Reliability Evaluation Of Cylinder Liner Based On Gamma Process And Bayes Inference

Internal combustion engine is the main power engine in transport equipment and modern advanced warship,more attention and continuous financial support have been paid to it by government and national defense department.As one of the key components of internal combustion engines,the reliability of cylinder liner usually affects greatly the whole performance and service reliability of internal combustion engines.In order to meet the demands of key components reliability evaluation of engine when engine is developing towards high performance and high service reliability.This thesis has carried out work on establishing cylinder liner degradation model,the Bayes inference of degradation model of the cylinder liner,reliability and remaining life evaluation of cylinder liner.And provided a reference for the reliability evaluation of high performance engines.The main contents are listed as follows:(1)Based on the degradation principle of the cylinder liner,the factors affecting the degradation of the cylinder liner are discussed.The empirical evaluation method is used to study the average wear and standard deviation of the cylinder liner,as well as the relationship between wear and the current degradation time and state.The results show that the average wear of the cylinder liner increases monotonically with the time,and the standard deviation increases initially,then decreases,and the degradation process of the cylinder liner is related to both of the current time and the state of wear.(2)Based on the degradation process characteristics of the cylinder liner,the transformed gamma process and the state dependent model are used to model the degradation process.The results show that compared with the state dependent model,the transformed gamma process has higher fitting accuracy for the observed data,which is an efficient method for modeling degradation process of cylinder liner.(3)Based on the sample prior information of cylinder liner degradation process,the Bayes method is used to implement the posterior distribution inference of the transformed gamma process model.As well as,the Markov Chain Monte Carlo(MCMC)method is used to calculate the posterior model parameters and the HDI(highest posterior density credible interval).The results show that the prior information on the cylinder liner degradation can be transformed into the prior information of the state and time functions,the Bayes inference based on prior information can efficiently implement the posterior distribution of the degradation model,which can provide more accurate estimations.(4)For the purpose of the reliability evaluation of the cylinder liner under the transformed gamma process,the Bayes inference and general entropy loss function are used to implement the reliability evaluation of the cylinder liner.Meanwhile,the dependence of wear increment on the current degradation time and state is studied.The results show that the transformed gamma process under the Bayes evaluation is superior to state dependent model and the transformed gamma process without prior information.The Bayes evaluation under the general entropy loss function is smaller than the Bayes posterior evaluation.In the future time interval,the wear increment of cylinder liner degradation has a strong dependence on the current wear and time,which is manifested as the influence of the prior information of the model parameters on the Bayes posterior evaluation results.The more prior information,the closer to the real observation value.