Characterization of Structural Steel Damage Under High-Cycle Fatigue at the Boundary of Inelastic Deformation

The correlation characteristics of strain defects in laboratory specimens of structural steel formed under multi-cycle loading have been obtained. A methodological approach to assessing the characteristics of the physical and mechanical state of damage preceding local material fracture is justified by the photometric analysis of the inhomogeneity of the microplastic strain of the metal surface. The fatigue damage of steel specimens was analyzed using computational and experimental methods to analyze the parameters of nonlocalized damage, according to which the cyclically deformed surface of the specimen is assessed to determine the limit state. The speckle interference images of the deformed metal surface are used to characterize the distribution of discrete surface properties after cyclic deformation. A methodological approach to analyzing the state of damage of structural steel in the range of microplastic surface strains is proposed, which makes it possible to take into account the influence of a group of factors (structural, technological, operational) on the metal failure process caused by elastic-plastic deformation under cyclic loading.