Acoustic Measurement of the Texture Characteristics of 15YuTA Construction Steel under Fatigue Failure

Abstract

This paper presents results from studies on the change in the texture and Poisson coefficients of 15YuTA construction steel upon fatigue failure in the range of high-cycle fatigue by the ultrasonic pulse-echo technique. The coefficients of the orientation distribution functions ($W_{4}^{{00}}$ and $W_{4}^{{20}}$) used for construction of the pole figures were obtained using bulk elastic waves and the precise measurement of its propagation time. As a parameter characterizing the texture sharpness, the intensity ratio in the center of the pole figure and at a point remote from the center by 45° along the rolling direction was used. It was shown that change in the texture sharpness is attributed to the development of microplastic strain and accumulation of microdefects. A nonmonotonic dependence of the change in the sharpness of the texture on the number of loading cycles is observed. At the initial (first) stage of loading, there is some increase in the sharpness, which can be attributed to the development of microstrains on the most favorably oriented sliding planes. At the second stage, the decrease in the sharpness is associated with the scattering of the texture upon the increase in the density of microdefects during the destruction of the alloy. The parameter characterizing the sharpness of the texture can be used as a pre-destruction indicator by the ultrasonic monitoring of a construction material.