Physics-based prognostics of rolling-element bearings: The equivalent damaged volume algorithm

This paper introduces a novel parameter related to bearing degradation, namely the Equivalent Damaged Volume (EDV). An algorithm capable of extracting EDV values from experimental data is detailed. To this end, the proposed technique relies on the comparison between experimental and numerical signals. The former are the result of an extensive campaign of run-to-failure tests performed on a dedicated test rig. On the other hand, the latter are obtained by means of a lumped parameter model that accounts for the angular extent and the depth of either localized or extended defects. The potential of this novel technique is demonstrated by exploiting the values obtained by the algorithm as inputs for a prognostic model. In particular, the developed model aims at predicting the time until a certain threshold on the equivalent damaged volume is crossed, regardless of the applied load and the shaft rotation speed. The advantages and downsides introduced by the proposed approach are thoroughly discussed by providing examples based on real degradation histories.