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Showing papers in "Archives of Computational Methods in Engineering in 2002"


Journal ArticleDOI
TL;DR: In this article, an overview of available theories and finite elements that have been developed for multilayered, anisotropic, composite plate and shell structures is presented. But, although a comprehensive description of several techniques and approaches is given, most of this paper has been devoted to the so called axiomatic theories and related finite element implementations.
Abstract: This work is an overview of available theories and finite elements that have been developed for multilayered, anisotropic, composite plate and shell structures. Although a comprehensive description of several techniques and approaches is given, most of this paper has been devoted to the so called axiomatic theories and related finite element implementations. Most of the theories and finite elements that have been proposed over the last thirty years are in fact based on these types of approaches. The paper has been divided into three parts. Part I, has been devoted to the description of possible approaches to plate and shell structures: 3D approaches, continuum based methods, axiomatic and asymptotic two-dimensional theories, classical and mixed formulations, equivalent single layer and layer wise variable descriptions are considered (the number of the unknown variables is considered to be independent of the number of the constitutive layers in the equivalent single layer case). Complicating effects that have been introduced by anisotropic behavior and layered constructions, such as high transverse deformability, zig-zag effects and interlaminar continuity, have been discussed and summarized by the acronimC -Requirements. Two-dimensional theories have been dealt with in Part II. Contributions based on axiomatic, asymtotic and continuum based approaches have been overviewed. Classical theories and their refinements are first considered. Both case of equivalent single-layer and layer-wise variables descriptions are discussed. The so-called zig-zag theories are then discussed. A complete and detailed overview has been conducted for this type of theory which relies on an approach that is entirely originated and devoted to layered constructions. Formulas and contributions related to the three possible zig-zag approaches, i.e. Lekhnitskii-Ren, Ambartsumian-Whitney-Rath-Das, Reissner-Murakami-Carrera ones have been presented and overviewed, taking into account the findings of a recent historical note provided by the author. Finite Element FE implementations are examined in Part III. The possible developments of finite elements for layered plates and shells are first outlined. FEs based on the theories considered in Part II are discussed along with those approaches which consist of a specific application of finite element techniques, such as hybrid methods and so-called global/local techniques. The extension of finite elements that were originally developed for isotropic one layered structures to multilayerd plates and shells are first discussed. Works based on classical and refined theories as well as on equivalent single layer and layer-wise descriptions have been overviewed. Development of available zig-zag finite elements has been considered for the three cases of zig-zag theories. Finite elements based on other approches are also discussed. Among these, FEs based on asymtotic theories, degenerate continuum approaches, stress resultant methods, asymtotic methods, hierarchy-p,_-s global/local techniques as well as mixed and hybrid formulations have been overviewed.

839 citations


Journal ArticleDOI
TL;DR: In this article, a review of structural and acoustic analysis techniques using numerical methods like the finite-and/or the boundary-element method is presented, followed by a survey of techniques for structural-acoustic coupling.
Abstract: Low noise constructions receive more and more attention in highly industrialized countries. Consequently, decrease of noise radiation challenges a growing community of engineers. One of the most efficient techniques for finding quiet structures consists in numerical optimization. Herein, we consider structural-acoustic optimization understood as an (iterative) minimum search of a specified objective (or cost) function by modifying certain design variables. Obviously, a coupled problem must be solved to evaluate the objective function. In this paper, we will start with a review of structural and acoustic analysis techniques using numerical methods like the finite- and/or the boundary-element method. This is followed by a survey of techniques for structural-acoustic coupling. We will then discuss objective functions. Often, the average sound pressure at one or a few points in a frequency interval accounts for the objective function for interior problems, wheareas the average sound power is mostly used for external problems. The analysis part will be completed by review of sensitivity analysis and special techniques. We will then discuss applications of structural-acoustic optimization. Starting with a review of related work in pure structural optimization and in pure acoustic optimization, we will categorize the problems of optimization in structural acoustics. A suitable distinction consists in academic and more applied examples. Academic examples iclude simple structures like beams, rectangular or circular plates and boxes; real industrial applications consider problems like that of a fuselage, bells, loudspeaker diaphragms and components of vehicle structures. Various different types of variables are used as design parameters. Quite often, locally defined plate or shell thickness or discrete point masses are chosen. Furthermore, all kinds of structural material parameters, beam cross sections, spring characteristics and shell geometry account for suitable design modifications. This is followed by a listing of constraints that have been applied. After that, we will discuss strategies of optimization. Starting with a formulation of the optimization problem we review aspects of multiobjective optimization, approximation concepts and optimization methods in general. In a final chapter, results are categorized and discussed. Very often, quite large decreases of noise radiation have been reported. However, even small gains should be highly appreciated in some cases of certain support conditions, complexity of simulation, model and large frequency ranges. Optimization outcomes are categorized with respect to objective functions, optimization methods, variables and groups of problems, the latter with particular focus on industrial applications. More specifically, a close-up look at vehicle panel shell geometry optimization is presented. Review of results is completed with a section on experimental validation of optimization gains. The conclusions bring together a number of open problems in the field.

152 citations


Journal ArticleDOI
TL;DR: A number of inviscid and viscous flow simulations, in different flow regimes, are analyzed to enable the reader to assess the performance of the surveyed formulations.
Abstract: The edge based Galerkin finite element formulation is used as the basic building block for the construction of multidimensional generalizations, on unstructured grids, of several higher order upwind biased procedures originally designed for the solution of the 1D compressible Euler system of equations. The use of a central type discretization for the viscous flux terms enables the simulation of multidimensional flows governed by the laminar compressible Navier Stokes equations. Numerical issues related to the development and implementation of multidimensional solution algorithms are considered. A number of inviscid and viscous flow simulations, in different flow regimes, are analyzed to enable the reader to assess the performance of the surveyed formulations.

50 citations


Journal ArticleDOI
TL;DR: An overview of explicit approximate inverse matrix techniques for computing explicitly various families of approximate inverses based on Choleski and LU—type approximate factorization procedures for solving sparse linear systems, which are derived from the finite difference, finite element and the domain decomposition discretization of elliptic and parabolic partial differential equations.
Abstract: The numerical treatment and the production of related software for solving large sparse linear systems of algebraic equations, derived mainly from the discretization of partial differential equation, by preconditioning techniques has attracted the attention of many researchers. In this paper we give an overview of explicit approximate inverse matrix techniques for computing explicitly various families of approximate inverses based on Choleski and LU—type approximate factorization procedures for solving sparse linear systems, which are derived from the finite difference, finite element and the domain decomposition discretization of elliptic and parabolic partial differential equations. Composite iterative schemes, using inner-outer schemes in conjunction with Picard and Newton method, based on approximate inverse matrix techniques for solving non-linear boundary value problems, are presented. Additionally, isomorphic iterative methods are introduced for the efficient solution of non-linear systems. Explicit preconditioned conjugate gradient—type schemes in conjunction with approximate inverse matrix techniques are presented for the efficient solution of linear and non-linear system of algebraic equations. Theoretical estimates on the rate of convergence and computational complexity of the explicit preconditioned conjugate gradient method are also presented. Applications of the proposed methods on characteristic linear and non-linear problems are discussed and numerical results are given.

47 citations


Journal ArticleDOI
TL;DR: A short review of numerical modelling of porous medium flow, heat and mass transfer is presented in this paper, where the focus of the article is mainly on the use of finite element method and velocity correction algorithm.
Abstract: In this article, a short review of numerical modelling of porous medium flow, heat and mass transfer is presented. The focus of the article is mainly on the use of finite element method and velocity correction algorithm. In addition to a detailed discussion on the velocity correction scheme, some essential fundamental and application problems are solved and results are presented. Many of these results are compared against available experimental and numerical data.

42 citations


Journal ArticleDOI
TL;DR: In this article, the authors analyzed the state-of-the-art and the recent developments in the numerical modeling of short fiber suspensions involved in industrial flows, and proposed an analytical model for short fiber reinforced composites.
Abstract: Short fiber reinforced composites have gained increasing technological importance due to their versatility that lends them to a wide range of applications. These composites are useful because they include a reinforcing phase in which high tensile strengths can be reached, and a matrix that allows to hold the reinforcement and to transfer applied stress to it. It is a well-known fact, that such materials can have excellent mechanical, thermal and electrical properties that make them widely used in industry. During the manufacture process, fibers adopt a preferential orientation that can vary significantly across the geometry. Once the suspension is cooled or cured to make a solid composite, the fiber orientation becomes a key feature of the final product since it affects the elastic modulus, the thermal and electrical conductivities, and the strength of the composite material. In this work we analyzed the state-of-the-art and the recent developments in the numerical modeling of short fiber suspensions involved in industrial flows.

26 citations


Journal ArticleDOI
TL;DR: In this article, an original algorithm for the front updating procedures as a part of the mesh generator is presented, which has been verified on the various domains with complex geometry and with nonuniform distribution of edge nodes such as the switched reluctance motor and power cable configuration, respectively.
Abstract: An automatic mesh generation dealing with domains of an arbitrary shape could be realized by an advancing front method. The mesh generator based on this method creates triangle elements inside a domain starting with the polygonal (polyhedral in 3D) discretisation of its border. In this paper an original algorithm for the front updating procedures as a part of the mesh generator is presented. The proposed algorithm provides an efficient mesh generation procedure. It has been verified on the various domains with complex geometry and with nonuniform distribution of edge nodes such as the discretisation of the switched reluctance motor and power cable configuration, respectively. The related finite element calculations are carried out.

12 citations


Journal ArticleDOI
Jeonghoon Yoo1
TL;DR: In this article, the homogenization design method (HDM) is applied to a structure in magnetic fields to reduce the vibration level of a structure excited by the magnetic forces, especially by magnetic harmonic forces.
Abstract: The homogenization design method has been expanded to obtain the optimal topology of a structure in magnetic fields to maximize the magnetic energy. In this study, the homogenization design method (HDM) is applied to a structure in magnetic fields to reduce the vibration level of a structure excited by the magnetic forces, especially by the magnetic harmonic forces. This is accomplished by obtaining the optimal material distribution of the structure to minimize the frequency response. The Maxwell stress method is used to compute the magnetic force and the HDM is applied for the optimization. It is verified that the HDM is useful to minimize the frequency response by some actual applications. The effects of mesh density of the design domain and the rotor-stator position are also examined.

1 citations