JPS5918452A - Electromagnetic ultrasonic measuring apparatus - Google Patents

Abstract

PURPOSE:To perform measurement effectively, by a method wherein a material to be inspected is used as a core and wound by an exciting coil to act magnetomotive parallelly. CONSTITUTION:DC magnetic flux generated by two DC coils 11, 12 is passed through the interior of a material 1 to be inspected and the direction thereof is made parallel with the surface thereof. That is, magnetic flux forms a magnetic field of a component parallel to the surface necessary in transmitting and receiving almost all longitudinal electromagnetic ultrasonic waves. Therefore, if an exciting amount is increased, the intensity of the magnetic field is increased almost proportionally to obtain a value of 10,000 Gauss or more. By this method, the enhancement in the detection signal level of longitudinal electromagnetic ultrasonic waves is attained.

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 ultrasound, 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 materials. There are drawbacks such as. Electromagnetic ultrasonic measurement devices have been widely researched as being free of these drawbacks and are being put into practical use, for example, non-destructive test
ing VOL, 5 A 3 june1972 P1
54-159 [EI electromagneto-ac
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ting in the 5oviet[Jnio
It is also specifically introduced in nJ.

In order to use an electromagnetic ultrasonic measuring device to detect scratches inside a material to be inspected with high sensitivity or to measure the entire thickness of the material to be inspected, it is clear in principle that the magnetic field acting on the surface of the material to be inspected must be strong. either by increasing the signal applied to the transmitter coil, or by strengthening the signal applied to the transmitter coil.
Or the only way is to strengthen both. Of these,
There is a safety limit to fully strengthening the signal applied to the transmitting coil, and it is effective to fully strengthen the magnetic field. Because it was said to be a force to be used, there was a limit to how much it could be strengthened.

That is, in the electromagnetic ultrasonic measuring device, transverse waves and longitudinal waves are selectively used depending on the purpose of h1 measurement.

In this case, when attempting to utilize longitudinal waves that are effective even on the test material at a relatively high temperature, a magnetic field acting parallel to the surface of the test material is required, but the cross section is E-shaped. If an iron core is used, the test material simply acts as a yoke, and a magnetic field parallel to its surface cannot be effectively obtained.

In the present invention cI, by adopting a structure in which the excitation coil is fully wound with the test material inside, in principle, all the magnetomotive forces A and III by the excitation coil act in parallel to the test material, and as a result, the We propose to effectively perform electromagnetic ultrasonic measurement using longitudinal waves by increasing the total magnetic field component that acts parallel to the surface of the specimen.

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

In the figure, the two DC coils 11.12 are each independently wound so as to surround the specimen 1, and the DC magnetic flux generated from the two DC coils 11.12 (in the figure (shown with dotted lines) are excited in such a way 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
Needless to say, the method of No. 3 is a so-called transmission type water scale in which the transmitting coil and the receiving coil are placed across the entire specimen 1, which can be placed at all times.

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

In the above configuration, most of the DC magnetic flux generated by the two DC coils 11 and 12 passes through the inside of the test material 1,
Moreover, the direction is parallel to the surface of the material 10 to be inspected. That is,
Almost all of the magnetic flux generated by the coils 11 and 12 forms a magnetic field whose components are parallel to the surface of the test material 1, which is necessary for transmitting and receiving all longitudinal electromagnetic ultrasonic waves. If the total excitation i' of the DC excitation coils 11, 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 detected signal level of longitudinal electromagnetic ultrasound is approximately 11 times higher than the average magnetic field strength (approximately 30,000 auss) according to the conventional method.
The sensitivity can be improved by = (10,000/3,000)21), and the effect is very large.

In addition, according to this configuration, the transmitting/receiving coil 13 can be placed anywhere on the surface, side surface, or layer surface of the material to be inspected as long as it is within the space between the DC excitation coils, and it is possible to arrange not only a single transmitting/receiving coil but also multiple transmitting/receiving coils. It is also possible to arrange them facing each other at a predetermined interval.

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 perspective cross-sectional view of this case is shown in FIG. 4. In the figure, the iron core 14 is configured to surround the DC excitation coils 11 and 12i.

Note that, of course, if a superconducting magnet is used instead of an electromagnet made of a normal conducting coil, the magnetic field strength can be increased, and therefore 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. Figure 6 shows test material 1
This is an example of trying to measure the wall thickness of a vibrator using a pipe.

In the examples shown in FIGS. 4 to 6, the iron core 14 is actually divided into two parts, such as being sandwiched from both sides of the coil, as shown in FIGS. 7 and 8 of the embodiment of the present invention, which will be described later. It is true.

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

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 coils 11 and 12 are fixed to the inner surface of each part by protective covers 21a and 21b. , as shown in FIG. 7, the coil 11. They are connected by a bolt 22 and a nut (not shown) in such a way that they face each other. 25a and 25b are cylindrical magnetic poles with tapered tips, each of which is connected to the iron core 14a.
.

It is inserted into a notch in the center of 14b and fixed to iron cores 14a and 14b with bolts 26. 27a.

27b is a cover, which is a circular plate 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 fully concentrated at the tip thereof, and a magnetic field parallel to the surface of the specimen can be effectively created. Test material 1
Changes in dimensions can be accommodated by changing the magnetic poles 25a and 25b. 1 more magnetic pole 25
By making the inner surfaces of a and 25b sloped 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 the metal from being biased between the two.

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, passes through a through hole in the magnetic pole 25a, passes through a crossover pipe (not shown) at the tip of the magnetic pole 25a, and is separated by 90 degrees from the magnetic pole 25a. is guided to the through hole located at the right position. The cooling water coming out of the 1L passage hole is further guided to a through hole located 90° away from the connecting pipe 30a. The cooling water flowing through the through hole is further guided to the through hole located 90 degrees away from the connecting pipe 31a at the tip of the magnetic pole 2551. The cooling water coming out of this through hole is pipe 28a
Cooling water discharge pipe located at the upper position corresponding to (not shown)
is discharged to the outside. That is, the magnetic pole 258 is cooled by the cooling water flowing through the through holes arranged at 90° increments and reciprocating twice. 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 crossing pipe (passing through the crossing pipe 31k1 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 being tested, the inner cylinder and the outer cylinder can be handled separately, reducing the amount of waste and making handling easier. There are some advantages.

(9) Reference numeral 40 denotes a transmitting/receiving unit storage block, which is formed from a flat hollow material into a circular shape, and transmitting/receiving units 51 to 56 (54 and 55 are not shown), which will be described later, are arranged at a 60° angle. The block 40, which has through holes 61 to 66 (64.degree. 65 is not shown), is supported by the tips of the magnetic poles 25a and 25b, respectively. Through hole 61 provided in block 40
Non-conductive covers 71 to 76 are placed on the test material 1 side of ~66.
(74° and 75 are not shown) are arranged, and transmitting/receiving units 51 to 56 are arranged on the opposite side. Since the transmitter/receiver section is made up of a molded transmitter coil and a receiver coil (not shown), for example, a protective cover 8 is provided to reinforce this strength.
1 to 86 (84 and 85 are not shown) are provided. The transmission coil, the reception coil and the external circuit are connected through cable piping 91 to 96 (94.degree. 95 is 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 to introduce cooling water. This cooling (10) water is divided from the hollow part 41 into the space between the cover 71 and the transmitting/receiving block 51 and the space between the cover 72 and the transmitting/receiving block 52, and hereinafter, the space between the hollow part, the cover, and the transmitting/receiving block and is discharged to the outside via a cooling water discharge conduit (not shown) provided at a position opposite to the piping 42. The introduction pipe 42 passes through the entire through hole 43 of the magnetic pole 25b.

The same applies to the lead-out piping (not shown). The water guide pipe 42 and the hollow part 41 of the block 40 have a small cross-sectional area, so if the cooling water is contaminated with impurities or algae grows inside, it may become clogged or the flow of the cooling water becomes uneven. 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 structure 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 diagram explaining all the basic concepts, Figure 4 is the iron core 'x 1A- in Figure 1.
Figure 5.255 is a cross-sectional perspective view of the configuration when the excitation coil is combined into one, and Figure 6 is the complete configuration when all pipes are used. Cross-sectional perspective view, FIG. 7. This is a plan view, and the sections are divided in the ■-■ and ■-■ directions, respectively. 1...Test material, 11, 12---fill, 14a
, 14b... Iron core, 25a, 25b... Magnetic pole, 40
...Sending and receiving storage block, 42, 28a, 28b.
...Cooling water amount (12) Figure 1 House 3 Figure 4 Hitachi Research Institute, Hitachi, Ltd., 3-1-1 Saiwai-cho, Hitachi City number 1

Claims (1)

[Claims] 1. An excitation coil that is wound with the material to be inspected inside and is fully exposed to direct current voltage, and mechanical strain is produced on the surface of the material to be inspected on which the magnetic field from the excitation coil is acting. The excitation coil consists of a transmitting coil for detecting that the mechanical strain is propagated throughout the interior of the test object and detecting that it has formed on the surface of the test material. Surrounded by iron, a magnetic pole is disposed on the surface of the coil facing the test material and supported by the yoke, and the transmitting coil or receiving coil is supported by the magnetic pole. An electromagnetic ultrasonic measuring device characterized by: 2. The electromagnetic ultrasonic measuring device according to item 1, wherein the magnetic pole is replaced depending on the size of the material to be tested. 3. The electromagnetic ultrasonic measuring device according to item 1, further comprising piping for cooling the magnetic pole, the transmitting coil, or the receiving coil with water. 4. The electromagnetic ultrasonic measuring device according to item 1, wherein at least one side of the magnetic pole has a tapered surface with respect to the insertion direction of the test material. 5. The electromagnetic ultrasonic meter 611] device according to item 1, characterized in that a plurality of sets of transmitting coils and receiving coils are arranged around the specimen. 6. The electromagnetic ultrasonic measuring device according to item 1, characterized in that a retention cover made of a non-conductive material is placed between the transmitting coil and the receiving coil facing the test material.