JP3579145B2 - Ultrasonic probe - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is intended to transmit ultrasonic pulses through acoustic coupling via a material to be inspected and a water film when detecting a material to be inspected such as a railroad rail, a thick steel plate, a billet steel, and the like. The present invention relates to an ultrasonic probe that receives waves.
[0002]
[Prior art]
FIG. 8 is a perspective view showing a state of measurement of flaw detection by ultrasonic waves on a rail (a material to be inspected) of a conventional railway or the like, and FIG. 9 is a block diagram showing an electrical configuration thereof. FIG. 10 is a diagram for explaining a bonding state between the ultrasonic probe and the test object.
8, 9, and 10, in this example, an ultrasonic probe 4 provided at the tip of a cable 3 connected to an ultrasonic inspection device 2 is attached to a rail (inspection material) 1 to be inspected. The rail 1 is moved for flaw detection. In this case, as shown in FIGS. 9 and 10, flaw detection is performed via the water film 5 between the ultrasonic probe 4 fixed to the probe holder 4a and the rail 1. The surface member (delay material) of the ultrasonic probe 4 facing the rail 1 has a smooth structure. Acoustic coupling with the rail 1 of the material to be inspected is achieved via the surface member and the water film 5.
[0003]
In the ultrasonic flaw detector 2 shown in FIG. 9, the ultrasonic probe 4 or the rail 1 is moved via the water film 5. At this time, a transmission signal output from the transmission unit 7 at a constant cycle is input to the ultrasonic probe 4, and an ultrasonic pulse from an internal vibrator (not shown) is incident on the rail 1 via the water film 5. The ultrasonic pulse is reflected by the scratch on the rail 1, and the reflected wave is received by the transducer of the ultrasonic probe 4.
[0004]
The received wave signal is input to the receiving unit 8, where amplification is performed, and the received wave signal is extracted through the gate circuit of the signal processing unit 9. Further, the signal processing unit 9 performs digital signal processing, compares the received wave with the determination level to detect a flaw on the rail 1, and detects the flaw data and the rail 1 based on the amount of movement from a travel distance sensor (not shown). The position and the like are displayed on a screen on a display unit 10 such as a cathode ray tube (CRT).
[0005]
Further, flaw detection information such as a flaw waveform output from the signal processing unit 9 and the position of the rail 1 is stored and stored in a memory or the like of the recording device 11, and further printed and output on recording paper as necessary. .
In such flaw detection, the thickness of the water film 5 changes with the movement of the rail 1 or the ultrasonic probe 4 of the material to be inspected during the flaw detection, and the flaw detection sensitivity fluctuates. There is a problem that the constant value cannot be maintained.
[0006]
FIG. 11 is a diagram for explaining a change in flaw detection sensitivity due to transmission and multiple reflection of a transmission ultrasonic pulse, and FIG. 12 is a diagram for explaining a change in flaw detection sensitivity based on the phase state of a transmitted wave and a multiple reflection wave. is there. FIG. 13 is a characteristic diagram showing a change in the flaw detection sensitivity with respect to a change in the water film thickness.
In FIG. 11, the transmission ultrasonic pulse generated by the transducer 4c of the ultrasonic probe 4 enters the water film 5 from the surface of the ultrasonic probe 4 via the delay member. The transmitted ultrasonic pulse passes through the water film 5 as a transmitted wave a, and enters from the surface of the material to be inspected on the rail 1. At the same time, a part of the transmitted wave a is reflected on the surface of the material to be inspected, and this reflected wave is reflected back toward the surface of the ultrasonic probe 4 and again travels toward the surface of the material to be inspected on the rail 1. become. That is, a multiple reflection wave b is generated.
[0007]
In this case, as shown in FIG. 12A, when the phases of the transmitted wave a and the multiple reflected wave b are inverted in the water film 5, the transmitted wave a and the reflected wave a incident from the surface of the material to be inspected on the rail 1 cancel each other out. Wave height level decreases. When the transmitted wave a and the multiple reflected wave b in the water film 5 have the same phase as shown in FIG. 12B, the peak levels of the transmitted wave a and the multiple reflected wave b are added, and the rail 1 is inspected. The crest level of the transmitted wave a incident from the material surface increases. Therefore, if the thickness of the water film 5 changes in accordance with the movement of the rail 1 or the ultrasonic probe 4 of the material to be inspected during the flaw detection, the flaw detection sensitivity changes. For example, as shown in FIG. 13, when the thickness of the water film 5 is 0.2 mm and 0.6 mm, the sensitivity (dB) is greatly reduced. The sensitivity (dB) increases. As described above, in the conventional ultrasonic probe, the flaw detection sensitivity greatly varies (about 10 dB) due to a change in the thickness of the water film 5.
[0008]
[Problems to be solved by the invention]
However, in such a conventional ultrasonic probe, the thickness of the water film 5 changes with the movement of the rail 1 or the ultrasonic probe 4 of the material to be inspected when performing a flaw detection. Therefore, when a certain level of flaw detection sensitivity is required, there are drawbacks that the flaw detection accuracy is deteriorated and that reliable reproducibility cannot be obtained.
[0009]
The present invention solves such a drawback in the conventional technology, and eliminates a change in the flaw detection sensitivity due to a change in the thickness of the water film due to the movement of the material to be inspected or the ultrasonic probe. It is an object of the present invention to provide an ultrasonic probe in which the reproducibility and the like are improved.
[0010]
[Means for Solving the Problems]
In order to achieve this object, the present invention is an ultrasonic probe that acoustically couples with a material to be inspected via a water film, transmits an ultrasonic pulse, and receives a reflected wave, And a plurality of grooves having a depth of at least 1/4 wavelength are provided on the surface member for transmitting the reflected wave.
[0011]
In the ultrasonic probe according to the present invention, the longitudinal direction of the groove having a depth of 1/4 wavelength is formed in the direction in which the water film flows.
Further, the ultrasonic probe according to the present invention is provided with a hollow having a depth of at least 1/4 wavelength, including a column, a triangle, a polygon, and an ellipse, instead of the groove.
Further, in the ultrasonic probe of the present invention, the width of the groove, the interval between the grooves, the opening width of the depression, and the interval between the depressions are set to about one wavelength.
[0012]
Further, the ultrasonic probe according to the present invention has the same opening area of the depression and the same area of the flat portion in the surface member that transmits the ultrasonic pulse and receives the reflected wave.
Further, the present invention is an ultrasonic probe which acoustically couples with a material to be inspected via a water film, transmits an ultrasonic pulse, and receives a reflected wave. A delay material that delays a wave and an acoustic impedance that is provided on one side of the delay material that is the surface of the ultrasonic probe and that has a thickness of 1/4 wavelength and a geometric mean of the acoustic impedance of water and the delay material And a matching film.
[0013]
As described above, the ultrasonic probe according to the present invention is capable of transmitting an ultrasonic pulse and receiving a reflected wave on a surface member having a depth of 1/4 wavelength and a recess provided at an interval of about 1 wavelength. And the reflected wave at the flat portion are mixed and incident. At this time, the reflected wave in the groove or the recessed path has a length of 波長 wavelength in the round trip because the depth of the groove is ４ wavelength, and the reflected wave in the concave portion of the groove or the recessed portion The phase of the reflected wave at the flat portion is inverted by 波長 wavelength (180 degrees) and canceled.
[0014]
Therefore, the operation is the same as when there is no reflection on the surface of the ultrasonic probe, and interference such as a decrease in the peak level or an increase in the peak level does not occur. That is, even if the thickness of the water film changes due to the movement of the inspection material or the ultrasonic probe, the flaw detection sensitivity does not change. As a result, flaw detection accuracy and reproducibility are improved.
[0015]
Further, in the present invention, since the longitudinal direction of the groove is formed in the flow direction of the water film, the water of the water film accompanying the movement of the material to be inspected or the ultrasonic probe flows smoothly, and stable acoustic coupling is achieved. Can be obtained. Furthermore, it becomes easy to visually check the wear or damage state when the surface of the ultrasonic probe comes into contact with the inspection object.
Further, the reflection is performed by a matching film having a thickness of 1/4 wavelength, which is disposed on the other side of the delay member serving as the surface of the ultrasonic probe, and an acoustic impedance matching the geometrical average of the acoustic impedances of water and the delay member. The wave does not re-reflect, the number of multiple reflected waves becomes extremely small, and interference with the transmitted wave does not occur. As a result, the variation in the flaw detection sensitivity due to the change in the thickness of the water film is reduced, and the same operation as in the case where there is no reflection on the surface of the ultrasonic probe is obtained, so that the flaw detection accuracy and reproducibility are improved. .
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of an ultrasonic probe according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view and a bottom view showing the configuration of a first embodiment of the ultrasonic probe of the present invention. In FIG. 1, this ultrasonic probe 20 performs ultrasonic flaw detection on a rail (inspected material) such as a railway shown in FIG. 8 and is not shown on an exterior body (housing) 21. The cable 22 connected to the transmission / reception unit of the ultrasonic flaw detector is connected.
[0017]
Further, a delay member 23 inserted and fixed from the opening surface is disposed in the exterior body 21. A vibrator 24 that generates an ultrasonic pulse, receives a reflected wave, and outputs an electrical converted reception signal is attached to the inside (one side) of the exterior body 21 of the delay member 23. The other side of the delay member 23 is an uneven portion 23a in which groove-shaped unevenness is formed.
[0018]
The depth of the groove of the concave-convex portion 23a is set to １ ／ of the wavelength of the ultrasonic signal transmitted by the transducer 24. In the following description, all wavelengths are represented by λ. Further, the width of the groove (concave portion) and the width of the flat portion (convex portion) are set so that the reflected wave of the concave portion and the reflected wave of the convex portion in the concave and convex portion 23a are mixed and surely canceled out. Approximately 1λ.
[0019]
Next, an operation and a function in the first embodiment will be described.
FIG. 2 is a diagram for explaining the change in the flaw detection sensitivity due to the transmission and multiple reflection of the transmission ultrasonic pulse by the uneven portion 23a of the ultrasonic probe 20. FIG. 3 is a diagram for explaining a change in the flaw detection sensitivity from the phase states of the transmitted wave and the multiple reflected waves.
In FIG. 2, an ultrasonic pulse generated by the transducer 24 of the ultrasonic probe 20 is incident on the water film 40 through the uneven portion 23 a of the delay member 23. The transmitted ultrasonic pulse passes through the water film 40 as a transmitted wave a1 from the convex portion (A) of the concave-convex portion 23a, and enters from the surface of the inspection object 41. At the same time, a part of the transmitted wave a1 is reflected on the surface of the inspection object 41, and the reflected wave b1 returns to the convex portion (A) of the concave / convex portion 23a of the ultrasonic probe 20.
[0020]
Further, the transmitted ultrasonic pulse passes through the water film 40 as the transmitted wave a2 from the concave portion (B) of the concave-convex portion 23a and enters from the surface of the inspection object 41. At the same time, a part of the transmitted wave a2 is reflected on the surface of the inspection object 41, and the reflected wave b2 returns to the concave portion (B) of the concave and convex portion 23a of the ultrasonic probe 20.
As described above, the ultrasonic pulse transmitted by the transducer 24 of the ultrasonic probe 20 is reflected on the two kinds of paths of the convex part (A) and the concave part (B) of the concave and convex part 23a. Here, in the reflection on the path of the concave portion (B), the depth of the groove is ４ wavelength, and in the reciprocation, the length is 波長 wavelength. In this case, the reflected waves on the two types of paths, that is, the convex portion (A) and the concave portion (B), mix in the water film 40. Therefore, as shown in FIG. 3, the phase of the reflected wave b1 at the convex portion (A) and the phase of the reflected wave b2 at the concave portion (B) are inverted by 波長 wavelength (180 degrees). Canceled within. That is, the operation is the same as the case where there is no reflection on the surface of the ultrasonic probe 20 (the uneven portion 23a). As described above, there is no reflection on the surface (the uneven portion 23a) of the ultrasonic probe 20, and as described with reference to FIGS. 11A and 11B, the crest level is reduced or the crest level is reduced. Interference such as an increase in height does not occur, and even if the thickness of the water film 40 changes due to the movement of the test object 41 or the ultrasonic probe 20, the flaw detection sensitivity does not change.
[0021]
FIG. 4 is a characteristic diagram showing a change in the flaw detection sensitivity with respect to the change in the water film thickness. In FIG. 4, before the improvement without providing the concave and convex portions 23 a of the ultrasonic probe 20, the sensitivity (dB) of the water film 40 is significantly reduced when the thickness of the water film 40 is 0.2 mm and 0.6 mm, and The sensitivity (dB) is extremely high when the thickness of the film 40 is 0.4 mm, and the flaw detection sensitivity varies due to a change in the thickness of the water film.
[0022]
On the other hand, after the improvement in which the irregularities 23a of the ultrasonic probe 20 are provided as in the first embodiment, the thickness of the water film 40 is 0.2 mm and 0.6 mm, and the sensitivity ( (dB) is slightly lowered, and the sensitivity (dB) is slightly higher when the thickness of the water film 40 is 0.4 mm. Therefore, the change in the flaw detection sensitivity due to the change in the thickness of the water film, which was about 10 dB before the improvement, has been improved to a flat characteristic of about 1 to 2 dB, and the surface of the ultrasonic probe 20 (the uneven portion 23 a) has been improved. The same operation as when there is no reflection is obtained, and the reproducibility is improved.
[0023]
In the first embodiment, when the concave and convex grooves of the concave and convex portions 23a of the ultrasonic probe 20 are formed in the direction in which the water film flows, smooth water flow can be performed, and stable acoustic coupling can be achieved. You will be able to obtain. Further, the surface of the ultrasonic probe 20 often comes into contact with the material to be inspected as the ultrasonic probe 20 moves, and wear and damage are likely to occur. It is easy to visually confirm the worn or damaged state of the uneven portion 23a.
[0024]
FIG. 5 is a bottom view showing a modified example of the uneven portion 23a of the delay member 23 of the ultrasonic probe 20. In this example, a large number of cylindrical depressions 45 are formed on the surface of the delay member 23 of the ultrasonic probe 20 in place of the concave and convex portions 23a. The columnar recess 45 is also formed to have a depth of 1 / 4λ, a width of the opening of the columnar recess 45, and a flat portion between the columnar recesses 45 of about 1λ. The same operation as that of the uneven portion 23a is obtained, and the same effect is obtained.
[0025]
It should be noted that a similar effect can be obtained by using a square, triangular, polygonal, or elliptical hollow instead of the cylindrical hollow 45. Also in this case, the depth is set to ４λ, and the width of the opening and the flat portion therebetween are set to about 1λ.
In addition, since the two reflected waves whose phases are inverted between the dent and the flat portion are mixed and canceled, the total opening area of the dent and the total area of the flat portion are formed to be the same. It is effective if the recessed portion and the flat portion are formed adjacent to each other at an interval of about 1λ.
[0026]
FIG. 6 is a side view showing the configuration of the second embodiment.
6, in this example, a vibrator 24 is attached to one side of the delay member 23 similar to the configuration of FIG. 1, and a matching film 50 is disposed on the other side of the delay member 23 instead of the concave and convex portions 23a. . The matching film 50 is joined to the test object 52 via the water film 51. The matching film 50 is a member having a thickness of 1 / 4λ and an acoustic impedance having a geometric mean value of the acoustic impedance Z1 of the delay member 23 and the acoustic impedance Z2 of water (water film 51).
[0027]
Next, the operation and functions of the second embodiment will be described.
In the ultrasonic probe, a matching film 50 is provided on the delay member 23, and the ultrasonic probe is bonded to the test object 52 via the matching film 50 and the water film 51. In this case, the thickness of the matching film 50 is ４λ. The acoustic impedance of the matching film 50 is a geometric mean value of the acoustic impedance Z1 of the delay member 23 and the acoustic impedance Z2 of water (water film 51), and the impedance value of the delay member 23 and the water film 51 is Approximate and their impedances match. Accordingly, when the transmitted ultrasonic pulse passes through the delay member 23, the matching film 50, and the water film 51, and passes through the inspection target material 52, and the reflected wave at that time reaches the matching film 50, this matching film 50 Is easily incident on the delay member 23 without being reflected on the surface (the surface of the ultrasonic probe).
[0028]
Therefore, multiple reflected waves at the water film 51 are extremely reduced, and interference with transmitted waves does not occur. As a result, a change in the flaw detection sensitivity due to a change in the thickness of the water film is reduced, and the same operation as in the case where there is no reflection on the surface of the ultrasonic probe 20 is obtained, and the reproducibility is improved.
In the improved example, characteristics similar to the characteristics shown in FIG. 4 are obtained. That is, the change in the flaw detection sensitivity due to the change in the thickness of the water film, which was about 10 dB before the improvement, is improved to a flat characteristic of about 1 to 2 dB.
[0029]
In the first and second embodiments, an example is described in which one vibrator is provided on one side of the delay member. However, the present invention can be applied to other configuration types without change. For example, as shown in FIG. 7A, the present invention can be applied to an oblique type in which an ultrasonic pulse is transmitted in an oblique direction and a reflected wave is received. Further, as shown in FIG. 7 (B), a separate transducer for transmission and reception is arranged on a delay member or the like to transmit an ultrasonic pulse and also to a vertical division type for receiving a reflected wave. is there.
[0030]
Incidentally, in the above embodiments, the concave-convex portion 23a, but Ru had an example a case where the alignment film 50 and the 1 / 4λ, 1 / 4λ of odd multiples of 3 / 4.lamda, a 5 / 4.lamda etc. Is also good.
[0031]
【The invention's effect】
As described above, according to the ultrasonic probe of the present invention, a reflected wave is mixed and incident on grooves and depressions having a depth of 1/4 wavelength provided at approximately one wavelength interval and flat portions. At this time, the phase of the reflected wave that has passed the length of 波長 wavelength in the groove or the recessed path is inverted by と wavelength with respect to the reflected wave in the flat portion and is canceled out. The operation is the same as in the case where there is no reflection at the surface, and no interference such as a decrease in the crest level or an increase in the crest level occurs. As a result, even if the thickness of the water film changes due to the movement of the material to be inspected or the ultrasonic probe, the flaw detection sensitivity does not change, and the flaw detection accuracy and reproducibility are improved.
[0032]
Further, in the present invention, since the longitudinal direction of the groove is formed in the flow direction of the water film, the water of the water film accompanying the movement of the material to be inspected or the ultrasonic probe flows smoothly, and stable acoustic coupling is achieved. Is obtained, and the abrasion and damage when the surface of the ultrasonic probe comes into contact with the material to be inspected can be easily visually confirmed.
Further, reflection is caused by a quarter-wavelength-thickness film disposed on one side of the delay member serving as the surface of the ultrasonic probe and a matching film of acoustic impedance which is a geometric mean of acoustic impedances of water and the delay member. The wave does not reflect on the surface, and the multiple reflection wave on the water film is extremely small, so that interference with the transmitted wave does not occur. As a result, a change in the flaw detection sensitivity due to a change in the thickness of the water film is reduced, and the same operation as in the case where there is no reflection on the surface of the ultrasonic probe is obtained, thereby improving the flaw detection accuracy and reproducibility.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view and a bottom view showing the configuration of a first embodiment of an ultrasonic probe according to the present invention. FIG. 2 is a diagram showing a configuration of an ultrasonic probe shown in FIG. FIG. 3 is a diagram illustrating a change in flaw detection sensitivity due to transmission and multiple reflection. FIG. 3 is a diagram illustrating a change in flaw detection sensitivity based on the phase state of a transmitted wave and a multiple reflection wave in the first embodiment. FIG. 5 is a characteristic diagram showing a change in flaw detection sensitivity with respect to a change in water film thickness in the first embodiment. FIG. 5 is a cross-sectional view and a bottom view showing a modification of the ultrasonic probe in the first embodiment. 6 is a side view showing the configuration of the second embodiment. FIG. 7A is a side view showing an application example of the first and second embodiments. FIG. (B) showing a schematic configuration of an oblique type for receiving a signal is a schematic configuration of a vertical division type provided with a separate vibrator for transmission and reception. FIG. 8 is a perspective view showing a conventional state of measurement of flaw detection by ultrasonic waves on a material to be inspected. FIG. 9 is a block diagram showing an electrical configuration of the configuration shown in FIG. 8; FIG. FIG. 11 is a diagram for explaining a bonding state between an ultrasonic probe and a material to be inspected. FIG. 11 is a diagram for illustrating a change in flaw detection sensitivity due to transmission and multiple reflection of a transmission ultrasonic pulse in a conventional example. FIG. 7A for explaining the variation in the flaw detection sensitivity based on the phase state of the transmitted wave and the multiple reflected wave in the conventional example is shown in FIG. Waveform diagram showing the case where transmitted wave and multiple reflected wave are in phase. [FIG. 13] Characteristic diagram showing variation of flaw detection sensitivity with respect to change of water film thickness in the conventional example.
20: Ultrasonic probe 21: Outer body (housing)
22: cable 23: delay member 24: vibrator 23a: concave and convex portions 40, 51: water films 41, 52: inspected material 45: cylindrical depression 50: matching film

Claims (5)

In the ultrasonic probe that acoustically couples with the material to be inspected via the water film, transmits ultrasonic pulses, and receives reflected waves,
An ultrasonic probe, wherein a plurality of grooves each having a depth of 1/4 wavelength or an odd multiple thereof are provided on a surface member for transmitting an ultrasonic pulse and receiving a reflected wave. In the ultrasonic probe according to claim 1,
An ultrasonic probe, wherein a longitudinal direction of a plurality of grooves having a depth of 1/4 wavelength or an odd multiple thereof is formed in a direction in which a water film flows. In the ultrasonic probe according to claim 1 ,
An ultrasonic probe comprising a hollow having a cylindrical shape, a triangular prism, a polygonal prism, and an elliptical cylinder having a depth of 1/4 wavelength or an odd multiple thereof , instead of the groove. In the ultrasonic probe according to any one of claims 1, 2, and 3,
An ultrasonic probe, wherein a width of a groove, a distance between grooves, or an opening width of a depression, and a distance between depressions are set at around one wavelength. The ultrasonic probe according to claim 3 ,
An ultrasonic probe, wherein an opening area of a depression and an area of a flat portion in a surface member for transmitting an ultrasonic pulse and receiving a reflected wave are formed to be the same.

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