Finite Element Models of Progressive Failure of Grain Boundaries

Integranular cracking is among the most notable material degradation processes in operating nuclear power plants. Examples include intergranular stress corrosion cracking of austenitic steels and nickel based alloys and irradiation assisted stress corrosion cracking of stainless steel baffle bolts. Recent advances in computational methods and computational resources facilitated development of multiscale computational methods with increasing degrees of realism, stemming mostly from the explicit treatment of randomly shaped and oriented anisotropic grains. Such methods can simulate the polycrystalline aggregates of a few hundred or even thousand grains and are receiving increasing support from the non-destructive experimental techniques such as for example X-ray diffraction contrast tomography. Further development of increasingly realistic multiscale simulation methods requires resolution of some modeling issues. These include reliable, accurate and numerically efficient modeling of the progressive damage along the grain boundaries. Critical appraisal of a number of possible approaches to model the progressive damage along the grain boundaries represents the core of the proposed paper.