Use of dynamic speckle interferometry for contactless diagnostics of fatigue crack initiation and determining its growth rate

Steel 09G2S specimens are subjected to cyclic tests, and real-time monitoring of the initiation of a fatigue crack and its growth kinetics is performed by dynamic speckle interferometry. The time averaging of speckles are used to reveal a relation between the parameters that characterize random and deterministic changes in the relief height and speckle images of the surface near the notch during crack initiation.