Abstract
In this work, to study the damage kinetics of metal samples, we used the method according to which local areas of the surface of the object being scanned are scanned by an elastic wave created in the material from resonant high-frequency excitation of the rod piezoelectric sensor, and phase displacement due to interaction of the probe wave with damaged local elements of the sample structure is recorded. The results of studies have shown that under cyclic loading, a polycrystalline material reveals a dynamic instability of the structure, characteristic of a multilevel dissipative system, which is manifested in structural changes of a polycrystalline material, determining its ultimate state. To determine the microdeformation state of the surface layer of a structural material, a statistical analysis of the fractal properties of non-localized damage was applied in phase diagrams of amplitudes of cyclic load stresses and mechanical deformations of local surface elements at the points of contact interaction with the vibrating sensor of the material during sequential scanning of the material surface. The Hurst index H of diagram, which in double logarithmic coordinates corresponds to the slope of a straight line (in radians) approximating the diagram, allows us to conclude about the current state of the fractal dimension of the local stress structure, and therefore about the degree of randomness of the microstrained state of the surface of the structural material as a result of the force load. In order to monitor of damage, an experimental information system has been developed for analyzing the quantitative characteristics of scattered damage of an elastoplastic material by coherent-optical scanning of a deformed surface with a resolution of 0.2 μm/pixel. As a result of analyzing the obtained characteristics of damage to the surface layer of steel X18H10T under monotonic stretching, it was found that the patterns of development of microplastic deformations on the surface of the samples exhibit correlation properties with the kinetics of the parameters of the statistical characteristics of the coherent beam speckle reflected from the surface of the analyzed object.
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