Accelerating dislocations to transonic and supersonic speeds in anisotropic metals

The dynamics of stress-accelerated dislocations in copper is investigated using molecular dynamics simulations. The structure and motion of dissociated edge dislocations are analyzed using the common neighborhood parameter and local stresses. Dislocations are accelerated by high shear stresses and reach stable velocities in the two transonic regimes. Supersonic dislocations are generated but are transient, as they require high stresses, which trigger nucleation of multiple dislocation dipoles. A velocity plateau in the first transonic regime indicates a radiation-free state in agreement with theoretical predictions. (C) 2008 American Institute of Physics.