This paper described a new nondestructive measurement of the in-depth distribution of residual stresses by using monochromatic high energy X-rays from synchrotron radiation source of SPring-8. The measurement was carried out by using the sin2ψ method with the Ψ-diffractometer. It was first proved to have a high accuracy in measuring the loading stress by four-point bending.
The diffractions with five different penetration depths obtained by X-rays with three energy levels, 30, 60, and 72keV, were adapted to measure the residual stress below the surface of shot peened steels. The residual stress distribution measured by five penetration depths agreed well with the residual stress distribution determined by the conventional Cr-Kα radiation combined with the method of the successive removal of the surface layer by electropolishing. The compressive zone extended 150 and 300μm below the surface depending on the intensity of shot peening.
