Study On Fatigue Life Prediction Of Catenary Suspension Dropper Of High-Speed Railway

As an important part of pantograph catenary contact suspension,the dropper plays the role of transmitting stress and vibration between catenary and contact wire.In the long-term service process of dropper,the frequent vibration of dropper caused by pantograph catenary interaction becomes the normal behavior of dropper,which is easy to cause fracture failure.At the same time,because most of the sections are exposed to the open air for a long time,they are easily affected by bad weather such as wind,frost,rain and snow,which also aggravates the fatigue failure of the dropper.Considering that there are still many deficiencies in the current research on the service life of droppers,especially in the research on the fatigue life of droppers under environmental conditions,and the fatigue life prediction method needs to be improved.Therefore,the paper attempts to carry out research from the fatigue life prediction of the catenary integral dropper,and focuses on considering the additional stress of the dropper from the environmental factors to study the fatigue life of the integral dropper,and further analyzes the fatigue life prediction of the integral dropper.Firstly,according to the design parameters of Beijing Shanghai high speed railway,the catenary finite element model was established,and the static form finding analysis was carried out according to the installation specification.By applying icing load to the pantograph catenary model,the contact line elasticity under different icing thickness was calculated,and the contact line elasticity law under different icing thickness and contact line at different position of dropper was explained.Then,the static force of dropper at different positions in a span is solved by simulation analysis method and moment balance method,which showed that there are significant differences in the static force of dropper at different positions,providing model basis for subsequent analysis.Secondly,in order to study the comprehensive influence of wind and icing conditions on the dropper,the appropriate wind power spectrum function was used to simulate the fluctuating wind,which was superimposed with the average wind to construct the random wind field.According to the coupling relationship among mean wind,fluctuating wind and wind angle of attack,the wind loads acting on the messenger wire,contact wire and suspender are derived,which was discretely loaded to five typical suspender nodes.Through the transient dynamic analysis in ANSYS,the dynamic force time history of the whole dropper was finally solved.By analyzing the dynamic time history curve of the dropper,the result showed that the time course from violent vibration to gentle vibration of the dropper near the positioner was short,and the vibration resistance was large,and vice versa.Lastly,the rain flow counting method was used to discretize the dynamic stress time history of the dropper into random cyclic load,and the zero mean standard fatigue load spectrum was obtained by Goodman algorithm.Fatigue test was carried out on the suspender specimens,and the tensile force and tensile times of the suspender at fracture were calculated,and then the S-N curve of the specimens was fitted.According to miner cumulative damage theory,the fatigue life of dropper under different working conditions was finally estimated.The result showed that in terms of the distribution position of droppers,the fatigue life of the suspender near the positioner is shorter than that of the suspender at the mid span.From the working condition point of view,the speed is the main factor affecting the life of the dropper.In addition,for the strong wind area,the wind speed is a significant impact on the life of the dropper.Because the continuous vibration of the dropper affects the ice adhesion,the icing thickness cause the least impact on the life of the dropper.