Background: Given that the device possibly suffers the abnormal condition before it finally reaches the critical failure threshold in the degradation process.
Methods: In this paper, an abnormal failure judgment method of the device is proposed based on the performance degradation data itself. In this method, the device degradation process is considered to be an independent incremental process by probabilistic approximation, and then according to Grubbs criterion, all of degradation quantity is divided as two population, and an abnormal failure occurs only if a new observed sample belongs to abnormal class, and conversely, and no abnormal failure occurs.
Results: The standard deviation values of all the degradation quantity can be then obtained by dealing with the performance degradation dates between adjacent moments, statistically. In addition, we still estimate the cumulative failure probability of the device, and consider the accumulated cost losses arising from the continuous degradation, and then the expected maintenance cost model is established.
Conclusion: Finally, a practical case on a certain type of Electric Motor Unit (EMU) brake pad thickness analysis shows that the method presented is quite effective and feasible.