Research On Dynamic Characteristics And Fracture Mechanism Of Catenary Droppers In High-speed Railway

In recent years,high-speed railways have developed rapidly,and at the same time,higher requirements have been imposed on railway-related supporting facilities.The catenary,as an important part of the traction power supply system,is in direct contact with the pantograph of the train to complete the task of transmitting electrical energy.Among them,the dropper is a key component connecting the contact line and the support in the contact net.The good flexible characteristics allow it to buffer the periodic vibration between the pantograph and the carenary.It takes part of the current distribution function during the train flow process,reduces the overall impedance of the contact network,and improves the current transmission efficiency.However,in the context of trains speeding up multiple times and traction power being doubled,accidents of breakage of droppers occur frequently.After the droppers breaks,it may cause the local contact line to collapse,destroy the fluctuation characteristics and power transmission performance between the pantograph and the catenary,and seriously affect the safety of the train.Therefore,the dynamic parameters,electrical parameters,and final fracture mechanism under the service condition of the dropper to ensure the safety and reliability of the dropper work are very important for the development of railway operations.In this paper,the dynamic characteristics and electrification parameters of the dropper are solved through simulation,and the actual impact of their respective participation in the final fracture of the dropper is analyzed in combination with the above two aspects.The relevant experiments are designed based on the theory of electroplasticity effect and the judgment of force-electric coupling,the mechanism of the breakage of the dropper,and provide guidance for the optimization of the performance of the catenary dropper.The article first takes a simple chain catenary as the research object,obtains the lifting load spectrum at a speed of 200 km / h?400km / h by solving the pantograph-catenary coupling dynamic equation,calculates the static geometric parameters of the catenary by the partial model method,and establishes a pantograph-catenary system Three-dimensional model,using the finite element software ANSYS to perform transient dynamic analysis of the pantograph-catenary system,and for the elastic deformation factors such as the vibration deformation characteristics,swing deformation characteristics,compression bending characteristics,and deformation vector direction of all droppers in a span,Independent analysis of the causes of typical accidents;then based on the Carson theory and the principle of coupled parallel conductor circuit calculation,a current distribution model of the catenary was established,combined with the actual current supply data of the railway site,and the pantograph was located in the middle and in the end of the catenary,compare the allowable current carrying capacity and the maximum current carrying capacity of each part of the catenary in the current standard to determine the true current receiving status under the service condition of the dropper.Finally,based on the fatigue temperature theory,electroplasticity effect theory and other reasonable explanations of the experimental phenomena,the working temperature of the dropper,the observation of the fracture morphology,the comparison of the metallographic structure,and the force-electric coupling tensile test were finally made.Finally,determine the mechanism of droper fracture.According to the analysis of this article,it is known that the periodic elastic deformation of the suspension string caused by the pantograph-catenary system vibration brought by the train flow is the primary cause of various typical accidents of the dropper.Among them,the dropper in the middle spain has the worst stress environment and is more prone to fracture.;The pantograph's current drawing process will cause local current redistribution of the catenary,and the dropper directly above it will participate in a large proportion of the shunt,and it will be overloaded for a long time.Periodic compression and bending of the dropper is the root cause of fatigue crack initiation.With current overload,it is easier to form oxidative corrosion and local high temperature in corrosive media,which promotes crack growth and accelerates fatigue fracture;under the action of current,it promotes grain recovery,recrystallization,and grain growth inside the dropper.This process reduces the deformation resistance and plasticity of the dropper,and causes large scale deformation of the dropper under periodic vibration,which will cause deviations in the geometric parameters of the catenary,adversely affect the fluctuation characteristics of the catenary,and accelerate the string breaking.