Penetration into concrete targets by a hard projectile

Two dimensionless numbers, termed impact function I and geometry function N, are introduced as dominant parameters to control the penetration depth into concrete targets subjected to a hard projectile impact [1,2]. A definition of nose shape factor is defined quantitatively to eliminate the vagueness of the nose shape definitions in empirical formulae. A unified formula on penetration depth into concrete target, proposed based on dimensional analysis and dynamic cavity expansion model in [1,2] is applicable for a wide range of impact velocities, nose shapes and concrete strengths and reinforcements. The validity of the proposed penetration formula is verified through comparison with all major empirical formulae, e.g., modified NDRC, ACE, UKAEA, and experimental results. There exists an upper limit of the rigid projectile assumption, beyond which, the penetration is dominated by semi-hydrodynamic regime. The proposed formula can also be extended to metallic and earth targets.