Since there are backlash friction and time-varying stiffness, the characteristics of gear pair has strong
nonlinearity. When a gear has faults such as pitting, spalling and tooth breakage, there are often some nonlinear
characteristics as super-harmonics or sub-harmonics along with vibration signal. These characteristics will cause some
difficulty for fault diagnostics, so it is necessary to study the mechanism of nonlinear vibration. Fourier expression was
used to describe time-varying stiffness, a factor was used to depict gear fault level and nonlinear dynamics model for gear
fault level was established. Simulation results show that, with certain friction and rotating speed, the nonlinear vibration
has direct relationship with rotating speed and gear friction and has no direct relationship with fault types.
Nonlinear dynamics of a spinning shaft with non-constant rotating speed
