Fault Tree Importance Analysis Method And Its Applications

Describing the importance measure of the contribution to the top event when the basic event occurs is an important indicator in the quantitative analysis of the fault tree.Importance measure can be used not only to discover vulnerable components of the system,but also to improve,optimize and distribute the reliability of the system and guide the operation,maintenance and diagnosis of the system.At present,in the research on the importance measure of each fault tree(conventional fault tree,T-S fault tree,Dugan dynamic fault tree and T-S dynamic fault tree),it mainly focuses on the importance measure of conventional fault tree.The importance measure of other three fault tree are either incomplete or blank.At the same time,the importance measure of fault trees are all based on a random model.When the numbers of samples are limited,there is a problem that the reliability data of the components cannot be obtained accurately.To this end,the conventional fault tree importance measure is extended to T-S fault tree,Dugan dynamic fault tree and T-S dynamic fault tree.Furthermore,the interval convex model and fault tree importance measure analysis methods are combined to propose the importance measures analysis of each fault tree method.Further,to verify the proposed method and analyze the importance measures of different systems.First,there is a problem that the failure probability of components cannot be accurately obtained for the conventional fault tree importance measure analysis method.Fussell-Vesely importance measure,differential importance measure,risk achievement worth,risk reduction worth,upgrading function and integrated importance measure of the conventional fault tree based on interval convex model are proposed.By comparing with the importance measures analysis method of conventional fault tree based on stochastic model,the feasibility of the proposed method is verified.Importance measures analysis of conventional fault tree is carried out for the landing gear system of the carrier aircraft.Secondly,in order to solve the problem of any failure behavior characterization and importance measure of static systems,Fussell-Vesely importance measure,differential importance measure,risk achievement worth,risk reduction worth,upgrading function and integrated importance measure of T-S fault tree are proposed.By comparing with the conventional fault tree importance measures analysis method,the feasibility of the proposed method is verified.Importance measures analysis of T-S fault tree is carried out for the small chamber cover system of chamber cover mechanism system.Then,in order to solve the problem of characterizing dynamic system failure behavior and its importance measure,criticality importance,Fussell-Vesely importance measure,differential importance measure,risk achievement worth,risk reduction worth,upgrading function and integrated importance measure of Dugan dynamic fault tree are proposed.By comparing with the conventional fault tree importance measures analysis method,the feasibility of the proposed method is verified.Importance measures analysis of Dugan dynamic fault tree is carried out for the hydraulic system and the heat exchanger system.Finally,in order to solve the problem of any static and dynamic failure behavior characterization and its importance measure and reliability data of components cannot be obtained accurately,Fussell-Vesely importance measure,differential importance measure,risk achievement worth,risk reduction worth,upgrading function and integrated importance measure of T-S dynamic fault tree based on interval convex model are proposed.By comparing with the conventional fault tree and Dugan dynamic fault tree importance measures analysis method,the feasibility of the proposed method is verified.Importance measures analysis of T-S dynamic fault tree is carried out for the measurement system and pneumatic braking system.