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    INVESTIGATION OF MECHANICAL AND METALLOGRAPHIC PROPERTIES OF TWO DIFFERENT ALUMINUM ALLOYS JOINED WITH FRICTION STIR WELDING METHOD USING DIFFERENT WELDING PARAMETERS
    (Yildiz Technical University, 2020) Öcalir, Şeref; Eşme, Uğur; Boğa, Cem; Külekci, Mustafa Kemal
    In this study two aluminum alloy materials of EN AW-5083-H111 and EN AW-6082-T651 were joined with Friction Stir Welding considering the parameters as the tool shoulder diameter, spindle speed and feed rate. The mechanical properties of the weld joints such as yield strength, tensile strength and micro-hardness and metallographic properties were investigated comparatively with the use of these welding parameters. The yield strength of the weld joints were determined to be between 136-217 MPa while the tensile strengths were between 159-230 MPa and the percent elongations were between 2.28-5.44 %. The hardness values measured in weld areas were higher in the EN AW-6082 base metal side compared with EN AW-5083 base metal side. © 2020 Yildiz Technical University.
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    Multi Response Optimization of Friction Stir Spot Welding Process
    (2021) Er, Onur; Külekci, Mustafa Kemal; Eşme, Uğur; Boğa, Cem
    Friction stir spot welding (FSSW) is a solid state welding method mainly used to join non-ferrous metalsand their alloys. When opposed to other welding processes, FSSW has the benefits of being pollution-freeand having no filler material. In this study an attempt was made for multi response optimization offriction stir spot welded EN AW 5005 aluminum alloy using Taguchi method and Grey relational analysis(GRA). Pin height (h, mm), tool rotation (S, rpm), and welding time (t, s) were used as input parameterswhile tensile shear strength (TSS, MPa) and joint efficiency (JE, %) were used as multi responseparameters. Therefore, Taguchi’s L8 orthogonal design matrix was used in order to plan the experiments.GRA was then applied to determine the optimum condition which gives the higher grey relational degree.Analysis of Variance method (ANOVA) was also carried out in order to show the most significantparameter. Finally, confirmation test was applied to confirm the results and determine the improvement ingrey relational grade throughout this method. The best results were obtained with parameters such as2.6 mm pin height, 1500 rpm tool rotation and 10 s welding time with 122.16 MPa TSS and 111.05 JE. Asignificant improvement of 0.310 was obtained in the optimal parameter in grey relation grade.
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    Optimization of the Effect of Processing Parameters on Surface Roughness and Cutting Energy in CNC Milling of Al-7075 Material
    (2020) Pınarbaşı, Ali Talip; Külekçi, Mustafa Kemal; Eşme, Uğur; Boğa, Cem
    In this study, it is intended to determine the most suitable process parameters for surface roughness and cutting energy of the 7075 series aluminum material in dry environment conditions by using Taguchi method in CNC milling. The process parameters were determined as, cutting speed, feed rate and cutting depth and the effects of these parameters on surface roughness, current flow through the grid and the energy consumed were examined. As a result, optimum process parameters were determined and the results were analyzed by graphs. It was observed that the most effective parameter on the surface roughness was the feed rate, while the most effective parameter on the current drawn from the network was the cutting depth. As a result of the experiments, the best surface roughness value was found to be 0.39 ?m and the lowest current value was 0.9 A. In addition, considering the determined current amount and processing time, the lowest energy amount consumed was calculated as 7089.28 J.