Wearout

Wearout （消耗品）

Wearout items can be modeled in TEMPO by using variance-to-mean ratios less than 1. A random failure item with constant demand rate has a variance-to-mean ratio of 1 (Poisson demand). A wearout item with constant times between failure has a variance-to-mean ratio of 0.  We would suggest that most wearout items be given an intermediate value such as 0.5 for variance-to-mean ratio.