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 J8: Particulate Matter I: Silicates |
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Chair: Stephan Bless, New York University Room: Grand Ballroom C |
Tuesday, July 11, 2017 11:15AM - 11:30AM |
J8.00001: Multiple wave compression of poly-disperse granular materials using the Split-Hopkinson Pressure Bar Danyal Magnus, Liam Smith, William Proud The compaction of poly-disperse granular materials under compression in a Split-Hopkinson Pressure Bar was investigated for multiple wave traversals through the specimen. Rough sand and fine soda-lime glass granular specimens were studied to provide a comparison between materials of differing strength and morphology. Both materials had a nominal average grain diameter of 0.5mm. By observing compression of the granular specimen for long-durations (up to 10ms), the global plastic response of the granular specimen was observed. After an initial compaction, the material behaviour was found to depend upon strength, achieving either a locked-up state for the glass spheres indicative of force equilibrium, or a ``quasi-locked-up'' state indicative of continued deformation/fracture. In the case of force equilibrium, this is associated with the formation of a force chain network. Hence, any assumption of force equilibrium may only apply after an initial rearrangement within the granular bed. The number of wave reflections before compaction was found to depend on volume fraction. Similarly, the macroscopic sound speed was observed to increase with time during compaction. [Preview Abstract] |
Tuesday, July 11, 2017 11:30AM - 11:45AM |
J8.00002: Effect of Mesostructure and Fragmentation on Planar Shock Response of Dry Sand Sunil Dwivedi, Benjamin Hatanpaa, Kijana Effs, Brian Ferri, Naresh Thadhani The objective of the present work is to gain insight into the role of grain arrangements (mesostructure) and fragmentation on the shock response of dry sand under planar plate impact loading. Mesoscale simulations of the dry sand sample were carried out for initial porosities of 20{\%} and 30{\%} using CUBIT, LS-DYNA, and TECPLOT software. The mesostructure was varied as ordered (grains with edge contacts) and disordered (grains with point contacts) for the same porosity. The grain fragmentation was modeled by erosion method with erosion parameter of 0.5 and 0.75. The results show that computed Us-Up slope for 20{\%} porosity with ordered mesostructure is negative at lower impact velocities and changes to positive when velocity is increased. However, the disordered mesostructure yields positive Us-Up slope at 20{\%} porosity irrespective of the impact velocity. The Us-Up slope for 30{\%} porous sand is positive irrespective of the mesostructure and impact velocity. More importantly, allowing grain fragmentation, the in-situ average longitudinal stress reduces from the computed Hugoniot stress by more than 25{\%}. These results suggest the need for detailed simulations with varying mesostructure and more realistic fragmentation model as well experiments for a dry sand sample at lower porosities. [Preview Abstract] |
Tuesday, July 11, 2017 11:45AM - 12:00PM |
J8.00003: Shock and Release Behaviour of Silica Based Granular Materials Chris Braithwaite, James Perry, Nicholas Taylor A large number of experiments have been conducted using the Cavendish single stage gas gun to investigate the dynamic properties of sand. The results included successful measurements of release in dry materials, demonstrating that this is markedly different to the loading path. The effect of moisture was examined and shown to be strongest where the material was close to saturation, at which point the microstructure of the exact sample configuration plays a significant role in the response. Finally, the effect of sample morphology was probed, and whilst it was found to be significant at low rates, in the shock regime impedance appears to be more strongly influenced by the presence of moisture or a fraction of small particle size debris. [Preview Abstract] |
Tuesday, July 11, 2017 12:00PM - 12:15PM |
J8.00004: Investigating the shock response of dry and water-saturated sand: flyer-plate experiments and mesoscale simulations Jeff LaJeunesse, John Borg, Sarah Stewart, Naresh Thadhani The effect of grain size and moisture content on the dynamic response of high purity, Oklahoma {\#}1, sand was explored by performing uniaxial planar impact experiments on samples sieved to either fine (0.075 - 0.150 mm) or coarse (0.425 - 0.500 mm) grain sizes in either dry or fully water-saturated conditions. Sand samples were dynamically loaded to pressures between 1-11 GPa. Three-dimensional mesoscale simulations using CTH were created to model the response of each permutation of sand sample. Particle velocity profiles measured from the rear surface of the sand reveal that fine grain samples have steeper rise characteristics than coarse grain samples and water-saturated samples have an overall much stiffer response than dry samples. The experimentally determined particle-shock velocity response of dry sand was linear, with little difference between the two grain sizes investigated. The experimental response for the water saturated sand exhibited a piecewise continuous response with a transition region between pressures of 4.5 -- 6 GPa. Hypotheses for the cause of this transition region are drawn based on results of the mesoscale simulations. [Preview Abstract] |
Tuesday, July 11, 2017 12:15PM - 12:30PM |
J8.00005: Microscale investigation of dynamic impact of dry and saturated glass powder Eric Herbold, Ryan Crum, Ryan Hurley, Jonathan Lind, Michael Homel, Minta Akin The response of particulate materials to shock loading involves complex interactions between grains involving fracture/comminution and possible interstitial material.~ The strength of saturated powders is attributed to ``effective stress'' where the fluid stiffens the material response and reduces the shear strength.~ However, detailed information regarding the effects of saturation under dynamic loading is lacking since static equilibrium between phases cannot be assumed and the interaction becomes more complex. Recent experiments at the dynamic compression sector (DCS) have captured in-situ images of shock loaded soda lime glass spheres in dry and saturated conditions.~ The differences between the modes of deformation and compaction are compared with mesoscale simulations to help develop our ideas about the observed response. This work was performed under the auspices of the U.S. Department of Energy (DOE) by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LDRD tracking code 16-ERD-010.~ The Dynamic Compression Sector (DCS, sector 35) is supported by DOE/NNSA award number DE-NA0002442.~ The use of Advanced Photon Source is operated by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. [Preview Abstract] |
Tuesday, July 11, 2017 12:30PM - 12:45PM |
J8.00006: Molecular dynamics study of shock compression in porous silica glass Keith Jones, J. Matthew D. Lane, Tracy J. Vogler The shock response of porous amorphous silica is investigated using classical molecular dynamics, over a range of porosity ranging from fully dense (2.21 g/cc) down to 0.14 g/cc. We observe an enhanced densification in the Hugoniot response at initial porosities above 50$\%$, and the effect increases with increasing porosity. In the lowest initial densities, after an initial compression response, the systems expand with increased pressure. These results show good agreement with experiments. Mechanisms leading to enhanced densification will be explored, which appear to differ from mechanisms observed in similar studies in silicon. \\ 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] |
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