PSI - Issue 75

26

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

417

• Fatigue test overview The 10 small-sized i-Clip prototypes enable us to identify damage initiation under various dynamic loads. The first conclusion is that estimation using the S-N curve from DNV BM3 is overly conservative and does not allow structural design to be optimized. Fatigue design can be reliably predictive when actual material properties, such as the S-N curve, are considered. The stress range is reasonably well-estimated using the Von Mises stress variation. However, the mean stress correction remains a topic of discussion. Fig. 27 illustrates that the corrected stress range, according to (DNV GL RP C203, 2020), can be less conservative (indicated by the brown circle in Fig. 27). Despite the limited number of tests, which prevents statistical analysis, our proposed methodology defines a stress range (indicated by the green triangle) that is slightly higher than the DNV standard. This ensures a conservative approach for all test predictions. All tests conducted represent significant dynamic loading conditions to show the very good behaviour of our i-Clip material. Test solicitations exceed normal operating scenarios.

Fig. 27: Comparison of test results on small-sized i-Clip prototypes with DNV-BM3 and i-Clip material S-N curve.

6. Conclusion The development of the i-Clip-Riser TM illustrates significant advancements in structural design. By implementing innovative methodologies for fatigue resistance estimation, such as finite element modelling, strain gauge analysis and acoustic emission monitoring, the team optimized the product for enhanced fatigue resistance. Future qualification tests will validate these design improvements. Our experimental diagnostic system enables the detection of crack initiation in advance, utilizing various sensor technologies (strain gauges, Acoustic Emission). This study is based on experimental tests conducted on a 1:5 small scale prototype made of i-Clip material. This approach ensures representativeness of the full-scale product, as validated by finite element modelling. The small-scale prototype enables numerous tests that would be impractical at full scale.