The spot weld of high tensile steel does not improve as base metal strength. The previous study has investigated that a stress Intensity Factor mixed mode (mode I and mode II) can evaluate the fatigue strength. However, influence of residual stress is still not obvious which is important for the design of fatigue or spot weld conditions. Therefore, this study accomplish to clarify the fatigue limit diagram of notched specimen to evaluate fatigue strength of spot weld toe. Then, it become obvious that the compressive residual stress make extensive improvement of the fatigue strength.
