Issue 49

D. E. Belhadri et alii, Frattura ed Integrità Strutturale, 49 (2019) 599-613; DOI: 10.3221/IGF-ESIS.49.55 606 Fig. 9 shows the behavior of the K I along the crack front for different values of crack depth (a) and for a repaired pipe. We can say that the SIF keeps the same behavior regardless of the depth, but we also note that there are three areas as already mentioned before where there is a variation of the SIF and to illustrate this effect, we trace Fig. 10 to differentiate the variation of K I as a function of the depth (a) for the three zones noted in Fig. 9. The K I is inversely proportional to the depth (a) for the three positions, this is essentially due to the composite's behavior towards the deformation caused by the opening of the crack.; this confirms the beneficial effect of the composite repair even at 86% of the thickness of the pipe. Figure 10: Variation of the K I along the front of the elliptical crack pipe for different crack depth in position 1, 2 and 3 (c = 60mm). Fig. 11 shows the variation of the K II at the crack front as a function of the depth (a), the results show that the depth a/t=0.87 presents a major risk of rupture with a maximum value of 57 MPa mm 0.5 . This observation confirms that the failure behavior of the progress of the crack is more influenced by shear mode (K II ) without neglecting the presence of the two other modes. 0 10 20 30 40 50 60 70 80 90 100 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 a/t=0,39 a/t=0,55 a/t=0,71 a/t=0,79 a/t=0,87 K II (MPamm 0,5 ) Normalized distance Figure 11: Variation of the K II along the front of the elliptical crack pipe for different crack depth (c = 60mm). 5 6 7 8 9 10 11 12 -5 0 5 10 15 20 a (mm) K I MPa.mm 0.5 position 1 position 2 position 3