An Experimental Evaluation of Plasticity Theories for Anisotropic Metals

An experimental investigation was undertaken to evaluate anisotropic plasticity theories which have been proposed in the literature. Three different metals in the form of 2.5-in-dia bars were considered: SAE 1020 steel preloaded in tension to a strain of 8 percent, copper alloy 360 (free-cutting brass) preloaded in tension to a strain of 3 percent, and 2024-T351 aluminum alloy as received. All metals had approximately the same properties in the radial and circumferential directions with greatly different properties in the axial direction. Tension and compression tests were conducted on specimens having directions of axial, circumferential, and 45 deg to the axis. Hollow torsion tests were conducted on axial specimens. Biaxial tests were conducted on thin-walled cylinders. All loading was monotonic and proportionate and extended well into the plastic region. Anisotropic plasticity theories were evaluated by comparing theoretical and experimental yield curves for each material and by comparing theoretical load-deformation curves with experimentally determined curves for tension and compression specimens at 45 deg to the axis, for hollow torsion specimens, and for biaxial loading. In most cases, good agreement was found between theory and experiment.