Study On Life Prediction Method And Life Test Of Intershaft Bearing

As a key part of aircraft engine, working in the bad environment of high temperature, high speed, heavy load and strong vibration, the performance reliability of the inter-shaft bearing has a profound effect on the safety of the flight and the performance of the aircraft. Therefore, further studying on how intershaft bearing works, monitoring intershaft bearing's working state and making fault diagnosis and life prediction about intershaft bearing have practical significance in on-condition maintenance, less maintenance cost and improving the level of aircraft engine health management. Focused on intershaft bearing, this paper studies the theory of life prediction based on Cox proportional hazards model, designs the intershaft bearing test bench for life test and develops the corresponding condition monitoring and life prediction system of intershaft bearing. Main content of this paper is as follows:First, this paper discusses the selected topic background and the research status of life prediction theory and bearing test-bench at home and abroad, introduces the general situation of intershaft bearing, analyzes the common failure forms of intershaft bearing, expounds the vibration mechanism of intershaft bearing and the extraction methods of vibration signal feature in time domain, frequency domain and time-frequency domain.Secondly, this paper introduces the related indexes such as reliability and service life, studies Cox proportional hazards model, selects the best life benchmark functions and proposes the proportional hazards model based on weibull distribution. The model parameter estimation method is studied based on maximum likelihood estimation. Model covariate is selected based on correlation analysis and Model covariate trend prediction method is selected based on auto regressive-model. According to rolling bearing full cycle accelerated life test data provided by FEMTO-ST Institute (Besancon-France), three collaborators variables are selected, Cox proportional hazards model based on weibull distribution is established, reliability function diagram is made, reliability life is obtained and Validity and reliability of the model is verified.Then, taking intershaft bearing as the main research object, this paper simulates the actual support structure and the working environment of aircraft engine. Intershaft bearing double rotor test bench is designed and developed. Intershaft bearing accelerated life test is carried out. The suitable accelerated stress is analyzed and selected. The selection of threshold downtime is analyzed deeply and studied. The Intershaft bearing monitoring scheme of accelerated life test is designed. The selection and placement of sensors are explained in detail. The typical test in the process of life be done and the intershaft bearing life test be analyzed in different damage degree.Finally, intershaft bearing condition monitoring and life prediction system is developed. The system software and hardware development environment is introduced. According to the experiment requirement, condition monitoring part including temperature monitoring, rotational speed monitoring, displacement monitoring and vibration monitoring are realized; life prediction system part including vibration signal feature extraction, model of variable selection and trend analysis, model parameter estimation and reliability life estimation are realized. User login, alarm Settings and data storage can also be realized through this system and a good man-machine relationship is made.