Mission Statement

Scientists and engineers use the HB-2B High Intensity Diffractometer for Residual stress Analysis (HIDRA) to study residual stresses in steel, aluminum, superalloys like Inconel, and other such structural materials. Elastic strain in these materials can be determined by measuring their interplanar atomic spacing, and this instrument is designed to use the high- penetration power of neutrons to generate “maps” of the strain resulting from residual or applied stresses in bulk materials. A detailed understanding of residual stresses is critical for the safe and effective functioning of virtually every type of structural engineering material.

Instrument Description

The HB-2B HIDRA beam line is optimized for strain measurement and determination of residual stress in engineering materials. The incident beam is delivered at a fixed angle of 88° by elastically bent silicon crystal monochromators. Both vertical and horizontal focusing are used. The wavelength is chosen from a variety of monochromator crystal settings with a selection of wavelengths from 1.45 to 2.7 Å. The sample goniometer is designed for spatial scanning of residual stresses at depths from a millimeter to several centimeters. Spatial resolution at a fraction of a millimeter is possible depending on the material. The scattering from the test sample is recorded with a 30 cm x 30 cm position sensitive detector located approximately 1 meter from the sample scattering position. The nominal scattering angle (at the center of the position-sensitive detector) can be set at any value from 30° to 140° but is normally located near 90°. The top and bottom of the detector span approximately 17° both in and out of the horizontal scattering plane. In strain scanning, “gauge volume” is defined by the intersection of the incident and scattered beams. The dimensions of the incident beam slits range from 1-cm to less than 1-mm. The scattering slit with the same size range is set close to the test specimen. The location of these slits controls the size of the gauge volume and defines the translation range over which the test specimen can be scanned. The determination of residual stress from measurements of residual strain requires measurements of strain in at least three, orthogonal strain directions. In some instances, it is not feasible to carry forward a complete stress determination, and in such cases, it is advisable to use a comparison of strain measurements and calculated strains for validation of residual stress calculations. Ancillary equipment available for use at HIDRA include a Huber Eulerian cradle and high-temperature furnaces (vacuum or air). Load frame experiments are currently discouraged on HIDRA given the superior load frame capabilities at VULCAN. Built sample environments, such as high-temperature furnaces and magnets, can be accommodated on the XYZ- positioning stage but requires coordination with the instrument staff.

Applications

The penetrating power of neutrons is very useful in mapping residual stresses in engineering materials. HIDRA is used for strain mapping of heat-treated samples, forgings, extrusions, bearings and races, fasteners, components for transportation and aerospace, pressure vessels and piping, nuclear engineering components, and parts made through additive manufacturing. Neutron diffraction studies of materials under applied stress reveal phase- and grain- level knowledge of deformation processes, which are fundamental for developing finite-element and self-consistent field models of materials behavior. More complex experiments have included functional materials such as piezoelectric materials in applied fields, and shape-memory alloys under varying load and temperature conditions.

Specifications

Beam Spectrum Thermal
Selectable Wavelength (Monochromator setting)

88°, λ = 1.452 Å (Si 511); 1.452 Å (Si 333); 1.540 Å (Si 422); 1.731 Å (Si 331); 1.886 Å (Si 400); 2.275 Å (Si 311); 2.667 Å (Si 220)

Flux on sample 3 x 107 n/cm2/s
(Si 331 and Si 400)
Detector angle range 70 – 110° optimal
Detection system 30x30 cm 2D Denex
2D Detector Coverage 17° 2θ
Z elevator Z translation

Z ± 250 mm
39 cm table to beam height

Nominal Gauge volume

Slits:
Width: 0.3–5 mm;
Height: 0.3–20 mm
Radial Collimator:
Width: 3 mm

Peak location precision 0.003° 2Θ
Sample environments Huber Eulerian cradle and/or phi-chi stage for tensor and texture
Vacuum and environmental furnaces
CrESL creep electrostatic levitator
Integration with flexible specialized sample environments
Max. Sample Size Weight Limit: 50kg
Dimensions: consult with team