Home / Journals / CMES / Vol.2, No.1, 2001
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  • Open Access

    ARTICLE

    Three dimensional BEM and FEM stress analysis of the human tibia under pathological conditions

    C.M. Müller-Karger1, C.González2, M.H.Aliabadi3, M.Cerrolaza4
    CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 1-14, 2001, DOI:10.3970/cmes.2001.002.001
    Abstract In this paper, a three-dimensional Boundary Element model of the proximal tibia of the human knee is described and stresses and displacements in the tibial plateau under static loading are computed. The geometry is generated via three-dimensional reconstruction of Computerized Tomographies and Magnetic Resonance Imaging. Various models of different lengths from the tibia plateau are calculated. The BEM results are compared with a Finite Element model having the same geometry and tibia FE models available in the literature. Also reported are investigations of some pathological situations, including fractures. The results of the comparisons show that BEM is an efficient and… More >

  • Open Access

    ARTICLE

    The Effect of a Rotational Spring on the Global Stability Aspects of the Classical von Mises Model under Step Loading

    D. S. Sophianopoulos1, G. T. Michaltsos2
    CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 15-26, 2001, DOI:10.3970/cmes.2001.002.015
    Abstract The present work deals with the global stability aspects of a simple two-degrees-of-freedom autonomous initially imperfect damped model, under step (conservative) loading. The proposed system is an extension of the classical limit point one firstly introduced by von Mises, with the addition of a linear rotational spring. The effect of its properties (stiffness and damping) are fully assessed and under certain combinations of the parameters involved a third possibility of postbuckling dynamic response is revealed. This is associated with a point attractor response on a stable prebuckling fixed point, although dynamic buckling has already occurred, a finding validating new relevant… More >

  • Open Access

    ARTICLE

    Boundary Element Stress Analysis of Thick Reissner Plates in Bending under Generalized Loading

    A. El-Zafrany1
    CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 27-38, 2001, DOI:10.3970/cmes.2001.002.027
    Abstract In a recent publication, the author has introduced boundary integral equations for thick plate bending problems, for cases with generalized types of loading. Internal bending moments and shear forces, required for stress analysis, were calculated by means of a finite difference procedure, which requires fine boundary element meshes to achieve an acceptable degree of accuracy. In this paper, boundary integral equations for internal bending moments and shear forces are presented for thick Reissner plates in bending. Domain loading terms in those boundary integral equations have also been simplified for a variety of loading types including concentrated loading, linearly-distributed loading, and… More >

  • Open Access

    ARTICLE

    Coupling of Underground Pipelines and Slowly Moving Landslides by BEM Analysis

    A. Mandolini1, V. Minutolo1, E. Ruocco1
    CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 39-48, 2001, DOI:10.3970/cmes.2001.002.039
    Abstract Many sloping areas in the world are affected by slow movements. If they are occupied by settlements or are crossed by roads, pipelines or other infrastructures, a correct evaluation of future displacements is crucial for land management and sometimes for men safety. It is widely recognized that rainfall is the main triggering factor, producing an intermittent and delayed recharge of the groundwater; as a consequence, the displacement rate is cyclic, following a seasonal trend. In Italy this problem is particularly relevant since many exploited sloping areas are affected by slowly moving landslides that interact with man-made works. In present paper… More >

  • Open Access

    ARTICLE

    Three Dimensional Wave Scattering by Rigid Circular Pipelines Submerged in an Acoustic Waveguide

    António Tadeu, Andreia Pereira, Luís Godinho1
    CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 49-62, 2001, DOI:10.3970/cmes.2001.002.049
    Abstract The Boundary Element Method (BEM) is used to compute the three-dimensional variation pressure field generated by a point pressure source inside a flat waveguide channel filled with a homogeneous fluid, in the presence of infinite rigid circular pipelines. The problem is solved in the frequency domain, using boundary elements to model the pipeline and an appropriate Green's function to simulate the free surface and the rigid floor of the channel. Because of the 2 ---1/2 ---D geometry of the problem, the separation of variables has been used, and the solution at each frequency is expressed in terms of waves with… More >

  • Open Access

    ARTICLE

    Modeling and Numerical Computation of Necking in Round Bars Using a Total Lagrangian Elastoplastic Formulation

    A. Le van1, P. Le Grognec1
    CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 63-72, 2001, DOI:10.3970/cmes.2001.002.063
    Abstract Necking is a bifurcation phenomenon observed in round bars under tensile loading and has been investigated in numbers of papers. In the present work, it is modeled within the framework of finite rate-independent plasticity. The theory is based on thermodynamic foundations developed for standard materials and results in a total Lagrangian formulation for finite plasticity, where the total strain is decomposed additively according to [Green and Nagdhi 1965)] and the hardening is characterized by a nonlinear isotropic hardening law of the saturation type.
    The discretization and consistent linearization of the elastic-plastic equation set using the standard finite element procedure… More >

  • Open Access

    ARTICLE

    Determining the Unknown Traction of a Cracked Elastic Body Using the Inverse Technique with the Dual Boundary Element Method

    Ru-Min Chao, Yen-Ji Chen, F.C. Lin1
    CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 73-86, 2001, DOI:10.3970/cmes.2001.002.073
    Abstract The two-dimensional elasticity problem of an isotropic material, containing a centered-crack with unknown boundary traction is studied by the inverse procedure. The dual boundary integral equations are used to analyze the problem. While solving the ill-posed inverse problem, both of the conjugate gradient method and the regularization method are used. A scaling factor depending upon the material constant μ is introduced into the sensitivity matrix in order to keep the order of magnitude the same throughout the formulation. The result by using the displacement measurement will be compared with those by stress measurement, and an extensive discussion will be given.… More >

  • Open Access

    ARTICLE

    An Efficient Mesh-Free Method for Nonlinear Reaction-Diffusion Equations

    M.A. Golberg1, C.S. Chen2
    CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 87-96, 2001, DOI:10.3970/cmes.2001.002.087
    Abstract The purpose of this paper is to develop a highly efficient mesh-free method for solving nonlinear diffusion-reaction equations in Rd, d=2, 3. Using various time difference schemes, a given time-dependent problem can be reduced to solving a series of inhomogeneous Helmholtz-type equations. The solution of these problems can then be further reduced to evaluating particular solutions and the solution of related homogeneous equations. Recently, radial basis functions have been successfully implemented to evaluate particular solutions for Possion-type equations. A more general approach has been developed in extending this capability to obtain particular solutions for Helmholtz-type equations by using polyharmonic spline… More >

  • Open Access

    ARTICLE

    To Generate Good Triangular Meshes, Conforming to Control Spacing Requirements

    Xiang-YangLi1, Shang-Hua Teng2, Peng-Jun Wan3
    CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 97-116, 2001, DOI:10.3970/cmes.2001.002.097
    Abstract To conduct numerical simulations by finite element methods, we often need to generate a high quality mesh, yet with a smaller number of elements. Moreover, the size of each of the elements in the mesh should be approximately equal to a given size requirement. Li et al. recently proposed a new method, named biting, which combines the strengths of advancing front and sphere packing. It generates high quality meshes with a theoretical guarantee. In this paper, we show that biting squares instead of circles not only generates high quality meshes but also has the following advantages. It is easier to… More >

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