Osmotic forces in cartilaginous tissues

abstract onl

Thermo-chemo-electro-mechanical formulation of saturated charged porous solids

A thermo-chemo-electro-mechanical formulation of quasi-static finite deformation of swelling incompressible porous media is derived from a mixture theory including the volume fraction concept. The model consists of an electrically charged porous solid saturated with an ionic solution. Incompressible deformation is assumed. The mixture as a whole is assumed locally electroneutral. Different constituents following different kinematic paths are defined: solid, fluid, anions, cations and neutral solutes. Balance laws are derived for each constituent and for the mixture as a whole. A Lagrangian form of the second law of thermodynamics for incompressible porous media is used to derive the constitutive restrictions of the medium. The material properties are shown to be contained in one strain energy function and a matrix of frictional tensors. A principle of reversibility results from the constitutive restrictions. Existing theories of swelling media should be evaluated with respect to this principle

Preface on physicochemical and electromechanical interactions in porous media

Abstract. The focus of science and engineering shifts towards smaller length scales. Porous media mechanics has a vital role to play in the translation of microstructural data into macroscopic models of multicomponent systems. As the length scales shrink, more fundamental levels of understand-ing of natural laws, cause the boundaries between disciplines to blur. In particular, geosciences, polymer sciences and biosciences find a common ground of interest in high specific surface mixtures. Key words: living cells, biomechanics, geomechanics, high specific surface. The focus of technological development is shifting towards smaller length scales. The development of advanced experimental techniques allows us to fathom more subtle levels of the material than ever before. The advent of cheap and high com-putational power opens the way to translate measured material properties on the molecular level towards workable macroscopic models which are useful for techno-logical applications in industry and medical practice. A spin-off of these develop-ments is that as one moves towards the molecular level, the boundaries between the different disciplines of engineering fade away. Multi-physics problems are the rul

A validation of the quadriphasic mixture theory for intervertebral disc tissue

The swelling and shrinking behaviour of soft biological tissues is described by a quadriphasic mixture model. In this model four phases are distinguished: a charged solid, a fluid, cations and anions. A description of the set of coupled differential equations of this quadriphasic mixture model is given. These equations are solved by the finite element method using a weighted residual approach. The resulting non-linear integral equations are linearized and solved by the Newton-Raphson iteration procedure. We performed some confined swelling and compression experiments on intervertebral disc tissue. These experiments are simulated by a one-dimensional finite element implementation of this quadriphasic mixture model. In contrast to a triphasic mixture model, physically realistic diffusion coefficients can be used to fit the experiments when the fixed charge density is relatively large, because in the quadriphasic mixture model electrical phenomena are not neglected