Fracture Behaviors and Analysis under Biaxial Loading of Friction Stir Spot Welds of Aluminum Sheets

• Main Authors: Hsiao, Chenghao, 蕭承浩
• Other Authors: Lin, Paichen
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/80656359586815669137

碩士 === 國立中正大學 === 機械工程學系暨研究所 === 99 === Fracture behaviors of friction stir spot welds (FSSW) in 6061-T6 aluminum sheets under biaxial loading were investigated based on experimental observations. A tool with a triangle probe was used to make FSSW’s in U shaped, square-cup, and cross-tension specimens with sheet thicknesses of 1.0 and 1.6 mm. The FSSW’s in U-shape specimens made under various rotational speeds, dwelling times and indentation depths were first examined. Appropriate welding parameters were then obtained by the maximum failure loads. Biaxial tensile tests for three types of specimens were conducted. Photos and optical micrographs for specimens before/after tests were examined. The experimental results indicate that for specimens with different thicknesses and under different angles, the failure loads of square-cup specimens are greater than U-shape specimens, and those of U-shape specimen are greater than cross-tension specimens. Nugget pullout failure mode can be seen in all cases. Finally, two general failure criterions of spot welds proposed by Lin et al.[4] and Song et al. [24], respectively, were considered to estimate the failure loads of FSSW’s under different loading conditions. The curves of Lin et al. [4] are in general higher than the experimental results, while those of Song’s et al. [24] agree well with the experimental results.