High Space-Resolutive Evaluation of Subsurface Stress Distribution by Strain Scanning Method with Analyzer Using High-Energy Synchrotron X-Rays ∗

The surface aberration effect in the strain scanning method with a Ge analyzer was examined using high- energy X-rays from the undulator synchrotron source. The synchrotron X-rays from the undulator source had an enough intensity for the strain scanning method using a goniometer with the analyzer. The use of a Ge (111) analyzer showed remarkable reduction of the surface aberration effect. However, there still existed the surface aberration for the very-near surface region from the surface to the depth of 50µm. A correction method was proposed by taking into account of the effects of the divergence of the Ge analyzer, the mis-setting of the analyzer and the X-ray attenuation. The proposed correction method was very useful for eliminating the surface aberration effect. The correction method enables a high space-resolutive evaluation of the subsurface stress distribution. The method was successfully applied to the determination of the residual stress distribution of the shot-peened steel. A precise d0 value of the strain-free lattice spacing necessary was determined from the surface stress measured by the conventional sin2ψ method using Cr-Kα radiation.