| Summary: | 碩士 === 國立中正大學 === 機械工程所 === 96 === In this paper, the global and local stress intensity factor solutions for spot welds in U-Shape specimens are investigated by finite element analyses. Two-dimensional and Three-dimensional finite element models are developed for U-shape specimens to obtain accurate global and local stress intensity factor solutions. Based on the approach of Wang et al. (2005a, 2005b), various geometric factors of U-shape specimens, sheet thickness, base sheet width, base sheet length, flange length and radius of fillet between base sheet and flange are considered in this investigation. The computational results are compared with the analytical global stress intensity factor solutions of Zhang (2001) and Lin and Pan (2007). The computational results provide some geometric functions to analytical global stress intensity factor solutions of Zhang (2001) for U-shape specimens. The computational results also indicate that the flange length has significant effects on the global stress intensity factor solution. Next, based on the approach of Wang and Pan (2005), the effects of the kink depth to the local stress intensity factor solutions for kinked crack are investigated. The computational results provide geometric functions to mode I local stress intensity factor solution for vanishing kink depth. The computational results also indicate that as the kink depth increases, the mode I local stress intensity factor solution increases and then decreases. As the kink depth increases over 90% of the sheet thickness, the mode I local stress intensity factor solution becomes negative.
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