Use of electronic speckle pattern interferometry in the detection of fatigue failure in high strength steels

The fatigue behaviour of next generation high strength steels (σUTS = 950–1000 MPa) has been studied. Specifically, this study is focused on the initiation stage of fatigue microcracks. With this purpose, high cycle fatigue tests under uniaxial loading have been performed. During these tests, the deformation history of the specimen has been tracked by means of speckle interferometry. This technique allows monitoring the evolution of the displacement field and its derivatives on the specimen surface, so that it can be used as a tool for detecting microcracks in the first stages of crack initiation. The observation of the fracture surfaces provides complementary information about the localization of the initiation of failure thus, a correlation between the observations made by interferometry and the actual location of the fatigue nucleus and the evolution of the crack during its propagation can be established. Results appoint speckle interferometry as a promising technique for the detection of fatigue failures.