Penetration resistance and the critical cavitation velocity for an ogive-nosed rigid projectile penetrating into a semi-infinite metallic target

This paper studies penetration resistance and projectile-target separation for an ogive-nosed rigid projectile penetrating into a metallic target. A prescribed normal velocity field is introduced to determine the contact stress on the projectile nose, based on which the dynamic equation of a rigid projectile is formulated. Projectile-target separation occurs when the impact velocity of the projectile is greater than the critical cavitation velocity according to Hill's cavitation criterion. Target material is assumed incompressible in both elastic and rigid, perfectly plastic regions in order to simplify the analyses. It shows that the penetration resistance derived from the prescribed velocity field has a different form from that based on the dynamic cavity expansion model. When the impact velocity is greater than the critical cavitation velocity, the projectile-target separation point moves further to the nose tip, leading to the reduction of the contact area between the projectile nose and the target and a large increase of the inertia term (velocity square term) in penetration resistance. The predicted penetration depth and critical cavitation velocity agree reasonably with experimental and numerical results.