Safety is of principal importance during the handling, processing and storage of explosives. It has been shown in previous work that the low speed spigot impact of consolidated Plastic Bonded Explosive is a significant threat. However, the occurrence of ignition and growth to reaction in these non-shock impacts is difficult to predict. An initial mechanical impact introduces a large amount of damage into the material bed in the form of cracks and increased porosity; this damage leads to an increase in the surface area available for burning. This increase is difficult to measure during an experiment as the measurement relies on visual estimates, which renders predictions of the burn difficult. To seek a better understanding of this issue, an investigation has been made into the pinching of explosive moulding powder, over a range of known particle sizes and packing densities in an idealised heavily confined cylindrical explosive bed. An embedded spigot struck by a projectile penetrates the cylindrical bed and initiates a small volume of the explosive through pinch at the far end of the cylinder. The resulting burn front then travels through the explosive bed at a pressure-dependent velocity, eventually evolving into a Deflagration to Detonation (DDT) response. In this paper experimental results indicating the threshold spigot impact velocity for initiating the moulding powder in this configuration and comparisons of the explosive burn front velocity and growth to detonation are reported. Modelling of the reaction growth from ignition at the pinch point through laminar burning to detonation is undertaken using the High Explosive Reaction to Mechanical Stimulus (HERMES) model. The predicted burn front velocity is compared with the experimental results.
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