• Title/Summary/Keyword: axisymmetric model

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Determination of Two Dimensional Axisymmetric Finite Element Model for Reactor Coolant Piping Nozzles (원자로 냉각재 배관 노즐의 2차원 축대칭 유한요소 모델 결정)

  • Choi, S.N.;Kim, H.N.;Jang, K.S.;Kim, H.J.
    • Proceedings of the KSME Conference
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    • 2000.11a
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    • pp.432-437
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    • 2000
  • The purpose of this paper is to determine a two dimensional axisymmetric model through a comparative study between a three dimensional and an axisymmetric finite element analysis of the reactor coolant piping nozzle subject to internal pressure. The finite element analysis results show that the stress adopting the axisymmetric model with the radius of equivalent spherical vessel are well agree with that adopting the three dimensional model. The the radii of equivalent spherical vessel are 3.5 times and 7.3 times of the radius of the reactor coolant piping for the safety injection nozzle and for the residual heat removal nozzle, respectively.

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Stress intensity factors for 3-D axisymmetric bodies containing cracks by p-version of F.E.M.

  • Woo, Kwang S.;Jung, Woo S.
    • Structural Engineering and Mechanics
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    • v.2 no.3
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    • pp.245-256
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    • 1994
  • A new axisymmetric crack model is proposed on the basis of p-version of the finite element method limited to theory of small scale yielding. To this end, axisymmetric stress element is formulated by integrals of Legendre polynomial which has hierarchical nature and orthogonality relationship. The virtual crack extension method has been adopted to calculate the stress intensity factors for 3-D axisymmetric cracked bodies where the potential energy change as a function of position along the crack front is calculated. The sensitivity with respect to the aspect ratio and Poisson locking has been tested to ascertain the robustness of p-version axisymmetric element. Also, the limit value that is an exact solution obtained by FEM when degree of freedom is infinite can be estimated using the extrapolation equation based on error prediction in energy norm. Numerical examples of thick-walled cylinder, axisymmetric crack in a round bar and internal part-thorough cracked pipes are tested with high precision.

Axisymmetric Modeling of Dome Tendons in Nuclear Containment Building II. Verification through Numerical Examples (원전 격납건물 돔 텐던의 축대칭 모델링 기법 II. 수치예제를 통한 검증)

  • Jeon Se-Jin
    • Journal of the Korea Concrete Institute
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    • v.17 no.4 s.88
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    • pp.527-533
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    • 2005
  • Axisymmetric modeling of the nuclear containment building has been often employed in practice to estimate structural behavior for the axisymmetric loadings, where the axisymmetric approximation is required for the actual non-axisymmetric tendon arrangements in the dome. In the preceding companion paper, some procedures are proposed for the domestic CANDU and KSNP type containments that can implement the actual 3-dimensional tendon stiffness and prestressing effect into the axisymmetric model. In this paper, the proposed schemes are verified through some numerical examples comparing the results of the actual 3-dimensional model with those of some axisymmetric models. The results of the proposed axisymmetric analyses show relatively good agreements with the actual structural behavior especially for the CANDU type. Also, it is shown that proper level of the prestressing in a hoop direction plays an important role to predict the actual prestressing effect in the axisymmetric dome modeling. Finally, correction factors are discussed that can revise some approximations introduced in the derivations.

Analytical and numerical analysis for unbonded flexible risers under axisymmetric loads

  • Guo, Yousong;Chen, Xiqia;Wang, Deyu
    • Ocean Systems Engineering
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    • v.6 no.2
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    • pp.129-141
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    • 2016
  • Due to the structural complexity, the response of a flexible riser under axisymmetric loads is quite difficult to determine. Based on equilibrium conditions, geometrical relations and constitutive equations, an analytical model that can accurately predict the axisymmetric behavior of flexible risers is deduced in this paper. Since the mutual exclusion between the contact pressure and interlayer gap is considered in this model, the influence of the load direction on the structural behavior can be analyzed. Meanwhile, a detailed finite element analysis for unbonded flexible risers is conducted. Based on the analytical and numerical models, the structural response of a typical flexible riser under tension, torsion, internal and outer pressure has been studied in detail. The results are compared with experimental data obtained from the literature, and good agreement is found. Studies have shown that the proposed analytical and numerical models can provide an insightful reference for analysis and design of flexible risers.

Non-axisymmetric dynamic response of imperfectly bonded buried orthotropic pipelines

  • Dwivedi, J.P.;Mishra, B.K.;Upadhyay, P.C.
    • Structural Engineering and Mechanics
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    • v.6 no.3
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    • pp.291-304
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    • 1998
  • This paper deals with the non-axisymmetric dynamic response of an imperfectly bonded buried orthotropic pipeline subjected to longitudinal wave (P-wave) excitation. An infinite cylindrical shell model, including the rotary inertia and shear deformation effects, has been used for the pipeline. For some cases comparison of axisymmetric and non-axisymmetric responses have also been furnished.

Axisymmetric Modeling of Dome Tendons in Nuclear Containment Building I. Theoretical Derivations (원전 격납건물 돔 텐던의 축대칭 모델링 기법 I. 이론식의 유도)

  • Jeon Se-Jin;Chung Chul-Hun
    • Journal of the Korea Concrete Institute
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    • v.17 no.4 s.88
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    • pp.521-526
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    • 2005
  • Prestressing tendons in a nuclear containment building dome are non-axisymmetrically arranged in most cases. However, simple axisymmetric modeling of the containment has been often employed in practice to estimate structural behavior for the axisymmetric loadings such as an internal pressure. In this case, the axisymmetric approximation is required for the actual tendon arrangements in the dome. Some procedures are proposed that can implement the actual 3-dimensional tendon stiffness and prestressing effect into the axisymmetric model. Prestressing tendons, which are arranged in 3 or 2-ways depending on a containment type, are converted into an equivalent layer to consider the stiffness contribution in meridional and hoop directions. In order to reflect the prestressing effect, equivalent load method and initial stress method are devised and the corresponding loads or stresses are derived in terms of the axisymmetric model. In a companion paper, the proposed schemes are applied into CANDU and KSNP(Korean Standard Nuclear Power Plant) type containments and are verified through some numerical examples comparing the analysis results with those of the actual 3-dimensional model.

수정 Eshelby등가 개재물 방법을 이용한 단섬유 금속 복합재료의 열적잔류응력의 해석에 관한 연구

  • 손봉진;이준현;김문생
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1993.10a
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    • pp.660-665
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    • 1993
  • An elastic model is developed to predict the average thermal residual stresses in the matrix and fiber of a misoriented short fiber composite. The thermal residual stresses are induced by the mismatch in the coefficient of the thermal expansion of the matrix and fiber when the composite is subjected to a uniform temperature change. The model considers two special cases of fiber misorientation ; two-dimensional in-plane and three-dimensional axisymmetric. The analytical formulation of the model is based on Eshelby's equivalent inclusion method and is nuque in that it is able to account for interactions among fibers. The model is more general than past models and it is able to treat prior analyses of the simpler composite systems as extram cases. The present model is to investigate the effects of fiber volume fraction, distribution type, distribution cut-off angle, and aspect ratio on thermal residual stress for both in-plane and axisymmetric fiber misorientation. Fiber volum fraction, aspect ratio, and disturbution cut-off angle are shown to have more significant effects on the magnitude of the thermal residual stress than fiber distrubution type for both in-plane and axisymmetric misorientation.

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Computation of Wake Flow of an Axisymmetric Body at Incidence (받음각을 갖는 축대칭 물체의 후류 유동 계산)

  • Kim, Hee-Taek;Lee, Pyoung-Kuk;Kim, Hyoung-Tae
    • Journal of the Society of Naval Architects of Korea
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    • v.43 no.2 s.146
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    • pp.186-196
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    • 2006
  • The turbulent wake flow of an axisymmetric body at incidence of $10.1^{\circ}$ is investigated by commericial CFD code, Fluent 6.2. Reynolds stress turbulence model with wall function is applied for the turbulent flow computation. For the grid generation, the Gridgen V15 is used. Numerical predictions are compared with experimental data for the validation. The computed results show goof agreements with the experimental measurements, implying that the CFD analysis is a useful and efficient tool for predicting turbulent flow characteristics of wake field of an axisymmetric body at incidence.

Numerical simulation of cavitating flow past axisymmetric body

  • Kim, Dong-Hyun;Park, Warn-Gyu;Jung, Chul-Min
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.4 no.3
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    • pp.256-266
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    • 2012
  • Cavitating flow simulation is of practical importance for many engineering systems, such as marine propellers, pump impellers, nozzles, torpedoes, etc. The present work has developed the base code to solve the cavitating flows past the axisymmetric bodies with several forebody shapes. The governing equation is the Navier-Stokes equation based on homogeneous mixture model. The momentum is in the mixture phase while the continuity equation is solved in liquid and vapor phase, separately. The solver employs an implicit preconditioning algorithm in curvilinear coordinates. The computations have been carried out for the cylinders with hemispherical, 1-caliber, and 0-caliber forebody and, then, compared with experiments and other numerical results. Fairly good agreements with experiments and numerical results have been achieved. It has been concluded that the present numerical code has successfully accounted for the cavitating flows past axisymmetric bodies. The present code has also shown the capability to simulate ventilated cavitation.