Issue 50

M. Belhamiani et alii, Frattura ed Integrità Strutturale, 50 (2019) 623-637; DOI: 10.3221/IGF-ESIS.50.53 627 near the crack tip with an element dimension of 0.06mm [24]. Fig. 2 shows the mesh of the specimen and the mesh refinement in the crack tip region. The variation of diverse crack parameters by repairing the crack was investigated. We used in the step option, the static general to analysis the first criterion and the static risks was applied to calculate the limit load. R ESULTS AND DISCUSSION n what follows we will use the variables J* and PLP*, which will represent the improvement provided by the repair where: * unrepaired repaired unrepaired J J J J   (5) * repaired unrepaired unrepaired PLP PLP PLP PLP   (6) First criterion The pipeline was subjected to an applied internal pressure of P = 7 MPa, and the longitidinale crack geometrie was defined in Fig.1(d). a. Choice of the reference point The maximum of J inegral in crack tip line (1) and (2) by loading pressure as shown in Fig. 3. Fig. 3 shows the J integral distribution along the crack tip line (1) for a longitudinal crack for a repaired pipe. As seen that the maximum values of J integral lie in the middle of the crack tip, which implies that the crack tends to propagate radially more than longitudinally. Also, this figure shows that at c/t=10 the maximum value of the J integral remains constant and independent of the crack length. As an example, for a c/t =10 to 15.75 the J =1.1 J/mm 2 . in other words, the repaired system blocks the rise of the J integral by a good absorption of stresses when the ration c/t exceeds 10 and length recovery composite L=200mm. To confirm the result, Fig. 4 presents the variation of maximum J integral value in the crack tip line (1,2) with the loading pressure for both repaired and unrepaired pipes. In what follows we will consider the middle of the crack tip line (1) as a reference point for the entire study. Figure 3 : J integral distribution along the crack tip line (1) for longitudinale crack for repaired pipe(a/t=0.5) I y z