Issue 30

F. Curà et alii, Frattura ed Integrità Strutturale, 30 (2014) 446-453; DOI: 10.3221/IGF-ESIS.30.54 451 It may be observed that the initial crack orientation, in all models, doesn’t affect the crack propagation path independently form the initial crack position. As an example Fig. 9 shows the results obtained for the gear with m B = 1 and considering the initial point A; it is possible to observe that after the initial propagation phase the cracks follow the same direction. For sake of clarity, in Fig. 7 only cracks propagating from points A, C, D are shown. In Fig. 8 cracks from points A and D are reported. Figure 8 : Crack paths for different initial crack positions for thin rim gear (m B = 0.5). Finally, considering the effect of the rim thickness, results show that for the full gear, as written above, the crack propagates always in the tooth direction independently form the initial crack position but, if backup ratios 0.3<m B ≤1 are considered, the crack growth direction depends on the initial crack position and for m B <0.3 the crack propagates always in the radial direction, potentially bringing the gear to a catastrophic failure (Fig. 10). Figure 9 : Effect of initial crack orientation (gear with m B = 1, nucleation point A).