PSI - Issue 75

18

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

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Fig. 13: Strain gauges on the male lug small-sized prototype

To get more details about the failure, additional strain gauge gauges were positioned closed to each edge of lug. Small sized prototype male part is equipped with a total of 24 strain gauges. The female part is not instrumented due to the difficulty in ensuring reliable measurements caused by limited accessibility. 4.3. Specific Acoustic Emission sensor Acoustic Emission is, by definition, the transformation of a physical phenomenon into a mechanical wave. It is an NDT method widely used in industry, based on the recording, conversion and analysis of acoustic signals generated within the material being monitored, by a local release of energy in a material under stress. It is thus capable of detecting dynamic and irreversible microstructural phenomena, right through to macroscopic phenomena linked to critical damage to structures and processes. Because of its sensitivity to the propagation of mechanical waves in a material, Acoustic Emission is intrinsically very sensitive to parasitic noise that may occur in the vicinity of the monitored scene. These phenomena are particularly prevalent in the case of a test of reduced dimensions, carried out on a hydraulic testing machine, as in the case presented here. Countermeasures have long been known and used to reduce ambient noise or, failing that, to identify and isolate it. In the present case, Acoustic Emission is theoretically particularly well-suited to detecting the onset of cracking in the lug of Clips-Riser. Numerous articles and scientific reference documents, among them (Bassim et al. , 1994), (Catty, 2024), (Dumousseau et al., 1979), (Dunegan et al., 1972), (Roget, 1988), (Waldley et al., 1984) have highlighted the significant change in acoustic response in the vicinity of crack initiation in metallic materials. On the basis of these findings and the experience accumulated by the Institut de Soudure over the years in the field of Acoustic Emission, filtering/identification parameters were determined as characteristic of crack initiation in the assembly under consideration. Using Vallen's VisualAE analysis software, the appearance of these particular bursts was correlated with the number of fatigue cycles performed by IFPEN's hydraulic machine and compared with the evolution of strain gauges. The possible correlations between these multiple parameters are detailed in this article. For the entire test, the Acoustic Emission system consists of 8 VS150-M (Vallen) resonant transducers, with a resonant frequency of 150kHz. The transducers are connected to AEP5H preamplifiers (Vallen) using 1.2m microdot cables. The preamplifiers feature a gain of 34dB and a nominal bandwidth of 20-1200 kHz. All Acoustic Emission equipment is tested annually in accordance with EN 13477-2. The maximum amplitude of each transducer's response to a simulated Hsu-Nielsen AE source, at a specific distance of 5 cm, must be at least 80 dBea on average, for at least 3 tests (without system saturation). Every transducer coupled to small-sized i-Clip prototype n°987 achieved this value, in compliance with the standard.