• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.7
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• pp.1120-1131
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• 2003

A recently developed numerical method based on a mixed volume and boundary integral equation method is applied to calculate the accurate stress intensity factors at the crack tips in unbounded isotropic solids in the presence of multiple anisotropic inclusions and cracks subject to external loads. Firstly, it should be noted that this newly developed numerical method does not require the Green's function for anisotropic inclusions to solve this class of problems since only Green's function for the unbounded isotropic matrix is involved in their formulation for the analysis. Secondly, this method takes full advantage of the capabilities developed in FEM and BIEM. In this paper, a detailed analysis of the stress intensity factors are carried out for an unbounded isotropic matrix containing an orthotropic cylindrical inclusion and a crack. The accuracy and effectiveness of the new method are examined through comparison with results obtained from analytical method and volume integral equation method. It is demonstrated that this new method is very accurate and effective for solving plane elastostatic problems in unbounded solids containing anisotropic inclusions and cracks.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.12
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• pp.1072-1087
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• 2008

A mixed volume and boundary integral equation method (Mixed VIEM-BIEM) is used to calculate the plane elastostatic field in an isotropic elastic half-plane containing an isotropic or anisotropic inclusion and a void subject to remote loading parallel to the traction-free boundary. A detailed analysis of stress field at the interface between the isotropic matrix and the isotropic or orthotropic inclusion is carried out for different values of the distance between the center of the inclusion and the traction-free surface boundary in an isotropic elastic half-plane containing three different geometries of an isotropic or orthotropic inclusion and a void. The method is shown to be very accurate and effective for investigating the local stresses in an isotropic elastic half-plane containing multiple isotropic or anisotropic inclusions and multiple voids.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.12
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• pp.2298-2305
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• 1992

To obtain the convenient solution of the multibody dynamic systems composed of flexible beams, linear finite element technique is adopted and the nodal coordinates are interpolated in the global inertia frame. Mass matrix becomes an extremely simple constant matrix and the force vector also becomes extremely simple because Coriolis acceleration and centrifugal force are not required. And the elastic force is also simply computed from the moving frame attached to the material. To solve the global differential algebraic euation. an ODE technique is adopted after Lagrange multiplier is computed by the accelerated iterative technique, and the time demanding procedures such as Newton-Raphson iterations and decomposition of the big matrix are not required. The accuracy of the present solution is checked by a well-known example problem.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2002.08a
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• pp.287-293
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• 2002

조석을 수치모의하기 위해 North carolina 대학의 R.A. Luettich와 Notre Dame 대학의 J.J. Westerink가 개발한 ADvanced CIRCulation model for oceanic, coastal and estuarine waters(ADCIRC) 유한요소모형 (Luettich, et al., 1992)은 수심 적분된 2 차원 모형(2DDI)과 3차원 모형(3DL)으로 구성되어 있는데, 그 중 2차원 ADCIRC 유한요소모형은 천수방정식에서 연속방정식과 운동방정식을 합성하여 수면변위에 대해 하나의 식으로 표현한 파동방정식(wave equation)을 지배방정식으로 사용하고 있다. (중략)

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05a
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• pp.173-178
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• 1996

특정한 방향성분에 대한 방향중성자속을 정의하는 방향차분 수송 방정식(discrete ordinates or S$_{N}$ transport equation)과 달리 방향변수를 구분된 방향영역에 대하여 적분하고, 해당 방향영역 내에서의 방향중성자속이 일정하다고 가정하는 영역상수법(piecewise constant method)을 이용하여 유사방향차분방정식(discrete ordinates-like equation)을 유도하여, 이를 Boltzmann 수송식과 2계 우성수송식(even-parity transport equation)에 적용하여 기존의 방향차분법의 단점인 광첨두현상(ray effects)을 감소시키고, 우성수송식의 교차미분항을 제거한 단순우성방정식(simplified even-parity equation)을 사용하여 광첨두현상을 제거하였다. 이는 단순우성방정식의 또 다른 장점을 제시한다.

• Journal of the KSME
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• v.22 no.4
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• pp.316-323
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• 1982

전고에서는 후리에변환에 의하여 그 해를 구할 수 있는 문제중 Wiener-Hopf 방법의 사용을 요 하는 문제들에 대하여 고찰하였고 예제들의 해를 구하므로서 그 해석 방법을 알아보았다. 본 강좌에서는 적분 방정식의 해를 그 인수가 초등할수인 다른 핵으로 대체하여 근사해를 구하는 방법과 마지막으로 dual 적분방식을 다루고 Wiener-Hopf 방법에 대한 강좌를 끝내고자 한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.240-240
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• 2003

V-노치 균열에서 열하중이 작용하는 경우는 비제차형 경계조건의 문제가 되고, 이 조건에 대한 방정식의 일반해를 구하기 위해서 재차형 연립방정식에 대한 일반해(Homogeneous solution)와 비제차형 연립방정식에 대한 특수해(Particular solution)의 두 가지 해를 구할 수 있다. 이들 해는 V-노치 균열에 대한 고유치가 되고 이 고유치가 중복근을 가지게 되는 경우에는 로그항(1n[r])이 나타나게 되고 이 항에 의해서 응력을 무한대로 발산시키므로 이를 대수응력특이성이라 한다. 열하중이 작용할 때 대수응력특이성을 나타내는 로그항의 계수가 영(0)이 되어 대수응력특이성이 사라지게 되므로 V-노치 선단에서의 응력특이성은 고유치와 그에 대한 고유벡터에 의해 결정된다. 본 논문에서는 비정상상태 열하중이 가해지는 등방성 이종재료 내의 V-노치 균열문제에서 패기 각도와 이종재료의 기계적 성질에 의해 결정되는 응력특이성지수를 구하고 이에 대한 응력강도계수를 유한요소해석 프로그램인 ANSYS와 상반일 경로 적분법(RWCIM)을 이용하여 구하였다.

• Economic and Environmental Geology
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• v.27 no.1
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• pp.41-47
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• 1994

A fast Hankel transform (FHT) algorithm (Anderson, 1982) is applied to numerical evaluation of many Green's tensor integrals encountered in three-dimensional electromagnetic modeling using integral equations. Efficient computation of Hankel transforms is obtained by a combination of related and lagged convolutions which are available in the FHT. We express Green's tensor integrals for a layered half-space, and rewrite those to a form of related functions so that the FHT can be applied in an efficient manner. By use of the FHT, a complete or full matrix of the related Hankel transform can be rapidly and accurately calculated for about the same computation time as would be required for a single direct convolution. Computing time for a five-layer half-space shows that the FHT is about 117 and 4 times faster than conventional direct and multiple lagged convolution methods, respectively.

• Journal of Korea Water Resources Association
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• v.31 no.2
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• pp.177-187
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• 1998

The spatially integrated model (SIM) which can evaluate temporal variation of groundwater quality is proposed in the stream-aquifer setting entered by nonpoint source contaminants. And the developed SIM included unsaturated soil zone and was tested against the spatially distributed model (SDM) of the coupled advection-dispersion and Richards equations for the various hydrologic and aquifer simulating conditions. The result of the comparison showed that the average concentration responses of saturated aquifer and groundwater outflow between the SIM and the SDM was in good agreement, except for the case of the large dispersivity ratio and thick aquifer system. And it is shown that for the cases of the large dispersivity ratio and thick aquifer system the performance of the nonlinear SIM is better than that of the linear SIM for evaluating the average concentration of groundwater outflow response.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.3
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• pp.282-288
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• 1982

크랙탄성평판의 굽힘문제가 경계적분방정식으로 구성되었다. 자연변수인 변위, 수직기울기, 굽힘 모우멘트, 등가전단적과 크랙끝에서 응력의 성장율로 정의되는 응력확대계수들이 주변수로 포함 된다. 이 적분방정식들은 가역에너지 적분이론(Green-Rayleigh)을 기초로 크랙응력분포특성에 맞 게 발전되었으며 해당되는 핵함수들이 유도되었다. 등분석 모우멘트를 받는 중앙크랙이 있는 정 4각형 모형에 대한 응력확대계수가 계산되어 기존의 유한요소법의 해와 비교되었다.