Research On Vibration Fatigue Performance And Optimization And Experiments Of Fastener Clips For High-speed Railway

During the long-term operation of China's high-speed railway,short-wave wheel-rail irregularities such as wheel high-order polygons and rail corrugation have caused fatigue and fracture of the spring clips of the fasteners,which seriously affects the service life and driving safety.In this dissertation,referring to the relevant research results of domestic and foreign scholars,the resonance fatigue performance,resonance fatigue optimization method and resonance fatigue test of fastener spring clips are systematically studied.The main research contents include:1.Model updating of finite element model of high-speed railway fastener systemBased on the nonlinear contact theory,a refined finite element model of the fastener system including all parts is established.Based on the theory of finite element model updating based on sensitivity analysis,the elastic clip contact stiffness parameters and elastic pad modulus parameters are corrected,so that the error between the theoretical and experimental values of the elastic clip modal frequency is within 3%,and a high-precision finite element model of the fastener system is obtained.The revised model shows that the maximum equivalent stress of the elastic clip appears on the inner surface of the arc of the back bending fulcrum,which is consistent with the on-site fracture position of the elastic clip.The dynamic characteristics of the elastic clip's natural frequency,modal shape,modal stress,acceleration frequency response function,etc.are analyzed,and the dynamic nature of the elastic clip's vibration fatigue is revealed.2.Dynamic response analysis of high-speed railway fastener systemBased on the vehicle-track coupling dynamics model and the refined finite element model of the fastening system,the joint simulation is carried out.The influence of wheel polygon amplitude and order,rail corrugation amplitude and wavelength,and train speed on wheel-rail force,rail acceleration,and clip acceleration are systematically studied.From the time domain and frequency domain,the vibration transmission law of high-frequency excitation under the path of wheel-rail force-rail-spring clip is analyzed.The resonance state of the spring clip under different working conditions is analyzed,and the most sensitive wheel polygon order and corrugation wavelength of the spring clip vibration at different speeds are obtained.A spring clip vibration monitoring method based on improved L-P wavelet is proposed,which can effectively identify wheel polygons and rail corrugations.3.Research on vibration fatigue performance of high-speed railway fastener spring clipsBased on the combined simulation of the vehicle-track coupling dynamics model and the refined finite element model of the fastener system,the dynamic maximum equivalent stress at the dangerous point of the elastic clip is extracted,the time-domain method and the frequency-domain method for the vibration fatigue life prediction of the elastic clip considering the mean stress is established based on the fatigue theory.And the applicability of the narrowband method,Dirlik method and Zhao-Baker method is analyzed.The time-domain method was used to study in detail the influence of wheel polygon amplitude and order,rail corrugation amplitude and wavelength,and train speed on the stress amplitude and fatigue life of the elastic clip,revealing the mechanism of resonance fatigue fracture of the elastic clip.The limit requirements for rail grinding and wheel repair at different train speeds based on the fatigue life of the spring clips are proposed.The frequency domain method is used to study in detail the influence of high and low frequency combined displacement loads on the fatigue life of the elastic clip,and the requirements for the fatigue displacement of the elastic clip under different frequencies are proposed.4.Research on optimization of anti-resonance fatigue of high-speed railway fastener elastic clipsIn order to avoid resonant fatigue fracture of the elastic clip,the dynamic characteristics of the elastic clip are changed by two methods,namely,increasing the natural frequency of the elastic clips and adding a dynamic vibration absorber,so as to control the vibration fatigue.A refined finite element model of the high-frequency spring clip fastener system was established.And based on the equivalent mass identification method of the multi-degree-of-freedom system,the mass,stiffness,damping and additional position of the spring clip additional dynamic vibration absorber were determined,and the dynamic vibration absorber refined finite element model of fastener system was established.The static and dynamic characteristics of the high-frequency elastic clip and the elastic clip with dynamic vibration absorber are discussed.The dynamic response analysis and fatigue life analysis of the high-frequency elastic clip and the elastic clip with dynamic vibration absorber are carried out.Through comparison with the original elastic strips,the ability of high-frequency elastic clips and elastic clips with dynamic vibration absorbers to resist rail corrugation and wheel polygons is revealed,and the optimization effect of the elastic clips against resonance fatigue is determined.5.Resonance fatigue test study on spring clips of high-speed railway fastenersIn order to carry out the spring clip resonance fatigue test,a fastener high-frequency vibration fatigue test system was independently developed based on the electric vibration test bench,and the fastener system was swept frequency test to find out the spring clip resonance frequency.The acceleration transfer rate of the rail transferred to the arm of the spring clip,the middle bend of the spring clip,and the strain transfer function of the curved arc surface of the spring clip are obtained,and the resonance resistance ability of the spring clip at a specific frequency is assessed.In order to simulate the impact of on-site high and low frequency combined loads on the fatigue performance of the spring clip,a high frequency wheel was designed on the basis of the existing eccentric wheel,and a spring clip high and low frequency combined fatigue test machine was independently developed.The test machine was used to perform high and low frequency combined displacements.The fatigue test reproduced the fatigue fracture of the elastic clip.