Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session J4: Inelastic Deformations, Fracture and Spall VII |
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Chair: Ryan Austin, Lawrence Livermore National Laboratory Room: Regency Ballroom A |
Tuesday, July 11, 2017 11:15AM - 11:45AM |
J4.00001: Cross-scale MD simulations of dynamic strength of tantalum Invited Speaker: Vasily Bulatov Dislocations are ubiquitous in metals where their motion presents the dominant and often the only mode of plastic response to straining. Over the last 25 years computational prediction of plastic response in metals has relied on Discrete Dislocation Dynamics (DDD) as the most fundamental method to account for collective dynamics of moving dislocations. Here we present first direct atomistic MD simulations of dislocation-mediated plasticity that are sufficiently large and long to compute plasticity response of single crystal tantalum while tracing the underlying dynamics of dislocations in all atomistic details. Where feasible, direct MD simulations sidestep DDD altogether thus reducing uncertainties of strength predictions to those of the interatomic potential. In the specific context of shock-induced material dynamics, the same MD models predict when, under what conditions and how dislocations interact and compete with other fundamental mechanisms of dynamic response, e.g. twinning, phase-transformations, fracture.\\ \\In collaboration with: Luis Zepeda-Ruiz, Lawrence Livermore National Laboratory; Alexander Stukowski, Technische Universitat Darmstadt; Tomas Oppelstrup, Lawrence Livermore National Laboratory.\\ \\This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
Tuesday, July 11, 2017 11:45AM - 12:00PM |
J4.00002: Modeling the constitutive response of tantalum across experimental platforms Nathan Barton, Ryan Austin, Justin Brown, Marty Marinak, Hye-Sook Park, Shon Prisbrey Given the complexities of the mechanics related to strength and the wide range of conditions of interest, it is useful to make comparisons across experimental platforms and across computational methods where possible. Modeling results will be presented from one such cross-platform study; including results from plate impact, ramp compression, and Rayleigh-Taylor instability growth experiments. Observables from strength experiments at more extreme conditions are influenced by a variety of material response characteristics, not just by the material's resistance to plastic deformation. Results include sensitivities to some of these other aspects, such as equation of state and shear modulus formulations. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 (LLNL-ABS-724459). [Preview Abstract] |
Tuesday, July 11, 2017 12:00PM - 12:15PM |
J4.00003: Diamond Single Crystals Shocked to Multi-Megabar Stresses: Anisotropy and Deformation M. D. Knudson, J. M. Winey, C. A. McCoy, Y. M. Gupta Although the shock wave response of diamond at high stresses is of wide-ranging scientific and technical importance, it remains poorly understood. To gain insight into material strength/deformation and crystalline anisotropy effects at high stresses, plate impact experiments are underway on diamond single crystals shocked along the [100], [110], and [111] orientations to 300--700 GPa using the Sandia Z facility. Thin copper flyers are launched against diamond crystals, backed by quartz windows, to examine the shock compression and release response. Shock wave transit times in diamond samples and shock velocity histories of the optically reflective wave front in the quartz window are measured using laser interferometry. Preliminary results at $\sim$500 GPa and $\sim$700 GPa peak stresses reveal two-step wave profiles (elastic-inelastic response), with large elastic waves, for [110] and [111] diamond. In contrast, single (overdriven) wave profiles were determined for [100] diamond. Numerical simulations, undertaken to analyze and understand the measured velocity histories, suggest loss of strength for [110] and [111] diamond shocked beyond the elastic limit. Further experiments and comprehensive analysis are underway to understand the strong anisotropy at high stresses. [Preview Abstract] |
Tuesday, July 11, 2017 12:15PM - 12:30PM |
J4.00004: Shock response to solid germanium Kohei Miyanishi, Norimasa Ozaki, Takeshi Matsuoka, Satoshi Matsuyama, Kenjiro Takahashi, Hideaki Habara, Tatiana Pikuz, Anatoly Faenov, Kazuto Yamauchi, Ryosuke Kodama, Kazuo Tanaka, Yusuke Seto, Yoshinobu Tange, Toshinori Yabuuchi, Yuichi Inubushi, Tadashi Togashi, Makina Yabashi, Tetsuya Ishikawa, Michel Koenig, Tommaso Vinci, Takuo Okuchi, Nicholas Hartley, Osami Sakata, Toshimori Sekine, Emma McBride We present a study of shock response to a solid germanium using in-situ femtosecond x-ray diffraction showing anomalous elastic, normal elastic and inelastic deformations. A 3 ns 532 nm laser pulse was used to apply shock stress to a single-crystalline germanium sample along $\langle 001 \rangle$ direction. SACLA x-ray pulse (7 fs, 10 keV), diffracted from the stressed sample, was recorded by a 2D detector. We observed uniaxial deformations with the strain higher than reported Hugoniot elastic limit (HEL) and with the strain corresponding to HEL, and non-uniaxial deformation. These results indicate that a complex strain structure constituting anomalous elastic, normal elastic and inelastic deformations occur in the shocked germanium. [Preview Abstract] |
Tuesday, July 11, 2017 12:30PM - 12:45PM |
J4.00005: ABSTRACT WITHDRAWN |
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