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 L02: Impact Microphysics IRecordings Available
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Chair: Frank Cherne, Los Alamos Natl Lab Room: Anaheim Marriott Platinum 6 |
Tuesday, July 12, 2022 2:00PM - 2:15PM |
L02.00001: Sequencing the Twinning-Detwinning Microstructural Footprint from Normal, Oblique, Converging, and Diverging Rarefaction Waves in AZ31B-H24 Magnesium at the Extremes Cyril L Williams, Scott A Turnage, Jeffrey T Lloyd, Saryu J Fensin, Eric N Brown Materials under extreme dynamic loading such as in ballistic and planetary impacts undergo elevated pressures, temperatures, and strain rates. It is well known that extreme dynamic loading can lead to profound changes in microstructure, microstructure evolution, and consequently residual mechanical properties. Experimental techniques for ascertaining the macroscopic response of materials to shock loading are well established, but insight into fundamental mechanisms of deformation requires the ability to characterize the microstructure and its evolution in real-time (in-situ) and post-mortem (ex-situ). Majority of plate impact shock experiments utilize planar free surfaces to study microstructure evolution in condensed matter. For this research, we seek to study the twinning-detwinning behavior of AZ31B-H24 magnesium alloy via shock recovery experiments using flyers with planar, concave, convex, and oblique free surfaces. These experiments will guide in understanding the role of the shear component of the rarefaction wave at the fundamental level. Samples were shock compressed to approximately 0.8 GPa and 1.7 GPa respectively along the plate normal, transverse, rolling, and off-axis directions, then released back to ambient conditions. The as-received and residual microstructures were characterized and sequenced to understand the role of shear waves on the evolution of crystallographic texture. The acquired results will provide insight into the complex twinning-detwinning behavior of this AZ31B-H24 magnesium alloy under shock compression and release. |
Tuesday, July 12, 2022 2:15PM - 2:30PM |
L02.00002: Hypervelocity impacts of polymer spheres on graphite: experiments and simulation Bertrand Aubert, David Hébert, Jean-Luc Rullier, Benjamin Jodar Space debris is a major concern for aerospace industry, which has to design structures able to withstand hypervelocity impacts of small projectiles at several km/s. To study this phenomenon, a series of nine shots has been performed on a two-stage gas gun at velocities ranging from 2100 m/s to 6300 m/s. Projectiles were 2 mm diameter spheres made of Delrin, a polymer of density 1425 kg/m3. Targets were 15 mm thick and made of EDM3, a porous and homogeneous graphite of density 1754 kg/m3. Ultrarapide camera was used with a laser shadowgraph system to provide movies of impacts. After each shot, the generated crater has been measured using an optical profilometer. Experimental setup and results are detailed in this paper. Especially, the evolution of crater dimensions as a function of projectile velocity is shown and a scaling is proposed to compare these data to others obtained with aluminum projectiles on the same facility. Furthermore, some 2D-axisymetrical Eulerian simulations have been performed with the Hesione hydrocode developed at CEA. Our modeling of EDM3 and Delrin, which is fully described in this paper, allows to reproduce the nine shots with a good agreement. |
Tuesday, July 12, 2022 2:30PM - 2:45PM |
L02.00003: In Situ Analysis and Modeling of High Velocity Microparticle Impacts On Tin Tyler J Lucas, Jasper Lienhard, Alison Saunders, Jeremy L White, Christopher Schuh Microparticle impacts achieve strain rates significantly higher than bulk-scale high-rate mechanical tests. Using the high spatial and temporal resolutions of the Laser Induced Particle Impact Test (LIPIT), these highly dynamic impacts can be studied in-situ. Previous studies have found that, upon impact, particles can produce many types of phenomena in addition to plasticity, including bonding and erosion. These phenomena have significant influence on resulting material properties and are essential to understanding material deformation under ultra-high strain rate loading conditions. This work seeks to quantify the influence of melting and ejecta produced when steel microparticles impact tin. Both phenomena can occur concurrently, and this work will deepen understanding of these mechanisms and the interplay between them. |
Tuesday, July 12, 2022 2:45PM - 3:00PM |
L02.00004: Ejecta size distributions from large-scale molecular dynamics simulations of the high velocity impact of droplets of liquid metal on rigid and liquid surfaces Olivier Durand, Laurent Soulard, Killian Babilotte, Thierry Carrard The impact of a solid or liquid drop on a rigid/solid or liquid surface, and the possible breakup that may result (the so-called splashing), is a frequently encountered phenomenon in shock physics. However, the mechanisms at the origin of the drop fragmentation are not yet well understood. This comes, on the one hand, from the difficulty to characterize experimentally a phenomenon which occurs at sub-microsecond timescales and sub-micrometer lengthscales, and, on the other hand, from the difficulty to simulate such a process from hydrocodes having no fragmentation models in their equations. To bring insight in the physics of fragmentation during splashing, we perform large-scale molecular dynamics (MD) simulations of the impact of droplets of liquid tin on rigid and liquid surfaces, with velocities ranging from 300 m/s to 1500 m/s. We measure the resulting secondary particle (ejecta) size distributions, and we show that they are different following the fragmentation mechanisms involved. The implementation of ejecta size distributions measurements in experiments should be therefore considered as helpful to improve the understanding of splashing physics. |
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