PSPC MICRO AREA X-RAY STRESS ANALYZER - Rigaku

The Rigaku Journal
Vol. 5/ No. 2/1988
Product Information
PSPC MICRO AREA X-RAY STRESS ANALYZER
1. Introduction
As one of the recent trends, there is a demand for
X-ray stress analyzers to conduct stress measurement
of micro areas. For X-ray stress measuring techniques,
aggregates of fine crystal grains like ceramics
are ideal objects to handle from the viewpoint of
isotropy. However, for conventional X-ray stress analyzers,
it has been customary to broaden the irradiation
area and use a broad focus X-ray tube so as to be
able to get continuous Debye rings even from crystal
grains of several tens of microns or so. As a result, for
example it has become necessary to make available a
thin incident beam to cope with stress measurement of
very small sections ranging from 2 to 3mm. So far,
there has been a lack of proper X-ray intensities to
meet this requirement.
The micro area X-ray stress analyzer introduced
here uses the same type of X-ray generator routinely
employed for general-purpose X-ray diffractometers.
It has an X-ray source that yields a maximum output
of 2kW and has a point-focus of 1 x1 mm 2 at 6° take
off angle. Moreover, the analyzer is equipped with a
position sensitive proportional counter (PSPC) as the
detector so that the measurement time has been drastically
reduced to 1/10 to 1/100 or less of the time
required by a scanning unit. The new X-ray stress
analyzer thus features the performance of rapid measurement
along with high reproducibility of data.
2. System Configuration
Fig. 1 through Fig. 3, show the configuration of
this X-ray stress analyzer. Computer automatically
controls goniometer 2θ driving and ψ 0 driving. Set of
data for each ψ angle obtained by PSPC system consisting
of PSPC, spatial analysis circuit, and multichannel
analyzer (MCA) are stored on to floppy disk
to be processed subsequently by the standard stress
analysis software provided.
35 The Rigaku Journal

3. Specifications
(1) Goniometer
X-ray source-to-sample distance: 205 mm
Sample-to-detector distance:
280 mm
Incidence slit 4, 2, 1, 0.5, 0.3, 0.1 5 mm di a.
ψ measuring range:
Iso-inclination method: ψ 0 =−35° ~ 50° method
Side-inclination method: ψ 0 =-3° ~ 48°
Tilt oscillation angle of X-ray incidence: ± l° ~ 1-°, available only for the iso-inclination method
Driving:
2θ driving, with a digital motor
ψ 0 driving, with a digital motor
Alignment method:
Microscope method or optical reflection method
Arm (horizontal) length:
Iso-inclination method: 150 mm or less
Side-inclination method:
240 mm or less
(2) Standard sample stage
Sample stage dimensions: 200 x 300 mm 2
Fine adjustment direction:
Front-rear, right-left, height and arc
Front-rear stroke:
20 mm
Right-left stroke:
20 mm
Height direction:
30 mm
Arc adjustment: ± 30°
Between sample plane and sample stage: 20~ 50mm
Max. load amount Approx.:
3 kgf
(3) Software
(i) Residual stress measurement program (iso-inclination method, side-inclination method)
(ii) Residual stress analysis program
• Peak position determination: Smoothing, background subtraction, LP correction, peak position determination
(FWHM mid-point method, center of gravity method, parabolic approximation method)
• Data output: 2θ peak angle, max. intensity, FWHM, integral width, integrated intensity, stress value, reliability
limit of stress value, slope, 2θ-sin 2 ψ diagram
(iii) Retained austenite quantitative measurement program.
(iv) Retained austenite quantitative data analysis program
Fig. 2 Goniometer
Vol. 5 No. 2 1988 36

Fig. 3 System block diagram
4. Measurement Example
(1) Test piece
β-Silicone nitride (Si 3 N 4 ) and carbon steel (S45C)
that were vacuum brazed by the active metal
method
(2) Measured portion
Jointed surface
(3) Measurement condition
X-ray tube Cr(Kα), 30 kV, 45 mA
Collimator: 0.3, 0.5, 1 mm dia.
ψ angle: Side-inclination method
ψ = 0, 1 5, 2 5, 30, 40°
Stress constant K=-90.08kg/mm 2 /deg.
(4) X-ray irradiation
When stresses concentrate in an exceedingly
small portion of the jointed surface as in the case of
this sample, smoothing of the profile of a stress distribution
curve can be made depending upon the area of
X-ray irradiation. Fig. 4 shows the relations between
the divergent optical system of the micro area X-ray
stress analyzer and the irradiation area when the sideinclination
method is applied.
The collimator is referred to in terms of d, the
pinhole diameter. The divergence angle ω is determined
by the scatter pinhole φS and the collimator
length L 1. The designed values are shown in Table 1.
The irradiation area φA will extend as the incidence
angle ψ is inclined. Eq. (1) represents the relationship
between the irradiation area φA and the incidence
angle ψ
Fig. 4 X-ray optical system and irradiated area A for
residual stress measurements with collimated X-rays.
Table 1. The variation of X-ray irradiated area φA
with collimated diameter φd and divergent angle ω.
φd ω° φA(ψ=0) φA(ψ=40)
0.1 0.13 0.15 0.38
0.3 0.40 0.41 0.53
0.5 0.68 0.67 0.88
1 1.32 1.36 1.77
37 The Rigaku Journal

where
[
A = d − 2 tan θ
1
( )
+ l
⎛ 2
1 ⎞
⎜ ⎟ + ⎛ 1 ⎞
⎜ ⎟ − 2cos
θ1
+ θ ⎤
2 ⎥ 1
⎝cos
θ1
⎠ ⎝cos
θ2
⎠ cos θ1 ⋅cos θ 2
cos ψ
⎦⎥
(1)
tan θ 1 =(S-d)/2L 1
tan θ 2 =(S+d)/2L 1
(5) Measurement result
Fig. 5 shows the measurement result of a residual
stress distribution in the longitudinal direction on the
center line of the sample by the use of collimators 0.3,
0.5 or 1 mm diameter. The abscissa denotes the distance
from the jointed surface on the center line of the
Si 3 N 4 surface, and the ordinate represents the residual
stress value. The circles on the center line indicate the
X-ray irradiation area at ψ=40° for the respective collimators.
For reference, shown on the ordinate are the
sample width values identical to those on abscissa.
5. Conclusion
As mentioned above, this new rapid X-ray stress
analyzer provides high X-ray intensities from a 2 kW
X-ray tube and is equipped with a PSPC. These design
characteristics have made it possible to carry out
measurements that were previously considered difficult.
It offers a substantial reduction in the measurement
time, with improved data reproducibility.
Also available is an optional system with the X-Y
stage used as the sample stage with a stepping motor
to permit automatic shifting of the measurement area
Fig. 5. Residual stress distribution with different
irradiated area on the same specimen A.
position by computer control. Con­tinuous storage of
collected measurement data is made on a floppy disk.
Thus, the micro area stress analyzer is expected to
find a wide range of application for the future.
Reference
S. Tanaka, K. Oguiso, collected lecture papers for the 25th
Symposium on X-ray Material Strength, p. 213, Jul. '88,
The Society of Materials Science, Japan.
Vol. 5 No. 2 1988 38