Use of nested renewals to model availability under opportunistic maintenance policies

The idea of nested renewal processes is used to define availability models for equipment subjected to age-based opportunistic preventive maintenance policies. The description of equipment behavior in terms of sample paths that do not result in opportunistic replacement leads to compact models of system availability. The models are expressed in terms of the policy parameters. Core model analyses are explained and example numerical results are provided. Reasonable conclusions appear to be that the nested renewal concept provides an effective means of representing availability behavior under policies that have not previously been successfully modeled and that the models provide a vehicle for further study and optimization of opportunistic preventive maintenance plans.