A 3D full-field study of cracks in a nuclear graphite under mode I and mode II cyclic dwell loading conditions

3D full-field deformation around crack tips in a nuclear graphite has been studied under mode I and mode II cyclic dwell loading conditions using Digital Volume Correlation (DVC) and integrated finite element (FE) analysis. A cracked Brazilian disk specimen of Gilsocarbon graphite was tested at selected loading angles to achieve mode I and mode II cyclic dwell loading conditions. Integrated FE analysis was carried out with the three-dimensional displacement fields measured by DVC injected into the FE model, from which the crack driving force J-integral was obtained using a damaged plasticity material model. The evolution of near-tip strains and the J-integral during the cyclic dwell loading was examined. Under cyclic dwell, residual strain accumulation was observed for the first time. The results shed some light on the effect of dwell time on the 3D crack deformation and crack driving force in Gilsocarbon under cyclic mode I and II loading conditions.