Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session Q1: ME.3 Inelastic Deformation, Fracture, and Spall VI |
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Chair: Naresh Thadhani, Georgia Institute of Technology Room: Grande Ballroom I |
Wednesday, July 10, 2013 1:45PM - 2:00PM |
Q1.00001: Taylor Impact Tests on PBX Composites: Imaging and Analysis Darla Graff Thompson, Racci DeLuca A series of Taylor impact tests were performed on three plastic bonded explosive (PBX) formulations: PBX 9501, PBXN-9 and HPP (propellant). The first two formulations are HMX-based, and all three have been characterized quasi-statically in tension and compression. The Taylor impact tests use a 500 psi gas gun to launch PBX projectiles (approximately 30 grams, 16 mm diameter, 76 mm long) at velocities as high as 215 m/s. Tests were performed remotely and no sign of ignition/reaction have been observed to date. High-speed imaging was used to capture the impact of the specimen onto the surface of a steel anvil. Side-view contour images have been analyzed using dynamic stress equations from the literature, and additionally, front-view images have been used to estimate a tensile strain failure criterion for initial specimen fracture. Post-test sieve analysis of specimen debris correlates fragmentation with projectile velocity, and these data show interesting differences between composites. Along with other quasi-static and dynamic measurements, these impact images and fragmentation data provide a useful metric for the calibration or evaluation of intermediate-rate model predictions of PBX constituitive response and failure/fragmentation. Intermediate-rate tests involving other impact configurations are being considered. [Preview Abstract] |
Wednesday, July 10, 2013 2:00PM - 2:15PM |
Q1.00002: Shock and High Strain Rate Characterization of HTPB with Varying Plasticizer Didier Montaigne, Christopher Neel, Peter Gould, Christopher Molek, Jennifer Jordan Hydroxy-terminated polybutadiene (HTPB) has long been used as a binder in propellants and explosives. However, cured HTPB rubbery polyurethanes have not been characterized in a systematic fashion as function of plasticizer content. In this study, four isocyanate-cured HTPB variants with different amounts of plasticizer have been formulated. The materials were characterized using dynamic mechanical analysis and quasi-static and dynamic compression experiments. Additionally, the shock Hugoniot was measured on the two extremes of the material -- no plasticizer and maximum plasticizer. The properties of the HTPB were predicted using the Porter-Gould model for polymers. [Preview Abstract] |
Wednesday, July 10, 2013 2:15PM - 2:45PM |
Q1.00003: Polymorphism and Decomposition of HE Single Crystals: Insights from Static and Shock Compression Experiments Invited Speaker: Zbigniew Dreger Understanding the reactive behavior of high explosive (HE) crystals at thermo-mechanical conditions generated by shock-waves is an important step toward understanding shock wave initiation of these crystals. Despite the significant differences in time scales and loading rates, static high pressure and high temperature (HP-HT) experiments can provide key results regarding structural and chemical processes in HE crystals at pressures and temperatures relevant to shock initiation. Here, we review recent progress in utilizing optical spectroscopy to understand molecular processes in HE crystals at static HP-HT conditions to gain insight into their shock initiation mechanisms. The relevant results obtained from static studies up to 20 GPa and 700 K on polymorphism, decomposition and phase diagrams will be presented for selected HE crystals: primarily for RDX and PETN, and initial results on DADNE. The significance of the stress state and the use of single crystals in these processes will be highlighted. Finally, we demonstrate that the static HP-HT results in conjunction with shock-wave experiments provide an important approach to elucidate processes related to the initiation of shocked HE crystals, including polymorphic transitions, conformational changes, identification of crystal phases at decomposition, and mechanisms governing shock induced decomposition. Work was supported by DOE/NNSA and ONR/MURI, and carried out in collaboration with Y. M. Gupta. [Preview Abstract] |
Wednesday, July 10, 2013 2:45PM - 3:00PM |
Q1.00004: Computational and Experimental Investigation of the Shock Compression Response of Cold-Rolled Ni/Al Multilayers Paul Specht, Naresh Thadhani, Timothy Weihs Heterogeneities at the meso-scale strongly influence the shock compression response of composite materials. In reactive material mixtures, such as Ni and Al, these heterogeneities greatly affect material mixing, heating, and activation, often initiating a reaction. Cold-rolled multilayered composites of Ni and Al provide a unique and potentially beneficial reactive material system, due to their full density, periodic layering, and intimate particle contacts. The shock-compression response of cold-rolled Ni/Al multilayers was investigated under uniaxial strain loading conditions using plate-impact experiments. Time-resolved diagnostics, including VISAR, PDV, and PVDF stress gauges, were used to obtain the equilibrium Hugoniot response of the multilayers. The experimental results were coupled with a computational investigation using the multi-material, finite-volume, Eulerian hydrocode CTH, developed by Sandia National Laboratories. The computations employed real, heterogeneous microstructures, obtained from optical microscopy, enabling their correlation with the experimental results to provide validation of the models and computational method used for describing the response of the cold-rolled Ni/Al multilayers. Research funded by ONR/MURI grant No. N00014-07-1-0740. [Preview Abstract] |
Wednesday, July 10, 2013 3:00PM - 3:15PM |
Q1.00005: Prediction of Probabilistic Ignition Behavior of PBXs from Microstructural Stochasticity Seokpum Kim, Ananda Barua, Yasuyuki Horie, Min Zhou A novel approach is developed to computationally predict and quantify the stochasticity of the ignition process in polymer-bonded explosives (PBXs) under impact loading. The method involves subjecting sets of statistically similar microstructure samples to identical overall loading and characterizing the statistical distribution of the ignition response of the samples. The focus of the analyses is exclusively on the influence of microstructure geometry variations on the critical time to ignition at given load intensity and the critical impact velocity below which no ignition occurs. Results show that the probability distribution of the time to criticality follows the Weibull distribution. The quantification of this probability distribution as a function of microstructural attributes including grain volume fraction, grain size and specific binder-grain interface area along with the stochastic variations of these attributes within each set of samples yields relations that reveal microstructural parameters that play dominant roles in determining the ignition behavior of the materials. In particular, it is found that the specific interfacial area directly influences the critical time to ignition and the critical impact velocity below which no ignition is observed. [Preview Abstract] |
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