Physicists Ted Orzechowski, Omar Hurricane, and colleagues are exploding cylindrical samples of metals and monitoring how they fracture and then fly apart. The researchers analyze the failure of the metal cylinders through high-speed images and characterize the fragments that are explosively produced. "We're missing a fundamental understanding of material failure. Just having a big computer, without the correct physics models, is not going to help," says Hurricane. Hurricane, in collaboration with Lalit Chhalabildas and his group at Sandia National Laboratories, is looking at the failure of metals at high strain rates caused by 2.5-centimeter-long. Lexan~(TM) flyers fired from a gas gun and traveling at about 2 kilometers pet-second. The flyer slams into another piece of Lexan inside a metal cylinder about 5 centimeters long, with an inner diameter of 1.2 centimeters, and 1, 3, or 5 millimeters thick. The cylinder materials are 1045 steel (a common steel formulation), nitinol (nickel-titanium alloy), and tantalum-tungsten alloy. "Upon impact, the Lexan behaves a bit like a 'working fluid.' driving the cylinder radially outward," says Hurricane.
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