EFFECT OF SLIP RATIO ON ROLLING CONTACT FATIGUE OF BEARING STEEL ROLLERS LUBRICATED WITH TRACTION OIL

摘要

Using a two-roller testing machine, the rolling contact fatigue life of bearing steel rollers with mirror-like smooth surfaces was examined. A pair of rollers were driven under nearly pure rolling (slip ratio s≈0%) or rolling with sliding conditions of s=-0.5% ～ -3.2%, and a maximum Hertzian stress in the range of P_H=3.2GPa～4.2GPa was applied in point contact condition. A synthetic traction oil with viscosity grade of ISO VG 32 was used as the lubricant. As a result of experiments, the bearing steel rollers lubricated with traction oil showed a fairly high durability in pure rolling conditions, while the fatigue life decreased remarkably with a slight increase in slip ratio. Based on the numerical results of thermal EHL analysis, the authors discuss the mechanism which causes such a difference in the fatigue life.