Analysis of the velocity relationship and deceleration of long-rod penetration

The relationship between the average penetration velocity, U¯ , and the initial impact velocity, V, in long-rod penetration has been studied recently. Experimental and simulation results all show a linear relationship between U¯ and V over a wide range of V for different combinations of rod and target materials. However, the physical essence has not been fully revealed. In this paper, the U¯ - V relationship is comprehensively analyzed using the hydrodynamic model and the Alekseevskii–Tate model. In particular, the explicit U¯ - V relationships are derived from approximate solutions of the Alekseevskii–Tate model. In addition, the deceleration in long-rod penetration is discussed. The deceleration degree is quantified by a deceleration index, α=2μ¯/(KΦJp)≈Ypρp-1/2(ρp-1/2+ρt-1/2)V0-2, which is mainly related to the impact velocity, rod strength, and rod/target densities. Thus, the state of the penetration process can be identified and designed in experiments.