Anisotropic nonlinear kinematic hardening rule parameters from reversed proportional axial-torsional cycling

A procedure for determining parameters for anisotropic forms of nonlinear k inematic hardening rules for cyclic plasticity or viscoplasticity models is described. An earlier reported methodology for determining parameters for isotropic forms of uncoupled, superposed Armstrong-Frederick type kinematic hardening rules is extended. For this exercise, the anisotropy of the kine matic hardening rules is restricted to transverse isotropy or orthotropy. A limited number of parameters for such kinematic hardening rules cart be de termined using reversed proportional tension-torsion cycling of thin-walled tubular specimens. This is demonstrated using tests on type 304 stainless- steel specimens and results are compared to results based on the assumption of isotropic forms of the kinematic hardening rules.