The Influence Of Temperature And Track Excitation On Contact Stress Of High Speed Train Axle

As the most basic part of the train,wheels and axles are the important guarantee for the stable and reliable operation of EMUs.The assembly of the two is completed through interference connection.In the actual operation process,the load situation is relatively complex.Under the combined action of alternating load,the reliability and safety of wheel-shaft coordination will be affected,and even the connection failure and fatigue crack will occur.In severe cases,the dangerous situation of axle or wheel fracture will occur,which seriously endangers the safety of train operation and affects the safe operation of train.Therefore,in this paper,for the speed of 350 km/h ’Fuxing’,the wheel shaft may be subjected to load simulation,to provide a theoretical basis for the actual traffic safety.Firstly,this paper considers the influence of interference fit on the contact stress between wheel-shaft fit surfaces.According to the standard,the value range of interference is determined,and the influence of different interference amounts on the contact stress is analyzed.At the same time,considering that the high-speed running wheel will reduce the interference under the action of rotation,different speed levels are selected for comparison according to the actual operating conditions.According to the simulation results,the change of interference has a significant impact on the contact stress between the mating surfaces.When the interference increases,the contact stress in the hub hole and the wheel seat increases significantly.At the same time,under the effect of rotational speed,the contact stress on the wheel seat and the hub hole decreases with the increase of rotational speed when the same interference is taken.Moreover,due to the uneven distribution of wheel mass,the decrease effect in the middle of the wheel seat and the hub hole is more obvious.Secondly,the convective heat transfer coefficient varying with braking time is obtained by simulating the air flow velocity on the surface of the brake disc,the cooling rib and the wheel surface in the actual braking process.Then,the energy conversion method is used to determine the value of heat flux.According to the calculation results,the temperature field distribution of each component on the motor vehicle axle and the trailer axle at the end of the braking is obtained.Due to the large temperature gradient after the braking,the heat conduction after the parking is simulated,and the temperature field at the maximum temperature of each component is finally obtained.According to the temperature field,the contact stress between the matching surfaces under the combined action of thermal stress and interference fit is simulated.The results show that the temperature of each component on the motor vehicle is lower than that on the brake disc hub and wheelbase of the trailer.Due to the large temperature difference between the corresponding parts of the motor vehicle and the trailer,the distribution of the contact stress between the two is quite different under the action of thermal stress.At the end of the paper,by analyzing the common track irregularity phenomenon,the mathematical model of track irregularity is established,the vertical load of the train axle is calculated,and the wheel-rail force when the train passes through all kinds of irregularities is calculated.The results show that only under the action of vertical load,the circumferential distribution of contact stress in the wheel seat area and the hub hole on both sides of the axle is uneven,and the bottom is greater than the top.When the wheel-rail force is applied on the wheel tread,the distribution of contact stress in the wheel seat and the hub hole does not change much,but the difference between the top and the bottom is gradually increasing.