The localization of plastic deformation in expanding metal shells has been studied for several years in CEA/DAM. In addition to explosively driven shells, the laser driven expansion of thin metal sheets yields biaxial tension conditions representative of shell pieces. This kind of set-up is being developed in CEA/DAM and generates strain rates around 10000/s on sheet parts of centimetric width. The evolution of the experimental set-up to millimetric geometries will allow to reach higher stretching rates, unexplored up to now. For all these geometries, for which the sheet thickness is low with respects to the grain size, the influence of the material microstructure is probably significant and the deformation process shall be analyzed at this scale.
The aim of this PhD work is to study plastic strain localization in a sheet of a body centered cubic (BCC) metal under laser shock loading. The phenomenon will be investigated with finite element simulations incorporating the physics at the mesoscale: plastic slip and twinning. An homogenized polycrystalline approach, using an isotropic constitutive model with mean dislocation density as an internal state variable, and a full field approach including grains, their crystal orientations and slip systems, will be compared.