Effect Of Abrasive Block On Wheel/Rail Adhesion And Wheel Wear Of High-Speed Trains

With the substantial increase in vehicle speed and train braking power,the traditional brake shoe braking is gradually replaced by disc braking.The wheel-rail adhesion performance decreases without the friction of brake shoe on the tread surface,the flat sliding and polygon problems become more serious.Along with the opening of the world’s first high-speed railway in 1964,abrasive block was developed and widely used in the braking system of high-speed trains and urban rail vehicles in the following half century,which has been playing an important role in the wheel/rail adhesion improving and wheel profiling.However,the research on abrasive block started late,which is not yet mature.In order to have a clearer understanding of the abrasion function and achieve the optimal control of the abrasive block equipped on high-speed trains,this thesis has applied finite element software,dynamic analysis software and control simulation software to carry out the following research work:(1)The microscopic principle and law of the wear process among abrasive block,wheel and rail are explained.On the basis of the classic wear theory,the spherical and conical single abrasive particle wear models are established using ABAQUS software,where material properties and simulation conditions are assigned appropriately to study the wear process of abrasive block and wheel tread.For the wheel-rail wear,based on the initial wheel-rail profile,route condition and track excitation,the CR400 BF EMU vehicle dynamics model is established in SIMPACK software,and the contact geometric parameters are obtained through simulation.Based on the Hertz contact theory and FASTSIM algorithm,the size and distribution of parameters,such as creep force and creepage in the wheel-rail contact patch are calculated.Combined with the Archard wear model and the tread update algorithm,the complete wheel wear prediction model is established.(2)In order to study the influence of abrasive block on wheel-rail adhesion,the original friction coefficient in the Polach adhesion force algorithm is replaced by the friction factor measured in a certain experiment,which solves the problem that the value of the Polach model is too large when calculating the adhesion coefficient under the water-oil medium.The revised calculation model is used to analyze the factors of the adhesion performance and the effect of the of the adhesion improvement of abrasive block.Since the adhesion improvement principle of abrasive block is similar to the wear principle,the abrasive wear model is used for simulation to analyze the stress and strain changes of the material during the wear process,and the key parameters: speed,indentation depth,friction coefficient,abrasive particle radius and quantity are discussed,which provides the basis for the optimization of the parameters of abrasive block and the formulation of its control strategy.(3)In order to study the influence of abrasive block on wheel wear,based on the conclusion that the wear rate in abrasive wear is basically unchanged,the effect of different abrasion grades is added to the wheel wear prediction model for comparative simulation analysis,and it is found that abrasive block can reduce the width of the tread wear and slow down the growth of the equivalent conicity in a certain range,which improves the lateral stability of the vehicle,but the maximum wear depth is slightly increased.(4)According to the above wear law and functional effects,the abrasive fuzzy control system is designed according to the constant abrasion strategy and the traditional adhesion control method,and the fuzzy rules under traction and braking conditions are established respectively.Comparing the output result of the fuzzy control system and the wheel slip signal,it is found that the control system can respond quickly when the improving adhesion demand is detected within the specified vehicle speed range.The wheel-rail relationship can be improved by increasing the pressure of abrasive block.The abrasion frequency can be adjusted intelligently according to the wheel adhesion and repairing demand,which minimizes the material loss and maintenance costs to the greatest extent,and provides a new direction and idea for the optimal control of abrasive block.