• 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.21 no.2
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• pp.93-102
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• 2011

In spite of being unable to take into the effect of intermediate principal stress, Mohr-Coulomb and Hoek-Brown criteria are very popular as rock failure criteria. The recent researches reveal that the influence of intermediate principal stress on the failure strength of rock is substantial, so that 3-D failure criteria in which the intermediate principal stress could be considered is necessary for the safe design of the important rock structures. In this study, the likely application of the 3-D failure criterion proposed by Jiang & Pietruszczak (1988) to the prediction of the true triaxial strength of rock materials is discussed. The failure condition is linear in the meridian plane of principal stress space and it is represented by the smooth surface contacting the corners of the Mohr-Coulomb surface. The performance of the Jiang & Pietruszczak's criterion is demonstrated by simulating the actual true triaxial tests on the rock samples of three different rock types.

• Computational Structural Engineering
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• v.6 no.3
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• pp.89-97
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• 1993

General formulation to analyse the rectangular thin plate on a soil medium by energy method is developed. In the problem, Boussinesque's formular needs to be integrated after assuming the contact stress distribution. Two different functions, i.e., power series and Chebychev polynomials are used to approximate the contact stress distribution. It was found that Chebychev polynomials are better function to describe the contact stress than power series. Chebychev polynomials considering stress singularity around plate boundary is recommended as the desirable shape function for future research.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.5
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• pp.1530-1537
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• 1991

본 연구에서는 반무한 직선 계면균열의 상하면에 임의로 분포하는 어떠한 하 중에 대해서도 그 해석이 가능한 그린함수(Green's function)를 구하고자 한다. 이 를 위하여 반무한 직선 계면균열상의 임의의 한 점에 평면 집중하중이 작용하는 문제 와 비평면 집중전단하중이 작용하는 문제를 각각 택하였고, 이때 계면균열의 선단은 열려있다고 가정하였다. 이 문제를 풀므로써 균열선단부근의 응력성분을 결정하고 이로부터 그린함수의 의미를 지니는 응력강도계수에 대한 폐형해를 얻었다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.3
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• pp.295-300
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• 1985

본 논문에서는 Dhir의 이론에 따라서 Mapping함수로 고차다항식을 사용하여 여러가지 하중상태에 따른 최적형상을 연구하고 Mapping함수에 포함되어 있는 계수가 응력집중 및 형상변화에 미치는 영향을 검토하며 광탄성 실험을 통하여 이론의 타당성 을 입증하고자 하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.2
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• pp.257-264
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• 1986

무한평판에 묻혀진 크랙에 대한 응력확대계수를 결정하는 전위분포법을 반무한 평판에서의 표면크랙에 확장 적용하였다. 이를 위해 반평면에서의 전위응력의 기본 해가 간단한 복소수 응력함수형태로 얻어졌다. 평형을 이루는 절편적인 분포로부터 응력확대의 계수를 계산하는 새로운 방식을 제안하였으며, 수직표면 크랙과 묻혀진 경사크랙에 대한 기존해와 이 방법의 결과가 상호 비교되었다. 경사진 표면크랙에 대한 계산결과는 유한평판에서의 기존하는 Mapping Collocation 해석과 비교되어 좋은 일치를 보여 주었다. 구부러진 크랙과 대칭으로 가지친 크랙에 대해서는 표면크랙과 묻혀진 크랙사이에 상당한 차이가 있음이 나타났다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.851-858
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• 2010

A generalized elastic solution for a transient mode III crack propagating along the gradient in functionally graded materials (FGMs) is obtained through an asymptotic analysis. The shear modulus and density of the FGMs are assumed to vary exponentially along the gradient. The stress and displacement fields near the crack tip are obtained in terms of powers of radial coordinates, and the coefficients depend on the time rates of the change of the crack tip speed and stress intensity factors. The influence of nonhomogeneity and transients on the higher order terms of the stress and displacement fields is discussed.

• Tunnel and Underground Space
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• v.24 no.1
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• pp.81-88
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• 2014

In the course of performing the stability analysis of rock structures, there are times when the strength of the Hoek-Brown rock mass needs to be understood in terms of the internal friction angle and cohesion. In this case, the original Hoek-Brown criteion, giving the relationship between ${\sigma}_1$ and ${\sigma}_3$ at failure, have to be transformed to the corresponding Mohr envelope. A new approach to derive the Mohr envelope of the Hoek-Brown criterion is suggested in this study. The new method is based on the Londe's transformation making the stress components dimensionless. The correctness of the derivation leading to the new ${\tau}-{\sigma}$ relationship is confirmed by comparing the calculation results with the Bray's solution through a verification example.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1069-1078
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• 1990

It is shown that the performance of finite element based on energy orthogonal functions may be superior to conventional formulation for plane stress problem. Using this finite element, it is then attempted to show the distribution of stress concentration effect for subsurface under loading point. It turned out that the stress concentration effect for subsurface is not dependent on the width of the member but the loading area. And then it is shown that the solution attained by taking the stress function as a Fourier series is not satisfactory in y<0.1B.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5654-5663
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• 2015

In the unsaturated soil, suction, the negative pore water pressure leads to increases of the yield stress and the plastic shear stiffness of the soil skeleton due to the growth in interparticle stress. Therefore, in this study, the stress-strain relationship based on cyclic elasto-plastic constitutive model extended for unsaturated soil considering the 1st and the 2nd yield functions was induced in order to account for these effects of suction under the dynamic loading condition such as the earthquake. Through the program code considering this relationship and the routine of the cyclic loading with the reversion of loading direction, the numerical simulation of the cyclic triaxial test under the unsaturated condition would be possible. It is expected that the results of this study possibly contribute to the accuracy improvement on the prediction of unsaturated soil behavior under the dynamic loading condition.