• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.1
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• pp.34-41
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• 2003

A Green's function approach is adopted for analyzing the thermoelastic deformation and stress analysis of a plate made of functionally graded materials (FGMs). The solution to the 3-dimensional steady temperature is obtained by using the laminate theory. The fundamental equations for thermoelastic problems are derived in terms of out-plane deformation and in-plane force, separately. The thermoelastic deformation and the stress distributions due to the bending and in-plane forces are analyzed by using a Green’Às function based on the Galerkin method. The eigenfunctions of the Galerkin Green's function for the thermoelastic deformation and the stress distributions are approximated in terms of a series of admissible functions that satisfy the homogeneous boundary conditions of the rectangular plate. Numerical examples are carried out and effects of material properties on thermoelastic behaviors are discussed.

• Journal of the KSME
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• v.28 no.3
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• pp.248-256
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• 1988

극한해석은 이제까지 주로 소성구조물의 설계에 응용되어 왔다. 초기의 구조물들은 탄성에너지 이론에 의하여 설계되었고 모든 권위자들은 이를 당연하게 받아들였다. 그러나 Broek 교수와 같은 사람들의 노력에 의하여 극한설계의 타당성과 유용성이 입증되었고, 구조물의 건설에 많은 경비를 절약하게 되었다. 철탑과 같은 트러스 구조물이 그 대표적인 예로서 카나다의 수력발 전회사는 1910년 철탑을 평지에 세워놓고 모든 악조건을 부과하며 수년간 극한해석의 타당성을 실험하여 입증하였다. 트러스에 대한 극한해석 문제는 최소화 기법의 구속최소화 문제로 유도할 수 있고, 트러스문제는 소성가공의 해석에도 직접 응용할 수 있다. 왜냐하면, 예를 들어 평면변 형문제가 앞에서 보인바와 같이 똑같은 구속최소화 문제로 유도되었기 때문이다. 결론적으로, 트러스문제나, 평판문제나, 평면응력문제나, 평면변형문제가 극한해석에서는 모두 같은 문제로 간주될 수 있고 같은 공식과 같은 방법으로 풀 수 있는 것이다. 이를테면, 소성구조물에서의 한 계하중은 소성가공에서는 가공하중이 되며 모두 극한하중이 되는 것이다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.2
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• pp.121-131
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• 2011

An object oriented programming(OOP) framework is presented to solve plane elastostatic contact problems by means of the boundary element method(BEM). Unified modeling language(UML) is chosen to describe the structure of the program without loss of generality, even though all implemented codes are written with C++. The implementation is based on computational abstractions of both mathematical and physical concepts associated with contact mechanics involving geometrical nonlinearities and the corner node problems for multi-valued traction. The overall class organization for contact analysis is discussed in detail. Numerical examples are also presented to verify the accuracy of the developed BEM program.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.6
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• pp.1070-1081
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• 1989

본 논문의 목적은 일반적인 곡면을 갖는 냉간단조 공정을 컴퓨터 시뮬레이션 을 통해 해석하고자 강소성 유한요소법의 프로그램을 개발하고, 이를 축대칭 및 평면 변형 단조성형에 적용하고자 한다. 축대칭 문제로는 산업적으로 이용이 많은 치차 블랭크(gear blank) 형태의 예제를 선택하였고 평면변형으 경우 정밀 단조품의 하나인 터어빈 블레이드(turbine blade)를 평면변형 문제로 보아 해석하였다. 한편 심한 변형을 하는 후방압출과 같은 문제의 수렴성을 향상시키고 공정을 계속적으로 해석하 기 위하여 격자 재구성기법을 도입함으로서 냉간단조 문제의 일반적인 해석을 하도록 한다.

• Computational Structural Engineering
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• v.8 no.4
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• pp.65-74
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• 1995

Direct method developed for the inelastic analysis of planar frames subjected to monotonic loads is extended to cyclic loads. Two frame elements for Direct Method(inelastic truss and inelastic beam) are developed. The accuracy and reliability of the preposed method is verified by comparing the analysis results of example with step-by-step analysis. Direct Method is superior to Step-by-step analysis in view of reliability of solution and analysis cost.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.8
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• pp.91-100
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• 2004

A Green's function approach is adopted for analyzing the thermoelastic deformations and stresses of a plate made of functionally graded materials(FGMs). The solution to the 3-dimensional unsteady temperature is obtained by using the laminate theory. The fundamental equations for thermoelastic problems are derived in terms of out-plane deformation and in-plane force, separately. The thermoelastic deformation and the stress distributions due to the bending and in-plane forces are analyzed by using a Green's function based on the Galerkin method. The eigenfunctions of the Galerkin Green's function for the thermoelastic deformation and the stress distributions are approximated in terms of a series of admissible functions that satisfy the homogeneous boundary conditions of the rectangular plate. Numerical analysis for a simply supported plate is carried out and effects of material properties on unsteady thermoclastic behaviors are discussed.

• Tunnel and Underground Space
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• v.18 no.4
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• pp.252-262
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• 2008

In the uniaxial compressive test of a single specimen of transversely isotropic rock, its 5 independent elastic constants can not be defined since maximum 4 independent strain measurements are available theoretically. In order to solve this problem, one equation proposed by Saint Venant in 19C and confirmed by Lekhnitskii through the test experiences has been used for long time. Accordign to authors' experiences, however, this equation turned out to give erroneous elastic constants in some cases. Three new equations are suggested and their compatibilities are discussed in this paper. As the results of the analyses of the models, Lekhnitskii's suggested equation is effective for the specimen with the high dip angle whereas it results in the large erred output for that with dip angle less than $25{\sim}30$. It was found that the effectivenesses of three suggested equations and their compatibilities are subject to the dip angle and not to the amounts of elastic constants. Guide map to the selection of the compatible one of those suggested equations is presented as a result of the study.

• Tunnel and Underground Space
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• v.11 no.1
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• pp.72-78
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• 2001

A method to determine elastic constants for transversely isotropic rock using a single uniaxial compression test was proposed by Kim(1995). However, some problems were found when this method was applied. We derived two different equations in determination of elastic constants using V$\sub$12/ and V$\sub$21/ and performed uniaxial compression tests for two specimens whose angles between transversely isotropic plane and horizontal plane are 30$^{\circ}C$ and 65$^{\circ}C$. The anisotropic elastic constants should be calculated with different equations depend on the angle. If the anisotropic angle is lower than 45$^{\circ}$, V$\sub$21/ may be used. However, if the anisotropic angle is higher than 45$^{\circ}$, V$\sub$12/ may be used.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.2
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• pp.127-136
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• 2007

In this paper, the equations of the scaled boundary finite element method are derived for non-homogeneous half plane and analyzed numerically In the scaled boundary finite element method, partial differential equations are weaken in the circumferential direction by approximation scheme such as the finite element method, and the radial direction of equations remain in analytical form. The scaled boundary equations of non-homogeneous half plane, its elastic modulus varies as power function, are newly derived by the virtual work theory. It is shown that the governing equation of this problem is the Euler-Cauchy equation, therefore, the logarithm mode used in the half plane problem is not valid in this problem. Two numerical examples are analysed for the verification and the feasibility.

• Computational Structural Engineering
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• v.10 no.3
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• pp.185-193
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• 1997

The order of the stress singularity that occurs at the termination of an interface between materials exhibiting bilinear stress-strain response under plane strain conditions has been calculated, The governing equation of elasticity together with traction-free boundary condition and interface continuity condition defines a two-point boundary value problem. The stress components near the free edge are assumed to be proportional to r/sup s-1/, with solutions existing only for certain values of s. Finding these values entails the solution of an eigenvalue problem. Because it has been impossible to integrate the differential equations analytically, the integration has been performed numerically with a shooting method coupled with a Newton improvement scheme.