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  • Open Access


    ALE Formulation and Simulation Techniques in Integrated Computer Aided Design and Engineering System with Industrial Metal Forming Applications

    A. Gakwaya1, H. Sharifi2, M. Guillot1, M. Souli3, F. Erchiqui4

    CMES-Computer Modeling in Engineering & Sciences, Vol.73, No.3, pp. 209-266, 2011, DOI:10.3970/cmes.2011.073.209

    Abstract A mechanical computer aided design and engineering system can be used to reduce the design-to-manufacture cycle time in metal forming process. Such a system could be built upon a solid modeling geometry engine and an efficient finite element (FE) solver. The maintenance of a high-quality mesh throughout the analysis is an essential feature of an efficient finite element simulation of large strain metal forming problems. In this paper, a mesh adaptation technique employing the Arbitrary Lagrangian-Eulerian formulation (ALE) is applied to some industrial metal forming problems. An ACIS boundary representation of the solid model is employed. This type of representation… More >

  • Open Access


    Application of the Gradient Smoothing Technique to the Natural Neighbour Galerkin Method for the Couple-Stress Elasticity

    K. Wang1, S.J. Zhou2,3, Z.F. Nie4

    CMES-Computer Modeling in Engineering & Sciences, Vol.73, No.1, pp. 77-102, 2011, DOI:10.3970/cmes.2011.073.077

    Abstract The natural neighbour Galerkin method is tailored to solve boundary value problems of the couple-stress elasticity to model the size dependent behaviour of materials. This method is based on the displacement-based Galerkin approach, and the calculation of the global stiffness matrix is performed using gradient smoothing technique combined with the non-Sibsonian partition of unity approximation scheme. This method possesses the following properties: the complex C1-continuous approximation scheme is avoided without using either Lagrange multipliers or penalty parameters; no domain integrals involved in the assembly of the global stiffness matrix; and the imposition of essential boundary conditions is straightforward. The validity… More >

  • Open Access


    A C2-Continuous Control-Volume Technique Based on Cartesian Grids and Two-Node Integrated-RBF Elements for Second-Order Elliptic Problems

    D.-A. An-Vo1, N. Mai-Duy1, T. Tran-Cong1

    CMES-Computer Modeling in Engineering & Sciences, Vol.72, No.4, pp. 299-336, 2011, DOI:10.3970/cmes.2011.072.299

    Abstract This paper presents a new control-volume discretisation method, based on Cartesian grids and integrated-radial-basis-function elements (IRBFEs), for the solution of second-order elliptic problems in one and two dimensions. The governing equation is discretised by means of the control-volume formulation and the division of the problem domain into non-overlapping control volumes is based on a Cartesian grid. Salient features of the present method include (i) an element is defined by two adjacent nodes on a grid line, (ii) the IRBF approximations on each element are constructed using only two RBF centres (a smallest RBF set) associated with the two nodes of… More >

  • Open Access


    A High-Fidelity Cable-Analogy Continuum Triangular Element for the Large Strain, Large Deformation, Analysis of Membrane Structures

    P.D.Gosling1,2, L. Zhang2

    CMES-Computer Modeling in Engineering & Sciences, Vol.71, No.3, pp. 203-252, 2011, DOI:10.3970/cmes.2011.071.203

    Abstract The analysis of a continuum membrane by means of a discrete network of cables or bars is an efficient and readily tractable approach to the solution of a complex mechanics problem. However, is so doing, compromises are made in the quality of the approximation of the strain field. It is shown in this paper that the original form of the cable-analogy continuum triangle formulation is degraded by an inherent assumption of small strains in the underlying equations, in which the term ßmall" is shown to be "negligibly small". A revised version of this formulation is proposed in which a modification… More >

  • Open Access


    Shape Optimization in Time-Dependent Navier-Stokes Flows via Function Space Parametrization Technique1

    Zhiming Gao2, Yichen Ma3

    CMES-Computer Modeling in Engineering & Sciences, Vol.66, No.2, pp. 135-164, 2010, DOI:10.3970/cmes.2010.066.135

    Abstract Shape optimization technique has an increasing role in fluid dynamics problems governed by distributed parameter systems. In this paper, we present the problem of shape optimization of two dimensional viscous flow governed by the time dependent Navier-Stokes equations. The minimization problem of the viscous dissipated energy was established in the fluid domain. We derive the structure of continuous shape gradient of the cost functional by using the differentiability of a saddle point formulation with a function space parametrization technique. Finally a gradient type algorithm with mesh adaptation and mesh movement strategies is successfully and efficiently applied. More >

  • Open Access


    An Improved Unsplit and Convolutional Perfectly Matched Layer Absorbing Technique for the Navier-Stokes Equations Using Cut-Off Frequency Shift

    Roland Martin1, Carlos Couder-Castaneda1

    CMES-Computer Modeling in Engineering & Sciences, Vol.63, No.1, pp. 47-78, 2010, DOI:10.3970/cmes.2010.063.047

    Abstract We develop an unsplit convolutional perfectly matched layer (CPML) technique to absorb efficiently compressible viscous flows and their related supersonic or subsonic regimes at the outer boundary of a distorted computational domain. More particularly subsonic outgoing flows or subsonic wall-boundary layers close to the PML are well absorbed, which is difficult to obtain without creating numerical instabilities over long time periods. This new PML (CPML) introduces the calculation of auxiliary memory variables at each time step and allows an unsplit formulation of the PML. Damping functions involving a high shift in the frequency domain allow a much better absorption of… More >

  • Open Access


    Slow Motion of a General Axisymmetric Slip Particle Along Its Axis of Revolution and Normal to One or Two Plane Walls

    Huan J. Keh1, Yu C. Chang2

    CMES-Computer Modeling in Engineering & Sciences, Vol.62, No.3, pp. 225-254, 2010, DOI:10.3970/cmes.2010.062.225

    Abstract A theoretical study of the Stokes flow caused by a rigid particle of revolution translating axisymmetrically perpendicular to two parallel plane walls at an arbitrary position between them in a viscous fluid, which may slip at the particle surface, is presented. A method of distribution of a set of spherical singularities along the axis of revolution within a prolate particle or on the fundamental plane within an oblate particle is used to find the general solution of the fluid velocity field that satisfies the boundary conditions at the plane walls and at infinity. The slip condition on the particle surface… More >

  • Open Access


    A Finite Element enrichment technique by the Meshless Local Petrov-Galerkin method

    M. Ferronato1, A. Mazzia1, G. Pini1

    CMES-Computer Modeling in Engineering & Sciences, Vol.62, No.2, pp. 205-224, 2010, DOI:10.3970/cmes.2010.062.205

    Abstract In the engineering practice meshing and re-meshing complex domains by Finite Elements (FE) is one of the most time-consuming efforts. Meshless methods avoid this task but are computationally more expensive than standard FE. A somewhat natural improvement can be attempted by combining the two techniques with the aim at emphasizing the respective merits. The present work describes a FE enrichment by the Meshless Local Petrov-Galerkin (MLPG) method. The basic idea is to add a limited number of moving MLPG points over a fixed coarse FE grid, in order to improve the solution accuracy in specific regions of the domain with… More >

  • Open Access


    Efficient Cohomology Computation for Electromagnetic Modeling

    Paweł Dłotko1, Ruben Specogna2

    CMES-Computer Modeling in Engineering & Sciences, Vol.60, No.3, pp. 247-278, 2010, DOI:10.3970/cmes.2010.060.247

    Abstract The systematic potential design is of high importance in computational electromagnetics. For example, it is well known that when the efficient eddy-current formulations based on a magnetic scalar potential are employed in problems which involve conductive regions with holes, the so-calledthick cutsare needed to make the boundary value problem well defined. Therefore, a considerable effort has been invested over the past twenty-five years to develop fast and general algorithms to compute thick cuts automatically. Nevertheless, none of the approaches proposed in literature meet all the requirements of being automatic, computationally efficient and general. In this paper, an automatic, computationally efficient… More >

  • Open Access


    Error Bounds forDiscrete Geometric Approach

    Lorenzo Codecasa1, Francesco Trevisan2

    CMES-Computer Modeling in Engineering & Sciences, Vol.59, No.2, pp. 155-180, 2010, DOI:10.3970/cmes.2010.059.155

    Abstract Electromagnetic problems spatially discretized by the so called Discrete Geometric Approach are considered, where Discrete Counterparts of Constitutive Relations are discretized within an Energetic Approach. Pairs of oriented dual grids are considered in which the primal grid is composed of (oblique) parallelepipeds, (oblique) triangular prisms and tetrahedra and the dual grid is obtained according to the barycentric subdivision. The focus of the work is the evaluation of the constants bounding the approximation error of the electromagnetic field; the novelty is that such constants will be expressed in terms of the geometrical details of oriented dual grids. A numerical analysis will… More >

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