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Article Citation - Scopus: 5Micro-Wedm of Ni55.8ti Shape Memory Superalloy: Experimental Investigation and Optimisation(Inderscience Publishers, 2021) Meshri,H.A.M.; Akar,S.; Seyedzavvar,M.; Kiliç,S.E.Nickel-titanium superalloy has gained significant acceptance for engineering applications as orthotropic implants, orthodontic devices, automatic actuators, etc. Considering the unique properties of these alloys, such as high hardness, toughness, strain hardening, and development of straininduced martensite, micro-wire electro-discharge machining (μ-WEDM) process has been accepted as one of the main options for cutting intricate shapes of these alloys in micro-scale. This paper presents the results of a comprehensive study to address the material removal rate (MRR) and surface integrity of Ni55.8Ti shape memory superalloy (SMA) in the μ-WEDM process. The effects of discharge current, pulse on-time, pulse off-time, and servo voltage on the performance of this process, including MRR, white layer thickness, surface roughness, and micro-hardness of the machined surface, were investigated by multi-regression analysis using response surface methodology (RSM). The optimisation of input parameters based on the gradient and the swarm optimisation algorithms were also conducted to maximise the MRR and minimise the white layer thickness, surface roughness, and micro-hardness of the machined samples. © 2021 Inderscience Enterprises Ltd.. All rights reserved.Article Citation - WoS: 22Citation - Scopus: 27Modeling and Analysis of Surface Roughness of Microchannels Produced by Μ-Wedm Using an Ann and Taguchi Method(Korean Soc Mechanical Engineers, 2017) Jafari, Rahim; Kahya, Muge; Oliaei, Samad Nadimi Bavil; Unver, Hakki Ozgur; Ozyurt, Tuba OkutucuMicrochannel heat exchangers are used to remove the high heat fluxes generated in compact electronic devices. The roughness of the microchannels has a significant effect on the heat transfer characteristics, especially the nucleate boiling and pumping power. Therefore, development of predictive models of surface texture is of significant importance in controlling heat transfer characteristics of these devices. In this study, micro-Wire electrical discharge machining (mu-WEDM) was employed to fabricate metal-based microchannel heat sinks with different surface textures. First, experiments were conducted to achieve the desired surface roughness values. Oxygen-free copper is a common material in the cooling systems of electronic devices because of its high thermal conductivity and low cost. Design of experiment approach based on the Taguchi technique was used to find the optimum set of process parameters. An analysis of variance is also performed to determine the significance of process parameters on the surface texture. An artificial neural network model is utilized to assess the variation of the surface roughness with process parameters. The predictions are in very good agreement with results yielding a coefficient of determination of 99.5 %. The results enable to determine mu-WEDM parameters which can result in the desired surface roughness, to have a well-controlled flow and heat transfer characteristics for the microchannels.Article Citation - WoS: 27Citation - Scopus: 31Experimental Investigation of Surface Roughness Effects on the Flow Boiling of R134a in Microchannels(Elsevier Science inc, 2016) Jafari, Rahim; Okutucu-Ozyurt, Tuba; Unver, Hakki Ozgur; Bayer, OzgurThis study experimentally investigates the effect of surface roughness on the hydrodynamic and thermal performance of microchannel evaporators. Three micro-evaporators of the same dimensions and different surface roughness have been fabricated by micro-WEDM. Each micro-evaporator consists of forty rectangular microchannels of 700 mu m height, 250 mu m width, and 19 mm length. A microscale vapor compression refrigeration cycle has been constructed to carry out the experiments. R134a is used as the refrigerant. Heat transfer coefficient, pressure drop and COP results are presented at variously imposed heat fluxes, and at mass fluxes of 85 and 200 kg/(m(2)s). The results demonstrate up to 45% enhancement in the two-phase heat transfer coefficient at low to moderate heat flux values as the surface roughness increases. Considering the surface roughness effect of the microchannel walls, a new correlation is developed to predict the heat transfer coefficient of R134a boiling in microchannels. (C) 2016 Elsevier Inc. All rights reserved.Article Citation - WoS: 19Citation - Scopus: 21Plateau Honing of a Diesel Engine Cylinder With Special Topography and Reasonable Machining Time(Elsevier Sci Ltd, 2020) Sadizade, Babak; Araee, Alireza; Oliaei, Samad Nadimi Bavil; Farshi, Vahid RezaeizadDeep valleys and flattened peaks are essential characteristics of the finished cylinder bore surface, which is known as the plateau surface. Generally, a honing process is done in three steps to achieve a plateau surface, which is costly and time-consuming and acts as a bottleneck for cylinder block machining line. The real challenge is to select optimum levels of honing process parameters to achieve desired surface characteristics with minimum machining time. The aim of this study is to examine the influence of the input parameters of the honing process on the surface texture of diesel engine cylinder bore. The Rk family parameters are used for surface roughness evaluation and the honing crosshatch angle, in accordance with engine design requirements, which was fixed for all experiments. Optimization by means of the desirability function technique allowed determining most appropriate conditions to desirable roughness (surface quality) and/or minimize machining time (productivity). Based on the findings of this study the conventional three-stage honing process has been replaced by the two-stage process. Using the proposed two-stage honing process the intended plateau surface in cylinder bores are achieved and a remarkable reduction in the honing process time is obtained. Consequently, the process efficiency is improved significantly.
