The Research Of The Refined Model Of Vehicle System And The Mechanism Of Vibration Transmission

With the increase in running speed,the action time of external excitation such as track irregularity,out-round of wheelset and turnout is shorten,The frequency band of the excition is widened,resulting in increasing sensitivity of the train to excition,expressed as the wheel-rail interaction increasing,instability of bogie vibration,and fluttering of the carbody's local position.Therefore,the safety and ride comfort of the vehicle are influenced.Vibration transfer characteristics,a connection between the system response and external excitation,is usually able to reflect the most essential characteristics of the dynamic system.The running safety,stability and many other problems in the service process,are largely associated with the transfer characteristics of the system.A refined modeling can not noly widen the frequency the response range of computation model,but also make the interaction relationship between the parts more close to the real system,Which lays the foundation for the accurate vibration transmission characteristic of the system.In this paper,the high-speed EMU vehicle system is studied as research object,aiming at a refined modeling of vehicle system and a comprehensive analysis of vibration transfer characteristics.The research contents and main conclusions are as follows:1.Based on a variety of classic vehicle-ballast(or ballastless)track vertical and lateral dynamic model,by analytic solution way,an uniformed displacement,and acceleration frequency domain transfer function from the track irregularity to the parts of vehicle system and track system are established.For different problems,based on these transfer function we've got,a series of new type transfer function related to system frequency domain characteristics are established,such as space frequency domain transfer function,power flow transfer function and stability transfer function.Under different computing models,different types of frequency domain transfer characteristics are analysed.The results show that,with the speed of 250-350km/h,the main energy transfer range is 0.4?1.2(l/m)and 6?8.5(l/m).The acceleration and the 1 change rate of the acceleration have less effect on the transmission characteristics than the initial velocity.The power flow from the excitation to the vehicle components is mainly concentrated in several low frequency sections and the energy flowing to the rails is concentrated in the high frequency section.The influence of bending stiffness and structure damping ratio of the carbody on the stability index is not obvious.With the increase of speed,the frequency of snake movement is increasing,and the frequency transfer function near this frequency band is also enlarged.Closed to the critical speed,a smaller line excitation can cause a strong snake movement.2.The main process of elastification of the main body of the vehicle and the refined modeling of the traction parts are described by mathematical expression,and also the interaction between the components.The elastification of the main part includes:the modeling of motor wheelset is established by transfer matrix method and modal superposition method.The space beam element is used to simulate the dynamic model of the bogie and motor hanger by FEM.The rigid-flexible coupling model of carbody is obtained.The refined modeling of the traction parts includes:simulation of gear and motor shaft's vibration through rotor dynamics FEM;solution of dynamic acting force between the extended end and the coupler;simulation of dynamic meshing modeling of the main and driven helical gears;dynamic modeling of gearbox and other rigid body.3.Based on the fast explicit integral method,an explicit integral scheme and its prediction-correction scheme for the numerical calculation of the vehicle-track system under refinement model are constructed by increasing the acceleration term of integral scheme.The results show that the error of the frequency domain transfer characteristic problem studied in this paper is smaller than the fast explicit method.Combining with the IFFT method,the random phase angle is reconstructed to obtain the irregular sequence with certain statistical characteristics and the irregular random time domain sequence under two kinds of accelerating conditions.The results show that whether it is uniform or variable speed conditions,power spectrum of the smooth sequence can be consistent with the original power spectrum.4.With same external conditions,the similarities and differences of main components' time domain response and the safety index under different system models are compared.Based on the rigid and refinement system model,the difference of time domain vehicle system components' response under different speed and curve conditions is analyzed.By STFT method,acceleration time-frequency response of the main components during acceleration and uniform process are given.The results show that the difference of acceleration response is obvious for different models,meanwhile,the difference of displacement response is small.With the same velocity,the acceleration of vehicle's component are different for different models.With the refinement model,the acceleration of bogie and wheel are several times bigger than that of the rigid body model.The attenuation effect of secondary suspension is more pronounced than that of primary suspension,the attenuation effect in vertical direction is pronounced than that in lateral direction.The traction system has a certain attenuation effect on the vibration tranfers along the path.The wear index of the circular curve is bigger than that of the transition curve,when the train enters and goes out of the curve,the wear index is to reach maximum.The radius of high-speed railway is usually very large,therefore,the influence of curve on response characteristics such as vehicle safety,wear and vibration is relatively small.These response characteristics are mainly affected by external excition.If the uniform process and acceleration process have the same average speed,the difference in the trend and value of components' vibration acceleration near the excitation source,is more obvious than that of the components away from the excitation source.The high energy area of Wheel vibration are in the frequency range of 75?90Hz and 300?600Hz.The energy delivered to the gearbox is dominated by high frequency bands.5.Based on time domain response,the overall amplitude frequency transfer characteristics and path transfer characteristics of primary and second suspension are established by FFT and OTPA.The influence of different models and working conditions and damping parameters on the overall amplitude transfer characteristics of components is analyzed.The difference between the transmission rate and the contribution of different paths is compared.The results show that in the low frequency range,the overall transfer characteristics of different calculation models are small.If the frequency band near the natural frequency of the vehicle componenent's mode such as carbody's bending mode,bogie and motor hanger's elastic mode and gearbox's rigid mode,the difference of response charecteristics under different calculation models are more obvious.A simple changing of damping parameters can not keep the main components' transfer characteristics to be optimized over a wide frequency band.Besides the frequency band corresponding to the carbody's bending mode,in other frequency band the vibration transmission rate from the bogie to the carbody is relatively small.The transmission rate and contribution of the bogie's vertical vibration to the carbody's vibration,the direct transmission path is to a certain extent higher than other transmission paths.In the frequency range less than 400Hz,the contribution to bogie's vertical vibration is mainly from the axlebox path.In the frequency range more than 400Hz,the total contribution to the bogie's vertical vibration is mainly from the axle and gearbox connection path.In the low frequency range,the lateral vibration energy of bogie's each position is mainly from the wheel's lateral vibration.In the middle and high frequency range,the lateral vibration energy of bogie's each position is mainly from the wheel's vertical vibration.6.Through the field measurement,the acceleration signal of the vehicle's key location is obtained,and time domain and statistical characteristics of the main part are analyzed,service conditions such as the uniformity straight line,curve and acceleration process are distinguished.The time domain and statistical characteristics of the main parts of the system are analyzed.By STFT method,the time-frequency characteristics of the main components under uniform condition,accelerating condition and typical impact condition are obtained.By FFT method,given the acceleration,under uniform and other conditions,the overall transfer characteristics between the main parts connected with the primary and secondary suspension.By OTPA method,the*transmission rate and contribution of the two transmission paths are obtained.The results show that the acceleration of bogie's different positions are obviously different,especially in the vertical direction.During the acceleration process,there are a lot of curves whose shapes are similar to the velocity-time history,which are correspond to each periodic multiplier irregularities of the slab and each order of wheelset's out-round.During the acceleration process,when the excitation frequency is close to the natural frequency band of the system's component,the vibration energy of the component increases at this frequency band.The action time of typical impact process is 0.06-0.08s,vibration energy concentrates in the frequency range around 31.5Hz,304Hz,505Hz.The axlebox spring is the most important vibration tranfer path,and the wheel-rail vibration energy tranfers along the traction system with a wider and stable frequency band.When the vibration's frequency is close to natural frequency of the gearbox's rigid body mode and motor hanger's elastic mode,a local peak of amplitude frequency transmission characteristics appears from the axlebox to the motorbox and gearbox.The vertical vibration energy of the carbody mainly comes from the bogie's vertical vibration.In the frequency range of 0 to 2.5 Hz,the total contribution of the lateral path is maintained at 50%?80%,In the frequency range bigger than 2.5Hz,the total contribution of the vertical path is obviously greater than that of the lateral path.