A timeliness-based optimal inspection interval associated with the delay time model

The delay-time concept has been widely applied to prevent failure of an item with a deteriorating failure mode by implementing a periodic inspection scheme. The inspection interval is usually optimized based on a cost rate model, and the optimal solution is sensitive to the cost parameters so that the cost model can be inappropriate for the situation where the cost parameters are hard to be accurately determined. In this paper, an inspection timeliness measure is defined, which is the expected time between the last inspection and the item failure. The measure reflects the timeliness of inspections and is a function of inspection interval. There exists an optimal inspection interval where the timeliness measure achieves its minimum. This timeliness-based optimal inspection interval can be obtained using Monte Carlo simulation approach. The proposed approach is illustrated by an example.