Issue 43

F. Berto et alii, Frattura ed Integrità Strutturale, 43 (2018) 1-32; DOI: 10.3221/IGF-ESIS.43.01 14 2.20 for V-notched ones, which would give 1.58 and 1.48 respectively once reconverted a posteriori into equivalent stress- based scatter indexes T  . Also in this case the values of the scatter index are very satisfactory, given that the synthesis are based on fatigue data respectively from un-notched specimens under pure tension and torsion with different values of the load ratio and from V-notched specimens under pure tension, pure torsion or combined tension-torsion loading, with different values both of the load ratio and the phase angle. Finally in Fig. 19 the synthesis in terms of SED of all the fatigue strength data presented in this contribution is shown. Again two different control radii equal to R 1 = 0.051 mm and R 3 = 0.837 mm respectively have been adopted. The scatterband includes all the data from un-notched and V-notched specimens under pure tension, pure torsion and multiaxial loading, regardless of the load ratio and the phase angle. It is also characterized by an inverse slope k equal to 5.90, a scatter index T W = 2.5 and a value of the strain energy density at the reference number of cycles, N A = 2  10 6 , that equals 3.08 MJ/m 3 . The equivalent stress-based scatter index T σ results to be 1.58, that is comparable with that observed in the Haibach scatterband ( T σ = 1.50). From Fig. 20 the unifying capacity of the SED approach can be easily observed, in fact it is capable of synthesize all the fatigue strength data in a single quite-narrow scatterband regardless of the loading mode and the specimens geometry. Figure 15: Synthesis by means of local SED of series data with R = 0. Figure 16: Synthesis by means of local SED of series data with R = -1.