Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session T04: Strength and Constitutive Behavior IFocus Recordings Available
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Chair: J Matthew Lane, Sandia National Laboratories Room: Anaheim Marriott Platinum 2 |
Thursday, July 14, 2022 9:15AM - 9:45AM |
T04.00001: Quantum-accurate molecular dynamics shock simulations at experimental time and length scales Invited Speaker: Ivan Oleynik Recent experiments using powerful lasers, pulsed power and bright X-ray sources enable transformative insights into behavior of matter at extreme conditions. To obtain significant science return from these sophisticated and expensive experiments, predictive atomic-scale simulations of dynamic compression at experimental time and length scales are urgently sought. In this talk I describe recent advances in developing machine learning interatomic potentials that provide description of bond-breaking and remaking at extreme conditions with unprecedented quantum accuracy. Efficient implementation of these potentials on GPU based supercomputers opens up an unprecedented opportunity to perform quantum accurate molecular dynamics simulations at time and length scales that allows direct comparison with laser-driven shock experiments. Shock MD simulations of micrometer thick diamond samples uncovered atomic-scale mechanisms of anomalously high strength and orientational dependence of inelastic deformations. The latter persist up to the point of complete melting along diamond Hugoniot. |
Thursday, July 14, 2022 9:45AM - 10:00AM |
T04.00002: Modeling the Shock-induced Phase Transformation Behavior in Fe microstructures at the Atomic Scales and Mesoscales Ke Ma, Avanish Mishra, Avinash Dongare Shock compression of Fe microstructures above threshold pressures results in a BCC to HCP phase transformation. MD simulations are carried out to investigate the role of loading orientations and shock pressures above the thresholds of phase transformation and identify the correlations between loading orientations, and shock pressures using MD simulations, and unravel the conditions of reverse transformation induced twinning during shock release in single-crystal microstructures. To model the shock response of polycrystalline microstructures, a novel mesoscale modeling method, Quasi-Coarse-Grained Dynamics (QCGD), is used to extend the study to experimental scales with grain sizes of up to a few microns. The QCGD method retains the atomistic mechanism of dislocation slip, twinning, and phase transformation as predicted using MD simulations. The phase transformation and twinning variants in the atomic scale and mesoscale microstructures are characterized using orientation matrix and angle/axis pair from virtual texture analysis at different stages of shock evolution. MD and QCGD simulations reveal that Fe oriented along [110] direction is prone to twin. The talk will discuss the mechanisms of the formation of various HCP variants during shock compression and the mechanisms of reverse transformation and twinning during shock release to identify the role of loading orientations and shock pressures using MD and QCGD simulations. |
Thursday, July 14, 2022 10:00AM - 10:15AM |
T04.00003: A Simulated and Experimental Investigation into the Effect of Casing Material Fracture on the Axial Explosive Performance of Cylindrical Charges Emily M Johnson, Catherine E Johnson, Kelly R Williams Current models to predict the damage and fracture response of solids are based on empirical data from indirectly applied shocks or gradual strain increases. Neither of these conditions accurately represent the conditions a solid charge casing undergoes during explosive detonation: extremely high pressures, with zero buildup, over a short duration. The response to such conditions have been validated in air, as the shock wave can be easily observed experimentally. Validation for solids, with low visibility in the immediate contact region and an inability of most sensors to operate under the harsh conditions produced by detonation, results in the need to observe, not the response of a solid casing, but the secondary response of a witness material. This report presents information from the Plate Dent Test as a way of identifying measurable differences in the behavior of charge casings. One inch diameter Composition-B charges are cased in polyurethane, acrylic, or metal and detonated on top of a metal witness plate. The dent produced by the explosive on the witness plate is compared to three predictive simulations to validate the test's ability to distinguish between casing materials and to identify the most accurate simulation technique. |
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