Tech Briefs

Mechanism for Self-Reacted Friction Stir Welding

This mechanism performs better than others that have been tried.

A mechanism has been designed to apply the loads (the stirring and the resection forces and torques) in self-reacted friction stir welding. This mechanism differs somewhat from mechanisms used in conventional friction stir welding, as described below.

The tooling needed to apply the large reaction loads in conventional friction stir welding can be complex. Self-reacted friction stir welding has become popular in the solid-state welding community as a means of reducing the complexity of tooling and to reduce costs. The main problems inherent in self-reacted friction stir welding originate in the high stresses encountered by the pin-and-shoulder assembly that produces the weld.

ImageThe design of the present mechanism solves the problems. The mechanism (see figure) includes a redesigned pin-and-shoulder assembly. The welding torque is transmitted into the welding pin by a square pin that fits into a square bushing with setscrews. The opposite or back shoulder is held in place by a Woodruff key and high-strength nut on a threaded shaft.

The welding pin and shoulder can be assembled and disassembled quickly. An additional advantage of the present mechanism is that it affords positive sealing on the root-side shoulder to reduce winking of the material being welded. This mechanism has been proven superior to all mechanisms tried before in self-reacted friction stir welding.

This work was done by Richard Venable and Joseph Bucher of Lockheed Martin Corp. for Marshall Space Flight Center. For further information, contact Gary L. Wilett at (504) 257-4786. Title to this invention has been waived under the provisions of the National Aeronautics and Space Act {42 U.S.C.2457(f)} to Lockheed Martin Manned Space Systems. Inquiries concerning licenses for its commercial development should be addressed to: Lockheed Martin Manned Space Systems P.O. Box 29304 New Orleans, LA 70189 Refer to MFS-31914, volume and number of this NASA Tech Briefs issue, and the page number.