Issue 33

P. Lorenzino et alii, Frattura ed Integrità Strutturale, 33 (2015) 215-220; DOI: 10.3221/IGF-ESIS.33.27 218 R ESULTS 3D crack analysis 3D image of the small initiating defect and of the non-propagating fatigue crack was obtained for every defect geometry and steel type. Fig. 3 shows the results in the case of the annealed JIS-S45C steel. Figures on the left show 3D images of non-propagating cracks found at the fatigue limit and figures on the right corresponds to the crack projection (minimum intensity values) in to Z, Y and X planes, Z being the direction parallel to the loading axis. Figure 3 : Left: 3D images of non-propagating cracks found at the fatigue limit. Right: Crack projections in to Z, Y and X axis (minimum intensity). Material: Annealed JIS-S45C steel. S15C S45C SNCM 435 O.M. (  m) 3D (  m) Diff. (%) area (  m) O.M. (  m) 3D (  m) Diff. (%) area (  m) O.M. (  m) 3D (  m) Diff. (%) area (  m) 652 658 -0.9 320 497 492 1.0 265 356 357 -0.2 219 650 655 -0.8 332 495 515 -4.0 278 433 440 -1.6 249 730 756 -3.6 334 485 497 -2.4 252 409 411 -0.4 226 Table 1 : Non-propagating crack length measured by Optical microscope (O. M.) and the analysis of 3D images (3D). The area values were obtained analyzing Z projection images (i.e. Fig. 3 right). Tab. 1 shows a comparison between the length of non-propagating crack measured at the specimen surface by optical microscope and the surface length obtained by analyzing the 3D images. These measurements are very similar, having a maximum difference of 4 % for the case of S45C steel, 30º notch. Regarding the different materials, the NPC size varied A