• 전기의세계
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• v.39 no.3
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• pp.4-8
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• 1990

전자장의 거동은 Maxwell의 방정식으로 표현할 수 있다. 이 방정식을 풀때는 그 경계조건을 만족하여야 하므로 전자장의 해석은 경계치 문제로 귀착된다. Maxwell 방정식의 해법은 해석적인 해법과 수치적인 해법으로 크게 나누어지는데 전자의 경우는 경계의 형상이 간단하거나 매질의 특성이 선형일때만 가능하다. 따라서 공학적인 실제의 문제를 다룰때는 수치적인 해법이 필수불가결하다. 근래에 와서는 전기기기의 고효율화, 경량화, 고성능화등의 필요성에 의하여 전기기기 내에서의 전자장을 정확히 해석할 필요성이 증대되었다. 이를 위하여 효과적인 수치해석기법의 연구가 활발히 진행되어 왔는데 세계적으로 보면 1960년대 말부터 유한요소법이 전자장해석에 이용되었고 근래에 괄목할만한 발전을 이루었다. 국내에서는 선진외국보다는 10여년 늦게 1970년 후반부터 이에 대한 연구가 시작되어 지금은 대학, 산업체에서 전자장수치해석에 대한 연구와 응용이 활발하고 어떤 분야는 세계적인 수준에 달하고 있다. 본고에서는 주로 국내의 유한요소법 및 경계요소법의 연구와 응용현황을 기술하고 앞으로의 전망을 기술하기로 한다. 그리고 본고를 작성하는 과정에서 자료조사의 미흡으로 모든 분야가 충분히 기술되지 못한 점에 대하여 깊은 이해가 있기를 바란다.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.4 no.1
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• pp.38-43
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• 1993

A Hybrid Finite Element Method(HFEM) is applied to solve the electrormagnetic scattering from multi-layered dielectric cylinders. An unbounde region is divided into local boundary regions where a practical differential equation solution is obtained, with the remaining unbounded region represented by a boundary integral equation. If sources, media inhomogeneities, and anisotropies are local, a surgace may be defined to enclose them. Therefore the integral region so defined is bounded, and differential techniques may be used there. Also, in the re- maining unbounded region a boundary integral equation may be formulated using only a simple free - space green's function. Therefore, The local boundary is represented by a boundary - value problem with boundary conditions and solved by the finite element method. The advantage of the proposed method is simple and efficient in the work of electromagnetic scattering. The validity of the results have been verified by comparing results of other method(boundary element method). Examples has been presented to calculate the scattered fields of lossy dielectric cylinders of arbitray cross section.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.82-87
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• 1987

In this study a method of shape optimization is applied to two dimensional heat transfer system. For this the optimization problem is defined in a functional form including cost, constraints and the system governing equation. Then the material derivative concept in continuum mechanics and the adjoint variable method are employed for the shape design sensitivity analysis. With the sensitivity analysis results, an optimum is sought with the gradient projection optimization algorithm. The two dimensional isoparametric finite elements are used for accurate analysis and sensitivity calculations. The above method is employed to find the boundary shape to achieve a desired temperature distribution along a segment of the boundary subject to the maximum area constraint.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.213-224
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• 2008

Flexible pavement responses to vehicular loading, such as critical stresses and strains, in each pavement layer, could be predicted by the multilayered elastic analysis. However, multilayered elastic theory suffers from major drawbacks including spatial dimension of a numerical model, material properties considered in the analysis, boundary conditions, and ill-presentation of tire-pavement contact shape and stresses. To overcome these shortcomings, three-dimensional finite element (3D FE) models are developed and numerical analyses are conducted to calculate pavement responses to moving load in this study. This paper introduces a methodology for an effective 3D FE to simulate flexible pavement structure. It also discusses the mesh development and boundary condition analysis. Sensitivity analyses of flexible pavement response to loading are conducted. The infinite boundary conditions and time-dependent history of calculated pavement responses are considered in the analysis. This study found that the outcome of 3D FE implicit dynamic analysis of flexible pavement that utilizes appropriate boundary conditions, continuous moving load, viscoelastic hot-mix asphalt model is comparable to field measurements.

• Journal of the Korean Magnetics Society
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• v.1 no.2
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• pp.79-84
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• 1991

A variational approach employing localized functional is presented to solve alternating magnetic field problems with open boundary. The functional used in the approach consists of the domain integral of finite element region only and the boundary integral of the interfacial boundary between the finite and infinite element regions. The boundary integral is obtained by transforming the infinite domain integral for the infinite element region into the interfacial boundary integral. The proposed algorithm is then applied to a simple two-dimensional problem where the analytic solutions are available. It is shown that the algorithm makes it possible to yield good agreements between the numerical and analytic solutions. and that it requires less computer storage memory and computation time than the conventional finite element method due to the reduction of the computing region.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.11
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• pp.1097-1102
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• 2010

In this paper, the energy flow analysis(EFA) of the body-in-white door of a real automotive was performed using the energy flow finite element method(EFFEM) to effectively predict the vibrational responses of built-up structures in the medium to high frequency range. To increase the validity of EFA results, the structural hysteresis damping loss factor was measured by the experiment using the concept of statistical energy analysis(SEA). As the excitation frequency increases, the predicted results simulated with EFFEM generally agree with the experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.5
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• pp.404-411
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• 2007

new domain/boundary decomposition method is suggested to perform efficient finite element analyses of contact problems. A penalty method is used for connecting an interface or contact interfaces with neighboring subdomains that satisfy continuity conditions. As a result, the derived effective stiffness matrices are always positive definite, and computational efficiency can be improved to a considerable degree. Moreover, any complex-shaped domain can be divided into independently modeled subdomains without considering the conformity of meshes along the interface. Using a computer code based on the present method, these advantageous features are confirmed through a set of numerical examples.

• The Journal of the Acoustical Society of Korea
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• v.31 no.3
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• pp.142-150
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• 2012

The waveguide finite element (WFE) method is a useful numerical technique to investigate wave propagation along waveguide structures which have uniform cross-sections along the length direction ('x' direction). In the present paper, the vibration and radiated noise of the submerged pipe with fluid is investigated numerically by coupling waveguide finite elements and wavenumber boundary elements. The pipe and internal fluid are modelled with waveguide finite elements and the external fluid with wavenumber boundary elements which are fully coupled. In order to examine this model, the point mobility, dispersion curves and radiated power are calculated and compared for several different coupling conditions between the pipe and internal/external fluids.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.2
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• pp.199-208
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• 2008

In this paper, to analyze the initial valued non-homogeneous elastic half space by the scaled boundary analysis, the infinite element approach was introduced. The free surface of the initial valued non-homogeneous elastic half space was modeled as a circumferential direction of boundary scaled boundary coordinate. The infinite element was used to represent the infinite length of the free surface. The initial value of material property(elastic modulus) was considered by the combination of the position of the scaling center and the power function of the radial direction. By use of the mapping type infinite element, the consistent elements formulation could be available. The performance and the feasibility of proposed approach are examined by two numerical examples.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.10a
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• pp.90-96
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• 1992

경계면 요소를 이용하여 철근콘크리트 구조물의 접촉면 문제를 유한 요소법으로 해석하는 기법에 대하여 연구한다. 본 연구에서는 경계면 요소의 수치해석의 이론과정을 전개하고, 실험 관찰된 부착 시험체에 적용하여 이형철근과 콘크리트 부착기구의 접촉면을 해석한다. 경계면은 특별한 연결요소를 이용하여 재현하며 Mohr-Coulomb의 마찰 이론을 응응한다. 해석의 주요점으로 하중상태에 따라 변화되는 경계면의 접촉상태, 즉 고정(stick), 미끄러짐(slide), 분리(separation)를 묘사하여 경계면 재료의 비선형 거동을 관찰한다. 부착모델의 해석결과는 실험실의 결과와 대체로 일치되며 따라서 철근콘크리트 접촉면의 응력해석을 위해 경계면 요소가 활용될 수 있음을 보여준다.