Study On The Effect Of Wheel Flats On Wear And Rolling Contact Fatigue Of Wheel Materials

With the rapid development of high-speed railway transportation,the people's requirements for the quality of vehicle operation also increases,it makes the problem of wheel and rail damage become more prominent.The wheel flat is one of the most serious wheel damage.Wheels running with wheel flats will bring great safety risks to traffic.So,in order to ensure the safe operation of the vehicle,the study of the formation process of the wheel flat and the influence mechanism of the wheel flat on the subsequent operation of the vehicle have very important significance and practical value.In this study,The JD-1 wheel-rail simulation tester was used to simulate the emergency braking process of the vehicle and the wheel flats formed under different influencing factors were prefabricated,and the rolling contact fatigue tests were performed with the wheel flats.The formation mechanism of wheel flats and the effect of different wheel flats on the operation of wheel materials were studied by a variety of analytical methods.Meanwhile,the ABAQUS finite element simulation software was used to dynamically simulate the temperature field distribution and temperature variation during the formation of the wheel flats zone.The main conclusions are as follows:(1)The wheel flats increase the wear loss of the wheel,and continued running of the wheel with wheel flats causes more wear.The plastic deformation layers and white etching layers are found in the wheel flats zone.And it is proved that the white etching layer in the wheel flat zone is mainly caused by temperature.The operation of wheels with the wheel flats will have a serious impact on the life of the wheel,and different surface damage patterns are formed in the front,middle and back parts of the wheel flats zone after rolling.(2)With the increase of braking speed or braking time,the wear loss of the sample,the surface hardness of the wheel flats zone,the thickness of the plastic deformation layer and the white etching layer all increase.Meanwhile,with the braking speed or braking time increasing,the fatigue damage of wheel flat zone worsens which brings an increase of fatigue crack length and propagation angle.(3)Different wheel materials have little effect on the wear loss of wheel specimens,surface damage in the wheel flat zone,and the thickness of white etching layer.With the carbon content of wheel material increasing,the thickness of plastic deformation layer in the wheel flat zone decreases,and the resistance to deformation of the wheel material increases.And with the increase of the carbon content in the wheel materials,the martensite transformation rate in the white etching layer of the wheel flat zone is improved,the brittleness of the white etching layer is improved,and the white etching layers are more likely to be fractured to form a more serious vertical crack.(4)During the braking process,the temperature field of the wheel flat zone is a distribution pattern with a high center temperature and a low edge temperature.With the increase of braking speed or braking time,the range of heat affected zone formed in the wheel flat zone and the maximum temperature of the wheel flat zone increase.And the temperature exceeds the austenitizing phase transition temperature of the wheel steel.The temperature at the central point of the wheel flat zone rapidly rises and then drops,which corresponds to the rule of the formation of martensite white etching layer and white etching layer thickness variation in the wheel flat zone.