Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session T5: PPCM: Advances in Granular Materials |
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Chair: John Lang, LANL Room: Broadway I/II |
Thursday, June 20, 2019 2:00PM - 2:15PM |
T5.00001: Shear Enhanced Dynamic Compaction of a Granular Ceramic Xiangyu Sun, KT Ramesh Dynamic flow of granular media is ubiquitous phenomenon in many scenarios, including earthquakes, asteroid impact and ballistic impact into ceramics. As a promising candidate for protection applications, boron carbide has drawn attention due to its high mechanical strength and low density. The granular flow of boron carbide particles under multi-axial stress states has a significant influence on ballistic performance. However, granular flow at such extreme conditions has not been well characterized. In the current study, an ESK commercial boron carbide powder with average particle size $0.7\mu m$ was compacted in a fixture and loaded at strain rates around $10^{5}s^{-1}$ and pressures of several $GPa$, using the technique called pressure shear plate impact. Both normal and shear stress as well as strain rate histories were obtained. The granular boron carbide is observed to undergo large compaction with a clear shear enhanced compaction, suggesting a particle rearrangement mechanism. We also discuss granular material behavior and particle size evolution under these dynamic conditions. [Preview Abstract] |
Thursday, June 20, 2019 2:15PM - 2:30PM |
T5.00002: In situ observation of material flow in composite media under shock compression David Bober, Jonathan Lind, Mukul Kumar Internal reverberation, multiphase drag, and particle-particle force transfer determine the rate of compression in a shock loaded particulate composite. Since it is nearly impossible to deconvolve these effects using bulk velocimetry data, it has been difficult to develop models or simulations capable of predicting the outcome of novel compositions or loading scenarios. Instead of trying to solve this difficult inverse problem, we have conducted in situ radiography to directly observe the evolving internal configuration of an impact loaded composite with enough spatiotemporal resolution to build accurate direct numerical simulations. Tracking the motion of individual particles with nanosecond precision reveals how momentum transfer proceeds between the phases. This is complemented by measurements of the flow field in the surrounding polymer. Using dense tungsten particles embedded in a soft/light polymer matrix creates a strong impedance mismatch and a useful model system in which to explore shear mediated effects. These observations make it possible to parametrize a simple shear resistance model for the polymer matrix at the extreme pressures and strain rates encountered. This in turn leads to simulations of the bulk composite that better reproduce conventional velocimetry results. [Preview Abstract] |
Thursday, June 20, 2019 2:30PM - 2:45PM |
T5.00003: Stochastic Shock Observations from Plate Impact of Porous Tantalum Nathan Moore, Gary Chantler, Andrew Vackel, Jack Wise, Reeju Pokharel, Donald Brown Comparative multi- and single-point velocimetry measurements were made and used to explore spatial variability in the shock response of porous tantalum films prepared by thermal-spray deposition. The material pore structure was elucidated using x-ray tomography at the Advanced Photon Source. Multi-point velocimetry included frequency-based Photonic Doppler Velocimetry (PDV) and quadrature-based Photonic Displacement Interferometry (PDI), each with two different optical configurations allowing up to 13 measurements per sample, with up to three samples per shot. In addition, complementary single-point VISAR data were acquired. Variations in loading history are compared between identically-impacted sapphire and porous tantalum for flyer-plate velocities up to \textasciitilde 300 m/s. [Preview Abstract] |
Thursday, June 20, 2019 2:45PM - 3:00PM |
T5.00004: Shock Loading and Unloading Experiments on Thermally-Sprayed Porous Tantalum$^{\mathrm{\ast }}$ J. L. Wise, N. W. Moore, A. Vackel, W. M. Scherzinger, C. A. McCoy, G. R. Chantler Gas-gun tests expanded the database for impact loading and unloading response of porous tantalum samples generated by a controlled thermal-spray deposition process. Velocity interferometer (VISAR) diagnostics provided time-resolved, single-point observations of sample motion under one-dimensional ($i.e.$, uniaxial strain) shock compression to peak stresses between 1 and 4 GPa. The resultant transmitted-wave measurements from forward-ballistic testing were analyzed to assess sample-to-sample variability in the presence and magnitude of detectable evidence for a Hugoniot Elastic Limit (HEL) and high-pressure yield strength. Reverse-ballistic experiments featuring porous tantalum impactors and witness windows (PMMA, LiF, and sapphire) with different characteristic shock impedances yielded Hugoniot data for multiple peak stresses. Sample-related fluctuations in material velocity during the peak compression state were quantified to further assess the magnitude of stochastic effects for this spray-formed material. *Supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. [Preview Abstract] |
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