Motion Functional Reliability Modeling Methods And Applications For Typical Mechanisms Of Aircraft

Motion mechanisms are widely used in aircrafts and their reliability directly influence the performance and safety of the aircrafts.Many reliability problems of motion mechanisms were exposed during the design process of the aircrafts in our country,which seriously affected the design process.The traditional reliability evaluation of the motion mechanisms mainly relies on fail data and performance degradation data;however,these methods are quite limited in the mechanism reliability analysis.Therefore,it is quite urgent to research the motion functional reliability evaluation system and modeling method according to the failure characteristics of mechanisms.This paper focuses on three aspects and it is divided into seven chapters: In chapter II failure characteristics of mechanism are studied and motion functional reliability system considering component damage is proposed.From chapter III to chapter V,reliability modeling methods of three typical mechanisms(including slat with rack and pinion,retracting mechanism composed with linkages and lock mechanisms)are studied,and applications are formed.In chapter VI,a general synchronization reliability evaluation method is proposed to solve the synchronization reliability of the mechanisms.Main contents of this paper are as follows:(1)The failure modes,failure reasons and failure characteristics of mechanisms are studied at macroscopic level.Firstly,failure of mechanisms is divided into two types,including components failure and motion function failure;Secondly,it is concluded that the uncertainty of influence factors and accumulation of damage are the two fundamental failure reasons of mechanisms,and the effects of several random factors and main damage types for the mechanism failure are studied in detail;Thirdly,it is concluded that coupling effect and time-variety are the two main failure characteristics of mechanisms.(2)Aimed at the failure reasons and characteristics,a reliability evaluation system considering components damage is proposed.Firstly,qualitative analysis of the mechanisms' reliability is conducted to obtain the main failure modes,influence factors and damage types;then,focuses on the failure modes,the degradation model of the mechanism is established;after validating,the model can be used for reliability analysis.The evaluation system can reflect the failure modes,failure reasons and failure mechanisms of products essentially,which can provide substantive improvement advices.Besides,this reliability evaluation system can also be applied in mechanical systems such as aircraft mechanisms,artillery mechanisms and automobile mechanisms.(3)Failure modes and failure reasons of slat mechanism with rack and pinion are deeply studied.In order to evaluate the reliability,the mathematical model is derived and the simulation modeling method with four key technologies are studied,including the method of modeling the aerodynamic load,torsion bar and wing deformation.Based on the slat model,the reliability of the slat mechanism of an aircraft is evaluated,and the performance under failure condition is studied.(4)Modeling method of kinetic reliability analysis is proposed to solve the kinematic reliability problems of linkage mechanisms,including the deformation of assembly bodies,the even wear and uneven wear in joints and the kinematic errors considering the machining error and joint clearances.Among them,the model of uneven wear can better simulates the real situation of mechanisms.Then the modeling method is applied for two linkage mechanisms of cabin doors,and the degradation trend of the reliability performance is obtained,which can provide guidance for the design improvement and maintenance process.(5)Failure reasons and failure modes of aircraft lock mechanisms are studied,and the modeling method to analyze seizer reliability is presented.Based on the study,reliability of a lock mechanism of an aircraft's cabin door are analyzed.Firstly,failure modes and failure reasons are analyzed and the reliability analysis model is built.The reliability analysis results shows that the low hardness of the material of the roller and the high load are main failure reasons.In order to improve the reliability,two improvements are proposed,including: 1)replace the roller's initial material 0Cr18Ni9 with 30 CrMnSiA,2)reduce the lock key slope from 65° to 60°.Finally,considering the accumulation of the damage,reliability degradation law with work time is analyzed,and the reliable life is obtained.(6)Action time of the mechanism are always different distributed,including distribution types or parameters,which leads to synchronization reliability evaluation method based on poor statistics no longer works.This paper proposes a new method for the synchronization reliability evaluation of mechanisms.The method starts from the synchronization of two mechanisms,and use a recursive algorithm to obtain the synchronization reliability of multiple mechanisms.In order to consider both the action time requirements and synchronous requirements,the previous method is developed and both accurate reliability evaluation method and interval estimation method are proposed.The numerical case shows that the results of the proposed method are very close to the results by Monte-Carlo simulation,which verifies the effectiveness of the proposed method.Then the method is applied on the folding wings.At last,relationship between synchronization reliability,number of the mechanisms and the ratio of range and standard deviation are investigated,the results are of great importance to the design of synchronized mechanisms.