Modelling friction characteristics in turbine blade vibrations using a fourier series expansion of a real friction hysteresis

Abstract

A new contact model is proposed to simulate the forced response of a two degree of freedom mechanical model which resembles the simplest form of a friction damped turbine blade. The model scales a measured friction hysteresis to the current state of the mechanical model to obtain the contact force. The equations of motion are solved iteratively with a Newton-Raphson method using an analytical Jacobian. Furthermore the nonlinear system is linearised by using the Monoharmonic Balance Method. Based on experiments functions are found that scale a single hysteresis in such a way that a wide range of contact states can be predicted sufficiently well. The forced response of the mechanical model using the proposed contact model shows good agreement with the forced response using an Elastic Coulomb Friction Model.