Research On Rolling Contact Fatigue Behavior And Optimal Control Of Stright Switch Rail In High-speed Railway Turnout

The RCF(Rolling Contact Fatigue)of rails in railway turnout is one of the important factors which will affect the service life of rails and the running safety of vehicle.Referring to the relevant research results of domestic and foreign scholars,this paper systematically studied the wheel-rail rolling contact behavior,numerical simulation of RCF and optimal control of RCF in switch panel of railway turnout.The major research contents include:1.Wheel-rail multi-point contact analysis in switch panelBased on the spatial relative position and the supporting conditions of stock/switch rails in switch panel of railway turnout,the wheel-rail contact characteristics are studied.A method for solving the wheel-rail multi-point contact is presented taking into account the relative motion of stock/switch rails.A computer program is coded to calculate the distribution of vertical contact forces on stock and switch rails.Based on this program,the effect of some parameters such as lateral displacement of wheel-set,vertical contact forces,wheel profiles and the vertical stiffness of rubber pad are studied on the wheel-rail contact geometries and transfer and distribution of contact forces,the results are compared with those witch not consider the relative motion of stock/switch rails.2.Non-hertzian wheel-rail rolling contact behavior in switch panelThe wheel-rail rolling contact behavior in switch panel is systematically studied based on the non-hertzian wheel-rail rolling contact methods,and a program is coded taking into account the relative motion of stock/switch rails.A new profile called LMA at the section which is at the switch rail head width of 35 mm is selected as example in this paper.The positions,shapes and areas of wheel-rail contact patches and normal contact stresses are calculated to compare the applications of Kalker 3D non-hertizian wheel-rail rolling contact method,Sichani method,Ayasse-Chollet method and Kik-Piotrowski method into analysis for solving the normal contact problems in switch panel.The tangential contact stresses,the relationship between creep forces and creepages,the distribution of adhesion/slip region and computational efficiency are calculated to compare the applications of the four methods for solving the tangential contact problems in switch panel.The results can provide guidance for selecting the wheel-rail rolling contact model used to the numerical simulation of RCF in switch panel.3.Key affecting factors analysis of RCF in switch panelThe failure criterion and model of RCF are investigated in this paper,and the RCF behavior of rail and the remarkable factors which affecting dynamic response of rail RCF are focused on.Based on orthogonal table design,three levels of unrepeatable saturated tests are designed.Based on the dynamics responses,the effect of each factor on rail RCF is analyzed using the H,P and B test methods.The key affecting factors of rail RCF are selected,which provide a support to the numerical simulation of rail RCF in switch panel.4.Numerical simulation and analysis of switch rail RCFOn the basis of analysis process of rail damages in switch panel,the simulation method of rail wear and RCF is established.By synthesizing the vehicle-turnout system dynamics,Latin hypercube random sampling method,non-hertzian wheel-rail rolling contact theory,prediction model of rail wear and RCF,the coupled relationship between wear and RCF,data smoothing,accumulation,interpolation and other processing methods,the program of rail RCF in switch panel is coded.Take the norminal and worn rail profiles as example,the value and distribution of rail RCF are compared and analyzed with different vehicle passes,and the causes of cracks on the filed side of switch rail are analyzed using the results.Furthermore,the effects of vehicle speeding,axle load,gauge and friction coefficient on rail RCF in switch panel are analyzed.5.Optimization study of rail profiles to control switch rail RCFBased on the causes of cracks on the filed side of switch rail,the effect of arc radius on the top of switch rail on reducing the internal equivalent stress and increasing its position to the filed side of switch rail are analyzed.The reasonable value of arc radius Is selected according to the above results,and the switch rail RCF is compared before and after the rounding of switch rail.In addition,according to the relationship between the rail RCF and wheel-rail dynamic interaction,taking the rolling radius different of wheel-set as the optimal target,making the optimal control strategy for adjusting the variable section switch rail,the profiles of straight stock rail are optimized using the SQP method.The wheel-rail contact geometries,wheel-rail dynamic interaction and switch rail RCF are compared and analyzed.