JPH0726939B2 - Ultrasonic flaw detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an ultrasonic flaw detection method for flaw detection in an object to be inspected by using ultrasonic waves, and detects an object to be inspected in a medium such as water. The present invention relates to an ultrasonic flaw detection apparatus capable of flaw detection in a flaw detection target layer that is very close to the surface of an object to be flaw-detected, in ultrasonic flaw detection by a water immersion method in which flaw detection is performed.

[Prior Art] A conventional ultrasonic flaw detection method of this type will be described with reference to FIGS. 3 to 6. FIG. 3 is a front view of a partial cross section showing a conventional example, in which the flaw detection object 20 is arranged in a medium 22 such as water as shown in the figure, and a relatively deep distance t ₂ from the surface of the flaw detection object 20. 3 shows a state in which the flaw detection target layer 30 in FIG. That is, the pulsed transmission wave (T) 24 transmitted from the probe 40 in the medium 22 propagates in the medium 22, enters the flaw detection target 20, and further propagates and reaches the flaw detection target layer 30. . At this time, a part of the transmitted wave (T) 24 is reflected by the surface of the flaw detection object 20 to become a surface reflection wave S, and the rest propagates into the flaw detection object 20 and is flawed or cracked in the flaw detection target layer 30. If there are any 32, they are reflected by the defect 32 to form a defect reflected wave F, which returns to the probe 40 and is received as shown in FIG.
FIG. 4 shows the transmitted wave (T) 24 by the flaw detection shown in FIG.
It is an oscillogram 42 showing the respective reflected waves S and F. In Fig. 4, the horizontal axis is time, the vertical axis is the wave height, and usually shows a flaw detection pattern observed by a cathode ray oscilloscope. In both cases, T is the transmitted wave 24 and S is the pulsed waveform. Surface reflected waves and F are defect reflected waves F. Figures 3 and 4
Since the distance t ₂ between the surface of the object to be inspected 20 and the defect 32 of the layer to be inspected 20 is sufficient in the object to be inspected 20 as shown in the drawing, the surface reflected wave S and the defect reflected wave F are as shown in the oscillogram 42. ,
The defect 32 is sufficiently separated on the horizontal axis, and the defect reflected wave F overlaps the surface reflected wave S without obstructing the observation.
It is possible to observe the presence or absence of and its size. That is, FIG. 3 shows a state in which the flaw detection of the flaw detection target layer 30 is possible.

FIG. 5 is a partially sectional front view showing a conventional example,
The difference from FIG. ₃ is that the distance t ₃ between the surface of the object to be inspected 20 and the defect 32 of the layer 30 to be inspected is extremely short and shallow. Therefore, the surface reflected wave S and the defect reflected wave F are As shown in Fig. 5, the oscillograms 44 shown in Fig. 6 are very close to each other.
As shown in the figure, the surface reflected wave S and the defect reflected wave F overlap each other and it is difficult to separate them on the horizontal axis, and it is impossible to observe the defect reflected wave F, that is, the state where the flaw detection target layer 30 cannot be flaw-detected. ing.

[Problems to be solved by the invention]

In order to detect a defect 32 that is very close to the surface of the object to be detected 20, the probe 40 is brought into direct contact with the surface of the object to be detected 20 via a thin grease layer or the like, and the influence of the surface reflected wave S is exerted. Although there is a method of observing the defect reflected wave F by avoiding, the probe 40 is moved in the XY directions of two orthogonal directions in the horizontal plane while keeping the probe 40 in contact with the surface of the flaw detection object 20. Since it is impossible to continuously detect the defects 32 of the layer 30 to be inspected having a large area, there is a problem that practical ultrasonic inspection cannot be performed by such a method.

According to the ultrasonic immersion flaw detection method described above, the probe 40 is an object to be detected.
Since the probe 40 is not in direct contact with the surface of the probe 20, the probe 40 is moved in the XY directions of two orthogonal directions in the horizontal plane to continuously detect the defects 32 of the detection target layer 30 having a large area as shown in FIG. As shown in FIGS. 4A and 4B, when the distance t _{2 from} the surface of the flaw detection object 20 is sufficient, flaw detection is possible, but as shown in FIGS. 5 and 6, the flaw detection is performed. When the distance t _{3 from} the surface of the object 20 is extremely short, it is difficult to separate the surface reflected wave S and the defect reflected wave F, and there is a problem that flaw detection cannot be performed. Generally, the surface reflected wave S is always obtained during flaw detection.
Further, since the wave height of the surface reflected wave S is much larger than the wave height of the defect reflected wave F, it is a very disturbing existence. As explained above, the ultrasonic pulse is
In the case of incident light that is incident and reflected almost perpendicularly to 20, the longitudinal wave is used as the wave mode of the ultrasonic pulse.

According to the present invention, by removing the surface reflected wave S that interferes with flaw detection or by making the wave height of the surface reflected wave S extremely small, flaw detection of the defect 32 of the flaw detection target layer 30 close to the surface of the flaw detection target 20 can be performed. An object is to provide an ultrasonic flaw detector that can be used.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention transmits a pulsed transmission wave from a transmitting probe to an object to be inspected installed in a medium through the medium so that the inside of the object to be inspected is transmitted. When there is a defect in the layer to be flaw-detected, the ultrasonic wave flaw detection device by the water immersion method is used in which the reflected wave from the defect is received by the receiving probe and flaw detection is performed by the oscillogram displaying each of these waves. , A transmission probe and a reception probe that are provided separately, and a holding mechanism that freely adjusts and holds the distance and the angular direction between the transmission point of the transmission probe and the reception point of the reception probe. And an XY drive unit in which both probes attached via the holding mechanism are driven in two XY directions orthogonal to each other in a horizontal plane, and a cylindrical shape on the outer surface below the transmission probe. One end is inserted and fixed, and the other end is formed into a truncated pyramid tube, and the inner surface of the It shall comprising a sound absorbing cylinder sound absorbing material to complement Suk scattering surface reflected wave is provided.

[Action]

The present invention is an ultrasonic flaw detection apparatus by a water immersion method performed on a flaw detection object placed in a medium such as water, in which one end is formed into a cylindrical shape and the other end is formed into a truncated conical tube, and an inner surface is formed. At the incident point of the transmitted wave on the surface of the object to be inspected, a transmitting probe that transmits a transmitted wave with a sound absorbing tube provided with a sound absorbing material is installed at an angle such that a transverse wave with a refraction angle of 45 degrees is generated. The surface reflection wave reflected at the incident point by the transmission wave that is the longitudinal ultrasonic wave is scattered and absorbed by the sound absorbing cylinder, while the transverse wave generated inside the flaw detection object This is a device in which when a defect is present in the substrate, a defect reflected wave reflected by this defect is received by a reception probe and each of these waves is detected by a display oscillogram.

The present invention enables flaw detection of a defect in a flaw detection target layer close to the surface of the flaw detection object, which has conventionally been difficult to perform flaw detection due to interference of surface reflected waves.

The distance between the transmitting point of the transmitting probe and the receiving point of the receiving probe and the angle direction differ depending on the material of the flaw detection object and the depth of the flaw detection target layer. And adjust it to hold it freely.
-Attached to the Y drive.

〔Example〕

FIG. 1 is a partial sectional front view showing an embodiment of the present invention. The columnar transmission probe 2 and the reception probe 4 are freely movable in the annular holder 6 in the axial direction, and are fixed by set screws 8 and held by the holder 6. Adjustment screws 10, which can fix the holders 6, 6 at any mounting angle.
It is attached to the XY drive 12 by 10. The holding mechanism 13 including the holder 6, the set screw 8 and the adjusting screw 10 can freely set the distance and the angular direction between the transmitting point A of the transmitting probe 2 and the receiving point B of the receiving probe 4. It is adjusted, held and attached to the XY drive 12. The XY driving unit 12 is driven in the XY directions which are two orthogonal directions in the horizontal plane. One end of a cylindrical sound absorbing tube 14 is inserted on the outer surface below the transmitting probe 2 and is fixed to the transmitting probe 2 by a set screw 16. The other end of the sound absorbing cylinder 14 is formed in a truncated cone shape, and a sound absorbing material 15 is provided on the inner surface of the sound absorbing cylinder 14. As described above, the transmission probe 2 and the reception probe 4 are attached to the XY drive unit 12 to form the flaw detection device 18.

The flaw detection object 20 is installed in a medium 22 such as water as shown in the figure, and the flaw detection device 18 is arranged toward the flaw detection object 20 as shown in the figure, and a pulsed transmission wave 24 is transmitted from the transmission probe 2. Will be sent. A part of this transmitted wave 24 is reflected as a surface reflected wave 26 from the surface of the flaw detection target 20, and as shown in the figure, a sound absorbing cylinder
The sound is absorbed by the sound absorbing material 15 on the inner surface of the sound absorbing cylinder 14 after being scattered and scattered inside the sound absorbing cylinder 14. On the other hand, the transmitted wave 24 is P on the surface of the flaw detection object 20.
It is refracted at a point and propagates in the flaw-detected object 20 as a propagating wave 28 and propagates in the flaw-detecting object 20, and is reflected by a defect 32 existing in the flaw-detection target layer 30 as a propagating defect reflected wave 34 to be detected. It reaches the point Q on the surface of 20, and is refracted at this point Q, and again becomes a defective reflected wave 36 in the medium 22 and reaches the receiving probe 4 to be received.

The adjustment angle and distance of the transmitting probe 2 and the receiving probe 4 with respect to the surface of the flaw detection target 20 and the distance between the points A and B of both the probes 2 and 4 are adjusted by the adjusting screw 10 of the holding mechanism 13. , 10 and holder 6,6
By adjusting the positions of both the probes 2 and 4 inside, a flaw detector 18 in a state where a predetermined geometrical arrangement is maintained is constructed, and the flaw detector 18 scans in the two-dimensional X-Y direction. Then, the flaw detection target layer 30 in a predetermined range of the flaw detection target 20 is scanned to detect the defect 32.

FIG. 2 is an explanatory view showing the path of ultrasonic waves in order to show the principle of the present invention. That is, in the medium 22, the transmitting probe 2 and the receiving probe 4 are plumbed as shown in FIG.
It is inclined inwardly by an angle β with respect to 23 and 35, and is arranged toward the flaw detection object 20 whose surface is horizontally installed in the medium 22. This is actually adjusted to the angle β by adjusting the adjusting screws 10 and 10 of the holding mechanism 13 as described in FIG. 1 above to make the flaw detection device 18 as a whole and to approach the flaw detection object 20, It is arranged as shown in FIG.

As a result, when the transmission wave 24 is transmitted from the point A of the transmission probe 2, an angle β is formed at a point P on the surface of the flaw detection object 20 with respect to the vertical line 23.
At a point P, a part of the transmitted wave 24 is reflected at an angle 2β and becomes a surface reflected wave 26, which is reflected in the direction of arrow S. On the other hand, the remainder of the transmitted wave 24 is at an angle α with respect to the vertical line 23 at point P.
When the propagating wave 28 hits the defect 32 in the flaw detection target layer 30 at a depth of t ₁ from the surface of the flaw detection object 20, the propagating wave 28 is propagated through the flaw detection object 20 by refracting to the propagating wave 28, Here, the reflected wave 34 is reflected by the propagation defect reflected at an angle 2α and reaches the point Q on the surface of the flaw detection target 20. At this point Q, the propagating defect reflected wave 34 is refracted and is again reflected in the medium 22 at an angle β with respect to the vertical line 35.
36 and propagated in the direction of arrow F, and point B of the receiving probe 4
Is reached and received.

Here, the geometrical arrangement of the transmitting probe 2 and the receiving probe 4 is as follows.

That is, the transmission wave transmitted from the transmission probe 2 to the medium 22.
Although the wave mode of 24 is a longitudinal wave, the transmitted wave 24 is transmitted to the point P of the flaw detection target 20 arranged in the medium 22 as shown in the figure.
Is incident, and is refracted at an angle α = 45 degrees at this point P to be converted into a transverse wave and a propagating wave 28 is generated, so that the angle β of the transmitting probe 2 is determined. Further, in the reception probe 4, the propagation defect reflected wave 34, which is the propagation wave 28 reflected by the defect 32 at an angle 2α = 90 degrees, is converted into a longitudinal reflection wave at the point Q on the surface of the flaw detection target 20. 36 are arranged so that they arrive at an angle β.

At the points P and Q, the ultrasonic pulse is refracted and the medium 22
When the sound velocity of the longitudinal ultrasonic wave in the medium is Cl and the sound velocity of the transverse ultrasonic wave in the flaw detection object 20 is C _S , according to Snell's law regarding refraction, therefore In addition, the layer to be inspected where defects 32 exist from the surface of the inspected object 20
If the distance to 30 is t _1, then the distance between point P and point Q ▲
▼ is ▲ ▼ = 2t ₁ × tan 45 ° = 2t ₁ (3) Also, the distance ▲ ▼ between the point A of the transmitting probe 2 and the point B of the receiving probe 4 is the point A, If the vertical distance from the point B to the surface of the flaw detection object 20 is h, then ▲ ▼ = 2 · h · tan β + ▲ ▼ = 2 (h · tan β
+ T ₁ ) (4) Here, the reason why the transverse wave is incident on the flaw detection object 20 at the angle α = 45 ° is that the distance (2t ₁ ) between the point P and the point Q is separated as much as possible. This is to prevent the surface reflected wave 26 at the point P from entering the receiving probe 4 as much as possible.
However, as it is, the transmitting probe 2 and the receiving probe 4 are close to each other, so that part of the surface reflected wave 26 is received by the receiving probe 4.
Since it is incident on, it is necessary to have a means for removing it. Therefore, as shown in FIG. 1 described above, the transmission probe 2
One end of the cylindrical sound absorbing cylinder 14 is inserted into the outer surface below the
The sound absorbing cylinder 14 is fixed by the set screw 16, the surface reflected wave 26 is complemented and scattered in the sound absorbing cylinder 14, and the sound absorbing material 15 on the inner surface of the sound absorbing cylinder 14 is provided.
The surface reflected wave 26 is absorbed by the above, and only the defective reflected wave 36 can be received by the receiving probe 4 by utilizing the interval PQ.

Other reasons are that the incident wave at α = 45 ° and the highest reflectivity are obtained for the transverse wave, and the longitudinal wave in the flaw detection object 20 becomes a critical angle and is launched into the medium 22 again. There is no need to consider because there is no
It is easy to handle.

The acoustic velocity C _S of the transverse ultrasonic waves in the flaw detection object 20 differs depending on the material of the flaw detection object 20, and the distance t ₁ to the flaw detection target layer 30 from the surface of the flaw detection object 20 also differs depending on the specifications of the flaw detection. , (2) above
Β and ▲ ▼ are calculated by the formulas and the formula (4), and the holding mechanism 13 freely adjusts according to the obtained result,
Adjust the flaw detector 18 to the correct β and ▲ ▼ values.

In the flaw detection device of the present invention, the surface reflection wave 26 from the flaw detection object 20 is made to be scattered and absorbed by the sound absorbing cylinder 14 attached to the transmission probe 2 on its inner surface.
The interference of the surface reflected wave 26 with respect to 36 can be eliminated. As a result, the object to be inspected 20 which was conventionally difficult to inspect
The present invention enables the flaw detection of the defect 32 in the flaw detection target layer 30 close to the surface of the.

The embodiment of the present invention is not limited to the one described above,
A pair of sliders that can move in the horizontal direction are provided on the horizontal beam of the character-shaped XY drive unit, and a feed screw having left and right threads is screwed onto this slider to allow axial movement of the feed screw by a thrust bearing. By supporting and rotating the feed screw, a pair of sliders can be opened and closed by equal distances. Next, each slider is provided with a rotation support shaft, which rotatably supports the holders of the transmitting probe and the receiving probe, and from each of these holders, an arm with an elongated hole is formed in a substantially horizontal inward direction. It is made to project in the state where it overlaps.
A pair of sliders is provided in the elongated holes of the pair of arms, and the pair of sliders can rotate in opposite directions by moving the sliders in the vertical direction by a moving mechanism.

Since the probe device is configured by the holding mechanism as described above, the distance between the transmitting point and the receiving point of both the transmitting and receiving probes, the transmitting wave, The adjustment of the inclination angle (β) of the defect reflected wave with respect to the vertical line can be performed more easily and accurately than in the embodiment shown in FIG.

〔The invention's effect〕

According to the present invention, the transmission wave of the ultrasonic wave from the transmission probe dedicated to transmission is incident on the flaw detection object installed in the medium from an oblique direction, and the surface reflection wave from the surface of the flaw detection object, When there is a defect in the layer to be inspected inside the object to be inspected, the defect reflected wave from the defect can be taken out separately from each separate position of the object to be inspected, which is an obstacle to flaw detection. Since it becomes possible to remove the surface reflected wave from the surface of the flaw detection object, this surface reflected wave is compensated by the sound absorbing cylinder inserted and fixed in the transmitting probe, scattered, and made to absorb sound, and only the defect reflected wave is obtained. It is possible to detect flaws by receiving with the receiving probe.

According to the present invention, it is possible to detect a defect in a layer to be detected, which is shallow especially near the surface of the object to be inspected, in contrast to the point that the conventional surface reflection wave and the defect reflection cannot be separated. It is possible to provide an inexpensive ultrasonic flaw detector with a simple structure.

[Brief description of drawings]

FIG. 1 is a partially sectional front view showing an embodiment of the present invention, and FIG.
The figure is an explanatory view showing the path of an ultrasonic wave to show the principle of the present invention. FIGS. 3 to 6 are views for explaining a conventional ultrasonic flaw detection method. FIG. 3 is a part showing a conventional example. FIG. 4 is a front view of a cross section showing a state in which a relatively deep layer to be inspected is being inspected from the surface of an object to be inspected, FIG. 4 is a waveform diagram by the flaw detection shown in FIG. 3, and FIG. 5 is a conventional example. FIG. 6 is a waveform diagram of the flaw detection shown in FIG. 5, showing a state in which the flaw detection target layer is extremely short and shallow from the surface of the flaw detection object in a front view of a partial cross section. 2 ... Transmitting probe, 4 ... Receiving probe, 12 ... XY drive, 14 ... Sound absorbing cylinder, 18 ... Flaw detector, 20 ... Flawed object, 22 ... Medium (water ), 24 …… transmit wave, 30 …… flaw detection layer, 32 …… defect, 36 …… defect reflected wave, 40 …… probe, 4
2,44 ... Oscillogram.

Claims (2)

[Claims] 1. A flaw is present in a layer to be inspected inside a flaw detection object, in which a pulsed transmission wave is transmitted from a transmission probe to the flaw detection object placed in the medium. In this case, the ultrasonic wave flaw detection device by the water immersion method detects flaws reflected waves from the flaw by the reception probe, and flaws are detected by the oscillogram displaying each of these waves. And a receiving probe, a holding mechanism that freely adjusts and holds the distance between the transmitting point of the transmitting probe and the receiving point of the receiving probe, and the angle direction, and the holding mechanism is attached via this holding mechanism. And an XY drive unit in which both probes are driven in two XY directions orthogonal to each other in a horizontal plane, and a cylindrical one end portion of which is inserted and fixed to an outer surface below the transmission probe. The end is shaped like a truncated cone, and its inner surface absorbs and scatters the surface reflected waves of the flaw. That ultrasonic flaw detector sound absorbing material is characterized in that it comprises a sound absorbing tube provided. 2. A device according to claim 1, wherein a holder for holding each of the transmitting probe and the receiving probe so as to be movable in the axial direction thereof, and the holder is fixed at a freely attaching angle. An ultrasonic flaw detector comprising a holding mechanism that is fixed to an XY drive unit by an adjustable screw.