Bulletin of the American Physical Society
17th Biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 56, Number 6
Sunday–Friday, June 26–July 1 2011; Chicago, Illinois
Session D2: Energetic Materials I |
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Chair: Hugh James, Atomic Weapons Establishment Room: Grand Ballroom IV-VI |
Monday, June 27, 2011 2:00PM - 2:15PM |
D2.00001: Predicting Run Distances for a Modified Wedge Test Robert Dorgan, Richard Lee, Gerrit Sutherland Simulations were used to aid in the development of a modified wedge test (MWT). This explosive sensitivity experiment allows the shockwave curvature to be defined in order to investigate the effect of combined shock-shear loading on sensitivity. Various widths of PBXN-110 donor slabs were used to define the shockwave curvature introduced to wedge samples of the same explosive. The donor slabs were initiated with a linewave generator and a Detasheet booster, and the shock wave was attenuated using a slab of PMMA. In developing simulations for these three material experiments, calibrations of the PBXN-110 ignition and growth model and of the PMMA constitutive model were investigated in order to choose between several models found in the literature. A calibration shot from the MWT was also used to demonstrate the appropriateness of the models selected. Experimental results were compared to CTH calculations to indicate if there were effects associated with highly curved shock fronts that could not be adequately predicted. The run distances predicted in CTH for the thicker donor slab compare very favorably with the actual experiments; however, for thinner donor slabs, the actual experimental results seem to suggest a more sensitive behavior than the simulations are able to capture. [Preview Abstract] |
Monday, June 27, 2011 2:15PM - 2:30PM |
D2.00002: Reactive Flow Calibration for Diaminoazoxyfurazan (DAAF) and Comparison with Experiment Carl Johnson, Elizabeth Francois, John Morris Diaminoazoxyfurazan (DAAF) has a number of desirable properties; it is sensitive to shock while being insensitive to initiation by low level impact or friction, it has a small failure diameter, and it has a manufacturing process that is relatively straightforward and inexpensive with minimal environmental impact. In order to facilitate hydrocode modeling of DAAF we have developed a set of reactive flow parameters which were calibrated using published experimental data as well as recent experiments at LANL. Hydrocode calculations using the DAAF reactive flow parameters developed in the course of this work were compared to rate stick experiments, small scale gap tests, as well as hemispherical acceptor/cylindrical booster experiments. The hydrocode calculations were compared directly to streak image results using numerous tracer points and an external algorithm to match the data sets. The calculations display a reasonable agreement with experiment with the exception of effects related to shock desensitization of explosive. [Preview Abstract] |
Monday, June 27, 2011 2:30PM - 3:00PM |
D2.00003: Implications of the Crest Reactive-Burn Model Invited Speaker: The CREST reactive-burn model has been remarkably successful in modelling shock initiation and detonation propagation behaviour in plastic-bonded explosives. Previous publications have shown that, using reaction-rate parameters tuned only to a limited set of data, CREST is able to predict the effect of thin-pulse and double-shock inputs, porosity, and initial temperature on one-dimensional shock-initiation experiments. In two dimensions, CREST also matches detonation propagation and failure behaviour. This has been achieved by using a reaction rate that depends on shock strength (measured using a function of entropy of the unreacted explosive) and time since the shock passed, and not on evolving parameters of the flow like pressure or temperature. Such a reaction rate was implied by a detailed analysis of embedded particle-velocity gauge shock- initiation data which identified scaling phenomena that can not be explained using a pressure-dependent rate, as a companion paper will demonstrate. While the majority of reactive-burn models have pressure or temperature-dependent rates, as has been the historical precedence, it is difficult to make direct comparisons between models which use different equations of state. In this paper, one set of equations of state will be used to investigate the advantages and disadvantages of entropy, pressure or temperature-dependent reaction rates for modelling a variety of one and two-dimensional shock initiation and detonation propagation phenomena. The implications for the future development of reactive-burn models will be discussed. [Preview Abstract] |
Monday, June 27, 2011 3:00PM - 3:15PM |
D2.00004: Simulation of the detonation process of an ammonium nitrate based emulsion explosive using the Lee-Tarver reactive flow model Jose Ribeiro, Cristovao Silva, Ricardo Mendes, Igor Plaksin, Jose Campos The use of emulsion explosives [EEx] for processing materials (compaction, welding and forming) requires the ability to perform detailed simulations of its detonation process [DP]. Detailed numerical simulations of the DP of this kind of explosives, characterized by having a finite reaction zone thickness, are thought to be suitable performed using the Lee-Tarver reactive flow model. In this work a real coded genetic algorithm methodology was used to estimate the 15 parameters of the reaction rate equation [RRE] of that model for a particular EEx. This methodology allows, in a single optimization procedure, using only one experimental result and without the need of any starting solution, to seek for the 15 parameters of the RRE that fit the numerical to the experimental results. Mass averaging and the Plate-Gap Model have been used for the determination of the shock data used in the unreacted explosive JWL EoS assessment and the thermochemical code THOR retrieved the data used in the detonation products JWL EoS assessment. The obtained parameters allow a good description of the experimental data and show some peculiarities arising from the intrinsic nature of this kind of composite explosive. [Preview Abstract] |
Monday, June 27, 2011 3:15PM - 3:30PM |
D2.00005: Modeling compressive reaction and estimating model uncertainty in shock loaded porous samples of Hexanitrostilbene (HNS) Aaron Brundage, Jared Gump Neat pressings of HNS powders have been used in many explosive applications for over 50 years. However, characterization of its crystalline properties has lagged that of other explosives, and the solid stress has been inferred from impact experiments or estimated from mercury porosimetry. This lack of knowledge of the precise crystalline isotherm can contribute to large model uncertainty in the reacted response of pellets to shock impact. At high impact stresses, deflagration-to-detonation transition (DDT) processes initiated by compressive reaction have been interpreted from velocity interferometry at the surface of distended HNS-FP pellets. In particular, the Baer-Nunziato multiphase model in CTH, Sandia's Eulerian, finite volume shock propagation code, was used to predict compressive waves in pellets having approximately a 60{\%} theoretical maximum density (TMD). These calculations were repeated with newly acquired isothermal compression measurements of fine-particle HNS using diamond anvil cells to compress the sample and powder x-ray diffraction to obtain the sample volume at each pressure point. Hence, estimating the model uncertainty provides a simple method for conveying the impact of future model improvements based upon new experimental data. [Preview Abstract] |
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