Failure behavior of hole hemmed joints with a novel configuration for hybrid busbars in electric vehicle batteries

This study, for the first time, investigates the failure behavior of hole hemmed joints with a novel configuration in shear tests. These joints are formed through plastic deformation without the need for additional elements, heat, or welding. The aim is to evaluate their potential for connecting hybrid copper–aluminum busbars in electric vehicle batteries. Initially, copper’s fracture limits are characterized under various loading conditions, and the Modified Mohr-Coulomb criterion is calibrated. The hole hemming process is then used to join AA6082-T4 aluminum and Cu-ETP R240 copper sheets by deforming and folding the outer aluminum sheet onto the inner copper sheet, creating a mechanical interlock. This is followed by shear tests on the resulting joints. A comprehensive finite element model is developed to simulate both the joining process and the shear test. Results indicate that the joints fail gradually through hole bearing, with cracks forming and propagating in the copper sheet. The mechanical interlock, influenced by punch displacement, enhances failure load and displacement while reducing the initial load. Only the copper inner sheet is damaged during shear tests, while the aluminum outer sheet is damaged during the joining process. With a maximum shear strength of 4.54 kN and a displacement of 13.84 mm for a mechanical interlock of 0.9 mm, these joints show significant potential for hybrid busbar applications in electric vehicle batteries.