Damage detection of a rotating cracked shaft using an active magnetic bearing as a force actuator - analysis and experimental verification

The active health monitoring of rotordynamic systems in the presence of breathing shaft cracks is considered in this work. The shaft is assumed to be supported by conventional bearings, and the active magnetic bearing (AMB) is used in a midshaft or outboard location as an actuator to apply specified, time-dependent forcing on the system. These forces, if properly chosen, induce a combination resonance that can be used to identify the magnitude of the time-dependent stiffness arising from the breathing mode of the shaft crack. The technique is verified experimentally on a high speed test rotor with a healthy and a cracked shaft.