Reliability Evaluation Method Of Mechanical Products Under Small Samples And Its Application In Ram Air Turbine

Ram air turbine is an emergency power unit on the plane.It is the necessary guarantee for the safe navigation of the aircraft.It is necessary to evaluate the reliability of each key component of the turbine.In addition,the ram air turbine is almost composed of mechanical components,therefore,the reliability evaluation of mechanical products is of great significance.In the life reliability test of mechanical products,the obtained data are always small sample test data because of its characteristics of long life and high reliability.According to the research of this kind of data,this paper mainly adopts two methods: The first method is using Bayesian method to analysis the data.The prior information is obtained from Handbook of Reliability Prediction Procedures for Mechanical Equipment,and the prior distribution can be constructed by the maximum entropy method.Combining with a small amount of field test information,the Bayes principle is used for statistical inference,so as to determine the posterior reliability data of the product;The second method is sample regeneration which is used for sample data satisfying Weibull distribution to expand capacity.The method proposed in this paper can use the present small sample test data to imitate the unknown distribution,and make full use of the objective information of the sample itself,so as to increase the credibility of the reliability feature.The application of the reliability evaluation method of mechanical products under small sample to reliability evaluation of ram air turbine,and the reliability of ram air turbine modeling,prediction and allocation,is the specific application of the theory.Through the analysis of the structure and function of ram air turbine,the air turbine is divided into different functional layers.Then the reliability model can be established.After the reliability model is built,the reliability evaluation is carried out from bottom to top,and the reliability level of the whole ram air turbine is obtained.Finally the optimal allocation algorithm is used to assign the specified reliability index to the component level.