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ORAL PRESENTATION
Session: 5 Non-equilibrium thermodynamics: Approaches and formalisms
(scheduled: Wednesday, 10:20 )
Nonequilibrium thermodynamics of elasto-viscoplastic deformation
M. Hütter, T.A. Tervoort, H.C. Öttinger
Department of Materials, ETH Zurich, Switzerland
Plasticity theories describe the transition from compressible elastic behavior at low stress to isochoric plastic deformation at high stress levels, and are often formulated by relating the elastic strain rate to an objective stress rate. In this contribution, the modeling of such behavior by way of nonequilibrium thermodynamics is examined, namely by using the GENERIC formalism. First, nonisothermal general elasticity is formulated in terms of the left Cauchy-Green strain tensor, the temperature, and the momentum density. In a second step, we study specific relaxation mechanisms of the strain tensor to describe elasto-viscoplastic behavior with emphasis on volume relaxation, and discuss the relation to common inelastic deformation models. For various equations of state, predictions of the model for specific mechanical tests are presented. © IWNET 2006
POSTER PRESENTATION
Tuesday, 15:40, Panel No. 7
Nonequilibrium thermodynamics aspects of a disspative electromagnetism
A. Jelic, M. Hütter, H.C. Öttinger
ETH Zurich, Department of Materials, Switzerland
The standard macroscopic Maxwell equations are obtained from the microscopic ones by spatial and/or ensemble averaging. However, in both cases, only single time properties are considered, while temporal correlations and two-time ensemble averages are neglected. In this work we examine specifically dissipative effects in electromagnetism on macroscopic scales by coarse-graining the microscopic Maxwell equations with respect to time. Particular emphasis is put on the derivation of the dissipative effects on the macroscopic scale by using a Green-Kubo type expression in terms of the microscopic fluctuations and the correlations between them, which give rise to dissipative processes such as Ohmic currents, the thermoelectric effect, and also to irreversible contributions to the electric and magnetic fields. In order to capture the interplay between the thermodynamic behavior of the medium and the electromagnetic field, and to discuss dissipative effects in electromagnetism in a consistent manner we have used the General Equation for the Non-Equilibrium Reversible-Irreversible Coupling (GENERIC) framework. The results are compared to the ones of Liu and coworkers, who previously incorporated dissipative effects into the Maxwell equations [1]. © IWNET 2006
[1] Phys. Rev. Lett. 70, 3580 (1993) and later papers.
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and Kleanthi for IWNET 2006