Research On Transient Impact Behavior Of Wheel And Rail At Rail Welded Joints Of High Speed Railway

With the continuous development of China’s high-speed railways,the current maximum speed of China’s high-speed railways has been increased to 350km/h.At the same time,with the advent of the new era,the requirements of the country and society on the speed of high-speed railways continue to increase.Research on key technologies for kilometer-level high-speed railways is included in the next step of the plan.However,in such a complex and high-frequency railway operation,there are endless problems caused by wheel-rail contact,such as track surface damage caused by wheel-rail impact and damage to parts of the track system,noise problems caused by high-speed railways,and high-speed railways.High maintenance and repair costs brought by high standards and requirements.And with the continuous increase in the speed of high-speed railways,the dynamic relationship between wheel and rail has intensified,which has increased the damage between wheel and rail to a certain extent.The seamless line that connects the standard rails through the increasingly mature welding technology has solved the limitation of high-speed lines in operating speed and midweek to a certain extent.However,some inferior welded joints have brought new problems to the operation of vehicles.When vehicles pass through inferior welded joints,they are accompanied by high wheel-rail impact,which can cause damage or even breakage of the rail.Secondly,large temperature tensile stress will be generated inside the rail in winter and spring,and it is difficult to maintain good strength and stability at the rail welded joints.Inferior welded joints may even break the rail under the condition of high temperature stress,which directly affects Driving safety with seamless circuit.Therefore,research and analysis of rail welded joints and broken seams on higher-speed operating lines is of great significance to driving safety and CWR maintenance.In this paper,a three-dimensional wheel-rail transient rolling contact finite element model is established based on the display finite element method and using standard LMA wheel treads and CHN60 rail profiles.In Chapter 2,the modeling method of the transient model and the wheel-rail rolling simulation process are described in detail.At the same time,the quasi-steady-state rolling contact state is simulated and validated with the CONTACT algorithm,and the quasi-steady-state rolling contact state of the wheel and rail is shown Contact the solution result.In Chapter 3,based on the three-dimensional transient rolling finite element model established in Chapter 2,an ideal weld irregularity excitation is introduced on the rail to simulate the transient impact behavior of the rail welded joint.The dynamic response of the wheel and rail caused by the convex weld and the concave weld under different wavelengths and wave depths is calculated under the condition of 400km/h.The flatness limits of convex welds and concave welds for high-speed operation lines of 400km/h are put forward to provide reference for the maintenance and repair work of railway public works departments.At the same time,the maximum dynamic force and geometric gradient fitting curve of the wheel-rail maximum dynamic force and geometric gradient under different wave depths of the convex and concave welds under the condition of 400km/h is established.The measured welds prove that the curve can effectively predict the rail weld joints.Wheel-rail dynamic force is convenient for engineering application.In order to simulate the wheel-rail transient impact behavior at the rail gap,in Chapter 4,a three-dimensional wheel-rail transient rolling finite element model considering the rail gap is established based on the display finite element method,and the cross-gap form of the wheel is analyzed in detail,and the fracture is selected.The gap width of 10 mm and the broken gap width of 70 mm are used as a typical working condition analysis to show the dynamic response of the wheel when it crosses the gap.At the same time,the influences of passing speed,gap width,gap position,and fastener stiffness on the dynamic force and step value of the wheel cross seam are calculated by parameterization,and the influence of different conditions on the dynamic response induced by the wheel cross seam is analyzed.Based on the most unfavorable working conditions,the limit value is studied based on the position of the broken joint.The corresponding limit values are proposed from the two angles of wheel-rail contact relationship and wheel-rail vertical contact force,which are for the safety of high-speed railway and railway engineering.The maintenance work of the department provides certain guidance.