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JP2004245598

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DESCRIPTION JP2004245598
The present invention provides a probe capable of evaluating deterioration, damage, and the like
of a test body without being affected by surface reflected waves and the like, and a material
evaluation test method using the same. A transmitter 3 and a receiver 4 are provided, each
having a delay material 11,12. A holding body 15 for interposing the contact medium W between
the test body side facing surface 14 of the delay members 11 and 12 and the test body surface
101 is provided. The waveform of the backscattered wave from the target depth H of the test
body 100 and the waveform of the surface reflected wave reflected on the test body surface 101
and generated between the test body facing surface 14 of the test body surface 101 and the
delay members 11 and 12 The thickness D of the holding body 15 is set so as to be
distinguishable from the waveform of the multiple reflected wave. In addition, an acoustic
separator 16 for blocking a multiple reflection wave or crosstalk generated between the test
object surface 101 and the delay members 11 and 12 is provided on the test object side facing
surface 14 between the pair of delay members 11 and 12. Set up. [Selected figure] Figure 3
Probe and material evaluation test method using the same
[0001] The present invention relates to a probe used in a material evaluation test by ultrasonic
waves and a material evaluation test method thereof. More specifically, it is suitable for
evaluating deterioration or damage of equipment used in a high temperature or high pressure
environment, such as equipment and devices used in petroleum and petrochemical plants,
thermal power plants, etc. The present invention relates to a probe that can be used to evaluate
deterioration / damage of a steam pipe or the like of a boiler in a power plant and an evaluation
test method thereof. 2. Description of the Related Art For example, a heating furnace tube used in
a petrochemical plant or a thermal power plant etc. directly heats the outer surface with a burner
etc. Creep damage is likely to occur, and it is necessary to evaluate such deterioration / damage.
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Conventionally, as a method for evaluating such deterioration or damage of a material, there is
known a method of evaluating using a leaky elastic wave (LASW) as seen in Patent Document 1
described later (leakage elastic wave Law). According to the same method, as shown in FIG. 1 (a),
since the penetration depth of the ultrasonic wave is about one wavelength, the evaluation target
is limited to the surface layer of the test body, It was not possible to obtain deep data. [Patent
Document 1] Japanese Patent Application Laid-Open No. 2000-131297 On the other hand, using
the single transducer type vertical probe shown in FIG. There is known a method of evaluating
deterioration and damage of materials by capturing ultrasonic waves. According to the same
method, deterioration, damage, etc. in the deep part of the test body can be grasped. However,
when the probe is in direct contact with the test body (direct contact method), the transmission
pulse is applied, and when water is interposed between the probe and the test body (water
immersion method), the surface of the test body In order to receive surface reflection waves that
are reflected by the above, it has been difficult to distinguish between these signals and the
signal backscattered near the surface of the test body. As described above, even when the
material evaluation test is performed using the leaky elastic wave method and the backscattered
wave method in combination, the several mm-deep portion in the vicinity of the surface of the
test body is a dead zone. SUMMARY OF THE INVENTION In view of such a conventional
situation, it is an object of the present invention to evaluate deterioration, damage, etc. of a test
body without being affected by surface reflected waves etc. A probe and a material evaluation
test method using the same. SUMMARY OF THE INVENTION In order to solve the abovementioned problems, a first feature of the probe according to the present invention is to transmit
ultrasonic waves to a test object and to use backscattered waves from the test object. And a
transmitter and a receiver, each having a delay material, provided between the sample-side facing
surface of the delay material and the surface of the sample. A holder for interposing a contact
medium is provided, and a waveform of a backscattered wave from a target depth of the test
body, a waveform of a surface reflected wave reflected by the surface of the test body, the
surface of the test body and the delay material The thickness of the holding body is set so as to
be distinguishable from the waveform of the multiple reflected wave generated between the
facing surfaces of the test body.
According to the same feature configuration, the contact medium improves the transmission and
reception accuracy of the ultrasonic waves. Then, since the thickness of the contact medium can
be always maintained at a constant small thickness by the holder, a minute backscattered wave
can be detected. In addition, by providing a mechanism to maintain the small thickness of this
couplant and by making the transmitter and the receiver separate, the backscattered wave
generated in the test body and the surface reflection wave and multiple reflections reflected on
the surface of the test body The arrival time of the wave to the receiver can be different. The
second feature of the probe according to the present invention is for evaluating a test body by
transmitting ultrasonic waves to the test body and receiving backscattered waves from the test
body. A transmitter and a receiver each having a delay material, and a holder for interposing a
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contact medium between the sample-side facing surface of the delay material and the surface of
the sample; The present invention is characterized in that an acoustic separator is provided on
the test body side facing surface between the delay materials in order to block multiple reflection
waves or crosstalk generated between the surface of the test body and the delay material.
According to the same feature configuration, multiple reflected waves or crosstalk generated in
the contact medium are blocked by the acoustic shield. Therefore, it is possible to prevent the
harm due to the multiple reflection wave and the crosstalk and to receive the signal from the
above-mentioned test object dead zone portion with certainty. In any of the above features, the
thickness of the contact medium is desirably 1 mm or more. Furthermore, in any one of the
above-described features, a ring-shaped elastic member may be used as the holding body, for
example. According to the same feature configuration, by using the elastic member, the posture
of the transmitter-receiver can be maintained constant by elastic deformation appropriate to
surface roughness such as unevenness on the surface of the test body. Also, the surface of the
test body is not scratched. The feature of the material evaluation test method according to the
present invention is that ultrasonic waves are transmitted to the test body using the probe having
any of the above-described features and the backscattered wave from the test body is received.
Evaluation of the test body. According to the features of the present invention, cross
contamination of the backscattered wave originating from the test body and the surface reflected
wave and multiple reflected waves reflected by the test body surface is prevented, and the test
body surface is prevented. It has become possible to accurately evaluate deterioration, damage,
etc. at a depth of several millimeters in the vicinity. Other objects, configurations, actions, and
effects of the present invention will be clarified in the section of “Embodiments of the
Invention” described below.
BEST MODE FOR CARRYING OUT THE INVENTION Next, the embodiment of the present
invention will be described in more detail with reference to FIGS. In the present invention, a
position in the vicinity of the surface 101 of the test body 100 having a depth H of about several
mm (hereinafter referred to as “target depth H”). It is suitable for the evaluation of creep
damage such as grain boundaries generated in the above and voids caused by hydrogen attack.
In the present embodiment, a flat steel plate having a thickness of several mm is used as the test
body 100. FIG. 2 is a logic block diagram showing an outline of the evaluation device 1. The
evaluation device 1 includes a pulser 31 that generates an ultrasonic pulse from the transmitter
3 to the test object 100, and a receiver 32 that receives a reception wave from the receiver 4.
The acoustic signal from the receiver 32 is amplified by the amplifier 33, low frequency and high
frequency noises are removed by the filter 34, and then A / D converted by the A / D converter
35 to be digitized. Then, it is stored in a memory such as a RAM or a hard disk in the personal
computer 36. The personal computer 36 includes instruction means for instructing the pulser 31
to transmit, and analysis means for analyzing data from the A / D converter 35. The processing
results in the personal computer 36 are as shown in FIGS. 6, 7 and 8 and can be displayed by the
display 37 and can be output on paper by the printer 38. The transmitter / receiver 2 is
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generally configured such that the transmitter 3 and the receiver 4 are housed in the housing 10,
and a holder 15 is provided on the periphery of the test body side facing surface 14 of the
transmitter / receiver 2. In the housing 10, the transmitter 3 and the receiver 4 are acoustically
isolated by the acoustic isolation surface 13. The transmitter 3 and the receiver 4 are provided
with delay members 11 and 12 made of acrylic resin, and vibrators 11 a and 12 a attached to the
upper surfaces of these. Moreover, the test body side opposing surface 14 of the delay members
11 and 12 is exposed without being covered by the housing. In the present specification,
“surface reflected wave” refers to a reflected wave that is transmitted from the transmitter 3
and reflected by the test object surface 101 and immediately reaches the receiver 4, and
“multiple reflected wave” After being transmitted from the transmitter 3 and reflected by the
test object surface 101, it refers to a reflected wave in which the reflections on the lower surface
14 of the delay members 11, 12 and the test object surface 101 are repeated. As shown in FIG. 3,
the transmitters 3 and the receivers 4 have the transducers 11 a and 12 a so that the
intersection point P of the transmitter central axis X and the receiver central axis Y is located at a
specific depth h. Each is inclined with respect to the specimen surface 101 and aimed within the
above-mentioned target depth H range.
In the present embodiment, the transmitter 3 and the receiver 4 are arranged so as to be planesymmetrical with respect to the normal plane of the test object surface 101. The present
invention is different from vertical flaws that capture bottom echoes in that they capture
backscattered waves. A ring-shaped holding body 15 made of an elastic member such as silicone
rubber is provided along the periphery of the lower surface 14 of the delay members 11 and 12
in the transmitting and receiving element 2. A downward concave portion 17 is formed between
the transmitter-receiver 2 and the test object surface 101 by the holder 15, and the concave
portion 17 is filled with the contact medium W. The distance between the transmitter-receiver 2
and the surface of the test object 101 can be kept constant by the holder 15. Further, by using
the holding body 15 as an elastic member, the holding body 15 and the test body surface 101
are in close contact with each other by appropriate elastic deformation even with respect to
surface roughness such as unevenness on the surface of the test body 101. In addition, since the
holding body 15 is an elastic body, it is preferable to handle the thickness of the holding body 15
and the thickness of the contact medium W at the time of contact with the surface 101 of the test
body. As the couplant W, for example, glycerin, water, machine oil or the like is used. These
contact media W can propagate ultrasonic waves to the test body 100 without reducing the
transmission efficiency of ultrasonic waves, and can receive a minute backscattered wave S3. The
ultrasonic wave transmitted from the transmitter 3 is to be incident on the test body 100
through the contact medium W, but as shown in FIG. Multiple reflections are repeated between
the lower surfaces 14 of the members 11 and 12. In order to prevent the multiple reflected wave
S2 and the direct wave (crosstalk) from reaching the receiver 4, as shown in FIG. 5B, the contact
medium W is divided into two on the transmitter 3 side and the receiver 4 side. A planar acoustic
separator 16 is provided. In the present embodiment, the acoustic isolator 16 is linearly disposed
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immediately below the acoustic isolation surface 13 in the housing 10. The acoustic separator 16
may be configured by extending a part of the acoustic separation surface 13 downward. As
shown in FIGS. 3 and 4, when water is used as the contact medium W, it is known that the
longitudinal sound velocity in the steel is about four times the velocity of sound in the contact
medium, and the contact medium is The inside 1 mm corresponds to the movement speed of 4
mm in the steel material. Therefore, in order to evaluate the vicinity of a depth of 4 mm from the
surface of the steel sheet, by setting the thickness of the contact medium to 1 mm or more,
preferably 1.5 mm or more, the backscattered wave S3 and the surface reflected wave S1 and the
multiple reflected wave S2 The arrival times of the receiver 4 can be made different to prevent
these signals from crossing each other.
According to such a principle, in combination with the thickness D of the contact medium W and
the acoustic separator 16, the above-described dead zone can be evaluated with high accuracy.
EXAMPLE In this example, an evaluation test was conducted using a carbon steel plate having a
thickness of 10 mm as the test body 100. As the transmitter-receiver 2, one having a frequency
of 10 MHz was used. The thickness D of the contact medium W was adjusted so that the rise time
of the surface reflected wave S1 was 8 μs. The received signal obtained by the receiver 4 was
filtered with a 5 MHz high pass filter, stored as a digital signal of 100 MHz sampling, and
waveform analysis was performed. Moreover, while using O-ring 15 made of rubber as a holding
body, glycerol was used as the contact medium W with which the recessed part 17 is filled. In
this evaluation test, two types of tests were performed: the case where the acoustic separator 16
was not provided in the recess 17 and the case where the acoustic separator 16 was provided.
FIG. 6 and FIG. 7 are graphs of received waveforms obtained in each test, where the vertical axis
represents the amplitude of the output signal and the horizontal axis represents time. FIG. 6
shows the received waveform when the acoustic shield 16 shown in FIG. 5A is not provided. FIG.
6A is a graph when the gain is 0 dB, and FIG. 6B is a graph when the gain is 6 dB. It is. As shown
in the graph, the backscattered wave group S3 was observed between the surface reflected wave
group S1 and the multiple reflected wave group S2, and it was confirmed that these waves were
distinguishable without crossing each other. On the other hand, FIG. 7 is a graph showing the
reception waveform when the acoustic shield 16 shown in FIG. 5 (b) is provided, where (a) is a
gain of 0 dB and (b) is a gain. (C) is a graph when the gain is 12 dB. In the graph, the multiple
reflected waves S2 were not observed, and it was confirmed that the surface reflected wave
group S1 and the backscattered wave group S3 were distinguishable without crossing each other.
Further, it is understood that the amplitude of the surface reflected wave S1 is significantly
attenuated as compared with the amplitude distribution in the case where the acoustic separator
16 shown in FIG. 6 is not provided. Finally, the possibilities of other embodiments of the
invention will be mentioned. The following embodiments can be implemented in combination as
appropriate. By appropriately combining the evaluation test using the single transducer type
probe shown in FIG. 1 (b) and the evaluation test using the leaky elastic wave method shown in
FIG. 1 (a) in addition to the above evaluation test, It is possible to evaluate the deterioration /
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damage distribution in the thickness direction. According to the experiments of the inventors, the
leaky elastic wave method is used up to 0.8 mm below the surface, and the method using the
probe 2 according to the present invention is used up to 1.5 to 4 mm below the surface. The
deep part was evaluated by the water immersion method using a single transducer type probe, so
that the deterioration / damage distribution in the thickness direction could be evaluated.
In the above embodiment, the deterioration / damage of the test body 100 was evaluated from
the time-series data of the backscattered wave amplitude, but in addition to this, from the signal
sampled for each time gate in cooperation with a timer not shown. The test body 100 can also be
evaluated by obtaining a frequency spectrum using an FFT means or the like (a spectroscopy
method). Since the high frequency components are attenuated by the scattering, the spectrum
distribution of the backscattered wave shifts to the low frequency side and the spectrum intensity
on the low frequency side increases as the degree of deterioration or damage in the test body
becomes stronger. FIG. 8 (b) compares the frequency distribution of the spectrum intensity of the
backscattered wave between a sound test body and a test body having a creep damage inside. It
can be seen that the spectrum distribution of the specimen having the creep damage shifts to the
low frequency side and the spectrum intensity increases on the low frequency side, as compared
with the sound specimen. In the above embodiment, the transmitter / receiver 2 is disposed on
the test object surface 101 and the evaluation test is performed. However, the transmitter /
receiver 2 may be scanned along the test object surface by a motor controller (not shown). In
addition to the flat steel plate as the test body 100, for example, the probe according to the
present invention can be disposed on the surface of a test body that is a curved surface such as a
pipe, and a material evaluation test can be performed. At that time, by moving the probe by the
motor controller, it is possible to evaluate the deterioration / damage distribution in the vicinity
of the surface of the test body in the circumferential direction and the axial direction of the tube.
Then, the data obtained at each point is displayed in color tone using the above-described display
37 or the like as shown in FIG. 8C. The figure is a scan of the range of 50 mm in the tube axis
direction and the tube circumferential direction at a distance of 1 mm, and the partial integrated
values of the backscattered wave amplitude and the low frequency component (5 to 8 MHz) of
the frequency spectrum at each scan position The color tone of B1 is displayed. In the abovedescribed embodiment and the like, a steel material is used as the test body 100. However, the
test body 100 is not limited to a steel material, and the thickness D of the holding body 15 can
also be obtained from the relative relationship with the acoustic impedance of the test body 100
and the holding body 15. The reference numerals in the claims are for the purpose of making the
contrast with the drawings convenient only, and the present invention is not limited to the
configuration of the attached drawings by this entry. . BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view comparing the present invention with the prior art, where (a) is a leaky elastic
wave (LSAW) method, and (b) is a single transducer type probe. When using a backscattered
wave, (c) shows the case where a backscattered wave is detected using the probe according to
the present invention.
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FIG. 2 is a logic block diagram of an evaluation device using a probe according to the present
invention. FIG. 3 is a cross-sectional view showing a relationship between a transmitter-receiver
and a test body in a cross-section including a transmitting side central axis and a receiving side
central axis. FIG. 4 is a diagram schematically showing the loci of surface reflection waves and
multiple reflection waves and the received waveforms thereof. FIG. 5 is a view showing the
relationship between a transmitter, a receiver, a holder, and an acoustic separator, wherein (a) is
a cross-sectional view of the transmitter-receiver and its AA cross section in the case of including
the holder; b) shows a cross-sectional view of the transmitter-receiver in the case of including a
holder and an acoustic separator, and its AA cross-sectional view. FIG. 6 shows a received
waveform when there is no acoustic separator, where (a) corresponds to a gain of 0 dB and (b) to
6 dB. 7 is a view corresponding to FIG. 6 in the case of interposing an acoustic separator, where
(a) corresponds to a gain of 0 dB, (b) to 6 dB, and (c) to 12 dB. 8 shows data obtained using the
probe according to the present invention, wherein (a) shows the time-series distribution of
amplitude, (b) shows the frequency distribution of spectrum intensity, and (c) the color tone of
scan Show the display. Explanation of the code 1: Evaluation device 2: Transmitter and receiver
3: Transmitter 4: receiver 10: housing 11 and 12: acoustic delay material 11a: transmission side
transducer 12a: reception side transducer , 13: acoustic isolation surface, 14: lower surface
(facing side of test body), 15: support, 16: acoustic isolation, 17: recess, 31: pulser, 32: receiver,
33: amplifier, 34: filter, 35: A / D converter, 36: personal computer, 37: display, 38: printer, 100:
test body, 101: test body surface, P: intersection point, S1: surface reflection wave, S2: multiple
reflection wave, S3: back scattering Wave, W: Contact medium, X: Transmitter center axis, Y:
Receiver center axis
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