Fatigue Characteristics Analysis Of Catenary Droppers In High-speed Railway

With the increase of the train speed and opening of high-speed rail lines in china, the accidents of dropper fatigue fracture occur with high frequency, and60dropper accidents happened in Wuhan-Guangzhou line in2011.So it is important for railway transportation to analyze the causes of dropper fatigue fracture, study fatigue characteristics of the dropper, research the dynamic characteristics of droppers in Pantograph and catenary dynamic contacting to ensure the reliability of components of catenary.In this paper, the complete set of droppers used in high-speed rail now were observed. The fatigue behavior of the complete set of droppers are analyzed by theoretical,calculation and finite element simulation. Firstly, the influencing factors of fatigue life of droppers are analyzed by using the fatigue theory, such as temperature, surface characteristics, environmental and so on. And the influencing factors of fatigue life of droppers are analyzed by the expression of dynamic forces of droppers, such as contact line tension, load, moving speed of pantograph. Secondly, the dynamic dropper force, compression amplitude, and displacement of connection point of droppers with contact line are studied when the pantograph movement speed is300km/h and350km/h in Wuhan-Guangzhou line using ANSYS. And the stress distribution in the dropper line is analyzed by using ANSYS Workbench with axial tensile load. Finally, dropper fatigue test rig simulating the actual running state of droppers is established referring to the relevant standards for fatigue testing requirements. And the influencing factors of fatigue life of droppers by fatigue test, such as the load, the compression amplitude, the test frequency are analyzed to study the impact on the fatigue life of the dropper.The theoretical analysis indicates that the dropper force has relation to the load, train speed and the tension of the contact line. The bigger the load is, the faster the speed is, the smaller the tension is, the larger the dropper force is, and the shorter the fatigue life of the dropper is. The dropper force changes with dropper load linearly. The simulating results show that the second dropper has biggest dropper force. The ANSYS Workbench analysis shows that there has obvious stress concentration on the contact position between paraphyses and cored wire of the dropper. Fatigue crack initiation life is shorter on the contact position between paraphyses and cored wire of the dropper when the dropper is curved. When the test frequency is0.5Hz, and compression the width is20mm, the curve of droppers force with load is a straight line through the origin. When the vibration frequency is0.8Hz and the load is90N, the biggest dropper force is326N, and when the vibration frequency is0.8Hz and the load is130N, the biggest dropper force is423N. The result is similar to the dropper force of dynamic simulation300km/h in Wuhan-Guangzhou line. The experiments indicate that75percent droppers fracture occurs on the repeated bending position.