Study On Fatigue Performance Of Fasteners Clips For Ballastless Track In Large Slope Curve Section

In order to adapt to the steep terrain when designing mountain railway lines,it is often necessary to set curves on larger slopes.In addition,ballastless tracks are mainly used in the selection of track structures due to abundant tunnel structures.In order to maintain the good service state of the ballastless track under the repeated load of the train,the fatigue resistance of its fastener clips is very important.However,under the coupling action of multiple factors of line-vehicle-track,the stress conditions of the clips of the fastener system are complex in the section of ballastless track with large slope curves.This will affect the fatigue performance of the clips.Therefore,the ballastless track fastener system in the large slope curve section was taken as the object,and the fatigue performance analysis model of the elastic strip was established in this paper.Combined with line conditions,running speed conditions and clip installation conditions,the fatigue performance of clips was studied in depth to find out the influence of special line conditions on the fatigue performance of clips.The purpose is to provide a certain theoretical basis for the design of mountain railway lines and the maintenance of fasteners.The main research work of this paper is as follows:(1)The vehicle-track rigid-flexible coupling dynamics model was established by applying dynamics theory.A three-dimensional finite element model of the ballastless track fastener system was established with the finite element method.The fatigue life calculation model of clips was established using fatigue analysis theory.These three models were combined to form a joint analysis model for the fatigue performance of ballastless track fasteners.And the validity of the relevant models was verified.(2)The established vehicle-track rigid-flexible coupling dynamic model was used to analyze the influence of different slopes,curve radii and running speeds on the dynamic displacement of the rail in the large-slope curve section,and determine the value of the rail displacement load under the relevant special line conditions.In order to carry out the fatigue performance analysis of the clips in this section,the fatigue load conditions were clarified.(3)Based on the rail displacement load conditions obtained from the analysis,the clip stress under different rail displacement loads was calculated and analyzed using the established three-dimensional finite element model of the fastener system.The effects of different slopes,curve radii,running speeds and bolt preload conditions on the mechanical properties of the clips were studied in the large-slope curve sections.And the most unfavorable position of the clip maximum stress value was found at the arc of the rear limb of the clip.These provide the basis for the fatigue performance analysis of clips.(4)The effects of different slopes,curve radii,running speeds and bolt preload conditions on the clip fatigue life were obtained in the large-slope curve section by the established joint analysis model for the fatigue performance of ballastless track fastener clips.Among them,the curve radius and running speed have a relatively great influence on the clip fatigue life,and the preload has a significant effect on the clip fatigue life.Based on the analysis results of the fatigue performance of the clips,relevant suggestions were put forward for both the railway line design and the fastener maintenance.