Bulletin of the American Physical Society
16th APS Topical Conference on Shock Compression of Condensed Matter
Volume 54, Number 8
Sunday–Friday, June 28–July 3 2009; Nashville, Tennessee
Session C4: CM-2: Continuum Modeling of Initiation and Burn |
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Chair: John Borg, Marquette University Room: Hermitage D |
Monday, June 29, 2009 11:00AM - 11:15AM |
C4.00001: Prediction of Ignition of High Explosive When Submitted To Impact Didier Picart, Franck Delmaire-Sizes, Cyril Gruau, Herve Trumel High explosive structures may unintentionally ignite and transit to deflagration or detonation, when subjected to mechanical loadings, such as low velocity impact. We focus our attention on ignition. The Browning and Scammon~[1] criterion has been adapted. A concrete like constitutive law is derived, with an up-to-date experimental characterization. These models have been implemented in Abaqus/Explicit [2]. Numerical simulations are used to calibrate the ignition threshold. The presentation or the poster will detail the main assumptions, the models (Browning et al, mechanical behavior) and the calibration procedure. Comparisons between numerical results and experiments [3] will show the interest of this method but also its limitations (numerical artifacts, lack of mechanical data, misinterpretation of reactive tests{\ldots}). [1] R.~Browning and R.~Scammon, \textit{Shock compression of condensed matter}, pp. 987-990, (2001). [2] C.~Gruau, D.~Picart\textit{ et al.}, $17^{th}$\textit{ Dymat technical meeting}, Cambridge, UK, (2007). [3] F.~Delmaire-Sizes\textit{ et al.}, $3^{rd }$\textit{International symposium on energetic materials}, Tokyo, Japan, (2008). [Preview Abstract] |
Monday, June 29, 2009 11:15AM - 11:30AM |
C4.00002: Meso-Structural Influences on Energetic Material Response to Thermal Mechanical Loading Joseph C. Foster, Jr., D. Scott Stewart, Sunhee Yoo The engineering design of energetic material is often application specific. In order to analyze the functional relationship between design and application we have adopted the position that the design is defined by the suite of specifications and processes used to fabricate the component. An analysis of this statement leads us to the conclusion that depending on the proposed function there exist a myriad of physical realization of the configuration at the subcomponent level in the design where there exist significant gaps in the specifications. This is particularly true when analyzing the meso-structure of the energetic material. This leads us to an investigation of the relationship between the family of physical configurations allowed by the design specification and our physically based understanding of the functional requirements. Preliminary analysis of specific realizations of allowed configurations high light the range in structure and response based upon specification. [Preview Abstract] |
Monday, June 29, 2009 11:30AM - 11:45AM |
C4.00003: Some numerical and theory issues with 2-phase mechanical equilibrium reactive burn models James Quirk, Mark Short The most widely used two-phase mixture reactive flow models for condensed phase explosive ignition and detonation modeling can be cast as reductions of a full two-phase mixture system, with various equilibrium and other assumptions (Kapila et al., Physics of Fluids, 2001). The Ignition and Growth (I\&G) model, for example, assumes mechanical (pressure and velocity) phase equilibrium with an additional assumption of temperature equilibrium. The CREST model, on the other hand, fixes the post-shock entropy of the solid reactant in lieu of temperature equilibrium. The reduction to a mechanical equilibrium model from the full 2-phase system introduces a number of potential thermodynamic, conservation and numerical difficulties. Some of these issues are explored in the context of a 2-phase Stiffened Gas model for which some analytical results are available. [Preview Abstract] |
Monday, June 29, 2009 11:45AM - 12:00PM |
C4.00004: Grain Scale Simulations of Hot Spot Initiation of TATB* Michael Howard, Fady Najjar, Laurence Fried High-energetic (HE) material consists of large-sized grains with micron-sized embedded impurities and pores. Under various mechanical/thermal insults, these pores collapse generating high-temperature regions leading to ignition. A computational study has been performed to investigate the mechanisms of pore collapse and hot spot initiation in TATB crystals, employing the thermo-hydrodynamics arbitrary-Lagrange-Eulerian code ALE3D. This initial study includes non-reactive dynamics to isolate the thermal and hydrodynamical effects. Two-dimensional high-resolution large-scale meso-scale simulations have been undertaken. We study an axisymmetric configuration for pore radii ranging from 0.5 to 2$\mu $m, with initial shock pressures in the range from 3 to 11 GPa. A Mie-Gruneisen Equation of State (EOS) model is used for TATB, and includes a constant yield strength and shear modulus; while the air in the pore invokes a Livermore Equation of State (LEOS) model. The parameter space is systematically studied by considering various shock strengths, pore diameters and material properties. We find that thermal diffusion from the collapsed pores has an important effect in generating high-temperature hot spots in the TATB. [Preview Abstract] |
Monday, June 29, 2009 12:00PM - 12:15PM |
C4.00005: Simulations of Hot-Spot Initiation with Reactive Kinetics for Shocked TATB F.M. Najjar, M.W. Howard, L.E. Fried Under mechanical or thermal insults, micron-sized pores created due to defects or impurities are embedded in high-energetic material and might collapse generating high-temperature regions, leading to ignition. A multiphysics computational study is undertaken to understand the formation, ignition and growth of these hot spots. Two-dimensional high-resolution simulations are performed on an axisymmetric pore configuration in a shocked TATB material using \textsf{ALE3D}. \textsf{ALE3D} is a massively parallel multiphysics framework using an arbitrary Lagrangian-Eulerian (ALE) approach and includes thermal transfer, hydrodynamics, and chemistry along with an extensive suite of advanced EOS models. Further, a reactive kinetics model has been used to capture the chemical processes occuring in TATB. We will present results obtained from these large-scale simulations and discuss key thermo-hydro-chemical processes leading to hot-spot initiation. [Preview Abstract] |
Monday, June 29, 2009 12:15PM - 12:30PM |
C4.00006: On the relationship between the non-reacted and detonation products equations of state for a reacting explosive Brian Lambourn, Nicholas Whitworth, Caroline Handley, Hugh James In many reactive flow models for explosives, the non-reacted (NR) and detonation products (DP) equations of state (EOS) are treated independently, each just matching some appropriate experimental data. As a result, the NR and DP EOS usually conflict in some parts of the pressure-volume-internal energy space. This presentation suggests a general criterion for the relationship between the two EOS and develops the criterion for the often used Mie-Gruneisen type of equations of state. [Preview Abstract] |
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