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  • Open AccessOpen Access

    ARTICLE

    3-Dimensional Analysis of Flow Patterns and Temperature Profiles for the Growth of InGaSb by Rotational Bridgman Method

    T. Ozawa1, N. Ishigami1, Y. Hayakawa2, T. Koyama2, M. Kumagawa2
    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 1-6, 2000, DOI:10.3970/cmes.2000.001.161
    Abstract To investigate the solution convection in the rotational Bridgman method, both flow patterns and temperature distributions were calculated by solving three equations in 3-dimensional analysis: Navier-Stokes, continuity and energy. We focused on the relationship between ampoule rotational rate and temperature distribution in the growth solution reservoir. In the 3-dimensional model, In-Ga-Sb solution was put between GaSb seed and feed crystals, where seed and feed crystals were cylindrical in shape, and the In-Ga-Sb solution was semi-cylindrical. The ampoule rotational rate was changed in a range of 0 to 100 rpm. By increasing the ampoule rotational rate, the More >

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    1700

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    1264

  • Open AccessOpen Access

    ARTICLE

    Non-Linear Rigid Body Dynamics: Energy and Momentum Conserving Algorithm

    Fernando A. Rochinha1, Rubens Sampaio2
    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 7-18, 2000, DOI:10.3970/cmes.2000.001.167
    Abstract The dynamics of flexible systems, such as robot manipulators, mechanical chains or cables, is becoming increasingly important in engineering. The main question arising from the numerical modelling of large overall motions of multibody systems is an appropriate treatment for the large rotations. In the present work an alternative approach is proposed leading to a time-stepping numerical algorithm which achieves stable solutions combined with high precision. In particular, in order to check the performance of the proposed approach, two examples having preserved constants of the motion are presented. More >

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    1663

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    2102

  • Open AccessOpen Access

    ARTICLE

    Kinematic Limit Analysis of Periodic Heterogeneous Media1

    V. Carvelli2, G. Maier2, A. Taliercio2
    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 19-30, 2000, DOI:10.3970/cmes.2000.001.179
    Abstract Homogenization of periodic fiber-reinforced ductile composite materials is performed as for the material strength, i.e. the carrying capacity with respect to macroscopic (average) stresses. Rigid-plastic limit analysis is formulated by the kinematic theorem applied to the representative volume with periodicity boundary conditions and von Mises yield criterion. The iterative procedure adopted for the numerical solution of the minimization problem is comparatively discussed on the basis of applications to various ductile heterogeneous media. More >

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    1723

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    1352

  • Open AccessOpen Access

    ARTICLE

    Approximation of the grad div Operator in Nonconvex Domains

    D. Boffi1, C. Chinosi2, L. Gastaldi3
    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 31-44, 2000, DOI:10.3970/cmes.2000.001.191
    Abstract In this paper we are dealing with the approximation of the grad-div operator in nonconvex polygonal domains. A penalization strategy is considered in order to obtain a formulation of the original eigenproblem which is associated with an elliptic operator. However the presence of singular eigensolutions, in the case of nonconvex domains, is the origin of major troubles in the numerical approximation of the problem. A mixed-type approximation, based on a projection procedure, is introduced and analyzed from the theoretical and numerical point of view. Several numerical experiments confirm that in presence of singularities the projection More >

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    1569

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    1316

  • Open AccessOpen Access

    ARTICLE

    Meshless Local Petrov-Galerkin (MLPG) Method for Convection-Diffusion Problems

    H. Lin, S.N. Atluri1
    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 45-60, 2000, DOI:10.3970/cmes.2000.001.205
    Abstract Due to the very general nature of the Meshless Local Petrov-Galerkin (MLPG) method, it is very easy and natural to introduce the upwinding concept (even in multi-dimensional cases) in the MLPG method, in order to deal with convection-dominated flows. In this paper, several upwinding schemes are proposed, and applied to solve steady convection-diffusion problems, in one and two dimensions. Even for very high Peclet number flows, the MLPG method, with upwinding, gives very good results. It shows that the MLPG method is very promising to solve the convection-dominated flow problems, and fluid mechanics problems. More >

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    1821

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    1485

  • Open AccessOpen Access

    ARTICLE

    Numerical Solution of Nonlinear Exterior Wave Problems Using Local Absorbing Boundary Conditions

    Igor Patlashenko1, Dan Givoli2
    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 61-70, 2000, DOI:10.3970/cmes.2000.001.221
    Abstract The method of Absorbing Boundary Conditions (ABCs) is considered for the numerical solution of a class of nonlinear exterior wave scattering problems. Recently, a scheme based on the exact nonlocal Dirichlet-to-Neumann (DtN) ABC has been proposed for such problems. Although this method is very accurate, it is also highly expensive computationally. In this paper, the nonlocal ABC is replaced by a low-order local ABC, which is obtained by localizing the DtN condition in a certain "optimal'' way. The performance of the new local scheme is compared to that of the nonlocal scheme via numerical experiments More >

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    1762

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    1272

  • Open AccessOpen Access

    ARTICLE

    Shape Optimization of Body Located in Incompressible Navier--Stokes Flow Based on Optimal Control Theory

    H. Okumura1, M. Kawahara1
    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 71-78, 2000, DOI:10.3970/cmes.2000.001.231
    Abstract This paper presents a new approach to a shape optimization problem of a body located in the unsteady incompressible viscous flow field based on an optimal control theory. The optimal state is defined by the reduction of drag and lift forces subjected to the body. The state equation used is the transient incompressible Navier--Stokes equations. The shape optimization problem can be formulated to find out geometrical coordinates of the body to minimize the performance function that is defined to evaluate forces subjected to the body. The fractional step method with the implicit temporal integration and More >

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    1913

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    1334

  • Open AccessOpen Access

    ARTICLE

    A Computational Method Based on Augmented Lagrangians and Fast Fourier Transforms for Composites with High Contrast

    J.C. Michel1, H. Moulinec, P. Suquet
    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 79-88, 2000, DOI:10.3970/cmes.2000.001.239
    Abstract An iterative numerical method based on Fast Fourier Transforms has been proposed by \cite{MOU98} to investigate the effective properties of periodic composites. This iterative method is based on the exact expression of the Green function for a linear elastic, homogeneous reference material. When dealing with linear phases, the number of iterations required to reach convergence is proportional to the contrast between the phases properties, and convergence is therefore not ensured in the case of composites with infinite contrast (those containing voids or rigid inclusions or highly nonlinear materials). It is proposed in this study to… More >

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    3327

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    1890

  • Open AccessOpen Access

    ARTICLE

    Fatigue Damage Development in a Steel Based MMC

    V. Tvergaard1, T. Ørts Pedersen1
    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 89-94, 2000, DOI:10.3970/cmes.2000.001.249
    Abstract The development of fatigue damage in a tool-steel metal matrix discontinuously reinforced with TiC particulates is analysed using a numerical cell model. The material is subjected to cyclic loading, and the matrix material is represented by a cyclic plasticity model, which uses a superposition of kinematic and isotropic hardening, with continuum damage mechanics incorporated to model fatigue damage evolution. The cell model represents a material with transversely staggered particulates. With focus on low cycle fatigue, the effect of balanced as well as unbalanced cyclic loading is studied. More >

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    1731

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    1288

  • Open AccessOpen Access

    ARTICLE

    Static and Dynamic Analysis of Shell Panels Using the Analog Equation Method

    A.J. Yiotis1, J.T. Katsikadelis1
    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 95-104, 2000, DOI:10.3970/cmes.2000.001.255
    Abstract The Analog Equation Method is applied to the static and dynamic analysis of thin cylindrical shell panels. The Fl\"{u}gge theory is adopted. The three displacement components are established by solving two membrane and one plate bending problems under the same boundary conditions subjected to "appropriate'' (equivalent) fictitious loads. Numerical results are presented which illustrate the efficiency and the accuracy of the proposed method. More >

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    1620

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    1462

  • Open AccessOpen Access

    ARTICLE

    Porous Metals with Developing Anisotropy: Constitutive Models, Computational Issues and Applications to Deformation Processing

    M. Kailasam1, N. Aravas2, P. Ponte Castañeda3
    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 105-118, 2000, DOI:10.3970/cmes.2000.001.265
    Abstract A constitutive model for a porous metal subjected to general three-dimensional finite deformations is presented. The model takes into account the evolution of porosity and the development of anisotropy due to changes in the shape and the orientation of the voids during deformation. A methodology for the numerical integration of the elastoplastic constitutive model is developed. Finally, some sample applications to plane strain extrusion and compaction of a porous disk are considered using the finite element method. More >

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    2039

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    1227

  • Open AccessOpen Access

    ARTICLE

    Micromechanics of Hydride Formation and Cracking in Zirconium Alloys

    J. Lufrano1, P. Sofronis1
    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 119-132, 2000, DOI:10.3970/cmes.2000.001.279
    Abstract Transient hydrogen diffusion and hydride formation coupled with material deformation are studied in Zr-2.5Nb alloys used in the pressure tubes of CANDU nuclear generating stations. The energetics of the hydride formation is revisited and the terminal solid solubility of hydrogen in solution is defined on the basis of the total elastoplastic work done on the system by the forming hydride and the external loads. Probabilistic precipitation of hydride is modeled in the neighborhood of a crack tip under mode I plane strain loading and a uniform initial hydrogen concentration below the stress free terminal solid More >

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    1725

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    1470

  • Open AccessOpen Access

    ARTICLE

    Laminar Film Flow Along a Periodic Wall

    V . Bontozoglou1
    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 133-142, 2000, DOI:10.3970/cmes.2000.001.293
    Abstract Laminar, gravity-driven flow of a liquid down an inclined wall with large-amplitude sinusoidal corrugations is studied numerically by a spectral spatial discretization method. The synchronous resonance between the wall and the free surface is investigated for corrugations with wavelength 0.002 m, which – according to linear theory – lead to strongest interaction. Free surface profile and flow structure are studied as a function of the film Reynolds number and the wall amplitude. Streamline patterns are computed and conditions leading to flow reversal are established. The distribution of the shear stress along the wall and of the More >

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    2268

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    1408

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