Vibration Analysis of Tapered Pre-Twisted Functionally Graded Rotating Blade

Abstract

Structural dynamic analysis of pre-twisted blades is one of the classical problems dealt earlier by several researchers. In present study a blade made up of functionally graded (FG)metal-ceramic composite material having a pre-twist is considered. Free vibration analysis of rotating pre-twisted blades is conducted and all the modal parameters are determined as a function of pre-twist at different operating speeds. Approach followed is based on Rayleigh-Ritz’s technique for decomposing the equation of motion of rotating blade into generalized coordinates. The three dimensional finite element, FE approach is employed to obtain the natural frequencies via ANSYS modelling. For FG material modelling, the power distribution law is considered and the stiffness and mass matrices are derived with geometric effects including taper, twist and cross-section. Initially, rectangular sections are tried followed by aerofoil type. The three dimensional solid models developed for the blade are analysed with ANSYS. The important material and geometric parameters affecting the free vibration
characteristics are identified