Failure behaviour of an aluminium plate under impact loading

In this paper, the penetration and perforation of an aluminium plate by a steel projectile is investigated. The striking velocity was 275 m/s. At this velocity, the projectile remained nearly undeformed and the material separation occured via shearing effect almost undisturbed by other failure mechanisms. The target is plastically deformed only in the vicinity of the hole. The numerical results show that maximum shear strain and equivalent stress arise along a cylindrical surface within the target plate with a diameter slightly exceeding that of the projectile. Thus, the assumed location of the slideline, where crack opening may happen, was confirmed. By the application of the theory of constant energy of distortion, crack initiation starts at the impact side of the target after 5 mys, followed by a crack propagation of about 30% of sound velocity. The plastic deformation of projectile and target and the residual velocities of projectile and plug show in this case a good agreement betw een experiment and calculation. Therefore, the used failure model proves to be a suitable method to describe the influence of material failure on the ballistic resistance. (IFAM