Bulletin of the American Physical Society
2005 14th APS Topical Conference on Shock Compression of Condensed Matter
Sunday–Friday, July 31–August 5 2005; Baltimore, MD
Session C4: Continuum & Multiscale Modeling I |
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Chair: Scott Stewart, University of Illinois Room: Hyatt Regency Constellation E |
Monday, August 1, 2005 11:00AM - 11:15AM |
C4.00001: Numerical modeling of anisotropic effective moduli of media with microcrack damage Dan Su, Michael Santare, George Gazonas A generalized self-consistent method (GSCM) is used to calculate the anisotropic effective moduli of a medium containing damage consisting of microcracks with an arbitrary degree of alignment. Computational finite element methods are also used to determine the anisotropic effective moduli of the damaged medium and are found to be in excellent agreement with those determined using the GSCM. Since cracks respond differently under tension and compression, the moduli under both types of loads are evaluated and shown to be significantly different. Computational finite element methods are used to investigate the influence of crack face contact and friction on the resulting effective moduli of the medium. If the crack faces are frictionless, a particular medium under tensile loads can be anisotropic while the same material is isotropic when compressive loads are applied. As a result, waves propagating through the medium under different loading conditions will show different wave speeds. Several examples are shown in the presentation. [Preview Abstract] |
Monday, August 1, 2005 11:15AM - 11:30AM |
C4.00002: Two-Scale FEM Approach in the Dynamic Response of a Heterogeneous Material Axinte Ionita, Eric Mas, Brad Clements It is common in the numerical simulation of the dynamic response of a heterogeneous material to use the average material properties, which usually are obtained through a homogenization technique. This approach would lead to an average response of the composite. However, if one interested in the local response of the material then a localization technique needs to be used. This paper addresses the localization problem in the dynamic response of such material, using a two-scale FEM approach. The basic equations for coupling between first (or coarse) scale to the second (or fine scale) are presented together with two strategies for solving the local fields. Numerical examples are included. [Preview Abstract] |
Monday, August 1, 2005 11:30AM - 12:00PM |
C4.00003: Collective properties of mesodefect ensembles and nonlinear aspects of relaxation and failure in shocked materials Invited Speaker: Statistical theory allowed definition of parameters for mesodefects ensemble and formulation of nonequilibrium potential as generalized Ginzburg-Landau expansion. Kinetics of parameters determines relaxation property during plastic slip and damage-failure transition. Generation of mesodefects collective modes (solitary wave of structural-scaling transition and ``blow-up'' dissipative structures) is consequence of nonlinear properties of solid with defects, leads to steady-state structure of plastic wave front and delay of damage-failure transition (failure wave). Four power law is consequence of self-similar behavior of mesodefects ensemble. Structural scaling properties in shocked copper plate were studied in cross-section of wave propagation direction with interferometer New View and support high correlation in microshear ensemble related to steady-state plastic front. Simulation of strain kinetics showed importance of nonlocality effects as mechanism responsible for group velocity of plastic wave front with feature of ``plastic strain diffusion''. Shock failure (spall, failure waves) was studied experimentally in linkage with scenario of crack dynamics in preloaded PMMA plate by high-speed camera coupled with photo-elasticity method, correlation analysis of stress recording data with laser system and New View scaling analysis of failure surface. It was shown existence of ``blow-up'' scenario of damage-failure transition for crack dynamics, spall and failure wave as resonance excitation of ``blow-up'' damage kinetics in microshear ensemble under compressive shock. Direct observation of failure wave dynamics in modified Taylor test and plate impact experiment for fused quartz and lead-field glass established correlations with theoretical predictions of mechanisms of failure wave generation and propagation. [Preview Abstract] |
Monday, August 1, 2005 12:00PM - 12:15PM |
C4.00004: The Equation of State (EOS) of a Solid or Liquid Containing Bubbles Wilhelm Wolfer, David Reisman, Roger Minich We consider materials which contain dispersions of other phases or other materials in the form of fluid bubbles, and assume that the EOS are known separately for each of the phases. We derive an effective EOS of the composite or inhomogeneous material in terms of the equations of state of the phases or materials present, and in terms of their spatial distributions. However, we show that it is not sufficient to be in possession of only the equations of states for the different phases. One also needs to know the pressure and temperature dependences of all the elastic constants of the different phases. This problem is similar to determining the effective elastic moduli of a composite material. Numerical results are presented for Pd and Ni with a dispersed second phase in the form of helium bubbles or void with a volume fraction of $S$. We have implemented this effective equation of state in a hydrocode, and specifically analyzed a magnetically driven isentropic compression experiment (ICE) for samples having bubble volume fractions ranging from 0-3{\%}. We find that using the Z machine ICE drive we can easily distinguish between samples that have bubble fractions of a few per cent and obtain their compression isentropes. [Preview Abstract] |
Monday, August 1, 2005 12:15PM - 12:30PM |
C4.00005: Self-organization and feedback effects in the shock compressed media Tatyana Khantuleva New theoretical approach to the transport in condensed matter far from equilibrium combines methods of statistical mechanics and cybernetic physics in order to construct closed mathematical model of a system with self-organization and self-regulation. Mesoscopic effects are considered as a result of the structure formation and the feedback effects in an open system under dynamic loading. Nonequilibrium state equations had been involved to incorporate the velocity dispersion. Integrodifferential balance equations describe both wave and dissipative transport properties. Boundary conditions determine the internal scale spectra. The model is completed by the feedback that introduces the structure evolution basing the methods of cybernetic physics. The obtained results open a wide prospective for the control methods in applications to new technologies, intellectual systems and prediction of catastrophic phenomena. [Preview Abstract] |
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