JP2000180419A - Ultrasonic flaw detecting method by sh-waves and sh- wave skew angle probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flaw detecting method dispensing with a highly viscous contact medium in ultrasonic flaw detection by an SH wave probe and eliminating the necessity for pressing the probe to an object to be inspected by predetermined pressing force. SOLUTION: In a method and probe for performing ultrasonic flaw detection by bringing an SH wave skew angle probe 1 into contact with the surface of an object 5 to be inspected through a contact medium 3, a polymeric film 2 having predetermined acoustic impedance and predetermined thickness is formed on the flaw detecting surface of a skew angle forming wedge and SH waves are sent to the object 5 to be inspected by the propagation path of the wedge, the polymeric film 2, the contact medium 3 and the object 5 to be inspected and the SH waves reflected from the object 5 to be inspected are detected by the propagation path in the direction reverse to that of the above mentioned propagation path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for performing an ultrasonic flaw detection by bringing an SH wave oblique probe into contact with the surface of a subject via a couplant and an SH wave oblique probe to which this method is applied. Things.

[0002]

2. Description of the Related Art Among transverse waves, those in which the direction of the particle velocity is parallel to the incident boundary surface are referred to as SH waves (S is a shear wave in a shear wave, H is a horizontal wave in a horizontal sense). When this SH wave is used, mode conversion by reflection does not occur at any incident angle, so that reflection is the same as ordinary specular reflection,
Because of its easy processing, it has been conventionally used for ultrasonic flaw detection.

FIG. 3 is an explanatory view of an ultrasonic flaw detection method using a conventional SH wave probe. FIG. 1A is a conventional SH wave probe, and 3a is a conventional high viscosity contact for SH wave. The medium 4 is a cable, and 5 is a subject. In the conventional flaw detection using the SH wave probe, a high-viscosity couplant 3 for SH wave is used for each flaw detection location.
a is provided between the subject 5 and the flaw detection surface of the SH wave probe 1a, and the SH wave probe 1a is pressed against the subject 5 with a constant pressing force (for example, a force of about 20 kg) for a certain period of time. (For example, about 10 minutes). This is for transmitting and receiving SH waves in this pressed state. The conventional S
The viscosity of the H-wave couplant 3a was, for example, about 1400 Pascal · sec (Pa · sec), and handling was not easy due to high viscosity.

[0004]

In the conventional ultrasonic flaw detection using the SH wave probe, a highly viscous couplant is required.
Difficult to handle. In addition, since it is necessary to press the SH wave probe against the subject with a predetermined pressing force for about 10 minutes for each flaw detection location, there are problems such as poor work efficiency and the inability to perform continuous inspection by scanning. Was.

[0005]

According to a first aspect of the present invention, there is provided an ultrasonic flaw detection method using an SH wave, wherein an SH wave oblique probe is brought into contact with a surface of a subject via a couplant to perform ultrasonic flaw detection. In the method, a polymer film having a predetermined acoustic impedance and a predetermined thickness is formed on a flaw detection surface of a wedge for forming a bevel, and SH waves are applied by a propagation path of the wedge, the polymer film, the couplant and the specimen. The SH wave is transmitted to the sample, and the SH wave reflected from the subject is received by the propagation path in the direction opposite to the propagation path.

According to a second aspect of the present invention, there is provided an ultrasonic flaw detection method using an SH wave according to the first aspect of the present invention, wherein the wedge for forming the oblique angle is formed on a flaw detection surface. The acoustic impedance of the molecular film is set to a value between the acoustic impedance of the wedge and the acoustic impedance of the couplant, and the thickness of the polymer film is substantially equal to the wavelength of the SH wave and a predetermined integer ratio. It is to become.

An SH-wave oblique probe according to a third aspect of the present invention is a SH-wave oblique probe that performs ultrasonic flaw detection by bringing the surface of a test object into contact with the surface of a subject through a couplant. A polymer film having a predetermined acoustic impedance and a predetermined thickness is provided on a flaw detection surface of a wedge.

The SH wave oblique probe according to a fourth aspect of the present invention is the SH wave oblique probe according to the third aspect, wherein the height of the wedge for forming the oblique angle is formed on the flaw detection surface. The acoustic impedance of the molecular film is set to a value between the acoustic impedance of the wedge and the acoustic impedance of the couplant, and the thickness of the polymer film is substantially equal to the wavelength of the SH wave and a predetermined integer ratio. It is to become.

An SH wave oblique probe according to a fifth aspect of the present invention is a SH wave oblique probe for performing ultrasonic flaw detection by scanning a surface of a subject through a couplant, and a vibrator and an oblique angle probe. A roller shaft integrally attached so that the horn forming wedge is at a fixed position, and a cylindrical polymer film having a predetermined acoustic impedance and a predetermined thickness with the roller shaft as a central axis, The inner periphery of this cylindrical polymer film is in contact with the flaw detection surface of the bevel forming wedge via a couplant, and the outer periphery is mounted on a rotatable mechanism in contact with the subject surface via the couplant. And the above-mentioned polymer film.

The SH wave oblique probe according to claim 6 of the present invention is the SH wave oblique probe according to claim 5, wherein the cylindrical polymer film is mounted on the rotatable mechanism. The acoustic impedance of the wedge is set to a value between the acoustic impedance of the wedge and the acoustic impedance of the couplant between the subject surface and the outer periphery of the polymer film, and the thickness of the polymer film is The wavelength ratio of the SH wave is set to be substantially a predetermined integer ratio.

[0011]

Embodiment 1 FIG. 1 is a diagram showing a configuration of an SH wave probe according to Embodiment 1 of the present invention. The SH wave probe 1 shown in FIG. 1 is obtained by forming a polymer film 2 such as polyethylene on the flaw detection surface of the conventional SH wave probe 1a shown in FIG. The couplant 3 of FIG. 1 has a high viscosity (1400 Pa ·
For example, a low viscosity (viscosity of about 100 Pa · sec) such as an aqueous glycerin solution may be used.

Next, the reason why the polymer film 2 is formed on the SH wave probe 1 will be described. Now, when the SH wave is incident on the steel sheet, the acoustic impedance value of each propagation path from the acrylic resin wedge of the probe to the couplant and the steel sheet is as follows:
Acrylic resin is about 3.2 kg / m ² s, general couplant (eg, glycerin aqueous solution) is about 2.4 kg / m ² s, and steel sheet is about 45.3 kg / m ² s, Since the reflection occurs at the boundary surfaces having different impedances, the transmittance of the ultrasonic wave is not good.

Therefore, as shown in FIG. 1, the flaw detection surface of the SH wave probe 1 has an acoustic impedance intermediate between the wedge resin and a general couplant (for example, about 3.0 kg / m ² s).
Then, a polymer material having excellent adhesion to the couplant is selected, and a predetermined thickness d (for example, d is about 0.2 to 0.8 mm, and this thickness d and the wavelength of the SH wave The film is formed so as to have a substantially predetermined integer ratio.

As an example, if the polymer material is polyethylene, the propagation speed v of the SH wave in the polymer film 2 is 530 m / m
sec. Now, the frequency f of the SH wave is 5 MHz.
If the above value is substituted for the wavelength λ = v / f, the wavelength is about 0.1 mm. Therefore, if the thickness d of the polymer film 2 is 0.2 mm, 0.3 mm,... 0.8 mm, the thickness d becomes twice, three times,. When the thickness d of the polymer film 2 is set to an integral multiple of the wavelength λ of the SH wave, the phase of the incident point and the phase of the emission point when the SH wave passes through the polymer film 2 are the same. Becomes
The transmission efficiency of the SH wave is improved. As a result, the signal transmittance (reception sensitivity) in transmission and reception of ultrasonic waves is improved.

When the polymer film 2 is provided on the flaw detection surface of the SH wave probe as described above, the acoustic impedance value of each propagation path is 3.2 kg / m ² s of the wedge resin, 3.0
kg / m ² s, and 2.4 kg / m ² s of the couplant, the reflection signal at the interface between the different propagation paths is reduced, and the signal transmittance is improved. Further, since the reciprocal transmittance due to the transmission and reception of the ultrasonic wave is the square of the one-way transmittance, even if the one-way transmittance is slightly improved, the reciprocal transmittance is greatly improved. In addition, the smoothness of the surface of the polymer film such as polyethylene improves the slip of the probe, so that the scanning property is improved. The roller type SH wave probe of the second embodiment can be configured using this good scanning property.

Embodiment 2 FIG. 2 is a view showing a configuration of a roller type SH wave probe according to Embodiment 2 of the present invention, wherein 2 is a polymer film, 3 is a couplant, 5 is an object, 6 is a wedge, 7 is a vibrator, 8 is a roller shaft, 9 is a bearing, and 10 is a disk or a rib. 2A is a longitudinal sectional view passing through a center line of a roller shaft including a disk (or a rib), and FIG. 2B is a sectional view in a direction perpendicular to the center line of the roller shaft.

In FIG. 2, the wedge 6 and the vibrator 7 are integrally attached to a roller shaft 8 so as to be at a fixed position.
The polymer film 2 is formed with a predetermined acoustic impedance and a predetermined thickness in a cylindrical shape with the roller shaft 8 as a central axis, and the inner periphery of the cylindrical polymer film 2 is formed with the oblique angle. A mechanism that is in contact with the flaw detection surface of the wedge 6 via the couplant 3 and whose outer periphery is in contact with the surface of the subject 5 via the couplant 3 (in FIG. 2A, a rotatable mechanism) The cylindrical polymer film 2 can be rotated without rotating the roller shaft 8 by a pair of bearings 9 attached to the shaft and a pair of disks or ribs 10 attached to the rotating parts of these bearings 9. Is shown).

Roller type SH having this rotatable mechanism
When scanning the wave probe over the subject 5, the polymer film 2
The wedge 6, the vibrator 7, and the roller shaft 8 do not rotate while the outer periphery of the wrist rotates while being in contact with the surface of the subject 5 via the couplant 3. Therefore, the flaw detection surface of the wedge 6 has a circular cross section as shown in FIG. 2B, and the radius of this circular arc is slightly smaller than the inner radius of the polymer film 2. Then, a slight gap between the flaw detection surface of the wedge 6 and the inner periphery of the polymer film 2 is filled with the couplant 3. The provision of a couplant between the outer periphery of the polymer film 2 and the subject 5 is the same as in the first embodiment. With such a configuration, when the roller type SH wave probe is scanned on the subject 5 while rotating the polymer film 2, the subject 5 is fixed at a fixed angle from the vibrator 7 via the wedge 6. To transmit and receive SH waves.

In comparison with the case of the prior art in which the roller type probe of the second embodiment scans the surface of the object to perform measurement and flaw detection, the second embodiment shows that the measurement and flaw detection are different from those of the prior art. Since there is no need to press the probe against the subject for each location, the work efficiency of measurement and inspection is significantly improved. Also, when comparing the scanning operation by the probe of the first embodiment and the scanning operation by the roller type probe of the second embodiment, in the case of the first embodiment, the probe having the polymer film formed on the flaw detection surface is covered. The second embodiment is superior in terms of workability and stability of contact between the polymer film and the subject because it is necessary to slide on the surface of the sample. The effect of improving the transmittance of the SH wave in the polymer film by setting the thickness of the polymer film and the wavelength of the SH wave to a substantially predetermined integer ratio is the same as that of the first embodiment.

[0020]

As described above, according to the present invention, in a method and an apparatus for performing ultrasonic flaw detection by bringing an SH wave bevel probe into contact with a surface of a subject via a couplant, the wedge for forming a bevel is provided. A polymer film having a predetermined acoustic impedance and a predetermined thickness is formed on the flaw detection surface, and an SH wave is transmitted to the subject through the wedge, the polymer film, the couplant and the propagation path of the subject, and the The SH wave reflected from the probe is received by the propagation path in the direction opposite to the propagation path, so that a probe having a high viscosity couplant as in the prior art is used, and the probe is pressed at a predetermined pressure for a predetermined period of time. Eliminating the need to press against the surface has improved the workability of measurement and inspection.

According to the present invention, the acoustic impedance of the polymer film formed on the flaw detection surface of the wedge for forming an oblique angle in the SH wave oblique probe is different from the acoustic impedance of the wedge and the acoustic impedance of the couplant. And a thickness between the polymer film and the SH.
Since the wavelength ratio of the wave is set to a substantially predetermined integer ratio, the signal transmittance in the transmission and reception of ultrasonic waves is improved by reducing the reflected signal at the interface between different propagation paths and increasing the transmitted signal in the polymer film. did.

Further, according to the present invention, in the SH-wave oblique probe for performing ultrasonic flaw detection by scanning the surface of the object through the couplant, the vibrator and the oblique angle forming wedge are set at fixed positions. And a cylindrical polymer film having a predetermined acoustic impedance and a predetermined thickness centered on the roller shaft, the inner periphery of the cylindrical polymer film. Is in contact with the flaw detection surface of the bevel forming wedge via a couplant, and its outer periphery is provided with the polymer film mounted on a rotatable mechanism in contact with the subject surface via the couplant. Therefore, the contact between the polymer film and the subject is stabilized and the scanning operation is performed, as compared with the case where the probe having the polymer film formed on the flaw detection surface of the bevel forming wedge slides on the surface of the subject. The performance has also been greatly improved.

Further, according to the present invention, the acoustic impedance of the cylindrical polymer film mounted on the rotatable mechanism is the acoustic impedance between the wedge and the surface of the subject and the outer periphery of the polymer film. The thickness of the polymer film is set to be substantially a predetermined integer ratio with the wavelength of the SH wave, so that the thickness of the polymer film is set to a value between the acoustic impedance of the couplant and each boundary of the ultrasonic wave propagation path. The transmittance of the ultrasonic signal during scanning was improved due to the decrease in the reflection signal on the surface and the increase in the transmission signal in the polymer film.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an SH wave probe according to Embodiment 1 of the present invention.

FIG. 2 is a diagram illustrating a configuration of a roller type SH wave probe according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of an ultrasonic flaw detection method using a conventional SH wave probe.

[Explanation of symbols]

 1, 1a SH wave probe 2 polymer film 3, 3a couplant 4 cable 5 subject 6 wedge 7 vibrator 8 roller shaft 9 bearing 10 disk or rib

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshiaki Fujita 14% 1187, Ikutsucho, Kumoe, Tsu-shi, Mie Japan F-term in Japan Techno Mate Co., Ltd. 2G047 BB02 BC07 CB00 CB02 EA10 GB04 GB27 GB28 GE01 5D019 AA22 FF05 GG01

Claims (6)

[Claims] 1. A method for performing ultrasonic flaw detection by bringing an SH wave bevel probe into contact with a surface of a subject via a couplant, wherein the flaw detection surface of a wedge for forming a bevel has a predetermined acoustic impedance and a predetermined thickness. The SH wave is transmitted to the subject through the wedge, the polymer film, the couplant, and the propagation path of the subject, and the SH wave reflected from the subject is inverted from the propagation path. An ultrasonic flaw detection method using SH waves, wherein waves are received by a propagation path in a direction. 2. The acoustic impedance of a polymer film formed on a flaw detection surface of the wedge for forming an oblique angle is set to a value between the acoustic impedance of the wedge and the acoustic impedance of a couplant. The thickness of the polymer film is
2. The ultrasonic flaw detection method according to claim 1, wherein the wavelength of the SH wave is set to a substantially predetermined integer ratio. 3. An SH-wave oblique probe for performing ultrasonic flaw detection by bringing it into contact with a surface of a test object via a couplant, wherein the flaw detection surface of a wedge for forming a bevel has a predetermined acoustic impedance and a predetermined thickness. An SH-wave oblique probe characterized by comprising a polymer film formed on the probe. 4. The acoustic impedance of a polymer film formed on a flaw detection surface of the wedge for forming an oblique angle is set to a value between the acoustic impedance of the wedge and the acoustic impedance of a couplant. The thickness of the polymer film is
4. The SH-wave oblique contact according to claim 3, wherein the SH-wave has a substantially predetermined integer ratio with the wavelength of the SH-wave. 5. An SH-wave oblique probe for performing ultrasonic flaw detection by scanning a surface of a subject through a couplant, wherein a transducer and a wedge for forming an oblique angle are integrally attached so as to be at fixed positions. A roller shaft, and a cylindrical polymer film having a predetermined acoustic impedance and a predetermined thickness with the roller shaft as a central axis, and the inner periphery of the cylindrical polymer film is formed at the oblique angle. SH, comprising: a flaw detection surface of a wedge, which is in contact with the surface of the test object via a couplant, and an outer periphery of which is provided with the polymer film mounted on a rotatable mechanism in contact with the surface of the test object via the couplant. Wave bevel probe. 6. The acoustic impedance of the cylindrical polymer film mounted on the rotatable mechanism is the acoustic impedance of the wedge and the acoustic impedance of the couplant between the surface of the subject and the outer periphery of the polymer film. 6. The SH wave oblique angle according to claim 5, wherein the polymer film has a thickness substantially equal to a predetermined integer ratio with the SH wave wavelength. Probe.