Study On Ultrasonic-Based Wheel-Rail Contact Patch And Stress Test System

With the development of high-speed and heavy-haul railway transportation,the wheel-rail contact condition has been gradually deteriorating,and the resulting problem of wheel-rail damage is getting worse,which leads to the change of wheel-rail contact geometric relationship,and affects the stability and safety of train operation.The wheel-rail contact patch and stress distribution directly affect the vehicle dynamic performance,but there is still no effective test method for it.Therefore,researching an effective test method and system to detect the wheel-rail contact patch and stress distribution is of great significance and engineering application value for analyzing the wheel-rail contact state,evaluating the wheel-rail wear,and optimizing the wheel-rail design.By analyzing and comparing the relevant detection methods of the wheel-rail contact state at home and abroad,the ultrasonic method for wheel-rail contact patch and stress detection was determined.According to the propagation characteristics of ultrasonic waves and the quasi-static spring model of the contact interface,a theoretical model for ultrasonic measurement of wheel-rail contact patch and stress was established.And according to the ultrasonic measurement principle of wheel-rail contact patch and stress,the functional requirements of the test system were analyzed,and the overall scheme design of the system was completed.The whole test system is mainly composed of three parts: mechanical structure,hardware circuit and software.The mechanical structure is mainly composed of a wheel-rail loading mechanism and an ultrasonic scanning mechanism,which can realize the hydraulic loading of wheel specimen and rail,and the ultrasonic C-scanning of wheel-rail contact interface.The hardware circuit part is mainly composed of the embedded core control module,the ultrasonic excitation and data acquisition circuit,and the optocoupler isolation drive circuit of scanning mechanism,which can realize the functions of high-voltage ultrasonic excitation,ultrasonic signal preprocessing,high-speed signal acquisition,and ultrasonic C-scan drive control.The software mainly includes three parts: ultrasonic excitation and data acquisition control module,data transmission and communication module,data analysis and display interface module,which can realize the control of the whole test process,the visual display of test data,and processing results and other functions.After the test system was established,the calibration experiment was completed,and the relationship between the ultrasonic sound pressure reflection coefficient of the wheel-rail contact interface and the contact stress was established by analyzing and processing the calibration test data.The wheel-rail contact patch and stress test experiments were carried out under different lateral displacements and rail surface defects on the track bed rail,and the two-dimensional nephograms of the wheel-rail contact patch and stress distribution under different loads were obtained.The thesis also established the three-dimensional model of the wheel-rail system according to the profile data of the wheel specimen tread and the parameters of the rail,and the two-dimensional nephograms of the wheel-rail contact patch and stress distribution corresponding to the actual test were obtained by finite element analysis.The experiment and simulation results showed good overall consistency,indicating that the ultrasonic test system studied in this thesis can accurately detect the geometric size of the wheel-rail contact patch and the stress distribution on the contact patch.The research work in this thesis provides an effective test method for the analysis and research of the wheel-rail contact state.