Dynamic structures in shock-loaded copper

Abstract

Shock loading of polycrystalline copper under uniaxial strain conditions at $6.2\textdiv{}7.3\text{ }\text{GPa}$ results in nucleating the dissipative structures of $5\textdiv{}25\text{ }\ensuremath{\mu}\text{m}$ in diameter. Interior of each structure is a network of microshear bands of $100\textdiv{}300\text{ }\text{nm}$ spacing. Nucleation of structures occurs at the impact velocity where particle velocity dispersion begins to grow faster than mean particle velocity or when the local strain rate at the mesoscale becomes higher than the macroscopic strain rate. Simultaneously, defect of particle velocity at the plateau of compressive pulse, macrohardness, and spall strength grow in the same manner. Physically, nucleation of dissipative structures is estimated to be initiated under resonance condition between space periods of polarized dislocation structure and driving plastic front.