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Residual Stress Instrument(RSI) is to measure residual
stress distribution in metal or composite materials.
When collimated monochromatic neutron beam impinges
on specimen, diffraction peals of neutrons scattered
by the sample appear according to Bragg's law. If interlayer
distance do of material is changed by internal residual
stress, the position of diffraction peak shifts. Using
a position-sensitive detector one can measure the small
shift of position of diffraction peak i.e., strain.
One can calculate stree if Poison ratio and Young's
modulus of material are known.
RSI was installed
at ST2 sharing neutrons ith HRPD in early 2000. It will
be reinstalled at ST1 in late 2003.
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Fig 1. Schematic diagram of residual stress measurement by neutron
diffraction
Fig.
2. A complete view of HANARO RSI
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Design Characteristics
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○ Monochromator : Focusing
mosaic Ge (331) -ST2
:
bent perfect silicon crystal Si(220) -ST1
○ Take off angle : 10
- 65 (variable)
○ Wavelength
: 1.0
- 1.9 (variable)
○ Collimator
:
one-slit open collimator
○ Detector
:
One-dimensional position-sensitive detector
(100mm(w)
200mm(h), 2mm resolution)
○ Distance
btw monochromator-specimen : 2.0m - 3.5m
○ Distance
btw specimen-detector : 1.0m - 1.5m
○ Neutron
flux at specimen position : 5 106
○ X-Y-Z
translator table : stroke - 20cm, accuracy
- 0.025mm
○ Measurable specimen
: 5cm thickness, 1m length, 50kg weight
Automatic measurement
with individual time for each point
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By the end of 2003 the RSI will be installed
at ST1 and will start operating with
optimized bent perfect crystal Si(220) monochromator.
The Si(220) monochromator increased intensity
about 2.5 times in comparison with vertical
focusing mosaic Ge(331) monochromator.
Position-sensitive
detector with 200mm high active window specially
designed for RSI instrument decreased measurement
time about 8 times in comparison with commercial
position-sensitive detector.
The gauge
volume is defined by fine cadmium slits
fixed on snouts attatched to the slit boxes.
A
computer controlled X-Y-Z translator table
allowing to move the sample with accuracy
0.025mm is mounted on the diffractometer
table to provide scanning of strain distribution.
A software was developed,
which allows to set individual measurement
time for each point and thus save scanning
time.
In late 2004 a tensile jig
will be installed to study charateristics
of material and origin of residual stress.
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Measurement of residual stress in welded
components and composite
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Major components
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Representative publications
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1. Residual Stress Mapping in Welded
Stainless Steel Tubes, Submitted to
KSME International Journal
(2003).
2. Residual stress instrument
at th HANARO, Appl. Phys A74[Suppl.] S1437-S1439(2002).
3.
A High-Luminosity Position Sensitive Neutron
Detector for Residual Stress
Measurements,
IEEE Transctions on nuclear science, Vol.
49, No. 5 (2002) pp. 2411-2414.
4. Development
of 1-D Position Sensitive Neutron Detectors
for Residual
Stress
Measurements, J. Phys. Soc. Jpn. 70(2001)
Suppl. A pp.474-476.
5. Residual Stress
Measurements at HANARO Reactor, Proceedings
of the KSME 2000
Fall
Annual Meeting A, pp. 298-303.
6. Present
Status and Perspective of Residual Stress
Measurements at HANARO Reactor,
한국비파괴검사학회
2001 춘계학술발표회논문집 3-18.
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