Fatigue life assessment of Al-steel resistance spot welds using the maximum principal strain approach considering material inhomogeneity

A large fatigue test program was performed on a variety of Al-Al and Al-steel resistance spot welds (RSWs) using novel multi-ring domed electrodes. The results support the hypothesis that fatigue life is influenced not only by the weld nugget diameter and the sheet thickness, but also by the plastic deformation of the aluminum sheet. Finite element models considering material inhomogeneity in the RSWs were developed to determine the maximum principal strain. The results demonstrate that for stack-ups with different sheet thickness or material combinations, the maximum principal strain exhibited a better correlation with fatigue life when considering material inhomogeneity.