PSI - Issue 75

Mehdi Ghanadi et al. / Procedia Structural Integrity 75 (2025) 457–466 Mehdi Ghanadi et al./ Structural Integrity Procedia (2025)

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Figure 6. Variation of angular misalignment.

6. Fatigue assessment After laser scanning, uniaxial fatigue tests have been performed on welded specimens under constant amplitude loading with stress ratios of 0.1 and a frequency of 20-27 Hz. Fig. 7 presents the fatigue test results as S-N curves, depicting the nominal stress range against the number of cycles to failure for a fixed design slope of m = 5. The angular misalignment effect has been considered in the results. Runouts and cumulative stresses are omitted from the plot. Comparing the test data with the S-N lines for this welded joint type, defined as FAT 80 with a slope of 3 in IIW recommendations, reveals a slightly conservative assessment of the fatigue test data.

Figure 7.Nominal stress versus number of cycles to failure.

The standard deviation of the logarithmic value of the Basquin coefficient is calculated according to IIW recommendations, and the scatter indicators with respect to stress, T  , are assessed. As indicated in Tab. 2, for specimens with a 2 mm plate thickness, the variation in fatigue strength reduced with improving weld quality, highlighting the increased sensitivity of thinner plates to weld quality variations.