Open AccessEstimation of Possibilities of Using Fractal Dimension and Information Entropy of Elastic Waves for Assessment of Damage to Steel 20 at Low Cycle Fatigue
Author(s) -
А. А. Хлыбов,
Yu. G. Kabaldin,
М. С. Аносов,
D. A. Ryabov,
Д. А. Шатагин,
Andrey Kiselev
Publication year - 2021
Publication title -
vestnik iževskogo gosudarstvennogo tehničeskogo universiteta/vestnik ižgtu imeni m.t. kalašnikova
Language(s) - English
Resource type - Journals
eISSN - 2413-1172
pISSN - 1813-7903
DOI - 10.22213/2413-1172-2021-3-17-25
Subject(s) - fractal dimension , amplitude , ultrasonic sensor , fractal , materials science , attractor , entropy (arrow of time) , acoustics , mathematical analysis , mathematics , structural engineering , physics , optics , thermodynamics , engineering
The paper presents the results of experimental studies of specimens made of steel 20 for low-cycle fatigue (cantilever bending). A fatigue curve was obtained for the material under study in the range of stress amplitudes from 210 to 380 MPa. In logarithmic coordinates, this dependence is linear. According to the research results, it has been shown that one of the structure-sensitive characteristics is the shape of an elastic wave pulse transmitted through the medium under study. To analyze the pulse shape of an elastic wave, an algorithm is proposed for assessing the damage of materials, using the values of the fractal dimension of the attractor and the information entropy in the process of fatigue loading. It was found that according to the obtained dependences, the process of fatigue damage accumulation can be conditionally divided into 2 phases. In the first phase, the entropy of the ultrasonic signal practically does not change and remains within the range of 0.05-0.1 nat. The fractal dimension of the attractor of the ultrasonic signal increases from 1.5 to 1.8. During the transition to the second phase, the maximum values of the fractal dimension of the attractor of the ultrasonic signal are observed, the values of which decrease in the second phase to 1.4 before the destruction of the sample. The information entropy values in the second phase increase monotonically up to 0.55 nat. Studies have shown that the obtained dependences practically do not change with a change in the stress amplitude. The results of studies at various stress amplitudes have shown that the characteristics of the fractal dimension of the attractor and the information entropy of elastic wave pulses that have passed through the zones of accumulated damage in the metal expand and supplement the capabilities of acoustic methods in the problems of assessing the performance of materials with low-cycle fatigue and make it possible to identify the stage of destruction of steel 20.