Free vibration analysis of a rotating varying-thickness-twisted blade with arbitrary boundary conditions

Abstract

A novel dynamic model of a rotating variable-thickness pre-twisted blade with elastic constraints is established by using the shallow shell theory. The effects of Coriolis and centrifugal force due to the rotational motion are considered in the formulation. Based on the Lagrange equation, the natural frequencies and modes of a rotating pre-twisted blade are obtained by using orthogonal polynomials as admissible functions. The convergence analysis is studied, and the accuracy of the proposed model is verified by comparing it with the literature results and ANSYS data. A comprehensive parameter investigation of the effects of thickness-taper ratio, pre-twist angle, rotational speed, and connection stiffness on blades' modal characteristics is conducted. The results show that the phenomena of frequency locus veering, crossing, and coincidence. Furthermore, mode shape exchanging occurs with parameter changes.