Using the mass centralized method

a six degree of freedom transverse-torsional coupled nonlinear gear-rotor-bearing vibration model with multiple clearances and tooth surface friction was established

while time-varying meshing stiffness

gear backlashes

bearing clearances were considered in the model as well. By studying Poincare maps and global bifurcation diagrams under above parameters

the bifurcation characteristics of the system were obtained. Under a certain gear backlash

meshing damp and low tooth surface meshing friction

the system enters into a chaos state by the way of quasi-periodic motion with the increase of the rotation rate. While the tooth surface meshing friction coefficient increases

namely system is changed from well lubricated state to dry lubrication

the window of the chaos motion is split into two pieces at a critical point

and the system motion enters into a chaos state again by the way of crisis; Under a certain rotation speed

meshing damp and tooth surface friction coefficient

the system enters into a chaos state by way of crisis with the increase of the gear backlash

and the bifurcation and chaos motion happens when dimensionless gear backlash is less than 3 or bigger than 7

and the system motion is locked into a period motion by channel of reverse bifurcation; Under a certain rotation rate

meshing damp and gear backlash

the system enters into a chaos state by the way of crisis with the increase of the tooth surface friction coefficient. Meanwhile

it could be observed that

with the increase of the meshing damp

the window of the chaotic motion is split into 2

3 and 4 sub-windows subsequently. But at last

system always is locked into a period motion by channel of quasi-periodic motion.