Analysis on mass loss of different sized projectiles penetrating into concrete targets

During high speed penetration into concrete targets, projectiles will suffer different degrees of mass loss, which will generate severe changes in nose shape and significantly decrease the efficiency of penetrators. In this study, a semi-empirical model is developed for predicting the mass loss and nose shape change, in which thermal melting of projectile materials generated by friction work is considered as the primary mechanism of mass loss. The dynamic friction between the target and projectile is considered as a Coulomb friction and simplified as a product of a proportional coefficient and the unconfined compressive strength of concrete targets. In conjunction with experimental data, parametric analysis demonstrates that the proportional coefficient is related to the relative strength and hardness of projectile and target materials. Note that for larger projectiles whose diameter is defined as larger than 30.5mm in this study, a size effect of the projectile is also introduced and expressed as an inverse correlation between the projectile diameter and the proportional coefficient. Namely, larger projectiles will suffer much less relative mass loss, and the nose shapes after penetration tend to be sharper than smaller projectiles with the similar conditions of impact velocity.