Predicting failure mode by trouble prediction table and evaluation index for reliability and safety

Abstract

As one of the typical methods for the preventive analysis of troubles, failure mode and effects analysis (FMEA) is frequently used in many situations. The FMEA method is used for examining proposed measures and preventing troubles by predicting failure modes that can occur while using a product and a system. Additionally, an effects analysis based on both occurrence frequencies and the effects of failure modes is performed. However, troubles may occur in markets if possible failure modes were imperfectly predicted by the FMEA. Furthermore, it is often difficult to quantify the occurrence frequency of a trouble in many cases if a new product is developed without sufficient knowledge. In this study, we propose a novel trouble prediction table to identify all important failure modes of troubles that may occur in markets. Moreover, a novel evaluation index of the design completeness of reliability or safety aspects is proposed as a substitute of occurrence frequencies when the values of the occurrence frequency are not quantifiable. In order to evaluate the effectiveness of the trouble prediction table, the numbers of estimated failure modes in an actual new product obtained by using a conventional method by experts and those obtained by the proposed method by beginners were compared. The numbers obtained by using the proposed index is also compared with those obtained by using a conventional method. The validity of the methods is shown by a case study of a product.