Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session L23: Materials in Extremes: Dynamic CompressionFocus Live
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Sponsoring Units: GSCCM Chair: J Matthew Lane, Sandia National Laboratories |
Wednesday, March 17, 2021 8:00AM - 8:12AM Live |
L23.00001: Kinematics of slip-induced rotation during uniaxial compression Patrick Heighway, Justin Stephen Wark When a metallic specimen is plastically deformed, its underlying crystal structure must often rotate in order to comply with its boundary conditions. There is growing interest in the dynamic compression community in exploiting x-ray diffraction measurements of lattice rotation to infer which combinations of plasticity mechanisms are operative in uniaxially shocked crystals, and thus inform materials science at extreme pressures and strain rates [see for example Wehrenberg et. al., Nature 550, 496-499 (2017)]. However, it is not widely appreciated that many existing models linking rotation to slip activity are fundamentally inapplicable to a planar shock-loading scenario. We have conducted classical molecular dynamics simulations of single crystals suffering true uniaxial strain, and have found that the Schmid and Taylor analyses frequently used in traditional materials science fail to predict the ensuing texture evolution. We propose a simple alternative framework that successfully recovers the observed rotation, and can further be used to correctly identify the active slip systems in the idealised cases of single and conjugate slip. We also explore the implications of the Taylor ambiguity for our simple model. |
Wednesday, March 17, 2021 8:12AM - 8:24AM Live |
L23.00002: Extreme Tension Wave Profile in Al6061 Seokbin (Bin) Lim, Angel Chavira, Matthew Hirsch, donghyeon Ryu An understanding of the extreme tension wave is necessary to study various applications including fragmentation, crack formation, etc. This information is also useful to see the whole spectrum of extreme materials behavior ranging from the compression to tension. Historically this analysis has depended on the series of empirical tests with multi-dimensional (or finite sized) configurations preventing the proper analysis of the fundamental of the extreme tension wave propagation. This is mainly due to the propagation of necking or edge release wave into the local area of interest. |
Wednesday, March 17, 2021 8:24AM - 8:36AM Live |
L23.00003: Modeling of Shock Wave Propagation in Woven Composites Nicholas Scott, Arunachalam Rajendran Plate impact simulations of a metallic flyer impacting a woven glass-fiber reinforced plastic (GRP) at various velocities are performed using the ALE3D finite element code. GRP VISAR data from a series of one-dimensional strain-based shock wave experiments available in open literature by Tsai et al. (2009) were utilized in the calibration of a hyperelasticity constitutive equations based continuum damage mechanics (CDM) model. The damage model considered various failure modes, such as delamination, matrix cracking, bulking, and fiber failure. The experimental data included D7 Tool Steel and 7075-T6 aluminum flyer plates and two different GRP thicknesses (6.8 mm or 13.6 mm) with a range of impact velocities from 8.5 m/s to 418 m/s. The damage model realistically captured several salient features of the experimental wave profiles in terms of the shock rise time and the shape of the non-linear portions beyond the Hugoniot Elastic Limit (HEL). |
Wednesday, March 17, 2021 8:36AM - 8:48AM Live |
L23.00004: Exploring the Limits of Material Strength Quantified Through Experiment and Theory Mitchell Wood, James Stewart, Joseph D Olles Experiments to study materials at high pressure are challenging and time consumptive, therefore we turn to modeling tools to refine and predict outcomes beforehand. Efficient models balance absolute physical accuracy against approximate but computationally lightweight constitutive inputs. By using a relatively small number of high-fidelity simulations and experiments we have been able to broaden the predictive power of the shock response in metals and polymers. We have tailored the analysis of these simulations to determine a size dependent material strength, which can be used as constitutive model inputs for continuum hydrodynamics codes. Simulations of shocked Cu utilizing Molecular Dynamics(MD) simulations show a yield strength from Richtmeyer-Meshkov Instability(RMI) jet growth of approximately 450MPa that depends on the details of the free surface geometry. This is in agreement with our experiments at the Dynamic Compression Sector where an elastic-perfectly-plastic strength model was parameterized from phase-contrast imaging of the RMI jetting. The same analysis applied to MD simulations of PMMA jetting resulted in no clear determination of yield strength, implying a more complex RMI process in polymeric materials. |
Wednesday, March 17, 2021 8:48AM - 9:00AM Live |
L23.00005: Dynamic crystal plasticity modeling of single crystal tantalum and validation using Taylor cylinder impact tests Thao Nguyen, Saryu Fensin, Darby J Luscher We have significantly extended a previous dislocation-density based constitutive theory to enable modeling the strong influence of temperature and strain rate on the thermomechanical behavior of single crystal body centered cubic (BCC) tantalum. The extension include an expression of saturation dislocation density as a function of instantaneous strain rate and temperature and a dynamic recovery fraction that effectively saturates the immobile dislocation density. Crystallographic slip along <111> on the {110} or {112} planes as well as their combination are examined. The model is calibrated using a Bayesian approach against experimental measurements include uniaxial stress-strain curves obtained from quasi-static and split Hopkinson pressure bar (SHPB) compression tests in a wide range of strain rate and temperature, and velocity-time histories from single crystal flyer plate impact experiments. The calibrated model was applied to simulate previous Taylor cylinder impact experiments. The comparison of deformed Taylor cylinder shapes between the simulation and experiments sheds light on activated slip systems in single crystal tantalum. |
Wednesday, March 17, 2021 9:00AM - 9:12AM Live |
L23.00006: Using time-resolved XRD to understand the behavior of the elastic properties along the Hugoniot and shock melting Matthew Beason, Brian Jensen Traditional shock experiments have measured the velocity of the leading edge of a rarefaction wave following shock to determine the melting point on the Hugoniot. For a typical metal, the velocity of the rarefaction front increases with pressure before thermal softening occurs along with a significant reduction in velocity before again increasing with pressure. This reduction in velocity is associated with the melt transition, as the leading edge shifts from propagating at the longitudinal sound speed in the solid (CL) to the bulk sound speed of the liquid phase (CB). Typically, incipient melt (melt onset) is determined by an empirical fit to the transition from CL to CB or determining the point where CL is equal to the bulk sound speed in the solid phase using an equation of state. We have examined shock melting in both Mg and Ce by combining sound speed measurements taken at LANL with time-resolved diffraction experiments performed at the Dynamic Compressions Sector (DCS). The results, presented here, have yielded insight into the behavior of CL leading into the melt boundary and the melt transition, leading to a greater understanding of shock melting and methods for determining incipient melt and melt completion from sound speed data. |
Wednesday, March 17, 2021 9:12AM - 9:24AM Not Participating |
L23.00007: Particle based studies in support of high-power laser experiments to study metal ejecta interactions Tomorr Haxhimali, Marco J Echeverria, Kyle Mackay, Suzanne J Ali, Jon Henry Eggert, Brandon E Morgan, Fady Michel Najjar, Hye-Sook Park, Yuan Ping, Camelia V Stan, Alison Saunders Shock-driven material can emit a fine spray of ejecta from its free surface. Understanding the dynamic and interaction of the metal ejecta is important to areas of study as diverse as industrial safety, astrophysics, spacecraft shielding, and inertial confinement fusion. |
Wednesday, March 17, 2021 9:24AM - 10:00AM Live |
L23.00008: Studies of materials at extreme states of pressure and density on the NIF and Omega lasers Invited Speaker: Bruce Remington A selection of recent studies of materials at extreme states of pressure and density on the National Ignition Facility (NIF) and Omega lasers will be reviewed. We will illustrate measurements of the equation of state (EOS) of materials, phase, temperature, and solid-state plastic flow at high pressures and strain rates. Specific examples include ramp compression EOS of deuterium, carbon, and iron under planetary core conditions using VISAR diagnostics. We will also present examples of phase measurements using time resolved diffraction of water to 4 Mbar and lead to pressures of 20 Mbar. Experiments to measure the temperature of matter at HED systems up to 6 Mbar using the extended x-ray absorption fine structure (EXAFS) diagnostic will be described. Radiography experiments have been done in spherically converging geometry to measure matter at white dwarf envelop conditions. And finally, ramp driven Rayleigh-Taylor experiments have measured the solid-state plastic flow of ductile metals at pressures of 1-8 Mbar on NIF and Omega. |
Wednesday, March 17, 2021 10:00AM - 10:12AM Live |
L23.00009: Simulations of Phonon Modes in Laser-Plasma Compressed Solids Oliver Karnbach, Patrick Heighway, Andrew Comley, David McGonegle, Robert E Rudd, Gianluca Gregori, Justin Stephen Wark Shock and quasi-isentropic compression of solid-state matter via laser-ablation affords the creation of high energy density states of matter, with pressures and temperatures of relevance to core conditions within planets in our own solar system and beyond. Crystallographic phase and density can be discerned via ultra-fast x-ray diffraction, whilst pressure is deduced from VISAR measurements. Temperature is more difficult to determine, but techniques based on inelastic scattering from phonons are being considered [1,2]. It is in this context that we present here multi-million atom molecular dynamics simulations of the phonons present in fcc crystals shocked beyond their elastic limit. Despite high dislocation densities behind the shock front, distinct phonon modes can still easily be discerned, though such defects do contribute to the quasi-elastic peak that will compete with any inelastic scattering signal in a real experiment. Changes in the dispersion curves due to compression and the high number of stacking faults can also be observed. |
Wednesday, March 17, 2021 10:12AM - 10:24AM Not Participating |
L23.00010: Experiments studying the flow strength of tantalum up to 30 GPa Frank Cherne, Matthew Hudspeth, Michael Prime, Brian Jensen In the recent years, there has been a number of experiments performed looking at different platforms or techniques to probe the strength of tantalum. The focus of this research has been to applya shock/double shock drive conditions to determine the flow strength in tantalum up to about 30 GPa. Theelastic/plastic response of tantalum and its interaction with typicallower impedancewindow materials complicatesthe design of these experiments. In this work, we present the results where we applied the shock/reloading techniqueto determine the flow strength of tantalumatinitial loading stress states up to 30GPa. Simulations with and without a PTW strength model are also compared to the experimental data. |
Wednesday, March 17, 2021 10:24AM - 10:36AM Not Participating |
L23.00011: Experiments and Simulations of Shocked and Ramp-Compressed Metals Jeffrey Nguyen, Minta C Akin, Paul D Asimow In this report, we present data from a series of shock and ramp-compression experiments on various metals including tantalum, iron, and tin. We used graded density impactors (GDIs) to design compression pathways reaching as high as 5 Mbars. To analyze these data, we utilize both backward (characteristics) and forward analyses. The former method does not require a priori knowledge of the pressure drive but often fails in the presence of material strength or phase transitions. By employing simulations in the analysis of these experiments, we can reduce experimental uncertainty while both correcting for and gaining better understanding of phase transition and strength effects during ramp compression. We will also report on recent simulation efforts to optimize GDI design and manufacture for equation of state experiments and to refine criteria for GDI quality assurance. |
Wednesday, March 17, 2021 10:36AM - 10:48AM Live |
L23.00012: Investigating spall failure in shock compressed iron Gaia Righi, Carlos Ruestes, Camelia V Stan, Suzanne J Ali, Robert E Rudd, Hye-Sook Park, Marc A Meyers The spall response of pure iron was studied using high power pulsed laser experiments at the LLNL Janus facility. Thin iron foils of varying initial microstructures were subjected to peak pressures of about 60 GPa and strain rates ranging from 106 s-1 – 107 s-1. Simultaneous time-resolved free surface velocity measurements and recovery techniques were used to investigate spall strength and failure mechanisms. These uniaxial strain experiments yielded strengths between 5 and 10 GPa for nanocrystalline and single crystal iron, respectively. Post-shock characterization and Molecular Dynamics simulations verify that this difference in strength is due to void initiation sites. Grain boundaries in nano and polycrystalline iron are favorable sites for voids to form and will consequently cause failure to occur along grain boundaries perpendicular to the shock direction. In contrast, the formation and interaction of twin boundaries in single crystal iron are the cause for void initiation, growth, and coalescence that ultimately cause ductile failure. |
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