Research On Degradation Test And Reliability Evaluation Method Of Hydraulic Reciprocating Seal

Hydraulic reciprocating seals are important components in hydraulic system,and they are the important guarantee for the normal operation of the whole hydraulic system.In the actual work,the sealing performance will gradually decline with the increase of reciprocating operation times,eventually lead to leakage or more serious consequence.Performance reliability evaluation for hydraulic reciprocating seal can be used as a basis for making maintenance plan,it will effectively avoid seal failure.The research objective of this thesis is to analyze the reliability evaluation of hydraulic reciprocating rod seal based on the performance degradation data of test samples.The following aspects are mainly studied:(1)The study on the mechanism and characteristics of hydraulic reciprocating seal provides a theoretical foundation to determine the test scheme and extract the degradation parameters.In addition,two main methods of reliability evaluation based on degradation are analyzed,which are the reliability evaluation method based on the performance degradation trajectory and performance degradation distribution.And the flow chart of steps of the two methods are shown.(2)For hydraulic reciprocating piston rod seal,the polyurethane Y ring is taken as the test samples,and the special test bench is designed.In addition,the pressure sensor,displacement sensor,pull pressure sensor and fiber Bragg grating sensors are used to monitor the reciprocating motion state.The test data are collected in the initial stage,500 times,1000 times and 1500 times of the reciprocating motion.It will facilitate the next step of the extraction of the performance degradation parameters.(3)A meaningful attempt is made to extract the degradation parameters of piston rod seal performance.Based on the analysis of test data,the energy ratio of lowest frequency band and the wavelet packet energy entropy are extracted from the pressure signal,and the waveform index,the peak index,the pulse index,the margin index and the kurtosis index are extracted from the fiber Bragg grating signal.Based on the conditions of performance degradation parameters,the energy ratio of lowest frequency band and the wavelet packet energy entropy are chosen as the performance degradation parameters,and the reasons why other indexes cannot be used as the degradation parameters are analyzed.(4)Based on the analysis of test data,the reliable degree is taken as the important index of reliability.On the basis of study of degradation trajectory,the reliability analysis of the energy ratio of lowest frequency band and wavelet packet energy entropy are carried out by using the regression model method.And the reliability of hydraulic rod seal is evaluated by considering the correlation between the energy ratio of lowest frequency band and wavelet packet energy entropy.