Experimental Study And Calculation Of Wheel-Rail Contact Of High-Speed Train Under The Action Of The Third Medium

In recent years,with the rapid growth of China’s economy,China’s high-speed railways have made leapfrog progress.By the end of 2019,the total length of high-speed railways in operation in China had exceeded 35,000 km,accounting for over 70% of the total length of high-speed railways in operation in the world.With the increase of running speed,a large number of technical problems have emerged,including the increasingly serious wheel-rail adhesion problem.Wheel-rail adhesion characteristics greatly affect the traction,braking performance and running quality of high-speed railway,and the third medium for wheel-rail adhesion can not be ignored.Therefore,it is of great significance to study the influence of different third media on the wheel-rail contact of high-speed trains for extending the service life of wheels and reducing the operating cost of vehicles.In this paper,the wheel-rail contact of high-speed train is studied by two methods of experiment and simulation calculation,and a wheel-rail contact test rig is built.The wheelset and 60kg/m rail of high-speed train after wear are machined by wire cutting technology,and the wheel test blocks and rail test blocks required for the experiment are obtained.The main conclusions are as follows:(1)The wheel-rail contact experiments were carried out at different positions of the transverse motion between the wheels and rails of high-speed trains.The geometric shape of the worn wheel tread changed,and the contact state changed with the different transverse motion.The shape of the contact spot is elliptical with the center position as the center and away from the wheel rim.The contact spot area is large with the multi-point contact phenomenon near the wheel rim.(2)According to the experimental results,the friction coefficient between dry cleaning wheel and rail is about 0.45,and the change of axle load has a small effect on the friction coefficient between wheel and rail.Under the action of water,oil,leaves and other media,the friction coefficient between wheel and rail ranges from 0.24 to 0.32,which decreases by27.27%-45.45% compared with the friction coefficient between dry cleaning wheel and rail.Under the action of quartz sand,the friction coefficient is 0.98,and the friction coefficient between wheel and rail increases by 122% compared with that between dry cleaning wheel and rail.(3)The influences of different axle loads and different third media on the friction coefficient between wheel and rail of high-speed trains were investigated.The friction coefficient between wheel and rail would be reduced if the water medium,oil medium and leaves medium existed alone between wheel and rail.Quartz sand medium can increase the friction coefficient between wheel and rail.When water and fallen leaves exist at the same time,the friction coefficient between wheel and rail will decrease sharply.Quartz sand can obviously improve the traction deficiency caused by water,oil and fallen leaves.(4)A three-dimensional finite element model of wheel-rail contact was established,and the finite element calculation was carried out for the starting condition of high-speed train.The experimental results were compared with the finite element calculation results,and the equivalent stress and wheel-rail contact force under different friction coefficients were analyzed.The maximum Mises equivalent stress and the maximum wheel-rail contact normal force near the wheel rim were greater than those far from the wheel rim,and the maximum Mises equivalent stress and the wheel-rail contact force were less affected by the transverse displacement.