Abstract: The superplastically formed structural assembly includes first and second structural members having facing surfaces. The first and second structural members can include a first outer structural member, a second outer structural member or at least one intermediate structural member. In one embodiment, the first and second structural members include first and second outer structural members. In another embodiment, the first and second structural members include first and second intermediate structural members. The structural assembly includes at least one friction stir weld joint joining the first and second structural members. In one embodiment, the facing surface of the first structural member is at least partially covered with oxide to prevent thermo-compression welding of the first and second structural members adjacent the at least one friction stir weld joint. In another embodiment, the facing surface of the second structural member is at least partially covered with oxide.

Abstract: The superplastically formed structural assembly includes first and second structural members having facing surfaces. The first and second structural members can include a first outer structural member, a second outer structural member or at least one intermediate structural member. In one embodiment, the first and second structural members include first and second outer structural members. In another embodiment, the first and second structural members include first and second intermediate structural members. The structural assembly includes at least one friction stir weld joint joining the first and second structural members. In one embodiment, the facing surface of the first structural member is at least partially covered with oxide to prevent thermo-compression welding of the first and second structural members adjacent the at least one friction stir weld joint. In another embodiment, the facing surface of the second structural member is at least partially covered with oxide.

Abstract: The superplastically formed structural assembly includes first and second structural members having facing surfaces. The first and second structural members can include a first outer structural member, a second outer structural member or at least one intermediate structural member. In one embodiment, the first and second structural members include first and second outer structural members. In another embodiment, the first and second structural members include first and second intermediate structural members. The structural assembly includes at least one friction stir weld joint joining the first and second structural members. In one embodiment, the facing surface of the first structural member is at least partially covered with oxide to prevent thermo-compression welding of the first and second structural members adjacent the at least one friction stir weld joint. In another embodiment, the facing surface of the second structural member is at least partially covered with oxide.

Abstract: A method and apparatus for friction stir welding that produces a weld of significantly reduced surface roughness at significantly higher welding rates, in materials that are difficult to weld, such as non-extrudable aluminum alloys. The method includes cooling the stir welding tool during the welding process, thereby reducing the tendency of softened metal to adhere to the rotating pin and shoulder of the tool. The apparatus includes a tool with internal spaces or an external jacket, through which coolant can be pumped to remove heat and cool the tool during welding operations. In another embodiment, the apparatus includes a device for spraying a coolant onto exterior surfaces of the distal end of the welding tool to thereby remove heat from the tool, and the surrounding workpiece, during welding.

Abstract: The superplastically formed structural assembly includes first and second structural members having facing surfaces. The first and second structural members can include a first outer structural member, a second outer structural member or at least one intermediate structural member. In one embodiment, the first and second structural members include first and second outer structural members. In another embodiment, the first and second structural members include first and second intermediate structural members. The structural assembly includes at least one friction stir weld joint joining the first and second structural members. In one embodiment, the facing surface of the first structural member is at least partially covered with oxide to prevent thermo-compression welding of the first and second structural members adjacent the at least one friction stir weld joint. In another embodiment, the facing surface of the second structural member is at least partially covered with oxide.

Abstract: A method of root closure of friction stir welds in all types of stir weldable materials, especially difficult to weld materials, such as non-extrudable aluminum alloy 2024, 2014, 2090 and 7075. The method includes providing a backing device that has a recess, such as a groove or channel, sized to receive the tip of the pin of the welding tool and to contain the bead of the weld being formed. The workpiece rests on the backing device, with the proposed weld line aligned with the recess. Thus, as the weld is formed, material is extruded into the recess, completing closure of the weld root, and forming a small bead on the rear side of the workpiece. Optionally, this bead may be removed by a machining process. In one embodiment, the backing device is a plate with a channel machined in its surface so that the workpiece may be temporarily affixed to the plate, with weld line aligned with the channel, for welding.

Abstract: A friction stir welding tool for welding workpieces of variable thickness. The tool is characterized in that the displacement between a shoulder that presses down on an upper surface of the weld, and a tip of a rotating pin that penetrates and softens the workpiece to form the weld, is variable. In one embodiment, when the tool is used in conjunction with an apparatus that allows the shoulder of the tool to ride on and track the workpiece surface, the shoulder is stationary relative to the tool body, and the pin reciprocates relative to the shoulder to maintain contact with the backing plate, thereby providing a weld throughout the workpiece. In another embodiment, when the tool is used on an apparatus that holds the tool in fixed relationship to a backing plate on which the workpiece is held, the shoulder is able to reciprocate relative to the tool, following the upper surface contours of the workpiece, while the pin is able to penetrate through to the rear side of the workpiece to produce a uniform weld.