Identification of Nonlinear Constitutive Properties of Damping Coatings

Abstract

Scheduled and unscheduled maintenance actions are a significant cost for gas turbines.Advanced life prediction capabilities help to mitigate these costs. However, the protective thermal and damping coatings applied to the turbine rotors which can help significantly extend component life simultaneously increase the difficulty of modeling the behavior of the components due to the nonlinearity they introduce. This research addresses modeling and analysis of nonlinear coatings for turbine blades and blisks using a nonlinear constitutive law model for the coating. The theoretical frequency response of the nonlinear system is solved for using the harmonic balance method.The coefficients of the nonlinear constitutive law are then identified by correlating the theoretical nonlinear system responses to experimental data in a minimization function. This approach more accurately identifies the nonlinear coefficients of the system by fitting the model to the full frequency response of the system at resonance as opposed to using just a few points such as with half-power peak picking. The identified nonlinear coating model can later be used in finite element analysis to both optimize the coating within the operating conditions of the turbine and improve life prediction capabilities of the system.