NUMERICAL ANALYSIS ON THE RESIDUAL DISTORTION OF Al ALLOY SHEET AFTER FRICTION STIR WELDING

Although the residual distortion of 6056 Al alloy sheet after friction stir welding (FSW) is smaller than that after fusion welding, it is still a significant defect for the assembly and application of welded structure. In order to investigate and predict the residual distortion of Al alloy sheet after FSW, a 3D thermo–mechanical model was established based on experimental conditions to simulate the FSW process. In the model, heat input was computed based on the torque data measured during experiment, and heat transfer between welded sheet and fixtures was simplified in the way of convection, and the properties of 6056 Al alloy were considered as temperature function, and tool loads were taken into account during the mechanical analysis. The simulation results show that the distribution of longitudinal residual stress along the width of sheet is asymmetrical, and the residual distortion corresponds well with experimental results both in distortion pattern and deformation values on the whole sheet.