Study On Load Characteristics And Compilation Of Load Spectrum On Bogie Frames Of Beijing Metro

With the rapid development of society,urban rail transit is increasingly valued,and its passenger flow and operating mileage continue to hit new highs.Urban rail transit vehicles represented by subways have the characteristics of poor wheel-rail relationship,multi-curved curves with small radius,frequent acceleration and deceleration of vehicles,and large loads,which makes the vehicle operating environment more complicated.As the most important structure in a vehicle,the bogie's fatigue life plays a vital role in the safe and reliable operation of the vehicle.However,during the routine maintenance of the vehicle,many fatigue cracks were found on the bogie frame,which shows that the current technical specifications of the bogies can no longer meet the actual requirements of domestic vehicles,so it is urgent to form a Reliability design specification of bogie frame under actual operating conditions.Based on the measured load data of the EMU bogie frame during the operation of the vehicle,this paper studies the above-mentioned operating characteristics of metro vehicles and the law of load changes,and compiles a full life cycle load spectrum that can be used for frame fatigue testing,which provides data support for assessment of bogie.The main research contents are as follows:(1)The paper analyzes the type of load on the subway vehicle bogie during operation and obtains the load calibration coefficient and load-stress transfer coefficient through the calibration test.According to the actual characteristics of the test vehicle,the test plan for the line test is determined.(2)By decomposing the measured load signals of the framework into trend loads and dynamic loads,the time-domain characteristics and frequency-domain characteristics of the straight lines and curves,acceleration and deceleration are analyzed.The results show that the time-domain characteristics of the local loads of the framework are strongly correlated with the vehicle operating state and the change of the main body load of the frame is strongly related to the line conditions.The characteristics of the load and frame damage of the vehicle under different passenger loads are analyzed.Under the same vehicle operating mode and line conditions,the increase in passenger load can reduce the load of the lateral shock absorber.The passenger capacity increases and the damage to key parts of the structure also increases with the passenger capacity.The stress on the key parts of the frame is analyzed,and it is found that the curve section of the line accounts for much more damage to the frame per kilometer than the straight section,so the quality maintenance of the curve section of the track needs to be strengthened.(3)According to the time domain characteristics of the load under different working conditions,the measured load is separated according to the three working conditions of linear acceleration,curve and linear deceleration.In order to ensure that the sample data used for compiling has a certain representativeness,a method of determining the length of the vehicle load sample based on Bayesian theory is used,considering the logarithm of the load amplitude is subject to the prior information of the normal distribution,combined The square loss function calculates the average value of the logarithmic magnitude of the load that contains prior information,and determines the minimum number of samples tested based on the t test.(4)In order to compile the load spectrum of the framework in the whole life cycle,the variation law of the load spectrum with the test mileage was studied.The results show that in the load cycle area of low amplitude and high frequency,its frequency at the same amplitude is the same as the test mileage Linear positive correlation;in the load cycle area of large-value low-frequency times,the frequency of the load and the test mileage are linear and have a certain randomness.Based on the above conclusions,the combined load extrapolation method of linear extrapolation and adaptive kernel density estimation is proposed,which greatly improves the calculation efficiency of extrapolation.The K-S goodness-of-fit test and extrapolation of the load to a specified frequency are compared with the actual load at that frequency,which proves that the method meets a certain accuracy.Finally,according to the approximate linear relationship between the cumulative frequency of the vehicle load and the actual running mileage,the load spectrum of the full life cycle of the bogie frame is compiled.In this paper,the load spectrum of the subway bogie frame based on the measured data of the line provides support for the design and maintenance of the bogie frame.