Issue34

R. Citarella et alii, Frattura ed Integrità Strutturale, 34 (2015) 514-523; DOI: 10.3221/IGF-ESIS.34.57 521 The crack growth rates are calculated with the NASGRO formula (Eq. 1) whose calibration parameters are reported in Tab. 1, whereas results in terms of crack sizes vs cycles are shown in Fig. 13. The crack shape variation during growth is shown in Fig. 14. Von Mises stresses on the final cracked scenario are showed in Fig. 15: it is possible to observe that as expected the propagation proceeds under nearly pure mode I with no appreciable crack kinking due to the prevailing bending load case.   1 1 1 p n th q c K C K da K dN K R K                      (1) Parameter Value C 1.23085 E-12 n 2.8 p 0.5 q 0.5 th K  152.89 c K 5097.242 Table 1 : NASGRO3 parameters (SIF units [MPa*mm 0.5 ] and growth rates units [mm/cycle]). Figure 13 : Crack sizes (mm) vs cycles: A and B are the crack length measured at break through points whereas C is the crack depth. C ONCLUSIONS he impact on the crack behavior, and specifically on the SIF values along its front, of the superposition between the main bending loading case and the secondary axle-hub coupling interference is showed. A relevant impact of the press fit loading condition on the overall SIFs along the initial crack front is evident, suggesting the designer to T