Abstract: A multi-degree-of-freedom dynamic model of a geared rotor bearing system is developed, which includes hydrodynamic journal bearings and nonlinearity associated with meshing stiffness, backlash, separation, back-sided impacts and double-sided impacts between a gear pair. The mass unbalance response of the system is investigated by applying the numerical integration. With increasing speed, the dynamic response of the system first changes from periodic into quasiperiodic motion due to the meshing stiffness of the gear pair, After speed exceeds some value, the motion will change from quasiperiodic to chaotic state. Because of the chaotic motion, the rotor is large deformed in the centerline direction of the gear pair, and separation, back-sided impacts and double-sided impacts also occur, which may cause the system damaged.

Key words: Backlash, Bifurcation Chaos, meshing stiffness, Time-varying