Multiscale model of the role of grain boundary structures in the dynamic intergranular failure of polycrystal aggregates

A multiscale approach to investigate the influence of the grain boundary (GB) lattice structures on the dynamic intergranular failure in 3D polycrystalline materials is proposed. The model comprises the meso- and atomistic scales using the boundary element method (BEM) and molecular dynamics (MD), respectively. At the mesoscale, stochastic grain morphologies, random crystalline orientations and initial defects are included in the physical model. Moreover, a dynamic high-rate load is imposed to produce dynamic stress and strain waves propagating throughout the polycrystal, inducing the material to be susceptible to fail. The intergranular failure is governed by the critical energy density for shear and cleavage modes, evaluated from a set of nano GBs at the atomistic scale. The novelty is the assessment of the energy density considering its dependency on the interface lattice, leading to a group of failure criteria distributed along the aggregate. The difference in the order of magnitude between these length scales is a challenge for the transition multiscale model. Hence, an asymptotic scaling methodology is adapted for bridging the mechanical strength. Finally, it is worth noting that the level of detail of this criterion, is a remarkable enhancement over other intergranular failure models.