Abstract
When stress gradient exists in the irradiated area of X-ray diffraction measurement on the surface of a specimen, the half value breadth of diffraction profile (Hw) increases in comparison with that without stress gradient (Hw0).
When the stress distribution in the irradiated area is uniaxially linear, the change of stress in the irradiated area is proportional to the difference of diffraction angle or peak shift in the area because the diffraction angle at each position in the irradiated area changes linearly. Furthermore, the half value breadth of the profile with stress distribution must be related to the peak shift because the diffraction profile with stress distribution is measured as the integrated sum of the profile at each position in the irradiated area.
In the present study, the quantitative relation between the half value breadth ratio Hw/Hw0 and the peak shift of profile in the irradiated area was analyzed numerically and experimentally. And a technique to measure simultaneously the stress gradient by using the half value breadth ratio and the X-ray stress was proposed.
Cyclic stress was applied on a thin steel specimen, and the X-ray stress and stress rate as dynamic stress gradient were measured as the mean values during a time interval for the measurement of diffraction profile. And it was verified that the measurement of stress gradient with high accuracy required the incident angle of X-ray beam as large as possible and the error of stress gradient increased with decreasing change of stress in the irradiated area.
