Limited and unlimited spike growth from grooved free surface of shocked solid.

Richtmyer–Meshkov instability developed at a solid–vacuum interface after reflection of a shock wave is studied using the smoothed particle hydrodynamics (SPH) method. SPH simulations are performed for aluminum, copper, and tantalum samples with free surfaces having machined grooves of sinusoidal shape. The obtained simulation results agree well with the experimental data for different loading regimes. Our simulations demonstrate three regimes of material response to shock loading, where conditions depend on the yield strength for a given strain rate. First, at weak elastic shocks, the grooved surface experiences shear oscillations only. Then, a more intense shock loading produces plastic strain resulting in a plastic spike with the limited run from the surface. It is found that after the arrest of the plastic motion, the formed spike oscillates with the same period as in the elastic regime. Finally, the heavy load produces the unlimited growth of plastic or liquid jet, which leads to its fragmentation at later times. The transition from limited to unlimited jet growth depends on the geometry of the corrugated surface. We estimate the critical amplitude of corrugations required for unlimited spike growth. The used simulation techniques can provide the more accurate mechanical properties of materials to achieve a better agreement. [ABSTRACT FROM AUTHOR]