Failure Mode Analysis Of SADA And Fatigue Reliability Evaluation Of Its Rotating Saft

With the development of space technology,high requirement in satellite technology has become more and more significant in China.As an important part of the satellite system,the Solar Array Drive Assembly(SAD A)is difficult to repair once an accident occurs in space,and it will cause the satellite to fail and lead to huge economics losses.Thereby,the study of failure mode and reliability of SADA is particular vital to extend the service life and operating performance of satellites.Based on a certain type of SADA,the structure hierarchy division,fault mode analysis,fault tree construction,bayesian network analysis,fatigue damage calculation,fatigue life calculation and reliability modeling of the SADA were carried out.The specific research contents are shown as follows:Considering the influence of space environment on the operational reliability of the SADA in orbit,the working principle and structural composition of the SADA were introduced.According to its tracking law,the system was divided into five levels:drive device,transmission mechanism,connection mechanism,signal transmission system and control system.Failure mode analysis was carried out for each level,and a FMEA table was developed for entire SADA system.According to the FMEA table of the SADA,the fault subtree of each level of the SADA was constructed firstly and further expanded to form a system fault tree,and the fuzzy processing method was adopted to assign a failure rate of the bottom event missing from the fault tree.The results of the evaluation were transformed into fuzzy probabilities,and the mean area method was used for defuzzification to obtain the exact failure probability of each bottom event.The Bayesian network was used to solve the posterior probability of the remaining basic events after the fault tree top event occurs,and the weak link of the entire SADA system——the rotating shaft fatigue failure of the transmission mechanism was obtained.Considering the fatigue failure induced environment of the transmission shaft in different stages of launch,the failure problem was divided into two types:random vibration fatigue failure and on-track thermal fatigue failure in the launch phase,and Abaqus finite element software was used for simulation analysis.Based on the combination of Miner’s linear fatigue cumulative damage theory and the S-N curve of the material,the Dirlik formula under the frequency domain method was used to convert the dangerous point stress power spectral density function into a probability density function to calculate the vibration fatigue damage of the rotating shaft.The rain flow counting method on the domain was used to figure out the load-time history of the thermal stress on the rotating shaft and find the thermal fatigue damage of the four typical units of the rotating shaft(element A with large random vibration stress but zero thermal stress,element B with no random vibration response but thermal stress,element C with random vibration stress response but the highest thermal stress,and element D with the largest random vibration stress response but low thermal stress).By comprehensively comparing the fatigue life of four typical units,the fatigue life of the entire shaft of the S ADA was determinedBased on the stress-strength interference model,the fatigue reliability model of the rotating shaft of the SADA was established.According to the simulation results of the fatigue damage of the rotating shaft of the SADA,the wavelet train and the rain flow counting method were used to obtain the stress history and the fitting distribution of the maximum stress response of the random vibration and the thermal stress in the time domain.And used the P-S-N curve of the shaft material to derive the probability distribution of the strength of the material at a given life.The Monte Carlo method was used in Matlab for random sampling to calculate the reliability of the random vibration fatigue reliability model.Finally,the reliability of the two stages of random vibration fatigue and thermal fatigue in the series system were multiplied,and the fatigue reliability of the satellite SADA was obtained.