Analysis And Prediction Of Wheel/Rail Vibration And Squeal Noise

In recent years,with the laying of urban rail lines in residential and commercial areas,the problem of wheel squeal has attracted increasing attention.At present,the generation mechanism of wheel squeal is not clear enough,and it is difficult to predict and control wheel squeal effectively.Therefore,this paper conducts relevant experimental and theoretical research on the phenomenon of frequent squeal noise on the small radius curve of wheel/rail,and the main research contents and conclusions are as follows:(1)A wheel squeal noise test rig with two wheels rolling contact as the core is designed and built.Based on this test rig,the angle of attack of wheels is adjusted and measured using a laser distance measurer,and the contact force between wheels is measured using Fiber Bragg Grating sensing technology.In addition,this test rig is used to measure the contact force of wheels,lateral vibration and squeal noise under a series of rolling speeds and angles of attack.(2)The vibration characteristics of upper wheel and lower wheel are investigated by finite element analysis,analytical calculation and modal hammering experiment,and are compared with the squeal noise spectrum measured by experiments.The results show that the lateral vibration of upper wheel is the source of wheel squeal noise,and the dominant frequency of squeal noise is about 1100 Hz.(3)Based on the negative damping theory,the vibration model of squeal noise involving vertical dynamics is developed,and the results show that the negative damping theory plays a dominant role in the generation of squeal noise.On this basis,a transient prediction model of squeal noise is devloped based on a simplified friction creep model.The prediction results by prediction model are compared with the simulation results by vibration model.It is proved that the transient prediction method based on simplified creep curve is effective for the prediction of squeal noise.(4)The simulated friction creep curve correlates well with the experimental measured results at different rolling speeds and angles of attack,which verifies the correctness of friction creep model,and indicating the existence of ‘negative damping’.Furthermore,the predicted sound pressure level of squeal noise correlates well with the measured results,which verifies the vibration model and prediction model of squeal noise.(5)The sensitivity analysis of parameters involved in the prediction model of squeal noise is investigated.The results show that squeal noise is sensitive to creep parameters and contact parameters.Both two parameters can be controlled easily by external means,so squeal noise can be mitigated by controlling them.(6)When the friction creep curve has a zero or positive slope,the results show that a stable lateral vibration still can be generated when vertical dynamics is involved.The mechanism for the generation of wheel squeal when vertical dynamics is involved is illustrated from the view of power input.Furthermore,the sound pressure levels of squeal noise are simulated using this model and the results correlate well with the experimental measurements on a two disc test rig,indicating vertical dynamics may be the reason why squeal noise still exists when there is no negative damping.The above research work and results of wheel squeal noise can provide experimental evidence for relevant models,and theoretical reference for the prediction and mitigation of squeal noise on railway site.