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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. [ABSTRACT FROM AUTHOR]

Electrodynamic bearings exploit repulsive forces due to eddy currents to produce positive stiffness by passive means. Such a feature would make this type of bearing a viable alternative to active and permanent magnet bearings. Although electrodynamic bearings do not violate Earnshaw’s theorem, the open issue remains the stabilization system that is needed to make the rotating body stable, due to the low rotational speeds. Stabilizing solutions proposed in the literature are partially effective and not totally convincing. This limits real industrial applications.The present paper proposes a combination of electrodynamic and active magnetic bearings. At low speed the active part behaves as a conventional active magnetic bearing, while at high speed it provides damping. The readiness of the proposed solution is demonstrated by experimental results obtained using a dedicate test rig. [ABSTRACT FROM AUTHOR]

Hydrodynamic Rolling Hybrid Bearing (HRHB) is dual bearings combination where a hydrodynamic bearing and a rolling bearing with a clearance are assembled coaxially and side by side. The clearance of rolling bearing is a significant parameter for HRHBs. This paper aims to investigate the vibration characteristics of rotor supported by HRHBs to determine the permissible value of clearance of rolling bearing. The maximum dynamic eccentricity ratio is proposed based on the noninterference conditions of rolling bearing and rotor. Then an evaluation method of the maximum dynamic eccentricity ratio is developed. This paper also investigates the effects of the operation parameters such as rotational speed, perturbed force and structure parameters such as bearing span, diameter of rotor, and overhanging length on the maximum dynamic eccentricity ratio. The maximum dynamic eccentricity ratio on the front rolling bearing section is obviously larger than that on the back rolling bearing section. Moreover, the maximum dynamic eccentricity ratio reduces with the increase of the rotational speed and diameter of rotor, but increases with the augmentation of the perturbed force, bearing span, and overhanging length. When the maximum dynamic eccentricity does not go beyond the bound of the radius of the rolling bearing’s clearance circle, the rolling bearing does not interfere with the rotor. The paper provides theoretical basis for design of the minimum value of the rolling bearing’s clearance in HRHBs. [ABSTRACT FROM PUBLISHER]