| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 102 === In this thesis, the effects of different process parameters on material flow with different geometric tools during friction stir spot welding (FSSW) are discussed. The experimental were divided into two parts. In the first, the welding specimens were used to investigate the material flowing behaviors during FSSW, and the strength under tensile tests was compared, Tool speeds range from 450 rpm to 2700 rpm, a plunging rate of 1 mm/s, a plunging depth of 2.8 mm and holding time of 1s, 1.2s, 1.5s, 2s, 3s, 3.6, 4.5s, 6s, 9s, 18s. In the second part, tool force and the material temperature were measured during FSSW.
Experimental results show that forces was higher in low rotational speed than those in high rotational speed due to the resistance of material, and the temperature of the upper sheet was the highest when using tool B, while an obvious temperature rising of the lower sheet was observed when using tool M、T. Due to the effect of effective thickness on the upper sheet, hardening made by tools and grain coarsening caused by temperature rising, the strength of welds has a great improvement when using tool T under the process parameter with low tool rotational speed during FSSW.
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