Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session L21: Materials in Extremes: Energetic MaterialsFocus
|
Hide Abstracts |
Sponsoring Units: GSCCM DCOMP DMP Chair: Tariq Aslam, Los Alamos National Laboratory Room: 320 |
Wednesday, March 16, 2016 11:15AM - 11:51AM |
L21.00001: Modeling the anisotropic shock response of single-crystal RDX Invited Speaker: Darby Luscher Explosives initiate under impacts whose energy, if distributed homogeneously throughout the material, translates to temperature increases that are insufficient to drive the rapid chemistry observed. Heterogeneous thermomechanical interactions at the meso-scale (i.e. between single-crystal and macroscale) leads to the formation of localized hot spots. Direct numerical simulations of mesoscale response can contribute to our understanding of hot spots if they include the relevant deformation mechanisms that are essential to the nonlinear thermomechanical response of explosive molecular crystals. We have developed a single-crystal model for the finite deformation thermomechanical response of cyclotrimethylene trinitramine (RDX). Because of the low symmetry of RDX, a complete description of nonlinear thermoelasticity requires a careful decomposition of free energy into components that represent the pressure-volume-temperature (PVT) response and the coupling between isochoric deformation and both deviatoric and hydrostatic stresses. An equation-of-state (EOS) based on Debye theory that defines the PVT response was constructed using experimental data and density functional theory calculations. This EOS replicates the equilibrium states of phase transformation from alpha to gamma polymorphs observed in static high-pressure experiments. Lattice thermoelastic parameters defining the coupled isochoric free energy were obtained from molecular dynamics calculations and previous experimental data. Anisotropic crystal plasticity is modeled using Orowan's expression relating slip rate to dislocation density and velocity. Details of the theory will be presented followed by discussion of simulations of flyer plate impact experiments, including recent experiments diagnosed with in situ X-ray diffraction at the Advanced Photon Source. Impact conditions explored within the experimental effort have spanned shock pressures ranging from 1-10 GPa for several crystallographic orientations. Simulation results will be used to motivate conclusions about the nature of dislocation-mediated plasticity in RDX, as well as, future directions to improve these models and quantitatively compare them to the average lattice response recorded with in situ X-ray diffraction. [Preview Abstract] |
Wednesday, March 16, 2016 11:51AM - 12:03PM |
L21.00002: Role of microstructure and thermal transport in determining the rate of hot spot growth in aluminized PBX Kaushik Joshi, Santanu Chaudhuri The mechanisms of initiation and propagation of a hot spot in non-ideal explosives with aluminum additives are poorly understood due to greater complexity introduced by the different thermal and mechanical behavior of the components. In aluminized composites such as PBXN-109, the binder, RDX and Aluminum phases have been studied separately. However, not much is known about deflection of hot spots in the microstructured composite. Especially, the role of adhesion, debonding and thermal conductivity of binder phase is critical in moderating the sensitivity of such interfaces. Using reactive molecular dynamics simulations, the primary binder interfaces in PBXN-109 was investigated. Depending on the temperature of the growing hot spot reaching an RDX or Al/Al2O3 grain, the thermal conductivity and viscoplastic behavior of the binder interface determine the attenuation of reaction front and thermal shock leading the hot spot. Different mechanisms like melt-dispersion and failure of oxide layer for the release of Al in the hot spot regions remain underexplored to connect the chemistry to the microstructure. Although Al/Al2O3/RDX and Al/Al2O3/HTPB interfaces are chemically stable, the hot spot melts the AlxOy layers and create shear bands in aluminum domain due to thermomechanical strain created due to different thermal environment. In a shock-compressed microstructure without voids, the cohesive interaction and chemical composition of such interfaces for different phases of RDX will be presented. [Preview Abstract] |
Wednesday, March 16, 2016 12:03PM - 12:15PM |
L21.00003: An extreme pressure attenuation in metals from a miniaturized pyrotechnic train configuration Jack Yoh, Bohoon Kim, Hyeonju Yu A pyrotechnic device that consists of donor/acceptor pair separated by a bulkhead relies on shock attenuation in metal and shock sensitivity of the energetic materials. Despite of its common use, full-scale numerical simulation of such explosive train configuration is seldom reported because the proper modeling of the entire process requires precise capturing of extreme pressure waves from the donor charge during its attenuation in the metal before triggering of an acceptor charge and the accurate material modeling of high strain rate dynamics of both reactive and inert solids. The considered train consists of HMX as donor, STS 304 as the bulkhead, and RDX as acceptor. The simulation of such multi-material configuration reveals the critical bulkhead thickness for successful initiation of a pyrotechnic device. Furthermore, the miniaturization of such system is considered by obtaining the distance to shock front sharpening for building an analytical theory of pressure attenuation in STS sample of microscale thickness, and a new shock Hugoniot data is provided from the laser-based shock experiment using such samples. [Preview Abstract] |
Wednesday, March 16, 2016 12:15PM - 12:27PM |
L21.00004: Mechanisms of laser-induced photocatalytic decomposition of high explosives Anatoly Mitrofanov, Anton Zverev, Sergey Rashkeev, Roman Tsyshevsky, Maija Kuklja Using laser irradiation for triggering explosive decomposition of high density energy materials opens up new opportunities in design of safe optical detonators by removing primary explosive from the devices. Precise tuning of sensitivity to initiation of detonation via photo-excitation appears challenging because all secondary explosives are insulators with the band gap of 4-8 eV. We will discuss our combined experimental and theoretical studies that suggest feasible mechanisms of photocatalytic decomposition of explosives triggered by the laser excitation with the energy of 1.17 - 2.3 eV and the wavelength of 1064-532 nm. The first approach considers tuning the optical absorption via the controlled modification of the electronic structure of the explosive-metal oxide interfaces. The second approach involves incorporating photoactive organic molecules in the crystalline matrix of the explosive material. [Preview Abstract] |
Wednesday, March 16, 2016 12:27PM - 12:39PM |
L21.00005: Emergent molecular theory of initiation of detonation: the effect of molecular and crystal structure on thermal stability of high density energy materials Maija Kukla, Roman Tsyshevsky, Onise Sharia The sensitivity to detonation initiation of high density energy materials along with their performance are two most important criteria for choosing the best material for explosive formulations, booster engines, detonators, \textit{etc}. After numerous experimental and theoretical attempts to develop a single parameter describing sensitivity of different classes of energetic materials, one concludes that the complexity of physical and chemical explosive properties cannot be trivialized. We report here the results of our theoretical and computational studies of thermal decomposition mechanisms and kinetics of five classes of EM: pentaerythritol tetranitrate (PETN), nitramine cyclotetramethylene-tetranitramine (HMX), diamino-dinitroethene (DADNE), bis-(nitrofurazano)-furoxane (BNFF) and benchmark triamino-trinitrobenzene (TATB). Our modeling reveals how the thermal stability depends on the molecular structure of the material and how the crystal structure may additionally hinder or catalyze decomposition reactions. We will also discuss an effect of crystalline defects on sensitivity and performance of materials. [Preview Abstract] |
Wednesday, March 16, 2016 12:39PM - 12:51PM |
L21.00006: Ignition Prediction of Pressed HMX based on Hotspot Analysis Under Shock Pulse Loading Seokpum Kim, Christopher Miller, Yasuyuki Horie, Christopher Molek, Eric Welle, Min Zhou The ignition behavior of pressed HMX under shock pulse loading with a flyer is analyzed using a cohesive finite element method (CFEM) which accounts for large deformation, microcracking, frictional heating, and thermal conduction. The simulations account for the controlled loading of thin-flyer shock experiments with flyer velocities between 1.7 and 4.0 km/s. The study focuses on the computational prediction of ignition threshold using James criterion which involves loading intensity and energy imparted to the material. The predicted thresholds are in good agreement with measurements from shock experiments. In particular, it is found that grain size significantly affects the ignition sensitivity of the materials, with smaller sizes leading to lower energy thresholds required for ignition. In addition, significant stress attenuation is observed in high intensity pulse loading as compared to low intensity pulse loading, which affects density of hotspot distribution. The microstructure-performance relations obtained can be used to design explosives with tailored attributes and safety envelopes. [Preview Abstract] |
Wednesday, March 16, 2016 12:51PM - 1:03PM |
L21.00007: The Dynamic Behaviors of Single Crystal RDX Under Ramp Wave Loading to 15GPa Guiji Wang, Jintao Cai, Jianheng Zhao, Feng Zhao, Gang Wu, Fuli Tan, Chengwei Sun Based on high pulsed power generator CQ-4, the single crystal RDX explosive was researched along different crystal orientations under ramp wave loadings up to 15 GPa. The typical three-wave structures were obtained by means of laser interferometry PDV, which show the elastic-plastic transition and $\alpha $ to $\gamma $ phase transition. The ramp elastic limit (REL) and yield strength of RDX along 210 and 100 crystal orientations were respectively calculated and the resuts show obvious effects of crystal orientaions for RDX. The ramp elastic limit $\sigma_{\mathrm{IEL}}$ of RDX along 210 orientation is 0.688-0.758GPa, and the $\sigma _{\mathrm{IEL}}$ of RDX along 100 is 1.039 -1.110 GPa. The $\alpha $ to $\gamma $ phase transformation characteristics were also analyzed based on the experimental data. The initial phase transition pressure for the two crystal orientation of RDX are about 3.5 to 4 GPa, which agree well with the data of about 4-5GPa given by MD simulation. The data directly validate the results given by Raman Spectrum under shock compression and static high pressure, which couldn't be observed by wave profiles. The experimental data can be used to verify and validate the new models of RDX under dynamic loading. Supported by NSFC of China under contract No.11327803 and 11176002 [Preview Abstract] |
Wednesday, March 16, 2016 1:03PM - 1:15PM |
L21.00008: Experimental and numerical study of deformation modes of a pressed HMX-based explosive composition Didier Picart, Jerome Vial, Patrice Bailly Safety of industrial or military explosives is still studied to prevent inadvertent ignition of pressed HMX-based explosive compositions submitted to a low-velocity impact. Our aim is to determine the dissipative mechanisms leading to the local heating of the material. To observe the dissipative mechanisms, a reversed edge-on impact test has been developed. This test enables real-time observations of the microstructural scale. No friction is observed between the biggest HMX grains and the matrix (the smallest grains, the binder and the porosity). Plasticity of HMX grains is obtained as well as damage by micro-cracking. Meanwhile, a biphasic numerical representation (HMX grains and matrix) is used to mimic our material. A comparison between experimental observations and simulations is used to determine the yield stress of HMX. The behavior of the matrix has been determined to account for the effect of strain rate and damage. Lastly, a comparison between tests and simulations has highlighted (1) that heating should rather be located in the matrix than in the biggest HMX grains and (2) that the most likely heating mechanism is the friction of micro(or meso)-cracks lips. [Preview Abstract] |
Wednesday, March 16, 2016 1:15PM - 1:27PM |
L21.00009: Decomposition products of TATB under high static pressure. Jonathan Crowhurst, Elissaios Stavrou, Joseph Zaug We have investigated the decomposition products of 2,4,6-triamino-1,3,5-trinitrobenzene (TATB) at static pressures up to 50 GPa using Raman and IR absorption spectroscopy. Decomposition was driven by various continuous wave and pulsed laser drives. We compare decomposition behavior and products obtained at the different pressures. Preliminary results at lower pressures indicate the formation of carbon dioxide, nitrogen, amorphous carbon and possibly hydrogen. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 [Preview Abstract] |
Wednesday, March 16, 2016 1:27PM - 1:39PM |
L21.00010: ABSTRACT WITHDRAWN |
Wednesday, March 16, 2016 1:39PM - 1:51PM |
L21.00011: ABSTRACT WITHDRAWN |
Wednesday, March 16, 2016 1:51PM - 2:03PM |
L21.00012: Secondary decomposition reactions in nitramines Igor Schweigert Thermal decomposition of nitramines is known to proceed via multiple, competing reaction branches [1], some of which are triggered by secondary reactions between initial decomposition products and unreacted nitramine molecules. Better mechanistic understanding of these secondary reactions is needed to enable extrapolations of measured rates to higher temperatures and pressures relevant to shock ignition. I will present density functional theory (DFT) based simulations of nitramines that aim to re-evaluate known elementary mechanisms [2,3] and seek alternative pathways in the gas and condensed phases. [1] S. Maharrey and R. Behrens, J. Phys. Chem. A, 109, 11236 (2005) [2] C. F. Melius and M. C. Piqueras, P. Combust. Inst., 29, 2863 (2002) [3] K. Irikura, J. Phys. Chem. A, 117, 2233 (2013) [Preview Abstract] |
Wednesday, March 16, 2016 2:03PM - 2:15PM |
L21.00013: \textbf{Shock-induced decomposition of high energy materials: A ReaxFF molecular dynamics study} Subodh Tiwari, Ankit Mishra, Ken-ichi Nomura, Rajiv Kalia, Aiichiro Nakano, Priya Vashishta Atomistic simulations of shock-induced detonation provide critical information about high-energy (HE) materials such as sensitivity, crystallographic anisotropy, detonation velocity, and reaction pathways. However, first principles methods are unable to handle systems large enough to describe shock appropriately. We report reactive-force-field ReaxFF simulations of shock-induced decomposition of 1, 3, 5-triamino-2, 3, 6-trinitrobenzene (TATB) and 1,1-diamino 2-2-dinitroethane (FOX-7) crystal. A flyer acts as mechanical stimuli to introduce a shock, which in turn initiated chemical reactions. Our simulation showed a shock speed of 9.8 km/s and 8.23 km/s for TATB and FOX-7, respectively. Reactivity analysis proves that FOX-7 is more reactive than TATB. Chemical reaction pathways analysis revealed similar pathways for the formation of N$_{\mathrm{2\thinspace }}$and H$_{\mathrm{2}}$O in both TATB and FOX-7. However, abundance of NH$_{\mathrm{3\thinspace }}$formation is specific to FOX-7. Large clusters formed during the reactions also shows different compositions between TATB and FOX-7. Carbon soot formation is much more pronounced in TATB. Overall, this study provides a detailed comparison between shock induced reaction pathway between FOX-7 and TATB. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700