Showing papers on "Representative elementary volume published in 1986"
TL;DR: In this article, the authors present a systematic development of a continuum model of a porous medium and of transport processes occurring in it, and the concept of a Representative Elementary Volume (REV) as opposed to any arbitrary volume of averaging quantities at the micro-scale, is quantified.
Abstract: This is the first of two papers presenting a systematic development of a continuum model of a porous medium and of transport processes occurring in it. The concept of a Representative Elementary Volume (REV) as opposed to any arbitrary volume of averaging quantities at the micro-scale, is quantified. A universal criterion for selecting the size of an REV as a function of measurable characteristics of a porous medium and selected tolerance levels of estimation errors, is developed. The rules of spatial averaging are extended by including the effects of both the configuration of the solid matrix and of interphase transfer phenomena within an REV.
223 citations
01 Jan 1986
TL;DR: In this article, the macroscopic properties of elastoplastic material with or without damage are determined in terms of the unknown properties of each constituent phase of the heterogeneous body.
Abstract: This chapter is mainly concerned with the determination of general relationships between microscopic and macroscopic mechanical properties for elastoplastic material with or without damage. The overall properties are determined in terms of the unknown properties of each constituent phase of the heterogeneous body. At first we must define a representative volume element (RVE) of the heterogeneous material for which the macroscopic mechanical fields are some spatial average of the microscopic one. The determination of local quantities is achieved by solving some particular boundary value problem on the RVE, from which macroscopic quantities are derived. The essential structure of micro-macro relationships is presented in the case of elastoplastic material. A generalisation is given to take the temperature field into account. We present also a model of damage and its averaging process. Finally we discuss the determination of macroscopic temperature through continuum thermodynamics.
27 citations
TL;DR: In this paper, the influence of the hard fiber and the mesophase layers in a soft-hard-soft composite of a biphase plate subjected to a dynamic tensile load, on the fracture mode and bifurcation process in both phases was investigated.
Abstract: The influence of the hard fiber and the mesophase layers in a soft-hard-soft com bination of a biphase plate subjected to a dynamic tensile load, on the fracture mode and bifurcation process in both phases was investigated. It was assumed that the soft matrix envelops the hard-fiber layer of the plate, so that this plate constitutes a merid ianal section of a representative volume element of a unidirectional fiber com posite.
20 citations
TL;DR: In this article, the influence of a soft fiber inclusion and the mesophase layer surrounding it in a hard-soft-hard bi-phase representative volume element (RVE), on the fracture and bifurcation processes in both phases was undertaken.
Abstract: An experimental study of the influence of a soft-fiber inclusion and the mesophase layer surrounding it in a hard-soft-hard bi-phase representative volume element (RVE), on the fracture and bifurcation processes in both phases was undertaken. The influence of the mechanical properties of each phase and the effect of the external loading-rate on the crack propagation velocity and the initiation of the crack bifurcation was studied by using high speed photography and dynamic caustics. It was shown that the propagating crack tended to bifurcate either in the hard or in the mesophase layer, and the bifurcation of the crack depended strongly on the strain rate, the elastic modulus and the Poisson ratio of the phases, as well as on the extent of the mesophase layer, which relies upon the degree of adhesion between phases.
17 citations
TL;DR: In this paper, the mesophase layer between the fiber and the matrix in the representative volume element surrounding the typical fiber is modified by adding a mesophases layer between them.
Abstract: Expressions for the evaluation of the transverse and longitudinal elastic moduli and the major Poisson ratio of unidirectional fiber composites are derived. The model described is based on the correct version of Kerner's model, which in our case is conveniently modified by introducing a mesophase layer between the fiber and the matrix in the representative volume element surrounding the typical fiber. The expression for the longitudinal elastic modulus derived in this paper, and the law of mixtures already presented in previous papers, give concordant results. Therefore, the law of mixtures, taking the mesophase also into account, and the two-term unfolding model for the mesophase are used for the evaluation of its extent and its properties. The model was applied to a glass filament-epoxy resin composite and its predictions were found to be in good agreement with the experimental data.
17 citations
TL;DR: This paper presents the conceptual part of a theory that defines the mechanical behavior of the brain and skull under various conditions through a continuum model of a mixed stress-displacement boundary value type, which defines the dynamics of the visco-elastic brain tissue in mathematical terms.
Abstract: Modern, very sensitive, and noninvasive devices (strain-gauges, accelerometers, etc) detect deformations and motions in the order of a few microns. The observation that the rise in intracranial pressure produces measurable suture strain suggests that noninvasive determination of mechanical parameters in the intracranial cavity, such as density, velocity, pressure, energy, and their time rates, is clearly possible. Based on the above premise, and utilizing the concept of representative elementary volume (REV), this paper presents the conceptual part of a theory that defines the mechanical behavior of the brain and skull under various conditions. The systematic review of brain tissue mechanics leads to a continuum model of a mixed stress-displacement boundary value type, which defines the dynamics of the visco-elastic brain tissue in mathematical terms. (J Child Neurol 1986; 1:119-125).
6 citations
01 Jan 1986
TL;DR: In this paper, a complete set of equations dealing with the coupled stress and fluid flow analysis of rock masses are treated as anisotropic, elastic porous media in order to get a complete framework for the analysis of the cracks.
Abstract: Rock masses, which commonly contain a large number of discontinuities such as faults and joints, are treated as anisotropic, elastic porous media in order to get a complete set of equations dealing with the coupled stress and fluid flow analysis. Two basic assumptions are adopted: (1) geological discontinuities behave like tiny cracks in an elastic continuum; (2) each crack is modeled by a set of parallel planar plates connected by two springs. Elastic compliance and permeability tensors are successfully formulated in terms of crack tensors, which depend only on the geometry of the related cracks, plus the shear and normal stiffness values equivalent to the elasticity of the cracks.