The optimal maintenance policy proportion and used period for the repairable warranty equipment using fixed-failure-rate-reduction method

In this study, we define the time interval [0, w) as warranty period and the time interval [w, w+m(w/n+1)] as the outside of warranty period. The manufacturers provide the customer with preventive maintenance as well as repair policy for free when the equipment was used in the warranty period; consumers need to pay for the same degree of preventive maintenance when the equipment was used in the outside of warranty period. In this research, the method of preventive maintenance is the fixed failure rate reduction. After each implementation of preventive maintenance which reduced the failure rate, there is the level of imperfect preventive maintenance of limited proportion. The proportion of maintenance was divided into a fixed maintenance proportion. We obtained the optimal number of maintenance, the optimal proportion of maintenance degree, the cost of preventive maintenance for fixed maintenance proportion model. We also used the decision-making model to find the optimal number of preventive maintenance, the preventive maintenance cost for fixed maintenance proportion model, when the equipment is used in the outside of the warranty period. In the final, numerical and sensitivity analysis verify the results.