Modal analysis of rotating Pre-twisted functionally graded sandwich blade

Abstract

Modal analysis of rotating turbine blades is an inevitable step during the design process to avoid resonance conditions and related catastrophic failures. The need for such analysis arises because of vibration of supporting machine components like rotor and other dynamic forces involved. Mimicking actual structural and environmental conditions for the analysis to achieve close-form solution is very challenging, therefore approximations of real-time situations are adopted to analysis further. Here, functionally graded sandwich pre-twisted cantilever shell structure with metal core and functionally graded (metal/ceramic) face sheets is considered as thermal barrier coated turbine blades. The present work focuses on the modal analysis of rotating pre-twisted blade model under elevated temperature. Material gradation has been done using power-law distribution and Voigt’s model. The kinematics of the present model is based on the first-order shear deformation theory. The Hamilton principle is adopted to obtain the motion equations. Subsequently, the blade model is discretized and solved using 2D finite element approach via quadrilateral elements. The validation of the proposed work has been confirmed by comparing with the earlier published work. In addition, frequency responses are computed for different composite blade parameters such as twist angle, volume fractions, rotational velocity. The occurrence mode shape exchange phenomena with these parametric variations have been observed and discussed in detail.