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Optimization of Friction Stir Processing parameters for manufacturing silicon carbide reinforced aluminum 7075-T651 surface composite
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 18 (2019) 4549–4555
www.materialstoday.com/proceedings
ICMPC-2019
Optimization of Friction Stir Processing parameters for manufacturing silicon carbide reinforced aluminum 7075-T651 surface composite Veeresh Murthya*, Dileep Kumar. Sb, Saju. K. Kc, B. M. Rajaprakashd, R. Rajashekare a
*
Research scholar, Department of Mechanical Engineering, UVCE, Bangalore, INDIA Assistant Professor, Department of Mechanical Engineering, DSATM, Bangalore, INDIA b PG Student, Department of Mechanical Engineering, UVCE, Bangalore, INDIA c PG Student, Department of Mechanical Engineering, UVCE, Bangalore, INDIA d Professor, Department of Mechanical Engineering, UVCE, Bangalore, INDIA e Assistant Professor, Department of Mechanical Engineering, UVCE, Bangalore, INDIA
Abstract Metal Matrix Composites are extensively used in several engineering applications with Aluminum as the matrix material because of their higher specific strength. In this proposed work, Aluminum Al 7075-T651 is used as matrix and Silicon Carbide (SiC) is used as reinforcement to develop a Metal Matrix Surface Composite by Friction Stir Processing technique. Optimization of Friction Stir Processing (FSP) is done by Taguchi technique where the process parameters including Tool Rotational (TR) Speed, Tool Traverse (TT) Speed and diameter of hole used to fill reinforcement is optimized for high Tensile Strength (TS) of the produced surface Composite. The relative significance of the FSP process parameters with respect to TS is investigated by Analysis of Variation (ANOVA). © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019 Keywords: FSP, Taguchi technique, Analysis of Variation (ANOVA), TR speed, TT speed, Tensile strength.
* Corresponding author. Tel.:+91-9008169799. E-mail address: [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
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V. Murthy et al./ Materials Today: Proceedings 18 (2019) 4549–4555
1. Introduction FSP was established as a common tool for microstructural alteration based on the basic working principles of Friction Stir Welding. FSP is illustrated in Figure 1. To carry out FSP, a region within a plate is selected and a specifically designed rotating FSP tool is plunged into the selected region of workpiece. The FSP tool has a predefined pin and shoulder features. When it is plunging into the workpiece, the rotating pin and shoulder face contacts with the workpiece and rapid friction heats and softens a small column of metal. The FSP tool pin and shoulder control the penetration depth [10] [11][12]. The FSP tool shoulder provides compressive force that includes upward plasticized metal flow, with narrow zone caused by the tool pin. In essence, FSP is a local, thermomechanical metal processing method that alters the local properties without influencing properties in the rest of the structure [1][2][3].
Figure 1. Schematic illustration of FSP
The Tensile strength of the resulting surface composite is the significant performance parameter of interest which depends on FSP process parameters including TR speed, TT speed, number of tool passes, diameter of the hole on the work piece, tool tilt angle, tool plunge depth, and process distance. Among these input parameters, TR speed, TT speed, diameter of the hole on the work piece, have been studied for experimental design [4][5]. FSP Process parameters are controllable machining input factors that resolve the conditions in which machining is accomplished. They impact the process performance results, which are measured using several performance techniques. Among several optimizing techniques available, Taguchi technique is found to be very efficient and provides systematic path to design the experiments and optimize the manufacturing processes [6]. The aim of this research paper is to determine the optimum FSP process parameters by using Taguchi technique for maximum tensile strength of the resulting surface composite fabricated using Al 7075-T651 as matrix material & SiC as reinforcement material. 2. Materials and methodology 2.1. Materials used: Aluminum Al-7075-T651: The alloy chosen for this work is Al 7075 alloy as base material. It is one of the high strength aluminum alloys, that renders itself favorably to heat treatment, and its chemical composition is given in the Table 1 Table 1. Chemical composition of base material Content Weight %
Al
Cu
90.245 1.597
Mg
Si
Fe
2.215
0.057
0.257
Mn
Ni
Pb
Sn
Ti
Zn
Cr
0.074 0.047 0.024 0.010 0.031 5.206 0.237
Silicon carbide(SiC): SiC has been recognized as an important structural ceramic material because of its unique combination of properties, such as excellent mechanical and thermal properties. Such a combination of properties is
V. Murthy et al./ Materials Today: Proceedings 18 (2019) 4549–4555
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determined by the highly covalent (up to 88%) chemical bonding between silicon and carbon atoms. SiC selected has a grain size in the range of 10 to 20 micrometer and the weight percentage of Silicon in SiC is 98.30% and Carbon in SiC is 1.7% [7][8]. 2.2. FSP Methodology FSP was conducted by using 5 – axis friction stir welder on plate with 1mm, 2mm and 3mm hole diameters to fill SiC powder. The parameters selected for FSP are listed in Table 2. Table 2. Selected FSP parameters for experimentation. PROCESS PARAMETERS FSP Tool rotational speed (rpm) Tool Traverse speed (mm/min) Tilt angle (deg) Process distance (mm) Plunge depth(mm)
Single pass 710/900/1000 10/20/30 2 65 4.2
a. Preparation of Al-7075 plate: Commercial heat treated Al-7075 T651 plate was machined by using milling machine to the dimension of 300 x 75 x 6mm as depicted in Fig.2.
Figure. 2. Aluminum Plate.
By using 5 Axis FSW machine 1mm, 2mm and 3mm diameter holes with the pitch distance of 5mm are drilled on the plate to fill SiC powder as illustrated in below Fig. 3 (a-c).
a
b
c
Figure. 3: Holes drilled on Aluminium plate a) 1mm Diameter, b)2mm Diameter and c) 3mm Diameter.
b. Friction Stir Processing: In the process of development of Metal Matrix Composite, the surface composite material is prepared by impregnating silicon carbide powder into the drilled hole of 1mm, 2mm and 3mm diameters. Table 3 shows the FSP tool nomenclature used for friction stir processing. Friction stir process was carried out by using 5 – axis friction stir welder on plate with 1mm, 2mm and 3mm hole diameters to fill Silicon Carbide (SiC) powder, as shown in Fig. 4.
4552
V. Murthy et al./ Materials Today: Proceedings 18 (2019) 4549–4555 Table 3. Selected FSP tool. Tool profile
Tool material Shoulder diameter Shoulder length Pin shape Pin length
High carbon high chromium die steel (HCHCr) 30mm 20mm Truncated Pentagon 4mm
Figure. 4. FSPing using FSW machine.
c. The Taguchi method is a powerful Design of Experiment (DoE) technique to decrease the number of trials significantly by a specially planned Orthogonal Array (OA), which can accommodate the selected manufacturing parameters for the analysis. Furthermore, Signal to Noise ratio (S/N) reflecting both the amount of variation present and the mean response of several repetitions can be used in Taguchi method to measure the amount of variability in the response data. The S/N can minimize the effects of noise and identify control factors settings, thus reducing the sensitivity of the system performance to a source of variation. The Taguchi method has been actively used to examine the contributing effects of manufacturing parameters on the enhancement of surface composite performance [6]. 3. Experimentation Plan 3.1. Selected FSP parameters and Levels. In order to optimize the FSP for high Tensile Strength of surface composites, it is necessary to get the range of parameters. The range selected Tool Rotational speed is 710, 900 and 1000 rpm. [7], [8]. In case of FSP tool traverse speed (Feed rate), the range selected is 10, 20 and 30 mm/min and hole diameter range selected is 1, 2 and 3 mm. Table. 4 shows the control parameters selected, and their corresponding levels for developing surface composite with an objective to achieve high tensile strength.
Table 4. Control Parameters and Levels Sl.No.
Level 1
Level 2
Level 3
1
Tool Rotational speed (rpm)
Control Parameters
710
900
1000
2
Tool Traverse speed (mm/min)
10
20
30
3
Hole diameter (mm)
1
2
3
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3.2. Design of experiments and data analysis. For the three control parameters and three levels selected, a set of 9 experiments are performed based on L9 orthogonal array as listed in Table 5. The Ultimate Tensile Strength (UTS) determined from experiments and S/N ratio computed are tabulated. 3.3. Mechanical Characterization. Ultimate tensile strength is the maximum stress that a material can withstand while being stretched before fracture. The tensile test specimen was prepared according to ASTM E8 standard. The specimens of length 45mm, width 6 mm, thickness 6 mm and gauge length of 20 mm were tested with a cross head speed of 0.9 mm / min. The Universal Testing Machine, Instron 1195 used in tensile testing is shown in Fig.5 and tensile test specimen is illustrated in Fig.6. Table 5. Experimental Design using L9 Orthogonal Array. Expt No 1 2 3 4 5 6 7 8 9
Tool Rotational Speed (rpm)
Tool Traverse Speed (mm/min)
(A) 710 710 710 900 900 900 1000 1000 1000
Hole Diameter (mm)
Tensile Strength
(B)
(C)
(MPa)
10 20 30 10 20 30 10 20 30
1 2 3 2 3 1 3 1 2
290.80 348.50 290.80 351.60 236.75 292.30 294.90 321.60 297.80
Figure. 5. UTM setup for Tensile test
S/N ratio
49.2738 50.8440 49.2718 50.9209 47.4857 49.3165 49.3934 50.1463 49.4784
Figure. 6. Prepared Tensile test dog bone specimens.
4. Results and Discussion 4.1. Determination of optimum parameters The effect of three process parameters on UTS is shown in graphically in Fig.7. Using MINITAB 18, response tables for S/N ratio of UTS is calculated as shown in Table 6. Based on the analysis of S/N ratio, the optimum volume fractions for UTS along with their corresponding levels are obtained and is listed in Table 7. Main Effects Plot for SN ratios Data Means
A
M eanof SNratios
50.5
B
C
50.0
49.5
49.0
48.5 710
900
1000
10
20
30
Signal-to-noise: Larger is better
Figure.7. Main effects plot for UTS.
1
2
3
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V. Murthy et al./ Materials Today: Proceedings 18 (2019) 4549–4555
From Figure. 7, the optimum percentage of reinforcements for maximum tensile strength is identified and shown in Table 7. Table 6. Response table for S/N ratio
LEVEL 1 2 3 Delta Rank
Tool Rotational Speed (rpm) (A) 49.7965 49.2410 49.6727 0.5555 2
Tool Feed Rate (mm/min) (B) 49.8627 49.4920 49.3555 0.5072 3
Table 7. Optimum Composition of Reinforcements Parameter
Hole Diameter (mm) (C) 49.5788 50.4144 48.7169 1.6975 1
Level
Optimum Value
Tool Rotation Speed (rpm) (A)
1
710
Feed rate (mm/min) (B)
1
10
Hole diameter (mm) (C)
2
2
4.2. Ultimate tensile strength Tensile test was conducted for surface composite developed using optimum FSP parameters and Al 7075-T651 base material. Table 8 lists the UTS of surface composite and base material. Table 8 Ultimate tensile strength of surface composite Trial #1 1 2 3
UTS (MPa) 350.13 348.20 346.99
Average UTS of Surface Composite(MPa)
UTS of Base Material Al 7075-T651(MPa)
348.44
383.60
4.2. Confirmation experiment for Ultimate Tensile Strength Table 9. Optimal conditions of experimental and predictions
S/N Ratio Tensile strength(MPa) Error %
Prediction 50.929
Experimental 50.885
351.96
348.44 1
The best combination of FSP control parameters has been determined by using optimization method. However, the last step is to predict and verify the enhancement of the observed values through the use of the best combination level of volume fractions. The confirmation experiments were performed by conducting a quantifying test with particular combination of the process factors and levels previously assessed. After determining the best conditions and predicting the response under these conditions, a new experiment was designed and conducted with the optimum levels of the selected reinforcement volume fractions. Table 9 shows the comparisons of the experimental results for the optimal conditions with predicted results for optimal TS. 4. Conclusion The experimental investigation on the development of surface composites by FSP by optimization of its process parameters for high tensile strength leads to the following conclusions: The successful development and fabrication of a surface composite by FSP using Al 7075-T651 as matrix material and SiC as the reinforcement. The optimum process parameters in FSP for higher tensile strength is determined for surface composite using Taguchi’s technique. The optimum FSP parameters for higher tensile strength determined is Tool rotational speed =710 rpm, Tool traverse speed=10mm/min and Hole diameter on base material =2mm. The experimental tensile strength obtained by UTM for surface composite specimen fabricated by optimum FSP parameters is 348.44MPa. The tensile strength of base material Al 7075-T651 is 383.60MPa. Hence, there is a decrease of 9.16% in the Tensile Strength of produced surface composite due to the dynamic recrystallization of material during the single pass FSPing applicable only to a limited depth from the surface.
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Acknowledgements The Author* wishes to express deep gratitude to Dr. Satish. V. Kailas, Professor, Department of Mechanical Engineering, IISc, Bangalore who provided support, inputs and discussions during the course of research and the help extended towards our experimentation. References [1]. M. Puviyarasan, C. Praveen.(2011) "Fabrication and Analysis of Bulk SiCp Reinforced Aluminum Metal Matrix Composite using Friction Stir Process". World Academy of Science, Engineering and Technology, International Journal of Mechanical and Mechatronics Engineering. vol:5, No: 10. [2]. R. Dhayalan, K. Kalaiselvan, R. Sathish Kumar. (2014) "Characterization of AA6063/SiC-Gr Surface Composite Produce by Friction Stir Processing Technique". Procedia Engineering 97. 625 - 631. www.elsevier.com/locate/procedia. [3]. Vipin Sharma, U. Praskash, B. V Manoj Kumar. (2015) "Microstructure and Mechanical Characteristics of AA2014/Sic Surface Composite Fabricated by Friction Stir Processing ", Materials Today: Proceeding 2. 2666 - 2670. www.sciencedirect.com. [4]. Rajesh and Prabhakar Kaushik. (2017). "Wear Analysis of Surface Composites of AA6063/SiC Produced by Friction Stir Processing using Taguchi Technique". International Journal of Applied Engineering Research ISSN 0973 - 4562 volume 12, pp. 11981 - 11988. [5]. Sahil Nagia, Deval Kulshrestha, Prabhat Kumar, V. Jeganathan, Ranganathan M. Sinagari. (2017) "Analysis of Microstructure, Microhardness, Tensile Strength and Wear Properties of Al6082/SiC Composite using Multi-Pass Friction Stir Processing ". International Journal of Mechanical and Production Engineering, ISSN : 2320 - 2092. volume 5, Issue - 4, April - 2017. [6]. M.Puviyarasan, V. S. Senthil Kumar (2012). "Optimization Of Friction Stir Processing parameter In Fabricating AA6061/Sic Composites". Procedia Engineering 38. 1094 - 1103. www.elsevier.com/locate/procedia. [7]. Sert, O. N. Celik.(2014). "Wear Behavior of SiC Reinforced Surface Composite Al4075-T651 Aluminium Alloy Produced using Friction Stir Processing ". Indian Journal of Engineering and Materials Sciences. vol. 21, pp.35 – 44. [8]. Rajesh and Dr. Prabhakar Kaushik. (2017). "Wear Analysis of Surface Composites of AA6063/SiC Produced by Friction Stir Processing using Taguchi Technique". International Journal of Applied Engineering Research ISSN 0973 - 4562 volume 12, pp. 11981 - 11988. [9]. Veeresh Murthy, B.M.Rajaprakash, “Investigation on the effect of Friction Stir Processing on Tribological and Mechanical properties of Al 7075-T651 Alloy”, American Institute of Physics (AIP)1943, 020049(2018); DOI:10.1063/1.5029625. [10].Veeresh Murthy, Kalmeshwar Ullegaddi, Mahesh.B, B.M. Raja Prakash, “Application of Image Processing and Acoustic Emission Technique in Monitoring of Friction Stir Welding Process”, Elsevier Materials Today: Proceedings**, Vol 4, Issue 8, 2017, Page No 9186– 9195, https://doi.org/10.1016/j.matpr.2017.07.276. [11].Kalmeshwar Ullegaddi, Veeresh Murthy, Harsha R N, Manjunatha “Friction Stir Welding Tool Design and Their Effect on Welding of AA6082 T6”, Elsevier Materials Today: Proceedings, Vol 4, issue 8, Page No 7962–7970, 2017, https://doi.org/10.1016/j.matpr.2017.07.133. [12].Veeresh Murthy, Kalmeshwar Ullegaddi, Mahesh.B, B.M.Rajaprakash, “Study on influence of concave geometry shoulder tool in Friction Stir Welding (FSW) by using image processing and acoustic emission techniques”, Elsevier Materials Today: Proceedings5(2018), ISSN 2214-7853, Vol 5/13P3, PP 27004-27017. Van der Geer, J.A.J. Hanraads, R.A. Lupton, J. Sci. Commun. 163 (2000) 51–59.
ScienceDirect Materials Today: Proceedings 18 (2019) 4549–4555
www.materialstoday.com/proceedings
ICMPC-2019
Optimization of Friction Stir Processing parameters for manufacturing silicon carbide reinforced aluminum 7075-T651 surface composite Veeresh Murthya*, Dileep Kumar. Sb, Saju. K. Kc, B. M. Rajaprakashd, R. Rajashekare a
*
Research scholar, Department of Mechanical Engineering, UVCE, Bangalore, INDIA Assistant Professor, Department of Mechanical Engineering, DSATM, Bangalore, INDIA b PG Student, Department of Mechanical Engineering, UVCE, Bangalore, INDIA c PG Student, Department of Mechanical Engineering, UVCE, Bangalore, INDIA d Professor, Department of Mechanical Engineering, UVCE, Bangalore, INDIA e Assistant Professor, Department of Mechanical Engineering, UVCE, Bangalore, INDIA
Abstract Metal Matrix Composites are extensively used in several engineering applications with Aluminum as the matrix material because of their higher specific strength. In this proposed work, Aluminum Al 7075-T651 is used as matrix and Silicon Carbide (SiC) is used as reinforcement to develop a Metal Matrix Surface Composite by Friction Stir Processing technique. Optimization of Friction Stir Processing (FSP) is done by Taguchi technique where the process parameters including Tool Rotational (TR) Speed, Tool Traverse (TT) Speed and diameter of hole used to fill reinforcement is optimized for high Tensile Strength (TS) of the produced surface Composite. The relative significance of the FSP process parameters with respect to TS is investigated by Analysis of Variation (ANOVA). © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019 Keywords: FSP, Taguchi technique, Analysis of Variation (ANOVA), TR speed, TT speed, Tensile strength.
* Corresponding author. Tel.:+91-9008169799. E-mail address: [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
4550
V. Murthy et al./ Materials Today: Proceedings 18 (2019) 4549–4555
1. Introduction FSP was established as a common tool for microstructural alteration based on the basic working principles of Friction Stir Welding. FSP is illustrated in Figure 1. To carry out FSP, a region within a plate is selected and a specifically designed rotating FSP tool is plunged into the selected region of workpiece. The FSP tool has a predefined pin and shoulder features. When it is plunging into the workpiece, the rotating pin and shoulder face contacts with the workpiece and rapid friction heats and softens a small column of metal. The FSP tool pin and shoulder control the penetration depth [10] [11][12]. The FSP tool shoulder provides compressive force that includes upward plasticized metal flow, with narrow zone caused by the tool pin. In essence, FSP is a local, thermomechanical metal processing method that alters the local properties without influencing properties in the rest of the structure [1][2][3].
Figure 1. Schematic illustration of FSP
The Tensile strength of the resulting surface composite is the significant performance parameter of interest which depends on FSP process parameters including TR speed, TT speed, number of tool passes, diameter of the hole on the work piece, tool tilt angle, tool plunge depth, and process distance. Among these input parameters, TR speed, TT speed, diameter of the hole on the work piece, have been studied for experimental design [4][5]. FSP Process parameters are controllable machining input factors that resolve the conditions in which machining is accomplished. They impact the process performance results, which are measured using several performance techniques. Among several optimizing techniques available, Taguchi technique is found to be very efficient and provides systematic path to design the experiments and optimize the manufacturing processes [6]. The aim of this research paper is to determine the optimum FSP process parameters by using Taguchi technique for maximum tensile strength of the resulting surface composite fabricated using Al 7075-T651 as matrix material & SiC as reinforcement material. 2. Materials and methodology 2.1. Materials used: Aluminum Al-7075-T651: The alloy chosen for this work is Al 7075 alloy as base material. It is one of the high strength aluminum alloys, that renders itself favorably to heat treatment, and its chemical composition is given in the Table 1 Table 1. Chemical composition of base material Content Weight %
Al
Cu
90.245 1.597
Mg
Si
Fe
2.215
0.057
0.257
Mn
Ni
Pb
Sn
Ti
Zn
Cr
0.074 0.047 0.024 0.010 0.031 5.206 0.237
Silicon carbide(SiC): SiC has been recognized as an important structural ceramic material because of its unique combination of properties, such as excellent mechanical and thermal properties. Such a combination of properties is
V. Murthy et al./ Materials Today: Proceedings 18 (2019) 4549–4555
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determined by the highly covalent (up to 88%) chemical bonding between silicon and carbon atoms. SiC selected has a grain size in the range of 10 to 20 micrometer and the weight percentage of Silicon in SiC is 98.30% and Carbon in SiC is 1.7% [7][8]. 2.2. FSP Methodology FSP was conducted by using 5 – axis friction stir welder on plate with 1mm, 2mm and 3mm hole diameters to fill SiC powder. The parameters selected for FSP are listed in Table 2. Table 2. Selected FSP parameters for experimentation. PROCESS PARAMETERS FSP Tool rotational speed (rpm) Tool Traverse speed (mm/min) Tilt angle (deg) Process distance (mm) Plunge depth(mm)
Single pass 710/900/1000 10/20/30 2 65 4.2
a. Preparation of Al-7075 plate: Commercial heat treated Al-7075 T651 plate was machined by using milling machine to the dimension of 300 x 75 x 6mm as depicted in Fig.2.
Figure. 2. Aluminum Plate.
By using 5 Axis FSW machine 1mm, 2mm and 3mm diameter holes with the pitch distance of 5mm are drilled on the plate to fill SiC powder as illustrated in below Fig. 3 (a-c).
a
b
c
Figure. 3: Holes drilled on Aluminium plate a) 1mm Diameter, b)2mm Diameter and c) 3mm Diameter.
b. Friction Stir Processing: In the process of development of Metal Matrix Composite, the surface composite material is prepared by impregnating silicon carbide powder into the drilled hole of 1mm, 2mm and 3mm diameters. Table 3 shows the FSP tool nomenclature used for friction stir processing. Friction stir process was carried out by using 5 – axis friction stir welder on plate with 1mm, 2mm and 3mm hole diameters to fill Silicon Carbide (SiC) powder, as shown in Fig. 4.
4552
V. Murthy et al./ Materials Today: Proceedings 18 (2019) 4549–4555 Table 3. Selected FSP tool. Tool profile
Tool material Shoulder diameter Shoulder length Pin shape Pin length
High carbon high chromium die steel (HCHCr) 30mm 20mm Truncated Pentagon 4mm
Figure. 4. FSPing using FSW machine.
c. The Taguchi method is a powerful Design of Experiment (DoE) technique to decrease the number of trials significantly by a specially planned Orthogonal Array (OA), which can accommodate the selected manufacturing parameters for the analysis. Furthermore, Signal to Noise ratio (S/N) reflecting both the amount of variation present and the mean response of several repetitions can be used in Taguchi method to measure the amount of variability in the response data. The S/N can minimize the effects of noise and identify control factors settings, thus reducing the sensitivity of the system performance to a source of variation. The Taguchi method has been actively used to examine the contributing effects of manufacturing parameters on the enhancement of surface composite performance [6]. 3. Experimentation Plan 3.1. Selected FSP parameters and Levels. In order to optimize the FSP for high Tensile Strength of surface composites, it is necessary to get the range of parameters. The range selected Tool Rotational speed is 710, 900 and 1000 rpm. [7], [8]. In case of FSP tool traverse speed (Feed rate), the range selected is 10, 20 and 30 mm/min and hole diameter range selected is 1, 2 and 3 mm. Table. 4 shows the control parameters selected, and their corresponding levels for developing surface composite with an objective to achieve high tensile strength.
Table 4. Control Parameters and Levels Sl.No.
Level 1
Level 2
Level 3
1
Tool Rotational speed (rpm)
Control Parameters
710
900
1000
2
Tool Traverse speed (mm/min)
10
20
30
3
Hole diameter (mm)
1
2
3
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3.2. Design of experiments and data analysis. For the three control parameters and three levels selected, a set of 9 experiments are performed based on L9 orthogonal array as listed in Table 5. The Ultimate Tensile Strength (UTS) determined from experiments and S/N ratio computed are tabulated. 3.3. Mechanical Characterization. Ultimate tensile strength is the maximum stress that a material can withstand while being stretched before fracture. The tensile test specimen was prepared according to ASTM E8 standard. The specimens of length 45mm, width 6 mm, thickness 6 mm and gauge length of 20 mm were tested with a cross head speed of 0.9 mm / min. The Universal Testing Machine, Instron 1195 used in tensile testing is shown in Fig.5 and tensile test specimen is illustrated in Fig.6. Table 5. Experimental Design using L9 Orthogonal Array. Expt No 1 2 3 4 5 6 7 8 9
Tool Rotational Speed (rpm)
Tool Traverse Speed (mm/min)
(A) 710 710 710 900 900 900 1000 1000 1000
Hole Diameter (mm)
Tensile Strength
(B)
(C)
(MPa)
10 20 30 10 20 30 10 20 30
1 2 3 2 3 1 3 1 2
290.80 348.50 290.80 351.60 236.75 292.30 294.90 321.60 297.80
Figure. 5. UTM setup for Tensile test
S/N ratio
49.2738 50.8440 49.2718 50.9209 47.4857 49.3165 49.3934 50.1463 49.4784
Figure. 6. Prepared Tensile test dog bone specimens.
4. Results and Discussion 4.1. Determination of optimum parameters The effect of three process parameters on UTS is shown in graphically in Fig.7. Using MINITAB 18, response tables for S/N ratio of UTS is calculated as shown in Table 6. Based on the analysis of S/N ratio, the optimum volume fractions for UTS along with their corresponding levels are obtained and is listed in Table 7. Main Effects Plot for SN ratios Data Means
A
M eanof SNratios
50.5
B
C
50.0
49.5
49.0
48.5 710
900
1000
10
20
30
Signal-to-noise: Larger is better
Figure.7. Main effects plot for UTS.
1
2
3
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V. Murthy et al./ Materials Today: Proceedings 18 (2019) 4549–4555
From Figure. 7, the optimum percentage of reinforcements for maximum tensile strength is identified and shown in Table 7. Table 6. Response table for S/N ratio
LEVEL 1 2 3 Delta Rank
Tool Rotational Speed (rpm) (A) 49.7965 49.2410 49.6727 0.5555 2
Tool Feed Rate (mm/min) (B) 49.8627 49.4920 49.3555 0.5072 3
Table 7. Optimum Composition of Reinforcements Parameter
Hole Diameter (mm) (C) 49.5788 50.4144 48.7169 1.6975 1
Level
Optimum Value
Tool Rotation Speed (rpm) (A)
1
710
Feed rate (mm/min) (B)
1
10
Hole diameter (mm) (C)
2
2
4.2. Ultimate tensile strength Tensile test was conducted for surface composite developed using optimum FSP parameters and Al 7075-T651 base material. Table 8 lists the UTS of surface composite and base material. Table 8 Ultimate tensile strength of surface composite Trial #1 1 2 3
UTS (MPa) 350.13 348.20 346.99
Average UTS of Surface Composite(MPa)
UTS of Base Material Al 7075-T651(MPa)
348.44
383.60
4.2. Confirmation experiment for Ultimate Tensile Strength Table 9. Optimal conditions of experimental and predictions
S/N Ratio Tensile strength(MPa) Error %
Prediction 50.929
Experimental 50.885
351.96
348.44 1
The best combination of FSP control parameters has been determined by using optimization method. However, the last step is to predict and verify the enhancement of the observed values through the use of the best combination level of volume fractions. The confirmation experiments were performed by conducting a quantifying test with particular combination of the process factors and levels previously assessed. After determining the best conditions and predicting the response under these conditions, a new experiment was designed and conducted with the optimum levels of the selected reinforcement volume fractions. Table 9 shows the comparisons of the experimental results for the optimal conditions with predicted results for optimal TS. 4. Conclusion The experimental investigation on the development of surface composites by FSP by optimization of its process parameters for high tensile strength leads to the following conclusions: The successful development and fabrication of a surface composite by FSP using Al 7075-T651 as matrix material and SiC as the reinforcement. The optimum process parameters in FSP for higher tensile strength is determined for surface composite using Taguchi’s technique. The optimum FSP parameters for higher tensile strength determined is Tool rotational speed =710 rpm, Tool traverse speed=10mm/min and Hole diameter on base material =2mm. The experimental tensile strength obtained by UTM for surface composite specimen fabricated by optimum FSP parameters is 348.44MPa. The tensile strength of base material Al 7075-T651 is 383.60MPa. Hence, there is a decrease of 9.16% in the Tensile Strength of produced surface composite due to the dynamic recrystallization of material during the single pass FSPing applicable only to a limited depth from the surface.
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