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  • Open Access

    ARTICLE

    Computational Characterization and Evaluation of Deformation Behavior of Spherulite of High Density Polyethylene in Mesoscale Domain

    Y. Tomita 1, M. Uchida 1

    CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.3, pp. 239-248, 2005, DOI:10.3970/cmes.2005.010.239

    Abstract In this study, we clarified the micro- to mesoscopic deformation behavior of a semicrystalline polymer by employing a large-deformation finite element homogenization method. The crystalline plasticity theory with a penalty method for the inextensibility of the chain direction and the nonaffine molecular chain network theory were applied for the representation of the deformation behavior of the crystalline and amorphous phases, respectively, in the composite microstructure of the semicrystalline polymer. The 3D structure of lamellae in the spherulite of high-density polyethylene was modeled, and the tensile and compressive deformation behaviors were investigated. A series of computational simulations clarified the difference in… More >

  • Open Access

    ARTICLE

    Non-uniform Hardening Constitutive Model for Compressible Orthotropic Materials with Application to Sandwich Plate Cores

    Zhenyu Xue1, Ashkan Vaziri1, John W. Hutchinson1

    CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.1, pp. 79-96, 2005, DOI:10.3970/cmes.2005.010.079

    Abstract A constitutive model for the elastic-plastic behavior of plastically compressible orthotropic materials is proposed based on an ellipsoidal yield surface with evolving ellipticity to accommodate non-uniform hardening or softening associated with stressing in different directions. The model incorporates rate-dependence arising from material rate-dependence and micro-inertial effects. The basic inputs are the stress-strain responses under the six fundamental stress histories in the orthotropic axes. Special limits of the model include classical isotropic hardening theory, the Hill model for incompressible orthotropic solids, and the Deshpande-Fleck model for highly porous isotropic foam metals. A primary motivation is application to metal core structure in… More >

  • Open Access

    ARTICLE

    A Comparative Investigation of Different Homogenization Methods for Prediction of the Macroscopic Properties of Composites

    Qing-Sheng Yang1,2, Wilfried Becker3

    CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.4, pp. 319-332, 2004, DOI:10.3970/cmes.2004.006.319

    Abstract The present paper focuses on the comparative investigation of different homogenization methods for fiber composites, void solids and rigid inclusion media. The effective properties of multi-phase media are calculated by three methods, i.e. direct average method of stress and strain, direct average method of strain energy and two-scale expansion method. A comprehensive comparison, in principle and numerically, of these methods is emphasized. It is obvious that the two direct average methods are identical in principle and therefore they give the same numerical results. It is shown that the two-scale expansion method is the same as the direct average concept of… More >

  • Open Access

    ARTICLE

    A Level Set Approach to Optimal Homogenized Coefficients

    Dongwoo Sheen1, Sangwon Seo2, Jinwoo Cho3

    CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.1, pp. 21-30, 2003, DOI:10.3970/cmes.2003.004.021

    Abstract The reconstructing optimal microstructures of given homogenized coefficients of steady diffusion equation is studied. In the reconstruction, the governing equation of level set function is approximated by adding viscosity term and the numerical procedure for the evolution of the level set function for the solution is examined. The numerical experiments of reconstruction are obtained by applying a finite element method with locally fitted mesh. More >

  • Open Access

    ARTICLE

    A Micromechanical Theory of Flow in Pulmonary Alveolar Sheet

    Z. Zhong1, Y. Dai1,2, C. C. Mei3, P. Tong1,4

    CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.1, pp. 77-86, 2002, DOI:10.3970/cmes.2002.003.077

    Abstract In this paper we reexamine the sheet-flow model proposed by Fung and Sobin (1969) for blood flow in capillaries in the pulmonary alveoli from micromechanical point of view. The pulmonary alveolar capillary is assumed to be two parallel membranes connected by periodic tissue posts. Blood is spread out into the very thin layer or sheet between the two membranes. The pulmonary alveolar sheet thus has a microstructure of hexagonal cells. A two-scale theory of homogenization is used to establish the canonical equations for the unit cell. The microscale solution is obtained by means of finite element method and the macroscopic… More >

  • Open Access

    ARTICLE

    Micro-macro Approaches Coupled to An Iterative Process for Nonlinear Porous Media

    S. Smaoui1, A. Ben Hamida1, I. Djeran-Maigre2, H. Dumontet1

    CMC-Computers, Materials & Continua, Vol.4, No.3, pp. 153-162, 2006, DOI:10.3970/cmc.2006.004.153

    Abstract An iterative homogenization approach is proposed in order to predict the nonlinear hydro-mechanical behaviour of porous media. This process is coupled to classical and modified secant extended methods and linear homogenization predictive schemes. At convergence of the iterative process, same equivalent behaviour is obtained for any secant method, any simplified homogenization used for the linear comparison material and for any initial porosity of the media. An application to the study of the nonlinear behaviour of clayey sediments is presented. The model parameters quantification is based on oedometric experimental results for different clays. More >

  • Open Access

    ARTICLE

    Finite Element modeling of Nomex® honeycomb cores : Failure and effective elastic properties

    L. Gornet1, S. Marguet2, G. Marckmann3

    CMC-Computers, Materials & Continua, Vol.4, No.2, pp. 63-74, 2006, DOI:10.3970/cmc.2006.004.063

    Abstract The purpose of the present study is to determine the components of the effective elasticity tensor and the failure properties of Nomex® honeycomb cores. In order to carry out this study, the NidaCore software, a program dedicated to Nomex®Cores predictions, has been developed using the Finite Element tool Cast3M-CEA. This software is based on periodic homogenization techniques and on the modelling of structural instability phenomena. The homogenization of the periodic microstructure is realized thanks to a strain energy approach. It assumes the mechanical equivalence between the microstructures of a RVE and a similar homogeneous macroscopic volume. The key point of… More >

  • Open Access

    ARTICLE

    On the Homogenization Analysis of Electromagnetic Properties for Irregular Honeycombs

    Lianhua Ma1, Qingsheng Yang2

    CMC-Computers, Materials & Continua, Vol.40, No.2, pp. 79-98, 2014, DOI:10.3970/cmc.2014.040.079

    Abstract Honeycombs are widely used in aerospace structures due to their low density and high specific strength. In this paper, effective electromagnetic properties of irregular honeycombs are investigated, by using the three dimensional homogenization theory and corresponding computational procedure. This homogenization method, being the extension of two-scale asymptotic approach, is employed to determine the expressions of the effective dielectric permittivity, magnetic permeability and electrical conductivity. To verify and validate the proposed model and procedure, effective permittivities of a typical irregular honeycomb are studied and compared with those of semi-empirical formulae. Moreover, the effect of geometry of honeycomb's unit cell on effective… More >

  • Open Access

    ARTICLE

    Corotational Formulation of Reduced Order Homogenization

    V. Filonova1, Y. Liu1, M. Bailakanavar1, J. Fish1, Z. Yuan2

    CMC-Computers, Materials & Continua, Vol.34, No.3, pp. 177-198, 2013, DOI:10.3970/cmc.2013.034.177

    Abstract A corotational formulation for reduced order homogenization is presented. While in principle the proposed method is valid for problems with arbitrary large strains, it is computational advantageous over the classical direct computational homogenization method for large rotations but moderate unit cell distortions. We validate the method for several large deformation problems including: (i) hat-section composite beam with two-dimensional chopped tow composite architecture, (ii) polyethylene microstructure consisting of 'hard' and 'soft' domains (segments), and (iii) fiber framework called fiberform either embedded or not in an amorphous matrix. More >

  • Open Access

    ARTICLE

    Application of Cosserat Theory to the Modelling of Reinforced Carbon Nananotube Beams

    Veturia Chiroiu1, Ligia Munteanu2 and Antonio S. Gliozzi3

    CMC-Computers, Materials & Continua, Vol.19, No.1, pp. 1-16, 2010, DOI:10.3970/cmc.2010.019.001

    Abstract This paper develops a mechanical model for multifunctional reinforced carbon nanotube (CNT) beams. The model is obtained by introducing the couple stresses into the constitutive equations of linear viscoelastic theory. The material functions are determined using the homogenization method. More >

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