A three-dimensional computational model for intergranular cracking

A three-dimensional mechanical model for intergranular crack propagation is presented. The model follows the spirit of existing percolation-like models but offers the inclusion of mechanical effects. This is necessary in order to account more accurately for the crack driving force and the effect of crack bridging ligaments, observed experimentally to be formed by fracture resistant boundaries. The model uses a regular representation of the material’s microstructure and a categorisation of grain boundaries as beneficial and detrimental to fracture. This categorisation makes the model applicable to assessing material’s resistance to intergranular stress corrosion cracking. The model mechanical behaviour is consistent with experimental observations and demonstrates its capability of simulating the development of bridges in the crack wake as well as crack coalescence. Results show that increasing the fraction of resistant boundaries increases the degree of crack tip shielding developed. This is expected to increase the resistance to stress corrosion crack propagation. The model offers a significant reduction of the computational resources usually needed to simulate intergranular propagation.