Failure behavior of a concrete slab perforated by a deformable bullet

This paper presents a study of the typical failure of a concrete target consisting of coarse aggregate perforated by a 7.62 mm mild steel core (MSC) bullet. Numerical simulations are carried out using a two-phase 3D mesoscopic model in which basalt aggregate grains are represented by randomly distributed spheres. The mortar and aggregate are described using the Karagozian-Case Concrete (KCC) constitutive model, and a procedure for determining strength parameters based on experimental tests supplemented with available literature data is presented. The KCC model with the determined parameters is further validated in basic experimental tests. Next, numerical predictions of perforation using different modeling approaches (e.g. application of the smooth particle hydrodynamics (SPH) method and homogenization of material) are performed. Comparisons of the results with selected empirical formula for determining the residual velocity of a projectile confirm the sensitivity of the analytical models to the adopted assumptions. Finally, the ballistic perforation test of a concrete target is simulated, and a parametric study is conducted to analyze the influence of different erosion criteria parameters on the failure of the concrete target. Comparisons of the numerical results with experimental outcomes in terms of scabbing and spalling confirm the efficiency of the model. However, a study of the local distribution of the coarse aggregate under the 7.62 mm MSC bullet demonstrates that a single 3D meso-scale model with one set of randomly generated aggregate spheres is not universal and sufficient for simulating the perforation of concrete targets with a deformable projectile with a diameter equal to or smaller than the maximum aggregate size. The influence of the quantity and arrangement of aggregates on the trajectory of the bullet strongly affects the response of the concrete target and the residual velocity of the bullet.