Detection and monitoring of crack in a coast-down rotor supported on fluid film bearings

A Jeffcott rotor with a transverse crack has been considered in the present study. Equations of motion for transient response have been developed and dynamic analysis has been carried out to consider the effects of fluid film bearings. The coast-down phenomenon was analysed by considering the dissipation through the journal film and by evaluating the deceleration for each speed. Characteristic sub-critical response peaks have been found when the cracked rotor decelerates through its critical speed. The continuous wavelet transform (CWT) has been used as a tool to extract the above sub-harmonics from the time domain signals. The use of CWT has been suggested for crack detection and monitoring in a rotor system coasting down through its critical speed.