Improvement of Properties: Proceedings of the International RILEM Symposium (Vol. 5, p. 106). CRC Press, 1990.

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Applied Load on Blade Bearing in Horizontal Axis Wind Turbine Generator Chen L.1, a, Xia X. T. 1,2, Qiu M. 1 1 – College of Mechatronics Engineering, Henan University of Science & Technology, Luoyang, China 2 – Collaborative Innovation Centre of Machinery Equipment advanced Manufacturing of Henan Province, China a – haustchenlong@163.com DOI 10.2412/mmse.3.51.716 provided by Seo4U.link

Keywords: applied load, blade bearing, horizontal axis, slewing ring, wind turbine.

ABSTRACT. Rolling bearing life is typically calculated on the basis of its load ratings relative to the applied loads and the requirements regarding bearing life and reliability. Variation of applied load influences the load distribution in blade bearing directly and the load on maximum-loaded ball fluctuates with the applied load. Life of blade bearing is influenced by these variations eventually. Analysis and calculation method of applied load on blade bearing is illustrated by the case of a horizontal axis wind turbine.

Introduction. Wind turbine generator (WTG) is the equipment, which translates wind power to electrical energy, it can be divided into horizontal axis and vertical axis wind turbine. WTG can also be classified by the types of control modes. They are fixed speed stall regulated, fixed speed pitch regulated, variable speed stall regulated and variable speed pitch regulated, respectively. Horizontal axis wind turbine generator (HAWT) by variable speed pitch regulated is rapid developed in recent years and there are four kinds of bearings in the turbine. Structural rigidity is an important characteristic of WTG, and many investigators published relative results. For example, Jianhong et al. [12] analysed Dynamic Behaviour of Wind Turbine by a Mixed Flexible-Rigid Multi-Body Model. Blade is the component which gaining energy from the wind. Hence, the relationship between blade shape and velocity attracted more attention, for instance, Yukimaru [11] investigated the flow around blade tip of a HAWT. As for rolling bearings being used in HAWT, it mainly includes yaw bearing, blade bearing, mainshaft bearing and gearbox bearing, as illustrated in Fig. 1. There are various structures of rolling bearing. Many researchers developed special researches on determining appropriate structure of rolling bearing for HAWT. Chen et al. [3] discussed better choice of rolling bearings mounted on different positions in HAWT. Nobuyuki and Souich [6] illustrated technical trends of wind turbine bearings.

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

Mainshaft bearing Gearbox bearing

Blade bearing Yaw bearing

Fig. 1. Bearings in wind turbine generator. Slewing ring is usually adopted as yaw bearing and blade bearing. Slewing is defined as the rotation of an object about an axis. Thus a slewing ring is a bearing used in slewing applications for transferring or supporting axial, radial, and moment loads, singularly or in combination, consisting of rings mounted with threaded fasteners, and usually having a gear integral with one of the rings. In the last decades, a lot of research efforts have been devoted to study application characteristics of slewing ring. Prebil et al. [10] established calculation model of load distribution onto rolling elements in a rotational connection. Zupan et al. [7] validated the theory analysis by experiment. With the deepening of research on slewing ring, many researchers developed special researches on relations between inner geometry structure and performance of slewing ring. Zupan et al. [8] established relation between carrying angel and carrying capacity of four-point-contact slewing bearing. Chen et al. [3] presented influence of groove shape on clearance in four-point-contact slewing bearing.as can be seen in Fig. 2 (a), is mounted between adjustable blades and hub. A pitchBlade bearing, regulated wind turbine has individual pitch actuators for each blades, the possibility arises to send different pitch angle demands to each blade. In order to guarantee proper functioning of wind turbine, pitch system (as shown in Fig. 2 (b) drives blade rotating around its own axis under different wind velocity. Four-contact-point slewing ring is widely used as blade bearing in current application. The detail of blade bearing mounted in WTG is shown in Fig. 2 (c). Both double-row and single-row four-contact-point slewing rings are adopted according to different power level of wind turbine. Working conditions of blade bearing is more complex than yaw bearing in HAWT. Hence, some special investigations on blade bearing were developed in recent years. Chen et al., 2010 introduced contact stress and deformation of blade bearing in HAWT. Rolling bearing life is typically calculated on the basis of its load ratings relative to applied load and the requirements regarding bearing life and reliability. Load rating of the bearing is only one kind of key factor, which influences bearing life and applied load is the other key factor, which impacts it. Applied load on blade bearing is a dynamic variable value and it must be analysed and calculated strictly to ensure service life of blade bearing. This paper draws its attention on analysis & calculation of applied loads on blade bearing.

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954

Bolts

Blade

Blade bearing

Motor

Drive gear

c) b) Fig. 2. a) The photo of the blade bearing, b) Electric pitch control system, c) Hydraulic pitch control system. Applied load types. Energy resource of HAWT is the natural wind and, gusts and turbulence are inevitable. Variation of instantaneous wind speed causes enormous impulsive load on HAWT. Several other factors, such as wind shear, varying wind direction and tower shadow effect, bring aerody-namic loading on blades. In addition, controlling action processes, i.e. braking, yawing and pitching, produce variation of loads on HAWT components. All these loads mentioned above are applying on blade bearing and influence bearing service life. Applied loads on HAWT can be divided as dynamic load, random load and static load according to different working stages. Aerodynamic force on blades, gravitational force of blades, centrifugal force and gyroscopic torque due to yawing are main loads on blade bearing. Coordinates and velocity vector. In accordance with the characteristics of movement and structure of HAWT, four appropriate coordinates are established which is shown in Fig. 3. They are tower coordinate (T), cabin coordinate (B), hub coordinate (R) and blade coordinate (S), respectively. The tower coordinate system is established on the tower as an inertial coordinate system and the cabin coordinate system is on the cabin. The hub coordinate system is established on the main shaft and the blade coordinate system is established on one blade. All these coordinates interact with each other and they are dynamic in working and adjusting process. For the sake of simplifying calculation, tower is considered as installing on a stationary base and then the tower coordinate is fixed. Some special application cases, for example offshore HAWT, are not considered in following analysis.

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954 XS Mx-s Fx-s Φ

ZS Mz-s

YS My-s

Fy-s

Fz-s

Xb Mx-b Zb Zr

My-b

Fx-b

Fy-b

Fz-b

Mz-r Fz-r

Zt Mz-t

Mz-b

Fz-t My-t Fy-t

en er

Yt Fx-r Fy-r

Fx-t

Yr My-r

Mx-t

Mx-r Xr

Fig. 3. Coordinates in a horizontal axis wind turbine. Coordinates transformation. Relation between coordinates of T and B is the yaw rotation movement. There are two adjusting movements in yaw rotation process. One is the rotation on xt-axis for tracking wind direction and the other is on yt-axis for aiming wind angle. Conversion relation between can be given by

0 0 cos tilt 0 sin tilt 1 aTB 0 1 0 0 cos yaw sin yaw 0 tiltcos cos  0 sin yaw tiltsin  yaw   

1 0 0 01 0 0 0a1



(1)

Where ϴtilt – is the angle between wind direction and horizontal plane of coordinate T; ϴyaw – is the elevation of the cabin. The difference between coordinates of B and R is only that zr-axis on coordinate R is rotating in working process of WTG. Then the relation of these two coordinates may be written as

coswing wing sin  sin wing cos wing 0 0

0 0  1

 

(2)

Where ϴwing is the rotational angle of the hub around zr-axis. The blades are rotating with the hub together in working process. The difference between coordinates of R and S is only that zs-axis on coordinate S is rotating in pitching process. Then the relation of these two coordinates can be expressed as





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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

cos

sin

cone RS

cone

1 0 sin cone  0 cos cone



(3)

Where ϴcons is the pitching angle of the hub around zs-axis. Speed variation in coordinates Generally, wind speed is defined as a value relative to a fixed-coordinate system. The speed relative to the blade is really caring about in this paper. Supposed the speed in a coordinated system is v0, wind speed on the blades v1 is

(4)

The real relative speed of the blade consists of the portions caused by wind speed (v1), blade rotating speed (vrot), induced velocity (W) owing to blade shape and yawing speed (vyaw) due to yawing, as can be seen in Fig.4. Then the real relative speed can be expressed by a vector expression as vrel v1 vrot W v yaw

(5)

Fig. 4. Speed triangle in wind turbine blade. Calculation of applied load. With regard to blade bearing load analysis, loads on blades are the most critical factor. As discussed previously, aerodynamic force, gravity and inertia force are main loads on blade bearing. They will be analysed one on as following. Aerodynamic force. There are several theories, such as blade element-momentum theory, Computational Fluid Dynamics (CFD) etc., for calculating aerodynamic force. Blade elementmomentum theory has simple forms, less calculation for convenient application. It is applied to calculate aerodynamic force in the following. The blade is supposed to be consisted of many tiny sections, namely the blade elements, and there is no interference between each section in the theory. Momentum theory can be used to calculate the force and momentum in each element, the force and momentum of the whole blade can be obtained by integration as

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

a1 )dr )1  dF 4 ra1V2 1 ,  3 2 d M dr 4 r V (1 a )a    1 1 2 

(6)

where a1 – is a normal inducible factor; a2 – is a tangential inducible factor; ω – is the blade rotating angular velocity; ρ – is the air density; V1 – is the wind speed; r – is the length from blade root to hub centre. Load applied to the blade can be decomposed into a tangential force and horizontal pressure force, as shown in Fig. 5 (a). The tangential force drives the blade to rotate for electric power generation and there is no benefit of the other force of power generation. Thereupon, the relative velocity can be divided into two directions, as can be seen in Fig. 5 (b), and they can be expressed as

   

  arctan[

(1  1 )a V ] (1 2

(7)

 

Based on aerodynamics theory, lift and drag force can be calculated as

dFL  1 2  dFD  1 2  

d d

2 rel

cc r (8)

2 rel

c c r

 



 o

(1V )

Fr 2

Fig. 5. a) Applied load on blades, b) Inflow angle and velocity resolution. Where FL – is the lift force in blade element due to aerodynamic pressure;

) a

 r

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Vrel

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

FD – is the drag force in blade element due to dynamic pressure; c – is the blade element chord; v – is the relative velocity; cL – is a lift force coefficient; cD – is a drag force coefficient. For the sake of more intuitive axial load, radial load and overturning moment applied to the blade bearings, the lift force and drag force can be divided into axial and radial directions in a hub coordinate which is shown in the following:  dFa  dFL sin  wing  dFD cos  wing   dFr  dFL cos  wing  dFD sin  wing

(9)

Gravity and inertia force calculation Flexure moment in the shimmy direction of blades produced by its gravity presents a periodic variation law with its varying direction angles, as shown in Fig. 6 (a). Because of its gravity, each blade element has a lumped mass mi, so the total gravitational torque in a whole blade can be obtained as M j    mi grdr  sin  wing  0  R

(10)

Where g – is the gravitational acceleration; R – is turning radius of the blade. Inertial loads on the blade include centrifugal force and gyro force. The centrifugal force caused by the wind wheel rotating directs outside. It has an effect to reduce the deflection as flexible blades deviating from the rotation plane of the wind wheel, and it is known as centrifugal stiffening effect. Inertia force on the blade section depends on the rotational velocity, the radial location and the blade element mass. It can be expressed as n

Fc   mi 2 ri

(11)

i 1

Where mi – is the mass of the ith element of the blade; ri – is distance between gyration centre and the ith element of the blade; ω – is the angular velocity of the blade around main-shaft. As is shown in Fig.6b, centrifugal force is consisted of tangential force (Fc sinϴ cone) and normal force (Fccosϴ cone). Gyroscopic moment (Mo) applied normally to its rotating plan will turn up when rotating and yawing and can be expressed as

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954 n

M o  2k  mi ri

(12)

i 1

Where ωk – is angular velocity of yawing. Composition of applied load. On account of the different loads applied to the blade, the axial load and the radial load were combined together, respectively.

 Ftot a  Fa  Fca  mg  sin  wing   Ftot r  Fr  Fcr  mg  cos  wing

(13)

Where Ftot-a – is the total axial force; Fa – is the axial component of dynamic force; Fc-a – is the axial component of centrifugal force; Ftot-r – is the total radial force; Fr – is the radial component of dynamic force; Fc-r – is the radial component of centrifugal. Applying mode shape symmetry, bending moment arising from the axial component is neglected and it is not from the radial component. The bending moment can be decomposed into x-direction and ydirection as  M tot  x  0R ridFx r  M c  x r  M j  x r  M o x    M  R ridFy r  M c  y r  M j  y r  M o y   tot  y  0

Where Mtot-x – is the total flexural moment in x-direction; Fx-r – is the radial component force in x-direction; Mc-x-r – is the radial component of centrifugal force in x-direction; Mj-x-r – is the inertial moment component in x-direction; Mo-x – is the yawing moment component in x-direction; Mtot-y – is the total flexural moment in y-direction; Fy-r – is the radial component force in y-direction; Mc-y-r – is the radial component of centrifugal force in y-direction; Mj-y-r – is the inertial moment component in y-direction; Mo-y – is the yawing moment component in y-direction.

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(14)

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954 n

dFc   rmdr

Fc   mi  2 ri

i 1

Fc sin  cone

Fc cos  cone r

 cone

Fig. 6. a) Additional load caused by velocity variation, b) variation of centrifugal force. Blade bearing loading model. As is shown in Fig.7, a single-row-four-contact-point slewing ring is adopted to connect the hub and the blade. The blade bearing under study has the outer ring fixed to a rigid hub and the blade is supposed as rigid. The mass of the blade is equivalent to a mass-block located at centroid position. Then blade-bearing loading model can be regarded as a simple beam model. Single row ball bearing. For a pitch control system adopting single-row-four-contact-point slewing ring as blade bearing, suppose that the distance between the equivalent action point of aerodynamic force and the contact point close to the blade of the bearing is r1, and suppose that the distance between mass-block and the contact point mentioned-above is r2. Generally, the clearance in blade bearing is a negative value. Namely, the bearing is pre-loaded before it is mounted on the WTG. Then the bearing load consists of pre-load and applied load. As for the calculation method of the pre-load, it has been introduced completely in reference named “Load Distribution for Blade Bearing”, and there is no more repeat here. hub 叶

Fy1

Fx1



R 0

ridFyr



R 0

ridFxr

Moy

M jyr

M cyr M cxr

M jxr

Mox 叶 blade

2 Rw 2

Fig. 7. Loads acting on a blade bearing. The bending moment can be expressed as   M tot  x  Fx   M  Fy   tot  y

2  Dw 2 2  Dw 2

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(15)

Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954

Double rows ball bearing. To a high-power wind turbine generator, a double-row-four-contact-point slewing ring is a better choice for blade bearing. It takes the same analytical procedure to obtain the radial force Fx and Fy. Noted that the contact position is changed. Suppose that the distance between two rows is h, the distance between two contact points in load zone is

L  h-

2 D 2 w

(16)

Case study. A 850 kW horizontal axis WTG is taken as an example for case study. According to the guidelines of wind turbine design published by Harris et al. [1] the fundamental structure of WTG can be determined. It consists of three blades and every blade is regulated by individual variablespeed-pitch system. The diameter of wind wheel is 56.3 m, the swept area is 2490 m2, the cut-in wind speed is 3 m/s, the rated wind speed is 12 m/s, the cut-out wind speed is 20 m/s, the extreme wind speed is 52.5 m/s, the blade top speed ratio is smaller than 7 and the tip speed under rated speed is 70.7 m/s. Based on specified wind speed conditions in planed region for mounting of WTG, the values of force and torque applied to blades are calculated by rain-flow algorithm, and it is shown in Fig. 8. Ultimate load is calculated by the methods provided by Peter et al. [2]. According to Fig. 8, the minimum value of radial blade load is -24 kN, the maximum value is 224 kN and the mean value in operating time is 98.7 kN. The minimum value of turning force is -40 kN, the maximum value is 60 kN and the mean value is 4.7 kN. The minimum value of waved force is -48 kN, the maximum value is 92 kN and the mean value is 30.5 kN. The minimum value of pitching moment is -13 kN·m, the maximum value is 6 kN·m and the mean value is -3 kN·m. The minimum value of waved moment is -1472 kN·m, the maximum value is 896 kN·m and the mean value is -460.8 kN·m. The minimum value of waved moment is -480 kN·m, the maximum value is 704 kN·m and the mean value is 69.8 kN·m. Using safety coefficient from IEC61400-1 and substituting above loads into Eqs. (13) ÷ (16), applied load is obtained as list in Tab. 1. Table 1. Loads and torques in one 850KW wind turbine blade bearings. Design Load Condition

Fa (kN)

Fr (kN)

Mk (kN·m)

Ma (kN·m)

Applied gust wind

3599

725

939.3

-73

Extreme turbulence fatigue model

1764

1418

2150.4

-145

Extreme wind speed model

-252

999

1194

509

Extreme wind shear model

2053

1418

2204.4

-166

According to required load ratings in the Tab. 1, blade bearing for the WTG is designed as shown in Fig. 9. It is a double rows four point contact slewing bearing with inner gear. The inner gear module is 12, the number of teeth is 108 and the modification coefficient is +0.5. The diameter of gyration centre is 1500 mm for meeting the requirement of the hub.

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Mechanics, Materials Science & Engineering, September 2017 â&#x20AC;&#x201C; ISSN 2412-5954 1. 80E+05

1. 80E+05

1. 60E+05

1. 40E+05

1. 40E+05 1. 20E+05

1. 20E+05 1. 00E+05

1. 00E+05

Hours Hours(akk)

8. 00E+04

Hours Hours(akk)

8. 00E+04

6. 00E+04

4. 00E+04

2. 00E+04

0. 00E+00

-8

4 10

0 12

6 13

2 15

8 16

4 18

0 20

6 21

-4

-3

-2

-8

-1

1. 80E+05

1. 60E+05

1. 40E+05

1. 20E+05

1. 00E+05

Hours Hours(akk)

8. 00E+04

Hours Hours(akk)

8. 00E+04

6. 00E+04

4. 00E+04

2. 00E+04

2. 00E+04 0. 00E+00

0. 00E+00

2 0 8 47 28 08 -1 -1 -1

-8

04 -7

-5

-3

-1

6 25

8 44

0 64

2 83

-4

80 416 352 288 224 160 -96 -32 -

96 160 224 288 352 416 480 544 608 672

1. 80E+05

1. 60E+05

1. 40E+05

1. 40E+05 1. 20E+05

1. 20E+05 1. 00E+05

1. 00E+05

Hours Hours(akk)

8. 00E+04

Hours Hours(akk)

8. 00E+04

6. 00E+04

4. 00E+04

2. 00E+04

-2

-6

-8

-4

-1

2 -1

-2

-1

-2

-1

6 -3

0. 00E+00

1. 80E+05

-4

-2

Fig. 8. a) radial force and working hours, b) turning force and working hours, c) waved force and working hours, d) pitching moment and working hours, e) waved moment and working hours, f) turning moment and working hours.

Fig. 9. A blade bearing design in one 850 kW wind turbine generator.

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Fig. 10. Load capacity curve in one 850 wind turbine blade bearing. Carrying capacity curve, namely the nonlinear curve on the top of the Fig, is plotted as shown in Fig. 10. An approximately linear diagonal line on the top left of the Fig is the overturning curve. Safe zone locates at region which under both curves. The static load rating and dynamic load rating are depicted on the Fig too. Obviously, these two points are in safe zone. Summary. Generally, load ratings of rolling bearing are provided by bearing manufactures according to raw material, roller diameter, roller number etc. However, rolling bearing life is typically calculated on the basis of its load ratings relative to the applied loads as above-mentioned. Applied load varies with different working conditions. With regard to blade bearing in WTG, different mounting location means different wind speed and eventually different load on blade bearing. Usually, applied load on blade bearing depends on load spectrum provided by supposing. In this paper, relative accurate calculating equations are derived for applied load. The numerical data through calculating equations provide evidence for designing blade bearing and the reliability of calculating life is enhanced. Acknowledgements This project is supported by National Natural Science Foundation of China (Grant No. 51475144) and Natural Science Foundation of Henan Province of China (Grant No. 162300410065). References [1] T. Harris, J. H. Rumbarger, C. P.Butterfield. Wind Turbine Design Guideline DG03: Yaw and Pitch Rolling Bearing Life. USA: NREL/TP-500-42362(2009). [2] H. M. Peter, P. Kirk, B. Marshall. Predicting Ultimate Loads for Wind Turbine Design. USA: NREL/ DE-AC36-83CH10093, (1999). [3] L. Chen, H.W. Du. Bearings in Wind Turbine. Bearing, 12 (2008), pp.45–50 (in Chinese). [4] L. Chen, Z.G. Li, M. Qiu, X.T. Xia. Influence of groove shape on clearance in four-pointcontact slewing bearing, Journal of the Brazilian Society of Mechanical Sciences and Engineering, Vol.36, No.3(2014), pp.461-467, DOI 10.1007/s40430-013-0118-7 [5] J.H. Wang, D.T. Qin, Y. Ding. Dynamic Behavior of Wind Turbine by a Mixed Flexible-Rigid Multi-Body Model, Journal of System Design and Dynamics, Vol.3, No. 3 (2009), pp.403-419. [6] Y. Souich and N. Nobuyuki. Technical Trends in Wind Turbine Bearings, NTN Technical Review, No.76 (2008), pp.113–120. [7] S. Zupan and I. Prebil. Experimental Determination of Damage to Bearing Raceways in Rolling Rotational Connections. Experimental Techniques, Vol. 30, No. 2 (2006), pp. 31-36.

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[8] S. Zupan and I. Prebil. Carrying Angel and Carrying Capacity of a Large Single Row Ball Bearing as a Function of Geometry Parameters of the Rolling Contact and the Supporting Structure Stiffness, Mechanism and Machine Theory, Vol.36, No.10(2001), pp. 1087-1103. [9] L. Chen, Y.P. Zhang and X.T. Xia. Contact stress and deformation of blade bearing in wind turbine, 2010 International Conference on Measuring Technology and Mechatronics Automation (2010), pp. 833-836. [10] I. Prebil, S. Zupan and P. Luci. Load distribution onto rolling elements of a rotational connection, Proceedings of the 3rd International Congress on Air and Structure Borne Sound and Vibration (1994), pp. 1949-1956. [11] S. Yukimaru, I. Edmond, M. Takao, K.P Yasunari. Investigation on the flow around blade tip of a HAWT equipped with MIE type tip vane by velocity measurements using LDV (effect of blade plane configuration, blade aspect ratio and number of blades), Proceedings of the 5th JSME-KSME Fluids Engineering Conference, CD-ROM, OS13-1, pp.1318-1323, 2002. [12] J. Wang, D. Qin, Y Ding. Dynamic Behavior of Wind Turbine by a Mixed Flexible-Rigid MultiBody Model. Journal of System Design and Dynamics, Vol.3, No 3(2009), pp. 403-419.

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A Refined Technique for the Automated Determination of Friction Losses in the Toothing of Multithreaded Transmissions with Differential Mechanisms and Planetary Gears D. Volontsevich1,a, Ie. Veretennikov1, I. Kostianyk1, S. Pasechnyi1 1 – Transport Machine Building Faculty, National Technical University "Kharkov Polytechnic Institute", Kharkov, Ukraine a – vdo_khpi@ukr.net DOI 10.2412/mmse.13.52.575 provided by Seo4U.link

Keywords: friction losses in the toothing, multithreaded transmissions, differential mechanisms, planetary gears, matrix method.

ABSTRACT. Multithreaded transmissions, which using differential mechanisms for separating and summing up power flows, have been widely used in the transmissions of transport vehicles and special drives. The quality of such transmissions and the magnitude of frictional losses in the toothing significantly depend on the adopted kinematic scheme and the ratio of powers passing through the corresponding links of the differential mechanisms. With the existing automated analysis and synthesis of such transmissions, a matrix approach has recently been widely used. The proposed work provides a refined technique for the automated determination of friction losses in the toothing of multithreaded transmissions which containing differential mechanisms and planetary gears. It makes it possible to more accurately determine friction losses in the toothing and at the same time preserves the linear structure of the system of equations, which permit to continue using the matrix approach to analyze and synthesize such transmissions. Examples are given for the formation of equations systems describing the force interaction between the elements of the scheme for all variants of the links commutation of planetary rows operating as three-link differential mechanisms and planetary gears with one stopped link. The work is based on the analysis of existing methods for determining friction losses in the toothing and personal practical experience in the design and study of multithreaded stepped and stepless transmissions. The received results allow to apply the offered technique in the modern program complexes focused on the automated analysis and synthesis of multithread transmissions with use of the matrix approach. This makes it possible to significantly reduce the time to develop new multithreaded transmissions and increase their technical characteristics.

Introduction. In modern transmissions of vehicles and other drives of machines, planetary gears are widely used as differential mechanisms. It is, first of all, the summation or separation of power flows in dual-threaded and multithreaded transmissions, as well as their use in planetary gearboxes. A feature of differential transmissions is the essential dependence of the magnitude of the losses in the mechanism on the kinematic transmission scheme and the ratio of the powers passing through the corresponding links of the differential. Therefore, the study and refinement of the technique for determining losses on differential mechanisms in multithreaded transmissions is an actual task. Analysis of recent achievements and publications. In the modern technical literature, as a differential transmission, it is customary to consider an automotive inter-wheel differential: – a differential is a gear train with three shafts that has the property that the angular velocity of one shaft is the average of the angular velocities of the others, or a fixed multiple of that average [Wikipedia] (access mode: https://en.wikipedia.org/wiki/ Differential_(mechanical_device));

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– a differential gear is a device that is fitted to the axle of a vehicle that allows the wheels to turn at different rates when going around a corner. However, we will talk about the use of classical 2k-h planetary gears as differential mechanisms for the summation and separation of power flows in multithread transmissions. The issue of determining the efficiency of planetary gears and differential mechanisms has always been of interest to engineers and scientists who create vehicle transmissions and technological drives. The foundations of the theory of power losses in these gears were laid in the writings of such scientists as R.H. MacMillan, J.H. Glover, P.W. Jensen [1–4]. In the USSR this problem were solving with by A.D. Vashets, K.I. Zablonsky, A.N. Ivanov, Yu.N. Kirdyashev, V.I. Krasnenkov, M.A. Kreines, M.K. Kristi, V.N. Kudryavtsev and others [5], [6], [7]. With the introduction of the matrix method in the analysis of planetary mechanisms and transmissions in general [8], [9], a new era in the automation of this process began. There was an opportunity to completely formalize and automate the process of determining the efficiency of planetary and differential transmissions. However, the proposed variants are either not very convenient for automated matrix analysis [10], [11], [12], [13], or are convenient, but they give a large error in special zones [14]. In modern publications on planetary gears, authors, as a rule, solve specific applied problems: consider the particular constructions of conventional and stepless transmissions consider the influence of lubricants and tooth geometry on the efficiency of planetary gears, and study the issues of increasing their load capacity [15–21]. The aim and problem statement. Therefore, it was decided to return to the problem of creating a universal algorithm that allows to correctly take into account the mechanical losses in arbitrary kinematic schemes of transmissions containing planetary transmissions and differential mechanisms. To ensure the possibility of using the matrix approach in analyzing and synthesizing planetary gears, this algorithm must be completed by compiling a basic system of equations, which contain all the necessary information for determining the losses in each of the branches of multithreaded gears with differential mechanisms. Materials research. The classical matrix approach to the analysis of planetary transmissions assumes the decomposition of the kinematic scheme into elementary structural elements (planetary rows, stop brakes, locking clutches, etc.) and recording of a set of characteristic equations for each of them. To the resulting system of linear equations, the constraint equations that describe the connection scheme of the elements, and the equations of inclusion of the selected gear are added. So, for example, for the classical 2k-h planetary row (differential mechanism), the kinematics description uses the Willys equation:

a  kb  h k  1  0 , where  a – angular velocity of the sun gear;

b – angular velocity of the epicyclic gear;  h – angular velocity of the carrier (lever or arm); k – internal (basic) gear ratio of planetary row, corresponding to the gear ratio from the sun gear to the epicyclic gear when the carrier is stopped, taking into account the direction of rotation.

To describe the force interaction without taking losses into account, use equations

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Mechanics, Materials Science & Engineering, September 2017 – ISSN 2412-5954 * * *  M a  M b  M h  0;  * *  kM a  M b  0,

where M a* – the torque input or output to the sun gear without taking losses into account;

M b* – the torque input or output to the epicyclic gear without taking losses into account; M h* – the torque input or output to the carrier (lever or arm) without taking losses into account. When determining the efficiency of a planetary transmission composed of planetary and differential mechanisms, it is necessary to carry out an analysis of the kinematics and the force analysis of the circuit without taking losses into account. As a result, at each gear on all links, we will have the values of angular velocities and torques, which will allow us to analyze the directions of power flows and determine the relative magnitudes of the powers transferred in relative and figurative motion. Just as in the book [6], we divide and consider separately the modes of operation of the planetary row in the role of planetary or differential transmission. Planetary transmission is obtained by stopping one of the central links of the differential mechanism (planetary row). Consider a planetary row as a separate element of the general structural scheme of a planetary or combined transmission. In this case, it is possible to distinguish three combinations of elements commutation for a planetary row operating in the planetary transmission mode (fig. 1), end six – for a planetary row operating in differential transmission mode (fig. 2).

in (out)

a h

out (in)

h in (out)

a b

in (out)

Fig. 1. Options of elements commutation for a planetary transmission: a) – the epicyclic gear is stopped; b) – the sun gear is stopped; с) – the carrier (lever or arm) is stopped in 1

in 1

a h

out

b in 2

out a

out

out 1

b) out 1

a h

in h

a h

out 2

out 1

b out 2

in 1

b out 2

h in 2

in 2

Fig. 2. Options of elements commutation for a differential transmission: with one output in the form: a) the carrier (lever or arm); b) epicyclic gear; с) sun gear; d)with one input in the form: d) the carrier (lever or arm); e) epicyclic gear; f) sun gear. MMSE Journal. Open Access www.mmse.xyz

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For example, for the scheme in Fig. 1(a) with the internal gear ratio k = –3 after the kinematic and preliminary force analysis in relative units, we will have the results given in Table. 1. Table 1. The power characteristics of planetary transmission in Fig. 1 without losses. Input

Element a

Element b

Element h

Element c

Output

(satellite) 

0,25

0,75

0,25

М*

-1

-3

-4

-1

In Table. 1 N is the power on the corresponding element. It should be noted that the power entering the element is negative, and the output from the element is positive. According to the procedure described in [14], the torqueses on the elements, taking into account transmission losses, are determined as follows: n 1 n 1     *  h h  *  h    M 1  sign  M     0 , 5    M 1  sign  M     0 , 5  a  cd   b   ch d    M h  0; a a  a c b b  b c 1 1        (1)  n 1 n 1          * h h * h h     kM a 1  sign a M a   a  c  0,5 c  d    M b 1  sign b M b   b  c  0,5 c  d    0, 1 1       













where M a , M b , M h – torque on the links in the light of losses;

c – relative angular velocity on the bearings of satellites; h  a c – coefficient of friction losses in the gearing “sun gear – satellite” with the carrier (lever

or arm) stopped (for external gearing  ahc  0,02 ); h  b c – coefficient of friction losses in the gearing “epicyclic gear – satellite” with the carrier

(lever or arm) stopped (for internal gearing  bhc  0,01 ); h  c d – coefficient of friction losses in the gearing “satellite 1 – satellite 2” with the carrier

(lever or arm) stopped if the planetary row contains several successively meshed satellites (for external gearing  ahc  0,02 , in the absence of successively meshed satellites  ch d  0 );

 – the fraction of power transmitted in relative rotation through the gearing, which is c calculated from formula   . c  h c

0,75  0,75 , internal gear ratio k = –3. In accordance with c  h 0,75  0,25 Table. 1, assuming that rotation with angular velocity (+1) and torque (–1) is applied to the sun gear, system (1) can be written in the form:

In this example  



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 11  0,750,02  0  M b 1  0,750,01  0  M h  0;   3 11  0,750,02  0  M b 1  0,750,01  0  0,  0,985  1,0075M b  M h  0;   3 0,985  1,0075M b  0, wherefrom M b  2,933 and M h  0,985  1,0075  2,933  3,94 .   i  M h / M a  3,94 /( 1)   0,985 . Here i Accordingly, the efficiency of the scheme will be    i a / h 1/ 0,25 – power ratio, i – kinematic ratio. It should be noted that the technique [14] prescribes, with a power on the link equal to zero due to the zero speed of rotation, to take the power sign as positive. The first drawback of this method is that in the presence of one stopped central gear and the passage of power by a single flow from the other central gear to the carrier (or vice versa), the overall efficiency does not take into account the share of losses at the stopped element. So, in fact, the efficiency obtained from the passage of 75% of power through the gearing of “the sun gear - the satellite”, which is equal to 0,985, has become the overall transmission efficiency. This fact is confirmed by calculation using a method [6] repeatedly tested experimentally, which gives a smaller value of the efficiency:

 1





k  ah c   bh c 3  0,02  0,01 1  0,9775 . k 1 4

The magnitude of the error that we get when using the technique [14] for the analysis of losses in planetary gears is shown in Fig. 3 and Fig. 4.

Error in determining the mechanical efficiency, %

1,2 1 0,8 0,6 0,4 0,2 0 -5

-4,5

-4

-3,5

-3

-2,5

-2

-1,5

Basic speed ratio Fig. 1a

Fig. 1b

Fig. 1c

Fig. 3. Dependence of the magnitude of the error in determining the mechanical efficiency of the planetary row by the technique [14].

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Error in determining the mechanical energy losses, %

50 45 40 35 30 25 20 15 10 5 0 -5

-4,5

-4

-3,5

-3

-2,5

-2

-1,5

Basic speed ratio Fig. 1a

Fig. 1b

Fig. 1c

Fig. 4. Dependence of the magnitude of the error in determining the mechanical losses of the planetary row by the technique [14]. A similar picture arises when the planetary row works as a differential mechanism, when one of the three central elements is the mover, and the other two are driven. The power on the differential mechanism is divided into two flows, with one part of the power passing both gearing, and the second part – only one. The technique given in [14] works completely adequately only for the case of summation of two power fluxes, if both of them enter the differential mechanism through the sun gear and epicyclic gear, and not the carrier (lever or arm). To eliminate the described inaccuracies in the methodology [14], while retaining the possibility of using it in the matrix approach to the analysis and synthesis of planetary gears, the following is proposed. For the variant in Fig. 1(a), the system of equations describing the load balance can be written in the form:

M   sign  a M a*  M   b  M h  0; a      * kM   sign  a M a   M b  0, a   

(2)

where   – the total efficiency at the passage of power by a single flow in accordance with [6]:

  1 





k  ahc   bhc . 1 k

For the variant in Fig. 1 (b) the system of equations describing the load balance can be written in the form:

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Ma  sign b M b*   M   M h  0; b      *  kM a  M   sign b M b   0, b   

(3)

where  – the total efficiency at the passage of power by a single flow in accordance with [6]:

  1 





1  ahc   bhc . 1 k

For the variant in Fig. 1(c), the system of equations describing the load balance can be written in the form: M   sign a M a*   M   sign b M b*   M  0;  a a b b h   sign  a M a*   sign b M b*    M bb  0, kMaa

(4)

where  a – efficiency in gear “sun gear – satellite” a  1  ahc ;

 b – efficiency in gear “satellite – epicyclic gear” b  1  bhc . For schemes with a differential mechanism the system of equations that describing the load balance will contain 4 equations. The first two equations of the system represent the balance of torque at the differential mechanism. And two additional equations allow you to distribute losses along the branches of the input (output), observing the overall balance of losses in accordance with [6]. It is assumed that the loss on the external toothing of the “sun gear – satellite” is twice as large as on the internal toothing of the “satellite – epicyclic gear”. So for the variant in Fig. 2(a): M aa  M bb  M h  0; kM   M   0; b b  a a  * M aaa  M b*bb  M a*a  M b*b  ;  1   a  2, 1  b



where the overall efficiency in accordance with [6]   1 







a  h h  a  c   bh c , and the loss k  1h

values at each input (output)  a and  b are determined from the last two equations on the basis of a preliminary calculation without taking losses into account before solving the general system of equations. With the reverse power flow in the same scheme (Fig. 2(d)), the system will look like:

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Ma Mb      M h  0; b  a  kM a M b      0; b  a  * * * *  M aa  M bb  M aa  M bb ;  a b   1   a  2, 1  b

which allows recording it for the schemes in Fig. 2(a) and Fig. 2(d) in the generalized form: M   sign  a M a*   M   sign b M b*   M  0; b b h  a a kM   sign  a M a*   M   sign b M b*   0; b b  a a *  *  sign  a M a   sign b M b*  sign  h M h*  * * * M    M    M   M   ; a a a b b b a a b b   1   a  2.  1  b





(5)

Here it should be kept in mind that if the scheme really corresponds to Fig. 2(a) or Fig. 2(d), then for simplicity it is possible to equate

sign(a M a* )  sign(b M b* )  sign(h M h* ) .

(6)

Similarly for the variant in Fig. 2(b):

Mb  M aa    M h  0; b  Mb  kM a a    0; b   M *   M *   M *  M *  ; h h b a a h h   a a a 1  a 1    2, h 







where the overall efficiency in accordance with [6]   1 







b  h h  a  c   bh c , and the loss b

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With the reverse power flow in the same scheme (Fig. 2(e)), the system will look like Ma    M bb  M h  0;  a  kM a    M bb  0;  a  * * *  M aa  M *  1  M aa  M hh ; h h   a   b  1   a 1    2, h 

which allows recording it for the schemes in Fig. 2(b) and Fig. 2(e) in the generalized form: M   sign  a M a*   M   sign b M b*   M  0; b b h  a a * *      sign  M  sign  M kM  a a b b  M bb  0;  a a *  M *   sign  a M a   M *  sign b M b*   M *  M *   sign  a M a* ; h h a a h h   a a a  b 1   a   2. 1   h





(7)

Similarly for the variant in Fig. 2(c)

Ma    M bb  M h  0;  a  kM a    M bb  0;  a  M *   M *   M *  M *  ; h h a b b h h   b b b 1  a 1    2, h 







where the overall efficiency in accordance with [6]    1 







a  h h  a c  bhc , and the loss a

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Mb  M aa    M h  0; b  Mb  kM a a    0; b   * * *  M bb  M *  1  M bb  M hh ; h h  b   a  1  a 1    2, h 

which allows recording it for the schemes in Fig. 2(c) and Fig. 2(f) in the generalized form: M   sign  a M a*   M   sign b M b*   M  0; b b h  a a * *      sign  M  sign  M kM  a a b b  M bb  0;  a a  M *   sign b M b*   M *  sign  a M a*   M *  M *  sign  a M a* ; h h b b h h   b b b  a 1   a   2. 1   h





(8)

Summary. 1. Kinematics analysis, load distributions and loss determination in modern multithreaded transmissions containing differential mechanisms and planetary rows are performed sequentially on each step of gear or operating mode. At the same time, the same planetary rows on some transmissions can play the role of differential mechanisms, and on others – simple planetary gears with one stopped link. The classical algorithm for analysis of kinematics and distribution of loads without loss is universal and does not require the use of different formulas for one or the other case. When performing an accurate loss analysis in such schemes, the algorithms for analyzing simple planetary gears with one stopped link and differential mechanisms differ significantly from each other. 2. When analyzing losses in multithreaded transmissions, first, using the matrix analysis, calculate the kinematics and load distribution without taking into account the losses to determine the direction of the power flows and the preliminary values of the torque on the links along all branches of the circuit. 3. Further, for all planetary rows with one stopped link, equations (2), (3) or (4) are written into the system of equations, depending on the type of the stopped element. 4. For all differential mechanisms, the last two equations from systems (5), (7) or (8), depending on the direction of the power flows, are solved before composing a general linear system of equations. After this, the first two equations from the same systems are written in the general system. Such a sequential solution of the equations allows solving nonlinear equations for given differential mechanisms at the stage of preparation of a large general linear system of equations that describes the entire scheme. This makes it possible to solve a large linear system by a matrix method and to save the computation time. This is especially important in carrying out the structural-parametric synthesis of multithreaded transmissions, which is performed by multiple analysis of the generated circuits and sets of their parameters. References [1] MacMillan, R.H. (1949). Epicyclic gear efficiencies. The Engineer, 23, 727–728. MMSE Journal. Open Access www.mmse.xyz

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[2] MacMillan, R.H. (1961). Power flow and loss in differential mechanisms. Journal of Mechanical Engineering Science, 3, 37–41. [3] Razimovsky, E.I. (1956). A simplified approach for determining power losses and efficiencies of planetary gear drives. Machine Design, 9, 101–110. [4] Glover, J.H. (1965). Efficiency and speed ratio formulas for planetary gear systems. Product Engineering, 27, 72–79. [5] Kristi, M.K., Krasnenkov, V.I. (1967). New transmission mechanisms, Mashinostroenie, 216 pp. [6] V.N. Kudryavtsev, Yu.N. Kirdyashev. (1977). Planetary transmissions: Handbook, 535 pp. [7] Krasnenkov, V.I., Vashets A.D. (1986). Designing of the planetary mechanisms for transport vehicles, Mashinostroenie, 272 pp. [8] Tian, L., Li-qiao, L. (1997). Matrix system for the analysis of planetary transmissions. ASME Journal of Mechanical Design, 119, 333–337, DOI 10.1115/1.2826352 [9] Samorodov, V.B. (1998). Fundamentals of the theory of automated generation of transmissions mathematical models. Mekhanika ta mashynobuduvannya, 1, 109-115. [10] Yu, D., Beachley, N.H. (1986). Mechanical efficiency of differential gearing. Gear Technology, July/August, 8–48. [11] Jose M. del Castillo. (2002). The analytical expression of the efficiency of planetary gear trains. Mechanism and Machine Theory, 37, 197–214. [12] David Pinho Silva Dias da Costa. (2002). Power loss in planetary gear transmissions lubricated with axle oils. Mechanism and Machine Theory, 37, 197-214. [13] Cemil Bagci. (1990). Efficient methods for the Synthesis of Compound Planetary Differential Gear Trains for Multiple speed Ratio Generation. Gear Technology, July/August, 14-35. [14] Volontsevich, D.O. (2001). Method for determining losses in the gearing of planetary gears and differential mechanisms in the automated analysis and synthesis of kinematic transmission schemes. Visnyk NTU "KhPI", Zbirnyk naukovykh prats'. Seriya: Transportne mashynobuduvannya, NTU «KhPI», 12, 9-14. [15] Chepikova, T.P. (2008). Development and justification of rational schemes of differential stepless-controlled transmissions with internal power flow separation. The dissertation thesis on theory of mechanisms and machines, 25 pp. [16] Kapelevich, A. (2014). High Gear Ratio Epicyclic Drives Analysis. Gear Technology, June, 6267. [17] Schulze, T. (2013). Design and Optimization of Planetary Gears Considering All Relevant Influences. Gear Technology, November/December, 96–102. [18] Joachim, F.J., Börner, J. and Kurz, N. (2012). How to Minimize Power Losses in Transmissions, Axles and Steering Systems. Gear Technology, September, 58–66. [19] Hermann J. Stadtfeld. (2014). Less Energy Consumption with High-Efficiency Bevel Gears and their Usage in the U.S. Gear Technology, September/October, 42–49. [20] Langhart, J. (2015). How to Get the Most Realistic Efficiency Calculation for Gearboxes. Power Transmission Engineering, April, 54–58. [21] Fashiev H.A., Salahov I.I., Voloshko V.V. (2013). Calculation of the efficiency of the differential mechanism of automatic transmissions. Vestnik mashinostroeniya, 2, 14–19.

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The Vehicle Controlling Near the Screening Surface Using Thrust Vector Deflection of the Electric Motor with Gimbal Mounted Propeller 1

Kravets V.V. 1, a, Kravets Vl.V.2, b, Artemchuk V.V.2 1− State Higher Educational Institution “National Mining University”, Dnipro, Ukraine 2− National University of Railway Transport, Dnipro, Ukraine a – prof.w.kravets@gmail.com b − vladkravetsphd@gmail.com DOI 10.2412/mmse.2.35.544 provided by Seo4U.link

Keywords: gimbal system, rotational scheme, quaternionic matrices, Rodrigues-Hamilton parameters, components of control forces and moments.

ABSTRACT. The controlled spatial motion of the combined vehicle near the screening surface is considered. A propeller motor in a gimbal mount forms control forces and moments. The gimbal mount scheme can be defined on a finite set of successive three independent turns with recurrence, which is represented by 96 variants. The constructive scheme of the gimbal mount of propeller electric motor is proposed, which provides control of combined vehicle in the three main modes: Lifting force (helicopter scheme); Traction mode (aircraft scheme); Lateral traction (course control). The rotative axis of the propeller is combined in coincidence with rotor axis of electric motor determining the first turning of the gimbal mount. The electric motor’s stator is located on the inner ring of the gimbal and its rotation axis determines the second finite turn. The turning axis of the outer race of the gimbal relatively the case of the combined vehicle defines the third finite turning movement. This constructive solving of the gimbal mount provides the combined control of thrust vector in wide range of finite turning angles. Basis of movable Cartesian coordinate system is coincides with the rotation axes intersection point. For the entered reference systems and the accepted sequence of finite independent turning movements matrixes of the forward and inverse transform of coordinates in the form of quaternion matrixes are formed. In the form of quaternion matrices, depending on the angle of the thrust vector and the arrangement of the gimbal mount, the driving forces and moments in the reference frame that is associated with the vehicle are determined.

Introduction. The movement of the aircraft in space is defined by the control forces and moments formed by the control system [1]. Traditionally, the magnitude of control forces is determined by small deflection of the thrust vector relative to the aircraft’s center of mass. On rarely - with applying a small deflection of the aircraft center of mass relative to the thrust vector, by displacing the carried mass [2]. In both methods of control, the gimbal system has been widely used [3]. Different sequences of three independent turning in space form a finite set consisting of 96 variants [4]. In this study, among these options, the turning scheme of gimbal motion for propeller electric motor is selected, which provides control of the thrust vector over a wide range of angles. Formulation of the problem. We regard a propeller electric motor, the thrust of which is directed along the axis of rotation of the electric motor rotor. It is necessary to provide the control of the combined vehicle's movement by applying the turning of the thrust vector in the required range of angles, which providing a combination of the basic propeller motor modes of action: - Lifting force mode; - Traction mode; - Lateral traction. 1

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Scheme of turns. The first infinite turn in the positive direction by angle  is determined by the axis of the propeller’s rotation together with the electric motor rotor in the gimbal and is denoted by [5]: еy 1 ,

(1)

The second finite turn in the positive direction by the angle is determined by the axis of rotation of the inner gimbal, which connected to the stator of electric motor and is denoted as: еy 2 ,

(2)

The third finite turn with a reiteration in positive direction е y1 by the angle  is determined by the axis of rotation of the outer gimbal attitude to vehicle’s body and is denoted as follows: еy 1 ,

(3)

Here,е with a gimbal mount, the basis of movable Cartesian coordinate system y1 е y 2 , isy 3 е associated, the starting of which is combined with the point of intersection of the turning axes. The proposed system of three independent turning with reiteration composed the third variant of a possible set of 96 rotations with reiteration [4]. This system is designated as: S3  ,, , where the first turn corresponds to the angle of rotation of the propeller or rotor of the electric motor, i.e. ; Second turn - pitch angle, i.e. v  ; Third turn - course's angle, i.e. . The general view of the gimbal with the described sequence of turns is shown in Fig. 1.

Fig. 1. Constructive scheme of the thrust vector turns ( Р) for propeller electric motor in the gimbal The intervals of changing the angles of turn are as follows: MMSE Journal. Open Access www.mmse.xyz

 ..

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0    ;

2.  90  v  90 ;

(4)

3.  90    90 .

The main modes of control action of the propeller’s thrust vector for a combined vehicle in flight mode are provided by the second and third finite turn of the gimbal mount with the angles’ values: Lifting force (helicopter scheme): v  0,   0;

(5)

1. Traction mode (aircraft scheme): 2.

  0;

(6)

   90 .

(7)

v   90 ,

3. Lateral traction mode (course control): 4.

v   90 ,

Rodrigues-Hamilton parameters. Two consecutive turns of the Cartesian coordinate system mobile basis associated with the gimbal mount, regarding the basis of the reference frame fixed on the vehicle, are characterized by the following set of Rodrigues-Hamilton parameters [5]:

v b0  cos , 2 c0  cos



v b2  sin , b3  0, 2

b1  0,

, c1  sin

 2

c 2  0,

(8)

c 3  0.

Quaternionic matrices. According to these Rodrigues-Hamilton parameters, two sets of quaternionic matrices of the form [6] are formed:

B, B t ,

C, C t ,

Bt , Ct

or in expanded form:

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(9)

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cos

v 2

0 B

v  sin 2 0

 sin

0 cos

v 2

cos

 sin

0 v cos 2

0  sin

v 2

 sin , C

cos



v 2

 sin

 2

cos

 2



cos

 sin

 2

 sin cos



. (10)



Then, for the formation of quaternionic matrices, the operation of external − t B , t C , internal − B t , C t and complete − t B t t C t transposition is used [6]. The quaternionic matrices of the resulting turn are determined in the form [5]:

R  B  C,

R  t B  tC.

(11)

Similarly, there are matrices of the resultant turn, which are equivalent to the conjugate quaternion: t

R t  t C t  t Bt , Rt  C t  B t .

(12)

Tables of directing cosines. The directing cosine tables for direct and inverse transformations of the thrust vector in the reference frames associated with the gimbal system and a vehicle are determined respectively in the core of the product of two resultant matrices that are equivalent to a quaternion [4]: R  t R or

RR

(13)

Rt  Rt .

(14)

and the conjugate quaternion Rt  t Rt or

Components of control forces and moments. The problems of dynamic design of the motion of a combined vehicle near the screening surface [7] are solved using a computational experiment. Here we apply a mathematical model of nonlinear dynamics in the form of Euler-Lagrange spatial motion equations and quaternion matrices [8, 9]. The components of the control forces and moments depend on the module ( Р ) and the direction of the thrust force, which is set by the angles of the turn in the gimbal ( v,  ), the point of application of the thrust force in the gimbal system relative to the layout axes − х10 , х20 , х30 . These components are defined as follows:

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1 0  X0  t X0  2 P          R  tR  , 0 E 0

(15)

where Е − the identity matrix (4x4); X 0 , t X 0 − quaternionic matrix:

0  x10 X0   x20  x30

x10 0 x30  x20

x20  x30 0 x10

x30 0 0 x2 t x10 , X0  0  x10 x2 0 x30

 x10 0 x30  x20

 x20  x30 0 x10

 x30 x20 .  x10 0

(16)

Summary. A constructive scheme of the finite turns of thrust vector for propeller electric motor in the gimbal mount is proposed for motion controlling of the combined vehicle near the screening surface. The components of the control forces and moments are determined in the form of quaternionic matrices that are compiled according to the Rodrigues-Hamilton parameters, the gimbal's placement coordinates in the vehicle's layout axes, and adapt to the equations of the EulerLagrange spatial motion. References [1] Igdalov, I.M., Kuchma, L.D., Polyakov N.V., Sheptun Yu.D. Rocket as a control object (in Russian), Dnipropetrovsk, Art-Press Publ., 2004, 544 P. ISBN: 966-7985-81-4. [2] Kravets V.V. 1978. Dynamics of solid bodies system in the context of complex control (in Russian), Applied Mechanics, Issue 7, P. 125-128. [3] Ishlinskij, A.Yu. Orientation, gyroscopes and inertial navigation, (in Russian). Moscow, Nauka Publ., 1976, 672 P. [4] Kravets, V., Kravets, T., Burov, O (2017). Applying Calculations of Quaternionic Matrices for Formation of the Tables of Directional Cosines. Mechanics, Materials Science & Engineering, Vol. 10. In press. [5] Victor Kravets, Tamila Kravets, Olexiy Burov. Application of Quaternionic Matrices for Finite Turns’ Sequence Representation in Space. MMSE Journal, Vol. 9. 2017. P. 408-422. DOI http://seo4u.link/10.2412/mmse.17.56.743. [6] Kravets, V., Kravets, T., Burov, O. Monomial (1, 0, -1)-matrices-(4х4). Part 1. Application to the transfer in space. LAP, Lambert Academic Publishing, Omni Scriptum GmbH&Co. KG., 2016, 137 P. ISBN: 978-3-330-01784-9. [7] Kravets V.V., Kravets Vl.V., Fedoriachenko S.A. (2016) On Application of the Ground Effect For Highspeed Surface Vehicles MMSE Journal, Vol. 4, P. 82-87. Open access: www.mmse.xyz, DOI: 10.13140/RG.2.1.1034.5365. [8] Kravets V.V., Bass K.M., Kravets T.V., Tokar L.A. (2015) Dynamic design of ground transport with the help of computational experiment, MMSE Journal, Vol.1, 105-111. ISSN 2412-5954, DOI 10.13140/RG.2.1.2466.6643. MMSE Journal. Open Access www.mmse.xyz

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[9] Kravets, V.V., Kravets, T.V. & Kharchenko, A.V. Using quaternion matrices to describe the kinematics and nonlinear dynamics of an asymmetric rigid body, Int. Appl. Mech., 2009, 45, (223). DOI 10.1007/s10778-009-0171-1.

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III. Electrical Complexes and Systems M M S E J o u r n a l V o l . 1 2

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Investigation of the Process Parameters Influence on the Energy Efficiency of an Induction Motor under Model Predictive Control GRAMPC G.G. Diachenko1, a, O.O. Aziukovskyi1, b 1 – State Higher Educational Institution “National Mining University”, Dnipro, Ukraine a – diachenko.g@nmu.one b – azalex@nmu.one DOI 10.2412/mmse.5.86.76 provided by Seo4U.link

Keywords: induction motor drives, model predictive control, field oriented control, energy efficiency.

ABSTRACT. This paper presents the implementation of the nonlinear gradient based model predictive control (MPC) software GRAMPC (GRAdient based MPC) for the energy efficient control of three-phase induction motor drives. GRAMPC is appropriate for controlling nonlinear systems with input constraints in the (sub)millisecond range and is based on real-time solution strategy. The effect of the model algorithmic parameters: prediction horizon, the maximum number of iterations and number of data points is considered and default values in terms of real-time demands are determined. Additionally, some comparison results with conventional methods are provided, which demonstrate the advantages and performance of GRAMPC. The analysis for appropriate choice of the algorithmic parameters is based on simulation results for three different induction motors with different rated powers.

Introduction. The question of increasing the energy efficiency of asynchronous machines is a topic that is widely discussed is research and development nowadays. Induction motors are the most frequently used type of asynchronous machine for variety of industrial applications due to their robustness, low cost and simple structure. The two main reasons for solving the energy efficiency issues of this type of motors is, on one hand, an eager desire to make an induction motors more attractive compared to the synchronous machines and, on the other hand, applications which require a higher energy efficiency as well as users who want as energy-saving function in real-time for various reasons. As can be seen from the overview [1] and the references cited therein, numerous methods exist for energy efficient operation management both for field-oriented control methods and other methods like V/f control methods. These methods are mainly appropriate for applications in which the asynchronous machine operates in stationary operating points over considerable time intervals. Thus, in applications where load torque changes occur, these methods lead to total power consumption increase. Only a comparatively small number of papers are devoted to energyefficiency improvement in dynamic mode of operation due to changing load torque. One of the first treatment of this problem is presented in [2]. This solution gave a significant improvement compared to the operation under constant flux reference. However, the proposed offline optimization is not feasible in many applications, because precalculated offline optimal trajectories are valid only for one specific application under certain conditions. In [3] a brief review of the previous optimization procedures for dynamics is given and a new online implementable approach is proposed using parametrized curve with a good approximation for dynamic transitions. Another recent work that is also based on online optimization is presented in [4]. It is shown that high fieldgenerating current values due to step change in load torque could be avoided by filtering magnetic flux linkage reference. An appropriate choice of the filtering coefficients was numerically investigated in [5]. The present paper takes a different approach. In this context a methodology described in [6] is used. It is suited for dynamic systems and uses predictive solution approach. The algorithm and its properties are investigated in [7]. The efficiency of the gradient based model predictive control MMSE Journal. Open Access www.mmse.xyz

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scheme and time requirements are also presented. In this paper it will be used to solve the problem of the energy efficient operation of an induction motor in transient behaviour when load conditions are changing. The selection of process parameters in the application is discussed and simulation results are provided. Background. Consider the Γ-inverse equivalent circuit of an induction motor (IM) given in Figure 1.

Fig. 1. Γ-inverse equivalent circuit of IM. It is assumed that the speed and current regulators of the field-oriented control have high enough performance to ensure the control characteristic close to perfectly rigid that is, the dynamics of the speed and current controllers can be disregarded. All variables are transformed from the three-phase system (abc) to an orthogonal amplitude invariant (dq) reference frame. The differential equations of the reduced motor model can be written as follows: R  2   2  2  R2 I1d , L  M



3 Z  I , 2 p 2 1q

(1)

(2)

where  2 – is the rotor flux linkage; Zp

– is the number of pole pairs;

 – is the mutual inductance;

I1d – is the field-generating current; I1q

– is the torque-generating current;

M M – is the motor torque.

It is also assumed that all the necessary preparations for solving the optimal control problem are made, e.g. the first-order optimality conditions following from the Pontryagin’s Maximum Principle as well as the Hamiltonian are defined using simplified system of differential equations of the induction motor above. The influence of the process parameters. The algorithms for particular process stages have been already implemented in GRAMPC. However, it is required from the user to set the algorithmic options regarding the numerical integrations in the gradient algorithm (this question was addressed in [6]), the line search implementation the number of gradient iterations per model predictive control (MPC) step, the prediction horizon, the number of discretization points for the numerical integration,

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vectors with initial and desired states, constraints as well as further settings. In this paper, the attention is given to the following settings affecting the time of the whole calculation procedure:  The prediction horizon Thor ;  Maximum number of gradient iterations N maxIter per MPC step to adjust the rate of convergence and improve the solution of the optimization problem;  The number of discretization points N hor for the numerical integration, which are calculated at the first step of the basic algorithm, to predict the optimal trajectory for the rotor flux linkage and the backward time integration. To make a reasonable choice of the parameter for the prediction horizon lets proceed from the following reasoning. The functional principle of the predictive control is actually not far from our real life and it represents a kind of “natural” predictive control. One of the most convenient examples to demonstrate this principle is the situation when driving the car. Millions and billions of people get behind the wheel of their cars every day. And most of them do it at the same time, because a car remains the most popular type of transport. When driving, you endanger not only yourself, but also the others. You have to watch the movement in general and anticipate the actions of the other drives. You have to monitor the situation on several cars in advance and use your peripheral vision to observe the behaviour of pedestrians and cars. Thus, you do not look immediately in front of your car, but you look far enough ahead and change the actuating variables, e.g. the steering, the gas pedal and brake before you approach for instance a red traffic light, a curve or some hindrance on the road. You as a driver precalculate the behaviour of the car for a certain distance in front of you up to a finite horizon taking future values of the actuating variables into account, and moreover, you optimize the amount of acceleration or braking according to your own optimization criteria for this distance and make a decision how to act every moment perhaps without even noticing it to such extent. As many men, so many opinions, e.g. many optimization criteria are possible, leading to various results. If you do not want to waste your time for a long duration trips, most likely you will increase the rate of acceleration and braking in this case if a reduction of fuel/energy consumption is an optimization criterion. Due to the precalculation of the system behaviour up to the prediction horizon, MPC inevitably leads to a high computation demands. Hence, a reasonable value for the selection of the prediction horizon is obviously:

Thor  3T2  3

L R2

(3)

Since the rotor flux linkage  2 and thus the power losses PV reach their stationary values after three rotor time constants T2 corresponding to (1). The optimum value for the field-generating current I1d in steady state with respect to power losses can be calculated using the known methods from the paper [5]. For the analysis of the parameters left within the list N maxIter and N hor , firstly, a value as small as possible is chosen for the two parameters. Afterwards, these values are increased until the visible improvement is observed. For the calculation of the field-generating current I1d two methods are used for comparison purposes:  Method 1. Steady state optimal value for magnetic flux  2 is calculated according to the next formula

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 2,stationary 

2 M M L 3 Zp

R1  R2 . R1

(4)

This reference value is set via flux regulator and the controlled variable of the regulator is the fluxgenerating current I1d . The given method as was discussed in [4] and [5] leads to high instantaneous power loss overshoot during a load torque, because with the step change in the magnetic flux linkage, a rapid change in current I1d is observed.  Method 2. Gradient based model predictive control according to [6]. For both methods, the integral of power loss is determined by method 1, WM 1 and predictive method 2, WM 2 respectively, during transients according to the next formula: 2  T MM R2 3 2 3 R2 2  J    ( R1  R2 ) I12d  ( R1  R2 )    3  I 2 2 1d dt . 2 2 2 2 3 2 L Z  L  0 p 2  

(5)

The comparison of WM12  WM1  WM 2 for the case when both N maxIter and N hor are changed is shown in Figure 2. This study is based on a very simple model of an asynchronous machine in Figure 1 with a rated power output of 370W, where only rotor flux dynamics  2 corresponding to (1) is considered. The torque-generating current I1q is determined from the rotor flux linkage and the torque with (2). A torque jump from 25% to 100% of the motor rated torque is used as the load jump. The left plot shows trajectories for the case when the number of discretization points changes and the number of maximum iterations equals 2. On the right-hand side, the plot shows trajectories for the case when the number of maximum iterations changes and the number of discretization points equals 9.

Nhor = 50 Nhor = 18 Nhor = 9 Nhor = 5

NmaxIter = 2 NmaxIter = 50

2 ΔWM12 / J

ΔWM12 / J

100 t / ms

150

200

100 t / ms

150

200

Fig. 2. Change of Nhor (left) and NmaxIter(right) at a load step change from 25% to 100%. By analogy the same test is made for the case of load torque step change from 100% to 25%. The trajectories are shown in Figure 3. The results show that in all cases the WM 2 is lower than when using method 1 compared to WM 1 . Also, it can clearly be seen that a very good result can be achieved MMSE Journal. Open Access www.mmse.xyz

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with the number of gradient iterations N maxIter  2 . In addition, the number of discretization points for the numerical integration used for prediction can be relatively small Nhor  9 . These applies both for the cases of load step up and load step down. The difference between the results for N hor  9 and N hor  18 is clearly visible, but still acceptable. The number of iterations has no significant effect in this case.

4 3

ΔWM12 / J

2 Nhor = 50 Nhor = 18 Nhor = 9 Nhor = 5

100 t / ms

150

200

0 0

NmaxIter = 2 NmaxIter = 50

100 t / ms

150

200

Fig. 3. Change of Nhor(left) and NmaxIter(right) at a load step change from 100% to 25%. The same analysis is carried out with the data of two more asynchronous motors with rated powers of 4 kW and 11 kW. For all three motors, comparable results are obtained with respect to the choice of the two parameters. Thus, the optimal choice is N maxIter  2 , N hor  9 .

To keep the integrity of the choice, let us take a look at curves obtained using these two values of the field-generating current and torque-generating current for the case of load step from 100% to 25% of the motor rated torque that are shown in Figure 4.

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0.6 0.5

0.4 I1d / A

I1q / A

-0.5

-2.5 0

100 t / ms

150

Method 1 Method 2

0.2

Method 1 Method 2

-1.5

0 0

200

100 t / ms

150

200

Fig. 4. Comparison of the stator current components Comparison of the currents obtained by method 1 and method 2 shows why the model prediction control yields better results: the field regulator attempts to establish a new steady-state optimal value for the rotor flux linkage as quickly as possible and as a result uses a high magnitude of the fieldgenerating current and reaches its output almost in no time. This is the main contribution to shortterm high losses according to method 1. This fact means that it is not profitable to use the conventional flux controller in dynamic mode of operation due to high instantaneous power loss overshoots during a load torque steps. Simulation of speed control closed loop. For the verification of the proposed approach a simulation with a motor with the current and speed control loops is performed in MATLAB/Simulink environment. The optimal parameters choice defined in the previous section is used as default in algorithmic options. The motor data of the induction motor with 370W rated power is used in the investigation. The simulation results for a speed ramp are shown in Figure 5. A load torque of 25% of the rated value is applied to the motor shaft initially. The speed ramp is selected such that acceleration process takes place in the period đ?&#x2018;Ą â&#x2C6;&#x2C6; [0 200]ms. A load torque step change from 25% to 100% is done at đ?&#x2018;Ą = 0. In addition to method 1 and method 2, another method is used for comparison purposes: ď&#x201A;ˇ Method 3 Constant reference of ď š 2 for optimal operation under 100% load condition. 40

500 Method 1 Method 2 Method 3

300

WM / J

PM / W

400

200

Method 1 Method 2 Method 3

100

200 t / ms

300

400

100

Fig. 5. Power and energy consumption

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200 t / ms

300

400

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The comparison of loss energies calculated from the power loss shows that at the time period đ?&#x2018;Ą â&#x2C6;&#x2C6; [0 200]ms the loss energy obtained by method 3 is lower than is the other cases. Such a result was expected as the level of magnetic flux linkage of the methods 1 and 2 is lower at the time range đ?&#x2018;Ą â&#x2C6;&#x2C6; [0 100]ms. The trajectories of energies calculated by methods 1 and 2 are very close in range đ?&#x2018;Ą â&#x2C6;&#x2C6; [100 200]ms. A detailed analysis shows that the latest gives slightly better results than method 1. At đ?&#x2018;Ą = 200ms, the speed setpoint is reached due to ramp-shaped speed reference signal and load torque drops stepwise from 100% to 25% of the rated motor torque. From power and energy trajectories shown in Figure 5 it can be clearly seen that from this point onwards methods 1 and 2 have much better behaviour compared to method 3. Moreover, predictive method 2 leads to the best possible results throughout the given operation range. Concerning the comparison results throughout the entire operation range of the induction motor, it can be concluded that loss energy obtained by method 3 is significantly higher, since in part-loaded mode of operation the efficiency of the motor dramatically decreases due to over-excitation and redundant power dissipation in contradistinction to method 1 and method 2.

1 I1q / A

I1d / A

The curves of the stator current components, e.g. field-generating current and torque-generating current are shown in Figure 6.

0 Method 1 Method 2 Method 3

-1

Method 1 Method 2 Method 3

-1 -2

-2 0

100

200 t / ms

Fig. 6. Simulation results for

300

I1q

400

100

200 t / ms

300

400

and I1d

The same behaviour of the trajectories is obtained for the methods 1 and 2, as in the previous section for the simplified model. It means that assumption concerning the neglect of the dynamics of the speed and current controllers stated at the beginning of the paper appears to be justified. Summary. This paper has described how a known control method with a gradient-based predictive algorithm can be used to optimize the energy efficiency of an asynchronous motor in dynamic mode of operation. The effect of the model algorithmic parameters: prediction horizon, the maximum number of iterations to improve the solution of the optimization problem and number of data points for the control trajectory is considered and default values for optimal control in terms of real-time demands are determined. It allows for a reliable operation of the drive throughout its whole operation range. Comparison with other methods without optimization, e.g. when the magnetic flux linkage is kept at the nominal level throughout the entire load range and when it is set to its new optimum value for each new load step change, shows the advantages of the gradient-based model predictive control which is well suited to control nonlinear and input constrained systems. GRAMPC is licensed under the GNU Lesser General Public License (version 3) and can be downloaded from http://sourceforge.net/projects/grampc. References MMSE Journal. Open Access www.mmse.xyz

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[1] Bazzi, A. M., Krein, P. T. (2010). Review of Methods for Real-Time Loss Minimization in Induction Machines. IEEE Transactions on Industry Applications, 46(6), 2319-2328. DOI 10.1109/tia.2010.2070475 [2] Klenke, F., Hofmann, W. (2011). Energyâ&#x20AC;&#x201C;Efficient Control of Induction Motor Servo Drives With Optimized Motion and Flux Trajectories. Proceedings of the 14th European Conference on Power Electronics and Applications (pp. 1-7). [3] Stumper, J., Dotlinger, A., Kennel, R. (2013). Loss Minimization of Induction Machines in Dynamic Operation. IEEE Transactions on Energy Conversion,28(3), 726-735. DOI 10.1109/tec.2013.2262048 [4] Qu, Z., Ranta, M., Hinkkanen, M., Luomi, J. (2011). Loss-minimizing flux level control of induction motor drives. 2011 IEEE International Electric Machines & Drives Conference (IEMDC). DOI 10.1109/iemdc.2011.5994597 [5] Diachenko, G., Schullerus, G. (2015). Simple dynamic energy efficient field oriented control in induction motors. In Proceeding of the 18th International Symposium on Power Electronics. Novi Sad. [6] Kapernick, B., Graichen, K. (2014). The gradient based nonlinear model predictive control software GRAMPC. 2014 European Control Conference (ECC), 1170-1175. DOI 10.1109/ecc.2014.6862353 [7] Graichen, K., Kapernick, B. (2012). A Real-Time Gradient Method for Nonlinear Model Predictive Control. Frontiers of Model Predictive Control, 9-28. DOI 10.5772/37638

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VI. Environmental Safety M M S E J o u r n a l V o l . 1 2

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Understanding the Nature of Wet Air Deposition on Rooftops in Uyo Metropolis Ihom A.P.1, Uko D.K. 1, Markson I.E. 1, Eleghasim O.C. 1 1 – Department of Mechanical Engineering, University of Uyo, Uyo, PMB, Uyo, Nigeria a – ihom@uniuyo.edu.ng DOI 10.2412/mmse.34.45.452 provided by Seo4U.link

Keywords: wet air, nature, pollutants, particulates, deposition, rooftops, Uyo metropolis.

ABSTRACT. The work titled Understanding the Nature of Wet Air Deposition on Rooftops in Uyo Metropolis was Carried out by determining the extent of air pollution in four different places in Uyo metropolis. Attair 5X was used to determine the gaseous pollutants in the wet air, while filtration technique using High Volume Sampler was used to determine the suspended particulates in the air, and the concentration was calculated in mg/l over a 24hrs period. The composition of the deposition on the rooftops was analysed using EDX-X-Ray Fluorescence (EDX-XRF) and the characterization of the deposit was done using Scanning Electron Microscope (SEM). The result of the work showed that gas pollutants existed in all the four stations but were not to the level of health concern since air quality standard specifications were not exceeded. However, impact on rooftop was noted since SO3 was in the composition of the deposit on the rooftops. The suspended particulate matter exceeded air quality standard value of 200 µg/m3 in all the four stations, and so was of both health and environmental concern since it influenced the deposition on the rooftops. The SPM composition elements were also found in the composition of the deposits on the rooftops. SEM characterized the dark-black deposit on the rooftop and the micrograph showed areas of high and low deposition on the roofs. The study concluded that a better understanding of the nature of wet air deposition on rooftops in Uyo metropolis has now been established.

Introduction. The quantity of atmospheric deposition depends on the amount and types of air pollutants emitted in the vicinity and upwind of a site [15], and the length of time between precipitation events [11]. A recent study of the Puget Sound Basin evaluated heavy metals, polycyclic hydrocarbons (PAHs), and other compounds in wet and dry atmospheric depositions. This study found that concentrations of the chemicals of concern in the highly urbanized area sampled were an order of magnitude greater than outside the urban area [17]. To differentiate between materials leaching and air deposition, recent studies have attempted to control for the contribution of air deposition, thereby evaluating the concentrations that leach from the roofing materials themselves. Wet and dry deposition contributes to the contaminants from commercial, residential and industrial roofs. Plate I with dark-black deposit on the rooftop is a typical building in Uyo metropolis. Contaminants associated with wet air deposition on rooftops comprise a portion of roof runoff. For example, Sabin [10] found that more than 50% of the metals in storm water runoff in Los Angeles were associated with air deposition. In a Swiss study, the ratio of the concentrations of metals in runoff compared to wet and dry atmosphere deposition ranged from as high as 27: 1 for copper to less than 1:1 for zinc depending on the roofing type and the location [16].

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Fig. 1. Building Roof Completely Covered with Dark-Black Coating/Deposit. The dispersion of air pollutants at a particular place are influenced by meteorological factors, such as wind speed, wind direction, and turbulence. Precipitation and humidity also influence the pollution potential. Air quality standards indicate the levels of pollutants that cannot be exceeded during a specified time period in a specified geographic area with due reference to the method of measurement, units of measurement, concentration, and time of exposure. The primary air-quality standards define the levels judged necessary to protect the public health with, an adequate safety margin. Air pollutants affect man and his environment. The materials that may be affected by air pollutants include metals, building materials, rubbers, elastomers, paper, textiles, leather, dyes, glass, enamels, and surface coatings. The types of possible damage to these materials by air pollutants include corrosion, abrasion, deposition, direct chemical attack and indirect chemical attack. Air pollutants, such as sulphurdioxide, HF, particulate, fluorides, smog, oxidants like ozone, ethylene (from automobiles), NOx, chlorine, herbicide and weedicide sprays exert toxic effects on vegetation. Arsenic, lead and fluorides are the main pollutants which cause damage to livestock. These air-borne contaminants accumulate in vegetation and forage and poison the animals when they eat the contaminated vegetation [1]-[3], [5]-[9]. Particulates (solid or liquid) are one important constituent of the atmosphere. About 2000 million tonnes of particulate matter per year are released from natural agencies such as volcanic eruptions, wind and dust, storms, salt sprays etc. man-made activities, such as burning of wood, coal, oil and gaseous fuels, industrial processes, smelting and mining operations, fly-ash emissions from power plants, forest fires, burning of coal refuse and agricultural refuse etc. release about 450 million tonnes of particulates per year. The diameter of particulates may range from 2 x10-4 to 5 x 102 Âľm with varying life times depending upon the size and density of the particles and turbulence of air which control their settling rate. Fine particulates having size of < 3 Âľ (such as air-borne toxic metals like Be and air-borne asbestos) which can penetrate through nose and throat, reach the lungs and cause breathing problems and irritation of the lungs capillaries. Similarly pulmonary fibrosis in asbestos mine workers, black-lung disease in coal miners and emphysema in urban population are attributed to the particulate pollution. Further, air-borne particulate such as dust, mist, fumes, and soot can cause damage to various materials; particulates may accelerate corrosion of metals and cause damage to roofs, paints and sculptures. Solid particles or liquid droplets including fumes, smoke, dust and aerosols. Solid particles can adsorb various chemicals. Effect of particulate matter vary with the MMSE Journal. Open Access www.mmse.xyz

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nature of the particulates; carbon particles and other particles cause scarring of lungs via complex walling off and fibrogenic reactions leading to a disease condition known as ‘’pneumoconiosis’’. Cadmium inhalation of fumes and vapours causes kidney damage, bronchitis, gastric and intestinal disorders, cancer, disorders of heart, liver, and brain, renal dysfunction, anaemia, hypertension, bone-marrow disorder and cancer with chronic and acute poisoning. Lead absorption through gastro-intestinal and respiratory tract and deposition in mucous membranes, cause liver and kidney damage, mental retardation in children, abnormalities in fertility and pregnancy. Zinc fumes have corrosive effect on skin and can cause irritation and damage mucous membrane [1]-[3], [5]-[6]. This present work is particularly focused on understanding the nature of wet air deposition on rooftops in Uyo metropolis and the effects of the wet air deposition on the roofs and human beings. The wet air comes into contact with the roofs creating various effects like deposition, roof leaching, biological organisms’ growth, corrosion, surface erosion and discoloration. This effects are caused by SOx, NOx, COx and other acid gases, acid mist, sticky particulate matter. Other environmental factors influencing the rate of attack include moisture, freezing, and temperature [2]-[3]. Materials and method Materials. The materials used for this research work included the following: the sampled air in raining season, dark-black deposit from the rooftops, chemicals used for the analysis and specimens cut from the rooftops. Equipment. The equipment used for the work included Attair 5x Multigas detector, EDX-X Ray Fluorescence, Scanning Electron Microscope, scissors, petri dish, filter paper, analytical weighing balance, electric oven, desicator with silica gel, thongs, sample collectors and ladder. The Study Area. The study area of this research work is Uyo metropolis. Uyo is the Capital of Akwa Ibom state. It is a major oil producing state in Nigeria, with a lot of gas flaring activities going on from the oil exploiting companies. The population of Uyo according to the 2006 Nigerian census which comprises Uyo and Itu is 436,606. The metropolitan area covers an estimated area of 168 km2 (65sq.mi). Uyo is a fast-growing city and has witnessed some infrastructural growth in recent years. It is located on coordinates 502`N and 7056’E. The average annual rainfall in the study area is between 2000-4000mm with the period of fall usually between April and October. The rainfall reaches its peak in the months of June and September, while the dry period falls between November to March. The relative humidity of the area varies between 75% and 95% with mean annual temperatures of about 26 to 36oC. Fig.1 is the map of the study area. The samples for the work were taken in different areas of the metropolis covering, Use Offot on Nwanniba road (station 2), University of Uyo, main campus on Nwanniba road (station 1), Ikot-Okubo on Abak road (station 3), and Mbaibong on Oron road (station 4). The town is characterized by high usage of generators as a result of incessant power failure from the national grid and high vehicular traffic typical of a growing metropolis.

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Fig. 2. The Map of Uyo Metropolis the Study Area. Method. Air sampling in the four stations was made possible through the use of Attair 5X Multigas detector. The device is equipped with catalytic sensor that detect a variety of gases in the atmosphere and displays the reading. Fig. 3 shows the technologist sampling the air at station 1 (University of Uyo, Main campus). The sampling of the wet air took place 10th September, 2016 during the peak of raining season period in Uyo metropolis. The High Volume Sampler was used to determine the Suspended Particulate Matter in the air that remained for extended periods. Sampling was done for 24 hrs. Particulate matter collected on the filter paper was extracted and digested with acid mixture for chemical analysis of some selected elements like iron, lead, cadmium, copper, zinc, and sodium. The SPM was determined according to specifications by Ambient Air specification methods and American Society for Testing Materials (ASTM). The dark-black deposit on the rooftops was scraped for analysis using EDX-X Ray Fluorescence. Specimens were equally cut from the roofs for SEM analysis using Scanning Electron Microscope.

Fig. 3. Show the Technologist Sampling the Air at Station 1using Attair 5X (University of Uyo, Main campus).

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Results and discussion Results. The results of this research work are as presented in Tables 1-2. Table 1 is the quality of the wet air, which was sampled in the raining season in four different locations of Uyo metropolis. Table 2 is the elemental composition of the suspended particulate matter which was measured in dry season in four different locations of Uyo metropolis. Table 3 is the air quality standard Table. Table 4 is the EDX-X-Ray Fluorescence analysis of the dark-black deposit on the rooftops of buildings in Uyo metropolis. Fig. 4 is the SEM micrograph of the dark-black deposit on the rooftops in Uyo metropolis. Table 1. Analysis of Air Pollutants in Four Different Stations in Uyo Metropolis. S/No Parameter

Station 1

Station 2

Station 3

Station 4

SOX (ppm)

< 0.01

NOX (ppm)

< 0.01

CO (ppm)

< 0.01

0.02

0.01

0.05

CO2 (ppm)

272.0

276.0

274.0

278.0

H2S (ppm)

<0.01

SPM (Âľg/m3)

0.68

3.25

2.91

3.15

Table 2. Chemical Analysis of Suspended Particulate Matter (SPM) from Four Stations in Uyo Metropolis. S/No Parameter

Station 1

Station 2

Station 3

Station 4

Lead (Pb) mg/l

<0.0001

0.0002

<0.0001

Iron (Fe) mg/l

0.0008

0.0009

0.0008

Copper (Cu) mg/l

0.0027

0.0026

0.0028

0.0026

Zinc (Zn) mg/l

0.0029

0.0031

0.0036

0.0003

Cadmium (Cd) mg/l

<0.0001

0.0002

0.0004

0.0003

Sodium (Na) mg/l

0.0002

0.0003

0.0005

0.0002

Key: Station 1: University of Uyo, main campus on Nwanniba road. Station 2: Use Offot on Nwanniba road. Station 3:Ikot-Okubo on Abak road. Station 4: Mbaibong on Oron road.

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Table 3. Ambient Air Quality Standards. Pollutant

Time weighted average

Residential, Rural and mixed used area

Sulphur dioxide

Annual average

60µg/m3 (0.023 ppm)

(SO2)

24hrs

80µg/m3

Oxides of Nitrogen

Annual average

60µg/m3

(NOx)

24hrs

80µg/m3

Carbon Monoxide

Annual average

2.0mg/m3

(CO)

1 hr

4.0 mg/m3

Suspended Particulate

Annual average

140µg/m3

Matter (SPM)

24 hrs

200µg/m3 (0.077ppm)

Respirable Particulate

Annual average

60µg/m3

Matter (size less than 0µm), RPM

24 hrs

1000µg/m3 (0.38 ppm)

Lead (Pb)

Annual average

0.75µg/m3

24 hrs

1.00µg/m3 (0.00038 ppm)

Annual average

80µg/m3 (0.03ppm)

24 hrs

365µg/m3 (0.14 ppm)

H2S

Annual average

CO2

24 hr

600 ppm

Oxidants

1 hr

160µg/m3 (0.08 ppm)

Sox

Source: Dara [3]

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Table 4. Chemical Composition of Dark-Black Material Scrapped from Roof-Tops (Analysed at NMDC Jos). S/No Sample

Al2O3

SiO2

P2O5

SO3

K2O

CaO

TiO2

V2O5

Blackish powder from roof-top

16.00

43.80

1.20

2.71

3.20

1.62

2.93

0.11

Cr2O3

MnO

Fe2O3

NiO

Co2O3

CuO

ZnO

Rb2O

SrO

0.10

0.31

10.55

0.05

0.09

0.22

0.07

0.03

0.05

ZrO2

Yb2O3

Re2O7

PbO

Carbonaceous and volatile matter

0.20

0.001

0.06

0.11

16.59

Fig. 4. Scanning Electron Microscope (SEM) Micrograph of Dark-Black Deposit on Zinc-Coated Base Roofing Sheet. The light areas have low deposit of the material; the substrate is still shining and the dark areas have large deposit of the material; the substrate is covered. Discussion Table 1 is the Analysis of Air Pollutants in four different stations in Uyo metropolis. The Table shows that the values of the gaseous pollutants are actually lower than the standard specification for residential and mixed used area in all the four stations of the wet air sampling. This may not really pose any health challenge. According to several researchers, the pollutants can affect the roofs of buildings and other materials. The wet air comes into contact with the roofs creating various effects like deposition, roof leaching, biological organismâ&#x20AC;&#x2122;s growth, corrosion, surface erosion and discoloration. These effects are caused by SOx, NOx, COx and other acid gases, acid mist, sticky particulate matter. Other environmental factors influencing the rate of attack include moisture, freezing, and temperature [1]-[3], [5]-[6].

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The SPM in all the four stations were higher than the standard specification for air quality in residential and mixed used area of 200 µg/m3. This can be attributed to gas flaring activities, automobiles exhaust fumes and emissions, particulates (generating sets and others) the health implications needs to be investigated, but according to Dara [3] Solid particles or liquid droplets including fumes, smoke, dust and aerosols. Solid particles can adsorb various chemicals. Effect of particulate matter vary with the nature of the particulates. Carbon particles and other particles cause scarring of lungs via complex walling off and fibrogenic reactions leading to a disease condition known as “pneumoconiosis”. Cadmium inhalation of fumes and vapours causes kidney damage, bronchitis, gastric and intestinal disorders, cancer, disorders of heart, liver, and brain, renal dysfunction, anaemia, hypertension, bone-marrow disorder and cancer with chronic and acute poisoning. Lead absorption through gastro-intestinal and respiratory tract and deposition in mucous membranes, cause liver and kidney damage, mental retardation in children, abnormalities in fertility and pregnancy. Zinc fumes have corrosive effect on skin and can cause irritation and damage mucous membrane [1]-[3], [5]-[9]. The effect of the pollution in Table 1 can be noticed by the presence of SO3 in Table 4, which is the composition of the deposit on the rooftops of buildings in all the four stations. Table 2 is the chemical composition of the SPM from the four stations in Uyo metropolis. Some of the values of the elements in the SPM actually exceeds standard specifications a little and may have some health implications particularly the lead and the cadmium but not in all stations. Stations 2 and 3 for lead and stations 23 for cadmium. The health implications of these metals have been clearly stated by these authors [2][3], [8]. On the impact of the SPM on the rooftops of building in Uyo metropolis; some of the elements in Table 2 are found in the chemical analysis of the deposit on the rooftops presented in Table 4. This agrees with the effects of SPM on building rooftops as shown by several authors [4], [10], [15], [17]. These researchers have argued that, air-borne particulate such as dust, mist, fumes, and soot can cause damage to various materials; particulates may accelerate corrosion of metals and cause damage to roofs, paints and sculptures [12], [14], [16]. Solid particles or liquid droplets include fumes, smoke, dust and aerosols. Solid particles can adsorb various chemicals and also produce depositions on rooftops. Sticky particulate matter from the wet air settles on rooftops producing dark black deposit on the roofs [2], [3]. The characterization of the SPM deposit on rooftops in Uyo metropolis is shown in Plate III. The dark areas indicate thick deposit of the SPM and light shining areas indicate thin deposit of the SPM on the roof. This study has explicitly thrown light on the nature of wet air deposition on rooftops in Uyo metropolis. Table 1 has highlighted the gaseous pollutants in the wet air and Table 2 the particulate pollutants associated with the wet air and the impact of the wet air on rooftops is the dark-black deposition on the rooftops. Table 3 is the ambient air quality standard with which the analyses in Tables 1-2 were compared with. Summary. This study “Understanding the nature of wet air deposition on rooftops in Uyo metropolis” has been executed and the following conclusions drawn from the study 1. Study has shown that the deposition from the wet air unto the rooftops is in two parts viz. the deposit from gaseous pollutants and deposits from particulate matter. 2. Gaseous pollutants and the particulate matter from the wet air affect the rooftops in different ways, which include, corrosion, deposition of sticky matter, erosion and leaching. 3. Deposit on the rooftops contain compounds and elements from both the gaseous and particulate matter pollutants 4. Scanning Electron Microscope micrograph showed that the distribution of the deposit on the rooftops is not uniform 5. Suspended particulate matter may have some health implications since in all the four stations it was higher than standard specification and therefore there may be need for relevant government agencies to investigate the health implications. Sponsorship MMSE Journal. Open Access www.mmse.xyz

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This work is part of a major work that has been sponsored by TETFUND Institutional based Research Grant for University of Uyo-Uyo-Nigeria. References [1] Asanusung, K.E. (2014) Investigation of the possible causes of Aluminium Roofing Sheet Discolouration and its remedy: A Case Study of the University of Uyo Male Hostel Roof, Permanent Site, PGD Project, Department of Mechanical Engineering University of Uyo, Uyo, Nigeria. [2] Bhatia, S.C.(2008) Environmental Chemistry, 4th Edition Reprint, published by Satish Kumar Jain for CBS Publishers & Distributors, Darya Ganj, New Delhi (India) p. 1-20. [3] Dara, S.S. (2007) A Text book of Environmental Chemistry and Pollution Control, Seventh Reprint, S. Chand and Company Ltd, Ram Nagar New Delhi, p. 24-31. [4] Dangelo, S. (2016), How White Roofs Can Help Your Home Cool, assessed at http//www.dangeloandson.com. [5] Ihom, A.P. (2014) Environmental Pollution Prevention and Control: The Current Perspective (A Review), Journal of Multidisciplinary Engineering Science and Technology (JMEST), Vol. 1 Issue 5, 93-99. [6] Ihom, A.P. and Offiong, A. (2014) Zinc-Plated Roofing Sheets and the Effect of Atmospheric Pollution on the Durability of the Sheets, Journal of Multidisciplinary Engineering Science and Technology (JMEST), Vol. 1, Issue 4, 125-132. [7] John, A.J. (2016) Combustion Analysis of Vehicular Emission: Effect on Air Quality in Uyo, Akwa Ibom State-Nigeria, M. Eng Degree Dissertation in the Department of Mechanical Engineering, University of Uyo-Nigeria [8] Okedere, O.B. and Elehinafe, F. (2016) Particulate Pollution from Diesel Generators of Mobile Telecommunication Industries in Lagos Nigeria, UniOsun Journal of Sciences, vol.1 (1), 37-42 [9] Ola, S.A., Salami, S.J., Ihom, P.A.(2013) The Levels of Toxic Gases; Carbon Monoxide, Hydrogen Sulphide and Particulate Matter to Index Pollution in Jos Metropolis, Nigeria, Journal of Atmospheric Pollution, Vol. 1, No. 1, 8-11. [10] Sabin, L.D.J.H., Lim, K.D., Stolzenbach, and Schiff, K.C. (2005) Contribution of Trace Metals from Atmospheric Deposition to Storm Water Runoff in a Small Impervious Urban Catchment, Water Research 39(16):3929-3937 [11] Thomas, S.K., Greene, M.T. (1993) Effect of Seasonality on Rain Water Quality in California, Journal of Applied Biotech, 1(2): pp18-23 [12] E. A. Tice (1962) Effects of Air Pollution on the Atmospheric Corrosion Behavior of Some Metals and Alloys, Journal of the Air Pollution Control Association, 12:12, 553-559, DOI 10.1080/00022470.1962.10468127 [13] WHO (2014), WHO Report Worsening Air Quality in Cities. The Guardian Mobile, 7 May, 2014 [14] Woods, J. (2017) Reflective Surfaces (Geoengineering) Accessed at http//en.wikipedia.org/ [15] Foster, J. (1996) Patterns of Roof runoff contamination and their Potential Implications on Practice and Regulation of Treatment and local infiltration, Water Science and Technology. 33 (6):pp39-48 [16] Zobrist, J., Muller, S.R., Bucheli, T.D. (2000) Quality of Roof Runoff for Groundwater Infiltration, Water Resources, 34: 1455 [17] Brandenbergen, C.P. Julius, M., Remteke, S.G. (2011). Chemical and Biometric Analysis of Puget Sound Basin, Pakistan-Journal of sciences 4 (1): pp. 111-618

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VII. Economics & Management M M S E J o u r n a l V o l . 1 2

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Effect of Maintenance Methods and Manufacturing of Track Components on the Profitability Rates in Egyptian National Railways and Comparison with Global Railway Networks Karim Mohamed Eldash1,a, Ahmed Abdel Moamen Khalil2, b, Lobna Hane Mostafa3, c 1 – Prof., Dr. of Structural Engineering, Faculty of Engineering at Shoubra, Benha University, Cairo, Egypt 2 – Associate prof., Dr. of Railway Engineering, Faculty of Engineering at Shoubra, BenhaUniversity, Cairo, Egypt 3 – Railway Engineer at Egyptian Company for Cairo Metro a – karim.aldosh@feng.bu.edu.eg b – ahmed.khalil@feng.bu.edu.eg c – Lobnahany360@yahoo.com DOI 10.2412/mmse.40.42.927 provided by Seo4U.link

Keywords: railway track, maintenance cost, construction cost, profitability rates, train operation.

ABSTRACT. The aim of this paper is studying the prices of the different types of railway track components that are used in Egyptian National Railways, determining the percentage of the imported track components and calculation of the construction cost per one kilometre of track. Thus, the effect of importing of track components in Egypt on the profitability rates has been obtained and compared with other countries. This paper also presents the different methods of track maintenance, the used equipment, and machines owned by Egyptian National Railways. The annual costs of maintenance and construction have been obtained and compared with some other countries. Also, the effect of imported track components percentage on the periodical maintenance, number of train accidents has been studied.

Introduction. Railway transportation in Egypt is one of the most important means of transportation and most comfortable for passengers but increasing of the percentage of imported Track components comparing with the local track components leads to increase of construction and maintenance costs and that affects badly on the Profitability rates in ENR. Satish Chandra & M.M. Agarwal ]1 [and A. Lopez Pita ]2[ stated that track or permanent way is the railroad on which trains run. The track consists of two parallel rails fastened to sleepers with a specified distance between each other. The sleepers are embedded in a layer of ballast with specified thickness spread on level ground known as (formation). The ballast provides a uniform level surface and drainage, and transfers the load to a larger area of the formation. The rails are joined in series by fish plates and bolts and these are fastened to the sleepers with various types of fasteners. The sleepers are spaced at a specified distance and held in position by the ballast. Each component of the track has a specific function to perform. The rails act as girders to transmit the wheel load of trains to the sleepers. The sleepers hold the rails in their proper positions, provide a correct gauge with the help of fastenings, also sleepers transfer the load to the ballast. The formation takes the total load of the track and also the trains moving on it. Michael T. McHenry, Jerry G. Rose ]3[ explained that subgrade includes the formation and subsoil and the train loads which transferred from the superstructure adequately, subgrade acts as a quasi-sub ballast, but it is extremely varied in composition and difficult to assess. Malcom Kerr ]4[, Australian Rail Track Corporation LTD ]5[ studied the defects of rails that happen to the rails such as:

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a – Tache oval that results from thermal effects during rail manufacture, it expands to reach the rail surface, b – Horizontal cracking is horizontal cracks occur in the rolling surface of the rail at the manufacturing stage, c – Rolling (running) surface disintegration corresponding to a gradual disintegration of the rolling surface of the rail, surface defects can be detected by maintenance inspections and the defected rails are replaced, d – Short-pitch corrugations that consist of corrugation on the rail surface with a wave length 3→9 cm and the oscillation motion of the train leads to higher rail stresses, sleeper fatigue with cracking in the rail seat area, loosing of the fastenings, accelerated wear of pads and clips, failure occurrence of ballast and subgrade, increasing of the noisy by 5→15 db in the noise level. This defect is detected by visual inspection or by recording equipment, it is detected by grinding this corrugation using the grinding machine. ENR guide line for permanent way work ]6[ classified the maintenance works to be : (inspection, manual maintenance, mechanical maintenance and rehabilitation). Quandel consultants, LLC [7] illustrated that infrastructure cost estimating policy requires studying of all costs for transport, that depending on prediction of the total cost of a project by estimating the actual costs of all elements in the project, including plant, labour, materials etc. Cost estimating is required in railway networks to optimize the asset management strategies and reduce the costs. CE Delft, INFRAS & Fraunhofer ISI ]8[ defined the external costs as the costs that impose on non-users of the transport system. Marginal social cost of infrastructure is the total cost entailed by the running of an additional train on a particular infrastructure and it is composed of: 1 – marginal cost related to infrastructure, which measures the increase in maintenance and renewal costs resulting from an additional train running, 2 – marginal congestion cost, expressing in monetary terms the value of delays and constraints imposed on the rest of the traffic by an additional train running, 3 – marginal external cost, representing the increase in other costs to the society incurred by the running of an additional train. This cost measures principally the variation of costs of accidents, pollution (air and sound), climate change, etc. Daniel Ling ]9[ illustrated that maintenance process is concerned with the optimal use of materials, maintenance technique is carried out to increase the operational life of track components and that will lead to reduce the cost. Maintenance concerned with replacing of any defected part of track components with another new one. The aim of the maintenance management is to reduce the effects of failure and to reduce the cost. Von Brown ]10[ explained that construction of a new railway line should be based on an accurate knowledge of costs and type of costs. Also, operation process of a railway line needs to an accurate and detailed knowledge of costs. So the definition of the cost is the amount of available resources, that are spent related to the construction or operation of a railway activity. Railway costs can refer either to the construction of a line, in this case the cost is called construction cost, or to operate a line service such as passenger, freight, combined, terminal. This cost is the operation cost. When the infrastructure is separated from operation activities, this cost is called the infrastructure cost, which is the sum of track costs related to the use of a track. These costs include maintenance and operation costs related to subgrade, ballast, sleepers, rails, signalling, telecommunications, electric traction installations, lighting, inspection, as well as station constructions and the staff needed to operate the infrastructure. Periodic maintenance works are closely joined with the costs of operation, which are related to tasks undertaken to maintain the serviceable condition of the road infrastructure on a short term or seasonal basis. The costs for regular maintenance in a tunnel relate

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to the requirement to maintain the fire safety systems, ventilation equipment and, drainage pumps, etc. ]11[, ]12[ . The costs differ greatly in the various categories of rail passenger traffic: urban and suburban, between cities, local ]13[, ]14[. Statistics of rail operators usually refer to the whole activity and lack Analytical data, which they should have for every specific category of traffic and even more for every route. Railways should introduce analytical accounting techniques in order to have the possibility of an accurate measure of costs for every segment of the market and for every route ]14[ . It is essential to determine the time that railway components may be used or replaced, so the definition of economic life is the period, during which the specific component is expected to be usable, with normal repair and maintenance, and it is usually less than physical life i.e. any railway component should be replaced before the end of its economic life and this may differ from one country to another country ]15[. Percentage of imported track components, its effect on the profitability rates and percentage of maintenance cost to construction cost of one kilometre of track are evaluated in this paper focuses on the following items:  determination of the imported track components percentage and comparing it with the local track components.  determination of the construction cost and maintenance cost per one km of track for some countries. 

financial and operational analysis for local and imported track components percentages.

 determination of the effect of imported track components percentage on the profitability rates in Egyptian national railways. Materials and Data. This item presents the data, which have been collected from different resources such as the ENR and railways in other countries references. Data, which were shown in tables, will be discussed later in details. Data focus on the costs of construction and maintenance, which are spent on the track components and on the maintenance machines. Also collected data declared the financial issues of ENR. Methods of track maintenance. The railway track should be maintained properly in order to enable trains to run safely at the highest permissible speeds, also to provide passengers with safe and comfortable journey. Railway tracks can be maintained either by manual labour or by machines such as mechanical tamping machines, maintenance activities are carried out according to a timetable that outlines the track maintenance work to be done around the year in order to raise the efficiency of the lines Track maintenance includes three types, which are followed in E.N.R and all over the world, they are summarized in the following: Inspection: Inspection includes the visual inspection by walking on the track or by trip on the locomotive and manual measuring of the track and turnouts after that comparing the measured values with the corresponding theoretical values with taking into account the permissible tolerances, then the evaluation of the recorded values of the actual condition will indicate if the track need to maintenance or not. Manual maintenance: Manual maintenance includes some activities must be carried out such as: replacement of rails or sleepers - grinding of turnouts- welding of the track- renewal of the track for a distance less than or equal 100 m, replacement of turnout parts such as stock rail, switches, guard rail, crossing and some sleepers.

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Mechanical maintenance: This type of maintenance is carried out by machines such as: Tamping and lining machine (as shown in figure 1) Ballast distributing and profiling machine (as shown in figure 2) Ballast bed cleaning machine (as shown in figure 3) Rehabilitation: Rehabilitation includes some activities to be carried out such as: replacement of the track for distance less than or equal 100 m-renewals of the sleepers, turnouts and ballast cleaning and replenishing of ballast.

Fig. 1. Tamping and lining machine 08.

Fig. 2. Ballast distributing and profiling machine.

Fig. 3. Ballast bed-cleaning machine. MMSE Journal. Open Access www.mmse.xyz

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Construction cost. Construction cost per one km of track in the cases of using different fastening systems (K-Type, Vossloh and Pandrol) is given in table 1. Table 1. Construction cost for one km of track according to different fastening systems. Construction cost for one kilometre of track (€) K-Type fastening system

Vossloh fastening system

Pandrol fastening system

311934.42

221465.52

227161.89

Comparison between construction cost of one Km of track in Egypt, Australia, USA, Germany and Switzerland according to year 2016 (including embankment and labour costs) is given in table 2. Table 2. Comparison between the construction cost for one Km of track in some countries. Country

Construction cost (investment cost)per Km of track (€) In 2016

Germany (Deutsche Bahn’s network)

400000

Egypt

734000

Australia (Melbourne-Brisbane route)

655000

USA

832000

Switzerland

350000

Japan

220000

Maintenance cost. Comparison between maintenance cost of one Km of track in Egypt, USA, Germany, Japan and Switzerland according to year 2016 is given in table 3. Table 3. Comparison between the maintenance cost for one Km of track in some countries. Country

Maintenance cost per Km of track (€) in 2016

Germany (Deutsche Bahn’s network)

7700

Egypt

100000

USA

3800

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Switzerland

7000

Japan

6000

Financial analysis. Construction of a new railway line should be based on an accurate knowledge of types of costs Also, operation process of a railway line also needs to accurate and detailed knowledge of costs. So the definition of the cost is the amount of available resources that are spent related to the construction or operation of a railway activity. Railway costs can refer either to the construction of a line, in this case the cost is called construction cost, or to operate a line service such as (passenger, freight, combined, terminal), this cost is called operation cost. The construction cost for one km of track according to different fastening systems (K-Type, Vossloh and Pandrol) is shown in figure 4.

350000 300000 250000 200000 150000

Construction cost for one kilometer of track (€)

100000 50000 0 K-Type fastening system

Vossloh fastening system

Pandrol fastening system

Fig. 4. Comparison between the Construction cost for one km of track according to different fastening systems that used in E.N.R. Referring to table 1 and figure 4 it is observed that construction cost of one km of track using KType system is higher value than Vossloh fastening system, and Pandrol fastening system because, in this system, a large number of components is used. The percentage of the imported track components is calculated for some cases as follows:  In case of K-type with concrete sleepers (mono-block): The percentage of the imported track components is about 33.59 %.  In case of K-type with concrete sleepers (twin-block): The percentage of the imported track components is about 33.53%.  In case of K-type with timber sleepers: The percentage of the imported track components is about 71.56 %. 

In case of Vossloh (SKL 14 ): percentage of the imported track components is about 45.51 %. MMSE Journal. Open Access www.mmse.xyz

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ď&#x201A;ˇ

In case of Pandrol: percentage of the imported track components is about 44.37 %.

The percentage of the imported and local track components for different fastening systems is illustrated in figure (5).

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

local track components Imported track components

Fig. 5. Different percentages of the imported and local track components in different fastening systems for first class tracks (for year 2016). According to figure 5, it is observed that case of K-Type with timber sleepers has the largest percentage because the cost of imported timber sleepers is very high. However, the timber sleepers are not used in the other systems. Referring to table 2 and figure 6, it is observed that the construction cost in USA has the largest value. It is found that the cost of construction in ENR is in the second order, however, Japan comes in the last order because of local manufacturing of the track components. 900000 800000 700000 600000 500000 400000 300000 200000 100000 0 Germany

U.S.A

Egypt

Australia Switzerland

Japan

Fig. 6. Different values of construction cost for one kilometre of track. Referring to table 3 and figure 7 it is observed, that Egypt has the largest value for maintenance cost that is because of increasing the percentage of imported track components that used in maintenance MMSE Journal. Open Access www.mmse.xyz

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works. In Egypt, importing of the maintenance machines and most of railway lines in Egypt are assigned for passengers (i.e., these lines need to be maintained continuously for safety) affecting the value of cost. However, USA has the least value of maintenance cost, although it has the largest value of construction cost that is because most of railway lines in USA is freight transport so it does not need to be maintained continuously. For Germany, Switzerland, and Japan the maintenance costs are close to each other and the maintenance costs are larger than USA and less than Egypt because most of railway lines in these countries are assigned for passengers, so it need to be maintained continuously for safety. In addition, these countries manufacture the track components and machines of maintenance locally.

12000 10000 8000 6000 4000 2000 0 Germany

U.S.A

Egypt

Switzerland

Japan

Fig. 7. Different values of maintenance cost for one Km of track in some countries. Comparisons of the values of maintenance cost with the values of construction cost and percentage of the maintenance cost to the construction cost for the given countries are shown in figure (8). It is observed, in case of Japan, the percentage is the largest because it has the least value of construction cost and manufacturing the track component locally. However, the percentage in the case of USA is the least one because it has the largest value of construction cost and the least value of maintenance cost, because the most of railway lines in USA are freight transport. It is also observed that Egypt, Germany and Switzerland are lying in moderate range.

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40.9%

20.43%

30%

28.87% 6.85%

Egypt

Germany

U.S.A

Switzerland

Japan

Fig. 8. Percentage of the maintenance cost to the construction cost for one kilometre of track. Operational analysis in Egypt. The lack of maintenance works to bet executed in its time such as: replacing of the worn rails and replacing of the broken sleepers or bolts, resulted in increasing the number of train accidents and affects badly on the operation performance. Figure 9 shows the number of train accidents in the period from year 2001/2002 to year 2012/2013.

Fig. 9. Number of railway accidents. It is observed that the number of train accidents in years 2010/2011 and 2011/2012 is decreased because of stopping the train movement due to 25 th January revolution. However, in case of the other years number of train accidents is large because of the bad maintenance which resulted in increasing the number of train accidents and affects badly on the train operation performance. Summary. The conclusions of this paper have been summarized in the following: 1. Increasing the percentage of imported track components than the local track components resulted in increasing the construction and maintenance costs, and affects badly on the profitability rates for ENR. 2. Vossloh fastening system is the cost effective because its components have the minimum cost. 3. The construction cost for ENR equals 734000 â&#x201A;Ź, and comparing it with some other countries ( Germany, Switzerland, Australia, Japan), it has the second order. MMSE Journal. Open Access www.mmse.xyz

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4. The annual maintenance cost for ENR equals 10000 € and it has the largest value comparing with the studied cases. 5. The Percentage of the maintenance cost to the construction cost of one Km of track in Egypt equalsis 20.43 %. 6. The high value of maintenance cost in Egypt resulted in lack of periodical required maintenance activities which led to many train derailment accidents.. References [1] Satish Chandra, M.M. Agarwal (2007), Railway Engineering, 1st edition, Oxford university press, pp. 72, 338-339 [2] A. Lopez Pita, (2014), Railway Management and Engineering 4st edition, Ashgate publishing limited. [3] Michael T. McHenry, Jerry G. Rose, (2012), Railroad Subgrade Support and Performance Indicators, Report No.KTC-12-02/FR 136-04-6F [4] Malcom Kerr, (2012) Rail Defects Handbook, ch. 6, pp.49-63 [5] Australian Rail Track Corporation LTD, (2006), Rail defects handbook (paper) pp.14-17. [6] E.N.R., Guideline for Permanent way work, September, 1994. [7] Quandel consultants, LLC, (2011), Cost Estimating Methodology for High-Speed Rail on Shared Right-of-Way, pp. 3. [8] CE Delft, INFRAS &Fraunhofer ISI, (2008), External Costs of Transport in Europe, 2008. [9] Daniel Ling, (2005), Railway Renewal and Maintenance Cost Estimating, PhD Thesis Cranfield University (2005). [10] Jeffrey Tyler Von Brown (2011), Planning methodology for railway construction cost estimation in north America, master of science, Iowa State University. [11] Richard Lyon, (2012), Review of Lower Thames Crossing Capacity Options Output 3: Operating Costs, Maintenance Costs and Revenues Report, pp.5 [12] ARTC, Melbourne – Brisbane Inland Rail Alignment Study – Working Paper No. 11: Stage 2 Capital Works Costing, p p.27 [13] Georgios Michas, (2012), Slab Track Systems for High-Speed Railways, master degree project, Stockholm 2012, pp 77-79. [14] Heike Link, (2003), Rail Infrastructure Charging and on –Track Competition In Germany, Association for European Transport 2003. [15] J.P. Baumgartner (2001), Prices and costs in the Railway sector, January 2001, PP.1-3.

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VIII. Philosophy of Research and Education M M S E J o u r n a l V o l . 1 2

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About Teaching English Writing and Composition in the Active Technology-Enhanced Environment (on the Material of an Experimental 1 Project) M.S. Staton1,a, S.R. Nedbailik2,b 1− assistant professor, Ball State University, Muncie, USA 2 – assistant professor, Petrozavodsk State University, Petrozavodsk, Russia a – polyakov@bsu.edu b − snedbailik@mail.ru DOI 10.2412/mmse.91.38.737 provided by Seo4U.link

Keywords: project method, interactive environment, collaborative (team) work, constructivist theory, active studentcentered learning, teaching process intensifying, skills.

ABSTRACT. This paper regards different aspects of project method applying in teaching English writing and composition in the active technology-enhanced environment in higher schools. The authors describe their impressions of a joint multi-stage experimental research, carried out in Ball State University (Muncie, USA) in the frame of ILS (Interactive Learning Space) project. In this connection a special attention is paid to such problematic aspects as: interactive environment and , in particular, specially equipped node type classrooms configuration using in special subjects teaching; collaborative projects implementing advantages and disadvantages; students` team work organizing and supervising; assignments, tasks and exercises specially aimed at active students` learning working out; scholars` wide using their own electronic devices stimulating and real advantages in higher schools classrooms, etc. As far as the final experimental data and results obtained are concerned, one can obviously state most students` writing and composing skills and competences considerable progress in case of interactive environment enhanced active learning practice applying. The authors come to a conclusion, that the teaching process intensifying by means of interactive technologies and methods mass introducing as the result of learning process orientation towards the subject himself can doubtlessly provide effectiveness and success not only in higher schools system, but in the whole education space. In general, project methods can be considered as one of personally oriented technologies, based on the idea of developing learners` cognitive skills and competences, creative initiative, habits of independent thinking, what is especially important in the actual Life-long learning globally acknowledged concept.

Introduction. As far as it is known, the theoretical concept of active student – centered learning had originated in the constructivist philosophy long before it became the leading philosophy in education [10]. It is based on the concepts of apprenticeship and entrepreneurship (critical thinking and problem solving and postulates that new ideas take root in the prior knowledge of learners; therefore, the best educational projects are those that require the use of students’ personal interests and experiences [11]. Another tenet of this philosophy is that learners construct their own new knowledge, as they interact with reality or other students with different perspectives [8, 14]. Under this framework the teacher’s task is to help students personal interest in class assignments, require them to conduct hands-on, ex-periential research, and encourage collaboration. In this connection a particular importance is at-tributed to practically tended (inter)active technology enhanced PLM (Project learning methods) as optimal ones being primarily aimed at the key professional competences forming, gaining visible and valuable results what is in the actual context of LLL (lifelong learning) globally acknowledged con-cept [7], [9]. As a matter of fact, PLM using in foreign languages learning practice, for example, in scientific groups, research circles and societies is stipulated by an actual necessity of gaining suffi-cient competences and adequate skills in the sphere of independent research, such as collecting and treating of special material to be used in further oral and written speech activity. It goes without saying 1

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that in the process of projects (collective, individual, pair ones, etc.) fulfilling students are supposed to attain so much needed habits of creative thinking, new information independent analyzing, taking adequate decisions in non- standard situations frequently emerging in our life context. At the same time, they can also estimate fully enough the proper results of their own personal activity, using at most scholar, scientific, methodological and reference literature. Main text. The theoretical foundations of (inter)active learning itself were built primarily in the 1990s in connection with the massive introduction of computer-based technology in western education, in particular through the world-wide web (www), e-mail, forums and internet guiding systems (Smart-Board, Blackboard etc.). Of course, students` active role in teaching process presumes their constant using of various digital technical devices which become at present more and more indispensable in their every - day life and help to get new information [7]. One can state that in the frame of interactive learning students become the center of education process and obtain knowledge in course of research and experiments, and any teacher plays the role of a mentor or adviser and not a source of ready to use information [11]. Evidently, the emergence of multiple mobile and ubiquitous technologies in the 2000s gave a new impulse to using in education practice and theories of social nets and digital learning favoring learning-in-context scenarios [2]. Worldwide, frameworks are recently being de-veloped for the acquisition of digital competences, including the National Educational Technology Standards (ISTE) and the Framework for the 21st Century Learning (P21) in the United States, which “set a standard of excellence and best practices in learning, teaching and leading with technology in education” (ISTE 2012). The extensive research on technology-assisted active learning has yielded generally favorable results. Its quantitative aspect presumes that in active-learning classrooms teach-ers are becoming facilitators who supervise students to learn new ideas and practices [4]. At the same time, teachers promote student autonomy, self-determination, and choice [4]. In their turn, students are increasingly demanding excellence in teaching [3], seeking class environments where they can apply their knowledge and develop expertise. These two conditions considered, the benefits of learn-ing in an active environment, which is also technology-rich, seem to be obvious [5]. However, it has been suggested that technology in the classroom works best when it is “both pervasive and minimalist” [13], that is, provides many options, but is simple to use and not overwhelmingly present. More-over, for classroom technology to be used to its full advantage, faculty should be provided with qual-ity hands-on training, theoretical support, and a clear link between teaching in interactive classrooms and their individual teaching, research, and career interests. Still, a qualitative research on technology enhanced teaching has expressed some concerns. One of them is the divide between the digital haves and have nots, or between those learners who use or have access to telecommunications and infor-mation technologies and those who do not [16]. Another concern is the generational divide, which is similar to the digital one, but in regards of the age rather than income. The third obstacle to prolifer-ation of educational technology is insufficient teacher’s training, which makes teachers feel as per-petual novices having the need to catch up with the everchanging devices [6]. Under the circum-stances, “A disconnect exists between students’ comfort with using technology for learning and ttu-tors’ comfort in using technology for teaching. Students report the desire for more engaging technol-ogy-based assignments. Teachers cite multiple reasons for their hesitancy to use technology in their teaching” [6]. However, all three of the obstacles have never been considered insurmountable. As mandated by the American Recovery and Reinvestment Act (ARRA), on March 16, 2010, the FCC publically released its report, Connecting America: The National Broad band Plan. It seeks to “create a high-performance America,” which the FCC defines as “a more productive, creative, efficient America in which affordable broadband is available everywhere and everyone has the means and skills to use valuable broadband applications” [1]. The specific tasks leading to universal affordable access to broadband service are planned to be fulfilled by 2020 [1]. Beginning in the mid 1990s, many American universities started launching projects on active, technology-assisted learning. The pio-neering project was SCALE-UP (Student-Centered Active Learning Environment for Undergraduate Physics, later changed to Undergraduate Programs) in the North Carolina State University. The basic idea is that students are given something interesting to investigate. While they work in teams on these MMSE Journal. Open Access www.mmse.xyz

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"tangibles" (hands-on measurements or observations) and "ponderables" (interesting, complex problems), the instructor is free to roam around the classroom, asking questions, sending one team to help another, or asking why someone else got a different answer [1]. A similar project TEAL (Technology-enabled Active Leaning) was started in 2001 in Massachusetts Institute of Technology. It merges lectures, simulations, and hands-on desktop experiments to create a rich collaborative learning expe-rience in physics classes («TEAL»). Another such project is TILE (Transform, Integrate, Learn, En-gage) at the University of Iowa. A particular strength of the TILE Initiative is, first, its reach beyond the natural sciences to include social studies and humanities, and, second, its focus on providing training to the participating faculty (“TILE”). A similar active learning project was launched in the fall of 2012 at Ball State University under the title ILS (Interactive Learning Space). As a matter of fact, we started experimental teaching English Composition 104 and Composing Research in newly remodeled and equipped classrooms of the UniversityTeachers’ College, i.e. the node chair and the mediascape ones. The node chair classroom has twenty-four chairs on wheels with writing surfaces attached and a well for books and backpacks underneath. It also features three interactive Eno-boards and three portable huddle boards, besides the traditional dry board, and a teacher’s lap top station (Fig. 1).

Fig. 1. The node chair classroom. On one side is a nook with two armchairs, a traditional table and chairs, and a projector screen on the wall in the front. The other room is mediascape, which has four oval-shaped tables with six chairs around each of them, and a screen attached to one end. Besides, there is a teacher’s lap top station, a large screen attached to the wall, and a traditional dry board (Fig. 2). The screens can be operated from the teacher’s station or from individual students’ laptops.

Fig. 2. The mediascape classroom.

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The initial students’ reaction to the classroom configuration was unfavorable; the chairs arrangement seemed disorganized and not conducive to any serious learning. Our own reaction was somewhat similar; we spent more effort on trying to navigate around the chairs than delivering the class material. After several weeks, however, a nice solution was found by asking students to form a large circle and sitting in the circle with them ourselves. By the end of the first semester in ILS, we got the results of a survey conducted by the ILS administration. One comment stood out: “I like it [the classroom] but I do not think this class is the right one for it,” and I could see the point. To us, writing was taught as a heavily structured activity, done alone over many hours of rigorous work, and to start teaching it interactively, collaboratively, and on top of that with the use of the state-ofart technology, was going against our ingrained expectations. One more obstacle probably encountered when teaching English composition in a transparent interactive environment can concern the mental processes involved in writing [4]. This can be best demonstrated on a writing sample, undoubtedly not typical, taken from a junior student`s essay on the topic «Smiling as a habit»: «Many people in the United States and other western countries believe smile as distinct culture and fixed manner, it is essential in everyday activities. Still, in some places of the world the habit of smiling is not stereotyped. They smile only on the spot and not by habit. As for me, I do believe that to smile is always possible and sometimes necessary. First, smile hides all the bad emotions and gives us definite pleasure. People think that this man is all well and they themselves will be better from this. But the main thing is not to overstate this, but it may think that you are not all right in the head and you will be shunned. Smile always disposes a man to himself and helps to find a common language. Really, it is a magic key that can open practically every door. If people tried to smile more often at each other all the world would be probably much better and brighter». Of course, this citation (errors are in italics) clearly shows some gaps in a scholar`s knowledge that can be fairly easily filled in by referring to clear and specific rules in writing. Any possible teacher`s comments on it can`t be specific and clear enough for one reason: one is not sure what is going on here. The writer`s mental processes become to us quite opaque. Since we don`t know what made the student come up with this sentence, we can`t be thus sure how to lead him through the process of revising, let alone organize this process in such a manner that it is active, collaborative and technology-effective. Just for these reasons, even before we started the project implementing several strategies were developed to teach writing in an active, student-centered environment. First, we started making assignments, which were conducive to active learning, asking students to select topics that were relatable to them, preferably based on their previous knowledge and experience; besides, most of assignments required fieldwork. Second, we started giving students frequent feedback on their multiple drafts (or, more commonly, sample paragraphs). Over two or three semesters of using these two strategies, one could see a significant increase in the quality of the final projects we were getting, which was an indication that these strategies worked. About the effectiveness of two other strategies having been used we are not so sure. One is collaborative writing projects. As a rule we like them because they save time and effort; instead of commenting on, for example, twenty five individual projects, one has to deal with twelve or fewer. However, our students more than once expressed their dislike towards collaboration in class, primarily because of team loafers and having to pick up their shares in order to get a decent grade. Another problem consisted in our learners` usual overcharge with studies hindering much our meetings in extra school time. Besides all of them had undoubtedly quite different writing styles, which could hardly be adapted to each other. So in the very beginning of our experiment the pupils were given enough time for adapting to a collective style of essays composing by diving the whole work into several parts, for example, introduction, one or two paragraphs, etc., each of them being successively checked and commented upon. At last, a serious challenge is the «state-of-art» technology itself, i.e. special type interactive boards and mediascape. To tell the truth, the Microsoft Office with its builtin tools of dictionary, thesaurus, bibliography, and so on fits the purpose of writing, revising, and editing better than the ultra-modern equipment that we have got in our school classrooms. So, during our project experiment we did our best trying to find a way to use these devices in a manner, engaging for the students. In particular, we have just MMSE Journal. Open Access www.mmse.xyz

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tried to guide them through specially prepared materials or asked them to explore the web on their own with the help of personal digital devices having access to the internet. Another, more substantial, reason why we are still not sure about the benefits of collaboration in writing is that so far one has been unable to supervise the team work in classes effectively. A recent example is a group project on writing a literature review on “Steroids in Sports: Recent Discoveries and Sanctions.” The three students working on the project came up with three subsections of the review, each written individually, and failed to edit the final paper for a unified voice and style; as a result, the paper turned out to be three individual efforts instead of one collaborative. In our turn, we were unable to detect the problem in time or successfully reverse the process. Another challenge is the ILS technology, the Eno-boards and mediascape. So far, we have not found a way to use these devices in a manner that would be integral to our pedagogy, engaging for students, and personally satisfactory to us. One feels that the Microsoft Office with its built-in tools of dictionary, thesaurus, bibliography, and so on fits the purpose of writing, revising, and editing better than the interactive equipment we have in our classrooms. However, we did make other discoveries in the pedagogical use of technology. Thus, one seldom stands at the teachers’ lap top station anymore; instead, we sit in a large circle at the same eye level with students and either guide them through the materials prepared for a particular class or ask them to explore the web on their own with the help of their own digital devices with access to the internet. For example, in our discussion about visual rhetoric we ask them to log into the home page of New York Museum of Modern Art (MOMA) and navigate through its whole collection, directing them to particular pieces for discussion. Alternatively, they are asked to find certain information on the web using sets of key words. In this way our instructions become at once student-centered (active) and technology-enhanced. Therefore, gradually the students are getting used to a so called «collaborative (team) writing». While working at the project we have also discovered, that our instructions and guiding actions alone turn out to be not sufficient; one should also pay attention to the psychological factor, that is considering the students` personal character, temperament features. It`s quite necessary in order to eliminate arguing, conflicts, quarrels, possibly emerging in such a context. In this connection we tried to use the so called Leadership Compass2 - a special guide elaborated for collaborative work on the base of North American Indians` practice of keeping healthy relations in a tribe [8], [9]. Therefore, just at the first project studies the scholars were to guess what personal type they can relate themselves to: the northern type – a warrior, the southern type - a quack, the western type – a teacher or the eastern type – a prophet. After that we lead a discussion on the point: what features of this or that personal type should be taken into consideration while working in a team. All over the period of project learning, the students were also offered to fulfill the following tasks: to estimate their own contribution into the whole work, to express their wishes towards other group members and to analyze the results of collaborative efforts. At the final stage of our project activity we could see quite clearly a considerable improving of students` speech habits and, in particular, of their writing and composing skills, what can be proved by their successful participation in a multi-serial quiz «Discovery» elaborated and carried out by our teachers within 2013-2015 academic period. The first prizes in the final rating were taken by scholars – participants of the experiment, having gained maximal points in the second contest tour devoted to free composition. Of course, it shows high effectiveness of PLM, presenting a so called «starting ground» for applying various teaching technologies, and this is provided primarily by its basic person- tended approach, making a student an active subject of learning process. It is quite obvious that the teaching process intensifying by means of interactive technologies and methods mass introducing as the result of learning process orientation towards the subject himself provides its effectiveness and success not only in the higher schools system, but in the whole education space. In particular, in modern life-long learning context interactive teaching stimulating methods such as business and role games, case-methods, Evristic conversations, brain attacks, discussions, etc. are used rather widely as most 2

For the first time we learned about Leadership Compass from the materials of a scientific - research conference On Course (On Course National Conference), Long Beach, California, 2012. The description and recommendations for using this Compass are widely accessible in the Internet, for example, Leadership compass: Appreciating Diverse Work Styles http://bonnernetwork.pbworks.com/f/BonCurLeadershipCompass.pdf . MMSE Journal. Open Access www.mmse.xyz

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adequately corresponding to the main tasks of key competences forming. In this connection the highest value is also attained by higher schools practical (collaborative) projects claiming the necessity of systematic and multi-aspect problematic research. In the course of such projects (pair, team, individual) realizing students also gain necessary habits of effective using scholar, methodical, scientific and reference literature. As for educational technology, it can be broadly viewed as an array of tools that prove helpful in advancing students` learning, that is computers and other digital devices, as well as encompassing methods, approaches, and techniques. The Greek word “techne” itself initially means “craft” or “art,” so the concept of educational technology may be extended to include any techniques an educator uses for the advancement of knowledge in his or her class. Summary. On the whole, project methods can be considered as one of personally oriented technologies, based on the idea of developing learners` cognitive skills and competences, creative initiative, habits of independent thinking, making prognoses, using original sources, finding and solving problems, orienting in the information space, estimating the results of personal activity, adapting to rapidly changing conditions of every-day life. Any teacher, working in the interactive environment has to know the bases of education constructivist theory and resulting concepts. But of course not less important is constant communication with colleagues - practitioners while discussing emerging in teaching practice problems and searching for appropriate ways of their solving. Evidently, the most effective method is stimulating the experience permanent exchange by means of conferences and seminars organizing in the form of so called workshops, where one can demonstrate any methodological findings, as well as carrying out «open classes» and master-class type studies with publishing methodological materials in various editions. Also valuable are periodical technical trainings of teachers, who not only acquire professional support, but also have at their disposal a wide scope of different didactic, technical skills and a whole collection of needed methodological elaborations. All this will surely contribute to the interactive learning level enhancing, what stimulates in its turn students` interest for higher education in general. References [1] H.T. Alert, About the SCALE-UP Project, NC State University, 2007. [2] K. Aesaert, The content of educational technology curricula: a cross-curricular state of the art, Educational Technology Research and Development, Plenum Press, 2013, P. 131-151. [3] E.R. Auster, K.K. Wylie (2006), ‘Creating active learning in the classroom: A systematic approach’, Journal of Management Education, Vol. 30, No 2, pp 333–353. [4] J.S. Brown, New Learning Environments For The 21st Century: Exploring The Edge. Change. New scientific research, 2006, 38 (5), P. 18-24. [5] Y.J. Dori, How Much Have They Retained? Making Unseen Concepts Seen in a Freshman Electromagnetism Course at MIT. Journal of Science Education and Technology, (2007), 6(4), P. 299-323, DOI 10.1007/s10956-007-9051-9 [6] M. Dornisch, The Digital Divide in Classrooms: Teacher Technology Comfort and Evaluations. Computers In The Schools, Academic Search Premier, 2013, P. 210-228. [7] C.T. Fosnot, Constructivism: Theory, Perspectives, and Practice, College Teachers Prints, 1996, P. 234-278. [8] B. Jaworski, Investigating Mathematics Teaching: A Constructivist Enquiry, Bristol, P. Falmer Print, 1994. [9] J. Keengwe, G. Onchwari, P. Wachira, Computer Technology Integration and Student Learning: Barriers and Promise, Journal of Science Education and Technology, December 2008, 17(6), P. 560565, DOI 10.1007/s10956-008-9123-5 [10] A. Kukla, J. Walmsley, Mind: A Historical and Philosophical Introduction to the Major Theories, Indianapolis, Hackett Pub. Co, 2006. MMSE Journal. Open Access www.mmse.xyz

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[11] R.S. Prawat, R.E. Floden, Philosophical Perspectives on Constructivist Views of Learning. Ed-ucational Psychology, 1994, 29 (1), P. 37-48, DOI 10.1207/s15326985ep2901_4 [12] Rotgans JI, Schmidt HG (2011) The role of teachers in facilitating situational interest in an active-learning classroom. Teaching and Teacher Education 27(1): 37–42. [13] P.A. Soderdahl, Library Classroom Renovated as an Active Learning Classroom, Library High Tech, 2011, 29(1), P. 83-90, DOI 10.1108/07378831111116921 [14] L. Steff, J. Gale, Constructivism in Education, N.J., Hillsdale Press, 1995. [15] K. Terner, TEAL – Technology Enabled Active Learning, MIT iCampus, 1999-2013. [16] L. Wei, D. Hindman, Does the Digital Divide Matter More? Comparing the Effects of New Media and Old Media Use on the Education-Based Knowledge Gap, Mass Communication and Society, 2011, 14 (1), P. 216-235. [17] R. Zevenbergen, S. Lerman, Learning Environments Using Interactive Whiteboards, New Learning Spaces or Reproduction of Old Technologies? Mathematics Education Research Journal, 2008, P.78-94.

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