Multiaxial effects on LCF behaviour and fatigue failure of AZ31B magnesium extrusion

Multiaxial cyclic tests were performed on wrought AZ31B magnesium extrusion. Axial, torsional and multiaxial cyclic behaviours of the material are presented. Effects of phase angle on stress–strain response, cyclic hardening and fatigue life are discussed. It was found that the material exhibits additional cyclic hardening due to non-proportional loading. However, the phase angle has no pronounced effect on fatigue life. Fatigue cracking behaviour was examined and two characteristics of crack geometry, i.e., size and orientation, are presented. Multiaxial fatigue lives using the Fatemi–Socie and the Smith–Watson–Topper models were predicted. In addition, the Jahed–Varvani energy model was used for fatigue life prediction and was shown to have a potential to be evaluated at plane of maximum axial strain energy density. Reverse analysis for predicting fatigue life by pre-defined critical plane as the observed plane is discussed in details.