Comparative research on delay-time-based models in case of non-homogeneous defect arrival rate

To deal with problems of how to use the theory of delay time to revise the basic Preventive Maintenance (PM) model and to optimize PM interval of equipment in the case of the Non-Homogeneous Poisson Process (NHPP) of defect arrivals and non-negligible failure downtime. Firstly, the concept of delay time and its maintenance theory were introduced. Then, a basic PM model for complex system was established. Secondly, amendatory model I and model II were established, which was based on the case that failure downtime was short compared to inspection cycle, and the case of NHPP of defect arrivals. Finally, a case study was provided to compare the differences of inspection cycle in basic PM model and the revised PM models. The revised downtime model was a more precise model with which to determine the optimal inspection interval.