Acoustic study of the texture characteristics of 15YuTA construction steel in fatigue failure conditions

Ultrasonic echo-pulse method is used to study the texture changes and Poisson’s coefficients of 15YuTA construction steel upon fatigue failure in the range of high-cycle fatigue. To describe the texture change, pole figures were constructed using the values of the orientation distribution functions (W400 and W420) obtained from the results of precise measurements of the propagation time of elastic bulk waves in sheet materials. The intensity ratio in the center of the pole figure and the point remote from the center of the pole figure by 45° along the rolling direction was used as a parameter characterizing the texture sharpness. It is shown that change in the texture sharpness is attributed to the development of microplastic strain and accumulation of the microdamages. A nonmonotonic dependence of the change in the texture sharpness on the number of loading cycles is observed. At the initial stage of loading, there is some increase in the sharpness of the texture, which can be attributed to the development of micro-strains on the most favorably oriented sliding planes. At the second stage, a decrease in the texture sharpness is associated with the scattering of the texture as the density of microdefects increases during the destruction of the alloy. The parameter characterizing the texture sharpness can be used as a pre-destruction indicator when monitoring the material of the structure by the ultrasonic method.