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Vibration Analysis of Thin/Thick, Composites/Metallic Spinning Cylindrical Shells by Refined Beam Models
No full textThis paper evaluates the vibration characteristics of thin/thick rotating cylindrical shells made of metallic and composite materials. A previous theory of the authors is extended here to include the effects of geometrical stiffness due to rotation. To this end, variable kinematic one-dimensional (1D) models obtained by applying the Carrera Unified Formulation (CUF) were used. The components of the displacement fields are x, z polynomials of arbitrary order N, making it possible to go beyond the rigid cross section assumptions of the classical beam theories. A significant contribution of this formulation consists in the possibility to include the in-plane cross-sectional deformations allowing the introduction of the in-plane initial stress effects, e.g., the effect of the geometrical stiffness. Equations of motions, including both Coriolis and in-plane initial stress contributions, were solved through the finite element method. Several analyses were carried out on both thin and thick cylinders made of either metallic or composite materials with different boundary conditions. The results are compared with analytical and numerical shell formulations and three-dimensional solutions available in the literature. Various laminate lay-up have been considered in the case of composites shells. Numerical evaluations of the effect of geometric stiffness are provided, demonstrating its importance in the analyses presented. The 1D models appear very effective to investigate the dynamics of spinning shells and, contrary to shell theories, they do not require any amendments with thick shell geometry. From the computational point of view, the present refined beam models are less expensive than the shell and solid counterpart
Aerodynamic and mechanical hierarchical aeroelastic analysis of composite wings
No full textThe coupled bending-torsion flutter is here investigated through Carrera Unified Formulation (CUF). The hierarchical capabilities of CUF offer a procedure to obtain refined one-dimensional models that, by going beyond the assumptions of classical theories, accurately describe the kinematics of structures. Aerodynamic loadings have been determined according to Theodorsen theory, from which the steady formulation can be easily obtained. The displacement variables over the cross section (x-z plane) are approximated by x,z polynomials of any order, N. The finite element method is used to solve the governing equations, which are derived in a weak form through the principle of virtual displacements. The equations are written in terms of "fundamental nuclei,"which do not vary with the theory order, N. Several wing configurations have been studied, giving great attention to thin-walled box beams made of orthotropic material. The effects of sweep angle and lamination scheme on flutter conditions have been investigated, and the results have been comparedwith solutions obtained fromtwo-dimensional theories, experimental tests, and aeroelastic analyses carried out with the doublet latticemethod (DLM). The unsteady theory, combinedwith advanced beam theories, represents a computationally cheap tool for preliminary aeroelastic studies of complex wing structure
Variable kinematic one-dimensional theories for dynamic analysis of rotating layered shells
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A refined one-dimensional rotordynamics model with three-dimensional capabilities
Full text linkThis paperevaluatesthevibrationcharacteristicsofvariousrotatingstructures.Thepre- sent methodologyexploitstheone-dimensionalCarreraUnified Formulation(1DCUF), whichenablesonetogobeyondthekinematicassumptionsofclassicalbeamtheories. Accordingtothecomponent-wise(CW)approach,Lagrange-likepolynomialexpansions (LE) arehereadoptedtodeveloptherefined displacementtheories.TheLEelementsmake it possibletomodeleachstructuralcomponentoftherotorwithanarbitrarydegreeof accuracy usingeitherdifferentdisplacementtheoriesorlocalizedmeshrefinements. Hamilton'sPrincipleisusedtoderivethegoverningequations,whicharesolvedbythe Finite ElementMethod.TheCUFone-dimensionaltheoryincludesalltheeffectsdueto rotation,namelytheCoriolisterm,spinsofteningandgeometricalstiffening.The numericalsimulationshavebeenperformedconsideringathinring,discsandbladed- deformableshafts.Theeffectsofthenumberandthepositionofthebladesonthe dynamicstabilityoftherotorhavebeenevaluated.Theresultshavebeencompared,when possible,withthe2Dand3Dsolutionsthatareavailableintheliterature.CUFmodels appearverypracticaltoinvestigatethedynamicsofcomplexrotatingstructuressince they provide2Dandquasi-3Dresults,whilepreservingthecomputationaleffectivenessof one-dimensionalsolution
Free Vibration Analysis of Rotating Composite Structures by 1D-Variable Kinematic Theories
Full text linkA Refined One-Dimensional Model Applied to Rotor-Dynamic Problems Including Rotary Wings
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