Introduction to the Latest European and American Standard Test Methods for Residual Stress Measurement by X-ray Diffraction

Detail introduction was done to the latest European standard test method for residual stress measurement by X-ray diffraction EN 15305-2008 in the aspects of measurement principles, material characteristics, instruments selection, limited cases and handling methods. While measuring residual stress by X-ray diffraction, special attention should be taken in following aspects. EN 15305-2008 and American standard ASTM E915-2010 both specified the adoption of complete formula which did not assume zero shear stress and use of ellipse fitting, otherwise systematic errors may occur. At least 7 times measurement in the sin2ψ range were necessary with negative and positive values of ψ in order to analyze the ψ-splitting in ellipse fitting, and more than 9 times measurement were recommended. It was suggested to use Cu target X-ray source to measure the stress of titanium alloy. If other targets were used, consideration should be taken as the result should be different to the standard ones due to different penetration depths. Detectors with good energy resolution and not sensible to radiation saturation should be selected. Measurement precision on zero stress iron powder should be ±6.9 MPa as normal and ±14 MPa as maximum.