In the past work, the main factors to be considered in the dynamic modeling of gear system with pitting corrosion fault are the reduction of meshing stiffness caused by the pitting fault of tooth surface, and the influence of the change of sliding friction force on the dynamic response of gear system is largely ignored. For the sliding friction, researchers pay more attention to the heat and energy consumption caused by sliding friction, but the vibration of gear system caused by friction excitation is not paid enough attention to. In fact, in addition to the translational vibration of the gear along the vertical meshing line, the sliding friction force will also form friction moment to restrict the torsional vibration of the gear system. When the lubrication of the tooth surface is poor or the tooth surface is slightly damaged, the friction excitation of the gear will become an important vibration source.

Zhang Jing et al. Established a 6-DOF nonlinear gear dynamic model considering the influence of sliding friction on the gear system. By analyzing the influence of friction on the response of gear system, the results show that the friction force of tooth surface will inhibit the vibration in the direction of meshing line, but it will aggravate the vibration in the direction of friction, which will lead to the increase of vibration amplitude of gear system. There are many kinds of gear friction models mentioned: Coulomb friction model, Benedict and Kelley friction model, smooth Coulomb friction model, etc. by studying the influence of the above different friction models on the dynamic response of gear system, it is concluded that different friction models have little influence on gear transmission error.

The sliding friction of tooth surface has an important influence on the dynamic response of gear system, so the influence of sliding friction force should be introduced in the dynamic modeling of gear system with pitting corrosion fault. In the later research of this paper, the change of gear meshing stiffness and the change of sliding friction force on the tooth surface are taken as the dynamic excitation of the gear system to preliminarily evaluate the influence of the two on the dynamic response of the gear system.