Abstract
The rolling contact fatigue (RCF) model is commonly used to predict the contact fatigue life when the sliding is insignificant in contact surfaces. However, many studies reveal that the sliding, compared to the rolling state, can lead to a considerable reduction of the fatigue life and an excessive increase of the pitting area, which result from the microscopic stress cycle growth caused by the sliding of the asperity contact. This suggests that fatigue life in the rolling-sliding condition can be overestimated based only on the RCF model. The rubbing surfaces of spiral bevel gears are subject to typical rolling-sliding motion. This paper aims to study the mechanism of the micro stress cycle along the meshing path and provide a reasonable method for predicting the fatigue life in spiral bevel gears. The microscopic stress cycle equation is derived with the consideration of gear meshing parameters. The combination of the RCF model and asperity stress cycle is developed to calculate the fatigue life in spiral bevel gears. We find that the contact fatigue life decreases significantly compared with that obtained from the RCF model. There is strong evidence that the microscopic stress cycle is remarkably increased by the rolling-sliding motion of the asperity contact, which is consistent with the experimental data in previous literature. In addition, the fatigue life under different assembling misalignments are investigated and the results demonstrate the important role of misalignments on fatigue life.
Highlights
Surface pitting is a major form of primary failure for mechanical components, such as roller element bearings, wheel rails, and various types of gears
Note that the present study focuses on the comparative evaluation of fatigue life under assembling misalignments with the consideration of the stress cycles of asperity contact, and the material parameters are considered irrelevant in this study
The grinding surface roughness measured by the optical profiler is fitted by sinusoid-like profiles to derive the equation for asperity stress cycle counting, with the consideration of rolling-sliding contact and contact geometry in spiral bevel gears
Summary
Surface pitting is a major form of primary failure for mechanical components, such as roller element bearings, wheel rails, and various types of gears. When the components periodically suffer high contact stresses, cracks may initiate near the surface and propagate towards the surface to form a surface spall or pit, the components are properly assembled, loaded, and lubricated [1]. Rolling contact fatigue (RCF) theories have been widely used in roller element bearings, rail-wheel contacts, and spur gears [1], when the sliding velocity between two surfaces is insignificant. A considerable sliding can be found in the cross-axis gear transmission, especially for spiral bevel and hypoid gears. It is evident that the engineering machined surface is not ideally smooth, which may complicate the surface contact.
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