Role of initial surface roughness in the localization and failure of AA6111 sheet

Localization and failure of sheet materials is known to be sensitive to the presence of surface asperities. In the present study, characteristic frequencies and amplitudes of surface roughness have been obtained from undeformed and deformed AA6111 sheet specimens. The undeformed measures are then incorporated into a two-dimensional finite element method (FEM) model to study the relationship between surface roughness and microstructural damage in sheet forming failures. The FEM model is capable of simulating the coupled effect of shear bands and voids on localization by employing a mixed isotropic/kinematic hardening form of the Gurson-Tvergaard-Needleman (GTN) constitutive softening equations. (author)