Grain-boundary modelling of hydrogen assisted intergranular stress corrosion cracking

Abstract

A novel hybrid strategy for modelling intergranular hydrogen embrittlement in polycrystalline microstructures is proposed. The technique is based on a grain-boundary integral representation of the polycrystalline micro-mechanics, numerically solved by the boundary element method, coupled with an explicit finite element model of the intergranular hydrogen diffusion. The intergranular interaction between contiguous grains in the aggregate is modelled through extrinsic cohesive-frictional traction-separation laws, whose parameters depend on the concentration of intergranular hydrogen, which diffuses over the interface according to the Fick's second law, inducing the weakening of the interface itself. The model couples the advantages of the boundary element representation of the polycrystalline micro-mechanics, namely the reduction of the mechanical degrees of freedom, with the generality of the finite element modelling of the diffusion process, which in principle allows the straightforward coupling of the interfacial effective diffusivity with other local mechanical parameters, e.g. the interfacial damage or displacement opening. Several numerical tests complete the study, showing the potential of the proposed technique.