FREE VIBRATION ANALYSIS OF TRIPLY COUPLED PRE-TWISTED ROTOR BLADES BY THE DIFFERENTIAL QUADRATURE METHOD

Key parameters on the dynamic characteristics of triply coupled pretwisted rotor blades are investigated. The issues of concern include the combined flap-wise bending, chord-wise bending, and torsion vibrations of the pretwisted rotor blade, considering the centrifugal force and Coriolis effects. The governing differential equations of motion presented by Houbolt and Brooks for the rotor blade are used as the basis of study, which contain many factors previously ignored. The differential quadrature method is adopted as the method of solution for its ease in implementation, accuracy, and fast convergence. The dynamic responses of the rotor blade are obtained for different cases of coupling and geometries, which agree well with existing results. The dynamic responses of the rotor blades are plotted against parameters such as angular velocity, pretwisting angle, and hub radius in proper curves and discussed in details.