Evaluation Of Maintenance Quality And Optimization Of Overhaul Time Of Repairable Systems

The engineering system is usually repairable.During its using time,the repairable system is constantly affected by factors such as manufacturing quality,operating conditions and environments,maintenance activities,and degradations,the number of failures increase with the age of system.The failure process of a repairable system is often described by the failure point process.Commonly used model for a repairable system is power law model.The mean number of accumulated failures as a function of system age can be used to describe the failure process of repairable system.The differential of the mean cumulative function is the system's failure strength function.Repairable system usually experience periodic different levels of maintenance(ie preventive maintenance)and overhaul.Maintenance leads to local,limited improvements in the failure process(called microscopic trends).Although the maintenance could improve the failure process,it cannot fundamentally reverse the macro-deterioration trend of the system.In this way,overhauls or replacements become necessary.How to make maintenance decisions of system based on field failure data is a matter of concernThis paper focuses on the application of the model.First,we introduces the concept and model of repairable system failure point process,introduces the method of parameter estimation,and discusses two important topics with field data.One is to detennine the optimal time for overhaul,the other is to evaluate the quality of maintenance.This method can provide the basis for the company's overhaul decision-making and maintenance quality improvement.Based on the power law model,a weight function proportional to the normal density function is used to reflect the importance of failure data at different times,a heuristic method is used to determine the value,and finally a weighted least squares method is used to the data was fitted to a power law model,and the results obtained by the least-squares method and the weighted least-squares method were compared to evaluate the maintenance effect of the vehicle's secondary maintenance.With true examples,the results obtained by the weighted and unweighted least square method are compared.The results show that for the maintenance quality evaluation,the weighted least square method is better than the ordinary least squares method.Based on the cost rate model,the optimal overhaul time of the repairable system is obtained by processing the field data.This method can provide a basis for improving the quality of maintenance.