Fatigue cumulative damage assessment of longitudinal fillet welded gusset in welded frame based on different stress approaches

Based on the global FE model of structural stress calculating for welded frame and considering the geometry of fillet welds and 1mm fictitious notch radius, the local hot spot stress and effective notch stress FE model of longitudinal fillet welded gusset, connecting the axle lever plate and box side-beam lower flange, were refined. The 9 levels equivalent fatigue load spectra were determined according to dynamic fatigue testing loads. The cumulative damage calculations based on nominal stress, hot spot stress and effective notch stress were carried out respectively by using the relative fatigue design S-N curves recommended by ⅡW. The result shows that, the resultant cumulative damage based on effective notch stress is far greater than nominal stress and hot spot stress, and the assessment result may be too conservative. In order to take advantage of the effective notch stress approach better, the more real notch geometries and notch strength data should be used.