Issue 48

B. Chen et alii, Frattura ed Integrità Strutturale, 48 (2019) 385-399; DOI: 10.3221/IGF-ESIS.48.37 397 Since the control point is located at the weld and the weld is T-shaped, the GSFLD corresponding to Eqn. (10) should be selected as the standard for evaluating the fatigue strength of the control point. In order to compare the results of two fatigue strength evaluation standard, the fatigue strength of control points is calculated based on Eqn. (10) and traditional method, respectively, as illustrated in Fig. 14. Figure 14 : Comparison of fatigue strength analysis results of control points. Figure 15 : Comparison of safety factor of fatigue strength at control points. From Fig. 14, it can be seen that the fatigue strength analysis results based on the NGSFLD are higher than the importance sampling results. Although the control points fluctuate to a certain extent due to the uncertainty of design parameters, the fatigue strength is still within the fatigue limit diagram, indicating that the fatigue strength of bogie frame basically meet the requirements. However, the results of fatigue strength analysis based on traditional method are lower than those of importance sampling. The reason is that the control point is beyond the scope of fatigue limit diagram when it is selected. Although the uncertainty of design parameters leads to the fluctuation of control points, all the results are still out of the fatigue limit diagram, indicating that the fatigue strength of bogie frame does not meet the requirements. In order to further analyze whether the fatigue strength meets the requirements or not, Fig. 15 plots the results of safety factor under two evaluation standards. It can be observed from the figure that the safety factors of the NGSFLD are all greater than 1.1, and basically remain at about 1.2. It meets the requirement of safety factor for fatigue strength analysis of bogie frame. On the contrary, the safety factors obtained by traditional method are less than 1, which does not meet the