Mesoscale simulations of pressure-shear loading of a granular ceramic

Numerical simulations of pressure-shear loading of a granular ceramic are performed using the shock physics code CTH. A simple mesoscale model for the granular material is used that consists of a randomly packed arrangement of solid spherical grains of uniform size separated by vacuum. The grain material is described by a simple shock equation of state, elastic perfectly plastic strength model, and fracture model with baseline parameters for WC taken from previous mesoscale modeling work on shock compaction of granular WC. Simulations using the baseline material parameters are performed at the same initial conditions as pressure-shear experiments on dry WC powders. Except for some localized flow regions appearing in simulations with an approximate treatment of sliding grain interfaces, the samples respond elastically during shear, which contrasts with experimental observations. By extending the simulations to higher shear wave amplitudes, macroscopic shear failure of the simulated samples is observed in simulations with intergranular sliding with the shear strength increasing with increasing stress confinement. At low stress confinement, the shear strength is found to be strongly dependent on the fracture strength of the grains with the shear strength decreasing with decreasing fracture strength. Preliminary simulations indicate worsening agreement with experiment at higher stress confinements even when treating the fracture strength as a variable parameter.