Abstract: The present invention provides a novel pin design for a friction stir welding (FSW) tool that can penetrate more deeply into workpieces to form a thicker weld joint without overloading the tool. The pin is provided with threads on its surface. Some portions of the threads are in a positive hand (d2, d3); positive threads screw in to draw the pin into workpieces when the pin is rotated. Other portions of the threads are in a negative hand (d1, d4); negative threads screw out to oppose drawing-in of the pin. When the pin is rotated and driven into workpieces under an applied vertical load, the positive threads encourage penetration of the pin into the workpieces while the negative threads enhance shearing of workpiece material into particles. The positive threads thus reduce the amount of vertical load required to drive the pin, and therefore allow the pin to penetrate more deeply into workpieces to form a thicker weld joint without overloading the tool.

Abstract: The present invention provides novel joint designs and methods for holding together and drawing together interface edges of workpieces during friction stir welding. The method includes providing an interface edge (30A) on a first workpiece (20A), and an interface edge (30B) on a second workpiece (20B) that is complementary with the interface edge of the first workpiece. The interface edges cooperate with consumable pins (38) to hold the first and second workpieces together. In a preferred embodiment, the interface edges cooperate to draw the first and second workpieces together when a load in a direction normal to the interfaces is applied along the mated interfaces.

Abstract: The present invention provides an in-process method to repair voids in an aluminum alloy, particularly a friction stir weld in an aluminum alloy. For repairing a circular void or an in-process exit hole in a weld, the method includes the steps of fabricating filler material of the same composition or compatible with the parent material into a plug form to be fitted into the void, positioning the plug in the void, and friction stir welding over and through the plug. For repairing a longitudinal void (30), the method includes machining the void area to provide a trough (34) that subsumes the void, fabricating filler metal into a strip form (36) to be fitted into the trough, positioning the strip in the trough, and rewelding the void area by traversing a friction stir welding tool longitudinally through the strip. The method is also applicable for repairing welds made by a fusing welding process or voids in aluminum alloy workpieces themselves.