Reliability And Risk Assessment Of Machining Center Based On The Failure Rate Correlation

Machining center is a kind of numerical control equipment with a variety oftechniques, complex structure,centralized process and composite technology,and thereliability of the whole machine system was determined by the inherent reliabilityand the fault correlation of each subsystem.The traditional reliability and riskevaluation of subsystem based on actual fault test data ignored the fault correlation.Itbrings certain errors to the system reliability and the failure risk assessment,andseriously affect the work of reliability design, repair,reliability growth. Therefore,the research of reliability and the failure risk assessment based on fault correlationanalysis had important theoretical significance and practical value.This paper is supported by the National Natural Science Fund project,combined with the fault information of a series of domestic machining center,withthe help of directed graph theory to analyze fault correlation structure of themachining center subsystems.The Pagerank algorithm was introduced to calculatethe fault correlation effect of each subsystem. According to the fault correlationeffect and the total probability formula, calculated the inherent reliability model ofsubsystem and evaluate their inherent reliability.Finally, considering all kinds offault risk factors and fault correlation, use the Grey correlation degree-TOPSISmethod to evaluate the comprehensive failure risk of subsystem.The main contents were as follows:(1)Fault correlation analysis of machining center subsystem based on the faultgraph and Pagerank algorithmThe fault correlation of subsystem was abstracted as directed graph model,anddirected graph was transformed into matrix with the help of the concept of adjacencymatrix in graph theory.In fault directional graph,the failure correlation of eachsubsystem was divided into fault influence degree and fault influenced degree.Thenthe problem of fault influence degree was transformed into the problem ofcalculating node important degree in complex network.Using Pagerank algorithm,the adjacency matrix and Markov transfer probability matrix, calculated the faultinfluenced degree based on fault correlation.Then transposed adjacency matrix toobtain new probability transfer matrix,calculated the fault influence degree based onfault correlation. (2)Reliability modeling and assessment of machining center subsystem basedon total probability formulaFor the subsystem with high fault influenced degree, determined the optimaldistribution trend test by using the Minitab software,obtain the Weibull model ofcomprehensive reliability.With the help of the full probability formula,the inherentreliability model was derived from the relationship between composite reliability,inherent reliability, fault influence factor.The trapz function in the Matlab is called tointegral solution, and then got the point estimates of inherent MTBF of subsystem.(3) Failure risk evaluation of machining center subsystem based on the methodof grey correlation degree-TOPSISConsidering the failure correlation, fault repair time, the fault frequency andseverity of fault, fault risk comprehensive evaluation of machining center subsystemwas conducted by the method of grey correlation degree-TOPSIS, and it providedthe basis for equipment repair and maintenance strategy.Then formulated thecorresponding equipment maintenance and repair measures according to the failurerisk value of subsystem.