| Difference between rail transport mode and other modes is the dynamic interaction between wheel and rail, which upward transfers to the locomotive and down imposes on the track structure, and the wheel-rail contact point is regarded as its interface. Today rail transport of China is in the face of major development, it will bring greater challenges to the rail transport. Then, the fatigue issues of locomotive and track structure which are resulted from the interaction will become more prominent than ever before. In this paper, based on the research results of the wheel-rail dynamic interaction and structural fatigue life prediction, the fatigue damage of the locomotive key components, which are resulted from the wheel-rail impact, will be researched and discussed.Based on the latest research results of wheel-rail impact at home and abroad, the wheel-rail impact system was simplified as three degrees of freedom system with only vertical vibration, and the differential equation was established, the load histories of wheel-rail impact were solved by Rung-Kutta formula. Secondly, the finite element model of Co-Co locomotive was established consisting of carbody, bogie frame and wheelsets. In order to validate the veracity of this model, the static stress analysis and mode analysis were done. The stress histories of the frame were obtained by transient dynamics analysis technology. Then, the dynamic stresses of the structure were counted with the rain-flow counting method and the average stresses were modified. Finally, the structural fatigue life of frame was predicted based on material S-N curve and linear damage cumulative theory applying fatigue analysis software nSoft.The results show that the fatigue life of frame is rather short under the effect of wheel-rail impact, especially subjected pulse interference from the wheel-rail impact, then the welding parts between the first vertical absorber block and the side frame will be damaged easily.
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