ONR CEN/TS 18094

This document describes the test method for determining residual stresses in polycrystalline materials by the synchrotron X-ray diffraction method. The method can be applied to both homogeneous and inhomogeneous materials including those containing distinct phases. Information on how to carry out residual stress measurements by the synchrotron X-ray diffraction technique is provided as: - the selection of appropriate diffracting lattice planes on which measurements should be made for different categories of materials, - the specimen directions in which the measurements should be performed, - the volume of material examined in relation to the material grain size and the envisaged stress state, - the selection of the stress-free reference (sample) facilitating the residual strain calculation, and - the methods available for deriving residual stresses from the measured strain data. Procedures are presented for calibrating synchrotron X-ray diffraction instruments, enabling: - accurately positioning and aligning test pieces; - precisely defining the volume of material sampled for the individual measurements; and also for: - making measurements; - carrying out procedures for analysing the results; - determining their uncertainties. The principles of the synchrotron X-ray diffraction technique are described and put into perspective with EN 15305:2008 and EN ISO 21432:2020, which are used to measure stresses in the bulk of a specimen.