SYSTEM RELIABILITY ANALYSIS WITH DEPENDENT COMPONENT FAILURES DURING EARLY DESIGN STAGE

It is desirable to predict product reliability accurately in the early design stage, but the lack of information usually leads to the use of independent component failure assumption. This assumption makes the system reliability prediction much easier, but may produce large errors since component failures are usually dependent after the components are put into use within a mechanical system. The bound of the system reliability can be estimated, but is usually wide. This wide reliability bound makes it difficult to make decisions, such as evaluating and selecting design concepts, during the early design stage. This work develops a new methodology that makes the system reliability prediction more accurate by considering the dependence between component failures. The following situation is addressed: the reliability of each component and the distribution of its load are known, but the dependence between component failures is unknown. With a physics-based approach, an optimization model is established so that a narrow bound of the system reliability can be generated. Two examples demonstrate that the proposed methodology produces a narrower system reliability bound than the traditional reliability bound, thereby better assisting decision making during the early design stage.