Development of Type II Residual Strains in Inconel 690 Steam Generator Materials

Abstract

The development of lattice strains as a function of applied compressive loads was evaluated employing TOF (time of flight) neutron diffraction techniques. Tests were carried out with the compression axis directed at each of the principal directions of an Inconel 690 thick-walled tube specimen. Strain measurements were carried out following sequential in-situ loading and unloading of the specimen with the scattering vector directed both parallel and perpendicular to the compression axis. The strong anisotropic elastic and plastic response observed gave rise to intergranular constraints within the material. This is verified by the crystallographic dependence on the sign and the magnitude of the residual strains measured for several different reflections.