| The analytical methods of traditional mechanical reliability have evolved from the reliability of electronic products,such as Reliability Block Diagram(RBD),Fault Tree Analysis(FTA),Failure Mode Impact & Crisis Analysis(FMECA),which are firstly applied to the electronic products.With the continuous development of science and technology,however,modern mechanical products are increasingly complicated,precise and intelligent,and often integrated with electronic control systems,hydraulic systems,etc.The traditional methods based on electronics can't meet the requirements of mechanical parts.On the other hand,most of the existing reliability theory of multi-state systems assume that the process of performance distributing is independent between the mechanical components.But in the practical engineering environment,the problem of performance coupling caused by the interaction between components is inevitable,which is incongruent with the above assumption.Under such a background,with the support of the National Natural Science Foundation of China,this paper has carried out a multi-state reliability analysis method of mechanical systems based on the units interaction.The main research contents are as follows:Firstly,the traditional process of the structural decomposition is complicated,and the decomposition result is not comprehensive.So,based on the characteristics of “Movement deciding Function” of the mechanical system,the "Function-Motion-Action"(FMA)decomposition theory is proposed to get the meta-action chain and meta-action units.The meta-action unit,as the research object of the multi-state reliability,is described by the multi-state judgment basis.The structural performance function which expresses the process of the performance transmit from the meta-action unit to the mechanical system is introduced with the common function types.The advantages of the FMA theory are discussed in the decomposition example of the turntable subsystem,which lays a foundation for the later chapters.Then,the evolution process of the multi-state meta-action unit is described by the non-homogeneous Markov model.On the meta-action chain,the interaction between the upstream and downstream among meta-action units is analyzed based on the internal structure of the meta-action unit.Then the dependency characteristic existing is built considering the function role parts and the sharing parts among the meta-action units.By introducing the state transition coefficient,the change of the state transition matrix is zhengused to characterize the strength of the dependence characteristic,and the method of getting the state transition coefficient is given.Based on above all,the calculation model that expresses the steady state probability of every meta-action unit considering the dependency characteristic is established.The meta-action unit decomposed by the turntable subsystem is used as an example to verify the applicability of the calculation model,which provides supporting for the multi-state reliability evaluation of the mechanical system.Finally,according to the steady state probability of the meta-action unit containing the dependency group,the Vector Universal Generation Function(VUGF)is proposed to characterize the multi-state and the corresponding probability distribution of the mechanical system,and the structure operators of the UGF are suitable to represent the structural performance function of the mechanical system.The different VUGF are discussed corresponding to the different types of dependent groups in the mechanical system.According to the performance degradation characteristics of the mechanical system,the performance threshold is set,and the reliability formulas of the mechanical system also are built.Compared with the multi-state reliability of mechanical systems without considering the dependence characteristics,it is found that there is a link between the reliability of different states of the mechanical system and the strength of the unit-dependent features. |
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