Issue 37

C. M. Sonsino et alii, Frattura ed Integrità Strutturale, 37 (2016) 200-206; DOI: 10.3221/IGF-ESIS.37.26 204 shear stress amplitude τ a,xy is, at same time, the principal stress amplitude and the equivalent stress amplitude has the value σ a,eq = σ a,1 = τ a,xy . Figure 4 : Comparison of experimental and calculated results for combined fully reversed loadings according to the Normal Stress Hypothesis Figure 5 : Comparison of experimental and calculated results for combined pulsating loadings according to the Normal Stress Hypothesis However, from Figs. 2 and 3, it can be seen that the lines for pure torsion are inferior to those lines for pure bending, revealing differences in the slopes (k σ = 5 and k τ = 8), knee points (N k,σ = 1·10 6 and N k,τ = 5·10 6 ) and stress levels up to factor of 1.5. The differences in the slopes of these lines, determined under load control for the failure criterion of total