The Influence of the Tool Tilt Angle on the Heat Generation and the Material Behavior in Friction Stir Welding (FSW)

Abstract

In practical FSW, tool tilt angle plays a significant role in enhancing the weld quality due to the generated forging force in the trailing side. For thermomechanical analysis of FSW, most models did not consider the tool tilt angle or used a simplified assumption, which caused the inconsistence with the practical cases due to inappropriate treatment of the tool/workpiece contact conditions. To improve the accuracy of numerical simulation of FSW process, the tool tilt angle must be considered. In this study, specific considerations for mechanical boundary conditions in Eulerian domain is employed to investigate the tool tilt angle influence on the thermomechanical behavior in FSW. Aluminum 6061-T6 with the thickness of 6 mm under the rotational speed of 800 RPM, the transverse speed of 120 mm/min and the plunging depth of 0.1 mm were employed for the simulations. Results showed an almost symmetric temperature profile predicted by the model without considering the tool tilt angle, while after incorporating the tool tilt angle, the peak temperature point is moved to the tool backside, resulting in better material bonding, enhancing the weld joint quality. Without accounting for the tool tilt angle the highest temperature of 389°C is observed, while with the tilt angle the maximum temperature of 413°C is achieved. The temperature variations at different points of the leading and the trailing sides of the welding tool were measured. It was observed that, after considering the tilt angle, as the tool moves, a smooth and quick increase for the temperature at the tool leading side achieves. This smooth and quick increasing of the temperature at the leading side results in reducing the possibility of the formation of defects, cracks and voids. Finally, comparisons showed that the model computational time is acceptable and using Eulerian formulation leads to achieving a remarkable accuracy.