Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session B24: Focus Session: Materials in Extremes: High-Strain-Rate Phenomena |
Hide Abstracts |
Sponsoring Units: GSCCM DCOMP DMP Chair: Igor Schweigert, Naval Research Laboratory Room: 326 |
Monday, March 18, 2013 11:15AM - 11:51AM |
B24.00001: Iron and Aluminum at Ultrahigh Strain Rates Invited Speaker: Jonathan Crowhurst In recent years, techniques based on table-top laser systems have shown promise for investigating dynamic material behavior at high rates of both compressive and tensile strain. Common to these techniques is a laser pulse (the ``pump'') that is used in some manner to rapidly deliver energy to the sample; while the energy itself is often comparatively very small, the intensity can be made high by tightly focusing the pump light. In this way pressures or stresses can be obtained that are sufficiently large to have relevance to a wide range of basic and applied fields. Inherent to these techniques too, is relatively low cost and high throughput. Also, by using additional laser pulses (the ``probe'') to measure the response of the sample, very high time resolution can be achieved. The latter in particular is desirable when studying, for example shock waves, in which the time for the material to pass from undisturbed to fully compressed (the ``rise time'') can be extremely short (order 10 ps or less) even at fairly small peaks stresses. Since much of the most interesting physics comes into play during this process it is important to be able to adequately resolve the shock rise. Furthermore, the associated time scale is comparable to that typically considered in state-of-the-art molecular dynamics simulations which are emerging as the theoretical tool of choice for investigating shock waves in condensed matter. It should be pointed out however, that a general drawback to these techniques is that, depending on the aim of the experiment, a small pump energy imposes limits on the nature of the sample; if for example the aim is to study steady shock waves, the compressed region has to be thin, and its internal structure cannot vary on a scale that is not much smaller than the compressed dimensions. We consider and illustrate these concepts in the context of various metals, primarily aluminum and iron, and show how current methods are capable of making meaningful and useful measurements of material behavior at ultrahigh strain rates up to or exceeding 10$^{\mathrm{10}}$ s$^{\mathrm{-1}}$, corresponding to more than 40 GPa in aluminum. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 with Laboratory directed Research and Development funding (12ERD042), as well as being based on work supported as part of the EFree, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award No. DESC0001057. [Preview Abstract] |
Monday, March 18, 2013 11:51AM - 12:03PM |
B24.00002: Orientation-dependent structure of elastic and plastic shock waves in Nickel single crystals Brian Demaske, Vasily Zhakhovsky, Nail Inogamov, Ivan Oleynik The response of Ni single crystals to shock loading has been investigated using molecular dynamics (MD) simulations. It was found that within the elastic-plastic split-shock-wave regime, the amplitude of the elastic precursor in the [111] direction depends strongly on the pressure of the plastic wave; whereas in the [110] direction the pressure of the elastic precursor is pinned. Coupling of the elastic and plastic waves in the [111] direction and lack thereof in the [110] direction is attributed to different activation mechanisms for homogeneous dislocation nucleation (HDN), the major relaxation process observed in our MD simulations. In the [111] direction, thermodynamic fluctuations activate HDN randomly within a metastable elastic zone separating the elastic and plastic fronts, while in the [110] direction HDN is induced by the high levels of shear stresses produced at the plastic front. We will discuss how thermally-activated HDN gives rise to a new pulsating regime of single two-zone elastic-plastic shock waves, where the elastic zone width undergoes significant oscillations in time. [Preview Abstract] |
Monday, March 18, 2013 12:03PM - 12:15PM |
B24.00003: Atomistic simulations of high strain rate loading of nanocrystals E.M. Bringa, D. Tramontina, C.J. Ruestes, Y. Tang, M.A. Meyers, N. Gunkelmann, H.M. Urbassek Materials loaded at high strain rates can reach extreme temperature and pressure conditions. Most experiments on loading of simple materials use poly crystals, while most atomistic simulations of shock wave loading deal with single crystals, due to the higher computational cost of running polycrystal samples. Of course, atomistic simulations of polycrystals with micron-sized grains are beyond the capabilities of current supercomputers. On the other hand, nanocrystals (nc) with grain sizes below 50 nm can be obtained experimentally and modeled reasonably well at high strain rates, opening the possibility of nearly direct comparison between atomistic molecular dynamics (MD) simulations and experiments using high power lasers. We will discuss MD simulations and links to experiments for nc Cu and Ni, as model f.c.c. solids, and nc Ta and Fe, as model b.c.c. solids. In all cases, the microstructure resulting from loading depends strongly on grain size, strain rate and peak applied pressure. We will also discuss effects related to target porosity in nc's. [Preview Abstract] |
Monday, March 18, 2013 12:15PM - 12:27PM |
B24.00004: Rarefaction shock waves in shock-compressed diamond \textless 110\textgreater\ crystal Romain Perriot, You Lin, Vasily Zhakhovsky, Carter White, Ivan Oleynik Piston-driven shock compression of diamond \textless 110\textgreater\ crystal was simulated by molecular dynamics using the REBO potential. At piston velocities between 2 and 5 km/s and corresponding pressures 117 GPA \textless\ P \textless\ 278 GPa, diamond sample undergoes a polymorphic phase transition, characterized by the coexistence of two elastically compressed phases, low-pressure phase A and high-pressure phase B. This phase transition results in the splitting of the shock wave into two elastic shock waves, composed of pure phase A and a mixture of phases A and B. Upon removal of the piston, a release wave is observed at the rear of the sample, turning into a rarefaction shock wave where the material undergoes the reverse phase transition from coexisting phases to the original low-pressure phase. For strong plastic waves induced by larger piston velocities the release wave propagates as a rarefaction wave without any phase transition corresponding to the adiabatic expansion along the plastic branch of the Hugoniot. [Preview Abstract] |
Monday, March 18, 2013 12:27PM - 1:03PM |
B24.00005: Efficient semiclassical quantum nuclear effects for shock compression studies Invited Speaker: Evan Reed A fast methodology is described for atomistic simulations of shock-compressed materials that incorporates quantum nuclear effects in a self-consistent fashion. We introduce a modification of the multiscale shock technique (MSST) that couples to a quantum thermal bath described by a colored noise Langevin thermostat. The new approach, which we call QB-MSST, is of comparable computational cost to MSST and self-consistently incorporates quantum heat capacities and Bose-Einstein harmonic vibrational distributions. As a first test, we study shock-compressed methane using the ReaxFF potential. The Hugoniot curves predicted from the new approach are found comparable with existing experimental data. We find that the self-consistent nature of the method results in the onset of chemistry at 40\% lower pressure on the shock Hugoniot than observed with classical molecular dynamics. The temperature shift associated with quantum heat capacity is determined to be the primary factor in this shift.\\[4pt] In collaboration with Tingting Qi, Department of Materials Science and Engineering, Stanford University. [Preview Abstract] |
Monday, March 18, 2013 1:03PM - 1:15PM |
B24.00006: Study of Plastic flow at high pressures and strain rates via the Rayleigh-Taylor instability Hye-Sook Park, J. Belof, K. Blobaum, R. Cavallo, B. Maddox, C. Plechaty, S. Prisbrey, B. Remington, R. Rudd, C. Wehrenberg, M. Wilson We present the results from study of tantalum material strength at high pressures and high strain rates using the Omega laser system. The Ta sample is maintained in the solid state via a quasi-isentropic ramped drive using a reservoir-gap-sample configuration at high pressures (\textgreater\ 1 Mbar) and high strain rates (10$^{6}$ - 10$^{8}$ sec$^{-1})$. The strength is inferred by measurement of Rayleigh-Taylor induced growth in pre-imposed sinusoidal ripples on a Ta sample [1]. Our study of the samples with single crystal, 0.25, 15 and 90 micron average grain sizes shows that there is no obvious Hall-Petch effect under such extreme conditions. We also show that RT growth is linear as long as the RT growth is below 0.15 of the original sample thickness. We show a comparison of experimental results with the recently developed Livermore Multiscale model that integrates the atomistic scale physics to macro hydro flow simulations. The NIF experimental design will also be presented \\[4pt] [1] H. S. Park et al., PRL. 104, 135504 (2010). [Preview Abstract] |
Monday, March 18, 2013 1:15PM - 1:27PM |
B24.00007: Dynamic diffraction measurements of Ta lattice response under Mbar shock loading conditions Bruce Remington We will report on experiments done on the Omega laser to determine the strength of shock-loaded single-crystal [100] tantalum using in-situ broadband x-ray Laue diffraction. The inferred strength reaches 350 kbar at a shock pressure of 1.8 Mbar and is in excellent agreement with a multiscale strength model, which employs a hierarchy of simulation methods over a range of length and time scales. Laser driven shock experiments using in situ Bragg diffraction were also performed at the Omega-EP laser on single crystal tantalum to study the dynamic yield strength and lattice dynamics. Both techniques will be described, comparisons to the strength models made, and interpretations of the results given. ~Recent results from recovery experiments in shocked single crystal Ta will also be given, showing features such as the residual dislocation density and slip-twinning threshold. [Preview Abstract] |
Monday, March 18, 2013 1:27PM - 1:39PM |
B24.00008: Mesoscale Modeling of Shock Wave Propagation and Dynamic Failure in Metallic Systems Avinash Dongare The response of materials under conditions of thermomechanical extremes is very complex and involves damage creation and propagation, phase transformation, heat generation and transfer, etc. A principal challenge in predictive modeling of failure behavior is presented by the gap between the atomistic description of micromechanisms of the relevant processes and the macoscale response in continuum simulations/experiments. This difficulty can be approached through the development of a robust mesoscopic computational model that retains the relevant physics and is capable of representing the material behavior at time- and length-scales intermediate between the atomistic or continuum levels. \quad Mesoscale models typically reduce a group of atoms by a mesoparticle system with much smaller number of collective degrees of freedom, and hence are often difficult to apply for problems such as heat transfer, phase transformation, and dissipation of mechanical energy during wave propagation. To achieve this goal, a novel mesoscopic model is being developed based on the idea of coarse-graining with the energetics defined for the particles based on interatomic potentials used in molecular dynamics (MD) simulations. The coarse-grained molecular dynamics simulations (CGMD) allows larger size systems and improved time-steps for simulations and thus able to extend the capabilities of MD simulations to model materials behavior at mesoscales. The successful application of the CGMD method is demonstrated by prediction of the phase-transformation, heat generation and wave-propagation behavior under the conditions of shock loading, as would be predicted using MD simulations. [Preview Abstract] |
Monday, March 18, 2013 1:39PM - 1:51PM |
B24.00009: Microstructure in the Extreme Environment: Understanding and Predicting Dynamic Damage Processes Darcie Dennis-Koller, Ellen Cerreta, Curt Bronkhorst, Pablo Escobedo-Diaz, Ricardo Lebensohn The future of materials science: strategic application for functionally controlled materials properties is emphasized by the need to control material performance in extreme environments. This study examines the separate effects of kinetics (in the form of dynamic loading rate and shock wave shape) from that of length-scale effects (in the form of microstructural defect distributions). Recently available mesoscale modeling techniques are being used to capture a physical link between kinetic and length-scale influences on dynamic loading. This work contributes innovative new tools in the form of shock-wave shaping techniques in dynamic experimentation, materials characterization, lending insight into 3D damage field analysis at micron resolution, and the physics necessary to provide predictive capabilities for dynamic damage evolution. Experimental are obtained to provide the basis for the development of process-aware material performance models. [Preview Abstract] |
Monday, March 18, 2013 1:51PM - 2:03PM |
B24.00010: Kinetics of a Fast Moving Partial Dislocation Nitin Daphalapurkar, K.T. Ramesh Plastic deformation in materials under extreme stresses requires a kinetic description of moving dislocations. The velocities with which the partial dislocations can propagate under an applied stress has implications for plasticity at high strain rates, specifically, the rate of plastic deformation and the rate-sensitivity. In this work, we focus our attention on motion of a twinning partial dislocation in a face-centered cubic (FCC) material, Ni. We use molecular dynamics simulations to simulate the velocity of a propagating twinning partial dislocation and investigate the effect of applied shear stress. Results suggest a limiting value for the speeds of a propagating partial dislocation. The material speeds based on the nonlinear part (under high stresses) of the stress-strain curve are shown to have an influence on the velocity with which a partial dislocation can propagate. Predicted velocities from simulations will be related to observations from high rate impact experiments. [Preview Abstract] |
Monday, March 18, 2013 2:03PM - 2:15PM |
B24.00011: Characterization of several martensitic phase transitions under extreme conditions Manling Sui, Shujuan Wang, Wei Zhang, Pengfei Yan In shock-compressed $\alpha $-iron, transmission electron microscopy (TEM) investigations revealed a refined microstructure with tale-telling features that are indicative of $\alpha \to \varepsilon \to \alpha $ sequential martensitic transformations, even though no $\varepsilon $ phase was retained. The unique microstructural fingerprints enable a quantitative assessment of the volume fraction transformed during explosive loading. In a Ti--6Al--4V alloy, an unusual martensitic transformation from $\alpha $-Ti to $\beta $-Ti occurred by a high-density current pulse, instead of the conventional martensitic transformation from $\beta $-Ti to $\alpha $-Ti. A large amount of the high-temperature phase remained. By pulsed laser irradiation, a solid-state phase transition from the $\alpha $ to the $\gamma $ phase of aluminum oxide was observed for the first time. High resolution TEM reveals that the transformation is achieved via the glide of quarter partial dislocations on every other basal plane of $\alpha $-Al$_{2}$O$_{3}$. This martensitic transformation is associated with a positive volume change and substantial shear strain. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700