Detection of prefracture zones in structural materials by magnetic and optical methods

The study of the applicability of magnetic and optical methods to the detection of prefracture zones under fatigue degradation of structural materials is exemplified by the 09G2S steel. The regularities of changes in the signal of an attached fluxgate gradiometer with the increasing number of loading cycles have been revealed; namely, significant changes in the gradiometer readings on individual specimen surface areas prove to result from the formation of fracture zones. The change in the value of the coefficient of correlation among the speckle images is studied at different stages of cyclic testing. Speckle image heterogeneity is shown to appear due to fracture nucleation. Thus, the applicability of magnetic and speckle-interferometric methods to detecting prefracture zones in objects under cyclic loading is substantiated.