NUMERICAL ANALYSIS OF CYCLIC THERMO-ELASTOPLASTIC CREEP BASED ON CHABOCHE AND NORTON-BAILEY MODELS

Under the interaction of thermomechanical cyclic loadings, structures are susceptible to creep-fatigue failure. Aiming at the structural response under the coupled effects of cyclic plasticity and creep caused by long-term load holding, this paper presents a constitutive model within the framework of the decoupled constitutive theory, which is capable of describing the thermally cyclic elastoplastic creep behavior of materials. The consistent tangent stiffness matrix for the coupled constitutive models is rigorously re-derived. An iterative scheme for the plastic multiplier based on the successive substitution method is obtained, which accounts for the contributions from both temperature and creep effects. The proposed methodology was programmed in C++ and validated through element tests, confirming the correctness of the implementation. The ratcheting evolution rates were compared between cases considering or neglecting creep effects. The failure mechanism of paperclip was investigated, revealing that the initial plastic yielding (without subsequent reverse plasticity) predominantly determines the structure's post-yield load-bearing capacity. Through numerical analysis of a notched round bar specimen under various stress ratios, the coupled effects of creep and temperature were systematically examined. The results demonstrate that plastic work dissipation serves as the primary driver for temperature field evolution, while simultaneously elucidating the characteristic progression patterns of plastic zones under thermomechanical loading conditions. The decoupled constitutive model proposed in this study enables effective solutions for thermo-cyclic elastoplastic creep problems, facilitating the acquisition of stress-strain response histories at arbitrary structural locations, providing valuable references for fatigue life prediction and material design optimization.