Residual stress analysis using x-rays

X-ray diffraction is a suitable method for residual stress analysis of crystalline and relatively fine-grained ceramic or metallic material provided that a diffraction peak of suitable intensity and free of interference from neighbouring peaks can be produced with the available radiation. Both macroscopic and microscopic stresses can be determined. The principles of the measurement technique are explained and the procedures for sample preparation are described. The surface radiation process, the time required for measurement and the determination of diffraction peaks are explained. Possible defect causes include instrumental and positional faults, the influence of sample shape, and errors in determining the x-ray elastic constant. Measurement of residual stresses below the surface can be carried out if electrolytic polishing is used to bring the lower layers to the surface. The use of x-ray analysis on pipes made from Inconel 600 for use in steam generators is described.