Internal Blast Effect Reduced by Dust Created by Fragments

Abstract

The attenuation effect on pressure and impulse of the metallic casing of an explosive charge, namely, Fano's effect, is a well‐known phenomenon thanks to the founding works of Fano and Fisher. It is mainly attributed to the kinetic energy transferred from the high explosive (HE) to the casing. Later, few authors quantified the contribution of secondary mechanisms to this phenomenon, such as the yield stress of the metal, see, for example, Hutchinson. More recently, Baum et al. and Ohrt have suggested an additional attenuation effect when the detonation of cased charges occurs inside closed or vented rooms. The metallic debris produced by the fragmentation of the envelope strikes the walls, generating secondary debris and dust. This later consumes energy (kinetic and thermal) from the detonation products, implying a decrease in the apparent pressure and impulse. The present work experimentally verifies this phenomenon thanks to cylindrical bare and cased charges of various HE types and mass detonating at the center of a small‐scale vented concrete building. Internal impulses are estimated by several measurement methods, which all evidence that the impulse decrease endorsed by the secondary dust is highly significant. It is indeed of the same order of magnitude that the impulse diminution attributed to Fano's effect. These results may pave the way for a better insight into internal detonation effects, particularly for safety studies on munition storage.