The NASA Marshall Space Flight Center has developed an apparatus for joining two cylindrical (i.e., pipe-shaped) sections together with a friction stir weld. Friction Stir Welding is a relatively new welding technique for joining like materials together. The friction stir technique uses a friction heat source to plasticize adjoining sections of the same material. Once plasticized, the frictional heat source is removed and the sections joined together. A rapidly spinning probe, which must be capable of sustaining the requisite plasticized temperatures, is commonly used as the frictional heat source. The spinning probe also facilitates mixing of the material in the plasticized region.

Benefits

Potential Commercial Uses

Within both the aerospace industry and the commercial sector there is considerable interest in the development of the friction stir welding process for use in manufacturing. The weld process is optimized for use in straight line, constant thickness welds. And, the process is safe-no high voltage, liquid metals, or arcing. Aero-space companies such as McDonnell Douglas, Lockheed-Martin, and Boeing are pursuing the process.

The Technology

The Orbital Friction Stir Weld System is comprised of a base frame, a cylindrical clamping mechanism for securing a cylindrical work piece, a weld head, a reaction support, a means for transmitting load from the weld head to the reaction support, and a means for rotating the weld head in conjunction with the reaction support around the longitudinal axes of the clamping mechanisms. Since the cylindrical work piece will probably be in two sections, the cylindrical clamping mechanism must be capable of securing both sections of the work piece. The weld head and the reaction support separate the two pieces of the cylindrical clamping mechanism. The weld head and the reaction support are rotationally mounted to the base frame such that the weld head can rotate completely around the longitudinal axis of the cylindrical clamping mechanism and the reaction support can be maintained in a position diametrically opposed to the weld head. The rollers are mounted on the cylindrical clamping mechanism. They provide the mechanism by which the weld held and the reaction support are rotated around the circumference of the cylindrical work piece. The weld head is movable in a radial direction. The reaction support also has a roller to facilitate movement of the reaction support around the perimeter of the work piece. The means for transmitting load from the weld head to the reaction support is a radial load bar that is able to rotate and stay aligned with the weld head and the reaction support. Synchronized rotation may be accomplished with a motor and gearing mechanism and with a control mechanism that coordinates the rotation of the radial load bar with the weld head and the reaction support. The means for rotating the weld head in conjunction with the reaction support around the longitudinal axis of the cylindrical clamping mechanism includes a ring gear that is attached to both the weld head and the reaction support and is concentric with the cylindrical clamping mechanism; a drive gear engaged with the ring gear; and a motor for controlling the rotation of the drive gear. A second ring gear connected to a second drive gear and a second motor may be used to rotate the weld head and the reaction support. The motors can also be used to synchronize rotation of the radial load bar with the weld head and reaction support.

Patent Number

6,259,052

Contact for Licensing Information