Metallographic observations of armor steel specimens from plates perforated by shaped charge jets

In each of four experiments, a plate of rolled homogeneous armor (RHA) was perforated by a copper jet from a shaped charge warhead. Optical and scanni ng electron microscopy were performed on RHA specimens prepared from a rema ining perforated target plate and from various recovered fragments. In the remaining plate, white-etched (in 2 pct nital) adiabatic shear bands were f ound to emanate from the hole wall and enter the interior. These blended in to dark-etched bands of concentrated shear. Some cracks were found to enter from the hole wall and run along a shear band. Tips of these cracks were p lanar, suggesting brittle cleavage. A crack not associated with a shear ban d was formed by the coalescence of ductile voids. Recovered fragments were bounded by white-etched adiabatic shear bands. Shear bands also entered int eriors of fragments, where they sometimes meandered and bifurcated. One fra gment exhibited a dendritic pattern, possibly indicative of melting. Microh ardness measurements were obtained in the dendritic region, a nearby white- etched band, and the martensitic matrix. A mechanism coupling local reducti ons in spall strength to the presence of adiabatic shear banding is propose d. Published by Elsevier Science Ltd.