Issue 74

P. Zuliani et alii, Fracture and Structural Integrity, 74 (2025) 385-414; DOI: 10.3221/IGF-ESIS.74.24

[11] and it is possible to see that the smooth specimens as well as the notched specimens do not show a fatigue limit up to 10 9 cycles. Moreover, the slope of the notched specimens is smaller than the slope of the smooth specimens. To evaluate this effect, the Authors computed the fatigue strength reduction factor (K f ) as the ratio of the fatigue strength of smooth specimens to the ratio of the notched fatigue strength. Its correlation with the number of cycles is reported in Fig. 20(a), where it is also compared with the same variable computed with the data of Yang et al. [24]. The plot shows that, although K f is not constant in the VHCF regime, the value provided by Neuber [30] is closer to the real values than the values provided by Peterson’s formulation [31]. Gao et al. also did the same comparison for the notch sensitivity factor (q) computed with Eqn. 2.

(a)

(b) Figure 19: S-N curves for INCONEL 718 in VHCF regime: (a) load ratio R=0.1 (b) load ratio R=0.5. Experimental data digitized from [29]. Also q has a clear dependency to N, as shown in Fig. 20 (b).

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