Quality assessment of friction stir welding joints via an analytical thermal model, iSTIR

An inverse engineering approach has been implemented in order to demonstrate the feasibility of using the analytical thermal code iSTIR to establish correlations between the parameters of friction stir welding (FSW) and the properties of the resulting joints.The fundamentals of the iSTIR code are reviewed, and applications to two examples are presented. The components of the force and the torque applied by the tool to the parts and the temperature field were measured. The mechanical data allowed calculation of the mechanical power delivered by the tool into the weld joint, and the thermal field was used as an input for the iSTIR code, resulting in calculations of the heat power dissipated during the stationary state of the welding process. Correlations were then established between the thermal efficiency and the FSW parameters, allowing a comparison of the mechanical properties with the process parameters.The results show maximum thermal efficiency for intermediate FSW conditions, and that the evolution of the thermal efficiency is in accordance with the evolution of the assessed mechanical properties.