Strain localization analysis in materials containing randomly distributed voids: Competition between extension and shear failure modes

International audienceIn ductile fracture, strain localization can often be a precursor to the failure of the material. The paper proposes to investigate this phenomenon in the case of random microstructures. Such microstructures are cubic cells made of an elastic-perfectly plastic matrix embedding distribution of identical spherical voids. They allow a better representation of the interaction between voids and greater diversity of failure modes than single-void (or unit) cells. The cells are simulated by finite element for proportional stress loading paths. Strain localization is detected with Rice's criterion computed at the level of the cell. This criterion is shown to accurately detect the onset of localization and the type of failure mode: in extension or in shear. Moreover, the influence of the loading orientation (that is, the orientation of the principal frame of the applied stress with respect to the microstructure) is systematically studied. A strong anisotropy of failure behavior is observed, which can be attributed to the intrinsic anisotropy of the simulation cells. Finally minimal failure strain values on all loading orientations are found. A zone of reduced ductility is observed in generalized shear