Issue 50

J. Papuga et alii, Frattura ed Integrità Strutturale, 50 (2019) 163-183; DOI: 10.3221/IGF-ESIS.50.15 169 Figure 2 : This sketch based on Socie’s findings reported in [33] shows the differences in crack initiation and growth phases for tension and torsion load modes . The final test data Paper [36] reports on a complete set of 15 IP/OP pairs before additional requirements were applied (removal of bar specimens, and removal of bending loading). If the target set is isolated according to the criteria described above, only 5 pairs will remain, see Tab. 1, for which a summary of the test setup and the material properties are given in Tab. 2. The quality of the experimental data can also be judged from Figs. 3-5, which show how many data points were used to derive the S-N curves, and how they are scattered. The Basquin two-parametric formula was used only for the two-load level S-N curve setup of Simbürger’s experiments [7], because alternative Kohout-Věchet function [37] does not provide a good regression for fatigue tests just on 2 load levels. Material N Test case ID  a,N [MPa]  a,N [MPa]  a,N  a,N   [deg]  MMP,OP /  MMP,IP Ck45 [7] 100000 SiB011 326.8 187.9 1.74 0 0.94 SiB013 308.2 177.2 1.74 90 ČSN 41 1523 [25] 500000 FF001 99.4 153.4 0.65 0 1.04 FF003 99.4 158.9 0.63 90 FF002 194.4 108.2 1.80 0 1.15 FF004 194.0 143.6 1.35 90 2124-T851 [38] 200000 FAD007 98.7 98.3 1.00 0 0.96 FAD009 89.7 89.6 1.00 90 FAD008 154.8 51.6 3.00 0 0.97 FAD010 143.6 48.0 2.99 90 Table 1 : Data from in-phase and out-of-phase experiments gathered in the final test set. Set ID Material S u [MPa] N [-] p -1 ,N [MPa] t -1 ,N [MPa]  N [-] D [mm] d [mm] d/D [-] SiB Ck45 850.0 100000 419.6 286.2 1.47 35 32 0.91 FF ČSN 41 1523 560.0 500000 250.8 170.6 1.47 11 8 0.73 FAD 2124-T851 477.1 200000 177.2 120.1 1.48 18 16 0.89 Table 2 : Material parameters related to the experiments in Tab. 1. Nomenclature: S u – tensile strength, p -1, N – fatigue strength at N cycles in fully-reversed push-pull loading, t -1, N – fatigue strength at N cycles in fully-reversed torsion,  N = p - 1, N / t -1, N – fatigue strength ratio at N cycles, D – major diameter of the specimen in the critical section, d – minor diameter of the specimen in the critical cross-section.