| Metro vehicles have the characteristics of large time-varying load changes,short distance between stations,harsh operating environment,frequent start and braking,which lead to serious wear of wheels in the operation process,and even prone to abnormal damage such as groove,polygons,and flat.These damages directly lead to the deterioration of wheel-rail contact relationship,which is harmful to running safety.Especially in the curve track running with the influence of external rail superelevation and irregularity,which makes the wheel-rail interaction intense,vehicle adaptability poor,and the possibility of derailment greatly improved.Vehicle derailment is a very complicated process and is influenced by many external factors.It is difficult to be effectively evaluated by a single theoretical formula.Therefore,it is necessary to comprehensively analyze the common damage forms of metro wheels by using different operating conditions of vehicles,and more comprehensively study its impact on vehicle derailment,which has a positive effect on ensuring the safety and stability of vehicle systems and improving the economic and social benefits of urban rail transit operations.In this paper,the vehicle system dynamics model is established based on the actual metro train parameters.In accordance the common damage of the metro wheel,the influence of damaged wheels on wheel-rail dynamic action and operation safety when the vehicle curve is in normal operation is calculated by simulation.At the same time,the dynamic derailment process of vehicle curve is simulated by applying the lateral load at the center of gravity of the vehicle body,and the influence of wheel damage on the dynamic derailment of metro vehicles is analyzed,so as to comprehensively analyze the influence of wheel damage on the dynamic characteristics of vehicle curve derailment.The following research work has been carried out in this paper :(1)Based on the theory of multi-body system dynamics,the model of a certain type of metro vehicle in China is constructed in SIMPACK software.According to the actual operation conditions,300m and 1000m radius curve tracks are set respectively,and the influence of rail irregularity is considered,which provides a theoretical model basis for subsequent research.(2)The vehicle curve derailment process is simulated by applying the increasing lateral force on the center of gravity of the vehicle body during the curve track operation,and the dynamic behavior of the vehicle and the wheel-rail interaction in the dynamic derailment process are analyzed in detail to determine the dynamic derailment index that can accurately describe the vehicle derailment process.(3)According to the characteristics of groove damage forms,the grooved wheel profiles with different depths and widths are established.The analysis shows that groove damage makes the wheel-rail dynamic effect and operation safety index fluctuate slightly when the curve track is running normally,which is not much different from that when the wheel is not damaged,and its influence on vehicle dynamic derailment is also small.However,under the small radius curve track,with the increase of groove damage degree,the vehicle derailment tends to advance.(4)Through the analysis of the dynamic characteristics of curve derailment under polygonal wheel damage with different orders and wave depths,it is found that the polygonal damage has a great influence on the vertical effect of wheel-rail in normal running,and the increase of wave depth can significantly reduce the operation safety.Under the 300m radius curve track,the wheel unloading rate exceeds the specified limit when the 9th order polygonal wave depth is 0.2mm.At the same time,the polygonal wave depth also has a great influence on the dynamic derailment process.The increase of wave depth makes the derailment time of vehicle advance on the curve track.In order to ensure the safety of running,the turning repair cycle of polygonal wheel should be considered from the wheel unloading rate under small radius curve operation.(5)The flat damage data with different lengths are generated by MATLAB software,and the dynamic characteristics of vehicle curve derailment are analyzed.It is concluded that under normal running conditions,the increase of flat length leads to the wheel-rail vertical force,wheelset lateral force and wheel unloading rate exceeding the safety limit.When the flat length is 20mm in the 300m radius curve track,the wheel unloading rate exceeds the specified limit.Under the condition of vehicle derailment,the derailment time of the two kinds of curve tracks is advanced when the flat length reaches 20mm,and the flat damage leads to the influence of large radius curve track on vehicle dynamic derailment is greater than that of small radius curve track.Through the comprehensive analysis of the two conditions,the wheel flat length turning repair limit is advanced to 20mm,which can minimize the influence of flat damage on vehicle derailment. |
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