Despite advances made in metallic/intermetallic alloys and surface treatments to increase performance and decrease component weight in turbine engine components, standard inspection technologies are limited in their ability to nondestructively characterize operational damage buildup and the effect of surface treatments on component performance. Key areas where nondestructive characterization is required include the ability to quantify surface and subsurface residual strain in operational components, and cold work and surface treatments that are used to improve component life. The inability of current NDI techniques to nondestructively quantify surface and bulk residual stress in turbine engine components, especially single crystal and complex geometry components, leads to overly conservative engineering designs, maintenance procedures, and operational life estimates. Photon Induced Positron Annihilation and related portable technologies have been successfully utilized to quantify surface residual stresses and structural subsurface strain in turbine engine components subjected to high stress/high temperature environments.

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