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KURTULMUŞ, MEMDUH

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KURTULMUŞ

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MEMDUH

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Subject: mechanical properties ×

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Now showing 1 - 2 of 2
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    The effects of undercut geometry on the static stress concentration factor of welds
    (ICE PUBLISHING, 2021) KURTULMUŞ, MEMDUH; Kurtulmus, Memduh; Dogan, Ezgi
    Undercutting is a welding defect that appears as a groove in the base metal directly along the edges of the weld metal. It is inevitable in fillet and butt joints if improper welding parameters are used in the operation. It is a discontinuity in the welding that produces stress concentration and lowers the strength of the weld. The stress concentration factor of an undercut is due to the reinforcement angle, undercut width, undercut depth and undercut root radius. In this study, 20 mm thick mild steel plates were welded by automatic gas metal arc welding with the carbon dioxide (CO2) shielding gas process. A single-V butt joint was obtained after welding. Before welding, 30 degrees groove angles were obtained by milling on the longitudinal side of each workpiece. Two plates were welded with several passes. After welding, the weldment was tested with a radiographic non-destructive testing process. A defect-free weldment was obtained. Then, standard tensile test samples were machined from the weldment. A groove was drilled in the heat-affected zone, adjacent to the weld metal boundary on every tensile test sample. Each groove resembled an undercut. The length, root radius and depth of grooves were varied. Then, the samples were broken on a tensile test machine. From the test results, the static stress concentration factor of each groove was calculated. The effects of groove geometry on stress concentration factors were determined.
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    Experimental investigation and optimization of welding parameters on weld strength in friction stir spot welding of aluminum using Taguchi experimental design
    (ICE PUBLISHING, 2020) KURTULMUŞ, MEMDUH; Kurtulmus, Memduh
    Nineteen years ago, the automotive industry started using the friction stir spot welding (FSSW) process in joining metallic parts. The popularity of this welding process became higher every year. In this study, aluminum (Al) 1020 sheets of 2mm thickness were joined with the FSSW process. The effects of FSSW parameters (plunge depth, tool rotation speed and dwell time) on the mechanical properties of weldments were investigated. The mechanical performance of the welds was evaluated by using the lap-shear tensile test. The optimization was done by using the Taguchi method. 'The-higher-the-better' quality control characteristic using the analysis of variance (Anova) method was applied to determine the optimum welding parameters. The signal-to-noise ratio was computed to calculate the optimal process parameters. The percentage contributions of each parameter were validated by using the Anova technique. The experimental results were analyzed by using the Minitab 17 software. The tool rotation speed was found as the dominant welding parameter on the weld strength of aluminum 1020 sheets for the FSSW process. The weld that had been produced with the optimum welding parameters gave a 23% higher fracture load than the initial welds.