| The intermittent failure is one of the most important sources of No Fault Found(NFF)events,which brings great potential safety hazards to the operation of equipment and heavy burden to maintenance.How to detect,evaluate and dispose an intermittent failure has became an difficult problem.With the support of the National Natural Science Foundation of China and the key basic research projects of the Foundation Strengthening Program,the electrical connectors are taken as the research object.To solve the using state evaluation problem for electrical connector,the mechanism of electrical connector intermittent failure is analyzed in depth,the key technology of electrical connector intermittent fault duplication and evaluation is studied in this paper.The main research contents of this paper include:(1)Study on the intermittent failure mechanism and dynamic model of electrical connectorFor the fact that the intermittent failure mechanism of electrical connector and the dynamic characteristics are unclear,the qualitatively mechanism of electrical connector is analyzed by taking the contact damage and external stress into consideration synthetically.By analysising the influence of vibration on intermittent failure,the dynamic model of electrical connector is constructed.Then the intermittent failure mechanism of electrical connector under the vibration stress is analyzed.Further more,the contact surface statistical model of electrical connector is constructed by introducing the G-W(Greenwood-Williamson)model.Combined with the mechanism of intermittent failure and the statistical model of electrical connector,the parameter framework the dynamic model of intermittent failure are studied.By simulating the dynamic characteristics of electrical connector intermittent failure under different degradation stages and different vibration stress,the correctness of the mechanism analysis of electrical connector intermittent faults is verified,which lays a foundation for the electrical connector intermittent faults duplication and evaluation.(2)Research on intermittent failure duplication method of electrical connector based on constant stress test.Aiming at the problem that intermittent faults of electrical connectors are difficult to duplicate,the design principle and schedule for the duplication scheme of intermittent failure are proposed based on the purpose of intermittent failure duplication.To ensure the reality of intermittent failure duplication,the research on profile design of intermittent failure duplication based on service environmental stress is carried out.In order to further improve the efficiency of intermittent failure duplication.A duplication method of intermittent faults based on constant stress test is proposed.By analyzing the principles of accelerated duplication,an accelerated duplication model of intermittent faults is constructed,then the method of goodness-of-fit test of A-D(Anderson-Darling)is introduced to analysis the statistical characteristic of intermittent failure number.Finally,the validity of the method was verified by carrying out constant stress vibration stress test.(3)Optimization design of intermittent failure of electrical connector based on step stress testAiming at the problem of high complex price in the accelerated recurrence test of constant stress,the accelerated recurrence test of intermittent faults of electrical connectors based on step stress is studied.Firstly,the principle and key technology of accelerated recurrence of intermittent faults based on step stress are systematically analyzed,and the step stress recurrence test is given.Optimum design problem is put forward,and the idea of optimum design is put forward,which is constrained by maximizing the recurrence of intermittent faults and minimizing the damage of step-by-step test.Optimum design of intermittent faults accelerated recurrence test for electrical connector with progressive stress is studied.Optimum design algorithm of stepping stress recurrence test scheme is put forward.Optimum test scheme case is designed.Finally,the effectiveness of the optimized scheme is verified by comparative test.(4)Based on the intermittent fault characteristics of the electrical connector use state evaluation and residual life predictionBased on the mechanism analysis and recurrence study of intermittent faults,the service state of electrical connectors can be evaluated and the remaining life can be predicted by acquiring the dynamic characteristics of intermittent faults.Firstly,in view of the defect that single feature is inadequate in describing intermittent faults,combined with the dynamic model of electrical connector intermittent faults,the sensitivity of the number,duration and amplitude of intermittent faults to the deterioration of electrical connectors is analyzed respectively,and the advantages and disadvantages of each index are synthetically considered.A new method is proposed,which is composed of contact resistance and fault threshold.The area is defined as the characteristic strength of the intermittent fault of the electrical connector,which is defined as the generalized strength of the intermittent fault.Based on the principle of four-wire contact resistance measurement,a method for extracting generalized strength characteristics of intermittent faults is proposed.By analyzing the relationship between degradation process and intermittent faults of electrical connectors,Hidden Semi-Markov Model(HSMM)is introduced to analyze the state transition process of electrical connectors.Describes and constructs the electrical connector service state evaluation model and residual life prediction model under the HSMM framework respectively.Through studying the evaluation and prediction algorithm,proposes the electrical connector service state evaluation and residual life prediction method and process based on the generalized strong intermittent fault.The effectiveness of the evaluation and prediction methods is verified.This paper takes the state evaluation of electrical connector as the demand traction,analyzes the intermittent failure mechanism of electrical connector deeply,develops the technology of accelerating the intermittent failure under constant stress and step stress,extracts the characteristics of generalized strength of intermittent failure,and evaluates the state of electrical connector,and solves the problem of electrical connector intermittent failure in engineering practice.It is very important for the reliable operation and efficient support of equipment that intermittent faults are difficult to recur and the state evaluation accuracy is rough. |
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