Research On Reliability Estimation Methods Of Space Pulse Tube Refrigerator Based On Accelerated Degradation Data

Satellites based on infrared detector components play an important role in the field of earth observation and space exploration.As a core component of infrared detection systems,space pulse tube refrigerator provides the low temperature environment necessary for normal operation of infrared detector components.Space pulse tube refrigerator has advantages of compact size,low vibration,high efficiency,long life and high reliability.In recent years,it has become the most promising technique for space mechanical refrigerators.At present,the designed life of remote sensing satellite in China is generally required to be 10 years.The cooling performance of a new type of domestic space pulse tube refrigerator has met the requirements of space application,but it is unclear whether it can work reliably within the design life of up to 10 years.Accurate life prediction and reliability estimation is a bottleneck problem that needs to be solved in the promotion and application of the new type of domestic space pulse tube refrigerator used in satellite.Considering requirements for reliability estimation of the new type domestic space pulse tube refrigerator with characteristics of high reliability,long life and small sample,this paper comprehensively considers both test efficiency and estimation accuracy on life and reliability.On one hand,accelerated degradation test is introduced to establish efficient test methods for machine-level equipment;on the other hand,the Bayesian theory and fusion of multi-source reliability information are combined to improve the accuracy of reliability evaluation.A multi-source information fusion reliability estimation methodology based on accelerated degradation test is proposed and established,which would provide technical support for reliability estimation and design of accelerated degradation test for the new developed domestic major equipment.The main contributions of this dissertation are summarized as follows.1.A performance degradation model of the pulse tube refrigerator based on contamination failure is established.Main potential failure modes such as leakage,fatigue,wear and contamination of the pulse tube refrigerator are systematically and comprehensively analyzed.Theoretical and experimental results show that leakage,fatigue and wear failure can be effectively controlled.However,the contamination failure mode caused by non-working gas released from non-metallic materials in the refrigerator is the key factor that restricts long-term and reliable operation of the pulse tube refrigerator.Through the study of the outgassing law of non-metallic materials,it is shown that ambient temperature is a major sensitive stress that causes contamination failure of the pulse tube refrigerator.Based on the outgassing characteristics of non-metallic materials,a cooling performance degradation model of the pulse tube refrigerator expressed by sensitive stress and running time is established,which provides a theoretical support for the accelerated degradation test and reliability estimation of the pulse tube refrigerator.2.Numerical simulation and experimental study over the effect of temperature on the performance of the pulse tube refrigerator is carried out.The influence of temperature change of the hot end on the performance of the pulse tube refrigerator is studied.According to on-orbit environment and the accelerated degradation test design of the pulse tube refrigerator,the temperature change of the hot end is set within the range of 243?353K.Temperature distribution,phase difference of mass flow,pressure wave in key components and the whole machine cooling performance of the pulse tube refrigerator are analyzed and calculated via numerical simulation.A domestic space pulse tube refrigerator is used to carry out the high temperature test,which verifies the validity of the numerical simulation results.Thermal environment adaptability of the pulse tube refrigerator in complex space environment is analyzed,which provides theoretical support for the accelerated degradation test design and reliability estimation of the pulse tube refrigerator.3.A method for analyzing the constant-stress and cyclic-stress accelerated degradation test data of space pulse tube refrigerators based on multi-source information fusion is proposed,which provides theoretical support for the lifetime prediction and reliability estimation of space pulse tube refrigerators working in different orbits.(1)For the problem of accelerated degradation data modeling and reliability evaluation under constant-stress test,a reliability estimation method based on multi-source reliability information fusion method and the Bayesian theory is proposed and established under the hypothesis of that the product lifetime is subject to exponential and Weibull distribution respectively.Mathematical expression of the posterior distribution of the reliability model parameters is established.After the field accelerated degradation data is obtained,Bayesian formula is used to update the model parameters,and the Gibbs sampling is used to solve the high dimensional integral calculation problem in the Bayesian formula.The proposed method is applicable to multiple life distribution occasions and can effectively improve the accuracy of reliability evaluation on small samples.(2)A design method of cyclic-stress accelerated test scheme is proposed for data modeling and reliability evaluation of cyclic-stress accelerated degradation test.Then,a equivalent processing model of cyclic-stress degradation data based on cumulative exposure model is established.Moreover,a nonlinear degradation model is established based on joint effects of non-working gas diffusion and thermal stress fatigue caused by temperature cycle.The reliability model based on Bayesian theory is proposed and established using pseudo-failure life distribution model and prior information.Finally,the Gibbs sampling is used to obtain the reliability model parameters.4.The application and verification of the theory and method are carried out on a domestic space pulse tube refrigerator.An accelerated degradation test platform of the pulse tube refrigerator is built,and accelerated degradation test programs based on both constant-stress and cyclic-stress are designed.Accelerated degradation tests of the pulse tube refrigerator are carried out at different accelerated temperatures.A nonlinear performance degradation model of pulse tube refrigerator is established based on failure mechanism.Integrating prior information and degradation information,Gibbs sampling method is used to improve the reliability estimation accuracy of pulse tube refrigerator based on the pseudo failure life distribution and Bayesian theory.In summary,systematic study is conducted on the lifetime and reliability estimation of a type of domestic space pulse tube refrigerator,which is based on failure mechanism,numerical simulation,degradation model,information fusion and accelerated test.The research findings have great theoretical significance and engineering value for efficient and accurate lifetime prediction and reliability estimation of newly developed domestic equipment with characteristics of high reliability,long life and small sample.