Cost minimization for periodic maintenance policy of a system subject to slow degradation

This paper considers a repairable system which undergoes preventive maintenance (PM) periodically and is minimally repaired at each failure. Mostpreventivemaintenancemodelsassumethat thesystemimprovesateachPMsothat thehazardrate isreducedtothatofanewsystemortosome specified level. In this paper, we consider the situation where each PM relieves stress temporarily and hence slows the rate of system degradation, whilethehazardrateof thesystemremainsmonotonicallyincreasing.Theoptimalnumberandperiodfor theperiodicPMthatminimizetheexpected cost rate per unit time over an infinite time span are obtained. We also consider the case when the minimal repair cost varies with time. Explicit solutions for the optimal periodic PM are given for the Weibull distribution case. q 2000 Published by Elsevier Science Ltd. All rights reserved.