Issue 35

H. Dündar et alii, Frattura ed Integrità Strutturale, 35 (2016) 360-367; DOI: 10.3221/IGF-ESIS.35.41 364 Thus, initially, this effect is only near the tips of the slanted crack (tips C and D). It can be seen from the above paths that, the 45-degree slanted crack becomes nearly perpendicular to the loading direction after the first step of the crack propagation analysis. However, it also seen that as the cracks keep growing, especially between crack tips B and C, stress re-distributions take place, which cause these crack tips to continue changing directions. This can be seen in Figs. 4 and 5, where K I and K II SIFs are plotted as a function of absolute (curved) crack length. It is seen from these figures that crack tips A and D keep propagating purely in mode-I after the initial mixed-mode deflection, i.e., K II SIF is very close to zero for these crack tips during crack growth. It should also be noted that during the analyses presented in this paper, the maximum crack length increment among all propagation steps is taken to be nearly one-tenth of the largest crack length and that these steps can further be refined to further check the convergence of the crack path and life predictions. However, the chosen steps yield good agreement with Ref. [15] in terms of the paths of the crack tips. Figure 4 : Mode-I and mode-II stress intensity factors during crack growth – crack tips A and B. Figure 5 : Mode-I and mode-II stress intensity factors during crack growth – crack tips C and D. In an effort to compare the predictions of the current study with those of Yan’s, equivalent SIFs vs. number of cycles are plotted in Fig. 6. To be able to make comparisons, equivalent SIFs are calculated in the same way as Ref. [15].   0 0 0 1 cos 1 cos 3 sin 2 2 e I II K K K              (6) In Eq. (6),   0 is the crack growth angle, K I and K II are mode-I and mode-II stress intensity factors.