On the hydrodynamic approximation for long-rod penetration

Steady-state hydrodynamic theory, or variations thereof, has been applied t o long-rod penetration since the 1940s, It is generally believed that proje ctile strength is of little consequence at high velocities, and that hydrod ynamic theory is applicable to long-rod penetration when penetration pressu res are much greater than the target flow stress. Substantiating this belie f is the observation that at approximately 2.5 km/s, for tungsten alloy pro jectiles into armor steel, normalized penetration (P/L) nominally saturates to the classical hydrodynamic limit of the square root of the ratio of the projectile to target densities. Experimental data herein, however, show pe netration velocities and instantaneous penetration efficiencies fall below that expected from hydrodynamic theory, even at impact velocities as high a s 4.0 km/s, Numerical simulations, using appropriate strength values, are i n excellent agreement with the experimental data. Parametric studies demons trate that both projectile and target strength have a measurable effect eve n at such high impact velocities. (C) 1998 Elsevier Science Ltd. All rights reserved.