Finite Element Analysis Of Wheel/rail Plastic Matching In Heavy Haul Railway

As the axle load of freight train increases,the load-carrying capacity is improved,but the damage of heavy haul railway is also aggravated.Good material performance matching of wheel-rail is of vital importance to prolong the lives of wheel and rail.The existed researches on material performance matching of wheel-rail mainly focused on the wear from the perspective of hardness,but the researches on wheel-rail plastic matching was rarely reported so far.Due to the application of the latest generation high-strength rail steels,the contact wear of wheel-rail has been effectively suppressed,but the damage caused by the rolling contact fatigue is increasing.Therefore,in this work,experimental investigations on the ratcheting behavior of four rail steels were carried out,and then a cyclic plasticity constitutive model was established to reasonably describe the ratcheting behavior of four rail steels.Through the finite element analysis of three-dimensional heavy haul wheel-rail rolling contact,the optimal plastic matching results for wheel and rail were presented.The research results have an importance significance to prolong lives of heavy haul rail steels.The main work of this dissertation is summarized as follows:(1)In order to compare the cyclic plastic behavior of four rail steels,i.e.heat-rolled U71 Mn,heat-treated U71 Mn,heat-rolled U75 V,heat-treated U78 Cr V,considering similar initial ratcheting strain and same peak stress,the asymmetric stress cycling experiments were carried out.The results show that the initial ratcheting strain is similar,subsequent evolution of ratcheting strain does not depend entirely on the yield strength and tensile strength of rail steels.Both at the initial and stable stages,the ratcheting strain rate of the heat-treated rail steel is higher than that of the hot-rolled rail steel.In the term of the ratcheting evolutions,they are similar,i.e.,the ratcheting strain rate is high at the initial stage,and then rapidly decreases to a quasi-stable state;(2)The ratcheting parameters related to the cumulative plastic strain was introduced into the Abdel-Karim-Ohno kinematic hardening rule,an improved cyclic plastic model was established,a user material subroutine of ABAQUS was compiled,the steps of material parameters calibration were provided,and then the uniaxial tension and asymmetric stress cycling of four rail steels were predicted reasonably;(3)A three-dimensional finite element model of wheel-rail rolling contact was established.The finite element analyses of rolling contact between four different rail steels and the ER7 wheel steel under different conditions in service were carried out.The results show that the peak contact stress and Mises equivalent stress increase with the increasing axle load,yield strength and tensile strength.The friction coefficient mainly affects the shear strain.The ratcheting strain of wheel steel is much larger than that of rail steel under a same condition.With the increasing strength of rail steel,the equivalent plastic strain of wheel steel increases while the equivalent plastic strain of rail steel decreases.Under the experimental axle load,progressively increasing ratcheting strain occurs in the hot-rolled U71 Mn steel,hot-rolled U75 V steel and heat-treated U71 Mn steel,as well as ER7 steel.The high strength heat-treated U78 Cr V steel occurs plastic deformation under the axle load of 30 t,and the plastic shakedown is observed and no evolution of ratcheting strain is found;(4)Through the relationship between the stable ratcheting strain rate and ultimate strain,the fatigue crack initiation life prediction equation was established,and the fatigue crack initiation life of rail/wheel steels in different conditions in service was analyzed.The results show that,under the axle load of 25 t and 30 t,the matching rank of ER7 wheel and different rail steels from is listed as the heat-treated U78 CrV steel,hot-rolled U75V steel,heat-treated U71 Mn steel and hot-rolled U71 Mn steel.Under the considered 27 t axle load,the matching rank is the heat-treated U78 Cr V steel,heat-treated U71 Mn steel,hot-rolled U75V steel and hot-rolled U71 Mn steel.