Mixture theory

About: Mixture theory is a research topic. Over the lifetime, 616 publications have been published within this topic receiving 19350 citations.

On the Theory of Viscoelastic Mixtures and Stability

Abstract: A theory is developed for binary mixtures of viscoelastic materials. The basic equations of a nonlinear theory of heat conducting viscoelastic mixtures are derived in Lagrangian description. The individual components of the mixture are modeled as Kelvin—Voigt viscoelastic materials. A nonlinear constitutive relation which generalizes Darcy's law is derived. The linearized version of the theory is established. In the present theory the diffusive force depends on relative displacement and relative velocity. Stability results are presented in the context of materials which are non-conductor of heat.

Coupled Axisymmetric Thermo-Poro-Mechanical Finite Element Analysis of Energy Foundation Centrifuge Experiments in Partially Saturated Silt

Abstract: The paper presents an axisymmetric, small strain, fully-coupled, thermo-poro-mechanical (TPM) finite element analysis (FEA) of soil–structure interaction (SSI) between energy foundations and partially saturated silt. To account for the coupled processes involving the mechanical response, gas flow, water species flow, and heat flow, nonlinear governing equations are obtained from the fundamental laws of continuum mechanics, based on mixture theory of porous media at small strain. Constitutive relations consist of the effective stress concept, Fourier’s law for heat conduction, Darcy’s law and Fick’s law for pore liquid and gas flow, and an elasto-plastic constitutive model for the soil solid skeleton based on a critical state soil mechanics framework. The constitutive parameters employed in the thermo-poro-mechanical FEA are mostly fitted with experimental data. To validate the TPM model, the modeling results are compared with the observations of centrifuge-scale tests on semi-floating energy foundations in compacted silt. Variables measured include the thermal axial strains and temperature in the foundations, surface settlements, and volumetric water contents in the surrounding soil. Good agreement is obtained between the experimental and modeling results. Thermally-induced liquid water and water vapor flow inside the soil were found to have an impact on SSI. With further improvements (including interface elements at the foundation-soil interface), FEA with the validated TPM model can be used to predict performance and SSI mechanisms for energy foundations.

Video Foreground Detection Based on Symmetric Alpha-Stable Mixture Models

Abstract: Background subtraction (BS) is an efficient technique for detecting moving objects in video sequences. A simple BS process involves building a model of the background and extracting regions of the foreground (moving objects) with the assumptions that the camera remains stationary and there exist no movements in the background. These assumptions restrict the applicability of BS methods to real-time object detection in video. In this letter, we propose an extended cluster BS technique with a mixture of symmetric alpha-stable (SαS) distributions. An online self-adaptive mechanism is presented that allows automated estimation of the model parameters using the log moment method. Results over real video sequences from indoor and outdoor environments, with data from static and moving video cameras are presented. The SαS mixture model is shown to improve the detection performance compared with a cluster BS method using a Gaussian mixture model and the method of Li et al.

Finite-deformation phase-field chemomechanics for multiphase, multicomponent solids

Abstract: The purpose of this work is the development of a framework for the formulation of geometrically non-linear inelastic chemomechanical models for a mixture of multiple chemical components diffusing among multiple transforming solid phases. The focus here is on general model formulation. No specific model or application is pursued in this work. To this end, basic balance and constitutive relations from non-equilibrium thermodynamics and continuum mixture theory are combined with a phase-field-based description of multicomponent solid phases and their interfaces. Solid phase modeling is based in particular on a chemomechanical free energy and stress relaxation via the evolution of phase-specific concentration fields, order-parameter fields (e.g., related to chemical ordering, structural ordering, or defects), and local internal variables. At the mixture level, differences or contrasts in phase composition and phase local deformation in phase interface regions are treated as mixture internal variables. In this context, various phase interface models are considered. In the equilibrium limit, phase contrasts in composition and local deformation in the phase interface region are determined via bulk energy minimization. On the chemical side, the equilibrium limit of the current model formulation reduces to a multicomponent, multiphase, generalization of existing two-phase binary alloy interface equilibrium conditions (e.g., KKS). On the mechanical side, the equilibrium limit of one interface model considered represents a multiphase generalization of Reuss-Sachs conditions from mechanical homogenization theory. Analogously, other interface models considered represent generalizations of interface equilibrium conditions consistent with laminate and sharp-interface theory. In the last part of the work, selected existing models are formulated within the current framework as special cases and discussed in detail.