Numerical and Experimental Investigation of Asymmetrical Contact Between a Steel Plate and Armor-Piercing Projectiles

The study presents the discussion on modeling of interactions between armor-piercing (AP) projectiles and add-on perforated plates realized by the experimental investigation, numerical finite-elements simulation and the simplified modeling based on the integration of the equations of motion of a rigid projectile. It is known that relatively thin steel plates with an array of holes, i.e. perforated plate, are efficient against impacts of small-caliber projectiles, which makes them applicable for light-weight armored vehicles as passive add-on armors. A number of holes in such plates increases the probability of asymmetrical contact between the plate and a small-caliber projectile, which causes its destabilization or fragmentation. Depending on the hit-point, AP projectiles behave differently; they may be strongly rotated if hit inside a hole, while hitting an area between holes, the damaged projectile core deviates from the initial trajectory. Impact on a hole-edge is the most efficient case of reducing the projectile’s perforation capacity, as its core may be broken or shattered. Due to the extensive, experimental ballistic testing performed on the bainitic, slotted plates impacted by 7.62 x 51 .308 Winchester AP projectiles, the failure modes of bullets were analyzed and constituted a basis for the numerical model validation. The reference numerical, Lagrangian model was implemented in LS-DYNA by 8-node constant-stress solid elements with one integration point and stiffness-based hourglass control. The modeling of impacts confirmed dependence between the projectile failure and the hit point. The localized-interaction model based on the integration of the equations of motion of a 6 DOF rigid projectile may be considered as a simplified method in the design of perforated pre-armors, in which obtaining the largest projectile distraction is the optimization aim. In such a robust model, the projectile-plate interactions are simplified and based on the integration of stress components, which are normal and tangent to the projectile’s contact surface. The target plate and projectile are discretized by a spatial grid of points, at which interaction forces are calculated. The performed numerical and experimental modeling proves a high protective efficiency of perforated steel plates against small-caliber AP projectiles. The asymmetrical contact between them results in a significant reduction of the bullet energy. The discussed methodology leads to improvements in the light-weight armors design.