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Constitutive Properties (constitutive + property)
Selected AbstractsCHARACTERIZATION OF THE NONLINEAR VISCOELASTIC CONSTITUTIVE PROPERTIES OF MILD CHEDDAR CHEESE FROM INDENTATION TESTSJOURNAL OF TEXTURE STUDIES, Issue 5-6 2005S.M. GOH ABSTRACT A methodology to convert the indentation force,displacement response into the stress,strain properties of nonlinear viscoelastic materials was evaluated. Mild cheddar cheese was used as the test material, and indentation tests were performed using two spherical indenters of different sizes. The indentation tests were performed at different speeds, and the corresponding force,displacement responses were fitted with an analytical solution to obtain the time-dependent constants and the instantaneous force,displacement response. An inverse analysis based on the finite element method was performed to obtain the strain-dependent constants from the instantaneous force,displacement response. The predictions of the viscoelastic stress,strain properties from the indentation tests were compared to independent measurements through uniaxial compression tests, and a reasonable agreement was obtained. [source] Micromechanical viscoelasto-plastic models and finite element implementation for rate-independent and rate-dependent permanent deformation of stone-based materialsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2010Qingli Dai Abstract This paper presents parallel and serial viscoelasto-plastic models to simulate the rate-independent and the rate-dependent permanent deformation of stone-based materials, respectively. The generalized Maxwell viscoelastic and Chaboche's plastic models were employed to formulate the proposed parallel and serial viscoelasto-plastic constitutive laws. The finite element (FE) implementation of the parallel model used a displacement-based incremental formulation for the viscoelastic part and an elastic predictor,plastic corrector scheme for the elastoplastic component. The FE framework of the serial viscoelasto-plastic model employed a viscoelastic predictor,plastic corrector algorithm. The stone-based materials are consisted of irregular aggregates, matrix and air voids. This study used asphalt mixtures as an example. A digital sample was generated with imaging analysis from an optically scanned surface image of an asphalt mixture specimen. The modeling scheme employed continuum elements to mesh the effective matrix, and rigid bodies for aggregates. The ABAQUS user material subroutines defined with the proposed viscoelasto-plastic matrix models were employed. The micromechanical FE simulations were conducted on the digital mixture sample with the viscoelasto-plastic matrix models. The simulation results showed that the serial viscoelasto-plastic matrix model generated more permanent deformation than the parallel one by using the identical material parameters and displacement loadings. The effect of loading rates on the material viscoelastic and viscoelasto-plastic mixture behaviors was investigated. Permanent deformations under cyclic loadings were determined with FE simulations. The comparison studies showed that the simulation results correctly predicted the rate-independent and rate-dependent viscoelasto-plastic constitutive properties of the proposed matrix models. Overall, these studies indicated that the developed micromechanical FE models have the abilities to predict the global viscoelasto-plastic behaviors of the stone-based materials. Copyright © 2009 John Wiley & Sons, Ltd. [source] Inelastic constitutive properties and shear localization in Tennessee marbleINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 2 2001D. J. Holcomb Abstract The inelastic response of Tennessee marble is modelled by an elastic plastic constitutive relation that includes pressure dependence of yield, strain-softening and inelastic volume strain (dilatancy). Data from 12 axisymmetric compression tests at confining pressures from 0 to 100 MPa are used to determine the dependence of the yield function and plastic potential, which are different, on the first and second stress invariants and the accumulated inelastic shear strain. Because the data requires that the strain at peak stress depends on the mean stress, the locus of peak stresses is neither a yield surface nor a failure envelope, as is often assumed. Based on the constitutive model and Rudnicki and Rice criterion, localization is not predicted to occur in axisymmetric compression although faulting is observed in the tests. The discrepancy is likely due to the overly stiff response of a smooth yield surface model to abrupt changes in the pattern of straining. The constitutive model determined from the axisymmetric compression data describes well the variation of the in-plane stress observed in a plane strain experiment. The out-of-plane stress is not modelled well, apparently because the inelastic normal strain in this direction is overpredicted. In plane strain, localization is predicted to occur close to peak stress, in good agreement with the experiment. Observation of localization on the rising portion of the stress,strain curve in plane strain does not, however, indicate prepeak localization. Because of the rapid increase of mean stress in plane strain, the stress,strain curve can be rising while the shear stress versus shear strain curve at constant mean stress is falling (negative hardening modulus). Copyright © 2001 John Wiley & Sons, Ltd. [source] Fresnel coefficients for a permittivity-permeability phase space encompassing vacuum, anti-vacuum, and nihilityMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2006Akhlesh Lakhtakia Abstract The concept of the electromagnetic trinity comprising vacuum, anti-vacuum, and nihility is extended to a zone in the 4-D ,r -,r phase space that was largely inaccessible until the recent emergence of negative-phase-velocity materials. Expressions for Fresnel coefficients are derived for the reflection of plane waves at the planar interface of vacuum and a homogeneous, isotropic, dielectric-magnetic medium with constitutive properties lying in that zone. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 265,270, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21323 [source] An Elasto-Plastic Formulation of a Soil-Foundation InterfacePROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003Wolfgang Ehlers Prof. Dr.-Ing. In this paper, a special interface formulation for the continuum mechanical description of the contact zone between soil and geotechnical foundation is presented. The proposed model is based on the Theory of Porous Media (TPM), a consistent approach to describe geomaterials in a macroscopic frame [1]. Assuming quasi-static conditions, strains in the porous soil body are due to an elasto-plastic work-hardening model, whereas the constitutive properties of the interface are based on the continuous elasto-plastic behaviour of the soil body and on the failure kinematics of the contact zone. Using the FE method, a 3-d initial-boundary-value problem of a soil-foundation interaction is discussed with a close look on the occurring localization phenomenon. [source] The Relevance of Coercion: Some Preliminaries*RATIO JURIS, Issue 3 2009NICOS STAVROPOULOS Many philosophers take the view that, while coercion is a prominent and enduring feature of legal practice, its existence does not reflect a deep, constitutive property of law and therefore coercion plays at best a very limited role in the explanation of law's nature. This view has become more or less the orthodoxy in modern jurisprudence. I argue that an interesting and plausible possible role for coercion in the explanation of law is untouched by the arguments in support of the orthodox view. Since my main purpose is to clear the ground for the alternative, I spell out the orthodox view in some detail. I then briefly sketch the alternative. Finally, I turn to Jules Coleman's discussion of the alternative. [source] | ||||||||||