Dynamic Stress Analysis Of Primary Steel Spring Under Medium And High Frequency Excitation

With the increasing passenger load and vehicle speed in China's metro,rail corrugation and wheel polygon phenomenon are becoming more and more common,followed by frequent fatigue damage of vehicle components.Wheel-rail corrugation leads to the deterioration of wheel-rail relationship,which will stimulate wheel-rail vibration at medium and high frequencies and transmit it to components of the vehicle,which has an important impact on the dynamic stress characteristics of primary steel springs.Therefore,it is necessary to study the dynamic stress of primary steel springs in metro vehicles under high frequency excitation.The vibration characteristics and dynamic stress of primary steel springs in a B-type metro vehicle under medium and high frequency excitation are studied by the on-site test and simulation calculation.The main work and conclusions are as follows:(1)The research status of medium and high frequency excitation of train primary steel spring and wheel-rail corrugation at home and abroad is discussed.The research methods of structural dynamic stress are summarized.The research significance and method of dynamic stress of train primary steel spring under medium and high frequency excitation are clarified.(2)Through the measurement of wheel-rail irregularity,vibration acceleration of vehicle components and stress of primary steel springs on a metro line,it is found that the polygon wear of the vehicle is slight and the rail wear is serious;the wave length of rail corrugation is mainly 125 mm-500 mm,The main frequency of vibration of vehicle components(axle box,spring seat and frame)in the range of medium and high frequency is 50~70 Hz,and the main frequency of spring dynamic stress is 60 Hz.(3)The finite element model of primary steel springs is established using finite element software ANSYS.The modes,the dynamic stiffness and the sensitive frequencies of external excitation of the steel springs are analyzed.The influence of displacement excitation amplitude and vehicle axle load on the stress of steel spring under sensitive frequency is studied.The results show that the spring stiffness frequency varies when the excitation frequency is higher than the first natural frequency of the steel spring;the sensitive frequency of the inner spring to the vertical displacement load is 60 Hz,and the stress of the inner spring is positively correlated with the amplitude of the displacement excitation and the axle load of the vehicle.(4)The rigid-flexible coupling dynamics model of vehicle system considering the flexibility of primary steel springs is established by using the multi-body dynamics software SIMPACK.The accuracy of the vehicle dynamics model is verified by the test data.Based on the established vehicle rigid-flexible coupling dynamics model,the effects of rail wave length,wave depth and speed on the dynamic stress of steel spring are calculated and analyzed.The results show that the dynamic stress of spring has an important relationship with the wave length and the speed.At a certain speed,the approximation of the passing frequency of corrugation to the natural frequency of spring will lead to a significant increase in the dynamic stress of spring.The greater the wave depth,the greater the dynamic stress of steel spring.(5)Aiming at the rail corrugation of the actual metro line,the mitigation measures of the dynamic stress of the steel spring are studied from the aspects of rail grinding,running speed,rubber pad stiffness and diameter of spring wire.The results show that rail grinding,optimizing running speed and reducing the stiffness of rubber pad can effectively reduce the dynamic stress and vibration acceleration level of steel spring.Simply changing the diameter of spring wire can't effectively reduce the dynamic stress of steel spring.