Assessment of the fracture toughness of neutron-irradiated nuclear graphite by 3D analysis of the crack displacement field

Abstract

Digital volume correlation of in situ synchrotron X-ray computed tomographs has been used to measure the three-dimensional displacement fields around quasi-static propagating cracks in neutron irradiated and unirradiated graphite in small test specimens of the double cleavage drilled compression geometry. The crack tip location and crack opening were extracted from the displacement fields using a phase congruency edge detection method as cracks were propagated over ~5 mm. The cracks propagated in mode I, maintaining a constant crack opening angle that was ~50% smaller for the irradiated graphite. 3D finite element simulations, using the measured full field displacements as boundary conditions, obtained the critical elastic strain energy release rate for crack propagation by calculation of the domain * Author's copy of paper accepted for publication in Carbon,

J-integral analysis of the elastic strain fields of ferrite deformation twins using electron backscatter diffraction

“…In fracture studies, it has been shown that the J-integral can be evaluated from experimental full-field measurements of the crack tip displacement [39], [40] or elastic strain field [41]- [43]. For conditions of small-scale yielding, the J-integral can be decomposed into the elastic stress intensity factors (KI, KII and KIII), by use of the interaction integral [44], to describe the opening, in-plane shear and out-of-plane shear of the stress concentration [45].…”