Wheel Profile Optimization Of Speed-up Freight Train Based On Multi-population Genetic Algorithm

The speed-up operation of freight trains can greatly enhance railway transport capacity,improve transportation efficiency and competitiveness.In recent years,my country’s railway freight transport has developed in this direction.As the running speed of freight train vehicles increases,the traction,braking force,and dynamic wheel-rail forces will increase during operation,which will affect the running stability of the vehicle.Damage to vehicle equipment and goods,accelerate the wheel and rail wear rate,increase the frequency of line maintenance and vehicle repair,and cause derailment accidents in severe cases.Reasonable wheel-rail matching profile can improve the wheel-rail contact state,reduce the wheel-rail dynamic force,thereby reducing wheel-rail wear and improving the running performance of the train.This paper takes the wheels of freight trains as the research object.Based on the actual problems in the operation of freight trains,a wheel profile optimization design method is proposed to optimize the wheel tread profile suitable for the speed-up operation of freight trains.Firstly,the wheel-rail contact geometric parameters,mechanical parameters,vehicle system dynamics parameters and their solution methods required for the optimal design of the wheel-rail profile are introduced.Based on the theory of vehicle system dynamics,a freight train system dynamics model was established using the actual parameters of freight trains operated in my country,and the dynamic performance parameters and evaluation indicators of freight trains were clarified.The dynamics simulation model was verified by combining with the actual data on the dynamics of the freight train.Then,the effect of the equivalent conicity of the wheel profile on the critical speed of the vehicle is analyzed,and the optimal equivalent conicity of the wheel tread suitable for the selected vehicle model is found and as a constraint variable for the optimal design of the wheel tread.The wheel profile curve is geometrically deduced,and the optimal design variables of the wheel profile are determined.According to the dynamic characteristics of freight trains,a comprehensive objective function of train dynamics is determined.Finally,a mathematical model for optimization of the wheel profile of a freight train is established.According to the characteristics of the model,the multi-group genetic algorithm is improved,and a numerical calculation program to solve the optimization problem was written.The improved multi-population genetic algorithm numerical calculation program is used to optimize the design of the wheel profile,and finally two wheel profiles with better performance are obtained,and various performances are analyzed theoretically.The analysis results show that,compared with the LM profile,the optimized wheel profile slightly increases the vehicle’s nonlinear critical speed,effectively reduces the RMS value of the wheelset acceleration when the vehicle runs straight,the lateral stability of the bogie and the vehicle stability has seen an increase.The difference in the rolling circle radius and the equivalent conicity of the wheel set when the wheel set is large transversely is increased,so that the wheel-rail lateral force,the derailment coefficient,and the wheel load reduction rate are reduced when the train passes through the curve.This method provides a feasible way to ensure the safe and stable operation of speed-increasing freight trains.