Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session P1: Detonation and Shock-induced Chemistry VI: Shock Propagation |
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Chair: Terry Salyer, Los Alamos National Laboratory, Richard Lee, Naval Surface Warfare Center, Dahlgren Room: Grand E |
Wednesday, June 17, 2015 11:15AM - 11:30AM |
P1.00001: A comparative study of chemical kinetics models for HMX in mesoscale simulations of shock initiation due to void collapse Nirmal Rai, Igor Schweigert, H.S. Udaykumar The development of chemical kinetics schemes for use in modeling the reactive mechanics of energetic materials such as HMX has been an active area of research. Decomposition, deflagration and detonation models need to predict time to ignition and locations of onset of chemical reaction in energetic materials when used in meso- and macro-scale simulations. Modeling the chemical processes and development of appropriate kinetic law is challenging work because of lack of experimental data. However, significant work has been done in this area. Multistep kinetic models by Tarver and Tran, Henson and Smilowitz have provided plausible chemical kinetic rate laws for HMX. These models vary in the way they model the details of the decomposition process. Hence, a comparative study of different models will provide an understanding of the uncertainties involved in predicting ignition in HMX. In the current work, hot-spot ignition due to void collapse in shock compressed HMX has been analyzed using several reaction rate models, including the Tarver-Tran 4-equation model, the Henson-Smilowitz 7-equation model, and a new rate model that combines the condensed-phase decomposition rates measured by Brill et al and the detailed mechanism of nitramine flame chemistry due to Yetter et al. The chemical models have been incorporated in a massively parallel Eulerian code SCIMITAR3D. The variations in the predicted thresholds due to differences in the rate models will be discussed. [Preview Abstract] |
Wednesday, June 17, 2015 11:30AM - 11:45AM |
P1.00002: Development of a reactive burn model based upon an explicit visco-plastic pore collapse model Eric Bouton, Alexandre LeFran\c{c}ois, Robert Belmas Our aim in this study is to develop a reactive burn model based upon a microscopic hot spot model to compute the initiation and shock to detonation of pressed TATB explosives. For the sake of simplicity, the hot spots are supposed to result from the viscoplastic collapse of spherical micro-voids inside the composition. Such a model has been incorporated in a lagrangian hydrodynamic code. In our calculations, 8 different pore diameters, ranging from 100 nm to 1.2 $\mu $m, have been taken into account and the porosity associated to each pore size has been deduced from the PBX-9502 void distribution derived from the SAXS. The last ingredient of our model is the burn rate that depends on two main variables. The first one is the shock pressure as proposed by the developers of the CREST model. The second one is the number of effective chemical reaction sites calculated by the microscopic model. Furthermore, the function of the reaction progress variable of the burn rate is similar to that in the SURF model proposed by Menikoff. Our burn rate has been calibrated by using pressure profile, material velocities wave forms obtained with embedded particle velocity gauges and run distance to detonation. The comparison between the numerical and experimental results is really good and sufficient to perform a wide variety of simulations including single, double shock waves and the desensitization phenomenon. In conclusion, future works are described. [Preview Abstract] |
Wednesday, June 17, 2015 11:45AM - 12:00PM |
P1.00003: Characterization of Shock-dependent Reaction Rates in Non-ideal Perfluoropolyether-Aluminum Explosives Dennis Wilson, John Granier, Richard Johnson, Donald Littrell Explosive formulations of perfluoropolyether (PFPE) and aluminum are highly non-ideal. They release energy via a fast self-oxidized combustion wave rather than a true self-sustaining detonation. Unlike high explosives, the reactions are shock dependent and can be overdriven to control energy release rate. Reaction rate experiments show that the velocity can vary from 1.25 to 3 km/s. This paper examines the effect of the initial shock conditions -- shock strength, shock duration, and shock ``planarity'' -- upon the reaction rate of the explosive. The following conditions were varied in a series of sixty-four (64) reaction rate experiments: PFPE-Al composition; the high explosive booster mass and geometry; shock attenuation; confinement; and rate stick diameter and length. Several experiments designed to isolate and quantify these dependencies are described and summarized. [Preview Abstract] |
Wednesday, June 17, 2015 12:00PM - 12:15PM |
P1.00004: Shockwave Processing of Composite Boron and Titanium Nitride Powders Matthew T. Beason, I. Emre Gunduz, Alexander S. Mukasyan, Steven F. Son Shockwave processing of powders has been shown to initiate reactions between condensed phase reactants. It has been observed that these reactions can occur at very short timescales, resulting in chemical reactions occurring at a high pressure state. These reactions have the potential to produce metastable phases. Kinetic limitations prevent gaseous reactants from being used in this type of synthesis reaction. To overcome this limitation, a solid source of gaseous reactants must be used. An example of this type of reaction is the nitrogen exchange reaction (e.g. B $+$ TiN, B $+$ Si$_{3}$N$_{4}$ etc.). In these reactions nitrogen is ``carried'' by a material that can be then reduced by the second reactant. This work explores the possibility of using nitrogen exchange reactions to synthesize the cubic phase of boron nitride (c-BN) through shockwave processing of ball milled mixtures of boron and titanium nitride. The heating from the passage of the shock wave (pore collapse, plastic work, etc.) combined with thermochemical energy from the reaction may provide a means to synthesize c-BN. [Preview Abstract] |
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