A specialized welding tool, developed by a NASA engineer, is overcoming a "key" problem in the joining of metals - by welding shut a troublesome "keyhole."
Jeff Ding, a welding engineer at NASA's Marshall Space Flight Center in Huntsville, Ala., and Peter Oelgoetz, of the Boeing Co. in Huntsville, have designed a revolutionary automatic retractable pin tool for use in a weld process known as friction stir welding.
Friction stir welding uses high rotational speed and the resulting frictional heat created from contact to crush, "stir" together, and forge a bond between two metal alloys. This welding technique is more reliable and maintains higher material properties than other methods. However, friction stir welding has a major drawback - reliance on the single-piece pin tool.
When welding with a single-piece pin, a hole - specifically, a keyhole - is left at the end of the weld. This can create problems when welding items such as drums, pipes and cylindrical storage tanks.
The original application Ding had in mind for the automatic retractable pin tool was for this very type of tank. "You need to make a 360-degree weld without a hole in it," said Ding. "A hole defeats the purpose."
"That's when the idea for an automatic retractable pin tool began to develop," he explained. The tool Ding and Oelgoetz have patented provides the capability to make complete, 360-degree circular welds - essential for cylindrical objects. As the retractable pin tool passes the original starting point, it begins to slowly retract the welding pin up into the shoulder of the pin tool - rewelding at lesser and lesser depths - until the keyhole is closed.
Friction stir welding is currently being implemented into manufacturing of the Space Shuttle's External Tank. The plan is to use a retractable pin, similar to Ding's invention, to weld the transition joints where the metal varies in thickness. "This new welding process will allow for stronger and more reliable welds on NASA's Space Shuttle External Tanks," said Ding. Ding and Oelgoetz's retractable pin tool is also being tested for use in repairing Shuttle Solid Rocket Booster hardware.
While the technology is currently applicable mainly in the aerospace and aircraft airframe industries, its application in many other fields is beginning to be explored. Ding said defense firms are considering using the technology for manufacturing armored vehicles - such as an advanced amphibious assault vehicle. And, there is interest in the technology as a method of welding shut canisters for containment of radioactive waste.
Ding and Oelgoetz also have another idea nearing completion of the patent process - a manually retractable pin tool, allowing the operator to manually adjust the pin. Ding himself has another patent-pending technology called an orbital weld head that uses a retractable pin tool to weld pipes. Additional inventions by Ding are also being evaluated for possible patenting action by NASA.
Government employees who achieve inventions in the course of their work are rewarded for their innovative ideas. In Ding's case, his reward so far is a sizable initial installment of the royalties he is expected to receive.
He received a bachelor's degree in biology from Bowling Green State University in Bowling Green, Ohio, in 1976. In 1986, he earned a bachelor's degree in welding engineering from Ohio State University in Columbus. In 1993, he obtained a master's in engineering management from the University of Tennessee in Knoxville.
Employed at the Marshall Center for 14 years, Ding plans to continue not only retractable pin-tool development, but also friction stir weld process improvements in support of NASA and private sector applications. Ding resides in Athens, Ala.
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