Cyclic behaviour of wrought magnesium alloy under multiaxial load

This paper investigates the multiaxial cyclic behaviour of extruded AZ31B magnesium alloy. Tubular specimens were machined from large AZ31B extrusion sections. Two loading modes were considered for multiaxial testing: axial and torsional. All tests were performed at standard laboratory and in as-received conditions. In- and out-of-phase loading at a wide range of strain amplitudes were considered. Nonproportional loading tests were conducted at 45° and 90° phase angle shifts. Correlations between hysteresis shape and deformation mechanisms have been made. Twinning has a major role in deformation under multiaxial loading. Also, it was found that nonproportionality has no significant influence on the fatigue life. Axial and torsional modes were found to have different cyclic behaviour. Fatigue life of AZ31B was examined using different fatigue parameters. Two strain-based parameters based on the critical plane concept were examined. Furthermore, an energy approach was employed as a damage parameter. It was shown that the Fatemi–Socie critical plane model and the Jahed–Varvani energy model provided good estimates to the fatigue life of AZ31B under proportional and nonproportional loading.