Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session J1: ME.3 Inelastic Deformation, Fracture, and Spall I |
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Chair: Jonathan Crowhurst, Lawrence Livermore National Laboratory Room: Grand Ballroom I |
Tuesday, July 9, 2013 11:00AM - 11:15AM |
J1.00001: The model of particle ejection from a metal free surface Alla Georgievskaya, Michael Antipov, Vladislav Igonin, Alexander Lebedev, Margarita Lebedeva, Konstantin Panov, Vadim Knyazev, Victor Raevsky, Valeriy Sadunov, Alexander Utenkov We present theoretical and computational results of ejecta investigations. We have developed a new model of ejecta taking into account the influence of a shock wave profile on an areal mass (unit area) of ejected particles, a temporal and spatial particle density distribution. According to our analytic solution when the metal free surface interacts with the Taylor wave the mass of ejected particles is less than in case of interaction of the free surface with a supported shock wave. Furthermore, according to this model the total mass of ejecta is independent of shock wave pressure but depends on a correlation of initial perturbations on the free surface and a shock wave pulse duration $\Delta x$, i.e. $m_{\mathrm{s}} =$ $f(k^{2}\cdot a_{0}\cdot \Delta x)$, where $a_{0}$ --a perturbation amplitude, $k =$ 2$\pi $/$\lambda -- $a mode number, $\lambda $ -- a perturbation wavelength. The model also determines the ejecta time which depends on the metal free surface velocity, the shock wave pulse duration and the initial perturbations. This solution is applied to metals when the strength does not affect the Richtmyer-Meshkov instability. We evaluated the total mass of ejected particles and particle density distribution. These estimates conform to the experimental results. [Preview Abstract] |
Tuesday, July 9, 2013 11:15AM - 11:30AM |
J1.00002: Using High Energy Diffraction Microscopy to Assess a Model for Microstructural Sensitivity in Spall Response Nathan Barton, Joel Bernier, Moon Rhee, Shiu Fai Li, Mukul Kumar, John Bingert, Jonathan Lind We present results from a model validation effort that employs detailed non-destructive three-dimensional microstructure data obtained from High Energy Diffraction Microscopy (HEDM) experiments. By focusing validation efforts on models that connect directly to experimentally measurable features of the microstructure, we can then build confidence in use of the models for components prepared under different processing routes, with different impurity distributions, or subjected to different loading conditions. The computational model makes use of a crystal mechanics based constitutive model that includes porosity evolution. The formulation includes nucleation behavior that is fully integrated into a robust numerical procedure, enhancing capabilities for modeling small length scales at which nucleation site potency and volume fraction are more variable. Three-dimensional experimental data are available both pre-shot and post-shot from the same volume of impact-loaded copper. Crystal lattice orientation and porosity data are obtained, respectively, from near-field HEDM and tomography techniques. Starting from the as-measured initial microstructure, simulation results will be compared to post-shot experimental results as a function of modeling assumptions. [Preview Abstract] |
Tuesday, July 9, 2013 11:30AM - 12:00PM |
J1.00003: Fragmentation Under Extreme Conditions: Applications to Risk Assessment and Diagnostic Development at Mega-Joule Class Laser Facilities Invited Speaker: James Stolken The development of Mega-Joule class laser facilities (NIF, USA; LMJ, France, SG-IV, China) has driven the need to understand, predict, and control the risks associated with experimental operations due to ablation, blast, and impact hazards. These hazards potentially jeopardize a broad range of facility assets, such as Targets, Laser Optics, Diagnostics, and other Infrastructure. This presentation shall focus on the application of high-performance computer modeling and simulation (M{\&}S) to quantify and mitigate the risk posed by blast, ablation, and impact hazards. The overall risk management strategy is discussed and the role of M{\&}S outlined. The M{\&}S activities fall within two broad categories, Laser-Material interaction (LM) and Hydro-Structural (HS) simulations. The LM class of simulations addresses the high energy, short time phenomena including laser energy deposition, radiation, ablation, heat-flow, and hydrodynamic motion. The HS class of simulations addresses lower energy, longer time phenomena including hydrodynamic motion, heat-flow, material failure, fracture, and fragmentation. Recent efforts to assess and improve fragmentation simulation capabilities are reviewed. Existing simulations methodologies are evaluated and compared to high fidelity fragment data. Applications to diagnostic development and experimental design are reviewed.\\[4pt] In collaboration with Nathan Masters, Aaron Fisher, Brian Pudliner, Mukul Kumar, Matthew Barham, and Cal Smith, Lawrence Livermore National Laboratory. [Preview Abstract] |
Tuesday, July 9, 2013 12:00PM - 12:15PM |
J1.00004: Surface nano-structuring produced by spallation of metal irradiated by ultrashort laser pulse Nail Inogamov, Vasily Zhakhovsky, Yusuf Emirov, Ivan Oleynik, Sergey Ashitkov, Mikhail Agranat, Anatoly Faenov, Tatiana Pikuz, Masahiko Ishino, Nobory Hasegawa, Masaharu Nishikino, Tetsuya Kawachi Response of metal to heating by ultrashort laser pulse was studied using both two-temperature hydrodynamics modeling and molecular dynamics simulation. Our simulations of Al, Ni and Ta showed that deposition of laser energy in range of $\sim$ 50-200 mJ/cm$^{2}$ in a thin surface layer leads to high electron temperature, which propagates supersonically into the bulk of metal. As a result, the thicker heated layer of $\sim$ 100 nm deep with molten metal in electron-ion thermal equilibrium is formed after several picoseconds. Because expansion of the layer into vacuum, the tensile wave propagates into metal and may produces significant negative pressure. Above some critical energy deposition where the tensile stress exceeding the strength of liquid metal, many voids start to nucleate beneath the surface forming a foam-like material, which may lead to spallation of a liquid shell if its kinetic energy is enough to overcome the tensile strength of foam. We found that the fluence threshold for cavitation is about a few tens percent less than the spallation threshold. Simulated evolution of surface liquid foam, including its breakings and freezing with formation of 3-D nanostructures on surface, was compared with our experimental observations. [Preview Abstract] |
Tuesday, July 9, 2013 12:15PM - 12:30PM |
J1.00005: Ejecta size distribution from the dynamic fragmentation of shock-loaded Cu and Sn metals under melt conditions Olivier Durand, Laurent Soulard Large scale molecular dynamics (MD) simulations are performed to study and to model the ejecta production from the dynamic fragmentation of shock-loaded metals under melt conditions. A generic 3D crystal with about 10$^{\mathrm{8}}$ atoms in contact with vacuum and with a sinusoidal free surface roughness is shock loaded above its fusion point. Two metals are studied (Cu and Sn) and the amplitude of the roughness is varied. The simulations show that the associated time resolved ejecta mass (or size) distributions exhibit a generic behavior with the sum of two distinct terms: in the small size limit, the distribution obeys a power law dependence and in the large size limit, it obeys an exponential form. With the help of additional simple simulations, we show that these two components are the signature of two distinct basic mechanisms of fragmentation. The power law dependence results from the fragmentation of a 2D fractal network of ligaments of liquid metals generated during the ejection process. The exponential distribution results from a 1D Poisson fragmentation mechanism of the largest ligaments previously generated. [Preview Abstract] |
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