二段多重変動振幅荷重下のスポット溶接継手の疲労寿命特性

抄録

In this study, a two steps variable amplitude load fatigue test was carried out on peeling test specimens using a mild steel sheet (SPCE) with a thickness t = 1.6 [mm]. In the fatigue testing, the amplitude number of the higher load was fixed at 100 [cycle], and that of the lower load was changed. As a result, it was found that the fatigue life increased as the amplitude number of lower load increased. It was presumed that this is caused by generating the large plastic zone due to peak load. The plastic zone was verified by the hardness testing and the size was theoretically calculated based on linear fracture mechanics. The specimen loaded with a peak load had the higher values of hardness in the vicinity of the crack compared with the unloaded specimen. Moreover, theoretically calculated size of the plastic zone is large enough to exceed the sheet thickness.