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Michael De Leon,Mark Angelo Diaz,Hyung-Seop Shin 한국초전도저온학회 2023 한국초전도저온공학회논문지 Vol.25 No.4
This study presents a comprehensive procedure for the low cycle fatigue test of ultrasonically welded (UW) coated conductor (CC) lap-joints. The entire process is examined in detail, from the robust fabrication of the UW REBCO CC joints to the reliability testing under a low number of repeated cycle fatigue conditions. A continuous Ic measurement system enables real-time monitoring of Ic variations throughout the fatigue tests. The study aims to provide a step-by-step procedure that involves joint fabrication, electromechanical property (EMP) tests under uniaxial tension for stress level determination, and subsequent low-cycle fatigue tests. The joints are fabricated using a hybrid method that combines UW with adding In-Sn soldering, achieving a flux-free hybrid welding approach (UW-HW flux-free). The selected conditions for the low cycle fatigue tests include a stress ratio of R=0.1 and a frequency of 0.02 Hz. The results reveal some insights into the fatigue behavior, irreversible changes, and cumulative damage in the CC joints.
Michael de Leon,Hyung‑Seop Shin 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.4
Recently, battery capacity and performance improvements have become the most important issues for improving the performanceof electric vehicles. Improvement of the aluminum and copper junctions used as battery tab materials is also required. The dissimilar tab materials are connected either in series or parallel to deliver the required battery power and capacity tothe vehicle. Ultrasonic welding is increasing in popularity for joining dissimilar materials, and the automotive industry islikely to benefit the most. However, the industry is dealing with variations in joint quality due to the numerous weldingparameters involved, such as the welding time, vibration amplitude, welding pressure, etc. Therefore, in this study, an appropriatedesign-of-experiment method was used to optimize the selected welding parameters with a reduced number of testsin terms of weld strength quality (either under lap-shear or T-peel tests) and electrical joint resistance. The signal-to-noiseratio and strength-reduction ratio analyses were employed to investigate the influence of different welding parameters foreach joint-quality category and to predict the optimum welding parameters within the limits of the parameters studied. Theanalyses were successful and effective in identifying the most influential welding parameter for each category. The resultsof analyses and predictions generated were satisfactorily comparable with the validation experiment results.