Study On Dynamic Characteristics And Fatigue Reliability Of High Speed Train Gearbox Housing

Gearbox system is an important part of high speed train bogie,and it is important to guarantee the safe operation of high-speed train by transmitting the traction torque and braking torque between train motor and wheel set.With the rapid development of high-speed railway in China,the service mileage of gearbox structure is increasing and the service environment is deteriorating.How to ensure the power transmission reliability of high speed train gearbox and its safety during service is widely concerned by the railway industry.The analysis of the dynamic characteristics and fatigue reliability of the gearbox is mainly concentrated in the traditional mechanical field,and the research on the railway industry is less.Combined with the measured signal data of the gearbox,the dynamic characteristics and fatigue reliability of high speed train gearbox housing are studied in a comprehensive way.The main contents are as follows:(1)According to the structural characteristics of gearbox,the load types of gearbox are analyzed.By establishing the finite element model of vibration isolation rubber,the influence law of preload and vibration amplitude on the nonlinear stiffness of rubber is obtained.The gearbox suspender is made into force sensor,and the time history of gearbox load is tested.Combined with vehicle GPS signal,the gearbox load characteristics under typical operation conditions are analyzed.According to the loading condition of gearbox,the test load is decomposed into trend load and dynamic load.The gearbox load is compiled by the rain flow counting method,and the influence of trend load on the dynamic load and the load spectrum is analyzed.The relationship between trend load and dynamic amplitude is analyzed by the method of mean amplitude two-dimensional spectrum.Finally,the trend load spectrum,dynamic load spectrum and test load spectrum of gearbox are compiled.(2)By establishing the finite element model of gearbox housing,the modal parameters such as the natural frequency and the elastic vibration mode of the housing are analyzed.At the same time,the natural frequency,damping and other parameters of the housing are obtained by the test method,and compared with the finite element simulation results,which verified the validity and accuracy of the finite element analysis results.According to the structure and related parameters of high speed train,a vehicle dynamic model considering gear transmission system is established to analyze the acceleration and dynamic stress response characteristics of gearbox housing under the action of motor output torque.Combined with the test data of the line,the validity of the simulation analysis is verified.Meanwhile,the equivalent stress of different parts of the gearbox is calculated according to the fatigue damage consistency criterion,and which is used to analyze the influence rule of different motor output torque on the fatigue strength of the housing.(3)Based on the measured vibration acceleration of gearbox,the vibration characteristics of housing in time domain and frequency domain are analyzed,and the influence of train running speed and though the turnout on vibration of housing is obtained.The acceleration amplitude spectrum is compiled to analyze the relationship between the acceleration amplitude and the number of action,and the average acceleration amplitude is calculated to reflect the vibration relationship between different positions of gearbox.The transmission relation of housing vibration at different frequencies is studied by amplitude method,and the 1/3 octave analysis is carried out,which reflects the distribution and transmission relationship of the bandwidth energy.Finally,the vibration safety of high speed train gearbox is evaluated by the method of vibration intensity evaluation and the vibration evaluation method of nuclear density function.The vibration amplitude of the gearbox vibration evaluation is given from the angle of probability and statistics,which can provide some reference for the development and design of the new type gearbox housing and the vibration evaluation.(4)According to the change characteristics of the gearbox load,the stress response characteristics of the housing under different loads are analyzed.The results show that the amplitude of the stress under the trend load changes greatly,and the response of the different positions has a certain linear relationship.The train running speed,operation direction and line condition have different influence on the stress response of the dynamic load.The influence parameter of fatigue damage is defined to reflect the influence of different loads on the fatigue damage of gearbox structure,and the change rule of fatigue damage parameters with the increase of train running speed is obtained.The stress data of gearbox housing is calculated by mathematical statistics,and the distribution characteristics of the stress are obtained.For different distribution functions,the combined distribution function is proposed,and the chi square test method is used to test and compare the distribution functions.On this basis,the maximum stress is calculated,and the estimated stress spread spectrum and the measured stress spread spectrum are compiled to evaluate and analyze the damage of the gearbox housing.(5)In view of the optimization and reduction of the stress measurement point in the test case,the equivalent stress correlation analysis is carried out.The equivalent stress transfer coefficient is defined to represent the stress corresponding relationship between different measuring points and reference points.Based on the correlation analysis of structural fatigue reliability,the equivalent stress transfer coefficient under different occurrence probability is obtained.According to the interference relation between the equivalent stress and fatigue strength,the fatigue reliability model of the equivalent stress-fatigue strength of the gearbox housing is established to analyze the fatigue reliability under typical working conditions such as train running direction,line condition and wheel wear condition.The relationship between the service mileage and the fatigue reliability of gearbox is obtained,which provides a theoretical reference for the fatigue life design of the high speed train gearbox housing.