Prognostics of rolling element bearings with the combination of paris law and reliability method

In this research, a combination of the physical model based on Paris law and probability method is proposed for remaining useful life prediction of rolling element bearings. Level crossing is used as a feature that represents a linear relationship with defect size. Considering this linear relationship and using Paris law, a new model has been developed for bearings that follow degradation pattern with two stages. In this pattern, a bearing starts working in the healthy condition. Then it starts slow degradation stage and finally it goes to fast degradation stage until it reaches to the failure threshold. Considering a normal distribution for transition point from the slow degradation to the fast degradation stage, the model proposed in this article presents a probability distribution for the remaining useful life at any working point in slow degradation stage. In addition, the model presents a good and accurate prediction results in the fast degradation stage. The bearing run-to-failure vibration condition monitoring record is used for investigating the purpose of this study.