Issue 48

B. Chen et alii, Frattura ed Integrità Strutturale, 48 (2019) 385-399; DOI: 10.3221/IGF-ESIS.48.37 389 It is seen from Fig. 3 that the maximum utilization rate of all welds in the frame is 1.28, which occurs at the junction of the motor hanger and the cross beam, indicating that the welds in the frame do not meet the standard requirements. Fig. 4 is the corresponding fatigue assessment results based on GSFLD. The GSFLD given in Fig. 4 is a traditional GSFLD, which is a fatigue strength diagram with comprehensive consideration of fatigue stress amplitude, average stress and mechanical property limitation of materials. It is often used in the fatigue design of railway vehicle structural components. For example, JIS E4207-1992 (Track frames for railway rolling stock-General rules for design) and UIC ORE B12/RP17 (Tractive units-Bogies and running gear–Bogie frame structure strength tests) all take this diagram as design standard. This diagram is usually understood as "fatigue limit diagram", which mainly includes the GSFLD of the base metal (outermost), butt weld (middle) and other weld (innermost). The corresponding limit values of turning points are shown in Tab. 4. It can be observed from the Fig.4 that some points have exceeded the weld evaluation area. It shows that under traditional GSFLD, the over-standard points do not meet the standard requirements and the frame needs to be optimized. Base metal Butt welds Other welds x y x y x y 240 240 220 220 220 220 152 240 188 220 200 220 -88 65 -110 22 -118 8 -240 -240 -240 -240 -240 -240 -85 -240 -108 -240 -116 -240 152 64 185 150 198 176 240 240 220 220 220 220 Table 4 : Turning point value of GSFLD of steel with tensile strength greater than 520MPa (a) Strain gauge measuring point (b) Rosette measuring point Figure 5 : Platform and support mode of fatigue test Figure 6 : Frame measuring point Experimental verification The object of fatigue test that is performed based on the fatigue conditions specified in Tab. 1 and Tab. 2. It is to verify the fatigue strength of bogie frame experimentally and to study the reliability of the fatigue analysis results. Fatigue test is carried out on the ZJZ (JP) 144 MTS multi-channel fatigue test bed. The test loads are applied and distributed by the test tooling to the exact locations where these forces are generated in actual operation. The loading frequency is 5 Hz, and the loading waveform refers to UIC 615-4-2003 standard, which mainly includes the following three stages: (1) vertical and transverse loads  6 6 10 cycles, twisted loads  6 6 10 cycles; (2) vertical and transverse loads  6 2 10 cycles, static load remains unchanged, quasi-static and dynamic loads are multiplied by 1.2. Twist load is multiplied by 1.2 and cycle  6 0.2 10 times; (3) vertical and transverse loads cycles  6 2 10 times while static load remains unchanged. Quasi-static and