Effect of mass and shear center offset on the dynamic response of a rotating blade

Abstract

In this work, a model that accounts for the extensional, chordwise, flapwise and torsional vibrations of a flexible rotating blade was developed. The model also takes into consideration the offset between the elastic and inertial axes of the blade. In order to account for the centrifugal stiffening effect, expression for the strain energy was obtained based on an ordering scheme that retains terms up to 2nd order. Hence, a set of four nonlinear coupled partial differential equations governing the deformations of the blade was derived. The linearized equations were non-dimensionalized and then spatially discretized by the FEM (Finite Element Method). State space techniques were used to obtain the blade's natural modes and response to initial excitation. Effect of the mass and shear center offset on the coupling between the modes and veering regions at different rotor speeds were investigated.