Fatigue Assessment Of Welded Bogie Frame For High-speed Train

The bogie is one of the most significant components of the high-speed train and bogie frame is the basic component for other parts of the bogie to be installed on. Nowadays, under the high-speed, heavy load circumstances, the external applied load carried on by the bogie is becoming serious. As typical welded structures, the bogie is pone to be damaged because of fatigue problems which may lead to catastrophe, thus it is extremely necessary to research on the fatigue evaluation method for bogie frame. In this paper, the following aspects have been researched:(1) First, a brief introduction of the bogie frame is made. Then, the characteristics of fatigue problem for welded components and its influencing factors have been reviewed. Also, the fatigue evaluation methods used widely in the recent years are introduced.(2) Utilizing the powerful preprocessor of HYPERMESH software, the hexahedral mesh and hybrid of shell and solid mesh have been completed. The two different FEM models are verified and compared.(3) By utilizing the PATRAN/NASTRAN software from MSC corporation, the finite element analysis of the bogie frame is done with the hexahedral mesh according to the UIC615-4standard from the International Union of Railways. Using the finite element results combined with UIC standards and the Goodman curve, fatigue evaluation for the bogie frame is accomplished.(4) A relatively detailed introduction of surface extrapolation method and its computation procedure, which is widely used in recent years, is presented. Then, the hybrid mesh of shell and solid is employed to do the finite element analysis. In order to improve the accuracy of calculation, higher order elements are employed in the welding area we concern. Utilizing the linear extrapolation of two points which is recommended by the IIW standard from International Welding Institute, the weld roots which are pone to fatigue damage are analyzed using the post-processsing code programmed by MATLAB.(5) Illustrate the Battelle hot spot method proposed by Dr. P. Dong. In particular, the Battelle in this method is mesh-insensitive and the corresponding master S_N curve can be applied to any type of welds in any welded structures. According to the characteristics of Battelle method, the finite element analysis is performed by taking the hybrid mesh of shell and solid. The results obtained from the FEM analysis are empolyed to calculate the Battelle structural stress. Thus, the corresponding maser S-N curve is applied to access the fatigue life of the weld. A comparison of the two methods is made at last.(6) Detail one of the widely used local approaches-fictitious notch rounding approaching, especially the finite element mesh which is most important aspects in using this method. The mesh at the connection weld between the traverse beam and the longitudinal beam is refined based on the principles recommended by the ⅡW literature. The superelement method in NASTRAN is adopted to perform the finite element analysis. The notch stress amplitude is acquired through the post process with PATRAN. Fatigue assessment of the concerned area is done with FAT225S-N curve.