| In order to adapt to the rapid development of the city,the metro has become the main development object of urban rail transit.Under the continuous operation of metro vehicles,cracks appear in the key fatigue control parts of the bogie frame,which seriously affects the traffic safety.It is a common method to establish load spectrum to evaluate the structure according to the measured data of the line.Due to the factors such as test cost,it is impossible to track the whole service cycle.According to the limited sample statistics,the overall load spectrum and stress spectrum can provide the basis for the fatigue reliability research of the frame.Based on the long-term tracking test of a certain type of metro bogie frame,this paper obtains the data information of the time span of 16 months,and carries out the following research(1)Through the pretreatment of the measured load signal,the load signal is divided into main load and local load,and the characteristics of straight curve and acceleration and deceleration conditions are studied from the perspective of time domain and frequency domain.The results show that the main load of the frame is associated with the line conditions,and the local load is associated with the vehicle speed.The frame is dominated by low frequency vibration in the frequency domain,and the high frequency vibration associated with the natural frequency of the frame and the rotation frequency of the motor is generated under the influence of the line and the running speed.(2)Through the pretreatment of the measured stress signal,16 measuring points in four key fatigue control areas of the frame are selected to analyze the stress changes in different regions of the frame during different periods of line driving.The results show that the equivalent stress of key parts of the frame is relatively large when the vehicle is running in the second period of downlink.At the same time,according to the vehicle speed and angular velocity signal,it is found that the equivalent stress of the measuring point is larger when the vehicle runs at a faster speed between station 1 and station 11 with more curved lines.(3)Eight measuring points with large equivalent stress in different regions of the frame and the diamond load and braking load that can be directly obtained through the actual test are selected.The one-day measured spectrum samples are obtained by the rain-flow counting method,and the Weibull distribution fitting and fitting test are carried out.The abnormal values are eliminated,and the parameter samples 167–183are obtained.Through the statistical inference of each parameter,the variable parameters are in line with the normal distribution,and the statistical stress spectrum and load spectrum are compiled on this basis.(4)The obtained parameter samples are divided into three groups according to the sample size for the data of the whole test cycle,and each group is studied separately.The minimum sample size representing the overall distribution of the interval is obtained through the homogeneity test of the variance of the sample and the overall interval and the independent sample t test,and then the minimum tracking cycle representing the distribution of the data of the whole test cycle is obtained.The results show that at least 29 one-day test samples are needed for eight stress measuring points.For diamond load and braking load,at least 13 one-day test samples are required.60 Figures,27 Tables,77 References... |
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