Study on Bending Fatigue Strength of Helical Gears : 3rd Report, Mechanism of Bending Fatigue Breakage

In this paper, the relations between the stress distributions on root fillet and the crack initiation and propagation in helical gear, thin rim gear teeth and cantilever plate were examined and the mechanism of bending fatigue breakage of helical gears was investigated. It was found that a crack of helical gear teeth occurs at the position of maximum root stress on the tensile fillet and the directions of crack propagation differ in each normal section. Furthermore the existing testing methods of bending strength for helical gear teeth were compared on the basis of the experimental results.