Grant: Collaborative Research and Development Grants

Recent increase in aluminum spot welding applications has created a high demand for the means of quality assurance of aluminum spot welds. The in-depth understanding of metallurgical and mechanical properties of aluminum joints is needed to properly characterize the weld quality. The analysis of growth, deformation and fracture of A1 spot-welded joints, and use of this knowledge to make predictions about the weld performance, would greatly enhance the safety of automotive structures. That is why development of real-time acoustic method for metallurgical analysis of spot grain structure and fatigue properties would result in creation of the unique database of A1 spot weld properties and acoustic data for spot weld characterization. Although the general principles of aluminum spot welding are similar, there is a set of distinct differences from steel welding. These differences make application of the ultrasonic system for steel welding impossible for analysis of aluminum welding. Our preliminary trials on welding and testing aluminum joints using the equipment for steel welding have proven the necessity to develop a different system with some physical and technological principles borrowed from our well-developed steel welding characterization technique. The goal of this proposed research is to develop a new technology for real-time characterization of the aluminum resistance spot welds using an ultrasonic transducer incorporated into the weld gun electrode. The research will rely heavily on the finite element modeling of the processes of weld formation and acoustic wave propagation through the weld structure. These results will be used for development of the new transducer and other hardware to fit the requirements of the aluminum weld characterization. The research will involve the us of neural network for proper weld quality characterization based on acoustic signal processing. The computer modeling will be conducted in parallel with the extensive experimental trials using the most recent industrial equipment for better understanding of wave propagation within the structure of molten weld and for prediction~ of the most reliable acoustic parameters for weld quality characterization.