Fatigue Life Analysis On Ballastless Track Structures In Turnout Zone Under Complex Loads

Aiming at the fatigue damage problem of ballastless track structure in turnout zone of high speed railway,an analytical method was presented to calculate its fatigue life.The fatigue life of ballastless track structure in turnout zone under complex loads was estimated,and the evolution rule of fatigue life was revealed,which can provide some theoretical reference for making maintenance method.The main research results were as follows:(1)An analytical method was presented to calculate the fatigue life of ballastless track structure in turnout zone.Firstly,a high speed railway vehicle-turnout-ballastless track model was established by using the self-developed co-simulation platform which reflects rigid-flexible coupling characteristics.The dynamic responses were analyzed and the accuracy of model were verified.According to simulation results,the fatigue sensitive location of ballastless track structure in turnout zone was confirmed.Then,aiming at the fatigue sensitive location,the fatigue analysis models were established and the time history curves of track structure stress and strain were obtained.Finally,the fatigue life of track structure was analyzed by rainflow counting method and fatigue analysis theory.(2)Through the statistical analysis of vertical wheel/rail force,the fatigue sensitive location of ballastless track structure was confirmed.The results show that the wheel/rail force fluctuates violently in frog zone,and the maximum wheel/rail force occurs in frog zone,which causes large deformation of ballastless track structure.The point rail,spring clip and slab in frog zone are fatigue sensitive structures,which is consistent with the literature research.(3)Through the fatigue analysis of point rail,the evolution rule of fatigue life of point rail is studied.The fatigue life of point rail is affected by rail profile and wheel/rail force,and the minimal fatigue life occurs on the surface of rail head.The improvement of speed is beneficial to the fatigue life,but the track irregularity is not beneficial to it.Temperature gradient of slab and stiffness reduction of fastener and slab have no significant effect on the fatigue life of rail.(4)Through the fatigue analysis of spring clip,the evolution rule of fatigue life of spring clip is studied.The fatigue life of spring clip is affected by fastener vertical displacement and fastenning force,and the minimal fatigue life occurs on the bending of outer arm of spring clip which closes to the iron plate.With the increase of stiffness reduction of fastener,the fatigue life of the spring clip and another two spring clips which along the running direction decreased rapidly.With the increase of fastenning force,the fatigue life decreased rapidly.Speed,temperature gradient of slab,track irregularity and stiffness reduction of slab have no significant effect on the fatigue life of spring clip.(5)Through the fatigue analysis of slab,the evolution rule of fatigue life of slab is studied.The fatigue life of slab is affected by displacement and initial stress,and the minimal fatigue life focus on the fastener area.During actual operation,the prestress of slab can counteract the tensile stress produced by temperature,the fatigue life of slab is much higher than the design life.With the increase of stiffness reduction of fastener,the stress amplitude of slab increased gradually,and the fatigue life decreased rapidly.Speed,track irregularity and stiffness reduction of slab have no significant effect on the fatigue life of slab.(6)According to the evolution rule of fatigue life of ballastless track structure in turnout zone,some suggestions about maintenance method were presented.The point rail should be pre-polished.When the stiffness reduction of fastener occurred,the fastener should be repaired in time.If the spring clip fracture occurred by the stiffness reduction of fastener,the two spring clips on both sides of it also need to be replaced.If the spring clip fracture occurred by other reasons,replacing the fractured spring clip.If the damage can increase the stress amplitude of slab,it should be controlled in time.