A general impact-rub model is established according to the classical impact theory.Then the suitable impact-rub model for aeroengine is found out.Two special examples of this general model are analyzed.The impact-rub dynamic equations of an eccentric and unbalanced rotor system are derived

which take the stiffness of stator into account.The equations are calculated numerically and the results are analyzed.The results reveal that the system possesses varied chaotic motions and bifurcation phenomena

besides periodic and quasi-periodic vibrations.The chaotic motions and related phenomena discovered in the impact-rub fault of the eccentric rotor system can be taken as its remarkable features and serve as symptoms to diagnose the impact-rub fault.