Fatigue strength evaluation of cross-tension spot weld joints of cold rolled mild steel sheet

In this study, cross-tension type specimens of cold rolled mild steel sheet were prepared varying the welding conditions in order to investigate the effect of welding time and current on the tensile strength and fatigue life. A decrease of 2 kA from the normal current condition of 10 kA caused a large amount of reduction in both the static joining strength and fatigue life. And increase of 2 kA in the nominal welding current resulted in an increase of static joining strength and an increase in low cycle regime but a decrease in high cycle regime, suggesting the fact that fatigue strength rather than static joining strength could be an important factor in the design process in view of the durability performance of the body. Compared to notch stress and equivalent stress intensity, the J-integral parameter can properly predict the current experimental fatigue life, including data with different specimen geometries. The J-integral parameter can be expressed as ΔJ (kJ/m2) = 5.75 × 105(Nf)−1.43.