Ultrasonic criteria of carbon steel fatigue wear

Abstract

The results of ultrasonic wave velocity and acoustic nonlinearity measurement in carbon steels are presented in this paper. Samples were tested by fatigue loading in the range from 0 to 100 thousand cycles with the step of 10,000 cycles to obtain the dependence of the acoustic properties on fatigue wear. It was found that the dependences of the Rayleigh wave velocity on the number of loading cycles have three stages. In the first stage, the velocity decreases. This stage corresponds to the burn-in period in the lifetime of metalworks. During the longest, second stage, the Rayleigh wave velocity remains constant, and this corresponds to the operating life. During the final, third stage, corresponding to the catastrophic wear of the metal, the ultrasonic velocity decreases again. The acoustic nonlinearity grows with the number of cycles exponentially, and it does not depend on the carbon content in the steel. Whereas an open fatigue crack leads to a decrease in the acoustic nonlinearity.