In situ characterization of projectile penetration into sand targets

Abstract

Abstract. This work presents the results from dynamic penetration experiments in which long rod projectiles were launched into Ottawa sand at velocities ranging from 90 m/s to 350 m/s. A unique aspect of these experiments was that the sand targets were visually accessible, which allowed for the penetration event recorded using high-speed digital photography. The images were processed using two different correlation methods. In addition, stress measurements of the transmitted waveforms were simultaneously collected from a piezoelectric load cell that was buried in the sand at various locations relative to the shot line. The results indicate that impact results in two waves: one similar to a detached bow shock and one near the projectile that forms force chains. Grains are damaged and broken by the force chains which allows the projectile to penetrate the target.

Simulation of Bullet Fragmentation and Penetration in Granular Media

“…The numerical simulation predicted a penetration distance of 237 mm and the appearance of compaction waves along the penetration trajectory showing fragmentation of the brass after 204 mm. In the simulation and the X-ray photograph, an expanded distribution of the compacting wave is observed [ 50 ]. Even when the final penetration distances are not the same, both circumstances show brass jacket fragmentation before the steel core stops.…”

Numerical modelling study of a modified sandbag system for ballistic protection

“…Additionally, the initial peak in specific internal energy and its subsequent reduction can be attributed to the penetration process reaching temporary equilibrium until the layer of compressed sand is interacting with the rigid plate [39,40]. The term 'temporary equilibrium' refers to the equilibrium being established between the transfer of energy from the projectile to the sand and the dissipation of energy from the sand [3,4,18,39,40]. Key markers for the process reaching equilibrium were the constant size of the layer of compressed sand, and the reduced fluctuation in density as well as specific internal energy.…”

“…The use of sensors and high speed cameras along with processes such as digital image correlation have been used in recent years to measure the response of sand to impact and study its energy absorption characteristics [8]. The caveat with this experimental method is the cost of equipment and the increased source of human error given the increased complexity of the setup [6,18]. Furthermore, the challenge with an experimental method is the pre-processing (drying and mixing of sand to ensure a uniform measure of moisture throughout the sample) of material required to ensure a uniform setup, coupled with the opaque nature of sand.…”