Study On Influence Of Wheel-rail Dynamics By Track Rubber Pad Aging Of 30t Axle Load Heavy Haul Railway

The track rubber pad is an important elastic component in the track structure of heavy haul railway,which plays an important role in vibration and noise reduction.In recent years,with the increase of axle load and speed of heavy haul freight car,the load on the track is increasing,which leads to the aging rate of rubber pad is accelerated,and geometry state of the track is difficult to be maintained,this situation has posed a serious threat to the safety of train operations.For the above problems,it is necessary to study the influence of the rubber pad aging on the dynamic performance of the wheel-rail system.Based on the Multi-body dynamics as the theoretical basis,and in order to solve the problem that the track structure was overly simplified in the previous study,it is necessary to refine and stratify the track model of SIMPACK software,and the 30 t axle heavy wheel-rail dynamics model with double-layer track structure is established.The stiffness and damping of the rubber pad can not only be adjusted,the stiffness and damping of the track bed can also be adjusted in the model,which solves the problem that the stiffness and damping of the rubber pad,track bed and other track parts are concentrated together,so the model closer to the real situation.The influence of rubber pad aging on the dynamic performance of the whole system is analyzed under the condition of 60,80 and 100km/h.The results show that when the speed of the vehicle is different and the stiffness of the rubber pad increases gradually in the range of 20~300MN/m,the maximum value of the lateral acceleration and smoothness of the freight car have a slight fluctuation in a certain range;The maximum value of vertical acceleration and smoothness of the freight car increases slightly;The maximum value of wheel/rail lateral force and disengage rail factor are fluctuating within a certain range and have no regularity,and the variation law of both is similar;The wheel/rail vertical force is increased obviously,the maximum value increased by 7.45%,9.37% and 12.45% respectively in the case of three different speeds,due to the increase of vertical force will accelerate the damage to the wheel-rail system,so it is necessary to regularly check the aging degree of the rubber pad and replace them in time.The vertical displacement and acceleration of the rail are obviously reduced,and the displacement of the rails exceeds 60% in the range of 20~100MN/m,which indicates that the influence of the rubber pad on the displacement of rail is particularly prominent;The vertical acceleration and vertical displacement of sleeper are increased,and the influence of the stiffness of the rubber pad on the acceleration of the sleeper is more obvious than its displacement.When the stiffness of the rubber pad is constant,the dynamic performance of the vehicle and track are more sensitive to the speed.From the above results we can see,if the stiffness of the rubber pad is too large(the stiffness of the rubber pad aging is usually greater than 200MN/m),which will increase the wheel/rail vertical force and the vertical displacement and vibration acceleration of sleeper,resulting in more intense wheel/rail interactive force and wear,and aggravate the vibration of the track structure to enhance its own damage,further Further worsen the line condition.In turn,the deterioration of the line conditions will intensify the interaction between wheel and rail,and forming vicious circle.Therefore,in order to extend the service life of the sleeper,ballast and rail,as well as to reduce on-site maintenance workload and operating costs,so it is necessary to regularly check the aging degree of the rubber pad and replace them in time.