In situ velocity and stress characterization of a projectile penetrating a sand target: Experimental measurements and continuum simulations

Understanding the impact, penetration and cavity formation of heterogeneous granular systems is of fundamental importance to a wide variety of research endeavors. In this work a series of experiments were conducted in order to investigate the penetration dynamics of loose dry sand. High-speed photography coupled with a particle image velocimetry (PIV) technique was used to capture both the grain and bulk response of the penetration event, while buried quartz gages simultaneously recorded transmitted stress wave profiles. Depth of penetration was measured via postmortem examination. Experiments were conducted over a velocity range of 30–200 m/s using both cylindrical and spherical projectiles in a unique semi-infinite experimental configuration in order to directly observe a cross-section of the impact and penetration event. The experimental results are compared to simple continuum Eulerian hydrocode simulations and an analytic penetration model. The simulations are not able to resolve both stress and velocity measurements. However, the simulations do reproduce the depth of penetration for a wide variety of penetration experiments.