Effect of loading-path on the evolution of yield surface for anisotropic metals subjected to large pre-strain

A theory of plasticity previously formulated by the author to discuss the free-end torsion problem has been extended to the more general case of combined axial-torsion of a thin-walled tube. This paper is devoted to the discussion of evolution of the yield surface due to different (proportional and non-proportional) loading paths with pre-strains in the large strain range. Experimental yield surfaces with axial and torsion pre-strains of magnitudes up to 40 and 45%, respectively, are presented, and theoretical results are compared with the experimental data.