Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session K1: Poster Session II |
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Room: Fairmont Orchid Hotel Salon III |
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K1.00001: CONTINUUM AND MULTISCALE MODELING |
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K1.00002: Critical Diameter Prediction for Steady Detonation in Gassless Metal-Sulfur Compositions Francois-Xavier Jette, Andrew Higgins Since many heterogeneous mixtures whose reaction products contain no gas are highly exothermic, a possibility exists for steady gassless detonation. Theoretical investigations have focused on approximating the product Hugoniot, which depends to a large extent on the amount of heat released and the volumetric expansion resulting from the reaction. If the products Hugoniot curve lies above the unshocked state on the pressure-volume plane, the Chapman-Jouguet tangency criterion gives the detonation velocity. Such Hugoniot analysis assumes that the rate of energy loss is negligible compared to the reaction rate, a condition approached only when the charge diameter is much greater than the critical detonation diameter. For charges of practical dimension, the lateral losses are not negligible. The current study accounts for the competition between lateral losses and reaction rate in order to predict the critical diameter of a mixture of manganese and sulfur. The reaction rate is based on experimental data obtained via temperature measurements during shock initiation of the mixture. [Preview Abstract] |
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K1.00003: Composite Material Behaviour Under Shock Loading R. Vignjevic, J.C. Campbell, P. Hazell, N.K. Bourne Composite materials have been of significant interest due to widespread application of anisotropic materials in aerospace and civil engineering problems. For example, composite materials are one of the important types of materials in the construction of modern aircraft due to their mechanical properties. The strain rate dependent mechanical behaviour of composite materials is important for applications involving impact and dynamic loading. Therefore, we are interested in understanding the composite material mechanical properties and behaviour for loading rates between quasistatic and 1x108s-1. This paper investigates modeling of shock wave propagation in orthotropic materials in general and a specific type of CFC composite material. The determination of the equation of state and its coupling with the rest of the constitutive model for these materials is presented and discussed along with validation from three dimensional impact tests. [Preview Abstract] |
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K1.00004: DETONATIONS AND SHOCK INDUCED CHEMISTRY |
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K1.00005: Thermodynamic and chemical behavior of benzene under shock conditions Jean-Bernard Maillet, Nicolas Pineau, Emeric Bourasseau The thermodynamic and chemical behavior of benzene along its hugoniot curve is investigated using Molecular Dynamics simulations with reactive potentials. The simulated hugoniot curve is in good agreement with experimental data at low pressures. Moreover, the decomposition threshold is well reproduced. In the high pressure regime, reactive simulations show that benzene rapidly decomposes, but resulting pressures do not match experimental ones anymore. Simulations starting with diamond nanoparticules and hydrogen gas give good pressures along the hugoniot. These simulations seem to confirm the existence of carbon clusters with diamond structure in the decomposition products of benzene. [Preview Abstract] |
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K1.00006: Interaction between a steady detonation wave in nitromethane and geometrical complex confinement defects. Blandine Crouzet, Noel Carion, Philippe Manczur It is well known that detonation propagation is altered if the explosive is encased in an inert confining material. But in practice, explosives are rarely used without confinement and particular attention must be paid to the problem of explosive/confinement interactions. In this work, we have carried out two copper cylinder expansion tests on nitromethane. They differ from the classical cylinder test in that the liner includes evenly-spaced protruding circular defects. The aim is to study how a detonation front propagating in the liquid explosive interacts with the confining material defects. The subsequent motion of the metal, accelerated by the expanding detonation products, is measured using a range of diagnostic techniques: electrical probes, rapid framing camera, glass block associated with streak camera and velocity laser interferometers. The different experimental records have been examined in the light of a simple 2D theoretical shock polar analysis and 2D numerical simulations. [Preview Abstract] |
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K1.00007: Shock Compaction of MnAs1-xSbx Powder using Underwater Shock Wave Young Kook Kim, Hirofumi Wada, Shigeru Itoh MnAs1-xSbx material is one of the ferromagnets which can contribute to a magnetic refrigeration system that is useable at room temperature. In order to obtain further high ferromagnetic properties with grain refinement, consolidation experiments of MnAs1-xSbx powder is carried out by shock compaction using underwater shock wave. A water container which is a part of the shock compaction device is very important because the shock pressure distribution and the pressure magnitude of underwater shock wave depend on the shape of water container. Therefore, the water container is investigated numerically and experimentally in terms of the phenomenon of underwater shock wave. As result, we successfully obtained MnAs1-xSbx bulk material by shock compaction using underwater shock wave, and the MnAs1-xSbx bulk material is investigated in terms of magnetic properties. [Preview Abstract] |
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K1.00008: ABSTRACT WITHDRAWN |
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K1.00009: Research for Two-dimensional Critical Initiating State of Pressed TNT Huan Shi, Huang Fenglei, Tan Xiangqian For two-dimensional(2-D) axial-symmetric non-steady detonation process, there is a considerable difference between an initiating and a failure process. The critical condition for both processes depends on the kind of explosive, the charge diameter, density and confinement, the initiating fashion, the inert additions and so on. In this paper, we have studied the 2-D critical initiating and failure conditions of pressed TNT charge. The critical initiating 2-D experiments have carried out for general granule, gross granule, casting and watered pressed TNT. The critical gap thickness has been used to compare with the relative shock initiating sensitivity. The pressure waves are got by manganin-constantane composite 2-D Lagrange sensor. The process of initiation and extinction has been calculated near the critical point by 2-D Lagrangian analysis method, and discussed the reason why exists the discrepancy. The results show that initiation and extinction are the entirely different dynamic process, which has little difference in original condition. It causes the pressure increase of the combustion peak's rapid reaction behind precursor shock wave. [Preview Abstract] |
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K1.00010: EXPERIMENTAL DEVELOPMENTS |
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K1.00011: Measurement of Shock Propagation and Metal Plasma Expansion in Underwater Wire Explosion by Utilizing CW Laser Light Source Sung-Hyun Baek, Eun Soo Lee, Inho Kim In order to get simultaneous high speed streak and framing images of exploding metal wires in water environment, we have employed cw green laser as a backlight source and laser beam splitter as a device separating images of exploding wires. By filtering the light emitted from the exploding wire with the help of a laser line filter, the images could become much finer than those taken with normal flash light source. The evolution and stability of the cylindrical plasma column together with the shock wave and metal plasma expansion speeds in water bath have been measured, and the data were applied to understand the plasma characteristics, e.g., electrical conductivity or thermodynamic properties of warm dense metal plasmas. [Preview Abstract] |
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K1.00012: Decreasing Impact Tilt on a High Performance Two-Stage Gas Gun M.E. Byers, P.A. Rigg, J.S. Esparza There are four high-performance two-stage light gas guns in operation in the DOE complex. All four guns are similar in performance and diagnostics capabilities. Projectile velocity on these guns has typically been measured using a combination of magnetic coils and two frames of flash radiography. This requires that the projectile be in 'free flight' for a long distance (18 to 25 inches typical) in order to capture the projectile in flight. This leads to typical projectile tilt at impact in excess of 10 mrad. Recently, we have replaced the coil/x-ray system on the LANL high performance two-stage gun with Photonic Doppler Velocimetry (PDV) to obtain high accuracy (0.1\%) projectile velocity measurements. This allows us to move the target very close to the end of the barrel to potentially decrease the impact tilt significantly. We will present the results of this study and compare them to the performance of the gun when the free flight section was present. [Preview Abstract] |
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K1.00013: Detonation wave structure studies in high explosives by means of proton radiography Sergei Kolesnikov, Sergei Dudin, Victor Mintsev, Alexander Utkin, Victor Demidov, Alexander Fertman, Alexander Golubev, Mark Katz, Nikolai Markov, Boris Sharkov, Gennady Smirnov, Vladimir Turtikov Proton radiography is the unique experimental technique for obtaining direct information about important material characteristics of real solid objects under dynamic conditions. The aim of the present work is the application of this method to the investigation of evolution of density in shock and detonation waves in high explosives (HE). Obtained information will be very useful for the improvement of existing detonation models and equations of state of HE. For this purpose a proton radiography facility for dynamic experiments on the basis of TWAC-ITEP accelerator is being constructed. A special containment chamber for explosive experiments was built. Static experiments with imitators of detonating HE charges were performed; as a result the proton radiographic images of imitators with time resolution of up to 10 ns were obtained. Dynamic experiments on the registration of detonation wave structure in pressed TNT are underway. [Preview Abstract] |
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K1.00014: Confocal microscopy of water under static pressure Matthew McCluskey, Bobbie Riley, Michael Knoblauch Developments in confocal microscopy have revolutionized the imaging of samples. Unlike conventional microscopes, which illuminate a wide area, confocal microscopes focus light onto a single spot on the sample. The sample is scanned, data are collected point by point, and an image is reconstructed from the data. Samples can be scanned in three dimensions, allowing one to obtain 3D image reconstructions. We have used confocal microscopy to obtain high-quality images of water freezing in a moissanite anvil cell. This technique could prove useful for a variety of equation-of-state investigations. [Preview Abstract] |
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K1.00015: New Optical Diagnostics for Equation-of-State Experiments on the Janus Laser Dylan K. Spaulding, Damien G. Hicks, Raymond F. Smith, Jon H. Eggert, R. Stewart McWilliams, Gilbert W. Collins, Raymond Jeanloz We report on the first implementation of both a streaked optical pyrometer (SOP) and nanosecond broadband reflectometry diagnostic for observation of $\sim $Mbar laser-driven dynamic compression experiments on the Janus laser at Lawrence Livermore National Laboratory. Temporally and spatially resolved optical pyrometry has been performed in the visible spectrum to measure self-emission from the sample in parallel with velocimetry and reflectivity measurements. A variety of materials have been investigated under ramp-compression (ICE) and shock-loading conditions with absolute temperatures obtained via a greybody comparison. Furthermore, a nanosecond, time-resolved, broadband reflectivity diagnostic has been successfully demonstrated and is being developed for permanent use in combination with pyrometry for equation-of-state measurements. Results from both diagnostics are discussed for materials including SiO2, diamond, MgSiO3 and MgO. [Preview Abstract] |
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K1.00016: Accurate measurement of shock front sharp in two-stage light-gas gun. Xiang Wang, Chengdai Dai, Hua Tan, Qingsong Wang, Jingui Wang A two-stage light-gas gun is widely used for a variety of dynamic physics-property measurements up to 500 GPa or higher. The tilt and distortion of the impactor and of the resulting shock front have been precisely measured with sub-nanosecond resolution at the projectile velocities range from 2 to 7 km/s with Cu,Ta and Pt impactors. We describe our methods for data-analysis that permit us to measure the order of micron distortion of the impactor in free flying. The results of planar target experiments indicate that the distortion of shock front is non-axially symmetrical at most time and significantly different from previously reported results at LLNL. [Preview Abstract] |
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K1.00017: Line-VISAR diagnostics for isentropic compression experiments at the LLNL two-stage gas gun Klaus Widmann, Jeffrey Nguyen, Lynn James, David Erskine, Reed Patterson, Gilbert Collins, Leon Berzins The spatial uniformity and flatness of a launched gradient- density flyer plate is of utmost importance for a successful implementation of isentropic compression experiments. A Mach- Zehnder based line VISAR instrument, named B-VISAR, has been fielded at Livermore's large two-stage gas gun facilty. With the B-VISAR it was possible to record the time history of the shock breakout along a 10-mm line at the target surface. We report results of this proof-of-principle experiment and provide some comparison with simultaneously conducted point VISAR measurements. [Preview Abstract] |
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K1.00018: Experimental and Theoretical Assessment of a Device Used for Evaluation of Blast and Fragmentation Effects Anatoly Resnyansky, Samuel Weckert An alternative to traditional momentum pendulum and pressure gages is sought to resolve an improved temporal response to blast and fragmentation and protect the evaluation device from damage when positioned closely to the source of blast. Evaluation concepts based on the use of strain gages have been used for some time in the scientific community. However, those devices either produce extensive parasitic oscillations or are restricted for use in close proximity to the source of the blast and during a short time only. An alternative design is suggested and analysed that can extend the analysis time to several milliseconds and can be used both in close proximity and at relatively large stand-off distances from the source of the blast. The device employs conventional strain gauges that are heavily protected from the blast and fragmentation. Numerical analysis demonstrates ways to minimise the system oscillations and these ways were partly implemented in the present system. A gas gun fitted with a diverging nozzle has been used to validate a version of the system, which was tested in the range of pressures representative of those occurring several meters from a moderate size explosive charge. The test results and simulation demonstrate the potential for using this type of devices in the field trial settings that involve the blast and fragmentation effects. [Preview Abstract] |
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K1.00019: INELASTIC DEFORMATION, FRACTURE, AND SPALL |
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K1.00020: Dynamic fracture and failure of silica glass: Void nucleation and growth Qi An, Sheng-Nian Luo, Aaron Koskelo We investigate dynamic fracture and failure of isotropic silica glass using classical molecular dynamics simulations, under both constant strain rate and shock wave loading. Two- and three-dimensional glasses were subjected to uniaxial and isotropic strains. We characterized the fracture and failure processes by following the nucleation and growth of nanovoids. The temperal and spatial evolutions of voids were quantified, and connected to classical nucleation and growth theories for fracture. [Preview Abstract] |
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K1.00021: Front Face Spall of Concrete Adam Collins, David Chapman, William Proud Concrete cylinders (150 mm x 115 mm diameter) were impacted with half-inch steel spheres over a range of velocities (100 -500 m s$^{-1})$. Crater growth and debris cloud evolution were observed using high speed cameras aligned perpendicular and parallel to the impact direction. In-plane displacements of the impact face were tracked using Digital Speckle Photography (DSP). Radial cracking was seen to precede circumferential cracking on the high speed sequences and DSP showed bulk motion of fragments surrounding the impact zone. The profile images revealed no significant out-of-plane perturbations. [Preview Abstract] |
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K1.00022: Study of Elastic Precursor Decay in ultra fine copper Stanislav Finyushin, Anatoliy Mikhailov, Alexey Fedorov, Dmitriy Nazarov, Tatiana Govorunova, Olga Ignatova Laser interferometer was used to investigate elastic precursor decay in ultra fine copper M1 with the grain size of 0.5 microns. Samples with the thickness of 0.7-12 mm were loaded by shock wave pulse with the pressure of 12GPa. In this particular range of thickness elastic precursor amplitude decays from 1.87 GPa to 1.04 GPa. Ultra fine copper and coarse-grained copper M1 with the grain size of 110 microns were compared with respect to the elastic precursor decay values. It is shown, that elastic precursor amplitude in ultra fine copper samples is in 2 - 3 times higher than in coarse-grained copper samples. [Preview Abstract] |
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K1.00023: Experimental Study on Shear Response of 92.93 wt{\%} Alumina under Combined Pressure-Shear Loading Yao Guowen, Liu Zhanfang Pressure-shear plate impact experiments and soft recovery experiments were performed for 92.93 wt{\%} aluminas with 75-mm-diameter compressed-gas gun. The in-material longitudinal and transverse particle velocities were traced by embedded electromagnetic velocity gauges. The decoupled transverse particle velocities show an attenuation of shear waves with decreasing of material shear rigidity. SEM analysis of intact samples shows heterogeneous meso-structures, and that of recovered samples shows the transit of intergranular microcracks to transgranular microcracks with increasing shock loading. Shear component promotes the microcracks nuclearing and expanding, and these microcracks result in remarkable dilation of alumina samples after unloading. [Preview Abstract] |
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K1.00024: Simulation of a Shock Recovery Experiment K. Hughes, R. Vignjevic, N.K. Bourne It is difficult to obtaining experimental data for the behaviour of material under shock loading due to dynamic nature of this process and finite time available in which measurement can be taken. As a result shock recovery technique have been developed to allow examination of a material after shock propagation. The main goal of this experimental technique is to examine material properties after a single, well-defined shock wave followed by a single release wave have been introduced. The process should be such that any change found in the sample after recovery can only be attributed to the shock process alone. In order to achieve this, the geometry and design of the target and the fixture play an important role. In this work the simulations were performed using the Lagrangian hydrocode DYNA3D in order to size lateral and longitudinal momentum traps for the material being investigated. The investigation of the shock wave propagation in the simulation entails examining the stress, and velocity time histories for the whole fixture as well as for the single element, or block of elements of interest. In addition residual velocity of the sample was minimised to reduce its damage in the process of sample catching. [Preview Abstract] |
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K1.00025: On Beryllium Deformation at High-Velocity Oblique Impact Anatoly Mikhaylov At oblique impact of metals, intensive plastic shear strains and zones of strong heating are growing in neighborhood of contact point. Shear flows with velocity gradient depending on angle and velocity of impact of plates occur for short time. Due to intensive deformation, heating in local zones causes significant softening of substance. In these areas, shear modulus and yield strength are significantly less comparing to those at normal conditions.The mentioned effects result in distortion of profile of interface between metals after impact. Regular waves, non-symmetric distorted waves, melt layers of mixed components are formed.The process of high-velocity oblique impact of beryllium samples (beryllium and stainless steel) was experimentally studied. Though having low plasticity, beryllium has high ability for wave formation without significant plastic flow of material along sliding line (see fig.1). During high-velocity oblique impact of beryllium and stainless steel, their welded connection was achieved (see fig.2). [Preview Abstract] |
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K1.00026: Feature in Accumulation of Microdefects in Copper Under Shock-Wave Loading Alexander Pavlenko, Alexander Shestakov, Alexander Nurgaleev, Demetrius Kazakov The microscopy and X-ray diffraction methods were used to investigate distribution of micro-, and macro-defects in copper samples recovered after shock-wave loading. The electric gun GNUV was used to generate the shock wave. Sample loading dynamics was recovered by the free surface velocity measured based on the Doppler shift in the wavelength of the probe laser radiation (IFP and push-pull VISAR technique). In-depth distribution of defects was compared for two modes of sample loading. In the first mode, samples were loaded by the shock wave whose amplitude was insufficient for spalling, which was initiated by the shock wave in the second mode. [Preview Abstract] |
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K1.00027: Molecular dynamics study of tantalum spallation Laurent Soulard, Joelle Bontaz We present in this paper a molecular dynamics study of tantalum spallation. The spallation is the final stage of the damaging caused by a series of shock and rarefaction waves. This complex process is due to the nucleation, the growth and the coalescence of pores within a thin zone corresponding to the crossing of two rarefaction waves. Various experimental works allowed a partial description of this process. We present here a complementary analysis based on large classical molecular dynamics simulations in single and polycristal of tantalum. We use a rather sophisticated potential function (MEAM) associated with multi-million particle samples. The simulations were made on the TERA 10 computer of CEA-DAM, and needed several hundred processors. We examine at various times the apparition and the evolution of pores, and provide their spatio-temporal distribution. The one dimensional (in the hydrodynamics sense) and 3D cases are considered in order to understand the effects of lateral rarefaction waves in the spallation phenomenon. Comparisons with experimental data are shown. [Preview Abstract] |
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K1.00028: GEOPHYSICS AND PLANETARY SCIENCE |
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K1.00029: Measurement of the delayed failure in the shock compressed AOW rock Hongliang He, Dengping Chen, Fuqian Jing The failure property of AOW (Amphibolized Olivine Websterite) rock has been studied by measuring the velocity histories on the rear surface of the specimens at stresses much below the Hugoniot elastic limit. A delayed failure zone has been detected. It expands into the stressed material with a velocity comparable to the shock wave front, and follows the propagation of the shock wave with a time delay that decreases with the increasing of shock stress. The time delay is 1.2 microsecond at shock stress of about 0.9 GPa and 0.5 microsecond at about 3.7 GPa. A physical explanation considering the in situ activation and growth of the pre-existing microcracks by the local shear stress under shock compression is proposed for these observations. The results provided a new insight into the dynamic fracture of inhomogeneous brittle materials under the shock wave loadings. [Preview Abstract] |
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K1.00030: Impact pressures generated by spherical particle hypervelocity impact on Yorkshire sandstone Katarina Miljkovic, Emma Taylor, Bill Proud, Kostas Tsembelis, Charlie Cockell, John Zarnecki We characterise the pressures achieved in spherical particle impact, as a precursor to investigating the possibility of shock-driven DNA modification in sandstone targets, which could occur at lower pressures than those previously established to cause extinction e.g. for \textit{B. subtilis} [1, 2]. Hypervelocity impact experiments at 5 km/s using spherical chrome stainless steel projectiles onto Yorkshire sandstone were carried out using the Open University's Hypervelocity Impact Facility [3]. Noting that the impact tests cannot be carried out in a completely sterile environment, we also establish the degree of background microbial contamination present by examining post-impacted targets. Hydrocode simulations (2-D and 3-D) are used to estimate the peak loading time and pressures as a function of target geometry, supported by 1-D hydrocode simulations using the CAV{\_}KO software and published flyer plate data from the Cambridge Plate Impact Facility [4, 5]. 1) D. St\"{o}ffler et al, Icarus, 186 (2), 585-588, 2007; 2) M. J. Burchell et al, Mon. Not R. Astron. Soc., 352, 1273-1278, 2004; 3) E. A. Taylor et al, 37$^{th}$ ARA Conf, Sept 2006; 4) E. A. Taylor et al., APS 2005; 5) E. A. Taylor et al., ESTEC Impact Conf., May 2005 [Preview Abstract] |
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K1.00031: ENERGETIC MATERIALS |
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K1.00032: FOX -- 7 Cp PREDICTION FOX -7 Specific heat prediction from a proposed nominal / generic specific heat for CHNO energetic materials. James Billingsley The importance of the specific heat (Cp) of CHNO energetic polymers relative to their impact shock sensitivity has been documented in U.S. Army technical reports and papers in the shock compression of condensed matter conferences. Another recent U.S. Army technical report (AMR-SS-06-35) documents a proposed nominal / generic (N/G) Cp for CHNO energetic materials. The motivation for this proposed N/G Cp was it's utilization to predict Cp for energetic polymers whose Cp was unknown. The present paper documents the ``successful'' application of the (N/G) Cp concept to predict the Cp for a relatively new CHNO explosive, FOX--7. This application is called ``successful'' because it agrees very well with a more complex and sophisticated FOX-7 Cp prediction contained in the SCCM-2005 conference proceedings. [Preview Abstract] |
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K1.00033: High-Rate Characterisation of Hexanitrostilbene Robert Claridge, Adam Parker, William Proud Hexanitrostilbene (HNS) is a nitro-aromatic insensitive secondary explosive currently used in a number of insensitive munitions (IM) applications and under consideration for several others. The physical behavior of HNS is therefore important for the development of safe and reliable weapons systems. As part of a comprehensive suite of shock characterisation experiments, one-dimensional plate impact experiments have been performed on HNS IV at two different densities. The unreacted Hugoniot curve was established at each density and the results compared to those reported in the literature. The data obtained from these experiments will assist in the modelling of ignition and growth within HNS based explosives systems. [Preview Abstract] |
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K1.00034: Initiation of Polymer Bonded Explosive (PBXN-110) by Combined Shock and Shear Loading Jennifer Jordan, Robert Dorgan, Michael Nixon, Richard Dick Combined shock and shear loading of explosives has been shown to result in detonation of explosives at input pressures less than those required with a nearly planar shock (Cart, APS-SCCM 2003). In this study, the effect of combined shock and shear loading on PBXN-110 is investigated. The explosive sample is loaded by a TNT/Octol plane wave lens in contact with a layer of PMMA followed by a cylindrical wave shaper that has one one side angled at 45 degrees. The experiment is repeated for different thicknesses of the PMMA layer in order to vary the input pressure. In addition, the experiment is modeled using the Lagrangian finite element hydrocode EPIC, and the results of the experiments are compared with the numerical simulations. [Preview Abstract] |
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K1.00035: The evolution of sensitivity in HMX-based explosives during the reversion from delta to beta-phase Paul Peterson, Kien-Yin Lee, David Moore, Gabe Avilucea In an effort to better understand the evolution of sensitivity in HMX-based explosives formulations during the reversion from delta to beta-phase, we have performed friction and impact experiments on a 3:1 mixture of Class 1 and Class 2 HMX. Initial baselines for Type 12 Drop Wt. Impact and BAM friction sensitivities were taken for the beta-HMX. The HMX was then heated at approx 180 degrees C for 14 hours. Raman spectroscopy was used to confirm the conversion to delta-phase. Impact and friction tests on the delta-HMX indicated a 20 percent increase in sensitivity for the delta-HMX in both impact and friction. Three weeks later we re-examined the HMX using Raman to determine the amount of reversion to beta-phase. However Raman spectroscopy indicated that the delta-HMX had instead converted to alpha-phase. Impact and friction tests were then repeated showing an additional 20 percent increase in sensitivity for the alpha-HMX. The alpha-HMX appears to be fairly stable over time as illustrated by Raman spectrum. [Preview Abstract] |
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K1.00036: EQUATION OF STATE |
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K1.00037: Shock Induced Equation of State of Polyvinylchloride Sian Butler, Jeremy Millett, Neil Bourne The shock response of the common industrial polymer, polyvinylchloride (PVC) has been investigated by measurements of stress, shock velocity and particle velocity through embedded manganin stress gauges. Results in terms of shock and particle velocity show close agreement with established data within the literature. Stress measurements show an increasing difference with literature pressure values, but the calculated hydrodynamic pressure is in agreement with the literature. This suggests that the shear strength of PVC has a strong positive shock stress dependence. [Preview Abstract] |
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K1.00038: The dissociation and thermodynamics of dense fluid oxygen by self-consistent fluid variational theory Q.F. Chen, Y. Zhang, L.C. Cai, Y.J. Gu The dissociation, pressure, internal energy, and entropy of dense fluid oxygen at high temperatures and densities have been calculated from the free-energy functions using the self-consistent fluid variational theory. The accurate high-pressure and high-temperature effective pair potentials are adopted to describe the intermolecular interactions, which are made to consider molecular dissociation. In this paper, we focused on a mixture of oxygen atoms and molecules and investigated the phenomenon of pressure dissociation at finite temperature. The single-shock Hugoniot derived from this equation of state agrees well with gas-gun experiments for pressure vs density. As density and pressure increase along the Hugoniot, the system appears to undergo a continuous transition from a molecular to a partially dissociated fluid containing a mixture of atoms and molecules. The equation of state and dissociation degree are predicted in the ranges of temperature of 5000- 16 000 K and density of 0.1-4.5 g/cm$^{3}$. These data are formulated in the analytical form of dissociation degree-density-temperature and pressure-density-temperature equation of state. [Preview Abstract] |
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K1.00039: Density Measurement Method of Isentropically Compressed Hydrogen at Megabar Pressures Nikolay Egorov, A. Bykov, G. Boriskov, Yu. Kuropatkin, N. Lukyanov, V. Mironenko, V. Pavlov A radiography method of density measurement of condensed hydrogen at its isentropic compression up to megabar pressures is described in the paper. Experimental x-ray images of hydrogen compression devices in the megabar pressure ranges are presented. Measurement results of densities of condensed hydrogen and aluminum isotopes are presented. These results are used for hydrogen isotopes equations of state building. [Preview Abstract] |
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K1.00040: The Effect of Fibre Orientation on the Shock Response of a Glass-Fibre Epoxy Composite. Yann Mezieres, Jeremy Millett, Neil Bourne The response of a 2-D glass-fibre epoxy composite to one-dimensional shock loading has been investigated as a function of orientation of the fibres to the loading axis, in terms of its equation of state. When the shock axis is normal to the fibres, the response appears to be dominated by the epoxy matrix. In contrast, when the shock axis is parallel to a fibre direction, the shock front appears ramped at low stresses, steepening as the impact stress increases. Analysis of these traces suggests that a low stress amplitude wave is transmitted along the fibres at a high velocity, with a lower velocity wave is transmitted through the matrix between those fibres, taking the material to its final stress amplitude. [Preview Abstract] |
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K1.00041: The Hugoniot of Polychlorotrifluroethylene Chris Stennett, Susan Sorber, Malcolm Burns, Jeremy Millett, Neil Bourne The shock response of polymers has attracted considerable interest of the past few years, in particular as they are often used as the binder phase in plastic-bonded explosives (PBXs). One such material, polychlorotrifluroethylene (PCTFE) is used in just this application. It has also been used as an inert impedance match for some explosive compositions. Therefore there is a requirement that its response to shock loading be clearly understood. The work presented in this investigation examines the shock-induced equation of state in terms of stress, shock velocity and particle velocity. We also show that this material has an extremely high release speed, which must be accounted for when making comparisons with live compositions. [Preview Abstract] |
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K1.00042: HIGH ENERGY DENSITY PHYSICS |
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K1.00043: Self-similar flows in spherical geometry Jean Gerin-Roze If we are looking at the implosion of a sphere starting with a strong shock, the study of self-similar flows is a classical problem. We will assume that: - The sphere contains a perfect gas with a polytropic coefficient $\gamma $=5/3. - The shock follows the equation: r$_{c}$=A(-t)$^{\alpha}$ with t$_{0}<$t$<$0. There are two known solutions to that problem: - The G.Guderley solution corresponding to $\alpha =\alpha _{ref}$ = 0.68838. In this solution, the outer implosion velocity is almost constant and the compression rate at focalization is $\rho $/$\rho _{0}$=9.6. - The Y. Saillard solution corresponding to the same value of $\alpha $ (see SCCM-2005 Proceedings p1515). In this solution, the outer velocity is increasing and the compression rate is tending to infinity. We will exhibit a new family of solutions: there is one solution for each value of $\alpha $ from 0 to $\alpha _{ref}$. As in the Y. Saillard solution, outer velocity and compressing rate are tending to infinity. These new solutions (with two parameters, initial outer velocity and shock shape coefficient $\alpha)$ can provide us with benchmarks and perhaps also with ICF target design tool. [Preview Abstract] |
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K1.00044: ISENTROPIC AND OFF HUGIONOT LOADING |
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K1.00045: VELOCE - A Compact Pulser for Magnetically Driven Isentropic Compression Experiments Gilles Avrillaud, Michael Delchambre, Jean Guerre, Frederic Bayol, Fabrice Cubaynes, Boris Kovalchuk, Mathias Bavay, Joe Mervini, Rick Spielman, James Asay, Clint Hall, Randy Hickman, Tommy Ao, Michael Willis, Yogendra Gupta, James Asay, Cory Bakeman Sharing similarities with the Gepi pulser dedicated to Isentropic Compression Experiments, Veloce, an even more compact electrical pulser has been designed and built in duplicate for SNL and WSU (LxWxH=3.5x2.5x2m$^{3})$. This type of machines complements gun facilities in the study of materials. In order to achieve a broad loading capability and fast turn around, the design is built around a solid dielectric transmission line to couple current from eight low inductance capacitors and switches. Peaking capacitors enhanced by a low inductance, multi-channel sharpening switch reduces the quarter period of the pulser down to 470 ns (0-100{\%}). Gas mixtures in the switch cavity and inductances in parallel allow modifying the shape of the induced pressure wave. At 80kV of charge voltage, the peak current reaches approximately 3.5MA. Design of the pulser, range of pressures and velocities, as well as potential applications will be presented. [Preview Abstract] |
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K1.00046: A numerical investigation of sleeved Taylor anvil specimens J.C. Campbell, R. Vignjevic, N.K. Bourne The Taylor anvil test is widely used for the validation of constitutive models in non-linear continuum mechanics codes. Numerical simulations have been performed on two modified specimen geometries: a sleeved cylindrical projectile and a sleeved conical projectile. In this study the core material is aluminium and the sleeve material is tungsten alloy, providing a large difference in impedance. The objective is to develop concepts that allow the stress profile along the axis of the projectile to be controlled and varied, allowing a greater range of material behaviour to be investigated through anvil tests. The simulations show that by altering the lateral stress relief waves the stress profiles are significantly altered. The sleeved conical projectile achieves significantly higher compressive pressure on the axis than achievable through uniaixal compression for a given velocity. [Preview Abstract] |
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K1.00047: An investigation of surface velocimetry of shocked polyethylene using HetV Nathan Routley, Ed Price, Jeremy Millett, Neil Bourne, Eric Brown, George Gray The velocity history of a shocked free surface has traditionally been carried out using established techniques such as VISAR or Fabry-Perot. In recent years a third type of velocimetry has been developed by LLNL which uses Heterodyne techniques, PDV. This technique generates a Doppler beat frequency between light incident on the surface and light internally reflected within the system. Unlike the other two techniques PDV does not use an interferometer, instead it relies upon having the ability to directly record the high beat frequency. The setting up and fielding of PDV is therefore much simpler. A low power (Class 1 laser) system using this principle, locally known as HetV, has been developed and assembled. A series of experiments has been carried out to investigate the Hugoniot of polyethylene using HetV and embedded stress gauges. The results obtained with HetV have been directly compared with the embedded gauge data from the same experiment. [Preview Abstract] |
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K1.00048: Isentropic Compression Studies With High Explosive Pulsed Power Douglas Tasker, James Goforth, Henn Oona An extensive study of the one-dimensional isentropic compression experiment (ICE), performed with High Explosive Pulsed Power (HEPP), has been completed at the Los Alamos National Laboratory (LANL); the findings will be summarized. The study has demonstrated that accurate, high pressure, isentropic Equations of State (EOS) data may be obtained with the HEPP-ICE technique. It will be shown that the HEPP-ICE target configuration is capable of producing magnetic pressures that are uniform to 1 part in 1000 over the central 87{\%} of the sample faces, and that HEPP-ICE provides exact matching of the pressures between opposing samples; both of these features are key to obtaining accurate isentropic EOS data. An analysis of the overall accuracy of this technique will be given, together with the methods required for the highest accuracy. Isentropic EOS data have been obtained with the prototype LANL HEPP-ICE system, and the results for tungsten and copper will be presented. Moreover, some interesting structure was observed in the elastic to plastic failure of tungsten. [Preview Abstract] |
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K1.00049: STRESS-STRENGTH MEASUREMENTS |
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K1.00050: The Response of Concrete to Shock-Loading Tony Andrews, David Chapman, William Proud A series of plate impact experiments has been performed to assess the dynamic behaviour of dry and water saturated concrete. Information was obtained on the Hugoniot curve and dynamic shear properties using manganin gauges. This extends our previous data obtained on cement paste, mortar, and micro-concrete to full-size concrete. Despite the varying heterogeneous composition of concrete it has been found that all materials Hugoniot curves lie within a close range in pressure -- particle-velocity space. [Preview Abstract] |
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K1.00051: Incremental Stress-Strain Response of Polymers Using Instrumented Reverse Taylor Impact Experiments Louis Ferranti, Jr., Naresh Thadhani Instrumented reverse Taylor impact experiments were conducted on pure epoxy and epoxy-cast Al+Fe$_{2}$O$_{3}$ composites to determine the incremental stress-strain response under dynamic loading. High-speed camera images were used to measure transient (axial and areal) deformations and velocity interferometry was used to record complex elastic and plastic wave propagation behavior. For polymeric materials, elastic strains are generally not negligible compared to plastic strains and the rigid-plastic material behavior assumed in typical Taylor tests for metallic materials cannot be applied. Hence, in this work, a one-dimensional elastic-plastic wave propagation analysis developed by Hutchings$^{\ast}$ to account for the appreciable elastic strains that can develop before the material yields, was used. The calculations obtain stress-strain behavior for each polymer composition and permit the characterization of internal elastic and plastic wave propagation response. These results are used to compare relative strengths between each composition and ascertain the influence particle reinforcement has on material properties. \newline $^{\ast}$\textit{J. Mech. Phys. Solids (1979)} [Preview Abstract] |
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K1.00052: Hugoniots of Geological Materials and relationships to static properties A.R. Guest, C.H. Braithwaite, W.G. Proud, J.E. Field The Hugoniots for a suite of rocks have been found through investigations carried out using a plate impact facility. These Hugoniots form the database for a numerical model used in the mining industry. It is of use to have a means of linking the quasi-static to the dynamic rock strength. Therefore, a series of comparisons have been made between the Hugoniot data and a variety of static tests. A charaterisation method is suggested. [Preview Abstract] |
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K1.00053: ABSTRACT WITHDRAWN |
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K1.00054: Deformation Twinning and Dynamic Strength of Copper During High-Rate Strain Victor Raevsky We will present the results of a study of the conditions under which microstructural changes involving the formation of complex bi-periodic twin structures occurs in copper during shock wave and high strain rate ($\dot {\varepsilon }>$10$^{7}$ s$^{-1})$ shock-less loading. The overall morphology of the observed twin structures is rather complex, consisting of what we shall refer to as ``packages,'' with each ``package'' being composed of two sets of parallel twins aligned in a quasi-herringbone pattern. It is widely accepted that deformation twinning results in increased shear strength in samples recovered after shock wave loading. We have observed in this work a significant temporal component to the effect that these complex twin structures have upon shear strength. We have observed, for example, that the formation of these bi-periodic (herringbone-type) twin structures results in an initial loss of shear strength that is significant over a time period of about 0.2 to 0.4 $\mu$s. Following the initial loss of shear strength, deformation hardening produces an increase in shear strength that can be as great as several multiples of the initial value. [Preview Abstract] |
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K1.00055: Strength of polyethylene, polypropylene and polystyrene behind a shock front Christine Tyler, Neil Bourne, Jeremy Millett There is a recent interest in the response of thermoplastics to shock. Previous work on three simple polymers has indicated that the shear strength increases as the complexity of the side group increases. Shear strength measurements have been conducted using lateral stress measurements with manganin gauges that have been recalibrated for use in the low stress regime. The present work aims to investigate the effect of configuration of the thermoplastic's chain when side groups are added. In particular, whether steric effects are present when the groups become larger. Results show that whilst polyethylene has the lowest shear strength, polypropylene and polystyrene have similar values. In all cases the strength of polymer increases with time after the shock has past. As the applied stress increases, polystrene and polypropylene strengthen to a higher degree when compared with polyethylene. [Preview Abstract] |
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K1.00056: FIRST PRINCIPLES AND MOLECULAR DYNAMICS CALCULATIONS |
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K1.00057: Molecular dynamics simulation of shock-induced melting and alloying Shijin Zhao, Timothy C. Germann, Alejandro Strachan We observe sequent shock-induced melting processes occurring in Ni/Al nanonaminates by means of molecular dynamics simulations. We find a nice collaboration between the melting and alloying: the heat released from the exothermic alloying reactions facilitates the local melting in the respective Ni/Al bilayer; the liquid films from the local melting accelerate the exothermic alloying reactions. On the other hand, we uncover a keen competition between the melting and alloying from the overall pressure variation: the structural expansion upon melting leads to an increase of the pressure while the alloying reactions tend to decrease the pressure. [Preview Abstract] |
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K1.00058: MATERIALS SCIENCE |
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K1.00059: Updated Cask for Prevention against Possible Accidental Situations Andrey Drennov Design of an updated cask for transportation of hazardous substances is suggested. This method allows us actually to exclude totally any risk at fragment -- bullet effect from outside. Namely, internal cavity of a standard cask with hazardous substance is filled with fine-dispersed loose material. An individual part of this material has high strength. At low velocities of a fragment (W $<$ 1.5km/s), kinetic energy of this fragment is spared for heating and motion of microspheres. At average velocities (1.5 km/s $\le $ W $\le $ 1.85 km/s), kinetic energy of a fragment is spared for heating, motion, and work for collapse of some microspheres. At high velocities (W $>$ 2 km/s), the effect of super deep penetration occurs. If to connect the coordinate system with a moving fragment, we will get a steel target and several echelons of microparticles moving towards this target with high velocity. Since there are a lot of particles, the effect of super deep penetration occurs many times. Fragment is consecutively fragmented to sizes corresponding to sizes of microspheres. [Preview Abstract] |
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K1.00060: Hugoniot Measurement on a Gel-binder system. Ray Flaxman, William Proud, Caroline Handley, David Chapman Gel systems are finding increasing use in composites where a degree of compliance with limited residual stress is required. In this poster the results of a series of plate impact experiments are presented. The material has been characterised to obtain the principal Hugoniot, this is compared to the points obtained from a ring-up experiment, the effects of the shock heating are seen. [Preview Abstract] |
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K1.00061: Dynamic compaction of iron disilicide powders Valery Lashkov, Alexander Selezenev, Andrey Strikanov, Anya Tikhonova, Vladimer Rybakov Iron disilicide is attractive material for semiconductor thermoelectric cells. When made mechanochemically, the ground disilicide is very difficult to compact, which is particularly the case for nanopowders. This is a technology problem that seriously hinders the use of this material in industry. The work presented in the paper is where dynamic compaction method is used for compacting iron disilicide powder. Specific feature of this method is that the powder to be compacted is placed into a metal container, which is exposed to shock wave pressure from detonating HE. Dynamic compaction of the powder can produce strong chemical bonds at the contact between material grains, which is an advantage of this method. An experimental dynamic compaction setup has been developed that provides variation of the shock wave pressure from a few to dozens of GPa. The experiments were performed there using plane shock loading of a pre-compacted cylindrical iron disilicide sample in metal container surrounded by a thick frame of steel. The experiments used two types of loading, which were direct and reverse shocks. For the iron disilicide samples made by dynamic compaction, their density was found as a function of shock wave intensity and physical properties of material were measured such as electric and heat conductivity and thermalelectromotive force. [Preview Abstract] |
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K1.00062: High Pressure Equation of State of a Zirconium-Based Bulk Metallic Glass Morgana Martin, Toshimori Sekine, Takamichi Kobayashi, Laszlo Kecskes, Naresh Thadhani The high pressure $U_{s}-U_{p}$ Hugoniot equation of state of (Zr$_{57}$Nb$_{5}$Cu$_{15.4}$Ni$_{12.6}$Al$_{10}$ bulk metallic glass (BMG) was determined using plate impact experiments. The National Institute for Materials Science (NIMS) two-stage light-gas gun was utilized for the high pressure measurements ($\sim $26-115 GPa) and the Georgia Institute of Technology (GT) single-stage gas gun was utilized for the relatively low pressure measurements ($\sim $5-23 GPa). NIMS experiments were instrumented with streak photography and the inclined mirror method to simultaneously measure shock velocity and free surface velocity. GT experiments utilized polyvinylidene fluoride (PVDF) stress gauges and velocity interferometry (VISAR) to simultaneously measure the shock velocity, free surface velocity and stress. Results from the streak camera records and PVDF gauges + VISAR traces, as well as impedance matching calculations, were used to generate the $U_{s}-U_{p}$ Hugoniot equation of state data and determine the high pressure stability of the BMG. [Preview Abstract] |
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K1.00063: Microstructures produced by dynamic friction Chris Poulter, Ron Winter, Hong Jin Kim An experimental technique in which an explosive charge induces sliding between two metals has been developed as part of a study of dry friction at very high sliding velocities and pressures. Aluminium alloy/stainless steel and pure aluminium/pure copper tribo-pairs have been investigated. Optical studies of cross-sections of the aluminium samples have shown that, depending on the stress/sliding velocity conditions, the sub-surface deformation is either deep, suggesting high friction, or concentrated near the surface suggesting low friction. Recent further studies of the microstructure near the surface of the samples are described. Transmission electron microscopy reveals that a clearly delineated layer of nanocrystalline material about 1 micron thick is developed at the surface of the aluminium samples. Spectroscopic analysis shows evidence of inter-penetration of the two materials with mixing occurring at a very fine scale. The observations support the contention that, in a mechanism akin to adiabatic shear, thermal softening of the material at the sliding interface plays a key role in shock-induced friction. [Preview Abstract] |
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K1.00064: Semi-Empirical Model for the Electrical Behavior of Explosively Driven Ferroelectric Generator Minsu Seo, Myung-Hwan Park, Inho Kim Ferroelectric ceramic compressed by a strong shock releases a large amount of bound surface charges and it is the reason why it has been widely utilized in compact pulse power devices. The origin of charge release from the ceramic has not known clearly but inferred as either domain reorientation or stress induced phase transformation. ~In this work we introduce a semi-empirical model to describe the electrical behavior of explosively driven ferroelectric generator. A PZT ceramic is considered as a ferroelectric material into which the shock wave is induced normally to its polarization vector. A series of experiments has been performed to obtain the shocked properties of PZT. The parameters in the semi-empirical model have been determined from measurement. A comparison of the calculated and experimental results for both resistive and capacitive loads shows in good agreement. [Preview Abstract] |
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K1.00065: Discharge of PZT 95/5 Ferroelectric Ceramics under Tilted Shock Wave Compression. Fuping Zhang, Jinmei Du, Yi Zhang, Yusheng Liu, Gaomin Liu, Hongliang He The current waveform of Ferroelectric ceramics PZT 95/5 depoling under tilted shock wave compression has been studied. Analytic model was established to analyze the effects of incident angle on the rising time, duration and peak amplitude of the depoling current. Experiments were conducted as well to confirm these effects. Result indicted that with the increasing of incident angle, the depoling current rises with longer time, pulse duration becomes broad and the peak amplitude keeps constant until the waveform decays into triangular form. [Preview Abstract] |
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K1.00066: OTHER TOPICS |
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K1.00067: Jumps across an outgoing spherical shock wave front Yukio Sano, Tomokazu Sano Two types of jump equations are derived from the equations of conservation of mass and momentum in a moving coordinate system and in the inertial coordinate system. The first equations, of Rankine-Hugoniot (RH) type, show that the geometrical effect may be neglected at distances of movement of the rear of the wave front that are more than ten times as long as the effective wave front thickness. Furthermore, using conditions required to satisfy the RH jump conditions, which are shown by the RH type equations, a method is developed to judge the applicability of the RH jump conditions to the jumps. The second equations are those of general form obtained by expressing a volumetric strain wave $\varepsilon $ in the wave front by any form. In the neighborhood of the center of the wave front, for $\varepsilon \quad <$0.09, radial particle velocity in the jump in any materials is inversely proportional to the square of a dimensionless distance from the center to the rear, and for $\varepsilon \quad <$0.04, radial stress in the jump in some viscous fluids and solids is inversely proportional to the distance. In conclusion, an outgoing spherical wave front attenuates greatly near the center due to the geometrical effect as well as rarefaction waves overtaking from behind, while the geometrical effect is negligible at the specified positions that are distant from the center. [Preview Abstract] |
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K1.00068: Reevaluation of the precursor decay anomaly in single crystal lithium fluoride Yukio Sano, Tomokazu Sano The precursor decay anomaly in single-crystal lithium fluoride has been reevaluated by estimating dislocation densities along the Sano's decay curve [Sano, J. Appl. Phys. 85, 7616 (1999)] that are much lower and slower than the Asay's decay curve [Asay et al., J. Appl. Phys. 43, 2132 (1972)]. It is demonstrated that the density at the leading edge of the follower depends only on the slopes of the decay curves for particle velocity and stress, irrespective of the form of the follower and the slope at the leading edge. The maximum dislocation density at the beginning of the decay process is about 1/22 times as large as that estimated along the Asay's decay curve. Thus, the anomaly is reduced significantly. In addition, by estimating the density at the rear of the precursor, it is also shown that a large number of dislocations are multiplied in the vicinity of the leading edge of the follower. This increase in dislocation may be responsible for the multiplication of dislocations at the subgrain boundaries in the bulk as well as that of initial dislocations in the bulk. [Preview Abstract] |
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K1.00069: Dynamic yielding behind near-steady precursors Yukio Sano, Tomokazu Sano In materials where shocks induce large shear stresses, plastic flow occurs and the stress state becomes more isotropic. The resulting compressibility change causes a single shock wave to be unstable and to separate into a precursor and a follower, which is followed by a plastic wave. The analysis performed here demonstrates that followers C, I, II, R', and Rb appear in the decay process of the precursor in sequence, and that dynamic yielding occurs at the leading edges of the followers I, II, R', and Rb. Here the followers C, I, II, R', and Rb are the contraction wave, the degenerate contraction waves I, II, the subrarefaction wave R', and the rarefaction wave Rb. [Preview Abstract] |
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K1.00070: PHASE TRANSITIONS |
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K1.00071: A Multi-Phase Equation of State for Bismuth Geoffrey Cox This paper considers a multi-phase equation of state for bismuth. At a phase transition there are changes in volume, energy, and properties of a material that should be included in an accurate model. Modifications are made to a previously published EoS [1] with the aim of extending the pressure and temperature range of the EoS and producing a reasonable estimate of shock melt. This new EoS contains five solid phases and a liquid phase. Comparisons are shown between experimental data and the modified and unmodified EoS. \newline \newline [1] J. N. Johnson, D. B. Hayes, and J. R. Asay, J. Phys. Chem. Solids, 35, 501-515 (1974) [Preview Abstract] |
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K1.00072: Shock-Melting of Tin from Sound Velocities Measurements Jian Bo Hu, Xian Ming Zhou, Hua Tan In this paper, an improved reverse-impact technique was used to measure sound velocities of tin at the pressure range of 37GPa $\sim $ 80GPa, using time-resolved velocity interferometer system for any reflector (VISAR). Bulk and longitudinal sound velocities can be obtained simultaneously by this technique with the precision of about 5{\%} and 2{\%}, respectively. Experimental results are consistent with the thermodynamic calculations for the $\gamma $ phase of tin. Results also show elastic-plastic transition in the release process disappears gradually and longitudinal sound velocity is changed gradually to bulk sound velocity with Hugoniot stress increasing. In combination with phase diagram of tin, it is suggested that pre-melting is occurred before the bulk melt because of the energy depositing in the grain boundary. Only the location of completely shock-melted state can be determined from sound velocities measurements. [Preview Abstract] |
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K1.00073: Retention of the Alpha-Prime Phase in a Pu-Ga Alloy After Hydrostatic Compression A.J. Schwartz, M.A. Wall, D.L. Farber, K.T. Moore, K.J.M. Blobaum Delta-phase Pu-Ga specimens, 2.3 mm diameter by 100 microns thick were compressed to approximately 1 GPa in a large volume moissanite anvil cell to induce the transformation to the alpha-prime phase. The recovered samples were characterized at ambient pressure with optical microscopy, x-ray diffraction, and transmission electron microscopy. Optical microscopy revealed a very fine microstructure that appears to be single phase. This preliminary conclusion was supported by x-ray diffraction, which showed only the monoclinic reflections from the alpha-prime phase. However, transmission electron microscopy revealed small regions of delta-phase with a very high dislocation density. From these results, we conclude that hydrostatic compression to 1 GPa is not fully sufficient to form and retain 100\% alpha-prime. [Preview Abstract] |
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K1.00074: Surface Specularity as an Indicator of Shock-Induced Solid-Liquid Phase Transitions G.D. Stevens, S.S. Lutz, W.D. Turley, L.R. Veeser, P.A. Rigg, B.J. Jensen, R.S. Hixson When highly polished metal surfaces melt upon release after shock loading, they exhibit a number of features that suggest that significant surface changes accompany the phase transition. The reflection of light from such surfaces changes from specular (pre-shock) to diffuse upon melting. A familiar manifestation of this phenomenon is the loss of signal light in velocimetric measurements typically observed above pressures high enough to melt the free-surface. Unlike many other potential material phase-sensitive diagnostics (e.g., reflectometery, conductivity), changes in the specularity of reflection provide a dramatic, sensitive indicator of the solid-liquid phase transition. Data will be presented from multiple diagnostics that support the hypothesis that specularity changes indicate melt. These diagnostics include shadowgraphy, infrared imagery, high-magnification surface images, interferometric velocimetry, and most recently scattering angle measurements. [Preview Abstract] |
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K1.00075: Phase Transformations of Graphite at Shock-Wave Loading in Steel Targets with Conic Cavities Andrey Zhuk, Alexander Charakhchyan, Vladimir Milyavskiy, Konstantin Khishchenko, Dmitriy Zhernokletov, Tatiana Borodina, Georgiy Valiano Phase transformations of graphite with various densities and microstructure at shock-wave loading in steel targets with conic cavities were studied. Graphite GMZ ($\rho $=1.70 g/cc), MPG-7 ($\rho $=1.91 g/cc) and MF-307 ($\rho $=2.01 g/cc) were used in the experiments. The recovered specimens were studied by means X-ray phase analysis. The maximal degree of graphite-diamond transformation having a place in the experiments was estimated. Experimental data were compared to results of 2D numerical modeling. The detailed description of the numerical methods is presented in [1]. We have found that with growth of a degree of three-dimensional regularity and a size of crystal grains of graphite, transition onset pressure and speed of phase transformation falls. [1] V.V. Milyavskii, V.E. Fortov, A.A. Frolova, K.V. Khishchenko, A.A. Charakhchyan, L.V. Shurshalov, Comp. Math. {\&} Math. Phys. 46 (2006) 873. [Preview Abstract] |
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K1.00076: SPECTROSCOPY AND OPTICAL STUDIES |
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K1.00077: Optical Shock Generation Integrated with Time-resolved Spectroscopy G. Saini, T. Pezeril, S.E. Kooi, E.L. Thomas, K.A. Nelson A detailed understanding of how materials respond to ballistic shock-loading is critical for the design and development of new protective materials. However, nonlinear viscoelastic deformation present in polymers during and immediately following a ballistic impact event is not currently well understood. The dynamic mechanical responses of materials during shock-loading are quite complex, with large amplitude compressions resulting in strain rates of 10$^{6 }$s$^{-1}$ and pressures exceeding several GPa. The mechanical properties of multilayered thin films are measured using impulsive stimulated thermal scattering, a laser-based photoacoustic technique. Since the data can be acquired on a single shot basis, the measurement is compatible with laser shock loading. To this end, a novel pairing of optical shock generation and time-resolved spectroscopy is used, providing an insightful tool for studying the material response to large-amplitude short-time mechanical transients. Laser-induced shock loading has been synchronized with ISTS measurement of acoustic waves so that dynamical evolution of mechanical properties in laser-shocked materials can be examined. The results could complement those from a recent gas gun-ISTS combination that permits measurement of acoustic and mechanical properties during steady-state shock loading. This work is supported by the U.S. Army Research Office. [Preview Abstract] |
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K1.00078: Simulating EXAFS Patterns of Shocked Crystals Andrew Higginbotham, Robert Albers, Tim Germann, Brad Holian, Kai Kadau, Peter Lomdahl, William Murphy, Justin Wark Extended X-ray absorption fine structure (EXAFS) can be a useful tool in structural determination for solid state systems. Simulation of signals from EXAFS experiments is usually carried out using the FEFF package. Although fast, the standard FEFF approach is based on perfect crystals and includes temperature effects using a Debye model. In the case of a shocked crystal it is not clear that such a simulation can encapsulate the full physics of the system, especially if mixed crystallographic phases, dislocations or grain boundaries have a significant effect on the signal. Molecular dynamics (MD) can provide detailed information on these features in many shocked materials of interest and so an EXAFS averaging technique based on MD data could allow a more meaningful comparison with experimental data. We will present a comparison of the standard FEFF approach with a configurational averaging technique based on MD data. The relative merits of the two methods will be highlighted and the implications for simulating EXAFS spectra for shocked samples discussed. [Preview Abstract] |
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K1.00079: Prospects for Using X-Ray Free-Electron-Lasers to Investigate Shock-Compressed Matter Bob Nagler, Andrew Higginbotham, Giles Kimminau, William Murphy, Justin Wark, Thomas Whitcher, James Hawreliak, Dan Kalantar, Richard Lee, Hector Lorenzana, Bruce Remington, Jorgen Larsson, Nigel Park, Klaus Sokolowski-TInten Within the next few years hard X-ray Free Electron Lasers will come on line. Such systems will have spectral brightnesses ten orders of magnitude greater than any extant synchrotron, with pulse lengths as short as a few femtoseconds. It is anticipated that alongside the X-ray source large-scale optical lasers will be sited, capable of shock-compressing matter to multi-megabar pressures. We discuss the opportunities that such systems may afford to further our knowledge of shocked and isochorically heated matter, in particular investigating the potential to perform small angle and/or diffuse scattering that may allow in situ measurements of dislocation densities in shocked crystals, and the creation of warm dense matter. [Preview Abstract] |
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