Damage Prediction of Projectile Penetration Process Based on Energy Dissipation Rate

摘要

The projectile penetration process covers a wide range of failure modes depending on impact velocity, configuration and material of the projectile and target. This study overcomes previous difficulties in such mathematical descriptions by applying a concept which assumes that material damage occurs nonhomogeneously throughout the target and can be uniquely associated with the rate at which energy is dissipated in a unit volume of material. Introduced as a corollary of the strain energy density theory are the quantities dV/dA and dW/dV which represent, respectively, the rate of change of volume with surface area and the strain energy density function. Together they deterime the energy used to damage a differential area in the projectile penetration process. Orientations of the damage planes form the failure path. A numerical procedure is developed for modeling the material damage process during projectile penetration. The progressive damage pattern for each time increment is exhibited where the elements fail nonhomogeneously. For blunt projectiles impacting relatively hard targets, the conditions for plugging failure are met soon after impact with little radial flow of material. This failure mode is investigated by invoking different assumptions in the state of the failed elements. This model can also treat the phase transformation of solid where shear bands are formed in regions of highly localized energy states.