A new method for FMECA using expert system and fuzzy theory

Failure Mode Effects and Criticality Analysis (FMECA) is one of most widely used methods in modern engineering system to investigate potential failure modes and its severity upon the system. Although there are several FMECA standards, the most popular one is MIL-STD-1629A from U.S. department of defense. While carrying out FMECA, experts evaluate criticality and severity of each failure mode and visualize the risk level matrix putting those indices to column and row variable respectively. This kind of subjective evaluation inevitably brings ambiguousness on the result. In order to handle the ambiguousness, this paper proposes a new FMECA procedure using Proposed Structural Importance (PSI) and fuzzy theory. Severity is evaluated by structural importance called PSI using minimal cut set, while criticality is determined by failure rate. Finally, the risk level is compounded of these indices by fuzzy expert system in order to resolve the ambiguousness of traditional methods.