Theoretical Analysis And Finite Element Simulation Of Elastic-plastic Mechanical Behavior Of Wheel-rail Contact

The wheel-rail system is the most important part of high-speed railway;serious wheel-rail failure will cause disastrous consequences and huge economic losses.As a result,the wheel-rail interaction has always been one of the most important research topics in the field of high-speed railway.With the development of higher speed and larger axle load for train,the dynamic interaction between wheel and rail become more prominent,which will directly affects the safety,stability and comfort of high-speed train in service,resulting in the wheel-rail rolling contact behavior is very complex and needs to be solved urgently.In this thesis,a combination of theoretical investigation and numerical simulation was used to conduct the elastic-plastic analysis of the static and dynamic behavior of wheel-rail contact.The main research contents and achievements of this dissertation are drawn as follows:(1)Based on the Hertz contact theory and the bilinear hardening model,the elastic-plastic static analysis of wheel-rail contact was performed and typical mechanical responses,such as wheel-rail contact spot characteristics,contact pressure distribution and contact deformation were obtained.The influence of axle load on contact pressure and contact deformation was discussed and theoretical error coefficients were introduced to investigate the differences of elastic and bilinear hardening model on the prediction results of wheel-rail contact mechanic response.The results indicate that the wheel-rail contact pressure and contact deformation increase with the increase of axle load.The Hertz contact theory overestimates the wheel-rail contact stiffness,while the elastic-plastic contact theory underestimates the wheel-rail contact stiffness,and the theoretical error coefficient of the bilinear hardening model is smaller,so the bilinear hardening model can accurately predict the elastic-plastic mechanical behavior of wheel-rail contact.(2)Based on the classic rolling contact theory of Carter and Vermeulen-Johnson(V-J)and the bilinear hardening model,the elastic-plastic analysis of the two-dimensional and three-dimensional wheel-rail rolling contact behavior was carried out,and the distribution law of stick/slip in the elastic-plastic contact area of wheel-rail was expounded.The elastic-plastic creep force/creepage analytical formula was derived,the wheel-rail rolling contact elastic-plastic creep force/creepage mapping relationship was constructed,the difference between the elastic and elastic-plastic creep force/creepage curves was analyzed,and the influence of strain rate effects of wheel/rail materials on the wheel-rail contact elastic-plastic creep force/creepage curve was discussed.The results indicate that under the same working conditions,the initial slope of the elastic-plastic creep force/creepage curve is smaller than that of the elastic creep force/creepage curve,and the elastic-plastic saturated creepage is greater than the elastic saturated creepage.As the strain rate increases(the wheel-rail contact load is constant),the initial slope of the elastic-plastic creep force/creepage curve gradually increases and approaches the elastic creep force/creepage curve.(3)Based on the three-dimensional wheel-rail rolling contact finite element model considering the rail infrastructure and primary suspension system,the ANSYS/LS-DYNA software was adopted to simulate the wheel-rail transient rolling contact behavior,and the influence of different traction coefficients and strain rate effects of wheel-rail materials on the stick/slip characteristics of contact spot,contact pressure,tangential stress,von-Mises stress and equivalent plastic strain were explored.The obtained results show that,with the increase of the traction coefficient,the wheel-rail contact creepage increases,the adhesion area in the contact spot is significantly reduced,and the sliding area increases until it reaches full slip state.And the maximum von-Mises stress position shifts from the wheel-rail contact subsurface position to the wheel-rail contact surface,which reveals that the wheel-rail contact state with high creepage is more likely to cause damage to the wheel-rail contact surface.The strain rate effect of wheel/rail materials increases the von-Mises stress and reduces the plastic strain in the wheel-rail contact area,but it has little effect on the wheel-rail contact stick/slip state.The theoretical analysis and simulation study of elastic-plastic wheel-rail contact response were presented,and the elastic-plastic creep force/creepage mapping relationship was constructed to reveal the elastic-plastic stick/slip mechanism of wheel-rail rolling contact in this study,which can provide theoretical basis and technical support for the safe service and damage assessment of high-speed wheel/rail system.