Surface residual stresses are induced in critical aerospace system components, such as engine disks and landing gear, in order to prevent or delay fatigue crack initiation and growth. However, the potential for allowing increased service life of these components due to the residual stresses is not being realized due to an inability to determine how much stress remains in the component after some portion of the service life has been used.  Research on nondestructively measuring residual stresses in some aerospace materials has recently focused on using two methods: a highly enhanced version of traditional eddy current nondestructive testing (EC NDT) and a specialized high-energy x-ray diffraction technique.  Each method measures the residual stress as a function of depth beneath the surface of the component, thus overcoming the limits of other techniques that only make surface measurements.  The EC NDT technique was found to be applicable to many nickel-based alloys, commonly used in high value fighter engine turbine disks.  The high-energy x-ray diffraction system has shown promise to measure residual stress in titanium disks and certain nickel-based alloy disks, which can’t be measured by the EC NDT method.
     Previous research has initiated the development of both methods, but significant research tasks remain to be answered before a complete technology transition program can be implemented.  The current Science for Sustainment program is targeted at advancing both of these methods by systematically measuring the effects of cold work, heat treatments and residual stress in IN718 material, working to eliminate measurement issues identified with specific material conditions.  A series of specimens has been created that, when fully characterized, will allow for separation of experimental variables and more accurate measurement of residual stress profiles in aerospace materials.  The presentation will cover measurements made with high-energy x-ray diffraction equipment and eddy current conductivity measurements.