Development Process Simulation And Influencing Factors Of Wheel Polygonal Wear Of EMU

With the development of high-speed railway in China,the speed of EMU operation is constantly improving.Some problems are gradually revealed.Polygon abrasion of wheels is one of the problems to be solved.In view of the serious problem of polygon wear of EMU wheels,this paper establishes the rigid flexible coupling dynamic model of vehicles based on multi-body dynamics theory,and combines the Archard wear model and the cyclic iteration model to establish a long-term wear iterative model.The longterm wear iterative model is used to simulate the whole development process of polygon wear of EMU vehicles when the running speed is 250km/h and 300km/h respectively.The results are compared with the literature report and the measured wheel polygonal wear.The simulation and the actual results agree with the test results to verify the accuracy of the long-term wear iterative model.In order to explore the reasons of wheel polygon abrasion,the influence of the modal vibration characteristics of rail and wheel pair on the development of wheel polygon wear is analyzed by using the long-term wear iterative model.The reason for the wheel polygon abrasion is further determined by studying the influence of stiffness and damping characteristics of fastener pad on the development of wheel polygon wear.In addition,the influence of external factors such as uniform speed and variable speed operation,variable speed mode,wheel surface state and rail wave wear on the development of wheel polygon wear is studied.The specific research work is as follows:1.Based on the theory of multi-body dynamics,the dynamic model of multi rigid body vehicle is established based on the actual operating parameters of a high-speed EMU Trailer.The finite element model of flexible wheel set and flexible track is constructed,and the rigid wheel set and rigid track in the multi rigid body dynamic model are replaced,so as to obtain the rigid flexible coupling dynamic model of vehicle.The experimental results show that the calculated vibration acceleration peak value is less than the measured peak value.The reliability of the coupling dynamic model of vehicle rigid and flexible rail is proved.2.The wheel circumference is evenly divided into several points by programming,and the sampling frequency of the dynamic model is set to obtain the dynamic data of each sampling point.The results of dynamic calculation are extracted,and the FASTSIM algorithm is combined with the Archard wear model to obtain the wear distribution on the wheel rail contact spot.The longitudinal superposition of wear is taken as the mean value to represent the wear amount of the point generated by rolling one circle of the wheel.The circular wear is smoothed by Fourier series,and the appropriate amplification coefficient is set.The abrasion after the magnification is combined with the original polygon of the wheel to obtain the polygon abrasion after abrasion.The new parameter is input.Through continuous iteration,a long-term wear iterative model can be built to simulate the whole process of wheel polygon wear development.The accuracy of the long-term wear iterative model is verified by comparing the literature report and the measured wheel polygon with the simulation results.3.The development of polygon wear of EMU vehicles from scratch to existing is simulated by using long-term wear iterative model.The main order of wheel polygon wear is statistically analyzed.It is found that the excitation frequency of the main order of wheel polygon wear under different speed is within 550-600 hz.Through this phenomenon,it is inferred that there is a fixed frequency excitation source between the wheel and rail,which can promote the polygon abrasion of the wheel.The excitation source should be structural modal vibration,which exists in one of the wheel sets and rails or both.4.The reasons of wheel polygon abrasion are studied.The influence of the modal vibration characteristics of wheel pair and rail on the development of wheel polygon wear is analyzed by using the long-term wear iterative model.The results show that the modal vibration characteristics of rail have certain promotion effect on the generation and development of wheel polygon wear.The influence of stiffness and damping characteristics of rail fastener pad on the development of wheel polygonal wear is studied.The effect of modal vibration of rail on the development of wheel polygonal wear is further determined.5.The influence of external factors such as wheel surface condition,vehicle speed and rail corrugation on wheel polygonal wear is studied by using long-term wear iterative model.The results show that the development of wheel polygonal wear can be restrained to a certain extent by improving the quality of wheelset lathing,reducing the initial out of roundness amplitude and improving the wheel surface hardness.The order and development speed of wheel polygonal wear are different under different running speeds.The reason for this phenomenon lies in whether the excitation wavelength can divide the wheel circumference at different speeds.When the excitation wavelength can divide the wheel circumference,it will promote the development speed of wheel polygonal wear.In the process of vehicle operation,the inhibition effect of frequent change of speed on wheel polygonal wear is obvious,and the inhibition effect of random change of speed is the best.The existence of rail corrugation will promote the generation and development of wheel polygonal wear.When the wavelength can divide the wheel circumference,the promotion effect is the most obvious.With the increase of rail corrugation amplitude,the promotion effect on wheel polygonal wear will gradually increase.