• Title/Summary/Keyword: 비대칭 유한 요소 방정식

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The Effects of Fuel Pellet Eccentricity on Fuel Rod Thermal Performance (핵연료의 편심이 연료봉 열적 성능에 미치는 영향)

  • Suh Young-Keun;Sohn Dong-Seong
    • Nuclear Engineering and Technology
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    • v.20 no.3
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    • pp.189-196
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    • 1988
  • This study investigates the effect of fuel pellet eccentricity on fuel rod thermal performance under the steady state condition. The governing equations in the fuel pellet and the cladding region are set up in 2-dimensional cylindrical coordinate (r, $\theta$) and are solved by finite element method. The angular-dependent heat transfer coefficient in the gap region is used in order to account for the asymmetry of gap width. Material propeties are used as a function of temperature and volumetric heat generation as a function of radial position. The results show the increase of maximum local heat flux at the cladding outer surface and the decrease of maximum and average fuel temperatures due to eccentricity. The former is expected to affect the uncertainties in the minimum DNBR calculation. The latter two are expected to reduce the possibility of fuel melting and the fuel stored energy. Also, the fuel pellet eccentricity introduces asymmetry in fuel pellet temperature and movement of the location of maximum fuel pellet temperature.

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A Study on Buckling Behavior of Shallow Circular Arches (낮은 원호아치의 좌굴거동에 대한 연구)

  • 김연태;허택녕;오순택
    • Journal of the Earthquake Engineering Society of Korea
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    • v.2 no.2
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    • pp.87-94
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    • 1998
  • Behavioral characteristics of shallow circular arches with dynamic loading and different end conditions are analysed. Geometric nonlinearity is modelled using Lagrangian description of the motion. The finite element analysis procedure is used to solve the dynamic equation of motion, and the Newmark method is adopted in the approximation of time integration. The behavior of arches is analysed using the buckling criterion and non-dimensional time, load and shape parameters which Humphreys suggested. But a new deflection-ratio formula including the effect of horizontal displacement plus vertical displacement is presented to apply for the non-symmetric buckling problems. Through the model analysis, it's confirmed that fix-ended arches have higher buckling stability than hinge-ended arches, and arches with the same shape parameter have the same deflection ratio at the same time parameter when loaded with the same parametric load.

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Improved Method Evaluating the Stiffness Matrices of Thin-walled Beam on Elastic Foundations (탄성지반위에 놓인 박벽보의 강성행렬산정을 위한 개선된 해석기법)

  • Kim, Nam-Il;Jung, Sung-Yeop;Lee, Jun-Seok;Kim, Moon-Young
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.20 no.2
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    • pp.113-125
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    • 2007
  • Improved numerical method to obtain the exact stiffness matrices is newly proposed to perform the spatially coupled elastic and stability analyses of non-symmetric and open/closed thin-walled beam on elastic foundation. This method overcomes drawbacks of the previous method to evaluate the exact stiffness matrix for the spatially coupled stability analysis of thin-walled beam-column This numerical technique is accomplished via a generalized eigenproblem associated with 14 displacement parameters by transforming equilibrium equations to a set of first order simultaneous ordinary differential equations. Next polynomial expressions as trial solutions are assumed for displacement parameters corresponding to zero eigenvalues and the eigenmodes containing undetermined parameters equal to the number of zero eigenvalues are determined by invoking the identity condition. And then the exact displacement functions are constructed by combining eigensolutions and polynomial solutions corresponding to non-zero and zero eigenvalues, respectively. Consequently an exact stiffness matrix is evaluated by applying the member force-deformation relationships to these displacement functions. In order to illustrate the accuracy and the practical usefulness of this study, the numerical solutions are compared with results obtained from the thin-walled beam and shell elements.

A Study on the Dynamic Post-Buckling Behavior of the Plane Frame Structures Subjected to Circulatory Forces (Circulatory Force를 받는 평면(平面)뼈대 구조물(構造物)의 동적(動的) 후좌굴(後座屈) 거동(擧動)에 관한 연구(硏究))

  • Kim, Moon Young;Chang, Sung Pil
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.8 no.2
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    • pp.13-24
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    • 1988
  • A geometrically nonlinear analysis procedure for plane frame structures in order to study the static and dynamic post-buckling behavior of these structures subjected to circulatory forces is presented. The elastic and geometric stiffness matrices, the mass matrix and load correction stiffness matrix are derived from the extended virtual work principle, where the tangent stiffness matrix becomes non-symmetric due to the effects of non-conservative circulatory forces. The dynamic analysis of plane frame structures subjected to circulatory forces in pre- and post-buckling ranges is carried out by integrating the equations of motion directly by the numerically stable Newmark method. Numerical results are presented in order to demonstrate the vality and accuracy of the proposed procedure.

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In-Plane Buckling Behavior of Fixed Shallow Parabolic Arches (고정지점을 갖는 낮은 포물선 아치의 면내 좌굴거동)

  • Moon, Jiho;Yoon, Ki-Yong;Lee, Hak-Eun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.1A
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    • pp.79-87
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    • 2008
  • This paper investigates the in-plane stability of fixed shallow arches. The shape of the arches is parabolic and the uniformly distributed load is used in the study. The nonlinear governing equilibrium equation of the general arch is adopted to derive the incremental form of the load-displacement relationship and the buckling load of the fixed shallow arches. From the results, it is found that buckling modes (symmetric or asymmetric) of the arches are closely related to the dimensionless rise H, which is the function of slenderness ratio and the rise to span ratio of such arches. Moreover, the threshold of different buckling modes and buckling load for fixed shallow arches are proposed. A series of finite element analysis are conducted and then compared with proposed ones. From the comparative study, the proposed formula provides the good prediction of the buckling load of fixed shallow arches.