No abstract

In the course of the electrification of powertrains, rolling element bearings are increasingly subject to electrical damage. In contrast to mechanically generated pittings, voltage-induced surface damage is a continuous process. Though several approaches for the description of the damage state of a bearing are known, a generally accepted quantification for the bearing damage has not been established yet. This paper investigates surface properties, which can be used as a metric damage scale for the quantification of the electric bearing damage progression. For this purpose, the requirements for suitable surface properties are defined. Afterwards, thrust ball bearings are installed on a test rig, with constantly loaded mechanically and periodically damaged electrically in multiple phases. After each phase, the bearings are disassembled, the bearing surfaces are graded and measured for 45 different standardized surface properties. These properties are evaluated with the defined requirements. For the ones meeting the requirements, critical levels are presented, which allow for a quantified distinction between grey frosting and corrugation surfaces. These values are compared with measurements presented in the literature showing that the identified surface properties are suitable for the quantification of electrical bearing damages.

This work presents an investigation on the influence of pitting in EHL rolling contact. The pit-ting geometry comes as an extension on the architecture for multi-physical numerical calculations ofrolling element bearing contacts based on OpenFOAM. The model utilized is built according to thestate-of-the-art for fluid-solid interaction and electro-quasi-static fields. In this framework, the con-tact is reduced to be two dimensional in order to reduce the computing costs needed. The changesin the electric properties, that are caused by pittings, are measured using the electric capacitanceof the contact and put in perspective to the EHL contacts geometry. The investigation deliversan evaluation on how surface degradation, in both the pitting width w and pitting depth d ofthe contact, affects the electric properties. It can be seen that the electrical capacitance changeof different initial geometries has different gradients; both in terms of absolute pitting geometrieslike pitting width w and pitting depth d and relative compared to the reduced radius w/Rr.