Diffraction Angle Determination Using Cross-Correlation Algorithm for Double Exposure Method

Abstract

A double exposure method (DEM) was proposed as a stress measurement method using hard synchrotron X-rays for coarse-grained materials or welded parts. Up until now in the DEM, methods such as function approximation and finding straight lines from diffraction spots have been tried. However, sufficient accuracy could not be obtained for images containing a mixture of diffraction spots and rings. In this study, a new method to determine the diffraction radius is proposed. We obtain the waves of circumferential integrals for regions of interest in the front and the rear area detectors, and then determine each diffraction radius using a cross-correlation algorithm. When this method was applied to the measurement of the residual stress in the specimen of the butt-welded pipe, the diffraction radius could be determined with good accuracy. Using the cross-correlation algorithm, the diffraction radius can be determined regardless of the patterns of the diffraction spots or diffraction rings, and this method is the robust and efficient angle determination method suitable for the DEM.