CMES-Vol. 5, No. 3, 2004

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ARTICLE

Determination of Stress Intensity Factors for Interfacial Cracks Using the Virtual Crack Extension Approach
W.M.G.. So¹, K.J. Lau¹, S.W. Ng¹
CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.3, pp. 189-200, 2004, DOI:10.3970/cmes.2004.005.189
Abstract A new finite element analysis procedure is implemented for the determination of complex stress intensity factors in interfacial cracks. Only nodal displacements and strain energies of the near-crack-tip elements are involved in this procedure so that element stiffness matrices need not be made available. The method is first tested using a closed form solution for infinite media to obtain a suitable finite element mesh. It is then applied to finite plates and four-point bending specimens containing interfacial cracks. In cases where reference values are available for comparison, good agreement of results can be obtained with relatively coarse element meshes. More >

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On the application of MQ-RBF to the valuation of derivative securities
S. Choi¹, M.D. Marcozzi¹
CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.3, pp. 201-212, 2004, DOI:10.3970/cmes.2004.005.201
Abstract The general intractability of derivative security pricing models to numerical techniques arguably remains one of the preeminant problems of mathematical finance. In particular, the valuations of such models may be represented as solutions of variational inequalities of evolutionary type typically characterized by their high number of degrees of freedom, unbounded domains, and asymptotic behavior. We consider the application of Multi-Quadratic Radial Basis Functions (MQ-RBF) to the problem of option pricing. More >

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Generating optimised partitions for parallel finite element computations employing float-encoded genetic algorithms
A. Rama Mohan Rao¹, T.V.S.R. Appa Rao², B. Dattaguru³
CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.3, pp. 213-234, 2004, DOI:10.3970/cmes.2004.005.213
Abstract This paper presents an algorithm for automatic partitioning of unstructured meshes for parallel finite element computations employing float-encoded genetic algorithms (FEGA). The problem of mesh partitioning is represented in such a way that the number of variables considered in the genome (chromosome) construction is constant irrespective of the size of the problem. In order to accelerate the computational process, several acceleration techniques like constraining the search space, local improvement after initial global partitioning have been attempted. Finally, micro float-encoded genetic algorithms have been developed to accelerate the computational process. More >

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Multiscale Simulation Based on The Meshless Local Petrov-Galerkin (MLPG) Method
gping Shen¹, S. N. Atluri¹
CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.3, pp. 235-256, 2004, DOI:10.3970/cmes.2004.005.235
Abstract A multiscale simulation technique based on the MLPG methods, and finite deformation mechanics, is developed, implemented, and tested. Several alternate time-dependent interfacial conditions, between the atomistic and continuum regions, are systematically studied, for the seamless multiscale simulation, by decomposing the displacement of atoms in the equivalent-continuum region into long and short wave-length components. All of these methods for enforcing the interface conditions can ensure the passage of information accurately between the atomistic and continuum regions, while they lead to different performances at short wavelengths. The presently proposed Solution Method 2 reduces the phonon reflections at the interface, without increasing the… More >

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Thermal Fluid Transport Phenomena in Concentric Annulus with Movement and Rotation of Inner Core
S. Torii¹
CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.3, pp. 257-268, 2004, DOI:10.3970/cmes.2004.005.257
Abstract A numerical study is performed to investigate the thermal fluid-flow transport phenomena in the concentric annulus with a slightly heated rotating inner core moving in the flow direction and a stationary insulated outer cylinder. Emphasis is placed on the effects of the axial rotation and streamwise movement of inner core on the flow structure and heat transfer performance. A k-ε turbulence model is employed to determine the turbulent viscosity and the turbulent kinetic energy. The turbulent heat flux is expressed by Boussinesq approximation in which the eddy diffusivity for heat is determined using two-equation heat transfer model. The governing equations… More >

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Crashworthiness Analysis and Simulations of Vehicles Impacting a Roadside Guardrail
W. Uddin¹
CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.3, pp. 269-278, 2004, DOI:10.3970/cmes.2004.005.269
Abstract This paper presents the results of a three-dimensional finite element study to simulate impacts of the models of a car and a pickup truck against a model of modified thrie-beam guardrail and to analyze the crashworthiness of the roadside guardrail. Nonlinear springs were used to simulate the rotation of the post below ground level. The simulation results of an event of a pickup truck impacting the modified thrie-beam guardrail model are presented. The ``reduced'' version of the pickup truck model is redirected after impact and leaves the guardrail without any significant problem. These results compare well with the results of… More >

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Frequency-Shifting Analysis of Electrostatically Tunable Micro-Mechanical Actuator
Wan-Sul Lee, Kie-Chan Kwon, Bong-Kyu Kim, Ji-Hyon Cho, Sung-Kie Youn¹
CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.3, pp. 279-286, 2004, DOI:10.3970/cmes.2004.005.279
Abstract A numerical approach for eigenvalue analysis of the electrostatically tunable micro-mechanical actuators is presented. An efficient algorithm for calculating the natural frequency shifting in the micro-mechanical actuators due to applied DC turning voltage is proposed. In the calculations of the coupled field problem, the three-dimensional FEM/BEM approaches and iterative staggered algorithm are employed. The numerical examples for actually fabricated actuators are presented and the numerical analysis results are compared with experimental data. More >

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