Experimental research on fatigue crack initiation mechanism by high-resolution DIC measurements

Experimental study on mechanistic understanding of fatigue failure at micro-scale in nickel-based superalloy was performed. A high-resolution DIC (digital image correlation) based experimental device was developed. The evolution of the inhomogeneous strain field due to the random distribution of grains during the fatigue crack initiation at room temperature was measured using the high-resolution DIC technique. A clear link was observed between fatigue crack nucleation and inhomogeneous accumulated plastic deformation among grains at low stress level. Fatigue failure occurred once the cumulative plastic deformation reaches a critical value.