Processes of plastic deformation and damage accumulation in polycrystalline structural alloys are investigated under block-type, nonstationary, nonsymmetric cyclic loading. In the framework of damage mechanics, a mathematical model is proposed that effectively describes elastoplastic deformation and fatigue related damage accumulation processes under low-cycle loading. This model can be subsumed under three main parts: the relations defining elastoplastic behavior of the material; the equations describing damage accumulation kinetics; the strength criterion of the damaged material. For validating the model, we perform a numerical analysis and a comparison with the data from full-scale experiments. We demonstrate that the proposed model qualitatively and quantitatively describes the main effects of plastic deformation and damage accumulation processes in structural alloys under complex loading scenarios. Moreover, fatigue related lifetime of the structure is accurately captured by this model as well.
The problem of evaluating the strength and service life of operating properties of critical engineering facilities which are characterized by multivariable non-stationary thermomechanical effects, leading to degradation of initial strength properties of structural materials (metals and alloys) on the mechanisms of fatigue and creep is considered. A mathematical model describing the processes of unsteady creep of metals under complex stress state is constructed. A theoretical-experimental method of determining the material parameters and scalar functions defining transient creep ratios is developed. The results of numerical modeling of the creep process 304 at block thermocyclic complex modes of deformation are presented. The numerical results are compared with those of full-scale experiments. Particular attention is paid to issues of simulation of creep for complex deformation processes, accompanied by the rotation of the main sites of stress and strain tensors and creep strains.
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