Etsuya Yanase

High-Energy X-Ray Synchrotron Radiation Analysis of Residual-Stress Distribution of Shot-Peened Steel

A high-energy X-ray beam from a synchrotron radiation source, SPring-8, was used to determine the residual stress distribution below the shot-peened surface of a carbon steel plate. By using the monochromatic X-ray beam with three energy levels of 30, 60 and 72 keV, the stress values were determined by the sin 2 ψ method with the side-inclination method (ψ diffractometer). The stress value was estimated from the slope of the linear approximation of the relation between 2θ and sin 2 ψ in the range of sin 2 ψ = 0 to 0.5. The estimated stress agreed with the distribution of the residual stress measured by removing the surface layer and repeating the X-ray measurement with Cr-Ka radiation. The nonlinearity of the sin 2 ψ diagram can be used to estimate the distribution of the residual stress. A new method was proposed to estimate the stress value of the distributed residual stress. The new method was a combination of the side-inclination method and the iso-inclination method (ω diffractometer) to maintain the penetration depth constant. The stress value at a given penetration depth was successfully determined by the new method.

A proposal of depth profile analysis method of strain distribution in surface layer using x-ray diffraction at small glancing angles of incidence

Diffracted x-rays at small glancing angle of incidence on surface materials were investigated as function of incidence angles for the studies of residual stresses of surface layers. The intensity of x-ray propagation in surface layer materials characterized by a complex refractive index that changes continuously with depth was derived, and with use of the result, an analyzing method for evaluating the depth profiles of the strain distribution in the surface layer was studied. The derived analyzing method can be applied to the residual stress distribution analysis of the surface layer materials of which densities change continuously in depth as multi thin films, compound plating layers. Now, the analyzing method for the depth profile of the strain distribution in the surface layer using x-ray diffraction at small glancing angles of incidence was discussed with correction on some errata of equations in the previous studies.

X-ray diffractometer designed for industrial applications at SPring-8 BL24XU

An X-ray diffractometer for industrial applications has been designed, installed at SPring-8 BL24XU and tested by measuring a standard Al(2)O(3) powder sample. The measurement results prove the high precision of the diffractometer. The diffractometer was also tested by conducting grazing-incidence X-ray diffraction measurements of ion-implanted chromium-coated steel. The validity of a new method for X-ray stress measurements of polished stainless steel is also proposed and confirmed. The results prove the suitability of this diffractometer for industrial applications.

XAFS analysis of corroded metal surfaces with molten salts by conversion-electron-yield method.

We have measured XAFS spectra of metal surfaces corroded with melting salt (NaCl, KCl, and Na2SO4). Steel samples used were S45C, SCM435, SUS310S, and SUS304. We measured the Fe K-edge XAFS spectra for all samples and the Ni K-edge for SUS310S and SUS304 samples before and after the corrosion. The XANES spectra of samples before the corrosion show metallic structure because surface oxide thickness is thinner than probing depth with a conversion yield XAFS method. Each result of these XAFS spectra gives good agreements with the FEFF calculation in the assumption of bcc and/or fcc structure. The Fe K-edge spectra of steel samples except SUS310S after corroded treatment show existence bonding between Fe and another light element although the spectra of SUS310S samples before and after corroded treatment are much the same.

Non-Destructive Estimation of Residual Stress Distribution of Shot-Peened Steels Based on Nonlinear Analysis of Sin2 .PSI. Diagrams

A new method of nondestructive estimation of the in-depth distribution of residual stresses is proposed by using monochromatic high-energy X-rays from synchrotron radiation source SPring-8. The X-ray with 72 keV energy was used for stress measurements of shot-peened steel samples, whose compressive zone extended a few hundred micrometers below the surface. The measurements were carried out by using the sin2 φ method in a Ψ-diffractometer. The obtained results of sin2 φ diagrams showed nonlinearity due to the in-depth distribution of the residual stress. The stress distribution below the surface was estimated from the analysis to the nonlinearity of sin2φ dragrams. The estimated stress distribution agreed well with that determined by the conventional sin2 φ method with Cr-Kα radiation corrected by surface removal effect.

Sin2 ψ stress measurement method with maintaining probing depth

Abstract A new method was proposed to estimate the distribution of residual stress in a sample surface. When a sample surface has stress gradient, we cannot easily understand the stress distribution due to non-linearity of Sin2 ψ diagram. This non-linearity is because probing depth varies with ψ angle. We discussed a new method to estimate Sin2 ψ diagram with maintaining the X-ray incident angle. By using this method, we can obtain Sin2 ψ diagram without changing the probing depth and measure the stress up to the depth in a sample. We report the results of stress measurement in ground stainless steel sample by using our method. The validity of our method is discussed.