Abstract
It is very important to detect the occurrence of a crack on rotating machinery in early stages. In this study, dynamic characteristics of a cracked rotor with a excitation force using active magnetic bearing(AMB) are investigated. Due to the open-close mechanism of the rotor crack, the equations of motion of a cracked rotor have linear and nonlinear parametric terms. When a harmonic electric current is applied to AMB and sweep its frequency, various kinds of resonances, which are not observed in a symmetric rotor and an asymmetric rotor with linear spring characteristics, occur due to the unique spring characteristics of a cracked rotor. We clarify characteristics of these resonances theoretically. Furthermore, obtained theoretical results are validated by experiment using the rotating shaft system with actual fatigue crack.
