Numerical simulation of dissimilar friction stir welding for electric vehicle busbar assembly: An arbitrary Lagrangian–Eulerian approach

Achieving a robust metallurgical bond between AA7072 aluminum alloy and C11000 pure copper is a critical challenge in the manufacturing of high-efficiency electric vehicle busbars. While friction stir spot welding mitigates the defects commonly associated with conventional fusion welding, the highly non-linear material flow makes empirical optimization both costly and time-consuming. This study develops a three-dimensional arbitrary Lagrangian–Eulerian finite element framework to numerically simulate the complex thermo-mechanical interactions inherent in the dissimilar Al-Cu friction stir spot welding process. The model maps the equivalent plastic strain, stress distribution, and thermal cycles across varying tool rotational speeds ranging from 800 to 1600 r/min. The numerical results reveal that rotational speed primarily governs peak temperatures and strain accumulation, predicting an optimal thermal window that maintains interface temperatures below the 548 °C eutectic threshold to help minimize brittle intermetallic compound formation. Ultimately, this computational framework provides a predictive capability for assessing thermomechanical behavior and material flow, which may serve as a computational aid for optimizing friction stir spot welding process parameters for electric vehicle busbar applications. It should be noted that the predictions remain to be validated against experimental measurements in future work.