Damage Evaluation of Rolling Contact Fatigue Using Ultrasonic Spectroscopy

Abstract

For maintenance of the back-up roll used in iron and steel rolling, it is important to establish evaluation technique for the rolling contact fatigue damage. Thus far, progress of fatigued zone below the surface of rolls has been evaluated using profile analysis of half value breadth of X-ray diffraction line. However, the development of quantitative evaluation of the rolling contact fatigue damage is moreover expected. Therefore, in this study, we estimated the density of movable dislocation under the rolling contact fatigue process by measuring ultrasonic surface wave velocities with three-different propagating frequencies via Granato-Lucke's dislocation string theory. The comparison of changes of the loop density of movable dislocation with changes of half value breadth of X-ray diffraction line profile analysis under the rolling contact fatigue process suggests promising availability of the proposed method. As a result, the ultrasonic surface wave velocities with three-different propagating frequencies (5, 10 and 14 MHz) decrease due to increase of the rolling number of rolling contact fatigue. And, the loop density of movable dislocation estimated by Granato-Lucke model increases as the fatigue damage progresses.