Faculty Publications
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Item Experimental investigations on performance characteristics in wire electro discharge machining of Ti50Ni42.4Cu7.6 shape memory alloy(2013) Narendranath, S.; Manjaiah, M.; Basavarajappa, S.; Gaitonde, V.N.This article investigates the effect of pulse on time, peak current and pulse off time on wire electro discharge machining characteristics of Ti 50Ni42.4Cu7.6 shape memory alloy. A Ti 50Ni42.4Cu7.6 alloy was prepared by conventional tungsten arc melting. The machining experiments were performed as per Box-Behnken design on computer control wire electro discharge machining machine using molybdenum wire electrode. The relationships between the process parameters (pulse on time, peak current and pulse off time) and wire electro discharge machining responses (surface roughness and material removal rate) have been established using response surface methodology-based quadratic models. The analysis of variance has been employed to test the significance of the developed second-order mathematical models. The parametric analysis-based results reveal that low peak current with prolonged pulse on duration leads to reduced surface roughness. However, combination of low peak current with low pulse on time is beneficial for achieving better material removal rate for machining of shape memory alloy. © IMechE 2013.Item Wire electric discharge machining characteristics of titanium nickel shape memory alloy(Nonferrous Metals Society of China B12 Fuxing Road Beijing 100814, 2014) Manjaiah, M.; Narendranath, S.; Basavarajappa, S.; Gaitonde, V.N.TiNi shape memory alloys (SMAs) have been normally used as the competent elements in large part of the industries due to outstanding properties, such as super elasticity and shape memory effects. However, traditional machining of SMAs is quite complex due to these properties. Hence, the wire electric discharge machining (WEDM) characteristics of TiNi SMA was studied. The experiments were planned as per L27 orthogonal array to minimize the experiments, each experiment was performed under different conditions of pulse duration, pulse off time, servo voltage, flushing pressure and wire speed. A multi-response optimization method using Taguchi design with utility concept has been proposed for simultaneous optimization. The analysis of means (ANOM) and analysis of variance (ANOVA) on signal to noise (S/N) ratio were performed for determining the optimal parameter levels. Taguchi analysis reveals that a combination of 1 ?s pulse duration, 3.8 ?s pulse off time, 40 V servo voltage, 1.8×105 Pa flushing pressure and 8 m/min wire speed is beneficial for simultaneously maximizing the material removal rate (MRR) and minimizing the surface roughness. The optimization results of WEDM of TiNi SMA also indicate that pulse duration significantly affects the material removal rate and surface roughness. The discharged craters, micro cracks and recast layer were observed on the machined surface at large pulse duration.Item Effect of electrode material in wire electro discharge machining characteristics of Ti50Ni50-xCux shape memory alloy(Elsevier Inc. usjcs@elsevier.com, 2015) Manjaiah, M.; Narendranath, S.; Basavarajappa, S.; Gaitonde, V.N.Abstract TiNiCu alloy belongs to new class of shape memory alloy (SMA), which exhibits superior properties like shape memory effect, super elasticity and reversible martensitic transformation phase and thus find broad applications in actuators, micro tools and stents in biomedical components. Even though, SMA demonstrates outstanding property profile, traditional machining of SMAs is fairly complex and hence non-traditional machining like wire electric discharge machining (WEDM) has been performed. Hence, there is a need to investigate the WEDM performance characteristics of shape memory alloys due to excellent property profile and potential applications. In the present investigation, various machining characteristics like material removal rate (MRR), surface roughness, surface topography and metallographic changes have been studied and the influence of wire material on TiNiCu alloy machining characteristics has also been evaluated through ANOVA. Ti50Ni50-xCux=10, 20 was prepared by vacuum arc melting process. The proposed alloy as-cast material exhibits austenite property (B2 phase) and having higher hardness when compared to TiNi alloy. The investigation on WEDM of Ti50Ni50-xCux alloy reveals that the machining parameters such as servo voltage, pulse on time and pulse off time are the most significant parameters affecting MRR as well as surface roughness using both brass and zinc coated brass wires. However, machining with zinc coated brass wire yields reduced surface roughness and better MRR and also produces less surface defects on the machined surface of Ti50Ni50-xCux alloys. © 2015 Elsevier Inc. All rights reserved.Item Influence of process parameters on material removal rate and surface roughness in WED-machining of Ti50Ni40Cu10 shape memory alloy(Inderscience Publishers, 2016) Manjaiah, M.; Narendranath, S.; Basavarajappa, S.; Gaitonde, V.N.Among the shape memory alloys (SMAs), TiNi SMAs have been typically used as the functional elements in the larger part of the industries due to exceptional properties like super elasticity and shape memory effect. However, traditional machining of these alloys is fairly complex due to these properties. The non-traditional machining process like electric discharge machining (EDM) exhibits outstanding capability in machining of these alloys. The poor selection of machining parameters may cause increased roughness of workpiece and lesser material removal rate. Hence, an effort has been made in the present work to explore the effects of three process parameters, such as pulse on time, pulse off time and servo voltage in wire electric discharge machining (WEDM) of Ti50Ni40Cu10 shape memory alloy (SMA) using zinc coated brass wire electrode on material removal rate and surface roughness using response surface methodology (RSM)-based mathematical models. The experiments were planned as per central composite design (CCD). The investigations revealed that pulse on time and servo voltage have predominant effects in maximising material removal rate and minimising surface roughness. The best combination of the process parameters for multi-response optimisation was obtained through desirability function. ©2016 Inderscience Enterprises Ltd.Item Wire Electro Discharge Machining Performance of TiNiCu Shape Memory Alloy(Springer Netherlands, 2016) Manjaiah, M.; Narendranath, S.; Basavarajappa, S.The study presents the effect of Wire Electro Discharge Machining (WEDM) system parameters on the Material Removal Rate (MRR), surface roughness and surface morphology of Ti 50Ni 45Cu 5 SMA developed using vacuum arc melting. The WEDM parameters such as pulse on time, peak current, pulse off time and table feed were selected as control factors over MRR and surface roughness. The results reveal that the surface roughness and MRR increases with increased peak current, pulse on time and table feed but decreases slightly with pulse off time. Higher MRR was attained at 5Amps peak current and 70 ?m/s table feed. Better surface roughness was obtained for a combination of lower pulse on time, peak current and table feed with high pulse off time. Surface defects such as recast layer, craters, micro–cracks, pockmarks and voids were found on the machined surface. The globule of appendages formed around the craters and the intensity of the crater was evident for the higher surface roughness with an increase in peak current and pulse-on time during WEDM. © 2015, Springer Science+Business Media Dordrecht.Item Effect of Wire Material on Productivity and Surface Integrity of WEDM-Processed Inconel 706 for Aircraft Application(Springer New York LLC barbara.b.bertram@gsk.com, 2016) Sharma, P.; Dupadu, D.; Narendranath, S.Inconel 706 is a recently developed superalloy for aircraft application, particularly in turbine disk which is among the most critical components in the gas turbine engines. Recently, wire electrical discharge machining (WEDM) attained success in machining of gas turbine components which require complex shape profiles with high precision. To achieve the feasibility in machining of these components, the research work has been conducted on Inconel 706 superalloy using WEDM process. And, the effect of different wire materials (i.e., hard brass wire, diffused wire, and zinc-coated wire) on WEDM performance characteristics such as cutting speed, surface topography, surface roughness, recast layer formation, residual stresses, and microstructural and metallurgical alterations have been investigated. Even though, zinc-coated wire exhibits improved productivity, hard brass wire was found to be beneficial in terms of improved surface quality of the machined parts. Additionally, lower tensile residual stresses were obtained with hard brass wire. However, diffused wire has a moderate effect on productivity and surface quality. Under high discharge energy, higher elemental changes were observed and also the white layer was detected. © 2016, ASM International.Item Effect of wire diameter on surface integrity of wire electrical discharge machined Inconel 706 for gas turbine application(Elsevier Ltd, 2016) Sharma, P.; Dupadu, D.; Narendranath, S.Inconel 706 superalloy has established itself in the field of gas turbine industry because of its easy fabricability combined with high mechanical strength. Due to its high stress rupture and tensile yield strength, conventional machining of this superalloy exhibits poor surface and low dimensional accuracy of the machined components. It is well known that most of the gas turbine components include complex shaped profile with high precision and hence, wire electrical discharge machining (WEDM) of Inconel 706 has been performed to achieve the feasibility in manufacturing of complex shaped components for gas turbine application. In the current investigation, the effect of wire diameter on WEDM performance characteristics such as cutting speed, surface roughness, surface topography, recast layer formation, microhardness, microstructural and metallurgical changes have been evaluated. It was investigated that smaller diameter wire is advantageous over the larger diameter wire since it improves productivity as well as surface quality of the machined components under the same settings of control parameters. In addition, smaller diameter wire has shown comparatively lower recast layer thickness, minimum hardness alteration and shorter manufacturing time. The XRD result has confirmed the presence of residual stress within WED machined component. © 2016 The Society of Manufacturing EngineersItem Experimental Investigation on Effects of Wire Electro Discharge Machining of Ti50Ni45Co5 Shape Memory Alloys(Springer Netherlands rbk@louisiana.edu, 2018) Soni, H.; Narendranath, S.; Ramesh, M.R.TiNiCo shape memory alloy is most popular shape memory alloy for biomedical applications due to their outstanding properties such as shape memory effect, pseudoelasticity and transformation temperature. Machining of such kind of alloys is very difficult through conventional machining process is very difficult because they may affect their internal properties of these alloys. However conventional machining processes give poor surface quality during the machining hence non-conventional machining processes such as (wire electro discharge machining, water jet machining and electro discharge machining etc.) are more suitable for machining of such kind of alloy. From the literature it has been found that Wire electro discharge machining (WEDM) is more suitable non-conventional machining process for such kind of alloy. Present study exhibits the effects WEDM characteristics of Ti50Ni45Co5 shape memory alloy. L-9 orthogonal array has been created by using Taguchi as a design method for machining of selected alloy and machined surface characterization has been carried out at the optimized process parameters with respect to microstructures, surface topography, microhardness, XRD analysis and residual stresses. To find the optimum setting of the input process parameters a couple of optimization techniques are used, namely principal component analysis (PCA) and Gray relational analysis (GRA) technique. 125?s pulse on time (Ton), 35?s pulse off time (Toff) and 40V servo voltage (SV) were found as an optimal setting for the higher material removal rate (MRR) with better surface roughness (SR) in the present study. Moreover, characterization of the machined surface is performed with respect to microstructures, surface topography, microhardness analysis, XRD and residual stresses. Harder surface observed near the cutting edge and TiNio3 Tio2 and CuZn were noticed on the surface of machined component through XRD analysis. However, compressive residual stress has been noticed on the machined surface during WEDM process. © 2018, Springer Science+Business Media B.V., part of Springer Nature.Item Impact of variation in wire electro discharge machining responses of homologous TiNiCu shape memory alloys for smart applications: An experimental investigation(Institute of Physics Publishing helen.craven@iop.org, 2018) Roy, A.; Narendranath, S.In this study, three distinct TiNiCu alloys were processed using wire electro discharge machining. These alloys are potential materials for smart applications owing to their fast actuation response resulting from suitable martensitic transformation temperatures. Due to differences in their physical property (thermal conductivity in this case), these alloys exhibit variation in machining response during wire electro discharge machining. Based on wire electro discharge machining responses of these alloys, order of thermal conductivity of these alloys are concluded in this study. This investigation aims at addressing the variation in terms of kerf width, recast layer thickness and machined surface microhardness to form the basis for production of intricate components. Ti50Ni40Cu10 alloy exhibited diverging machining response compared to its counterparts. Influential parameter for a given machining response changes depending on thermal property of the workpiece which makes it vital to investigate and choose the parameters in a more sensible manner while machining such materials. It was found that kerf width decreases with increasing servo voltage whereas recast layer thickness (mostly influenced by pulse off duration) increases with increasing pulse off duration. Microhardness of the machined surface (mostly influenced by pulse on duration) increases at higher discharge energy levels owing to presence of oxides formed during spark erosion process. Microhardness of Ti40Ni50Cu10 was found to be high (approximately 560 Hv) compared to its counterparts which was due to presence of Ni rich and ?-CuTi precipitates which also affected its phase transformation temperatures. © 2018 IOP Publishing Ltd.Item Effects of Wire Electro-Discharge Machining Process Parameters on the Machined Surface of Ti 50 Ni 49 Co 1 Shape Memory Alloy(Springer Netherlands rbk@louisiana.edu, 2019) Soni, H.; Narendranath, S.; Ramesh, M.R.Wire electro-discharge machining is one of the advanced machining processes which can machine all conductive materials without changing their internal properties. Pulse on time and servo voltage are the most influential process parameters of wire electro-discharge machining. In the present study, attempts have been made to study the effects of these process parameters on the machined surface of Ti 50 Ni 49 Co 1 shape memory alloy by adopting a two process parameters experimental design approach. Cutting speed and surface roughness were considered as output parameters; surface crack density, microhardness and XRD analysis were carried out at the higher and lower values of these parameters. Higher surface crack density has been found at high values of cutting speed (125 ?s pulse on time and 20 V servo voltage) while it is lower at the lower value of cutting speed (105 ?s pulse on time and 60 V servo voltage). Moreover, a harder surface was found near the machined surface. By XRD analysis it was found that the crystal size of the WED machined surface was reduced at high T on and lower SV. © 2018, Springer Science+Business Media B.V., part of Springer Nature.