Sliding Instabilities and Hypervelocity Gouging

Abstract

Hypervelocity gouging occurs in material systems with high sliding speeds and has been observed in rocket sleds, light-gas guns, and railguns. Gouging takes the form of teardrop-shaped craters on the rail surface and usually occurs above a threshold speed that is material-pair dependent. The best predictive tools developed for gouging rely on semiempirical relationships that relate material hardness to shock pressure and hydrocodes that model the fluid-like behavior of materials under high stresses and strain rates. A parallel field of research is explosive welding. In explosive welding, the interface between two sliding surfaces impacted at high speeds undergoes a transition between flat bonded surfaces to a wavy interface. The onset of these interface waves, like hypervelocity gouging, is primarily dependent on the relative sliding speed of the materials, with other operating conditions being second order. Of particular interest is the fact that gouging and explosive welding waves occur at similar speeds for similar material pairs. This paper explores the parallels between these two fields of research and assesses the applicability of the respective predictive tools in determining the onset of gouging/interface waves.