| With the rapid development of China's transportation,urban rail transit is increasingly becoming an important infrastructure in the construction of urban modernization with its advantages of fast speed,comfort,large traffic volume,less pollution and less land occupation.But the noise and vibration produced by the wheel/rail system have a great influence on the environment along the railway.The resilient wheels,with rubber elements with damping properties installed between the wheel hub and the wheel rim,can effectively reduce the wheel/rail noise and vibration.However,due to many nonlinear factors in the structure of resilient wheels,such as contact nonlinearity,nonlinear of rubber materials and so on.,it has brought many inconveniences to its analysis and study.In view of this,this paper,taking a press-shear resilient wheel as the object of study,focuses on the equivalent stiffness,dynamic performance,wheel/rail wear,longitudinal vibration and dynamic characteristics of resilient wheels.Rubber element is an important factor affecting the performance of resilient wheels.By comparing the load-deflection curve of the rubber element obtained from the compression-testing machine with the finite element analysis results,the constitutive modal parameters of the rubber material are obtained,and the performance of the resilient wheel is analyzed by using these parameters.The vibration mode of the resilient wheel is solved based on the stiffness matrix and the mass matrix.When the frequency is greater than 250 Hz,the vibration of the resilient wheel is mainly determined by the mode of vibration of the wheel hub or rim,and the vibration frequency of the resilient wheel is basically consistent with that of the wheel hub or rim;when the frequency is less than 250 Hz,the vibration mode of the resilient wheels presents the deformation of the rubber material.The equivalent stiffness of the resilient wheels directly affects its dynamic performance,so the influence of the pre-compression of the rubber elements,the material parameters and ambient temperature on the equivalent stiffness of the resilient wheels is studied.The influence of rubber elements of the resilient wheel on the wheel/rail contact relationship is studied with the bilinear kinematic hardening elastic-plastic model of metal materials,and the wheel/rail contact area of the resilient wheel is increased by 17.4% relative to that of the rigid wheel,the maximum contact pressure reduced by 3.5% and the maximum wheel/rail von Mises equivalent stress reduced by 3.4%.The resilient wheel can reduce the overall stiffness of the bogie,and will have a certain influence on the dynamic performance of the vehicle.Taking the 70% low-floor tramcar independently developed in China as the object of study,the 6 degree of freedom compound model of the resilient wheel is put forward on the basis of the traditional model.An optimal method based on the agent model and genetic algorithm is used to study the optimal matching relationship between the equivalent stiffness of the resilient wheel and the suspension parameters of the bogie,and the feasibility of this method in vehicle dynamics analysis is proved.The results show that the lateral stability of the vehicle with resilient wheels is better than that of the rigid wheel,and the nonlinear critical speed is 6.6% lower than that of the rigid wheel.The wheel-axle lateral force,the wheel/rail lateral force,the rate of wheel load reduction and the derailment coefficient are all reduced in varying degrees for the resilient wheel.The increase of the axial stiffness and deflection stiffness of the resilient wheel is beneficial to the curve negotiation performance,and the change of the equivalent stiffness has no influence on the stability of the vehicle.The resilient wheel can reduce the wheel/rail action force,thus reducing the wheel/rail wear.In order to quantitatively study the wear problem of the resilient wheel,the wear prediction model of the resilient wheel tread and the rail profile is established based on the Archard model.The influence of the line condition and the equivalent stiffness of the resilient wheel on the wear performance of the resilient wheel is studied.The analysis of the wear performance of the resilient wheel shows that the worse the line conditions are,the more obvious the wear reduction effect of the resilient wheel is relative to the rigid wheel.The resilient wheel outside the curve with a radius of 500 m achieve the best wear reduction effect,for which the ratio of wear reduction is obviously higher than that outside the curves with a radius of 100 m and 200 m,which is mainly because the vibration is small due to the small radius of the curve and the flange always in contact with the rail at low operation speed.The maximum cumulative wear of the rail with resilient wheels running on it is 33% lower than that of the rail with rigid wheels running on it.A lot of studies have been done by scholars on the longitudinal vibration of rigid wheels,but that of the resilient wheels has not been paid much attention to for a long time.In this paper,the dynamic analysis model of the longitudinal vibration of resilient wheels based on Polach theory and Fastsim theory is established according to the stick-slip characteristics under different working conditions to study the law and influence factors of the longitudinal vibration of the resilient wheels under start-up,low viscosity and high speed operation,high speed operation considering the negative slope characteristic of the stick-slip curve and the coasting conditions respectively.Under startup,the resilient wheels vibrate more violently than rigid ones,and the resilient wheels slip more greatly at the viscosity limit than not at viscosity limit.Under low viscosity and high speed operation,the wheel hub of the resilient wheel resonates with the wheel rim when a large amplitude vibration of the wheel hub relative to the rim is caused due to the frequency and amplitude of the wheel/rail force increased to a certain extent.Under the high speed operation considering the negative slope characteristic of the stick-slip curve,the viscosity recovery time of the wheel is reduced with the decrease of the driving torque.Under coasting conditions,improving the primary positioning longitudinal damping is an effective and reasonable method to restrain the longitudinal vibration of the resilient wheel.The stick-slip vibration of the resilient wheel has a certain influence on the vibration of the frame,but the vibration of the resilient wheel has little effect on the vibration of the body.The elastic deformation of wheelsets will have some influence on the wheel/rail contact point and the creepage.A rigid-flexible coupled dynamic model of resilient and rigid wheels that takes the elastic contact of the wheel and rail into account is established to study the dynamic characteristics of resilient wheels.The elastic lateral displacement of the nominal contact point of the resilient wheel is about two times that of the rigid wheel under the curve working condition.The elastic lateral shift of the nominal contact point of the resilient wheel is about twice that of the rigid wheel in case of curve working conditions;the longitudinal creepage of the resilient wheel outside the curve is larger than that of the rigid wheel,and the wheel/ rail lateral force of the resilient wheel outside the curve is 7.5% lower than that of the rigid wheel.The elastic vertical deformation at the nominal wheel/rail contact point of the resilient wheel is several dozen times that of the rigid wheel when the sinusoidal excitation is imposed.Large elastic deformation can mitigate the wheel/rail rigid impact and reduce the vibration acceleration,and the vibration acceleration at the axle box is reduced by 29%. |
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