Chapter 8 - Methods of Modeling

Abstract

This chapter focuses on methods of modeling reliability prediction. It gives a detailed description of these methods and includes, block diagrams and repairable systems, repairable systems (revealed failures), repairable systems (unrevealed failures) and systems with cold standby units and repair among others. A general approach to analyze reliability block diagrams involves, establishing failure criteria, creating a reliability block diagram, failure mode analysis, calculation of system reliability and reliability allocation. Common cause failures (CCF) frequently dominate the unreliability of redundant systems by virtue of defeating the random coincident failure features, which is the essence of redundancy. A formula for calculation the failure rate of the redundant element is given. Common mode failures (CMF) refers to coincident failures on the same mode, in other words failures that have an identical appearance or effect, while on the other hand, the term CCF implies that the failures have the same underlying cause. It is possible for two CMFs not to have a common cause and for two CCFs, not to manifest themselves in the same mode.