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

Abstract

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.