Fatigue analysis of novel hole hemmed joints for hybrid busbars in electric vehicle batteries

This study investigates the fatigue behavior and failure modes of novel hole-hemmed joints, assessing their suitability as hybrid aluminum-copper busbars for electric vehicle batteries. The hole-hemmed joining process, which avoids the need for additional elements, heat, or welding, presents a sustainable solution for hybrid busbar manufacturing. The joints undergo quasi-static shear tests to determine failure mechanisms, strength, and failure displacements. A finite element model of the hole-hemmed process and shear test is developed to evaluate the impact of mechanical interlock on joint performance and to predict regions prone to crack initiation during fatigue testing. Shear fatigue tests and quasi-static shear post-fatigue tests reveal two primary failure modes: cracking at the edge of the aluminum outer sheet branch and bending of the copper inner sheet. The study also examines stiffness degradation and damage evolution during fatigue tests. A normalized load-cycle curve, plotting normalized fatigue load against fatigue life, is created to better predict joint fatigue life. Through comprehensive testing and modeling, the research provides a deep understanding of the mechanical performance of these novel hole-hemmed joints, underscoring their potential for use in hybrid busbars.