Use of Positron Annihilation Spectroscopy for Stress-Strain Measurements: Quarterly Progress Report (September 01 – November 30, 2004)

Accomplishments: ● A technical paper titled “Residual Stress Characterization in Structural Materials by Destructive and Nondestructive Techniques” has been accepted for publication in the Journal of Materials Engineering and Performance, ASM International, Ohio. ● The PAS method has been applied to develop calibration curves for line shape parameters (S and T) using unstressed and stressed (different magnitude) tensile specimens of martensitic stainless steels. These curves will enable the determination of residual stresses in plastically-deformed materials once the magnitude of S or T parameter is determined by the PAS technique. ● The tensile and welded specimens have been irradiated by low energy photon beam at ISU to compare the residual stresses, with and without radiation. ● Measurements of residual stresses have been performed by the PAS technique on both welded and post-weld thermally-treated specimens to evaluate the effect of thermal treatment on the residual stresses generated due to welding. ● Use of transmission electron microscopy (TEM) has been initiated to analyze voids and dislocations in cold-worked/welded materials