JP2538596B2 - Electromagnetic ultrasonic transducer - Google Patents

Description

The present invention relates to an electromagnetic ultrasonic transducer used in an ultrasonic flaw detection test, and particularly to an electromagnetic ultrasonic wave capable of performing a flaw detection test with high accuracy. Regarding transducers.

(Prior Art) In order to carry out an ultrasonic flaw detection test on a welded portion of a material to be inspected, an ultrasonic transducer is required. Various types of ultrasonic transducers have been conventionally proposed. An electromagnetic ultrasonic transducer is known as one of these ultrasonic transducers. This electromagnetic ultrasonic transducer is different from the one using a magnetostrictive element or an electrostrictive element in that it generates an ultrasonic wave in the material to be inspected by Lorentz force, and it is in a non-contact state with the material to be inspected. It has the feature that it can be set. Therefore, even if unevenness exists on the surface of the material to be inspected, the test can be performed without any special treatment.

By the way, such an electromagnetic ultrasonic transducer is usually provided with a permanent magnet 4 as shown by reference numeral 30 in FIG.
And a conductor 3 for forming a high-frequency current path, which is laminated and fixed on one side surface orthogonal to the magnetizing direction of the permanent magnet 4 via a thin electric insulator 2. The permanent magnet 4 is magnetized by the thickness method. As shown in FIG. 8, the conductor 3 is formed in a zigzag shape so that the U-shaped portions alternate with each other by conductive strips.
b, 3c, ... Are arranged at a constant distance (pitch p).

When the flaw detection test of the material 20 to be inspected is performed using the electromagnetic ultrasonic transducer 30 configured as described above, the conductor 3 forming the high frequency current path is inspected as shown in FIG. Both ends 7 and 8 of the conductor 3 are connected to a high-frequency power source and a signal transmitting / receiving device (neither is shown) so as to face the surface of the material 4 with a predetermined gap 18 therebetween.

Here, the operation of the electromagnetic ultrasonic transducer 30 is as follows.

When the electromagnetic ultrasonic transducer 30 is set with its conductor 3 facing the surface of the material 20 to be inspected, as shown by the broken line arrow in FIG. It is incident on the surface at a right angle. Therefore, the inspected material 20
On the surface of, the bias magnetic field 15 perpendicular to this is applied. Next, when a high-frequency current is applied to the conductor 3, the parallel conductors 3a, 3b, 3c, ...
Alternating currents 12 flow alternately. Therefore, the current 12 causes the induction eddy current 14 of high frequency, which is in the opposite direction to the current 12 and alternately in the opposite direction, to flow on the surface of the inspection object 20. Then, due to the interaction between the induced eddy current 14 and the bias magnetic field 15, a Lorentz force 16 that is parallel to the surface of the inspected material 20 is generated in the inspected material 20, and the Lorentz force 16 also alternates. The phases are opposite. As a result, the transmission ultrasonic wave 17 generated in the inspection target material 20 is a transverse wave and propagates as an oblique beam oblique to the direction perpendicular to the surface of the inspection target material 20.

When performing an ultrasonic flaw detection test in the vicinity of the welded portion using such an electromagnetic ultrasonic transducer 30, the electromagnetic ultrasonic transducer 30 is arranged as shown in FIG.
That is, the electromagnetic ultrasonic transducer 30 is arranged in the vicinity of the welded portion 35 of the inspected material 20, and the transmitting ultrasonic wave 17 is transmitted. If there is a defect 32, the transmitting ultrasonic wave 17 is reflected and returns to the electromagnetic ultrasonic transducer 30 as a receiving ultrasonic wave 22. At this time, when the electric waveforms at both ends 7, 8 of the conductor 3 of the electromagnetic ultrasonic transducer 30 are observed, the electric waveform shown in FIG. 11 is obtained. In FIG. 11, reference numeral 33 is a transmission pulse for transmitting ultrasonic waves using the electromagnetic ultrasonic transducer 30, and reference numeral 34 is a reflection pulse from the defect 32. In the ultrasonic flaw detection test, the reflection pulse 34 is detected to determine the presence or absence of a defect, and at the same time, the time T between the transmission pulse 33 and the reflection pulse 34 is measured to determine the position of the defect 32.

(Problems to be Solved by the Invention) As described above, in the ultrasonic flaw detection test, the reflection pulse 34 of FIG. 11 is detected to determine the presence / absence of a defect, and at the same time, between the transmission pulse 33 and the reflection pulse 34. The time T is being measured.

Meanwhile, the transmission pulse 32 of the electromagnetic ultrasonic transducer 30
Generally have a constant duration T '.
However, for example, when flaw detection is performed on a thin plate material, the time T between the transmission pulse 33 and the reflection pulse 34 becomes short, and
As shown in the figure, the reflection pulse 34 may be hidden in the transmission pulse 33 because of T <T '. If the reflection pulse 34 is hidden in the transmission pulse 33 in this way, there is a problem that the reflection pulse 34 cannot be detected and the ultrasonic flaw detection test cannot be performed accurately.

The present invention has been made in consideration of such points, and an object thereof is to provide an electromagnetic ultrasonic transducer capable of performing a flaw detection test with high accuracy.

[Structure of Invention]

(Means for Solving the Problems) The present invention provides two kinds of conductors that are bent and formed in a zigzag shape so that the U-shaped portions are alternately continuous by the conductive strips, and One conductor is laminated on one side surface orthogonal to each other through an electric insulator, and the other conductor is connected to this one conductor via the electric insulator, and the branch conductor is a space between the one branch conductor. In the electromagnetic ultrasonic transducer, the two kinds of conductors are laminated so as to match with each other, and the two kinds of conductors are divided into a transmitting conductor and a receiving conductor.

(Operation) According to the present invention, since transmission and reception of ultrasonic waves are performed by separate conductors, interference between the transmission pulse and the reflection pulse is prevented. Further, since the receiving conductor is arranged such that the branch conductor is aligned with the space between the branch conductors of the transmitting conductor, the receiving conductor is affected by the high frequency input to the transmitting conductor. There is no such thing.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

1 to 6 are views showing an embodiment of an electromagnetic ultrasonic transducer according to the present invention. As shown in FIGS. 1 to 3, the permanent magnet 1 is magnetized in the thickness direction, and the transmission conductor 3 is provided on one side surface orthogonal to the magnetization direction of the permanent magnet 1 via a thin electric insulator 2. Are laminated and fixed. This transmission conductor 3 is formed by zigzag bending so that the U-shaped portions are alternately continuous by conductive strips, and the transmission branch conductors 3a, 3b, 3c, ... Are arranged at a constant distance. ing.

Further, a receiving conductor 6 is laminated and fixed to the transmitting conductor 3 with a thin electric insulator 5 interposed therebetween. Similar to the transmission conductor 3, the reception conductor 6 is formed in a zigzag shape so that the U-shaped portions are alternately continuous by the conductive strips, and the reception branch conductors 6a, 6b, 6c ,. It is placed at a certain distance.

The receiving conductor 6 is a receiving branch conductor 6a, 6b, 6c,
Are arranged so as to be aligned with the space between the branched conductors 3a, 3b, 3c, ... Of the conductor 3 for transmission. That is, as shown in FIG. 3, the receiving conductor 6 is displaced from the transmitting conductor 3 by a half pitch.

Both ends 7 and 8 of the transmitting conductor 3 are connected to an ultrasonic transmitter (not shown), and both ends 9 and 10 of the receiving conductor 6 are connected to an ultrasonic receiver (not shown). ing.

Next, the operation of this embodiment having such a configuration will be described.

FIG. 4 is a diagram showing an operation when ultrasonic waves are transmitted using the electromagnetic ultrasonic transducer 1.

When the electromagnetic ultrasonic transducer 1 is set with its transmission conductor 3 facing the surface of the material 20 to be inspected,
As shown by the broken line arrow in the figure, the magnetic field lines from the permanent magnet 4
13 is incident on the surface of the material 20 to be inspected at a right angle. Therefore, on the surface of the material 20 to be inspected, the bias magnetic field 15 perpendicular thereto is applied. Next, when a high-frequency current is passed through the transmission conductor 3, opposite currents 12 flow alternately in the transmission branch conductors 3a, 3b, 3c, ... Therefore, the surface of the material 20 to be inspected by the current 12 is
It is the opposite of the current 12. High-frequency induced eddy currents 14 of opposite directions flow alternately. Then, due to the interaction between the induced eddy current 14 and the bias magnetic field 15, a Lorentz force 16 that is parallel to the surface of the inspected material 20 is generated in the inspected material 20, and the Lorentz force 16 also alternates. The phases are opposite. As a result, the transmission ultrasonic wave 17 generated in the inspection material 20 is a transverse wave and propagates as an oblique angle beam with respect to the direction orthogonal to the surface of the inspection material 20.

Next, the transmitting ultrasonic wave 17 propagating in the inspection target material 20 is reflected by the defect in the inspection target material 20 and returns as the receiving ultrasonic wave 22.

FIG. 5 is a diagram showing an operation when receiving an ultrasonic wave. As shown in FIG. 5, when the receiving ultrasonic waves 22 propagating inside the inspection target material 20 reach the surface of the inspection target material 20,
On the surface of the material 20 to be inspected, vibration 23 is generated as shown in FIG. Subsequently, the vibration 23 interacts with the bias magnetic field 15, and an induced eddy current 24 flows on the surface of the inspection target material 20. A high-frequency magnetic field 25 is generated in the gap 18 by this eddy current 24. This high-frequency magnetic field 25 corresponds to the corresponding receiving branch conductors 6a, 6b, 6c,
… Each time goes in the opposite direction.

When the high-frequency magnetic field 25 passes through the magnetic receiving section 29 of the receiving dielectric 6 (the portion between the receiving branch conductors 6), a voltage is induced at both ends 9 and 10 of the receiving conductor 6 and ultrasonic waves for reception are received. 22 is received.

As described above, ultrasonic waves are transmitted by passing a high-frequency current through the transmitting conductor 3, and ultrasonic waves are received by inducing a voltage in the receiving conductor 6. Therefore, the transmission and reception of ultrasonic waves are separated by separate conductors 3,6.
The reflected pulse does not interfere with the transmitted pulse to be hidden.

Further, the reception of the ultrasonic wave is performed by the magnetic field receiving portion 29 of the receiving conductor 6, but the magnetic receiving portion 29 is not affected by the high frequency current input to the transmitting conductor 3. .

That is, as shown in FIG. 6, when a high frequency current 12 is passed through the transmitting conductor 3, a high frequency magnetic flux 27 causes a transmitting branch conductor.
Corresponding to 3a, 3b, 3c, ..., they occur alternately in opposite directions. In this case, since the receiving conductor 6 is arranged so as to be displaced from the transmitting conductor 3 by a half pitch, the high frequency magnetic flux 27 does not pass through the magnetic receiving portion of the receiving conductor 6. Therefore, no voltage due to the high frequency magnetic flux 27 is generated at both ends 9 and 10 of the receiving conductor 6 and is not affected by the high frequency current 12 input to the transmitting conductor 3.

As described above, according to the present embodiment, the transmission and reception of ultrasonic waves are performed by the separate conductors 3 and 6, so that the reflected pulse does not interfere with the transmission pulse. Further, since the receiving conductor 6 is arranged so as to be displaced from the transmitting conductor 3 by a half pitch, the magnetic receiving portion 29 of the receiving conductor 6 is affected by the high frequency 12 input to the transmitting conductor 3. There is no such thing.

〔The invention's effect〕

According to the present invention, since the transmission and reception of ultrasonic waves are performed by separate conductors, the reflected pulse does not interfere with the transmitted pulse and are hidden. Further, the receiving conductor is not affected by the high frequency input to the transmitting conductor. For this reason, it is possible to accurately and accurately detect flaws even in a defective portion near the surface of the inspected material.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of an electromagnetic ultrasonic transducer according to the present invention, FIG. 2 is a view taken along the line II-II in FIG.
FIG. 3 is a diagram showing an arrangement relationship between a transmission conductor and a reception conductor, FIG. 4 is a diagram showing an operation when transmitting an ultrasonic wave, and FIG. 5 is an operation when receiving an ultrasonic wave. 6 and 6 are views showing that the receiving conductor is not affected by a high frequency current inputted to the transmitting conductor, FIG. 7 is a side view of a conventional electromagnetic ultrasonic transducer, and FIG. Of Figure 7
VIII-VIII line arrow view, FIG. 9 is a diagram showing an operation when transmitting ultrasonic waves, FIG. 10 is a diagram showing a case of flaw detection in the vicinity of a welded portion, and FIG. 11 is a view showing both ends of a conductor. FIG. 12 is a diagram showing an electric waveform, and FIG. 12 is a diagram showing a state in which the reflected pulse is hidden by the transmitted pulse. 1 ... Electromagnetic ultrasonic transducer, 2 ... Electrical insulator, 3 ... Transmission conductor, 4 ... Permanent magnet, 5 ... Electrical insulator, 6 ... Reception conductor, 12 ... High-frequency current, 14…
… Induced eddy current, 15 …… Bias magnetic field, 16 …… Lorentz force, 17 …… Transmission ultrasonic wave, 20 …… Inspected material, 22 …… Reception ultrasonic wave, 23 …… Vibration, 24 …… Induction vortex Current, 25 …… High frequency magnetic field, 29 …… Magnetic receiving part.

Claims (1)

(57) [Claims] 1. A pair of conductors, which are bent and formed in a zigzag shape so that the U-shaped portions are alternately continuous by a conductive strip, are provided, and an electric insulator is provided on one side surface orthogonal to the magnetizing direction of the permanent magnet. One of the conductors is laminated via this, and the other conductor is laminated on this one conductor via an electrical insulator so that the branched conductor is aligned with the space between the one branched conductor, and An electromagnetic ultrasonic transducer characterized in that two kinds of conductors are divided into a transmitting conductor and a receiving conductor.