The role of the shear and normal stress gradients on life estimation of notched Al7050-T7451 under multiaxial loadings

The aim of this work was to investigate the role of the normal and shear stress gradients on the life estimation of notched Al 7050-T7451 components under multiaxial stress states. In this setting, a new concept of an equivalent critical distance, Leq, was proposed. To validate the analysis a wide number of experimental fatigue data were generated for smooth and notched specimens under push-pull, torsion and combined in phase axial-torsional loadings. From these data, critical distance versus life curves (L-Nf) were obtained under torsion and push-pull loading conditions. The Modified Wöhler Curve Method (MWCM) critical plane based multiaxial model was used in conjunction with these curves and with the new Leq-Nf relationship to estimate lives. The results showed that the L-Nf curves obtained from the fully reversed torsion and push-pull tests had opposite behaviours. The best life estimates for the notched specimens under combined in phase axial-torsional loadings were obtained considering the new Leq-Nf relationship curve proposed in this work.