JP2002365267A - Ultrasonic flaw detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic flaw detector capable of accurately detecting the presence of a flaw such as a crack or the like especially in a structure comprising a concrete material. SOLUTION: The ultrasonic flaw detector is equipped with the transmission probe 1a held to a first oblique angle fixture 2a, and the receiving probe 1b held to a second oblique angle fixture 2b to extract narrow band component waves centering around predetermined frequency to detect the flaw of a concrete column CP on the basis of the narrow band component waves. The first oblique angle fixture 2a is compored of the bottom surface 8 brought into close contact with the surface of the concrete column CP to propagate the ultrasonic waves transmitted from the transmission probe 2a to the surface of the concrete column CP, the rear surface 10 formed so as to be inclined with respect to the bottom surface 8 and having the transmission probe 1a held thereto, and an uneven surface wherein all of other surfaces are formed unevenly and the distance between the ridges and troughs of this unevenness becomes 1/8 or more the wavelength of the narrow band component waves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detector for detecting a defect such as a crack in a concrete structure.

[0002]

2. Description of the Related Art For example, a concrete pillar as a concrete building is buried under the ground and vertically constructed, and a transmission line, a communication line and the like are laid above the pillar. Concrete columns may have natural cracks that occur over time on their surfaces or external enemy cracks that occur due to some external load. In this case, the reinforcing steel inside the concrete corrodes due to intrusion of rainwater or the like from the crack.

[0003] When inspecting internal defects such as cracks in a con- structed building, the ultrasonic flaw detection method described in JP-A-10-62395 is most used. According to the description of this publication, a pair of ultrasonic transducers is arranged on the surface of a concrete building to be inspected, and ultrasonic waves are radiated from one ultrasonic transducer to the concrete building, and the concrete building An ultrasonic flaw detector which receives a reflected echo at a defective portion of an object or a bottom echo reflected at the bottom by the other ultrasonic transducer is described. Also, by changing the interval between the transmitting and receiving positions where ultrasonic waves are radiated to the concrete building, based on the multiple reflected echo data obtained by this, surface noise, which is unnecessary noise in flaw detection measurement of the concrete building, is There is also described a flaw detection method in which echo data is reduced to enhance the reflected echo at the defective portion and the bottom echo reflected at the bottom.

[0004]

By the way, cracks generated on the surface of the concrete column occur not only on the ground portion of the concrete column but also on the buried portion of the concrete column. In the buried part of the concrete pillar, it is impossible to visually confirm it, and it is necessary to excavate around the concrete pillar to see it, which requires considerable man-hours.

For example, when the ultrasonic flaw detection method described in the above-mentioned Japanese Patent Application Laid-Open No. 10-62396 is used, it is possible to detect an internal defect in the above-ground portion of a concrete column, but it is not possible to detect the internal defect in the embedded portion of the concrete column. Is impossible.

The inventor of the present invention uses a conventional angled jig shown in FIG. 9 to direct the emission direction of the transmitting probe and the incident direction of the receiving probe toward the buried portion of the concrete column. Inspection of the concrete pillars was carried out.

The transmitting probe 101a and the receiving probe 1
Each of 01b is inserted and fixed in a concave portion 100b formed on the slope 100a of the bevel jig 100. Also, slope 1
The vertical surface 100c opposing 00a is formed in a bellows shape to prevent the ultrasonic wave reflected from the vertical surface 100c from being incident on the transmission probe 101a or the reception probe 101b. The bottom surface 100d of the bevel jig 100 is formed in a shape corresponding to the surface shape of the concrete column CP so as to be in close contact with the surface of the concrete column CP, and the transmission probe 101a and the reception probe fixed to the bevel jig 100. Probe 10
1b was installed on the surface of the above-ground portion Cb of the concrete column CP via the contact medium as shown in FIG. The transmission probe 101a and the reception probe 101b are arranged in the axial direction of the concrete column CP from the buried portion Ca side.
a, the receiving probe 101b is arranged in this order. Therefore, the ultrasonic wave emitted from the transmitting probe 101a in the direction of the buried portion Ca of the concrete column CP is reflected from the crack K generated in the buried portion Ca of the concrete column CP, and the echo thereof is reflected by the receiving probe. It will be received at 101b.

FIG. 11 shows the result of the flaw detection inspection performed in the state shown in FIG. FIG. 11 shows a waveform obtained by analyzing an echo received by the receiving probe by an analyzer using an ultrasonic flaw detector described later, and a time series in which the horizontal axis represents elapsed time and the vertical axis represents echo intensity. FIG. The echo E from the crack K generated in the buried portion Ca of the concrete column CP shown in FIG. 10 is received at the elapsed time T in FIG.
The echo E is, as shown in FIG. 12A, the oblique jig 10 of the ultrasonic waves emitted from the transmission probe 101a.
0 without direct reflection inside the concrete column CP
The ultrasonic wave emitted to the surface of the ground portion Cb is an echo reflected from the crack K and incident on the receiving probe 101b. At the time before and after the echo E, other noise echoes E1 and E2 are received.

As a result of verifying the above-mentioned noise echoes E1 and E2, the present inventor found that the noise echo E1 received at a time prior to the echo E was generated from the crack K as shown in FIG. Not the reflected echo, but the transmitting probe 101
The ultrasonic wave emitted from a is reflected inside the bevel jig 100, intermittently emitted to the surface of the ground portion Cb of the concrete column CP, and directed toward the receiving probe 101b. It turned out that the sound wave was an echo directly incident on the receiving probe 101b and received.

On the other hand, the noise echo E2 received at a time after the echo E is an echo reflected from the crack K as shown in FIG. 12C, but is emitted from the transmission probe 101a. Ultrasonic wave reflected inside the angled jig 100, and intermittently the ground portion C of the concrete column CP.
The ultrasonic wave emitted to the surface of b and directed in the direction of the crack K was found to be an echo reflected and received by the crack K.

When such a noise echo is received, it becomes extremely difficult to distinguish between the echo E and the noise echoes E1 and E2. Inspection becomes impossible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an ultrasonic flaw detector capable of accurately detecting the presence of a defect such as a crack in a concrete structure. Aim.

[0013]

According to a first aspect of the present invention, there is provided an ultrasonic testing apparatus, comprising: a transmitting probe for transmitting an ultrasonic wave; a transmitting probe mounted on a surface of the subject; A first oblique angle holding member for holding the transmission probe so that the transmission probe is directed obliquely from the surface of the subject and the direction side is set to the detection direction; A receiving probe that is installed on the surface of the subject so as to be at the same position or far side with respect to the transmitting probe, and receives an ultrasonic echo transmitted from the transmitting probe. Comprising, from the echo received by the receiving probe, to extract a narrow band component wave centered on a predetermined frequency,
In the ultrasonic flaw detector that performs flaw detection on a subject based on the narrowband component wave, the first bevel holding member is in close contact with the surface of the subject, and receives the ultrasound transmitted from the transmitting probe. A propagation surface that propagates to the surface of the sample, a holding surface that is formed by a surface inclined with respect to the propagation surface, and that holds the transmission probe, and a side surface that is located farther from the reception probe. It is characterized in that the surface is formed in an uneven shape, and the unevenness is formed of an uneven surface in which the distance between the peak and the valley of the unevenness is 1/8 or more of the wavelength of the narrow band component wave.

According to a second aspect of the present invention, there is provided an ultrasonic flaw detector for transmitting an ultrasonic wave, and a transmitting probe mounted on a surface of the object and transmitting the ultrasonic wave to the object. Direction from the surface of the subject obliquely,
And a first oblique holding member for holding the transmitting probe so that the direction side is the detecting direction side, and the subject is positioned so as to be at the same position or far side with respect to the transmitting probe in the detecting direction. A receiving probe that is installed on the surface and receives an ultrasonic echo transmitted from the transmitting probe, and a predetermined frequency centered on the echo received by the receiving probe. In the ultrasonic flaw detector which extracts a narrow-band component wave and performs flaw detection on the subject based on the narrow-band component wave, the first bevel holding member is in close contact with the surface of the subject, and is used for transmission. A propagation surface for transmitting the ultrasonic wave transmitted from the probe to the surface of the subject, a holding surface formed with a surface inclined with respect to the propagation surface and holding the transmission probe, and all other surfaces Are formed in irregularities, and the distance between the peaks and valleys of the irregularities is Characterized in that it is constituted by an uneven surface to be 1/8 or more of the wavelength of the waves.

An ultrasonic flaw detector according to a third aspect of the present invention is provided on the surface of the subject, and the receiving probe is directed obliquely from the surface of the subject with respect to the subject. And a second oblique angle holding member for holding the receiving probe so that the receiving probe is directed toward the detecting direction.

The ultrasonic flaw detector according to claim 4 of the present invention is characterized in that the uneven surface is formed in a saw blade shape.

The ultrasonic flaw detector according to claim 5 of the present invention is characterized in that the subject is a concrete material.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a block diagram showing a configuration of an ultrasonic flaw detector according to the present invention. FIG. 2 is a top view showing a bevel jig to which a transmission probe or a reception probe is attached, and FIG. Is a side view, FIG. 4 is a front view, and FIG. 5 is a rear view.

In FIG. 1, a concrete pillar CP as a subject is formed in a hollow shape with a donut shape in cross section, and one end thereof is buried in the underground M and is vertically built. It is assumed that a crack K is generated on the surface of the embedded portion Ca of the concrete column CP due to deterioration due to an external load or a change with time, and the crack K is detected by a reflection method using the present ultrasonic flaw detector T. Is what you do. On the surface of the ground portion Cb of the concrete column CP, a transmission probe 1a is installed via a first bevel jig 2a (corresponding to a first bevel holding member in the claims). The receiving probe 1b is installed via a second bevel jig 2b (corresponding to a second bevel holding member in the claims). The ultrasonic flaw detector T includes a pulse generator 3 and the pulse generator 3.
The transmitting probe 1a which receives a pulse wave generated from the above and transmits an ultrasonic wave to the surface of the ground portion Cb of the concrete column CP via the first angled jig 2a, and an echo from the inside of the concrete column CP. Probe 1b that receives the signal via the second angled jig 2b and converts it into an electric signal, an amplifier 4 that amplifies the electric signal obtained by the receiving probe 1b, and the amplifier 4 An analyzing device 5 for analyzing the amplified electric signal, a display device 6 for displaying an analysis result by the analyzing device 5 and a pulse wave generated by the pulse generator 3, an operating device for inputting a measurement start signal, a measurement condition, and the like. 7 are provided.

The pulse generator 3 includes a pulse generation circuit 3a for generating a pulse wave having a wide band frequency, a pulse interval change circuit 3b for changing the generation interval of the pulse wave, and a pulse generator connected to these for generating the pulse wave. 3 is provided with a pulse drive circuit 3c for sending out to outside.

The broadband ultrasonic wave as a pulse wave output from the pulse generator 3 is transmitted from the transmitting probe 1a to the surface of the concrete column CP, and the echo is received by the receiving probe 1b. The signal is amplified by the amplifier 4 and input to the analyzer 5.

The analyzer 5 includes an amplifier circuit 5a for further amplifying the input electric signal, and a filter such as a low-pass filter, a high-pass filter, and a band-pass filter for removing unnecessary signals from the amplified signal. The filter circuit 5b formed is an analog / digital converter (AD) for converting the filtered signal.
C) 5c, a gate array 5d and a CPU 5e are provided. The gate array calculates the average of the received waves at the same point.

Further, a storage device (not shown) is connected to the CPU 5e, and a processing program is stored in the storage device. Further, the pulse generator 3, the amplifier circuit 5a, the filter circuit 5b, and the ADC 5c
Is controlled by the CPU 5e.

Unnecessary signals are removed from the signal input to the analyzer 5 by the filter circuit 5b, and only a narrow-band component wave centered on a predetermined frequency is extracted. The presence or absence of a defect in the concrete column CP is determined based on the narrow band component wave.

Next, based on FIGS. 2, 3, 4 and 5, the first bevel jig 2 holding the transmission probe 1a will be described.
a will be described. Note that the second angled jig 2b holding the receiving probe 1b has the same shape as the first angled jig 2a, and thus the description is omitted. This first bevel jig 2
As shown in FIG. 3, the shape of “a” is a three-dimensional shape formed into a trapezoid with one corner of the base being a right angle when viewed from the side, and is mainly formed of an acrylic resin. The bottom surface 8 (corresponding to the propagation surface in the claims) of the first bevel jig 2a is the concrete column CP.
The first bevel jig 2a is formed in an arc shape when viewed from the front so as to correspond to the surface shape of the first bevel jig 2a, and is formed from the front surface 9 to the rear surface 10 of the first bevel jig 2a. Therefore, the first bevel jig 2a is installed on the surface of the ground portion Cb of the concrete column CP such that the direction from the front surface 9 to the rear surface 10 is the same as the axial direction of the concrete column CP. First
The rear surface 10 (corresponding to a holding surface in the claims) of the bevel jig 2a is formed by a slope inclined at a predetermined angle with respect to the bottom surface 8, and the rear surface 10 has the transmission probe 1a or the reception probe. The tentacle 1b (indicated by a two-dot chain line in FIG. 3) is held.
As shown in FIG. 5, a substantially cylindrical concave portion 10a corresponding to the outer shape of the transmitting probe 1a is formed on the rear surface 10, and the transmitting probe 1a or the receiving probe 1b is formed in the concave portion 10a. Is inserted and held. Front 9 of first bevel jig 2a
And the side surface 11 has a saw-toothed uneven shape when viewed from above,
The first angled jig 2 a is formed from the upper surface 12 to the bottom surface 8. The upper surface 12 of the first bevel jig 2a has a saw-toothed uneven shape when viewed from the front or the rear, and the first bevel jig 2a
From the front surface 9 to the rear surface 10.

Here, the saw-toothed irregularities formed on the front surface 9, the side surface 11, and the upper surface 12 (corresponding to the irregular surface in the claims) of the first bevel jig 2a will be described. This uneven shape is set based on the narrow-band component wave extracted by the filter circuit 5b of the analyzer 5 described above. That is,
The distance L between the peak and the valley shown in FIG. 2, FIG. 3, FIG. 4, and FIG. 5 is set to １ ／ or more of the wavelength of the narrowband component wave. Thereby, it is possible to prevent the specular reflection of the ultrasonic wave incident on the front surface 9, the side surface 11, and the upper surface 12 of the first bevel jig 2a,
The incidence of the noise echo on the receiving probe 1b can be suppressed.

As shown in FIG. 3, the first bevel jig 2
The direction of the ultrasonic wave (indicated by a dashed line in FIG. 3) of the transmission probe 1a held by the first
has a predetermined angle α (hereinafter, referred to as an incident angle) with respect to a normal h to the bottom surface of a. The incident angle α is set by the inclination angle of the rear surface 10 of the first oblique jig 2a with respect to the bottom surface 8 in accordance with the thickness of the subject, the inspection location, and the like. The above concrete column CP
When the embedded portion Ca is inspected for flaws, the ultrasonic beam directing direction of the first angled jig 2a, that is, the front surface 9 is set toward the detecting direction, that is, toward the embedded portion Ca of the concrete column CP.

Next, referring to FIG. 6, the first bevel jig 2
a probe for transmission 1a and second bevel jig 2b held at a
The installation state of the receiving probe 1b held in the concrete column CP on the surface of the ground portion Cb will be described. FIG.
As shown in the figure, the transmission probe 1a and the reception probe 1b
Are arranged on the surface of the ground portion Cb of the concrete column CP in the axial direction of the concrete column CP in the order of the transmitting probe 1a and the receiving probe 1b from the buried portion Ca side. Each of the transmission probe 1a and the reception probe 1b embeds the front surface 9 of the first angled jig 2a and the second angled jig 2b in the embedded portion Ca.
And the transmitting probe 1a is placed in the embedded portion Ca.
The receiving probe 1b is arranged near the transmitting probe 1a at a predetermined separation distance in the axial direction of the concrete column CP while being arranged near.

Here, when the arrangement is as shown in FIG. 6, the first bevel jig 2a for holding the transmission probe 1a is
It is necessary to form an uneven shape on the side surface located on the far side with respect to the receiving probe 1b, that is, on the front surface 9. This is shown in FIG.
As shown in FIG. 2 (b), the ultrasonic wave transmitted from the transmitting probe 1a is reflected on the front surface 9 and the noise echo directed to the anti-detection direction side, that is, the direction of the transmitting probe 1a is received. This is to prevent the probe 1b from receiving. FIG.
As shown in FIG. 2C, the ultrasonic wave transmitted from the transmitting probe 1a is reflected at the front surface 9 and is repeatedly reflected inside the first angled jig 2a, so that the detecting direction is intermittently detected. That is, this is for preventing the reception probe 1b from receiving the noise echo transmitted from the crack K and from the crack K.

As shown in FIG. 7, the transmission probe 1
a and the receiving probe 1b may be arranged at a predetermined distance in the circumferential direction of the concrete column CP. Both the transmission probe 1a and the reception probe 1b are installed with the front surface 9 of the first angled jig 2a and the second angled jig 2b oriented toward the buried portion Ca.

Here, in the case of the arrangement shown in FIG. 7, the first bevel jig 2a for holding the transmission probe 1a is
It is necessary to form an uneven shape on the side surface located farther from the receiving probe 1b, that is, on the left side surface 11 in FIG. This is because the ultrasonic wave transmitted from the transmitting probe 1a is reflected by the left side surface 11 in FIG.
This is to prevent the reception probe 1b from receiving the noise echo directed in the direction b. Further, it is preferable that the front face 9 of the first bevel jig 2a is also formed with an uneven shape. This is because the ultrasonic wave transmitted from the transmitting probe 1a is reflected at the front surface 9 and further repeatedly reflected inside the first angled jig 2a, so that the ultrasonic wave is intermittently moved in the detection direction, that is, the direction of the crack K. This is to prevent the receiving probe 1b from receiving the transmitted echoes from the crack K.

The first bevel jig 2a in this embodiment has all surfaces except the bottom surface 8 and the rear surface 10, that is, the front surface 9 and the side surface 1.
1 and the upper surface 12 were formed in an uneven shape. Thereby, all the ultrasonic waves caused by the noise echo can be attenuated by repeating the reflection inside the first bevel jig 2a, and
The attenuated ultrasonic wave can be diffused from the surface of the concrete column CP as an omnidirectional wave.

The space between the transmitting probe 1a and the receiving probe 1b and the concave portion 10a and between the bottom surface 8 and the concrete column C
A medium such as water, oil or grease is applied between the surface of P and the surface of P.

Next, the embedded portion C of the concrete column CP
The operation of inspecting the crack K of a will be described. The inspector first examines the name of the subject, the thickness, the sound velocity value of the ultrasonic wave measured in advance, the average number of times, the separation distance between the transmission probe 1a and the reception probe 1b, the measurement range, and the like. The conditions are input by the operation device 7. By this input, the inspection condition is stored in the storage device in the analyzer 5. The inspection is started when the inspector presses any key of the operation device 7. Thereby, the ultrasonic wave is transmitted from the transmitting probe 1a into the concrete column CP, and the echo reflected from the inside of the concrete CP is received by the receiving probe 1b. The averaging process is performed by the analyzer 5 based on the received echo, and a graph showing a time series as shown in FIG. 8 is displayed on the display 6.

FIG. 8 shows the results obtained by the flaw detection inspection.
This will be described with reference to a graph showing the time series of the above. FIG.
This is a time-series graph in which the horizontal axis represents elapsed time and the vertical axis represents echo intensity. The echo E from the crack K is received at the elapsed time T in FIG. At the time before and after the echo E, no other noise echo is received. As a result, of the ultrasonic waves emitted from the transmission probe 1a, the ultrasonic waves are not reflected inside the first bevel jig 2a,
Only the ultrasonic waves directly emitted to the surface of the concrete column CP are reflected from the crack K and received. That is, of the ultrasonic waves emitted from the transmitting probe 1a, the ultrasonic waves reflected inside the first angled jig 2a are the front 9, the side surfaces 11, and the upper surface 12 of the first angled jig 2a. Due to the saw-tooth-shaped uneven shape formed in the above, the reflection is repeated and attenuated inside the first bevel jig 2a, and the attenuated ultrasonic wave is diffused from the surface of the concrete column CP as an omnidirectional wave. Will be. Therefore, based on the time series graph shown in FIG. 8, the buried portion Ca of the concrete column CP is used.
Can be determined, and the position of the crack K can be specified by the elapsed time T.

[0036]

According to the flaw detection inspection apparatus of the present invention, it is possible to accurately determine the presence or absence of a defect such as a crack generated in an object and its position.

[0037]

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an ultrasonic flaw detector according to the present invention.

FIG. 2 shows a first example to which a transmission probe according to the present invention is attached.
It is the top view which shows a bevel jig.

FIG. 3 is a side view of FIG. 2;

FIG. 4 is a front view of FIG. 2;

FIG. 5 is a rear view of FIG. 2;

FIG. 6 is a diagram for explaining the arrangement of a transmission probe and a reception probe according to the present invention.

FIG. 7 is a diagram for explaining an arrangement of a transmission probe and a reception probe according to the present invention.

FIG. 8 is a graph showing a time series obtained as an inspection result using the ultrasonic flaw detector according to the present invention.

FIG. 9 is a perspective view showing a conventional angled jig to which a transmission probe or a reception probe is attached.

FIG. 10 is a diagram showing an arrangement of a transmission probe and a reception probe.

FIG. 11 is a graph showing a time series obtained as an inspection result using a conventional angle beam jig.

12A is a diagram illustrating a propagation route of an echo E, FIG. 12B is a diagram illustrating a propagation route of an echo E1, and FIG. 12C is a diagram illustrating a propagation route of an echo E2. is there.

[Explanation of symbols]

 1a Transmitting probe 1b Receiving probe 2a 1st bevel jig 2b 2nd bevel jig 8 Bottom 9 Front 10 Back 11 Side Side CP Concrete column T Ultrasonic flaw detector

Claims (5)

[Claims] 1. A transmitting probe for transmitting an ultrasonic wave, and a transmitting probe installed on a surface of a subject and having the transmitting probe directed in a direction oblique to the subject from the surface of the subject. A first bevel holding member for holding the transmitting probe so as to face and the direction side to the detecting direction side, and to be at the same position or farther side with respect to the transmitting probe in the detecting direction. A receiving probe is provided on the surface of the subject and receives an ultrasonic echo transmitted from the transmitting probe, and a predetermined number of echoes are received from the receiving probe. In the ultrasonic flaw detector which extracts a narrow band component wave centered on a frequency and performs flaw detection of the subject based on the narrow band component wave, the first oblique angle holding member is in close contact with the surface of the subject, Propagation for transmitting ultrasonic waves transmitted from the transmitting probe to the surface of the subject Surface, a surface inclined with respect to this propagation surface, a holding surface on which the transmitting probe is held, and a surface of a side surface located on a side far from the receiving probe are formed with irregularities, An ultrasonic flaw detector wherein the distance between the peaks and valleys of the irregularities is an irregular surface where the distance is 1/8 or more of the wavelength of the narrow band component wave. 2. A transmitting probe for transmitting an ultrasonic wave, and a transmitting probe installed on the surface of the subject and having the transmitting probe directed diagonally from the surface of the subject with respect to the subject. A first bevel holding member for holding the transmitting probe so as to face and the direction side to the detecting direction side, and to be at the same position or farther side with respect to the transmitting probe in the detecting direction. A receiving probe is provided on the surface of the subject and receives an ultrasonic echo transmitted from the transmitting probe, and a predetermined number of echoes are received from the receiving probe. In the ultrasonic flaw detector which extracts a narrow band component wave centered on a frequency and performs flaw detection of the subject based on the narrow band component wave, the first oblique angle holding member is in close contact with the surface of the subject, Propagation for transmitting ultrasonic waves transmitted from the transmitting probe to the surface of the subject Surface, a surface inclined with respect to this propagation surface, a holding surface on which the transmitting probe is held, and all other surfaces are formed with irregularities, and the distance between the peaks and valleys of the irregularities is An ultrasonic flaw detector comprising an uneven surface having a wavelength equal to or more than 1/8 of the wavelength of the narrow-band component wave. 3. The receiving probe is placed on the surface of the subject, and the receiving probe is directed obliquely from the surface of the subject with respect to the subject, and the direction of the receiving probe is set in the detecting direction. The ultrasonic flaw detector according to claim 1, further comprising a second oblique angle holding member that holds the receiving probe so as to make the ultrasonic probe flawless. 4. The ultrasonic flaw detector according to claim 1, wherein the uneven surface is formed in a saw blade shape. 5. The ultrasonic flaw detector according to claim 1, wherein the subject is a concrete material.