PSI - Issue 17

696 Michal Vyhlídal et al. / Procedia Structural Integrity 17 (2019) 690–697 Vyhlídal et al./ Structural Integrity Procedia 00 (2019) 000 – 000 7 length 0 = 12 mm is much higher than the experimental results introduced in Fig. 5. The applied forces F app are equal when the crack length a 0 is approximately 13.5 mm (for specimens 1 and 2) or 13 mm (for specimen 3). Table 2. Maximum applied force in dependence on crack length Crack length a 0 [mm] 12 12.5 13 13.5 Distance d [mm] 2.34 1.84 1.34 0.84 Maximum applied force F app [kN] 0.671 0.595 0.509 0.406

Fig. 4. Von Mises Stress between the initial crack and the cavity Thus, the calculated F – CMOD diagram for crack length 0 = 13.5 mm in comparison with the experimental measurements of fracture tests can be found in Fig. 5. As you can see, the ascending branch is similar to the measured ones, while the descending branch is different. Reason for this behaviour is an application of LEFM, which do not take tensile softening into consideration. However, the most important variable for the design of structures is still the maximum load. Thus, the modified MTS criterion (7) has shown that the initial crack length a 0 must be greater than it is supposed. In other words, in case of the notch tip near the cavity, the diamond blade saw introduces cracks ahead of the notch tip and it is necessary to account for this fact.

Fig. 5. Calculated F – CMOD diagram with the experimental results at background.