ANALYSIS OF THE MECHANICS OF NORMAL PERFORATION OF METALLIC PLATES BY HIGH-SPEED PROJECTILES

An analytical model that considers the projectile deformation has been developed to describe the plugging process due to the impact of high speed projectiles into metallic plates of finite thicknesses. Both projectile and target materials are considered as strain rate independent and are rigid/plastic linear work hardening with respect to nominal stress-engineering strain relationships. The model identifies two projectile modes: heading and rigid. For each projectile mode, the target perforation process is described consisting of the following stages: (i) erosion, (ii) indentation. (iii) plug formation, and (iv) plug ejection. The plastic wave theory is used with the equations of motion to predict the sequence of the perforation stages of the different projectile modes that represent the complete perforation process of metallic plates.
The model is capable of predicting the time histories of target resisting force, velocity of different moving masses, and projectile penetration depth through the target. It can also estimate the projectile residual velocity, the plug thickness and the final length of projectile after perforation. For each impact velocity, the initial interface area of the projectile front is the only empirical factor in the analysis which is needed to run the model. The model predictions are compared with the experimental results of other investigators; good agreement is obtained. In addition, two thicknesses of LY12-CZ aluminium alloy plates are used as targets to specify the perforation process due to their impact by steel projectiles with velocity range up to 650 m/s. Predicted samples of the model results are presented. The model is also used to discuss the influence of projectile deformation on the different predicted time histories and post perforation results.