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 1D: Early Career / Student Poster Session |
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Room: Atrium |
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1D.00001: 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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1D.00002: Fast mid-infrared spectroscopy of gases: measurement method during a H$_{\mathrm{2}}$/O$_{\mathrm{2}}$ deflagration(symp) MARIE DABOS, KHANH-HUNG TRAN, NICOLAS LECYSYN, GERARD BAUDIN, MARC GENETIER, ISABELLE RANC, BRUNO SERIO To study detonation products of condensed matter containing aluminum particles in the post-combustion phase, a preliminary work is carried on deflagrations. The study of molecules' radiative properties during this fast phenomenon is not simple in the MWIR range. The flame front of H$_{\mathrm{2}}$/O$_{\mathrm{2}}$ gas mixtures spreads in a few tens of meters per second, a fast IR detection system is required. Also, there are no standard source in that spectral range for the intensity and spectral position calibration. The important feature of the experimental set-up presented is the record of high-resolution spectra dynamically at high speed, up to 10 kHz. The set-up is composed of a cylindrical combustion chamber with optical accesses. The pressure evolution is measured by a high speed piezoelectric sensor. The ignition is synchronized with the camera trigger. The radiation is focused into a monochromator and at its exit slot a camera records in real time the spectra. The spectral intensity is calibrated using a blackbody. The correspondence between the spatial position of a pixel and the wavelength is fitted using an original method based on the application of a third degree polynomial taking into account optical aberrations. The method is presented with the example of a H$_{\mathrm{2}}$/O$_{\mathrm{2}}$/N$_{\mathrm{2}}$/CO$_{\mathrm{2}}$ gaseous deflagration. The resulting spectra can be used to determine the temperature and the emissivity of gases. [Preview Abstract] |
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1D.00003: Shock Compression/Release of Magnesium Single Crystals: Anisotropy and Time-Dependent Inelastic Response Pritha Renganathan, J. M. Winey, Y. M. Gupta To gain insight into the inelastic deformation mechanisms for shocked and released hexagonal close-packed (hcp) metals, magnesium single crystals were subjected to shock compression and release along c-axis, a-axis and a low-symmetry (LS) axis to two different impact stresses. The wave profiles, measured using laser interferometry, obtained along these orientations show significant differences (qualitatively and quantitatively) in both compressive and release wave profiles demonstrating that Mg exhibits strong anisotropy under both shock compression and release. In addition to the observed anisotropy, the wave profiles also demonstrated time-dependent inelastic deformation. Numerical simulations of the measured wave profiles using a time-dependent anisotropic modelling framework, that incorporated both dislocation slip and deformation twinning, showed that the inelastic deformation mechanisms governing the shock response of Mg single crystals can be understood in terms of dislocation slip on basal, prismatic, pyramidal I and pyramidal II planes, and deformation twinning along (10\={1}2) twinning planes. These inelastic deformation mechanisms have been observed previously for Mg single crystals under quasi-static loading/unloading. [Preview Abstract] |
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1D.00004: Mechanical and optical response of polymethylpentene under dynamic compression L. M. Barmore, M. D. Knudson Polymethylpentene, commonly referred to by its trade name TPX, is a thermoplastic polymer that has the potential to be a useful window material for x-ray measurements in dynamic compression experiments. An optically transparent or low x-ray absorptive window is often used to maintain stress within the sample during compression. TPX can be used as a low-impedance optical and x-ray window due to its good transmittance in most parts of the electromagnetic spectrum, very low density, and low x-ray absorption. In such experiments, laser interferometry can be used to determine the particle velocity at the interface between the sample and window. Because velocimetry measures the rate of change of the optical path length, commonly referred to as the apparent particle velocity, an experimentally determined window correction factor is needed to ascertain the actual particle velocity. Here we present the results of a series of dynamic compression experiments designed to characterize the mechanical and optical response of TPX, determine the range of stresses over which TPX is transparent, and determine the window correction factor. The index of refraction was found to be essentially linear in density, resulting in a simple constant correction factor. [Preview Abstract] |
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1D.00005: MOVE TO SESSION 1C.00004 |
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1D.00006: A comparison of Gaussian Process Classification to classical statistical methods in sensitivity tests Alex Casey, Nick Cummock, Ilias Bilionis, Steven Son The input at which there is 50\% probability of a `go' in a binary outcome test -- also known as the L50 -- is a commonly used safety metric when evaluating the sensitivity of energetic materials to impact and shock. The L50 of a given material is typically determined using the Neyer Sensitivity Test or the Bruceton Test. These tests can provide a framework for a sequential design of experiments in order to choose the subsequent input given the observed data. In the present work, Gaussian Process Classification (GPC) is similarly applied to sensitivity test data to estimate a material's L50 and design sequential experiments. The GPC model defines a probability distribution over function space which provides a rich representation of the underpinning function. The function space can be constrained to those with a physically-based rationale. Additionally, the GPC model is easily extensible to experiments with multivariate inputs. A comparison of the Neyer and GPC statistical methods is presented alongside their implementation on a multivariate input gap-test experiment involving PBX 9501 pellets of varying porosities. [Preview Abstract] |
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1D.00007: Ramp Compression of Gold to 690 GPa Sirus Han, June Wicks, Raymond Smith, Donghoon Kim, Jon Eggert, Thomas Duffy Gold is a face-centered-cubic (fcc) transition metal with wide applications as a pressure standard and experimental component in high-pressure science. At multimegabar pressures, theoretical studies have predicted transformations to hexagonal-close-packed (hcp), double hexagonal-close-packed, body-centered-cubic (bcc), or stacking disordered phases. Static experimental studies above 200 GPa have produced conflicting results on high-pressure polymorphism in gold. In this study, we used the Omega Laser Facility (U. of Rochester) to ramp-compress gold to 690 GPa. Our target packages consisted of a diamond ablator, gold foil and either a diamond or a LiF window. Samples were compressed over 5-10 ns timescales via laser-ablation. Pressure was determined from measured VISAR wave profiles. The \textit{in-situ }lattice-level structure was probed using X-ray diffraction with a laser-plasma X-ray source. We observe the fcc phase at pressures up to 240 GPa, a mixed or intermediate phase from 240-390 GPa, and the bcc phase from 390-690 GPa. Our results will be compared with existing theoretical calculations and experimental data. [Preview Abstract] |
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1D.00008: (symp) Shock-induced alpha-epsilon phase transformation in nanocrystalline iron: Plastic deformation and phase transitions Hoang-Thien Luu, Ramon J. Ravelo, Eduardo M. Bringa, Timothy C. Germann, Nina Gunkelmann Shock compression is widely used to examine the mechanical responses of iron under dynamic loading. It has been long known that $\alpha $-iron transforms to $\varepsilon $-iron under high pressure. Recently, molecular dynamics simulations have shown that plasticity occurs just before the parent phase transforms into $\varepsilon $-iron. However, due to computational reasons, only small grain sizes have been studied where dislocation emission will be partially accommodated by grain boundary sliding. To provide insights into elastic and plastic activities of shocked iron, we performed atomistic simulations of shock compression of nanocrystalline iron with a mean grain size of 20 nm comprising a total number of 267.5 million atoms. We observe elastic and plastic deformation before the phase transformation takes place. Dislocations nucleate and pile-up at grain boundaries. The results are in good agreement with experiments of similar time and length scales. [Preview Abstract] |
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1D.00009: symp-Modeling the effect of plasticity and damage in β-HMX single crystals under shock loading Camilo Duarte, Marisol Koslowski, Nicolo Grilli $\beta -$HMX is an energetic crystal commonly used in polymer-bonded explosives (PBX). In PBXs, ignition may occur due to the formation ``hot-spots'' in the material, which are regions of localized thermal energy. Several mechanisms of hot spot formation have been proposed such as void collapse, plastic flow, crack propagation, and crack surface/interfacial friction. Additionally, it is believed that regions of high stress concentration in the energetic crystal such as micro-cracks and voids are preferential nucleation sites of hot spots. However, experimental observation of hot-spots in energetic materials remains difficult due to the short time and length scale of the reactions. In order to understand which mechanisms may mitigate or not the formation of hot spots we study the effect of plasticity and fracture evolution in shock-loaded $\beta $-HMX single crystals. A thermodynamically consistent finite strain model is used with a crystal plasticity model for the energetic crystal. Fracture evolution is modeled using a phase field model of damage. Numerical results are compared with gas gun experiments on $\beta $-HMX crystals containing engineered defects.~ [Preview Abstract] |
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1D.00010: (symp) X-ray diffraction study of laser-shocked forsterite (Mg$_{\mathrm{2}}$SiO$_{\mathrm{4}})$ from 20-130 GPa D. KIM, E. Berryman, S. Han, T. Duffy, S. Tracy, A. Gleason, C. Blome, K. Appel, M. Schoelmerich, V. Prakapenka, H. Lee, B. Nagler, R. Smith, M. Akin, J. Eggert, P. Asimow Forsterite, Mg$_{\mathrm{2}}$SiO$_{\mathrm{4}}$, is of fundamental importance for geophysics as the magnesium end-member of the olivine (Mg,Fe)$_{\mathrm{2}}$SiO$_{\mathrm{4}}$ solid solution. Interest in the dynamic behavior of olivine is motivated by understanding the nature of shock-induced phase transition in silicates during hypervelocity collisions. While it is known from gas-gun experiments that olivine transitions to a high-pressure phase under shock compression, there are few constraints on the structure of the high-pressure phase. We have carried out an \textit{in situ} x-ray diffraction study of laser-shocked polycrystalline and single-crystal (a-, b-, and c- orientation) forsterite from 20 GPa to 130 GPa using the Matter in Extreme Conditions beamline of the Linac Coherent Light Source. Consistent with earlier gas-gun experiments (Newman et al., 2018), we observe forsterite III, a metastable structure of Mg$_{\mathrm{2}}$SiO$_{\mathrm{4}}$, from 50 to 110 GPa. When compressed above 110 GPa, forsterite III undergoes amorphization. Our results show a reversion to the ambient forsterite structure during release over nanosecond timescales. [Preview Abstract] |
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1D.00011: HyFIRE: Hypervelocity Facility for Impact Research at Johns Hopkins University Gary Simpson, Matthew Shaeffer, K.T. Ramesh The Hopkins Extreme Materials Institute (HEMI) has installed a hypervelocity impact facility (HyFIRE) including a two-stage light gas gun at the Homewood Campus of JHU in Baltimore, MD. The HyFIRE launcher has a launch tube bore diameter of 7.62 mm and can attain launch velocities in up to 7 km/s. The enclosed ballistic range and terminal test chamber provide multiple axes with which to view both projectile free flight and terminal impact, maximizing diagnostic access to events of interest. Initial test diagnostics include ultra-high-speed optical video and orthogonal 300 kV flash x-ray imaging. Photon doppler velocimetry for surface velocity measurement—currently used in HEMI’s laser shock facility—as well as emission spectroscopy/pyrometry are planned, providing researchers across multiple disciplines with the ability to investigate the coupling of mechanics, physics and chemistry present in high energy impact events. We present initial experiments on the fragmentation of inert and reactive impactors on anvil targets, with an aim towards identifying the dominant mechanisms controlling the fragmentation characteristics, temperature distributions and trajectories of generated debris fields. [Preview Abstract] |
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1D.00012: Engineered Defects in Single Crystal HMX (symp) 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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1D.00013: 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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1D.00014: 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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1D.00015: 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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1D.00016: Simulating the Propulsive Capability of Explosives Loaded with Inert and Reactive Materials Quentin Pontalier, Jason Loiseau, Aaron Longbottom, David 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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1D.00017: Quantum-accurate SNAP carbon potential for MD shock simulations Jonathan Willman, Ashley Williams, Kien Nguyen Cong, Mitchell Wood, Aidan Thompson, Ivan Oleynik The ability of molecular dynamics (MD) to realistically simulate the high-strain-rate physics is critically dependent on the availability of high fidelity interatomic potentials capable of capturing the major physics of materials response to high temperatures and pressures. We have developed a Spectral Neighbor Analysis Potential (SNAP) machine-learning potential for high-pressure carbon. SNAP is formulated in terms of the bispectrum components, a set of general four-body geometric invariants that characterize the local neighborhood of each atom. Statistical data analysis is used to train the SNAP potential to reproduce a large set of first-principles training data. In this presentation we describe (1) the generation of the training database comprising the consistent and meaningful set of first-principles DFT calculations; (2) the robust and physically guided fit of the SNAP parameters; and (3) the validation of the SNAP potential in large-scale MD simulations of shock compression of carbon materials. [Preview Abstract] |
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1D.00018: Data-Driven Retrosynthetic Predictions for Energetic Materials (symp) Michael Fortunato, Connor Coley, Brian Barnes, Igor Schweigert, Ariana Beste, Klavs Jensen We present recent work in computer-aided synthesis planning strategies of interest to synthetic chemists, and demonstrate the utility of a new neural network for predicting synthetic pathways to energetic material precursors. These data-driven machine learning techniques have shown great promise in the pharmaceutical industry, and are poised to have a dramatic impact on the research and development process for novel materials. This work expands on previously developed techniques by addressing the ``rare template" problem. Although there is an abundance of computationally accessible reaction data, a significant data imbalance can make models less inclined to recommend energetically relevant reaction templates. A data augmentation strategy leveraging cheminformatics toolkits and high performance computing was used to train a deep neural network to restore fidelity to the rare, energetically relevant templates. The performance of this new neural network is compared to the previous one to highlight its enhanced predictive power for new synthetic routes for energetic materials. A web application created for transitioning this new model to synthetic chemists for everyday use will also be demonstrated. [Preview Abstract] |
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1D.00019: First-principles molecular dynamics simulations of high-pressure phase diagram of carbon Kien Nguyen Cong, Jonathan Willman, Ashley Williams, Anatoly Belonoshko, Ivan Oleynik Although high-pressure phase diagram of carbon at extreme temperatures and pressures has been in the focus of intensive experimental and theoretical studies, there still exist outstanding problems including disagreement between theoretical predictions and experiment. We present results of first-principles molecular dynamics simulations of thermodynamic properties of carbon at high temperatures and pressures, which are performed with the goal of constructing an accurate phase diagram of carbon. To address the issue of accuracy and reliability, a relatively large number of atoms is used for calculation of melting transitions (melt curve) as a function of pressure. Accurate Gibbs free energies are calculated using temperature dependent effective potential method. We specifically focus on important region of phase diagram where diamond exhibits a negative melting line slope at pressures above 500 GPa. [Preview Abstract] |
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