Vibrations of a Helicopter Rotor Blade Using Finite Element-Unconstrained Variational Formulations.

摘要

In the past several years, a numerical method has been developed which is a generalized Rayleigh-Ritz - finite element discretization using the combined concept of Lagrange multipliers and adjoint variables. This approach enables one to deal with problems associated with nonconservative forces, coupling effects and all types of boundary conditions in a routine fashion; and it appears promising in solving the vibration and dynamic stability problems associated with the complicated equations of a helicopter rotor blade. This paper presents the first application of the general method of the vibration problem of such a rotor blade. The numerical results from some demonstrative examples show that instability of flutter can occur in the range of operational rotor speed due to the coupled motion of flapping and root torsion without any aerodynamic force, if the torsional spring (or the pitch control link) is not sufficiently stiff. This instability does not appear to have been reported previously.