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 T1: Energetic Materials VII |
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Chair: Michael Winey, Washington State University Room: Grand Ballroom II-III |
Thursday, June 30, 2011 11:00AM - 11:15AM |
T1.00001: Gap Test Calibrations and Their Scaling Harold Sandusky Common tests for measuring the threshold for shock initiation are the NOL large scale gap test (LSGT) with a 50.8-mm diameter donor/gap and the expanded large scale gap test (ELSGT) with a 95.3-mm diameter donor/gap. Despite the same specifications for the explosive donor and polymethyl methacrylate (PMMA) gap in both tests, calibration of shock pressure in the gap versus distance from the donor scales by a factor of 1.75, not the 1.875 difference in their sizes. Recently reported model calculations suggest that the scaling discrepancy results from the viscoelastic properties of PMMA in combination with different methods for obtaining shock pressure. This is supported by the consistent scaling of these donors when calibrated in water-filled aquariums. Calibrations with water gaps will be provided and compared with PMMA gaps. Scaling for other donor systems will also be provided. Shock initiation data with water gaps will be reviewed. [Preview Abstract] |
Thursday, June 30, 2011 11:15AM - 11:30AM |
T1.00002: Modeling Thermal Ignition in PBX 9502 Bryan Henson, Laura Smilowitz, Jerry Romero, David Oschwald We present a model of 2,4,6 trinitro-1,3,5-benzenetriamine (TATB) thermal ignition in the plastic bonded formulation PBX 9502 that is constrained by a global chemistry and parameterized almost entirely by independent and more elemental measurements of rate. We model solid decomposition using a cyclic mechanism coupling thermodynamic states of TATB that we have shown to be effective in models of thermal ignition for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) based plastic bonded explosives. We have shown that elements of these models are broadly applicable to the class of secondary solid organic explosives, and this model of TATB thermal ignition further indicates the similarity of mechanisms underlying thermal decomposition and ignition in this class of explosive. [Preview Abstract] |
Thursday, June 30, 2011 11:30AM - 11:45AM |
T1.00003: Hydrocode Simulation of Wedge Tests to Determine How the Test Method Affects the Pop Plot Gerrit Sutherland Most of the available shock reactivity data for explosives comes from either wedge tests or from embedded gauge data obtained from flyer plate tests. A question arises, what effect does the test method have on the Pop Plot obtained? A flyer plate test will impart a constant input pressure whereas wedge testing using a plane wave lens (PWL) system will not. To gauge this effect, explicit numerical simulations were performed for 4'' and 8'' diameter wedge tests using a PWL system and for flyer plate impact tests. For the flyer plate tests, the simulations modeled the flyer plate and explosive sample. For the PWL system, the simulations modeled the PWL, the booster explosive, the attenuator and the explosive sample. The simulations resulted in distance-time curves of the shock or detonation wave traveling into the sample. These curves, when differentiated, resulted in shock velocity versus distance and shock velocity versus time plots. Inspection of these plots for various input pressures allowed for prediction of pop plots (log of run distance versus log of time and log of run distance versus log of input pressure). Comparison of the Pop Plots indicated the effect of the test method on Pop Plot slope and intercept. Simulations were performed for both an ideal and a non-ideal explosive. [Preview Abstract] |
Thursday, June 30, 2011 11:45AM - 12:00PM |
T1.00004: Low Velocity Impact Experiments plus Modeling of the Resulting Reaction Violence in LX-10 Charges Steven Chidester, Frank Garcia, Kevin Vandersall, Craig Tarver A new gas gun facility and improved instrumentation were used to study the mechanisms of low velocity impact ignition and growth of violent reaction. Cylindrical charges of the HMX based explosive LX-10 (95{\%} HMX, 5{\%} Viton binder) encased by lexan were impacted by 6.35 mm diameter hardened steel projectiles at velocities ranging from 47 to 500 m/s. Fast Phantom v12 cameras were employed to capture the times of first ignition. The degrees of resulting reaction violence were determined using Photonic Doppler Velocimetry (PDV) probes to measure the free surface velocity histories of attached aluminum foils. Analytical and hydrodynamic reactive flow models were used to estimate the relative violence of these LX-10 reactions compared to the intentional detonation of an equivalent LX-10 charge. This work was performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344. [Preview Abstract] |
Thursday, June 30, 2011 12:00PM - 12:30PM |
T1.00005: Shock-induced chemistry in simple organic molecules Invited Speaker: Interrogating chemical reactions behind a shock front is immensely difficult, and as a result, the details of shock-induced chemistry remain poorly understood. Shock compression creates transient distorted structures from which molecular reactions initiate. Previous works have reported that dimerizations, polymerizations, ring-opening and decomposition reactions occur under shock compression, depending on molecular structure. Certainly for explosives, exothermic decomposition reactions ultimately drive self-supported detonation. Questions regarding the thresholds for incipient reaction for different chemical functional groups, the nature of first and subsequent reaction steps, and the influence of shock input conditions on reaction kinetics remain to be answered. Evidence of reaction can be discerned from discontinuities in the mechanical variables for reactions with a change in density along the reaction coordinate, similar to first-order phase transformations. Here, we have applied in-situ electromagnetic gauging at multiple Lagrangian positions to elucidate the evolution of multiple-wave structures associated with shock-induced reactions. We have applied in-situ gauging, in concert with reactive molecular dynamic simulations, to investigate shock-reactivity of several simple functional groups: carbon-carbon double (-C=C-) and triple bonds, and nitriles (e.g. phenylacetylene and acrylonitrile), and aromatic ring structures (benzene), all building blocks for explosives. From measurements of the reactive flow, we have obtained detailed information about the temporal evolution of the waves, and global kinetics associated with transformation(s) between partially- and fully-reacted states. Near the reactive threshold, evolution in particle velocities point to reaction timescales on the order of several hundred nanoseconds. We have defined the reactive cusp Hugoniot states, and established the relative order of group reactivity under single shock conditions. These observations will be compared with reactions from the solid phase under static high pressure/temperature conditions, with a description of crystalline phase, and identification of polymerized products by in-situ x-ray diffraction and spectroscopic methods. [Preview Abstract] |
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