Vehicle optimum maintenance period under availability objective

In order to accurately decide vehicle optimum maintenance period under availability objective, the renewal function of renewal theory and optimum concept was analyzed, two mathematical models of optimum maintenance period were established, and their optimum objectives were the greatest availability and the shortest total unworkable time in unit time respectively.The parameter estimate and hypothesis testing of failure distribution were made, utilizing the operating failure and cost data collected from 78 given type commercial vehicles in several years.It is affirmed that vehicle operating failures obey Weibull distribution when the confidence level is greater than 0.95, and the optimum maintenance period solved by the established models is 15 617 km.The result of verifying group test indicates that vehicle availability gets its greatest value 0.955 1 when class Ⅱ maintenance period is 15 122 km; the relative error between the model's solution and the optimum period mileage of the test is only 3.27%, so the model's solution is accurate, reliable, and conforms to reality.Combining the result of model research with the result of vehicle test, the optimum class Ⅱ maintenance period under the meaning of greatest availability is 15 000 km.