Research On Fatigue Assessment Of Motive Power Bogie Welded Frame

With the increasing of the speed, the loading and diversification of the train, security concerns have always been the lifeblood of rail transport. As bogie frame of the main bearing structure, especially the driving force of welded bogie frame, the study of fatigue strength has always been a key point and difficulty in the research of railway vehicle safety running. How to quickly and accurately predict the fatigue life of power bogie frame has become a research direction of the structure fatigue life prediction. This paper takes a type of power bogie frame as a carrier of the fatigue life prediction, using the theory of two kinds of new fatigue assessment methods respectively conduct a comprehensive evaluation in fatigue life of the process of operation to architect different welding position.This article first elaborated the advantage of equivalent stress method which is developed by Battelle laboratory in the application of welding frame, and draws up corresponding calculation program, apply the equivalent stress method to calculate fillet weld structure fatigue life of welded joint. Compared to the nominal stress fatigue life prediction result which has been grown up, the equivalent structure stress has many advantages in large complex structure fatigue life analysis. And then analyzed the theoretical basis of notch stress and fracture mechanics method, apply two different methods to conduct fatigue life prediction of root gaps which contain fusion flaw depth of weld. Respectively using notch stress method and fracture mechanics method to calculate life of the butt welding, and then compared the results of the two methods, we know that fracture mechanics method which based on the JIS E4207standard has many advantages in large complex structure fatigue life analysis.Established power bogie frame finite element model based on finite element pre-processing software, deeply analysed the power bogie frame through ANSYS and equivalent structural stress fatigue analysis software, calculated the frame’s cumulative damage value in TB/T2368tertiary fatigue test load using the method of equivalent structural stress and equivalent structural stress-life curve (ΔS-N), we obtained more accurate calculation results and provided a new weld root fatigue life prediction method based on structural mechanics.According to the standard of JIS E4207about the instructions of welding root of fatigue life prediction, to load the frame by TB/T2368standard, to calculate stress intensity factor range of standard assessment place by fracture mechanics method, to calculate cumulative damage value under the form of power bogie frame single-sided groove welding according to the stress intensity factor-life curve (ΔK-N), and compared the results of the fatigue life of welding roof under different fusion flaw depth, we provided effective weld fatigue design parameters for the structure fatigue design.