Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session C1: TMS: HE Initiation II |
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Chair: Mark Anderson, SNL Room: Grand Ballroom I |
Monday, June 17, 2019 11:00AM - 11:30AM |
C1.00001: Applying the HERMES Model to Non-shock Ignition and Post-ignition Violence Invited Speaker: John Reaugh The HERMES model (High Explosive Response to MEchanical Stimulus) [1] has been developed to study the behavior of energetic materials using computer simulations that are closely coupled with experiments. The material properties needed to analyze a specific experiment vary, but include the equations of state of the unreacted material and of the product gas mixture. In addition, the resistance of the unreacted solid to shear deformation as a function of stress state (including confining pressure) and deformation rate will generally be required. The resistance may include permanent deformation, widespread fragmentation, localized fracture, and porosity development, which all depend on the applied loads. Our non-shock ignition criterion follows the observation that shear localization with confining stress is the condition for ignition. Our shock initiation criterion is based on CREST [2]. We present examples of ignitions that self-extinguish quickly, ignitions that self-extinguish, but nevertheless produce measurable air blast, and ignitions that lead to delayed detonations. We assess the respective roles of the properties of energetic materials and the properties of the confinement on the violence of the response. 1. J. E. Reaugh, B. W. White, J. P. Curtis, and H. K. Springer, \textit{Propellants Explos. Pyrotech.} \textbf{2018}, 43, 703-720. 2. C. A. Handley, \textit{Proceedings 13}$^{th}$\textit{ Int. Detonation Symp}., Norfolk, VA, July \textbf{2006}, p864-870. JER's work was performed under the auspices of the United States Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-768150 [Preview Abstract] |
Monday, June 17, 2019 11:30AM - 11:45AM |
C1.00002: Modeling PBX 9501 High Explosive Cylinder Experiments and an Evaluation of WSD and AWSD Parameter Sets Marvin Zocher, Tariq Aslam, Matthew Price Cylindrical assemblies are often used in experiments aimed at calibrating and validating continuum level models of reactive burn, and of the so-called equation of state model (constitutive model for the spherical part of the Cauchy tensor). Such is the case in work to be discussed here. In particular, work will be described involving the modeling of a series of experiments involving PBX 9501 encased in a copper cylinder. The objective of the work is to test and perhaps refine a set of phenomenological parameters for the Wescott-Stewart-Davis (WSD) and Arrhenius-WSD (AWSD) reactive burn models. The focus of this talk will be on modeling the experiments, which turned out to be non-trivial. Always difficult to handle due to the extremely short reaction zone of PBX 9501, scaling is employed to address issues related to detonation velocity. The modeling is conducted using ALE methodology. [Preview Abstract] |
Monday, June 17, 2019 11:45AM - 12:00PM |
C1.00003: Can we predict how nano-scopic voids affect explosive performance? W. Lee Perry, Amanda Duque, John Yeager, Xia Ma, Brad Clements, Larry Hill, Von Whitley, Brian Patterson We know that microstructure and density affect the shock initiation of an insensitive high explosive (IHE), such as PBX 9502 (95{\%} TATB). We suspect that those factors also affect some performance and propagation metrics, especially curvature effects and the explosive's ability to turn corners. A recently developed hydrodynamic burn model, $\pi $SURF, provides insight and predictive capability for the initiation regime of shock response based partly on a statistical characterization of the microstructure. Here we examine the ability of the $\pi $SURF model to predict the effects of microstructural features on the propagation regime characteristics of curvature and corner turning of the IHE PBX 9502. Specifically, we explore the hypothesis that informing the model about the presence or absence of intra-granular porosity (the `nano-scopic' voids, as opposed to the larger, inter-granular `micro-scopic' voids), as revealed by a void size distribution, will predict the corner turning behavior observed in the Enhanced COrner Turning experiments for these two classes of PBX 9502. Indeed, we learned that the model does show the expected behavior. We also learned that the model smoothly predicts, without adjustment, both the initiation and propagation regimes of shock response (other models require mathematical or code switching between the regimes). [Preview Abstract] |
Monday, June 17, 2019 12:00PM - 12:15PM |
C1.00004: Grain-size effects in the shock heating of idealized PBXs Nisha Mohan, Marc J. Cawkwell, Frank L. Addessio, Kyle J. Ramos, D.J. Luscher Polycrystalline microstructure and material anisotropy in plastic bonded explosives (PBXs) lead to thermal localization even under sub-shock impacts. We performed a systematic study of how grain size affects temperature in model PBX using finite element simulations. The modeling framework combines a dislocation-based, anisotropic, single crystal plasticity model with a visco-elastic constitutive model for estane. Our simulations used constant binder thickness or volume as the grain size was varied in the range of 25 to 300 microns. In the set of PBX simulations with constant binder thickness, smaller grains gave rise to lower average temperatures. Dispersion of the shock wave occurs rapidly in smaller grain simulations because of the greater volume fraction of binder. This led to a more uniform strain rate and temperature distribution with run distance of the shock wave into PBX. A shock dispersion effect explained variance and localization of temperatures in larger grains. We also examined anisotropy, binder thickness, microstructural stress concentrators, and shock front width to grain size ratio as other contributors in simulations of smaller grain PBXs. [Preview Abstract] |
Monday, June 17, 2019 12:15PM - 12:30PM |
C1.00005: Computational studies of laser-driven flyer impact experiments to probe properties of inert and energetic materials Svjetlana Stekovic, H Keo Springer, Mithun Bhowmick, Dana D Dlott We present computational studies of laser-driven flyer impact experiments using a multi-material, arbitrary Lagrangian-Eulerian code, ALE3D. The Dlott research group has designed a tabletop apparatus in which a flyer plate is driven by a short-pulse laser to speeds of 1-5 km/s and impacts a multi-material medium. The multi-material medium consists of a transparent window and either an inert or nitromethane. These experiments provide high-resolution information on the dynamic material response and reactivity through the transparent window. Numerical results demonstrate agreement with experimental data for the laser launch of the aluminum flyer and the flyer impact response of window. These efforts have been used to improve the experimental design and provide further knowledge into the non-planar effects during the dynamic material response of inert materials. We also expand our computational approach to simulate a multi-material medium and observe the dynamic response of nitromethane. [Preview Abstract] |
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