Study On The Current Collection Quality And Contact Wire’s Fatigue Life Of The Double Pantographs And Catenary System With Small System Height In High-speed Railways

The catenary system is the only power source of the high-speed electrified railway.The train collects electric energy by sliding pantographs mounted on the train roof at high speed.The dynamic contact force between the pantograph and catenary directly determines the current collection quality.Due to the large span and the high maintenance difficulty,the catenary system needs to have a long design life.In the catenary system,the height difference between the contact wire and the messenger wire at the support of the cantilever is called the system height.The use of a small system height catenary can reduce the tunnel section and significantly reduce the construction cost.However,the reduction of the system height will reduce the length of the dropper and affect the current collection quality of the pantograph.The deterioration of the current collection quality will also aggravate the contact wire’s vibration and affect the fatigue life.Simultaneously,to improve the transportation capacity of high-speed rail,rail operators often use double pantographs to collect the current.The interaction of the leading and trailing pantographs will also affect the pantograph’s current collection quality and contact wire’s fatigue life.Therefore,it has essential theoretical research significance and practical engineering value to study the current collection quality and contact wire’s fatigue life of the high-speed rail pantographs-catenary system with a small system height.This paper studies the current collection quality and contact wire’s fatigue life of the pantograph-catenary system with a small system height and double-pantographs operation.The main contents include: Carry out bench tests to obtain the catenary constitutive relationship that describes the dropper compression characteristics and the catenary SN curve.A finite element model of pantograph-catenary is established based on the test results to study the current collection quality with a small structure height and double-pantographs operation.A solid finite element model of the contact wire section is established to study the stress distribution of the area near the steady arm.And the fatigue analysis is conducted to analyse the contact wire’s fatigue life.The main works of the paper are summarised as follows:Firstly,aiming at the defect that the existing dropper model is only under tension but not under compression,a set of dropper compression test devices is designed.The dropper has compression stiffness in the initial stage of compression,and the compressive force is linearly related to the amount of compression.When the compression force of the dropper reaches the threshold,it continues to compress,and the compression force remains unchanged.The compression force threshold is the maximum compression force of the dropper.By fitting the test results,the value of the compressive stiffness of the dropper and the relationship between the maximum compressive force and the length of the dropper is determined.Secondly,consider the geometric nonlinearity of the contact wire,the messenger wire,and the dropper’s tension-compression nonlinearity.A catenary model with small system height is established based on the nonlinear finite element theory and the elastic modulus of the contact line material measured by the uniaxial tensile test.A double pantographs-catenary coupling model with a small system height is established by coupling the finite element model of the catenary and the lumped model of the pantograph through the penalty function method.The new version of the European standard EN 50318 and the field test data were used to verify the model’s accuracy.This proves that the model can be used to simulate dynamic behaviours with a common system height.Then,the double pantographs-catenary dynamic simulation is carried out with different system height,respectively.The results show that the current collection quality based on the traditional model does not change with the decrease of system height.However,the model based on the small system height indicates that the current collection quality deteriorates with the decrease of the system height,which verifies that the model proposed in this paper can be used to study the catenary’s dynamics with small system height.The spectrum analysis of the contact force at different system heights finds that the changing trends of the contact force standard deviation and the frequency component corresponding to the dropper spacing in the contact force are the same.At the same time,the contact force waveforms at the two shortest droppers in the middle of the contact force waveform are significantly different,which demonstrates that the compressive force is the main factor causing the deterioration of the performance of the catenary with small system height.By comparing the simulation data and standard,the system height threshold of the catenary with a speed of 350 km/h is determined.Then,given the poor quality of the trailing pantograph when the double pantographs collect current,The optimization method of double pantographs interval for catenary systems with different system heights is proposed.By analysing the dynamic response of the contact wire under moving loads,the formula to calculate the favourable and unfavourable intervals of the double pantographs are proposed.The simulation results of different speeds and different lines are used to verify the proposed formula.The simulation results of pantographs-catenary with small system height and conventional system height are used to verify the adaptability of the proposed formula to catenary with different system height.Finally,considering the horizontal bending of the contact wire at the steady arm under large tension,it may cause stress concentration in the section and affect the fatigue life of the contact wire.The linear hardening model is established,and the SN curve of the material is determined.Considering that the contact wire beam element in the pantograph-catenary coupling model cannot accurately reflect the cross-sectional stress distribution,the solid element is used to establish the contact wire section finite element model.The stress distribution of the contact wire section is obtained,and the weak point of the section is determined.Based on the stress time-history of the key points of the section obtained by the simulation,the fatigue life of the contact wire under the different speed levels and small system height is estimated by the fatigue analysis method.The results show that the contact wire’s fatigue life will decrease under the condition of increasing speed and small system height,but both can meet the mechanical service life of 30 years.In conclusion,the paper establishes a simulation model of a small system height catenary and studies the current collection quality of the double pantographs-catenary system.At the same time,it also explores the improvement method of the current collection quality of the double pantographs and the fatigue life of the contact wire.The proposed method and the conclusions obtained in this paper can provide a reference for the design of the catenary system of the small system height and high-speed railway.