The widespread application of planetary gear trains is accompanied by inevitable crack failures, especially for the internal ring gear, which may lead to catastrophic accidents. There is relatively little research on internal ring gear cracks and mostly only make assumptions about the crack damage morphology at a certain stage. Moreover, there is no answer on what will happen in the next stage after the crack occurs, or how to avoid serious failure. In view of this, this study considers rim and support configurations, tooth geometries, and crack parameters, and analyzes crack evolution mechanisms. The results indicate that compared to the internal ring gear outer surface constraint condition, the use of pin support for the internal ring gear increases the risk of severe rim-fracture failure. A thicker rim can avoid rim failure, especially when the initial crack is close to the tooth root. In addition, a larger root fillet helps to reduce the occurrence of rim failure over tooth failure. Increasing pin support diameter and stiffness results in a tendency for the crack trajectory to move away from the rim. This study gives support for the cracked ring gear failure analysis and safety design.
Duan et al. (Fri,) studied this question.