Applying Finite Element Analysis to Determine the Subsurface Stress and Temperature Gradient in Highly Loaded Bearing Contacts

The stress and temperature gradient in the classic subsurface stress zone for rolling contact fatigue is determined using finite element analysis. The solution applies boundary conditions based on experimental life testing of 208 size ball bearings. Two thrust loads are considered to produce elastic Hertzian contact stress values of 3.10 and 3.58 GPa. X-ray diffraction data were used to superimpose the residual stress for a case carburized M50 NiL as compared to through hardened M50 material. An updated version of the Computer Optimized Ball and Roller Bearing Analysis, or COBRA, bearing analytical code was used to determine the heat load from friction and oil churning loss in the bearings. The effect of hybrid bearings with metal rings and silicon nitride rolling elements versus all metal bearings is considered in the thermal solution and is notable. Results of the stress and temperature gradient found in the bearings are used to provide a qualitative assessment of the microstructural damage found in experimental bearing testing. The results provide a foundation for a more comprehensive bearing rolling contact fatigue life model.