Pages 423-424
In the back-up roll using iron and steel rolling, establishment of evaluation technique for the rolling contact fatigue damage has been longed for. Thus far, fatigued zone below the surface of rolls has been evaluated using half value breadth of X-ray diffraction line profile analysis. However, the 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 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 15 MHz) decreased due to increasing of the rolling number of rolling contact fatigue. And, the density of movable dislocation estimated by Granato-Lucke's model increased in the fatigue damage progress.
