• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.2
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• pp.181-186
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• 1992

The scattering property of TMz illuminated perfectly conducting and dielectric cylinders of arbitrary cross section are analyzed by the boundary element techniques. The boundary element equations are formulated via Maxwell’s equations, weighted residual or Green’s theorem, and the boundary conditions. The unknown surface fields on the boundaries are then calculated by the boundary element integral equations. Once the surface fields are found, the scattered fields in from a perfectly conducting circular and elliptic cylinders, a dielectric circular and elliptic cylinders are numerically analyzed. A general computer program has been developed using the quadratic elements(higher order boundary elements) and the Gaussian quadrature.

• Structural Engineering and Mechanics
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• v.56 no.4
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• pp.605-623
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• 2015

A formulation of the boundary element method (BEM) based on Kirchhoff's hypothesis to analyse stiffened plates composed by beams and slabs with different materials is proposed. The stiffened plate is modelled by a zoned plate, where different values of thickness, Poisson ration and Young's modulus can be defined for each sub-region. The proposed integral representations can be used to analyze the coupled stretching-bending problem, where the membrane effects are taken into account, or to analyze the bending and stretching problems separately. To solve the domain integrals of the integral representation of in-plane displacements, the beams and slabs domains are discretized into cells where the displacements have to be approximated. As the beams cells nodes are adopted coincident to the elements nodes, new independent values arise only in the slabs domain. Some numerical examples are presented and compared to a wellknown finite element code to show the accuracy of the proposed model.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1474-1482
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• 1994

In order to study the influence of a circular inclusion on a stress field neat a crack tip, mutual interference of a crack and the circular inclusion is analyzed by using the two dimensional boundary element method program made for the analysis of a bimaterial inclusion. The stress intensity factor of an inclusion which has small stiffness is a little greater than that of large stiffness in the near-by crack tip, and similar values tends to appear for distant crack tips. A line crack shows the repetition phenomena which caused by stress mutual interference depending on the radius and stiffness of an inclusion, and the repetition phenomena becoms weak in the inclusion which has large stiffness. Stress mutual interference shows repetition phenomena after extension of a line crack by the length of the radius of the inclusion which has small stiffness.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.4
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• pp.458-465
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• 2003

The main objective of the research is to develop a research code solving transient incompressible Navier-Stokes equation. In this research code, Adams-Bashforth method was applied to the convective terms of the navier stokes equation and the splitted equations were discretized spatially by finite element methods to solve the complex geometry problems easily. To reduce the divergence on the boundaries of pressure poisson equation due to the unsuitable pressure boundary conditions, multi step approximation pressure boundary conditions derived from the boundary linear momentum equations were used. Simulations of Lid Driven Flow and Flow over Cylinder were conducted to prove the accuracy by means of the comparison with results of the previous workers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.560-566
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• 2000

Many researchers have dealt with the problems of fracture mechanics. Generally, these researches are concerned with crack in isotropic material without other micro defects. Actual structure, however, may contain micro defects as well as crack in manufacture processing or operation. If it contains mi defects near a crack, some different characteristics will be appear in fracture behaviors of the crack. This study examines the effect of the micro defect on stress intensity factor of center slant crack rectangular plate subjected to uniform uniaxial tensile stress. In this study, boundary element method(BEM) is used for analysis in stress intensity factor(SIF).

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.382-385
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• 2006

A high-order spectral/boundary-element method is newly adapted as an efficient numerical tool. In this method, the velocity potential is expressed as the sum of surface potential and body potential. Then, surface potential is solved fly using the high-order spectral method and body potential is solved fly using the high-order boundary element method. Through the combination of these two methods, the wave-making problems fly a submerged sphere moving with the large amplitude oscillation are solved in time-domain. With the example calculations, nonlinear effects on free-surface profiles and hydrodynamic forces are shown and discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.112-121
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• 1996

Applications of bonded dissimilar materials such as metal/ceramics and resin/metal joints, are very increasing in various industry fields. It is required to find crack propagation direction and path applying to the fracture mechanics on the bonded joint of dissimilar meterials. In this paper, crack propagation direction and path were simulated numerically by using boundary element method. Crack propagation angle is able to easily determine based on the maximum stress concept. Fracture tests of Al/Epoxy dissimilar materials with an interface crack are carried out under various mixed mode conditions by using the specimens of bonded scarf joints. It is found that the experimental results are well coincide with the analysis results of boundary element method.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.434-439
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• 2000

In this paper, in order to study the geometric factor effect of a circular hole near a crack tip in a semi-infinite plate, the Dimensionless Stress Intensity Factor, $F(=\frac K {\sigma {\sqrt{\pi a}}})$ is analyzed at the crack tip using a two Dimensional Boundary Element Method (BEM) program which is known as superior in Fracture Mechanics. Kelvin's solution was used as a fundamental solution in BEM analysis and displacement extrapolation method was used to determine Stress Intensity Factor.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.2
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• pp.304-311
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• 2001

The present work examines the influence of surface coating on the temperature and the thermo-mechanical stress field produced by friction due to sliding contact. A two-dimensional transient model of a layered medium submitted to a moving heat flux is prsented. A solution technique based on the boundary element method employing the multiregion technique is utilized. Results are presented showing the influence of coating thickness, thermal properties, Peclet number, and mechanical properties. It has been shown that the mechanical properties and thickness of coating have a significant influence on the stress field, even for low temperature increase. The effects of the ratios of shear modulus become more important for low temperature increase than the effects of the ratios of other mechanical properties.

• Journal of Mechanical Science and Technology
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• v.19 no.8
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• pp.1611-1620
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• 2005

This paper shows the use of wavelet transformation combined with inverse acoustics to reconstruct the surface velocity of a noise source. This approach uses the boundary element analysis based on the measured sound pressure at a set of field points, the Helmholtz integral equations and wavelet transformation for reconstructing the normal surface velocity field. The reconstructed field can be diverged due to the small measurement errors in the case of nearfield acoustic holography (NAH) using an inverse boundary element method. In order to avoid this instability in the inverse problem, the reconstruction process should include some form of regularization for enhancing the resolution of source images. The usual method of regularization has been the truncation of wave vectors associated with small singular values, although the order of an optimal truncation is difficult to determine. In this paper, a wavelet transformation is applied to reduce the computation time for inverse acoustics and to enhance the reconstructed vibration field. The computational speed-up is achieved, with solution time being reduced to $14.5\%$.