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 E1: Poster Session I |
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Room: Fairmont Orchid Hotel Salon III |
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E1.00001: CONTINUUM AND MULTISCALE MODELING |
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E1.00002: Discrete Particle Simulation of Shock Compression of Powder Mixtures Dan Eakins, Adam Jakus, Naresh Thadhani Numerical continuum simulations have been performed on real, imported powder microstructures, to explore the effect of heterogeneity on changes in configuration during shock compression. A technique has been developed to import two-dimensional micrographs in order to accurately reconstruct the irregular particle sizes, morphologies, and distributions of real powder mixtures. The mechanical response of powder mixtures of widely varying constituent behavior and initial density is investigated at particle velocities of 0.5, 0.75, and 1.0 km/s, through a range of length-scales. Results reveal a strong correlation between powder configuration and micromechanical response during the initial consolidation event. The analysis can be used to design systems for controlled reactions. [Preview Abstract] |
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E1.00003: ABSTRACT WITHDRAWN |
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E1.00004: Reduced Model for Detonation Wave Jean-Bernard Maillet, Laurent Soulard, Gabriel Stoltz We present a mesoscopic model for reactive waves which extends the model proposed by G. Stoltz (G. Stoltz, Europhys. Lett. {\bf{76}} (2006) 849). A complex molecule (or a group of molecules) is replaced by a single mesoparticle, evolving according to some Dissipative Particle Dynamics. Chemical reactions can be handled in a mean way by considering an additional variable per particle describing a rate of reaction. The evolution of this rate is governed by the kinetics of a reversible exothermic reaction. Numerical results show that the reactive wave behaves like a detonation wave. [Preview Abstract] |
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E1.00005: DETONATIONS AND SHOCK INDUCED CHEMISTRY |
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E1.00006: Eigenvalue Detonation of Combined Effects Aluminized Explosives Christos Capellos, Ernest Baker, Wendy Balas, Steven Nicolich, Leonard Stiel This paper reports on the development of theory and performance for recently developed combined effects aluminized explosives. Traditional high energy explosives used for metal pushing incorporate high loading percentages of HMX or RDX, whereas blast explosives incorporate some percentage of aluminum. However, the high blast explosives produce increased blast energies, with reduced metal pushing capability due to late time aluminum reaction. Metal pushing capability refers to the early volume expansion work produced during the first few volume expansions associated with cylinder wall velocities and Gurney energies. Our Recently developed combined effects aluminized explosives (PAX-29C, PAX-30, PAX-42) are capable of achieving excellent metal pushing and high blast energies. Traditional Chapman-Jouguet detonation theory does not explain the observed detonation states achieved by these combined effects explosives. This work demonstrates, with the use of cylinder expansion data and thermochemical code calculations (JAGUAR and CHEETAH), that eigenvalue detonation theory explains the observed behavior. [Preview Abstract] |
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E1.00007: Low Velocity Detonation of Nitromethane Affected by Precursor Shock Waves Propagating in Various Container Materials Hideki Hamashima, Akinori Osada, Yukio Kato, Shigeru Itoh It is well known that some liquid explosives have two detonation behaviors, high velocity detonation (HVD) or low velocity detonation (LVD) can propagate. A physical model to describe the propagation mechanism of LVD in liquid explosives was proposed that LVD is not a self-reactive detonation, but rather a supported-reactive detonation from the cavitation field generated by precursor shock waves. However, the detailed structure of LVD in liquid explosives has not yet been clarified. In this study, high-speed photography was used to investigate the effects of the precursor shock waves propagating in various container materials for LVD in nitromethane (NM). Stable LVD was not observed in all containers, although transient LVD was observed. A very complicated structure of LVD was observed: the interaction of multiple precursor shock waves, multiple oblique shock waves, and the cavitation field. [Preview Abstract] |
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E1.00008: A comparison of the blast {\&} fragment mitigation performance of several structurally weak materials Douglas Kirkpatrick, Andrew Argyle, Katherine Harrison, James Leggett Structurally weak materials are attractive for explosive blast and fragment mitigation applications because they break up easily into small particles and do not present a secondary hazards. A range of these materials have been investigated under a mitigation research programme aimed at developing a predictive capability. Experiments using 3kg-7.5kg charges confirmed earlier small scale results that porosity and particle density are dominant factors in reducing airblast. Measurement of incident overpressure however, effectively ignores the momentum acquired by the mitigant which has the potential to cause significant damage. Techniques to measure dynamic particle loading have been investigated and initial results are presented. Fragment mitigation performance has been studied with and without the presence of explosive blast. Indications are that for some materials, shock loading from an explosive blast may change the fragment retarding performance. It has also been shown that small quantities of low-density blast mitigant can significantly influence the effectiveness of ballistic protection materials placed close to an explosive. [Preview Abstract] |
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E1.00009: Mesoscale modelling of PBX. Binder effects. Alec Milne, Jim Dunnett, Neil Bourne In earlier work we have studied aspects of shock to detonation transition and detonation structure in polymer bonded explosives on the scale of the largest grains (the mesoscale) to augment continuum models for these processes. Building blocks have been unreacted Hugoniots of mixtures, mapping from experiment (2D micrographs and 3D tomography) for accurate initial conditions and details of cavity collapse mechanisms as hot spots for ignition. Recently we have applied continuum mixture theory (multi-phase modelling) to dirty binder (the mixture of explosive crystal fines and binder that surrounds the large grains) and validated it for the unreacted Hugoniot of a range of UK explosives. In this paper we build on all of this work and report our progress in using continuum mixture theory to model the reactive behaviour of dirty binder. We begin by considering the binder on its own and then use this continuum mixture mode in conjunction with mesoscale representations of PBX. We consider PBX9501 and a UK PBX as examples. We identify the numerical modelling issues that have arisen, our current approaches and our plans for further development and testing. [Preview Abstract] |
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E1.00010: Development of the wear- resistant composite material containing the diamond powder particle using underwater shock wave Shigeru Tanaka, Kazuyuki Hokamoto, Shigeru Itoh Recently there has been an effort in the development of new composite materials possessing combined properties of high heat conductivity and friction resistant. In this study developing a composite material with such properties using underwater shock wave was attempted. Underwater shock wave can be used to penetrate hard powders into a metal base without decomposition of the base material. In this method, hard powders are penetrated into a soft metal base to obtain a composite with improved surface properties. The purpose of this research is to clarify the experimental conditions for obtaining a new composite material with unique properties. Attempt has been made to obtain aluminum-based and magnesium alloy-based composites by introducing micro/nano-sized diamond particles to the surface of the base metal. The recovered samples showed improvement of wear resistance. [Preview Abstract] |
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E1.00011: EXPERIMENTAL DEVELOPMENTS |
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E1.00012: Improved Temperature Controller System for Gas Gun Targets S.M. Bucholtz, R.J. Gehr, R.R. Alcon, R.L. Gustavsen Since demonstrating a temperature controller system capable of cooling or heating a gas gun target over the range -75\r{ }C to +120\r{ }C, we have completed 14 gas gun shots with the system. Thirteen of the shots were on the high explosive PBX9502, all cooled to -55\r{ }C. On typical experiments, the sample was successfully maintained at temperature for 30 minutes to an hour while other shot preparations occurred. Occasionally, it was necessary to maintain temperature for several hours before shooting. Data from the magnetic gauge used to detect the shock wave suggest that the sample tilts while cooling. Calculations yield tilt angles around 10 milliradians. An inexpensive optical system, using the camera already present to observe the system cover plate, has been designed to look for and measure this shift. In addition, improvements have been made to the plumbing for cooling experiments, and modifications have been introduced to improve temperature uniformity and to make the system capable of heating gas gun targets up to +250\r{ }C. This work was supported by the NNSA Enhanced Surveillance Campaign through contract DE-ACO4-01AL66850. [Preview Abstract] |
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E1.00013: ABSTRACT WITHDRAWN |
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E1.00014: Measuring densities of high-velocity metallic sprays using piezoelectric sensors Carys Lloyd, William Proud Recent research efforts in large-scale hydrodynamic experiments have concentrated on the possibility of using piezoelectric sensors to study the evolution of ejecta. Ejecta are small ($<$100 $\mu $m diameter) particulates that are ejected at high velocity ($>$1 km s$^{-1})$ from a shocked surface. This paper investigates whether Dynasen PZT piezoelectric sensors are reliable and robust enough to measure accurate time-resolved stresses and densities in high-velocity metallic sprays. The sprays are assumed to have similar characteristics to ejecta sprays, and are generated by a gas gun and in a safe and reproducible manner. A complimentary diagnostic technique, utilising high-speed photography and fast x-radiography, measures the densities of the sprays independently, allowing the accuracy of the sensors to be assessed. The Dynasen sensors have been shown to perform relatively well in spray environments. Their accuracy can be improved by taking their mechanical impedance characteristics into account. [Preview Abstract] |
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E1.00015: A new versatile conductive/radiative heating device for gas gun targets in the 300 K -- 500 K range. Capability illustration for analyse of initial temperature influence on shock induced yielding and phase transitions. Gilles Roy, Gael Lanier, Christophe Voltz, Francois Buy, Patrice Antoine For off-Hugoniot shock loading purpose using existing gas guns, a temperature controller system has been designed to cover the range from 300 K to 500 K for various metals including some featuring low strength or poor thermal conductibility. The heating coil powered by low voltage drives from the impact face the bulk temperature of the target sample typically a few millimetres thick and 40 to 50 mm in diameter. The stainless steel heavy target holder is heated the same way, acting at the periphery as a thermal capacity to limit the thermal losses within the sample. Consequently front and rear sample interfaces remain free for full diameter impact and complete Doppler instrumentation. Typical measurements include DLI and VISAR velocity probing either at free surface or at a LiF window interface. Requested temperature is achieved within 1.5 hour, with an overall gradient better than 5 degrees. Some current applications are illustrated including analyse of temperature effect on TA6V alloy shock induced yielding and tin allotropic phase transition. The associated issue of LiF properties evolution up to 500 K is also addressed analytically. [Preview Abstract] |
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E1.00016: The Effect of Sample Preparation on the Release Measurements of Manganin Gauges. Dan Thomas, David Chapman, William Proud Sample preparation and alignment are recognized as essential parts of good experimental practice. As well as close attention to these factors it is also important to recognize that all measurement devices have an inherent resolution time. Depending on the parameter of interest the appropriate degree of sample preparation can be applied. In a previous paper [SCCM 2005] the effect of front surface roughness was compared, in this paper the effect of rear face preparation is addressed. Plate impact experiments on a PMMA sample are described and the stress history measured using Manganin gauges reported. [Preview Abstract] |
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E1.00017: ABSTRACT WITHDRAWN |
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E1.00018: Study of Small Dimension Specimens on SHPB Test Dawu Xiao, Yinglei Li, Shisheng Hu By SHPB tests combining with theoretical and numerical analysis of series dimension of 2024 aluminium alloy,we concluded that stress-strain curves by specimen of small dimension is reliable.also an attempt is made to get curves of strainrate over $10^4$s$^{-1}$ by small dimension specimen.Accuracy of measurements of transmitted wave is analysed and discussed by experiments and numerical simulation of eccentric compression tests of small specimen.it showed that the distortion of signals can be eliminated by mounting straingages in series or far away from the specimen-bar interfaces. [Preview Abstract] |
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E1.00019: INELASTIC DEFORMATION, FRACTURE, AND SPALL |
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E1.00020: Kinetic Behaviour of Failure Waves in a Filled Glass Anatoly Resnyansky, Neil Bourne Experimental stress and velocity profiles in a lead filled glass demonstrate a pronounced kinetic behaviour of failure waves in the material during shock loading. The present work summarises the experimental proofs of the kinetic behaviour obtained with stress and velocity gauges. The work describes theoretically this behaviour employing a kinetic model used earlier for a description of fracture waves in pyrex glass. This model is from the family of two-phase strain-rate sensitive models describing behaviour of damaging brittle materials. The modelling results describe well both decay of the failure wave precursor in stress profiles and the velocity attenuation when wave propagating. An influence of the kinetic mechanisms and wave interaction within the test assembly on the reduction of this behaviour is discussed. [Preview Abstract] |
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E1.00021: More on the response of ceramics to shock waves Eli Bar-on The strength properties of Coors AD995 alumina is investigated in the stress range from about HEL (5 to 7 GPa) and up to 120 GPa. Simulating the experimental work done by Grady, Furnish and Chhabildas and Reinhart and Chhabildas, we try to explain the structure of loading, unloading, reloading and cyclic loading profiles measured by velocity interferometry. Many physicists are talking about plasticity and slip systems as the mechanism behind the unique structure of the response of Alumina to shock waves, and many use pseudo elasto-plastic strength models to describe this response. Here we try to show that the strength properties of Alumina, being a brittle material, can be derived just from the combined effects of micro-mechanisms like pore crushing and cracks initiation and growth. Any, so called ``yield,'' is due to pore crushing and not to invoked slip systems. [Preview Abstract] |
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E1.00022: Investigations into Spall strengths of geological materials. J.E. Field, C.H. Braithwaite, A.R. Guest, W.G. Proud A number of geological materials e.g. hyperbyssal kimberlite, underwent shock loading in a spall configuration to determine the dynamic tensile strength. VISAR was used as the main diagnostic system. As expected the spall strength was found to be significantly lower than the corresponding dynamic compressive or shear strengths but significantly larger than the quasi-static value. It was also found that the visibility of spall signals decreased with increasing sample thickness, this difference is attributed to the progressive comminution of the material. [Preview Abstract] |
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E1.00023: Dynamic Ductility Measurements of Shocked Metals using Time Sequence Radiography R.G. Garza, J.D. Molitoris, H.G. Andreski, J.D. Batteux, L.M. Lauderbach, G.H. Campbell, J.S. Stolken, R.L. Krueger Using time sequence radiography we have measured ductility, fracture, and failure of various metals under dynamic shock loading. The metals being examined were in intimate contact with a high-explosive charge that was detonated to produce the transmitted shock. Using high-resolution radiography we obtained a set of images in time sequence detailing how the metal sample responds. Complete data sets to failure were measured for stainless steel and tantalum. As the experiments were designed for single-pass radiography, there are no interference effects. As the samples were shocked directly toward the detectors, fragment mitigation had to be 100{\%} successful. The experimental technique will be presented as well as results on tantalum, stainless steel, and possibly other materials. [Preview Abstract] |
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E1.00024: Spall Fracture of Metallic Circular Plates, Vessel Endplates and Conical Frustums Driven by Direct Explosive Loads Tetsuyuki Hiroe, Kazuhito Fujiwara, Hidehiro Hata, Daiki Tsutsumi Dynamic fracture experiments are conducted for circular plates, vessel endplates and conical frustums of A2017-7075 aluminum alloys and 304 stainless steel, using a testing apparatus developed applying wire-row explosion technique to initiation, where tensile stress waves are generated producing spall in the specimens by the direct incidence of plane detonation waves of the explosive PETN. A VISAR system is adopted to observe the free-surface velocity histories of the specimens. The signals for basic circular plate specimens indicate the characteristics of the failure for tested materials, effects of explosive thickness variations and the configuration of specimens. Hydro codes are satisfactorily applied to simulate the experimental signal data and observed damage phenomena of recovered specimens. Next, an explosive-filled cylindrical vessel with endplate at the one end is initiated at the other end surface and expanded by axially propagating explosive detonation to fracture. Both the VISAR signals and numerical simulation indicate a pullback signal of spallation at the endplate. Finally conic frustums are also loaded by plane detonation, showing different type of spall failure due to the additional reflected waves from the slopping side surfaces. [Preview Abstract] |
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E1.00025: A Study of the Critical Fracture Behavior of High Purity Aluminum in the Dynamic Loading Qi Meilan, He Hongliang, Yan Shilin One-dimensional strain impact experiments were performed for the High Purity Aluminum --- HPA (99.999{\%}).The measurement of free-surface velocity profile and the soft-recovery of the shocked specimen has been obtained at the same time and for the same piece of sample. The critical behavior of HPA in the dynamic tensile fracture has been discussed according to the quantitative metallographic analysis results for the shocked samples. By defining the product of the tensile stress and the time as a parameter called Tensile Impulse, the statistic results indicate that an obvious critical behavior for the damage evolution appears with the increasing of Tensile Impulse. When the Tensile Impulse is low, the damage grows slowly with a linear increment. While once the Tensile Impulse reaches a critical value, the damage grows rapidly and an increment as a power exponential function is observed. Our preliminary results indicate that the critical value of Tensile Impulse for HPA is about 0.34GPa $\mu$s. Such a critical transition behavior has shown by the macro-specimen experimentally for the first time. [Preview Abstract] |
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E1.00026: A study of the effect of potting voids on the fragmentation of an explosively driven Nitinol Shell. Robin Mukerji, Sam Myers, Glenn Whiteman An experimental geometry was designed to determine the effect of potting voids on the fragmentation of a Nitinol ( Ni 55{\%} Ti 45{\%}) Shell. The nitinol shell was subjected to a shock loading using a HE drive such that it would experience an near bi-axial expansion. The region between the HE and the nitinol was filed with a thin layer of potting (Sylgard 184 elastomer), in which two circular voids were positioned. Presented here and results from high speed framing camera and flash x-radiography that were recorded. It was observed that as the shock wave sweeps across the coupon from the centre to the edge, the potting voids cause premature fracture of the nitinol on the outer most point from detonation. The coupon then proceeded to fracture around the void from this point. It is believed that this was due to the build up of detonation products on the outer edge of the void. In addition, a strong effect of the orientation of the fragments was also noticed. This was believed to be due to the directional rolling of the material prior to it being pressed into the coupon. [Preview Abstract] |
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E1.00027: On the spall strengths and Hugoniot elastic limits of some strong ceramics Zvi Rosenberg, Yechezkel Ashuach The dynamic response of strong polycrystalline ceramics is relatively well documented, with high Hugoniot elastic limits (HEL) and very low spall strengths. In contrast, the response of single crystal ceramics is less researched and some of their findings are controversial. In the work presented here we were interested in the extremely high HEL which was reported recently for Gallium Gadolinium Garnet (GGG) as well as in strength of sapphire and magnesium aluminate spinel, on which there are very few reports. The measurements were made with manganin gauges embedded at the back of the specimens, with a thick Plexiglas backing for the gauge. These measured stress-time histories are very simple to interpret and accurate values for the HEL and spall strength of these materials can be easily extracted. Some of our results (e.g. the HEL of GGG) are quite different than those published by other workers. [Preview Abstract] |
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E1.00028: Two critical damage parameters for the dynamic tensile fracture of ductile metals Hongliang He, Yonggang Wang, Meilan Qi, Fuqian Jing A concept of critical fracture in the dynamic tensile spall has been developed via percolation model and two physical parameters, named as the critical linking damage Dl and the critical fracturing damage Df, are proposed. Dl indicates the critical value of damage for the onset of void coalescence, and Df the critical value for the occurrence of catastrophic fracture. With experimental measurements of the free-surface velocity profiles and the numerical simulations, we demonstrate that these two critical damage parameters are independent on the impact stress and the tensile strain rate, and it is also applicable to predicting the dynamic tensile fracture behavior in metal cylinders. Therefore, we may regard these parameters as the material constants to identify the intrinsic characteristic of the dynamic tensile fracture in explosion and shock wave events. [Preview Abstract] |
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E1.00029: GEOPHYSICS AND PLANETARY SCIENCE |
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E1.00030: Shock metamorphism of hornblende and plagioclase in conditions of step-like compression of polymineral rocks Irina Beljatinskaja, Tatiana Borodina, Vladimir Milyavskiy, Ludmila Sazonova, Dmitriy Zhernokletov The impact transformations of plagioclase (Pl)- hornblende (Hbl) schist with garnet (Southern Urals) and clinopyroxene-Hbl-Pl schist (Anabar Shield) have been studied with use of recovery assemblies of planar geometry. In the specimens, shock pressures were ranged from 26 to 52 GPa. It was found that an increase of content of F, Ti, and K in a composition of Hbl, as well as a decrease of content of Ca in a composition of Pl, make these minerals more stable to action of shock waves. In experiments with the stepwise shock compression of polymineral rocks the isotropization of Pl begins at lower pressures than in analogous experiments with monomineral specimens. Under relatively low pressures, Pl isotropization is caused by its fragmentation on a microscopic scale and is associated with the origin of maskelynite - a typical mineral of meteorites and astroblemes. At higher pressures, Pl isotropization is related to amorphization by means of melting. [Preview Abstract] |
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E1.00031: Numerical modeling of Deep Impact experiment V.G. Sultanov, V.V. Kim, I.V. Lomonosov, A.V. Shutov, V.E. Fortov The Deep Impact active space experiment has been done [1,2] to study a hypervelocity collision of a metal impactor with the comet 9P/Temple 1. The modeling of impact on solid or porous ice made it possible to conclude: the form and size of crater depends strongly on the density of comet material; the copper impactor does not melt and remains in the solid state; the temperature of ejecta varies from 5000 K for solid ice to 15000 K for porous ice. The impact on moist water- saturated sand demonstrated different results. In this case, the copper impactor practically does not penetrate the comet surface, melts, destroys and the ricochet process takes place. In the case of moist porous sand the produced crater is stretched in the direction of impact. The analysis of modeling results indicates to the presence of volatile easy-vaporized chemical compounds in the cometary surface. The hypothesis that the cometary surface consists of only ice does not agree with experimental and computational data on the forming and spreading of impact ejecta. [1] http://deepimpact.jpl.nasa.gov/home/index.html [2] M. F. A'Hearn et al, Deep Impact: Excavating Comet Tempel 1 // Science, 2005, v.310, pp. 258-264 [Preview Abstract] |
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E1.00032: ENERGETIC MATERIALS |
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E1.00033: Metastable Polymeric Nitrogen: The Ultimate Green High-Energy-Density Material Jennifer Ciezak High-energy-high-density materials offering increased stability, vulnerability, and environmental safety are being aggressively pursued to meet the requirements of the DoD Joint Visions and Future Force. Nearly two decades ago, it was proposed that polymeric nitrogen would exceed all of these requirements and possess nearly five times the energy of any conventional energetic material in use today. The present study details an investigation into nitrogen polymerization using a novel high-pressure approach utilizing sodium azide as the starting material. Due to the weaker bonding structure of the anionic azide chains in comparison to a N-N triple bond, one expects that the azide chains will create single-covalently bonded polymeric networks more easily than diatomic nitrogen. A polymeric form of sodium azide was synthesized at high pressures, but the material was not metastable at ambient conditions, which precluded performance testing. Quantum chemical calculations have indicated stabilization of the polymeric structure at ambient conditions may be possible with the addition of hydrogen. Vibrational spectroscopic characterization suggests that a meta-stable polymeric form of nitrogen has been synthesized under high-pressure using sodium azide/hydrogen as the starting materials. This material remains stable at ambient conditions upwards of two weeks depending on the storage conditions. [Preview Abstract] |
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E1.00034: Shock Initiation Experiments on the LLM-105 Explosive RX-55-AA at 25$^{\circ}$C and 150$^{\circ}$C with Ignition and Growth Modeling Frank Garcia, Kevin S. Vandersall, Craig M. Tarver, Paul A. Urtiew Shock initiation experiments on the LLM-105 based explosive RX-55-AA (95{\%} LLM-105, 5{\%} Viton by weight) were performed at 25\r{ }C and 150\r{ }C to obtain in-situ pressure gauge data, run-distance-to-detonation thresholds, and Ignition and Growth modeling parameters. A 101 mm diameter propellant driven gas gun was utilized to initiate the explosive sample with manganin piezoresistive pressure gauge packages placed between sample slices. The run-distance-to-detonation points on the Pop-plot for these experiments showed agreement at 25\r{ }C with previously published data on a similar LLM-105 based formulation RX-55-AB as well as a slight sensitivity increase at elevated temperature (150\r{ }C) as expected. Ignition and Growth modeling parameters were obtained with a good fit to the experimental data. 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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E1.00035: Computational evaluation on the sensitivity of energetic materials Yi Liu, Sergey Zybin, William Goddard An efficient computational procedure based on molecular dynamics (MD) simulation with ReaxFF reactive force field has been developed to evaluate the sensitivity of various energetic materials including TATB, RDX, PETN, HMX, and TATP. In this study, the two-dimensional slab model is first equilibrated at 300 K, followed by rapid heating up to 2000 K at a rate of 10 K/fs. The system is then allowed to evolve via MD at microcanonical ensemble, where the decomposition of energetic molecules mostly occurs. Another technique mimics the shock impact test and uses two moving wall driving by a constant force to create two impact waves running toward each other, followed by the shock reverberation and material decomposition. Our simulations show that sensitive energetic materials, in general, decompose more quickly than less sensitive ones, which agrees with experimental observations. The chemical reactions found in these simulations are analyzed to understand the mechanisms that account for diverse sensitivity of energetic materials. [Preview Abstract] |
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E1.00036: Pressing induced polymorphic phase transition in submicron-sized gamma-HMX David Moore, Kien-Yin Lee Submicron HMX has been produced and characterized to be less sensitive than impact standard HMX in small-scale sensitivity tests. The sm-HMX was found to be the gamma polymorph and to be stable under ambient conditions for at least a year. Pressing of sm-HMX in a small diameter pellet press at pressures from 10 000 psi to 31 000 psi and 1 to 5 minute hold times was found to promote the gamma to beta polymorphic phase transition. The fraction converted and rate of conversion versus time after pellet removal from the press were found to fit a sigmoidal curve, indicating nucleation and growth as a possible polymorphic transition mechanism. [Preview Abstract] |
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E1.00037: EQUATION OF STATE |
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E1.00038: Selection of Reference Material and Type of Its Isentropic Curve in Experiments on Isentropic Compression of Substances in Multi-Megabar Pressure Range Gennady Boriskov, Nikolay Egorov, V. Timareva Experimental geometry on isentropic compression of frozen gases in a facility based on a magneto-cumulative generator MC-1 is described. A goal of the experiments is building a ``zero'' isentropic curve in a pressure range higher 1 Mbar. A radiographing of a studied and reference samples, located in the compression chamber, is carried out during the compression process. A density of the studied sample is determined based on the measured sizes obtained in the result of the x-ray images analysis. Using the sizes of the reference sample and its isentropic curve one can determine the pressure in the studied sample taking into account a gradient correction. Selection of aluminum as the reference material and type of its isentropic curve is explained. The experimental results are compared with the calculation results made using different isentropic curves of Al. [Preview Abstract] |
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E1.00039: Isentropic Compression of Hydrogen Isotopes Crystal Phase up to 5 Mbar with Ultra-High Magnetic Field Pressure Alexander Bykov, G. Boriskov, N. Egorov, M. Dolotenko, Yu. Kuropatkin, N. Lukyanov, V. Mironenko, S. Belov, V. Belyashkin, M. Lomonosov A device for isentropic compression of condensed hydrogen isotopes with an ultra-high magnetic field pressure of a MC-1 generator is described in the paper. Experimental results of hydrogen and deuterium compression at initial temperature of $\le $7K and their comparison with \textit{P-$\rho $} diagram that extrapolates compression results on diamond anvils are presented. [Preview Abstract] |
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E1.00040: Software for X-Ray Images Calculation of Hydrogen Compression Device in Megabar Pressure Range Nikolay Egorov, Alexander Bykov, Valery Pavlov Software for x-ray images simulation is described. The software is a part of x-ray method used for investigation of an equation of state of hydrogen in a megabar pressure range. A graphical interface that clearly and simply allows users to input data for x-ray image calculation: properties of the studied device, parameters of the x-ray radiation source, parameters of the x-ray radiation recorder, the experiment geometry; to represent the calculation results and efficiently transmit them to other software for processing. The calculation time is minimized. This makes it possible to perform calculations in a dialogue regime. The software is written in ``MATLAB'' system. [Preview Abstract] |
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E1.00041: Experiment and Simulations of Ablatively Driven Shock Waves in Gadolinium Metal Richard Kraus, Eric Loomis, Shengnian Luo, Achim Seifter, Damian Swift Lanthanides are fascinating metals to study because they exhibit physical properties that vary with 4f occupancy. Specifically Gadolinium is interesting because there are multiple structural phase transitions accessible below 100 GPa. Experiments were performed on Gadolinium metal in which shock waves were driven in Gadolinium foils through direct laser ablation. The velocity at the opposite surface of the drive beam was measured with line-imaging laser Doppler velocimetry of the Velocity Interferometer System for Any Reflector (VISAR) type. Simulations of the experiment were done using a radiation hydrodynamic model which takes the measured irradiance history of the laser and predicts the pressure history at the ablation surface; this pressure history is then used as a time-dependant boundary condition for a continuum mechanics simulation. From this we obtain a simulated free surface velocity profile, which we then compare with the velocity profile obtained by the line VISAR diagnostic technique to validate the simulations. With this experimental series we were able to achieve shock pressures up to six gigapascals; specific experimental and simulated results to be presented. [Preview Abstract] |
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E1.00042: Measurement of the isentropic release data of Au by laser driven shock wave Fu Sizu, Huang Xiuguang, Shu Hua, Wu Jiang, Ye Junjian, He Juhua, Man Minxun, Gu Yuan Using the impedance invert-match target coupled with multi-materials, an intense shock pressure was produced in the high impedance material (Au) by high power laser, then its different isentropic release was realized simultaneously in the various lower impedance materials (Al, Cu, Zn, Sn, Ag, etc.). On the one hand, using the known EOS of the lower impedance materials, a group of the isentropic release data of Au can be obtained; On the other hand, if the EOS of Au is known, the first shock adiabatic data of all lower impedance materials also can be gotten from the experiment; This can verify systematically the EOS reliability of the various materials. Comparing the two methods of the experimental data processing, the isentropic release curve is more sensitive than the shock adiabat in the systemic verifying of the EOS data. The target manufacture is more difficult, perhaps the target had some distortions when it was employed, and the data from our primary experiment have not the enough precision yet. [Preview Abstract] |
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E1.00043: Phonon densities of states of Sn to 64 GPa E.A. Tanis, C. Chen, H. Giefers, X. Ke, M. Nicol, M. Pravica, E. Alp, J. Zhao, C. Greff, S. Rudin, W. Pravica We measured lattice dynamics of 3 phases of Sn to 64 GPa at ambient temperature by NRIXS and compare the results with DFT computations using the direct force method and all-electron PAW method as implemented in the VASP code. Calculations with either GGA or LDA approximations gave similar results. Other properties calculated from the results include: the Lamb-Mossbauer factor; the mean force constant; vibrational contributions to the Helmholtz free energy; the high and low temperature Debye temperatures; the Debye average phonon velocity; and the Debye-Gruneisen parameter. At all pressures, experimental and theoretical DOS agree well. [Preview Abstract] |
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E1.00044: HIGH ENERGY DENSITY PHYSICS |
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E1.00045: Numerical modeling of ferrous cylindrical liners compression. I.A. Mochalov, V.G. Sultanov A method of describing electroconductivity of metal taking into consideration phase transformations for numerical modeling of compression cylindrical liner is proposed and feature of value changing magnetic field induction is considered. Researched assembling consists of two cored cylinders with tiny walls (one inserted into another). External cylinder (impactor -- Cu) closely covered by chemical condensed HE. To create magnetic field inside the liner a tiny impulse solenoid is used, which is wound on the conductive liner (Fe). For searching distributions of liner material parameters (pressure, density, temperature) and magnetic field along radius with respect to time for several variants of liner conductivity type were calculated. In addition, phase diagram of realizable states, dynamics of magnetic field changing and temperature of liner internal surface were calculated. [Preview Abstract] |
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E1.00046: ISENTROPIC AND OFF HUGIONOT LOADING |
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E1.00047: Ramp Compression Experiments - Sensitivity of Inverted Isentropes to Experimental Uncertainties Marina Bastea, D. Reisman A wealth of experimental high pressure studies have been aimed in the last decades at understanding the fundamental behavior of matter under compression. Many of them employed well established techniques operating under either static - diamond anvil cell (DAC) or dynamic - shock Hugoniot, high-pressure conditions. More recent technical advancements however made also possible the study of new dynamic regimes by spreading the pressure loading from near-instantaneous, i.e. shock, to tens, hundreds and even thousands of nanoseconds, through the use of laser, electromagnetic and graded density impactor drivers respectively. We present the first sensitivity study of the material isentropes extracted from the ramp compression experiments. We perform hydrodynamic simulations of representative experimental geometries associated with ramp compression experiments and discuss the major factors defining the accuracy of the equation of state information extracted from such data. We discuss the impact of these uncertainties on all platforms. This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. [Preview Abstract] |
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E1.00048: Shockless compression of silicon using high-power laser Norimasa Ozaki, Tomokazu Sano, Ryosuke Kodama, Tomoaki Kimura, Akio Hirose, Michel Koenig, Keisuke Shigemori, Daigo Ichinose Shockless compression experiments for single-crystal silicon were performed using a high-power laser. Silicon is a typical interesting material exhibiting polymorphism, and the phase diagram is not understood well. For instance, Si is predicted to undergo a metallization transformation under compression. A polyimide reservoir target (75 $\mu$m) was irradiated with the GEKKO/HIPER laser ($\lambda =$ 0.35 $\mu$m), the reservoir plasma expanding to a vacuum gap ($\sim$ 200 $\mu$m) and colliding with a Si sample (20-30 $\mu$m). The rear-surface of Si was observed with 2-channel velocity interferometer system (VISARs) and a streaked optical pyrometer. The change of reflectivity from the VISARs may indicate phase transitions under the continuous quasi-isentropic compression. We also for the first time recovered the Si target shocklessly compressed by high-power laser. The structure of the recovered sample was analyzed using a large synchrotron radiation facility. [Preview Abstract] |
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E1.00049: The results of the application of Williamson-Hall procedure for analyses of diffraction maximum broadening of depleted unalloyed macrocrystalline uranium after shock-wave loading in range 20-50GPa Alexander Shestakov, Evgeny Kozlov, Igor Artamonov, Albert Nurgaleev, Irina Podgornova, Ekaterina Shestakova Williamson-Hall procedure for investigation low symmetry lattice sample after shock-wave loading was applied. A number of depleted unalloyed macrocrystalline uranium disks (20mm in diameter, 3mm thick) were used in this testing. The samples under went three different impulse loads of 20GPa, 30GPa and 50GPa. During our registration these loading condition provided the high-speed uniaxial deformation in initial alpha-phase. The state of the preserved uranium samples differed not only in the amplitude and the width of impulse but also in the deformation value, shock heating and the degree of residual temperature. The influence on the samples led to changes in microstructure, including dislocation density which correlates with lattice microstrain. It was shown that the level of the lattice microstrain grew in comparison with its initial states but changed regularly according to the loading conditions. Reducing of uranium crystalline to fragments less then 100nm was not revealed. [Preview Abstract] |
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E1.00050: Simultaneous determination of Hugoniot and Isentrope in gas gun experiments Robert Thoe We have been exploring the use of the `reverse ballistics' method to obtain Hugoniot and off Hugoniot Equation Of State. This method uses the unknown sample as the flyer and collides it into a window whose EOS is well known. A VISAR determines the particle velocity which when combined with the windows EOS gives a direct determination of the pressure. Since the pressure and particle velocity are continuous across the interface the shock speed in the flyer can be determined: Us = P/(rhoUp). Subtracting the time of arrival of the shock at the back of the flyer from the times of arrival of the rarefaction wave allows the determination of the release isentrope centered at the measured Hugoniot point and extending down to the release pressure as determined by the impedance of the sabot. Besides obtaining both Hugoniot and isentrope data on a single shot, this method has an advantage in that all the timing information is accomplished within the interferometer, i.e. no dependence of cable delays etc. [Preview Abstract] |
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E1.00051: STRESS-STRENGTH MEASUREMENTS |
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E1.00052: Explosive Welding of Pipes Olga Burtseva For connection by welding it is suggested to use the explosive welding method. This method is rather new. Nevertheless, it has become commonly used among the technological developments. This method can be advantageous (saving material and physical resources) comparing to its statical analogs (electron-beam welding, argon-arc welding, plasma welding, gas welding, etc.), in particular, in hard-to-reach areas due to their geographic and climatic conditions. The suggestion is to use water as filler. The principle of non-compressibility of liquid under quasi-dynamic loading is used. In one-dimensional gasdynamic and elastic-plastic calculations we determined non-deformed mass of water (perturbations, which are moving in the axial direction with sound velocity, should not reach the layer end boundaries for 5-7 circulations of shock waves in the radial direction). Linear dimension of the water layer from the zone of pipe coupling along axis in each direction is $\ge $ 2R, where R is the internal radius of pipe. Model experiments with pipes having radii R = 57 mm confirmed results of the calculations and the possibility in principle to weld pipes by explosion with use of water as filler. Reduction of pipe diameter after dynamic loading and explosive welding was $\sim $2{\%}. [Preview Abstract] |
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E1.00053: The Shock Induced Shear Strength of Polyoxymethylene and Polyethylene Stephen Goveas, Jeremy Millett, Neil Bourne In the past few years, a series of papers has examined the shock response of common engineering polymers in terms of their microstructure. In this latest work, the behaviours of two polymers, polyoxymethylene and polyethylene, are investigated under conditions of one-dimensional strain. The study focuses on the experimentally determined lateral component of stress and, from knowledge of the impact conditions, the shear strength. Variations with impact stress amplitude and pulse duration are discussed in terms of the polymer chain structure. [Preview Abstract] |
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E1.00054: The Response of Dry Limestone to Shock-Loading Dave Johnson, David Chapman, Kostas Tsembelis, William Proud The shock response of geological materials is of interest to many industries, in particular oil and gas exploration. The porous inhomogeneous composition of geological materials complicates characterisation under dynamic loading. The behaviour of dry limestone has been investigated under the condition of uniaxial strain using a plate impact facility. Manganin gauges were used to measure both longitudinal and lateral stresses within the limestone. The Hugoniot and shear data obtained are compared with that available in the open literature. [Preview Abstract] |
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E1.00055: Twinning and Dynamic Strength of Copper During High-Rate Strain Victor Raevsky The authors will present the results of a study of the conditions under which microstructural changes involving the formation of complex bi-periodic twin structures occurs in copper during shock wave and high strain rate ($\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. The effects of these complex twin structures are also complex. 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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E1.00056: Tension of Liquids Near Melting Point by Shock Waves Vasily Sosikov, Alexander Utkin, Vladimir Fortov The influences of strain rate on the negative pressure have been investigated in liquids near melting point by the example of water, hexadecane and pentadekane. The method of spall strength measurements was applied and wave profiles were registered by laser interferometer VISAR. It was cared out that in water and hexadecane there is a strong dependence between the strain rate and the registered negative pressure. It is unusual, because ordinarily the negative pressure is almost independent from the value of stain rate, when liquids are far from melting point. It is shown that the double metastable state of water was realized during our experiments. The process of destruction in hexadecane is double staged, like it is in methyl alcohol, unlike in methyl alcohol destruction is double staged only when the loading pressure exceed the threshold of about 250 MPa. 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. Anomal dependence of the loading pressure on the negative pressure was discovered in pentadecane. [Preview Abstract] |
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E1.00057: FIRST PRINCIPLES AND MOLECULAR DYNAMICS CALCULATIONS |
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E1.00058: Hugoniot of complex fluids from molecular simulation: application to nitromethane Emeric Bourasseau, Anais Hervouet, Nicolas Desbiens, Jean-Bernard Maillet The effect of molecular flexibility on the hugoniot shape is investigated using both MD and MC simulations. In the case of nitromethane, it is shown that molecular deformations with pressure play little role, and thus the rigid approximation may be used. A rigid model potential has then been fitted using a new technique, allowing fitting simultaneously several pressures on the hugoniot curve. This model is then used to simulate the behavior of nitromethane under shock conditions. Results are in good quantitative agreement with experimental data. [Preview Abstract] |
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E1.00059: Elastic and thermodynamic properties of post-perovskite MgSiO$_{3}$ from first-principles calculations Liu Zi-Jiang, Chen Qi-Feng, Cai Lin-Cang The elastic and thermodynamic properties of post-perovskite MgSiO3 polymorph are investigated at high pressures and temperatures using the plane wave pseudopotential method within the local density approximation. This phase may be the most abundant mineral in the D" region. It is found that the post-perovskite phase has similar bulk modulus and larger shear modulus than perovskite at relevant pressures. The athermal elastic constant tensor of post-perovskite MgSiO3 are calculated as a function of pressure up to 200 GPa. The calculated results are in excellent agreement with other predictions over the pressure regime studied. The thermodynamic properties of post-perovskite MgSiO3 polymorph are predicted using the quasi-harmonic Debye model; the heat capacity and thermal expansion coefficient accord with the other calculations at high pressures and temperatures. [Preview Abstract] |
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E1.00060: MATERIALS SCIENCE |
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E1.00061: Current Output from Sandwich-structured Ferroelectric Power Supply Jinmei Du, Gaomin Liu, Yusheng Liu, Haiyan Wang, Yi Zhang, Fuping Zhang, Hongliang He PZT 95/5 ferroelectric ceramics with niobium doped has been assembled for the pulsed power supply, and the electrical current output has been investigated under the action of shock wave in a ``normal mode.'' The PZT 95/5 ferroelectric ceramics are shocked simultaneously by two shock waves from the two parallel surfaces, so a sandwich-structured ferroelectric power supply is formed. Double current output has be obtained and a high-power electrical pulse over 5 kA is achieved. Theoretical calculation was conducted and a good agreement with the experiment is presented. [Preview Abstract] |
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E1.00062: Dynamic Shock Compression Response of Ta + Fe$_{2}$O$_{3}$ Powder Mixtures David A. Fredenburg, Naresh N. Thadhani, Joe Cochran The dynamic shock compression response of stoichiometric and equivolumetric mixtures of varying particle sizes of tantalum and iron oxide powder is investigated to determine their applicability for potential use as a structural energetic material. Compression data gathered in the quasi-static regime is combined with ambient pressure reaction energetics of powder mixtures to determine the optimal mixture configuration for investigation of the dynamic response. Instrumented parallel plate impact experiments are conducted to determine the compaction behavior, reaction threshold conditions, and aid in the development of a heterogeneous compaction model encompassing particle shape, configuration, and individual material properties. This information will be used to study the interactions and stress transfer characteristics in the case of linear cellular alloy structures filled with Ta + Fe$_{2}$O$_{3}$ powder mixtures upon their impact onto rigid targets. [Preview Abstract] |
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E1.00063: The Effect of Mechanical Deformation on the Glass Transition Temperature of Polyurea Gilbert Lee, Willis Mock, Jeffry Fedderly, Edward Balizer The glass transition temperature (T$_{g})$ of a polyurea was found to be a function of prior mechanical strain and strain rate. Differential Scanning Calorimetry (DSC) measurements were performed on a polyurea following mechanical deformations ranging from low speed tensile testing to high-speed impact from a gas gun. The high-speed impact experiment was done by impacting a steel plate coated with $\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} $ inch coating of polyurea with a pointed projectile. The highest strain rates and strain was localized at the center of the plate with the smallest at the circumference. Test specimens were taken from three locations on the coating: at the center free surface, center bounded to steel plate, and circumference (edge). The resulting T$_{g}$ of the soft domain was found to be, on average, 8$^{o}$C higher at the free surface than at the bounded surface and 6$^{o}$C higher than at the circumference. For the low strain rate tensile specimens, the T$_{g}$ increases with strain and reaches a maximum value at a strain of 3.6. These increases in the glass transition temperatures were interpreted as mixing of the hard and soft segments. The test specimens were subsequently thermally annealed at 100$^{o}$C. The T$_{g}$ was found to be about 7$^{o}$C lower than the previous value. Small angle x-ray analysis has also shown the formation of fibrils in the high strain regions. [Preview Abstract] |
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E1.00064: High-Strain Rate Response of Ultra-Fine Grained Copper: Experiments and Analysis A. Mishra, M. Martin, N.N. Thadhani, B. Kad, M.A. Meyers Equal Channel Angular Pressing (ECAP) is a severe plastic deformation technique that was used to produce ultra-fine grained copper. The microstructure was optimized using different deformation sequences. A steady state grain size of 200-500 nm was routinely obtained after eight passes (with an effective strain of $\sim$1 per pass). This resulted in a random texture evidenced by EBSD results. The mechanical response was obtained under quasi-static and dynamic conditions. The ultra-fine grained structure produced in Cu by ECAP was found to be thermally unstable. The microstructure recrystallized upon being dynamically deformed due to the adiabatic temperature rise imparted by plastic deformation. This was observed in three modes of high-strain rate plastic deformation experiments: cylindrical and hat-shaped specimens in Hopkinson bar experiments and cylindrical specimens in reverse Taylor impact experiments. [Preview Abstract] |
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E1.00065: Numerical simulation of the dynamic compaction process for fine iron disilicide powder Alexander Selezenev, Valery Lashkov, Alexey Aleynikov, Olga Sinkova, Yuri Yanilkin Iron disilicide is an attractive material for making thermoelectric generators and temperature sensors. One way to obtain high-density samples of iron disilicide is dynamic compaction technique. The paper summarizes the results of two-dimensional simulation study to optimize the performance of experimental setup for dynamic compaction of fine iron disilicide powder. This optimization was carried out in two-dimensional geometry and used EGAK code. Also, it describes the powder material temperature and pressure values calculated in relation to its loading conditions and initial powder density. The calculation found quantities of the equation of state in Mie-Gr\"uneisen form and the dependence of heat capacity on temperature for crystalline iron disilicide. Elastic pressure versus compression was calculated using ABINIT code, and thermal energy calculation was based on Debye model for the heat capacity of crystal structures. The numerical compaction data were compared against the experimental results. [Preview Abstract] |
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E1.00066: Shock Characterisation of a Carbon-Fibre Composite Michelle Willows, William Proud, Philip Church Composites provide a low-density alternative to many metals and alloys. Thay are increasingly used as structural components. In this paper carbon firbre re-inforced composite is characterised using a series of plate impact experiments using VISAR and manganin gauges as diagnostics. The results used to populate a hydrocode model and a ballistic impact scenario is used as a validation experiment. [Preview Abstract] |
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E1.00067: OTHER TOPICS |
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E1.00068: Reduction of steel-ball velocity using sand or water layer accelerated by high explosive Tomotaka Homae, Kunihiko Wakabayashi, Tomoharu Matsumura, Yoshio Nakayama The reduction of steel-ball velocity using sand or water was studied. A steel ball, diameter of 9.525 mm, was accelerated using comp. C-4 explosive of 37-52 g. After free flight of about 500-750 mm, the steel ball passed through a sand layer in thickness of 30-125 mm, or a water layer in thickness of 75 or 150 mm. The velocities before and after passage of the layer were determined using a high-speed camera. Although the velocity before the passage was varied from about 300 m/s to about 750 m/s, the velocity after passage was almost constant. The velocity depended only on the kind of materials or thickness of the layer. Sand was more effective in reduction than water for same areal density. Moreover, the steel-ball was accelerated in contact with sand layer in thickness of 30-125 mm. The terminal velocity in such case was comparable to that experienced free fright described above. [Preview Abstract] |
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E1.00069: Precursor decay anomaly in single-crystal lithium fluoride Yukio Sano, Tomokazu Sano The purpose of this study is to demonstrate that the precursor decay anomaly in single-crystal lithium fluoride (LiF) can be reduced using a macroscopic approach. To this end, a method of analyzing the evolving unsteady plane wave fronts created in the crystal upon impact is developed. The values of the parameters included in modeled strain waves in the wave fronts are determined such that the time variation of particle velocity predicted at the impact surface fits the detector current at the surface measured by Asay et al. [J. Appl. Phys. 43, 2132 (1972)]. Another condition is also used that the particle velocity-time histories at and near the surface are initially parallel. It is assumed that when the amplitude of a near-steady precursor in the predicted unsteady wave front, which increases from a static yield stress, becomes a maximum, a kink occurs at the rear of the precursor and then it begins to decay. The precursor decay curves estimated, based on this assumption, are much lower than Asay's decay curve. These lower curves are expected to reduce significantly the precursor decay anomaly in this crystal. [Preview Abstract] |
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E1.00070: Unsteady state Rankine-Hugoniot jump conditions Yukio Sano, Tomokazu Sano A theorem of equivalence regarding the discontinuity of the solution $\tilde {u}$ ($\tilde {u}^{(1)},\tilde {u}^{(2)},...,\tilde {u}^{(n)},\tilde {u})$ of an underdetermined system of $n$ quasi-linear partial differential equations in one spatial dimension is proven. It is also included in the proof that all the thicknesses of the discontinuities of $\tilde {u}^{(i)}$ (i=1,2,...,n+1) are the same. Unsteady state Rankine-Hugoniot (RH) jump conditions are derived from the system through its integration over the thickness. The jump conditions suggest a possibility that the jumps in $\tilde {u}$ evaluated from the conditions can differ significantly from those from the RH jump conditions. The significant differences in evaluation between both jumps are illustrated by demonstrating that infinitely large jumps in the particle velocity and stress across a spherical wave front are caused by an extremely intense explosion. [Preview Abstract] |
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E1.00071: CAV{\_}KO: A simple 1-D Langrangian hydrocode for MS Excel with automatic generation of x-t diagrams Kostas Tsembelis, Ben Ramsden, William Proud, John Borg Hydrocodes are widely used to predict or simulate highly dynamic and transient events such as blast and impact. Codes such as GRIM, CTH or AUTODYN are well developed and involve complex numerical methods and in many cases a large computing infrastructure. In this paper we present a simple 1-D Langrangian hydrocode developed at the University of Cambridge, called CAV{\_}KO. The motivation being to produce a code which, while being relatively simple, is useful for both experimental planning and teaching the rudiments of code development. Some studies are presented showing the output for a number of scenarios and comparison with experimental results. The code has been adapted from the original KO code written in Fortran by J. Borg, which, in turn, is based on the algorithm developed by Wilkins. The developed GUI within MS Excel and the automatic generation of x-t diagrams allow CAV{\_}KO to be a useful tool for quick calculations of plate impact events and for teaching. The code is licensed under the GNU General Public License and can be downloaded from www.shockphysics.com. [Preview Abstract] |
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E1.00072: PHASE TRANSITIONS |
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E1.00073: Phase transformation and spall fracture in laser shock-loaded iron Thibaut De Resseguier, Martine Hallouin Despite extensive research work on the $\alpha -\varepsilon $ phase transition occurring in shock-loaded iron, the kinetics of this transformation remain largely unknown. Here, we present time-resolved free surface velocity measurements in iron foils of thicknesses ranging from 150 to 500 $\mu $m subjected to laser shocks of peak pressure about 100 GPa and duration about 5 ns. The records clearly show an elastic precursor followed by a plastic front, but the double wave structure usually associated with the phase change does not appear clearly over such short propagation distances. The measured profiles are compared with the predictions of one-dimensional simulations involving time-dependent descriptions of both twinning and phase transition. Such comparisons provide an estimate of a time constant governing the transformation kinetics, which is found to strongly condition the attenuation of the pressure pulse during its propagation. They also allow testing the predictive capability of simple spall models. Metallurgical observations of the recovered samples confirm both the phase transition and the spall damage inferred from the velocity profiles. Finally, they show the very clear change of fracture surface morphology to the so-called smooth spall expected above the phase transformation. [Preview Abstract] |
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E1.00074: An Estimate for the Deviation from the Mirros Image Due to Solid Liquid Phase Transition of Metals at Shock Unloading. Shlomi Pistinner, Sharon Peker, Meir Werdiger, Shalom Eliezer We extend the underlying physical reasoning of Walsh and Christian (1955) in a manner which allows a reasonable estimation for the excepted deviation from the mirror image approximation due to solid liquid phase transition. This estimated is limited to a phase transition that occurs at the unloading phase in metals such as Tin and Lead. The idea underlying this estimate is the accumulation of various contributions to the entropy and an estimation of the expected expansion at atmospheric pressure. These estimates combined with the Lindmann melting law and the Clausius Clyperon equation are used to estimate the expansion at the phase transition and the resulting change in free surface velocity. [Preview Abstract] |
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E1.00075: Phase transitions of C$_{70}$ fullerite under step-like shock compression Sergey Sokolov, Vladimir Milyavskiy, Tatiana Borodina, Vladimir Fortov Shock-induced phase transitions of C$_{70}$ fullerite were studied with use of recovery assemblies of planar geometry at pressures 8 to 52 GPa. Two types of starting material were investigated: polyphase [1] and monophase C$_{70}$ with hcp-structure. We have found that the results of shock-wave compression of fullerite C$_{70}$ with various initial phase compositions qualitatively coincide in all explored pressure range. Rhombohedral modification of C$_{70}$ completely disappears already at pressure 9 GPa. At the same time, crystalline modification of C$_{70}$ with hcp-structure in conditions of step-like shock-wave compression does not undergo phase changes down to 9 GPa and practically completely disappears from the recovered material only at 23.5 GPa. Shock-induced transformation of hcp into fcc structure was fixed at pressures in the range 9 to 23.5 GPa. Depth of this transformation is increasing with growth of shock pressure. In the specimens recovered from 23.5 GPa, the only crystalline phase of fullerite C$_{70}$ with fcc structure is observed (about 5 {\%}) and for the first time formation of a graphite-like carbon is fixed (about 95 {\%}). With growth of shock pressure up to 26 GPa and higher, destruction of C$_{70}$ molecules occurs. The work was supported by RFBR and RSSF. [1] V.V. Milyavskiy, T.I. Borodina, S.N. Sokolov, A.Z. Zhuk. Diamond and Rel. Mat. \textbf{14} (2005) 1924. [Preview Abstract] |
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E1.00076: Hugoniot and phase transition in silicon nitride porous samples. Vladislav Yakushev, Alexander Utkin, Andrey Zhukov In this work by laser interferometer VISAR investigated the behavior of silicon nitride porous samples with porosity of $\sim $ 15{\%} in high pressure shock waves in the region of 15 -- 50 GPa. Hugoniot was constructed. The interest to the high density c -- modification mainly caused by its hardness, close to hardness of cubic boron nitride and diamond. In this work we investigate the phase transition from $\beta $ - Si$_{3}$N$_{4}$ to c- Si$_{3}$N$_{4}$ in porous samples by laser interferometer method for sample surface velocity registration. This method allows to obtain with high resolution mass velocity profiles of sample material at shock compression. The analysis of structure of such profiles gives the information about phase transition and its kinetics. Also by results of experiments Hugoniot is constructed. Having Hugoniots at different porosities allows to construct equation of state with maximal accuracy, which define the phase balance curve, in this case, balance between $\beta $ - and c -- phases. [Preview Abstract] |
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E1.00077: SPECTROSCOPY AND OPTICAL STUDIES |
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E1.00078: Study of the laser-induced decomposition of HNO3/ 2-Nitropropane mixture at static high pressures Viviane Bouyer, Philippe H\'ebert, Michel Doucet HNO3 / 2-Nitropropane is a well known energetic material on which Raman spectroscopy measurements at static high pressure in a diamond anvil cell (DAC) have already been conducted at CEA/LE RIPAULT in order to examine the evolution of the mixture as a function of composition and pressure [1]. The purpose of the work presented here was to study the laser-induced decomposition of these energetic materials at static high pressures by measuring the combustion front propagation rate in the DAC. First of all, the feasibility of the experimental device was checked with a well known homogeneous explosive, nitromethane. Our results were consistent with those of Rice and Foltz [2]. Then, we investigated the initiation of NA / 2NP mixture as a function of nitric acid proportion, for a given pressure. We chose the mixture for which both the combustion propagation rate and detonation velocity are maximum and we examined the evolution of the front propagation velocity as a function of pressure and energy deposit. [1] Hebert, P., Regache, I., and Lalanne, P., ``High-Pressure Raman Spectroscopy study of HNO3 / 2-Nitropropane Mixtures. Influence of the Composition.'' Proceedings of the 42nd European High-Pressure Research Group Meeting, Lausanne, Suisse, 2004 [2] Rice, S.F., et al., Combustion and Flame 87 (1991) 109-122. [Preview Abstract] |
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E1.00079: Temporal change of Raman spectra of carbon tetrachloride under laser-driven shock compression. Kunihiko Wakabayashi, Tomoharu Matsumura, Yoshio Nakayama, Eisuke Yamada, Mitsuo Koshi Nanosecond time-resolved Raman spectroscopy has been performed to study a molecular response of carbon tetrachloride under laser-driven shock compression at laser power density of 5 GW/cm$^{2}$. Shock wave was generated by using the glass-confined geometry target. Intense Raman bands of CCl$_{4}$ at 217, 314, and 460 cm$^{-1}$ in the Stokes and anti-Stokes region were clearly observed simultaneously at single-shot experiment. The most intense Raman band of CCl$_{4}$ at 460 cm$^{-1}$ showed red shift (18 cm$^{-1}$ at maximum), and its intensity increased along with the propagation of shock wave. The anti-Stokes and Stokes ratio increased during shock compression due to the shock induced temperature rise. The relationship between the change of Raman band and the propagation of shock wave will be discussed by using the hydrodynamic simulation and the measured particle velocity of shock compressed CCl$_{4}$. [Preview Abstract] |
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E1.00080: Simulating Picosecond X-ray Diffraction from Shocked Crystals using FFT Methods on MD Output Giles Kimminau, Andrew Higginbotham, William Murphy, Justin Wark, James Hawreliak, Dan Kalantar, Hector Lorenzana, Bruce Remington, Nigel Park Multi-million atom non-equilibrium molecular dynamics (MD) simulations give significant insight into the transient processes that occur under shock compression. Pico-second X-ray diffraction enables the probing of materials on a timescale fast enough to test such effects. In order to simulate diffraction patterns, Fourier methods are required to gain a picture of reciprocal lattice space. We present here results of fast Fourier transforms of atomic coordinates of shocked crystals simulated by MD, and comment on the computing power required as a function of problem size. The relationship between reciprocal space and particular experimental geometries is discussed. [Preview Abstract] |
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