Research On Alternating Stress And Fatigue Life Of AC25kV Pantograph Frame

Pantograph is a very important part of the train,as collector for the train to obtain electrical energy from overhead contact line.However,during the actual service of the pantograph,a large number of fatigue problems occurred in its frame structure,which directly led to an increase in the maintenance cost of the pantograph,affected the current quality and the reliability of the overhead contact line.Therefore,it is very important to study the fatigue of pantograph frame.The paper is based on an AC25kV pantograph,First,based on the three-mass calculation parameters of the pantograph and the simplified calculation model of overhead conductor rail,A differential equation with a running speed of 160km/h is established and solved,When only considering the vertical vibration of the pantograph,the contact force at the bow head is obtained.Then a three-dimensional model of the pantograph entity was established,and the transient dynamic finite element simulation was performed on it.The simulation results show that the stress generated by the components of the pantograph is different,and the degree of stress fluctuation is also different.Among them,the alternating stress of the stress concentration position of the lower arm,the underframe and the upper arm is relatively large,and it needs to be taken seriously.The alternating stress of the remaining components is very small,the fatigue damage can be ignored.The modal analysis of the whole pantograph is carried out,and its modal frequencies and mode shapes are found.Secondly,distribute the points near the stress concentration positions of the lower arm,the underframe and the upper arm,and use the pantograph vibration test bench and stress testing equipment to carry out dynamic tests and simulation verification on the pantograph.The analysis shows that the simulated curve of the alternating stress at each test point of the pantograph frame is in good agreement with the measured curve,and the error of the data is small.The alternating stress increases with the contact force,but there is a nonlinear relationship between them.The relationship between the alternating stress and the contact force is different at each test point.Test points 3 and 4 have the most intense alternating stress fluctuations.The average value and the maximum value of the alternating stress on the two test points are larger than those of the other test points,indicating that the stress intensity at the stress concentration position of the lower arm is the largest.When the pantograph-category contact force is constant,The frequency of the contact force will affect the alternating stress to a certain extent,but it is not obvious.Through the dynamic sweep frequency vibration test of the pantograph,the modal frequency range of the pantograph frame is verified.The analysis shows that the lower arm and the upper arm are greatly affected by the low-frequency part of the contact force frequency,while the underframe is affected by the high-frequency part of the contact force frequency.The dynamic test and simulation verification of the pantograph frame show that the simulation model and simulation method are reliable.Finally,the time-history data of the alternating stress obtained by the simulation is imported into the professional fatigue life simulation platform Ncode designlife,and the fatigue life simulation model of the pantograph frame is built based on the fatigue related theory.Considering the influence of average stress and survival rate on fatigue life,the fatigue life of pantograph frame is evaluated according to relevant standards.The evaluation results show that the stress fatigue life of the AC25kV pantograph frame is 1.6×10~7km,which is greater than the 1.2×10~7km specified in the standard,and its design life meets the requirements.