X-RAY AND NEUTRON DIFFRACTION STRAIN MEASUREMENT DEVELOPMENTS AT ORNL. C.R. Hubbard, T.R. Watkins, K.J. Kozaczek, S. Spooner, X-L. Wang, M.C. Wright, E.A. Payzant, and X. Zhu, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6064.

The Residual Stress User Center at Oak Ridge National Laboratory is a DOE designated User Facility for characterization of macro and micro residual stresses in materials. Flexibility and adaptability are required of the ORNL facilities to meet industrial and academic needs. Stress characterization in thin films, functionally graded ceramic to metal joints, and weldments in aluminum and steel, for example have been conducted. Recent developments to be presented include (1) use of grazing incidence x-ray diffraction methods for subsurface strain measurement in ground ceramics, (2) application of through thickness strain mapping to stresses from welding and casting, and (3) design and initial development of a new neutron residual stress facility.

Grazing incidence x-ray diffraction utilizing near parallel beam optics has been used to characterize changes in the in-plane, near surface stresses in thin metallic films and in ground ceramics using laboratory and synchrotron x-ray sources. Non destructive measurement of subsurface stresses provides a unique capability to characterize stresses introduced via grinding and to study the influence of grinding variables. Results for alumina and silicon nitride ground ceramics will be presented.

Through thickness, macro residual stress mapping in both research and industrial scale specimens is used to develop and validate FEM models for welding, forging, and casting processes. Stress mapping in a 2" thick by 12x12" plate with a multipass weld and in ceramic to metal joints (e.g. 6 mm diam. rods) are representative of the specimen range. New facilities with at least a 10-fold enhancement in capabilities are under development and involve focussing monochromators and an array of position sensitive detectors.

This research was sponsored by the U.S. Department of Energy, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Transportation Technologies, as part of the HTML User Program, under contract DE-AC05-96OR22464 with Lockheed Martin Energy Research Corp.