Influence of the mushroomed projectile's head geometry on long-rod penetration

Self-sharpening has been observed in experiments and simulations of long-rod penetration. Penetration performances are influenced by different nose shapes occurred in the penetration of long rods made by different materials. In this paper, to model this nose shape effect, the resistance of the target in the standard AlekseevskiiTate model is replaced by the resistance determined by the spherical cavity expansion approximation for general nose shapes. The function of nose shape is constructed to establish a modified model of long-rod penetration, in which the nose geometry during the long rod penetration is represented by two main parameters, i.e., the diameter ratio of rod nose and shank eta and the nose shape factor N*. The influences of eta and N* on long-rod penetration and their mechanisms are analyzed. The penetration performance decreases with an increasing diameter ratio eta, whose physical basis is the increased radial flow of rod material around the nose, which in turn, leads to the loss of kinetic energy due to larger cavity formed in the targets. The nose shape factor N* reflects the sharpness of nose shapes, and a smaller value of N* corresponds to a sharper nose. N* obviously affects the ballistic performance of long-rod penetration, however, depending on the initial impact velocity. In general, the influence of N* is relatively smaller than that of eta.