The Elasto-plastic Analysis And Fatigue Damage Research Of Wheel/rail Rolling Contact

Wheel/rail relationship is one of basic issues in rail transportation system. In which,wheel/rail contact is an important problem continuous studied by domestic and foreign scholars.Recently, with the development of numerical method and computer, the finite element method(FEM) is widely applied in rolling contact problem. To efficiently andaccurately research wheel/rail rolling contact, the static, steady and transient analyses ofwheel/rail contact are finished by using FEM in parallel computing environment. Based onthose analysis results, the wheel/rail contact fatigue life prediction and wheel/rail contactsurface crack propagation are studied combined with wheel/rail functional friction coefficient.Specific research work as follows:(1) When the sizes of mesh in wheel/rail contact zone are refined to1mm, the number ofnodes of3D finite element model of wheel/rail contact is in a million. So this model is difficultto process in single computer. The large-scale wheel/rail contact finite element model isparallel computed in MPI parallel computing environment with12nodes. According to theimplicit and explicit calculation, reasonable parallel computing nodes are choosen to gain highquality efficiency of parallel computation. The contradiction with calculation precision andcalculation efficiency of finite element model is solved better.(2)As analysis object of LMA worn profile wheel of CRH2EMU and Chinese standardrail CHN60, the wheel/rail rolling contact static model is established with Lagrangian methodand focuses on influence analysis of lateral displacements, attack angle, axle load, torque andfriction coefficient to wheel/rail contact static characteristic. The wheel/rail rolling contactfinite element model for steady analysis is constructed by using mixed Lagrangian/Eulerianmethod. The rolling of wheel is described with Eulerian, and Lagrangian method is used todescribe rail. There is no relative movement between wheel mesh and rail mesh. The steadyanalysis of wheel/rail rolling contact is computed by implicit method. The results of steadyanalysis as initial conditions, the finite element model for transient analysis of wheel/railrolling contact is established with Lagrangian method and computed with explicit method.Through static, steady and transient analysis results show that the friction coefficient influenceon the longitudinal shear stress and transverse shear stress of wheel/rail contact patch strongly.Their values change ratably with wheel/rail friction coefficient. So it should be attachedimportance to the wheel/rail rolling contact fatigue life analysis and simulation of crackpropagation.(3) Considering the influence of friction coefficient to wheel/rail rolling contact tangentialcharacteristic, the ratcheting finite element model is established. In this model, the functionalfriction coefficient replace conventional constant friction coefficient. The ratcheting analysisfor wheel/rail rolling contact is done by using metal plasticity constitutive model integrated in the nonlinear finite element software-ABAQUS. Based on the ratcheting analysis results, thewheel/rail rolling contact fatigue life analysis is done by using fatigue life prediction model ofJiang-Sehitoglu. The fatigue life analysis results are compared with wheel/rail contact fatigueanalysis results of the Japanese scholar AKAMA M and Swedish scholar Ringsbergrespectively. It is found that the results in this paper are close to the results by Japanesescholars due to wheel/rail material parameters and conditions parameters roughly same tocalculation parameters of Japanese scholar AKAMA M.(4) The extended finite element method is presented for solving discontinuous mechanicsproblem. It is no need high density mesh refinement to crack tip in solving crack problem andremeshing for crack in simulating crack growth. Based on wheel/rail rolling contact fatigueanalysis, the extended finite element crack model of wheel/rail contact is constructed. Theinfluence analysis of wheel/rail friction coefficient, crack location and size on the contactsurface crack growth are mainly done. The results show that J-integral value is large whenwheel/rail surface crack size of about8mm. It is beyond the fracture toughness of rail materialat room temperature. In this condition, crack propagation is so easy, may lead to lateral fractureof the rail. It is coincide with the results of the field observation.The existing wheel/rail functional friction coefficient can reflect the real state of thefriction between wheel and rail to a certain extent. However, for high speed wheel/rail, thereare coupling third mediums, such as water, oil, magnetic field. So it is need to conduct morein-depth studies to reveal friction behavior of high-speed wheel/rail and construct moreaccurate functional friction coefficient between wheel and rail. In addition, the wheel/railrolling contact fatigue life and surface crack propagation is also associated with multiplefactors. It is need to systematic study wheel/rail rolling contact surface damage by effectivelycombining test method and the numerical method.