| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 100 === In this thesis, the development of material flow during friction stir spot welding (FSSW) are discussed. The experimental were divided into two parts. In the first part of the study, tracing powders were embedded into the welding sheets to investigate material flowing behaviors during FSSW, FSSW at a tool speed of 2500 rpm, with a plunging rate of 1 mm/s, and dwell time of 0s、2s and 4s. In the second part of the study, those are a cylindrical pin with threads and a triangular pin without threads, were used to determine the geometric effects on FSSW.
Experimental results show that without established TCS, the desired mechanical properties of Al alloy A6061-T6 welds could not be obtained. In addition, the welds using the cylindrical pin with threads and shoulder-angle of 13 degree exhibited the largest elongation and highest tensile strength. A new model of material flow was proposed with the schematic diagrams to illustrate the differences caused by tool geometries, and it would be beneficial for further design of welding tools in the future.
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