PSI - Issue 2_A

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M. Perl, and M. Steiner / Structural Integrity Procedia 00 (2016) 000–000

M Perl et al. / Procedia Structural Integrity 2 (2016) 3625–3646

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4.1.3 Influence of crack ellipticity a/c The distribution of the normalized SIF K IA /K 0 as a function of the parametric angle ψ along the fronts of cracks of various ellipticities, a/c=0.2, 0.6, and 1.0, and of a relative depth of a/t =0.4 in a fully autofrettaged spherical vessels. of R 0 /R i =1.2 is presented in Figs 11, 8, and 12 respectively. As in most previous cases K IA /K 0 is practically the same for all arrays containing up to n≤8, and thus we can consider the case of a single crack to be the critical configuration. The smaller a/c of the cracks, the higher the influence of the number of cracks in the array. In the case of a/c=0.2, K IAmax for an array of n=20 cracks is ~21% lower with respect to the single crack case. In the cases of larger crack ellipticities, a/c=0.6 and 1.0 the reduction is only ~9%, and ~5% respectively. It is interesting to note that while for large ellipticities the influence of the number of cracks in the array is almost even along the whole crack front, in the case of a/c =0.2 the influence is very small around ψ≈ 0° and becomes larger approaching both ψ = ψ 0 and ψ = 90° .

Fig. 11. K IA /K 0 vs. ψ along the fronts of crescentic radial cracks of ellipticity a/c=0.2 in arrays of n=1-20 cracks (a/c=0.6, R 0 /R i =1.2, ε =100%).

Fig. 12. K IA /K 0 vs. ψ along the fronts of lunular radial cracks of ellipticity a/c=1.0 in arrays of n=1-20 cracks (a/c=0.6, R 0 /R i =1.2, ε =100%).