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

Abstract

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 J e composed of J I, J II, J III. The mechanism of the mixed mode fracture, which incites the use of J e, is discussed. The parameter J e 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.