Study On The Effects Of Wheel Polygon Wear On The Service Life Of The Primary Suspension Coil Spring Of Metro Vehicles

With the rapid development of urban rail transportation,the polygonal wheels are more and more commonly seen on metro vehicles,which may not only exacerbate the interaction between the wheels and rails,causing abnormal vibration and noise of the vehicles,but also cause damage to the vehicle and track components and threaten the safety of metro operation.In recent years,the fractures of vehicle components caused by the polygonal wheels occur frequently.The primary spring,as an important suspension part connecting the axle box and the frame,is directly exposed to the vibration from the wheel-rail interaction.When the wheels have serious polygon wear,it may lead to the damage to the primary springs,which was indicated by field investigations.Therefore,it is of great engineering significance to study the influence of wheel polygon wear on primary springs.The effects of polygonal wheels on primary spring were studied using field measurements and numerical simulation,based on the failures of primary springs of a metro line.The conclusions are as follows:(1)The polygonal wheel wear of the investigated metro vehicle was experimented and the results show that there is a correlation between the wheel polygon wear and the fracture of primary springs.(2)The finite element model of primary springs was established by ANSYS,and modal analysis and substructure analysis were researched.Then,the modal analysis results of primary springs were imported into the flexible body module of the multi-body dynamics software SIMPACK to establish the rigid-flexible coupling dynamic model,which considers the primary spring as flexible structure.(3)The dynamics performances of primary spring under different polygonal wheels were studied through simulation calculation,which show that when the vehicle speed is 90 km/h,the first-order mode of primary springs was induced by sixth-order polygonal wheels,which lead to the value of dynamic stress levels amplified.Under the same order of polygonal wheels,the larger the polygon amplitude is,the larger the spring vibration and dynamic stress value;The dynamic stress of primary spring can be significantly reduced by decreasing the rubber pad stiffness.Under the same order and amplitude of polygonal wheels,when the excitations from left and right wheel polygons are distributed in phase,the vibration acceleration and dynamic stress of primary spring are the smallest;when the phase of excitations from left and right wheel polygon phases differ by π,the vibration acceleration and dynamic stress of primary spring are the largest.(4)The fatigue life of primary springs under different polygonal excitations was predicted,based on the cumulative fatigue damage theory and the S-N curve of the material.The research results show that when the vehicle speed is 90 km/h,under the order of polygon wheels is 5～10,the fatigue life of primary springs is lower than the order is 1～4,and the fatigue life of primary spring was significantly reduced when the order of polygonal wheels is 6th.Under the same order of polygonal wheels,the larger the polygon amplitude is,the lower the spring life is;the greater the rubber pad stiffness is,the lower the spring life is;when the excitations from left and right wheel polygons are distributed in phase,the spring life is the highest;when the phase of excitations from left and right wheel polygon phases differ by π,the spring life is the lowest.(5)To improve the fatigue life of primary spring,the vibration and dynamic stress of primary springs excited by the measured wheel polygons were studied through simulation calculation,and the fatigue life was predicted.The results indicate that the fatigue life of primary spring can be effectively improved based on optimizing the driving speed,repairing the wheel or reducing the rigidity of rubber pad,while adjusting the damping of primary shock absorbers has no obvious effect on improving the spring life.