• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.219-224
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• 2012

In this paper, vibration and flow-induced flutter instability analysis of cantilever multiwall carbon nanotubes conveying fluid and modelled as a thin-walled beam is investigated. Non-classical effects of transverse shear and rotary inertia are incorporated in this study. The governing equations and the associated boundary conditions are derived through Hamilton's principle. Numerical analysis is performed by using extend Galerkin method which enables us to obtain more exact solutions compared with conventional Galerkin method. Cantilevered carbon nanotubes are damped with decaying amplitude for flow velocity below a certain critical value, however, beyond this critical flow velocity, flutter instability may occur. Variations of critical flow velocity with both radius ratio and length of carbon nanotubes are investigated and pertinent conclusion is outlined.

• Structural Engineering and Mechanics
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• 제6권7호
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• pp.747-756
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• 1998

In this paper the influence of rotary inertia, shear and compressibility on the value of the critical force for the Beck's column is analyzed. The constitutive equation is of Engesser's type. As a result, the critical load parameter for which instability of flutter type occurs is calculated for several values of the column's parameters.

• Structural Engineering and Mechanics
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• 제16권2호
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• pp.195-217
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• 2003

This paper, which is an extension of a previous work by Viola et al. (2002), deals with the dynamic stability of beams under a triangularly distributed sub-tangential forces when the effect of an elastically restrained end is taken into account. The sub-tangential forces can be realised by a combination of axial and tangential follower forces, that are conservative and non-conservative forces, respectively. The studied beams become unstable in the form of either flutter or divergence, depending on the degree of non-conservativeness of the distributed sub-tangential forces and the stiffness of the elastically restrained end. A non-conservative parameter ${\alpha}$ is introduced to provide all possible combinations of these forces. Problems of this kind are usually, at least in the first approximation, reduced to the analysis of beams according to the Bernoulli-Euler theory if shear deformability and rotational inertia are negligible. The equation governing the system may be derived from the extended form of Hamilton's principle. The stability maps will be obtained from the eigenvalue analysis in order to define the divergence and flutter domain. The passage from divergence to flutter is associated with a noticeable lowering of the critical load. A number of particular cases can be immediately recovered.

• 대한기계학회논문집
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• 제8권2호
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• pp.119-126
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• 1984

본 논문에서는 자유단에 부착된 질량의 관성모우멘트가 Beck's column의 안정 성에 미치는 영향을 연구하였다.

• Structural Engineering and Mechanics
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• 제60권1호
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• pp.1-19
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• 2016

In this study, the supersonic panel flutter of doubly curved composite sandwich panels with variable thickness is considered under aerothermoelastic loading. Considering different radii of curvatures of the face sheets in this paper, the thickness of the core is a function of plane coordinates (x,y), which is unique. For the first time in the current model, the continuity conditions of the transverse shear stress, transverse normal stress and transverse normal stress gradient at the layer interfaces, as well as the conditions of zero transverse shear stresses on the upper and lower surfaces of the sandwich panel are satisfied. The formulation is based on an enhanced higher order sandwich panel theory and the vertical displacement component of the face sheets is assumed as a quadratic one, while a cubic pattern is used for the in-plane displacement components of the face sheets and the all displacement components of the core. The formulation is based on the von $K{\acute{a}}rm{\acute{a}}n$ nonlinear approximation, the one-dimensional Fourier equation of the heat conduction along the thickness direction, and the first-order piston theory. The equations of motion and boundary conditions are derived using the Hamilton principle and the results are validated by the latest results published in the literature.

• Composites Research
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• 제15권1호
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• pp.1-8
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• 2002

본 연구에서는 실제 구조형상의 사각형 상자형 날개와 전투기 날개에 대하여 구조재를 표피(skin)부분은 복합재료로 대체하고, 나머지 스파(spar)와 리브(rib)는 알루미늄으로 하여 플러터 해석을 수행하였다. MS/PATRAN을 이용하여 실제 날개 구조에 근사한 3차인 유한 요소 모델이 구축되었고, MSC/NASTRAN을 이용하여 고유진동 해석이 수행되었다. 유한 요소는 멤브레인(membrane)요소, 1차원 막대(rod)요소, 전단패널(shear panel)요소를 사용하였다. 복합재료의 적층은 실제적인 적층각을 이용하여 다양하게 변화시켜 해석하였다. 아음속 영역에서 비정상 공력 해석을 위하여 주파수 영역에서의 선형 공기력 이론인 DLM코드가 적용되었고, 주파수 영역 공탄성 지배방정식의 해법으로 V-g방법 및 p-k방법이 적응되었다.

• 대한기계학회논문집
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• 제17권11호
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• pp.2762-2772
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• 1993

The paper deals with the flutter of a cantilevered beam subjected to a rocket thrust generated by a solid rocket motor. It is saaumed that the rocket thrust is to be a constant follower thrust, and produced by the installation of a solid rocket motor to the tip end of the cantilevered beam. The rocket motor is considered to be a rigid body having finite sizes, but not a mass point as it has been assumed so far. Governing equations are derived through the extended Hamilton's principle, and finite element method is applied to obtain the theoretical prediction for critical follower thrust. The maximum follower thrust is also calculated through the change of shear deformation parameter of the beam in the numerical simulation. The theoretical prediction for flutter or stability is verified by experiment. The experimental results show that critical follower thrust in theory agrees well with the experimental value taking account of the magnitude, rotary inertia of the rocket motor and the distance from the tip end of the beam to the center of gravity of the rocket motor.

• 한국항공우주학회지
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• 제33권7호
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• pp.26-32
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• 2005

본 논문에서는 위성체 태양전지의 진동응답을 분석하였다. 태양전지는 복합재료 얇은 벽보와 태양전지 판 및 보조 바로 구성되어 있다. 복합재료 얇은 벽보는 전단 변형, 12차 와핑, 회전 관성과 재료의 방향성 등을 고려해야 한다. 태양전지 판은 z 방향으로 일정한 장력이 가해지는 얇은 막이며 보조 바는 강체 구조물이다. 열적 구배에 따른 구조 변형에 의한 영향을 고려하여 연성된 열적 구조 해석을 수행하였으며, 열적 불안정성 조건이 되는 안정성 기준 인자들을 분석하였다.

• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1355-1360
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• 2006

This paper presents the dynamic stability of a cantilevered Timoshenko beam with a concentrated mass, partially attached to elastic foundations, and subjected to a follower force. Governing equations are derived from the extended Hamilton's principle, and FEM is applied to solve the discretized equation. The influence of some parameters such as the elastic foundation parameter, the positions of partial elastic foundations, shear deformations, the rotary inertia of the beam, and the mass and the rotary inertia of the concentrated mass on the critical flutter load is investigated. Finally, the optimal attachment ratio of partial elastic foundation that maximizes the critical flutter load is presented.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.99-104
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• 2001

Thermally induced vibration response of solar array is investigated. The solar array model consists of composite thin walled beam and solar blanket, spreader bar. The composite thin walled beam incorporates a number of nonclassical effects of transverse shear, primary and secondary warping, rotary inertia and anisotropy of constituent materials. The solar blanket is a membrane subjected to uniform tension in the z direction. The spreader bar is a rigid member. A coupled thermal structure analysis that includes the effects of structural deformations on heating and temperature gradient is investigated. A stability criterion given in parameters for establishes the conditions for thermal flutter.