Origin of crack versus rough crater features in partial disintegration regime

Establish whether, in normal high-velocity tungsten-on-tungsten impacts within the partial disintegration regime, the crater valley’s deep thick cracks observed at impact speeds roughly within 1500–2500 m/s are formed on adhered fragments of the partially disintegrated tungsten projectile, whereas the densely connected rugged pattern without cracks observed at higher impact speeds (above ~2500 m/s) is primarily formed on the tungsten target surface.

Background

The study investigates normal high-velocity impacts of spherical micrometric tungsten dust on bulk tungsten targets across target temperatures from −100°C to 400°C. Within the partial disintegration regime, the authors consistently observe a morphological transition in the crater valley: for impact speeds roughly within 1500–2500 m/s, the valley exhibits a few deep thick cracks, while for higher speeds (above ~2500 m/s) the valley shows a densely connected rugged pattern without cracks. This transition is correlated with a change in the valley surface from concave to convex.

To explain these observations, the authors conjecture that the thick cracks at lower speeds form on fragments of the partially disintegrated projectile that remain adhered to the target, whereas the rough pattern at higher speeds is formed primarily on the target itself, implying a gradual regime transition with residual adhered projectile fragments at lower speeds. Although supplementary tests with tungsten dust on molybdenum targets support adhesion at lower speeds, the proposed mechanism for tungsten-on-tungsten impacts remains to be established conclusively.