• Title/Summary/Keyword: 가우스적분점수정

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The Free Vibration Analyses by Using Two Dimensional 6-Node Element and Three Dimensional 16-Node element with Modification of Gauss Sampling Point (가우스 적분점을 수정한 2차원 6-절점 요소 및 3차원 16-절점 요소에 의한 자유진동해석)

  • 김정운;경진호;권영두
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.11
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    • pp.2922-2931
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    • 1994
  • We propose a modified 6-node element, where the sampling point of Gauss quadrature moved in the thickness direction. The modified 6-node element has been applied to static problems and forced motion analyses. In this study, this method is extended to the finite element analysis of the natural frequencies of two dimensional problems. We also propose a modified 16-node element for three dimensional problems, which behaves much like a 20-node element with smaller degree of freedom. The modified 6-node and 16-node elements have been applied to the modal analyses of beams and plates, respectively. The results agree well with the results of the 8-node or 20-node element models.

The Forced Motion Analyses by Using Two Dimensional 6-Node and Three Dimensional 16-Node Isoparametric Elements with Modification of Gauss Sampling Point (6절점 2차원 및 16절점 3차원 등매개변수 요소의 가우스 적분점 수정을 이용한 강제진동 해석)

  • 김정운;권영두
    • Computational Structural Engineering
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    • v.8 no.4
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    • pp.87-97
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    • 1995
  • For the same configuration of two-dimensional finite element models, 6-node element exhibits stiffer bending stiffness than 8-node element. This is true in the relation between 16-node element and 20-node element for three-dimensional model. This stiffening phenomenon comes from the elimination of several mid nodes from full-node elements. Therefore, this may be called 'relative stiffness stiffening phenomenon'. It seems that there are a couple of ways to correct the stiffening effect, however, we could find only one effective method-the method of modification of Gauss sampling points-which passes the patch test and does not alter other kinds of stiffness, such as extensional stiffness. The quantity of modification is a function of Poisson's ratios of the constituent materials. We could obtain two modification equations, one for plane stress case and the other for plane strain case. This method can be extended to 3-dimensional solid elements. Except the exact plane strain cases, most 3-dimensional plates could be modeled successfully with 16-node element modified by the equation for the plane stress case. The effectiveness of the modification method is checked by applying it to several examples with excellent improvements. In numerical examples, beams with various boundary conditions are subjected to static and time-dependent loads. Free and forced motion analyses of beams and plates are also tested. The beam and plate may be composed of isotropic multilayers as well as a single layer.

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Static and Dynamic Analyses of Bending Problems Using 3-Dimensional 10-Node Equivalent Element (3차원 10절점-상당요소에 의한 굽힘문제의 정적.동적해석)

  • 권영두;윤태혁
    • Computational Structural Engineering
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    • v.10 no.4
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    • pp.117-130
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    • 1997
  • In this paper, a modified 10-node equivalent solid element(MQM10 element), which has smallest degrees of freedom among 3-dimensional solid elements accounting bending deformation as well as extensional and shear deformations of isotropic plates, is proposed. The proposed MQM10 element exhibits stiffer bending stiffness due to the reduction of degrees of freedom from 20-node element or Q11 element. As an effective way to correct the relative stiffness stiffening phenomenon, the modification equation of Gauss sampling points is proposed. The quantity of modification is a function of Poisson's ratio. The effectiveness of MQM10 element is tested by applying it to several examples. It is noted that the results of static and free vibration analysis of isotropic plates using MQM10 elements show a good agreement with those using 20-node element.

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Static and Dynamic Analyses of Pure Bending Problems of Composite Plates using Non-Conforming 3-Dimensional 8-Node Solid Element (3차원 8절점 비적합 고체요소에 의한 복합재판의 순수굽힘문제의 정적.동적해석)

  • Yun, Tae-Hyeok;Gwon, Yeong-Du
    • Journal of Ocean Engineering and Technology
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    • v.12 no.2 s.28
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    • pp.1-21
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    • 1998
  • In this paper, a non-conforming 3-D 8-node solid element(MQM10) has beets applied to the analyses of static and dynamic bending problems of laminated composite plates The QM10 element exhibits stiffer bending stiffness which is caused by the reduction of degree of freedom from Q11 element. As an effective way to correct the relative stiffness stiffening phenomenon the modification of Gauss sampling points for composite plates is proposed. The quantity of modification is a function of material properties. Also, another two modified equations are obtained, one is modification for stress, and the other is modification of coefficient of shear modulus in free vibration. It is noted that MQM10 element can analyse the static and free vibration problems of various 3-dimensional composite plates composed of unidirectional laminae, woven laminae or braided laminae. The results of MQM10 element are in good agreement with those of 20-node element.

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Static and Natural Vibration Analyses of Bending Problems Using 5-Node Equivalent Element (5절점 상당요소에 의한 굽힘문제의 정적해석 및 자유진동해석)

  • Gwon, Young-Doo;Yun, Tae-Hyeok;Jeong, Seung-Kap;Park, Hyeon-Chul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.4
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    • pp.1320-1332
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    • 1996
  • In the present study, we consider modified 5-node equivalent solid element which has smallest degree of freedom among 2-dimensional solid elements accounting bending deformation as well as extensional and shear deformations, We shall investigate static and dynamic characteristics of this element, which is very effective in thin beam, thick beam, large displacement problems, beam of variable thickness, and asymmetrically stepped beam, etc., as well as relatively simple problems of beam. The degree of freedom of this element is 10, which is smaller than 18 of 9-node element, 16 of 8-node elemtns, 12 of modified 6-node element and Q6 element. Therefore, this element is expected to broaden the effective range of application of the solid elements in the bending problems further.

The Selective p-Distribution for Adaptive Refinement of L-Shaped Plates Subiected to Bending (휨을 받는 L-형 평판의 적응적 세분화를 위한 선택적 p-분배)

  • Woo, Kwang-Sung;Jo, Jun-Hyung;Lee, Seung-Joon
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.20 no.5
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    • pp.533-541
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    • 2007
  • The Zienkiewicz-Zhu(Z/Z) error estimate is slightly modified for the hierarchical p-refinement, and is then applied to L-shaped plates subjected to bending to demonstrate its effectiveness. An adaptive procedure in finite element analysis is presented by p-refinement of meshes in conjunction with a posteriori error estimator that is based on the superconvergent patch recovery(SPR) technique. The modified Z/Z error estimate p-refinement is different from the conventional approach because the high order shape functions based on integrals of Legendre polynomials are used to interpolate displacements within an element, on the other hand, the same order of basis function based on Pascal's triangle tree is also used to interpolate recovered stresses. The least-square method is used to fit a polynomial to the stresses computed at the sampling points. The strategy of finding a nearly optimal distribution of polynomial degrees on a fixed finite element mesh is discussed such that a particular element has to be refined automatically to obtain an acceptable level of accuracy by increasing p-levels non-uniformly or selectively. It is noted that the error decreases rapidly with an increase in the number of degrees of freedom and the sequences of p-distributions obtained by the proposed error indicator closely follow the optimal trajectory.

Application of Ordinary Kriging Interpolation Method for p-Adaptive Finite Element Analysis of 2-D Cracked Plates (2차원 균열판의 p-적응적 유한요소해석을 위한 정규크리깅 보간법의 적용)

  • Woo, Kwang-Sung;Jo, Jun-Hyung;Park, Mi-Young
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.19 no.4 s.74
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    • pp.429-440
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    • 2006
  • This paper comprises two specific objectives. The first is to examine the applicability of ordinary kriging interpolation(OK) to the p-adaptivity of the finite element method that is based on variogram modeling. The second objective Is to present the adaptive procedure by the hierarchical p-refinement in conjunction with a posteriori error estimator using the modified S.P.R. (superconvergent patch recovery) method. The ordinary kriging method that is one of weighted interpolation techniques is applied to obtain the estimated exact solution from the stress data at the Gauss points. The weight factor is determined by experimental and theoretical variograms for interpolation of stress data apart from the conventional interpolation methods that use an equal weight factor. In the p-refinement, the analytical domain has to be refined automatically to obtain an acceptable level of accuracy by increasing the p-level non-uniformly or selectively. To verify the performance of the modified S.P.R. method, the new error estimator based on limit value has been proposed. The validity of the proposed approach has been tested with the help of some benchmark problems of linear elastic fracture mechanics such as a centrally cracked panel, a single edged crack, and a double edged crack.