Ballistic limit predictions for perforation of aluminium armour plates by rigid nose-pointed projectiles

摘要

We start with a derivation of a new formula for the spherical cavitation yield stress of aluminium targets with Ludwik power-hardening response. As part of this analysis we have suggested simple and accurate formulae for spherical and Mises plane-strain cylindrical cavitation pressures. These algebraic relations simplify the wellknown integral expressions for quasi-static cavitation pressures in a material exhibiting Ludwik work hardening. A comprehensive comparison with experimental data has clearly demonstrated that the ratio between ballistic limits of targets with thicknesses kh and h, against the same threat, is higher than the commonly accepted value of root k. A new integral formulation of the specific cavitation energy, which directly depends on target material stress-strain curve, reveals the coupling between hole slenderness ratio and hardening characteristics of the target. This formulation is shown to be more accurate than currently existing models for perforation resistance, and has led to an efficient and accurate ballistic limit formula. While a general integral formulation is valid for arbitrary stress-strain relations, further simplifications are given for linear, power and Voce hardening laws in terms of classical functions from mathematical physics. Extensive comparison with about 200 available experimental results for perforation of different aluminium alloys by several armour-piercing bullets and nose-pointed projectiles is provided in support of main findings. The aluminium alloys response is mostly modelled by Ludwik stress-strain curve and also by the Voce hardening model, and the vast majority of ballistic limit predictions represent deviations of up to +/- 5% from experimental data. A few comparisons are made for Weldox steel alloys to demonstrate the accuracy of the specific formula for linear hardening response of material target.