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 L8: Particulate Matter II: Penetration and Cratering |
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Chair: Eric Herbold, Lawrence Livermore National Laboratory Room: Grand Ballroom C |
Tuesday, July 11, 2017 3:45PM - 4:00PM |
L8.00001: Interrogating heterogeneous compaction of meteoritic material at the mesoscale using analog experiments and numerical models James Derrick, Michael Rutherford, Thomas Davison, David Chapman, Daniel Eakins, Gareth Collins Chondritic meteorites were lithified during solar system formation by compaction of bimodal mixtures of mm-scale, spherical, solidified melt droplets (chondrules) surrounded by a porous matrix of much finer grained dust. A possible compaction mechanism is low-velocity planetesimal collisions, which were common in the early solar system. Mesoscale numerical simulations of such impacts indicate heterogeneous compaction, with large porosity and temperature variations over sub-mm scales in the matrix and chondrules largely unaffected. In particular, compaction and heating are enhanced in front of the chondrule and suppressed in its wake. Such observations may provide a new tool for interpreting evidence for impact in meteorites. Here we present impact experiments that replicate compaction surrounding an individual chondrule using analog materials: Soda Lime glass beads/rods and 70\% porous silica powder matrix (Sipernat). Real-time, X-ray imaging of the experiments, combined with mesoscale modelling, provides experimental confirmation of anisotropic matrix compaction surrounding individual chondrules, aligned with the shock direction. [Preview Abstract] |
Tuesday, July 11, 2017 4:00PM - 4:15PM |
L8.00002: Modeling the Shock Hugoniot in Porous Materials Kyle R. Cochrane, Luke Shulenburger, Thomas R. Mattsson, J. Matthew D. Lane, Philippe F. Weck, Tracy J. Vogler, Michael P. Desjarlais Porous materials are present in many scenarios from planetary science to ICF. Understanding how porosity modifies the behavior of the shock Hugoniot in an equation of state is key to being able to predictively simulate experiments. For example, modeling shocks in under-dense iron oxide can aid in understanding planetary formation and silica aerogel can be used to approximate the shock response of deuterium. Simulating the shock response of porous materials presents a variety of theoretical challenges, but by combining ab initio calculations with a surface energy and porosity model, we are able to accurately represent the shock Hugoniot. Finally, we show that this new approach can be used to calculate the Hugoniot of porous materials using existing tabular equations of state. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Tuesday, July 11, 2017 4:15PM - 4:30PM |
L8.00003: Engineering formulas for penetration of sand by high speed projectiles Stephan Bless, Mehdi Omidvar, Magued Iskander Penetration of sand can be described by a Poncelet equation. However, it is necessary to use two values for the Poncelet drag, depending on whether the penetration velocity is above or below the value at which significant grain crushing occurs. Published data for laboratory-scale time-resolved penetration of sand are reviewed and in some cases reanalyzed in order to determine values of Poncelet coefficients for silica sand. A variation with relative density (e.g. porosity) is needed for the drag parameter. A depth dependence for the Poncelet strength is also proposed. The calibrated Poncelet equation can be used to make prediction for penetration into silica sand by rigid projectiles for the velocity range of tens to hundreds of meters per second. [Preview Abstract] |
Tuesday, July 11, 2017 4:30PM - 4:45PM |
L8.00004: Shaped Charge Particle Jet Penetration in Limestone David Damm, Andrew Seagraves, Moises Smart Oil well perforators typically consist of shaped charges that use powdered metal liners to form high-velocity particle jets. Although the physics of jet penetration is well established for solid materials, the particle jet poses computational challenges. We report on the development of a particle-scale model of a jet penetrating a limestone (CaCO3) target. The particles vary in size (1--500 microns) and consist of one or more materials (e.g., tungsten or copper). Interparticle spacing is adjusted to match the apparent jet density (experimentally determined from flash X-ray images of powdered metal jets). The limestone target is 100{\%} calcite, with log-normal size distribution of circular voids randomly distributed throughout the matrix. Voids can be empty or filled with fluid, such as brine or hydrocarbons. At low-impact velocities, the strength of the particles and calcite matrix strongly influences penetration depth, tunnel diameter, and other tunnel features. At higher velocities, strength is less important; density and compressibility become the dominant parameters. Results of particle-scale simulations are compared with continuum calculations of multimaterial porous jets with bulk-averaged properties. The continuum models perform reasonably well under certain conditions, although some discrepancies between model results exist. Particle-scale simulations are being investigated as a means to parameterize the continuum models for full-scale simulations of oil well perforators.$^{\mathrm{ \newline }}$ [Preview Abstract] |
Tuesday, July 11, 2017 4:45PM - 5:15PM |
L8.00005: Impact cratering on high-porosity planetary bodies Invited Speaker: Gareth Collins Porous materials abound in the Solar System. Primordial solids accreted gently from dust into high-porosity aggregates; many asteroids appear to be loosely-bound rubble piles; and the crusts of airless planetary surfaces are heavily fractured from prolonged bombardment of asteroids. High porosity attenuates shock propagation and localizes shock heating, which has several important implications for the evolution of planetary surfaces. Most studies of impact cratering have focused on targets composed of common geologic materials, such as soils and rock, thought to be reasonable proxies for the surfaces of the terrestrial planets. However, it has become clear that those materials are not good analogues for the minor bodies of the Solar System. Here we present numerical and experimental results of impact cratering in high porosity materials that elucidate the compaction regime of planetary cratering: where crater growth is dominated by impactor penetration and compaction, while rapid shock attenuation and extensive collapse limit the volume and speed of ejected material. Understanding these effects is a crucial step in using crater populations to estimate impactor flux, date planetary surfaces and infer subsurface properties, as well as deflecting hazardous near-Earth asteroids.\\ \\In collaboration with: Kevin Housen, The Boeing Co. [Preview Abstract] |
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