Variation of Relief Topography and Hardness of Surface Layers of Materials Due to Impact-Oscillatory Loading

Abstract

It was shown previously that cyclic loading can be used to extend the fatigue life of sheet plastic materials subjected to the preliminary impact-oscillatory loading. This type of loading causes dynamic non-equilibrium processes (DNP) in materials, which lead to the formation of dissipative structures in materials and on their surface. The density of these dissipative structures is less than that of the base metal. In this paper, the results of investigations into the relief and hardness of surface layers modified by impact-oscillatory loading are analyzed on the example of five structural materials. The signs of a regular, orderly system of microextrusions formed on flat surfaces of all materials due to DNP are considered along with the alignment of roughness parameters Rz and Ra of relief profiles. The effect of impact-oscillatory loading is one of the main causes that lead to the extension of the fatigue life of materials.

Morphological Characteristics of Dimples of Ductile Fracture of VT23M Titanium Alloy and Identification of Dimples on Fractograms of Different Scale

“…The rounded dimples, in our case, up to 6 µm, were formed in areas of structural heterogeneity, in particular, in the vicinity of inclusions, which was accompanied by the accumulation of local strains and fracture of the material. The consolidation of dimples and the distortion of their shape is primarily due to the transition to a volumetric stressed state, which causes the growth and coalescence of defects with the formation of large dimples [25,34]. It was believed that a change in the roundness coefficient K c indicates the localization of the dimple deformation at the microlevel due to the propagation of a crack formed as a result of coalescence of dimples (Figure 9a).…”

“…In general, after the application of the proposed approach, arrays of dimples >30 μm were found. These dimples were outside microdimples (microdimples are located in the larger 30 µm dimples) formed by the mechanisms of shear and separation, the shape of which is far from rounded [26,27,34].…”

Investigation of the Rupture Surface of the Titanium Alloy Using Convolutional Neural Networks

“…( a ) SEM images of the titanium alloy VT23M (first image) and VT23 (second and third images) [26]; ( b ) visual representation of the result from the output of the neural network; ( c ) the result of detecting dimples (black spots), which is imposed on the initial SEM images.…”