Experimental study on the intrawave frequency modulation characteristic of rotor rub and crack fault

Rub and crack are two important rotor faults. In this paper, the rub, crack and rub-crack coupled fault experiments are performed on a rotor test rig and the instantaneous frequency signatures of the faults are analyzed using Hilbert-Huang transform. The intrawave frequency modulation property of the rub and crack rotor is revealed through the response of Jeffcott rotor model and experiments. It is demonstrated that the intrawave frequency modulation produces extra harmonic components in FFT spectrum. The relationship between the FFT spectrum and the modulation frequency is supplied. The simulated and experimental analysis results show that the different composition of the modulation frequency can be the feature to detect the local rub, crack and crack-rub coupled rotor fault.