Abstract: The nonlinear rigid rotor model with four degrees of freedom is constructed to study the rotor/stop rubbing vibration. Numerical integration method is used to extract the forced response of the rotor excited both by the unbalance and the low frequency excitation. The analysis on the rubbing contact ratio and the frequency spectrum of the vibration reveals the characters of the double-frequency precession, the partial rubbing, the quasi-full rubbing and the full rubbing. Both the numerical simulation and the experiments on the rotor/stop rubbing conclude that the increasing of the low – frequency excitation does not cause the full rubbing between the stop and the rotor with small unbalance. But the rising of the excitation makes the quasi – full rubbing turn into full rubbing under middle unbalances and makes the partial rubbing fall into full rubbing under large unbalances.

Key words: Rotor, Rubbing, Stop, Unbalance