Residual stress measurements at LLB: An overview

Residual stresses can be evaluated from displacements of atoms at a microscopic scale. The changes of the distances between atoms correspond to shifts of Bragg reflections, which can be measured accurately by X ray or neutron diffraction. Collimation allows to probe separately small volumes and in this way to obtain a complete map of all the displacements in material. Neutron scattering has the advantage of a large penetration, due to small absorption by most of the elements. Instruments are permanently dedicated to this kind of studies in many neutron facilities. The principle of the technique is relatively easy and does not need very high fluxes. Because of its interest in metallurgical industries, the instrument becomes an attractive technique to be developed around medium flux research reactors. (author)