• Title/Summary/Keyword: 회전셸

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Vibration Analysis of Rotating Thin Shells of Revolution by Finite Element Method (유한요소법에 의한 회전하는 얇은 축대칭 셸의 진동에 관한 연구)

  • 김현실;이영환
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.4
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    • pp.487-496
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    • 1985
  • 회전하는 축대칭 얇은 셸구조물의 진동 특성을 유한요소법에 의하여 해석하였다. 2개의 절점을 가진 Conical Frustrm 형태의 축대칭 요소를 사용하였으며 원주방향의 변위는 Fourier Series로 분해하여서 방정식의 수를 상당히 줄일 수 있었다. Sanders-Koiter의 셸이론을 사용하였으며 진 동 모우드는 회전의 영향을 설명하기 위하여 대칭 및 비대칭 모우드를 모두 고려하였다. Coriolis 행렬을 포함하는 운동방정식에서 고유 진동수를 계산하기 위해서 질량, 강성 및 Coriolis 행렬로 이루어지는 Hermitian 행렬의 Sturm Sequence Property를 이용하였으며, 좁은 밴드를 갖는 대형 행렬에 알맞는 Determinant Search 방법을 확장하여 고유진동수 및 벡터를 구하였다. 원통형 셸에 대하여 정지한 경우 계산한 고유진동수를 실험치 및 이론치와 비교한 결과 잘 일치됨을 알 수 있었다. 여러 가지 회전 속도에 대해서 얻어진 고유진동스를 이론치와 비교한 결과 잘 일치 됨을 알 수 있어\ulcorner며 회전의 영향으로 traveling wave진동의 현상이 나타남을 알 수 있었다.

Three-dimensional Vibration Analysis of Thick, Complete Conical Shells of Revolution (두꺼운 완전 원추형 회전셸의 3차원적 진동해석)

  • Sim Hyun-Ju;Kang Jae-Goon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.4 s.97
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    • pp.457-464
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    • 2005
  • A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of thick, complete (not truncated) conical shells of revolution, Unlike conventional shell theories, which are mathematically two-dimensional (2-D). the present method is based upon the 3-D dynamic equations of elasticity. Displacement components $u_{r},\;u_{z},\;and\;u_{\theta}$ in the radial, axial, and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in , and algebraic polynomials in the r and z directions. Potential (strain) and kinetic energies of the conical shells are formulated, the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four-digit exactitude is demonstrated for the first five frequencies of theconical shells. Novel numerical results are presented for thick, complete conical shells of revolution based upon the 3-D theory. Comparisons are also made between the frequencies from the present 3-D Ritz method and a 2-D thin shell theory.

Three-Dimensional Field Equations, Equations of Motion, and Energy Functionals for Thick Shells of Revolution with Arbitrary Curvature and Variable Thickness (임의의 곡률과 변두께를 갖는 두꺼운 축대칭 회전 셸의 3차원적 장방정식, 운동 방정식, 에너지 범함수)

  • 강재훈;이은택;양근혁
    • Journal of KSNVE
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    • v.11 no.1
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    • pp.156-166
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    • 2001
  • This work uses tensor calculus to derive a complete set of three-dimensional field equations well-suited for determining the behavior of thick shells of revolution having arbitrary curvature and variable thickness. The material is assumed to be homogeneous, isotropic and linearly elastic. The equations are expressed in terms of coordinates tangent and normal to the shell middle surface. The relationships are combined to yield equations of motion in terms of orthogonal displacement components taken in the meridional, normal and circumferential directions. Strain energy and kinetic energy functionals are also presented. The equations of motion and energy functionals may be used to determine the static or dynamic displacements and stresses in shells of revolution, including free and forced vibration and wave propagation.

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Study on Structural Vibration Analysis and Design Optimization of Rotating Composite Cylindrical Shells with Cutout (회전운동을 고려한 Cutout이 있는 복합재료 원통셸의 구조진동해석 및 최적설계)

  • 이영신;김영완
    • Journal of KSNVE
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    • v.8 no.3
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    • pp.467-476
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    • 1998
  • The free vibration analysis and design optimization of the rotating composite cylindrical shells with a rectangular cutout are investigated by theoretical method. The Love's thin shell theory is used to derive the frequency equation. The theoretical results are obtained by application of the energy method employing the Rayleigh-Ritz procedure. The used circumferential vibration modes are trigonometric functions, the axial modes are the beam modal functions chosen to satisfy the prescribed boundary conditions. To check the validity, the theoretical results are compared with experimental, FEM and other theoretical results.

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Development of a flat shell element by using the hybrid Trefftz plane element with drilling D.O.F. and the DKMQ element (면내 회전 자유도가 추가된 hybrid Trefftz 평면 요소와 DKMQ 요소를 이용한 4 절점 평면 셸 요소의 개발)

  • 최누리;추연석;이승규;이병채
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.10a
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    • pp.855-859
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    • 2004
  • We develop a new four-node flat shell element which is accurate, efficient, and suitable to be used on general purpose. The new element has a hybrid Trefftz element with drilling degrees of freedom as a membrane part. We define the two independent displacement field: the internal displacement field that satisfies governing equations in the domain a priori and the boundary displacement field that is usually used as a conventional finite element method. The hybrid Trefftz variational formulation connects these two displacement fields on the boundary of the domain. To add drilling degrees of freedom, we introduce the Allman's quadratic displacement field to the boundary displacement field. As a result, our flat shell element has 6 degrees of freedom per a node. We also use the well-known DKMQ plate bending element for the plate part of the proposed element. The DKMQ element satisfies Mindlin-Reissner‘s plate theory along the edge of the element and gives proper behavior regardless of the thickness. A series of numerical experiments shows that the performance of the new element such as accuracy, rate of convergence, robustness to mesh quality, and so on.

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Vibration Analysis of Annular Plate Combined Cylindrical Shells Considering Additional Deformations (추가변형을 고려한 환원판 결합 원통셸의 진동해석)

  • Kim, Young-Wann;Chung, Kang
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.551-556
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    • 2004
  • The theoretical method is developed to investigate the vibration characteristics of the combined cylindrical shells with an annular plate joined to the shell at any arbitrary axial position. The structural rotational coupling between shell and plate is simulated using the rotational artificial spring. For the translational coupling, the continuity conditions for the displacements of shell and plate are used. For the uncoupled annular plate, the transverse motion is considered and the in-plane motions are not. And the additional transverse and in-plane motions of the coupled annular plate by shell deformation are considered in analysis. Theoretical formulations are based on Love's thin shell theory. The frequency equation of the combined shell with an annular plate is derived using the Rayleigh-Ritz approach. The effect of inner-to-outer radius ratio, axial position and thickness of annular plate on vibration characteristics of combined cylindrical shells is studied. To demonstrate the validity of present theoretical method, the finite element analysis is performed.

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Free Vibration Analysis of Combined Cylindrical Shells with an Annular Plate Considering Additional Deformations (추가변형을 고려한 환원판 결합 원통셸의 자유진동해석)

  • Chung Kang;Kim Young-Wann
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.3 s.234
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    • pp.439-446
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    • 2005
  • The theoretical method is developed to investigate the vibration characteristics of the combined cylindrical shells with an annular plate joined to the shell at any arbitrary axial position. The structural rotational coupling between shell and plate is simulated using the rotational artificial spring. For the translational coupling, the continuity conditions for the displacements of shell and plate are used. For the uncoupled annular plate, the transverse motion is considered and the in-plane motions are not. And the additional transverse and in-plane motions of the coupled annular plate by shell deformation are considered in analysis. Theoretical formulations are based on Love's thin shell theory. The frequency equation of the combined shell with an annular plate is derived using the Rayleigh-Ritz approach. The effect of inner-to-outer radius ratio, axial position and thickness of annular plate on vibration characteristics of combined cylindrical shells is studied. To demonstrate the validity of present theoretical method, the finite element analysis is performed.