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 V1: Poster Session II |
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Room: Atrium Ballroom |
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V1.00001: ABSTRACT WITHDRAWN |
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V1.00002: Development of lower-adiabat drives for Rayleigh-Taylor strength experiments. T.E. Lockard, M.P. Hill, A.G. Krygier, A.B. Zylstra, P. Graham, P.D. Powell, D.C. Swift, S.T. Prisbey, H.-S. Park, J.M. McNaney We have used the expansion of a shocked reservoir assembly across a gap to induce ramp loading, precluding sample melting, and hence infer strength from the growth of ripples at an interface. For multi-megabar loading, the reservoir comprises a sandwich of several materials, and the resulting load history has a large amount of structure, including small shocks. This structure leads to a degree of shock heating, and some uncertainty in the heating that actually occurs. We report on progress in studies to improve the reservoir drive by reducing the shock heating via adjustments of reservoir density and thicknesses. We will discuss the sensitivity of the EOS models used for the components of the experiment in hydrodynamic simulations. [Preview Abstract] |
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V1.00003: Role of pre-existing dislocation loops on the shock compression and spall behavior of FCC metals Ke Ma, Jie Chen, Garvit Agarwal, Avinash Dongare Dislocation loops are ubiquitous in single-crystal and nanocrystalline metals, yet few studies have been devoted to understanding their role on the dynamic behavior of metals. In this work, large-scale molecular dynamics (MD) simulations are carried out to study the role of pre-existing dislocation loops on the shock induced deformation and spall behavior of single-crystal Cu and Al microstructures. This study investigates the role of pre-existing dislocation loops on the wave propagation, dislocation evolution, and void nucleation and growth behavior of single-crystal Cu and Al systems. The results suggest that the presence of dislocation loops results in a decrease of the shock wave velocity, and a substantial decay of the elastic precursor amplitude (HEL) as compared to defect free single-crystal microstructures. The resulting dislocation nucleation and evolution behavior, and void nucleation and growth behavior are also significantly modified due to the presence of dislocation loops. A series of MD simulations are carried out to investigate the effects of the shape (triangular, hexagonal and circular), type (vacancy and interstitial), and density of the dislocation loops for various loading orientations on the spall failure behavior of the metals. The correlations between defect distributions/types/structure and the associated strengthening and weakening behavior will be presented. [Preview Abstract] |
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V1.00004: Unraveling the Effect of Laser Fluence and Loading Orientation on the Spallation of Cu and Al microstructures at Atomic Scales. Marco Echeverria, Sergey Galitskiy, Avinash Dongare The spall response of metals under laser shock loading conditions is investigated using a hybrid approach that combines molecular dynamics (MD) simulations with a continuum two-temperature model (TTM). This hybrid methodology is able to accurately model the laser energy absorption, electron heat conduction, and electron-phonon interaction that results in the ablation/melting of the material and the generation of a shock wave that travels through the metal followed by wave reflections and interactions to initiate spallation failure. The hybrid MD/TTM simulations are carried out to investigate the role of laser fluence on the laser shock loading induced spall failure of single crystal Cu and Al systems for a range of laser fluences from 0.5 to 13 kJ/m2. In addition, MD/TTM simulations are also carried out to investigate the role of loading orientation on the defect/damage nucleation and evolution behavior for Cu and Al single crystal systems. The simulations suggest a correlation between the spall strength and the density of dislocations generated in the metal at the spall plane. The microstructure response and the role of solid-liquid interfaces, defects and voids evolution, and shock wave structure on the spall strength and Hugoniot Elastic Limit of these systems are presented. [Preview Abstract] |
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V1.00005: Damage Initiation and Evolution in Nanoscale Multiphase Metallic Microstructures Under Shock Loading Conditions at Atomic Scales. Marco Echeverria, Sumit Suresh, Sergey Galitskiy, Avinash Dongare Materials requirements for next-generation energy, defense, and nuclear applications call for the design and optimization of nanocrystalline multicomponent microstructures using a bottom-up approach. Multiphase metallic materials show promise in this regard due to inherent interfaces that can act as sources or sinks to defects propagation, a mechanism that ultimately determines damage tolerance behavior under shock loading conditions. The response of these interfaces in such extreme environments is observed to vary with the deformability of individual phases, and the creation of damage (void) nucleation sites that initiate spall failure. This study investigates the role of size and distribution of phases on the modifications in the behavior of shock wave propagation, defect evolution, and void nucleation using classical molecular dynamics (MD) simulations. The simulations are carried out to model Al/Si and Al/Ni microstructures and variations in size and distributions of Si/Ni phases in a nc-Al matrix. The MD simulations suggest that void nucleation behavior is observed along the Al/Si and Al/Ni interfaces. The nanoscale links between dislocations, nucleation and growth of voids, and the role these play in the spall strength of an Al/Si and Al/Ni multilayered system are presented. [Preview Abstract] |
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V1.00006: Molecular dynamics simulations of grain interactions in shock-compressed highly-textured columnar polycrystals Patrick Heighway, David McGonegle, Nigel Park, Andrew Higginbotham, Justin Wark When a polycrystal is shock-compressed, the grains of which it is composed cannot deform as they would do in isolation, but must do so in such a way as to accommodate the presence of their neighbours. This is to say that every grain must interact with those adjacent to it. While experimental studies abound demonstrating the range of physical effects that can be attributed to grain interactions under quasi-static loading conditions, little consideration appears to have been given to the detection of such interactions under the conditions of shock-loading. Here, we predict via molecular dynamics simulations the effect of grain interactions on the elastic strain state of a particular class of highly-textured polycrystal under shock-loading conditions. We find that cooperative elastic deformation of grains in directions transverse to the shock allows each crystallite to reach a state of reduced shear stress. We compare the extent of this relaxation for two different columnar geometries, in which the grains have either square or hexagonal cross-sections. Finally, we calculate the shifts in the x-ray diffraction (XRD) peaks that would result from these grain interactions, and hence assess the feasibility of detecting these interactions using ultrafast XRD techniques. [Preview Abstract] |
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V1.00007: Shock Compression of Niobium Oxides from First-Principles Philippe Weck, Kyle Cochrane, Nathan Moore In order to assess the impact of oxidation on the properties of niobium subjected to shock loading, the equations of states (EOSs) of NbO and NbO$_2$ were studied within the framework of density functional theory (DFT), with Mermin’s generalization to finite temperatures. NbO typically forms during the initial rapid oxidation of Nb films and crystallizes in the cubic Pm3-m structure; NbO$_2$ adopts a tetragonal superstructure with a subcell of the rutile type, with space group I41/a. The shock Hugoniots for fully-dense and slightly porous NbO and NbO$_2$ were obtained from canonical ab initio molecular dynamics (AIMD) simulations with Erpenbeck’s approach based on the Rankine-Hugoniot jump conditions. Results suggest that the degree of oxidation markedly impacts the Hugoniot curves at high pressure, owing in part to the presence of multiple phase transitions above $\sim 60$ and $\sim 30$ GPa for NbO and NbO$_2$, respectively. At lower pressure, below $\sim 10$ GPa, the effect of oxidation remains relatively limited according to the present AIMD simulations, although a study of Nb$_2$O$_5$ polymorphs subjected to shock loading would further rule out significant detrimental effect from higher oxidation. [Preview Abstract] |
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V1.00008: Modeling the structure of croconic and squeric acids under pressure. Iskander G. Batyrev Quantum mechanical simulations of modifications of structure of croconic and squeric acids under pressure up to 55 GPa indicate formation of a high-pressure extended network phase. Density functional theory plane wave calculations were performed to investigate the effects of isotropic and anisotropic compression on the structural transformation of croconic acid and elucidate the details of the transition. The onset of pressure-induced polymerization of croconic acid was observed near 12 GPa. Complete polymerization was noted at pressures near 25 GPa. The simulations revealed a hysteresis upon decompression in the pressure-volume curve as well as the O-H bond lengths; based upon the maximum pressure of confinement, the hysteresis was observed to shift. Calculated X-ray diffraction patterns and vibrational spectra of the high pressure acids crystals are in a reasonable agreement with previously published experimental diffraction and vibrational spectra. Strong H bonds were also found to result in the pressure-induced formation of an extended network in squeric acid, suggesting that the found phenomenon is common for oxocarbon acids. [Preview Abstract] |
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V1.00009: 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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V1.00010: Influence of Combined Normal and Shear Loading on the Hotspot Criticality Md Mahbubul Islam, Michael Sakano, Alejandro Strachan We are interested in understanding hotspot (HS) formation and criticality in energetic materials. The pore collapse is thought to be the dominant HS formation mechanism, and the process consists of expansion, compression, jetting, and shearing of the materials involved. Given the significant molecular disorder during the formation of hotspots, we contrast the criticality of hotspots in amorphous and crystalline RDX and observe that structural effects are relatively insignificant. Using ReaxFF molecular dynamics simulations, we further characterize how different types of mechanical loading affect the formation and criticality of the HS in RDX. We choose an initial planar configuration of the pore to independently control the relative contributions of the normal and shear loadings and investigate their role on the HS criticality. We evaluate how energy input to the HS, in the form of PV work and interfacial friction due to the impact and shear, respectively, regulates the HS temperature and chemical kinetics. We also elucidate the loading type dependency on the reaction initiation pathways and evaluate the role of dynamic loading and non-equilibrium states towards the HS criticality. [Preview Abstract] |
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V1.00011: ABSTRACT WITHDRAWN |
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V1.00012: A microtomographic toolchain to build models of energetic material microstructures at different level of complexity Steve Belon, Benjamin Erzar, Elodie Kaeshammer The initiation of solid explosives under shock loading is commonly related to the formation of hot spots. These hot spots are mainly formed at the heterogeneities of the microstructure: porosities, cracks, debondings, particle edges, etc. To study the initiation of these materials, their microstructural properties have thus to be taken into account. We use micro-computed tomography (microCT) to create 3D images of the microstructure of solid explosives. Several image processing tools have been specifically developed to characterize the microstructure of energetic materials with microCT results. Properties like granulometry of particles and pores, morphology of grains, surface characteristics of cracks... can be measured from the microCT images. Volume representations obtained through microCT are also exploited to build finite element models of the microstructure of solid explosives. Real models, including all heterogeneities identified on the microCT scans, can be simplified to study independently the influence of each microstructural parameter. Numerical simulations of shockwave propagation in heterogeneous microstructures with different level of realism are presented. These mesoscale models show that complex microstructures lead to more heterogeneous thermodynamical fields. [Preview Abstract] |
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V1.00013: Effects of natural variability on the dynamic strength of chondrite meteorites for asteroid hazard mitigation Benjamin Brugman, Dawn Graninger, Laura Riordan-Chen, Eric Herbold, Megan Syal, Susannah Dorfman, Damian Swift Successful mitigation of asteroid impact hazards requires accurate constraints on the rheology of potential impactors at strain rates relevant to the conditions required for deflection or disruption. Chondrite meteoroids are the most abundant near-Earth objects, and compositional analogs to potential asteroid hazards. They are heterogeneous, multiphase assemblages composed of remnant materials from the formation of the early solar system. To assess impact of compositional variability and texture on the dynamic strength of chondrites, we used laser-driven shock compression coupled with optical and SEM microanalysis of both shock-recovered and unshocked chondrites and their constituent silicate mineral phases. Chondrites and silicates were dynamically compressed using the Janus laser at the Jupiter Laser Facility at LLNL and the Trident laser, formerly at LANL. Results from the recovery analyses and velocity interferometry (VISAR) data will help constrain the effects of natural variability on strength and reduce uncertainty in planetary defense models. [Preview Abstract] |
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V1.00014: High Strain Rate Properties of Water Ice. Ryan Potter, Joseph Cammack, Tom Pollard, Christopher Braithwaite Understanding the properties of water ice at high rates is important for the application of understanding target materials for space penetrators. This paper discusses some of the challenges of studying ice at high rates including sample manufacture and preparation, environmental control of apparatus and how to achieve variation in the tested material to better simulate extra-terrestrial ice. Results from some of the experiments will be discussed, showing progress in investigating strain rate variation, density variation and ice-sand composites. [Preview Abstract] |
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V1.00015: 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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V1.00016: First experimental synthesis of Al$_{\mathrm{62}}$Cu$_{\mathrm{31}}$Fe$_{\mathrm{7}}$ icosahedral quasicrystals and their natural origin in a meteorite by impact processes Paul Asimow, Jinping Hu, Chi Ma, Luca Bindi Quasicrystals (QCs) produced by shock recovery experiments shine light on the impact origin of natural QCs in the Khatyrka meteorite [1,2]. Al$_{\mathrm{62}}$Cu$_{\mathrm{31}}$Fe$_{\mathrm{7}}$ i-phase II is a newly found natural QC that has not previously been synthesized in the laboratory [3]. The compositions of Al-Cu-Fe QCs synthesized by shock have so far been similar but not identical to natural icosahedrite (Al$_{\mathrm{63}}$Cu$_{\mathrm{24}}$Fe$_{\mathrm{13}})$ and i-Al$_{\mathrm{62}}$Cu$_{\mathrm{31}}$Fe$_{\mathrm{7}}$ [3]. Here we present the results of a new shock recovery experiment using a compositionally graded Al-Cu-W wedge in a SS304 chamber. Surprisingly, the Al-rich region did not produce QCs whereas the intermediate Al-Cu mixture reacted with the steel chamber to generate i-Al$_{\mathrm{62}}$Cu$_{\mathrm{30}}$Fe$_{\mathrm{7}}$Cr$_{\mathrm{1}}$, co-existing with Al$_{\mathrm{2}}$Cu (khatyrkite) and Al$_{\mathrm{3}}$Cu$_{\mathrm{2}}$ (stolperite) alloys. Conceivably, this results from the effects of shear flow during shock that stabilizes the new composition of icosahedral QC. More importantly, the synthesized i-phase II is a near-exact compositional, textural and assemblage match to its natural occurrence in the Khatyrka meteorite. [1] Asimow, P.D. \textit{et al.} (2016) \textit{PNAS}, 113, 7077. [2] Oppenheim, J. \textit{et al.} (2017) \textit{Sci. Rep.}, 7, 15629. [3] Bindi, L. \textit{et al.} (2016) \textit{Sci. Rep.}, 6, 38117. [Preview Abstract] |
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V1.00017: 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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V1.00018: Particle Size Effects on the Detonation Velocity of Nitramine Containing Compositions Victor Bellitto, Mikhail Melnik, Mary Sherlock, Joseph Chang, John O’Connor, Joseph Mackey Predictive tools are often employed to determine detonation parameters of explosives prior to development. However, thermodynamic-hydrodynamic based theoretical codes seldom take into account particle size as a basis for the computational analysis as they primarily focus on the equation of state of the detonation products, heat of formation and density of the explosive composition. The microstructure effects on the detonation velocity of RDX containing compositions have previously been reported. It was demonstrated that compositions containing smaller average particle sizes of RDX generated higher detonation velocities. The study utilized regression analysis to model the relationship between the microstructure characteristics and detonation velocity of the compositions. The principal characteristics examined were the average particle size, impurity within the explosive particles, method of manufacture, and compositional density. Statistical analysis demonstrated the relevancy of the microstructure influence on the detonation velocity of the experimental compositions. The developed model underscored the significance of the relationship between the average particle size and detonation velocity. In this study, we have continued the investigation to include other nitramines, such as HMX. [Preview Abstract] |
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V1.00019: Dynamic behaviour and spall fracture of laser shock-loaded AlSi10Mg alloy obtained by Selective Laser Melting Manon Laurencon, Thibaut De Rességuier, Didier Loison, Jacques Baillargeat In the ongoing development of additive manufacturing, the range of materials obtained by such processes constantly grows and comes with specific architecture and microstructure. In this study, the high strain rate behaviour of light aluminum alloy AlSi10Mg obtained by Selective Laser Melting (SLM) has been investigated under laser shock loading and impact of thin, laser-accelerated flyer plates. Both elastic-plastic response and spall fracture have been analysed on the basis of time-resolved measurements of free surface velocity, transverse visualization of shock-induced fragmentation and post-recovery observations (microscopy and tomography). Comparing two microstructures inherited from two sets of SLM building parameters reveals the strong influence of porosity and defects (lacks of fusion) on the Hugoniot Elastic Limit and spall strength. On the other hand, these properties do not depend much on the building direction, although fracture surface morphology is shown to be largely affected by the melt pools boundaries. [Preview Abstract] |
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V1.00020: Dynamic properties and behavior of 316L stainless steel Robert King, Anna Llobet-Megias, Guillermo Terrones, Saryu Jindal-Fensin, Russell Olson, George Gray III, Christopher Morris, Derek Schmidt, Alexander Saunders, Amy Tainter, Wendy Vogan-McNeil Understanding materials properties and the ability to accurately model and predict their behavior when implemented in large-scale hydrodynamic simulations, is essential to ensuring and assessing a wide range of industrial, engineering, and defense applications. This work provides insights into the accuracy of the strength models in the high pressure-high strain rate regime for 316L wrought austenite stainless steel through measurements of Rayleigh-Taylor (RT) instability. Experimental measurements using velocimetry and Proton Radiography (pRad) are used to test the accuracy of the current constitutive models using PAGOSA hydrodynamic simulations. Three commonly used strength models were com-pared with the data consisting of the time evolution of the peak-to-trough RT growth. Based solely on this metric, our results are in reasonable agreement with the data as long as the high explosive (HE) drive is modeled correctly. In addition, the data shows that the RT instability growth follows a simple power law behavior and that beyond the onset of instability, the growth rate progressively slows down as kh increases. [Preview Abstract] |
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V1.00021: Pressure-Shear Plate Impact Experiments at Very High Pressures Christian Kettenbeil, Zev Lovinger, suraj Ravindran, Michael Mello, Guruswami Ravichandran Recent modifications of the powder gun facility at Caltech have enabled pressure shear plate impact (PSPI) experiments on materials at very high strain rates \newline (\textgreater 10$^{\mathrm{7}}$ s$^{\mathrm{-1}})$ and pressures (\textgreater 20 GPa) that have not been reached before. The high strain rate/pressure regime expands significantly the advantages of this well studied technique, yet it requires a new approach for analysis of the experimental measurements to extract material's strength. At high pressures standard anvils such as tool steel and tungsten carbide do not remain elastic, and their inelastic behavior need to be accounted for in the analysis. In this work, we investigated the limits of different anvil materials and developed the requirements for anvils to withstand high pressures in the PSPI experiments, balancing ductility and strength. The methodology we have developed extracts the strength of the material in these experiments using a hybrid method, combining numerical simulations to simultaneously match both the normal and transverse free surface velocity measurements. The proposed methodology has the potential to expand the PSPI experiments to higher pressures, which may be also relevant to design and interpret MAPS experiments. [Preview Abstract] |
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V1.00022: Gas-Phase Ion-Neutral Reactions of Cerium Cluster Ions with Deuterium. Manuel Manard, Paul Kemper, Rusty Trainham, Peter Armentrout The gas-phase interactions of cerium cluster cations and deuterium neutrals have been investigated using a temperature-dependent reaction cell embedded between two quadrupole mass analyzers. Ce$_{\mathrm{m}}^{\mathrm{+}}$ (m $=$ 1 -- 20) have been generated with our instrumentation and evidence for reaction of these clusters with D$_{\mathrm{2\thinspace }}$to form cerium-deuterium adducts has been obtained. No evidence for fragmentation of cerium clusters via reaction with D$_{\mathrm{2}}$ was found. Accordingly, rate constants for the reaction of Ce$_{\mathrm{m}}^{\mathrm{+}}$ with D$_{\mathrm{2}}$ to form Ce$_{\mathrm{m}}$D$_{\mathrm{2m}}^{\mathrm{+}}$ (m $=$ 1 -- 3) products have been acquired as a function of temperatures ranging from approximately 235 -- 515 K. Arrhenius analysis of the data indicate activation energy barriers exists along the potential energy surfaces (PESs) for the reaction of Ce$_{\mathrm{2}}^{\mathrm{+}}$ and Ce$_{\mathrm{3}}^{\mathrm{+\thinspace }}$with D$_{\mathrm{2}}$, while a negative temperature dependence is observed for the rate constants of the Ce$^{\mathrm{+}}$/D$_{\mathrm{2}}$ reaction. Electronic structure calculations were performed using density functional theory (DFT) to characterize all reactant and product species. This combination of experimental and theoretical results suggest the cerium cluster ions dissociate the deuterium sigma bond to form Ce$^{\mathrm{+}}$-D bonds in an overall exothermic process. Preliminary data for extending these methods to larger cerium clusters is also presented. [Preview Abstract] |
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V1.00023: Shock-driven mixing and turbulence Adam Martinez, John Charonko, Kathy Prestridge Experiments using a powder gun driver are able to created Mach 9 shocks in xenon to drive Richtmyer-Meshkov mixing of a xenon-helium interface. At the Los Alamos Neutron Science Center (LANSCE), proton radiography (pRad) we acquire 21-frame movies of areal density of the mixing zone in the test section of the Xe-He shock tube for two different initial conditions at the interface. Analysis shows differences in growth rate and in mixing region structure, and the imprint of the initial condition perturbations is visible throughout the entire sequence of the experiment. Future plans for improvement in the radiography signal-to-noise and the initial condition configuration are also described. [Preview Abstract] |
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V1.00024: Dynamic strength and failure of additively manufactured Ti-6Al-4V alloy Vitaly Paris, Pinhas Fridman, Eithan Tiferet, Arnon Yossef-Hai Additive manufacturing of metallic alloys (AM) by Electron Beam Melting (EBM) or Selective Laser Melting (SLM) is an emerging field. Understanding the relationships between the AM and post-processing parameters and resulting microstructure and the mechanical (and particularly dynamic) properties is of great practical interest. The Ti-6Al-4V alloy made by EBM has been studied in series of Split Pressure Bar tests (SHPB). The effects of Hot Isostatic Pressing (HIP) and of orientation of loading to build direction on dynamic compressive strength and failure properties were investigated. Stopper rings were employed in the tests to softly recover the specimens for post-mortem characterization. Results indicate that the effect of HIP on flow stress is small. The strain to failure of HIPed alloy is significantly higher than of as-built alloy. Results display small effect of the relation of loading direction with respect to build direction on the flow stress. On the other hand, EBM Ti-6Al-4V demonstrates strong effect of the loading direction on the strain to failure. The fractography images of soft-recovered specimens loaded in or normal to build direction also indicate different fracture characteristics. [Preview Abstract] |
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V1.00025: Using Free Surface Velocity and X-Ray Imaging to Monitor the Closure of a Cylindrical Hole in Copper and Tantalum for Strength Measurements Under Pressure Andrew Robinson, Jonathan Lind, Matthew Nelms, Nathan Barton, Mukul Kumar The flow stress in a metal is dependent on a variety of factors such as strain, strain rate, microstructure, and temperature. Experiments (i.e. quasi-static tensile testing or Kolsky bar testing) with well characterized stress states have been used to determine the relation between flow stress and these many factors. However, for higher strain rates (\textgreater 10$^{\mathrm{5}}$/s) there is a dearth of high-fidelity data. Here, we present results of a recent in-situ gas-gun experimental technique that can probe strength effects at strain rates of \textgreater 10$^{\mathrm{5}}$/s. By measuring the diameter of a long cylindrical hole using x-ray imaging in conjunction with back surface velocimetry while the sample is subjected to controlled dynamic loading, the factors affecting flow stress can be inferred. Models of the experiment indicate that a relatively large volume of material around the hole experiences strain rates above 10$^{\mathrm{5}}$/s. Materials with higher dynamic flow stresses tend to exhibit less diameter reduction than materials with lower flow stresses all else being equal. Experimental results indicate that the hole diameter reduction is also dependent on the peak pressure of the loading pulse and the duration of the pressure pulse. [Preview Abstract] |
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V1.00026: Spall behavior of Aluminium with Helium Bubbles under Laser Shock Loading. Dawu Xiao, Dongli Zou, Hua Shu, Lifeng He The spall behaviors of Al-$_{\mathrm{10}}$B alloy targets and neutron irradiated Al-$_{\mathrm{10}}$B alloy targets with 5nm radius helium bubble subjected to direct laser ablation are presented. It is found that the spall strength increases significantly with the tensile strain rate, and the helium bubble or boron inclusions in aluminum reduces the spall strength of materials by 30{\%}. However, slight difference is observed in the spall strength of unirradiated samples compared with the irradiated sample with helium bubbles.. [Preview Abstract] |
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V1.00027: The Preston-Tonks-Wallace Model Parameterization of FCC-Cerium JeeYeon Plohr, Leonid Burakovsky, Sky Sjue Cerium (Ce) is a scientifically interesting material for which there are seven allotropies; it goes through phase transformation between alpha and gamma phases via localization/delocalization of f electron with a large volume collapse; the liquid phase has a larger volume than solid phase in low pressure regime (less than 3GPa), and it has a critical point at low pressure/temperature (475K, 1.5 GPa). As part of an effort to have a better material model parameters for Ce, we have fitted the Preston-Tonks-Wallace (PTW) viscoplasticity model. In doing so, we have used a thermoelasticity model that provides the analytic expressions of shear modulus and melt curve. The experimental data needed were provided by Russian Federal Nuclear Center (RFNC) where the split Hopkins bar tests were performed for seven sets of strain rate and temperature regimes from which stress-strain data were extracted, and we have used them to find the best fitting PTW model parameters. However, due to the lack of large strain data, there remains a big uncertainty in selecting the parameters. [Preview Abstract] |
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V1.00028: Characterization of phase transition on Ga$_{\mathrm{2}}$O$_{\mathrm{3}}$ induced by shock-recovery experiment Hiroaki Kishimura, Hitoshi Matsumoto Shock recovery experiments on Ga$_{\mathrm{2}}$O$_{\mathrm{3}}$ sample were carried out by the impact of a flyer plate accelerated by a single-stage powder-propellant gun. A sintered pellet and a single crystalline plate of Ga$_{\mathrm{2}}$O$_{\mathrm{3}}$ were used. Sample was encapsulated in copper container. The recovered samples were characterized by X-ray diffraction (XRD) analysis and Raman spectroscopy. The recovered single crystalline sample was reduced to grains. Analysis of the shocked samples suggests that the onset pressure for the transition from the $\beta $- to $\alpha $-Ga$_{\mathrm{2}}$O$_{\mathrm{3}}$ phase lies between 11 and 16 GPa. For the sample shocked at 20 GPa, most of Raman spectra were corresponding to $\beta $-Ga$_{\mathrm{2}}$O$_{\mathrm{3}}$ phase and the Raman spectra obtained from some of the grains that recovered from shock compression agreed with the $\alpha $-Ga$_{\mathrm{2}}$O$_{\mathrm{3}}$ phase. The XRD pattern consisted of a mixture of $\beta $- and $\alpha $-Ga$_{\mathrm{2}}$O$_{\mathrm{3}}$ phases. Although Ga$_{\mathrm{2}}$O$_{\mathrm{3}}$ exists five forms of crystal structure under ambient condition, all other structures except for $\beta $- and $\alpha $-Ga$_{\mathrm{2}}$O$_{\mathrm{3}}$ were not observed. [Preview Abstract] |
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V1.00029: Coupling between plasticity and phase transition in single crystal iron at ultra-high strain rate Nourou Amadou, Thibaut De Resseguier, Andre Dragon Solid materials behavior under ultra-high strain rate loading such as shock compression may involve various processes including plastic deformation, structural phase transformations, fracture, melting, etc., whose kinetics and coupling are complex functions of strain rate, initial conditions and microstructure. Here, we present molecular dynamics simulations of the dynamic response of single-crystal iron to either ramp or shock compression, at strain rates on the order of $10^{9}s^{-1}$, where we focus on the coupling between plastic deformation and the bcc-hcp phase transition. Defect-free crystal at 50 K initial temperature was found to yield via twinning when compressed along the [001] direction. Then, the onset of the bcc-hcp transformation was shown to be tightly dependent on the plasticity history through a shear-stiffening effect, which in some conditions inhibits the nucleation of the hcp phase [N. Amadou et al., Phys. Rev. B 98, 024104, 2018]. Yet, changing the initial temperature, direction of load application versus crystal orientation, or introducing lattice defects lead to very different behavior, including dislocation-mediated plasticity. [Preview Abstract] |
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V1.00030: Fast phase change dynamics as a rapid energy absorption mechanism Gareth Tear, William Proud Solid-solid phase transitions in materials are well documented. Kinetics play an important role in phase transitions during shock compression due to the extremely rapid nature of the compression. This allows metastable states to be reached, whether that is a state which has been compressed beyond its stable region but has not had time to relax, or an entirely new state only possible through rapid compression. Upon release, therefore, the material may revert or transform to another state, at a different pressure and temperature to its forward transformation pressure. This leads to hysteresis, releasing or dissipating kinetic energy as heat. Controlling the loading and unloading pressure using impedance matching allows this process to be maximized. A suitable candidate material has been selected and results demonstrating the feasibility of this method to reduce the velocity of projectiles, and the amplitude of transmitted shock waves, will be presented. [Preview Abstract] |
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V1.00031: ABSTRACT WITHDRAWN |
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V1.00032: ABSTRACT WITHDRAWN |
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V1.00033: Melting and recrystallization of Pb on nanosecond timescales Amy Lazicki, Christopher Wehrenberg, Jon Eggert, Ryan Rygg, James McNaney, Federica Coppari, Joel Bernier, Richard Kraus We have developed a platform on the NIF laser facility to monitor nanosecond changes in crystal structure using x-ray diffraction, by shaping laser drive pulses to compress a material along a desired path in phase space and probing it at multiple steps along the path with nanosecond-duration x-ray pulses. We will present work to demonstrate shock melting and recrystallization along compression in Pb. \textit{In situ} observation of melting and recrystallization from a liquid phase provide an important constraint on the high pressure melting curve as well as on the kinetics of crystal nucleation and growth. [Preview Abstract] |
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V1.00034: Shock-wave study of the metallization of alkali halides up to 5 Mbar Orianna Ball, R. Stewart McWilliams, Suzanne Ali, Jon Eggert, Gilbert W. Collins, Matt Diamond, Raymond Jeanloz Alkali halides are of fundamental interest to the shock wave community, for the number of fundamental phase transformations they exhibit under compression. However, the phase transition from wide band gap insulator into electrical conductor, observed in many insulators under shock and static compression (e.g in diamond [1] and quartz [2]) has been poorly explored for the alkali halides. Meanwhile legacy results of Russian experiments pose a number of unresolved questions such as the possibility of nonequilibrium behavior at Mbar shock pressures. In this study we investigate the optical properties of alkali halides, NaCl, KBr, CsBr and CsI, under shock loading up to 5 Mbar, by measuring shock wave speed and reflectivity using line VISAR in decaying-shock experiments. Significant increases in the optical reflectivity in all four cases indicate conditions of metallization at high pressures. The results are analyzed with respect to previous shock and dynamic measurements for the alkali halides. [1] Bradley, D.K., et al., Physical Review Letters, 2004. 93(19): p. 195506. [2] Hicks, D.G., et al., Physical Review Letters, 2006. 97(2): p. 025502. [Preview Abstract] |
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V1.00035: A Multiphase Equation of State for Gold. Jake Haynes, Geoffrey Cox Gold is commonly used as pressure standard thus an accurate EoS for this material is needed. This poster describes the development of a multiphase EoS for gold using the process described in Cox and Christie [1]. In this methodology, parameters for statistical-mechanics-based condensed matter physics models are obtained using a stochastic analysis technique called particle swarm optimization. Equation of state codes from both AWE and LANL were both implemented using this process. This poster highlights the types of analysis that can be performed with this method and shows a discrepancy between high pressure isentropic compression data and the resultant gold EoS. [1] Cox, G. A., Christie, M. A., Fitting of a multiphase equation of state with swarm intelligence. J. Phys.: Condens. Matter 27, 405201 (2015). [Preview Abstract] |
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V1.00036: Experimental sound velocities and Gr\"{u}neisen parameters for shocked Pb: Comparison with theory David Boness With its low melting temperature and high shock impedance, Pb is a metallic element that gives liquid state data over a broad range of pressures accessible with a two-stage light-gas gun. Sound velocity and Gr\"{u}neisen parameter data from the rarefaction overtake method are reanalyzed for Pb shocked beyond the Hugoniot-melting curve intersection, between 54 and 380 GPa, and are compared to recent static data and theoretical melting curve and equation of state computations. [Preview Abstract] |
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V1.00037: Studying the dynamic properties of cyanoacrylate adhesive in plate impact experiments Refael Hevroni, Natan Karaev, Eli Gudinetsky, Vitaly Paris, Arnon Yosef-Hai Cyanoacrylate adhesive are commonly used in plate impact experiments as binding for targets to optical windows and binding of multi-layered impactors. Thus, knowledge of the equation of state of cyanoacrylate adhesives improves the accuracy of the analysis of dynamic experiments. In this work, plate impact experiments were performed on transparent cyanoacrylate cast windows. The principle Hugoniot and the sound velocity were measured on shock-loaded cyanoacrylate Windows up to 7 GPa. A VISAR was used to monitor particle velocity of the impactor-window interface. In optical shock-loaded windows, the dynamic optical correction is typically reversed when the shock-wave reflects from the window's free surface, expressed by a sharp change in the measured particle velocity. This phenomenon was used estimate the shock-wave travel time, the arrival time of the rarefaction wave propagates from the window's free surface to the impactor-window interface observed as a continuous increase of the impactor-window interface velocity. This phenomenon was used to estimate the rarefaction wave travel time, and thus to calculate the sound velocity. From the experimental data a Mie-Gruneisen type equation of state for cyanoacrylate was proposed. [Preview Abstract] |
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V1.00038: Sound velocity measurements in shock compressed Al and Cu Alexander Fedotov Gefen, Eli Gudinetsky, Arnon Yosef-Hai, Benny Glam, Moris Sudai Sound velocity measurements are useful for mapping the phase diagram of materials and for calibration of their EOS outside the principle Hugoniot. A common method is the overtake method, in which a flyer plate is accelerated towards two or more targets of different thickness. In the present work, experimental results of sound velocity measurements in shock compressed Al and Cu are presented with comparison to data published in literature. The experimental setup was designed and optimized for obtaining high accuracy results. This design took into account the following factors: 2D effects such as edge rarefactions originating in the flyer plate, targets and the windows, EOS accuracy, thickness and diameters tolerances, error correlations and expected experimental uncertainties. [Preview Abstract] |
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V1.00039: Measurement of platinum phase to over 2 terapascals James McNaney, Damian Swift, Amy Lazicki, Ryan Rygg, Joel Bernier, Richard Kraus, Chris Wehrenberg, Jon Eggert We have performed a series of experiments in which samples of platinum were compressed dynamically using ramp-shaped laser pulses, and the crystal structure was probed using x-ray diffraction. Up to 2.1 TPa, the measured diffraction patterns were consistent with the face centered cubic (fcc) structure. The results demonstrate the near-isentropic nature of the loading path obtained in a laser-driven multi-layer sample and the suitability of Pt as a single-phase standard for use in high pressure experiments. [Preview Abstract] |
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V1.00040: ABSTRACT WITHDRAWN |
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V1.00041: Time-resolved x-ray imaging of void collapse at 10 micron length scales Michael Armstrong, Ryan Austin, Eric Bukovsky, Paul Chow, Paulius Grivickas, Joshua Hammons, Batikan Koroglu, Andrew Robinson, William Shaw, Trevor Willey, Yuming Xiao Pulsed x-ray imaging can provide substantial insight into a wide range of initiation-related phenomena, particularly the in situ imaging of dynamically compressed voids, which are thought to play a fundamental role in explosive initiation. Current models of the dynamic compression behavior of inhomogeneous materials are empirically calibrated to bulk, aggregate experimental data. The development of more fundamental models depends on detailed measurements and corresponding simulations which resolve single void collapse events. Further, since material strength depends on scale, experiments at the scale of actual voids (\textless 10 $\mu $m) are preferred. Since the field of view for these experiments is relatively small (\textasciitilde 100s $\mu $m) and void collapse occurs at low pressure, these experiments can be performed with a small scale (100 mJ) laser in a portable experimental setup. Here we present the results of x-ray imaging experiments at the Advanced Photon Source on voids embedded in TNT and silicon using both explosive and laser-driven shocks, which approach the spatial scale of void collapse in actual explosives, 1-10 $\mu $m. [Preview Abstract] |
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V1.00042: Experiments and modelling of explosive loading of several sands S.A. Weckert, A.D. Resnyansky The present work suggests an experimental set-up for analysing the shock transfer through porous materials such as sand. Within this set-up, the corresponding experiments observe the shock wave transmission through a porous material using flash X-ray images of the deformation of a circular thin metallic plate, where the plate is impacted by the material ejecta due to the loading by a buried high explosive charge. The materials analysed include calcite and several quartz-based sands. The loading is performed by two different charge configurations representing a variability in the loading input. The images demonstrate a good sensitivity of the suggested test set-up to the material variations, which enables one to employ the corresponding test results for model validation. The observations are used in the present work for validation of a two-phase material model implemented in the CTH hydrocode with constitutive equations obtained earlier with the Split Hopkinson Pressure Bar and shock consolidation tests. The CTH modelling employing the two-phase model demonstrates that the model is suitable for describing the test results. [Preview Abstract] |
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V1.00043: Role of Porosity in Dynamic Compaction via In-Situ X-Ray Probes Ryan Crum, Dorothy Miller, Eric Herbold, Jonathan Lind, Ryan Hurley, Michael Homel, Brian Jensen, Minta Akin Granular systems are ubiquitous in our everyday world and influence many scientific problems including mine blasts, projectile penetration, and astrophysical collisions. Despite its significance, a fundamental understanding of granular media's behavior falls short of its solid counterpart, limiting predictive capabilities. Granular response is complex in part to the intricate interplay between numerous degrees of freedom not present in its solid equivalent. To address the role of geophysically relevant porosity in granular media, previous studies use VISAR or PDV, diagnostics that focus on the aggregate effect leaving the principal interactions of these multiple degrees of freedom too entangled to elucidate. This study uses a gas gun platform coupled to in-situ X-ray probe diagnostics to probe the role of porosity in dynamic compaction. Analyses include evaluating displacement fields and diffraction profiles. Results herein are directly compared to previous studies that were unable to include in-situ X-ray diagnostics. [Preview Abstract] |
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V1.00044: Characterization of Powders using Scanning White Light Confocal Microscopy Adam Golder, Kyle Ramos, Claudine Armenta, Ramon Saavedra, John Lazarz, Ernie Hartline, Gary Windler, Cindy Bolme The distribution of size, shape, and defect density of crystalline explosive powders is known to have a profound effect on explosive processing, sensitivity, and performance. The field of powder sample characterization covers a wide variety of methods for obtaining such information. Scanning white light confocal microscopy (SWLCM) allows for direct measurement of particle height data in the Z direction, in addition to the traditional XY directions. This capability can provide an added level of confidence in data when compared with other methods that record 2D information and use stereological assumptions in parameter/distribution analysis (e.g. providing volume as opposed to area-based distributions). Oftentimes common assumptions of simple geometric shapes do not represent the morphology of explosive crystalline powders well. For optically transparent crystals, including HE powders, SWLCM can also be used to characterize crystal defects and morphology. Baseline measurements of NIST Standard Reference Material (SRM) powders with known PSDs are made using this method and results are shown. A broad view of powder handling and observation techniques will be presented, in addition to results and specific material challenges of SWLCM. [Preview Abstract] |
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V1.00045: Modeling Dynamic Rate Dependent Pore Closure with a Range of Pore Sizes Yehuda Partom Previously we presented a model (which we call PORT) for rate dependent pore closing/opening, for which we assumed that all pores close/open with the same dynamics. Here we upgrade PORT to take into account different dynamics as function of pore size. We represent different pore sizes by their volume (v), and we have k such pore sizes. We therefore call this model VK. For each pore size we have n$_{\mathrm{i}}$ (i$=$1,k) pores per unit mass. We're not aware of any concrete pore size distributions; we therefore assume that pore sizes are initially distributed with a log-normal distribution. Similar to PORT, we define quasistatic pore closure curves which depend on pore volume v, and we compute the rate of pore closure with a linear overstress relation relative to these curves. From the values of v and vdot (rate of change of v) we can then compute (for each computational cell, and for each time within a time step) the overall porosity $\phi $, and its rate of change $\phi $dot. Finally we compute Pdot and Tdot (P$=$pressure and T$=$temperature) in the same way as in PORT, using the equation of state of the porous material. To show how our VK model works we apply it to a simple 1D problem. A 20GPa sustained pressure pulse enters a porous aluminum target. We show histories of pressure, temperature and porosity at several locations into the target. We compare these curves with the ones obtained for k$=$1 (as in PORT). [Preview Abstract] |
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V1.00046: Formulation of experimental methods for measuring the shear strength of granular materials Christopher Coffelt In studies of the shock response of granular materials, multiple compaction models are available by which the pressure-density response of initially distended materials can be captured. These models are typically calibrated by one-dimensional shock compaction experiments, and by neglecting the strength of the underlying material, these pressure-density models can inaccurately capture the true densification response of shocked granular materials, while still matching experimental results in one-dimensional planar geometries. Using the multiphysics hydrocode FLAG, the impact of angled flyer plates of several materials into angled capsules containing thin layers of granular materials was simulated. Comparison of simulation with experiment provides confidence that the methods modeled in this investigation may be used to design future experiments that can help inform the interplay between pressure and shear driven compaction. [Preview Abstract] |
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V1.00047: Numerical simulations of shock wave propagation in granular materials with the multi-phase particle-in-cell method Kun Xue In this work, we numerically investigate the compression of granular phase and the gas infiltration during the shock propagation inside particle columns using the multi-phase particle-in-cell (MP-PIC) method. The gaseous phase is modeled by a high-order accurate five-equations compressible multiphase approach while the motions of discrete particles are governed by Newton's second law which incorporates the transfer of momentum and energy between particle and gaseous phases such that the coupling of particles and gases are fully taken into account. The simulation experiments of the head-on impacts between weak shock waves and particle columns with different permeability reveals how the pore pressure and the total pressure dissipate with the propagation depth. The former strongly depends on the permeability of particle phases while stresses formed inside the granular skeletons which are the total pressure subtracted by the pore pressure are correlated with the solid compression. Also the gas infiltration plays a crucial role in the formation of stresses. Complex, three-dimensional load transfer processes in the granular media, which are extremely difficult to understand from experiments, are visualized based on the results from the present MP-PIC simulation. [Preview Abstract] |
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V1.00048: Constitutive modelling of shock compression of porous materials with two condensed constituents A.D. Resnyansky Condensed constituents of porous materials in many civilian and military applications are usually heterogeneous either by phase or by constituent composition. In particular, the gaseous phase may be critically important for the shock response of porous reactive or energetic materials. In this case a two-phase consideration appears to be very restrictive. The present work introduced a gaseous phase within the three-phase formalism. The phase characterization and phenomenological description of a porous material are realised with the use of a set of parameters representing the bulk behaviour, via the characterisation of the material as a whole, and the phase specific behaviour, via an introduction of parameters responsible for the inter-phase exchange of physical quantities. Conservation laws for the bulk parameters and constitutive equations for the inter-phase exchange parameters form a set of equations of the model. The model is realised as a code for numerical modelling to be used for analysis of the shock response of porous compositions. The analysis shows a good description of the Hugoniot experiments available in literature for graphite-metallic porous mixtures. [Preview Abstract] |
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V1.00049: Molecular dynamic study of mechanical behavior of cis-PB under shock loading Nicolas Pineau, Gautier Lecoutre, Claire Lemarchand, Laurent Soulard Using molecular dynamics to generate relaxed configuration in order to characterize the mechanical behavior of polymers is an application of great interest but require a complex methodology. First of all, we use a versatile algorithm initiated by Lemarchand and al. [1] to generate long and realistic polymer chains of cis-polybutadiene. We performed non-reactive simulations using the OPLS force-field for intramolecular interactions and the Buckingham exponential-6 potential for intermolecular interactions [2]. Under shock compression, the principal aim is to study the mechanical response quantified by Hugoniot curves and the structural properties of the chains such as the radius of gyrations, the chains orientations, the shape… Using explicit shock and Hugoniostat simulation [3], we focus on the influence of different shock regimes and chain length. References [1] C. A. Lemarchand, D. Bousquet, B.Schnell, N.Pineau, submitted to J. Chem. Phys [2] Markus G. Fröhlich, Thomas D. Sewell, and Donald L. Thompson J. Chem. Phys. 140,024902 114:16, (2014) [3] J.-B. Maillet, M. Mareschal, L. Soulard, R. Ravelo, P. S. Lomdahl, T. C. Germann, and B. L. Holian Phys. Rev. E 63, 016121 (2000) [Preview Abstract] |
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V1.00050: Synthesis and Mechanical Characterization of Polyurethane Reinforced with Halloysite Nanotubes Rafaela Aguiar, Oren Petel, Ronald Miller, Anton Lebar, Andrew Oddy Polymer composites containing nano-additive reinforcements have attracted much attention in recent years, enabling tunable properties that benefit certain material applications. In the present work, Halloysite nanotubes (HNT) are introduced into polyurethane at various concentrations to produce a series of nanocomposites. HNT is a natural nanotube formed by surface weathering of aluminosilicate minerals. These polymer nanocomposite systems are investigated for their material properties under quasi-static loading and high-strain-rate conditions. Given that HNT are small enough to be dispersed at the scale of the macromolecular structure of the polymeric matrix, and due to the chemical interaction between the HNT and polyurethane, there is a reinforcement of the polymer matrix at the macromolecular level. HNT was incorporated into poly(propylene glycol), tolylene 2,4-diisocyanate~based polyurethanes, with different chain extenders, 4,4'-methylenebis(2-chloroaniline) and 1.4-butanediol. The degree of chemical interaction between HNT and polyurethane was analysed by Fourier-transform infrared spectroscopy study. The nanocomposite was characterized by using differential scanning calorimetry, scanning electronic microscopy, thermal gravimetric analysis, spall and tensile testing. The reinforcement of the polymer is seen through comparisons of the ultimate tensile strength, strain to failure and spall strength for the pristine and nanocomposite polymer. [Preview Abstract] |
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V1.00051: X-ray phase contrast imaging to study the effects of feedstock chemistry on shockwave behavior in additive manufactured foams Brittany Branch, Kwan-Soo Lee, Samantha Talley, Joshua Coe, Dana Dattelbaum There has been a large effort to develop unique polymer feedstocks containing carbon fiber, metal oxide and other filled inks with unique mechanical properties for the fabrication of polymer material assemblies through high spatial resolution additive manufacturing (AM) techniques. Advancement of these fabrication methods has led to the development of under-dense materials suitable for vibrational dampening applications. Here, we evaluate the dynamic behavior of these materials through x-ray phase contrast imaging coupled to shockwave experiments to understand how material properties at high strain rate are affected by additives that have an overall effect on material strength. The experimental methods and results comparing the mechanical response and the resulting shockwave behavior of a variety of feedstocks will be presented. LA-UR-19-21616 [Preview Abstract] |
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V1.00052: Electronic transport properties of Li$_2$Sn$X_3$($X$=S, Se) from first principles calculation Enamul Haque, Md. Anwar Hossain Lithium-based materials usually exhibit very attractive properties such as fast ionic conduction and high thermal stability. Here, the calculated electronic transport properties of fast ion conductors using the first-principles method will be presented. All the calculations have been performed by using Tran-Blaha-modified Becke-Johnson (TB-mBJ) potential. The obtained indirect bandgap of Li$_{\mathrm{2}}$SnS$_{\mathrm{3}}$ is 2.14 eV, which fairly agrees with the measured value of 2.38 eV. But Li$_{\mathrm{2}}$SnSe$_{\mathrm{3\thinspace }}$shows direct bandgap (1.95 eV). The energy bands of both materials are flat that lead to high Seebeck coefficient approaching \textasciitilde 326 \textmu V K$^{\mathrm{-1\thinspace }}$at 700 K. The combination of high Seebeck coefficient and conductivity leads to high power factor (reaching \textasciitilde 6 mW m$^{\mathrm{-1}}$ K$^{\mathrm{-1\thinspace }}$at 700 K). Because of their high thermal stability and high power factor, both materials are the potential candidate for thermoelectric device applications. The electronic structure and physical mechanism behind high power factor will be explained in details. [Preview Abstract] |
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V1.00053: Preparation of Graphene Materials through Pulsed Wire Discharge Xin Gao, Hao Yin, Chunxiao Xu, Shigeru Tanaka, Kazuyuki Hokamoto, Pengwan Chen Graphene is a two-dimensional structure of carbon atoms packed into a honeycomb lattice, which is known as the thinnest material thus far. The graphene materials feature multiple properties and have been used in various applications. Pulsed wire discharge refers to a series phenomena induced by a huge energy input in a conductive wire using pulsed discharge. Once the current passes through the wire, it melts and vaporizes in microseconds to produce a mixture of droplets and vapors at high temperature and pressure. The products scatter out with a shockwave in medium and cools down to form nanoparticles subsequently. In this study, graphene materials were produced using graphite stick and graphite wire via pulsed wire discharge in distilled water. The as-prepared samples were characterized by various techniques to confirm the formation of graphene materials. In this method, delicate control of energy input is critical for graphene formation. The graphitic layers were exfoliated from graphite materials by thermal expansion effect. On the basis of pulsed wire discahrge, the corresponding mechanisms that governs the graphene generation were carefully illustrated. [Preview Abstract] |
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V1.00054: Hypersonic Cryogenics: Stochastic Shock Compression Modelling Charles Janeke In order to beat shockwave formation blasting a cryogenic chilled copperball @M5x120K (atmospheric) oxygen saturation nexus was postulated early 2010 to beat shockwave formation at the Prandtl-Glauert singularity; that was successfully tested at the Virginia Tech (VT) Ocean and Aerospace lab Blacksburg, VA July 2010. The ensuing CRYSONIX© event opened the door to the science of hypersonic cryogenics, a stochastic (vortex transformation) process. By development the CRYSONIX art was subsequently transformed into the SPINNX© (extreme) vortex choke through the course of May 2013 and consequently the SPLINES/BLOTS© shockwave piercing nosecone/slats (outside the cryogenic zone) through the course of June 2016. The presentation will focus on (1) PRANDTL-JOUKOWSKY convergence (2) GAUSS-MARKOV harmonics (3) HYPERSONIC-STOCHASTIC-SWITCH© (4) SPINNX/SPLINES/BLOTS shockwave piercing attributes (5) emergence of stochastic CFD art (6) SHOCK COMPRESSION generally and (7) stochastic modeling of BLACK-HOLE-JETS (APS 01/23/2019) via superposition of stochastic and real tensors. [Preview Abstract] |
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V1.00055: Study of soft material blast mitigation effects using a shock tube Danyal Magnus, David R. Sory, James Lee, Mansoor Khan, William Proud Trauma inflicted by explosions can result in highly complex blast injury profiles that remain poorly understood. The extensive injury pathophysiology includes primary injuries, inflicted by the propagation of the blast wave, and secondary injuries, caused by ballistic impact. The latter threat may be effectively diminished by conventional personal protective equipment. However, mitigation of primary injuries to critical gas-containing structures, especially the lungs and gastro-intestinal tract, by lightweight armour practical for personal use has received relatively less attention. In this study, the blast mitigation performance of soft polymers and hydrogels in both homogenous and cellular form were investigated under differing loading conditions. Following mechanical characterisation, samples were loaded using a 60 mm air-driven shock tube to generate blast waves with peak pressures ranging from 200 to 800 kPa. The effect of rigid and intermediate strength, represented by a biofidelic gelatine tissue simulant, rear boundary conditions were considered in addition to the influence of an air gap between the sample and rear surface. The resulting mitigation or enhancement of peak pressure and impulse were measured. [Preview Abstract] |
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V1.00056: Probing ultrafast shock-induced chemistry in liquids using broad-band mid-infrared absorption spectroscopy Pamela Bowlan, Michael Powell, Romain Perriot, Enrique Martinez, Edward Kober, Marc Cawkwell, Shawn McGrane Chemical reactions can happen within picoseconds (ps) behind strong shock waves. To better understand shock-induced chemistry in explosives, we developed an experiment to probe ultrafast shock-induced changes in the vibrational spectrum which can be linked to changes in molecular and intramolecular structure and can give information about the rate of loss of reactants, intermediate states and reactants. We will present our recent results applying this to shocked liquids where we compare a reactive and nonreactive case. For nitromethane, which was laser shocked to 25 GPa and promptly reacts, we see the vibrational modes vanish in less than 50 ps and the appearance of a broad infrared spectrum corresponding to the complex mixture of products. For benzene shocked to 18 GPa, which does not react within the 300 ps window of our experiment, we see pressure and temperature broadening of the vibrational modes. Comparing these results to reactive molecular dynamics simulations, we found good agreement and confirmed our interpretation of the measurements. [Preview Abstract] |
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V1.00057: Shock Hugoniot Relationships for Crystalline and Amorphous HNAB: Insights from Atomistic Simulations and Virtual Diffraction Calculations James A. Stewart, Joseph D. Olles, Ryan R. Wixom, Remi Dingreville The equation-of-state (EOS) for energetic materials characterizes the physical state of a system, e.g., temperature, pressure, and volume, when the material is subjected to sufficient shock conditions. The exact configuration of the microstructure (crystalline vs. polycrystalline vs. amorphous) further complicates the realized shock properties. This is especially the case in a model energetic system such as hexanitroazobenzene (HNAB), which can exist in crystalline or amorphous states. However, a fundamental understanding of the shock Hugoniot relationship as a function of crystalline structure, or lack thereof, is not well studied. As such, the goal of this work is to utilize molecular dynamics (MD) simulations and virtual diffraction calculations to elucidate the complex interplay between microstructural configurations, atomic-level processes, and the shock Hugoniot EOS in HNAB. First, we calculate the Hugoniot EOS for both the crystalline and amorphous HNAB polymorphs to compare the Hugoniot relationships between different crystal structures of the same material. These simulations systematically provide insight into the role of atomic structure on the resulting shock properties. Second, we perform virtual diffraction calculations on these atomistic data sets to identify possible structural changes occurring during the simulated shock compression. Taken together, these simulations bring a new understanding to the complex relationship between microstructure and shock properties in molecular crystals. [Preview Abstract] |
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V1.00058: Flyer plate impact tests to investigate the spall fracture of two armor steels Hongxu Wang, Simon Higgs, Ali Ameri, Manny Gonzales, Brodie McDonald, Paul Hazell, Zongjun Li, Juan Escobedo-Diaz This study examines the dynamic fracture behavior and spall strength of a high hardness armor (HHA) steel and an improved rolled homogenous armor (IRHA) steel. Flyer plate impact tests were conducted at about 240 and 500 m/s, which provided peak stresses of 4.5 GPa that caused incipient damage, and 10 GPa which resulted in full spall, respectively. Free surface velocities were measured by Photon Doppler Velocimetry (PDV) and the damage examination was conducted by conventional light optical microscopy (LOM) and scanning electron microscopy (SEM). Results show that HHA specimens exhibited about 10{\%} higher spall strength and Hugoniot elastic limit (HEL) than IRHA specimens at the same peak compressive stresses. Post-mortem examinations revealed that the HHA steel exhibits brittle fracture indicated by shear banding seen on the fracture surface and crack propagation through the thickness. In contrast, a more ductile fracture indicative of void growth and coalescence fracture mechanisms, was observed throughout the fracture surface of IRHA. [Preview Abstract] |
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V1.00059: Unique Regimes of High Energy Density Physics Through the NIF Discovery Science Program Bruce A. Remington The Discovery Science program at the National Ignition Facility (NIF) laser at Lawrence Livermore National Laboratory (LLNL) offers access to unique regimes of high energy density (HED) science. Examples from recent Discovery Science experiments include VISAR measurements of the equation of state (EOS) of carbon up to 50 Mbar, [1] iron at 14 Mbar, [2] and hydrogen up to 6 Mbar [3]. We havealso measured the absolute EOS of polystyrene to 60 Mbar with radiography of a spherically converging shock wave. [4] And using two-dimensional, face-on, time resolved radiography of accelerated, Rayleigh- Taylor unstable foils, we have inferred the strength of ductile metals at peak pressures of ~3 Mbar or higher, and strain rates of ~1.e7 1/s. [5, 6, 7] Examples from these experiments on NIF will be given. \\ $[1]$ R.F. Smith, Nature 511, 330 (2014). \\ $[2]$ Raymond F. Smith et al., Nature Astronomy 2, 452 (2018). \\ $[3]$ Peter M. Celliers et al., Science 361, 677 (2018). \\ $[4]$ Tilo Doeppner et al., PRL 121, 025001 (2018). \\ $[5]$ Hye-Sook Park et al., PRL, in preparation (2019). \\ $[6]$ A. Krygier et al., PRL, submitted (2019). \\ $[7]$ B.A. Remington et al., Proceedings of the U.S. National Academy of Sciences (PNAS), Published: 2018-Jun-26 (Epub 2018 Jun 26). \\ [Preview Abstract] |
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V1.00060: Saturable Absorption of Shock Waves in Metal-Organic Framework Xuan Zhou The large mechanical energy storage capacity of metal-organic frameworks (MOFs) has suggested their promising potential as shock protective armor materials. Here, we performed shock compression of MOF (ZIF-8) film to understand the shock attenuation mechanisms in MOFs and develop a method that predicts the output shock energy from different thicknesses of shock absorbing materials. The shock wave was generated from the impact of an aluminum flyer plate and ZIF-8 film. The flyer plate (500 $\mu$m diameter, 75 $\mu$m thick) was accelerated to 0.6-1.9 km/s by a flat-top pulsed laser. It impacted the ZIF-8 film of 4-110 $\mu$m thick after stabilizing its transient in vacuum. The shock wave propagated through the ZIF-8 film and reached an ultra-thin gold mirror, whose motion was tracked by a photon-Doppler velocimeter (PDV). By carrying out a post-mortem study, we found that the shock wave was absorbed by MOFs through powder compaction, nanopore-collapse, and chemical bond breakage that were activated at distinct shock energies. The PDV energy profiles shows that ZIF-8 films are 2.5-7 times more efficient than PMMA in shock energy absorption. We also found that the shock wave energy follows a saturable absorption trend over the shock propagation distance in the material. [Preview Abstract] |
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