| 摘要 |
A friction stir spot welding tool having a rotatably driven shank. A shoulder adjacent to one end of the shank is generally circular in shape having a concave profile while a pin having a generally triangular cross-sectional shape protrudes axially outwardly from the shoulder. To perform the spot welding operation, the shank is rotatably driven and the shoulder is plunged into the workpiece such that the pin penetrates past the workpiece interface to a predetermined depth to perform the spot weld. The proposed triangular pin tool is found to significantly increase the weld strength when compared to conventional pin shaped tools due to the following: (1) it inhibits the formation of the vertical hook in the stir zone (the upward rise of the hook is arrested when the pin plunges into the workpieces interface), and (2) due to the asymmetric rotational pattern of the triangular pin it enhances the mixing of the material around the tool pin and oxide layer is dispersed (made discontinuous) in the stir zone.
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