Abstract: The fatigue failure behavior of new type hollow gear shaft in bench test was analyzed by means of optical microscope, microhardness tester and scanning electron microscope. The results show that the transition arc position is the failure position of the hollow gear shaft. The chemical composition of part material, austenite grain size and non-metallic inclusions all meet the design requirements, while the effective carburized layer depth just approaches the lower limit of the design requirements. The calculation results show that the radius of the transition arc of the hollow gear shaft should be greater than 3.16 mm, and during the carburizing the smaller transition arc radius is prone to the "sharp angle effect", resulting in coarse carbides and stress concentration, which may be one of the reasons for the low fatigue life. The simulation results of CAE software show that there is obvious stress concentration at the transition arc, and the maximum stress on the surface exceeds allowable stress of the part, which may be another reason for failure of the hollow gear shaft. The maximum stress on surface of the part increases with the increase of hollow size. The maximum size of the hollow should be less than Ø17.1 mm.

Key words: hollow gear shaft, carburizing, sharp angle effect, software simulation