Shape Memory Alloy Keeps on Going

Engineers in some circles have questioned the life expectancy of shape memory alloys (SMAs), which undergo a solid-state phase change when cooled and return to their original shape when heated. The flap over it may be unjustified. After seeing an article on SMAs in the 04.21.03 issue of Design News, astute reader Victor Rossi brought to our attention a demonstration that's been operating in the lobby of Dynalloy, a manufacturer of Flexinol(R) SMAs, since 1985. The butterfly, an early prototype of ones sold in stores, has been flapping its SMA-powered wings 6 million times a year for 18 years. Dynalloy President and Founder Wayne Brown says that the company is so confident of Flexinol's performance that it offers a one-year warranty on the butterfly, no questions asked. Of the 50,000 butterflies purchased each year, customers return only about 1%. "We perform a kind of equivalent of an Alien Autopsy to determine what went wrong, and even send the owner an official autopsy report," he says. "The SMA is never the culprit. It's almost always a circuit failure, or the dog ate it."