Fatigue Analysis Of Motor Structures Under Measured Loads On Transmission Lines

With the continuous improvement of the running speed of rail vehicles,the excitation of the running parts of rail vehicles in the working environment is becoming more and more complex,and the influence of high frequency random vibration load on the motor structure is becoming more and more important.Therefore,it is necessary to study the fatigue life of the motor structure under random vibration conditions.In this paper,the traction motor of an EMU is taken as the research object.The actual acceleration load of the motor frame end is measured and compared with the standard acceleration load,and the difference of fatigue life of the motor structure predicted by different load spectrum is studied.The main work of this paper is as follows :(1)The measured acceleration load is preconditioning,that is,the identification and elimination of parking data,the processing of test data zero drift to eliminate useless data and improve data accuracy.In order to study the difference of different fatigue methods,a typical measured acceleration load data is selected,and the fatigue life of motor structure is predicted by quasi-static method and frequency domain structural stress method respectively.The results show that the fatigue life calculated by the frequency domain structural stress method is lower than that obtained by the quasi-static method.(2)In order to study the difference of different load spectra to predict the fatigue life of the motor,the measured load spectrum is obtained by the statistics of the test data,and compared with the two kinds of load spectra in the IEC 61373-2010 standard.The dynamic fatigue simulation of the motor is carried out by using two kinds of load spectra.The results show that the fatigue life of the motor welds calculated by the measured spectrum is lower than that calculated by the standard spectrum.(3)Based on the tolerance upper bound method,the random load spectrum of the multi-channel measured data is summarized and integrated,and the spectrum analysis of the collected mixed signal is carried out to determine the frequency of the sinusoidal component in the mixed signal.Then,the sinusoidal signal is separated by the correlation integration method to obtain the sinusoidal plus random acceleration load spectrum,which is used as the reference spectrum of the standard load spectrum.According to the fatigue damage accumulation results of the key welds of the motor under sinusoidal excitation load,the influence of sinusoidal components on the fatigue of the motor structure cannot be ignored,which should be considered in the structural design process.Finally,the dynamic fatigue damage of the motor is calculated based on the sinusoidal plus random load spectrum,and compared with the calculation results of the standard load spectrum.The results show that the sinusoidal plus random measured load spectrum is superimposed on the random vibration,which is more in line with the actual operating environment of the traction motor.