Ultrasonic Metal Welding Process Robustness in Aluminum Automotive Body Construction Applications

Ultrasonic metal welding is a prom- ising joining method for aluminum automotive body construction applications. In order to achieve technology implementation readiness, process robustness to weld orientation, aluminum sheet rolling direction, residual stamping lubricant level, and material age must be assessed. Experiments were conducted to characterize variations in weld failure loads and microstructural features resulting from the directional nature of the energy input during ultrasonic welding to ensure that the angle at which components are ultrasonically welded together does not affect weld performance. These experiments were also designed to ascertain whether the orientation of a welding machine with respect to the rolling lines on an AA6111 sheet component or the relative orientation of the rolling directions of two components being joined is critical. A second set of experiments was conducted to determine the effects of surface lubricant level on tensile-shear and T-peel failure loads and fatigue performance for AA6111 and AA5754 sheet. Robustness to surface lubricant level is important because often in North American automotive production facilities, components are not cleaned prior to welding; rather, they are welded with residual stamping lu- bricant on the surfaces. Finally, because AA6111 naturally ages at room tem- perature for an extended period of time in the T4 temper, experiments were performed to ascertain the impact of AA6111 material age on ultrasonic weld tensile-shear and T-peel failure loads. For all factors considered in this study, ultrasonic metal welding process robustness was demonstrated.