Nonlinear Dynamics for Gear Fault Level

Su Xunwen*, 1, Liu Jinhao1, Wang Shaoping2
1 School of Technology, Beijing Forestry University, Beijing, 100083, China
2 School of Automation Science and Electrical Engineering, Beijing University of Aeronautics and Astronautics, Beijing, 100191, China

© 2014 Xunwen et al

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: ( This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the School of Technology, Beijing Forestry University, No.35 Tsinghua East Road, Haidian District, Beijing, 100083, China; Tel: 86-10-62338153; E-mail:


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.

Keywords: Dynamics, fault diagnostics, fault level, gear, nonlinearity.