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Selected Problems (selected + problem)

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Engineering	100%

Selected Abstracts

Meta-Optimization Using Cellular Automata with Application to the Combined Trip Distribution and Assignment System Optimal Problem

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 6 2001
Wael M. ElDessouki
In this paper, meta-optimization and cellular automata have been introduced as a modeling environment for solving large-scale and complex transportation problems. A constrained system optimum combined trip distribution and assignment problem was selected to demonstrate the applicability of the cellular automata approach over classical mixed integer formulation. A mathematical formulation for the selected problem has been developed and a methodology for applying cellular automata has been presented. A numerical example network was used to illustrate the potential for using cellular automata as a modeling environment for solving optimization problems. [source]

Implementation of the finite element method in the three-dimensional discontinuous deformation analysis (3D-DDA)

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 15 2008
Roozbeh Grayeli
Abstract A modified three-dimensional discontinuous deformation analysis (3D-DDA) method is derived using four-noded tetrahedral elements to improve the accuracy of current 3D-DDA algorithm in practical applications. The analysis program for the modified 3D-DDA method is developed in a C++ environment and its accuracy is illustrated through comparisons with several analytical solutions that are available for selected problems. The predicted solutions for these problems using the modified 3D-DDA approach all show satisfactory agreement with the corresponding analytical results. Results presented in this paper demonstrate that the modified 3D-DDA method with discontinuous modeling capabilities offers a useful computational tool to determine stresses and deformations in practical problems involving fissured elastic media with reasonable accuracy. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Constitutive model for quasi-static deformation of metallic sandwich cores

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2004
Zhenyu Xue
Abstract All-metal sandwich construction holds promise for significant improvements in stiffness, strength and blast resistance for built-up plate structures. Analysis of the performance of sandwich plates under various loads, static and dynamic, requires modelling of face sheets and core with some fidelity. While it is possible to model full geometric details of the core for a few selected problems, this is unnecessary and unrealistic for larger complex structures under general loadings. In this paper, a continuum constitutive model is proposed as an alternative means of modelling the core. The constitutive model falls within the framework of a compressible rate-independent, anisotropic elastic,plastic solid. The general form of the model is presented, along with algorithmic aspects of its implementation in a finite element code, and selected problems are solved which benchmark the code against existing codes for limiting cases and which illustrate features specific to compressible cores. Three core geometries (pyramidal truss, folded plate, and square honeycomb) are considered in some detail. The validity of the approach is established by comparing numerical finite element simulations using the model with those obtained by a full three-dimensional meshing of the core geometry for each of the three types of cores for a clamped sandwich plate subject to uniform pressure load. Limitations of the model are also discussed. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Non-Asymptotic Modelling of Medium Thickness Plates with Plane Periodic Structure

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008
Eugeniusz BaronArticle first published online: 26 FEB 200
The main aim of this contribution are presented a certain selected problems (aspects) of non,asymptotic modelling of medium thickness (or Reissner,type) rectangular plates with a plane periodic in,homogeneous structure. In course of non,asymptotic modeling, by using tolerance averaging technique (TAT), apart from the known separation for biperiodic and uniperiodic plates, it is necessary to introduce extra partitions. The four non,asymptotic models of plates with plane periodic structure can be led out independently (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]