Use of Positron Annihilation Spectroscopy for Stress-Strain Measurements: Annual Progress Report (May 2002 – May 2003)

The purpose of this collaborative research project involving the University of Nevada Las Vegas (UNLV) and Idaho State University (ISU) to evaluate the feasibility of determining residual stresses of welded, bent (three-point-bend), and cold-worked engineering materials using a new non-destructive technique based on positron annihilation spectroscopy. The proposed technique is the use γ-rays from a small MeV electron Linear accelerator (LINAC) to generate positrons inside the sample via pair production. This method can be used for materials characterization and investigation of defects in thick samples, which could not be accomplished by conventional positron technique or other non-destructive methods. The data generated will be compared to those obtained by other non-destructive methods such as neutron diffraction and X-ray diffraction (XRD), and a destructive method known as the ring-core technique. Materials that are currently being tested in the experimental program are Austenitic Type 304L stainless steel (SS), Martensitic Alloys EP-823 and HT-9