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 Z2: Energetic Materials X |
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Chair: Scott Bardenhagen, Los Alamos National Laboratory Room: Grand Ballroom IV-VI |
Friday, July 1, 2011 11:00AM - 11:15AM |
Z2.00001: Critical Detonation Thickness in Vapor-Deposited Pentaerythritol Tetranitrate (PETN) Films Alexander S. Tappan, Robert Knepper, Ryan R. Wixom, Michael P. Marquez, J. Patrick Ball, Jill C. Miller Films of the high explosive PETN (pentaerythritol tetranitrate) have been deposited through physical vapor deposition. PETN films were characterized with surface profilometry, and scanning electron microscopy. This work is an extension of previous work (Tappan et al., 14th International Detonation Symposium), in which critical detonation thickness for PETN was determined to be less than 200 microns in a configuration where charge width was similar to film thickness, and thus side losses played a role in detonation propagation. In this work, experiments will be presented where charge width was large compared to film thickness (``infinite width''). The results of these experiments will be discussed in the context of small sample geometry, deposited film morphology, and density. [Preview Abstract] |
Friday, July 1, 2011 11:15AM - 11:30AM |
Z2.00002: Mesoscale Analysis of Deformation Wave Structure and Dissipation in Metalized Solid Explosive Sunada Chakravarthy, Keith Gonthier Impact induced heating of metalized explosive is characterized by high frequency temperature fluctuations occurring in the vicinity of inter-particle contact surfaces due to plastic and friction work. Importantly, these fluctuations, which are difficult to experimentally resolve, are influenced by the material's meso-structure, composition, and porosity. In this study, a Lagrangian finite and discrete element technique is used to computationally examine quasi-steady, piston supported uniaxial deformation waves in granular metal (Al)-explosive (HMX) mixtures based on a plane strain, finite deformation, thermoelastic-viscoplastic, and friction constitutive theory. Emphasis is placed on characterizing how metal mass fraction, particle size distribution, and wave strength affect both the filtered spatial wave structure and the fluctuations in dissipation occurring near Al-Al, HMX-HMX, and Al-HMX particle contact surfaces. The potential relevance to impact sensitivity is discussed. [Preview Abstract] |
Friday, July 1, 2011 11:30AM - 11:45AM |
Z2.00003: Small-scale dynamic confinement gap test Malcolm Cook Gap tests are routinely used to ascertain the shock sensitiveness of new explosive formulations. The tests are popular since that are easy and relatively cheap to perform. However, with modern insensitive formulations with big critical diameters, large test samples are required. This can make testing and screening of new formulations expensive since large quantities of test material are required. Thus a new test that uses significantly smaller sample quantities would be very beneficial. In this paper we describe a new small-scale test that has been designed using our CHARM ignition and growth routine in the DYNA2D hydrocode. The new test is a modified gap test and uses detonating nitromethane to provide dynamic confinement (instead of a thick metal case) whilst exposing the sample to a long duration shock wave. The long duration shock wave allows less reactive materials that are below their critical diameter, more time to react. We present details on the modelling of the test together with some preliminary experiments to demonstrate the potential of the new test method. [Preview Abstract] |
Friday, July 1, 2011 11:45AM - 12:00PM |
Z2.00004: A Review of 3D imaging techniques for visualisation of the structure of energetic composites A.E. Carmichael, D.M. Williamson, R. Govier A review of imaging techniques which can be used to acquire three dimensional data on the structure of polymer composite materials is presented. The techniques chosen utilise a variety of mechanisms for forming contrast, and include x-ray tomography (XCT), nuclear magnetic resonance (NMR), and optical \& electron microscopy. Discussion is illustrated with reference to a particular HMX based UK PBX. The achievable contrast and spatial resolutions are considered, along with arguments relating to the destructive and non-destructive methods of acquiring data. Particular emphasis is given to the safety concerns and the added experimental complications which arise when studying energetic materials. [Preview Abstract] |
Friday, July 1, 2011 12:00PM - 12:15PM |
Z2.00005: Improving laser-driven flyer velocity with high absorptance layers H.R. Brierley, T.A. Vine Laser driven flyers are produced on the interaction of a laser pulse with a thin film of metal. When an Nd:YAG laser is focussed through a transparent substrate onto a 5 micron film of aluminium, a fraction of the metal is ablated. The associated expansion causes the remaining aluminium to be punched from the film and launched as a discrete flyer. Due to the high reflectivity of aluminium, some of the laser energy is lost through reflection at the substrate/metal boundary. By introducing metals which exhibit stronger absorption at the Nd:YAG wavelength (1064 nm), the laser coupling to the flyer is improved, resulting in faster flyer velocities for a given pulse energy. This paper discusses the results of using Hf, Ge, Zn and Ti to improve the coupling of the Nd:YAG laser to the flyer. [Preview Abstract] |
Friday, July 1, 2011 12:15PM - 12:30PM |
Z2.00006: A Binary Eutectic Mixture of TNAZ and R-Salt Explosives Mary Sandstrom, Virginia Manner, Steven Pemberton, Joseph Lloyd, Bryce Tappan TNAZ is a high performing explosive that is melt castable. However, the casting process can be problematic since TNAZ has a high vapor pressure exacerbated by a fairly high melting temperature. In order to mitigate the ill effects of its high vapor pressure, including a lower melting explosive was explored by making a series of mixtures of TNAZ and R-Salt. Initially, a eutectic temperature and composition was theoretically determined. Then a phase diagram was constructed from a series and mixtures by differential scanning calorimetery (DSC). The vapor pressure of the eutectic composition was determined by thermogravimetric analysis (TGA). Cylinder testing of the eutectic composition was carried out in copper tubes, 5'' long with 1/2 ``inner diameter and 1/16'' thick walls. The detonation velocity was measured using wire switches along the cylinder length and the expanding wall velocity was measured using PDV gauges. A rough evaluation of JWL equation-of-state parameters has been carried out. A more detailed evaluation is in progress. [Preview Abstract] |
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