Analysis On Mechanism And Modeling Of Composite Failure For Fuel Supply System Of Diesel Engine

In the previous studies about failure mechanism,it is often considered that the wear-out failure(degradation failure)and abrupt failure belong to the different fault types,and they are considered separately.However,in the practical operation of many products,these two types of failures are likely to occur at the same time,and there is a coupling or competition between them.The final result is not a separate degradation failure or abrupt failure,but composite failure(competing failure).In view of this,this thesis focuses on mechanism and modeling of composite failure for complex mechanical system,the diesel fuel supply system is studied.Specifically,the main research contents are as follows:(1)The reliability analysis of diesel fuel supply system based on key component conversion method is carried out.In this thesis,the reliability analysis of the system using the key component transformation method is proposed.By analyzing the failure modes,effects and criticality of the diesel fuel supply system,the key components of the fuel supply system,fuel injectors are obtained.The reliability evaluation of diesel fuel supply system is transformed into the reliability evaluation of injector.(2)A reliability analysis method for dealing with abrupt failure of injector based on average rank method is proposed.Aiming at the reliability modeling of the subsystems in the system,considering the truncation of the remaining components caused by the failure of any part in the system,the method of using the average rank method to revise the failure serial number is proposed.The problem of product reliability modeling with failure data and multiple censored data is solved.(3)A reliability analysis method for dealing with degradation failure of injector based on model selection using TOPSIS method is proposed.In order to solve the problem of subjective degradation path model selection in the process of degradation data analysis based on degradation path model,reliability analysis of degradation data based on model selection using TOPSIS method is proposed.By using the TOPSIS method to improve the existing degradation path modeling,the risk that the reliability assessment is wrong due to the inaccurate subjective hypothesis model is avoided,which solves the scientific problem of degeneration model uncertainty in the process of degradation data analysis.At the same time,the corresponding Matlab program is developed to realize the above method.(4)The reliability evaluation model of fuel injector based on competing failure is constructed.The competing failure model of the product is similar to the reliability model ofthe series system when the failure modes of abrupt failure and degradation failure are independent of each other.When the abrupt failure and the degradation failure are related,it is proposed to analyze the probability of the abrupt failure from the viewpoint of the degradation quantity,and the method for modeling the competing failure is obtained.Correspondingly,the parameter estimation method of the model is also given.