Crystal plasticity finite element modeling of slip system activity and post-localization behavior in magnesium alloys.

摘要

During recent years, application of light metals has greatly increased in various industries. Magnesium, the lightest of structural metals, and its alloys have gained special attention, and, therefore, the interest in modeling the behavior of these alloys has increased. In many studies, the goal has been finding ways to improve the low formability of Mg alloys.;The model is verified for the case of Mg single crystals which are highly anisotropic. The minimum required size of the representative volume element (RVE), i.e. the minimum number of grains and the degree of inhomogeneity in each grain required in the CPFE modeling of Mg alloys is determined. Next, the role of different slip systems present in Mg alloys is studied. The effects of strain-rate sensitivity on the micro- and macro-scale behavior of the material and the link between them are also discussed. Using the observed trends for the slip resistances and strain-rate sensitivity factor, new relations are proposed for the change in these values over the range of warm temperatures (75-250°C). The mechanical response of samples cut from hot-rolled plates is simulated and the results are compared to the experimental results available in the literature.;In the last part, localized necking and post-localization behavior of Mg alloys are closely studied. The interaction between slip system activity and localization phenomenon is investigated, and a link is established between the onset of localization and texture evolution in the localized area. The results are of great importance in improving the forming limit of the material and extending forming to the post-localization zone.;In this thesis, the effect of slip system activity on Mg alloy behavior in both the pre- and post-localization zones is examined. An available crystal plasticity model, that takes into account the initial texture of the material and its evolution with deformation, is modified for the case of HCP materials, and, then, implemented into the commercial finite element software ABAQUS. Employing the crystal plasticity finite element (CPFE) method, the link between micro-deformation on the slip systems in Mg alloys and the macro-scale response of these metals is established.