Chapter 5 - Global Observations & Post Mortem Analysis of Penetration in Sand

Abstract

The dependence of mesoscale penetration parameters is found to depend in a complex way on projectile parameters, granular properties, and penetration velocity. This is illustrated from the results of 80 subscale penetration tests over a parameter space that included impact velocities of 70-300m/s; four natural and synthetic granular materials, including Ottawa sand, crushed fused quartz, aragonite, and crushed coral; loose and dense packings; dry and wet targets; and four different projectiles, including spheres and long rods with conical, hemispherical, and blunt nose shapes. Two techniques are employed to obtain penetration time histories, including photonic Doppler velocimetry for high-velocity impact tests and high-speed imaging for low-velocity impact tests. Penetration time histories are differentiated to obtain velocity and acceleration time histories. Analysis of the time histories revealed that the role of nose shape, packing density, and saturation is material dependent. Silica sands and calcareous sands showed contrasting behavior across the parameter space considered. These observations point to the significance of particle crushing in rapid penetration into granular media.