Rivet with sliding cap for friction stir riveting
AssigneeGeneral Motors Corporation
InventorsRobin Stevenson, Pei-Chung Wang
Life of this patent
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Abstract
A friction stir rivet is rotated and driven through a first fusible workpiece into an engaged second fusible workpiece, causing local portions of the first and second workpieces to plasticize. A slideable cap contacts the exposed surface of the first workpiece shortly after the process begins. The contact causes the cap to act as a retaining element, limiting the escape of plasticized material from stir site. Once the rivet is driven into the first and second workpieces, rotation ceases and the plasticized material hardens around the rivet. A weld is thus created, joining the workpieces and encompassing the rivet, which provides additional mechanical strength.
Claims8
A method of joining first and second fusible workpieces at a point of engagement, comprising the steps of:
- providing a rivet having a body formed of a material with a substantially higher melting point than that of the fusible workpieces wherein the body extends through a slideable cap;
- rotating the body about a rotational axis and simultaneously driving the body downward through a first workpiece and into a second workpiece, thereby forming a cavity and plasticizing material surrounding the body;
- engaging the cap against the first workpiece while the body slides through the cap until the upper stop engages the cap;
- stopping further rotation and inward driving of the rivet after a desired depth is reached;
- and
- cooling the fusible workpieces and the rivet, until solidification of the plasticized material occurs whereby the fusible workpieces are held together by the solidified material and by the rivet retained within the workpieces at the point of engagement.
Dependencies are inferred from the claim text.