Abstract
CREST is an innovative reactive-burn model that has been developed at AWE for simulating shock initiation and detonation propagation behaviour in explosives. The model has a different basis from other reactive-burn models in that its reaction rate is independent of local flow variables behind the shock wave e.g. pressure and temperature. The foundation for CREST, based on a detailed analysis of data from particle-velocity gauge experiments, is that the reaction rate depends only on the local shock strength and the time since the shock passed. Since a measure of shock strength is the entropy of the non-reacted explosive, which remains constant behind a shock, CREST uses an entropy- dependent reaction rate. This paper will provide an overview of the CREST model and its predictive capability. In particular, it will be shown that the model can predict a wide range of experimental phenomena for both shock initiation (e.g. the effects of porosity and initial temperature on sustained-shock and thin-flyer initiation) and detonation propagation (e.g. the diameter effect curve and detonation failure cones) using a single set of coefficients.
Highlights
CREST is an innovative reactive-burn model for plastic bonded explosives, that uses entropy-dependent reaction rates
The CREST reaction rate was tuned to PBX 9502 experimental data at ambient temperature (23 ◦C) and a single density (1.89g/cm3)
The examples in this paper show that the CREST model for PBX 9502 can predict a wide range of experimental phenomena using one set of equation of state and reaction-rate coefficients
Summary
CREST is an innovative reactive-burn model for plastic bonded explosives, that uses entropy-dependent reaction rates. The CREST weighting factors m1, m2 and m3, and parameters b1, b2 and b3 which control the time to peak reaction rate, are functions of the entropy They are tuned to gas-gun particle-velocity gauge traces, the Pop-plot and the diameter effect curve. Once chosen, these coefficients are used without alteration to investigate a wide range of experimental phenomena. Published in 2007 and tuned only to one-dimensional gas-gun data, this model was found to be capable of predicting thin-pulse and initiation threshold data [4] It represented detonation failure behaviour in PBX 9502 rate sticks with remarkable accuracy, the calculated diameter effect curve did not capture the upturn observed in the experimental data at large charge sizes [5]. The CREST coefficients for PBX 9502 in [3] are used for all the simulations in this paper
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