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 1C: Material Properties, Phase Transition, and KineticsStudent Symposium
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Room: Anaheim Marriott Platinum 5-6 |
Sunday, July 10, 2022 9:15AM - 9:30AM |
1C.00001: Phase transitions of carbon at extreme conditions Kien Nguyen-Cong Accurate phase diagram of carbon at extreme pressures and temperatures is of critical importance for constructing interior models of carbon-rich exoplanets as well as for design of ablation capsules for inertial confinement fusion experiments. However, the stability of diamond and possible transitions to other high-pressure carbon phases above 1 TPa are still a matter of debate. We investigate the phase diagram and phase transitions of carbon materials in both crystalline and amorphous forms at high temperatures and pressures using machine-learning molecular dynamics (MD) simulations. Our results explain extreme metastability of diamond well beyond the previously predicted-region of its thermodynamic stability. We also predict experimentally viable synthesis pathways of elusive BC8 high pressure phase of carbon. |
Sunday, July 10, 2022 9:30AM - 9:45AM |
1C.00002: Recovery of forsterite high-pressure polymorphs in gas gun shock-wave experiments Wade Mans Hypervelocity impact experiments using a 30 mm, 2-stage light gas gun were performed to study the formation, rapid quench, and physical recovery of the olivine high-pressure(P) polymorphs wadsleyite and ringwoodite. A series of 3 tantalum impact experiments were performed over a range from 1.5 to 3 km/s to study the effects of increasing P and temperature(T) conditions on the formation and crystallization of these high-P phases. ALEGRA shock physics hydrocode was used to model shock wave propagation, P, T, and material conditions due to the impact. We utilize and expand upon both the steel recovery assembly and experimental processes detailed in Tschauner et al. (2009). These experiments are part of a larger campaign to expand the studied compositions from the pure Mg end member olivine forsterite to more Fe-enriched fayalitic compositions that are representative of what is observed and recovered in shocked meteorites. The main goal of this extended study is to constrain the incoherent olivine high-pressure phase formation mechanisms to better describe the shock history within meteorites. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. |
Sunday, July 10, 2022 9:45AM - 10:00AM |
1C.00003: Dynamic mechanical behavior of co-continuous metal composites Lauren L Poole The dynamic mechanical behavior of multiphase metal composites comprising dissimilar immiscible phases can be controlled through selection of constituents, processing routes and phase topologies. Here, we experimentally and computationally investigate a co-continuous tungsten-copper composite that is of interest because both constituents exist in significant fractions and exhibit highly dissimilar properties (CTE, density, yield stress, elastic modulus, crystal structure). Experiments on multiple composite compositions and across several strain rates (quasi-static, Kolsky bar, flyer plate) investigate the interplay of microstructure, strain rate and load state on dynamic mechanical behavior. Additionally, complimentary experiments on single phase tungsten and copper contextualize the bulk mechanical properties and rate sensitivities of the composite in terms of the constituent's responses. |
Sunday, July 10, 2022 10:00AM - 10:15AM |
1C.00004: Effect of impedance mismatch on flier plate impact response of metal laminates Liya Semenchenko We use experiments and modeling to investigate the effect of elastic impedance mismatch on the response of layered metal composites to flier plate impact. We choose Cu/Ta and Cu/Nb laminates as model materials for their high and low impedance contrast, respectively, while many other properties (flow stress contrast, lattice misfit, etc.) are comparable. Using elastic finite element modeling, we predict that the minimum impact velocity needed to initiate spall depends on impedance contrast, with the critical velocity being lower in Cu/Ta than in Cu/Nb. We process samples by accumulated roll bonding (ARB) and examine their dynamic failure using flier plate testing. This investigation sheds light on the role of impedance contrast in shock propagation and attenuation and in the resulting failure mechanisms. |
Sunday, July 10, 2022 10:15AM - 10:30AM |
1C.00005: Break I
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