A method for prediction of S-N curve of spot-welded joints based on numerical simulation

Abstract

Currently, ΔF-N curves are often used to predict the fatigue lives of spot-welded joints, but the method for obtaining these ΔF-N curves is time-consuming, laborious, and non-universal. Tensile-shear fatigue tests were performed to obtain the fatigue lives and the corresponding normalized S-N curves of spot-welded joints. Subsequently, the force acting at the spot-welded joints was obtained by extracting the force and moment of the beam element in the shell-element-based finite element model, and the equivalent structural stress at the spot-welded joint was obtained based on the equiva-lent structural stress method. Finally, the S-N curves of the spot-welded joints were fitted using the least-squares method. A comparison of the S-N curves of the spot-welded joints with those of different materials revealed that the material type had a significant influence on the S-N curve. To avoid this influence, a method for predicting the S-N curve of the spot-welded joints was proposed based on the relationship between the ratio of the ten-sile strength and that of the fatigue limit of each material. This research provides guidance for predicting the fatigue life of spot-welded joints in engineering applications.