JP2001124746A - Ultrasonic inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic inspection method in which a defect existing in the surface layer part of an object to be inspected and a defect existing at the inside of the object to be inspected can be detected simultaneously. SOLUTION: An ultrasonic probe 1A which is used is provided with an acoustic lens 3 in which a through hole 4 is opened and formed in the central part. The ultrasonic probe is provided with a vibrator 2 which is set in the plane part 3a of the acoustic lens 3 and whose planar shape is circular. In a state that the focus P of the acoustic lens 3 is situated in a part a little lower than the surface of an object 100 to be inspected, the vibrator 2 is started. A focused beam 11 which is focused by the acoustic lens 3 and vertical waves 12 which are not focused by the acoustic lens 3 are transmitted from the ultrasonic probe 1A. The echo of leaked waves generated at a time when the focused beam 11 is incident on the object 100 to be inspected is received by the vibrator 2. On the basis of the level of the echo, a defect in the surface layer part of the object to be inspected is flaw-detected. In addition, a defect echo or a bottom echo which is obtained at a time when the vertical waves 12 are incident on the object to be inspected is received by the vibrator 2. On the basis of the level of the echo, a defect at the inside of the object to be inspected is flaw- detected. In addition, on the basis of the time difference between the surface echo and the bottom echo, the thickness of the object to be inspected is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic inspection method applied to a nondestructive inspection of a structure made of a metal material, and more particularly to an inspection method for inspecting the soundness of a surface layer of an object and a defect inspection inside the object. The present invention relates to an ultrasonic inspection method that can be performed simultaneously.

[0002]

2. Description of the Related Art Conventionally, as a defect inspection method of an object using an ultrasonic wave, a method of vertically incident an unfocused beam on the object and a method of setting a focus on or just below the surface of the object. A method of inputting a focused beam is known.

FIG. 8 is an explanatory view of a water immersion type vertical ultrasonic flaw detection method which is an example of the former. As is clear from this figure,
In the ultrasonic inspection method of this example, an unfocused ultrasonic beam 201 is perpendicularly incident on the subject 100 from an ultrasonic probe 200 via water W as an ultrasonic medium, as shown on the right side of FIG. First, a method for obtaining a surface echo S1 and a bottom surface echo B1. As is apparent from FIG.
If the defect 101 exists inside the area 0, a defect echo F1 appears between the surface echo S1 and the bottom surface echo B1.
By detecting this, the occurrence position, size, shape, and the like of the defect 101 can be obtained.

FIG. 9 is a diagram showing an example of the latter ultrasonic inspection method, which is described in Japanese Patent Application Laid-Open No. 4-259853. The ultrasonic inspection method of this example has a frequency of 15
Using an ultrasonic probe 300 having a focal length of 12.7 to 38.1 mm at a frequency of ５０50 MHz, the ultrasonic probe 300
Is set on the surface of the subject 100 or directly below it, and the ultrasonic inspection is performed.
According to this method, the width of the surface echo S1 is shortened due to the use of the high frequency, and the ultrasonic beam 301 can be concentrated around the minute defect 102 existing near the surface because the focused beam is used. Therefore, as shown on the right side of FIG. 9, the minute defect 10 follows the surface echo S1.
Multiple echo groups Fr from 2 are observed. Transmission echo S
1 is short but has a width, so that the first defect echo from the minute defect 102 cannot be separated from the surface echo S1, but by capturing the multiple echo group Fr, a portion near the surface of the subject can be obtained. It is possible to grasp the presence or absence of a minute defect existing in the image.

[0005]

However, the former of the above-mentioned conventional ultrasonic examination methods is the subject 100
Since the unfocused ultrasonic beam 201 is incident on the object 100, the level of the surface echo S1 becomes very large, so that the level of the surface echo S1 is about 1 to 2 mm from the surface of the subject 100.
Dead zone NB where detection of minute defect 102 cannot be performed
Is disadvantageous.

On the other hand, the latter of the above-mentioned conventional ultrasonic inspection methods sets the focus of the ultrasonic beam 301 on the surface of the object 100 or directly below the object 100, so that the object 1
Although the defect detection from the vicinity of the surface of the specimen 100 becomes possible, the defect that the defect existing at a position other than the focal region, in particular, the defect 101 located at a position near the bottom surface of the subject 100 is deteriorated is disadvantageous. There is. This method is also applicable to a relatively large area defect extending in a direction parallel to the surface of the test object 100, such as nonmetallic inclusions existing in a steel material or peeling of a thermal spray coating, for example. Can be detected, but it is difficult to detect the multiple echo group Fr with respect to a minute defect extending in a direction perpendicular to the surface of the subject 100. According to experiments,
The method described in the above publication could not detect a vertical crack having a width of 2 to 5 μm existing in the WC-based thermal spray coating having a thickness of 0.1 mm.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned deficiencies of the prior art, and an object of the present invention is to simultaneously detect a microdefect present on the surface layer of a subject and a defect present inside the subject. It is an object of the present invention to provide an ultrasonic inspection method capable of detecting a small defect existing on the surface layer of an object with high accuracy regardless of the size and orientation of the defect.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a vibrator, a propagation path of a normal incident wave and an oblique incident wave to a subject, and a vertical reflection wave and a reflected wave from the subject. An acoustic lens having a propagation path of a leaky wave, wherein the propagation speed of the ultrasonic wave in the propagation path of the vertically incident wave and the vertically reflected wave is lower than the propagation speed of the ultrasonic wave in the propagation path of the obliquely incident wave and the leaky wave Using an ultrasonic probe having: and evaluating the soundness of the subject surface layer based on the received signal of the leaky wave, and defects other than the subject surface layer based on the received signal of the vertical reflected wave The inspection and / or the thickness measurement of the subject is performed.

When the ultrasonic probe having the above configuration is used, the propagation speed of the ultrasonic wave in the propagation path of the vertically incident wave and the vertically reflected wave is lower than the propagation velocity of the ultrasonic wave in the propagation path of the obliquely incident wave and the leaky wave. Therefore, as shown in FIG. 2 (b), the surface echo S1 due to the normal incident wave and the echo L1 of the leaky wave are separated on the time axis, and the echo L1 of the leaky wave.
Can obtain a received signal that precedes the surface echo S1. Therefore, from the echo level of the leaked wave,
0 can be detected at the surface layer portion of the specimen 100, and when the defect 101 exists inside the subject 100, the defect echo F1 appears between the surface echo S1 and the bottom echo B1. By detecting, the position, size, shape, and the like of the defect 101 can be obtained. Further, the surface echo S1 and the bottom echo B1
The thickness of the subject 100 can be measured from the time difference.

The detection of the minute defect 102 existing on the surface layer of the object 100 is performed as follows. That is, as shown in FIG. 1, among the ultrasonic waves transmitted from the ultrasonic probe 1A, the oblique incident wave incident on the surface of the subject 100 at the Rayleigh critical angle θL through the oblique path A → B → C. Is converted into a leaky surface acoustic wave and travels along the surface of the subject 100. This leaky surface acoustic wave propagates through the surface of the subject 100 from the point of incidence C and has a Rayleigh critical angle θ.
The leaked wave leaked at L and leaked at point D on the surface of the subject 100 is received by the vibrator 2 through the route D → E → F.

Here, if a defect such as a crack exists on the surface layer of the subject 100, the propagation of the leaky surface acoustic wave on the surface layer of the subject 100 is hindered by the crack or the like. The wave level will be lower. On the other hand, when there is no defect such as a crack in the surface layer of the subject 100, the propagation of the leaky surface acoustic wave in the surface layer of the subject 100 is not hindered by the crack or the like. The level of leaked waves increases. Therefore, the presence or absence of a crack generated on the surface layer of the subject 100 can be determined from the reception level of the leaked wave in the ultrasonic probe 1A.

The leaky surface acoustic wave is said to penetrate into the subject 100 by about one wavelength from the surface of the subject 100. For this reason, if a coating such as a thermal spray coating provided on the surface of the base material is peeled off, an air layer is formed between the base material and the coating, so that leaked surface acoustic waves penetrate into the base material. However, since the attenuation is reduced, the level of the leaky wave received by the vibrator 2 increases. On the contrary,
If no peeling occurs in the coating, the leaky surface acoustic wave penetrates into the base material by about one wavelength and the attenuation increases, so that the level of the leaky wave received by the vibrator 2 decreases. Therefore, it is possible to determine the presence or absence of peeling that has occurred in the coating from the reception level of the leaky wave in the ultrasonic probe 1A.

As described above, according to the present invention, it is possible to detect a defect occurring on a surface layer of a subject with high accuracy regardless of the shape and orientation of the defect.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an example of an ultrasonic probe applied to an ultrasonic inspection method according to the present invention will be described with reference to FIG. FIG. 1 is a sectional view and a plan view of a main part of an ultrasonic probe according to the present embodiment.

As is clear from FIGS. 1 (a) and 1 (b),
The ultrasonic probe 1A of this example includes a single-type vibrator 2 having a circular planar shape, and a concave lens-type acoustic wave that converges an ultrasonic wave transmitted from the vibrator 2 and enters the object 100. A lens 3 is provided, and a through hole 4 is formed in the center of the acoustic lens 3 so as to penetrate from the plane portion 3a where the vibrator 2 is set to the lens curvature surface 3b. The vibrator 2 is configured by a piezoelectric thin film having upper and lower electrodes 2U and 2L provided on upper and lower surfaces, respectively. On the other hand, the acoustic lens 3 is made of a material having a high ultrasonic wave propagation velocity such as aluminum, and has a plane facing the transducer and a spherical surface having a lens curvature. In addition, a damper material for suppressing the generation of unnecessary vibration may be attached to the upper electrode 2U side of the ultrasonic probe 1A, and a protective plate of the vibrator 2 may be attached to the lower electrode 2L side. Sometimes attached. In addition, the diameter of the through hole 4 is determined by the path G → (H) → I because the flaw detection inside the subject 100 is performed using the normal incident wave indicated by the path I → B →
It is preferable that the angle is made as large as possible within a range that does not hinder the propagation of the oblique incident wave shown by C and the leaky wave shown by routes D → E → F.

Next, an ultrasonic inspection method using the ultrasonic probe 1A of the present configuration will be described with reference to FIGS.

First, as shown in FIG. 1A, an ultrasonic probe 1A and a subject 100 are arranged to face each other in water W, and a focal point P of an oblique incident wave transmitted from the ultrasonic probe 1A is It is set at a position lowered by ΔZ from the surface of the subject 100. ΔZ is the amount of defocus of the focused beam required to generate a leaky surface acoustic wave on the surface of the subject 100, and is most preferably set to an amount that maximizes the leaky wave received by the ultrasonic probe 1A. However, the present invention is not necessarily limited to this, and it suffices to set the amount so that the leaked wave is received by the ultrasonic probe 1A.

The defocus amount ΔZ is adjusted by transmitting an ultrasonic wave from the ultrasonic probe 1A while moving the ultrasonic probe 1A in a direction approaching the subject 100 or in a direction away from the subject 100, and The position where the focal point P of the ultrasonic beam coincides with the surface of the object 100 is determined by monitoring the level change of the surface reflected wave from the object 100, and then the ultrasonic probe 1A is moved by a desired defocus amount ΔZ to the object 100. Can be performed by approaching. That is, when the vibrator 2 is activated, as shown in FIGS. 1A and 2, a focused beam 11 focused by the acoustic lens 3 and a non-focused beam not focused by the acoustic lens 3 are output from the ultrasonic probe 1A. (Vertical wave)
12 is transmitted. Then, the focal point P of the focused beam 11
Is matched to the surface of the subject 100,
Since the surface reflected wave from the object becomes the largest, by monitoring this, the focal point P of the focused beam 11 becomes
The position corresponding to the surface of the ultrasonic probe 1 can be grasped from this position by a desired defocus amount ΔZ.
By bringing A closer to the subject 100, the defocus amount ΔZ of the ultrasonic probe 1A can be set to a predetermined value.

In the state in which the ultrasonic probe 1A and the subject 100 are opposed to each other in the water and the setting of the defocus amount ΔZ has been completed as shown in FIG.
As shown in (a), between the oblique path A → B → C and D → E → F of the transducer 2 and the subject 100, the acoustic lens 3 (aluminum made of aluminum) having a high ultrasonic wave propagation speed is provided. In this case, sound velocity = about 6400 m / s) and water having a low ultrasonic propagation velocity (sound velocity = about 1500 m / s) are present, whereas the vertical path G → (H) → I and I of the vibrator 2 are present. → (H) → Between G and the subject 100, only water having a low ultrasonic wave propagation speed is interposed, so that the route A → B → C → D → E →
The propagation time of the normal incident wave and the vertical surface reflected wave passing through the route G → (H) → I → (H) → G is longer than the propagation time of the oblique incident wave, leaky surface acoustic wave and leaky wave passing through F. Become longer,
As shown in FIG. 2B, the surface echo S1 due to the vertical wave 12 and the echo L1 of the leaky wave are separated on the time axis, and the echo L1 of the leaky wave is ahead of the surface echo S1. Is obtained.

As an example, a thickness of 0.1 m
The defocus amount ΔZ is determined by using a steel object coated with a WC-based thermal sprayed coating of m and an acoustic lens made of aluminum (sound speed = 6400 m / s) having a throat thickness of 5 mm (between GH and FIG. 1A). 0.2mm, operating frequency 10MH
z, surface acoustic wave S1 due to vertical wave with sound velocity of leaky surface acoustic wave propagating in WC-based thermal spray coating at 2300 m / s (value measured in advance using the same thermal spray coating with polished surface) and Rayleigh critical angle of 41 degrees And the time difference between the echo L1 of the leaky wave and the propagation time of the ultrasonic wave propagating along the route A → B → C → D → E → F is about 10 μs, whereas the route G → (H) → I → (H) → The propagation time of the ultrasonic wave propagating through G is about 15 μs, and the difference is 5 μs (50 times the period of the used frequency), so that both echo waveforms can be clearly separated on the time axis. I understand. In addition, in the previous example, the used frequency was set to 10 MHz, but similar results were obtained when the frequency was changed in the range of 5 to 20 MHz.

On the other hand, when an ultrasonic probe provided with the acoustic lens 3 having no through hole 4 is used, the oblique paths A → B → C and D → E → F of the vibrator 2 are covered. Sample 100
And the vertical path G → H → I and I of the vibrator 2
Since an aluminum acoustic lens 3 having a high ultrasonic wave propagation speed and water having a low ultrasonic wave propagation speed are interposed between H → G and the subject 100, the path A → B → C → D → E →
The propagation time of the oblique incident wave, the leaky surface acoustic wave and the leaky wave passing through F and the propagation time of the normal incident wave and the vertical surface reflected wave passing through the route G → H → I → H → G become almost the same, The echo of the leaked wave is buried in the surface echo due to the vertical wave, so that the two echo waveforms cannot be separated, and the echo level of the leaked wave cannot be obtained.

That is, under the same conditions as when the ultrasonic probe 1A having the acoustic lens 3 having the through hole 4 is used,
When the difference between the propagation times of both echo waveforms is obtained, the route G → H →
The propagation time of the vertical surface reflected wave propagating in I → H → G is 1
While the time is 0.05 μs, the route A → B → C → D →
The propagation time of the oblique incident wave, leaky surface acoustic wave and leaky wave propagating in the E → F path is 10.1 μs, and the difference is 50
ns, which is only half the period of the used frequency (100 ns), so that even if the echo L1 of the leaky wave is received,
The echo L1 of the leaky wave is buried in the surface echo S1 due to the vertical wave, and the echo level of the leaky wave cannot be obtained.

Therefore, when the ultrasonic probe 1A of FIG. 1 is used, the inspection of the surface layer of the subject 100 based on the received signal of the leaked wave and the inside of the subject 100 based on the received signal of the vertical reflected wave are performed. And the thickness measurement of the subject 100 based on the received signal of the vertically reflected wave.

First, a description will be given of a method of inspecting the surface layer of the subject 100 based on the received signal of the leaked wave. As described above, among the ultrasonic waves transmitted from the ultrasonic probe 1A, the oblique path A → The oblique incident wave incident on the surface of the subject 100 at a Rayleigh critical angle θL through B → C is converted into a leaky surface acoustic wave, and travels along the surface of the subject 100. The leaked surface acoustic wave is transmitted from the incident point C to the subject 10
Leakage at the Rayleigh critical angle θL while propagating on the surface of 0,
The leaked wave leaked at the point D on the surface of the subject 100 has a path D →
It is received by the transducer 2 through E → F.

Here, if a defect such as a crack exists on the surface layer of the subject 100, the propagation of the leaky surface acoustic wave on the surface layer of the subject 100 is hindered by the crack or the like. The wave level will be lower. On the other hand, when there is no defect such as a crack in the surface layer of the subject 100, the propagation of the leaky surface acoustic wave in the surface layer of the subject 100 is not hindered by the crack or the like. The level of leaked waves increases. Therefore, the presence or absence of a crack generated on the surface layer of the subject 100 can be determined from the reception level of the leaked wave in the ultrasonic probe 1A.

FIG. 3 shows a first example of a C scope image obtained by scanning the subject using the ultrasonic probe 1A and visualizing the level of the obtained leaky wave. As a test object, a WC-based cermet material was
A sprayed coating having a thickness of 2 mm was formed, and a film subjected to a bending stress after the formation of the coating was used. As is clear from FIG. 3, a vertical stripe image in which the echo level of the leaked wave is clearly lower than that of the surrounding normal part appears at the center of the image. FIG. 4 shows a part of the result of enlarged observation of this part by a scanning electron microscope (SEM). From this observation result, it was found that the crack was a vertical crack having a width of 2 to 5 μm, and it was confirmed that a minute defect in a direction difficult to be detected by the conventional method could be detected.

The leaky surface acoustic wave is said to penetrate into the subject 100 from the surface of the subject 100 by about one wavelength. For this reason, if a coating such as a thermal spray coating provided on the surface of the base material is peeled off, an air layer is formed between the base material and the coating, so that leaked surface acoustic waves penetrate into the base material. However, since the attenuation is reduced, the level of the leaky wave received by the vibrator 2 increases. On the contrary,
If no peeling occurs in the coating, the leaky surface acoustic wave penetrates into the base material by about one wavelength and the attenuation increases, so that the level of the leaky wave received by the vibrator 2 decreases. Therefore, the presence / absence of peeling generated in the coating can be determined from the reception level of the leaky wave in the ultrasonic probe 1A.

FIG. 5 shows a second example of a C-scope image in which the level of a leaky wave is visualized. As a test object, a spray coating made of a WC-based cermet material is applied to the surface of a steel material as a base material without performing blast processing as a pre-treatment that should be naturally performed on a base material before forming a sprayed coating on a steel material as a base material. Is 0.1
What was formed in the thickness of mm was used. As is clear from FIG. 5, the echo level of the leaky wave in the central portion of the base material not subjected to the blast treatment is clearly higher than that in the surrounding normal portion, and the ultrasonic inspection method according to the present invention It can be seen that the peeling or insufficient adhesion of the thermal spray coating can be clearly imaged.

As described above, according to the ultrasonic inspection method of the present invention, by detecting the level of the leaky wave, regardless of the type and shape of the defect and the orientation with respect to the surface of the specimen,
Since the presence / absence, shape, size, and the like of the defect can be specified, the soundness of the surface layer of the subject can be widely determined.

Next, a method for detecting a flaw in a subject using a vertical wave will be described with reference to FIG. As described above, when the ultrasonic inspection of the subject is performed using the ultrasonic probe 1A including the acoustic lens 3 having the through hole 4 formed in the center, the ultrasonic probe 1A A focused beam 11 that excites the leaky surface acoustic wave and a vertical wave 12 that is vertically incident on the subject 100 are transmitted, and FIG.
As shown in FIG. 7, since the echo L1 of the leaky wave and the surface echo S1 due to the vertical wave 12 can be clearly separated on the time axis, the vertical wave 1 transmitted from the ultrasonic probe 1A can be separated.
By using the method 2, flaw detection inside the subject can be performed in the same manner as the conventional vertical flaw detection method shown in FIG. That is, when the internal defect 101 exists,
The defect echo F1 generated by the reflection of the vertical wave 12 that has entered the inside of the inside of the internal defect 101 appears between the surface echo S1 and the bottom surface echo B1. The presence or absence of a defect inside the sample 100 and the size and type of the defect can be detected.

As described above, according to the ultrasonic inspection apparatus of the present invention, not only can the soundness of the surface layer of the subject be determined based on the echo L1 of the leaky wave, but also the defect echo F1 due to the vertical wave 12 can be determined. The flaw detection inside the subject can be performed at the same time.

When imaging the presence / absence of a defect, it is necessary to provide a gate in the time region where the target echo appears. As a method of setting the gate, as shown in FIG. 2C, the gate G1 is set in a time region where the echo L1 of the leaky wave appears.
Is provided to extract the maximum echo height of the echo L1 of the leaky wave, and a gate G2 is provided in a time region where the defect echo F1 appears, specifically, in a range after the surface echo S1 and before the bottom echo B1. 2D, a method of extracting the maximum echo height of the leaked wave echo L1 by providing a gate G1 in the time region where the leaked wave echo L1 appears, as shown in FIG. A gate G3 is provided in the time region where the bottom echo B1 appears, and the bottom echo B
There is a method of extracting the maximum echo height of 1. FIG.
In the method (d), when the internal defect 101 exists,
The presence or absence of the internal defect 101 is detected by utilizing the fact that the level of the bottom surface echo B1 becomes lower because the ultrasonic energy reaching the bottom surface of the subject 100 decreases. Also,
Even when there is a defect in the bottom surface portion, the level of the bottom surface echo B1 becomes low. Therefore, by monitoring the bottom surface echo level, it is possible to know whether or not there is a defect in the inside and the bottom portion.

The configuration of the gate circuit is as follows.
And two gate circuits that form gates corresponding to the gates G2 (or G3) may be provided, or the gates G1 and G2 (or G3) may be alternately formed temporally by one gate circuit. .

Further, according to the ultrasonic inspection method of the present invention, the thickness of the object can be measured by using the vertical wave. Specifically, assuming that the time difference between the surface echo S1 and the bottom surface echo B1 is t, the thickness of the subject is L, and the sound speed of the ultrasonic wave propagating in the subject is V, the thickness L of the subject is Since it can be expressed by L = V · t / 2, the time difference t between the surface echo S1 and the bottom surface echo B1 is obtained by the ultrasonic probe, and the above calculation is performed to calculate the thickness L of the subject. be able to.

As described above, according to the present invention, the flaw detection of the surface layer of the subject based on the echo L1 of the leaky wave and the inside and bottom of the subject based on the defect echo F1 or the bottom echo B1 are performed. Defect flaw detection and thickness measurement of the subject based on the time difference between the surface echo S1 and the bottom surface echo B1 can be performed. In actual implementation, it is not always necessary to perform all of these defect inspections and thickness measurement at the same time.Depending on the purpose of ultrasonic inspection, defect inspection in the surface area of the subject and defects in the inside and bottom of the subject are performed. It is possible to perform only the flaw detection, or it is also possible to perform only the flaw detection of the surface area of the object and the thickness measurement of the object. If not only defect inspection of the specimen but also defect inspection of the specimen and measurement of the thickness of the specimen can be performed at the same time, the surface deterioration state of members with severe usage conditions, such as pipes used in chemical plants, etc. And the thinned state can be inspected at the same time, so that highly reliable inspection can be performed with high efficiency.

In the above embodiment, the ultrasonic probe 1A provided with the acoustic lens 3 having the through hole 4 in the center is used. However, the ultrasonic probe has a perpendicular incident wave to the subject. And the propagation path of the oblique incident wave and the propagation path of the vertical reflected wave and the leaked wave from the subject, and the propagation speed of the ultrasonic wave in the propagation path of the perpendicular incident wave and the vertically reflected wave is the oblique incident wave and the leaked wave. It suffices to have an acoustic lens that is slower than the propagation speed of the ultrasonic wave in the wave propagation path, and the gist of the present invention is not limited to the ultrasonic probe 1A having the above configuration. Hereinafter, other ultrasonic probes applicable to the ultrasonic inspection method of the present invention will be listed.

(1) The ultrasonic probe 1B shown in FIG.
Instead of the configuration in which the through hole 4 is formed in the center of the acoustic lens 3 (propagation path of the vertical incident wave and the vertical surface reflected wave), a depression 5 is formed in the center of the lens curvature surface 3b of the acoustic lens 3. Features.

When the ultrasonic probe 1B is used, similarly to the case of using the ultrasonic probe 1A shown in FIG.
Since the propagation time of the ultrasonic wave propagating through the route G → I → G can be relatively delayed from the propagation time of the ultrasonic wave passing through the route A → B → C → D → E → F, the surface echo due to the vertical wave And leakage wave echoes can be separated. In addition, FIG.
Since the transducer setting surface 3a of the acoustic lens 3 is closed, the ultrasonic probe 1B has an effect that the transducer 2 can be set easily and reliably.

(2) The ultrasonic probe 1C shown in FIG.
Instead of the configuration in which the hollow 5 is simply formed in the central portion of the acoustic lens 3 and the hollow 5 is formed, the material that forms the acoustic lens 3 in the opened through-hole 4 or the formed hollow 5 is superfluous. It is characterized by being filled with a filling material 6 made of a material having a low sound wave propagation speed.

FIG. 7A shows the case where the filler 6 is filled in the through hole 4 formed in the center of the acoustic lens 3.
FIG. 7C shows a case where the filler 6 is filled in the recess 5 formed in the flat portion (vibrator setting surface) 3 a of the acoustic lens 3.
Indicates a case where the filler 6 is filled in the recess 5 formed on the lens curvature surface 3b of the acoustic lens 3.

The material constituting the acoustic lens 3 and the filler 6 are preferably as large as the difference in the propagation speed of the ultrasonic wave. When the acoustic lens 3 is made of aluminum (sound speed = 6400 m / s), As the object 6, a resin material such as an acrylic resin (sound speed = 2000 to 2500 m / s) is suitably used. When a resin is used as the filler 6, the acoustic lens 3 can be manufactured by potting the resin as the filler into the opened through-hole 4 or the formed recess 5. When a solid is used as the filler 6, the required acoustic lens 3 can also be manufactured by press-fitting the solid as the filler into the opened through-hole 4 or the formed recess 5. .

The ultrasonic probe of this embodiment has a propagation path G → I of a vertical incident wave and a vertical surface reflected wave in the acoustic lens 3.
And I → G and propagation path A → B → of oblique incident wave and leaky wave
Since C and D → E → F are made of materials having different sound velocities, the difference between the propagation times of the ultrasonic waves passing through the respective paths becomes large, and it becomes possible to separate the surface echo from the vertical wave and the echo of the leaky wave. At the same time, since the vibrator setting surface of the acoustic lens 3 is closed, the setting of the vibrator 2 can be performed easily and reliably.

[0043]

As described above, according to the present invention,
Flaw detection of the surface area of the subject based on the echo of the leaky wave,
Since the defect inspection of the inside of the object and the bottom surface based on the defect echo or the bottom surface echo can be simultaneously performed, the inspection accuracy and the inspection accuracy of the object can be compared with the conventional method in which each of these defect inspections can be performed only separately. Inspection efficiency can be significantly improved. Further, according to the present invention, the defect detection of the object and the thickness measurement of the object can be simultaneously performed, so that the inspection accuracy and the inspection efficiency of the object can be reduced as compared with the conventional method which can only execute these separately. It can be significantly improved. Furthermore, according to the present invention, since the defect detection of the surface area of the subject based on the echo of the leaky wave is performed, regardless of the type and size of the defect existing in the surface area of the subject and the orientation with respect to the surface of the subject, etc. Defects can be detected with high accuracy, and highly reliable defect detection can be performed.

[Brief description of the drawings]

FIG. 1 is a sectional view and a plan view of a main part of an ultrasonic probe applied to an ultrasonic flaw detection method according to an embodiment.

FIG. 2 is an explanatory diagram of an ultrasonic flaw detection method according to the embodiment.

FIG. 3 is a diagram illustrating an example of C-scope image data of a leaky wave obtained by the ultrasonic flaw detection method according to the embodiment.

FIG. 4 is a surface photograph of a subject in which a defect is found from the data of FIG. 3 by a scanning electron microscope.

FIG. 5 is a diagram showing another example of C-scope image data of a leaky wave obtained by the ultrasonic flaw detection method according to the embodiment.

FIG. 6 is a fragmentary sectional view showing another example of the ultrasonic probe applied to the ultrasonic inspection method according to the embodiment.

FIG. 7 is a cross-sectional view of a main part showing still another example of the ultrasonic probe applied to the ultrasonic inspection method according to the embodiment.

FIG. 8 is an explanatory view showing a first example of a conventionally known ultrasonic flaw detection method.

FIG. 9 is an explanatory view showing a second example of a conventionally known ultrasonic flaw detection method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1A, 1B, 1C Ultrasonic probe 2 Transducer 3 Acoustic lens 3a Flat part (transducer setting surface) 3b Lens curvature surface 4 Through hole 5 Depression 6 Filling material 100 Subject 101 Internal defect 102 Surface defect

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G047 AA06 BB01 BB02 BC00 BC02 BC08 BC09 BC18 DA03 DB03 DB14 EA10 FA01 GB11 GB25 GG01 GG30

Claims (7)

[Claims] 1. An ultrasonic probe comprising a vibrator and an acoustic lens, wherein the acoustic lens has a propagation path of a normal incident wave and an oblique incident wave to a subject, and a vertical reflected wave from the subject. And the propagation speed of the ultrasonic wave in the propagation path of the vertically incident wave and the vertically reflected wave is lower than the propagation speed of the ultrasonic wave in the propagation path of the obliquely incident wave and the leaky wave. Using the ultrasonic probe formed as described above, the soundness of the surface layer of the subject is evaluated based on the received signal of the leaky wave, and the subject is evaluated based on the received signal of the vertical reflected wave from the subject. An ultrasonic inspection method characterized by evaluating the soundness of parts other than the surface layer. 2. The ultrasonic inspection method according to claim 1, wherein a vertical reflected wave other than a vertical surface reflected wave reflected on the surface of the subject is selectively detected from the vertical reflected waves, An ultrasonic inspection method, wherein a defect inspection is performed on a part other than the surface layer of the object. 3. The ultrasonic inspection method according to claim 2, wherein a vertically reflected wave reflected by a defect existing inside the subject is selectively detected, and a signal based on a received signal of the vertical reflected wave is detected. An ultrasonic inspection method, wherein a defect inspection is performed on a portion other than the surface layer of the subject. 4. The ultrasonic inspection method according to claim 2, wherein a vertical bottom surface reflected wave reflected by the bottom surface of the subject is selectively detected, and based on a received signal of the vertical bottom surface reflected wave, An ultrasonic inspection method, wherein a defect inspection is performed on a part other than the surface layer of the object. 5. The ultrasonic inspection method according to claim 1, wherein a reception timing of the vertical surface reflected wave reflected on the surface of the subject and a vertical bottom surface reflected wave reflected on the bottom surface of the subject. Measuring the thickness of the subject from the time difference of the ultrasonic inspection. 6. The ultrasonic inspection method according to claim 1, wherein, as the acoustic lens, a propagation path of the vertical incident wave and the vertical surface reflected wave from a setting surface of the vibrator to a lens curvature surface opposed thereto. An ultrasonic inspection method, characterized in that a through-hole is formed or a depression is formed in the propagation path of the normal incident wave and the vertical surface reflected wave of the lens curvature surface. 7. The ultrasonic inspection method according to claim 1, wherein, as the acoustic lens, a propagation path of the vertical incident wave and the vertical surface reflected wave from a setting surface of the vibrator to a lens curvature surface opposed thereto. A through-hole is opened or a depression is formed in the propagation path of the normal incident wave and the vertical surface reflected wave on the setting surface of the vibrator or the lens curvature surface, and the oblique incidence is formed in the through-hole or the depression. An ultrasonic inspection method characterized by using a material filled with a filling material made of a material having a different propagation speed of an ultrasonic wave from a material constituting a propagation path of a wave and a leaky wave.