JPH08220079A - Ultrasonic probe - Google Patents

Abstract

PURPOSE: To detect a defect signal with a high sensitivity by providing a focusing-type reception vibrator which is arranged nearly symmetrically so that a focusing part and an axis face each other with a specific gap for the focusing-type transmission vibrator where the focusing part is placed nearly on the surface of the test sample and the axis is inclined. CONSTITUTION: When ultrasonic waves are transmitted from a focusing-type transmission vibrator 5, they enter from a focusing part 7 the surface of a test sample 11 and propagate as ultrasonic waves with spread directivity 9. Namely, they uniformly disperse and propagate in the sample 11. A focusing-type reception vibrator 6 has reception characteristics with nearly the same spread directivity as that of the focusing-type transmission vibrator 5. Namely, it has a uniform reception sensitivity for the flaw-detection region of the sample 11. Surface wave is attenuated by providing a sound-absorbing material 4, thus receiving a signal from a defective part with a high S/N ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe used for ultrasonic flaw detection.

[0002]

2. Description of the Related Art There is a flaw detection method using an ultrasonic flaw detection method for inspecting a structure such as a metal. As one of them, there is a method of detecting the presence / absence of a defect and the depth of the defect based on a propagation signal of an ultrasonic wave, using opposing bevel probes.

FIG. 3 shows an example of a conventional device, which is a transmission probe 21 and a reception probe 2 which are arranged opposite to each other at a constant interval L.
The pair of two is applied to the surface of the subject 11 to detect flaws in the inspected portion. Further, FIG. 4 also shows the propagation paths of ultrasonic waves in the subject, and FIG. 4 shows an example of flaw detection signals obtained by a conventional probe.

A longitudinal wave is usually used as a propagating wave used at this time. The longitudinal wave is suitable for the longitudinal wave because it has the highest propagation velocity among the sound waves propagating through the subject and can detect the change in the propagation path in the shortest time.

In FIG. 3, when there is no defect, the transmitting probe 21
The ultrasonic wave transmitted in 2 is the sound wave 2 propagating on the surface of the subject 11.
The sound wave 24 of the path reflected by 3 and the bottom surface is received as the surface signal 31 and the bottom surface signal 32 as in the flaw detection signal example 27 of FIG. The temporal reception positions of the surface signal 31 and the bottom signal 32 are the plate thickness T of the subject, the probe interval L, and the subject 11.
Is received at a position determined by the relationship of the ultrasonic wave propagation velocity.

On the other hand, when there is a defect 12 existing in the subject, in addition to the surface signal 31 and the bottom surface signal 32, the sound wave scattered at the upper end of the defect is a signal 33 and the sound wave scattered at the lower end is a signal 34. , A flaw detection signal example 29 is received.

When there is a defect on the surface side of the subject, the surface signal is not received, and the bottom surface signal 32 and the signal 34 scattered at the lower end are received as in the flaw detection signal example 28. When there is a defect on the front surface of the back surface of the object, the bottom surface signal is not received, and the surface signal 31 and the signal 33 scattered at the upper end of the defect are received as in the flaw detection signal example 30.

Since the defect signal is scattered and propagated at the end of the defect, it propagates along a path longer than the sound wave propagating on the surface of the object and shorter than the bottom signal.
Depending on the depth of the defect, it is received between the surface signal and the bottom signal.

In order to know the size of the defect, an ultrasonic flaw detector connected separately reads the delay of the propagation time to the defect signal such as the upper and lower ends with reference to the position of the surface signal. Then, it is calculated based on the probe interval L and the ultrasonic wave propagation velocity of the subject 11.

[0010]

The conventional probe described above has the following problems. (1) The ultrasonic beam emitted by the probe has directivity 35 as shown in FIG. 5, and the distribution of sound waves in the plate thickness direction is different, so that the defect signal level differs depending on the defect position. That is, if the refraction angle is set so that the sound wave reaches the vicinity of the bottom surface, a large signal level can be expected for a defect on the central axis of the beam, but in other parts, the intensity of the sound wave is small and the defect signal level is small. As the size becomes smaller, the defect detection capability also decreases. (2) If the flaw detection is performed with a large amplification degree in order to supplement the region having a low defect signal level and improve the detectability, the surface wave signal 36 shown in the figure is detected, which becomes an obstacle to the flaw detection.

The surface wave is slightly amplified by the transmission probe when the ultrasonic wave is incident on the subject, and the surface wave signal other than the longitudinal wave is also amplified. Therefore, the surface wave signal is also amplified. The speed of sound of surface waves is slower than the speed of sound of longitudinal waves.
Depending on the arrangement of the probe, the propagation signal of the surface wave is received between the surface signal and the bottom surface signal even if there is no defect, which is an obstacle to flaw detection. Especially when detecting the height of the defect on the bottom side, it cannot be identified because it overlaps with the defect signal.
It becomes an obstacle to flaw detection. In addition, when flaw detection is performed from the inner surface of the pipe material, it is inevitable that the transmission probe and the reception probe are inevitably brought close to each other, which causes an obstacle. (3) A method of dividing the plate thickness direction into several regions and using a plurality of probes each having a dedicated refraction angle is conceivable.
The use of a large refraction angle to improve the defect signal level near the surface results in the detection of a larger surface wave signal, which is a greater obstacle. Also, the use of multiple probes requires a lot of time for work.

[0012]

The present invention employs the following means to solve the above-mentioned problems.

That is, as an ultrasonic probe, a focusing type oscillator having a focusing part placed on almost the surface of a subject and having its axis inclined, and a focusing part with a predetermined distance from the focusing oscillator. Further, there are provided a focusing type reception vibrator arranged substantially symmetrically so that the axes thereof face each other, and an adsorbent arranged on the subject between the vibrators.

[0014]

In the above invention, when an ultrasonic wave is transmitted from the focusing oscillator, it is incident from the focusing portion on the surface of the subject, is refracted in the direction of the focusing receiver oscillator, and has a wide directivity. And propagate. That is, it is uniformly dispersed and propagated in the subject. Further, the surface waves generated at the same time are attenuated by the sound absorbing material. The focused reception oscillator has a reception characteristic in which the directivity is substantially the same as that of the focused transmission oscillator, that is, the reception sensitivity is uniform with respect to the flaw detection area of the subject. On the other hand, the surface wave is greatly attenuated by the sound absorbing material. Therefore, the signal from the defective portion can be received with high S / N.

In this way, a highly sensitive and highly accurate probe can be obtained.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, the focusing oscillator 5 has a focusing portion (incident point) 7 near the surface of the subject 11, and its axis is inclined toward the focusing receiving oscillator 6 by a predetermined angle. . Further, the focusing type receiving oscillator 6 is also arranged with a predetermined distance from the focusing type transmitting oscillator 5, its axis is tilted in the direction of the transmitting oscillator 5, and the focusing part 8 and the axis are arranged substantially symmetrical to the transmitting oscillator 5. It

Further, the porous polyurethane of the sound absorbing material 4 is arranged on the surface of the subject 11 between them. Then, a couplant supply pipe 10 is provided on the couplant. In the figure, 1 is an ultrasonic probe, 2 is a transmitting probe, and 3 is a receiving probe.

In the above, when an ultrasonic wave is transmitted from the focusing oscillator 5, the ultrasonic wave is incident from the focusing portion 7 on the surface of the subject 11, refracted in the direction of the focusing receiving oscillator 6, and has a wide directivity. The ultrasonic wave of 9 propagates. That is, it is uniformly dispersed and propagated in the subject. The focused reception oscillator 6 has a reception characteristic in which the directivity is substantially the same as that of the focused transmission oscillator 1, that is, the reception sensitivity is uniform with respect to the flaw detection area of the subject 11. On the other hand, the surface wave is attenuated by the sound absorbing material 4. Therefore, a signal can be received from the defective portion with high S / N.

FIG. 2 shows an example of such an aspect with a flaw detection signal. The directivity of the sound wave in the subject formed by the ultrasonic probe of this embodiment is, as described above, compared with the conventional one. Since it is widely dispersed in the plate thickness direction, the distribution in the plate thickness direction, that is, the change in the signal level near the surface and near the bottom is reduced.
This figure shows an example of a flaw detection signal under the same conditions as the flaw detection signal example of FIG. 4 obtained with a conventional probe. Compared with the conventional one, the flaw detection signal example 28 of the surface defect corresponding to the area near the surface of the subject is detected.
It can be seen that the signal levels of the defect lower end signal 34 and the defect upper end signal 33 of the internal defect flaw detection signal example 29 are improved.

The couplant supply pipe 10 supplies couplant such as water necessary for flaw detection to improve workability.

Other examples of the sound absorbing material 4 include nitrile rubber, silicon rubber, urethane rubber, cork material, and foam metal.

[0023]

As described above, according to the present invention,
Since a wide directivity transmission / reception characteristic can be obtained, a defect signal can be detected with high sensitivity. Further, since the reception of the surface wave signal which becomes an obstacle is prevented, the flaw detection with improved accuracy can be realized such that the presence or absence of the defect and the defect depth can be accurately detected.

[Brief description of drawings]

FIG. 1 is a configuration cross-sectional view of an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation and effect of the same embodiment.

FIG. 3 is a configuration cross-sectional view of a conventional example.

FIG. 4 is a diagram illustrating the operation and effect of the conventional example.

FIG. 5 is an operation explanatory view of the conventional example.

[Explanation of symbols]

 1 Ultrasonic probe 2 Transmitting probe 3 Receiving probe 4 Sound absorbing material 5 Focusing type transmitting oscillator 6 Focusing type receiving oscillator 7 Incident point (focusing part) 8 Reception point (focusing part) 9 Directivity 10 couplant Supply pipe 11 Subject 12 Internal defect 21 Transmitting probe 22 Receiving probe 23 Sound wave propagating on the surface 24 Sound wave reflected on the bottom surface 27 Example of flaw detection signal without defect 28 Example of flaw detection signal of surface defect 29 Internal flaw detection signal Example 30 Example of flaw detection signal of bottom surface defect 31 Surface signal 32 Bottom surface signal 33 Defect upper end signal 34 Defect lower end signal 35 Directivity 36 Surface wave signal

Claims (1)

[Claims] 1. A focusing type oscillator having a focusing unit placed on substantially the surface of a subject and having its axis inclined, and a focusing unit and an axis facing each other with a predetermined distance from the focusing oscillator. An ultrasonic probe, comprising: focusing type receiving transducers arranged substantially symmetrically and an adsorbent disposed on the subject between the transducers.