Numerical Study Of Wheel-rail Elastic-plastic Contact Characteristics Based On ARCHARD Wear Model

With the rapid development of China’s economy,the load capacity and frequency of heavy-duty railroads have increased significantly,and the speed regulation of heavy-duty trains on the line is more frequent,and the thermal damage to the track tread caused by roll-slip and pure sliding of emergency braking between wheels and rails is increasing,which seriously threatens the driving safety of vehicles.Therefore,it is important to strengthen the mechanism research of track thermal damage to maintain the safe operation of trains and reduce the cost of railroad operation.The frictional heat generated in the friction pair during wheel sliding and rolling makes the material near the wheel-rail contact patch in a transient high temperature environment,and the mechanical and thermal performance parameters of the material change with temperature.In order to investigate the effects of friction coefficient,slip rate and frictional heat transfer on the contact characteristics and thermal damage between wheels and rails,a three-dimensional thermal direct coupling model of wheel-rail considering and not considering the change of material mechanical and thermal parameters with temperature is created using LM type wheel tread and 75kg/m type steel rail,and the differences in analysis results brought by different simulation models are compared,and the results show that the model without considering the material temperature rise effect and plasticity is better than the model with considering the material temperature rise effect and plasticity.The Archard wear model considering the material temperature rise effect is introduced into the three-dimensional elastic-plastic thermal direct coupled finite element model of the wheel-rail to analyze the effects of different slip rates and friction coefficients on the wheel-rail contact pressure,adhesion force,contact patch size and maximum equivalent force of the rail,normal stress,temperature distribution and variation,wear depth and width,and the main research results are as follows:(1)under the case of constant axle weight,wheel-rail contact pressure and friction coefficient is positively correlated,but the amplitude change is very small;adhesion force and friction coefficient is basically linear,in line with Cullen’s law of friction;maximum temperature rise and friction coefficient,adhesion force is positively correlated,frictional heat transfer range is mainly limited to the area near the track contact spot,track temperature along the depth direction exponentially decreases,more than 3mm depth of the region is basically the ambient temperature,ambient temperature.Contact spot short axis direction bandwidth of15 mm outside the region for the ambient temperature;track top contact spot sub-surface equivalent force in the wheel roll over after a sharp decay of 60%,after the frictional heat transfer generated by the thermal stress and back to the extreme value of about 50%,continue for a period of time and gradually reduce disappearance;3mm from the top of the track outside the region of the equivalent force is not affected by thermal stress,in the form of pulse;wear depth and width are related to Friction coefficient is positively correlated with the width,and increases exponentially with the friction coefficient.After the friction coefficient exceeds0.3,the contact spot flash temperature,contact pressure,adhesion,the maximum equivalent force of the rail and the amount of wear will increase significantly,which is not conducive to traffic safety.(2)axle weight,friction coefficient is unchanged,only wheel-rail slip rate changes,wheel-rail contact spot contact pressure,adhesion,contact spot,track temperature rise,track maximum equivalent force and wear and friction coefficient of a single variable change in the same law.When the slip rate is less than 10%,each physical quantity is less sensitive to the increment of slip rate,but when the slip rate is greater than 10%,the plastic strain of the material near the contact spot,friction temperature rise,equivalent force and wear will be amplified exponentially,and the slip rate over 50% will be detrimental to the driving safety.The results of the study reveal to some extent the influence of frictional heat transfer on the wheel-rail relationship and provide some reference guidance for the control of friction coefficient and slip rate of heavy-duty trains.