Study On Maitenance Policy Under Cumulative Repair-cost Limit For Deteriorating Systems Subject To Shocks

With the complex modern equipment systems becoming more and more intellectualized,automated and integrated,their structure is also becoming an interrelated multi-component system which is more mechanical,electrical,hydraulic,and most systems' operating environment becomes increasingly complex,resulting in the increasing difficulty of maintaining such a system.Such systems deteriorate not only with their interior own age and wear,but also suffer from the external random environmental shock impact,and the failure shock impact between internal components,called such a system "A deteriorating system subject to shocks".Avoiding the failure of such systems is very important because frequent failures will not only produce high maintenance and replacement costs,or even lead to serious safety hazards or accidents.Therefore,how to model more effectively and how to select a more appropriate maintenance policy in order to reduce maintenance costs and better measure the maintenance value of components and system have become an important issue in the field of Reliability and Maintenance Engineering.The content of this dissertation is as below:Firstly,for a single component deteriorating system subject to shocks,considering comprehensively the impact of external shocks and internal degradation on the failure rate of the system,a failure rate increasing shock model for the system has been established.And external shocks have been divided into non-serious and serious shock according to their impact on the system,the probability of their occurrence changes with the deteriorating state of system with the introduction of a related �Probability Adjustment Factor�.A two-dimensional(T,L)periodical maintenance policy based on cumulative repair-cost limit has been proposed,which means that a maintenance or replacement action will be taken to the system every T period or when the cumulative repair-cost of system surpasses the threshold value L.Under this policy,the long-term expected cost rate of the system has been established,including minimal repair and replacement cost,and the optimal maintenance(replacement)period and optimal cumulative repair-cost threshold can be obtained by minimizing the function of long-term expected cost rate of the system.Through the analysis of examples,we verified the validity of the model,and did a sensitivity analysis for parameters.Secondly,based on previous research,for a two-unit deteriorating system subject to shocks,considering comprehensively the impact of internal own degradation and failure shocks impact between units on the failure rate of unit,under the cumulative repair-cost limit L,a two-dimensional(n,T)replacement policy based on the number of minimal repair and placement period has been proposed.Through minimizing the function of long-term expected cost rate of the whole system,the optimal number of minimal repair and replacement period can be obtained.Through the analysis of examples,we verified the validity of the model,and did a sensitivity analysis for parameters.And through a comparative analysis,the conclusion that the result of a two-dimensional replacement policy is better than the one of a one-dimensional T or n replacement policy can be got.Therefore,this dissertation has some guiding significance and reference value in a practical maintenance in companies.