PSI - Issue 75

14

Fabrice Deleau et al. / Procedia Structural Integrity 75 (2025) 392–418 Deleau Fabrice, Emmanuel Persent, Guillaume Coudouel, Guillaume Perrin/ Structural Integrity Procedia (2025)

405

Table 3: Corrected stress range and corresponding number of cycles at the hotspot for each methodology and each S-N curve.

Number of cycles to failure with BM-3 Air S-N curve

Number of cycles to failure with i clip material S-N curve

Mean stress [MPa]

Stress range [MPa]

Corrected stress range [MPa]

Methodology

API 16F

35

874 785

866 669

3,694

138,123

DNV RP C203 Proposed methodology with pre-load Proposed methodology without preload

104

14,056



109

785

800

5,748

426,340

401

749

1,017

1,731

20,038

Then Fig. 10, shows the map of stress range   for each methodology on the small sized prototype. The fatigue hotspot (i.e. the location with the highest stress range) represents the most weakened area and therefore indicates the location where the crack should initiate, according to the fatigue criterion used. The three criteria propose a close location of the hotspot, which is quite reassuring. The stress concentration has a lower level when using the DNV-RP C203 approach compared to the API 16F method. This ranking is consistent with the values given in Table 3, i.e. the API16-F criterion being the most conservative, the DNV-RP-C203 one being the less conservative, and the proposed one being between the two previous ones. It can be observed in Fig. 10, that the stress range is much lower in the lug than in its groove, which corroborates the fact that, although the Von Mises stress in static loading is higher in the lug (cf. Fig. 2 and Fig. 5), the fatigue stress range is higher in the ellipse, which shall be confirmed by the experimental tests, which report a crack initiating in the ellipse.