Blunt missile perforation of thin plates and shells by discing

Abstract

Blunt missiles perforate thin plates and shells by a combination of ‘plugging’ and ‘discing’ modes of failure. Plugging is a failure mechanism associated with mode II fractures in a region of large shear strain at the periphery of a flat-nosed missile. By contrast, discing is a mode I fracture that develops in a region stretched by dishing of the shell outside the contact zone. While plugging is more common, discing occurs near the ballistic limit of thin ductile plates and shells when the nose radius is not very large in comparison with the missile radius. Collision tests at a normal angle of obliquity on mild steel plates have shown that discing is a consequence of localized radial necking; the value of the radial strain at which necking is initiated depends on the value of the circumferential strain ε_θ, and it is always smaller than the necking strain ε_n obtained in a uniaxial tensile test.