Structural model of mechanical twinning and its application for modeling of the severe plastic deformation of copper rods in Taylor impact tests

We propose a new structural model of the mechanical twinning applicable for description of severe plastic deformation in 2D formulation. The twinning model together with the dislocation plasticity model is applied to modeling of the dynamical axis-symmetric Taylor tests with copper samples. Contributions of the dislocation plasticity and twinning in the formation of the shape of the compacted rod are revealed; modification of the defect structure behind the propagating shock wave is considered. The dislocation plasticity gives the main contribution in the case of low impact velocities (about or less than 100 m/s), while the twinning predominates at high impact velocities (about 500 m/s). Substantial influence of both mechanisms of plasticity takes place at moderate impact velocities, which results in formation of an area of the intensively twinned material near the colliding base of the rod and an adjoined area with a high density of dislocations; all this reflects on the profile of the lateral surface of the deformed rod.