Shock Compression of Metals: From Monocrystals to Nanocrystals, from Explosives to Lasers

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• Marc André Meyers, University of California San Diego
• Tuesday 23 September 2008, 13:30-14:30
• The Committee Room, The Bragg Building, Cavendish Laboratory, Department of Physics.

If you have a question about this talk, please contact Stephen Walley.

Shock compression creates a state of uniaxial strain in which large deviatoric stresses, far surpassing the material strength, are generated. Ductile metals respond by the (profuse) generation and (limited) motion of dislocations. There is also an associated temperature increase, that seems, in a few cases, to significantly exceed the Rankine-Hugoniot predictions. We have subjected metallic specimens (copper, nickel, and vanadium) to high-amplitude shock waves using explosives, gas-guns, and lasers. The pulse durations varied from a few microseconds to a few nanoseconds. The predictions of molecular dynamics computations are compared with post-shock experimental measurements by transmission electron microscopy and there is an equivalence in the results. However, the defect spacings differ by orders of magnitude. This conundrum is resolved through the suggestion that most dislocations generated in shock compression are annihilated during the release and post-release portion. Time permitting, recent results on laser-induced fragmentation on vanadium will be presented.

This talk is part of the Physics and Chemistry of Solids Group series.

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