JPH10123106A - Method and device for evaluating degree of deterioration of test body by surface wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evaluate, for example, the degree of deterioration of a test body including the deterioration of, for example, the sharpness of a steel material and the damage of, for example, the grain boundary stress corrosion crack in a chemical plant and a generation plant. SOLUTION: A supersonic wave is applied obliquely onto the surface of a test body S in the direction of an arrow P from a probe 21. The intensity of a rear scattered wave Pr out of a reception wave due to the probe 21 in the direction of an arrow R is measured and an ultrasonic incidence angle (i) where the intensity is maximized is obtained, the surface wave sound velocity of the test body S is obtained, and for example the degree of deterioration of the test body S is evaluated according to the degree of the reduction in sound velocity. While the ultrasonic wave incidence angle of the probe 21 is maintained constantly and the probe 21 is moved, the surface of the test body S is scanned by an ultrasonic wave, the intensity of the rear scattered wave Pr is displayed for gates G1-G8 by a C scan, and a supersonic wave incidence angle (i) is properly changed and the similar scanning and display of ultrasonic wave are performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to the degree of material deterioration such as sensitization and the degree of damage such as intergranular stress corrosion cracking (hereinafter referred to as "deterioration degree") occurring in a specimen such as a steel material. The present invention relates to a method for evaluating by waves and an apparatus for evaluating the degree of deterioration thereof.

[0002]

2. Description of the Related Art Steel materials such as pipes, reaction towers, and turbines in chemical plants and power plants are heavily used under high-temperature and high-pressure environments, causing material deterioration such as sensitization and damage such as intergranular stress corrosion cracking. Since the progress will eventually lead to the destruction of facilities such as plants, establishment of a non-destructive method for estimating the life of each part of the facility by grasping the degree of progress of such material deterioration has been desired.

On the other hand, a method of obliquely incident an ultrasonic wave on the surface of a material to generate a surface wave and obtaining an incident angle at which the value of the backscattered wave is maximum, thereby obtaining a sound velocity of the surface wave of the material is described. Although it is known, a technique for evaluating the degree of deterioration of a material using the technique is not yet known.

[0004]

In view of such a conventional situation, the present invention provides a degree of deterioration capable of evaluating material deterioration such as sensitization and damage such as intergranular stress corrosion cracking by a non-destructive method. It is an object to provide an equal evaluation method and an evaluation device.

[0005]

In order to achieve the above object, a feature of the method for evaluating the degree of deterioration of a test piece due to a surface wave according to the present invention is that a minute portion on the surface of the test piece is stimulated by a surface wave generating means. In this case, a surface wave is generated, and the degree of deterioration or damage of the test object is evaluated based on the surface acoustic wave velocity of the test object.

Here, the "surface wave generating means" may be configured with a "probe for obliquely entering an ultrasonic wave into the surface of the test piece" or "exciting the surface of the test piece with a laser." Yes ". In the former case, the intensity of the backscattered wave among the waves received by the probe is measured, and the ultrasonic wave incident angle of the probe at which the intensity is maximized is determined, thereby determining the surface acoustic wave velocity of the test sample. .

According to the experiments performed by the inventors, the surface acoustic wave velocity of a steel specimen having undergone material deterioration such as sensitization or damage such as intergranular stress corrosion cracking tends to be lower than the surface acoustic wave velocity of a sound material. Turned out to be. Moreover, for backscattered waves,
It has been found that the strength of the deteriorated material is less likely to decrease even at a gate located at a position more distant from the incident portion of the ultrasonic wave, and it is easy to distinguish the material from a sound material. Therefore, when the intensity of the backscattered wave is measured by using two or more different gates, the degree of deterioration of the test object can be more accurately evaluated.

Further, the probe is moved while the ultrasonic wave incident angle of the probe is kept constant, and the surface of the test specimen is scanned by the ultrasonic wave, and the intensity of the backscattered wave is measured by C scan. And the same scan may be performed by appropriately changing the ultrasonic incident angle. "Display by C-scan" means that the intensity of the backscattered wave of the selected gate is displayed two-dimensionally by a color tone display or the like in association with the coordinates of the ultrasonic wave incident portion by the scanning means. And
By performing the C-scan display every time the “ultrasonic incident angle is appropriately changed”, an incident angle with a large backscattered wave intensity can be obtained.

On the other hand, the characteristics of the apparatus for evaluating the degree of deterioration used in these methods for evaluating the degree of deterioration, etc. are as follows. Ultrasonic waves are obliquely incident on the surface of the test piece and the backscattered wave of the surface wave generated on the surface of the test piece. A probe for receiving, scanning means of the probe for scanning the surface of the test object with ultrasonic waves from the probe, incident angle adjusting means for adjusting the angle of the probe, and reception by the probe Gate means for selecting a gate to be measured among the waves,
Processing means for measuring the intensity of the backscattered wave selected by the gate means and displaying the intensity in conjunction with the coordinates of the incident portion of the ultrasonic wave by the scanning means.

[0010]

Next, a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, a degradation degree etc. evaluation device 1 according to the present invention is configured by a sensor unit 20 for scanning a two-dimensional plane on a specimen S, a drive unit 30, a personal computer 40, and a CRT device 50. . The personal computer 40 is a general-purpose product in which software for realizing a specific function is incorporated. By operating the personal computer 40, the sensor unit 20 is controlled via the drive unit 30 to transmit and receive ultrasonic waves. Then, the received waveform is processed by the personal computer 40, and the processing result is displayed on the CRT device 50.

The driving unit 30 transmits ultrasonic waves from the probe 21 and drives a pulsar / receiver 31 for receiving ultrasonic waves received from the probe 21 and three driving motors 22. And a motor driver 32 for driving the motor. These pulsers / receivers 3
1 and the motor driver 32 are A / D converters 3
3 is controlled by the personal computer 40. Further, a digitized signal is input to the personal computer 40 via the A / D converter 33.
The trigger 41 and the motor controller 42 in the personal computer 40 are controlled by a control unit 4 such as a keyboard.
Activated by input from 3. Trigger 41 is A / D
An ultrasonic wave is transmitted from the pulsar / receiver 31 via the converter 33, and a timer 45 for setting a gate to be described later is started. The motor controller 42 drives the drive motor 22 via the A / D converter 33 and the motor driver 32,
The coordinate signal is sent to the memory 44.

The signal received by the pulsar / receiver 31 is digitized by the A / D converter 33 and then stored in the memory 44, and processed together with the coordinate signal of the motor controller 42 corresponding to the ultrasonic wave incident part (Si). The processing result is displayed on the CRT device 50 via the means 46. The received waveform stored together with the coordinate signal in the memory 44 is separated for each gate by a timer 45, subjected to signal processing via a processing means 46, and displayed as a color tone.
The analysis result is displayed on the RT device 50. In the present embodiment, a Rayleigh wave is used as a surface wave, but a creeping wave or a surface SH wave may be used as a surface wave. That is, in the present invention, waves propagating on all kinds of surfaces can be used as “surface waves”.

As shown in FIG. 2, a sensor unit 20 according to the present invention generally has a probe 21 for scanning, a water tank 24 for storing water W as a liquid storage means, and a probe 21 for scanning. And a scanning mechanism 25. In this scanning mechanism 25, a pair of Y-axis guides 25a, 25a oriented in the direction perpendicular to the paper of FIG. 1 are mounted on a water tank 24, and a pair of Y-axis sliders 25b, 25b are connected to a first drive motor 22 (not shown). And slides on each Y-axis guide 25a. Also, a pair of Y-axis sliders 25
The X-axis slider 25d slides along the single X-axis guide 25c straddling b and 25b by the driving of the second drive motor 22 described above. The angle holding portion 25e provided on the X-axis slider 25d can change the angle of the support rod 25f that supports the probe 21 by the third drive motor 22, and holds the angle.

The test sample S used in the present embodiment is formed in a flat plate shape, and is mounted on a mounting table 24a having a substantially horizontal upper surface. Previous Y-axis guide 25a and X-axis guide 25c
Are placed in parallel with the surface of the specimen S or the surface of the mounting table 24a, and the probe 21 is placed substantially in parallel with the upper surface of the specimen S and the mounting table 24a so that a gate position described later can be easily adjusted. Can be scanned. At the time of the test, a comparative test piece C made of a small sound material of about 1 to 2 mm is placed on the upper surface of the test piece S.

As shown in FIG. 4, the ultrasonic wave incident from the probe 21 through the water W to the surface of the test piece S as shown by the arrow P has an incident angle i satisfying the following equation (1). If you take
The light enters the specimen S as a surface wave Ps. C1 / Sin (i) = C2 / Sin90 ° (1) Here, the incident angle i is the incident angle of the ultrasonic wave from the probe 21, C1 is the sound speed of the ultrasonic wave in the water W, and C2 is The sound speed of the surface wave at S. C1 = 14 in equation (1)
By substituting 80 (m / s) and Sin 90 ° = 1, the following equation (2) is obtained. Therefore, the incident angle i
The sound velocity C2 of the surface wave is determined by the magnitude of C2 = 1480 / Sin (i) (m / s) (2)

[0016] With the generation of the surface wave Ps, the backscattered wave P is generated in a direction opposite to the traveling direction of the surface wave Ps.
r occurs. The backscattered wave Pr passes through the incident portion Si and again travels in the direction of arrow R opposite to the direction of arrow P,
It is received by the probe 21.

FIG. 3 is a graph showing a change in intensity of a received wave with respect to time. FIG. 6A shows a case where ultrasonic waves are incident on a sound Cr-Mo steel at an incident angle i = 29 degrees, and FIG. 6B shows a specimen S under the same conditions at an incident angle i = 35 degrees. This is a case where ultrasonic waves are incident on. Incident angle i = 29
In the case of degrees, the intensity of the received waveform is larger as a whole than in the case of the incident angle i = 35 degrees. As can be understood from this graph, when the value of the incident angle i becomes the most appropriate value for the surface acoustic wave velocity of the test sample S, the intensity of the received backscattered wave becomes highest. Therefore, by obtaining the value of the incident angle i at which the reception intensity of the backscattered wave at the selected gate is maximized, the surface sound speed C2 of the test object S is obtained.
Can be obtained.

In FIG. 3, the backscattered wave Pr corresponds to a portion after time ti when a received wave due to surface reflection is observed. In order to selectively receive the backscattered wave Pr, a plurality of gates G1 to G8 are provided. Is set. Each gate G1 to G
The interval of 8 is 1 μs in time and 1.44 m in distance.
m, but is appropriately changed according to the state of the received waveform. Although the value of the time ti can be estimated by observing the graph, the sound speed C1 of the water W, the probe 21 and the test piece S
Since the distance of the surface from the scanning mechanism 25 is a substantially constant known value, it can be grasped by the trigger 41 and the timer 45 in FIG. 1, and similarly, the interval between the gates G1 to G8 can be appropriately changed. is there.

On the other hand, FIGS. 3 (c) and 3 (d) show the results obtained by using a Cr-Mo steel damaged by intergranular stress corrosion cracking as a test specimen S and setting the incident angles to i = 29 ° and i = 35 °. FIG. As can be understood from the figure, the overall intensity of the signal at the gates G1 to G8 depends on the incident angle i =
In the case of 35 °, the incident angle i is larger than 29 °. This is opposite to the case where the specimen S is used as the sound material, and it can be seen that the sound velocity C2 of the surface wave is reduced in consideration of the equation (2). Therefore, by obtaining the incident angle i at which the intensity of the backscattered wave Pr is maximized, it is possible to evaluate the degree of deterioration of the surface of the specimen S or the degree of deterioration of the entire specimen by the sound velocity of the surface wave. Become.

Further, FIGS. 3A and 3D will be compared. The intensity of the backscattered wave in the sound material is determined by the second gate G
Whereas the size of the damaged material is considerably smaller around 2 points,
A considerable signal strength is maintained also in the vicinity of the gates G6 to G8 in the latter half. This is presumed to be due to the strong generation of backscattered waves due to the presence of minute spaces due to intergranular stress corrosion cracking and the like. Therefore, the incident part Si
, The sound speed near the incident portion Si is measured based on the intensity of the backscattered waves of the first and second gates G1 and G2, which are different from this, for example, the sixth to eighth gates G6 to G
By further measuring the intensity of the backscattered wave at eight or more separated positions, the degree of damage or the degree of deterioration of the test sample S can be more accurately evaluated. Even if the comparative test piece C is placed on the surface of the test piece S, if the thickness is about 1 to 2 mm, the displacement of the previous gate is very small. When the evaluation is performed at the gate, there is an advantage that the influence of the error is very small.

When the deterioration degree and the like of the test sample S are evaluated by the above-described deterioration degree and the like evaluation apparatus 1, the scanning mechanism 2 is used.
The probe 21 is moved in X and Y directions by 5 and the entire surface of the test sample S is scanned by ultrasonic waves. The maximum value of the signal intensity of the selected gate or the integrated value of the signal intensity of the gate for each of the gates G1 to G8 is displayed two-dimensionally by color tone display in conjunction with the coordinate value of each data. Such scanning is performed by the timer 45 and the processing unit 4 described above.
The information is displayed on the CRT device 50 or a color printer (not shown) by 6 and is provided for evaluation. By placing the comparative test piece C on the test piece S,
The degree of deterioration and the like can be more reliably evaluated.

Next, a second embodiment of the present invention will be described with reference to FIG. As shown in FIG. 5, the laser sound velocity measuring device 60 includes first and second lasers L1 and L2.
Then, the first and second laser beams P1 and P2 are incident so that their incident angles θ are the same to excite the vicinity of the incident portion Si, thereby generating a surface wave Ps. The sound speed of the surface Ps can be changed by interference between the two laser beams P1 and P2. The speed C2 of the interference fringe corresponding to the sound speed of the surface wave Ps
Is obtained by the following equation (3). C2 = (ω2−ω1) / (2KSinθ) (3) where K means the difference between the wave numbers of the second and third racer lights P1 and P2, and ω2 and ω1 are the third laser lights P2, respectively. And the frequency of the second laser light P1.

The third laser beam P3 perpendicularly incident on the surface of the test piece S near the incident portion Si from the third laser L3 via the half mirror 61 is reflected on the surface of the test piece S and goes deep in the half mirror. Be guided. The third laser light P3 guided to the back is combined with a comparative laser light (not shown), and the interference fringes are observed as indicating the intensity of the surface wave Ps. Due to such interference fringes, the first and second laser beams P1 and P1 are arranged such that the surface wave Ps has the highest intensity.
2 is changed, and the speed C2 of the interference fringes obtained at that time corresponds to the speed of the surface wave.

Next, still another embodiment of the present invention will be described. In the first embodiment, the water tank 24 is used as the water liquid means. However, instead of the water tank 24, a tank having a rubber film through which ultrasonic waves can easily pass is used as the liquid storage means, and the scanning mechanism 25 and the searching means are used. Ultrasonic scanning of the surface of the test piece is also possible using a portable sensor head containing the touch element 21. In the first embodiment, the degree of intergranular stress corrosion cracking in a steel material was evaluated. However, it has been confirmed by the inventors that the present invention can evaluate the degree of material deterioration such as damage other than grain boundary stress corrosion cracking and sensitization. In the present invention, “deterioration degree etc.”
Includes, for example, formation of an oxide film, carburization, nitriding, decarburization, surface modification such as element concentration, and the like. In each of the above embodiments, the present invention is applied to a steel material having a flat surface, but the present invention is also applicable to various shapes in which the surface of a steel pipe or the like is bent or a test piece of a material other than a steel material. .

[0025]

As described above, according to the method and apparatus for evaluating the degree of deterioration of a test piece due to the surface wave according to the present invention, the sound velocity of the surface wave of the test piece can be increased by increasing the sensitivity of the test piece such as steel. It has been found that the degree of deterioration caused by cracks and intergranular stress corrosion cracking is actually represented. The measurement of the sound speed makes it possible to non-destructively evaluate the degree of deterioration of a test piece such as a steel material.

When the sound wave velocity at which the intensity of the backscattered wave is maximized is determined to determine the sound velocity of the surface wave of the specimen, the distance from the ultrasonic wave incident part increases as the degree of deterioration or damage progresses. Since the backscattered wave of the gate corresponding to just the position also has a large value as compared with the sound material, the evaluation of the degree of deterioration and the like becomes easier. In particular, by measuring the intensity of the backscattered wave using two or more different gates, the degree of deterioration of the test specimen can be more accurately evaluated.

Further, in the case where the intensity of the backscattered wave is displayed by C-scan along with the scanning of the specimen surface using the ultrasonic wave, and the same scanning is performed by appropriately changing the incident angle of the ultrasonic wave,
By obtaining both the intensity distribution for each angle and the intensity distribution for each gate, it is possible to evaluate the degree of deterioration and the like due to the surface acoustic wave velocity C2 from multiple aspects.

It should be noted that reference numerals written 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 the writing. .

[Brief description of the drawings]

FIG. 1 is a logical block diagram of a degradation degree etc. evaluation device according to the present invention.

FIG. 2 is a side view showing an outline of a center unit in which a part of a water tank is switched.

FIG. 3 is a graph showing a change in intensity of a received wave of a probe with respect to time, wherein (a) is an incident angle i = 2 in a sound material;
In the case of 9 °, (b) is an incident angle i = 35 ° in a sound material.
(C) shows the case where the incident angle i of the damaged material is 29 °, and (d) shows the case where the incident angle i of the damaged material is 35 °.

FIG. 4 is an explanatory diagram showing a relationship between a surface wave and a backscattered wave incident on a test sample from a probe.

FIG. 5 is a diagram corresponding to FIG. 4, showing a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Deterioration degree etc. evaluation apparatus 20 Sensor unit 21 Probe 22 Drive motor 24 Water tank (liquid storage means) 24a Mounting table 25 Scanning means 25a X-axis guide 25b X-axis slider 25cY-axis guide 25dY-axis slider 25e Angle holder (incident angle adjustment) Means) 25f support rod 30 drive unit 31 pulser / receiver 32 motor driver 33 A / D converter 40 personal computer 41 trigger 42 motor controller 43 control means 44 memory 45 timer 46 processing means 50 CRT device G1-8 first to eighth gates Reference Signs List 60 laser apparatus L1 to 3 First to third lasers P1 to 3 First to third laser light i Incident angle θ Incident angle Ps Surface wave Pr Backscattered wave S Specimen Si incident part C Comparative test piece W Water. .

Claims (5)

[Claims] 1. A surface wave (Ps) is generated by stimulating a minute portion (Si) on a surface of a test object (S) by a surface wave generating means (1, 60), and the surface wave of the test object (S) is generated. A method for evaluating the degree of deterioration or the like of a test object due to surface waves, which evaluates the degree of deterioration or damage of the test object (S) based on the speed of sound (C2). 2. A probe (2) in which said surface wave generating means (1) makes ultrasonic waves obliquely incident on the surface of said specimen (S).
1), the intensity of the backscattered waves (G1 to G8) among the waves received by the probe (21) is measured, and the ultrasonic incident angle ( The method for evaluating the degree of deterioration of a test object due to a surface wave according to claim 1, wherein the sound wave velocity (C2) of the test object (S) is obtained by obtaining i). 3. The method according to claim 2, wherein the intensity of the backscattered wave is measured by two or more different gates. 4. The ultrasonic probe scans the surface of the specimen (S) by moving the probe while keeping the ultrasonic incident angle (i) of the probe constant, and the backscattering. Wave (G
The degree of deterioration of a test specimen due to a surface wave according to claim 2 or 3, wherein the intensity of (1) to (G8) is displayed by a C scan, and the same scan is performed by appropriately changing the ultrasonic incident angle (i). Evaluating method. 5. An apparatus for evaluating the degree of deterioration of a test piece according to claim 2, wherein the ultrasonic wave is obliquely applied to the surface of the test piece (S). (21) for receiving the backscattered waves (G1 to G8) of the surface wave generated on the surface of the test sample (S) while being incident on the sample (S)
Scanning means (25) of the probe (21) for scanning the surface of the test object (S) with ultrasonic waves from the probe (21); and incident angle adjusting means (25) for adjusting the angle of the probe. 25e), a gate means (45) for selecting a gate to be measured among the waves received by the probe, and measuring the intensity of the backscattered waves (G1 to G8) selected by the gate means (45), and The ultrasonic wave incident part (S) by the scanning means (25)
A device for evaluating the degree of deterioration of a test object due to a surface wave, comprising a processing means (46) for displaying the image in association with the coordinates of (i).