Localization of plastic deformation in stretching plates: effect of crystalline structure

The integration of the polycrystalline structure in the simulation of stretching plates, performed by the random generation of a grain aggregate and a set of lattice orientations, gives new insights into the phenomenon of plastic strain localization in the form of necking, albeit well predicted at the scale of continuum by instability analysis. A transition is displayed from initial grain scale heterogeneity, with some connection to crystal lattice orientation towards stress axes, to the onset of macroscopic localization patterns. Depending on the number of grains and on the stretching rate, it seems that a competition emerges between a “weakest link” process for which the final necks are located in places where initial deformation is high and an instable mode controlled process during which larger patterns emerge driving the location of the final necks. At high stretching rates, it seems that the second effect is enhanced with, accordingly, a pattern size almost insensitive to the grain size and a limited variability with the grain structure occurrence.