PSI - Issue 36

G. Pysarenko et al. / Procedia Structural Integrity 36 (2022) 30–35 Pysarenko G., Voynalovich O., Maylo A. et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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Fig. 5. Characteristics of damageability of St 20 steel under periodic loading by symmetric tensile-compressive cycles at a frequency of 100 Hz: ( a) σ а = 240 MPa, 10 5 cycles; ( b) σ а = 200 MPa., 2 · 10 7 cycles.

Correlation characteristics of accumulated damage, parameters of the specimen surface deformation relief are in correlation within the range of 0.70 - 0.97 with the physical and mechanical properties of the material at the stages of fatigue of St 20 steel specimens (see Fig.5). It is implied that regularity in correlation decrease coefficient to 5% (fig. 5), in the range of amplitudes of cyclic stresses, is similar to the effect on the coefficient k D of up to 15%, the duration of cyclic loading in Fig. 4. 3. Conclusions The paper proposed the methodological approach to assessing the state of accumulated changes in the deformation relief of the metal specimen surface within a cyclic loads range. It may be used for monitoring a current state of operational damage to metal structure durability. The process of microplastic deformation evolution indicates the signs of accumulative properties of damageability. The evolution of the material deformations volume is determined by the number of pixels of the certain gradation in the image of the speckle structure of the surface layer. An increase in the number of loading cycles corresponds to the increase in damage due to an increase in microplastic deformations of the polycrystal structural levels. The regularities of the decrease in the correlation coefficient imply the applicability of the method for the analysis of damage both with a regular and non-stationary nature of cyclic loading. References Alfyorova, E., Lychagin, D., 2018. Self-organization of Plastic Deformation and Deformation Relief in FCC Single Crystals. Mechanics of Materials 117, 202 – 213. Babinsk ý, T., Kub ě na, I ., Š ul á k, I., Kruml, T., Tobi áš, J., Pol á k, J., 2021. Surface Relief Evolution and Fatigue Crack Initiation in René 41 Superalloy Cycled at Room Temperature. Materials Science Engineering A 819, 141520. Lecompte, D., Sol, H., Vantomme, J., and Habraken, J., 2006. Analysis of Speckle Patterns for Deformation Measurements by Digital Image Correlation. Proc. SPIE. Speckle06: Speckles, From Grains to Flowers, 6341, 63410E. Maslak, T., Karuskevich, M., Pejkowski, Ł., 2019. New criterion for aircraft multiaxial fatigue analysis. 9 th EASN International Conference on “Innovation in Aviation & Space” . Athens, Greece, 304, 01020. Meireles, J., Da Silva, L., Caetano, D., Huguenin, J., 2012. Effect of metallic surface roughness on the speckle pattern formation at diffraction plane. Optics and Lasers in Engineering 50(12), 1731 – 1734. Moiseenko, D., Pochivalov, Yu., Maksimov, P., Panin, V., 2013. Rotational deformation modes in near-boundary regions of grain structure in a loaded polycrystal. Physical Mesomechanics 16(3), 248 – 258. Mughrabi, H., 2009. Cyclic slip irreversibilities and the evolution of fatigue damage. Metallurgical and Materials Transactions 40A, 1257 – 1279. Pysarenko, G., Mailo, A., Byalonovich, A., Voinalovich, O., 2019. Statistical characteristics of microplastic strains of the surface layer of austenitic steel under monotonic and high-cycle loadings. Strength of Materials 51, 879 – 886. Pysarenko, G., Voynalovych, O., Maylo, A., 2018. The influence to the patterns of the surface layer discrete deformations distribution for metal structure’s operational factors unde r high-cycle loading of samples. Mechanics and Advanced Technologies, 84(3), 39 – 44.