Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session G4: Isentropic and Off Hugoniot Loading I |
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Chair: Neil Holmes, Lawrence Livermore National Laboratory Room: Fairmont Orchid Hotel Plaza II |
Tuesday, June 26, 2007 10:30AM - 11:00AM |
G4.00001: Making and Characterizing Off-Hugoniot States in Gas Gun Experiments Invited Speaker: Understanding the high-pressure, high-temperature behavior of materials subjected to dynamic loading requires knowledge beyond typical Hugoniot EOS and sound speed experiments. Recent advances in the fabrication of Graded Density Impactors (GDIs) have enabled us to produce both smooth, continuous quasi-isentropes and complex tailored compression paths. In addition we have developed ellipsometry as an {\em in-situ} real-time diagnostic capable of measuring optical constants during gas gun experiments. Since measured optical constants can be related to crystal structures as well as emissivities, coupling ellipsometry with GDIs provides a means to create and characterize a wide region of thermodynamic space previously inaccessible in standard shock experiments. We present quasi-isentropic compression of Ta to over 1 Mbar, and ellipsometry measurements of solid-solid and solid-liquid phase transitions as well as pressure-induced solidification of water. [Preview Abstract] |
Tuesday, June 26, 2007 11:00AM - 11:15AM |
G4.00002: Ramp Compression Measurements of Al, Fe, Ta, and W to a Few Mbar Gilbert Collins, Jon Eggert, Ray Smith, Marina Bastea, Dave Reisman, Y. Gupta, J.R. Asay We present ramp compression measurements of Ta, W, Al, and Fe using both pulse power and laser ramp compression platforms. Comparing both platforms allows us to span material thicknesses from 10 $\mu$m to 1mm and compression timescales from 1 ns to several hundred ns. While it is difficult to study precisely the same material on both platforms, we compare the stress density and elastic plastic transition for each of these metals under ramp loading to Mbar stress levels. [Preview Abstract] |
Tuesday, June 26, 2007 11:15AM - 11:30AM |
G4.00003: Isentropic Compression Studies of Energetic Composite Constituents Melvin Baer, Clint Hall, Mike Hobbs, Rick Gustavsen, Daniel Hooks, Steve Sheffield A series of quasi-isentropic magnetic pulse compression experiments using the Sandia Z accelerator and DICE small pulser have provided new insights in material behavior of the various constituents typically used in energetic composites. In this presentation, we overview a method used to determine appropriate constitutive and EOS property data using the combination of forward and backward procedures with optimization software. Sensitivity analysis is presented to assess the uncertainties of the experimental measurements and their effects in determining material response. These data interrogation techniques were applied at a ramp loading condition up to 50 Kbar over duration of $\sim $500 ns in panel configurations containing explosive crystals (HMX and RDX), binders (Estane, Teflon, Kel F and HTPB) and composites (PBX9501, PBS9501, Al/Teflon). [Preview Abstract] |
Tuesday, June 26, 2007 11:30AM - 11:45AM |
G4.00004: Wave propagation in materials with non convex equation of state Olivier Heuze, Stephane Jaouen, Herve Jourdren Exhaustive studies have described the behaviour of materials and wave propagation across them when they obey to Bethe's first condition. This means that the equations of state and the isentropes in the (P,V) plane are convex and that the sound speed is an increasing function of the density. In that case, steady dynamic pressure waves are compression shock waves or expansion fans. But materials can often reach states where this condition is violated. This happens for instance with phase transitions, dissociations, near the critical point, and in BZT fluids. Across these thermodynamic states, wave propagation has been studied only in a few specific cases by Zel'dovitch, Duvall, Plohr, Menikoff, Brun and their co-authors, but the general case remained to be explained. Our purpose is to provide the explanation of the successive waves which can occur in the general case when a wave propagates through a material with a non convex equation of state. We show that decrease of the sound speed introduces isentropic compression waves in the middle of shock waves and released shocks in the middle of expansion fans. After basic phenomena explanations, we illustrate them on the example of a virtual material which gathers all these cases. Hydrocode calculations based on this material show the difficulties of numerical schemes to reproduce the physical features. [Preview Abstract] |
Tuesday, June 26, 2007 11:45AM - 12:00PM |
G4.00005: Solitary and shock waves in discrete double power law materials Eric Herbold, Vitali Nesterenko A novel strongly nonlinear metamaterial is composed using a periodic arrangement of toroidal rings between plates. The toroids are considered massless strongly nonlinear springs where the force versus displacement relationship is described by two additive power-law relationships. In these systems the nonlinearity is due to the dramatic change of the contact plane, which starts as an arbitrarily thin circle then increases in thickness with increasing compression. Solitary and shock waves are examined numerically and experimentally using three different types of polymer or rubber o-rings allowing mitigation of higher amplitude shock impulses in comparison with granular systems. In these systems a train of pulses can consist of two separate groups related to two strongly nonlinear regimes with different values of exponents, depending on the amplitude. In experiments two types of shock waves (monotonic or oscillatory) were observed depending on the type of o-rings. [Preview Abstract] |
Tuesday, June 26, 2007 12:00PM - 12:15PM |
G4.00006: Phase kinetics and Nonlinear Wave Propagation Roger Minich, Daniel Orlikowski, Jeffrey Nguyen The properties of phase transitions in high pressure experiments are primarily inferred from velocity time histories. The recent development of the graded density impactor for tailoring pressure drives has provided information concerning phase transitions for thermodynamic paths different from a Hugoniot. The phase kinetics are encoded in the nonlinear wave propagation where dissipative and dispersive effects along with the nonlinear elastic response influence the shape of the wave. The observation of traveling wave structures suggest how to determine the relative contributions from the competing effects. A brief discussion of how the dissipation and dispersion in the nonlinear wave is related to a Langevin representation for the generation of new phase will be presented. Comparison to experimental data for Bi, Fe, and water will be shown. [Preview Abstract] |
Tuesday, June 26, 2007 12:15PM - 12:30PM |
G4.00007: Improved EOS for describing high-temperature off-hugoniot states in epoxy R.N. Mulford, N.E. Lanier, D. Swift, J. Workman, Peter Graham, Alastair Moore Modeling of off-hugoniot states in an expanding interface subjected to a shock reveals the importance of a chemically complete description of the materials. Hydrodynamic experiments typically rely on pre-shot target characterization to predict how initial perturbations will affect the late-time hydrodynamic mixing. However, it is the condition of these perturbations at the time of shock arrival that dominates their eventual late-time evolution. In some cases these perturbations are heated prior to the arrival of the main shock. Correctly modeling how temperature and density gradients will develop in the pre-heated material requires an understanding of the equation-of-state. In the experiment modelled, an epoxy/foam layered package was subjected to tin L-shell radiation, producing an expanding assembly at a well-defined temperature. This assembly was then subjected to a controlled shock, and the evolution of the epoxy-foam interface imaged with x-ray radiography. Modeling of the data with the hydrodynamics code RAGE is unsuccessful under certain shock conditions, unless condensation of chemical species from the plasma is explicitly included. The EOS code CHEETAH was used to prepare suitable EOS for input into the hydrodynamics modeling. [Preview Abstract] |
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