A simplified dynamic model of aero-engine with dual-rotor system was established. Considering the non-linear factors such as Hertz contact force and radial clearance of the intermediate bearing

the local defect of the inner ring of the inter-shaft bearing was simulated as an inverted isosceles trapezoidal groove. The Runge-Kutta method of order 4 was used to simulate the fault system and draw the bifurcation diagram. The combination resonance characteristics of the bifurcation region were analyzed emphatically

and the results showed that there were three bifurcation regions in the bifurcation diagram of a dual-rotor system with local defect of inter-shaft bearing. Vibration response analysis showed that the first two bifurcation phenomena were caused by the combined resonance of inner-ring fault

and the last bifurcation phenomenon was caused by the induced resonance of inner-ring fault. In the bifurcation region

the periodicity of system motion would change correspondingly

mainly from approximate single-periodic motion to almost periodic motion and then to approximate single-periodic motion.