Research On The Occurrence Mechanism Of The Brake Squeal And Abnormal Wheel/Rail Wear Of The Railway Vehicle Based On Friction Self-excited Vibration

The brake friction pair and the wheel-rail friction pair are two important friction contact pairs in rail vehicle systems,and their working stabilities have important influences on the normal operation and driving safety of railway trains.When the self-excited vibration of friction pairs occurs,vibration and impact will be generated between the contact parts and transmitted to the relevant connecting parts.This will accelerate the wear and fatigue damage of the components,produce severe squeal noise and reduce ride comfort.Rail corrugation and wheel polygonalization are two typical wheel-rail damage problems,which seriously affect the accuracy,reliability and service life of track structures and related components.Previous studies have found that friction self-excited vibration may be an important reason for the generation of rail corrugation and wheel polygonal wear,but there is no generally accepted theory for its causes and relationship.Therefore,the research on the friction self-excited vibration characteristics of braking and wheel-rail systems and their mapping relationship with braking squeal noise,rail corrugation and wheel polygonalization has a strong academic innovation and engineering application background.In the present dissertation,the main research work involves:(1)The mechanism and influencing factors of disc brake squeal were studied by a field test and a numerical simulation.In the field test,the noise signal and the vibration signal of the braking device during train braking were collected.The noise and vibration characteristics were analyzed to explore the relationship between the self-excited vibration of the braking system and the disc brake squeal noise.In the numerical simulation,the complex eigenvalue analysis of the disc brake finite element model of was carried out to obtain the unstable vibration mode of the system.The consistency between the finite element prediction results and the field test results reveals that the friction self-excited vibration between the brake pad and the brake disc is the root cause of the brake squeal noise.Finally,the parameter sensitivity analysis of the material and structure of the brake pad was carried out.The results show that: improving the Young’s modulus and damping coefficient of the brake pads,or selecting the appropriate Poisson ratio can effectively suppress the friction self-excited vibration of the brake system,thus reducing the brake squeal;and changing the brake pad shape,such as triangular,hexagonal and grooved brake pads,has obvious effects on suppression of disc brake squeal,and grooved brake pads have the best effect.(2)The effects of wheel structure and braking parameters on the 22-23 order wheel polygonal wear of high-speed railway were studied.Firstly,the finite element model of a wheelset-rail-disc brake of high-speed train was established.The frequency distribution of friction self-excited vibration of the system was obtained by using the complex modal analysis method,the relationship between the friction self-excited vibration and wheel polygon wear of wheelset-rail-disc brake system was studied.In the prediction results,the self-excited vibration of frequency 652.8 Hz corresponding to the minimum equivalent damping ratio is most likely to occur.This frequency is close to the 23 rd order wheel polygon wear frequency in the actual line,which proves the accuracy of the model.Then,the effects of wheel structure and braking parameters on wheel polygon wear were studied by the parameter sensitivity analysis.Research findings that: the straight web plate wheel is more likely to cause 22-23 order polygon wear than the oblique web plate wheel and S-shaped web plate wheel under the same conditions.As the wheel diameter raises,the equivalent damping ratio for the system with the oblique web plate wheel or the S-shaped web plate wheel increases,indicating that the probability of 22-23 order wheel polygonal wear wheels is also decreasing.However,the change trend of the straight web plate wheel is just the opposite.The increase in the depth of wheel tread wear will result in a reduction in the equivalent damping ratio,which increases the probability of 22-23 order wheel polygonal wear.When the braking pressure is equal to about 10 k N,the 22-23 order wheel polygon wear is least likely to occur.The brake pad with a high damping coefficient can effectively inhibit the 22-23 order wheel polygonal wear.Increasing the Young’s modulus of the brake pad will cause the frequency of the most likely self-excited vibration increases,and the system is prone to higher-order wheel polygonal wear.The Poisson’s ratio of brake pads has little effect on wheel polygonization.(3)The finite element models of the leading wheel-track system under the track support structure with ordinary short sleepers,trapezoidal sleepers and Cologne-egg fasteners were established.The rail corrugation on small radius curve tracks with three different sleepers was studied using the complex eigenvalue analysis.The results of the dynamic analysis and complex eigenvalue analysis show that: when the train passes through the small radius curve track,the creep force between the wheel and rail of the leading wheelset reaches saturation,and the relative sliding occurs between the wheel and rail.The frictional self-excited vibration of the wheelset-track system occurs under the action of saturated creep force,and the deformation caused by unstable vibration of the low rail and inner wheel mainly occurs,which can explain the reason why the rail corrugation on small radius curve tracks mainly occurs in low rails.At the same time,the result difference of the rail corrugation finite element prediction models with spring-damping pair fastener,solid element fixed fastener and solid element contact fastener were studied.The research shows that compared with the spring-damping pair fastener model,the predicting rail corrugation using the solid element fastener model is closer to the measured data of the rail corrugation on the small radius curve line.In the two models of the fixed connection and contact connection between the rails and sleeper pads,the latter is significantly more accurate than the former in predicting rail corrugation on the metro lines.