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4
Shape Memory Alloys

Ryo Ota, a group manager for the Olympus Optical Company in Japan, holds a shape memory alloy tube. Engineers think these smart materials could prove handy in preventing earthquake damage to buildings.

© TWPhoto/Corbis

As we discussed earlier in the countdown, the plasticity of materials presents a major challenge to engineers trying to build earthquake-resistant structures. Plasticity describes the deformation that occurs in any material when forces are applied to it. If the forces are strong enough, the material's shape can be altered permanently, which compromises its ability to function properly. Steel can experience plastic deformation, but so can concrete. And yet both of these materials are widely used in almost all commercial construction projects.

Enter the shape memory alloy, which can endure heavy strains and still return to its original shape. Many engineers are experimenting with these so-called smart materials as replacements for traditional steel-and-concrete construction. One promising alloy is nickel titanium, or nitinol, which offers 10 to 30 percent more elasticity than steel [source: Raffiee]. In one 2012 study, researchers at the University of Nevada, Reno, compared the seismic performance of bridge columns made of steel and concrete with columns made of nitinol and concrete. The shape memory alloy outperformed the traditional materials on all levels and experienced far less damage [source: Raffiee].

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