A new phenomenological model of cyclic creep, which is suitable for applications involving finite creep deformations of the material, is proposed. The model accounts for 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-Rabotnov 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. The implicit time integration of the proposed evolution equations is discussed. The corresponding numerical algorithm is implemented into the commercial FEM code MSC.Marc. The model is validated using this code; the validation is based on 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, which simplifies the analysis of test data.

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A new material model of finite strain metal creep is proposed. Transient effects occurring shortly after abrupt changes of the applied stress are captured by the model using the concept of nonlinear kinematic hardening. The evolution of the backstress tensor is affected by the static and dynamic recovery. In order to broaden the applicability range, the model includes the classical Kachanov-Rabotnov damage evolution. Large strain kinematics is described using the assumption of a nested multiplicative split. The model is thermodynamically consistent, objective, and w-invariant. The model is validated in MSC.MARC, basing on experimental data for the D16T aluminium alloy.

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