Search for: computational-homogenization
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    A nonlocal computational homogenization of softening quasi-brittle materials

    , Article International Journal for Numerical Methods in Engineering ; Volume 119, Issue 8 , 2019 , Pages 712-736 ; 00295981 (ISSN) Khoei, A. R ; Saadat, M. A ; Sharif University of Technology
    John Wiley and Sons Ltd  2019
    In this paper, a computational counterpart of the experimental investigation is presented based on a nonlocal computational homogenization technique for extracting damage model parameters in quasi-brittle materials with softening behavior. The technique is illustrated by introducing the macroscopic nonlocal strain to eliminate the mesh sensitivity in the macroscale level as well as the size dependence of the representative volume element (RVE) in the first-order continuous homogenization. The macroscopic nonlocal strains are computed at each direction, and both the local and nonlocal strains are transferred to the microscale level. Two RVEs with similar geometries and material properties are... 

    Computational Homogenization of Inter-Facial Thermal Resistance in Heterogeneous Materials

    , M.Sc. Thesis Sharif University of Technology Akbari, Ramin (Author) ; Khoei, Amir Reza (Supervisor)
    The constitutive modeling of heterogeneous micro-structure of solids based on multi-scale theories has become the subject of intensive research. One of the most important problem at this scale is the interfacial effects of constituents. Investigation of thermal conduction in this area leads to a phenomenon known as Inter-facial Boundary resistance. The general reasons behind this phenomenon are imperfect contact interface and changing in energy carriers properties known as Kapitza resistance. A computational homogenization of conduction tensor by considering inter-facial resistance and effective factors on it, is proposed. In order to capture discontinuous field around this area and its... 

    Hierarchical Multi-scale Analysis using Nonlinear Finite Element & its Application to Porous Media

    , M.Sc. Thesis Sharif University of Technology Asgharzadeh, Mohammad Ali (Author) ; Naghdabadi, Reza (Supervisor) ; Sohrabpour, Saeed (Supervisor)
    Porous materials, with diverse applications in engineering branches, are categorized as multi-scale. A multi-scale material is one which shows different structure and/or behavior in two or more different length scales. There are physical models which can calculate the macroscopic properties of such materials by using both the properties and volume fractions of the ingredients. However, the number of such theories which can handle problems in the fields of elasticity and hydrodynamics is much less; the fields in which the tensor orders of the properties are more than one. Fortunately, in recent years, a new method named "Computational Multi-scale Homogenization" has been offered to homogenize... 

    Multiscale Modeling of Microstructure Discontinuities in Saturated Porous Media Using XFEM

    , M.Sc. Thesis Sharif University of Technology Misaghi Bonabi, Amin (Author) ; Khoei, Amir Reza (Supervisor)
    The main purpose of this study is computational modeling of saturated deformable porous media using multiscale finite element method and explicit modeling of discontinuities such as microcracks at the microscopic scale. The real engineering problems we deal with in the simulation of the phenomenas happening in nature or industrial applications, in contrast to the simplifications being assumed, occur in heterogeneous materials. Although most microscopic heterogeneities are not present in macroscopic scale, they do have their effects on material behavior. In the computational homogenization method, the problem is analyzed coupled in two scales, therefore, the macroscopic behavior of media is... 

    Multiscale Modelling of Non-Isothermal Multiphase Flow in Heterogeneous Porous Media with Computational Homogenization Approach

    , Ph.D. Dissertation Sharif University of Technology Saeedmonir, Saeed (Author) ; Khoei, Amir Reza (Supervisor)
    In the real engineering problems, the existing materials in the nature or human-made materials, contain different heterogeneities from the view of small scale. Reinforced composite materials and porous media containing grains or micro-cracks are some examples of these materials. Due to the large amount of these heterogeneities as well as the small size, direct modelling of these micro-structures requires extremely high computational and memorial cost. Also, the equivalent models introduced in the literature, have strong limitations and therefore, cannot capture accurate behavior of the material. Hence, multiscale methods have been proposed in order to model these heterogeneous media with... 

    Computational homogenization of fully coupled multiphase flow in deformable porous media

    , Article Computer Methods in Applied Mechanics and Engineering ; Volume 376 , April , 2021 ; 00457825 (ISSN) Khoei, A. R ; Saeedmonir, S ; Sharif University of Technology
    Elsevier B. V  2021
    In this paper, a computational modeling tool is developed for fully coupled multiphase flow in deformable heterogeneous porous medium that consists of complex and non-uniform micro-structures using the dual continuum scales based on the computational homogenization approach. The first-order homogenization technique is employed to perform the multi-scale analysis. The governing equations of two-phase flow of immiscible fluids, including an equilibrium equation and two mass continuity equations, are considered based on the appropriate main variables. According to the well-known Hill–Mandel principle of macro-homogeneity, the proper energy types are defined instead of conventional stress power... 

    Multi-Scale Modeling of Chemo-Hydro-Mechanical Analysis of Heterogeneous Porous Media

    , M.Sc. Thesis Sharif University of Technology Adeli, Mohammad Hesan (Author) ; Khoei, Amir Reza (Supervisor)
    The swelling phenomenon in the porous media causes many problems in various engineering issues, including foundation construction and oil and gas extraction. For this reason, in the last few decades, flow modeling in reactive porous media and investigation of coupled hydro-chemo-mechanical problems have attracted a lot of attention. On the other hand, despite the simplifications, porous media have a heterogeneous structure, and the numerical modeling of these heterogeneities directly increases the computational costs. A suitable method for modeling heterogeneous problems is the computational homogenization method. In this method, the problem is solved in two scales in a correlated manner and... 

    Fully coupled hydromechanical multiscale model with microdynamic effects

    , Article International Journal for Numerical Methods in Engineering ; Volume 115, Issue 3 , 2018 , Pages 293-327 ; 00295981 (ISSN) Khoei, A. R ; Hajiabadi, M. R ; Sharif University of Technology
    John Wiley and Sons Ltd  2018
    In this paper, a multiscale finite element framework is developed based on the first-order homogenization method for fully coupled saturated porous media using an extension of the Hill-Mandel theory in the presence of microdynamic effects. The multiscale method is employed for the consolidation problem of a 2-dimensional saturated soil medium generated from the periodic arrangement of circular particles embedded in a square matrix, which is compared with the direct numerical simulation method. The effects of various issues, including the boundary conditions, size effects, particle arrangements, and the integral domain constraints for the microscale boundary value problem, are numerically... 

    Hierarchical multiscale modeling of nanotube-reinforced polymer composites

    , Article International Journal for Multiscale Computational Engineering ; Volume 7, Issue 5 , 2009 , Pages 395-408 ; 15431649 (ISSN) Ghanbari, J ; Naghdabad, R ; Sharif University of Technology
    A finite element-based hierarchical multiscale modeling scheme is presented and used for the analysis of nanotube-reinforced polymer composites. The scheme presented here consists of micro- and macroscale boundary value problems linked together using a computational homogenization scheme. Using the presented hierarchical multiscale scheme, we have studied nanotube-reinforced polymer composites, and the elastic properties are determined. Using different representative volume elements (RVEs) representing different volume fractions of aligned nanotubes, the effect of the nanotube volume fraction and the existence of an interphase layer on the effective elastic modulus of the nanocomposite are...