Fatigue life prediction of multi-spot-welded panel structures using an equivalent stress intensity factor

Fatigue failure of spot-welded panel structures can be evaluated by means of a fracture parameter, since a weld-spot has an external crack type geometry. Recasting the load vs. fatigue life relations experimentally obtained from single-spot-welded specimens, we predict the fatigue life of spot-welded specimens with a parameter denoted the equivalent stress intensity factor (Ke). This crack driving parameter describes the effect of material ductility, specimen geometry and loading type on the fatigue failure in an inclusive manner. The proposed fatigue life formula for a single spot weld is used for assessment of multi-spot panels, as the fatigue strength of multi-spots is eventually determined by that of each constituent single spot. In this study, we consider three types of multi-spot seat belt anchors as analysis models. We obtain the effective crack driving parameter Ke using finite element analyses. The Ke concept is then confirmed to successfully predict the fatigue life of multi-spot panels represented by auto seat belt anchors here.