Contact Fatigue Test And Prediction Of Carburized Gears Considering Surface Integrity

As a critical component of power transmissions,the gear plays an important role in system performance and reliability.Gear contact fatigue is one of typical gear failure modes.Compared with other failure modes,mechanism of contact fatigue failure is more complex,restricting the fatigue life and reliability of gear,and becomes one bottleneck of high-end equipments.It is affected by many factors,including surface morphology,residual stress and microhardness,which are important surface integrity parameters affecting gear contact fatigue.However,the relationship between surface integrity and gear contact fatigue is still unclear.The gear anti-fatigue design and manufacturing rely on engineering experience,limiting the enhancement of power density.To support gear anti-fatigue design,the relationship between surface integrity and gear contact fatigue should be studied.This work conducts gear contact fatigue test and theoretical study,and clarifies the correlation between surface integrity and contact fatigue.This study provides support for the anti-fatigue design and manufacturing of gears.The gear contact fatigue P-N curve and fatigue limit test under four typical gear surface integrity states are conducted.Formulae of gear contact fatigue performance considering surface integrity are proposed.Main contents are summarized as follows:(1)Gear surface integrity states based on different manufacturing processes are generated.Four typical surface integrity states of carburized gears with surface roughness Sa value of 0.2～1.6 μm,compressive residual stress of-300～-1250 MPa and surface hardness of 650～700 HV are obtained by carburizing grinding,shot peening,barrel finishing and barrel finishing after shot peening,which provide a support for the study on the effect of surface integrity on gear contact fatigue.(2)Tests on gear contact fatigue P-N curve and fatigue limit are conducted.The gear contact fatigue P-N curve and fatigue limit test method based on qualitative comparison and accelerated test method are proposed.Based on the gear contact fatigue test rig,the contact fatigue life under constant heavy load and gear contact fatigue limit under four surface integrity states of carburizing grinding,shot peening,barrel finishing and barrel finishing after shot peening are obtained.(3)Formulae of gear contact fatigue performance considering surface integrity are proposed.The correlation and contributions of each surface integrity component on contact fatigue are explored with a Pearson correlation coefficient analysis and a random forest algorithm.For both the gear contact fatigue life and fatigue limit,it is revealed that the most significant surface integrity components are surface hardness,maximum compressive residual stress and surface roughness.Formulae of gear contact fatigue life and fatigue limit considering surface integrity are then proposed.The test verification that the predicted fatigue life is within 1.5 times of the dispersion band,and the maximum relative errors of fatigue limit is 2.1%,which provided a quantitative formula reference for the gear anti-fatigue design.