Research On Contact Fatigue Damage Of Rail Based On Wheel-Rail Transient Rolling Contact Model

China's railways are developing towards high-speed passenger transportation and heavy freight transportation.As the train speed increases and the axle load increases,the load on the rails will also increase significantly.Different damages are produced under the complex load of the rails,and wheel-rail rolling contact fatigue is a very common form of damages.After rolling contact fatigue damage occurs on the rail,uneven tread,rail head nuclear damage,or even broken rail will occur,affecting the safety,stability and comfort of the train operation.Therefore,in-depth study of wheel-rail rolling contact fatigue damage is of great significance for improving the service life of rail,maintaining the safety of train operations,and improving the efficiency of railway operations.Kalker's rolling contact theory is the basis of today's wheel-rail contact problems and plays an important role in the development of wheel-rail contact problems.However,this theory cannot achieve satisfactory results when analyzing nonlinear and complex contact problems.Therefore,it is necessary to study a method suitable for analyzing complex wheel-rail contact problems.Through wheel-rail contact fatigue analysis,it provides some guidance for preventing rail damage and provides a theoretical basis for exploring the problem of damage.Based on the wheel-rail transient rolling contact model,this paper analyzes the wheel-rail system vibration problems caused by rail corrugation in highspeed railways,establishes a wheel-rail transient rolling contact finite element model,and analyzes different influencing factors.At the same time,the problem of rail crack initiation and propagation in heavy-haul railway is analyzed,and the influence of different influence parameters on rail crack initiation and propagation is obtained.The research work carried out in this paper and the innovative results achieved are summarized as follows:(1)A wheel-rail transient rolling contact finite element model was established,and using the measured high-speed rail corrugation data,the vibration response of the vehicle passing through the rail corrugation was studied.By comparing the simulated data of the wheel-rail force with the measured data,it is concluded that the simulated data and the measured data have good consistency,and the effectiveness of the simulation model is verified.At the same time,the wheel and rail vibration response of the high-speed vehicle when passing through the simple harmonic corrugation is analyzed.When the vehicle speed is in the range of 200~350km/h,the higher the vehicle speed,the greater the vertical and longitudinal wheel-rail force when passing through the rail corrugation.The wheelrail contact force at the fastener on the sleeper is greater than between the two sleepers.The wheel-rail friction coefficient has little effect on the wheel-rail vertical force and wheel vertical acceleration.(2)The effect of rail cant of heavy-haul railway on wheel-rail contact state and rail head crack initiation was studied.Using LM wheel tread,75kg/m rail,1:40 rail cant,the location of the crack initiation obtained is basically consistent with the observed crack;When the rail cant is 1:40,1:30,1:20,1:10,as the rail cant increases,the position of the contact patch gradually shifts from the inner side of the rail top to the outer side of the rail top,and the total weight increases first and then decreases,the 1:20 rail cant can slow down the initiation of cracks.(3)The influence of crack initiation is analyzed when the wheel is moved laterally relative to the rail.The effects of different friction coefficients and different axle weights on crack initiation are analyzed when the wheel is not traversed,traversed 5mm,and traversed 10 mm.When the wheel is moved 10 mm,cracks are easy to initiate,and the cracks are more likely to initiate when the friction coefficient increases and the axle weight increases.At the same time,the influence of the rail wear and the two-point contact between the wheel and rail on crack initiation is analyzed.The multibody dynamics software is used to simulate the movement of the vehicle when passing through a curve with radius of 500 m into the finite element model for simulation.It is concluded that the wheel-rail contact statues after wear becomes better than before wear.The fatigue parameter value after wear is much smaller than before wear.It shows that a certain degree of wear can suppress the initiation of cracks.(4)The problem of crack propagation is analyzed.Select the virtual crack closure technology as the theoretical basis for crack propagation,a method for calculating the crack tip nodal force using the beam element in the virtual crack closure method is proposed.The error between the calculation result of this method and the theoretical solution is small and there is a good consistency.And when the virtual crack closure method is used to analyze the non-orthogonal mesh at the crack tip,it is proposed to use the envelope area method to calculate the crack tip area.(5)The problem of the crack propagation in heavy-haul railway is analyzed.The parallel cracks in the rail head are analyzed.It is concluded that the stress intensity factor of parallel double cracks is smaller than that of single cracks,indicating that multiple cracks can slow down the crack propagation compared to single cracks.At the same time,the stress intensity factor when the contact patch is in contact with the crack is larger than the value when the contact patch is not in contact with the crack.