PSI - Issue 57

Magnus Andersson et al. / Procedia Structural Integrity 57 (2024) 307–315

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M. Andersson et al. / Structural Integrity Procedia 00 (2023) 000–000

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Fig. 3. Current fatigue analysis process using the e ff ective notch method (RFCC = Rainflow Cycle Counting ASTM E 1049-85).

Fig. 4. FE model of frame (a) load positions; (b) welds (red lines).

3. Fatigue assessment of weld roots with the Simplified Fracture Mechanics (SFM) method

The SFM method also consists of superposition of unit load case results with time based load signals from vehicle simulations. However it is only the stress component perpendicular to the crack through the weld that needs to be extracted. This stress component is linearized and the membrane and the bending stress is used. For estimation of this structural stress the resolution of the element size should be 1.5 mm approximately (i. e. 4 elements through the weld cross section). This means that the size of the FE model will be drastically reduced compared to when the e ff ective notch method is used. The complete frame may be evaluated without any submodelling. The following steps are done in the process of the Simplified Fracture Mechanics method, see Fig. 5.

Fig. 5. Evaluation process with the SFM method.