JPH0146028B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an electromagnetic ultrasonic measuring device.

One method of non-destructive testing is the use of ultrasonic waves, which is widely used, but it requires the surface of the material to be tested to be smooth and cannot be applied to high-temperature test materials. There are drawbacks such as. Electromagnetic ultrasonic measurement devices have been widely researched and are being put into practical use as being free of these drawbacks.
non destructive testing VOL.5 No.3 june
1972 P154～159 “Electromagneto−acoustic
non-destructive testing in the Soviet Union
It is also specifically introduced in "Union".

As is clear in principle, in order to highly sensitively detect flaws inside a specimen material or measure the thickness of a specimen material using an electromagnetic ultrasonic measuring device, a magnetic field acting on the surface of the specimen material is required. The only way to do this is to strengthen the signal, strengthen the signal applied to the transmitter coil, or strengthen both. Of these, strengthening the signal applied to the transmitter coil has its limits from a safety perspective, and strengthening the magnetic field is effective, but conventionally, an iron core with an E-shaped cross section has been used to Since it was supposed to apply a magnetic field to the magnetic field, there were limits to its strength.

That is, in electromagnetic ultrasonic measurement devices, transverse waves and longitudinal waves are selectively used depending on the purpose of measurement. In this case, when trying to utilize longitudinal waves that are effective even for the test material at relatively high temperatures,
A magnetic field acting parallel to the surface of the material being tested is required, but if an iron core with an E-shaped cross section is used, the material being tested merely acts as a yoke, and the magnetic field is acting parallel to the surface. Therefore, it is not possible to effectively obtain a strong magnetic field.

The present invention has a structure in which the excitation coil is wound around the specimen material, so that in principle, all the magnetomotive forces A and T from the excitation coil act in parallel to the specimen material, and as a result, This paper proposes increasing the magnetic field component that acts parallel to the surface of the specimen to effectively perform electromagnetic ultrasonic measurements using longitudinal waves.

FIG. 1 and FIG. 2 show a basic configuration of an electromagnetic ultrasonic measuring device according to the present invention in a perspective view and a cross-sectional perspective view. In addition, the same reference numerals are attached to the same members in the figures.

In the figure, two DC coils 11 and 12 are each independently wound so as to surround the specimen 1, and the DC magnetic flux generated from the two DC coils 11 and 12 (indicated by dotted lines in the figure) ) are excited such that they add together. Here, each coil may be connected in series or in parallel. A transmitting/receiving coil 13 is arranged in a space between two DC excitation coils 11 and 12, facing the specimen 1. Transmitting/receiving coil 1
3 can of course be placed in the same place, and it goes without saying that the transmitting coil and the receiving coil can be placed with the specimen 1 sandwiched therebetween, that is, a so-called transmission type.

In FIG. 3, arrows indicate the directions in which the excitation currents of the two DC excitation coils flow.

In the above configuration, two DC coils 11, 1
Most of the DC magnetic flux generated by 2 is in the test material 1.
, and its direction is parallel to the surface of the specimen 1. That is, almost all of the magnetic flux generated by the coils 11 and 12 forms a magnetic field whose component is parallel to the surface of the test material 1, which is necessary for transmitting and receiving longitudinal electromagnetic ultrasonic waves. If the amount of excitation of the DC excitation coils 11 and 12 is increased, the magnetic field strength increases almost proportionally, and it is easy to obtain a value of 10,000 Gauss or more for this magnetic field strength. As a result, according to this embodiment, the detection signal level of longitudinal electromagnetic ultrasound is approximately 11 times higher than the average magnetic field strength (approximately 3000 Gauss) obtained by the conventional method.
(10000/3000) ² ] sensitivity can be improved, and the effect is very large.

In addition, according to this configuration, the transmitting/receiving coil 13 can be placed on the surface, side surface, or
A plurality of coils can be placed at any position on the back surface, and a plurality of transmitter/receiver coils can be placed facing each other at a predetermined interval. As a result, the multiple transmitter/receiver coils 13 can detect wall thickness, defects, etc. around the specimen 1, such as a steel pipe or round steel bar, with a single operation using a large detection signal, making detection work easier and more convenient. good. Further, since the transmitting/receiving coil 13 can be easily attached and detached from the magnetic pole, maintenance can be easily performed.

Next, it is natural to consider providing an iron core in the configuration shown in FIG. 1 in order to improve the efficiency of magnetic field generation. A cross-sectional perspective view in this case is shown in FIG. In the figure, an iron core 14 is constructed to surround DC excitation coils 11 and 12.

It goes without saying that if a superconducting magnet is used instead of an electromagnet made of a normal conducting coil, the magnetic field strength can be increased, and thus the measurement sensitivity can be further improved.

The configuration shown in FIG. 5 is an example in which the excitation coil is integrated into one, and is substantially the same as the above-described configuration. FIG. 6 shows an example in which the test material 1 is a pipe and the wall thickness of the pipe is to be measured.

In the examples shown in FIGS. 4 to 6, the iron core 14 is as shown in FIGS. 7 and 8 according to embodiments of the present invention described later.
It is practical to divide the coil into two halves by sandwiching the coil from both sides.

7 and 8 are a side view and a plan view, partially in section, showing a specific embodiment in which the present invention is applied to the example shown in FIG. 6. FIG.

The iron core 14 is divided into two parts 14a and 14b, each of which has a cylindrical U-shaped cross section with a notch in the center, and the coils 11 and 12 are fixed to the inner surface of each part by protective covers 21a and 21b. At the same time, as shown in FIG. 7, the coils 11 and 12 are connected to each other by bolts 22 and nuts (not shown) in a manner that they face each other. Reference numerals 25a and 25b are cylindrical magnetic poles with tapered tips, each of which has a tapered tip.
It is inserted into the central notch of 4a, 14b and fixed to the iron cores 14a, b with bolts 26. 2
7a and 27b are covers, which are discs with a hole in the center. In order to prevent the bolts 26 from protruding from the side of the core, this cover has a part cut out for the bolt 26, and also has a cutout in the area where the cooling water piping, which will be described later, is arranged, to prevent the bolt 26 from protruding from the side of the core. It has been devised.

Since the magnetic poles 25a and 25b are tapered, the magnetic field can be concentrated at the tip thereof, and a magnetic field parallel to the surface of the specimen can be effectively created. Changes in the dimensions of the specimen 1 can be accommodated by changing the magnetic poles 25a and 25b. Furthermore, magnetic poles 25a, 25
By making the inner surface of b inclined as shown in the figure, the material to be tested can be introduced smoothly. In this case, by pasting a protective member on the inner surface of the magnetic pole, even if the magnetic pole 25 and the test material 1 collide, it is possible to prevent them from being damaged.

Though not shown, the magnetic poles 25a and 25b are provided with through holes through which cooling water passes, thereby cooling the magnetic poles 25a and 25b. For example, looking at the iron core 14a side, cooling water is introduced from the cooling water introduction pipe 28a, and the magnetic pole 2
The tip of the magnetic pole 25a passes through the through hole in the magnetic pole 25a and is guided to the through hole located 90 degrees away from the magnetic pole 25a through a connecting pipe (not shown). The cooling water that has exited this through hole is further guided to a through hole located 90 degrees away by a crossover pipe 30a. The cooling water flowing through this through hole crosses over to the pipe 3 at the tip of the magnetic pole 25a.
1a leads to a through hole located further 90° away. The cooling water exiting the through hole is discharged to the outside through a cooling water discharge pipe (not shown) located at an upper position corresponding to the pipe 28a. That is, the magnetic pole 25a
The cooling water is cooled by going back and forth twice through the through holes arranged in 90° increments. Similarly, for the iron core 14b, cooling water is introduced from the pipe 28b, and is discharged from a pipe (not shown) while successively passing through the through hole of the magnetic pole 25b and the crossover pipe (passing the crossover pipe 31b on the way).

The magnetic poles 25a and 25b can be formed by combining two parts, an inner cylinder and an outer cylinder, into one body, as shown by broken lines in FIG. In this case, when replacing the magnetic pole 25 in response to a change in the dimensions of the material to be tested, the inner tube and the outer tube can be handled separately, reducing weight and making handling easier. There are advantages.

Reference numeral 40 denotes a transmitting/receiving unit storage block, which is formed from a flat hollow material into a circular shape, and has through holes 61 in which transmitting/receiving units 51 to 56 (54 and 55 are not shown), which will be described later, are arranged in 60° increments. ~66 (6
4 and 65 (not shown). Block 40 is supported by the tips of each of magnetic poles 25a,b. Through holes 61 to 66 provided in block 40
Non-conductive covers 71 to 76 are placed on the test material 1 side.
(74, 75 are not shown) are arranged, and transmitting/receiving units 51 to 56 are arranged on the opposite side. Since the transmitter/receiver unit is mainly composed of a molded transmitter coil and a receiver coil (not shown), protective covers 81 to 86 (84, 85
(not shown) is provided. The connection between the transmitting coil, receiving coil and external circuit is through cable piping 91-9.
6 (94 and 95 are not shown).
The cable pipes 91 to 96 are led out to the outside through through holes provided in the magnetic pole 25b, similar to the cooling water introduction pipes described later.

A cooling water introduction pipe 42 is connected to the hollow portion 41 of the block 40, and cooling water is introduced thereinto. This cooling water flows from the hollow part 41 to the space between the cover 71 and the transmitting/receiving block 51 and into the space between the cover 72 and the transmitting/receiving block 5.
2, and then sequentially flows through the hollow part and the space between the cover and the transmitting/receiving block,
The cooling water is discharged to the outside through a cooling water discharge conduit (not shown) provided at a position opposite to the piping 42 . The introduction pipe 42 passes through the through hole 43 of the magnetic pole 25b.
The same applies to the lead-out piping (not shown). Water supply pipe 42
Since the hollow section 41 of the block 40 has a small cross-sectional area, if the cooling water is contaminated with impurities or algae grows inside, it may become clogged or the flow of the cooling water may become unstable. This may result in insufficient cooling. Therefore, it is preferable to use distilled water as the cooling water so that it flows at a sufficient flow rate.

[Brief explanation of drawings]

FIG. 1 is a perspective view conceptually showing the basic configuration that is the basis of the present invention, FIG. 2 is a cross-sectional perspective view showing the relationship between the excitation coil and the transmitting/receiving coil in FIG. 1, and FIG. A line diagram explaining the basic concept, Fig. 4 is a cross-sectional perspective view showing the configuration when the iron core is used in conjunction with Fig. 1, Fig. 5 is a cross-sectional perspective view of the configuration when the excitation coil is combined into one, Figure 6 is a cross-sectional perspective view showing the configuration when the test material is a pipe;
8 are a side view and a plan view, partially in cross section, of the configuration of a more specific embodiment showing the application of the present invention to the configuration of FIG. 6, respectively.
It is a view seen in the − direction. 1... Test material, 11, 12... Coil, 14
a, 14b... iron core, 25a, 25b... magnetic pole,
40... Transmitter/receiver storage block, 42, 28a,
28b...Cooling water piping.

Claims (1)

[Claims] 1. At least two excitation coils that are wound around at least two locations in the longitudinal direction of the test material surrounding the test material, and that flow a magnetic field in the same direction;
A transmitter coil that generates mechanical strain on the surface of the test material on which a magnetic field is applied by the excitation coil, and detects the magnetic field that appears on the surface of the test material when the mechanical strain propagates into the test material. the excitation coil is surrounded by an iron core except for the surface facing the test material, and a magnetic pole is supported by the iron core on the surface of the excitation coil facing the test material. An electromagnetic ultrasonic measuring device characterized in that the transmitting coil and the receiving coil are supported by the magnetic poles, and a plurality of transmitting coils and receiving coils are arranged in a circumferential direction of the specimen.