Penetration mechanism of a high-speed projectile into a shelter made of spherical aggregates

Under the threat of earth penetration weapons (EPWs), the protective fortification should be further enhanced. The bursting layer is commonly used to increase the protective strength of the fortification. A hard spherical aggregate (aggregate for short) is often used to construct the bursting layer. The mechanism of a high-speed projectile into the aggregate was studied, and the dominant factors were investigated in the present paper. Based on the dynamic spherical cavity expansion theory, the model for the drag force of the projectile was constructed considering the free surface effect of the target and the strength of the aggregate. Detaching the projectile response from the target, the resistant force of the target was loaded on the projectile surface as a force boundary. The deformation and movement of the projectile was numerically researched when it obliquely penetrated into the high-strength concrete target including aggregates. The influences of aggregate strength, location and dimensions upon the projectile response were investigated. It indicates that the sheltering effect of the aggregate is mainly dominated by the gesture of the projectile impacting on the aggregate. However, the variation of the gesture does not follow a distinct law. It is shown that the higher the strength of the aggregate, the better the sheltering effect of the aggregate. The main sheltering mechanism transforms from ballistic trajectory deflection into combination of ballistic trajectory deflection and augment of the drag force of the projectile, when the radius of the aggregate increases from 1 time of projectile diameter to 10 times. Based on the above analyses, for the bursting layer made of one layer, the diameter of the aggregate should be larger than 10 times of the projectile diameter. However, when the size of the aggregate decreases, the bursting layers should be constructed by multiple and staggered layers of aggregates with total layer thickness larger than 10 times of the projectile diameter, in order to achieve the effective sheltering effect. © 2020, Editorial Staff of EXPLOSION AND SHOCK WAVES. All right reserved.