On finite plastic deformation of anisotropic metallic materials

The classical flow theory of plasticity has been extended to the large strain range for anisotropic metallic materials. The following concepts have been incorporated into the constitutive framework: (1) the convected coordinates and the contravariant true stress, (2) an observer independent yield function, (3) the convected rate for general kinematics of deformation, and (4) the rotation of material texture expressed by a constitutive spin. The theory has been applied to the problem of free-end torsion of a thin-walled tube. The predicted results of shear stress-strain curve, axial strain versus shear strain curve, back stress versus shear strain curve, and initial and subsequent yield surfaces compare favorably with experimental data obtained by the author and his co-workers. It has been shown that the yield function defined by the contravariant true stress can account for the distortion of the yield loci.