Specification of the DRM and the time for preventive maintenance for an aging resource

An attempt to capture resource aging and specify when to do preventive maintenance (PM) is presented in this paper. A composite measure termed the DRM (Deteriorating Response Measure) is defined. It is based on the analysis of the deteriorating speed of the resource against time and load. This speed is characterized as follows: 1) It decays with increased load. 2) It does not increase again when the load decreases. This indicates ´loss of elasticity´. The DRM is mathematically formulated based on a queueing system model. Specifying when to do preventive maintenance depends on the decision maker´s perspective of the manifestation of aging. The article tries to formalize this dependence. Three degrading performance metrics are defined for a DRM: 1) decaying restored speed value; 2) increasing speed offset ratio (plasticity index); and 3) increasing operation interval length offset ratio. These metrics can be used separately or aggregately.