  A new phenomenological model of cyclic creep is proposed which is suitable
for applications involving finite creep deformations of the material. The model
accounts for the the effect of the transient increase of the creep strain rate
upon the load reversal. In order to extend the applicability range of the
model, the creep process is fully coupled to the classical Kachanov-Rabonov
damage evolution. As a result, the proposed model describes all the three
stages of creep. Large strain kinematics is described in a geometrically exact
manner using the assumption of a nested multiplicative split, originally
proposed by Lion for finite strain plasticity. The model is thermodynamically
admissible, objective, and w-invariant. Implicit time integration of the
proposed evolution equations is discussed. The corresponding numerical
algorithm is implemented into the commercial FEM code MSC.MARC. Using this
code, the model is validated using real experimental data on cyclic torsion of
a thick-walled tubular specimen made of the D16T aluminium alloy. The
numerically computed stress distribution exhibits a "skeletal point" within the
specimen.
