JP3107951B2 - Tire type ultrasonic probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire-type ultrasonic probe, and more particularly to a tire-type ultrasonic probe capable of simultaneously transmitting and receiving a transverse wave and a surface wave from one probe. .

[0002]

2. Description of the Related Art Conventionally, a tire type ultrasonic probe is used to continuously detect flaws existing in an object such as a steel plate (hereinafter, a steel plate will be described as an example). A conventional tire-type ultrasonic probe will be described with reference to the drawings.

FIG. 8 is a sectional view showing a conventional tire-type ultrasonic probe, FIG. 9 is a sectional view taken along line AA of FIG. 8, and FIG. 10 is a sectional view taken along line BB of FIG. .

In FIGS. 8 to 10, reference numeral 1 denotes a bracket.
It is the axis | shaft of the tire type | mold ultrasonic probe which has 1A. Reference numeral 2 denotes a tire which is mounted on the shaft 1 so as to be rotatable around the shaft 1 and which rolls on a steel plate 5 as a subject. The tire 2 is made of butadiene-based rubber or the like that has a low attenuation of ultrasonic waves. Reference numeral 3 denotes a transducer fixed to the bracket 1A, and the ultrasonic transducer 7 is attached to a contact point 2A between the tire 2 and the steel plate 5. 4 is
It is an ultrasonic wave propagation material attached to the bracket 1A on the ultrasonic vibrator 7 side, and is made of butadiene rubber or the like which has a small attenuation of ultrasonic waves. Reference numeral 8 denotes a couplant such as water or oil filled in the space between the ultrasonic wave propagation material 4 and the tire 2.

According to the conventional tire-type ultrasonic probe described above, the flaw 6 in the steel plate 5 is detected as follows. That is, the ultrasonic pulse transmitted from the ultrasonic vibrator 7 of the transducer 3 propagates through the ultrasonic wave propagation material 4, the couplant 8 and the tire 2, and enters the steel plate 5. The ultrasonic pulse incident on the steel plate 5 is reflected by the flaw 6, propagates along the same path as the transmission path, is received by the ultrasonic vibrator 7, and is reflected by the echo of the ultrasonic pulse thus received. The flaw 6 in 5 is detected.

As described above, in the conventional tire type ultrasonic probe, as much as possible, an ultrasonic wave is made to enter the steel plate at a constant angle and in a single mode, and the ultrasonic echo from the reflection source is made to correspond to the incident path. In general, flaw detection was performed by receiving data through a reverse path.

[0007]

However, in practice, it is practically and economically advantageous to simultaneously transmit and receive two types of waves, for example, a transverse wave and a surface wave, using one tire-type ultrasonic probe. It may be. Conventionally, two tire-type ultrasonic probes have been used when performing oblique flaw detection using a transverse wave and flaw detection using a surface wave at the same time. Conventionally, the transverse and surface waves could not be transmitted and received simultaneously from a single tire-type ultrasonic probe because the transducer of the tire-type ultrasonic probe has a center sound pressure of -6 dB (central sound pressure). This is because an ultrasonic beam having a directivity of 3 ° or less, which can provide a sound pressure of 1/2 or more, was generally used.

Accordingly, it is an object of the present invention to provide a tire-type ultrasonic probe capable of transmitting and receiving a transverse wave and a surface wave simultaneously from one probe.

According to the present invention, a tire-type ultrasonic probe for obliquely irradiating an ultrasonic wave into a subject to detect a flaw in the subject can obtain a sound pressure of -6 dB or more at the center sound pressure. A transducer having one transducer having a directivity with an ultrasonic beam divergence angle of 4.5 ° or more is attached, and a transverse wave and a surface wave are simultaneously incident on the subject by the transducer. Have

[0010]

The basic principle of the present invention will be described. The refraction of a sound wave between different media is expressed by the following equation 1 according to Snell's law.

[0011]

V ₁ / sin θ ₁ = V ₂ / sin θ ₂ where V ₁ : sound velocity of one medium A, θ ₁ : one medium A
Incident (refraction) angle, V ₂ : sound velocity of the other medium B, θ ₂ :
Refraction (incident) angle of the other medium B.

Now, a butadiene rubber is selected as the medium A, and a steel plate is selected as the medium B. If V _{2 is set} to a shear wave speed of 3230 m / S in the steel and θ _{2 is set} to 70 °, a longitudinal wave speed of the butadiene rubber is obtained. Since V ₁ is 1520 m / S, θ ₁ is 26.2 °. Although a rough approximation, if the speed of sound of the surface wave 2980m / S of steel as V _2, theta ₂ and a 90 °, theta ₁ becomes 30.7 °. Therefore, if a transducer that can cover the entire range of the incident angle of 26.2 ° to 30.7 ° is used, the refraction angle of 70
It can be transmitted simultaneously with a transverse wave and a surface wave of more than °.

That is, as shown in FIG. 1, a sound pressure of not less than -6 dB (中心 of the center sound pressure) is obtained in practical use, and the divergence angle of the ultrasonic beam is 4.5 ° (30.7 ° − The transducer having the directivity of 26.2 ° or more may be arranged in the tire such that the incident angle at the central sound pressure is about 28.5 ((30.7 ° + 26.2 °) / 2). FIG. 2 shows the relationship between the sound pressure reciprocation rate and the longitudinal wave incident angle in butadiene rubber and the shear wave refraction angle in steel.

Further, as shown in FIG.
Assuming that the length of the contact cross section with (l) is (l), straight lines of 26.2 ° and 30.7 ° are drawn with respect to the normals set at both ends of (l), respectively, and a circle centered at the intersection (O) of these straight lines A transducer having a vibrator having a curved surface such as a kamaboko type (cylindrical surface shape) having two ends (P) and (Q) at which both points intersect with the two straight lines is disposed inside the tire. Even in the same manner as described above, a transverse wave and a surface wave having a refraction angle of 70 ° or more can be transmitted simultaneously.

The size of the vibrator depends on the size of the tire-type ultrasonic probe and the length (l) of the contact section related to the pressing force of the tire. Needless to say, there is.

When a longitudinal wave and a transverse wave are to be simultaneously incident on the steel sheet, the central sound pressure is -6 dB (1/2 of the central sound pressure).
The transducer may be arranged inside the tire so that the range of the incident angle of 14.9 ° or less is included in the spread of the ultrasonic beam that can obtain the above sound pressure.

[0017]

Next, an embodiment of the tire-type ultrasonic probe according to the present invention will be described with reference to the drawings.

FIG. 4 is a sectional view showing a propagation path of an ultrasonic wave incident on a steel plate by the tire type ultrasonic probe of the present invention. FIG. 5 is a view showing a directivity of a transducer of the tire type ultrasonic probe. FIG.

In FIG. 4, the same reference numerals as those in FIG. 8 denote the same items, and a description thereof will be omitted. When the vibrator 7 of the transducer 3 is vibrated at a high frequency, the ultrasonic wave propagates through the ultrasonic wave propagation material 4, the couplant 8, and the butadiene rubber tire 2 and enters the steel plate 5 (this path is indicated by m). )
The incident angle at the central sound pressure is (30.7 ° + 26.2 °) /2/228.5
The ultrasonic wave incident on the steel plate 5 at an angle of °
The angle of refraction is approximately 70 ° (transverse wave) to 90 ° (surface wave), propagates through the steel plate 5 (this path is indicated by n), and follows the reverse path due to the presence of a reflection source such as a flaw 6. Received by juicer 3. In this way, it is possible to detect the scratches 6 present on the front, inside and back of the steel plate 5 with one tire-type ultrasonic probe.

FIG. 6 is a diagram showing the position of the center point of the vibrator 7 in the tire type ultrasonic probe. In the tire type ultrasonic probe, the vibrator 7 vibrates at one point on the circumference of the upper surface of the inverted cone. By placing the probe 7 and setting the generating line to the path m, the refraction angle of 70 ° (transverse wave) to 90 ° (surface wave) in all directions in the steel plate 5 with respect to the traveling direction of the tire type ultrasonic probe. Ultrasonic waves are made incident (this path is indicated by n), and this echo can be received.

FIG. 7 is a graph showing the relationship between the spread of the ultrasonic beam at which a sound pressure of -6 dB (1/2 of the center sound pressure) or more is obtained and the diameter of the flat circular vibrator. In the case of the transducer used in the conventional tire-type ultrasonic probe, the diameter of the transducer is generally 0.5 inch (12.7 mm) or more.
It can be seen that the beam spread is 3 ° or less at a frequency of 2.25 MHz and 1.4 ° or less at a frequency of 5 MHz. Conversely, if a transducer having a diameter of 8.6 mm or less at a frequency of 2.25 MHz and a diameter of 3.8 mm or less at a frequency of 5 MHz is used, a beam spread of 4.5 ° or more can be obtained. In FIG. 7, A on the vertical axis represents a beam spread of -6 dB in butadiene rubber expressed by the following equation (2).

[0022]

## EQU2 ## where A = 2 sin ^-1 (0.5λ / D) where far field D: vibrator diameter, λ: wavelength.

[0023]

As described above, according to the present invention, it is possible to obtain an ultrasonic beam having a central sound pressure of -6 dB (1/2 of the central sound pressure) or more, and the divergence angle of the ultrasonic beam is 4.5 ° or more. By using a transducer having a characteristic, a transverse wave and a surface wave can be transmitted and received simultaneously from one probe, so that scratches existing on the front, inside and back of the steel plate can be detected by one tire-type ultrasonic probe. Useful effects such as the fact that it becomes possible to detect with a stylus are provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing the spread of an ultrasonic beam in a tire-type ultrasonic probe according to the present invention.

FIG. 2 is a graph showing a relationship between a sound pressure reciprocation rate and a longitudinal wave incident angle in butadiene rubber and a transverse wave refraction angle in steel.

FIG. 3 is a diagram showing the spread of an ultrasonic beam when a Kamaboko type transducer is used as the transducer of the tire type ultrasonic probe of the present invention.

FIG. 4 is a cross-sectional view showing a propagation path of an ultrasonic wave incident on a steel plate by the tire-type ultrasonic probe of the present invention.

FIG. 5 is a diagram showing the directivity of a transducer of the tire-type ultrasonic probe.

FIG. 6 is a diagram showing a propagation path of an ultrasonic wave when a transducer is arranged at one point on the circumference of the upper surface of the inverted cone.

FIG. 7 is a graph showing the relationship between the spread of an ultrasonic beam at which a sound pressure of -6 dB (1/2 of the center sound pressure) or more is obtained and the diameter of a flat circular vibrator.

FIG. 8 is a sectional view showing a conventional tire-type ultrasonic probe.

FIG. 9 is a sectional view taken along line AA of FIG. 8;

FIG. 10 is a sectional view taken along line BB of FIG. 8;

[Explanation of symbols]

 1: shaft, 1A: bracket, 2: tire, 2A: contact point between tire and steel plate, 3: transducer, 4: ultrasonic wave propagation material, 5: steel plate, 6: scratch, 7: ultrasonic vibrator, 8 : Couplant.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tadashi Morimoto 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Masamichi Matsuda 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan (72) Inventor Kazushi Nishida 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Naoki Kawanishi 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka Osaka Gas Co., Ltd. In-company (72) Inventor Yutaka Okajima 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka-shi Inside Osaka Gas Co., Ltd. (56) References Shokai Sho 62-91256 (JP, U) Shoko 47-5829 (JP, Y1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 29/00-29/28

Claims (2)

(57) [Claims] 1. An ultrasonic wave is obliquely incident on a subject,
In a tire-type ultrasonic probe for detecting a flaw in the subject, one having a directivity in which a divergence angle of an ultrasonic beam capable of obtaining a sound pressure of a central sound pressure of −6 dB or more is 4.5 ° or more.
A transducer having a vibrator is attached,
A transverse ultrasonic wave and a surface wave are simultaneously incident on the subject by the transducer. 2. The tire-type ultrasonic probe according to claim 1, wherein the ultrasonic transducer of the transducer is formed on a curved surface.