Domestic scholars have also carried out relevant research on the root crack fault mechanism. Shao Renping established the gear dynamic model with crack fault, and analyzed the influence of crack location and crack size on the vibration characteristics of gear transmission system. Guo Hui et al. Established a gear contact model with degree of freedom coupling method to analyze the stress field of gear. The finite element software ANSYS was used to simulate the crack propagation process of involute spur gear root. The correctness of the model was verified by comparing with the experimental results.

Based on ABAQUS, Liu Wenguang et al. Established a three tooth meshing finite element analysis model of gear pair, and proposed a double crack gear pair model with adjacent gears containing indexing circle crack and tooth root crack, and studied the relationship between crack location and crack life of gear pair. Lin Tengjiao et al. Proposed an improved algorithm for the time-varying meshing stiffness of helical gear pair with crack fault. The improved energy method was verified by finite element method, and the influence of different crack parameters on the time-varying meshing stiffness of helical gear pair was analyzed. Through the comparative analysis of finite element technology and modal curvature, cen Yuhui obtained the vibration characteristics of the gear with crack, and concluded that the change of modal curvature can clearly point out the location of the crack.

From the above research, it can be found that the research on the root crack fault mechanism of gear transmission system has become the hot research content of the theoretical system of condition detection and fault diagnosis of rotating machinery equipment. Many scholars at home and abroad have begun to explore to a certain extent, which provides a good foundation for further research on gear fault mechanism and diagnosis.