Fatigue of extruded AZ31B magnesium alloy under stress- and strain-controlled conditions including step loading

Fatigue of extruded AZ31B magnesium alloy under stress- and strain-controlled loading conditions was investigated. The experimental program included uniaxial and axial−torsion tests conducted under constant amplitude loading and step loading. Observed fatigue lives and cracking orientations were used to evaluate two critical plane multiaxial fatigue criteria, namely, the Jiang criterion and the Fatemi-Socie criterion. The Jiang criterion is found to give satisfactory fatigue life predictions and a reasonable description of the cracking behavior. The Fatemi-Socie criterion provides a similar performance for most of the loading cases. For some of the uniaxial stress-controlled experiments, the fatigue life and early cracking predictions by the Fatemi-Socie criterion do not agree well with the experimental results. A discussion on the implications of stress-controlled loading conditions to fatigue modeling is presented.