PNNL

Abstract

After friction stir welding/processing (FSW/P), an exit hole remains at the end of the run, which can be regarded as the weakest portion of the welded/processed workpiece due to the local mass reduction. Other than that, tensile residual stress around the exit hole coming from the heat influence during FSW/P facilitates an incipient cracking along the exit hole under external loading. Current solutions include cutting or repairing the exit hole, which are time- and cost-intensive. Therefore, in current work, we develop a novel method to fix the exit hole by applying an additional cycle pass around it, in such a way tensile residual stress around the exit hole is replaced by compressive residual stress. Under external loading, there is no evident strain accumulation around the exit hole, and the workpiece fails along the heat affected zone from FSW/P ultimately. The current method provides a more convenient pathway to fix the exit hole as compared with the current exit-hole repairing or removing methods for industrial applications.