Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session D6: Detonation Theory |
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Chair: Ed Kober, Los Alamos National Laboratory Room: Fairmont Orchid Hotel Promenade I/II |
Monday, June 25, 2007 3:45PM - 4:00PM |
D6.00001: JAGUAR Procedures for Detonation Behavior of Silicon Containing Explosives Leonard Stiel, Ernest Baker, Christos Capellos, William Poulos, Jack Pincay Improved relationships for the thermodynamic properties of solid and liquid silicon and silicon oxide for use with JAGUAR thermo-chemical equation of state routines were developed in this study. Analyses of experimental melting temperature curves for silicon and silicon oxide indicated complex phase behavior and that improved coefficients were required for solid and liquid thermodynamic properties. Advanced optimization routines were utilized in conjunction with the experimental melting point data to establish volumetric coefficients for these substances. The new property libraries resulted in agreement with available experimental values, including Hugoniot data at elevated pressures. Detonation properties were calculated with JAGUAR using the revised property libraries for silicon containing explosives. Constants of the JWLB equation of state were established for varying extent of silicon reaction. Supporting thermal heat transfer analyses were conducted for varying silicon particle sizes to establish characteristic times for melting and silicon reaction. [Preview Abstract] |
Monday, June 25, 2007 4:00PM - 4:15PM |
D6.00002: Porting Initiation and Failure into Linked CHEETAH Clark Souers, Peter Vitello Linked CHEETAH is a thermo-chemical code coupled to a 2-D hydrocode. Initially, a quadratic-pressure dependent kinetic rate was used, which worked well in modeling prompt detonation of explosives of large size, but does not work on other aspects of explosive behavior. The variable-pressure Tarantula reactive flow rate model was developed with JWL++ in order to also describe failure and initiation, and we have moved this model into Linked CHEETAH. The model works by turning on only above a pressure threshold, where a slow turn-on creates initiation. At a higher pressure, the rate suddenly leaps to a large value over a small pressure range. A slowly failing cylinder will see a rapidly declining rate, which pushes it quickly into failure. At a high pressure, the detonation rate is constant. A sequential validation procedure is used, which includes metal-confined cylinders, rate-sticks, corner-turning, initiation and threshold, gap tests and air gaps. The size (diameter) effect is central to the calibration. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. [Preview Abstract] |
Monday, June 25, 2007 4:15PM - 4:30PM |
D6.00003: Effect of Phase Transitions of Chemically Inert Additives on Detonation Properties of Composite Explosives. Raafat Guirguis One-dimensional calculations are used to investigate the effect of phase transitions of chemically inert additives on the detonation properties of high explosives. The resulting small changes in volume of the inert materials can lead to significant changes in the detonation properties when the phase transitions occur within the reaction zone where even the gaseous decomposition products are at high density. The predictions confirm the experimentally observed shift in detonation velocity that occurs when the initial density exceeds a threshold value at which the resulting pressures in the reaction zone correspond to a polymorphic phase transition of the additives. The shift in detonation velocity mostly depends on the sign of the change in volume induced by the transition and to a lesser extent on the sign of the energy released during the transition. Phase transitions causing an increase in volume yield a positive shift in the detonation velocity that is augmented or reduced depending on whether the transition is an exothermic or an endothermic one. The positive shift in detonation velocity is increased when the compressibility of the inert additives is decreased. [Preview Abstract] |
Monday, June 25, 2007 4:30PM - 4:45PM |
D6.00004: Monte Carlo Simulations of the Effect of Cross-potential Variations on the Equation of State of N$_2$/CO$_2$ Mixtures and of Detonation Products M. Sam Shaw The issues of mixing and cross-potentials were studied with particular emphasis on the implications for detonation products equation of state (EOS) and the prediction of measurable sensitivity to the cross-potential. A large number of Monte Carlo simulations were made with the choice of ensemble depending on the system being studied: NPT for uniform mixing, Gibbs for fluid-fluid phase separation, and Composite for full detonation products with chemical equilibrium and carbon clusters. Simulations with N$_2$/CO$_2$ mixtures demonstrate significant sensitivity to the cross-potential in the EOS values for uniform mixtures, in the shape of the isotherms and the location of rapid changes due to fluid-fluid phase separation, and in the location of the fluid-fluid phase separation line in pressure and temperature. Suggestions are made for experimental methods to characterize the cross-potential and mixing properties. Evaluation of the full EOS for HMX based explosives demonstrates an amplified effect of the cross-potential variation through dramatic shifts in thermodynamic equilibrium composition and the resulting EOS. [Preview Abstract] |
Monday, June 25, 2007 4:45PM - 5:00PM |
D6.00005: An effect of charged and excited states on the decomposition of FOX-7 Anna Kimmel, Peter Sushko, Alexander Shluger, Maija Kuklja Various decomposition mechanisms in 1,1-diamino-2,2-dinitroethylene (FOX-7) in both gas and solid phases have been investigated by means of density functional theory calculations using an embedded cluster model. We found that the molecular excitations and charge trapping have a dramatic effect on the decomposition process by facilitating some mechanisms of dissociation and precluding the others; the excited states not only reduce the energetic reaction barriers but also change the type of the dominating chemistry from endothermic to exothermic. We found that the decomposition of FOX-7 in the gas phase is defined by two competing low- energy mechanisms, the C-NO$_{2}$ scission and C-NO$_{2}$ to CONO isomerisation. Decomposition in solid state of FOX-7 is much more complex and is controlled by cooperative behavior, which involves the excitation processes and structural inhomogeneities in crystalline lattice. [Preview Abstract] |
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