A study of the failure mechanism of detonations in homogeneous and heterogeneous explosives.

摘要

The present study measured the critical diameter and critical thickness of a variety of explosives. The explosives tested included two "unstable" homogeneous explosives (nitromethane and a nitromethane/nitroethane blend); a model heterogeneous explosive consisting of a packed bed of glass beads (&phis; ∼ 80 mum) saturated with the homogeneous nitromethane/nitroethane blend; and a commercial heterogeneous explosive, Apex Elite(TM). The comparison of the critical diameter and thickness of an explosive is used to identify the dominant propagation and failure mechanisms of the various explosives. The ratio of critical diameter to critical thickness for nitromethane, the nitromethane/nitroethane blend, the beaded heterogeneous explosive, and Apex Elite(TM) were found to be 3.2 +/- 0.6, 3.6 +/- 0.4, 2.3 +/- 0.1, and 3.5 +/- 1.2 respectively. According to accepted detonation failure theories, the energy losses associated with detonation front curvature are responsible for detonation failure. The curvature model, which is elaborated upon in the present work, leads to a predicted critical diameter to critical thickness ratio of exactly 2. The present study has shown that the only explosive which follows the behaviour predicted by curvature failure models is the beaded heterogeneous explosive, which exhibits fine scale heterogeneities. This seems to indicate that unstable liquid explosives and heterogeneous explosives with large scale heterogeneities do not fail simply due to the wave front curvature, but rather by a local mechanism of failure and reinitiation which dominates the detonation propagation.