Measurement of Residual Stress Distribution by Strain Scanning Method using High Energy X-rays from Synchrotron Source

Abstract

A residual stress distribution in thermal barrier coatings can be measured using the strain scanning method with high energy X-rays from a synchrotoron source due to its large penetration depth. For the double slits optics, the peak aberration of the measured diffraction becomes large, when the gage volume crosses the surface. The analytical correction method for the peak aberration was proposed in this paper. The surface aberration effect was corrected by taking account of the difference between the center of the goniometer and the optical centroid of the gage volume. Using the correction method, the distribution of the residual stress in thermal barrier coatings were measured from the surface to about 0.26 mm inside. For the as-sprayed top coating, the in-plane residual stress was approximately 30 MPa, and out-of-plane stress increased near by interface. For the coating subjected to the heat cycle (1773 K), the both residual stress were relesed.