Study on fault mechanism and dynamics of spur gear pair with time-varying backlash

Dynamical modeling of spur gears with typical faults is crucial research topic for understanding fault features and vibration mechanisms. Meanwhile, the lubrication plays an important role in dynamic model. In this work, a novel coupled model combined dynamic model with elastohydrodynamic lubrication model is proposed by considering typical faults action mechanisms. A modified backlash error model takes into account the deformation and oil film backlash to calculate the time-varying backlash. The Runge–Kutta, multigrid integral and five-level Dmeyer wavelet transform method are combined to calculate the lubrication properties and dynamic characteristics at each meshing position along the line of action. Influences of typical faults on the contact performance, such as pressure distribution, oil film thickness, vibration response and bifurcation chaotic behavior are studied. The results show that the typical faults have a significant impact on both the lubrication and dynamic characteristics of the system. The spatial placement of faults can significantly alter the distribution of lubrication parameters. The disturbance of gear faults cause the system attractor unfold and the phase trajectory diffuse and make the system tend to be unstable. The typical faults are more sensitive at low excitation frequencies and less affected at high excitation frequencies. The research provides a basis for the fault diagnosis and detection of gearbox.