Modeling and experimental research on rough tooth surface contact fatigue calculation considering hardness gradient and residual stress

Surface integrity parameters such as surface topography, hardness gradient, and residual stress have significant impacts on contact fatigue of tooth surface. To meet the needs of efficient and stable contact fatigue calculations, efficient mixed lubrication calculations were achieved in this study by dividing the lubrication region and reconstructing the asperities. By considering the influence of the residual stress and hardness gradient on the tooth surface, a calculation model for gear contact fatigue was established and verified based on fatigue tests of gear contact. The results are as follows: (1) Due to the influence of rough surfaces, there were two high-stress peaks in the near-surface layer (6 μm) and sub-surface layer (245 μm) of the tooth surface, which corresponded to micro-pitting and pitting areas, respectively. (2) Ignoring the influence of various integrity parameters led to errors of several orders of magnitude in predicting the contact fatigue life of the tooth surface. (3) The fatigue failure area predicted by the model proposed in this paper was consistent with the experimental results, and the average error in the fatigue life was approximately 14.3%. The method proposed in this paper can effectively predict the contact fatigue life and dangerous areas of the tooth surface, with advantages of high computational efficiency and good stability, laying a foundation for research on tooth surface anti-fatigue design.