AN ELECTRICITY-ASSISTED FRICTION STIR WELDING PROCESS WITH CURRENT APPLIED FROM THE WORKPIECE SIDE SURFACES
Friction stir welding (FSW) has many promising industrial applications due to its solid-state nature and the associated benefits. However, some challenges still exist, such as: (i) a high tool loading force is required to generate the friction heat needed to soften the material, which often limits tool life, and (ii) FSW often desires a narrow temperature range near but below the melting point, which makes it challenging to get a deep welding depth without melting the top surface. Electricity-assisted FSW (EAFSW) has been previously studied in literature, where the current is applied from the tool. The electricity generates additional resistance heat, which may increase the welding efficiency and decrease the required tool loading force. However, this approach yields a relatively high temperature gradient in the depth direction, and is difficult to effectively enhance the welding depth without melting the top surface. In this thesis, a new EAFSW process is proposed and studied, where the current is applied from the workpiece side surfaces. The study is based on an experimentally tested physics-based model, and it shows that the new EAFSW process has a great potential to enhance the welding efficiency, decrease the required tool loading force, and increase the welding depth without melting the top surface.