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  • Open Access

    ARTICLE

    A Revision of Relaxed Steepest Descent Method from the Dynamics on an Invariant Manifold

    Chein-Shan Liu1

    CMES-Computer Modeling in Engineering & Sciences, Vol.80, No.1, pp. 57-86, 2011, DOI:10.3970/cmes.2011.080.057

    Abstract Based-on the ordinary differential equations defined on an invariant manifold, we propose a theoretical procedure to derive a Relaxed Steepest Descent Method (RSDM) for numerically solving an ill-posed system of linear equations when the data are polluted by random noise. The invariant manifold is defined in terms of a squared-residual-norm and a fictitious time-like variable, and in the final stage we can derive an iterative algorithm including a parameter, which is known as the relaxation parameter. Through a Hopf bifurcation, this parameter indeed plays a major role to switch the situation of slow convergence to a new situation with faster… More >

  • Open Access

    ARTICLE

    Atomistic Exploration of Deformation Properties of Copper Nanowires with Pre-Existing Defects

    H.F. Zhan, Y.T. Gu1

    CMES-Computer Modeling in Engineering & Sciences, Vol.80, No.1, pp. 23-56, 2011, DOI:10.3970/cmes.2011.080.023

    Abstract Based on the embedded atom method (EAM) and molecular dynamics (MD) method, in this paper, the tensile deformation properties of Cu nanowires (NWs) with different pre-existing defects, including single surface defects, surface bi-defects and single internal defects, are systematically studied. In-depth deformation mechanisms of NWs with pre-existing defects are also explored. It is found that Young's modulus is insensitive to different pre-existing defects, but yield strength shows an obvious decrease. Defects are observed influencing greatly on NWs' tensile deformation mechanisms, and playing a role of dislocation sources. Besides of the traditional deformation process dominated by the nucleation and propagation of… More >

  • Open Access

    ARTICLE

    A General Constitutive Model for Vascular Tissue Considering Stress Driven Growth and Biological Availability

    F. J. Bellomo1, S. Oller2, F. Armero3, L. G. Nallim1

    CMES-Computer Modeling in Engineering & Sciences, Vol.80, No.1, pp. 1-22, 2011, DOI:10.3970/cmes.2011.080.001

    Abstract Some of the key factors that regulate growth and remodeling of tissues are fundamentally mechanical. However, it is important to take into account the role of biological availability to generate new tissue together with the stresses and strains in the processes of natural or pathological growth. In this sense, the model presented in this work is oriented to describe growth of vascular tissue under "stress driven growth" considering biological availability of the organism. The general theoretical framework is given by a kinematic formulation in large strain combined with the thermodynamic basis of open systems. The formulation uses a multiplicative decomposition… More >

  • Open Access

    ARTICLE

    Unit Setting Method to Impose EBCs in Meshless Methods

    W.L. Yang1, Y.F. Nie2, Y.T. Wu1

    CMES-Computer Modeling in Engineering & Sciences, Vol.79, No.3&4, pp. 261-270, 2011, DOI:10.3970/cmes.2011.079.261

    Abstract Up to now, some methods have been proposed to impose essential boundary conditions (EBCs) in meshless methods to solve partial differential equations system. Based on the theory analysis about moving least square (MLS) approximation and numerical experimentation results, a very simple method to impose EBCs in element-free Galerkin methods, which is the same easy as in finite element methods, is posed here. Compared with Lagrange multiplier method, the new method is simple and gives better results at the distributed nodes. The new method dues to a view point, different from normal understanding, that taking generalized parameters in MLS approximations as… More >

  • Open Access

    ARTICLE

    A Stabilized Finite Element Formulation for Continuum Models of Traffic Flow

    Durgesh Vikram1, Sanjay Mittal2, Partha Chakroborty1

    CMES-Computer Modeling in Engineering & Sciences, Vol.79, No.3&4, pp. 237-260, 2011, DOI:10.3970/cmes.2011.079.237

    Abstract A stabilized finite element formulation is presented to solve the governing equations for traffic flow. The flow is assumed to be one-dimensional. Both, PW-type (Payne-Whitham) 2-equation models and the LWR-type (Lighthill-Whitham-Richards) 1-equation models are considered. The SUPG (Streamline-Upwind/Petrov-Galerkin) and shock capturing stabilizations are utilized. These stabilizations are sufficient for the 1-equation models. However, an additional stabilization is necessary for the 2-equation models. For the first time, such a stabilization is proposed. It arises from the coupling between the two equations and is termed as IEPG (Inter-Equation/Petrov-Galerkin) stabilization. Two behavioral models are studied: Greenshields' (GS) and Greenberg's (GB) models. Numerical tests… More >

  • Open Access

    ARTICLE

    A Numerical Technique Based on Integrated RBFs for the System Evolution in Molecular Dynamics

    N. Mai-Duy1, T. Tran-Cong1, N. Phan-Thien2

    CMES-Computer Modeling in Engineering & Sciences, Vol.79, No.3&4, pp. 223-236, 2011, DOI:10.3970/cmes.2011.079.223

    Abstract This paper presents a new numerical technique for solving the evolution equations in molecular dynamics (MD). The variation of the MD system is represented by radial-basis-function (RBF) equations which are constructed using integrated multiquadric basis functions and point collocation. The proposed technique requires the evaluation of forces once per time step. Several examples are given to demonstrate the attractiveness of the present implementation. More >

  • Open Access

    ARTICLE

    Simulation of Sloshing Effect on Vessel Motions by Using MPS (Moving Particle Simulation)

    K.S. Kim1, B.H. Lee2, M.H. Kim1, J.C. Park3

    CMES-Computer Modeling in Engineering & Sciences, Vol.79, No.3&4, pp. 201-222, 2011, DOI:10.3970/cmes.2011.079.201

    Abstract The coupling and interactions between vessel motion and inner-tank sloshing are investigated by a potential-CFD (Computational Fluid Dynamics) hybrid method in time domain. Potential-theory-based 3D diffraction/radiation panel program is used to obtain the hydrodynamic coefficients and wave forces for the simulation of vessel motion in time domain. The liquid sloshing in tanks is simulated in time domain by using the improved Moving Particle Simulation (PNU-MPS) method and it is validated through comparison against sloshing experiments. The calculated sloshing tank forces and moments are applied to the vessel-motion simulation as excitation forces and moments. The updated ship motion, which is influenced… More >

  • Open Access

    ARTICLE

    Particle-Packaging Methods for Computational Modeling of Bones

    I. Pérez1, R. Roselló1, C. Recarey1, M. Cerrolaza2

    CMES-Computer Modeling in Engineering & Sciences, Vol.79, No.3&4, pp. 183-200, 2011, DOI:10.3970/cmes.2011.079.183

    Abstract Modeling the geometry and behavior of human bones is of the most concern when dealing with bone remodelling (external and internal) and poroelastic analysis. Complex geometries are frequently found in the human skeleton as well as orthotropic behavior of bone tissue. Spongy bone has a completely different constitution as compared with compact bone, which adds another relevant consideration if we want to get reliable results in biomechanical analysis. The modeling of both compact and spongy human-bone tissue is carried out by using packaging-particle methods. The methods generate circles (2D domains) and spheres (3D domains) in a random manner for the… More >

  • Open Access

    ARTICLE

    Methodology for Numerical Simulation of Trabecular Bone Structures Mechanical Behavior

    M.A. Argenta1, A.P. Gebert2, E.S. Filho3, B.A. Felizari4, M.B. Hecke5

    CMES-Computer Modeling in Engineering & Sciences, Vol.79, No.3&4, pp. 159-182, 2011, DOI:10.3970/cmes.2011.079.159

    Abstract Various methods in the literature proposesequations to calculate the stiffness as a function of density of bone tissue such as apparent density and ash density among others[Helgason, Perilli, Schileo, Taddei, Brynjolfsson and Viceconti, 2008]. Other ones present a value of an equivalent elasticity modulus, obtained by statistical adjustments of curves generated through mechanical compression tests over various specimens[Chevalier, Pahr, Allmer, Charlebois and Zysset, 2007; Cuppone, Seedhom, Berry and Ostell, 2004]. Bone tissue is a material withdifferent behaviors according to the scale of observation. It has a complex composite hierarchical structure, which is responsible for assign optimal mechanical properties. Its characteristics,… More >

  • Open Access

    ARTICLE

    The Configuration Evolution and Macroscopic Elasticity of Fluid-filled Closed Cell Composites: Micromechanics and Multiscale Homogenization Modelling

    Lianhua Ma1, Bernard F. Rolfe2, Qingsheng Yang1,3, Chunhui Yang2,3

    CMES-Computer Modeling in Engineering & Sciences, Vol.79, No.2, pp. 131-158, 2011, DOI:10.3970/cmes.2011.079.131

    Abstract For fluid-filled closed cell composites widely distributed in nature, the configuration evolution and effective elastic properties are investigated using a micromechanical model and a multiscale homogenization theory, in which the effect of initial fluid pressure is considered. Based on the configuration evolution of the composite, we present a novel micromechanics model to examine the interactions between the initial fluid pressure and the macroscopic elasticity of the material. In this model, the initial fluid pressure of the closed cells and the corresponding configuration can be produced by applying an eigenstrain at the introduced fictitious stress-free configuration, and the pressure-induced initial microscopic… More >

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