Reliability Analysis Of Diesel Engine Crank And Connecting Rod Mechanism Considering Failure Dependence

As the power source of the vehicle,the reliability level of the engine directly affects the car reliability.As a universal feature of mechanical system,failure dependency also exists in diesel engine system.If ignoring the failure dependent in system,the system reliability estimation will have large error.In this paper,the crank connecting rod mechanism of diesel engine is taken as the research object.The correlation between failure modes of parts and the correlation between parts in the system are considered.Based on the Copula function theory,the reliability analysis of the crank and connecting rod mechanism of diesel engine is carried out by using life as a variable to measure the correlation between parts.The main work of this paper is as follows:(1)Statistical analysis of diesel engine fault data.Firstly,the main sources of diesel engine reliability data and the characteristics data from different source are analyzed,then the reliability index of the diesel engine is introduced and the corresponding analysis chart is given.Finally,a statistical analysis of the maintenance data of a certain type of diesel engine is carried out?The probability distribution method and the correlation coefficient method are given for the life distribution function of parts,and the distribution of the life distribution of the piston is determined by the Weibull distribution under the the crack failure mode.(2)Selection of proper Copula model.After simply introducing the concept and nature of Copula function and its characteristics in the correlation analysis,the method of building Copula function is given.According to the defined life distribution function of the parts,a corresponding two element frequency histogram is made.The Copula function is initially selected according to the two element frequency histogram shape and the feature of Copula density function image,and the most suitable model is determined by calculating the squared Euclidean distance between the primary Copula model and the empirical Copula function.(3)Establishment of reliability calculation model for multi failure mode parts based on Copula function.Based on the stress strength interference analysis,combining the Copula function theory and the Sklar theorem,the reliability model of parts with multiple failure modes is derived.At the same time the working characteristic of the diesel engine is taken into account,the performance function is replaced by the life distribution function to calculate the failure probablity of each failure mode.Finally,a multi failure mode components reliability calculation model based on the Copula function is obtained,and the reliability of the piston is analized.(4)Reliability analysis of crank and connecting rod mechanism of diesel engine considering part failure correlation.Based on the model of part reliability calculation under failure mode dependence,the life distribution function of main parts of the mechanism is obtained,and it is used as the marginal distribution function of the joint distribution function of the mechanism.Finally,the reliability of crank and connecting rod mechanism is calculated based on the reliability model of series,parallel and series-parallel system,and then the validity of the model is verified.