Cyclic Deformation and Anisotropic Constitutive Relations of Al-6061-T6 Under Biaxial Loading

Abstract

Anisotropic cyclic stress-strain curves (CSSCs) were obtained from fully reversed cyclic tests in controlled strain on two orientations of specimens made from an Al-6061-T6 plate (along the rolling direction and perpendicular to the rolling direction). The experiments were conducted at room temperature under three loading conditions: tension/compression, pure torsion and combined tension/torsion in-phase. Based on the CSSCs data, the anisotropic constitutive relations of the material were obtained using Hill’s anisotropic plasticity theory. The coefficients in the yield function were evaluated with a 0.2 percent effective plastic strain criterion. Yield loci and flow behavior were determined for tension/torsion biaxial loading and compared to theoretical predictions. Two anisotropic effective stress-effective strain criteria obtained from the anisotropic constitutive relations were evaluated. A Von Mises type criterion correlated very well with the test data of all specimens under all loadings. The Tresca type criterion did not correlate with the test data.