• Title/Summary/Keyword: Shear Flutter

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On vibration and flutter of shear and normal deformable functionally graded reinforced composite plates

  • Abdollahi, Mahdieh;Saidi, Ali Reza;Bahaadini, Reza
    • Structural Engineering and Mechanics
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    • v.84 no.4
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    • pp.437-452
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    • 2022
  • For the first time, the higher-order shear and normal deformable plate theory (HOSNDPT) is used for the vibration and flutter analyses of the multilayer functionally graded graphene platelets reinforced composite (FG-GPLRC) plates under supersonic airflow. For modeling the supersonic airflow, the linear piston theory is adopted. In HOSNDPT, Legendre polynomials are used to approximate the components of the displacement field in the thickness direction. So, all stress and strain components are encountered. Either uniform or three kinds of non-uniform distribution of graphene platelets (GPLs) into polymer matrix are considered. The Young modulus of the FG-GPLRC plate is estimated by the modified Halpin-Tsai model, while the Poisson ratio and mass density are determined by the rule of mixtures. The Hamilton's principle is used to obtain the governing equations of motion and the associated boundary conditions of the plate. For solving the plate's equations of motion, the Galerkin approach is applied. A comparison for the natural frequencies obtained based on the present investigation and those of three-dimensional elasticity theory shows a very good agreement. The flutter boundaries for FG-GPLRC plates based on HOSNDPT are described and the effects of GPL distribution patterns, the geometrical parameters and the weight fraction of GPLs on the flutter frequencies and flutter aerodynamic pressure of the plate are studied in detail. The obtained results show that by increasing 0.5% of GPLs into polymer matrix, the flutter aerodynamic pressure increases approximately 117%, 145%, 166% and 196% for FG-O, FG-A, UD and FG-X distribution patterns, respectively.

Parametric Study on Dynamic Stability Behaviors of Beck's Column considering Shear Deformation and Damping Effects (전단변형 및 감쇠효과를 고려한 비보존력을 받는 외팔기둥의 동적 안정성거동에 대한 매개변수연구)

  • Lee, Jun-Seok;Kim, Nam-Il;Kim, Moon-Young
    • Journal of the Earthquake Engineering Society of Korea
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    • v.9 no.6 s.46
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    • pp.1-12
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    • 2005
  • For a shear-deformable beam-column element subjected io non-conservative forces, equations of motion and a finite element formulation are presented applying extended Hamilton's principle. The influence of non-conservative force's direction parameter, internal and external damping forces, and shear deformation and rotary inertia effects on divergence and flutter loads of Beck's columns are intensively investigated based on element stiffness, damping and mass matrixes derived for the non-conservative system.

A Parametric Study on the Shear-deformation Effect for Beck's Column under Follower Force (비보존력을 받는 Beck 기둥의 전단변형효과에 관한 매개변수적 고찰)

  • Lee Jun-Seok;Kim Nam-Il;Kim Moon-Young
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2006.04a
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    • pp.985-991
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    • 2006
  • For a shear-deformable beam-column element subjected to non-conservative forces. equations of motion and a finite element formulation are presented applying extended Hamilton's principle. The influence of non-conservative force's direction parameter. internal and external damping forces, and shear deformation and rotary inertia effects on divergence and flutter loads of Beck's columns are intensively investigated based on element stiffness. damping and mass matrixes derived for the non-conservative system.

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Supersonic Flutter Analysis of Cylindrical Composite Panels with Structural Damping Treatments (구조 감쇠 처리된 원통형 복합적층 패널의 플러터 해석)

  • Shin, Won-Ho;Oh, Il-Kwon;Lee, In
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2002.05a
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    • pp.131-134
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    • 2002
  • Supersonic flutter analysis of cylindrical composite panels with structural damping treatments has been performed using the finite element method based on the layerwise shell theory. The natural frequencies and loss factors of cylindrical viscoelastic composites are computed considering the effects of transversely shear deformation. The panel flutter of cylindrical composite panels is analyzed considering structural damping effect. Various damping characteristics for unconstrained layer damping, constrained layer damping, and symmetrically co-cured sandwich laminates are compared with those of an original base panel in view of aeroelastic stabilities.

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An analytical approach for aeroelastic analysis of tail flutter

  • Gharaei, Amin;Rabieyan-Najafabadi, Hamid;Nejatbakhsh, Hossein;Ghasemi, Ahmad Reza
    • Advances in Computational Design
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    • v.7 no.1
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    • pp.69-79
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    • 2022
  • In this research, the aeroelastic instability of a tail section manufactured from aluminum isotropic material with different shell thickness investigated. For this purpose, the two degrees of freedom flutter analytical approach are used, which is accompanied with simulation by finite element analysis. Using finite element analysis, the geometry parameters such as the center of mass, the aerodynamic center and the shear center are determined. Also, by simulation of finite element method, the bending and torsional stiffnesses for various thickness of the airfoil section are determined. Furthermore, using Lagrange's methods the equations of motion are derived and modal frequency and critical torsional/bending modes are discussed. The results show that with increasing the thickness of the isotropic airfoil section, the flutter and divergence speeds increased. Compared of the obtained results with other research, indicates a good agreement and reliability of this method.

Ant colony optimization for dynamic stability of laminated composite plates

  • Shafei, Erfan;Shirzad, Akbar
    • Steel and Composite Structures
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    • v.25 no.1
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    • pp.105-116
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    • 2017
  • This paper presents the dynamic stability study of laminated composite plates with different force combinations and aspect ratios. Optimum non-diverging stacking is obtained for certain loading combination and aspect ratio. In addition, the stability force is maximized for a definite operating frequency. A dynamic version of the principle of virtual work for laminated composites is used to obtain force-frequency relation. Since dynamic stiffness governs the divergence or flutter, an efficient optimization method is necessary for the response functional and the relevant constraints. In this way, a model based on the ant colony optimization (ACO) algorithm is proposed to search for the proper stacking. The ACO algorithm is used since it treats with large number of dynamic stability parameters. Governing equations are formulated using classic laminate theory (CLT) and von-Karman plate technique. Load-frequency relations are explicitly obtained for fundamental and secondary flutter modes of simply supported composite plate with arbitrary aspect ratio, stacking and boundary load, which are used in optimization process. Obtained results are compared with the finite element method results for validity and accuracy convince. Results revealed that the optimum stacking with stable dynamic response and maximum critical load is in angle-ply mode with almost near-unidirectional fiber orientations for fundamental flutter mode. In addition, short plates behave better than long plates in combined axial-shear load case regarding stable oscillation. The interaction of uniaxial and shear forces intensifies the instability in long plates than short ones which needs low-angle layup orientations to provide required dynamic stiffness. However, a combination of angle-ply and cross-ply stacking with a near-square aspect ratio is appropriate for the composite plate regarding secondary flutter mode.

Stability Analysis of Multi-wall Carbon Nanotubes Conveying Fluid (유체유동에 의한 다중벽 탄소나노튜브의 안정성 해석)

  • Song, Oh-Seop;Yun, Kyung-Jae
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.6
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    • pp.593-603
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    • 2010
  • In this paper, vibration and flow-induced flutter instability analysis of cantilever multi-wall carbon nanotubes conveying fluid and modelled as a thin-walled beam is investigated. Non-classical effects of transverse shear and rotary inertia and van der Waals forces between two walls 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.

Flow-induced Vibration of Carbon Nanotubes Conveying Fluid (탄소나노튜브의 유체유발 진동)

  • Song, Oh-Seop;Choi, Jong-Woon;Gil, Bo-Ramm
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.242-249
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    • 2008
  • In this paper, flow-induced flutter instability of cantilever 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.

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Spring Position and Stiffness Effect on the Dynamic Stability of Elastically Restrained Cantilevered Beams under a Follower Force (종동력을 받는 탄성지지된 외팔보의 동적 안정성에 미치는 스프링위치와 상수의 영향)

  • 류봉조;권경우;명태식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.6
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    • pp.1496-1502
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    • 1994
  • The influences of spring position and spring stiffness on the critical force of a cantilevered beam subjected to a follower force are investigated. The spring attatched to the beam is assumed to be a translational one and can be located at arbitrary positions of the beam as it has not been assumed so far. The effects of transeverse shear deformation and rotary intertia of the beam are also included in this analysis. The charateristic equation for the system is derived and a finite element model of the beam using local coordinates is formulated through extended Hamilton's principle. It is found that when the spring is located at position less than that of 0.5L, the flutter type instability only exists. It is shown that the spring position approaches to the free end of the beam from its midpoint, instability type is changed from flutter to divergence through the jump phenomina according to the increase of spring stiffness.

Flow-induced Vibration of Carbon Nanotubes Conveying Fluid (탄소나노튜브의 유체유발 진동)

  • Choi, Jong-Woon;Gil, Bo-Ramm;Song, Oh-Seop
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.6
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    • pp.654-662
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    • 2008
  • In this paper, flow-induced flutter instability of cantilever 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.