Research On Load Spectrum For Frame Service Damage Prediction

As the life-cycle service structure of rail vehicle,accurate prediction of service fatigue damage of bogie frame is the fundamental and urgent requirement to ensure the safety of vehicle operation.The establishment of quantitative representation of load spectrum of service damage of bogie frame has become the most direct way to solve this problem.Taking the metro bogie frame as the research object,this paper excavates the correlation and action characteristics of the service load of the frame,studies the coupling relationship and reconstruction method of multi-source load,establishes the load spectrum for the reconstruction of the service damage of the frame,and studies the method of predicting the fatigue damage of different line frames by the load spectrum.This paper mainly carried out the following research work:（1）Based on the measured load data of frame 1^#,the correlation of each load in the time domain is studied.Combined with the correlation coefficient between the function of bogie system and the load,13 loads of frame are classified into three subsystems.After transforming the damage such as discrete load spectrum after rain flow counting into constant amplitude load spectrum,the reference load of each subsystem and its ratio of action times with other loads are established.On the premise of the ratio of the maximum action frequency of 10 million times to the given action frequency,the action frequency and amplitude of each load are further determined.（2）According to the correlation degree of the load in the subsystem,the load action mode under the same frequency action mode is established,and the load action sequence is established based on the Latin hypercube sampling method,so as to establish the frame load spectrum.The ratio of the predicted equivalent stress amplitudeσ_Aa of the load spectrum to the measured equivalent stress amplitudeσ_A of each fatigue control part of frame 1^#is between 1.0 and 1.5,indicating that the fatigue damage of frame predicted by the load spectrum can be actual service damage of coating cover,and the stress ratio of65%of the fatigue control part is between 1.0 and 1.3,indicating that the load spectrum has high fatigue damage prediction accuracy,and the completeness and effectiveness of the load spectrum are verified.（3）The rigid-flexible coupling dynamic model of the vehicle was established,and the track irregularity,wheel polygon and rail corrugation excitation were input.The influence of different corrugation wavelengths and depths on the dynamic stress of the frame was simulated and analyzed.The results show that the equivalent stress amplitude of the measuring points of the motor and the gearbox is the largest when the wave-grinding wavelength is 200 mm,and increases gradually with the increase of the wave depth,and the fastest growth occurs when the wave-grinding wavelength is 0.2～0.3 mm,it indicates that the elastic vibration response caused by rail corrugation cannot be ignored when frame 1^#is running on line 1.When the load spectrum of frame 1^#is applied to the damage prediction of frame 2^#,the damage consistent load calibration should be carried out from the perspective of adjusting the load of motor and gearbox.（4）The load–strain transfer coefficient of each fatigue control part of frame 2^#was obtained by simulation calculation.The equivalent stress amplitudeσ_Bb of each fatigue control part of frame 2^#was predicted by using the compiled load spectrum of frame 1^#.Compared with the measured equivalent stress amplitudeσ_B,it was found that although the fatigue damage predicted by frame 1^#load spectrum can cover the service damage of frame 2^#,the stress ratio of 30%fatigue control parts is more than 1.5,and the maximum is 1.99,which does not achieve the expected effect.（5）By studying the trend that the stress ratio of each fatigue control part changes with the load amplitude separately,it is determined that the vertical load of the motor,the vertical load of the motor and the vertical load of the gearbox are the loads that need to be adjusted.The BFGS optimization algorithm of quasi-Newton method is used to obtain the optimal calibration coefficient.After calibration,the ratio ofσ_{B b} andσ_B is between1.0 and 1.5,and the coverage accuracy is improved by 50%,and the ratio of 80%fatigue control parts is less than 1.3,which realizes the good coverage of frame 2^#service damage.There are 49 figures,14 tables and 80 references.