Study On Mechanism Of The Wheel Out-of Round Formation Of Metro

With the acceleration of urban rail transit construction process,the abnormal vibration and noise problems between the wheel and rail caused by the out-of round wear of the wheels have become increasingly prominent.There is no obvious conclusion about the mechanism research,even if scholars have already carried out many studies on the out-of round wear of the wheel.This paper studies based on the out-of round wear phenomenon of metro wheel:Starting from the analysis of time and frequency domain signal is presented through dynamic experiment;Researching the wheel material for the irregular wear mechanism of the wheel is explored based on the theory of engineering materials,The finite element model of track system is established to analyze the modal vibration characteristics of the rail with the P₂ force vibration frequency;According to the phenomenon of zero-point offset of the wheel-rail contact point and the vibration law for the corrugation of rail,the relationship about the out-of round wear of the wheel is analyzed.The main work and conclusions of this thesis are listed as follows:1)Through the dynamic and the wheel out-of-roundness test for metro vehicles with mature operation,it is clear that the out-of round wear problems of the 5-9th order of the wheels are common,and the 7-9th order is mainly.The dominant frequency is near 55Hz,which is 7-9 times as much the wheel rotating frequency.2)Before and after the wheel re-pro filing,there is an axle box vibration frequency of55Hz,which is not related with the speed,and the main frequency is the P₂ force vibration frequency under the wheel-rail coupling system when passing through fixed track.3)Based on the Euler-Bernoulli beam theory,the continuous beam finite element model of the unsprung mass-track system is established.The theoretical calculation and simulation both show that the P₂ frequency near 55Hz is obviously lower than the first-order natural vibration frequency of the rail.The mode order ratio for the three characteristic intervals of the rail is 1:5:2,and the P₂ force vibration frequency is closely related to the unsprung mass and distribution stiffness of the rail foundation.The rail length ratio of the three sections is equivalent to the ratio of rail bending deformation under the P₂ force vibration frequency.4)The upper bainite and martensite structure in the metallographic structure of the wheel material is the root cause for the uneven wear of the circumferential direction of the wheel.It also explains the low-order polygon of the wheel found by the wheel profile test,but the irregular wear phenomenon.5)The finite element model is used to analyze the zero-point offset phenomenon of the wheel-rail contact point,and explain why the theoretically calculated frequency value by rail vertical bending order differ from the actual values.The relationship between rail corrugation phenomenon and the 7-9th order out-of round formation of the wheel is analyzed.