Initiation Pressure Thresholds from Three Sources

Abstract

Pressure thresholds are minimum pressures needed to start explosive initiation that ends in detonation. We obtain pressure thresholds from three sources. Run‐to‐detonation times are the poorest source but the fitting of a function gives rough results. Flyer‐induced initiation gives the best results because the initial conditions are the best known. However, very thick flyers are needed to give the lowest, asymptotic pressure thresholds used in modern models and this kind of data is rarely available. Gap test data are in much larger supply but the various test sizes and materials are confusing. We find that explosive pressures are almost the same if the distance in the gap test spacers are in units of donor explosive radius. Calculated half‐width time pulses in the spacers may be used to create a pressure‐time curve similar to that of the flyers. The very‐large Eglin gap tests give asymptotic thresholds comparable to extrapolated flyer results. The three sources are assembled into a much‐expanded set of near‐asymptotic pressure thresholds. These thresholds vary greatly with density: for TATB/LX‐17/PBX 9502, we find values of 4.9 and 8.7 GPa at 1.80 and 1.90 g/cm3, respectively.

Small‐Scale Detonation of Industrial Urea‐Hydrogen Peroxide (UHP)

“…Indentation then drops rapidly and less reproducible responses are observed in the interval 1.1-1.2 g/cm 3 . This is probably explained by a decrease in shock sensitivity of pressed UHP due to pressurisation, which decreases the density of potential hotspots that play a key role in detonation propagation in heterogeneous explosives [15,27].…”

Density Distributions in TATB Prepared by Various Methods

“…The initiation and subsequent transition to sustained detonation of an explosive is believed to be associated with the adiabatic compression of voids or "hot spots" in the explosive [4,5]. It has been shown that for non-ideal explosives the critical energy or pressure of initiation is a function of the density [6]. This being the case, the quality of explosive crystals is expected to impact their initiability.…”

A Simple Reactive‐Flow Model for Corner‐Turning in Insensitive High Explosives, Including Failure and Dead Zones. I. The Model.

“…Of course, the choice of only a single parameter , rather than multiple, is already a grossly simplifying assumption; see, e. g ., higher‐order rate improvements to CREST to address just such a concern. Perhaps more importantly, there is empirical evidence to suggest that it may be better to use some combination of and the duration of the high‐pressure spike rather than alone. The need for such improvements is not surprising and indeed can be argued on very simple physical grounds.…”