JPH0623737B2 - Ultrasonic flaw detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic flaw detector for performing vertical flaw detection on a material to be inspected by a water immersion method using, for example, a pulse reflection method.

[Conventional technology]

FIG. 4 is a diagram of a conventional ultrasonic flaw detection apparatus shown in, for example, the ultrasonic flaw detection method (published by Nikkan Kogyo Shimbun, 1974). In the figure, (1) is the test material, (2) is the ultrasonic probe, (3) is the acoustic coupling material (for example, water), (4) is the defect inside the test material (1),
(5) is an ultrasonic beam, S is a surface reflected wave of the material to be tested (1),
F is a defect reflected wave inside the test material (1), and B is a bottom reflected wave of the test material (1). Further, FIG. 5 is a flaw detection figure by the conventional ultrasonic flaw detection equipment. In the figure, (8) is a flaw detection gate for flaw detection on the material to be inspected (1), T ₁ is the first transmission pulse, T ₂ is the second transmission pulse, Tn is the nth transmission pulse, and t is the transmission pulse. The pulse repetition time, S ₁ is the first surface reflection wave of the material under test (1) with respect to the transmission pulse T ₁ , and is referred to as S ₂ , S ₃ , S ₄ , S ₅ ......
… S _n is the 2nd, 3rd, 4th, 5th time ……… The nth surface reflected wave, B ₁ −S ₁ is the surface reflected wave S
In the first round of the bottom surface reflected wave of the test material (1) with respect to _1, or less B ₂
−S ₁ ……… B _n −S ₁ is the second reflection wave of the material (1) against the surface reflection wave S ₁ ………… the nth bottom reflection wave, B ₁ −S ₂ , B ₂ −S ₂
……… B _n −S ₂ ,, B ₁ −S ₃ ……… B _n −S ₃ ,, B ₁ −S ₄ ……… B _n −
S ₄ , B _n −S ₅ ………… B _n −S _n is the nth bottom reflected wave of the material (1) to be tested for the _nth surface reflected wave S _n , and F is the first surface. The defect reflection wave inside the test material (1) with respect to the reflected wave S ₁ , and F ′ is the defect reflection wave inside the test material (1) with respect to the _second surface reflected wave S ₂ . 1st as shown in the figure
Multiple echoes (S ₁ , S ₂ , ... …… S _n ) of the surface reflection wave of the material under test (1) at the transmission pulse T _{1 for the} second time, and the defect reflection waves (F, F ′) inside the object of measurement (1) ) And the respective surface reflected waves (S ₁ ,
S _2, ......... S material being tested against _n) bottom reflected wave of the multiple echo _{(1) (B 1 -S 1} , B 2 -S 1, ......... B n -S n) number of the reflected wave such as Appears. Also, the multiple echoes (S ₁ ……… S _n , B ₁ −S ₁ …)
...... B _n -S _n) is the transmitted pulse (T _1, T _2, appears the same in gap ......... T _n) to the repetition time for each t.

The conventional ultrasonic flaw detector is configured as described above, and when it is automated, it repeatedly transmits the transmission pulse T, and the test material (1)
Alternatively, by operating the ultrasonic probe (2),
Ultrasonic flaw detection is performed on the entire surface of (1). Further, the repetition time t of the transmission pulse T is determined according to the relative moving speed of the test material (1) and the ultrasonic probe (2).
That is, in order to increase the flaw detection processing capability of the material to be inspected (1), the repetition time t of the transmission pulse T must be shortened, so that the surface reflection wave S ₁ generated by the _first transmission pulse T ₁ To S _n and bottom reflected waves B ₁ −S ₁ to B _n −S _n have not completely disappeared, the transmission pulse T ₂ from the second time onwards
It becomes necessary to transmit T _n . In that case, as a reverberation echo between the surface reflected wave S ₁ and the bottom reflected wave B ₁ -S ₁ due to the _first transmission pulse T ₁ , the second and subsequent times are generated. Surface reflected waves S _n and bottom reflected waves S _n −B _n due to the transmission pulses T ₂ to T _n appear. Therefore, the surface reflected wave S _n and the bottom reflected wave S _n
-B _n will be erroneously detected as the defect reflected wave F.

[Problems to be solved by the invention]

As described above, in the ultrasonic flaw detector which only has water as the acoustic coupling material (3) between the test material (1) and the ultrasonic probe (2), the test material is
(1) About 95% of the reflected wave S on the surface is reflected, and the ultrasonic probe (2)
Since about 60% of light is reflected on the surface of the above, it is attenuated by about 5 to 6 dB each time it makes one reciprocation between the ultrasonic probe (2) and the test material (1). Therefore, the defect detectability normally required (for example, φ
_{From the} S / N ≧ 20 dB for _one lateral hole defect, the reduction amount of reverberation echo S _n , B _n −S _n with respect to the first surface reflected wave S ₁ is −60 dB
Must be: That is, if the second transmission pulse T ₂ is generated before the time between the ultrasonic probe (2) and the test material (1) reciprocating 10 to 12 times elapses, the reverberation echo is generated. As a result, S _n and B _n −S _n appear as pseudo defect echo F. In particular, this problem is a fatal drawback in an automatic flaw detection device with a high flaw detection processing speed.

The present invention has been made to solve the above problems, and the acoustic coupling material between the test material and the ultrasonic probe has a portion of 35 ° to 55 ° with respect to the traveling direction of the ultrasonic beam. Prevents reverberation echo by equipping the side wall in the direction in which ultrasonic waves are reflected by the angle between the perforated plate and the perforated plate made of acrylic resin with a uniform thickness within the ゜ angle range. The purpose is to shorten the repetition time of the transmission pulse.

[Means for solving problems]

The ultrasonic flaw detector according to the present invention is made of acrylic resin in which the acoustic coupling material between the test material and the ultrasonic probe has an angle range of 35 ° to 55 ° with respect to the traveling direction of the ultrasonic beam. The plate has a uniform thickness, and an ultrasonic sound absorbing material is provided on the side surface in the direction in which ultrasonic waves are reflected depending on the angle of the plate.

[Work]

In the present invention, an acrylic resin partition plate having a uniform thickness is provided at a portion of the acoustic coupling material between the test material and the ultrasonic probe at an angle of 35 ° to 55 ° with respect to the traveling direction of the ultrasonic beam. By providing the ultrasonic wave within the angular range, the attenuation amount of the transverse ultrasonic wave passing through the above-mentioned plate is utilized to increase the total attenuation amount of the ultrasonic wave that makes one round trip between the ultrasonic probe and the test material. As a result, it is possible to shorten the repetition time of the transmission pulse. Further, by providing an ultrasonic sound absorbing material on the side surface in the direction in which ultrasonic waves are reflected depending on the angle of the plate, it is possible to absorb unnecessary ultrasonic beams generated by providing the plate. It is possible.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention (1) to (5)
Is exactly the same as the conventional device shown in FIG.
In the figure, (6) is the acrylic resin plate according to the present invention, and (7) is the ultrasonic sound absorbing material (for example, silicone rubber) according to the present invention.

FIG. 2 is an enlarged view of the vicinity of the plate (6) in FIG. In the figure, x ₁ is the ultrasonic beam before passing through the plate (6), x ₂ is the ultrasonic beam after passing through the plate (6), x ₃ is the ultrasonic beam x ₁ is the plate (6) Ultrasonic beam reflected by the surface, y ₁ is a transverse ultrasonic wave beam penetrating the inside of the plate (6), α is a plate of the ultrasonic beam x ₁ (6)
The angle of incidence on the plate, β is the refraction angle inside the plate (6), and θ is the angle between the plate (6) and the ultrasonic beam (5).

FIG. 3 is a flaw detection figure when vertical flaw detection of the test material (1) is performed by the water immersion method using the pulse reflection method in the ultrasonic flaw detection apparatus configured as described above. In the figure (8)
The symbols (S ₁ , S ₂ , S ₁ -S ₁ ...) In the figure are exactly the same as those shown in FIG.

In the ultrasonic flaw detector configured as described above, a part made of an acrylic resin with a uniform thickness is formed on the acoustic coupling material (3) between the test material (1) and the ultrasonic probe (2). When the plate (6) is installed within the angle range of θ = 35 ° to 55 ° with respect to the traveling direction of the ultrasonic beam (5), the ultrasonic beam (5) generated by the ultrasonic probe (2) Can be distinguished into x ₁ , x ₂ , x ₃ and y ₁ . Assuming that the sound velocity of water is ν ₁ and the shear wave velocity of acrylic resin is ν ₂ , then Eqs. (1) and (2) hold between α, β, and θ.

Here, assuming that the sound velocity of water: ν ₁ = 1480 m / s (20 ° C) and the transverse wave sound velocity of acrylic resin: ν ₁ ≈ 1420 m / s, equation (1) becomes equation (3).

sinα ≒ sinβ ……………………………………………………
(3) From Eq. (3), the ultrasonic beam travels almost linearly as x ₁ → y ₁ .

Next, regarding the level of x ₃ that is the reflected wave on the plate (6), the reflectance γ is calculated by Eq. (4), where z _{1 is} the acoustic impedance of water and z ₂ is the transverse impedance of acrylic resin. To be

According to Eqs. (2) and (4), the reflectance γ of x ₃ is about 10% or less within the angle range of θ = 35 ° to 55 °, but in high-sensitivity flaw detection, this ultrasonic beam x ₃ Since the reflection level becomes a noise level that cannot be ignored yet and becomes a factor that reduces the defect detectability, an ultrasonic sound absorbing material (7) is provided on the side where the ultrasonic beam x ₃ reaches via the stop plate (6). Due to
It becomes possible to absorb and attenuate the ultrasonic beam x ₃ .

According to the above description, 90% or more of the ultrasonic beam x ₁ progresses as the ultrasonic beam y ₁ . Moreover, since the thickness of the divider plate (6) is uniform, the relationship between the ultrasonic beams y ₁ and x ₂ is the same as above.

Next, the attenuation of the ultrasonic beam will be described. Plate
(6) The ultrasonic beam y ₁ inside is propagated by the transverse wave in the acrylic material. Therefore, comparing the attenuation of ultrasonic waves propagating in water with the attenuation of ultrasonic waves propagating by transverse waves in the acrylic material, it is about 15 times greater when propagating in the acrylic material.

According to the above description, an acrylic plate with a uniform thickness in the acoustic coupling material (3) between the test material (1) and the ultrasonic probe (2) with respect to the traveling direction of the ultrasonic beam (5) , Θ = 35 ° to 55 ° within the angle plate (6), and the ultrasonic absorbing material provided on the side surface in the direction in which the ultrasonic waves are reflected by the angle of the plate (6). You can:

(I) The traveling direction of the ultrasonic beam (5) does not change.

(II) It is possible to reduce the sound pressure level by about 5 to 10 dB each time the diaphragm plate (6) is passed.

(III) It is possible to absorb the unnecessary ultrasonic beam x ₃ generated by providing the stop plate (6).

Due to the above (I), (II) and (III), the present invention reduces the number of multiple echoes of the reflected wave of the material (1) to be inspected by the _first transmission pulse T ₁ as shown in FIG. , It is possible to shorten the repetition time t of the transmission pulse T.

Although the present embodiment has been described by using the example of the acrylic resin plate, the present invention can be applied to other plastics, rubber materials, etc. because the same effect can be obtained although the angle condition is slightly different.

〔The invention's effect〕

As described above, the present invention is made of an acrylic resin in which the acoustic coupling material between the test material and the ultrasonic probe is within the angle range of 35 ° to 55 ° with respect to the traveling direction of the ultrasonic beam. It is possible to shorten the repetition time of the transmission pulse by equipping the end plate with a uniform thickness and the side surface in the direction in which the ultrasonic wave is reflected by the angle of the end plate, by absorbing the ultrasonic wave. In automating the ultrasonic flaw detector, it has the effects of shortening the processing time for the material to be inspected and increasing the flaw detection density, enabling high-speed flaw detection and high-density flaw detection.

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, and FIG. 3 is a flaw detection figure in the present invention.
FIG. 4 is a view showing a conventional ultrasonic flaw detector, and FIG. 5 is a flaw detection figure in the conventional ultrasonic flaw detector. In the figure, (1) is the test material, (2) is the ultrasonic probe, (3) is the acoustic coupling material, (4) is the defect inside the test material, (5) is the ultrasonic beam, and (6) ) Is a plate, (7) is an ultrasonic sound absorbing material, and (8) is a flaw detection gate. The same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A superfluid space having a distance of 1/4 or more of the thickness of the test material provided between the ultrasonic probe and the test material, wherein the space is filled with an acoustic coupling material such as water or oil. In the ultrasonic flaw detector, the thickness of the acrylic resin made uniform within the angle range of 35 ° to 55 ° with respect to the traveling direction of the ultrasonic beam on the ultrasonic propagation path between the ultrasonic probe and the test material. An ultrasonic flaw detector, characterized in that a sound absorbing material for ultrasonic waves is provided on a side surface in a direction in which ultrasonic waves are reflected depending on an angle between the endless plate and the above-mentioned plate.