Concepts and experiments for characterizing plastic anisotropy of round bars, wires and tubes

Starting from axial and radial anisotropy defined in previous publications, concepts for the description of plastic anisotropy of materials having axisymmetric properties (round bars, tubes, wires) are defined. A maximum of three- in most cases even less-independent parameters are needed. For solid materials like round bars it is recommended to use the axial-radial and the axial-tangential anisotropy as independent quantities for obtaining the yield locus according to Hill's quadratic yield criterion. Experiments for determining these parameters are described. For tubes, however, in most cases only the radial-tangential anisotropy can be determined from the transverse contraction in tensile tests. Hence the yield locus can only be obtained in the approximation of the Hosford-Backofen yield criterion. Effects or the anisotropy parameters on metal forming processes are discussed.