AEROELASTIC STABILITY OF HINGELESS ROTOR BLADE IN HOVER USING LARGE DEFLECTION THEORY

Abstract

The coupled flap-lag-torsion aeroelastic stability of a hingeless rotor blade in hover is investigated using finite elements based on large deflection beam theory. The finite element equations of motion for beams arbitrary large displacements and rotations, but small strains, are obtained from Hamilton's principle. The stability boundary is calculated assuming blade motions to be small perturbations about the nonlinear steady equilibrium deflections, which are obtained through an iterative Newton-Raphson method. The p-k modal flutter analysis based on coupled rotating natural modes is used. Various unsteady two-dimensional strip theories am used to evaluate the aerodynamic loads. The sensitivity of the stability boundary to these aerodynamic assumptions is examined. Numerical results of the steady deflections and stability boundaries are presented for some representative blade configurations and also compared with those given in previous moderate deflection type theories.