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 C6: ME.1 Particulate/Porous Materials II |
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Chair: John Borg, Marquette University Room: Cascade II |
Monday, July 8, 2013 11:00AM - 11:15AM |
C6.00001: Criticality of damage-failure transitions under dynamic and shock wave loading Oleg Naimark Specific type of criticality in defect ensembles -- structural-scaling transition related to damage-failure scenarios under dynamic and shock wave loading was established. It allowed development of phenomenology of damage-failure transition induced by defects collective modes, supported by experiments and high resolution ``in-situ'' study of dynamic crack propagation and spall failure in PMMA and vanadium, dynamic fragmentation statistics in glass and ceramics. Structural (SWFM and AFM) study in terms of scaling invariance established the linkage of evolution of these modes with material responses in large range of load intensity and interpretation of the links of dynamic crack branching and specific morphology of numerous spall failure in PMMA, multiscale invariance in defect ensembles as spall failure precursor in shocked vanadium, 1/f flicker noise statistics of fragmentation according to the temporal analysis of fracture luminescence data in fused glass and zirconium dioxide shocked bars. Simulation of mentioned experiments supported the features of universality related to the self-similar solution of collective modes of defects in the course of structural-scaling transition. [Preview Abstract] |
Monday, July 8, 2013 11:15AM - 11:30AM |
C6.00002: Shock Hugoniot Measurements in Foam Oren Petel, Simon Ouellet, David Frost, Andrew Higgins Foams are found in a variety of protective equipment, including those used in applications involving high-speed impact and blast waves. Despite their exposure to shock wave loadings, there is a considerable lack of shock Hugoniot data for these materials. Typical characterizations of foams have involved the use of split-Hopkinson pressure bars or quasi-static compression machines to determine the stress-strain relationship in the foams. As such, the elastic-plastic response of foam at intermediate pressure ranges continues to be a source of confusion. In the present study, Photonic Doppler Velocimetry is used to measure the shock Hugoniot of a foam for a comparison to its quasi-static compression curves. The deviation of these two curves will be discussed and compared to common plasticity models used to describe dynamic foam behaviour in the literature. [Preview Abstract] |
Monday, July 8, 2013 11:30AM - 11:45AM |
C6.00003: Modeling of laser-driven shocks into porous graphite Gabriel Seisson, David H\'ebert, Isabelle Bertron, Laurent Videau, Patrick Combis, Laurent Berthe, Michel Boustie This paper presents experiments of laser-driven shocks into a commercial grade of porous graphite. Intensities of about 3~GW.cm$^{-2}$ led to pressures close to 3~GPa on the front surfaces of the 0.5~mm samples. The rear surface velocities, recorded by a Velocity Interferometer System (VISAR), ranged from 250 to 325 m.s$^{-1}$. Two classical models for porous materials are discussed. The first one uses plates of dense graphite spaced out in order to obtain the correct average density. The second one models a continuous material and includes an experimental compaction curve of our porous graphite. They were implemented into hydrocodes and both gave quite correct maximum free surface velocities and shock break-out instants. Nevertheless, the continuous representation appeared to be more efficient to reproduce the experimental free surface velocity ramp. Discussions on the laser-matter interaction modeling are also provided. Finally, a protocol for the simulation of future laser experiments is proposed. [Preview Abstract] |
Monday, July 8, 2013 11:45AM - 12:00PM |
C6.00004: Mesoscale Simulations of the Shock and Release of an Aluminum-Polymer System John Borg, Russ Maines, Raymond Ryckman, Lalit Chhabildas Fundamental questions remain in developing a more complete understanding of the dynamic behavior of heterogeneous materials; the development of which is complicated by a lack of experimental data at the mesoscale. Whereas experiments measure the bulk response, mesoscale simulations facilitate a more complete understanding of the system's response. In this work mesoscale simulations were used to explore the dynamic response of aluminum foam filled with polyvinylidene fluoride (PVDF) over a range of impact velocities from 350 to 2220 m/s (20 GPa). The results are compared to experiments. The simulated bulk Hugoniot states agree with experiments; the distribution of stress and temperature along the Hugoniot will be presented. The release paths however are more sensitive to the polymer's equation of state (EOS). Like other polymers, PVDF exhibits a variety of complicated responses including a non-linear shock velocity-particle velocity Hugoniot especially at low particle velocities, a low melt temperature, a polymorphic phase transformation near 30 GPa and possibly an increase in the Grueneisen parameter with an increase in density. An EOS for PVDF that includes all of these phenomena was constructed; the result improved the simulated release paths when compared to the experimentally measured release paths. The effect of each phenomena on the shock and release will be presented; the Grueneisen parameter had the strongest affect on release. [Preview Abstract] |
Monday, July 8, 2013 12:00PM - 12:30PM |
C6.00005: Shock Propagation Modeling in Heterogeneous Materials Invited Speaker: Thomas A. Haill Shock compression of foams is an intriguing research area that challenges our abilities to model experiments using computer simulations that span 9 orders of magnitude in spatial scales from the atomistic scale through the mesoscale and up to the continuum levels. Experiments test shock compression of dense polymers, polymer foams, and high-Z doped foams. Random distributions of polymer fibers, variations in pore size, and non-uniformities in the bulk properties of the foam (such as mean density) lead to spread in the experimental data. Adding dopants to foams introduces new complexities and the effect of the distribution and sizes of dopant particles must be characterized and understood. Therefore we turn to computer simulation to illumine the intricacies of the experiments that cannot be directly measured. This paper overviews of our range of methods to model pure and platinum-doped poly-methyl-pentene (PMP) foams. At the nanometer scale, hydrodynamic simulations compare favorably to classical molecular dynamics (MD) simulations of porous foams, verifying models of foam vaporization under strong shock conditions. Inhomogeneous mesoscale and homogenized continuum simulations present contrasting pictures of shocked foams. Mesoscale simulations at the micron scale have diffuse shock widths that depend upon the pore size, and post-shock vorticity results in fluctuations about the mean post-shock state and lower mean pressures and temperatures. Homogenized simulations, in the limit of zero pore size, have narrow shock widths, steady post-shock states, and higher mean pressures and temperature that compare favorably with 1D analysis of experiments. We reconcile the contrasting mesoscale and continuum views using theoretical turbulent corrections to the Hugoniot jump condition to show a consistent picture of shocked foams over 9 orders of spatial scale. [Preview Abstract] |
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