Braking Process Simulation And Fatigue Life Prediction Of High Speed And Heavy Haul Train Tread

When the train with brake shoe braking is in emergency braking,on the one hand,the brake shoe and the tread rub violently,and the tread wear is more serious,resulting in the out of roundness of the tread,which will aggravate the vibration of the car body and accelerate the fatigue damage of the parts;on the other hand,when braking,the kinetic energy of the car body will be converted into heat energy in a short time,and the temperature of the wheel tread will rise rapidly,but the cooling effect of the rail on the tread will make the car body more unstable The temperature of the tread decreases rapidly,and the drastic change of the temperature often causes greater thermal stress.During the alternation of cold and hot,the metal on the surface of wheel tread will undergo phase transformation and eventually form a thin white layer of martensite.When the wheel with martensite white layer is in service,the fatigue damage of martensite white layer is more serious due to the cyclic action of extremely high wheel rail contact stress and thermal stress,which is also the cause of tread peeling damage.ABAQUS finite element simulation software is used to simulate the distribution of temperature field and thermal stress field of tread in braking process.The results show that during braking process,the temperature and thermal stress first increase rapidly to the peak value and then decrease rapidly,and the temperature and thermal stress at the wheel rail contact spot along the axial direction are the maximum.The control variable method is used to compare the effects of axle load,initial speed and deceleration on the temperature field and thermal stress field It is found that the temperature and thermal stress increase with the increase of axle load,initial speed and deceleration.Based on the modified Archard wear depth calculation mathematical model,combined with the secondary development of Python language post-processing,the wear depth and distribution of different contact areas of tread in braking process are obtained.The wear depth of tread under different axle load,different initial speed and different deceleration is compared,and the influence of three factors on the wear depth is analyzed.The CCT curve of CL60 wheel steel is simulated by JMat Pro software to determine the critical transformation temperature of austenite and martensite.Combined with the temperature field obtained by braking simulation,the secondary development program written in Python language is used to obtain the results that the radial depth of martensite white layer on the tread is 0.4mm and the axial distribution is in the range of 0.025 m ～ 0.046 m after an emergency braking condition.A three-dimensional finite element model of wheel with martensite white layer was established.The mechanical properties of CL60 steel quenched by experiments were used to simulate the braking process of wheel with martensite white layer.Using the local stressstrain method of multiaxial strain,the fatigue damage of tread after one braking is calculated,and the fatigue damage of wheel rail contact spot is the largest.Comparing the maximum fatigue damage of different axle load,initial speed and deceleration,increasing axle load,initial speed and deceleration will aggravate the fatigue damage of tread.