Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session T4: Materials Strength V: High-Rate Strength Modeling |
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Chair: Jow Ding, Washington State University, Channing Huntington, Lawrence Livermore National Laboratory Room: Grand H |
Thursday, June 18, 2015 11:15AM - 11:30AM |
T4.00001: Experiment to Measure the Strength of Lead to $\sim$ 1.5Mbar by Compression and Release using the Z Machine Stephen Rothman, Justin Brown, Jean-Paul Davis We are planning an experiment to infer the strength of lead at $\sim$ 1.5Mbar by ramp compression and release using the Z machine. Longitudinal and bulk sound speeds may be calculated from the measurement of the velocity of the interface between thin lead samples and a LiF window by an iterative process using either a transfer-function or characteristics-based method to map in-situ velocity onto measured window velocity. The hydrostatic response comes from analysis of the compression; the strength at each iteration step from the difference between the longitudinal and (extrapolated) bulk sound speeds. As lead is expected to be soft, the effect of its strength on the expansion on release is thought to be small, and may be treated as an error on the results, contrary to similar results for, e.g., Ta. (c) British Crown Owned Copyright 2015/AWE. [Preview Abstract] |
Thursday, June 18, 2015 11:30AM - 11:45AM |
T4.00002: Multiscale modeling of high-rate plastic deformation of polycrystalline bcc metals Robert E. Rudd, A. Arsenlis, N.R. Barton, R.M. Cavallo, D.A. Orlikowski, H.S. Park, S.T. Prisbrey, C.E. Wehrenberg, B.A. Remington Multiscale strength models for high-rate deformation have been developed for tantalum and vanadium starting with atomic bonding and extending up through the mobility of individual dislocations, the evolution of dislocation networks and so on until the ultimate material response at the scale of an experiment. [1] High energy laser platforms such as the National Ignition Facility offer the possibility to study plasticity at extremely high rates in ramp-compression waves [2], for validation of strength models. Experiments have been conducted on tantalum and vanadium at pressures of ~100 GPa and strain rates of ~10$^7$/s. [3,4] Remarkably, the predictions of the multiscale model agree well with the 1 Mbar experiments without adjustable parameters. We discuss the role of polycrystalline microstructure on the deformation of tantalum at these extreme conditions. We also consider the role of homogeneous nucleation of crystal defects in ramp compression experiments at 5 Mbar. [5] [1] R.E. Rudd et al., MRS Bulletin 35, 999 (2010). [2] N.R. Barton et al., J. Appl. Phys. 109, 073501 (2011). [3] H.-S. Park et al., Phys. Rev. Lett. 104, 135504 (2010). [4] H.-S. Park et al., Phys. Rev. Lett., to appear (2015). [5] R.E. Rudd et al., AIP Conf. Proc. 1426, 1379 (2012) [Preview Abstract] |
Thursday, June 18, 2015 11:45AM - 12:15PM |
T4.00003: A dislocation dynamics model of the plastic flow of fcc polycrystals Invited Speaker: Abigail Hunter Describing material strength at very high strain rates is a key component for investigating and predicting material deformation and failure under shock loading. However, accurately describing deformation physics in this strain rate regime remains a challenge due to the break down of fundamental assumptions that apply to material strength at low strain rates. We present a dislocation dynamics model of the plastic flow of fcc polycrystals from quasi-static to very high strain rates (10$^{6}$ s$^{-1}$ and above), pressures from ambient to 1000 GPa, and temperatures from zero to melt. The model is comprised of three coupled ordinary differential equations: a kinetic equation, which relates the strain rate to the stress, mobile and immobile dislocation densities, mass density, and temperature using a mean first passage time (MFPT) framework, and two equations describing the evolution of the mobile and immobile (network, forest) dislocation densities. [Preview Abstract] |
Thursday, June 18, 2015 12:15PM - 12:30PM |
T4.00004: Dynamic Characterization and Modeling of Potting Materials for Electronics Assemblies Vasant Joshi, Gilbert Lee, Jaime Santiago Prediction of survivability of encapsulated electronic components subject to impact relies on accurate modeling. Both static and dynamic characterization of encapsulation material is needed to generate a robust material model. Current focus is on potting materials to mitigate high rate loading on impact. In this effort, encapsulation scheme consists of layers of polymeric material Sylgard 184 and Triggerbond Epoxy- 20-3001. Experiments conducted for characterization of materials include conventional tension and compression tests, Hopkinson bar, dynamic material analyzer (DMA) and a non-conventional accelerometer based resonance tests for obtaining high frequency data. For an ideal material, data can be fitted to Williams-Landel-Ferry (WLF) model. A new temperature-time shift (TTS) macro was written to compare idealized temperature shift factor (WLF model) with experimental incremental shift factors. Deviations can be observed by comparison of experimental data with the model fit to determine the actual material behavior. Similarly, another macro written for obtaining Ogden model parameter from Hopkinson Bar tests indicates deviations from experimental high strain rate data. In this paper, experimental results for different materials used for mitigating impact, and ways to combine data from resonance, DMA and Hopkinson bar together with modeling refinements will be presented. [Preview Abstract] |
Thursday, June 18, 2015 12:30PM - 12:45PM |
T4.00005: Investigation on Grain Size Effect in High Strain Rate Ductility of 1100 Pure Aluminum Nicola Bonora, Neil Bourne, Andrew Ruggiero, Gianluca Iannitti, Gabriel Testa The effect of the initial grain size on the material ductility at high strain rates was investigated. Dynamic tensile extrusion tests (DTE) at different impact velocities on 1100 commercially pure aluminum, annealed at 350 $^{\circ}$C for different exposure times to induce grain growth, were performed. Extruded fragments were soft-recovered and the overall length of the extruded jet was used as measure of material ductility at high strain rates. Microstructure and texture evolution was investigated performing EBSD analysis of selected locations along the centerline of the fragment that remains in the extrusion die. The size and shape of retrieved fragments were used as validation metrics for the modified Rusinek-Klepaczko constitutive model used to simulate the deformation process. [Preview Abstract] |
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