Friction Stir Welding (FSW) is a relatively new solid-state welding process, and many industries are now relying on this technique to produce advanced structures. Industries employing this technique include, but are not limited to, aeronautical, motor vehicle, and maritime. As with any welding technique, the quality of a weld must be determined to ascertain reliability and safety. For this reason, a welded structure has to go through a rigorous screening process.

In order to test a weld’s quality, destructive and non-destructive tests are conducted; however, destructive tests damage the structure and cannot always be utilized. Consequently, non-destructive testing is typically conducted. One state-of-the-art nondestructive technique is phased array ultrasonic testing (PAUT), which is widely utilized for weld inspections; however, PAUT is difficult to achieve at high temperatures, and is not employed on-line during FSW. For this reason, an on-line, high-temperature PAUT scanner has been conceived to improve the manufacturing process of FSW and other automated welding techniques by allowing realtime scanning.

The scanner has a flexible design in which modular components allow the scanner to be applied to all major FSW platforms. Furthermore, with variable degrees of freedom, the scanner can adjust for various welding configurations. The position of the PAUT wedge can be adjusted with respect to the FSW tool. The on-line scanner has proven to successfully determine defects in friction stir welds. The design can be adjusted for other automated welding processes. The on-line FSW quality and safety system with PAUT greatly expedites the manufacturing process and reduces manufacturing costs. Currently, to determine defects in a weld, PAUT must be conducted after welding by removing extruded material and the FSW fixture. Removal of an industrial fixture, such as a pressure vessel, is a timely and costly endeavor. The on-line scanner has been designed to mitigate these issues; specifically, to improve and expedite the qualification of advanced structures that are welded.

Current PAUT technology only allows for scanning of a structure after it is welded. This is accomplished either by manual or automated off-line systems. High temperatures during welding cause issues to conventional PAUT transducers, and so it is not employed. Tight clearances between weld seams limit the application of on-line PAUT during welding as well. The invented PAUT scanner can easily be attached with FSW machines and determine weld defects online. The PAUT system has been designed to remedy the high-temperature affects that cause harm to PAUT transducers. Furthermore, the system has been designed to fit within FSW fixtures so that scanning during welding can be accomplished.

This work was done by Daniel Huggett, Mohammad Dewan, Mohammad Wahab, Thunshun Liao, and Ayman Okeil of Louisiana State University for Marshall Space Flight Center. NASA is seeking partners to further develop this technology through joint cooperative research and development. For more information about this technology and to explore opportunities, please contact Ronald C. Darty at This email address is being protected from spambots. You need JavaScript enabled to view it.. MFS-33327-1


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This article first appeared in the December, 2017 issue of Tech Briefs Magazine.

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