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|저자명||Namsu Park, Moonsu Park, Hoon Huh|
|Name||2014 KSAE Annual Conference|
This paper deals with the tensile properties acquisition of the nugget region in spot-welded joint at various strain-rates using micro material testing machine. The driving and load measuring part of Static Micro Material Testing Machine (SMMTM) and High-Speed Micro Material Testing Machine (HSMMTM) were replaced by considering the load requirement. A jig and a gripping device are designed to meet the requirements of the specimen shape and strength. Two kinds of specimens for the tensile tests were obtained each from the center of the welded spot and 1 mm away from the centerline at the spot welded joint of the DP980 by wire electric discharged machining (EDM). The thickness of the specimen was 0.3 mm and the gage length of the specimen was 1 mm. Digital image correction method (DIC) was applied to measure the longitudinal strain. The speckle pattern generation method was also improved for DIC method application. Quasi-static tests were performed with SMMTM at strain-rates of 0.001 s−1 and 0.1 s−1. Dynamic tests were performed with HSMMTM at strain-rates of 1 s−1, 10 s−1 and 100 s−1. A comparative evaluation was performed between the material properties of the base metal and the nugget region in spot welded joint, based on the obtained stress−strain curves.