Faculty Publications
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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 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.