Numerical Simulation Of Wheel Wear Of Metro Train And Cause Analysis Of Asymmetric Wheel Wear

During the operation of metro vehicle,wheel wear is an inevitable phenomenon with its increasing running mileage.Due to the existence of small-radius curves of metro lines,short station spacing,frequent starting and braking,etc.,various abnormal wear phenomena may occur on the wheelset,such as excessive wear rates and wheel asymmetrical wear.This can greatly shorten the service life of the wheels and brake shoes.In addition,wheel wear will affect the dynamic performance of the vehicle,and thus pose a threat to traffic safety.Therefore,it is necessary to carry out in-depth research on metro wheel wear.This thesis took a metro line of China as the research object.The abnormal wear phenomenon occurring on the wheelsets of the line was analyzed.The wheel wear of motor and trailer vehicles under the traction condition was investigated,and the measures to reduce the train wheel wear were proposed.The main work and conclusions are as follows.(1)Through the tracking test of the metro line,it is found that there is an obvious abnormal wear occurring on the wheel tread.On the same train the left wheels are mainly worn on the flange,while the right ones are mainly worn on the tread.(2)Based on the commercial multi-body dynamics software UM,a wheel wear prediction model including vehicle dynamics model,wheel-rail contact model and Archard material wear model was established.The predicted results of the wheel wear model are consistent with the measurement results,and the asymmetric wheel wear laws are in good agreement,which verifies the accuracy of the wheel wear prediction model.The results showed that the asymmetry of the distribution of the small radius curves is the main cause of the asymmetric wheel wear,and trains that take no turn to run make the problem of wheel asymmetrical wear more serious.(3)The prediction model above was used to simulate the wheel wear under different turning mileage of train.The simulation results showed that the regular turning of the train can alleviate the phenomenon of the asymmetric wheel wear,and the optimal turning mileage is from 20,000 km to 40,000 km.The proportion of the small radius curve has a great influence on the wheel wear.It does not need to take the measure of train turning when the percentage difference between the left and right curves is less than 3%.(4)Considering train formation,the models of traction and braking,the prediction model of vehicle wheel wear was extended to the prediction model of train wheel wear.The wear of motor and trailer wheelsets under the traction condition was studied.The results indicate that the increase of traction force increases the wheel wear of the motor vehicle significantly.The maximum wear depth increases about 15%～20%in the state of no traction for every 10‰increase of slope of the line.The traction force acting on the wheelset will cause the longitudinal and lateral creep forces to be redistributed.The increased traction force makes the steering ability of the wheelset weaker,and the steering ability of the trailer vehicle is better than that of the motor vehicle.The effect of different train formation modes on train wheel wear was investigated.For the train formation unit of M-T-M,the wheel wear of the motor vehicle is greater than that of the T-M-M,and the wear of the trailer vehicle is smaller than that of the T-M-M.As the key to provide the forward power of the train,the motor vehicle is not suitable as the head vehicle of the train.(5)Based on the metro train wheel wear prediction model,the wheel wear under train starting condition was studied.An increasing traction increases the starting acceleration and reduces the starting time.This,however,will cause greater wheel wear.In the case that the vehicle cannot avoid starting on the curve,the appropriate starting acceleration should be selected according to the length of the straight section before the curve.By comparing the wear laws of wheel tread and flange wear under different starting accelerations,the formula for selecting train starting acceleration is proposed.According to the formula,if the length of the straight section before the curve is short(less than 50 m),a large starting acceleration should be selected(1.5 m/s~2);if the length is long(more than 110 m),a small starting acceleration should be selected(1.0 m/s~2).