Torque Control of Friction Stir Welding

Longhurst Engineering, PLC and Vanderbilt University propose the innovation of torque control of friction stir welding (FSW) as a replacement to force control of FSW. The value of the torque is significant because it indicates how far the tool is plunged into the work piece. Proper engagement of the tool into the work piece is critical for producing reliable welds. The commercialized innovation will consist of three elements. First, a FSW tool will be developed to produce a linear relationship between the welding torque and the tool's plunge depth into the work piece. Second, the welding torque will be measured from outside the welding environment via the spindle motor current, thus eliminating the need for expensive force sensors associated with force control. Third, a closed-loop architecture will be designed and implemented to control the welding torque. Torque control of FSW can be applied by NASA to increase welding reliability with the Upper Stage of the Ares I launch vehicle. Torque control will also reduce capital investment and operations costs for NASA. The expected TRL is 4 at the beginning of the project and 5 at the end of Phase I.

Boeing, Lockheed Martin and other aerospace companies have FSW applications very similar to NASA that would benefit from torque control of FSW. As with NASA, these companies would increase the reliability of welding operations, in particular with very long linear and circumferential welds. In addition, they would experience reduced maintenance costs and the reduction in required capital investment for future endeavors with robotic FSW. Lastly, torque control of FSW could be used by numerous small businesses entering into the FSW market. This technology would provide a cost effective method for using traditional machine tools and industrial robots to perform FSW. Expensive force gauges and dynamometers would no longer be required. Potential small business users are the numerous automotive suppliers to General Motors, Toyota, Ford, and Chrysler. As these automotive companies begin to manufacture vehicles using FSW, many suppliers can utilize torque control of FSW.

Torque control of FSW can be applied to welding the Ares I launch vehicle. In particular, the long and circumferential welds where work piece variation, machine deflection and changing thermal conditions create manufacturing challenges. By applying torque control instead of force control, the welding reliability will increase. Increasing the reliability of linear and circumferential welds that can range up to approximately 30 feet in length will increase the productivity of welding operations at NASA. There would be less weld defects due to the welding controls becoming unstable and causing weld defects. The vertical and robotic welding tools at Marshall Space Flight Center would be able to apply this technology almost immediately after project completion. Along with increasing reliability, torque control will be effective at reducing operating costs associated with FSW. Operations cost would be reduced by not having to replace or repair existing force sensors.

This is early/mid-stage (TRL 5) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

None of these are guaranteed paths for this specific project — TechPort itself doesn't have an "apply" button. Reaching out to the contact(s) above with a specific question is usually the fastest way to find out what's actually open.