Research On Wheel-Rail Dynamic Effect At Welded Joint Area Of Metro Line Rail Based On Finite Element Method

Today’s high-speed rail and subway,fish plate rail joints are gradually eliminated by the time,seamless lines have become the preferred method of laying the line.Seamless rails can not only greatly reduce the impact load of wheel and rail vibration,but also can extend the service life of rail lines,and rail welded joints is undoubtedly the most important one of the key technology of seamless lines.With the increase of railway running speed and the increase of passenger traffic,the damage of rail welded joints becomes more and more serious,which not only increases the operation and maintenance cost of railway,but also directly reduces the safety of railway transportation.Therefore,the research work related to the rail welded joint has a strong practical significance and engineering application background.The three-dimensional finite element model is used to simulate the rail-welded joints.In this paper,the dynamic response of the rail-rail joint is analyzed in detail.Firstly,the research status and progress of rail welded joints are reviewed,and the necessity of using transient rolling model to study welded joint is pointed out.Then,the results of the on-site survey of the welded joints of the subway are analyzed and summarized,and it finds that the overlapped welded joints appeared most frequently in the field.Chapter 3 refers to the actual parameters of the subway line,and the finite element model of the three-dimensional wheel-rail transient contact is established by ANSYS/LS-DYNA.And a simple analysis of the transient contact solution when the wheel is rolled over the smooth rail.Chapter 4 explains in detail the simulation of rail welded joints,and takes into account material nonuniformity.Based on the established finite element model,The difference of the dynamic response between the long and short wave welded joints is analyzed and compared.At the same time,the dynamic response of the wheel and rail under the interference of the field testing welded joint is analyzed.The results show that the fluctuation of the wheel-rail contact force,the rail fulcrum reaction force and the wheel-rail contact stress fluctuates obviously in the welding area under the disturbance of the rail welded joints,and the dynamic response characteristic under the superimposed inconvenient disturbance has the characteristics of short-wave impact.And the measured saddle-shaped rail welded joint irregularity has a serious impact on the wheel-rail dynamic response.In chapter 5,the influence of parameters such as speed,welding geometrical irregularity type,welding joint uneven wave depth,welding joint position,fastener stiffness and traction coefficient on the dynamic response of wheel/rail system are discussed.It shows that the increase of subway driving speed can cause the violent fluctuation of dynamic response of wheel/rail in joint area.On the fluctuation of the transverse force of the wheel and rail under the oscillation of the singular and concave single harmonic irregularities.The increase in the wave depth of the welded joints can cause the deterioration of the wheel-rail dynamic response.When the rail welded joint uneven center is located in the middle of the sleeper,it will significantly reduce the wheel and rail contact force and rail fulcrum reaction.The dynamic response of the wheel/rail system can be significantly improved when the rigidity of the fastener system at the center of the rail welded joint is reduced.Chapter 6 combines the wheel force and the maximum wheel load shedding rate safety limit standard,and puts forward the safety limit of rail welded joints.Finally,the research conclusion and follow-up research prospect are given.