Experimental and simulation studies of microstructure-sensitive short crack growth in zirconium alloys using a stored energy density driving force

Short crack growth in Zircaloy-4 was investigated using a combined experimental and numerical approach to clarify its microstructurally sensitive behaviour and driving force. In situ digital image correlation, together with microstructural characterisation, was employed during three-point bending fatigue tests to capture crack evolution, crack-tip deformation and lattice rotation. The short crack exhibits a highly tortuous transgranular path and pronounced fluctuations in crack growth rate, with clear retardation observed as the crack traverses unfavourably oriented grains. Crack-tip plasticity is dominated by prismatic-⟨a⟩ slip and is accompanied by lattice rotation about the c-axis. Stored energy density (SED), extracted experimentally from full-field strain and stress measurements, shows trends consistent with the evolution of crack growth rate, particularly across grain boundaries, and a critical SED of approximately 0.5 J/m² is identified. Two crystal plasticity finite element frameworks, based on extended finite element method and continuum damage mechanics respectively, are employed to model short crack growth using the same SED criterion. Both approaches reproduce the main trends in crack-growth-rate evolution, supporting SED as a physically meaningful driving force for microstructurally sensitive short crack growth in zirconium alloys.