Computation of the optimal normal load of a friction damper under different types of excitation

In this paper, forced responses of a frictionally damped turbine blade are investigated for three different types of excitation: white noise excitation, narrowband random excitation, and deterministic sinusoidal excitation. To determine the steady-state nonlinear response, the harmonic balance method is used for sinusoidal excitation, and the equivalent linearization method is used for white noise and narrowband random excitations. Using a new set of nondimensionalized variables, the optimal value of normal load of a friction damper is found to be almost independent of the nature of excitation. The effectiveness of the damper in reducing the vibration level is also examined for the aforementioned three different types of excitation.