Ultrasonic welding of Cu/Al cables: a study on the finite element model and characteristics of the gaps

A thermomechanical coupling model for the ultrasonic welding of Cu/Al cables was developed using Abaqus software. The effects of ultrasonic softening and thermal softening on the yield strength of Cu/Al cables are evaluated within the finite element model. By incorporating heat flux equivalent to frictional heat generation and the heat generated by plastic deformation at the weld interface, a highly efficient and accurate thermomechanical coupling model for the ultrasonic welding of Cu/Al cables was established. The accuracy of the model was verified by the temperature measurements and morphological analysis of the welded joints. The simulation results indicate that the stress concentration at the edges of the Al wire, leading to a reduction in the effective load-bearing area, is the primary cause of joint degradation. In addition, the results of the joint gap analysis indicate that the joint quality is optimal when the gap volume is approximately 2.36 mm³, with the tensile strength reaching 398.6 N (300 J).