The effect of friction and fracture on weak shock propagation in granular salt

Researchers conducted computational modeling to study the impact of friction and fracture on weak shock propagation in granular salt. They used explicit grain-resolving hydrodynamics simulations, varying impact velocities from 95 m/s to 245 m/s, and compared the results to prior experimental data. An innovative algorithm was developed to incorporate inter-granular and intra-granular frictional forces, which influenced both particle and shock speeds within the sample.

An explicit fracture plane was introduced into each salt grain, significantly impacting shock propagation in systems with friction, but not in those lacking friction. The study revealed that the simulation incorporating both friction and explicit grain fracture most closely matched experimental data at high impact velocities, while the simulation with only friction provided the best match at low impact velocities.

This suggests that the presence of these factors becomes more crucial in weak shock regimes at higher velocities. Surprisingly, neither friction nor grain fracture notably affected the slope of the shock velocity-particle velocity Hugoniot, a critical material property, within the studied impact range. Additionally, the Rankine-Hugoniot jump conditions may underrepresent the pressure experienced by the bulk material in granular assemblies characterized by high friction and confinement.

This research was supported by the U.S. Department of Energy's ASC/PEM/Enabling Manufacturing project at Los Alamos National Laboratory.