The Research On Wheel Wear Prediction Of High-speed Train

Wheel-rail wear has always been an inevitable problem in wheel-rail system.Wheel profile can be changed due to wheel wear,which will further affect vehicle dynamic performance.Severe wheel wear will reduce the critical speed of the vehicle and affect the stability and safety of the vehicle.The high wheel-rail wear rate will greatly increase the operation and maintenance costs.Compared with the traditional common railway,high-speed trains are more sensitive to wheel-rail dynamic interaction force.And slight wheel wear may change wheel-rail contact geometry,thus deteriorating vehicle dynamic performance and shortening reprofiling-cycle.The causes of wheel-rail wear are very complex.Although the wear law can be summarized by tracking the wheel profile changes for a long time,it is still difficult to study the specific influencing factors of wheel wear.Therefore,the establishment of a long-distance wheel wear calculation model can help researchers analyze the measured data on the line on the basis of simulation numerical calculation,controlling variables and discussing the evolution law of wheel wear.At the same time,it can provide theoretical support for reducing wheel wear and lay a foundation for wheel profile optimization.This dissertation foccues studies on the wheel wear prediction model of high-speed trains and carries out the following research work:(1)Aiming at the normal problem of wheel-rail contact,the classical theoretical algorithm Hertz is introduced,and ANALYN model and Kik-Piotrowski model in nonHertz wheel-rail contact model are studied and deduced.Finally,the results of different wheel-rail contact profiles by the three models are compared with CONTACT complete theory.The results show that the shapes of elliptical contact patch obtained by Hertz theory,ANALYN model and Kik-Piotrowski model are consistent with the calculation results of CONTACT complete theory.In wheel-rail standard surface contact,Hertz theory can be adopted as the contact surfaces are relatively regular and its calculation efficiency is very high.When the wheel profile is worn,the elliptical contact patch obtained by Hertz theory has a large difference from the actual situation.ANALYN model considers both the penetration in the contact area and the local relative curvature of contact curves to solve the lateral and longitudinal boundaries of the contact patch.Therefore,the obtained contact patch is more similar to CONTACT.Kik-Piotrowski model only considers the influence of penetration on the shape of the contact patch.As a result,the calculation accuracy is slightly lower than ANALYN model,but there is no problem of local negative curvature.Kik-Piotrowski model can solve the wheel-rail contact problem that ANALYN model cannot solve.(2)To solve the tangential problem of wheel-rail contact,the Fastsim algorithm and the Fa Strip algorithm are studied.Meanwhile,the FATSIM algorithm and the Fa Strip algorithm which are respectively applicable to the ANALYN model and Kik-Piotrowski model are deduced,and then the complete non-Hertz wheel-rail contact models are obtained.The results show that the tangential stress distribution in the adhesion area of wheel-rail contact ptach by Fastsim is linearly increasing,the tangential stress saturation boundary in the sliding area is parabolic.While the tangential stress in the adhesion area of contact patch by Fa Strip is non-linear distribution,and the tangential saturation boundary in the sliding area is ellipsoidal which is consistent with the normal stress distribution.Therefore,the tangential stress distribution in a single strip obtained by Fa Srip algorithm is closer to the calculated result of CONTACT.In the calculation results of sliding velocities in the sliding area,Fastsim algorithm overestimates sliding velocities,which directly affects the calculation results of wheel-rail wear.By comparing the creep forces-creepages curves,the tangential forces obtained by three wheel-rail contact models based on Fa Strip algorithm are more consistent with CONTACT,and the calculation efficiency is basically the same as that of Fastsim algorithm.It is suggested that Fa Strip algorithm should be introduced into the wheel-rail contact calculation of vehicle-track coupling dynamics to obtain more accurate tangential forces of wheel-rail contact.(3)For wheel-rail wear models,different global wear models and local wear models are studied.Compared with the global wear model,the local wear model needs to completely solve the wheel-rail contact problem so that the process is time-consuming,but it can solve the wear distribution in the contact patch.By unifying the wear expressions of several models and calculating the wear of high-speed trains under different operating conditions,it is shown that the BRR model,the USFD global model and the USFD local model all define the wheel-rail wear into slight wear.The Zobory global model and the Zobory local model define the wheel-rail wear into severe wear.However elements in the sliding area of contact patch have different degrees of wear according to the judging conditions of the KTH local model.Therefore,in the wear calculation of high-speed train,the KTH local model defines wheel-rail contact wear more carefully,but it is more sensitive to the wheel-rail contact model.If the problem of computing efficiency can be solved,it is recommended to use ANALYN+Fastrip combined with the KTH local model to calculate wheel wear.(4)According to the methodology of wheel wear prediction,a wheel wear prediction model combined with measured data and actual track alignment for high-speed trains under long-distance running mileage is established.The model contains simulation cases including worn rail profiles,vehicle-track coupling dynamics model,wheel-rail contact model,wear model and smoothing and updating strategy of wheel wear.Wheel profiles of S1002 CN and LMB?10 are calculated for 400,000 kilometers and compared with the measured data.The simulation results of wheel wear are basically consistent with the measurement.The wheel wear prediction model is feasible to calculate and predict the change of wheel profile with mileages.(5)Based on the modified wheel wear prediction model,the effects of different track alignments and vehicle speeds on wheel wear are discussed and the simulation results of long-distance wear of LMA for high-speed trains are shown.The results show that slight changes in track alignments can change the distribution of wheel wear.The wheel wear rises with the increase of vehicle speed.The smaller the equivalent conicity of the wheel profile,the more uniform and gentle the radial wear distribution,and the wear volumn is significantly reduced.(6)In the aspect of wear prediction modeling,parallel calculation is introduced and the long-distance wear calculation results of different wheel-rail contact models and different wear models are analyzed.The results show that the calculation accuracy of nonHertz wheel-rail contact model is greatly improved compared with Hertz model,but in long-distance wear calculation,even if parallel calculation can greatly reduce the total calculation time,the calculation efficiency still needs to be improved.Different wear models adopt different calibrated coefficients for long-distance wear calculation.The wear distribution of Zobory model using tangential partial stress and sliding speed is almost same to that of USFD model using tangential resultant stress and creepage under different mileages.The modeling method of KTH wear model is different with others,so the obtained wear distribution is slightly different.