A thermodynamical consistent model for modeling of ionic electroactive polymers (EAPs) within the framework of the Theory of Porous Media

Ionic electroactive polymers are widely used in many engineering fields. These kind of materials can be stimulated to change their shape and size, see [1]. Since, the material under consideration has a complex multiphasic microstructure, such multiphasic materials are best described by a continuum mechanical approach. Thus, the presented model is based on the Theory of Porous Media (TPM), cf. [2]. In this contribution, we consider the Ionic Polymer Metal Composites (IPMCs). Stimulating by an electrical voltage, a structural deformation will be caused. Responsible for this deformation are the mobile ions. The focus of the presented model is to capture this material behavior, e.g. the distribution of the mobile cations. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modeling of Extrinsic and Autonomous Self-Healing phenomena within the Framework of the Theory of Porous Media

In this work a multiphase model is presented to describe the damage and healing behavior of a self-healing microstructure. In this academic example a single microcapsule is enclosed in a polymeric matrix. Attention is payed to the outflow of the liquid healing agents from the capsule into the damaged area and the subsequent phase transition from liquid to solid. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

微极性多组分多孔介质材料的混合物理论

将描述多组分系统的复合混合物理论与微极性连续介质力学理论相结合,建立了描述微极性多组分多孔介质材料的混合物理论.假定系统由多组分的微极性弹性固体和多组分微极性粘性流体组成.给出由混合物理论建立的系统的平衡方程.依据热力学第二定律以及本构假设建立了系统的本构方程,并使场方程闭合.为考虑固相的压缩性,在液相自由能函数中引入液相体积分数作为内变量,得到动力相容条件,用以限制固、液两相界面压力差的变化.最后,基于线性化理论得到线性化的本构方程和场方程,建立了考虑介质微极性的热-水力-力学组分输运模型.此理论框架可以运用到可变形多孔介质中污染物、药物以及农药输运等问题中,所得到的微极性多组分多孔介质系统的闭合场方程经退化后,可变为固、流相都为单一组分的多孔介质系统场方程,它与Eringen得到的结果一致.     

非线性多孔介质流动模型问题的分歧

本文讨论一类多孔介质流动模型非线性边值问题．对这类问题以及广泛的一类算子方程，我们得到了渐近歧点的存在性     

饱和多孔介质的超粘弹性本构理论研究

为了建立能考虑固体材料、多孔固体与流体可逆和不可逆变形的饱和多孔介质超粘弹性理论,以多孔固相为参考构型,以有效应力、材料真实应力和流相真实孔压作为状态变量,结合混合物均匀化响应原理获得各项均符合热力学功共轭特征的饱和多孔介质能量平衡方程,根据非平衡热力学熵分解理论求得熵流和熵产.结果表明,超弹塑性理论是该理论的一个特例;多孔固体的总变形可分为固相间隙和材料变形两部分,间隙应变与Terzaghi有效应力构成功共轭对,材料应变与材料真实应力构成功共轭对.饱和多孔介质的自由能可分为固相和流相两部分.当固相间隙和材料变形解耦时,固相所含的自由能又可分为间隙和材料两部分.证明了Skempton有效应力不是饱和多孔介质的基本应力状态变量.     

On the Description of Partially Saturated Soils by the Theory of Porous Media

In this contribution, a multi‐phase soil model based on the Theory of Porous Media (TPM) is presented. The model is fully coupled in the following constitutive phases: An elasto‐plastic or elasto‐viscoplastic solid skeleton, a materially incompressible pore‐liquid (water) and a materially compressible pore‐gas (air). The interaction of the solid skeleton and the pore‐fluids is specified by a capillary pressure‐saturation relation, whereas the mobilities of the fluid phases in the pore‐space of the solid skeleton are described by the so‐called relative permeabilities. Finally, a gravity governed initial‐boundary‐value problem solved by the FE method is presented.     

基于元胞自动机理论的孔隙介质渗流的模拟应用

基于元胞自动机理论,建立了四方形网格元胞空间和摩尔型元胞邻居为类型的时空动态演化模型,并设计了模拟流程.利用两点分布表征岩石骨架和孔隙空间的非均匀分布,设定了可表征流体在多孔介质中渗流的演化规则,对二维和三维岩石多孔介质流体渗流的元胞矩阵进行了模拟,分析得到了两点分布不同概率对渗流数学参数的影响,分析了不同注入方式对流体最终占据孔隙空间的分布形态的影响,注入方式包括点注入、线注入和面注入,最终对真实CT扫描的数字二维岩心进行了流体渗流过程模拟.基于以上的研究,为流体在多孔介质中渗流模拟提供了有效的方法.     

Modeling the quasi-static mechanical behavior of the extensible worm-like chain in the finite-element framework

A new modeling approach for the force-extension behavior of polymers and the solution scheme within the finite-element framework are presented. More specifically, the first variation of the energy function of an initially curved and extensible worm-like chain [1] and a geometrically exact beam-element formulation [2] were used to validate the model performing an optimization procedure [3]. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modeling of the effective viscoelastic material behavior of textile reinforced composites using a multi-scale approach

The increasing importance of constructive lightweight in modern engineering science involves the use of advanced materials like textile reinforced composites. In order to reduce development costs, efficient numerical simulations are needed to model the macroscopic behavior of the final product. Focussing on long term phenomena, which are important when parts made of composites with rate-dependent material behavior are assembled by bolted or screwed joints, a two-step homogenization procedure is used to obtain an effective homogeneous equivalent material at the macroscopic scale. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modeling and numerical simulation of multiscale behavior in polycrystals via extended crystal plasticity

The purpose of this work is to exploit the algorithmic formulation of models for multiscale inelastic materials whose behavior is influenced by the evolution of inelastic microstructure and the corresponding material or internal lengthscales. The models for extended crystal plasticity are based on the formulation of rate potentials whose form is determined by (i) energetic processes via the free energy, (ii) kinetic processes via the dissipation potential, and (iii) the form of the evolution relations for the internal-variable-like quantities upon which the free energy and dissipation potential depend. Examples for these latter quantities are the inelastic local deformation or dislocation densities as GNDs. Different algorithmic implementations are discussed, namely the algorithmic variational approach and the dual mixed approach. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural Stability for the Brinkman Equations of Porous Media

Explicit a priori continuous dependence estimates are derived for the Brinkman equations for non-isothermal flow in porous media. Continuous dependence on the cooling coefficient is shown when a boundary condition of Newton cooling type is employed. Continuous dependence on the model itself is proved when the Boussinesq model is allowed to change to one appropriate to penetrative convection. The final result derives an a priori continuous dependence estimate for the heat supply and body force.     

On Efficient Computation of the Optimization Problem Arising in the Inverse Modeling of Non-Stationary Multiphase Multicomponent Flow Through Porous Media

In this paper we discuss a method of solving inverse problems in non-isothermal multiphase multicomponent flow through porous media. The conceptual model is described by a system of non-linear partial differential equations which involve unknown parameters. These parameters are to be determined using a set of observations at discrete points in space and time by an optimization method. It is based on a reduced Gauss-Newton iteration in combination with an efficient gradient computation which takes advantage of a recently developed efficient numerical simulation technique. A sensitivity analysis is carried out for the optimum parameter set. Numerical experiments are performed for a one dimensional column experiment carried out at the VEGAS, University of Stuttgart, Germany.     

Structural Modeling in the Mechanics of Porous Materials

A new method for analyzing the deformation behavior of rigid and elastic foams with a small volume content of solid phase ( < 0.2) is developed. Various structural models for describing the elastic behavior of rigid and elastic plastic foams are used and compared. The results of structural simulation of anisotropic auxetic (i.e., having a negative Poisson ratio) foams with concave cells are presented. For cyclic uniaxial compression of rigid foams and volumetric deformation of elastic foams, the stress-strain curves are obtained. The general shape of the curves agrees well with the nonlinearly elastic behavior of plastic foams observed in experiments.     

On the simulation of textile reinforced composites and structures

This paper presents experimental and numerical methods to perform simulations of the mechanical behavior of textile reinforced composites and structures. The first aspect considered refers to the meso-to-macro transition in the framework of the finite element (FE) method. Regarding an effective modelling strategy the Binary Model is used to represent the discretized complex architecture of the composite. To simulate the local response and to compute the macroscopic stress and stiffness undergoing small strain a user routine is developed. The results are transfered to the macroscopic model during the solution process. The second aspect concerns the configuration of the fiber orientation and textile shear deformation in complex structural components. To take these deformations which affect the macroscopic material properties into account they are regarded in a macroscopic FE model. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Theory and Application of Characteristic Finite Element Domain Decomposition Procedures for Coupled System of Dynamics of Fluids in Porous Media

For a coupled system of multiplayer dynamics of fluids in porous media,the characteristic finiteelement domain decomposition procedures applicable to parallel arithmetic are put forward.Techniques suchas calculus of variations,domain decomposition,characteristic method,negative norm estimate,energy methodand the theory of prior estimates are adopted.Optimal order estimates in L~2 norm are derived for the error inthe approximate solution.