Residual stress states before irradiation in ESS target structural materials

The present work takes place in the framework of the European Spallation Source target research and development program. A wide spectrum of miniaturized, mechanical test specimens of different structural materials were placed into the SINQ target (Paul Scherrer Institute, Villigen, Switzerland) for post-irradiation investigations, including evaluation of the stress fields produced by irradiation using neutron-diffraction techniques. The measurements on irradiated specimens are planned at SINQ using a new diffractometer designed for this purpose. This paper presents initial stress measurements performed at ISIS (Chilton-Didcot, England) and ILL (Grenoble, France) on specimens which were not irradiated, in order to provide the reference residual stress states and validate the experimental procedure. Both experiments give evidence of a tensile stress state around the weld in electron-beam-welded specimens, while the presence of a crack does not seem to introduce high residual stresses into the center of the weld.