Finite Element Analysis Of Wheel-rail Rolling Contact Behavior Based On Cowper-symonds Constitutive Relation

The railway,which is an eco-friendly and energy-efficient transportation mode,has attracted more and more attentions in recent years.The wheel-rail interaction is a very attractive and important topic in the field of railway,since the serious wheel-rail failure will surely cause huge disasters.With the increase of train speed,especially for the high-speed case,the wheel-rail damage may be aggravated,and the inertia effect cannot be neglected and the strain-rate effect of materials becomes more and more remarkable then.However,due to the strong material,geometrical and contact nonlinearities,the dynamic contact behavior of high-speed wheel-rail system is very complex but it is also significant to be explored.Therefore,a three-dimensional wheel-rail rolling contact model was established using explicit finite element code LS-DYNA,where the material,geometry and contact nonlinearities of the wheel-rail contact were considered,and the strain-rate dependent material parameters were included,to investigate the dynamic wheel-rail contact behaviour.To obtain the real and reliable mechanical parameters of the wheel and rail,the dynamic tests on the D1 rim steel and U71 Mn rail steel were carried out at different strain rates using HTM5020 type high-speed tensile testing machine.The corresponding plastic flow stress-strain response curves were measured,and the dynamic constitutive relation was established based on Cowper-Symonds empirical model.Also developed the application range of the three-dimensional finite element model of wheel/rail rolling contact,the model was applied to the curve track,considering the curve superelevation,lateral displacement and roll angle of the wheelset.In the case of straight track,influences of train speed,axle load and the strain-rate effect of wheel-rail materials were discussed,while in the case of curve track,influences of curvature radius of the rail,axle load and the strain-rate effect of wheel-rail materials were discussed.The analysis results of dynamic wheel-rail responses(e.g.,wheel-rail contact force,von-Mises equivalent stresss,equivalent plastic strain,vertical acceleration of the axle,lateral displacement of the initial contact point on the tread in the case of straight track and lateral displacement of the axle in the case of curve track)indicate that: 1)The wheel-rail contact force is sensitive to speed;with the increase of speed,the maximum von-Mises equivalent stresss and the maximum equivalent plasticity strain of the wheel has an increasing trend,while rail instead,when the strain-rate effect unconsidered;vertical acceleration of the axle and the maximum lateral displacement of the initial contact point on the tread will decrease with the increase of the speed.2)The axle load has obvious influence on the dynamic wheel-rail responses;with the increase of the axle load,the maximum value of each dynamic response parameter has a trend of increasing linearly.3)The maximum contact forces in three directions,the maximum von-Mises equivalent stresss,the maximum equivalent plastic strain and the vertical acceleration of the axle,are negatively correlated with the curvature radius of the rail;when the curve superelevation is set at the same speed,the lateral displacement of the axle is positively correlated with the curvature radius of the rail.4)When the strain-rate effect of the material considered,the longitudinal contact force,the von-Mises equivalent stresss and equivalent plastic strain in the wheel-rail contact area have obvious changes,namely,the maximum longitudinal contact force is decreased;the increase of the maximum von-Mises stress is 40-60MPa;the value of the maximum equivalent plastic strain is reduced by 1/3-1/2.These findings are very helpful to guide the maintenance and repair of wheel-rail components in rail transportation.