Material reliability in critical systems such as nuclear power or military weaponry is not an option. Materials can fail in a variety of ways, but not all are sudden and catastrophic. Sometimes components simply wear out from age or repeated cycling. They can be thought of to “forget” their shape. Engineers are trying to improve material memory.
Researchers at Sandia National Lab have developed new materials which will “remember” their shape.
If you try to fit a small paperclip on that massive stack of papers on your desk, you’ll mangle it quite thoroughly. Imagine if you could dunk it in a cup of hot water and it would return to its original shape. That’s the idea.
But that’s not the only idea. It goes much further than that and gets much more sophisticated. Shape memory alloys have been around for quite some time, but they are still being advanced. The Sandia researchers have developed new materials that perform this shape-shifting task over a much wider range of temperatures.
The Sandia alloys can change shape at temperatures from below room temperature to greater than 500 degrees Celsius (about 930 degrees Fahrenheit). According to researchers Don Susan and Jim McElhanon, commercial varieties on the market now change shape at temperatures that don’t meet Sandia’s needs. As Susan explains, any shape change has to take place above the temperature at which components are manufactured. “You don’t want this to happen when you’re making the parts,” he said. “You don’t want it to happen when it’s sitting out in the sun either. It has to be higher than that.”
McElhanon adds, “I truly believe this research on [high-temperature] shape-changing alloys will allow us to create new devices that significantly impact nuclear weapon safety. The shape-memory alloys we are developing can passively change shape via exposure to a particular temperature or actively change shape by passing current, which generates heat, through the material.”
Shape memory alloys serve in applications from eyeglass frames to medical devices, such as stents and braces. The ability to be deformed in a pseudo-elastic (reversible) manner means they can be “reset” to their original shape or can be used as actuators or safety switches.
Where performance is critical, the device needs to be reliable. Most components wear out with time or fail to operate because they are put under conditions that require them to simply withstand force, temperature, friction, etc. By giving the material a mind of its own, so to speak, you can ensure its successful operation. After all, it’s doing what it naturally wants to do. What it’s engineered to do.
A video demonstrating the shape memory effect is below.
Image Courtesy of: http://blogs.dallasobserver.com/unfairpark/2010/01/to_the_full_ex-stent_of_the_la.php