With the structural parameters of the rotation machinery increased, the seal fluid induced force imposed on the rotor will significantly increase. Taking a cracked rotor-bearing-seal system as object the non-linear dynamic behaviours of the coupled system are investigated using numerical integration method. For the crack in shaft, the segmented switch function is applied to express the process of the crack’s opening and closing in rotation, and the cross stiffness originated from crack is considered. Various nonlinear phenomena compressing periodic, quasi-periodic and chaotic motions in the rotor system are analysed. The research results show that the unstable form of the rotor system is Hopf bifurcation when the crack depth is smaller. The influence to the response of the system increased along with the crack depth, the unstable form of the coupled system is period-doubling bifurcation. The seal clearance has an important impact on stability of the cracked rotor system. In other words, the fluid induced force can reduce the periodic responses of the rotor. It is indicated that this study can contribution to a further understanding of the nonlinear of such a rotor-bearing system with crack and seal.
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