Ballistic penetration of sand with small caliber projectiles

Abstract

Two dimensional mesoscale simulations of projectile instability during penetration in dry sand J. Appl. Phys.Abstract. In this work a series of experiments were carried out in which right-circular cylinders were launched into sand targets at velocities ranging from 70 to 150 m/s. The projectiles were launched along a view window in order to record the penetration event with high-speed photography. Stress measurements of the transmitted wave forms were simultaneously collected from a piezoelectric load cells buried in the sand. A particle image velocimetry (PIV) technique, which extracted information from the photographic images, was used to resolve transmitted wave profiles. A two wave structure was observed. The first wave, a compaction wave, moves at the bulk sound speed of the sand. The second is an attached fracture wave which is stationary relative to the projectile. Together these experiments further our understanding of high-speed granular penetration events.

Deceleration of projectiles in sand

“…This material is without doubt the very fine sand powder that has been noted previously [1] in cavities where the penetration velocity exceeds 100 m/s, and noted in high-speed pictures by [5]. It was observed in [1] that the powdered sand grains are 1,000× smaller than the initial sand grains, and they may be comprised of quartz crystals.…”

Munition penetration-depth prediction : SERDP SEED Project MR-2629

“…Previous studies have primarily explored the penetration-dynamics problem, ultimately to estimate penetration trajectory and depth, as a cavity-expansion problem where the projectile pushes the target material out of the way to create the cavity that the projectile then occupies. This strain due to cavity formation induces stresses on the cavity boundary (i.e., the projectile-soil interface) that act normal (cavity pressure) and tangentially (friction between projectile and target material) to the projectile surface, decelerating the body as it moves through the target medium (Bless et al 2012;Borg et al 2012). This deceleration can be described generally as where α, β, and γ are empirically determined constants, as with Young's equations (Young 1967(Young , 1997, or are obtained using a physics-based approach that uses cavity expansion theory (e.g., the work from Forrestal et al 1992 and more recently Shi et al 2014).…”

The significance of grain morphology and moisture content on the response of silica sand to ballistic penetration

“…Probing the internal deformation within a granular target is problematic due to sand's opaque nature. High-speed video has been employed in this regard 9 , but requires an impact path close to one edge of the target. Much of our understanding of stress propagation along force chains relies on experimental data from simplified 2D systems of photo-elastic disks 10 , which have illustrated the importance of force chains in projectile deceleration 11 .…”