The Induced Positron Annihilation (IPA) nondestructive evaluation technologies offer the potential to significantly advance the ability to assess component quality level from initial manufacture through failure and the effects of operational damage from a range of mechanisms on critical engine and structural components.  The IPA technologies nondestructively and very precisely (~0.1% measurement uncertainty) quantify changes in the actual atomic microstructure of material induced by various damage mechanisms. The IPA technology produces a unique “positron signature” for a material or component. Comparing the IPA responses for new, mid-life, and highly damaged components to operational components with unknown damage levels allows an accurate assessment of current damage and estimates of remaining life to be developed.  The IPA technologies have demonstrated the capability to quantify near-surface (1-3 mm sensitivity) damage and the effects of material treatments such as shot peening or thermal barrier coatings and the capability to detect buried damage (2-4 inches sensitivity) in thick multi-layer structures.

The behavior of positrons in materials, and the subsequent measurement and analysis techniques used for the quantification of material signatures and operational effects will be discussed.  The differences and capabilities of the Induced Positron Annihilation—Volumetric (IPA-V) and the Induced Positron Annihilation—Surface (IPA-S) will be discussed through the examination of specific case study results: 1) Application of the IPA-S technology to characterize surface and subsurface residual stresses/strains induced through mechanical surface treatments and the effects of component operation in single crystal and complex geometry polycrystalline components, which are used in critical hot-section aerospace turbine engines; 2) Application of the IPA-V technology to detect cracks within Taper-Lok fastener holes associated with thick, multilayer wing structures without removing the fasteners; and 3) Applications of both technologies in a fatigue life study of aluminum, titanium and steel materials.