Overload analysis and fatigue life prediction of spot-welded specimens using an effective J-integral

This paper proposes an integrated approach for predicting the fatigue life of spot-weld specimens. The approach is independent of specimen geometry and loading type. We establish finite element (FE) models reflecting the actual specimen behavior observed from the experimental load-deflection curves of four types of single spot-welded specimen. Using established FE models, we first evaluate J-integral as a fracture parameter for describing the effects of specimen geometry and loading type on the fatigue life. It is confirmed, however, that J-integral concept alone is insufficient to produce the generalized relationship between load and fatigue life of spot-welded specimens. On this ground, we introduce another effective parameter Je composed of JI, JII, JIII. The mechanism of the mixed mode fracture, which incites the use of Je, is discussed. The parameter Je is demonstrated to more sharply define the relation between load and fatigue life of spot-welded specimens. The crack surface displacement method is adopted for decomposition of J.