Discussions on constitutive equations of superplastic 5083 aluminum alloy

A constitutive equation for a fine-grain superplastic material, 5083 Al alloy, is proposed on the basis of combined loading experiments and the classical (mathematical, phenomenological) theory of plasticity using the potential function. The experiments are performed by applying the combined loads of axial force and torque to the thin-walled tubular specimen of 5083 Al alloy. A new potential function is proposed by incorporating the second invariant and third invariant of stress deviator. The proposed constitutive equation can predict the mechanical behavior of 5083 Al alloy under the combined loading conditions.