Original paper(Vol.45 No.7 pp.766)

Residual stress analysis on materials with steep stress gradient by using X-ray incidence at higher angles

Ohya Shin-ichi; Yoshioka Yasuo; Maeno Shigeki

Abstract:X-ray stress measurements for isotropic polycrystalline are materials are usually carried out by the sin²y method under the assumption of no stress gradient in X-ray penetration depth. When a steep stress gradient exists in the vicinity of surface layer, however, non-linear sin²y relation is observed and the sin²y method cannot be applied on such cases. Although several X-ray stress analyzers have been developed for materials with steep stress gradient in the surface layer, it is desirable to use diffraction data at higher incident angles of f₀ as possible as close on 90 degrees in order to determine the both values of surface stress and stress gradient with high accuracy.
In the present study, an X-ray stress analyzer based on Omega geometry was fabricated to enable X-ray incidence at higher angle of f₀. The X-ray detector was positioned on -eta side against X-ray incident beam. Both of the residual surface stress and stress gradient were determined by use of the cosy method on shot-peened steel and silicon nitride specimens. This prototype stress analyzer was found effective to perform a biaxial or triaxial stress analysis.

Key Words:X-ray stress analysis, residual stress, stress gradient, higher incidence technique, shot-peened steel, silicon nitride