• Title/Summary/Keyword: 해석적 해법

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A Study on the Dynamic Impact Response Analysis of Cask by Modal Superposition Method (모드중첩기법을 이용한 CASK의 동적충격응답해석)

  • Lee Young-Shin;Kim Yong-Jae;Choi Young-Jin;Kim Wol-Tae
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.18 no.4 s.70
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    • pp.373-383
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    • 2005
  • The cask is used to transfer the radioactive material in various fields required to withstand hypothetical accident condition such as 9m drop impact in accordance with the requirement of the domestic requlations and IAEA. So far the impact force has been obtained by the finite element method with complex computational procedure. In this study, the dynamic impact response of the cask body is analyzed using the mode superposition method, and the analysis method is proposed. The results we also validated by comparing with previous experimental results and finite element analysis results. The present method Is simpler than finite element method and can be used to predict the global impact response of cask

Methods of Nonlinear Structural Design Sensitivity Analysis (비선형(非線型) 구조(構造)의 설계민감도(設計敏感度) 해석법(解析法))

  • Ryu, Yeon Sun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.7 no.4
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    • pp.13-20
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    • 1987
  • Methods of nonlinear structural design sensitivity analysis are developed in parallel with the nonlinear finite element structural analysis methods and numerically evaluated. Direct decomposition and iterative solution methods for the secant stiffness approach and direct use of tangent stiffness in the design sensitivity analysis phase are derived and presented as the methods of nonlinear structural analysis and design sensitivity analysis are closely related. From the considerations of theoretical and numerical behavior, the tangent stiffness approach is shown to be efficient as the intermediate results of structural analysis can be effectively used in the design sensitivity analysis stage.

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Analysis of Steady and Unsteady Flow Around a Ship Using a Higher-Order Boundary Element Method (고차경계요소법에 의한 선체주위 유동해석)

  • Sa-Y. Hong;Hang-S. Choi
    • Journal of the Society of Naval Architects of Korea
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    • v.32 no.1
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    • pp.42-57
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    • 1995
  • An efficient and accurate scheme has been constructed by taking advantages of the hi-quadratic spline scheme and the higher-order boundary element method selectively depending on computation domains. Boundary surfaces are represented by 8-node boundary elements to describe curved surfaces of a ship and its neighboring free surface more accurately. The variation of the velocity potential complies with the characteristics of the 8-node element on the body surface. But on the free surface, it is assumed to follow that of the hi-quadratic spline scheme. By which, the free surface solution is free from numerical damping and has better numerical dispersion property. As numerical examples, steady and unsteady Neumann-Kelvin problems are considered. Numerical results for a submerged spheroid, Series 60($C_B=0.6$) and a modified support the proposed method. Finally, a new upstream radiation condition is derived using a wave equation operator in order to deal with problems for subcritical reduced frequency. The relevance of this operator has been confirmed in the case of unsteady Kelvin source potential.

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Analysis of Orthotropic Body under Ultimate Moment Load (극한(極限)모멘트 하중(荷重)을 받는 이방성(異方性) 구조체(構造體)의 해석(解析))

  • Chang, Suk Yoon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.5 no.3
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    • pp.95-105
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    • 1985
  • This dissertation presents an exact solution for the normal and shearing stresses of an orthotropic plane body loaded by a moment load. The solution satisfies the conditions of equilibrium compatibility equations concurrently and is governing for the body being in the elasto-plastic state. An Airy stress function is introduced to solve the problem related to an orthotropic half-infinite plane under a moment load. All the equations for orthotropy must be degenerated into the expressions for isotropy when orthotropic constants are replaced by isotropic ones. The author has evaluated all the equations of orthotropy and succeeded in obtaining exactly identical expressions to the equations of isotropy which were derived independently by of L'hosptials rule. The analytical results of isotropy are compared with the simple results of other investigator. Since moment Load under the elastic state and plastic state only is a particular case of moment load under the elasto-plastic state. All the equations of elasto-plastic state case are degenerated into the expressions for the each case. The formal solution is expressed in terms of closed form. The orthotropic constants are evaluated for two kinds and two different orientations of the grain of wood and two kinds of structures. The numerical results for orthotropy are evaluated for one kind and two different orientations of three-layered ply wood. The distribution of normal and shearing stresses are shown in figures. It is noted that the distribution of stresses of orthotropic materials depends on the type of materials and orientations of the grain and stiffening.

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A Novel Scheme to Depth-averaged Model for Analyzing Shallow-water Flows over Discontinuous Topography (불연속 지형을 지나는 천수 흐름의 해석을 위한 수심적분 모형에 대한 새로운 기법)

  • Hwang, Seung-Yong
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.35 no.6
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    • pp.1237-1246
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    • 2015
  • A novel technique was proposed to calculate fluxes accurately by separation of flow area into a part of step face which is dominated by flow resistance of it and an upper part which is relatively less affected by the step face in analyzing shallow-water flows over discontinuous topography. This technique gives fairly good agreement with exact solutions, 3D simulations, and experimental results. It has been possible to directly analyze shallow-water flows over discontinuous topography by the technique developed in this study. It is expected to apply the developed technique to accurate evaluation of overflows over weirs or retaining walls (riverside roads) and areas flooded by the inundation in the city covered in discontinuous topography.

Application of Sensitivity Analysis to Vehicle Handling with Equivalent Cornering Stiffness (등가 코너링강성을 사용한 차량의 조종안정성에 대한 민감도 해석)

  • Lee, Chang-Ro
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.4
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    • pp.1434-1439
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    • 2012
  • Vehicle is a dynamic system combined with various parameters. Dynamic characteristics of a vehicle can vary with the change of these parameters. To investigate the effect of the design parameter on vehicle handling performance the sensitivity analysis is carried out by the numerical method. The vehicle model is described by equivalent cornering stiffness that considers parameters of suspension and steering system. As the analysis results show the effect on the static and dynamic characteristics of the vehicle system, the sensitivity analysis can be used for synthesis of the design parameters to improve the vehicle handling characteristics at the design stage as well as during the vehicle test under development.

Free Vibration Analysis of Shell Structures with Elastic Supports (탄성지지를 갖는 셀구조물의 자유진동해석)

  • 문덕홍;여동준;김판석
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1995.04a
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    • pp.344-349
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    • 1995
  • 셀구조물은 선박, 항공기, 우주선 등의 산업분야에 자주 사용되는 중요한 구조요소로서, 이에 대한 연구도 공학적 필요성에 의해 많은 연구가 진행되어 왔다. Maddox등의 Rayleigh-Ritz법, Srinivasan and Bobby의 적분방정식 기법, Petyt의 유한요소법, Irie, Henderson등의 전달매트릭스법, 그 외 Webster, Petyt and Deb Nath, Blevins, Srinivasan and Krishnan등에 의해 여러가지 해석방법의 진동해석이 행해져 왔다. 현재 주로 사용되고 있는 매트릭스 구조해석 및 진동해석 방법으로는 유한요소법과 전달매트릭스법을 들 수 있다. 유한요소법은 범용적인 해석 프로그램의 개발은 수월하지만 대규모의 선형 연립방정식의 해법에 귀착되므로, 기억용량이 큰 대형컴퓨터가 필요하고, 반면 전달매트릭스법은 기억용량이 적은 퍼스널컴퓨터로도 계산수행이 가능하나 고차의 고유진동수를 구할 경우나, 중간에 단단한 경탄성지지가 존재할 경우 등에는 수치계산상의 문제점이 지적되고 있다. 이에 대한 대책으로, 상태변수를 바꾸어 넣은 Riccati방법, 각 절점의 기지의 상태변수를 제거하는 Frontal법, 전달매트릭스와 강성매트릭스를 결합시키는 방법 등이 보고 되고 있다. 이에 자자들은 퍼스널컴퓨터 이용에 적합한 고속, 고정도의 구조해석 및 진동해석 기법으로 전달영향계수법을 제안하여, 원판구조물, 사각판구조물, 원통형 셀구조물 등의 여러가지 형상구조물의 자유진동 해석에 적용해서, 종래의 전달매트릭스법에 비해 계산정도 및 계산속도의 양면에서 매우 우수함을 보고한바 있다. 본 연구에서는 동적영향계수의 축차전달에 그 개념을 두고 있는 전달영향계수법을 좀 더 일반화시키고 체계화시키기 위하여 탄성지지를 갖는 셀구조물에 적용하여 자유진동 해석 알고리즘을 정식화한 후, 간단한 모델에 대한 수치실험을 통해서 전달 영향계수법으로 구한 해를 전달매트릭스법의 결과와 비교.검토하여 본 방법의 유용성을 확인하였다.

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Convergence and Stability Analysis of LU Scheme on Unstructured Meshes: Part I - Euler Equations (비정렬 격자계에서 LU Implicit Scheme의 수렴성 및 안정성 해석 : Part I-오일러 방정식)

  • Kim, Joo-Sung;Kwon, Oh-Joon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.32 no.9
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    • pp.1-11
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    • 2004
  • A comprehensive study has been made for the investigation of the convergence and stability characteristics of the LU scheme for solving the Euler equations on unstructured meshes. The von Neumann stability analysis technique was initially applied to a scalar model equation, and then the analysis was extended to the Euler equations. The results indicated that the convergence rate is governed by a specific combination of flow parameters. Based on this insight, it was shown that the LU scheme does not suffer any convergence deterioration at all grid aspect ratios, as long as the local time step is defined using an appropriate parameter combination.

Thermochemical Performance Analysis of Liquid Rocket Nozzle (액체로켓 노즐의 열화학적 성능 해석)

  • Choe,Jeong-Yeol;Choe,Hwan-Seok
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.1
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    • pp.85-96
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    • 2003
  • For a design of rocket engine nozzle, chemical equilibrium analysis which shares the same numerical characteristics with frozen flow analysis can be used as an efficient design tool for predicting maximum thermodynamic performance of the nozzle. 10 this study, a chemical equilibrium flow analysis code was developed for the design of hydrocarbon fueled rocket engines. 10 oder to understand the thermochemical characteristics occurring in a nozzle through the expansion process, such as recombination of chemical components and the accompanying energy recovery, chemical equilibrium flow analysis was carried out for the KSR-III rocket engine nozzles together with frozen flow and non-equilibrium flow analyses. The performance evaluation based on the present KSR-III nozzle flow analyses has provided an understanding of the thermochemical process in the nozzle and additionally, it has confirmed that the newly designed nozzle shape modified to have a reduced exit area ratio is an adequate design for obtaining an increased ground thrust.

Simulation of Seismic Ground Accelerations and Seismic Analysis of Flexible Rotor-Bearing System Housed on the Rigid Base (지반가속도의 시뮬레이션과 강기반상(剛基盤上)에 설치된 회전측-베어링계의 지진해석)

  • Kim, Ki Bong
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.9 no.4
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    • pp.51-61
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    • 1989
  • The classical spectral analysis of random vibration is not applicable to the random vibration of nonlinear structures or the dynamic response of active mechanical systems whose governing equations contain random parametric and inhomogeneous excitations. If the random load is simulated, dynamic responses can be obtained with the application of numerical integration schemes to the governing equations of above problems. Thus, in this paper, efficient and practical methods of simulating nonstationary random seismic ground accelerations are presented by using the fast Fourier transform technique. Typical applications of the simulated ground accelerations are the simulations of the dynamic response of rotor-bearing systems under earthquake excitations. The study of accuracy is presented to determine the applicability and practicality of methods of simulation.

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