Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session O2: CM.1 Equation of State: Foams, Porous Materials, Database |
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Chair: Luke Shulenburger, Sandia National Laboratories Room: Grand Ballroom II |
Wednesday, July 10, 2013 9:15AM - 9:30AM |
O2.00001: Density Functional Theory simulations of shock compression of porous tantalum pentoxide K. Cochrane, T.J. Vogler, S. Root, M.P. Desjarlais, L. Shulenburger, T.R. Mattsson Density Functional Theory (DFT) based molecular dynamics has been established as a method capable of yielding high fidelity results for many materials at a wide range of pressures and temperatures and has recently been applied to complex polymers such as polyethylene, compounds such as ethane or CO$_{2}$, and oxides such as MgO. We use this method and a modification to the Rankine-Hugoniot relation inspired by the P-\textunderscore crush model to extend the DFT approach to the calculation of the shock response of an initially porous tantalum pentoxide. The experimental data have initial densities of approximately 1 g/cc, 3 g/cc, and 7 g/cc, reduced from a normal density of 8.36 g/cc, with final pressures up to 200 GPa. The DFT results compare well with the 3 g/cc and 7 g/cc over a wide range of pressures. The agreement with the 1 g/cc Hugoniot experimental data is reasonable at lower pressures, but with some larger discrepancies at higher pressures. Finally, we calculate the Gruneisen gamma as a function of density and found that it is density dependent but pressure independent for the lower densities and higher pressures. These results show that DFT methods may be capable of dealing with highly distended material with the proper modifications. [Preview Abstract] |
Wednesday, July 10, 2013 9:30AM - 9:45AM |
O2.00002: ABSTRACT WITHDRAWN |
Wednesday, July 10, 2013 9:45AM - 10:15AM |
O2.00003: International Shock-Wave Database: Current Status Invited Speaker: Pavel Levashov Shock-wave and related dynamic material response data serve for calibrating, validating, and improving material models over very broad regions of the pressure-temperature-density phase space. Since the middle of the 20th century vast amount of shock-wave experimental information has been obtained. To systemize it a number of compendiums of shock-wave data has been issued by LLNL, LANL (USA), CEA (France), IPCP and VNIIEF (Russia). In mid-90th the drawbacks of the paper handbooks became obvious, so the first version of the online shock-wave database appeared in 1997 (http://www.ficp.ac.ru/rusbank). It includes approximately 20000 experimental points on shock compression, adiabatic expansion, measurements of sound velocity behind the shock front and free-surface-velocity for more than 650 substances. This is still a useful tool for the shock-wave community, but it has a number of serious disadvantages which can't be easily eliminated: (i) very simple data format for points and references; (ii) minimalistic user interface for data addition; (iii) absence of history of changes; (iv) bad feedback from users. The new International Shock-Wave database (ISWdb) is intended to solve these and some other problems. The ISWdb project objectives are: (i) to develop a database on thermodynamic and mechanical properties of materials under conditions of shock-wave and other dynamic loadings, selected related quantities of interest, and the meta-data that describes the provenance of the measurements and material models; and (ii) to make this database available internationally through the Internet, in an interactive form. The development and operation of the ISWdb is guided by an advisory committee. The database will be installed on two mirrored web-servers, one in Russia and the other in USA (currently only one server is available). The database provides access to original experimental data on shock compression, non-shock dynamic loadings, isentropic expansion, measurements of sound speed in the Hugoniot state, and time-dependent free-surface or window-interface velocity profiles. Users are able to search the information in the database and obtain the experimental points in tabular or plain text formats directly via the Internet using common browsers. It is also possible to plot the experimental points for comparison with different approximations and results of equation-of-state calculations. The user can present the results of calculations in text or graphical forms and compare them with any experimental data available in the database. A short history of the shock-wave database will be presented and current possibilities of ISWdb will be demonstrated. Web-site of the project: http://iswdb.info. [Preview Abstract] |
Wednesday, July 10, 2013 10:15AM - 10:30AM |
O2.00004: Physical Sate of Shocked Silica Aerogel Carl Greeff, John Benage, Katerina Falk, Christopher Fryer, Thomas Boehly, Chad McCoy We have performed laser driven shock experiments on silica aerogel of initial density 0.2 g/cc. These experiments employed streaked optical pyrometry as a temperature diagnostic. The Hugoniot states accessed have densities between the critical density and the crystal density, and temperatures of a few eV. These densities are high enough that bonding is non-negligible and the electronic spectrum is strongly modified from that of the constituent atoms. The temperature is high enough for electronic excitation to be important, but low compared to the full ionization limit. We examine the physical basis of Sesame equation of state models in this regime with special attention to uncertainty in the calculated temperature. We present new results from quantum molecular dynamics simulations for the structural and electronic properties in the shocked state, and use these results to improve the Sesame models. [Preview Abstract] |
Wednesday, July 10, 2013 10:30AM - 10:45AM |
O2.00005: An Equation of State for Polyurea Aerogel Based on Multi-Shock Response Tariq Aslam, Diana Schroen, Richard Gustavsen, Brian Bartram The methodology for making foamed Divinylbenzene (DVB) is described. For a variety of initial densities, foamed DVB is examined through multi-shock compression and release experiments. Results from multi-shock experiments on LANL's 2-stage gas gun will be presented. A simple conservative Lagrangian numerical scheme, utilizing total-variation-diminishing interpolation and an approximate Riemann solver, will be presented as well as the methodology of calibration. It has been previously demonstrated that a single Mie-Gruneisen fitting form can replicate foam multi-shock compression response at a variety of initial densities; such a methodology will be presented for foamed DVB. [Preview Abstract] |
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