DISLOCATION-STRUCTURE FOR ONE-DIMENSIONAL STRAIN IN A SHOCKED CRYSTAL

Dislocation structures proposed to model plastic deformation at a shock front are analyzed. The creation and glide movement of the dislocations are considered. Glide-type movement violates the condition of one-dimensional strain except if dislocation dipoles with Burgers vectors parallel and antiparallel to the shock propagation direction are directly generated by alternating shear stresses as in a punching action. The stress, strain, and dilatation characteristics are presented for a dislocation structure proposed by Armstrong, Miller, and Sandusky (AMS) to give a residual one-dimensional strain state. The AMS dislocation structure is related to independent results from a molecular-dynamics description of shear displacements in a shocked triangular lattice and is used as a basis for estimating the extent of postshock strengthening levels. The shock-strengthening predictions are in reasonable agreement with postshock deformation measurements.