Faculty Publications
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Item Multi-objective Optimization of FSW Process Variables of Aluminium Matrix Composites Using Taguchi-Based Grey Relational Analysis(Springer Nature, 2019) Prabhu B, S.R.B.; Shettigar, A.K.; Herbert, M.A.; Rao, S.S.Successful joining of aluminium alloys using friction stir welding (FSW) opens a new window research in extending this technique to join aluminium matrix composites (AMCs). Current research is focused on optimization of process variables for multiple responses simultaneously. Experiments were performed using tool pin profile, rotational speed (RS) and welding speed (WS) as ideal process variables for multi-objective optimization in FSW of AMCs. Tensile strength, macro-hardness and elongation are considered as multi-response behaviour. Grey relational grade for the chosen multiple responses are obtained using grey analysis. Analysis of variance was utilized to understand the influence of process variables on the grey relational grade. Analysis reveals that RS and WS were the most influencing process variables on the output responses. Confirmation experiments were performed at optimized process variables to validate the present study. Predicted values were in good agreement with the experimental results. © 2019, Springer Nature Singapore Pte Ltd.Item Effect of mushy state rolling on age-hardening and tensile behavior of Al-4.5Cu alloy and in situ Al-4.5Cu-5TiB2 composite(Elsevier Ltd, 2011) Siddhalingeshwar, I.G.; Herbert, M.A.; Chakraborty, M.; Mitra, R.The effect of mushy state rolling on aging kinetics of stir-cast Al-4.5Cu alloy and in situ Al-4.5Cu-5TiB2 composite and their tensile behavior in solution-treated (495°C) or differently aged (170°C) conditions, has been investigated. As-cast or pre-hot rolled alloy and composite samples were subjected to single or multiple mushy state roll passes to 5% thickness reduction at temperatures for 20% liquid content. Peak-aging times of mushy state rolled composite matrices have been found as ?7.5-10% of that of as-cast alloy. Such enhancement in aging kinetics is attributed to homogeneity in Cu atom distribution as well as increase in matrix dislocation density due to thermal expansion coefficient mismatch between Al and TiB2, matrix grain refinement and particle redistribution, achieved by mushy state rolling. Uniform precipitate distribution in mushy state rolled composite matrices leads to greater peak-age microhardness with higher yield and ultimate tensile strengths than those in as-cast alloy and composite. © 2010 Elsevier B.V.Item Microstructural characterization and hardness evaluation of friction stir welded composite AA6061-4.5Cu-5SiC (Wt.%)(Defense Scientific Information and Documentation Centre, 2013) Shettigar, A.K.; Salian, G.; Herbert, M.A.; Rao, S.Recent developments in advanced materials research have led to the emergence of new materials having features like low density, high strength to weight ratio, excellent mechanical properties, heat and corrosion resistance. In friction stir welding (FSW), a non-consumable rotating welding tool is used to generate the frictional heat and plastic deformation of the material in the welding zone, which is in the solid state. The advantages of FSW as compared to the fusion welding are high joint strength, less defect weld, uniform distribution of grain structure in the weld zone and low power consumption. AA6061 with 4.5 % weight of copper and 5 % weight of SiC composite material has been prepared to conduct experiment and carry out characterization, evaluation of the mechanical properties. Micro-structural characterization of the weld zone is carried out by scanning electron microscope (SEM). Evaluation of hardness was also carried out across the weld zone. A successful method for FSW of AA6061-4.5(wt.%) Cu-5(wt.%) SiC has been developed. © 2013, DESIDOC.Item Effect of low temperature annealing on the properties of nano Ni-Ti alloys(Institute of Physics Publishing helen.craven@iop.org, 2019) Mukunda, S.; Mahesh, M.; Narendranath, S.; Herbert, M.A.Binary 1:1 Ni-Ti alloy has been the work horse for many industrial and of late biomedical applications amongst all shape memory alloys. Apart from being employed for endovascular applications like stents and filters, they are also used as orthodontic braces and in endodontic tools. Ni-Ti drills and files are used in a few procedures with sterilization between uses. However, the effect of these sterilizing heat-treatments on the properties of the tools is not clearly investigated. In addition to this, satisfactory metallurgical explanations for the wear resistance of these alloys in absent in the literature. Therefore, this paper attempts to define the transformational temperatures for the Ni-Ti as-received and low temperature heat-treated conditions have been investigated using Differential Scanning Calorimetry (DSC). Attempts are made to justify their suitability for endodontic applications by evaluating their mechanical strength parameters using the Tensile and Wear tests. It was found that the samples showed did not show much variations in strength when subjected to tensile tests whereas the same was not observed for DSC tests. Ambient temperature x-ray diffraction studies indicate the presence of Austenitic and Martensitic phases in all the samples. DSC results are strongly affected by presence of internal stresses but stress-induced-martensitic forms in all the samples with equal facility. © 2019 IOP Publishing Ltd.Item Microstructure and mechanical properties of rutile-reinforced AA6061 matrix composites produced via stir casting process(Nonferrous Metals Society of China B12 Fuxing Road Beijing 100814, 2019) Prabhu B, S.R.; Shettigar, A.K.; Herbert, M.A.; Rao, S.S.A novel process of fabricating aluminium matrix composites (AMCs) with requisite properties by dispersing rutile particles in the aluminum matrix was studied. A novel bi-stage stir casting method was employed to prepare composites, by varying the mass fractions of the rutile particles as 1%, 2%, 3% and 4% in AA6061 matrix. The density, tensile strength, hardness and microstructures of composites were investigated. Bi-stage stir casting method engendered AMCs with uniform distribution of the reinforced rutile particles in the AA6061 matrix. This was confirmed by the enhancement of the properties of AMCs over the parent base material. Rutile-reinforced AMCs exhibited higher tensile strength and hardness as compared with unreinforced parent material. The properties of the composites were enhanced with the increase in the mass fraction of the rutile particles. However, beyond 3 wt.% of rutile particles, the tensile strength decreased. The hardness and tensile strength of the AMCs reinforced with 3 wt.% of rutile were improved by 36% and 14% respectively in comparison with those of matrix alone. © 2019 The Nonferrous Metals Society of ChinaItem Evaluation of Microstructure, Hardness and Mechanical Properties of Friction Stir Welded Al–Ce–Si–Mg Aluminium Alloy(Korean Institute of Metals and Materials, 2020) D’Souza, A.D.; Rao, S.S.; Herbert, M.A.Abstract: A vast majority of the research on friction stir welding(FSW) is mainly focused on welding of aluminium alloys. The research studies in this paper are based on one such alloy known as Al–Ce–Si–Mg aluminium alloy, of which, the microstructure and other mechanical properties of the friction stir welded joints are yet to be studied. The plates of Al–Ce–Si–Mg aluminium alloy were friction stir welded using a non consumable, rotating tool with triangular profile pin and circular shoulder, with different combinations of tool rotation speeds and weld speeds. The microstructure, hardness and mechanical properties of the weld were analyzed. The microstructure of the weld zones revealed that, the average grain size at the bottom of the Nugget Zone (NZ) is 5 ± 0.12 ?m and gradually increases to 15 ± 0.23 ?m at the top of the NZ. In the TMAZ the grain size is 20 ± 0.14 ?m and is bigger compared to the NZ. In the HAZ, the grain size is around 37 ± 0.21 ?m and is bigger than that in the TMAZ. The maximum Vickers hardness value at the NZ center is 231.9 ± 2 Hv, and uniformly reduces to 100 ± 2.4 Hv in the TMAZ and 65 ± 1.3 Hv in the HAZ and then increases to 98 ± 1 Hv in the base material (BM). The maximum ultimate tensile strength (UTS) of FSW joint was found to be around 102.55 ± 3 MPa with elongation at fracture of 2.5%. The BM UTS was 154 ± 4.5 MPa. For a tool rotation speed of 800RPM and a weld speed of 20 mm/min a maximum joint efficiency of 67%. was obtained. Hence these were chosen as the optimum process parameters to join the alloy Al–Ce–Si–Mg by FSW. Graphic Abstract: [Figure not available: see fulltext.] © 2019, The Korean Institute of Metals and Materials.Item Mechanical and microstructural analysis of a AlSi-ZrO2 metal matrix composite using optimized artificial neural network and experimental data(Elsevier Ltd, 2021) Patil, I.S.; Anarghya, A.; Rao, S.S.; Herbert, M.A.Spray deposition methods has emerged as an alternative to powder metallurgy and ingot routes. This research aims to study the effect of flight distance as a potential key factor that changes the optimum percentage of aluminium silicon- zirconium oxide in terms of mechanical and microstructural properties. The alloy is sprayed at varying the flight distance from 320 mm to 480 mm. The composite were prepared by spray deposition technique and effects on microstructural properties were examined. The aluminium silicon- zirconium oxide composite was subjected to hot isostatic pressing for reducing the porosity of the deposit from 14.4% to 8.2%. A series of experimental study were carried out in the laboratory by varying the flight distance from 320 mm to 480 mm for aluminium silicon- zirconium oxide composite to characteristic loading. In this paper, an optimized artificial neural network using genetic algorithm are developed to predict the mechanical behaviour for aluminium silicon- zirconium oxide composites. Based on the experimental data, the ANN models were developed, trained and tested. The microstructure of the AlSi-ZrO2 composite consisted of finely divided globular shaped eutectic Si uniformly distributed in the Al matrix. With addition of zirconium oxide composition to AlSi alloy, the tensile strength and micro hardness increased from 123 MPa to 147 MPa and, 48 HV to 72 HV, respectively. The preferred flight distance for the current study is found to be 420 mm. Microstructural images obtained at flight distance consist of co-existing primary Si phase and needle like eutectic Si. The physical properties, such as tensile strength, compressive strength, yield strength, micro hardness and porosity of sprayed aluminium silicon- zirconium oxide can hence be adjusted by setting the optimized flight distance. The developed ANN-GA method proved to be accurate, reduced time and efficient to predict the numerous samples and it will help materials designers to design their future experiments effectively. © 2021 Elsevier LtdItem Experimental assessment of FSW process to join AA6061/Rutile composite and parametric optimization using TGRA(IOP Publishing Ltd, 2021) Prabhu B, S.R.; Shettigar, A.; Herbert, M.A.; Rao, S.S.Present study is focused on investigating the effect of various friction stir welding (FSW) process variables on AA6061/Rutile composites welding quality. FSWof composites was performed considering tool geometry (Tg), welding speed (Ws) and rotational speed (Ns) as ideal parameters for multi-response optimization. Experiments were designed based on the L9 orthogonal array. Analysis of variance (ANOVA) was utilized to evaluate the effects of these welding process variables on output responses namely hardness and ultimate tensile strength (UTS). Main effects plots were drawn to found out the optimal levels of these process parameters. Multi-response optimization of the welding process has been performed using Taguchi's grey relational analysis (TGRA). Analysis revealed that welding speed of 90mmmin-1, a tool with a square pin, and rotational speed of 1000 rpm produced an FSWjoint with excellent mechanical properties. Microstructure analysis revealed that refinement in the grain structure and redistribution of reinforced particles helped in improved joint strength. © 2021 IOP Publishing Ltd.Item Parameter investigation and optimization of friction stir welded AA6061/TiO2 composites through TLBO(Springer Science and Business Media Deutschland GmbH, 2022) Prabhu B, S.R.; Shettigar, A.; Herbert, M.A.; Rao, S.S.This paper explicates the joining of AA 6061/TiO2 composites by the friction stir welding (FSW) process. FSW experiments were conducted as per the three factors, three-level, central composite ivy– face-centered design method. Mathematical relationships between the FSW process parameters, namely tool geometry, welding speed, and tool rotational speed, and the output responses such as hardness, yield strength, and ultimate tensile strength were established using response surface methodology. Adequacies of established models were assessed through the analysis of variance method. Further, the paper elucidates the application of the teaching–learning-based optimization (TLBO) algorithm to identify the optimal values of input variables and to obtain an FSW joint with superior mechanical properties. The optimized experimental condition obtained from the TLBO yields an FSW joint with a UTS of 174 MPa, yield strength of 120 MPa, and hardness of 126HV. The study revealed that the result of the TLBO algorithm matched the findings of the FSW experiments. © 2021, The Author(s).Item Optimization of FSW process parameters for maximum UTS of AA6061/rutile composites using Taguchi technique(Sharif University of Technology, 2022) Prabhu B, S.R.; Shettigar, A.; Herbert, M.A.; Rao, S.S.In the friction stir welding process, preferred joint property is vastly reliant on the selection of optimal welding conditions. The present study aims to use the Taguchi technique to find the optimal process conditions for achieving superior Ultimate Tensile Strength (UTS) in friction stir welded Aluminum Matrix Composite (AMC) joints. AMCs reinforced with rutile particles which have a potential application in the aerospace, automotive, and marine industries are used in the present work. Taguchi parametric design technique was used to identify the effect of rotational speed, tool traverse speed, and tool geometry on joint strength. Taguchi approach confined the optimum level of process variables and these variables were optimized. The investigation showed that the parameters within the selected value range will seriously affect the output. The predicted value of the output response was 155.48 MPa, which was validated by further experiments using the optimum process variables. Analysis Of Variance (ANOVA) results indicated that the UTS of the composite joint is mainly affected by the tool traverse speed followed by rotational speed, and tool geometry. The microstructural study unveiled that grain size is dependent on process variables and finer grains offer better joint properties. © 2022 Sharif University of Technology. All rights reserved.