Numerical Simulation of Shock Propagation in Heterogeneous Solids

Abstract.

Hypervelocity impacts of asteroids and comets on Earth and other planets lead to shock compression of the affected rocks. Heterogeneities, which are ubiquitously present in rocks, are likely to influence the dynamic behavior of geological materials under shock loading. The presence of small-scale heterogeneities like lithological interfaces, fractures, pores, etc. influence the propagation, magnitude, and geometry of shock and subsequent release waves and need to be considered if pressure and temperature achieved during an impact process are derived on the base of observed shock effects. In this study, we performed numerical simulations using the hydrocode SALE to analyze the effects of a simple planar interface on the shock wave behavior, and determine the magnitude of temperature, pressure, and density near the interface. The simulated materials, their geometries, and the scale of the model are adapted to shock recovery experiments. The ANEOS equation of state has been employed. The samples are either composed of rectangular pieces of quartzite and dunite enclosed in an iron container and impacted by an iron flyer plate, or consisting of dunite with a wedge-shaped quartzite inclusion presenting an inclined interface and impacted by a dunite slab. The computations indicate that during shock compression, pressures and temperatures are achieved in quartzite, which lead to completely reversible solid-solid phase transitions in the target material that start to develop at the interface. Shock heating alone is not sufficient for melt formation in the systems considered in the present study, but localized shear in particular at inclined boundaries between different materials results in a significant additional temperature rise of up to 400 K in addition to regular shock heating in the present model. Further mechanisms of energy dissipation are needed for a proper description of experimentally observed melting.