Bulletin of the American Physical Society
2005 14th APS Topical Conference on Shock Compression of Condensed Matter
Sunday–Friday, July 31–August 5 2005; Baltimore, MD
Session F7: Poster Session I |
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Chair: Gerrit Sutherland, Naval Surface Warfare Center, Indian Head; Clint Hall, Sandia National Laboratories Room: Hyatt Regency MD Suite 5:30-7:00pm, Mon |
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F7.00001: ENERGETIC MATERIALS
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F7.00002: UK Marginal Initiation Characterisation Test for High Explosives Mark Wright, Peter Williams, John Richardson, Elizabeth Edmonds, Andrew Jones, Rodney Drake The UK Marginal Initiation Characterisation (MIC) Test has been developed to cover two areas of research: as an initial performance screening test for candidate energetic materials; and as a technique for characterising the effects of composition changes, ageing and temperature on reaction kinetics. Tests have been undertaken on UF-TATB, UF-TATB/HMX and a highly loaded HMX PBX. The initiation system has been tuned to deliver a suitable pressure/time profile to marginally initiate each of these compositions. Subsequently, a study of sensitivity and divergence as a function of charge attributes (e.g. composition and density) has been completed. In addition, first stage hydrocode modelling of the MIC Test has been completed using CTH. This has already proved useful in providing qualitative analysis of the experimental results. The modelling output has highlighted the relationship between the prominent features in the results and the confinement around the explosive sample. [Preview Abstract] |
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F7.00003: On Investigations into the UK Large Scale Gap Test S.J. Burley, N.K. Bourne, J.C.F. Millett, V. Fung, R. Hollands, A.M. Milne Knowledge of the sensitivity of high explosives to shock is important to avoid unwanted detonations in service. The large scale gap test (LSGT) is used in the UK as one of the key qualification tests for energetic materials. These tests consist of a donor charge, a PMMA attenuator (or gap) and a test or acceptor charge. The gap length is varied until 50\% of test acceptors are detonated. In this work the shock to detonation behaviour of a UK secondary formulation was measured. Manganin pressure gauges were embedded at various radii in acceptor charges of varying lengths, and the charges were subjected to varying gap output pulses, characterized in earlier work. For longer acceptor lengths and higher gap output pressures, detonation was observed. Curvature was also measured. The test configurations were modelled using a reactive model derived from parallel work done using plate impact. The predications of the hydrocode and the results of the experiments are compared and comments are made on the applicability of the test. [Preview Abstract] |
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F7.00004: Harnessing modified manganin technique to study processes of explosive transformation in pyrotechnic compositions Sergei Batalov, Zakhar Gorelik, Sergei Kiselev, Alexander Syrtsev The paper reviews results of the experimental study of explosive transformation in pyrotechnic compositions with modified manganin technique. In particular, experimental data on pressure profiles recorded with tiny manganin sensors are cited to characterize the effect of parameters of the loading pulse, dispersion and density on peculiarities of explosive transformation in studied pyrotechnic pieces under shock-wave initiation. In the paper are shown the experimental pressure profiles, characteristic for processes of explosive transformation of extended delay. The experimental results prove the effect of density variation of the specimens under study on the process of the explosive transformation. It is felt that for given range of pressures of the incoming shock wave the difference of the explosive transformation history, at equal parameters of loading pulse, is caused also by different dispersion of the initial powder and final porosity of studied specimens. The experimental results provide support for possibility of use of tiny manganin and constantan sensors in studying processes of explosive transformation of pyrotechnic compositions under initiation by divergent shock waves of large curve front and slumping pressure profile. [Preview Abstract] |
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F7.00005: Procedure to study kinetics and topography of the glow induced by the HE explosion decomposition initiated by laser and electron beams V.T. Gromov, A.V. Pavlenko, V.L. Stryakhnin, O.V. Nesterov, N.G. Orlov, O.V. Tkachev, B.G. Loboiko, V.P. Filin, N.V. Garmasheva Development of new methods to investigate explosives (HE) behavior under external actions is still important. Recent years saw a principally new approach to this task. This approach is based on the experimental study of the early stages of explosion decomposition (pre-explosion processes) in real time (10$^{-8}$ - 10$^{-4}$ s). This paper describes the measurement facility and the procedure for studying the pre-explosion processes in high explosives based on pulse-radiolysis methods. In this procedure, the neodymium laser (pulse duration is 1.5 ps, 150 ps, and 15 ns; energy - up to 1.5 J) and the high-current accelerator of electrons (pulse duration is 50 ps and 6-20 ns, beam energy is 250 keV) were used as initiators of explosion decomposition. The procedure helps measure the amplitude-time parameters of acoustic signals generated during explosive decomposition of explosives, as well as the velocity of the sound and the profile of electron energy absorption in solid bodies including high explosives. Optical measurements were made with 0.1 ns time resolution, and 100 microns spatial resolution. The scheme based measures electric signals with the time resolution of 2 ns. [Preview Abstract] |
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F7.00006: Thermal Cook-Off Experiments of the HMX Based High Explosive LX-04 to Characterize Violence with Varying Confinement Frank Garcia, Kevin S. Vandersall, Craig M. Tarver, Daniel W. Greenwood, Jerry W. Forbes Thermal cook-off experiments were carried out using LX-04 explosive (85{\%} HMX and 15{\%} Viton by weight) with different levels of confinement to characterize the effect of confinement on the reaction violence. These experiments involved heating a porous LX-04 sample in a stainless steel container with varying container end plate thickness and assembly bolt diameter to control overall confinement. As expected, detonation did not occur and reducing the overall confinement lowered the reaction violence. Modeling was also performed using Ignition and Growth kinetics with reasonable agreement to the experiment. These results suggest that controlling the overall system confinement can modify the relative safety in a given scenario. This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. [Preview Abstract] |
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F7.00007: Towards an Understanding of Gas Permeation in Thermally Damaged PBX 9501 Gary Parker, Peter Dickson, Blaine Asay, Laura Smilowitz, Bryan Henson, Lee Perry We will present data that indicate that thermally damaged PBX 9501 is substantially more permeable than the pristine material and that this may have a significant effect on the pre-ignition slow cook-off process, as well as the post-ignition flame spread process. experiments indicate that the mechanism responsible for the formation of interconnected matrix porosity is likely dominated by nitroplasticizer decomposition in the early stages of the permeability evolution history followed by secondary, slower HMX decomposition. Other experiments employing a planar section (simulating a constant aperture fracture) indicate that at elevated temperatures, the plastic nature of PBX 9501 can seal fractures and that the observed specific permeability is the likely result of matrix flow. Still there are many unanswered questions, and the continuation of parametric studies of the various dominant mechanisms is crucial in order to develop the modeling capabilities to eventually be able to make the\textit{a priori} predictions required in the future. [Preview Abstract] |
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F7.00008: Optical and Mechanical Characteristics of PETN Single Crystal V.T. Gromov, V.P. Shykailo, A.A. Ugodenko, A.S. Tishenko, T.N. Kryshinskaya, I.V. Vorozhtsova, O.V. Tkachev, N.G. Orlov, B.G. Loboiko, V.P. Filin, N.V. Garmasheva Pentaerythritol tetranitrate (PETN) is an extensively used crystalline high explosive. A good understanding of the laser- induced chemical decomposition and growth to detonation of PETN is important. This work on PETN single crystals focused primarily on its mechanical and optical properties under laser pulse interaction. Laser pulse ($E<2~ J$, $\tau = 150~ ps$, $\lambda~=~1.06~\mu m$) was focused on the single crystal surface to focal point size 80 .. 800 $\mu m$. The goal of this work was to study the early stages of laser-induced explosion decomposition. Crystal response to the laser radiation was determined by the luminescence and conductivity of crystals. Explosion decomposition of PETN single crystals failed to occur within the studied range of initiation energies. Experiments measured the threshold of the optical breakdown for PETN and determined energies when its mechanical destruction begins. Analysis of experiments allowed a new scheme to be proposed for experiments when the laser radiation energy is injected inside the crystal. [Preview Abstract] |
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F7.00009: One-Dimensional Shock and Detonation Characterization of Ultrafine Hexanitrostilbene Stephen Goveas, Jeremy Millett, Ivan Knapp, Neil Bourne A series of plate impact experiments was performed, using a single-stage gas gun, on die-pressed, high density (92{\%} theoretical maximum) samples of ultrafine hexanitrostilbene (HNS). This enabled investigation of the inert shock response and subsequent detonation of the material. Shock magnitudes up to ca. 6 GPa were investigated by varying the flyer and target plate materials, and impact velocities. In each case, the shock length was chosen to be longer than the pellet (ca. 3 mm). Shock wave profiles and transit times were diagnosed using embedded miniature (1 mm$^{2})$ manganin stress gauges placed at the front and rear of the shock assemblies. The results have been interrogated to establish the non-reactive Hugoniot of the HNS and deduce information on its run-to-detonation. Analysis of measured stresses and calculated pressures suggests that pressed HNS possesses little strength behind the shock front. These and other features are discussed and compared with existing data. [Preview Abstract] |
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F7.00010: Influence of nitrogroups positions in molecules of various classes of explosives on results of quantum-chemical calculation of dissociation energy Vladimir Golubev Results of quantum-chemical calculation of dissociation energies of nitrogroups in molecules of various classes of explosives such as aliphatic and aromatic nitrocompounds (C-NO2), aliphatic, heterocyclic (N-NO$_{2})$ and aromatic (C-NO$_{2}$, N-NO$_{2})$ amines, nitrates of spirits (O-NO$_{2})$ are presented. Molecules more than thirty explosives, from nitromethane to octogen and PETN are examined. Calculations were carried out with the use of the Gaussian 98 program. The density functional theory (DFT) method with the B3LYP combined functional was applied. Several basic sets of electronic functions, from the widely used polarizing 6-31G(d) basic set to the extremely large multifunctional 6-311++G(3df, 3pd) basic set, were used in calculations. The values of lengths of corresponding bonds and other structural and energetic characteristics of examined molecules are also deduced. Influence of structural isomerism and conformation was considered. The general tendencies of influence of nitrogroups positions in the molecules of explosives on the values of dissociation energy of the bonds were discoverd. For the majority of the considered molecules the certain interrelation of the dissociation energy of the weakest bond and the sensitivity to impact of corresponding explosive was recorded. [Preview Abstract] |
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F7.00011: Thermal Decomposition Models for High Explosive Compositions Jonathan Zucker, Peter Dickson, Bryan Henson, David Zerkle, Mary Sandstrom As interest in the cookoff response of high explosives expands to include commercially-available compositions, the need has arisen for a broad spectrum of predictive capabilities to describe the untoward thermal decomposition of these explosives. Empirical models for several compositions, including PETN, Semtex and Comp B, have been developed and tested against existing experimental data. [Preview Abstract] |
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F7.00012: Shear stresses in shock compressed energetic materials Sergey Zybin, Ivan Oleynik, Tahir Cagin There are numerous experimental indications of orientational dependence of shock-induced detonation phenomena in energetic materials (EM). The initial response of EM to shock wave loading can be related to such fundamental characteristics of EM as its elastic properties upon uniaxial compression. It is well-known in the case of covalent solids that shear stresses are the driving forces of shock induced plasticity and the formation of point and extended defects but their effect on shock induced deformations and chemical reactions in molecular crystals of EM is not certain. We report results of combined first-principles density functional theory (DFT) and reactive force field (ReaxFF) study of shear stresses in uniaxially compressed EM such as PETN, RDX and HMX as a function of crystalline orientation and the compression ratio of the load. The steric effects, changes in the bond lengths and angles, relative contribution of inter and intra-molecular interactions and possibilities of phase transitions are discussed in relation to experimental observations of orientational sensitivity of EM. [Preview Abstract] |
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F7.00013: PBX-9502 Shock Sensitivity Correlation with Specific Heat and Reactive Temperature Magnitudes James Billingsley This work is a supplementary follow-on to papers [1 and 2], presented in two previous SCCM conferences, that related plane impact shock sensitivity of CHNO energetic materials to specific heat (C$_{p}$ per average atom) magnitude and reactive temperature (T$_R )$ conditions. More specifically, plane impact shock energy input that is equal to the thermal vibratory energy increment (the area under the C$_{p}$ versus temperature data curve between an experimental temperature, T$_{EXP} $, and a reactive temperature) is sufficient to cause shock induced reactions, up to and including detonation, in CHNO energetic materials. This statement is demonstratively verified at four different test temperatures for PBX-9502 in this proposed paper. \begin{enumerate} \item Billingsley, J. P., paper in Shock Compression of Condensed Matter -- 1995, AIP Conference Proceedings 370, Part I, pages 429 -- 432. \item Billingsley, J. P., paper in Shock Compression of Condensed Matter -- 1999, AIP Conference Proceedings, 505, Part II, pages 899 -- 902. \end{enumerate} [Preview Abstract] |
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F7.00014: Decomposition of Nitroplasticizer in Plastic Bonded Explosive PBX 9501 Denise Pauler, Joel Kress In the plastic bonded explosive PBX 9501, a 50/50 mixture of Estane 5703, a polyester urethane random copolymer, and nitroplastizer (NP) binds the HMX explosive crystals. Chemical kinetic mechanisms are being developed for the thermal degradation of NP for high temperatures (explosions) and low temperatures (natural and accelerated aging studies). The goal of this work is to investigate reaction mechanisms using density functional electronic structure theory in addition to the data obtained from explosion and aging experiments. NP consists of a 50/50 mixture of bis-2,2-dinitropropyl acetal and formal. Using 2,2-dinitro-1-methoxypropane as a model compound, a library of reactions was investigated to propose a mechanism for the decomposition of NP. The current mechanism begins with the elimination of HONO, which remains trapped within the material. HONO then adds onto the backbone of NP, which can lead to the formation of esters and oximes that may react further to produce carbon monoxide, carbon dioxide, and NO$_{x}$ gases. This work is supported by the Enhanced Surveillance Campaign and the Advanced Simulation and Computing program. [Preview Abstract] |
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F7.00015: The dynamic compaction of sugar as a stimulant of HMX Caroline Lowe, Martin Greenaway The ability of confined porous energetic materials to transition to detonation under weak impact (less than 100 m/s) has been a safety concern for many years. Porosity increases the sensitivity of an explosive to impact by facilitating energy localisation to form ``hot spots.'' Granular materials have been studied for many years as mock porous explosives. Compaction dissipates energy; this can mainly be attributed to intergranular friction, material damage and material compression. Dissipation increases temperatures but key questions remain about how accurately continuum models quantify this dissipation. Quasi-static compaction experiments have demonstrated significant changes in bulk mechanical behaviour during loading and bed hysteresis, yet the models describe quasi-static compaction as fully reversible. To quantify the extent of dissipation during compaction, there is a need for dynamic compaction experiments undertaken over a range of strain rates. This article reports experiments on the loading response of sugar over a range of strain rates from quasi-static to fully dynamic. The experiments are used to provide closures for mathematical models of dynamic compaction and data to validate simulations. [Preview Abstract] |
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F7.00016: Interactions of Shape Charge Jets with Energetic Materials J.D. Molitoris, R.G. Garza, H.G. Andreski, J.D. Batteux In this research high resolution radiography was used to image the interaction between a shape charge produced jet and an energetic material target. The target material used here was cast Composition B. The image data details shock interactions and deflagration initiated by the jet. As the diagnostic recorded up to four images in time sequence, the evolution of these interactions could be studied. Void structure in the target due to the casting process complicated the interaction. This work was performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48. [Preview Abstract] |
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F7.00017: CONTINUUM & MULTISCALE MODELING
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F7.00018: 3D computer modeling of high-velocity impact phenomena Vadim Kim, Igor Lomonosov, Alexey Matveichev, Afanasy Ostrik The modified ``individual particles'' method has been developed for solving the system of gas dynamic equations in 3D setup. The continuous media in this approach is represented as an ensemble of finite-size particles, which carry all flow parameters. The special algorithm for splitting and merging of particles belonging to the same eulerian cell has been developed. It made it possible to solve common for PIC-type methods problems with the memory loading and unphysical oscillations. The computation procedure in the modified ``individual particles'' method performs calculations with the only one particle per cell, while splitting particles are smoothly redistributed in the rarefaction regions. Physical models library includes advanced equations of state for 150 structural materials (metals, alloys, polymers, composites, rocks and minerals), and constitutive relations. We present results of numerical modeling of hypervelocity impact process in 3D setup. The calculations were carried out for different initial velocities and shapes of impactor. Also the materials of impactor and target were varied. The comparison of the results of simulations with experimental X-ray photographs has been done. [Preview Abstract] |
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F7.00019: Shock Induced Polarization in Binary Electrolytes Yuri Skryl, Anna Belak, Maija Kuklja This study is aimed at explaining strong polarization in shock-compressed aqueous solutions of KF. An original computational method is developed for modeling the charge transfer and accompanied changes of the electric field. Zeldovich's idea of bi-component diffusion of plasma is used as a main mechanism for shock-induced polarization. As a result of this modeling, charge distribution maps as well as electric field potentials in a sample are calculated for various amplitudes of the shock wave. It was found that large potentials introduced in shock-compressed electrolytes can be mainly explained by enhanced diffusion, strong ionic solvation, and change of water permittivity induced by a shock wave. More so, a sign of EMF generated is a strong function of interplay between stress-assisted and inertial diffusion mechanisms. The results obtained bring about a better understanding of mechanisms of shock-induced polarization in liquids. [Preview Abstract] |
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F7.00020: Multi-scale dynamical simulations of steady shock waves using moleculardynamics and analytical equations of state Evan Reed, Laurence Fried, William Henshaw, M. Riad Manaa, Christopher Mundy, Craig Tarver, John Joannopoulos We have deveoped a multi-scale simulation method and applied it to the study of steadily propagating shock waves in materials. The method combines molecular dynamics and the Euler equations for compressible flow to provide up to 8 demonstrated orders of magnitude of computational savings over non-equilibrium molecular dynamics simulations of steady shock waves. Utilizing a recently developed coarse-grained approach with analytical equations of state, we explicitly show that spatial profiles of shock waves yielded by the method are identical to those of fully hydrodynamic simulations of steady shock waves in chemically reactive systems. [Preview Abstract] |
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F7.00021: HIGH ENERGY DENSITY PHYSICS
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F7.00022: Unusual self-similar spherical compression: theory and implementations Jean Gerin-Roze We are showing a family of spherical implosions involving high compression rate. It depends on two parameters and we can work all of it out. \textbf{I Theory} What is an ``unusual self-similar compression law''? Such a law is characterized by a classical self-similar law initiated by a convergent shock (cf Lazarus and Richtmyer LA6823MS-1977) followed by centred compression waves. We will explain completely the implosion given by this law. \textbf{II Implementations} We will apply such a law to a DT sphere (m=1.5 mug and $\rho _{0}$=0.003 g/cm3). We will describe the thermodynamical conditions obtained this way. Then we will compare these results to those obtained with a 1D hydrodynamical computational code under different hypotheses regarding outside conditions and gas EOS. We will discuss the agreement between model and computational code under the different hypotheses. \textbf{III Conclusion } Such a flow may be worth using: -It gives an accurate hydrodynamical benchmark with the difficult problem of spherical shock convergence. -It can be used to define laser experiments where very compressed matter is needed (spectroscopy experiments, thermonuclear ignition...). Indeed, it allows to build an optimized compression law for each problem. An interesting extension of this work will be to add a second medium surrounding the gas. By using the characteristic curves, we could obtain the outside conditions (pressure or speed versus time) for this more realistic geometry. [Preview Abstract] |
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F7.00023: Laser-driven compression of samples in the solid-state for high strain rate measurements of strength D.D.-M. Ho, B.A. Remington, K.T. Lorenz, H.-S. Park, S.M. Pollaine We are investigating new regimes of solid-state material science at extreme pressures, using high power lasers. \begin{enumerate} \item To study solid-state dynamics at high strain rates ($>$ 10$^{6}$ s$^{-1})$ and at high pressures ($>$ 10 Mbar), the compression of the sample must be nearly isentropic so that the sample can remain at solid state. We present laser-driven rad- hydro-code target designs for the NIF laser using a reservoir-gap-sample configuration. The novel feature employed here is that the reservoir has a graded-density on the back (gap) side. RT instability calculations indicate that the difference between the growth rates with different material strength models is sufficiently large that models of high pressure material strength can be tested by such measurements. \item Target designs for the Omega laser for testing the long laser pulse ($>$ 10 ns) drive required for the configuration described in part (1). Hydrodynamic characteristics of these designs will be compared with experimental results. \item Target designs for high strain rate strength measurements in high Z material using Richtmyer-Meshkov instability will be presented \end{enumerate} [Preview Abstract] |
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F7.00024: REALIZING THE PROMISE OF ICE
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F7.00025: Isentropic Compression Facility for the New Millennium Michael Willis Recent advances in the application of pulsed power to the study of dynamic material response have been made on the Sandia Z accelerator. Smoothly increasing multi-megabar pressure loads have been achieved allowing quasi-isentropes for these materials to be inferred. A significant amount of material research does not, however, require such intense pressure loading. In response to this, Sandia National Laboratories is constructing a facility that will house a compact Isentropic Compression Experiment (ICE) pulsed power driver capable of producing currents of $\sim $ 4 MA, and subsequent pressure loads on 4 samples up to $\sim $1 Mbar to provide a more cost effective, easily accessed machine for dynamic material studies. Additionally, a single stage air gun will be available to support the pulser as well as for standard, low velocity EOS experiments. Instrumentation will include conventional VISAR with ultra low VPF capability, spatially resolved VISAR, flash X-rays, and sample temperature control. An overview of the facility and unique capabilities will be shown. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-ACO4-94AL85000. [Preview Abstract] |
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F7.00026: Pulsed Radiography Magnetically Imploded Liners V.T. Gromov, E.I. Karnaykhov, D.N. Kazakov, A.V. Petrovtsev, O.N. Pan’shina, G.I. Shuranova, M.I. Serkov Investigation to find the material properties in magnetically imploded liner experiments with pulsed power techniques [1] have been applied to a variety of interesting questions broadly addressing the properties and behavior of condensed matter warping. For this purpose X-ray instrument with industrial X-ray tube IMA5-320D was created. The instrument easy making, because we utilize pulse voltage generator consist of ordinary industrial components. The efficiency of X-ray tube is decrease with operation time. Thus it demands special tuning the amplitude of voltage pulse. Hence pulse generator was modified. The instrument control scheme allows regulating the amplitude of voltage pulse over the range from 100 to 300 kV now. Pulse duration is about 20$\pm $7 nanosecond, therefore image degradation not exceed 0.2 mm for liner implosion velocity over some km/s. As well the results of liner dynamics investigations at the GNUV facility are presented. \newline \newline [1] R. E. Reinovsky, W. L. Atchison, R. J. Faehl, and I. R. Lindemuth, \textit{Advanced Liner Performance For Extended Experiments in Hydrodynamics and Material Properties}. 14$^{th}$ Pulsed Power Conference, Dallas, 2003. [Preview Abstract] |
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F7.00027: INELASTIC DEFORMATION, FRACTURE & SPALL
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F7.00028: Dynamic behaviour of birch and sequoia at high strain rates Bragov Anatoly, Lomunov Andrey, Sergeichev Ivan, George Gray III The paper presents results of experimental analysis for structural woods, i.e. birch and sequoia at high strain rates. Monotonic and cyclic compression testing at room temperature of these materials was performed by experimental Kolsky method, using the 20-mm diameter split Hopkinson pressure bar (SHPB). The cut out specimens were loaded along and across fibers of woods, as well as, in others angles of cutting out from wooden materials. There were obtained dynamic deformation diagrams in various above conditions for these materials. Directions of specimens' cutting out, as well as, confined conditions effect on mechanical dynamic properties of the woods tested. Loading and unloading branches of stress-strain diagrams obtained are nonlinear and strain rates sensitive. Post-failure behavior of woods' specimens tested results from various forms of their fracture, such cracking and spalling. Experimental stress-strain curves showed significant influence of cutting out angles of specimens on fracture stresses' values. Dynamic deformation diagrams at cyclic loading, obtained by original modification of SPHB, are also presented for tested materials. Alongside with the SHPB tests, plane-wave experiments were conducted and the shock adiabates for the wood samples were obtained. [Preview Abstract] |
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F7.00029: Compressive fracture of brittle materials under divergent impact loading A.S. Savinykh, G.I. Kanel, S.V. Razorenov, A. Rajendran, Zhen Chen Since the stress/strain states in impact and penetration problems are multiaxial, measurements from conventional planar shock wave experiments offer limited utilization and validation for these problems. This paper reports results from a novel shock-wave experiment in which divergent loading is generated in alumina and boron carbide ceramic plates through the use of an explosively driven convex copper flyer plate. The free surface particle velocity a 2.6 mm thick copper witness plate was measured using a VISAR. The experimental measurements clearly revealed, in addition to the longitudinal waves, the presence of shear waves. The results of measurements outlined the range of stressed states which are below the failure criterion. The experimental results were analyzed through one dimensional computer simulations. Compressive fracture was modeled by employing a simplistic damage model in the simulations of spherical shock wave propagation. The calculated wave profiles showed distinct signatures of the compressive fractures. [Preview Abstract] |
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F7.00030: Shear Strength Measurements in a Shock Loaded Alumina-Filled Epoxy Resin K. Kos, J.C.F. Millett, N.K. Bourne, D. Deas The variation of shear strength with impact stress in an alumina-filled epoxy has been measured with lateral stress gauges. At lower stresses, a degree of hardening behind the shock front has been observed, which decreases as impact stress increases. It is believed that this is due to a transition from a viscous response dominated by the epoxy matrix, to a more viscoplastic response. The measured shear strength has also been observed to reach a near constant level, as was suggested in a previous work. [Preview Abstract] |
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F7.00031: The Behaviour of a Glass-Fibre Epoxy Composite During Plate Impact M. Eatwell, J.C.F. Millett, N.K. Bourne, Y.J.E. Meziere The response to shock loading of a glass-fibre epoxy composite has been investigated. Measurements have been made of shock stress, particle velocity, shock velocity, release velocity and spallation behaviour. The shock velocity has a linear relationship with particle velocity, whilst shock stress lies a little above the corresponding hydrodynamic pressure. Results show that the likelihood of spallation increases with pulse duration, suggesting that damage in the material accumulates behind the shock front. This would seem confirmed by release wave speed measurements, that show the zero particle velocity intercept is lower than either C$_0$ (from the shock velocity-particle velocity relationship) and the longitudinal sound speed. [Preview Abstract] |
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F7.00032: Equation of State and Shear Strength of Nickel and Ni-60Co Under One-Dimensional Strain A. Workman, Y. Meziere, J.C.F. Millett, N.K. Bourne, A. Wallwork If the understanding of the behaviour of metallic materials under shock loading of materials is to increase, knowledge of the influence of an alloying element is required. The dynamic response of pure nickel (Ni), and its alloy, Ni-60Co (composed of 60\% by weight of cobalt), had been investigated during one-dimensional shock loading. Nickel and cobalt have similar atomic characteristics and the alloy Ni-60Co is face-centered cubic structure (fcc) as is nickel. Few materials' properties are thus changed. The only altered feature is the reduced stacking fault energy (SFE) for the Ni-60Co. The shear strength at high rates of strain has also been little considered for these two materials. This paper thus investigates the effect of this reduced SFE on the shear strength. New data are then presented, in the stress range 0-15 GPa, in term of shock stress, lateral stress, particle velocity and shock velocity. The influence on the shear stress $\tau$, of cobalt additions in nickel is then investigated and presented. Results indicate that the lateral stress is increasing in both materials with the increasing impact stress. It was found to be higher in the nickel than in the Ni-60Co. The progressive decrease of the stress during loading indicate a complex mechanism of deformation behind the shock front. [Preview Abstract] |
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F7.00033: Spallation in Ti-6Al-4V: Stress Measurements and Recovery I.P. Jones, J.C.F. Millett, N.K. Bourne Previous work by a number of authors has shown that the spall strength of the engineering alloy, Ti 6Al – 4V increases markedly with pulse duration. In this paper, we have reproduced those results in a low oxygen variant of the alloy, over a range of impact stresses. The microstructure consisted of a mixture of primary alpha grains in a matrix of transformed beta. Samples have also been shock loaded and recovered under conditions of one-dimensional strain, to compliment the results of the stress gauge experiments. In all the recovered samples, complete spallation occurred, but examination of damage at secondary sites showed spall occurred via nucleation and growth of pores. Ductile failure appears to progress along primary alpha / transformed beta boundaries. [Preview Abstract] |
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F7.00034: Spallation in NiTi Under One-Dimensional Shock Loading A. Wallwork, Y. Meziere, J.C.F. Millett, N.K. Bourne, A. Workman The dynamic response of the shape memory alloy NiTi has recently been found to be of great interest. The dynamic tensile strength (pull back strength) of NiTi had been investigated under one-dimensional shock loading. The pulse length and the impact stress were varied in order to carry on this study. The design of the experiments was such that the spall lay in the middle of the target. Varying the dimensions of the flyer/target combinations thus led to variations in tensile strain rate at the spall plane. The pull back stress (spbs) was found to increase with the applied pulse length. This suggests that the dynamic tensile strength is dependent upon the generation of a deformation microstructure that evolves behind the shock front. In contrast, increasing stress levels resulted in a near constant pull back stress, although at the lowest applied stress, spallation did not occur. [Preview Abstract] |
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F7.00035: Tension of ethyl alcohol and hexadecane by shock waves Alexander Utkin, Vasiliy Sosikov, Vladimir Fortov The influences of strain rate and initial temperature on the negative pressure in ethyl alcohol, and hexadecane under shock waves have been investigated. The method of spall strength measurements was applied and wave profiles were registered by laser interferometer VISAR. At initial temperature 298 K spall strength of ethyl alcohol was found. Unlike other liquids the process of destruction in methyl alcohol is double staged. At the first stage formation of cavities starts and there is a kinked at free velocity profile was observed. At the second stage the cavity grow rate increases and the spall pulse occurs. The dependence of negative pressure from the strain rate was instigated. The value of the negative pressure correspondent to the kinked at free velocity profile was practically constant and equal to 14MPa. The maximal strength value may be much higher and equal to about 50MPa. The Influence of temperature near melting point on negative pressure in hexadecane has been investigated. Theory of homogeneous bubble nucleation was used to explain the experimental results. [Preview Abstract] |
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F7.00036: Hugoniot Elastic Limit and Spall Strength of the Cubic Form of Boron Nitride Vladislav Yakushev, Alexander Utkin, Alexander Ananin, Victor Tatsy, Andrey Zhukov, Anatoly Dremin, Anatoly Bochko, Nikolai Kuzin The elastic-plastic properties and spall strength in dense forms of boron nitride have been investigated under shock wave compression. The wave profiles were registered by laser interferometer VISAR. Shock waves in the samples were produced by aluminum impactors accelerated up to 5.3 km/s by high explosive. The experimental results are the particle velocity profiles of the sample -- water window boundary. Samples with the initial density of 3.48 g/cm$^{3}$ were prepared by hot pressing of wurtzite-type and cubic BN powder in the high pressure hydrostatic chamber. During the pressing the wurtzite-type phase transfer to cubic form and the samples contain more than 90{\%} of cubic boron nitride. The amplitude of shock waves in experiments varied from 10 to 85 GPa. Two-wave structure determing by elastic-plastic properties of BN was observed at high pressure with Hugoniot elastic limit of 55 GPa, the latter corresponds to dynamic yield strength of 35 GPa. The spall strength measured in elastic region was equal to 1 GPa. [Preview Abstract] |
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F7.00037: Strength and structure aspects of fracture of some metals and alloys at shock wave loading Vladimir Golubev Results on research in spall fracture of iron and its nine alloys (steels), aluminum, titanium, tantalum, magnesium and their several alloys, copper, nickel and lead are presented. The samples up to 20 mm thick were loaded by the aluminum projectiles up to 4 mm thick. An initial state of some materials varied due to the use of various conditions of preliminary heat treatment. Loading time varied by proportional change of thicknesses of projectiles and samples. Cooling of samples up to a temperature of -196$^{\circ}$C and heating up to temperatures over the range of 800$^{\circ}$C were carried out. The ranges of projectile velocities corresponding to a total spectrum of material failure, from nucleation of microdamages to complete macroscopic spall fracture of samples were determined. Loading conditions were determined with the use of a method of numerical elastic-plastic calculation. The structural analysis of a state of materials before and after shock wave loading was carried out with the use of methods of metallographic, electronic-microscopic and X-ray analyses, and also by measurement of microhardness. The basic attention was given to metallography and fractography of the nature of spall fracture. Comparison of the obtained results on the spall strength and nature of spall fracture with the data of other authors was carried out. [Preview Abstract] |
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F7.00038: Experimental and Numerical Study Samuil Bakhrakh Oblique collision of metal layers is accompanied with wave formation at interface, if certain conditions are fulfilled on values of collision angle and velocity of contact point motion. Kelvin-Helmholtz instability is growing at the interface. In some cases, the process of Kelvin-Helmholtz instability can influence negatively on work of various systems. So, experimental studies were performed for searching ways to suppress instability by covering the surface with special cover. It was obtained that aluminum cover causes elimination at interface of aluminum samples. Perturbation amplitude is up to 20 times reduced. Numerical simulation was performed by the finite difference technique using regular counting grid, and by the concentration method for description of strongly deformed interfaces. All calculations were performed with use of Euler (immovable) grid. To explain the stabilizing effect of the cover made of material (aluminum) the same as for colliding plates, the supposition was made on localization (narrowing) of the zone of intensive plastic strains. When a cover is used, its substance is involved in intensive flow, and contribution of the plates is reduced. As a result, deformation localization occurs. [Preview Abstract] |
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F7.00039: Axial VISAR Velocity Measurements of the Non-planar Acceleration of a Plate from a Penetrating Shaped Charge Jet Eric Ferm, Mathew E. Briggs A Viper explosive shaped charge jet creates a stretching rod of metal, with its tip traveling 9.2mm/$\mu $s and slower portions traveling slower than 3 mm/$\mu $s. As this rod impacts and penetrates an obstructing steel plate, a highly non-planar flow evolves. We have recorded the free-surface velocity at the point of exit of the jet, which will ultimately be accelerated to the residual velocity of the jet. The thick target we have chosen allows the penetration to reach a quasi-steady subsonic penetration rate, before the wave structure begins to exit the plate. The resulting acceleration at the free surface is a continuous VISAR record with no required discontinuous fringe jumps. The free surface is first accelerated with an elastic wave, followed by a decaying shock wave, and plastic wave. Ultimately the release waves reach the penetrating jet and the surface begins to accelerate to velocities near the speed of the jet exiting the plate. We compare these results with previous experiments and calculations. [Preview Abstract] |
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F7.00040: Electromagnetic Radiation From The High Strain Rate Fracture Of Mild Carbon-Steel William Brown, Mark Schmidt, Kenneth Calahan We present results of an experimental study of the back surface emission of electromagnetic radiation resulting from the impact fracture of mild carbon-steel at strain rates of approximates 10$^{6}$/s. We obtained time-domain measurements of two perpendicular components of the electric displacement vector at distances of up to 20 m from the targets. Spectral analysis of these data provides results that are consistent with theoretical predictions of the strain-rate dependence of the Misra Effect. We provide evidence that this phenomenon, that has only been reported previously during quasi-static measurements, is also present during explosive and impact fracture conditions. This work supported by the Defense Threat Reduction Agency under contract DTRA01-01-C-0033. [Preview Abstract] |
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F7.00041: Simulations of spall experiments in 316L stainless steel conducted with square and triangular waves Lynn Seaman, G.T.(Rusty) Gray III Triangular stress waves are more like those from applications (laser, explosives, nuclear) but laboratory experiments for studying spall damage generally provide square-topped waves. Gray et al (2003) performed four impact experiments in 316L stainless steel, two with square waves and two with triangular, achieving void damage in all but the lower-stress (6.6 GPa) triangular-wave sample. Simulations with the nucleation-and-growth model DFRACT exhibit fair correspondence with the damage in those tests showing damage, but also indicate damage in the triangular-wave test showing no damage. We are examining mechanisms which may delay the initiation of void damage or otherwise alter the expected damage processes in the model. Reference: G.T. (Rusty) Gray III, N. K. Bourne, B.L. Henrie, and J.C.F. Millet, Influence of Shock-Wave Profile Shape (Triangular ``Taylor-Wave'' versus Square-Topped) on the Spallation Response of 316L Stainless Steel, J. Phys. IV France 110 (2003), page 773-778, [Preview Abstract] |
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F7.00042: A Rate-Dependent Viscoelastic Damage Model for Simulation of Solid Propellant Impacts Erik Matheson A viscoelastic deformation and damage model (VED) for solid rocket propellants has been developed based on an extensive set of mechanical properties experiments. Monotonic tensile tests performed at several strain rates showed rate and dilatation effects. During cyclic tensile tests, hysteresis and a rate-dependent shear modulus were observed. A tensile relaxation experiment showed significant stress decay in the sample. Taylor impact tests exhibited large dilatations without significant crack growth. Extensive modifications to a viscoelastic-viscoplastic model (VEP) necessary to capture these experimental results have led to development of the VED model. In particular, plasticity has been eliminated in the model, and the multiple Maxwell viscoelastic formulation has been replaced with a time-dependent shear modulus. Furthermore, the loading and unloading behaviors of the material are modeled independently. To characterize the damage and dilatation behavior, the Tensile Damage and Distention (TDD) model is run in conjunction with VED. The VED model is connected to a single-cell driver as well as to the CTH shock physics code. Simulations of tests show good comparisons with tensile tests and some aspects of the Taylor tests. [Preview Abstract] |
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F7.00043: Displacement Maps in Taylor impact using Speckle Radiography C.H. Braithwaite, W.G. Proud, S.G. Grantham A method was developed using the small gas gun facility at the Cavendish Laboratory, (Cambridge University) to determine the internal displacement characteristics of a polymer rod undergoing asymmetric Taylor impact. Using a layer of lead filings and Digital Speckle Radiography it was possible to build up a displacement map. It is hoped that this technique could be used to derive material properties such as yield strength. [Preview Abstract] |
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F7.00044: FAILURE WAVE
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F7.00045: Delayed Failure in a Shock Loaded Alumina G.A. Cooper, J.C.F. Millett, N.K. Bourne, D.P. Dandekar Manganin stress gauges have been used to determine the lateral stress in a shock-loaded alumina. In combination with known longitudinal stresses, these have been used to determine the shear strength of this material, behind the shock. The two-step nature of the lateral stress traces shows a slow moving front behind the main shock, behind which shear strength undergoes a significant decrease. Results also show that this front decreases markedly in velocity as the HEL is crossed, suggesting that limited plasticity occurs during inelastic deformation. Finally, comparison of measured shear strengths with other aluminas shows a high degree of agreement. [Preview Abstract] |
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F7.00046: MATERIALS SCIENCE
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F7.00047: Underwater explosive welding, Discussion based on weldable window Akihisa Mori, Keisuke Tamaru, Kazuyuki Hokamoto, Masahiro Fujita A new method of underwater explosive welding is introduced and its possibilities are suggested. In the underwater explosive welding, a high explosive with detonation velocity of 7km/s is placed at an initial inclined angle to decrease the horizontal collision point velocity, which is one of the important parameters to achieve welding. This method is effective to accelerate a thin metal plate rapidly. However, this arrangement makes a difference in the welding conditions with horizontal position when a constant thickness explosive is used, as the propagation distance of the underwater shock wave increases at the ends. Hence, a method of linearly increasing the thickness of explosive in proportion to the propagation distance is proposed. This investigation intends to clarify the welding conditions in using a constant thickness explosive and linearly increasing thickness explosive based on numerical analysis. Further, a method of designing the assembly is confirmed through numerical analysis and its validity with the experimental results is demonstrated based on the welding window. [Preview Abstract] |
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F7.00048: Influence of High-Velocity Shock Loading on Metals Svetlana Atroshenko, Natalja Naumova, Stanislav Novikov The work is devoted to investigation of metals under shock loading. Testing was realized under uniaxial shock loading and spherical action of waves. The materials under investigations were copper, aluminum, lead, titanium, titanium alloys VT5 and VT6, aluminum alloy AMg2 and different steels - 45 carbon steel, Cr-4Ni-Mo steel, austenitic stainless steel 18Cr-10Ni-Ti. Microstructure investigations carried out using optical microscopy, microhardness device and X-ray analysis [1]. It was determined widening of interference lines as indicator of second type stress level. The comparison of two types of dynamic loading was carried out. [Preview Abstract] |
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F7.00049: Principles for laser--launched flyer plates by confined plasma ablation, and related diagnostics Dennis Paisley For over a decade, laser confined-ablation plasmas have been used to accelerate 1-D flyer plates for shock physics experiments and initiation of energetic materials. We have conducted experiments with flyer plate thicknesses from 2 $\mu $m to 2 mm, 0.4 -- 8 mm diameter using 3 ns -- 2-$\mu $s pulses and 10 mJ to 400 Joules. Traditional metals (Al, Cu, Au, Ta, SS, multi-layers) have been accelerated to a wide range of velocities, 0.1 -- $\ge $5 km/s (not all plate sizes to all velocities). From these experiments, several general experimental trends have been observed and confirmed by models. The laser spatial and temporal profiles optimized to flyer plate parameters to properly launch 1-D plates at known conditions, and obtain the desired experimental results. These experimental methods and the diagnostics to confirm the desired results will be discussed, including the optical diagnostics and models. LA-UR-05-2665 [Preview Abstract] |
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F7.00050: Dynamic Response of Copper Subjected to Quasi-Isentropic, Gas-Gun Driven Loading Hussam Jarmakani, James McNaney, Mathew Schneider, D. Orlikowski, J.H. Nguyen, Bimal Kad, Marc Meyers A transmission electron microscopy study of quasi-isentropic high-pressure loading of copper is being carried out. The dynamic response of both polycrystalline and single crystalline copper isentropically loaded to peak pressures between 18GPa and 52GPa is being investigated. Deformation mechanisms and defect substructures at these different pressures are being analyzed. Current evidence suggests a deformation substructure consisting of heavily dislocated laths at the higher pressures and small and irregular dislocation cells accompanied by stacking faults at the lower pressures. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. [Preview Abstract] |
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F7.00051: Dynamic behavior of microstructural copper Bragov Anatoly, Lomunov Andrey Microcrystalline (grain size $\sim $100nm) copper of technical purity (99.98{\%}), obtained at intensive plastic deformation by the method of equichannel angular pressing and oxygen-free copper (purity 99.99{\%}) are investigated. The structure of metal after such processing has a high level of internal stresses. As a result of large plastic deformations in a sample the set of defects located near to borders of grains was formed. These borders on structure differ from borders of grains in usual copper: structure of such borders friable and wide, instead of thin, as at macrocrystalline copper. The dynamic loading of samples at compression by the Kolsky method was made in two directions: lengthways and across a plane of sliding. Some samples were subjected to thermal processing (annealing), at various temperatures. The nonlinear dependences of dynamic yield strength on annealing temperature are received. The qualitative model for explaining a change of yield strength in copper of technical purity and oxygen-free copper depending on time and preliminary annealing temperature is constructed. [Preview Abstract] |
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F7.00052: High-speed behavior of some shape memory alloys Bragov Anatoly, Lomunov Andrey In the message the results of dynamic tests of materials with shape memory effect are submitted. The high-speed tests at tension and compression of alloys TiNi and CuTiAl were executed by using the Kolsky technique with the split Hopkinson pressure bar. As a result the dynamic deformation diagrams were obtained. On some of them the phase transitions from austenite into martensite and back are observed obviously. Within the framework of the Kolsky method its updating is offered allowing at return transition, caused by a plastic deformation, at the expense of sample heating to study kinetics of phase transition: i.e. to estimate time of transition, its energy. The complex character of high-speed deformation of the investigated materials is marked. [Preview Abstract] |
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F7.00053: Recording of Dispersion of Elastic Wave Velocity in Natural Uranium Alexey Fedorov, A.L. Mikhailov, A.V. Men'shikh, S.A. Finyushin, D.V. Nazarov, V.A. Davydov, T.A. Govorunova, E.V. Filinov, N.A. Yukina, A.A. Khokhlov Under shock-wave loading of planar samples of natural uranium, difference in time of elastic wave arrival to free surface was recorded by Fabry-Perot laser interferometer. This difference reached 100-250ns at sample thicknesses of 3-10 mm. In tests, the recorded value of longitudinal sound velocity is in the range from 3.26 to 3.6 km/s. Value of dispersion of longitudinal sound velocity was $\sim$350 m/s ($\sim$ 10\%). In tests, dispersion of particle velocity was recorded at elastic precursor. It implies that different profiles and different amplitudes of elastic wave are recorded at different interferometric lines. Front of elastic wave in heterogeneous medium has complicated structure, which can be explained by shift and turning of structural elements of deformed medium at mesoscale. According to interferometric measurements, period of shear bands at elastic wave is 4-25 mm, and it is in good agreement with period of sliding lines recorded during microstructural analysis of recovered samples. At heterogeneous deformation of material, it is shown that plastic shears occur already at elastic precursor. [Preview Abstract] |
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F7.00054: Study of Relaxation of Elastic Precursor in Natural Uranium Stanislav Finyushin, A.L. Mikhailov, A.V. Fedorov, D.V. Nazarov, A.V. Men'shikh, V.A. Davydov, T.A. Govorunova, E.V. Filinov The laser interferometer method was used for research of relaxation of elastic precursor in natural uranium. Samples with thicknesses x=0.5-10 mm were loaded by shock-wave pulse with pressure of $\sim$15 GPa. In this thickness range, amplitude of elastic precursor is attenuated from 4.7 GPa to 1.5 GPa. Obtained experimental data on attenuation of elastic precursor are well extrapolated by dependence sel =3.4x-0.4. In this work, data are obtained for the first time in thickness range from 0.5 to 2 mm. It is shown that the elastic precursor is 10 times stronger attenuated in this range, comparing to that in the thickness range from 2 to 10 mm. It is caused by intensive nucleation of dislocation, by growth of evolution of defect structure of material, and by occurrence of energy dissipation. [Preview Abstract] |
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F7.00055: Influence of Martensitic Transformation on the Spall Strength and the Shear Strength of Ti$_{51.1 }$Ni$_{48.9 }$ at Shock Wave Loading in Temperature Range from 213 K to 413 K Vladimir Skripnyak, Evgenia Skripnyak, Gennadii Garkushin, Yurii Kolobov, Evgenii Dudarev In this paper we report new experimental results on the structure evolution and the mechanical behavior of binary Ti$_{51.1 }$Ni$_{48.9}$ alloy under shock-wave loading. This alloy shows a transformation from B2 austenite to B19' martensite in the temperature range 337-361 K. We have carried out the loading of TiNi by plane shock waves with amplitudes up to 5 GPa in a temperature range from 213 K to 413 K. Because of this variation of temperature the content of B2 and B19' phases and the mechanical properties of TiNi were changed. Within temperature range the spall strength\textbf{ }of Ti$_{51.1 }$Ni$_{48.9}$ varies between 3.7 GPa and 3.28 GPa and the Hugoniot elastic limit varies between 0.4 GPa and 2.7 GPa. The dependences of the spall strength and the Hugoniot elastic limit on the temperature for TiNi and Ti are different. [Preview Abstract] |
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F7.00056: Experimental investigation of rock fracture under impact pulse and static loading Yuri Petrov, Svetlana Atroshenko, Alexei Gruzdkov, Georgy Fedorovsky, Sergei Krivosheev, Alexander Utkin, Grigory Volkov For study of dynamic crack formation, shock loading in microsecond range using magnetic pulse installation was carried out. Testing specimens in the form of plate with the middle through notch was used. The load was applied to the faces of notch. The length of growing crack was established in testing. Spall fracture was investigated under impact applied to the end of rod specimens with determination of threshold fracture amplitudes. Propagation velocities of longitudinal and transverse waves in the mediums were measured using laser interferometer. Initial density of materials was measured. Static testing was conducted for identification of the main characteristics of dynamic and static strength of particular rocks. Static testing was realized using rupture machine under deformation velocity 10 mm/min of rod and beam specimens without notch, and also long plates and beam with notch, under uniaxial tension and three points bending. Investigation of surface and profile fracture was carried out using microscopy. The main parameters for dynamic range were determined using analytical solution of corresponding crack problems of mechanics for plate with notch and for rod subjected to threshold load. The main parameters of this approach are incubation time, static strength and fracture toughness. [Preview Abstract] |
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F7.00057: The Shock Hugoniot of Tuffistic Kimberlite Breccia and other~Geological Materials below 10 GPa John Field, Geoff Willmott, William Proud In recent~experimental work, the shock~response of~Tuffistic Kimberlite Breccia (TKB) was determined~in plate impact experiments. The shock Hugoniot was characterized between~0.3 and~8.4~GPa using embedded manganin gauges and VISAR. Lateral stresses were also measured using embedded manganin gauges and the shear response was derived between longitudinal stresses of 1.1 and 3.2 GPa. TKB has low shock impedance in comparison with similar investigations in the literature, consistent with its empirical reputation as a relatively weak rock. Although the shear stress data indicate a Hugoniot Elastic Limit (HEL) between 0.6 and 0.9~GPa, inelastic deformation probably occurs~at compressive stresses less than 0.3 GPa due to processes such as porous compaction~and pressure-induced liberation of~water from aqueous crystals. This investigation of TKB (along with~apparent inconsistencies~in the literature)~highlights the difficulties in applying simple hydrodynamic shock theory to inhomogeneous materials below 10 GPa.~In this regime, which is important for application to blast mining, geological materials deform inelastically but not necessarily hydrodynamically. Multiple indicators from direct experimental measurements should be considered before making firm~conclusions about the HEL, the presence of phase changes, or the onset of hydrodynamic shock waves. [Preview Abstract] |
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F7.00058: Shock-Wave Synthesis and HTHP Sintering of Cubic Silicon Nitride A. Yunoshev, V. Sil'vestrov, Yu Palyanov, A. Kalinin The shock synthesis of cubic silicon nitride (c-Si$_{3}$N$_{4})$ was realized in a flat recovery container. Initial samples were pressed mix of $\beta $-Si$_{3}$N$_{4}$ and copper powders. At fraction of copper more than 60~vol.~{\%} and shock pressure about 53 GPa in ampoule cover the yield of a high-pressure phase reaches 95-100~{\%}. About compaction or sintering of c-Si$_{3}$N$_{4}$ powder to bulk it is not known. The explosive compaction and static HTHP sintering at pressure 5-6 GPa and temperature 1100$^{\circ}$C were used to form the bulks from this nano-dispersive material. The bulks up to 6-8 mm in size were obtained. Vickers hardness of the bulks reaches HV=31 GPa at indentation force of 200 g, that is more than hardness for cubic silicon nitride bulks obtained in diamond anvils by the other researchers (Tanaka, et al., 2002). [Preview Abstract] |
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F7.00059: Ultra fine grain-sized zirconium by dynamic deformation M.A. Meyers, J.-M. Gebert, M.T. Perez-Prado, M.F. Kassner, B.K. Kad A polycrystalline zirconium alloy was subjected to high plastic strain at a high strain rate using the hat shape geometry in a split Hopkinson bar. A narrow shear deformation region was formed which cooled rapidly after deformation. The structure of this adiabatic shear band was analyzed by transmission and scanning electron microscopy (EBSD). It revealed equiaxed grains with approximate diameters of 200 nm. The process of microstructural evolution leading form an initial grain size of 14 um to the final size is modeled. This process can be described as rotational dynamic recrystallization and is the result of the intense plastic deformation and superimposed adiabatic heating. [Preview Abstract] |
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F7.00060: ULTRAFAST IN SITU DIAGNOSTICS
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F7.00061: Ultrafast Dynamic Ellipsometry Measurements of the Hugoniot of Unreacted HMX David Moore, Daniel Hooks, Shawn McGrane, David Funk Ultrafast interferometric microscopy has been used to measure time resolved surface motion in shocked metal films. However, the shock generally produces changes (via increased pressure and temperature, and/or phase transformation) to the complex refractive index of materials (including metals and transparent dielectrics), to which the interferometry measurements are also sensitive. Obtaining time- resolved interferometric data at two probe angles of incidence and two polarizations, a technique called ultrafast dynamic ellipsometry, allows the shock velocity, particle velocity, and shocked index of refraction to be unambiguously measured. Less than 100 ps worth of data is necessary (as little as 30 ps suffices), so that the shock and particle velocities can be obtained in a reactive material before appreciable reaction occurs, to higher pressures than other slower techniques. We have used ultrafast dynamic ellipsometry to measure the shock state in unreacted, oriented, single crystals of HMX. Details of the experiment and results will be presented. [Preview Abstract] |
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F7.00062: Time Shaping of Laser-Generated Drive Waves Using Layered Metal Targets Cynthia Bolme, David Funk, David Moore, Shawn McGrane Temporally-shaped ultrafast laser pulses have been used to drive sustained (longer than 200 ps) pressure pulses (tens to hundreds of GPa) with ca. 5 ps rise time through vapor plated aluminum films on thin glass substrates. A similar rise time was obtained (after shock runs of 0.25 to 2 microns) using 100 fs duration drive pulses. Similar rise times were also measured in vapor plated nickel films. However, these same drive pulses produce much slower rise time (ramp) waves in vapor plated gold films. The rise time and shape of these pressure pulses is determined by a combination of the complex index of refraction and electron-phonon coupling time of the metal, in addition to the drive pulse temporal characteristics. The ability to produce arbitrary drive wave shapes (such as ramps, steps, or square waves) using combinations of laser pulse shaping and multiple layer metal targets would be useful in ultrafast studies of material properties. Initial experiments have involved layered targets of gold on chromium (on glass). The results from these experiments and their implications will be presented. [Preview Abstract] |
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F7.00063: Diagnosis of laser produced shocks in metals using short pulse probes Will Grigsby, Stephan Bless, Michael Downer, Eric Taleff, Todd Ditmire, Kim Budil, Jeff Colvin, Wayne King We are studying extreme states of matter using laser produced shock waves in metal foils. At pressures on the order of 0.5 to 1 Mbar, the material behavior is complicated by various phase transitions such as melting. To study these dynamics we are using short pulse lasers in high time resolution pump-probe experiments to develop a real time diagnostic on the phase of a shocked material. This can enable a probing of the entire phase history of a material as it shock compresses and then releases from the back surface. In particular, we are interested in studying metals shock-melted on the Hugoniot. Our initial studies focus on driving 100-500 kbar shocks in tin and 1.6 Mbar shocks in aluminum using various lasers with energies of 1 to 1000J. Reflectivity of the metal is used to diagnose the state of the material in optical pump probe measurements, while two-dimensional interferometry is used to determine the shock parameters. [Preview Abstract] |
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F7.00064: Calculating the resistance of lateral gauges in a steel matrix. Ernie Harris, Ron Winter High resolution computer simulations of manganin gauges mounted to measure lateral stresses in a steel matrix subject to nominally 1-D shock have been run. The components of the stress and strain tensors for each of the cells in the manganin element have been obtained from the code. Piezo-resistive and plastic strain coefficients derived by previous workers have been used to compute the resistivity of each cell in the gauge and, ultimately, the total resistance change of the gauge. Calibration curves relating resistance change to a) stress in the polymer surrounding the gauge and b), the stress in the sample material remote from the gauge, are derived and compared with a similar relationships derived by previous workers. [Preview Abstract] |
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F7.00065: Simulation of padded lateral stress gauges Ron Winter, Ernest Harris In principle, the strength of a material subjected to a plane shock can be estimated by measuring the stress in a direction perpendicular to the shock direction. A prerequisite to developing an analysis to estimate lateral stress from the resistance change of a lateral piezoresistive gauge is a clear picture of the mechanical response of a lateral gauge to a shock wave. High resolution hydrocode calculations of manganin gauges mounted laterally in an elastic / perfectly plastic steel matrix have been conducted. The stress profiles obtained are shown to agree qualitatively with experiment. The simulations, run with various thicknesses of strength-less polymer mounting layer, show that the stress at the gauge varies with time and position along the polymer layer. During an initial, transient, phase the gauge is subject to deviatoric stresses which cause it to deform plastically. The deformation is more severe for thinner polymer layers. However, in the post-transient phase deviatoric stresses dissipate and the gauge acquires a pressure closely similar to the lateral stress at the matrix/polymer interface. [Preview Abstract] |
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F7.00066: SPECTROSCOPY & OPTICAL PROPERTIES
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F7.00067: Some Aspects of Shock-Induced Radiation of Transparent Media and Its Transformation with Pressure. Michael Gogulya, Michael Brazhnikov Radiation of shocked compressed water, glycerol, and sulphur and its transformation with pressure has been studied. It was shown that radiation of shocked water loaded through different metal barriers (Al, Mg, and Cu) depended both on shock pressure (varied from 10.0 to 39.5 GPa) and the nature of the metal. It was proposed that radiation histories measured in transparent or semitransparent materials could be explained in terms of ``contact'' radiation caused by the processes nearby barrier--transparent media interface and ``volume'' radiation emitted by a layer of shocked material. For verification of the hypothesis for glycerol loaded through Al barriers, there are given the data on radiation history transformation with pressure varied in the range 18.9 $\div $ 45.2 GPa. For glycerol, only ``contact'' radiation was recorded at low pressures, at which glycerol assumed to be transparent. While two-peak radiation caused both by ``contact'' and ``volume'' luminosity was observed in pressure range 29 $\div $ 31 GPa assumed to be a transition field between transparent and opaque shocked glycerol. At the highest pressure at which glycerol is opaque, the first peak and the second rise in radiation merge together. For a comparison, there are given the data on radiation of shocked optical glass and sodium salt, and liquid sulphur, which has been studied in the pressure range 23.7 $\div $ 55.0 GPa. [Preview Abstract] |
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F7.00068: High Temperature High Pressure Emissivities Jeffrey Nguyen, Reed Patterson, Lorin Benedict, John Klepeis, Neil Holmes Accurate temperature measurements at high temperatures and pressures require knowledge of the optical emissivity as a funcition of wavelength at similar conditions. Presently, many temperature measurements at extreme conditions assume a constant ambient-condition emissivity. Or, emissivity is often derived solely from a fitting procedure. From our ellipsometric measurements of phase transitions under dynamic compression, we observed changes in the complex dielectric constants of various solids and liquids. Since the optical emissivity is uniquely determined from the complex dielectric constants, we expect emissivity to change upon phase transition. Thus careful considerations must be given to materials with complicated phase boundaries. We will present here results on various solid- solid, solid-liquid and liquid-solid phase transitions. In particular, we will focus on the change in emissivity at the ($\alpha$,$\epsilon$) phase boundary in Fe and its implications for the Fe phase diagram. Work performed under the auspices of the U.S. DOE at the University of California/Lawrence Livermore National Laboratory under contract W-7405-ENG-48. [Preview Abstract] |
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