Issue 53

A. Chatzigeorgiou et alii, Frattura ed Integrità Strutturale, 53 (2020) 306-324; DOI: 10.3221/IGF-ESIS.53.24 320 In the Fig.19 is displayed the last (third) specimen using about 7680 plane elements with global mesh size 0.1mm. The comparison of the trajectory of this specimen, as the second one is almost identical to the experimentally obtained trajectory. Figure 19: Result of the trajectory from the FEA (a) and the comparison with the experimental (b) results (third specimen). Studying all of the above comparisons, the conclusion is that the code produces reliable trajectories, due to the fact that the trajectories of all specimens (from FEMAP [28]and experiments [30]) are quite similar, and in most cases identical. Verification of the fatigue lifetime estimation. In order to verify the results of the lifetime estimation produced by the proposed code in FEMAP, experimental result was used [31]. In Fig.20 it is shown the specimen from the experiment that was used. The modified compact specimen was originally proposed by Miranda et al. [32]. The idea was to put a through-thickness hole above the possible crack path, in order to produce mixed-mode behavior of the crack. The specimens used in the experiments of Lu et al. [31], were similar to Miranda et al. [32], but not the same since different materials and dimensions have been used. It should be mentioned, that the initial crack length was 10.5 mm [31]. The specimen used, is considered to be in plane strain condition, and the material was Al2024-T3. In addition to the geometrical characteristics, described in Fig.20, the data shown in Tab. 6 have also been used. Furthermore, the algorithm for calculating the number of loading cycles was based on the Paris rule [24]. P 4000 N E 71.7 GPa K TH 0.9 MPa m K IC 96 MPa m σ yield 470 MPa R ratio 0.05 C 9 1.41*10  n 3 Table 6: Additional data that were used in the experiment [31].