PSI - Issue 12

Venanzio Giannella et al. / Procedia Structural Integrity 12 (2018) 479–491 V. Giannella Structural Integrity Procedia 00 (2018) 000 – 000

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Figure 9. (a) DBEM cracked model with (b) close-up of the remeshed area in the crack surroundings; (c) tractions applied on crack face elements and J-paths (used for the J-integral evaluation) positioned along crack front.

Figure 10. DBEM SIFs for the initial crack for all the six mission points shown in Fig. 3. For each load case, the K values along the crack front (Fig. 11) are averaged to provide a single K value representative of the mission point; the six values obtained are plotted in sequence in order to build a K spectrum representative of the whole mission (Fig. 11); such spectrum is then used as input for the rainflow counting method (Sunder et al. 1984) whose output will be a sequence of baseline cycles. In this process, the condition K = 0 is assumed for those mission points characterized by negative K values (corresponding to a closed crack). The so obtained baseline constant amplitude cycles are cumulated when integrating the crack-growth law.