PSI - Issue 42

Abdulla Abakarov et al. / Procedia Structural Integrity 42 (2022) 1046–1053

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A. Abakarov and Y. Pronina / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 5. Interaction of big cracks with each other. (a) B; (b) BB; (c) BBB; (d) B22p.

normalized to the same values in configurations containing only big cracks. Calculations confirm that when the “small” cracks are really smaller than the big ones, at relatively small distances h , they slightly a ff ect the mode I SIFs at the tips of the big cracks. However, in configuration SBS, the presence of cracks (relatively large and close to the big one) in the relaxation zone of the big crack can lead to a decrease in the mode I SIF of the big crack by more than 10%. For every ratio L 0 / l 0 , there is a distance h / l 0 that gives a minimum to the relative mode I SIF of the big crack. The corresponding pairs ( L 0 / l 0 , h / l 0 ) lie outside the considered relaxation zone for all the configurations. The slightest e ff ect of the small cracks on the mode I SIF and the length of big cracks is observed in configuration BSB (for any L 0 / l 0 and h / l 0 ), since the e ff ect of the interaction of large cracks overlaps the e ff ect of the small central crack. At the same time, the mode II SIF of the big cracks in this configuration may increase significantly (several times) when the central crack lies, fully or partially, outside of the relaxation zone. Mixed mode conditions may alter the crack growth direction and thus its rate (see Wang et al. (1996); Abakarov et al. (2022)). Crack propagation direction may also be a ff ected by the presence of phase interfaces in the crack tip vicinity (see, e.g. Grekov and Sergeeva (2020); Piccolroaz et al. (2020); Pronina et al. (2020)). Analysis of the zigzag-type cracks may be done, for example, as described in the works of Martynyuk and Kachanov (2020); Kanaun (2021). We also mention that non-classical fracture modes were recently introduced by Piccolroaz et al. (2021).

4.4. The e ff ect of big cracks on small ones

The e ff ect of neighboring big cracks on a small one may be not unambiguous. Fig. 6 shows the lengths of small cracks in configurations SBS, BSB and BSBSB at t ∗ , normalized to the initial lengths of a single small crack. In all the considered configurations, for any ratio of big and small cracks lengths, there is a range of distance values, h , for which a small crack does not really grow with time. For configurations BSB and BSBSB — when the small cracks