Development of the Neutron Diffraction Technique for the Determination of NearSurface Residual Stresses in Critical Gas Turbine Components

摘要

The role of residual stress in improving the fatigue performance of a compressorassembly is outlined. One method of producing compressive residual stresses in the surface region of components to give improved resistance to fatigue fracture is shot peening. Neutron diffraction methods are successfully being used to determine through thickness engineering strains in polycrystalline materials. Results of measurements that were made on shot peened samples of a nickel superalloy are given. Good instrumental characteristics, sample positioning in the beam and the correction of near surface data resulted in the accurate determinations of the residual stress fields. It is observed that the stress profile has a characteristic shape irrespective of material or of the peening intensity employed, and also that the distribution of stresses balancing the surface compressive field results in a peak tension of approximately one third of the maximum surface compression.