SUPPRESSION OF VIBRATORY STRESSES IN MECHANICAL STRUCTURES DUE TO DYNAMIC LOADING

Abstract

Rotor assemblies particularly those used in flight vehicle turbines typically contain aerodynamically shaped blades, or airfoils, which operate at high speeds and in hostile environments. As a result, the rotor blades are subjected to steady and vibratory loads which generate significant internal and external stresses. These vibratory stresses are the main cause of failure in aerospace/mechanical structures and machine components. Failure occurs due to these vibratory stresses in gas turbine engines and rotating machinery components while operating at resonant frequency. To prevent blade failure, the excited resonant response needs to be attenuated to an acceptable level. Several approaches have been adopted to suppress blade vibration by providing additional damping through blade dampers. A magnetomechanical coating is used as a very effective method for damping of these stresses. Vibratory stress damping in components like turbine blades through magnetomechanical coating is already established in the literature. The objective of this research is to explore the feasibility of using a magnetomechanical surface coating material for increasing the high-frequency damping of turbine blades. This research involves formulation of a parametric expression for determining the optimum value of coating layer for a given geometry of a beams, curved plate and turbine blade under dynamic loading conditions. Finite element method (FEM) is used for modeling, simulation and analysis of the parametric model. Beam theory is applied as a mathematical model for obtaining the mode shapes for the beam. A finite element analysis procedure is performed to acquire the matrix of data and the data is correlated with beam theory model for initial verification. The data is further evaluated to form the required model for calculating thickness of coating for a beam, curved plate and turbine blade. The resulting parametric expression is verified through comparison with already published experimental data available in literature. This research has a wide ranging application in the areas of gas turbine engines and rotating machinery components.