JPS63186143A - Ultrasonic wave probe - Google Patents

Abstract

PURPOSE:To permit detection of the microdefect near the surface of a test specimen by disposing a 1st and 2nd oscillating bodies which transmit and receive longitudinal ultrasonic waves at the refractive angle near the critical angle to and from the inside of the test specimen in cascade in the same ultrasonic beam direction via an acoustic shielding plate. CONSTITUTION:Square plate oscillators 3-1 and 3-2 are fixed to the slopes on wedges 4-1, 4-2 respectively made of an acrylic resin in such a manner that the incident angle thetai of the ultrasonic beam in a perpendicular direction attains a prescribed refractive angle thetaO. The 1st oscillating body 1 and the 2nd oscillating body 2 are disposed in cascade to maintain a spacing (d) from each other via the acoustic shielding plate 5 so that the 1st and 2nd ultrasonic beams 7-1, 7-2 direct the same direction. The oscillating bodies 1, 2 has the divided structure in which said bodies are dispose in cascade separately for transmission and reception in the radiation direction of the ultrasonic waves. Since the blind zone of the oscillating body is small, the detection of the defect 8 at a short distance is facilitated even in the defect detection in the short propagation time of the ultrasonic wave in the test specimen 6 by intermittent oscillation of the oscillating body 1. The detection of the defect 8 at short distance ear the surface of the test specimen 6 with high revolving power is thus permitted.

Description

[Detailed Description of the Invention] Application field of RFB industry) This invention relates to a split-bevel type ultrasonic probe that transmits and receives ultrasonic waves, in particular, detects defects near the surface of an object using longitudinal waves. The present invention relates to an ultrasonic probe for detection.

[Conventional technology]

For example, FIG. 7 is a top view of a conventional ultrasonic probe, and FIG. 8 is a side view of FIG.
A vibrating body, or a second m moving body, 3-1.3-2 is a vibrator that performs electro-acoustic conversion and acoustic-electric conversion, 4-1.4-
2 is a wedge made of synthetic resin material that fixes the vibrator 3-1 and 3-2 to the inclined surface; 5 is an acoustic shielding plate that suppresses acoustic coupling between the vibrator 3-1 and the vibrator 3-2; and 6 is the object to be inspected, 8 is a defect existing in the object to be inspected 6, θ1 is the incident angle, θ. is the angle of refraction,
δ is the opening angle of the ultrasonic beam on the first vibrating body and the second vibrating body.

The conventional ultrasonic probe is constructed as described above, and the first vibrating body and the second vibrating body λ are arranged symmetrically on the left and right with the acoustic shielding plate 5 as the center with respect to the direction of transmitting and receiving ultrasonic waves. Further, the wedges 4-1 to which the vibrators 3-1 and 3-2 are fixed each have an incident angle of 01 to the subject 6. Furthermore, the vibrator 3-1.
3-2 is symmetrically inclined in the left and right directions with respect to the acoustic shielding plate 5, and has an opening angle δ in the ultrasonic transmission and reception direction so that both ultrasonic beams intersect at a predetermined position.

When detecting defects 8 near the surface of a flat steel object 6, the angle of refraction θ is determined by the angle of incidence θ1.

When , the longitudinal waves in the steel propagate near its surface.

The vibrator 3-1 on the first vibrator is excited, and the reflected wave from the defect 8 in the steel is received using the vibrator 3-2 on the second vibrator. When the intersection of the ultrasonic beams transmitted on the first vibrating body and received on the second vibrating body coincides with the position of the defect 8, the vibrator 3-2 reaches the maximum reception level.

When the ultrasonic beam crosses the position closer to the ultrasonic probe, the opening angle δ becomes larger, and when the ultrasonic beam propagates inside the object 6 and is reflected at the defect 8, it is directly facing the defect 8. When transmitting and receiving ultrasonic waves from any direction, at oblique incidence, some of the longitudinal waves are converted to transverse waves, so some of the reflected waves are converted to transverse waves, so some of the reflected waves are received. This results in a decrease in reflectance, and as the opening angle δ increases, the decrease in reflectance becomes more significant.

Figure 5 shows an example of seamless pipe defect detection.
0 is a seamless pipe made of stainless steel material, 11 is a beam path length of longitudinal ultrasonic waves, and 12 is a beam path length of transverse wave ultrasonic waves. Defects 8 near the surface of a thick seamless pipe 10 or the like are detected. When using a transverse wave from an ultrasound probe, the refraction angle θ. is small, so the beam path length is 1
2 is propagated to the defect 8 by %ffi reflection between the inner and outer surfaces of the seamless pipe 10, and is reflected and received by the ultrasonic probe again through the same beam path 12, so the propagation distance increases and the ultrasonic wave is attenuated. becomes significant.

Figure 6 shows an example of defect detection in a welded structure;
3 is a metal material, 14 is a welded part, and the beam path 12 of the ultrasonic beam when using transverse waves to detect a defect 8 occurring at a shallow position directly below the welded part 14 is the metal material 13.
The reflected wave is reflected by the lower surface of the beam and propagated to the defect 8, and the reflected wave passes through the same beam path 12 again and is received by the ultrasonic probe.

(Problems to be Solved by the Invention) In the conventional ultrasonic probe as described above, the transducer 3-1.
3-2 is arranged symmetrically with respect to the ultrasound transmission and reception direction with the acoustic shielding plate 5 as the center, so using longitudinal waves,
In order to increase the detection sensitivity when detecting a defect 8 located at a short distance within the object 6, the intersection position between the transmitting beam and the receiving beam on the first vibrating body and the second vibrating body coincides with the position of the defect 8. Ultrasonic probes cannot be used to cover a wide range of defect locations. Also, the opening angle δ is small for the defect 8 located at a long distance, but the opening angle δ becomes large for the defect 8 located at a short distance.
A part of the reflected waves are converted into transverse waves and the reflectance decreases, resulting in a decrease in the detection sensitivity of the defect 8 by the ultrasonic probe.

When using transverse waves, the refraction angle θ. Since the beam path 12 is small, when detecting a defect 8 near the surface of a seamless pipe 10 with a large wall thickness or a crack generated at the bottom of a welded part 14 in a welded structure, the beam path 12 is determined by multiple reflections inside the object 6. As the beam propagates, the beam path length 12 increases and the attenuation becomes significant, making it difficult to detect minute defects 8 and the like.

The present invention was made to solve this problem, and an object of the present invention is to obtain an ultrasonic probe having sufficient detection sensitivity for minute defects 8 near the surface of a subject at short distances.

[Means for Solving the Problems] The ultrasound probe according to the present invention includes a wedge made of a synthetic resin material and shaped so that the refraction angle of the longitudinal ultrasound beam in the subject's body forms an angle close to the critical angle. a first vibrator and a second vibrator, which are arranged in tandem in the direction of the ultrasonic beam through an acoustic shielding plate, and the directions of the ultrasonic beams from the vibrator coincide with each other; It is made up of the body.

[Function] In the present invention, the incident angle of the transducer for transmitting and receiving ultrasonic waves by the ultrasonic probe is selected so that the refraction angle of longitudinal waves in the subject is close to the critical angle, and the first vibration By interposing acoustic shielding plates between the body and the second vibrating body and arranging them in tandem so that the transmission and reception are directed in the same direction, the refraction angle of longitudinal waves within the subject becomes close to the critical angle, and the ultrasonic waves are directed toward the subject. Since defects are detected by propagating near the surface, the directivity of the transmitting and receiving beam patterns is the same for defects at a short distance, and the direct reflected wave from the defect is received, so the beam path is short and the transmission and reception Since the vibrating body is divided, the dead zone in defect position measurement becomes small, and even small defects can be detected with sufficient detection sensitivity and high resolution.

〔Example〕

FIG. 1 is a top view of an ultrasonic probe showing an embodiment of the present invention, and FIG. 2 is a side view of FIG. 1.
6.8 is the same as a conventional ultrasonic probe, 7-1 is a first ultrasonic beam generated by a first vibrating body, and 7-2 is a second ultrasonic beam generated by a second vibrating body.

The rectangular plate vibrators 3-1 and 3-2 are each made of an acrylic resin wedge 471, and the angle of incidence θ5 with respect to the direction perpendicular to the slope on the 4-2 is a predetermined refraction angle θ within the subject 6. The top of the first vibrating body and the top of the second vibrating body are fixed to each other so as to form the first and second ultrasonic beams through the acoustic shielding plate 5. -1,
7-2 are oriented in the same direction and arranged in tandem with a distance d between them. Therefore, the vibration 3-1 and the vibrator 3-2
Although the radiation position is different from the distance lid, the first and second ultrasonic beams 7-1, 7-2 exhibit the same characteristics with respect to the subject 6 and are used for transmitting and receiving ultrasonic waves, respectively.

FIG. 3 is a top view showing another embodiment in which an acoustic shielding plate is installed, and FIG. 4 is a side view of FIG. 3.

The configuration is the same as that of the above embodiment, and an acoustic shielding plate 5 is provided between the first vibrating body 1 and the second vibrating body to reduce the interference of the signal to the receiving vibrating body when ultrasonic waves are emitted. is the incident angle θ of the ultrasonic waves from the first and second vibrating bodies and from
When the angle of inclination is equal to 1, the distance d between the first and second vibrating bodies and S becomes smaller, and the distance between the transmitting position and the receiving position of the vibrators 3-1 and 3-2 is shortened. Therefore, loss in the ultrasonic propagation path is reduced, sensitivity can be improved, and the size of the ultrasonic probe can be reduced.

FIG. 5 shows an example of defect detection in the Seam System Vibrator. A seamless pipe 10 made of stainless steel is the object 6. An ultrasonic probe is brought into contact with the seamless pipe 10 through a couplant such as oil, and a wedge 4- When the vibrator 3-1, which is fixed to the stainless steel vibrator 10 and has an incident angle θ1, is intermittently excited, a refraction angle θ is generated within the stainless steel vibrator 10. Longitudinal ultrasound waves are emitted in the direction of.

Refraction angle θ. The first ultrasonic beam 7-1 propagates near the surface of the seamless pipe 10 when the incident angle θ1 is selected so that it is close to a critical angle of 75° or more.

The reflected wave from the defect 8 near the surface is multiplexed in the seamless pipe 10 by the transducer 3-2 of the second ultrasonic beam 7-2, which is arranged in tandem with the transducer 3-1 and whose beam direction directions coincide with each other. Since the direct propagation is received without receiving the reflected wave on the reflection propagation path, the beam path length 11 is shorter than the beam path length 12, and there is less signal attenuation, and the best beam gain characteristics are always used, so the signal It has an excellent noise-to-noise ratio and allows efficient reception.

The acoustic shielding plate 5 protects the oscillator 3- from the transmitted wave from the oscillator 3-1.
acts to reduce direct binding to 2.

The first vibration body and the second moving body have a divided structure in which transmitting and receiving bodies are arranged in tandem in the ultrasonic radiation direction, so that the first vibration body can be intermittently excited. Subject 6
Even in defect detection where the propagation time of ultrasonic waves is short, the second
Since the dead zone of the vibrating body is small, it is easy to detect defects 8 at short distances, and therefore defects 8 at short distances near the surface of the object 6 can be detected easily.

At the above incident angle θ1, a transverse wave is also generated within the object 6 at the same time, but the transverse wave has a refraction angle θ. Since the reflection wave is small, multiple reflection propagation in the direct downward direction is performed, and since the propagation speed is about 1/2 that of the longitudinal wave and the arrival times of the reflected waves are significantly different, it is easy to separate the two signals.

In detecting a defect in the welded structure shown in FIG. 4, the longitudinal wave generated directly below the weld 14 propagates directly, so the beam path 11 is shorter than the beam path 12 of the transverse wave and the propagation speed is different, so it is reflected. Wave identification is easy.

In the above embodiment, transmission is performed from the first vibrating body and reception is performed by the second vibrating body, but the same operation can be performed even when transmitting from the second vibrating body and receiving by the first vibrating body. I can do it.

Furthermore, even if the position of defect 8 moves and the distance from the ultrasound probe changes, there is no need to change the opening angle δ of transducers 3-1 and 3-2, and there is no need to tilt for the opening angle δ. Therefore, the structure of wedge 4-1 and 4-2 becomes very simple.

According to the present invention, a defect 8 located near the surface at a short distance in a subject 6 with large attenuation can be detected by using a longitudinal wave of oblique incidence using a divided oblique angle probe consisting of each vibrating body for transmitting and receiving. can be used for detection with good sensitivity and resolution.

[Effects of the Invention] As explained above, the present invention allows the first and second vibrating bodies, which transmit and receive longitudinal ultrasound into the subject at a refraction angle near the critical angle, to transmit and receive the same ultrasound through an acoustic shielding plate. An ultrasonic probe that uses longitudinal waves for detecting defects near the surface of a subject with a simple structure that is arranged in tandem in the direction of the acoustic beam and transmits and receives ultrasonic waves through intermittent excitation. Since the ultrasonic beams for transmission and reception are always oriented in the same direction, in order to improve detection sensitivity, the intersection position of the ultrasonic beams of the first and second vibrating bodies must match the defect position. Therefore, there is no need to adjust the aperture angle δ when fixing the vibrator to the wedge, and as the aperture angle increases, a portion of the reflected waves from the defects are converted into transverse waves, so the reflectance of longitudinal waves decreases. Since there is no ultrasonic beam, defects can always be detected using the maximum gain ultrasonic beam, and longitudinal waves near the critical angle are used, and the beam path does not undergo multiple reflections but direct propagation inside the object, so the propagation distance is short. Since it is short and has low attenuation, the signal-to-noise ratio in detecting minute defects can be increased, and since the transmission and reception are divided using the first and second vibrating bodies, the dead zone in defect position measurement is extremely small, improving resolution. Defects in the welded structure can be easily detected, and furthermore, by tilting the acoustic shielding plate, the size of the ultrasonic probe can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a top view showing one embodiment of the invention, FIG. 2 is a side view of the embodiment shown in FIG. 1, FIG. 3 is a top view showing another embodiment of the invention, and FIG. 5 is an example of defect detection in a seamless pipe, FIG. 6 is an example of defect detection in a welded structure, FIG. 7 is a top view of a conventional ultrasonic probe, and FIG. 8 is an example of defect detection in a welded structure. FIG. 7 is a side view of FIG. 7; In the figure, soil is the first imaging body or the second vibrating body, 3-1
．． 3-2 is a transducer, 4-1, 4-2 is a wedge, 5 is an acoustic shielding plate, 6 is a subject, 7-1 is a first ultrasonic beam, 7-2 is a second ultrasonic beam, 8 is a Defect, θ1 is the angle of incidence, θ. is the refraction angle, and d is the distance between the first and second vibrating bodies. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Patent Attorney Tadashi Sato Figure 4 Figure 5 Figure 6 8'13 April 20, 1988

Claims (2)

[Claims] (1) In an oblique-incidence ultrasonic probe in which a first vibrating body and a second vibrating body that transmit and receive ultrasonic waves are arranged separately through an acoustic shielding plate, the longitudinal ultrasonic beam inside the subject is A vibrator fixed to a wedge made of a synthetic resin material with a refraction angle close to the critical angle and an ultrasonic beam emitted by this vibrator are aligned in direction with each other and are transmitted through the acoustic shielding plate. An ultrasonic probe comprising a first vibrating body and a second vibrating body arranged in tandem at predetermined intervals in the direction of directivity of an ultrasonic beam. (2) Claim 1, characterized in that the acoustic shielding plate is inclined at an angle equal to the incident angle of the ultrasonic waves emitted by the vibrator.
Ultrasonic probe as described in section.