Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session F1: Poster Session I |
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Room: Atrium Ballroom |
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F1.00001: Rice-Walsh equation of state for unreacted high explosives based on isothermal compression data Kunihito Nagayama, Shiro Kubota Equation of state (EOS) for unreacted explosives, PETN has been formulated thermodynamically aiming at using with numerical code of shock to detonation transition processes. In this paper, a generalized procedure of providing {\em pressure-volume-enthalpy} EOS is proposed based on the available static isothermal high-pressure compression curve. The present procedure can be used to formulate the Rice-Walsh type EOS by using the specific heat at constant pressure as a function of entropy, {\em C$_p$}({\em S}), and pressure-dependent Wu-Jing parameter with the material parameter $\beta$ introduced by the author. Birch-Murnaghan functional form is adopted as an isothermal compression curve. Specific heat function was derived from the measured temperature dependence at atmospheric pressure. In order to estimate the parameter $\beta$ in the Wu-Jing parameter, shock Hugoniot curve for PETN were calculated varying the value, $\beta$ as a parameter. Both values of $\beta$ determined to reproduce the shock Hugoniot for TMD and porous samples were found to be very similar and were very small compared with those estimated for various metals. [Preview Abstract] |
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F1.00002: Overview of the First SHPB Experiments on Single Crystal Explosives Christopher Meredith, Daniel Casem, Cheng Liu, Benjamin Morrow, Carl Cady, Kyle Ramos Under plate impact experiments (uniaxial strain) single crystal explosives exhibit elastic-plastic mechanical behavior, however at quasi-static rates (uniaxial stress) they are brittle. We have conducted Split-Hopkinson Pressure Bar (SHPB) experiments to bridge the strain rate gap between the two extremes in an effort to tease out the effects of strain rate and pressure on the plasticity, and to probe the mechanisms of failure in single crystal RDX, PETN and HMX and PBX9501. Samples were compressed in different crystallographic orientations to promote different proposed deformation and fracture mechanisms, while utilizing in-situ synchrotron x-ray diffraction, phase contrast imaging, or high speed visible light imaging. Researchers have postulated that in sub-shock impacts, the mechanisms of stress dissipation an explosive possesses are very important to ``hot spot'' formation---which initiates the first chemical reactions within an energetic. This presentation will focus on the development of the mini- and micro-Kolsky bars utilized in order to maximize the strain rate within the samples, the initial results on the mechanical behavior and fracture mechanisms of these high explosives, and the challenges we have encountered and overcome. [Preview Abstract] |
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F1.00003: Introducing HEDONIST- A Low Explosive Mass Experiment That Attains Very High Pressures Carl Johnson, Anthony Fredenburg, Scott Ramsey, Bryce Geesey, Ernesto Martinez, Anna Llobet The proton radiography facility at LANL offers unique experimental capabilities, particularly the planned Pu@pRad line. Pu@pRad limitations however preclude the usage of large quantities of high explosives. We present the hydrocode analysis of a small-scale system (under 30g TNT equivalent) capable of reaching pressures in excess of 2 Mbar. This system utilizes a novel multipoint initiation system to establish converging detonation waves which deliver a strong shock wave onto a sample cell. HEDONIST has been designed to present a low areal density to the pRad beam thereby providing ample signal-to-noise ratio to discern shock waves in sample cell materials from other shocks present. Fragmentation mitigation, design modifications, and an example sample cell analysis will be discussed. [Preview Abstract] |
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F1.00004: Structure-property response of gold films with controlled microstructure Daniel Hooks, William Anderson, Anirban Mandal, George Gray, Brian Jensen Gold is of interest as a model system in high-pressure and dynamic research because of its high compressibility and inert character, especially because purity, defects, and grain structure can be carefully controlled. Further, because of its potential as a graded density alloy, baseline characterization is important. Gold can be prepared in several ways, leading to some different characteristics, and it is the goal of this research to characterize how these differences manifest in changes in physical properties. Characterizing the relationships between film thickness, grain size, and grain aspect ratio together is important in resolving the relative influences of scale, bulk material properties, and defect contributions to properties. We present a study of electroplated films of gold with tailored microstructures up to thicknesses of several mm, in which we relate the grain structure to mechanical response. Constant potential and pulsed plating techniques were used to create a variety of grain structures, including high aspect ratio columnar grains. These structures were compared to cast and wrought microstructures. Microscopy was correlated with mechanical characterization of the films at several rates and scales. This work is connected to impact experiments on these materials, presented elsewhere in this meeting. [Preview Abstract] |
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F1.00005: ABSTRACT WITHDRAWN |
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F1.00006: The Cause of Lost Time in an Exploding Bridgewire Detonator Elizabeth Lee, Rod Drake The initiation mechanism and functioning of exploding bridgewire (EBW) detonators has been the subject of investigation and debate since their first use in the 1940s. One aspect of their initiation for which a definitive cause has never been identified is the lost time i.e. the difference between the ideal explosive transit time and the experimentally measured explosive transit time. In this paper the various theories and available data are discussed and assessed in light of more recent findings. In addition to which they are related to the known physical processes occurring during the functioning of an EBW detonator. Finally, an explanation for the lost time and why it differs so greatly from that in a high density exploding foil initiator (EFI) is proposed. \copyright British Crown Owned Copyright / 2019. [Preview Abstract] |
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F1.00007: Effects of parametric uncertainty on multi-scale model predictions of shock response of a pressed energetic material Sangyup Lee, Oishik Sen, Nirmal Kumar Rai, Nick Gaul, K.K. Choi, HS Udaykumar A framework is presented for uncertainty quantification (UQ) in multi-scale models of shock-to-detonation transition (SDT) of a pressed energetic (HMX) material. The uncertainties are assumed to arise from variabilities in the material properties of HMX which are inputs to a Meso-informed Ignition and Growth (MES-IG) model. The input uncertainties are first used to quantify the variabilities in the hot-spot dynamics at the meso-scale. A Kriging-based Monte-Carlo method is used to construct probability density functions (pdfs) for the meso-scale reaction product formation rates; these pdfs are used to propagate the meso-scale uncertainties to the macro-scale, via surrogate models for the macro-scale reaction progress variables. The uncertainties in the run-to-detonation distances (RTD) in macro-scale computations are quantified. We evaluate uncertainties in RTD due to variabilities in six material properties, viz. the specific heat, Gruneisen parameter, bulk modulus, yield strength, thermal expansion coefficient and the thermal conductivity of the material. Among these six properties, RTD is found to be most sensitive to the variabilities in the specific heat of the material. It is also shown that uncertainties in the specific heat amplify exponentially across scales and results in logarithmic pdfs for RTD. Thus, the paper presents a UQ framework that not only propagates uncertainties across scales in multiscale models of SDT, but also allows to rank the sensitivity of the SDT response to the uncertainty of each property of the HE material. [Preview Abstract] |
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F1.00008: Investigation of non-critical pore size effects on detonation front shapes for conventional and 3D printed explosives Gabriel Montoya, Nick Cummock, Monique McClain, Diane Collard, Steven Son, Terry Salyer Micropores in explosives have been shown to play a role in detonation wave propagation even though it is unlikely that many of these pores reach critical temperature. Additive manufacturing allows for the controlled addition of these pores, making the understanding of their effects crucial for design and explosive performance tailoring. A series of experiments is used to observe the effects of pore diameter on detonation propagation in PBX 9501. Streak camera imaging is used to track detonation velocity into the pore, pore collapse, and detonation velocity variations downstream of the pore. Additional streak images are taken with the one-dimensional field of view perpendicular to the detonation direction to investigate wave profile distortion as a function of initial pore size and distance from the pore. Additional shots of 3D printed explosives with tailored pores will allow for comparison with detonation wave profiles from traditionally pressed pellets. This will then be used to help identify ideal pore structure and manufacturing tolerancing for 3D printed explosives. [Preview Abstract] |
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F1.00009: The Deflagration-to-Detonation Transition (DDT) in High Density Pentaerythritol Tetranitrate (PETN) Peter Schulze, Ian Lopez-Pulliam, Eric Heatwole, Trevor Feagin, Gary Parker The deflagration-to-detonation transition (DDT) is a mechanism by which explosives can transit from burning to detonating under suitable confinement and powder morphology conditions. The length that this transition is able to occur for specific explosives is an important safety consideration. The DDT length in Pentaerythritol Tetranitrate (PETN) has been studied extensively previously as PETN is a common explosive used in detonators. DDT has been observed to occur in PETN on length scales on the order of tens of millimeters for densities up to 1.56 g/cc, which is roughly 88{\%} of its theoretical maximum density (TMD; for PETN: 1.778 g/cc). However, standalone pellets of pressed PETN commonly exceed 90{\%} TMD. The DDT length versus density curve for PETN appears to approach an asymptote past 88{\%} TMD, and so previous work cannot answer definitively whether or not higher-density PETN pellets will undergo DDT nor what run length is required for the transition. In this work, we explore the DDT reaction in 1.65 g/cc PETN (93{\%} TMD). Two mechanisms for initiating a burn in the PETN are used: thermal ignition and piston driven ignition. The effect of confinement strength on the reaction progress is also explored by housing the PETN in three different tube materials: polycarbonate, sapphire, and steel. We find that confinement strength plays a major role in the ability of the PETN to undergo DDT. [Preview Abstract] |
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F1.00010: Modeling Material Diffusion in Combustion Processes Using Smoothed Dissipative Particle Dynamics Nikolai Petsev, Xia Ma, Bryan Henson, Brad Clements We describe a novel mesoscale particle-based strategy for modeling material diffusion in combustion processes. Importantly, this simulation framework gives the foundation for investigating the deflagration-to-detonation transition (DDT) in explosives, where the material transitions from burning at a rapid subsonic pace (deflagration) to the emergence of a shockwave (detonation). The basis for this approach is "smoothed dissipative particle dynamics" (SDPD), a stochastic thermodynamically consistent strategy for solving the fluctuating hydrodynamic equations of Landau and Lifshitz. Presently our new approach incorporates heat and mass transfer driven by conduction and diffusion, exchange of heat and chemical species due to thermal fluctuations, and source terms arising from the chemical reaction. In future work, this will be coupled to the fluctuating momentum equation, or included in multiscale molecular-continuum simulations, opening the possibility for simulations studying DDT in energetic materials. [Preview Abstract] |
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F1.00011: The Design and Testing of an Impact Ignited Deflagration-to-Detonation Experiment Ian Lopez-Pulliam, Peter Schulze, Eric Heatwole, Trevor Feagin, Gary Parker There are elements of the mechanism for DDT in weak confinement materials that are still poorly understood. At LANL, we have developed an impact-ignited DDT test to further explore ways in which the process varies from what has been well described when strong metal confinement is used. The experiment employs a smokeless-powder gun system to accelerate a machined projectile into a tube (DDT tube) containing a column of high explosives (projectile velocities \textasciitilde 120-160 meters per second). Precise control over the impact timing allows for the fielding of a suite of high-speed diagnostics to observe the increasingly rapid burn modes building to DDT. Projectile velocity/position, high-speed video, pyrometry data, and gun-bore pressure can be recorded for each test. The experiment allows selected variables to be changed between tests, including projectile length, projectile velocity, DDT tube material/design, and HE column composition/characteristics. From the more than 25 tests already completed using the gun system, we have observed interesting behavior pertaining to DDT in PETN with polycarbonate confinement (\textasciitilde 150 m/s impact velocity). The design, function, results of the experiment system will be discussed. [Preview Abstract] |
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F1.00012: Optimal Parameterization of DSD Programmed Burn Models in ALE3D with DAKOTA Kevin Miers, Adam Enea, Brian Travers Diverging curved detonation waves propagate slower than planar CJ detonations due to geometric source terms in the reaction zone equations, while still being decoupled from the products expansion region. When the reaction zone thickness is small compared to the radius of curvature of the front, the length and time scales for the reaction zone dynamics are much smaller than those for the flow in the reaction products, and the propagation can be considered quasi-steady. In this case, the reaction zone dynamics can be described by a simple dependence of the front propagation velocity Dn on its local curvature $\kappa $. This theory is often called Detonation Shock Dynamics (DSD), and enables curved detonation fronts to be accurately modeled in 2D/3D without directly resolving the reaction zone, achieving a substantial computational cost savings. The US Army CCDC-AC is developing the capability to obtain simple Dn--$\kappa $ relations for military explosives from rate stick experiments. In this work, constrained nonlinear optimization routines in DAKOTA are utilized in conjunction with the hydrocode ALE3D to optimally parameterize a DSD model for an already well-characterized explosive using available experimental data. The computational framework utilized is described, and the results of the methodology are compared with existing fits. [Preview Abstract] |
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F1.00013: Jones-Wilkins-Lee Product Equations of State for Overdriven PETN Detonation Craig Tarver \textbf{T}he Jones-Wilkins-Lee (JWL) equation of state (EOS) for detonation reaction products mixtures has long been used to quantitatively calculate the shock Hugoniot states of unreacted energetic materials plus the Chapman-Jouguet (C-J) detonation state and subsequent expansion states of the reaction products. JWL EOS's also quantitatively calculate the shock Hugoniot states of the reaction products at higher pressures than C-J created in piston compaction, multiple shock, and converging wave experiments. Early JWL EOS's fit to only detonation and expansion states were shown to be too compressible to predict experimentally measured overdriven detonations over 30 years ago. A revised JWL fitting method was devised and has been used since. JWL EOS's can now be generated using the CHEETAH chemical equilibrium code. These JWL EOS fits to CHEETAH C-J and reaction product expansion states closely match experimentally measured overdriven product Hugoniot states for many explosives. This paper presents experimental results and CHEETAH JWL EOS product predictions for overdriven detonation waves in PETN. This work was performed under the auspices of the United States Department of Energy by the Lawrence Livermore National Laboratory under Contact DE-AC52-07NA27344. [Preview Abstract] |
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F1.00014: Enhanced Blast from Partial Reaction of a Solid Propellant Yehuda Partom We performed tests with one of our propellants to determine its TNT equivalence. In these tests we measured the close in response with velocity gauges, and the blast effect at a distance of 10m. We expected the two diagnostics to agree, they did not. The velocity gauges show that only a small part reacts, but from the blast diagnostics it seems as if the whole propellant has reacted. We refer to this enhanced blast as a \textbf{spreading effect. }To demonstrate the spreading effect we make 1D simulations of outgoing detonations of an HB (H$=$HMX, B$=$Binder) explosive in spherical symmetry. For different runs we dilute the explosive with the binder to various extents, from W$=$1 (pure explosive) to W$=$0.01 (1{\%} explosive). For each such formulation we compute the detonation parameters using our in house chemical equilibrium code. For each formulation we adjust the explosive radius so that the total detonation energy stays the same. For all runs we monitor the reflected pressure (P$_{\mathrm{r}})$ at a radial distance of 12m. We get that as W decreases below 0.5, the total amount of HMX decreases, but P$_{\mathrm{r}}$ increases. For W$=$0.01, the total amount of HMX is only 6{\%} of the amount for pure HMX, but P$_{\mathrm{r}}$ increases by 12{\%} relative to that of pure HMX. We attribute the enhanced blast to the spreading effect. [Preview Abstract] |
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F1.00015: Exploring the Connections between Acoustic Nonlinearity and Performance Characteristics in Aged PETN Pellets Emily Pittman, Peter Schulze, Carly Donahue, Joseph Mang, Christopher Armstrong, TJ Ulrich, David Moore, James Ten Cate Nonlinear wave propagation in consolidated granular material, such as sandstones, concrete or in this case, pressed pellets of pentaerythritol tetranitrate (PETN), is a function of the microstructure and can be influenced by poor sintering of the grains, microcracks and grain distribution. In this work, we use Nonlinear Resonant Ultrasound Spectroscopy (NRUS) to investigate nonlinear elastic wave propagation properties in pristine and artificially aged PETN pellets. NRUS is a tool that is able to measure the bulk hysteretic nonlinearity by resonating a sample at different amplitudes and observing the shift in resonant frequency. We hypothesize that nonlinear elastic wave propagation properties may be sensitive to detonation threshold in PETN, particularly since detonation is caused by a shock wave, which is a nonlinear phenomenon. Herein, we demonstrate that average hysteretic nonlinearity increases with time at temperature and we report our findings on the dependence of the nonlinear nonclassical hysteretic parameter on sensitivity to initiation. [Preview Abstract] |
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F1.00016: Mesoscale modeling of TATB-HMX explosive mixtures H. Keo Springer, Sorin Bastea, Larry Fried, Craig Tarver, Bradley White TATB has outstanding safety characteristics but unremarkable initiability and corner turning response. Previous studies have shown that the addition of HMX to TATB formulations enhance shock sensitivity and detonation properties. However, the microscale mechanisms underlying such changes are not well understood. In this study, we numerically investigate the shock response of different TATB-HMX mixtures and examine changes to the unreacted equation of state (UEOS), reaction rate, and reaction zone size. Mesoscale simulations are performed with the multi-physics hydrocode, ALE3D, and coupled to a thermochemical code for the equation of state and the chemical kinetic properties. Simulations are performed for TATB-HMX-Kel F mixture ratios of 75-20-5, 50-45-5, and 20-75-5 with a fixed porosity. A range of shock pressures are considered. Initial results show that the UEOS does not dramatically change with mixture ratio, but the degree of reactivity increases with HMX content. These studies are important for developing properties used in reactive flow models especially when the constituents are mixed at length-scales below the reaction zone size. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
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F1.00017: Fragmentation of Brittle Reactive Materials Jake Kline, Joe Hooper Reactive materials commonly produce large quantities of fine, brittle debris. We discuss approaches to recover and analyze these fragments in explosive or impact tests without unwanted secondary fragmentation. A series of reactive materials were produced from pure aluminum powders and used to fabricate explosive cases and small preformed fragments. Lab-scale detonation and gun-launch experiments were used to fracture these samples in realistic scenarios, and the debris was carefully recovered for post-mortem analysis. We discuss both the soft-catch process as well as methods to analyze the enormous numbers of micron-scale fragments produced by these events. A series of explosive tests in artificial snow, argon, and air was used to show the evolution of the fragment distribution for the reactive cases and help understand the combustion energy release. [Preview Abstract] |
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F1.00018: A framework for propagation of uncertainties from meso- to continuum scale computational models for shock-to-detonation transition in energetic materials. Oishik Sen, Sidhartha Roy, Sangyup Lee, Nirmal Rai, Min-Yeong Moon, K.K. Choi, H.S. Udaykumar Predictive models of shock-to-detonation transitions in heterogeneous energetic (HE) materials must contend with uncertainties in the material properties, reaction kinetics and microstructural features of the material. These uncertainties affect the energy localization at hot-spots due to void collapse and other mechanisms at the meso-/grain scale of the material and are eventually propagated to the macro-/continuum scales, leading to variabilities in the run-to-detonation distances. This work presents a unified framework for propagating the uncertainties in constitutive and reaction models as well as in microstructural features across scales in an energetic material. The aforementioned uncertainties are fed as inputs to a Mesoscale-Informed Ignition and Growth (MES-IG) model, and their effects on the meso-scale hot-spot characteristics and reaction dynamics are studied by performing ensembles of high-fidelity reactive void-collapse computations. The uncertainties in the meso-scale hot-spot characteristics are propagated to the homogenized macro-scale model using a surrogate based Monte-Carlo method to determine the the uncertainties in the macro-scale run-to-detonation distances. The relative contributions of the individual uncertainties in the micro-structural features, thermo-mechanical models and the reaction kinetics to the overall uncertainties in the run distances are also quantified. [Preview Abstract] |
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F1.00019: Detonation Performance and Shock Sensitivity Analysis of Energetic Cocrystals Vasant Vuppuluri, Gabriel A. Montoya, Nicholas Cummock, Steven F. Son Development of new energetic materials is a challenging endeavor due to the difficulty of successful synthesis and scale-up of novel energetic molecules as well as the extensive characterization required. For this reason, cocrystallization has been explored as a possible route to simplifying the development of energetic materials. A number of cocrystals of CL-20 as well as other high-nitrogen materials have been reported that exhibit improved properties such as high density. However, their detonation and shock sensitivity characteristics are not well-understood, both of which are particular important for evaluating the potential of explosives for use in various applications. In addition, the effect of cocrystallization on these properties is not well-understood. Evaluating these parameters is challenging due to large amounts of material required for most experimental techniques. In this work, results of experiments involving streak camera measurements, floret tests, and PDV are presented to compare detonation performance and shock sensitivity of various cocrystals and their corresponding physical mixtures. [Preview Abstract] |
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F1.00020: The Role of Adhesion and Young's Modulus in Hot-Spot Formation in Energetic Materials Due to Ultrasonic and Impact Excitation Jason Wickham, Zane Roberts, Stephen Beaudoin, Steven Son In order to examine the possible mechanisms of heat generation (``hot-spot'' formation) for ultrasonic excitation, a mechanically-delaminated inclusion of HMX in polymer binder was subjected to ultrasonic excitation utilizing an ultrasonic transducer. The Young's modulus and surface energy of the polymer binders were varied in order to determine if a relationship existed between these properties and the heating rate. Drop weight impact tests were also performed with samples containing 85{\%} HMX by weight to investigate if these material properties had similar effects on the sensitivity of the composition. Experimental results suggest that the work of adhesion has no effect on the heating rate at the inclusion, but a positive correlation exists between the Young's modulus of the polymer material and the heating rate at the inclusion. Drop weight experiments demonstrated a strong negative trend between the modulus and the drop height, but no such relationship was observed with the work of adhesion. These results suggest that the stiffness of the material plays an important role in the energy dissipation mechanisms responsible for hot spot formation in these materials and that compliant materials exhibit a lesser degree of sensitivity. [Preview Abstract] |
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F1.00021: Engineered Defects in Single Crystal HMX Christian Sorensen, Camilo Duarte, Steven Son Phase contrast and optical high-speed imaging were applied to simplified explosives systems with a single, near-perfect HMX crystal with an(a) engineered defect(s). Five and ten MHz frame rates recorded impact experiments on engineered defects which include single voids, multiple voids in various configurations, and slots designed to create a stress concentration and nucleate shear crack networks. Data from these experiments will be presented along with simulations ranging in scale from molecular dynamics to mesoscale models with single crystal HMX or single crystal/polymer systems. Slip/cleavage plane data from models will be compared to observed crack networks in loaded single crystal HMX with engineered defects. Implications for hotspot locations will be discussed. [Preview Abstract] |
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F1.00022: Predicting localisation of aluminum particles during the post-detonation phase of high metalized explosives suarez jimmy, Courtiaud Sébastien, Baudin Gérard, Poinsot Thierry, Selle Laurent In the context of the study of high explosives, the afterburning is defined as the combustion between the detonation products and air. This phenomenon can liberate more energy than the detonation itself and results in an improved blast. When solid metal particles are included into the high explosive, their combustion increases the energy introduced into the flow and strengthens the effects of afterburning. In this paper the dispersion of non-reacting aluminum particles during the post-detonation phase of high explosives will be studied with numerical simulations. The influence of several parameters, such as the particles size or their ability to evaporate, will be assessed. The simulations are made in the frame of Large Eddy Simulation (LES and make use of a ``~thickened flame~'' combustion model. Particles are modelled using a lagrangian approach and the drag model of Schiller and Naumann. Results show that, depending on the size of the particles, it is possible to determine if they will be in the combustion zone between detonation products and the air. The analysis of the history of temperature and pressure around particles can indicate if a reacting particle would be likely to evaporate and ignite, thus supplying more energy in the afterburning. [Preview Abstract] |
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F1.00023: Simulating the Propulsive Capability of Explosives Loaded with Inert and Reactive Materials Quentin Pontalier, Jason Loiseau, Aaron Longbottom, David L. Frost Diluting high explosives with inert particles typically reduces metal-acceleration ability (AA). Previous experimental results using glass and steel particles embedded in C4 or nitromethane at 5--80\% mass fraction showed an up to 43\% reduction in flyer velocity compared to an equal volume of base explosive. However, the addition of large fractions of inert particles modifies the scaling of flyer velocity with charge mass, so the diluted explosive may become relatively more efficient at large M/C. Alternatively, the addition of small mass fractions ($<$ 20\%) of micrometric aluminum particles in nitromethane generally improved AA over an equal volume of base explosive. Reaction onset occurred within a few microseconds and exhibited enough exothermicity to overcome losses from heating and accelerating the particles. In the present study, numerical simulations of these configurations were performed using the EDEN multi-phase hydrocode. The acceleration, heating, compressibility, and reaction of the particles are quantified to better explain the partition of energy between the detonation products, accelerated flyer, and particles for these non-ideal systems. [Preview Abstract] |
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F1.00024: Flash ignition of nanoaluminum and fluoropolymer composites. Kyle Uhlenhake, Metin Ornek, Steven Son Nanoaluminum (nAl) is known to be sensitive to flash ignition at low packing densities, possibly due to its plasmonic properties as a nanoparticle, where it is suggested the particle absorbs more light energy than it scatters. However, at higher packing densities this energy is more rapidly conducted away, and the particles no longer flash ignite. In this work, the flash ignition of nAl particles incorporated in fluoropolymers such as polyvinylidene fluoride (PVDF) or tetrafluoroethylene hexafluoropropylene and vinylidene (THV). When mixed in a solvent, nAl, PVDF, and THV can be drop cast to produce a full density flash ignitable solid composite in the form of films. The flash ignition is studied through thermal imaging of the particles being flashed, as well as analysis of the fluoropolymer properties when combined with nAl such as piezoelectricity, thermal conductivity, and density. The flash ignition of the particles is also studied as additives in composite propellants, and has shown to be effective at igniting the propellant. This is then compared to the flash ignitability of other propellants with nanoparticle additives. [Preview Abstract] |
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F1.00025: Role of Heterogeneities on the Shock Compression Response of Mock-Additively Manufactured Energetic Materials (AMEMs) Andrew Boddorff, Greg Kennedy, Hannah Woods, Didier Montaigne, Blair Brettmann, Naresh Thadhani The role of process-inherent heterogeneities on the shock compression response of AMEMs comprised of high solids loaded composites with simulant particles (e.g. melamine, silicon dioxide) in a UV-curable binder matrix is investigated. Additive manufacturing introduces heterogeneities at the macro-scale, such as periodic and aperiodic voids and hierarchical layers, as well as particle aggregation and micro-voids on the meso-scale. These heterogeneities affect the shock compression response and influence the sensitivity of energetic materials. In the present work, AMEMs fabricated using direct write extrusion are investigated to study the role of AM process-inherent heterogeneities on their shock compression response. Samples obtained from sections cut from AM fabricated blocks are shock-compressed using gas gun plate-impact experiments with Photon Doppler Velocimetry used to measure shock and particle velocities, and 1-D photonic crystal multilayer optomechanical sensors to measure spectral shifts associated with shock pressure. The measured PDV particle velocity profiles and pressure distributions obtained from spectral changes are correlated to deduce the role of heterogeneities. The results obtained to date will be presented. [Preview Abstract] |
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F1.00026: Additive Manufacturing of Linear Shaped Charges for Curved Penetration Jason Ho, Cody Lough, Phillip Mulligan, Catherine Johnson Linear shaped charges (LSC) are typically manufactured in continuous lengths and formed into an inverted ``V'' and use explosive force to cut through a target with a straight blade, typically in the demolition industry but there is significant interest in cutting a circle with an LSC for military and breaching applications. While some curved LSCs do exist, there are limitations for the curve due to the manufacturing process; additionally depth of penetration is reduced as the blade is formed at an angle due to varying inside and outside dimensions of the LSC. Additive manufacturing allows for geometric complexity not possible in other manufacturing techniques. In this work, selective laser melting (SLM) with a Renishaw 250 system was used. LSCs were printed with varying density gradients along the outside tamping portion of the LSC. By varying the density stepwise along the outside edge and adjusting the confinement while keeping the internal liner consistent, a curve can be achieved while not affecting the penetration depth. LSC performance was evaluated by the depth of penetration and curvature in the cut compared to traditional liners. The aim of this work is to show the potential for curving the blade of an LSC by applying a density gradient throughout the liner through SLM. [Preview Abstract] |
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F1.00027: Effects of Inert Additives on Cyclotrimethylene-Trinitramine (RDX)/Trinitrotoluene (TNT) Detonation Parameters to Predict Detonation Synthesis Phase Production Martin Langenderfer, Catherine Johnson, William Fahrenholtz The following methodology was developed to predict temperature and pressure regimes achieved during detonation of RDX/TNT compositions as they relate to the formation of solid carbon-based phases precipitating from the detonation process. This study computationally assesses the effects of inert material additives on explosive compositions used in detonation synthesis experiments. Thermomechanical and thermochemical models are used to evaluate detonation parameters starting with an explosive base composition of 50 wt.{\%} RDX and 50 wt.{\%} TNT. The effects of mesoscale inclusions and porosity created by inert additives on the sensitivity of the explosive composition to undergo a shock-to-detonation transition are estimated using a limited scope approach regarding hotspot formation and collapse. On the continuum scale, the effect of inert additives on pressure and temperature generated behind the detonation wave and within the reaction zone are parameterized through reactive burn modeling using the Becker-Kistiakowsky-Wilson (BKW) equation of state (EOS). The Jones-Wilkins-Lee (JWL) EOS is compared to the post reacted BKW model, and predicted state variables are input into thermochemical equilibrium modeling software to evaluate the state of the detonation products at various levels of expansion. [Preview Abstract] |
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F1.00028: Front surface impact experiments using multiple windows for unreacted Hugoniot measurements of high explosives formulations Adam Pacheco, Cindy Bolme, Adam Golder, Claudine Armenta, Ramon Saavedra, John Lazarz, Ernest Hartline, Gary Windler, Kyle Ramos During development and evaluation of new high explosive formulations, reactant Hugoniots must be measured to ascertain the impact pressure for Pop-plots by impedance matching. To be able to compare and contrast formulations with slight composition changes, the impact pressures and hence the Hugoniots must be measured precisely. This is both a costly and technically challenging endeavor that must be expedited to inform formulation efforts. Toward this objective, a front surface impact experiment has been developed and evaluated. Typical Hugoniot determinations require 3-4 separate transmission-type experiments. However, reactant Hugoniots from transmission type experiments can be error prone as chemical reactions contribute to particle velocity. Front surface impacts are an obvious solution and are typically made with embedded magnetic velocity gauges, for example. However, this approach still requires multiple experiments. As an alternative, a multiwindow target consisting of LiF, PMMA, quartz and sapphire was built and the explosive impacted into it using a single stage gas gun. The methodology for construction and metrology of the window and the resulting Hugoniot data will be presented for HMX-based formulations with varying amounts of nitroplasticized Estane binder. [Preview Abstract] |
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F1.00029: Modeling of what may happen after a Thermal Explosion Yehuda Partom When thermal explosion happens in a small region of an explosive body, the events that follow, and their overall resultant violence may be quite diverse, like 1) slow decaying deflagration wave; 2) fast non decaying shear wave; and 3) strengthening shear wave that builds up to shock initiation and detonation. The outcome of a thermal explosion depends on: 1) the sensitivity (or reaction rate) of the explosive; 2) the temperature field throughout the explosive body at the time of thermal explosion; 3) the geometry of the explosive body; 4) the location of the thermal explosion point in the explosive body; and 5) the degree of confinement of the explosive body. To model what may happen after a thermal explosion we use our PDSR ($=$ Pressure Dependent Shear Reaction) together with our TDRR ($=$ Temperature Dependent Reaction Rate) reactive flow models. For each computational cell these two models work in sequence. Initially there is a shear reaction handled by PDSR. If, as a result, pressure and temperature there go beyond the threshold for reaction out of hot spots, TDRR takes over irreversibly (for that cell), to compute shock initiation and detonation. We present computed examples of outcomes of different thermal explosion events. [Preview Abstract] |
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F1.00030: Modeling Ratchet Growth as Porosity Creep Yehuda Partom Irreversible thermal cycling growth (or ratchet growth) of insensitive explosive formulations has been known for years. Traditionally it's attributed to material texture and to anisotropic thermal expansion. Although this understanding has been accepted for a long time, we're not aware of any model on the macroscale to connect these material properties to ratchet growth behavior. Thompson et al. [1] have observed that they also get growth from a long hold time at high temperature, and that such growth resembles creep response. Following their findings we propose here a predictive model for ratchet growth on the macroscale, where we assume that when temperature is increased, growth comes about by \underline {porosity (or volume) creep}. As is well known, PBXs are prepared by die or isostatic pressing, and at the end of such pressing the material is left at porosity of about 2{\%}, and with a substantial residual or internal stress fluctuations in self-equilibrium. We model ratchet growth by assuming that: 1) increasing temperature decreases porosity (or volume) strength in tension (negative pressure), causing the material (in a control volume) that is in tension to creep (slowly increase), and 2) increasing temperature increases the internal pressure/tension fluctuations because of thermal expansion anisotropy, thereby enhancing the rate of porosity creep and ratchet growth. We write down equations for porosity creep and the resulting ratchet growth, and we demonstrate that our modeled ratchet growth results are similar to test data. We do not calibrate the free parameters of our model to reproduce specific data, as we do not own such data. [Preview Abstract] |
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F1.00031: Thermal Stability of Solid and Molten Erythritol Tetranitrate (ETN) Daniel McDonald, Nicholas Lease, Geoffrey Brown, Bryce Tappan, Virginia Manner Erythritol tetranitrate (ETN) is a melt-castable, solid explosive with significant performance, similar to the established nitrate ester, pentaerythritol tetranitrate (PETN). Recent advances in synthesis coupled with the ease of procurement of erythritol make ETN a readily made improvised explosive, although research and development of the material has advanced as well. Uses of ETN in its molten form include additive manufacturing and melt-casting of explosive parts, which could expand the capabilities of munitions manufacturing and research not previously available. Because of the increased use and development of ETN, we have recently begun studying its thermal stability in the molten state. We report here the thermal stability and impact sensitivity of ETN at elevated temperature, and discuss the decomposition characteristics of batches prepared with different methods and purity. Specifically, we will discuss thermal stability at varying temperatures using Automatic Pressure Tracking Adiabatic Calorimetry (APTAC), differential scanning calorimetry (DSC), along with drop-weight impact sensitivity in the molten state. [Preview Abstract] |
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F1.00032: Double Shock in Polystyrene Zaire K. Sprowal, Thomas Boehly Boehly, Danae Polsin, Damien Hicks, J. Ryan Rygg, Gilbert Collins, Margaret Huff We present the findings of a double-shock experiment in polystyrene, where the reflectance of the second shock front through the transparent first shock was observed in addition to the resulting single shock. We deduce transport and optical properties of the double-shocked material with data obtained from the VISAR (velocity interferometer system for any reflector) and the SOP (streaked optical pyrometer) diagnostics. We conclude with a comparison of our findings to previous single-shock data conducted on polystyrene. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856, the University of Rochester, and the New York State Energy Research and Development Authority. [Preview Abstract] |
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F1.00033: Impactful Times: Memories of 60 Years of Shock Wave Research at Sandia National Laboratories Mary Ann Sweeney, James R. Asay, Lalit C. Chhabildas, R. Jeffery Lawrence Sandia National Laboratories' origin~began during World War II. In July 1945 our forerunner, Sandia Base,~was established to develop, test, and assemble non-nuclear parts of weapons. Shock~wave research became essential in the 1950s with the advent of supersonic and exoatmospheric missiles. A major concern was effects of radiation-produced shocks on materials. As a result, we developed a wide range of experimental, diagnostic, modeling, and computational capabilities. These have addressed complex issues related to both weapons and basic science. Notable applications have included analysis of the cause of the turret explosion aboard the USS Iowa, predicting the response to the Shoemaker-Levy comet impact on Jupiter, and evidence for an abrupt transition of dense liquid hydrogen from an insulator to a metal~at high pressures.~Six decades later, our research encompasses all aspects of material science from~high energy density physics to low density plasma surface interactions. [Preview Abstract] |
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F1.00034: Shock-Compressed Methane to 400 GPa G. Tabak, T. R. Boehly, G. W. Collins, L. Crandall, B. J. Henderson, J. R. Rygg, M. Zaghoo, M. Millot, S. Ali, P. M. Celliers, J. H. Eggert, D. E. Fratanduono, S. Hamel, A. Lazicki, D. C. Swift, S. Brygoo, P. Loubeyre, R. Kodama, K. Miyanishi, T. Ogawa, N. Ozaki, T. Sano, R. Jeanloz, D. G. Hicks Methane plays an important role in planetary physics and is a major constituent of giant planet atmospheres. Methane is predicted to have an intricate phase diagram at high pressures, including the conditions inside planet interiors.\footnote{ M. Ross, Nature \textbf{292}, 435 (1981).\par $^{\mathrm{2}}$ M. Ross and F. Rogers, Phys. Rev. B \textbf{74}, 024103 (2006).\par $^{\mathrm{3}}$ G. Gao \textit{et al.}, J. Chem. Phys. \textbf{133}, 144508 (2010).}$^{\mathrm{-3}}$ We present shock-compression data to 400~GPa for methane. The methane samples were precompressed in a diamond-anvil cell to access a broader range of extreme conditions. Data are referenced to a quartz standard. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856, the University of Rochester, and the New York State Energy Research and Development Authority. [Preview Abstract] |
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F1.00035: Examination of Shaped Charge Performance with ECAP Produced Liners Roy Ceder, Vitaly Leus, Yuri Khoptiar Shaped charge liner fabrication processes can improve penetration capabilities. For example, whether a liner has been machined, flow-turned or cold pressed can alter the liner material microstructure and in turn influence the jet elongation ability and its penetration capability. In this work we compare the performance of shaped charges with liners machined from copper processed by Equal Chanel Angular Pressing (ECAP) and from raw copper. We examine how the ECAP process affects the copper mechanical properties and microstructure, in particular, it is shown that the grain size is substantially decreased. The effect on the shaped charge performance for the two fabrication routs is explored through hydrocode simulations and experimental tests. We show that the ECAP process influences both jet ductility and breakup parameters compared to simple machining from raw material. [Preview Abstract] |
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F1.00036: Ejecta from Liquid Gallium During Planar Impact Experiments Jason Loiseau, Justin Huneault, William Georges, Andrew J. Higgins When a solid or liquid metal surface is subject to shock loading, asperities at the interface grow from Richtmyer--Meshkov instability, leading to ejecta from the free surface. In the present study, we impacted liquid gallium samples contained in sealed, evacuated capsules using explosively-driven steel flyer plates. Gallium free surface velocity and ejecta cloud velocity were recorded using photonic Doppler velocimetry and ejecta flux was measured with Dynasen piezeoelectric pins. For the incident shock strengths considered experimentally, no pull-back or strength-based arrest of the ejecta cloud was observed. This indicated minimal spall strength for melted Gallium. Ejecta areal density versus ejecta cloud velocity was extracted from integration of the pin voltage response assuming inelastic collision. Mass flux versus normalized ejecta velocity was broadly consistent with results reported for other shock-loaded metals that melt on release. [Preview Abstract] |
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F1.00037: Microstructure-based hypervelocity impact simulations of additively manufactured composite shielding Manny Gonzales, Lauren Poole, Matthew French, William Yarberry, Zachary Cordero It is desirable for lightweight armor to defeat projectile impact events through dispersion and dissipation mechanisms intrinsic to its design. Microstructural control afforded by additive manufacturing techniques can provide a topologically-dispersive armor material in a dimensionally-compact form. The dispersive response of a dual-phase interpenetrating metallic composite manufactured through a two-step processing approach is evaluated in this work via microstructure-based hydrocode simulations to assess its ability to dissipate shock compression and disperse shock waves. Real microstructures obtained via x-ray computed tomography are used to simulate hypervelocity impact experiments at a range of impact velocities in both 2D and 3D. The wave dispersion, rear spall, and dissipation in an interpenetrating composite are compared with experimental results and simulations of simpler lamellar configurations. The geometric origins of the dispersive properties of this composite are also discussed. [Preview Abstract] |
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F1.00038: Effects of metal/air barriers on sympathetic detonation mitigation Shawn Strickland, Robert Reeves, Clifton Mortenson, Dennis Baum, Bob Nafzinger, Kevin Hood The initiation of an explosive by the inadvertent or indirect transfer of a shock from a nearby explosive is known as sympathetic detonation and has significant implications to the safe handling and storage of explosives. In this study, the limits of sympathetic detonation mitigation by using metal/air/metal layered barriers to separate detonating explosives are explored. In the presented experiments, steel substrates containing the channel and barrier geometries were 3-D printed. The channels were filled with an HMX-based, cast-curable explosive. In these designs the steel barrier walls had material thicknesses varying from 0.35 to 1.2mm with air gaps from 0.7 to 1.8 mm wide. In sweeping through these parameters, we will look for to onset of sympathetic detonation of an HMX-based high explosive in channels separated by metal/air/metal barriers. The experiment utilizes piezo timing pins and high-speed imaging to track the detonation front and determine if sympathetic detonation occurs between channels. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-768320 [Preview Abstract] |
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F1.00039: Microstructure Effects on the Spall Response and Failure Mechanisms of Additively Manufactured Stainless Steel 316L (SS316L) Katie Koube, Kaila Bertsch, Greg Kennedy, Dan Thoma, Josh Kacher, Naresh Thadhani The influence of microstructure on the spall response of SS316L made via Powder Bed Fabrication (PBF) is investigated. The PBF fabrication process introduces columnar grain texture, dendritic chemical segregation, and porosity. The effect of initial defect structures and the crystallographic texture relative to shock wave propagation direction can lead to varied spall properties and failure responses. The present work is focused on determining the role of heterogeneities and process-inherent defects on the dynamic tensile and spall failure of PBF SS316L. Plate-impact experiments are performed at various impact velocities to generate varying degrees of spall failure using an 80-mm gas gun. The target fixture employees two samples; one sample is backed with PDV and VISAR probes to measure the spall properties. The other sample is soft recovered in the catch tank for post mortem microstructure characterization. EBSD and TEM are used to determine the role of PBF processing on spall initiation and propagation and are analyzed in comparison to the spall response of conventionally-manufactured steels. [Preview Abstract] |
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F1.00040: Commissioning of a Fiber-Coupled Equation-of-State Diagnostics Package in the UC Davis Shock Compression Lab Meral Basit, Dylan Spaulding, Erik Davies, Sarah Stewart Impact surface area in light gas gun experiments is constrained, particularly at high velocities where low-mass, small-diameter projectiles are required. Here, we present recent developments for equation-of-state (EOS) experiments using all fiber-coupled diagnostics on the UC Davis two-stage light gas gun. We have recently commissioned a compact commercial Photon Doppler Velocimeter (PDV), a streaked optical spectrometer (350-850 nm) and have modified a visible/NIR 6-channel pyrometer (650-5000 nm) for flexible simultaneous velocimetry and broadband temperature measurements. All diagnostics are fiber-coupled, allowing for flexible configuration and multi-point measurement in a compact target design and simultaneous pressure/temperature observations for complete EOS studies. [Preview Abstract] |
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F1.00041: Experimental Beamline Endstation Concepts for a Dynamic Mesoscale Materials Science Capability Jen Bohon, Adrianna Ortega, Cris W. Barnes, Richard L. Sheffield, Joseph A. O'Toole There is a recognized need for a Dynamic Mesoscale Materials Science Capability (DMMSC) to enable characterization, production and control of matter in extreme conditions. This is currently envisioned to take advantage of a high-energy coherent brilliant x-ray light source with a flexible pulse structure in time, with the potential for simultaneous additional probe particles. Programs demanding this capability can have dramatically different requirements for instrumentation and sample environments, creating a unique challenge for experimental systems design. Here, we introduce design concepts, leveraging experience gained from existing facilities, to optimize both beamline efficiency and flexibility using automation and exchangeable platforms. Such concepts will allow users to place different sample environments, instrument diagnostics and probes into the endstation between experimental campaigns, providing the possibility of performing sequences of unique experiments without significantly reducing available beamtime. The DMMSC aims to provide a comprehensive capability for materials discovery; input from the user community on design directions and desired functionality will be essential to maximize the impact of the new facility. [Preview Abstract] |
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F1.00042: Designing a novel perforated diamond anvil for laser-driven shock wave experiments with pre-compressed samples N. Nissim, G. Oren, L. Perelmutter, M. Werdiger, S. Eliezer, N. Sapir, M. Gorman, S. Ali, R. Smith, R. Jeanloz Performing laser-driven shock experiments with significantly increased static pre-compression provides access to far more compressed states than ever before. Specifically, using a new design we have developed for the diamond-anvil cell (DAC) that includes a partially perforated diamond anvil [1,2], allows us to generate 10-20 GPa pre-compression (vs. \textasciitilde 5 GPa with current methods). This design will enable the study of the properties of matter at the thermodynamic conditions of planetary interiors to far greater densities and depths than possible with current methods. In this work we numerically study the effect that the designed geometry has on the plasma, and on the shock that is delivered to the sample. The simulation results were compared to experimental results of laser driven shock waves in partially perforated diamonds of different designs, performed at the Janus laser at LLNL. A qualitative correlation was found between the experiments and simulations, which allowed us to produce a scaling law for a desired laser spot diameter to hole diameter ratio. [1] N. Nissim, S. Eliezer, M. Werdiger, and L. Perelmutter, Laser Part. Beams 31, 73 (2013). [2] N. Nissim, S. Eliezer, and M. Werdiger, J. Appl. Phys. 115, 213503 (2014). [Preview Abstract] |
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F1.00043: Recent BLR development at CEA Aurélie Azzolina, Patrick Mercier, Estelle Dubreuil In shock physics experiments, the knowledge of displacement versus time is very useful. Since 2015, the CEA is designing BLR (Broadband Laser Ranging) diagnostic, in addition to PDV (Photonic Doppler Velocimetry) measurements. This first set up is composed of a 20 MHz locked modes picosecond laser, delivering an infrared beam ($\lambda =$1.55 \textmu m) with a broad spectrum ( $\Delta \lambda =$40 nm), followed by a Mach-Zehnder interferometer and a dispersion fiber, which expands the spectrum versus time. The signal is recorded by a 33 GHz-bandwidth detector and digitizer. The system is designed to sample every 50 ns for a few tens mm target displacement range. In the poster, we will present the BLR setup, the calibration method and the post-processing software. The system was qualified on a powder gun experiment (target velocity: 2 km/s). The results are discussed and compared to the PDV measurements. [Preview Abstract] |
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F1.00044: Conceptual studies of a high-energy X-ray detector system for MaRIE/DMMSC Yancey Sechrest, John L. Barber, Chris W. Barnes, Jen Bohon, Chen Hu, Xuan Li, Quinn Looker, J. L. Porter, Liyuan Zhang, Renyuan Zhu, Zhehui Wang Current X-ray imaging cameras used in synchrotrons, such as the Advanced Photon Source (APS), and X-ray free-electron lasers, such as the Linac Coherent Light Source (LCLS), are limited to $\le $ 10 MHz frame-rate. Higher frame-rate, $\ge $100 MHz, X-ray cameras are recognized as an enabling technology for science applications at next-generation X-ray sources such as APS-U, LCLS-II, and Dynamic Mesoscale Material Science Capability (DMMSC, formerly MaRIE). In addition to an order of magnitude higher frame-rate, other requirements include: high-efficiency detection of high-energy (\textgreater 20 keV) photons, and sufficiently high spatial resolution. The necessary camera performance also depends on the scattering object/target under dynamic compression. Here, we summarize detector system requirements for DMMSC as a function of scattering angle, detector-target distance and other parameters. We conclude that a combination of different detector systems will allow the optimal capture of scattered X-rays over nearly the entire 4-pi solid angle. Possible alternative detector designs are presented, and community input is sought on best approaches to optimize the data yield from dynamic material experiments using high energy X-rays. [Preview Abstract] |
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F1.00045: Developing high performance preheating devices for ramp compression experiments on high pulsed powers drivers Thierry D'Almeida, Jérémy Vich, Gael Le Blanc, Camille Chauvin, Thierry Duvaut The CEA operates several High-Pulsed Power (HPP) drivers dedicated to Isentropic Compression Experiments (ICE). In these experiments, various types of materials are magnetically ramp-compressed to stress levels ranging from few kilobars to 1 Mbar. Several diagnostics, including laser Doppler interferometers, pyrometers and stress gauges, are fielded in order to characterize materials of interest in these quasi-isentropic states. The latter are usually produced starting from ambient conditions. Ramp compressing samples from various non ambient initial temperatures can significantly extend the range of our studies into previously unexplored thermodynamic paths and help constrain Equation of State models incorporated in numerical codes. Attempts to couple reliable, high performance pre-heating devices with HPP drivers have encountered numbers of technical limitations due to restricting experimental configurations and to severe electromagnetic environments associated with operations on HPP platforms. We have developed a novel configuration which allows nonmetallic and metallic samples to be heated to several hundred degrees with satisfying temperature uniformity and stability prior to their loading. A detailed description of these new devices is presented. Their performances and robustness are potentially valuable for extending the range of thermodynamic paths achievable under ramp loading using high pulsed power drivers in the near future [Preview Abstract] |
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F1.00046: Modernization of Los Alamos Impact Facilities: From Ancho Canyon to the new Dynamic Equation-of-State Facility (DEOS John wright, Joseph Rivera, Santiago Martinez, William Anderson, Braian Jensen Los Alamos National Laboratory (LANL) researchers have played key roles in the development of high-pressure science and shock physics since the 1950s. At the heart of the laboratory's experimental capabilities are multiple gun systems that span impact velocities from a 100 m/s up to those in excess of 8 km/s. In recent years, there has been a focus on modernizing this important capability from creating a new shock physics facility and upgrading the standard suite of diagnostics to modernizing the gun platforms themselves. In this poster, we present a history of the shock physics capabilities at LANL beginning with those in Ancho Canyon to the new Dynamic Equation-of-State (DEOS) facility currently in commissioning. The DEOS facility research will continue to lead efforts to study high-pressure phenomena including phase transitions and kinetics, strength and damage, and compaction for a wide range of materials from single crystals to polycrystalline metals and granular systems. [Preview Abstract] |
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F1.00047: Temperature control in shock physics experiments Santiago Martinez Recent efforts to upgrade and modernize shock compression facilities at Los Alamos National Laboratory includes the development of the new Dynamic Equation-of-State (DEOS) impact laboratory. This facility will consolidate the legacy gun systems that have operated in Ancho Canyon since the 1960s with new impact systems that support research around the complex including the TA-55 40mm powder gun, the pRad 40mm powder gun, and experiments at the Advanced Photon Source (Argonne, IL). A significant part of this is the development and modernization of diagnostics including radiance and velocimetry, and the ability to pre-heat and pre-cool targets prior to impact. The latter allows researchers to access different regions of the phase diagram (off the room temperature Hugoniot) to study shock-induced phenomena including solid-solid phase transitions, shock-induced melting, and strength {\&} damage effects, for example. In this presentation, we highlight our target preheating/cooling system available at the new DEOS facility. Bench-top testing that shows required cooling/heating rates, sample fabrication, and test experiments designed to study the melt boundary in materials will be presented. [Preview Abstract] |
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F1.00048: Construction and Calibration of a Streaked Optical Spectrometer for Shock Temperature Dylan Spaulding, Erik Davies, Sarah Stewart The UC Davis Shock Compression lab houses two light gas guns which are primarily applied towards equation-of-state and dynamic temperature measurements on shock and release to study mechanical and thermodynamic properties of geophysical samples. Here we describe the implementation and calibration of a temporally and spectrally-resolved spectrometer for studies of shock temperature, optical properties and/or emission/absorption spectroscopy. The system is based on an Optronis SC20 streak camera (permitting observation windows from 280ns to 700usec with 2K x 2K, 16-bit resolution) coupled to a Princeton Instruments SpectraPro HRS300 spectrometer with custom injection optics and secondary beam path for alignment and calibration. The overall system response permits observation from 400 - 850 nm with \textasciitilde nm spectral resolution. Fiber-optic coupling to the sample enables a small diagnostic footprint on the target and flexibility and operation on either of our light gas gun platforms without the need for open optics. We present details of absolute calibration using a tungsten-halogen spectral radiance standard as well as tunable blackbody source, line emission sources and optical comb generator. [Preview Abstract] |
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F1.00049: High Speed Microscopic Imaging of Initiation and Propagation of Adiabatic Shear Bands Pinkesh Malhotra, Pradeep Guduru We present an experimental technique to image the deformation fields associated with dynamic failure events such as adiabatic shear band initiation and propagation at high spatial and temporal resolutions simultaneously. The temporal resolution of the experimental system is 250 ns and the spatial resolution is $\sim $1$\mu $m, while maintaining a relatively large field of view ($\sim $1.11 mm x 0.63 mm). The experimental capability is used to resolve the deformation field near a notch tip at micron scale to identify the conditions for initiation of an adiabatic shear instability and the deformation field associated with a propagating shear band in polycarbonate and a martensitic stainless steel. An ordered array of 10 $\mu $m diameter speckles deposited on the sample surface near the notch tip serve as markers to track evolution of deformation field. The combination of high spatial and temporal resolutions allows us to study the role of microstructural heterogeneities on initiation and propagation of dynamic failure events. [Preview Abstract] |
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F1.00050: Technology Advancements in Digitizers: More then 8-bits, ultra-low noise and high ENOB Brian Hensley The Tektronix ASIC development team spent years designing and developing the Tek049, to consolidate a wide range of previously separate chips into a single, highly-integrated package. The chip includes advanced ADCs, a high-speed memory interface, high-speed communication bus, trigger circuitry, logic analysis, display formatting, rasterization, and other DSP components.
The new 12-bit ADC is the fastest in the world, running internally at 25 GS/ and with 12 bits allow for 4096 vertical digitizing levels, providing 16x more resolution than other oscilloscopes and digitizers in its performance range that typically utilize 8-bit ADCs. Each Tek049 includes four ADCs for a total throughput of 100 GS/s. Typical digitizer signal paths are quite complicated, as signals must pass through a variety of components including amplifiers, relays, filters, ADCs, and more before being processed for display.
Furthermore, this new technology is paving the way for next generation digitizers with more performance, in less rack space. The next gen digitizers from Tektronix were specifically designed with the physics market. Labs such as Sandia, Los Alamos and Livermore were consulted for the use of diagnostics and monitoring needs.
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F1.00051: Software for Simulation and Processing Photonic Doppler Velocimetry data and system characterization. Nikola Stan Traverse PDV Tools software instructs the user on how to characterize heterodyne photonic Doppler velocimetry (PDV) measurements systems in terms of frequency shifts based on estimated experiment velocities. The software answers the question that is often asked, ``Is the hardware available capable of measuring this velocity?'' The software is also a tool for extracting velocity information from the measured PDV data. The program uses discrete short-time Fourier transform approach to extract data and is entirely written in Python. [Preview Abstract] |
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F1.00052: Modeling of ultrashort pulsed laser induced stress field evolution. Jiamin Liu, Hao Jiang, Shiyuan Liu The energy deposition process and the mechanical response of materials under ultrashort pulsed laser irradiation are usually analyzed using Two Temperature Model combined with elasticity. However, the neglect of the dynamic optical property changes, the electron kinetic pressure and the dimensional effects may lead to the underestimation of the magnitude and the propagation length of laser-induced stress wave. Herein, we have propose a theoretical model to describe the interaction mechanism between the ultrashort pulsed laser and material, in which the effects of temperature-dependent optical constants on the energy deposition process and the contribution of electron hot-pressure to stress wave have been considered. The proposed model implemented based on the 3D implicit finite difference algorithm is then carried out to achieve the profile of stress field. The simulation results show that the maximum stress and the distribution depth achieved by the proposed method are both larger than the results of conventional method, with the increased percentage of 10{\%} and 24{\%}, respectively. [Preview Abstract] |
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F1.00053: Proton radiography of a double shock into cerium to get densities of the second shock state Frank Cherne, Brian Jensen, Zhaowen Tang, Matthew Freeman In traditional shock physics, the determination of density variations are inferred by applying the standard Rankine-Hugoniot jump conditions. Proton radiography (pRad) at LANL allows the direct measurement of density along with traditional particle and shock velocities via velocimetry. The introduction of the 40-mm powder driven gas gun in 2017 allows us to deliver well characterized shock profiles into a variety of materials. In this particular set of experiments, it will be shown that the densities obtained agree with a recently developed two-phase Mie-Gruneisen model for cerium. The model was tuned to capture the slowing down of the shock wave speed attributed to the crossing of the $\alpha-\epsilon$ phase boundary of cerium. Temperature measurements looking at similar shock loadings also suggest that we are below the melt boundary. In general, there is a good agreement between the calculations and the experimental densities in spite of the low proton transmission through the cerium samples. [Preview Abstract] |
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F1.00054: Explosive vessel for Synchrotron Experiments Joseph Rivera Recent experiments at the Advanced Photon Source have been successful in coupling gun systems to the synchrotron to take advantage of the X-ray diagnostics such as X-ray diffraction and X-ray phase contrast imaging (PCI) to examine matter at extreme conditions. There are many experiments that require explosive loading capabilities in addition to gun systems, e.g. detonator and initiator dynamics, small angle X-ray scattering (SAXS), and explosively driven flyer experiments. The current work highlights the qualification and commissioning of an explosive vessel that was designed specifically for use at a synchrotron facility with a requirement to confine up to 15 grams of explosives (TNT equivalent), couple the vessel to the X-ray beam line, and reliably position samples in the X-ray beam remotely. A description of this new, mobile capability including the remote positioning system, the vacuum/venting manifold, and results from qualification testing required to commission the system will be presented. [Preview Abstract] |
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F1.00055: Quantum dots as optomechanical sensors for mesoscale time-resolved probing of pressure during shock-compression of heterogeneous materials Karla Wagner, Gill Biesold-McGee, Greg Kennedy, Didier Montaigne, Zhitao Kang, Zhiqun Lin, Naresh Thadhani We are exploring quantum dots (QDs) as optomechanical sensors for mesoscale time-resolved sensing of pressure during shock-compression of heterogeneous materials. QDs are nanoscale semiconductors with size-dependent characteristic emission associated with band gap energy changes due to quantum confinement effects. Our past work (Kang et al., 2016) shows that QDs exhibit unique optical properties under shock compression, and show spectral intensity change and blueshift that scale with pressure. In the present work, various QDs (e.g. lead halide perovskite, gradient composition) are investigated to determine their response to shock-compression. QDs suspended in a polymer matrix are shock-compressed using a 3J Nd-YAG laser, while a UV laser excites the QDs. The time-resolved shifts in the photoemission of the QDs due to band-gap increase associated with compression is monitored by a streak camera and correlated with simultaneous measurements of particle velocity using Photon Doppler Velocimetry. The goal is to identify and calibrate the response of the various QDs used to record heterogeneous pressures. Results obtained to date will be presented. This project is funded by DTRA grant HDTRA-18-1-004. [Preview Abstract] |
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F1.00056: 6D Metaimaging; a new frontier for National Facility Science Christoph Rau, Michael Baker, Sarah Batts, Neil Bourne, Sofia Diaz-moreno, David Eastwood, Alex Greenaway, Sara Nonni, Christopher Parlett, Kalpani Vitherana, Paul Wady, Robert Weatherup We have created a portal to extreme science at the UK national laboratory site at Harwell (University of Manchester at Harwell; UoMaH). This partnership, between the UoM, STFC and DLS has created a core team to assist users and work with the facilities to drive innovation. Further, we have recruited ten fellows, each championing a strategic area, to build teams, grow and populate each theme. We are on course to create an international beacon across national facilities science, partnering with stakeholders and other research establishments. We work with other national labs around an agreed joint theme; \textit{meta-imaging}. This is the means to observe a structure and probe its mechanical state in 3D under differing applied electromagnetic fields, to determine the elemental and electronic state of constituent phases as a function of time; the 6D metaimaging of extreme dynamic behaviour. By combining sources (neutrons and X rays) and data analytics, we track chemical, mechanical and biological states, so mapping the \textit{genome of structures} in six dimensions$.$ [Preview Abstract] |
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F1.00057: Triboluminescent Sensor for Detection of Impacts of Sub-millimeter Explosion Fragments Geoffrey Chase, Sam Goroshin, David L. Frost Fine metallic fragments in the millimeter and submillimeter size ranges may result from high-velocity impact with an obstacle or from explosive dispersal. The size, velocity, and spatial distribution of the fine fragments are difficult to determine with available diagnostic systems. A novel detector based on a high-sensitivity triboluminescent screen that is developed and described in this paper can, in principle, fill this niche. The light-generating impact screen utilizes a triboluminescent manganese-doped zinc sulfide (ZnS:Mn) powder. The polycrystalline bulk material is synthesized in-house using the self-propagating high-temperature synthesis reaction between sulfur and manganese. The multilayered sensor screen is comprised of aluminum foil, a mono-layer of coarse polycrystalline particles, and transparent backing. The sensor is optically coupled to a photomultiplier via a fiber optic taper. The operation of the system is demonstrated by impacting the screen with spherical projectiles of different density in the 0.5--1.2 mm size range accelerated by a helium-driven light gas gun to speeds in the 0.2--1 km/s range. [Preview Abstract] |
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F1.00058: Correction of Flyer Velocimetry Traces for Experiments with Large Taylor Angles Jason Loiseau, XiaoCheng Mi, Andrew J. Higgins When a confining metal is accelerated by a grazing detonation it is launched outwards at an angle relative to its initial orientation. Consequently, the metal velocity vector contains both a lateral and longitudinal component. Since photonic Doppler velocimetry (PDV) can only resolve the component of velocity aligned with the collimated beam, recorded velocities must be corrected for this angular and longitudinal motion to obtain actual velocity and casing shape. Correction is particularly important for fitting detonation product equations of state. For standardized configurations like the cylinder test, the angle of tilt is small (typically less than 15 degrees). The error involved in approximative corrections in these configurations is thus negligible. However, if very thin flyers are launched, the tilt angles can approach 45 degrees and thus the magnitude of the correction becomes large. In the present study, we consider tilt-correction of PDV histories for explosively driven flyer experiments where large tilt angles were observed. We adapted the vector decomposition from Taylor's tubular bomb model, in addition to a Galilean transformation to account for translation of the steady, detonation-fixed wall expansion past a stationary, laterally observing PDV probe. Additionally, multiphase numerical simulations were used to validate the assumed relationship between the longitudinal and lateral components of the wall velocity, especially early in detonation product expansion. [Preview Abstract] |
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F1.00059: A Method for Obtaining Melt Curves using Laser Compression and X-Ray Diffraction Caroline Lumsdon, Andrew Higginbotham The phase boundary between solid and liquid is a key material property, influencing for example, planetary structures. In extremis, such as pressure relevant to supergiant planets, dynamic processes such as laser compression are generally necessary to reach the conditions of interest. In these experiments, x-ray diffraction can be recorded from solid and liquid material as the system crosses the P-T conditions of the melt curve, and thus the density in the two systems is directly measured. The densities and coexistence condition taken together allow the thermodynamic conditions on the melt curve to be constrained. However, since the melting temperature is dependent on the heating (and therefore loading) rate of the material care must be taken in interpreting dynamically determined melt curves. We present molecular dynamics simulations of dynamic melting during compression and release of samples. By utilising a dynamic-tamper technique we are able to simulate, at low computational cost, the effect of tamper material on release rate, and to investigate the effect of melting kinetics on observed melt onset. We will discuss the feasibility of experimental approaches to dynamic determination of melt curves, and of measuring melting kinetics. [Preview Abstract] |
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F1.00060: Dynamic compression of magnesium hydride in ultrahigh pressure regime using high intensity laser Shintaro Morioka, Norimasa Ozaki, Takuo Okuchi, Takayoshi Sano, Kohei Miyanishi, Yuhei Umeda, Kento Katagiri, Nobuki Kamimura, Ryosuke Kodama Hydrogen is the most abundant atom in the universe. It has many fascinating features. It is also known that hydride has interesting physical properties. In fact, it has been reported that hydrogen sulfide (H$_{\mathrm{2}}$S) undergoes structural change under static super-high pressure (approximately 150 GPa) and shows an extremely high Tc (203 K). Studies of hydride can lead to understand not only hydride but also hydrogen. In order to understand behavior of hydride in extreme conditions, the experimental data of hydride in the high-pressure region is necessary. In this study, we present the first high-pressure experiment on MgH$_{\mathrm{2}}$ hydride using laser-driven shock wave. The shock velocity and temperature were measured by VISAR and SOP. We obtained shock Hugoniot data of MgH$_{\mathrm{2}}$ up to 350 GPa using laser-driven shock waves. The obtained data were analyzed with following method to determine more reliable EOS data. Firstly, the mean velocity was calculated from the measurements of the initial sample thickness and shock transit time as a primitive shock velocity. Secondly, the shock velocity was updated by taking account of the effect of decay shock in MgH$_{\mathrm{2}}$ using the polystyrene as a witness and the rear-Qz. [Preview Abstract] |
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F1.00061: ABSTRACT WITHDRAWN |
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F1.00062: Ultrafast Spectroscopic Studies of Vibrational Energy Transfer in Energetic Materials Neil Cole-Filipiak, Michael Marquez, Robert Knepper, Robert Harmon, Paul Schrader, Mitchell Wood, Krupa Ramasesha Shock-induced detonation is a key property of energetic materials (EM) that remains poorly understood. We are developing novel ultrafast laser spectroscopy techniques to test one mechanism of shock-initiation in EM, the ``thermal'' mechanism, where shock excitation of lattice phonon modes is hypothesized to transfer energy to intramolecular vibrations resulting in breaking of chemical bonds and reaction. Using ultrafast pump-probe spectroscopy, we are studying vibrational energy transfer from phonon modes to intramolecular vibrations (phonon up-pumping), as well as from intramolecular vibrations to phonon modes (vibrational cooling) that competes with phonon up-pumping. Through combinations of plasma-generated supercontinuum infrared (IR; 3-15 um), tunable near infrared (1.2-2.6 um), and terahertz (THz; 100-1000 um) pulses in pump-probe spectroscopy, we explore the energy transfer processes on a sub-picosecond time scale. Theoretical work is being performed in parallel using a combination of Density Functional Theory and Molecular Dynamics Simulations to elucidate vibrational energy transfer pathways and lifetimes in EM. Here we highlight the progress to date, including the spectral and temporal characteristics of the IR and THz sources as well as preliminary results on EM. [Preview Abstract] |
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F1.00063: In situ X-ray diffraction of shock-compressed diamondoid Sovanndara Hok, Sulgiye Park, Arianna Gleason, Suzanne Ali, Dylan Rittman, Feng Ke, Jeremy Dahl, Robert Carlson, Eric Galtier, Nir Goldman, Wendy Mao, Yu Lin Diamondoids are a unique class of materials with a general chemical formula of C$_{\mathrm{4n+6}}$H$_{\mathrm{4n+12\thinspace }}$and have hydrogen terminated structures superimposable onto a diamond lattice. Static compression of lower diamondoids (ada-, dia- and tria-mantane) revealed diamond synthesis at significantly reduced transformation energy compared with conventional carbon phases. For instance, at 15 GPa, triamantane transforms to diamond at 1200 K, while \textgreater 2000 K is required for graphite-to-diamond transition [1, 2]. We investigated the effects of polymorphism and intermediate phases on the diamondoid-to-diamond transformation using laser-driven shock compression in the Matter in Extreme Conditions end-station at the Linac Coherent Light Source. Sub-picosecond time-resolved X-ray diffraction on four diamondoids allowed for direct structural characterization of intermediate phases that lead to diamond transformation. Our preliminary results show pressure-induced amorphization of diamondoid before recrystallization to diamond. [1]T. Irifune \textit{et al.}, \quad Physics of the Earth and Planetary Interiors \textbf{143--144}, 593 (2004). [2] S. Park \textit{et al.}, manuscript submitted [Preview Abstract] |
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F1.00064: Development and Characterisation of a Sapphire Material Graded Areal Density Ramp Loading System Michael Goff, Simon Finnegan, Jeremy Millett, James Ferguson A gas gun launched sapphire material ramp loading system has been experimentally tested and the results compared to 3-D SPH modelling. Impacts onto lithium fluoride targets were performed at 200-700 ms$^{\mathrm{-1}}$ and spatially separated Het-V probes observing the buffer/target interface showed that the loading was predominantly uniform across the 1-D zone of the target. The duration of the ramp varied over a range of a few microseconds depending on impact velocity and buffer thickness. These findings offer confirmation of the methodology functioning as intended that was not apparent from previous embedded PV gauge or single Het-V probe experiments using previous iterations of this method. In this technique, a flyer with a graded areal density spiked surface is impacted into a flat disc buffer of similar material using a gas gun, multiple wavelets are formed which coalesce in the buffer. This leads to a ramped/quasi-isentropic loading entering the target which is in intimate contact with the buffer. In these experiments, the flyers were constructed from machined Z-cut sapphire material offering a superior build quality to previous rapid prototype alumina examples. Good agreement was observed between Autodyn 3-D SPH modelling and experimental results, with the exception of low velocity impacts where it is apparent that the material strength models need further tuning. \copyright British Crown Owned Copyright 2019/AWE [Preview Abstract] |
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F1.00065: Results on preheated shock and ramp compressed material: experiments on Tin. Camille Chauvin, Thierry D'Almeida We propose to study experimentally the polymorphic transition of Tin under dynamic compression from non-ambient conditions. CEA Gramat operates several gas guns for shock loading and high pulsed power (HPP) drivers dedicated to Isentropic Compression Experiments (ICE) up to several GPa. These experimental devices associated with diagnostics (velocimetry and temperature measurements) help to begin to study kinetics under dynamic transition in a more rigorous manner verified on various compression paths and contribute to constrain equation of state (EOS) models incorporated in our numerical codes. The latter is usually produced starting from ambient conditions and loading metallic materials from various non ambient initial temperatures can significantly extend the range of our studies into previously unexplored thermodynamic paths. We have improved our understanding of such phase transformations through both experimental and theoritical means. Experimental velocity measurements have long suggested kinetics is an important part of the dynamic compression response of materials undergoing phase transformations. Empirical kinetic models can in a lot of cases reproduce the experimental velocity profiles but without clearly identifying the nature of the transition. [Preview Abstract] |
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F1.00066: An Explosively-Driven Multi-Flyer System for Investigating Fragment Impact Initiation of PBXs John Yeager, Patrick Bowden, Andrew Schmalzer, Joseph Lichthardt Recent experimental testing found that plastic-bonded explosives (PBX) can be initiated by metal-cupped detonators in a non-contact ``standoff'' configuration. Depending on the detonator type, and high explosive (HE) driver (e.g. PETN, HMX, or PBX 9407), a stochastic field of sub-mm fragments is generated which travel initially \textgreater 3 km/s. Determining the initiation mechanism in this scenario for the target PBX materials is difficult; the interplay between fragment size/shape, incident angle and velocity creates a highly complex variable set. Since each detonator cup breaks apart stochastically, each test potentially probes different initiation mechanisms; e.g. single large fragment versus multiple smaller fragments generating shock coalescence leading to detonation. To attempt to simplify this problem, and enable new hydrocode simulations, experiments were undertaken to design and parameterize a flyer system capable of launching multiple small flyers of a standardized size and shape simultaneously. Additionally, with the large stochastic dataset in hand, elucidating a James-type criterion for initiation was gained for various PBXs. 3D Simulations using reactive burn models in the CTH hydrocode were also performed to guide the experimental design and help analyze ignition criteria. LA-UR-19-21652 [Preview Abstract] |
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F1.00067: Plate Impact-Based Isentropic Compression Driver. Amit Tsabary Isentropic compression experiments (ICE) are a powerful tool in the research of phase diagrams of materials, dynamic strength and equation of state. Current ramp (isentropic) compression drivers are based on pulsed high-current generators, high-intensity lasers or graded density impactors, made with advanced manufacturing techniques. We introduce a simple, easily implementable target design for (plain) plate-impact ICE experiments. The novel design gives a smooth ramp compression profile at its output, at a fraction of the cost and complexity of existing technologies. The velocity of the target's free surface was measured to give a characterization of the ramp profile, and the peak pressure was extracted to be above 1 megabar. [Preview Abstract] |
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F1.00068: Explosive Compaction of Additively Manufactured Material Phillip Mulligan, Cody Lough, Douglas Bristow, Ed Kinzel, Catherine Johnson Selective Laser Melting (SLM) is an additive manufacturing (AM) technique that uses a laser to locally fuse material in a metal-powder bed. The process is performed in layers enabling significant geometric freedom over traditional manufacturing techniques. During the deposition process, the metal is locally melted and rapidly self-quenched, leading to rapid solidification with well-defined melt-pool boundaries. Analogies are often drawn to the microstructure created in welding, albeit extending to the entire part. The SLM process parameters are optimized to produce full density metal parts. The process parameters can be adjusted to produce local regions that are of un-melted or partially melted powders. The ability to tailor the density (and corresponding modulus, yield strength, and ductility) continuously on a volumetric basis, has significant potential to engineer effective properties. This paper reports on an experimental study of AM metal components subjected to dynamic loading by detonating an explosive in intimate contact with the material. The crystallographic structural behavior of the parts is characterized before and after explosive loading in an explosive compaction test. The results are compared to previous metal powder compaction studies and predictive equations for material strength. The findings will aid in designing AM components for explosively loaded systems. [Preview Abstract] |
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F1.00069: The Influence of Hydrogen on the Dynamic Strength and Phase transition of SAE 1020 Steel. Benny Glam, Shalom Eliezer, Daniel Moreno, Fredi Simca, Lior Bakshi, Dan Eliezer In this research we investigate the influence of hydrogen on the dynamic strength and phase transition in SAE 1020 steel. Exposure of carbon steel to hydrogen creates gaseous methane in the sample according to the reaction Fe$_{\mathrm{3}}$C $+$ 4H CH$_{\mathrm{4}} \quad +$ 3Fe. Plate impact experiments were carried out in gas gun or powder gun to shock compress the samples to pressures below and above the phase transition, respectively. The Hugoniot elastic limit, phase transition pressure and spall strength were obtained from free surface velocity measured by VISAR. It seems evident from our experiments that the spall strength increases at pressures above the phase transition. [Preview Abstract] |
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F1.00070: In-situ X-Ray Diffraction of Shock-Compressed Boron Carbide, B$_{\mathrm{4}}$C Benny Glam, Sally June Tracy, Ray Smith, June Wicks, Thomas Duffy In situ x-ray diffraction measurements under laser-induced shock compression of polycrystalline B4C were carried out up to 145 GPa at the Matter in Extreme Conditions end-station of the Linac Coherent Light Source. There is no evidence for a major crystallographic phase transition over this range, but we do find evidence for possible partial amorphization of the sample. Possible splitting of (021) peak to two peaks with the same texture at pressures of 80 and 114 GPa, implying for a fault or a subtle phase transition. Our shock compression data on lattice parameters dependence on pressure is different than static compression. Our diffraction data is consistent with previous shock continuum measurements which found compressibility changes along the pressure-density Hugoniot, confirming they are not a result of a large-scale structural phase change. Density after release was found to be lower than ambient density, probably as a result of residual temperature. The HEL stress for B$_{\mathrm{4}}$C was found to be 15.9-19.5 GPa, in a good agreement with previous continuum measurements. [Preview Abstract] |
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