Consideration of moving tooth load in gear crook propagation predictions

Robust gear designs consider not only crack initiation, but crack propagati on trajectories for a fail-safe design. In actual gear operation, the magni tude as well as the position of the force changes as the gear rotates throu gh the mesh. A study to determine the effect of moving gear tooth load on c rack propagation predictions was performed. Two-dimensional analysis of an involute spur gear and three-dimensional analysis of a spiral-bevel pinion gear using the finite element method and boundary element method were studi ed and compared to experiments. A modified theory for predicting gear crack propagation paths bused on the criteria of Erdogam and Sih [18] was invest igated. Crack simulation based on calculated stress intensity factors and m ixed mode crack angle prediction techniques rising a simple static analysis in which the tooth load was located at the highest point of single tooth c ontact was validated. For three-dimensional analysis, however, the analysis was valid only as long as the crack did not approach the contact region on the tooth.