Issue 50

M. Belhamiani et alii, Frattura ed Integrità Strutturale, 50 (2019) 623-637; DOI: 10.3221/IGF-ESIS.50.53 634 We note the repaired technic elevate all values of plastic limit load to an average value of PLP = 34 MPa independantly to the crack geometry where, for ρ=0.5, PLP = 36 MPa and ρ= 1.5, PLP = 32MPa. To cover another field where we know that the circumferential crack arises a difficult and dangerous problem regarding non destructive control technic, we evaluate the repair system of through wall circumferential cracked pipes (Fig. 13). Figure 13 : Comparison of the FE limit results for (circumferential through wall - cracked pipe) unrepaired pipe with Kanninen’s and Kastner’s solution. Two existing solutions are considered in the present study the most popular limit pressure solution is put forward by Kanninen [32]: 1 sin sin 1 2 1 2 L m y P R t                 (14) Another solution is given by Kastner et al [33]:     2 sin 2sin cos 2 1 2 sin 2 2 L m y sin P R t                                                   (15) In Fig. 13, for larger crack lengths   >0,3 the analytical solutions agree with the FEA results whereas Kastner et al under predict the FEA solutions. For shorter cracks both analytical solutions over predict the FEA results. The reason for this behavior is that they are based on the assumption that only the axial stress plays a role in plastic collapse thus as   approaches to 0 the limit dimensionless pressure reduces to 2 which is the limit pressure due to axial stress. However, for the uncracked pipes under pressure load, the hoop stress plays a role, not the axial stress, and thus the limit dimensionless pressure approach