• Allows the welding of more diverse materials, including composites and some materials previously thought unweldable
• Provides twice the fatigue resistance of fusion welds
• Offers higher retention of material properties
• Provides for safer operation, as it does not create such hazards as welding fumes, radiation, high voltage, liquid metals, or arcing.

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In spite of its many advantages, FSW had a couple of major drawbacks: (1) the reliance on a single-piece pin tool that left a small hole at the end of welds and (2) the requirement for different length pin tools when welding materials of varying thickness. MSFC, a licensee of the FSW process, has overcome these shortcomings with the development of the Auto-Adjustable Pin Tool, producing a technology that offers a smooth hole closure at the end of welds (which is essential when welding tanks and drums) and permits both pin angle and length to be adjusted for changes in material thickness.

MSFC has two existing license agreements for the pin tool. Licensee products are currently enabling FSW applications that are versatile, efficient, and cost competitive.

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MTS Systems Corporation, a leading supplier of mechanical testing and simulation equipment based in Eden Prairie, MN, recently introduced a new FSW product line employing the MSFC technology. The Intelligent STir welding for Industry and Research (ISTIR) products offer a flexible solution that enables advanced FSW applications on high-strength structural alloys.

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Nova-Tech Engineering, Inc., of Lynnwood, WA, also has a cutting-edge line of production stir welding equipment that uses the MSFC technology. Use of the Marshall pin tool has contributed to a range of production advantages for FSW applications in aerospace and other industries. Nova-Tech has used the tool successfully in a rocket tank production environment, eliminating the costs of plugging the close-out holes that are associated with other FSW welds.

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The FSW process utilizing the NASA pin tool technology is a recent upgrade to the Space Shuttle External Tank (ET) manufacturing program. New Space Shuttle weight requirements were established when the International Space Station was to be launched into low- Earth orbit. Overall Shuttle weight had to be reduced, and a decision was made to change ET material from aluminum alloy 2219 to a lighter weight material, aluminum lithium alloy 2195. Through FSW development work at MSFC, it was found that the FSW process was ideal for the welding and weld repair of the 2195 aluminum alloys--in fact it offers superior mechanical properties as compared to traditional fusion weld properties. ET project managers therefore elected to implement the FSW process at the Michoud Assembly Facility (MAF) where the Space Shuttle ET is manufactured. An increase in joint strength combined with a reduction in process variability provides for an increased safety margin and a high degree of reliability. The viability of the technology was demonstrated when MSFC used the pin tool to weld a full-scale simulated ET hydrogen barrel section.

Just as the Marshall technology has been employed for the Shuttle program, it will also be used for Ares. The pin tool will be an essential, integral component of the baseline weld process used to fabricate/weld the upper stage cyrogenic hardware for Ares I, and it is also expected to be used for Ares V.

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If you would like more information about this technology (MFS-xxxxx-1) or about other technologies available for license, please contact:

Sammy Nabors
NASA's Marshall Space Flight Center
Manager, Technology Commercialization and Licensing
Phone: (256) 544-5226
Fax: (256)-544-4810
E-mail: sammy.nabors@nasa.gov

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