The Neutron Residual Stress Facilities complement the x-ray facilities, permitting the
RSUC to provide the unique capability to measure stress both very near the surface as well
as throughout the volume of a specimen.
Neutrons penetrate many millimeters to
centimeters in most engineering materials; thus, through thickness, macro residual strain
measurements are possible. With use of incident and diffracted beam slits, a small
sampling volume within a bulk specimen can be examined. Measurements of residual strains
are possible over a large range of specimen sizes, e.g. from 6 mm diameter rods containing
a functionally gradient joint to 600 mm (24 in) diameter steel cylinders with girth welds.
Results may be used to quantify the effectiveness of various stress relief methods, to
check finite element model predictions, and for failure analysis, design, and life
prediction.
The micro residual stress
measurements utilizes the high resolution neutron powder diffractometer at HFIR. Because
of the penetrating nature of neutrons, micro residual strains measured by neutron
diffraction are free from surface effects and are particularly useful in characterizing
metal matrix composites.
Capability:
Acknowledgements:
The neutron diffraction facilities for macro residual stress mapping and micro residual
stress characterization are located at the High Flux Isotope Reactor (HFIR) at ORNL and
are operated in collaboration with the Neutron
Scattering Group, Solid State Division, ORNL. HFIR is supported by DOE-Energy
Research. The Neutron Scattering Group is supported by DOE-ER, Division of Materials
Sciences.
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