• Title/Summary/Keyword: 변분원리

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Nonlinear vibration analysis using variational principle (변분원리를 활용한 비선형 진동해석)

  • 박철희;이장무;박영필
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.11 no.3
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    • pp.519-527
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    • 1987
  • Simple procedures have been formulated to compute approximate natural frequency of nonlinear systems by the use of variational principle. These procedures are applicable to motion of large amplitudes, even to systems which are not linearizable. The results obtained by these procedures have been found to have good agreements with computer solutions and exact solutions for systems having piece-wise linear springs and polynomial springs.

A Mixed Variational Principle of Fully Anisotropic Linear Elasticity (이방성탄성문제의 혼합형변분원리)

  • 홍순조
    • Computational Structural Engineering
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    • v.4 no.2
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    • pp.87-94
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    • 1991
  • In this paper, a mixed variational principle applicable to the linear elasticity of inhomogeneous anisotropic materials is presented. For derivation of the general variational principle, a systematic procedure for the variational formulation of linear coupled boundary value problems developed by Sandhu et al. is employed. Consistency condition of the field operators with the boundary operators results in explicit inclusion of boundary conditions in the governing functional. Extensions of admissible state function spaces and specialization to a certain relation in the general governing functional lead to the desired mixed variational principle. In the physical sense, the present variational principle is analogous to the Reissner's recent formulation obtained by applying Lagrange multiplier technique followed by partial Legendre transform to the classical minimum potential energy principle. However, the present one is more advantageous for the application to the general anisotropic materials since Reissner's principle contains an implicit function which is not easily converted to an explicit form.

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Understanding of Finite Element Method for Stress Analysis (응력해석에 이용되는 유한요소법의 이해)

  • 민옥기;김용우
    • Journal of the KSME
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    • v.33 no.7
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    • pp.600-613
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    • 1993
  • 유한요소법은 구조공학분야에서 발전하여 과학기술 전반에 통용되는 수치해석의 한 방법 또는 기술로서 각광받고 있다. 이 기법은 변분원리에 수학적 기초를 두는 미분 방정식의 수치해법의 하나라고 할 수 있다. 이 글에서는 고체역학 부문에 한정하여 유한요소법의 기본체계, 응력계산과 관련하여 중요 수치현상, 그리고 최근 국내외학계의 연구동향 및 상용 패키지 사용시 주의 사항에 관하여 언급한다.

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Finite Element Analysis for Vibration of Laminated Plate Using a Consistent Discrete Theory Part I : Variational Principles (복합재료적층판의 진동해석을 위한 유한요소모델 I. 변분원리의 유도)

  • 홍순조
    • Computational Structural Engineering
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    • v.7 no.4
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    • pp.85-101
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    • 1994
  • A family of variational principles governing the dynamics of laminated plate has been derived using a variationally consistent shear deformable discrete laminated plate theory with particular reference to finite element procedures. The theoretical basis for the derivation is Sandhu's generalized procedure for the variational formulation of linear coupled boundary value problem. As the bilinear mapping to write the operator matrix of the field equations in self-adjoint form, convolution product was employed. Boundary conditions, initial conditions and probable internal discontinuity were explicitly included in the governing functionals. Some interesting extensions and specializations of the general variational principle were presented, which can provide many different finite element formulations for the problem.

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Hamilton제s Principle for the Free Surface Waves of Finite Depth (유한수심 자유표면파 문제에 적용된 해밀톤원리)

  • 김도영
    • Journal of Ocean Engineering and Technology
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    • v.10 no.3
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    • pp.96-104
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    • 1996
  • Hamilton's principle is used to derive Euler-Lagrange equations for free surface flow problems of incompressible ideal fluid. The velocity field is chosen to satisfy the continuity equation a priori. This approach results in a hierarchial set of governing equations consist of two evolution equations with respect to two canonical variables and corresponding boundary value problems. The free surface elevation and the Lagrange's multiplier are the canonical variables in Hamilton's sense. This Lagrange's multiplier is a velocity potential defined on the free surface. Energy is conserved as a consequence of the Hamiltonian structure. These equations can be applied to waves in water of finite depth including generalization of Hamilton's equations given by Miles and Salmon.

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The Study on Axisymmetric Deformation of Thin Orthotropic Composite Pressure Vessel (직교이방성 복합재료로 만든 두께가 얇은 압력용기의 변형에 관한 연구)

  • 김형원;최용규
    • Journal of the Korean Society of Propulsion Engineers
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    • v.7 no.2
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    • pp.36-43
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    • 2003
  • The analytic solution of radial displacements of thin cylindrical pressure vessel with carbon fiber T700/Epoxy orthotropic composites was obtained using equilibrium equations of the orthogonal curvilinear coordinate system. The governing equations with the simplified strain versus displacement relation of 3-dimensional curvilinear coordinate system were derived from the variational principle and the virtual work principle. Some theoretical analyses were presented and compared with the results of hydraulic tests for the pressure vessels with some various thicknesses. The results of the theoretical analysis and the hydraulic test were reasonably matched.

Time to Invest in Real Asset with Option Pricing Theory - Focused on REITs - (옵션가격결정이론에 기반한 실물자산의 투자시기 결정 - 부동산투자신탁회사(REITs)를 중심으로 -)

  • Jun, Jae-Bum;Lee, Sam-Su
    • Korean Journal of Construction Engineering and Management
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    • v.11 no.6
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    • pp.54-64
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    • 2010
  • A firm decides to go to the project based on its investment analysis. However, the cash flows generated from the real project can not be always coincident with what expected as it follows uncertain behavior and the asymmetric payoff caused by the managerial flexibilities involved in the real asset affects the project value. Amongst various managerial flexibilities entailed in most of the real assets, although investment delay has been known to enhance the project value thanks to its ability to provide new market information to management, the related research to select the time to invest have been just few. Therefore, this research aims to show the theoretical framework to decide when to invest reflecting the behaviors of increasing project value and loss recovery cost due to investment delay with option pricing, related financial economic, and variational theories.

Time-domain Finite Element Formulation for Linear Viscoelastic Analysis Based on a Hereditary Type Constitutive Law (유전적분형 물성방정식에 근거한 선형 점탄성문제의 시간영역 유한요소해석)

  • 심우진;이호섭
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.8
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    • pp.1429-1437
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    • 1992
  • A new finite element formulation based on the relaxation type hereditary integral is presented for a time-domain analysis of isotropic, linear viscoelastic problems. The semi-discrete variational approximation and elastic-viscoelastic correspondence principle are used in the theoretical development of the proposed method. In a time-stepping procedure of final, linear algebraic system equations, only a small additional computation for past history is required since the equivalent stiffness matrix is constant. The viscoelasticity matrices are derived and the stress computation algorithm is given in matrix form. The effect of time increment and Gauss point numbers on the numerical accuracy is examined. Two dimensional numerical examples of plane strain and plane stress are solved and compared with the analytical solutions to demonstrate the versatility and accuracy of the present method.

Advanced Finite Element Technology for Fracture Mechanics Analysis of Cracked Shells (균열된 쉘의 파괴역학해석을 위한 선진유한요소기법)

  • 우광성
    • Computational Structural Engineering
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    • v.4 no.2
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    • pp.77-85
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    • 1991
  • A new finite element technology based on the p-version of E.F.M. is discussed with reference to its potential for application to stress intensity factor computations in linear elastic fracture mechanics, especially cracked cylindrical shells. It is shown that the p-version model is far better suited for computing the stress intensity factors than the conventional h-version models with the help of three test problems. The main advantage of this technology is that the accuracy of approximation can be established without mesh refinement or the use of special procedures such as crack-tip element and mixed variational approach.

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Formulation of a Singular Finite Element and Its Application (특이 유한요소의 구성과 응용)

  • Kim, Myung-Sik;Lim, Jang-Keun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.23 no.6 s.165
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    • pp.1018-1025
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    • 1999
  • For the effective analysis of two dimensional plane problems with geometrical discontinuities, singular finite element has been proposed. The element matrix equation was formulated on the basis of hybrid variational principle and Trefftz function sets derived consistently from the complex theory of plane elasticity by introducing a conformal mapping function. In order to suggest the accuracy characteristics of the proposed singular finite element, typical plane problems were analyzed and these results were compared with exact solutions. The singular finite element gives the comparatively exact values of stress concentration factors or stress intensity factors and can be effectively used for the analysis of mechanical structures containing various geometrical discontinuities.