OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 – intensification of reagent diffusion through dislocation channels; – accumulation of residual stresses, which lowers the energy barrier for oxidation reactions. The above data show that the depth of corrosion damage depends on many internal factors. Estimating it using a single characteristic can yield both positive and negative results. However, when estimating multi-dependent parameters, it is possible to use methods that allow for a comprehensive determination of the influence of the considered values on the desired outcome. One such method is the group method of data handling (GMDH) [34-36]. The GMDH method does not perform an exhaustive search of all possible models. However, with a sufficient amount of initial data, it allows us to find the optimal solution, represented as a complex parameter that exhibits the best correlation with the considered value. Using the GMDH method, a complex parameter closely related to the corrosion damage depth of the studied material after plastic deformation was determined. This parameter is expressed by the following equation: 2 1 2 3 Ð k N k k σ ∆ (1) where N is the number of grains; σ is the internal residual stresses; Δ is the degree of grain anisotropy; k is the coefficient of mutual influence of the considered characteristics and the depth of corrosion damage. The obtained complex criterion reflects the influence of internal material parameters on the corrosion damage depth during plastic deformation (Fig. 12). When considering individual parameters, a significant scatter is observed, which, even with a coefficient of determination greater than 0.9, makes it difficult to estimate the value of interest accurately. When the complex parameter is applied, the scatter of median depth values determined from the image is reduced to a range of ±1 μm, and the coefficient of determination approaches 1. Fig. 12. Dependence of median corrosion damage depth on the complex parameter Conclusion – The study of the results obtained for St3 steel after aging in a 5 % hydrochloric acid solution demonstrates a direct correlation between the depth of corrosion damage and internal residual stresses, as well as between the depth of corrosion damage and grain size anisotropy and the total number of grains. – It was found that at a deformation of 6.6 % in the investigated material, the median depth of corrosion damage increases twofold. This is consistent with the data on the increased rate of corrosion of the material with increasing plastic deformation due to the increase in internal residual stresses.
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