The objective of this research is to fully characterize the effect of processing parameters on strength and durability of spot friction welds in aluminum sheets. The approach is to conduct a combined experimental, computational and analytical investigation. Processing parameters such as tool geometry, tool compressive force, tool speed and tool holding time for strength and durability of welds will be identified in the experiments. Failure and fatigue mechanisms will be examined for welds formed under different processing conditions. Finite element computational analyses will be conducted to understand the macroscopic plastic deformation of the interfacial surface. Shear localization theoretical analyses will be performed to identify the weld size for determination of strength and durability.
The traditional resistance spot welding of aluminum sheets has several technological challenges such as limited electrode tip life and high probability of poor welds. Alternative joining methods for aluminum sheets are currently sought by the automakers. The spot friction welding of aluminum sheets is a new technology. A fundamental understanding of spot friction welding will help the US automotive industry to quickly adopt the technology for the global competitiveness. Due to its extremely low energy consumption, the spot friction welding process to join aluminum sheets can save energy significantly. In addition, more lightweight aluminum sheets used in vehicle structures result in good fuel economy and energy conservation of the nation. Furthermore, spot friction welds can potentially be used to replace the rivets used in airplanes to save the weight and the manufacturing cost of the aerospace industry. The research results will be taught in three graduate courses. One graduate course entitled "Fatigue Testing and Analysis for Durability" will be taught through a distance-learning program for engineers in the automotive industry via the internet.
