Study of non-proportionnal loading paths : comparison between experimental results and simulations performed by finite element and homogenized models
Résumé
The plastic behavior of fcc materials is studied under complex loading path at room temperature. Multi-scale experimental results are compared to finite element computations of polycrystalline aggregates, and to simulation by homogenization techniques. Combinations of sequences of simple loading paths such as tension, simple shear, rolling, cyclic tension-compression, with different orientations with regard to rolling direction, are considered. The material used in the study has been cold rolled and annealed. Specimen are marked with several gold microgrids to measure local strain field by digital correlation of scanning electron microscope images, whereas global strains are measured by classical extensometry. A polycrystalline aggregate taking into account the material microstructure is used to perform finite element simulations corresponding to the experiments. The texture measured by X-ray diffraction is represented. Several single crystal models, using the 12 slip systems of the octahedral families, are introduced. Various assumptions are considered for the description of the self and latent hardening. The comparisons between the simulation and the experiments are made on three types of variables~: on a global level, with the description of the macroscopic stress-strain curve, on a local level, by considering the local fields, and in terms of phase averages. Informations about the consistency of the transition rules are deduced.