• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.3
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• pp.321-332
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• 2005

In this paper, the time-domain finite element formulations for axisymmetric linear viscoelastic problems, especially for the viscoelastic hollow sphere and cylinder, under various boundary conditions are presented with the theoretical solutions of them obtained by using the elastic-viscoelastic correspondence principle. It is assumed that the viscoelastic material behaves like a standard linear solid in distortion and elastically in dilatation. Numerical examples are solved based on the spherically symmetric, axisymmetric and plane strain finite element models. Good agreements are obtained between numerical and theoretical solutions, which shows the validity and accuracy of the presented method.

• Journal of the Korea Institute of Military Science and Technology
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• v.1 no.1
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• pp.128-144
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• 1998

The BEM for linear elastic stress analysis is applied to the highly rotating axisymmetric body problem which also involves the thermoelastic effects due to steady-state thermal conduction. The axisymmetric BEM formulation is briefly summarized and an alternative approach for transforming the volume integrals associated with such body force kernels into equivalent boundary integrals is described in a way of using the concept of inner product and vector identity. A discretization scheme for higher order BE is outlined for numerical treatment of the resulting boundary integral equations, and it is consequently illustrated by determining the stress distributions of the turbine rotor disk of the small turbojet engine(ADD 500) for which a FEM stress solution has been furnished by author.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.787-797
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• 1986

An implicit approach is employed to obtain a general boundary integral formulation of axisymmetric elastic problems in terms of a pair of singular integral equations. The corresponding kernel functions from the solutions of Navier's equation are derived by applying a three dimensional integral and a direct axisymmetrical approach. A numerical discretization schem including the evaluation of Cauchy principal values of the singular integral is described. Finally the typical axisymmetric elastic models are analyzed, i.e. the hollow sphere, the constant thickness and the V-notched round bar.

• 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.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.2
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• pp.207-216
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• 2003

In this paper, the finite element method for the elastodynamic axisymmetric fracture analysis is presented in matrix form through the application of the Galerkin method to the time integral equations of motion with no inertia forces. Isoparametric quadratic quadrilateral element and triangular crack tip singular elements with one-quarter node are used in the mesh division of the finite element model. To show the validity and accuracy of the proposed method, the infinite elastic medium with the penny shaped crack is solved first and compared with the analytical solution and the numerical results by the finite difference method and the boundary element method existing in the published literatures, and then the dynamic stress intensity factors of solid and hollow cylinders of finite dimensions haying penny-shaped cracks and internal and external circumferential tracks are computed in detail.

• Journal of the Korea Convergence Society
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• v.9 no.1
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• pp.283-289
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• 2018

In automotive disc brake systems, frictional heat is not uniformly dispersed for reasons such as heat flux and thermal deformation. The thermoelastic deformation due to the frictional heat affects the contact pressure distribution and the contact load may be concentrated on the contact portion on the the disc brake surface, resulting in thermoelastic instability. In this study, thermal analysis and thermal deformation analysis considering the contact between disk and pad occurred during braking through 3D axial symmetry model with reference to the experimental equation and Kao's analysis method of contact pressure of disk and pad. ANSYS is used to analyze the thermal and elastic instability problems occurring at the contact surface between the disk and the pad, considering both the thermal and mechanical loads. A 3D axisymmetric model with direct contact between the disk and the pad was constructed to more accurately observe the thermal behavior of the disk by observing the frictional surface temperature, thermal deformation and contact thermal stress of the disk.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05b
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• pp.659-665
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• 1995

액체금속로는 기존의 가압경수로와는 달리 55$0^{\circ}C$ 정도의 고온에서 운전이 되므로 고온 열응력이 중요한 문제로 대두되며 따라서 고은에서의 크립(Creep) 변형, 반복되는 기동과 정지 등으로 인한 되풀이 소성변형, 라체팅(Ratchetting), 크립과 소성의 상호작용 및 크립과 피로의 상호작용 등의 평가에 대한 기술 확립과 고온구조물에 대한 우리의 독자적인 설계방법을 개발하는 것이 필요하다 본 연구에서는 범용 유한요소해석코드인 ABAQUS의 축대칭 요소를 이용해서 액체 금속로 원자로용기와 이에 부착된 열소매(Thermal sleeve)를 Y-형태의 구조물로 모델링하여 반복되는 열천이하중에 대한 비탄성 구조해석을 수행하고 크립효과에 대한 영향을 분석하였다. 해석결과 액체금속로와 같은 고온구조물에 대하여 반복 열천이 하중과 고온 지속시간이 유발하는 크립효과가 크게 나타남을 알 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1451-1457
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• 1992

In hot strip rolling, the thickness of strip cannot be retained uniform by several irregular parameters. It has been shown that the load distribution can affect only a small fraction of the excess strip crown, whereas the thermal effects of working roll are the major reason on large changes in the strip center crown during hot rolling. In this study, the temperature distribution of working roll is represented by fourier series expansion. The analytical solution of the resulting thermo-elasticity problem is obtained by love's strain function. The results which are compared with those of the finite element method show good agreements.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.2
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• pp.197-206
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• 2003

A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of solid and hollow hemispherical shells of revolution of arbitrary wall thickness having arbitrary constraints on their boundaries. Unlike conventional shell theories, which are mathematically two-dimensional (2-D), the present method is based upon the 3-D dynamic equations of elasticity. Displacement components μ/sub Φ/, μ/sub z/, and μ/sub θ/ in the meridional, normal, and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in θ, and algebraic polynomials in the Φ and z directions. Potential (strain) and kinetic energies of the hemispherical shells are formulated, and the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies obtained by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Novel numerical results are presented for solid and hollow hemispheres with linear thickness variation. The effect on frequencies of a small axial conical hole is also discussed. Comparisons are made for the frequencies of completely free, thick hemispherical shells with uniform thickness from the present 3-D Ritz solutions and other 3-D finite element ones.