Elucidation of fatigue failure mechanism of laser spot welded joints with different number of joining points

Abstract

In this study, fatigue properties and fatigue failure mechanisms were investigated using joints made by applying multiple cross laser spot welds to a 590 MPa cold-rolled high-strength steel plate used for automotive steel. Compared to the joints with only one cross laser spot welding point, the joints with two points applied in the direction of the load axis and the joints with two points applied perpendicular to the load axis both showed an improvement in fatigue strength. It is suggested that the improvement in fatigue strength is due to the increase in bending rigidity in the former case and the dispersion of stress applied to each weld point due to the increase in the number of weld points in the latter case.