Optimum preventive maintenance for the mean TFSF of a repairable system with imperfect switchover

In this paper we study the optimum preventive maintenance (PM) for the Mean Time to First System Failure (Mean TFSF) of a 2-unit cold standby redundant system with repair, post-repair and imperfect switchover by considering four models I, II,III and IV. In models I and III, the two units are identical while in models II and IV are dissimilar. We discuss models I and II under PM of type (a) while models III and IV are discussed under PM of type (b). The Laplace-Stietjes (LS) transform of the distribution of the TFSF and the Mean TFSF are derived. Further numerical calculations for each model to comparison among them and to illustrate the results are presented.