PSI - Issue 75

21

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

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The crack initiation process is less explicit when considering the strain range (Fig. 17). However, the strain range signal indicates the onset of crack propagation around 2,500,000 cycles.

Fig. 17: Strain range values on lug n°1

Fig. 18 shows the average data from the 10 strain gauges on each lug. Our previous conclusions are quite similar for Lug No. 2. Crack initiation on Lug No. 2 begins at approximately 1,860,000 cycles. The absence of a decrease in the strain range indicates that, up to the termination of the test, crack propagation in Lug 2 has not yet started. However, it can be assumed that crack propagation is likely imminent.

Fig. 18: Strain range and average values of each lug during 70 kN +/- 50 kN dynamic loading

Two extensometers were positioned on both sides, in front of each lug. Although their measurements are less precise compared to those from strain gauges, an approximate increase of 10 µm indicates crack opening. While this data offers a general indication, it cannot be used for precise crack opening detection. Extensometer readings are primarily useful for determining the end of the test upon failure."