Formation of a bore-center annular shaped charge and its penetration into steel targets

The classical shaped charges are well known for their capability to yield a small ratio of the hole diameter to charge diameter in metallic targets. However, in specific situations, for instance the follow-through charge of tandem warheads and the fast establishment of a rapid rescue channel, the ratio of the hole diameter to charge diameter of 1:1 is demanded that cannot be achieved by normal shaped charges. To improve the penetration diameter and depth of the annular shaped charge on hard targets, in this work, a bore-center annular shaped charge (BCASC) is proposed and validated. An X-ray experiment is conducted to validate the reliability of numerical results. The maximal deviation of the head and tail diameters, length, axial and radial velocity of the BCASC projectiles at different times, between the simulation and X-ray experimental results, is only 4.9%. The numerical simulation results of penetrating into steel targets are also compared with the terminal ballistic performance including the diameter and depth of the penetration boreholes. Furthermore, based on the validated numerical models and the corresponding parameters, a series of numerical simulations are performed to investigate the influence of liner configurations (the radial distance (f) of circle centers, the thickness (b) of upper wall, the diameter (d) of center bore and the location of maximal wall thickness (θ)) on radial and axial velocity of BCASCs. Then, a series of BCASC penetration tests on steel targets are conducted. By assessing the penetration hole diameter and depth, the influences the key parameters on the target damage are numerically and experimentally discussed. The results indicate that, compared with other liner parameters (f, b, d), the location where the maximal wall thickness (θ) is placed has the most significant effect on both the radial and axial velocity of the projectile. As the value of θ increases, the radial velocity of the projectile head decreases, while the axial velocity of the projectile head increases. BCASCs with different parameter values can all penetrate into the steel targets and form annular bullet hole at a certain penetration depth. Within our research scope, the θ values imposes more influence on the penetration hole diameter and the depth. As the value of θ increases, a penetration hole diameter decreases, while penetration depth increases gradually. At θ = 30° the minimal distance between the outer wall of the penetration access is 0.92D (D indicates the charge diameter), and the mean value of the penetration access depth is 0.56D.