Open Access
Differential equations of motion for combined flapwise bending, chordwise bending, and torsion of twisted nonuniform rotor blades
John C. Houbolt,George W Brooks +1 more
TLDR
In this article, the differential equations of motion for the lateral and torsional deformations of twisted rotating beams are developed for application to helicopter rotor and propeller blades, and the generality is such that previous theories involving various simplifications are contained as subcases to the theory presented in this paper.Abstract:
The differential equations of motion for the lateral and torsional deformations of twisted rotating beams are developed for application to helicopter rotor and propeller blades. No assumption is made regarding the coincidence of the neutral, elastic, and mass axes, and the generality is such that previous theories involving various simplifications are contained as subcases to the theory presented in this paper. Special attention is given the terms which are not included in previous theories. These terms are largely coupling-type terms associated with the centrifugal forces. Methods of solution of the equations of motion are indicated by selected examples.read more
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Aeroelastic stability of rotor blades using finite element analysis
Inderjit Chopra,N. T. Sivaneri +1 more
TL;DR: In this article, the flutter stability of helicopter rotor blades in hover is investigated using a finite element formulation based on Hamilton's principle, where the blade is divided into a number of finite elements and nonlinear equations of motion are solved for steady-state blade deflections through an iterative procedure.
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A mathematical model for horizontal axis wind turbine blades
TL;DR: In this paper, a mathematical model describing the nonlinear vibration of horizontal axis wind turbine (HAWT) blades is proposed, which consists of a rotating blade and four components of deformation including longitudinal vibration (named axial extension), out-of-plane bend (named flap), in-plane/edgewise bend and torsion (named feather).
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Resonance avoidance for variable speed rotor blades using an applied compressive load
TL;DR: In this article, the authors investigated the use of a compressive load to reduce a blade's natural frequencies and its potential to be used as a resonance avoidance technique by improving separation between the natural and excitation frequencies of a blade.
A Historical Overview of Aeroelasticity Branch and Transonic Dynamics Tunnel Contributions to Rotorcraft Technology and Development
TL;DR: A historical account of the contributions of the Aeroelasticity Branch (AB) and the Langley Transonic Dynamics Tunnel (TDT) to rotorcraft technology and development since the tunnel's inception in 1960 is presented in this paper.
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Time-Periodic Stability of a Flapping Insect Wing Structure in Hover
TL;DR: In this article, a linear time-periodic assumed-modes analysis of a flapping wing undergoing out-of-plane bending and torsion is derived and a scalable stability diagram is presented.
References
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Theory of elasticity
TL;DR: The theory of the slipline field is used in this article to solve the problem of stable and non-stressed problems in plane strains in a plane-strain scenario.
Simplified Procedures and Charts for the Rapid Estimation of Bending Frequencies of Rotating Beams
TL;DR: In this paper, a Rayleigh energy approach utilizing the bending mode of the nonrotating beam in the determination of the bending frequency of the rotating beam was presented, which is evaluated and is found to give good practical results for helicopter blades.