Numerical examinations of different plastic material models on crack growth behaviour under elevated temperature

摘要

In the future, the energy supply will strongly fluctuate, which results in more frequently load cycles. For this reason, it is necessary to analyse fatigue crack growth under the aspect of reasonable load cases in relevant components not only under linear elastic, but also under elastic-plastic material behaviour. To obtain feasible results, it is necessary to explain the stress-strain-relation of the used material correctly. Therefore, the Chaboche and the Ohno-Wang model are evaluated. The first step was to determine model parameters based on results from cyclic tensile tests for an exemplary temperature of T=400°C. Those parameters were verified in FE-simulations with ABAQUS. For strain-controlled simulations the determined parameters of the Chaboche and Ohno-Wang model result in small deviations between numerical and experimental stresses. Next to strain-controlled, stress-controlled simulations were performed. Although the Chaboche model is adapted for strain-controlled simulations, ratchetting behaviour is not well mapped by this model. Alternatively, usage of the Ohno-Wang model leads to a good simulation of ratchetting behaviour. For calculating J-Integrals of cracked components of power plants afterwards, a study of different crack shapes in different simple models is performed. Results are analysed and compared in respect of the influence of different material parameters and mechanical material mechanisms.