NUMERICAL SIMULATION OF MATERIAL FLOW IN AA6082 DURING FRICTION STIR SPOT WELDING

Friction stir spot welding (FSSW) is a new solid state joining technology based on the linear friction stir welding which can be used to replace the conventional resistance spot welding as well as riveting. However, some key problems such as heat transfer and thermoplastic material flow have not yet been studied sufficiently and block the application of this advanced technology. This paper presents the coupled thermo-mechanical viscoplastic finite element formulation based on the character of FSSW. The model was calibrated by comparing temperature history between simulation results and experimental data and subsequently used to investigate the effective strain rate and material flow in joint. The temperature study showed that the simulation and experiment results coincided well with each other thus proofing the correctness of the model. The simulation results showed that the effective strain rate distribution were not uniform. The material close to the pin's cylindrical surface had a higher effective strain rate than that of the other material. The materials in weld centre mainly experienced a compression process and the other material under the tool experienced both compression and shear process.