Numerical simulation on friction stir spot welding of alumimum alloy using SPH method

Lightweight metals such as aluminum have been increasingly used in the automotive industry in order to save vehicle weight. Because of its advantages, Friction stir spot welding (FSSW) process is expected to apply to join automobile body parts made of aluminum sheet. In FSSW process, material flow is a key factor which affects weld microstructure and welding quality. The present paper investigated the material flow patterns and velocity during aluminum alloy FSSW process through numerical simulation using smoothed particle hydrodynamics (SPH) method. It is found that the material beneath the pin moves in downward and outward direction. At the pin periphery, the material is pushed downwards and outwards firstly and then upwards little by little, thus forms the hook. Close to the shoulder periphery, the material is pushed upwards and outwards, which shows up on the workpiece surface as burr. The research results can provide guidelines for process analysis and quality control of FSSW process.