Age Replacement Policy For Heterogeneous Items With Competing Failure Modes

In practice,due to the structural complexity of the items and the instability of the operating environment,most of the produced items are heterogeneous,and this heterogeneity cannot be ignored.In the paper,the maintenance of heterogeneous items under different failure modes is studied.Assuming that heterogeneous items are repairable and the number of repairs is limited,in order to avoid the catastrophic failure,this paper considers adding an additional screening before the predetermined age to increase the probability of preventive replacement of items at the predetermined age.Firstly,it is considered that the items have one sudden failure mode,it is assumed that the failure rate of weak items is not smaller than that of strong items,and the item is minimal repaired when sudden failure occurs.The item is replaced when the number of minimal repairs exceeds the upper limit,or the number of minimal repairs exceeds the screening threshold at the screening time,or the predetermined age is reached,whichever occurs first.This paper performs some probabilistic analysis of the proposed age replacement policy with repair number limit and additional screening,and demonstrat that the adding an additional screening is necessary,which is superior to the age replacement policy with repair number limit.In addition,the effectiveness of the proposed policy is verified in terms of cost and the numerical example.Secondly,the items with competing failure modes are considered.It is assumed that the degradation failure and sudden failure of the subpopulation are independent,the degradation process of the subpopulation is modeled by a non-homogeneous gamma process,and the item can be minimal repairs for a limited number when sudden failure occurs.The items with poor performance are screened out according to the number of minimal repairs and the degradation level at the screening time.In this paper,the influence of the screening threshold on the probability of preventive replacement for homogeneous items is discussed by using the mothod of stochastic orders,and the probabilities of preventive replacement of strong subpopulation and weak subpopulation is compared.Finally,it is proved that the policy with additional screening is superior to that without additional screening under competing failure modes,and the numerical example is given.