Study On Causes And Control Methods Of Fastener Clip Induced By Rail Corrugation

With the rapid development of rail transit construction,the increase of train operation speed and passenger capacity,as well as the complex and diverse operating environment,the damage problems of vehicles and rail components are more prominent.The service environment of the fastener system is complex and special,which is difficult to maintain and repair.The damage and fracture of the fastener clip will not only reduce the damping effect of the track system,but also endanger the safety of train operation.Combined with the filed investigation,it is confirmed that the small-radius curve section of metro and the long slope section of high-speed railway are the high-incidence sections of rail corrugation,which is accompanied by the fracture of the fastener clip.The fracture mechanism of the fastener clip in two typical rail corrugation sections is studied and the corresponding control methods are proposed.The main works and conclusions as follows:Firstly,the dynamics models of the vehicle-track system in the small-radius curve section of metro and the large slope section of the high-speed railway are constructed respectively.The wheel-rail contact characteristics and dynamics characteristics are analyzed.Then,the finite element model of the wheelset-rail-fasteners system of subway and high-speed rail are built and the frictional coupling vibration characteristics of the wheelset-rail-fasteners system are mastered.The fracture reasons of fastener clip are explored from the perspectives of resonance response and fatigue failure respectively.The failure mechanism of the fastener clip fracture is revealed which induced by rail corrugation.Finally,the influence of rail corrugation characteristics,the installation state of the fastener clip and the axle load on the fatigue life of the fastener clip is explored.Results shown:(1)The stress dangerous zones of the two fastener clips are consistent with the common fracture positions found on site.The stress dangerous zone of the e-type fastener clip is located at the connection between the rear arch and the heel,while the stress dangerous zone of the w-type fastener elastic clip is located at the heel.(2)The resonance response analysis results show that under the influence of typical rail corrugation,the main frequency of vibration of wheelset rail-fastener system is similar to the modal frequency of the fastener clip,which easily leads to the resonance of the fastener clip and then the fracture phenomenon.(3)The fatigue failure analysis results show that the existence of rail corrugation can lead to a reduction in the fatigue life of the fastener clip,making the fatigue life of the fastener clip much smaller than its design fatigue life,leading to fracture.(4)For the e-type fastener clip in the small radius curve sections,the fracture of the fastener clip can be suppressed by controlling the rail corrugation depth of the rail corrugation wavelength range of 40-60 mm to less than0.078 mm,the deformation range of the e-type fastener clip to 10-12 mm and the axle load of the vehicle to less than 14 t.For the w-type fastener clip in the long slope section of high-speed railway,the fracture of the fastener clip can be suppressed by controlling the rail corrugation depth of rail corrugation wavelength range of 120-160 mm is less than 0.006 mm,the range of bolt pretightening force is 200-250 N·m during installation of w-type fastener clip and the axle load of the vehicle to less than 15 t.This thesis is supported from the National Natural Science Foundation of China(52275176).