Issue 31

R. Citarella et alii, Frattura ed Integrità Strutturale, 31 (2015) 138-147; DOI: 10.3221/IGF-ESIS.31.11 143 a) b) Figure 6 : Edge crack geometric parameters: section view (a) and lateral view (b) . a) b) Figure 7 : Photograph of the cross section of specimens ( a -pure tension, b -tension+torsion). E XPERIMENTAL RESULTS he evolution of the crack growth rate of the elliptical-fronted edge cracks during the tests is determined using COD measurement and information from the microscope. In order to study the crack growth in shafts under fatigue tension loading with superimposed cyclic torsion, several specimens are tested with an initial notch depth equal to 1 mm. Fig. 8a-b show plots of the break through point advances a and of COD against the number of cycles N under pure tension and combined tension+torsion, respectively: in-phase cyclic torsion loading superimposed on cyclic tension leads to a fatigue life decreasing. a) b) Figure 8 : Fatigue crack growth (a) and COD curves on free surface of specimens (b) . T