Shock Induced Hot-Spot Formation and Subsequent Decomposition in Granular, Porous HNS Explosive

Abstract

Experimental and theoretical studies on granular porous hexanitrostilbene (HNS) explosive have yielded an increased understanding of microstructural processes occurring during initiation by shock loading. Experiments give time-resolved pressure, hence chemical decomposition history at the impact interface following planar impact of HNS specimens onto fused-sil ica targets. The data are interpreted in terms of a quantitative two-temperature model which considers hot spots to be formed at pore sites as a result of the irreversible work accompanying the shock. Subsequently, decomposition completion is achieved by burn fronts which propagate radially out from each hot spot at a velocity which can be inferred from the bulk decomposition rate. Analysis of the data in the context of the model leads to several observations: 1) The delay times corresponding to hot-spot decomposition are shorter than expected, based on extrapolated low-temperature kinetics. 2) Contrary to interpretation of data on other explosives, the velocity of the burn front which propagates radially from each hot spot does not have a strong dependence upon the prevail ing pressure but is more nearly constant. 3) The inferred burn velocity has a very strong dependence upon the initial shock pressure. Introduction It is generally accepted that the passage of a shock wave through a granular porous explosive leads to Presented at the 8th ICOGER, Minsk, USSR, Aug. 23-26, 1981. Copyright © 1982 by the U.S. Dept. of Energy. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Manager, Fluid and Thermal Science Department.