Application of a rolling bearing life model with surface and subsurface survival to hybrid bearing cases

A previously published rolling bearing life model that separates the surface and subsurface survival is briefly summarised. The model is applied to the case of hybrid bearings and discussed with regard to a selected set of application examples. Ball hybrid bearings under equal load condition show 12% higher Hertzian stress than all-steel bearings. However, field applications, typically under light load, poor lubrication and contamination, show that hybrid bearings have longer fatigue life than all-steel bearings. Traditional all-steel life models fail to predict this type of behaviour. In this paper, it is shown that hybrid bearing unique fatigue performance can be described using the idea of separation of surface and subsurface survival. The model applies the classical rolling contact fatigue in the subsurface region of the rolling contact while a newly developed tribologically dependent surface degradation models is used for the ceramic-steel raceway interface. It is found that the particular fatigue resistance of the ceramic-steel interface of the hybrid bearing raceway can, in most cases, compensate for the additional stress present in the subsurface region of the contact