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  • Open Access


    Size-Dependent Behavior of Macromolecular solids II: Higher-Order Viscoelastic Theory and Experiments

    D. C. C. Lam1, L-H Keung1, P. Tong2

    CMES-Computer Modeling in Engineering & Sciences, Vol.66, No.1, pp. 73-100, 2010, DOI:10.3970/cmes.2010.066.073

    Abstract Additional molecular rotations in long chained macromolecules lead to additional size dependence. In this investigation, we developed the higher order viscoelasticity framework and conducted experiments to determine the higher order material length scale parameters needed to describe the higher order viscoelastic behavior in the new framework. In the first part of the investigation of high order deformation behavior of macromolecular solids, the higher-order viscoelasticity theories for Maxwell and Kelvin-Voigt materials, and models of higher-order viscoelastic beam deflection creep are developed in this study. We conducted creep bending experiments with epoxy beams to show that the… More >

  • Open Access


    A Preconditioned JFNK Algorithm Applied to Unsteady Incompressible Flow and Fluid Structure Interaction Problems

    Peter Lucas1, Alexander H. van Zuijlen1, Hester Bijl1

    CMES-Computer Modeling in Engineering & Sciences, Vol.59, No.1, pp. 79-106, 2010, DOI:10.3970/cmes.2010.059.079

    Abstract Despite the advances in computer power and numerical algorithms over the last decades, solutions to unsteady flow problems remain computing time intensive.
    In previous work [Lucas, P.,Bijl, H., and Zuijlen, A.H. van(2010)], we have shown that a Jacobian-free Newton-Krylov (JFNK) algorithm, preconditioned with an approximate factorization of the Jacobian which approximately matches the target residual operator, enables a speed up of a factor of 10 compared to nonlinear multigrid (NMG) for two-dimensional, large Reynolds number, unsteady flow computations. Furthermore, in [Lucas, P., Zuijlen, A.H. van, and Bijl, H. (2010)] we show that this algorithm also greatly… More >

  • Open Access


    Vibration and Control of Rotating Tapered Thin-Walled Composite Beam Using Macro Fiber Composite Actuator

    Vadiraja D. N.1, A. D. Sahasrabudhe2

    CMES-Computer Modeling in Engineering & Sciences, Vol.27, No.1&2, pp. 49-62, 2008, DOI:10.3970/cmes.2008.027.049

    Abstract Rotating beams are flexible structures, which are often idealized as cantilever beams. Structural modelling of rotating thin-walled composite beam with embedded MFC actuators and sensors using higher shear deformation theory (HSDT) is presented. A non-Cartesian deformation variable (which represents arc length stretch) is used along with two Cartesian deformation variables. The governing system of equations is derived from Hamilton's principle and solution is obtained by extended Galerkin's method. Optimal control problem is solved using LQG control algorithm. Vibration characteristics and optimal control for a box beam configuration are discussed in numerical examples. Gyroscopic coupling between More >

  • Open Access


    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 More >

  • Open Access


    A Variational Multiscale Method to Embed Micromechanical Surface Laws in the Macromechanical Continuum Formulation

    K. Garikipati1

    CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.2, pp. 175-184, 2002, DOI:10.3970/cmes.2002.003.175

    Abstract The embedding of micromechanical models in the macromechanical formulation of continuum solid mechanics can be treated by a variational multiscale method. A scale separation is introduced on the displacement field into coarse and fine scale components. The fine scale displacement is governed by the desired micromechanical model. Working within the variational framework, the fine scale displacement field is eliminated by expressing it in terms of the coarse scale displacement and the remaining fields in the problem. The resulting macromechanical formulation is posed solely in terms of the coarse scale displacements, but is influenced by the More >

  • Open Access


    Three-dimensional Numerical Simulation of Unsteady Marangoni Convection in the CZ Method using GSMAC-FEM

    Haruhiko Kohno, Takahiko Tanahashi1

    CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.2, pp. 155-170, 2001, DOI:10.3970/cmes.2001.002.155

    Abstract Three-dimensional (3D) unsteady numerical simulations are carried out by means of the finite element method (FEM) with the generalized simplified marker and cell (GSMAC) method in silicon melt with a non-deformable free surface with Prandtl number Pr = 1.8534 × 10-2, Marangoni number Ma = 0.0 - 6.2067 × 102, Grashof number Gr = 7.1104 × 106, and the aspect ratio As = 1.0 in the Czochralski (CZ) method. The flow state becomes unstable earlier by increasing the absolute value of the thermal coefficient of surface tension in the range of σT =0.0 - 1.5 × 10-5N/mK. Although… More >

  • Open Access


    Dynamics of Machinery 2D Elastic Casing, with Central Hole, Subject to an In-Plane Deflection-Dependent Rotating Load

    F. M. A. El-Saeidy1

    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 33-42, 2000, DOI:10.3970/cmes.2000.001.335

    Abstract In rotating radial ball bearings supported on elastic casings with the bearing outer ring lightly fitted into the housing, the force due to the ball elastic contact is indeed a rotating load rolling over the housing. For accurate estimation of the dynamic deformations of the casing annulus (hole), which in turn affect the bearing tolerances and hence the magnitudes of the generated forces, effect of the load rotation (motion) should be considered. Considering the integral casing and the outer ring to be a plate, an isoparametric plane stress finite-element (FE) based analytical procedure is presented… More >

  • Open Access


    A Methodology and Associated CAD Tools for Support of Concurrent Design of MEMS

    B. F. Romanowicz1, M. H. Zaman1, S. F. Bart1, V. L. Rabinovich1, I. Tchertkov1, S. Zhang1, M. G. da Silva1, M. Deshpande1, K. Greiner1, J. R. Gilbert1, Shawn Cunningham2

    CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 45-64, 2000, DOI:10.3970/cmes.2000.001.045

    Abstract Development of micro-electro-mechanical systems (MEMS) products is currently hampered by the need for design aids, which can assist in integration of all domains of the design. The cross-disciplinary character of microsystems requires a top-down approach to system design which, in turn, requires designers from many areas to work together in order to understand the effects of one sub-system on another. This paper describes current research on a methodology and tool-set which directly support such an integrated design process. More >

  • Open Access


    Experimental Investigation on Thermal Diffusion in Ternary Hydrocarbon Mixtures

    S. A. Mousavi1, T. Yousefi2, Z. Saghir3

    FDMP-Fluid Dynamics & Materials Processing, Vol.13, No.4, pp. 213-220, 2017, DOI:10.3970/fdmp.2017.013.213

    Abstract The main goal of this study was to investigate the thermal diffusion in ternary hydrocarbon mixtures composed of 1, 2, 3, 4 Tetrahydronaphtalene (THN)-Isobutylbenzene (IBB)-Dodecane (C12) with mass fractions of 80/10/10, 70/10/20, and 60/10/30 at mean temperature of 25 °C. Optical interferometry technique with Mach-Zehnder arrangement was used to conduct the experiments. The mixture was placed in a convectionless cell which was heated from above. The results for the mixture with mass fraction of 80/10/10 were in a good agreement with the corresponding benchmark values. Finally, the Soret coefficient for the other two mixtures have More >

  • Open Access


    Towards a Numerical Benchmark for 3D Low Mach Number Mixed Flows in a Rectangular Channel Heated from Below

    G. Accary1, S. Meradji2, D. Morvan2, D. Fougère2

    FDMP-Fluid Dynamics & Materials Processing, Vol.4, No.4, pp. 263-270, 2008, DOI:10.3970/fdmp.2008.004.263

    Abstract In the literature, only few references have dealt with mixed-convection flows in the low Mach number approximation. For this reason, in the present study we propose to extend the standard 3D benchmark for mixed convection in a rectangular channel heated from below (Medale and Nicolas, 2005) to the case of large temperature variations (for which the Boussinesq approximation is no longer valid). The Navier-Stokes equations, obtained under the assumption of a low Mach number flow, are solved using a finite volume method. The results, corresponding to the steady-state case of the benchmark, lead to the More >

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