Friction Stir Spot Welding: Engineering Analysis and Design

Abstract

Friction stir spot welding (FSSW) presents automotive manufacturers with a process that is capable of joining light-weight aluminum alloys. The desire to eliminate the keyhole, a product of the process, is the main motivation of this dissertation. It is found that using a pinless tool offers a simple, low-cost, option capable of creating spot welds without the keyhole. The research presented in this dissertation, both experimental and numerical, greatly expands upon what was a limited understanding of the friction stir spot welding process (with a pinless tool especially.) The result of this work is a more fundamental understanding of the welding process, its parameters, and how they interact to affect the quality of the spot weld. A novel double-sided variation of the FSSW process is presented. In order to create double-sided friction stir spot welds a rotating anvil is designed, built, and experimentally qualified. The double-sided FSSW process is found to reduce cycle times and process forces, improve weld quality, and increase the maximum workpiece thickness that can be welded with a pinless tool.