Faculty Publications
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Item Assessment of influence of process parameters on properties of friction stir welded Al-Ce-Si-Mg aluminium alloy(Institute of Physics Publishing helen.craven@iop.org, 2019) D’Souza, A.D.; Rao, S.S.; Herbert, M.A.The research on friction stir welding is mainly focused on welding of aluminium alloys. The material of interest in this research is an aluminium alloy known as Al-Ce-Si-Mg aluminium alloy. The FSW of this alloy finds applications in aerospace industry like joining of aircraft structure parts such as fuselage, cladding and engine components and in automotive industry for welding of parts of body structure and engine. The quality of the weld produced by FSW such as macrostructure defects, average grain size, ultimate tensile stress and weld zone hardness etc are dependent on input parameters like tool revolution, tool feed rate and tool pin profile. The weld defects like tunnel hole, worm hole and pin holes were not predominant in the tool revolution range of 800 to 1200 rpm and tool feed rate range of 10 to 20 mm min-1. The maximum ultimate stress was found to be lesser in the low and high tool revolution and tool feed rates compared to the medium speeds. The maximum value of UTS noted was 102.55 MPa for the weld at a tool revolution of 800 rpm and tool feed rate of 20 mm min-1 with a triangular pin profile tool, giving a joint efficiency of 67%. The Vickers hardness values were less at lower and higher speed ranges of tool revolution and tool feed rates for all the tool pin profiles used. The maximum value of Vickers hardness was noted for a tool revolution of 1000 rpm and tool feed rate of 20 mm min-1 with a triangular pin profile tool. The lowest grain size was observed for the tool revolution of 1000 rpm and tool feed rate of 20 mm min-1 with a triangular pin profile tool, indicating the inverse relation between hardness and grain size. In all the experiments it was observed that the triangular pin profile tool gives the best results at medium tool revolution and tool feed rate ranges. © 2019 IOP Publishing Ltd.Item A Study on Areca nut Husk Fibre Extraction, Composite Panel Preparation and Mechanical Characteristics of the Composites(Springer, 2019) Muralidhar, N.; Kaliveeran, V.; Arumugam, V.; Srinivasula Reddy, I.Areca nut husk fibre is an agricultural waste, which does not contribute to the economy of areca nut plantation. The use of areca nut husk fibre as reinforcing material in the preparation of low-cost and lightweight composites provides utility value to areca nut husk fibre. Low-cost and lightweight composites have wide range of applications in construction industry, marine structures, automobile industry and aerospace industry. The present work focuses on extraction of areca nut husk fibre with alkali treatment process by using 6% of sodium hydroxide solution, composite panel preparation and determination of mechanical properties of composite panels. Different fibre compositions (fine fibre, coarse fibre and coarse fibre sandwiched with glass fibre) of 15% by weight were used in the present study. Tensile, flexural and impact tests were conducted to find the mechanical characteristics the composite materials. The tensile strength of composites made with fine fibre (15.1 MPa) is observed to be more than that of composites made with coarse fibre (10.8 MPa). Further improvement in tensile strength of composite panels made of coarse areca nut husk fibre layer sandwiched with two layers of glass fibre (24.8 MPa) is observed. The flexural strength of fine fibre composites is more when compared to that of the coarse fibre composites. The average flexural strength of composites reinforced with fine fibre, coarse fibre and coarse fibre sandwiched with glass fibre is observed as 73 MPa, 66.7 MPa and 284 MPa, respectively. The impact strength of coarse fibre composites is found to be higher when compared to that of fine fibre composites. © 2019, The Institution of Engineers (India).Item Multi-response optimization of the turn-assisted deep cold rolling process parameters for enhanced surface characteristics and residual stress of AISI 4140 steel shafts(Elsevier Editora Ltda, 2020) Prabhu, P.R.; Kulkarni, S.M.; Sharma, S.Surface and near-surface areas play an important role as far as safety and dependability ofengineering components particularly when it is subjected to fatigue loading. By applyingdiverse mechanical surface enhancement (MSE) strategies, close to surface layers can becustom-made bringing about enhanced fatigue strength. MSE methods are used to gener-ate surface hardened components without the time and energy-consuming heat treatment.Deep cold rolling (DCR) is one such method that can be employed where the mechanicalenergy induced enables surface-hardening of steels and thereby the combination of hard-ening and finishing in one single step. The objective of this work is to enhance residualstress and near-surface properties of AISI 4140 steel which is the most commonly usedmaterial in the automobile and aerospace industry. The samples were first turned and thendeep cold rolled with various process parameters. Microstructure, surface hardness, sur-face finish, fatigue life, and residual compressive stress after the treatment were examined.Response surface methodology (RSM) and desirability function approach (DFA) was used torelate the empirical relationship between the various process variables and responses andalso to determine the optimum parameter settings for better responses. Further, numericalsimulation of turn-assisted deep cold rolling (TADCR) process was done by utilizing ANSYS-LS-DYNA software to understand the state of residual stress under various treating settings.Confirmation experiments conducted with the optimum parameter setting to validate theimprovements in response and it is found that the deviation between optimum predictedand confirmatory experimental values is about 5%. © 2020 The Authors.Item Experimental Investigation and Parametric Optimization on Hole Quality Assessment During Drilling of CFRP/GFRP/Al Stacks(Springer, 2020) Janakiraman, A.; Pemmasani, S.; Sheth, S.; Kannan, C.; Balan, A.S.S.Carbon fiber/glass fiber-reinforced aluminum (Al) stacks are becoming predominant in the aerospace industries owing to their synergistic effect on numerous properties obtained by the combination of metal and composite material. This necessitates an investigation work to be performed on the machining characteristics of this special category of Al stacks. This research work focuses on studying the influence of cutting speed, feed rate and machining environment on thrust force, delamination and roughness of the finished surface of hybrid Al stacks. Dry, minimum quantity lubrication (MQL), and cryogenic environments are considered in this work. The impact of cutting speed on the responses is observed to be negligible in contrast to the feed rate. Moreover, the drilling under cryogenic environment is found to improve the surface finish and mitigated the delamination, while drilling under MQL environment minimized the thrust force. Regression models are also developed to determine the output responses. High-quality holes in aluminum stacks can be obtained under cryogenic conditions over other machining environments as revealed by multi-objective optimization. © 2020, The Institution of Engineers (India).Item Effect of Cryogenics-Assisted Low-Plasticity Burnishing on Laser-Clad Stellite 6 over SS420 Substrate(Springer, 2020) Anirudh, P.V.; Kumar, B.; Girish, G.; Shailesh, S.; Oyyaravelu, R.; Kannan, C.; Balan, A.S.S.The influence of modern additive manufacturing methods, especially from the direct energy deposition (DED) processes to the coat-like finished components, is crucial under present industrial circumstances. DED induces several traits like enhanced mechanical, thermal properties in shorter lead time, which extend their adaptation for diverse applications including aerospace and automobile industries. Among the several DED processes, laser cladding has been a prospect that explores various capabilities of improving the wear resistance of cobalt-chromium (Co-Cr)-based alloys. Rather than fabricating the complete component using expensive alloys, laser cladding has paved an approach to deposit particles possessing superior qualities over the conventional material. This research work attempts to evaluate the surface integrity of SS420 when cladded with Stellite 6. The vertical face milling is executed on the cladded component surface to facilitate either low-plasticity burnishing (LPB) or cryogenic burnishing (CB) as sequential post-treatment processes. The effects of these post-treatments on the surface and subsurface microhardness, surface topography and residual stress profiles are elaborated. Increased surface and subsurface microhardness, as well as improved residual stress profiles, are observed with CB over LPB-processed specimen samples. © 2020, ASM International.Item Recast Layer Formation during Wire Electrical Discharge Machining of Titanium (Ti-Al6-V4) Alloy(Springer, 2021) Pramanik, A.; Basak, A.K.; Prakash, C.; Shankar, S.; Sharma, S.; Narendranath, S.Titanium alloys, in particularly Ti-6Al-4V alloy is used enormously in many high-tech sectors specially in aerospace industries due to its superior properties. Machining process (for example wire electrical discharge machining) to reshape this alloy affects the integrity of the newly generated surfaces. This experimental study has identified three affected layers using scanning electron microscopy on the cross section of the machined titanium (Ti-6Al-4V) alloy surface generated from wire electrical discharge machining (WEDM). This study also explained the formation mechanism of those three layers as no detail investigation is available in this area so far. It was found that the top flaky layers are formed due to the highest cooling rate at the outermost surface, which is induced due to the low thermal conductivity of the titanium alloy as well as the quenching effect because of the existence of dielectric. The recast layer is formed at a cooling rate lower than that at the outer surface, where the melted material is resolidified very quickly without having any grain boundaries. The heat-affected zone appears at a slightly different color, which does not melt but experience heat treatment during the machining process. © 2021, ASM International.Item Electrodeposition of Zn–Co Coating and its Electrochemical Performance(Pleiades journals, 2022) Bhat, R.S.; Manjunatha, K.B.; Venkatakrishna, K.; Hegde, A.C.Abstract: We report the acid chloride bath based electroplating of Zn–Co alloy on low carbon steel (LCS). As additives, the sulphanilic acid (SA) and gelatin were used for electroplating. The bath exhibited an anomalous co-deposition with a higher deposition of Zn over nobler Co. The role of bath composition, current density, partial current density, pH, and temperature on thickness, hardness, and corrosion resistance of deposit was studied. The corrosion behavior in 3.5 wt % sodium chloride solution and electrochemical behavior in acid chloride solutions of Zn–Co alloy coatings were studied using the potentiodynamic polarization method and cyclic voltammetry technique respectively. Mott–Schottky plot with positive slope confirms the development of n-type semiconductor layer at the interface of substrate and coating, which results in superior corrosion resistance of coatings. The colorimetric method has been used to estimate the composition of the deposit and further verified by energy dispersive X-ray spectroscopy (EDX) technique. The surface features and the topographical structure of the alloy film were obtained by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The results indicate that the Zn–Co alloy films exhibited superior corrosion resistance with the lowest corrosion rate (138 µm y–1). Hence this alloy coating will find suitable applications in automobile and aerospace industries. © 2022, Pleiades Publishing, Ltd.Item Enhancing fatigue performance of AZ31 magnesium alloy components fabricated by cold metal transfer-based wire arc directed energy deposition through LPB(KeAi Communications Co., 2024) Manjhi, S.K.; Bontha, S.; Balan, A.A.S.Cold Metal Transfer-Based Wire Arc Directed Energy Deposition (CMT-WA-DED) presents a promising avenue for the rapid fabrication of components crucial to automotive, shipbuilding, and aerospace industries. However, the susceptibility to fatigue of CMT-WA-DED-produced AZ31 Mg alloy components has impeded their widespread adoption for critical load-bearing applications. In this study, a comprehensive investigation into the fatigue behaviour of WA-DED-fabricated AZ31 Mg alloy has been carried out and compared to commercially available wrought AZ31 alloy. Our findings indicate that the as-deposited parts exhibit a lower fatigue life than wrought Mg alloy, primarily due to poor surface finish, tensile residual stress, porosity, and coarse grain microstructure inherent in the WA-DED process. Low Plasticity Burnishing (LPB) treatment is applied to mitigate these issues, which induce significant plastic deformation on the surface. This treatment resulted in a remarkable improvement of fatigue life by 42%, accompanied by a reduction in surface roughness, grain refinement and enhancement of compressive residual stress levels. Furthermore, during cyclic deformation, WA-DED specimens exhibited higher plasticity and dislocation density compared to both wrought and WA-DED + LPB specimens. A higher fraction of Low Angle Grain Boundaries (LAGBs) in WA-DED specimens contributed to multiple crack initiation sites and convoluted crack paths, ultimately leading to premature failure. In contrast, wrought and WA-DED + LPB specimens displayed a higher percentage of High Angle Grain Boundaries (HAGBs), which hindered dislocation movement and resulted in fewer crack initiation sites and less complex crack paths, thereby extending fatigue life. These findings underscore the effectiveness of LPB as a post-processing technique to enhance the fatigue performance of WA-DED-fabricated AZ31 Mg alloy components. Our study highlights the importance of LPB surface treatment on AZ31 Mg components produced by CMT-WA-DED to remove surface defects, enabling their widespread use in load-bearing applications. © 2024Item Achieving ultra-fine grains in Ti-6Al-4V alloy welds through pre-weld friction stir processing(Elsevier B.V., 2024) Rao, R.N.; Rao, S.S.; Vijayan, V.Titanium Ti-6Al-4V alloy, recognized for its exceptional strength, is extensively employed in the aerospace, biomedical, and automotive industries. Friction Stir Processing (FSP) has been found to enhance the overall performance, while friction stir welding (FSW) is recognized as the most effective technique for joining the Ti-6Al-4V alloy. This study focusses on the implementation of friction stir welding on a Ti-6Al-4V alloy that had previously undergone friction stir processing. The objective was to analyse the microstructure and mechanical characteristics. The examination using Electron Backscatter Diffraction revealed notable alterations in the microstructure, such as variations in grain size, misorientation angle, and grain boundaries. The proportion of high angle grain boundaries (HAGBs) on the advancing side and stir zone of the friction stir treated Ti-6Al-4V were 59 % and 66 %, respectively. Signifying grain refinement, grains measuring sizes between 0.83 ?m and 1.05 ?m were achieved as result of processing. Subsequent, friction stir welding resulted in about 50 % further decrease in grain size compared to base metal, with HAGBs comprising 71 % and 52 % at the advancing side and stir zone, respectively. As a result the Vickers micro hardness values increased to 397 ± 13Hv upon friction stir processing to 444 ±7Hv upon subsequent friction stir welding respectively. © 2024 The Authors