Availability and reliability of system with dependent components and time-varying failure and repair rates
Conclusions-System reliability depends not only on the reliabilities of components in the system but also on their interactions, viz., the dependencies among them. Generally, in a system, not only s-independent failures but also s-dependent failures among components can occur; thus there are many studies where the s-dependencies among components are taken into account in system reliability & availability analysis, but in which the failure & repair rates were assumed constant. Whereas, from a practical viewpoint, the constant failure rate assumption for components has been, and is repeatedly challenged by knowledgeable reliability practitioners. Therefore, there are other studies which handled the problem of time-varying failure rates, among which all concerned repairable systems did not involve s-dependent failures. In most cases, however, to combine s-dependent failures and time-varying failure & repair rates in system reliability & availability analysis is the most appropriate for real systems. But it is very difficult to obtain the analytic solution and, in most cases, the closed-form solution for system reliability & availability does not exist, so that numerical or simulation methods must be used. This paper studies one kind of systems that endure environmental shocks, and where one or more components can fail simultaneously due to a cumulative shock-damage process. An approach for reliability & availability analysis of such kind of repairable systems is presented, where failure & repair rates of components can be varying with time. One type of special vehicles with such mechanical systems illustrates system reliability & availability solutions.
system reliability time-varying failure rate repairable system dependent failure markov chain system availability