Development of Fatigue Life Prediction Method for Spot-Welded Joints of Mixed Materials

Abstract

Spot-welded joints are widely employed in the construction of vehicle structures. Recently, due to the strategies for minimizing the fuel consumption and vehicle emissions, more and more applications of lightweight materials, such as aluminum (Al) alloys, are employed in spot-welded joints. Hence, a universal and simple fatigue life prediction method is needed for conventional steel spot-welded joints as well as mixed materials spot-welded joints. In this study, a new notch stress approach is developed for fatigue life evaluation of the spot-welded joint. The idea of this method originates from Rupp’s structural stress method, which has been successfully used in automotive industry. The structural stress method is simple enough, but there are nine parameters needed to be adjusted for each new experimental data. Thus, the primary goal of the new approach is to eliminate the troublesome parameters. Stress intensity factors SIFs and stress concentration factors are introduced to solve this issue. Then, having considered the boundary conditions and crack propagation effects, some correction factors are applied to the new notch stress approach in this study. Finally, three groups of spot weld fatigue data including steel, aluminum alloys and their combination are processed with the new notch stress approach for validation. Compared with Rupp’s structural stress method, distinct improvements are presented in this study.