• Title/Summary/Keyword: 4-node shell finite element

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The Finite element with Normal Rotational Degree Freedoms (유한요소의 Normal rotation 연구)

  • Cho, Soon-Bo
    • Journal of Korean Association for Spatial Structures
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    • v.4 no.4 s.14
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    • pp.85-89
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    • 2004
  • A frame element embedded normal to a shear wall or slab (shell element) is common in the structural systems. In that case there is a need for a membrane or shell element to have a normal rotation degree of freedom at each node in order to have a good result of stresses. Even if Many other people studied this area, All man, Cook and Sabir are representative investigators in this area. In this research paper, Sabir's methods of vertex rotation stiffness matrix in a membrane element are studied. New stiffness of vertex rotation are proposed by taking advantage of beam stiffness theory. Rectangular elements stiffness with rotational degree of freedom are compared in accuracy ratio each other.

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Finite Element Analysis of Unbalance Response of a High Speed Flexible Polygon Mirror Scanner Motor Considering the Flexibility of Supporting Structure (지지구조의 유연성을 고려한 고속 유연 폴리곤 미러 스캐너 모터의 유한 요소 불평형 응답 해석)

  • Jung, Kyung-Moon;Seo, Chan-Hee;Kim, Myung-Gyu;Jang, Gun-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.859-865
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    • 2007
  • This paper presents a method to analyze the unbalance response of a high speed polygon mirror scanner motor supported by sintered bearing and flexible supporting structures by using the finite element method and the mode superposition method. The appropriate finite element equations for polygon mirror are described by rotating annular sector element using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. The rotating components except for the polygon mirror are modeled by Timoshenko beam element including the gyroscopic effect. The flexible supporting structures are modeled by using a 4-node tetrahedron element and 4-node shell element with rotational degrees of freedom. Finite element equations of each component of the polygon mirror scanner motor and the flexible supporting structures are consistently derived by satisfying the geometric compatibility in the internal boundary between each component. The rigid link constraints are also imposed at the interface area between sleeve and sintered bearing to describe the physical motion at this interface. A global matrix equation obtained by assembling the finite element equations of each substructure is transformed to a state-space matrix-vector equation, and both damped natural frequencies and modal damping ratios are calculated by solving the associated eigenvalue problem by using the restarted Arnoldi iteration method. Unbalance responses in time and frequency domain are performed by superposing the eigenvalues and eigenvectors from the free vibration analysis. The validity of the proposed method is verified by comparing the simulated unbalance response with the experimental results. This research also shows that the flexibility of supporting structures plays an important role in determining the unbalance response of the polygon mirror scanner motor.

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Stiffened orthotropic corner supported hypar shells: Effect of stiffener location, rise/span ratio and fiber orientaton on vibration behavior

  • Darilmaz, Kutlu
    • Steel and Composite Structures
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    • v.12 no.4
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    • pp.275-289
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    • 2012
  • In this paper the influence of stiffener location, rise/span ratio and fibre orientation on vibration behavior of corner supported hypar shells is studied by using a four-node hybrid stress finite element. The formulation of the element is based on Hellinger-Reissner variational principle. The element is developed by combining a hybrid plane stress element and a hybrid plate element. Benchmark problems are solved to validate the approach and free vibration response of stiffened orthotropic hypar shells is studied both with respect to fundamental frequency and mode shapes by varying the location of stiffeners, rise/span ratio and fiber orientation.

A shell-dynamics model for marine pipelines of large suspended length

  • Katifeoglou, Stefanos A.;Chatjigeorgiou, Ioannis K.
    • Ocean Systems Engineering
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    • v.5 no.4
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    • pp.301-318
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    • 2015
  • The present investigations introduce the shell-finite element discretization for the dynamics of slender marine pipelines. A long catenary pipeline, corresponding to a particular Steel Catenary Riser (SCR), is investigated under long-standing cyclic loading. The long structure is divided into smaller tubular parts which are discretized with 8-node planar shell elements. The transient analysis of each part is carried out by the implicit time integration scheme, within a Finite Elements (FE) solver. The time varying external loads and boundary conditions on each part are the results of a prior solution of an integrated line-dynamics model. The celebrated FE approximation can produce a more detailed stress distribution along the structural surface than the simplistic "line-dynamics" approach.

Development of Finite Element Model for impact Human Brain Injury (인간 뇌의 충격 부상에 대한 유한요소모델 개발에 관한 연구)

  • 김영은;남대훈;왕규창
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.4
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    • pp.97-106
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    • 1996
  • The impact response of the human brain has been determined by three-dimensional finite element modeling. The model includes a layered shell closely representing the cranial bones with the interior contents occupied by an incompressible contimuum to simulate the brain. Flax and tentorium modeled with 4 node membrane element were also incorporated. The computed pressure-time histories at 4 locations within the brain element compared quite favorably with previously published experimental data from cadaver experiments. A parametric study was subsequently conducted to identify the model response when the impact were varied.

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An analysis of the Child Head Impact Injury with Finite Element Model (유한 요소 모형을 이용한 어린이의 머리 충격 부상에 관한 연구)

  • 김영은;남대훈;왕규창
    • Journal of the Korean Society of Safety
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    • v.12 no.4
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    • pp.169-179
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    • 1997
  • The dynamic response of the human brain to direct impact was studied by three-dimensional finite element modeling. The model includes a layered shell closely representing the cranial bones with the interior contents occupied by an incompressible continuum to simulate the brain. Falx and tentorium modeled with 4 node membrane element were also incorporated. The computed pressure-time histories at 4 locations within the brain element compared quite favorably with previously published experimental data from cadaver experiments. Therefore, the purpose of this study was to determine the effects of the impact direction on the dynamic response of the brain in children. A parametric study was subsequently conducted to identify the model response when the age and impact site were varied.

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Non-conforming modes for improvement of finite element performance

  • Choi, Chang-Koon;Lee, Tae-Yeol
    • Structural Engineering and Mechanics
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    • v.14 no.5
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    • pp.595-610
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    • 2002
  • This paper presents an efficiency of various non-conforming (NC) modes in development of a series of new finite elements with the special emphasis on 4-node quadrilateral elements. The NC modes have been used as a key scheme to improve the behaviors of various types of new finite elements, i.e., Mindlin plate bending elements, membrane elements with drilling degrees of freedom, flat shell elements. The NC modes are classified into three groups according to the 'correction constants' of 'Direct Modification Method'. The first group is 'basic NC modes', which have been widely used by a number of researchers in the finite element communities. The basic NC modes are effective to improve the behaviors of regular shaped elements. The second group is 'hierarchical NC modes' which improve the behaviors of distorted elements effectively. The last group is 'higher order NC modes' which improve the behaviors of plate-bending elements. When the basic NC modes are combined with hierarchical or higher order NC modes, the elements become insensitive to mesh distortions. When the membrane component of a flat shell has 'hierarchical NC modes', the membrane locking can be suppressed. A number of numerical tests are carried out to show the positive effect of aforementioned various NC modes incorporated into various types of finite elements.

Postbuckling and Damage Analysis of Composite Laminated Hollow Cylinder under Lateral Pressure (횡방향 압력을 받는 복합적층 원통실린더의 좌굴후 거동 및 손상해석)

  • Chongdu Cho;Guiping Zhao;HeonJu Kin
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.4
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    • pp.163-172
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    • 2000
  • The postbuckling behavior and progressive damage of composite laminated cylindrical shell under uniform external pressure were investigated by nonlinear finite element method programming. For the finite element analysis, nine-node 3-D degenerated elements were utilized, and arc-length method including line search was adopted for the iteration and load-increment along postbuckling equilibrium path. As results. buckling load, postbucking behavior, and progressive failure f3r various composite laminated cylindrical shells were discussed.

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Nonlinear dynamic analysis of reinforced concrete shell structures

  • Kim, T.H.;Park, J.G.;Choi, J.H.;Shin, H.M.
    • Structural Engineering and Mechanics
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    • v.34 no.6
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    • pp.685-702
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    • 2010
  • In this paper, a nonlinear finite element procedure is presented for the dynamic analysis of reinforced concrete shell structures. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), was used. A 4-node flat shell element with drilling rotational stiffness was used for spatial discretization. The layered approach was used to discretize the behavior of concrete and reinforcement in the thickness direction. Material nonlinearity was taken into account by using tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach was incorporated. The low-cycle fatigue of both concrete and reinforcing bars was also considered to predict a reliable dynamic behavior. The solution to the dynamic response of reinforced concrete shell structures was obtained by numerical integration of the nonlinear equations of motion using Hilber-Hughes-Taylor (HHT) algorithm. The proposed numerical method for the nonlinear dynamic analysis of reinforced concrete shell structures was verified by comparison of its results with reliable experimental and analytical results.

A 9-node Degenerated Shell Element for Inelastic Analysis of Reinforced Concrete Structures (철근 콘크리트 구조물의 비탄성 해석을 위한 9절점 퇴화 쉘 요소)

  • 이상진;서정문
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.14 no.4
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    • pp.481-494
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    • 2001
  • An enhanced degenerated shell finite element (FE), which has been developed for inelastic analysis of reinforced concrete structures is described in this paper. Generally, Reissner-Mindlin (RM) assumptions are adopted to develop the degenerated shell FE so that transverse shear deformation effects is considered. However, it is found that there are serious defects such as locking phenomena in RM degenerated shell FE since the stiffness matrix has been overestimated in some situations. As remedies of locking phenomena, reduced integration, incompatible mode and assumed strain method have been used. Especially, the assumed strain method has been successfully used in many FEs. But contrarily, there is a few investigation on the performance of the assumed strains in the inelastic analysis of concrete structures. Therefore, shell formulation is provided in this paper with emphasis on the terms related to the stiffness matrix based on assumed strain method and microscopic concrete material model. Finally, the performance of the present shell element is tested and demonstrated with several numerical examples. From the numerical tests, the present result shows a good agreement with experimental data or other numerical results.

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