Failure Cause Analysis—A Structural Approach

Abstract

The paper presents a methodology to analyze failure cause of a system using structural approach based on digraph and matrix method. Failure causality digraph models the failure cause considering contributing events and their interaction in terms of cause-effect relation, i.e., causality. Failure cause function (VPF − fc) is obtained from the permanent matrix, obtained from the digraph, which is characteristic of the failure cause. The procedure is useful, not only for the analysis, but also for identification, comparison, and evaluation of the failure cause. The coefficients of similarity and dissimilarity, and identification set based on these are also proposed. These are useful for comparison of two failure causes. In addition, failure cause index (Ifc) derived from VPF − fc is proposed which evaluates and ranks failure causes of the system. The method permits analysis, identification, and comparison at design as well as operating state of the system and provides the user directions for minimizing the failure causes leading to improvement of the system reliability. The procedure is developed using an example of weld defects.