Statistical Characteristics of Microplastic Strains of the Surface Layer of Austenitic Steel Under Monotonic and High-Cycle Loadings

The mechanical state of the surface layer of the studied metal is controlled by correlation between the ray energy of a coherent light source reflected from the surface of the metal polycrystal and the amplitude of microplastic strains of the elastically deformed surface, based on the analysis of statistical characteristics of the discrete brightness distribution of the image elements of the reflected ray. The regularities of the effect of mechanical loading on the statistical characteristics of the discrete strains distribution under elastic deformation of the surface layer of austenitic steel specimens are defined. An analysis of the sequence of correlation characteristics of the surface deformation defects allows one to reveal a linear dependence of the distribution of the discrete properties of the deformed surface relief on the load intensity factor. The obtained correlation characteristics show that with an increased load the brightness amplitude of the speckle pattern image elements drops due to the increase in the mean-square relief amplitude of the surface deformation defects. By analyzing statistical characteristics of the deformed surface of austenitic steel specimens, quantitative parameters of the descriptive statistics of scattered damage are defined. The regularities of the elastoplastic strain effect on the distribution of discrete surface deformations are obtained. A nonparametric evaluation of the loading intensity factor effect on the sequence of terms in series of mean-square sampled values of damage correlation characteristics under cyclic and static loadings, as well as the determination of strain amplitudes and loading durations as damaging factors during elastoplastic deformation of austenitic steel specimens, are performed.