A new three-dimensional grain-level formulation for intergranular degradation and failure in
polycrystalline materials is presented. The polycrystalline microstructure is represented as a Voronoi
tessellation and the boundary element method is used to express the elastic problem for each crystal of the
aggregate. The continuity of the aggregate is enforced through suitable conditions at the intergranular
interfaces. The grain-boundary model takes into account the onset and evolution of damage by means of an
irreversible linear cohesive law, able to address mixed-mode failure conditions. Upon interface failure, a
non-linear frictional contact analysis is introduced for addressing the contact between micro-crack surfaces.
An incremental-iterative algorithm is used for tracking the micro-degradation and cracking evolution. The
behavior of a polycrystalline specimen under tensile load has been performed, to show the capability of the
formulation
