Average Failure Rate and Its Applications of Preventive Replacement Policies

When a mission arrives at a random time and lasts for an interval, it becomes an important constraint to plan preventive replacement policies, as the unit should provide reliability and no maintenance can be done during the mission interval. From this viewpoint, this chapter firstly gives a definition of an average failure rate, which is based on the conditional failure probability and the mean time to failure, given that the unit is still survival at the mission arrival time. Next, age replacement models are discussed analytically to show that how the average failure rate function appears in the models. In addition, periodic replacement models with minimal repairs are discussed in similar ways. Numerical examples are given when the mission arrival time follows a gamma distribution and the failure time of the unit has a Weibull distribution.