Research On The Effect Of Brake On Wheel Polygonal Wear And Rail Corrugation

With the rapid development of rail transit systems towards the high speed and heavy load,the problems of wheel and rail damage become more and more prominent.Rail corrugation and wheel polygonalization are two of the most difficult problems in the rail transit.Rail corrugation and wheel polygonalization will worsen the contact interaction between the wheel and rail,cause strong vibrations of vehicle systems and rail systems,which will lead to looseness,falling off,fatigue and even fracture of structural parts of the vehicle and track systems,and affect the operation safety of trains.A lot of studies have been carried out on the generation mechanism and influence factors of rail corrugation and wheel polygonalization.But so far,there is no consensus on the causes of rail corrugation and wheel polygonalization.Therefore,it is of great significance to study rail corrugation and wheel polygonal wear.In this thesis,the author studied the wheel polygonalization of high-speed trains and rail corrugation in metro tracks based on the theory of friction self-excited vibration.The following works were carried out mainly in this dissertation:(1)The formation mechanism of the 22-23 order polygonal wear of Chinese high-speed train wheels was studied.A finite element model of a wheelset-track-disc brake system was established.The complex modal analysis of the braking process of the high-speed train was performed to study the frequency distribution and the occurrence possibility of the self-excited vibration of this system.The dynamic analysis was carried out to study the normal contact force between the wheel and rail.According to the research results,a new point of view on the formation mechanism of wheel polygonalization was put forward.When the high-speed train is braked,the friction self-excited vibration of the wheelset-track-disc brake system is induced by the friction force between the brake disc and pad,which causes the normal contact force between the wheel and rail to fluctuate at the same frequency,resulting in the friction work fluctuation between the wheel and rail,and finally leads to the generation of the wheel polygonal wear.In addition,the effects of the longitudinal creepage and the friction coefficient between the wheel and rail,the stiffness and damping of the fastening system on wheel polygonalization were studied.The results show that the about 650 Hz self-excited vibration of the wheelset-track-disc brake system induced by the friction force between the brake disc and pad is the main cause for the 22-23 order wheel polygonalization of Chinese high-speed trains.(2)The cause of rail corrugation at a long downhill braking section of a Shenzhen metro line was studied.A finite element model of a wheelset-track-brake shoe brake system was set up to study the self-excited vibration of the system using the complex modal analysis.According to the research results,a new point of view that the rail corrugation is caused by the self-excited vibration of the wheelset-track-brake shoe brake system was put forward.In this braking section,when the train is braked by the brake shoe brake system,the self-excited vibration of the wheelset-track-brake shoe brake system is excited by the friction force between the brake shoe and wheel tread.The vibration leads to the fluctuation of the normal contact force between the wheel and rail,and finally causes rail corrugation.The frequency of the most likely friction self-excited vibration is about 430 Hz,and the vibration mainly occurs on the inner wheels of the wheelsets.The vibration at 430 Hz will cause rail corrugation with a wavelength of about 55 mm on the surface of the low rail.The predicted wavelength and location of rail corrugation are consistent with the field measurement data,which verifies the accuracy of the finite element model.The parameter sensitivity analysis shows that the coverage angle and the location of the brake shoe have obvious influences on rail corrugation.The smaller the coverage angle of the brake shoe,the higher the occurrence probability of rail corrugation.When the brake shoe position is adjusted to the pressure angle of 8 °,the occurrence probability of rail corrugation is the minimum.(3)A finite element model of a wheelset-track system with rail suspension fasteners was set up based on the theory that rail corrugation is caused by the friction self-excited vibration of the wheelset-track system induced by the saturated creep force between the wheel and rail.The rail corrugation occurring at a sharp curved track equipped with rail suspension fasteners was studied.Some measures to suppress rail corrugation were developed.The results of the dynamic analysis and complex modal analysis show that when the leading wheelset passes through the sharp curved track,the creep force between the wheel and rail becomes saturated,and the wheels will slide on the rail.The friction self-excited vibration of the wheelset-track system will occur,which may lead to rail corrugation.The main cause of the rail corrugation is the friction self-excited vibration at 320 Hz,and the vibration mainly occurs on the low rail and the inner wheel of the leading wheelset.The results of parameter sensitivity analysis show that increasing the elastic modulus and damping of the rubber support block of the rail suspension fastener system can effectively suppress or even eliminate rail corrugation on the rail equipped with rail suspension fasteners.(4)Based on the theory that rail corrugation is caused by the friction self-excited vibration of the wheelset-track system induced by the saturated creep force between the wheel and rail,two finite element models of a wheelset-track-sleeper system with inner axlebox bogie and outer axlebox bogie were established.The influences of axlebox arrangement and primary suspension parameters on rail corrugation were studied by using complex eigenvalue analysis method.It is found that the inner axlebox bogie can effectively reduce the contact angle and the attack angle between the wheel and rail when the train passes through a tight curved track,restrain the friction self-excited vibration of the wheelset-track-sleeper system,and thus suppress the generation and development of rail corrugation at small radius curved tracks.The larger the lateral distance between the primary suspension points,the higher the occurrence probability of rail corrugation.The influence of the lateral distance between the primary suspension points of the inner axlebox bogie on the rail corrugation is greater than that of the outer axlebox bogie.