Investigations on crack propagation and meshing characteristics of planetary gear train considering crack closure effect

Abstract

The shape of spatial crack is more complex in practice and crack closure will occur due to deformation, which will result in partial contact of the crack surfaces. In previous researches, a simple linear plane assumption for the gear crack trajectory was usually made and the crack closure effect was ignored. Based on the principle of linear elastic fracture mechanics, a three-dimensional numerical model of planetary gear train crack propagation considering the initial crack location, ring gear backup ratio and constraint mode is built in this study. Considering the crack closure effect and the obtained crack trajectory, the meshing characteristics (including the time varying meshing stiffness (TVMS) and contact pressure) are investigated. The results indicate that when considering the crack closure effect, the reduction in the TVMS of the cracked gear decreases and the influence of the foundation crack closure effect on TVMS is greater than that of tooth crack closure effect. Appropriately constraining the outer rim of the thinner ring gear can help avoid catastrophic foundation crack, but the TVMS is more sensitive to the change in the backup ratio when only the pin support is restrained. The uneven distribution trend of cracked tooth contact pressure depends on the nonpenetrating crack type.