Gear drive is widely used in heavy industry and manufacturing industry, and is often used as reducer, speed increaser, differential, reversing mechanism and other special purposes, which is the focus of the development of mechanical drive in the world. But it also has its own certain defects, that is, gear fatigue, in which the largest proportion of fatigue broken teeth. Especially after the crack appears, it has a great influence on the fatigue life and contact engagement, and also on the overall effect. However, fatigue fracture will not occur obvious plastic deformation, which is relatively difficult to detect and prevent, which is an important factor affecting gear transmission efficiency and causing economic losses.

The research on the fatigue performance of internal meshing modified gear with cracks not only provides reference for engineering inspection and evaluation, but also helps to improve its reliability and life, and greatly improves its work efficiency.

From the stress distribution of the inner gear plate, the maximum stress is 168.44 × 108Pa。 The maximum stress is mainly in the tooth root position and the contact meshing point. The stress at the tooth root position is larger than that at the contact meshing point, and it is located on the contact side.

The fatigue life analysis of three ring drive shows that the length of the extended crack is 8.37mm, the final life times is 36891, and the life times are greatly reduced. The main mode of crack propagation is open crack, with sliding crack and tearing crack as auxiliary.