JP2004245598A - Probe and material evaluation test method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a probe allowing a specimen to be evaluated for deterioration/damage without being affected by surface reflected wave and a material evaluation test method using the probe. <P>SOLUTION: This probe comprises a transmitter 3 and a receiver 4 having delaying materials 11 and 12 and a holding body 15 for installing a contact medium W between the opposed faces 14 of the delaying materials 11 and 12 to a specimen and the surface 101 of the specimen. The thickness D of the holding body 15 is set so that the waveform of the surface reflected wave reflected on the surface 101 of the specimen and the waveform of multiplex reflected wave generated between the surface 101 of the specimen and the opposed faces of the delaying materials 11 and 12 on the specimen side can be identified. Also, a sound isolating body 16 for cutting off the multiplex reflected wave or crosstalk generated between the surface 101 of the specimen and the delaying materials 11 and 12 is installed on the opposed face 14 on the specimen side between the pair of delaying materials 11 and 12. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a probe used for a material evaluation test using ultrasonic waves, and a method for evaluating the material. More specifically, it is suitable for deterioration and damage evaluation of equipment used in high-temperature or high-pressure environments, such as equipment and equipment used in petroleum / petrochemical plants and thermal power plants. The present invention relates to a probe that can be used for evaluating deterioration and damage of a steam pipe or the like of a boiler in a power plant, and an evaluation test method thereof.
[0002]
[Prior art]
For example, heating furnace tubes used in petrochemical plants and thermal power plants are heated directly on the outer surface by a burner, etc., so that creep damage such as voids and fishers is likely to occur on the pipe fire side, and such deterioration・ It is necessary to evaluate damage.
[0003]
Conventionally, as a method for evaluating such deterioration / damage of a material, there is known a method of evaluating using a leaky elastic wave (LASW) as described in Patent Document 1 described below (leakage elastic wave method). According to this method, as shown in FIG. 1 (a), since the penetration depth of the ultrasonic wave is about one wavelength, the object to be evaluated is limited to the extreme surface layer portion of the test specimen, and The data in the deep part could not be obtained.
[0004]
[Patent Document 1]
JP 2000-131297 A
On the other hand, there is a known method for evaluating the deterioration / damage of a material by capturing ultrasonic waves scattered back at a deteriorated / damaged portion such as a void by using a single-element vertical probe shown in FIG. 1 (b). Have been. According to this method, deterioration, damage, etc. of the deep part of the test piece can be grasped. However, when the probe is brought into direct contact with the specimen (direct contact method), a transmission pulse is applied, and when water is interposed between the probe and the specimen (water immersion method), the surface of the specimen is exposed. Since these signals are received by the surface reflected waves reflected at the surface, these signals intersect with the signals backscattered in the vicinity of the surface of the test sample, and it is difficult to distinguish between the two.
[0006]
As described above, even when the material evaluation test was performed using both the leaky elastic wave method and the backscattered wave method, the dead zone at a depth of several mm near the surface of the test piece was found.
[0007]
[Problems to be solved by the invention]
In view of such a conventional situation, an object of the present invention is to provide a probe capable of evaluating deterioration and damage of a test body without being affected by surface reflected waves and the like, and a material evaluation test method using the same. Is to provide.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, a first characteristic configuration of the probe according to the present invention is to transmit a ultrasonic wave to a test object and to evaluate the test object by receiving a backscattered wave from the test object. Wherein a transmitter and a receiver each having a delay member are provided, and a holder for interposing a couplant between the specimen-side facing surface of the delay member and the specimen surface is provided, The waveform of the backscattered wave from the target depth of the specimen, the waveform of the surface reflected wave reflected on the surface of the specimen, and multiple reflections generated between the specimen surface and the specimen-facing surface of the delay member. The thickness of the holder is set so that the waveform of the wave can be identified.
[0009]
According to the characteristic configuration, the couplant improves the transmission and reception accuracy of the ultrasonic wave. Then, since the thickness of the couplant can be always maintained at a constant minute thickness by the holding member, a minute backscattered wave can be detected. In addition, a mechanism for maintaining the very small thickness of the couplant is provided, and the transmitter and receiver are separated, so that the backscattered wave generated in the specimen, the surface reflected wave reflected on the surface of the specimen and the multiple reflection The arrival times of the waves at the receiver can be different.
[0010]
Further, a second characteristic configuration of the probe according to the present invention is to perform evaluation of the test object by transmitting ultrasonic waves to the test object and receiving backscattered waves from the test object. , A transmitter and a receiver each having a delay member, a holder for interposing a couplant between the surface of the delay member facing the specimen and the surface of the specimen is provided, and the pair of delay members An acoustic isolator for blocking multiple reflected waves or crosstalk generated between the surface of the test object and the delay member is provided on the opposing surface on the test object side between the two.
[0011]
According to this feature, the multiple reflection waves or crosstalk generated in the couplant are blocked by the acoustic shield. Therefore, it is possible to prevent the harm caused by multiple reflected waves and crosstalk and to reliably receive the signal from the above-described dead zone of the test object.
[0012]
In any one of the above features, it is preferable that the thickness of the couplant is 1 mm or more.
[0013]
Furthermore, in any one of the above-described features, for example, a ring-shaped elastic member may be used as the holder. According to this characteristic configuration, by using the elastic member, the posture of the transmitter / receiver can be kept constant by appropriate elastic deformation even with respect to the surface roughness such as the uneven shape on the surface of the test body. Further, the surface of the specimen is not damaged.
[0014]
The feature of the material evaluation test method according to the present invention is that a probe having any one of the above-described features transmits ultrasonic waves to the specimen and receives backscattered waves from the specimen, thereby obtaining The point is to make an evaluation.
[0015]
【The invention's effect】
According to the features of the present invention, the backscattered wave caused by the test specimen, and the intersection of the surface reflected wave and the multiple reflected waves reflected on the surface of the test specimen are prevented, and at a depth of several mm near the surface of the test specimen. It is now possible to accurately evaluate deterioration, damage, etc.
[0016]
Other objects, configurations, operations, and effects of the present invention will be apparent in the following “Embodiments of the invention”.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described in more detail with reference to FIGS. The present invention evaluates creep damage such as voids due to grain boundaries and hydrogen erosion generated at a depth H of about several mm (hereinafter referred to as “target depth H”) near the surface 101 of the specimen 100. Suitable for. In the present embodiment, a flat steel plate having a thickness of several mm is used as the test body 100.
[0018]
FIG. 2 is a logical block diagram schematically showing the evaluation device 1. The evaluation device 1 includes a pulsar 31 that generates an ultrasonic pulse from the transmitter 3 to the test body 100 and a receiver 32 that receives a reception wave from the receiver 4. The acoustic signal from the receiver 32 is amplified by an amplifier 33, and low-frequency and high-frequency noise is removed by a filter 34, and then A / D converted by an A / D converter 35 to be converted into a digital signal. 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 pulsar 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 are displayed on the display 37 and can be output to paper by the printer 38.
[0019]
The transmitter / receiver 2 generally includes a transmitter 10 and a receiver 4 housed in a housing 10, and a holder 15 is provided on the periphery of the test object side facing surface 14 of the transmitter / receiver 2. In the housing 10, the transmitter 3 and the receiver 4 are acoustically isolated by an acoustic isolation surface 13.
[0020]
The transmitter 3 and the receiver 4 include delay members 11 and 12 made of acrylic resin, and vibrators 11a and 12a attached to the upper surfaces of the delay members 11 and 12, respectively. The test piece side facing surfaces 14 of the delay members 11 and 12 are exposed without being covered with the housing.
[0021]
In the present specification, the “surface reflected wave” refers to a reflected wave transmitted from the transmitter 3 and immediately reflected by the surface 101 of the test object and immediately reaching the receiver 4. 3 is a reflected wave that is repeatedly reflected on the lower surfaces 14 of the delay members 11 and 12 and the test object surface 101 after being reflected from the test object surface 101 and transmitted from the test object surface 101.
[0022]
As shown in FIG. 3, the transmitters 3 and the receivers 4 respectively test the vibrators 11a and 12a such that the intersection P of the transmitter center axis X and the receiver center axis Y is located at a specific depth h. It is aimed at the above-mentioned range of the target depth H by being inclined with respect to the surface 101, respectively. In the present embodiment, the transmitter 3 and the receiver 4 are arranged so as to be symmetrical with each other with respect to the normal to the surface 101 of the test object. Note that the present invention differs from vertical flaw detection in which a bottom echo is captured in that a backscattered wave is captured.
[0023]
A ring-shaped holder 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 transmitter / receiver 2. The holder 15 forms a downward recess 17 between the transmitter / receiver 2 and the specimen surface 101, and the recess 17 is filled with the couplant W. The distance between the transmitter / receiver 2 and the test object surface 101 can be kept constant by the holder 15. Further, by using the elastic member as the holding member 15, the holding member 15 and the test object surface 101 are brought into close contact with each other by appropriate elastic deformation even with respect to the surface roughness such as unevenness on the test object surface 101. Since the holding body 15 is an elastic body, the thickness of the holding body 15 and the thickness of the couplant W may be treated as those at the time of contact with the test object surface 101.
[0024]
As the couplant W, for example, glycerin, water, machine oil, or the like is used. These couplants W can transmit the ultrasonic waves to the test body 100 without lowering the transmission efficiency of the ultrasonic waves, and can receive the minute backscattered waves S3.
[0025]
The ultrasonic wave transmitted from the transmitter 3 is incident on the specimen 100 via the couplant W, but as shown in FIG. 4, a part of the surface 101 of the specimen 100 and the delay material 11, The multiple reflection is repeated between the lower surface 12 and the lower surface 14 of the light source 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 couplant W is divided between the transmitter 3 side and the receiver 4 side. A planar acoustic isolator 16 is provided so as to perform In the present embodiment, the acoustic isolator 16 is linearly arranged directly below the acoustic isolating surface 13 in the housing 10. The acoustic isolator 16 may be configured by extending a part of the acoustic isolating surface 13 downward.
[0026]
As shown in FIGS. 3 and 4, when water is used as the couplant W, it is known that the longitudinal sound velocity in the steel material is about four times as high as the sound velocity in the couplant. Corresponds to a moving speed of 4 mm in the steel material. Therefore, when trying to evaluate the vicinity of a depth of 4 mm from the surface of the steel sheet, the thickness of the couplant is set to 1 mm or more, preferably 1.5 mm or more, so that the backscattered wave S3, the surface reflected wave S1, and the multiple reflected wave S2 can be formed. The arrival times of the receivers 4 can be made different to prevent these signals from crossing each other. According to such a principle, the above-described dead zone can be accurately evaluated in combination with the thickness D of the couplant W and the acoustic separator 16.
[0027]
【Example】
In this example, an evaluation test was performed using a carbon steel sheet having a thickness of 10 mm as the test body 100. The transceiver 2 used had a frequency of 10 MHz. The thickness D of the couplant 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 by a 5 MHz high-pass filter, stored as a digital signal of 100 MHz sampling, and subjected to waveform analysis. In addition, a rubber O-ring 15 was used as the holder, and glycerin was used as the couplant W to be filled in the recess 17.
[0028]
In this evaluation test, two types of tests were performed: a case where the acoustic isolator 16 was not provided in the recess 17 and a case where the acoustic isolator 16 was provided. 6 and 7 are graphs of the received waveform obtained in each test, where the vertical axis indicates the amplitude of the output signal and the horizontal axis indicates time. 6A and 6B are reception waveforms 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, a 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 could be identified without intersecting each other.
[0029]
On the other hand, FIGS. 7A and 7B are graphs showing reception waveforms when the acoustic shield 16 shown in FIG. 5B is provided. FIG. 7A shows a case where the gain is set to 0 dB, and FIG. 7B shows a case where the gain is set to 6 dB. (C) is a graph when the gain is set to 12 dB. In this graph, the multiple reflected wave S2 was not observed, and it was confirmed that the surface reflected wave group S1 and the backscattered wave group S3 could be identified without intersecting each other. Further, it can be seen that the amplitude of the surface reflected wave S1 is greatly attenuated as compared with the amplitude distribution when the acoustic isolator 16 shown in FIG. 6 is not provided.
[0030]
Finally, reference is made to the possibilities of other embodiments of the present invention. It is to be noted that the following embodiments can be combined as appropriate.
In addition to the above-described evaluation test, an evaluation test using a one-element transducer shown in FIG. 1B and an evaluation test using a leaky elastic wave method shown in FIG. The deterioration / damage distribution in the thickness direction can be evaluated. According to the experiments by the inventors, the leakage acoustic 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 element type probe, and the deterioration / damage distribution in the thickness direction was able to be evaluated.
[0031]
In the above embodiment, the deterioration / damage of the test specimen 100 was evaluated from the time-series data of the backscattered wave amplitude. In addition, in addition to this, the FFT means etc. The specimen 100 can also be evaluated by calculating the frequency spectrum using (spectroscopy method). Since the high frequency component is attenuated by the scattering, as the degree of deterioration or damage in the test body increases, the spectrum distribution of the backscattered wave shifts to the lower frequency side and the spectrum intensity on the lower frequency side increases. FIG. 8B compares the frequency distribution of the spectrum intensity of the backscattered wave between the sound test piece and the test piece having creep damage inside. It can be seen that the spectrum distribution of the specimen having creep damage shifts to a lower frequency side as compared with a healthy specimen, and the spectrum intensity increases at the lower frequency side.
[0032]
In the above embodiment, the transmitter / receiver 2 is arranged on the surface 101 of the test object to perform the evaluation test. However, the transmitter / receiver 2 may be scanned along the surface of the test object by a motor controller (not shown). In addition, the test body 100 is not limited to a flat steel plate. For example, the probe according to the present invention can be disposed on a curved test body surface such as a pipe to perform a material evaluation test. At this time, by moving the probe by the motor controller, it is possible to evaluate the deterioration / damage distribution near the surface of the test specimen in the pipe circumferential direction and the pipe axial direction. Then, as shown in FIG. 8C, the data obtained at each point is displayed in a color tone using the above-described display 37 or the like. The figure is obtained by scanning a range of 50 mm in each of the tube axis direction and the tube circumferential direction at a pitch of 1 mm, and a partial integrated value of the backscattered wave amplitude and the low frequency component (5 to 8 MHz) of the frequency spectrum at each scanning position. B1 is a color tone display.
[0033]
In the above-described examples and the like, a steel material was used as the test body 100. However, the test body 100 is not limited to a steel material, and the thickness D of the holder 15 is also determined by a relative relationship with the acoustic impedance of the test body 100 and the holder 15.
[0034]
It should be noted that the reference numerals entered in the claims are merely for convenience of comparison with the drawings, and the present invention is not limited to the configuration of the attached drawings by this entry.
[Brief description of the drawings]
FIGS. 1A and 1B are diagrams comparing the present invention with a conventional technology, wherein FIG. 1A shows a case where a leaky elastic wave (LSAW) method is used, and FIG. 1B shows a case where a backscattered wave is captured using a single element type probe. Case (c) shows a case in which a backscattered wave is captured using the probe according to the present invention.
FIG. 2 is a logical block diagram of an evaluation device using a probe according to the present invention.
FIG. 3 is a cross-sectional view illustrating a relationship between a transmitter / receiver and a test body in a cross section including a transmission-side central axis and a reception-side central axis.
FIG. 4 is a diagram schematically illustrating a locus of a surface reflected wave and a multiple reflected wave, and a received waveform thereof.
5A and 5B are diagrams showing a relationship among a transmitter, a receiver, a holder, and an acoustic isolator. FIG. 5A is a cross-sectional view of a transmitter and a receiver having a holder, and FIG. b) shows a cross-sectional view of the transmitter / receiver in the case where the holder and the acoustic isolator are provided, and a cross-sectional view taken along line AA.
6A and 6B are reception waveforms when no acoustic isolator is interposed. FIG. 6A shows a case where the gain is 0 dB, and FIG. 6B shows a case where the gain is 6 dB.
7 is a diagram corresponding to FIG. 6 when an acoustic isolator is interposed, wherein (a) corresponds to a case where the gain is set to 0 dB, (b) corresponds to a case where the gain is set to 6 dB, and (c) corresponds to a case where the gain is set to 12 dB.
8A and 8B are data obtained by using the probe according to the present invention, wherein FIG. 8A shows a time series distribution of amplitude, FIG. 8B shows a frequency distribution of spectrum intensity, and FIG. Show the display.
[Explanation of symbols]
1: Evaluation device, 2: Transmitter / receiver, 3: Transmitter, 4: Receiver, 10: Housing, 11, 12: Acoustic delay material, 11a: Transmitter oscillator, 12a: Receiver oscillator, 13: Acoustic isolation Surface, 14: lower surface (surface facing the specimen side), 15: holder, 16: acoustic isolator, 17: recess, 31: pulser, 32: receiver, 33: amplifier, 34: filter, 35: A / D converter, 36: Personal computer, 37: Display, 38: Printer, 100: Specimen, 101: Specimen surface, P: Intersection, S1: Surface reflected wave, S2: Multiple reflected wave, S3: Backscattered wave, W: Contact Medium, X: center axis of transmitter, Y: center axis of receiver

Claims (5)

A probe for evaluating the test object (100) by transmitting ultrasonic waves to the test object (100) and receiving the backscattered wave (S3) from the test object (100),
Providing a transmitter (3) and a receiver (4) each having a delay material (11,12);
A holder (15) for interposing a couplant (W) is provided between the specimen-side facing surface (14) of the retarder (11, 12) and the specimen surface (101),
The waveform (S3) of the backscattered wave from the target depth (H) of the specimen (100), the waveform (S1) of the surface reflected wave reflected on the specimen surface (101), and the specimen surface (101) ) And the thickness (D) of the holder (15) such that the waveform (S2) of the multiple reflection wave generated between the opposing surfaces (14) of the delay members (11, 12) can be distinguished. A probe characterized by setting. A probe for evaluating the test object (100) by transmitting ultrasonic waves to the test object (100) and receiving the backscattered wave (S3) from the test object (100),
Providing a transmitter (3) and a receiver (4) each having a delay material (11,12);
A holder (15) for interposing a couplant (W) is provided between the specimen-side facing surface (14) of the retarder (11, 12) and the specimen surface (101),
A multiple reflection wave (S2) generated between the surface (101) of the test object and the delay members (11, 12) on the surface (14) facing the test object between the pair of delay members (11, 12). Alternatively, a probe provided with an acoustic isolator (16) for blocking crosstalk. 3. The probe according to claim 1, wherein the thickness (D) of the couplant (W) is 1 mm or more. 4. The probe according to any one of claims 1 to 3, wherein the holder (15) is made of a ring-shaped elastic member. An ultrasonic wave is transmitted to the test object (100) using the probe according to any one of claims 1 to 4, and a backscatter wave (S3) from the test object (100) is received. 100) A material evaluation test method for evaluation.

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