WO2005114165A1

WO2005114165A1 - Eddy current flaw inspecting probe and eddy current flaw inspecting apparatus

Info

Publication number: WO2005114165A1
Application number: PCT/JP2005/009282
Authority: WO
Inventors: Hiroshi Hoshikawa; Kiyoshi Koyama
Original assignee: Nihon University
Priority date: 2004-05-21
Filing date: 2005-05-20
Publication date: 2005-12-01
Also published as: JPWO2005114165A1

Abstract

An eddy current flaw inspecting probe (MP) for inspecting flaws on an inspecting object is composed of one rectangular inspecting coil (C1) and four pancake-shaped magnetizing coils (C21-C24). The inspecting coil (C1) and the magnetizing coils (C21-C24) are arranged to orthogonally intersect. The magnetizing coils (C21-C24) are arranged in an inspecting coil (C1). The eddy current flaw inspecting device (MP) is arranged on an inspecting object (T) so as to have the inspecting coil (C1) vertical to the inspecting object (T) and the magnetizing coils (C21-C24) parallel to the inspecting object (T). A magnetizing signal is applied on the magnetizing coils (C21-C24) through subsequent switching so as to evade interference.

Description

Eddy current inspection probe and eddy current inspection device

Technical field

The present invention relates to an eddy current flaw detection probe in which a quadrangle, triangular or other polygonal detection coil and an excitation coil are arranged orthogonal to each other, and an eddy current flaw detector equipped with the eddy current flaw detection probe.

Here, an eddy current flaw detection probe in which a quadrangular, triangular, or other polygonal detection coil and an excitation coil are arranged orthogonally is generally referred to as a probe.

This application claims priority based on Japanese Patent Application No. 2004-151469 filed on May 21, 2004 in Japan, and this application is incorporated herein by reference. Incorporated.

Background art

[0002] Conventionally, as this kind of eddy current flaw detection probe, Japanese Patent Application Laid-Open No. 2003-344361, "Summary of Lectures for the Fall Meeting of 2001," pp. 153 to 154, October 2, 2001, Japan Published by the Non-Destructive Inspection Association.

As shown in FIGS.1A to 1C, the eddy current flaw detection probe P includes a pancake-shaped excitation coil Ce and a rectangular detection coil Cd, and the detection coil Cd is arranged in the excitation coil Ce. The excitation coil Ce and the detection coil Cd are arranged so that the coil surfaces of both coils are orthogonal. As shown in FIG.1A, the eddy current flaw detection probe P has a coil surface of the exciting coil Ce parallel to an inspection surface of the inspection object T on an inspection object T such as a metal plate, and as shown in FIG. The detection coil is installed so that the coil surface of Cd is perpendicular to the inspection surface. As shown in FIG. 1B, the eddy current inspection probe P is placed on the test object T so that the detection coil Cd is parallel to the defect F of the test object T, and the Y is perpendicular to the longitudinal direction of the defect F. Flaw detection by scanning in the direction. Here, the coil surfaces of the excitation coil and the detection coil refer to surfaces surrounded by windings constituting both coils.

The conventional eddy current flaw detection probe P shown in FIGS. 1A to 1C is basically a lift-off noise, that is, noise caused by a change in the distance between the eddy current flaw detection probe and the test object, as described later. The detection coil Cd that does not generate a flaw detection signal that is a detection signal only when the test object T has a flaw F, does not generate a flaw detection signal when there is no flaw F. As described above, the conventional eddy current flaw detection probe P has excellent flaw detection characteristics, but since the detection coil Cd is disposed in the excitation coil Ce, the length of the detection coil Cd, that is, The length or width of the coil surface of the detection coil Cd in the direction parallel to the coil surface of the excitation coil Ce is shorter than the inner diameter of the excitation coil Ce. Therefore, as a result of the experiment of the present invention and the like, when the depth of the flaw F of the test object T is small, the conventional eddy current flaw detection probe P has the output level power of the flaw detection signal detected by the detection coil Cd, It became difficult, and it was difficult to perform high-precision flaw detection and evaluation. As shown in FIG. 1B, the eddy current flaw detection probe P described above can detect flaws F parallel to the detection coil Cd, but flaws perpendicular to the detection coil Cd were difficult to detect. In addition, the eddy current flaw detection probe proposed so far has only one excitation coil and one detection coil. In the case of an inspection object with a wide flaw detection range, such as in the above, it takes a long time for flaw detection. As a method of improving this point, a method of arranging a plurality of eddy current inspection probes P in a line and scanning at the same time can be considered.In this case, in order to avoid interference between the eddy current inspection probes P, eddy current inspection It is necessary to sequentially switch and drive the probe P, and the switching mechanism becomes complicated. In addition, it is necessary to accurately adjust the positional relationship between a large number of eddy current detection probes P, which makes assembly difficult.

Disclosure of the invention

Problems to be solved by the invention

In view of the above-mentioned problems of the conventional eddy current flaw detection probe, the present invention can detect flaws shallow without impairing the excellent flaw detection characteristics of the conventional eddy current flaw detection probe, and flaws perpendicular to the detection coil with high sensitivity. Another object of the present invention is to provide an eddy current inspection probe capable of detecting a wide range of flaws in one scan.

An eddy current flaw detection probe according to the present invention has a plurality of polygonal detection coils and an excitation coil arranged in the detection coils, and the detection coils and the excitation coils are arranged such that their coil surfaces cross each other. It is arranged.

In the eddy current inspection probe according to the present invention, the detection coil is longer than the excitation coil. It is desirable.

Further, it is desirable that the exciting coil has a pancake shape and that the detecting coil has a rectangular shape.

In the eddy current inspection probe according to the present invention, it is preferable that two or more excitation coils are arranged in parallel along the winding of the detection coil.

The eddy current flaw detector according to the present invention is arranged such that two or more excitation coils are arranged side by side along a winding of the detection coil in one polygonal detection coil, and the detection coil and the excitation coil are connected to each other. An eddy current flaw detection probe that is arranged so as to intersect each other's coil surface, an excitation signal generator that sequentially switches to two or more excitation coils to apply excitation signals, and detects a flaw detection signal from the detection coil And a flaw detection evaluation section for flaw detection and evaluation of flaws on the test object.

In the eddy current inspection probe according to the present invention, the excitation coil is arranged in a detection coil having a polygonal shape such as a square or a triangle, and the detection coil is made longer than the excitation coil. In addition, flaws can be detected and evaluated with high sensitivity and high accuracy for the presence, position and depth of flaws.

Further, in the eddy current inspection probe according to the present invention, since a plurality of excitation coils are arranged in parallel within one polygonal detection coil, the range that can be inspected by one scan is widened. Since the eddy current inspection probe according to the present invention sequentially drives a plurality of excitation coils, it is possible to identify the excitation coil in which the inspection signal is generated, and to identify the position of the flaw of the inspection object.

Furthermore, in the eddy current flaw detection probe according to the present invention, since one detection coil may be provided for a plurality of excitation coils, there is no need to switch the detection coil in accordance with the switching of the excitation coil. Therefore, there is no need to provide means for switching the detection coil.

Furthermore, the eddy current flaw detection probe according to the present invention requires only one detection coil to be disposed for a plurality of excitation coils, so that the structure is simplified and the assembly is facilitated. The eddy current flaw detection probe according to Since the phase of the flaw detection signal changes according to the depth of the flaw of the test object without being affected by the lift-off noise, the flaw depth can be evaluated based on the phase of the flaw detection signal. Still other objects of the present invention and advantages obtained by the present invention will become more apparent from the embodiments described below with reference to the drawings.

Brief Description of Drawings

FIG. 1A is a side view showing a conventional eddy current flaw detection probe, FIG. 1B is a plan view of the eddy current flaw detection probe, and FIG. 1C is a cross-sectional view taken along line AA of FIG. 1A.

FIG. 2 is a side view showing an embodiment of a multi-probe to which the present invention is applied.

FIG. 3 is a plan view of the multi-probe shown in FIG. 2.

FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG.

FIG. 5 is a perspective view showing a detection coil.

FIG. 6 is a perspective view showing an exciting coil.

FIG. 7 is a block diagram showing an eddy current flaw detector using the multi-probe according to the present invention.

[FIG. 8] FIG. 8 is a plan view showing a state where an inspection object is scanned by a multi-probe.

[FIG. 9] FIG. 9A is a plan view showing a state where a multi-Θ probe is placed on a test object, and FIG. 9B is a plan view of the test object showing a state of eddy current generated when the test object has no scratches. FIG. 9C is a plan view of the test object showing a state of an eddy current generated when the test object has a flaw.

[FIG. 10] FIG. 10A is a plan view showing a state in which a multi-Θ probe is scanned to detect a flaw parallel to the detection coil and the detection coil is in front of the flaw, and FIG. 10B is a detection view. FIG. 10C is a plan view showing a state where the coil is located directly above the flaw of the test object, and FIG. 10C is a plan view showing a state immediately after the detection coil has passed through the flaw of the test object.

FIG. 11A is a diagram showing a signal pattern of a flaw detection signal generated when the multi-probe according to the present invention scans an inspection object having a horizontal flaw in a detection coil, and FIG. Eddy current probe scans over test object with horizontal scratch on detection coil FIG. 6 is a diagram showing a signal pattern of a flaw detection signal generated when the detection is performed.

FIG. 12 is a diagram showing the relationship between the depth of a flaw and the amplitude of a flaw detection signal in a multi-layer probe to which the present invention is applied and a conventional eddy current flaw detection probe.

[FIG. 13] FIG. 13A is a plan view showing a state in which a multi-Θ probe is scanned to detect flaws perpendicular to the detection coil and the detection coil is in front of the flaw, and FIG. 13B is a detection view. FIG. 13C is a plan view showing a state where the coil is located directly above the flaw of the test object, and FIG. 13C is a plan view showing a state immediately after the detection coil has passed through the flaw of the test object.

FIG. 14A is a diagram showing a signal pattern of a flaw detection signal generated when the multi-beam probe according to the present invention scans an inspection object having a defect perpendicular to the detection coil, and FIG. FIG. 3 is a diagram showing a signal pattern of a flaw detection signal generated when the eddy current flaw detection probe scans an inspection object having a flaw perpendicular to a detection coil.

BEST MODE FOR CARRYING OUT THE INVENTION

The eddy current inspection probe to which the present invention is applied also has one polygonal detection coil and one or more excitation coil forces, and the excitation coils are juxtaposed and juxtaposed within the detection coil along the winding of the detection coil. And both coils are arranged such that the coil planes intersect or cross at right angles. Therefore, the length of the detection coil, that is, the length or width of the coil surface of the detection coil in a direction parallel to the coil surface of the excitation coil, is at least one of the excitation coil lengths in the length direction of the detection coil. It is longer than the length or width of the coil surface of the exciting coil over the entire surface. When the exciting coil has a pancake shape, the width of the coil surface of the exciting coil is the outer diameter of the exciting coil.

Here, an eddy current inspection probe in which one or more excitation coils are arranged within one polygonal detection coil and both coils are arranged so as to intersect or intersect the coil surface is hereinafter referred to as a multi- マルチ probe.

Hereinafter, embodiments of an eddy current inspection probe and a multi-probe to which the present invention is applied will be described with reference to the drawings.

In some embodiments described below, common reference numerals are used for description. As shown in FIGS. 2, 3, and 4, a multi-probe MP according to an embodiment of the present invention includes a rectangular detection coil C1 and pancake-like excitation coils C21 to C24. The multi-probe MP to which the present invention is applied, specifically, as shown in FIGS. 2 and 3, includes four excitations C21 to C24 and one detection coil C1, and the excitation coils C21 to C24 are It is located in the detection coil C1 and is arranged in parallel along the winding of the detection coil C1. The four excitation coils C21 to C24 and the detection coil C1 are arranged so that the coil surfaces intersect or intersect at right angles, as shown in FIGS. Here, the detection coil C1 is formed in a long rectangular shape as shown in FIG. 5, and the excitation coils C21 to C24 are formed in a ring shape as shown in FIG.

The detection coil C1 has four exciting coils C21 to C24 arranged in parallel, and is formed in a rectangular shape having a length C1L in which one side force also extends to the other side. Contrary to the arrangement, as shown in FIGS. 2 and 3, the four excitations C21 to C24 arranged in parallel are formed in a size large enough to be arranged inside.

Therefore, the length C1L of the detection coil C1 is formed longer than the outer diameter of at least one exciting coil, and is not limited to the inner diameter of the exciting coil as in the conventional eddy current testing probe described above. Can be set to length.

Here, the length C1L of the detection coil C1 is the length or width of the coil surface in a direction parallel to the coil surfaces of the excitation coils C21 to C24, and the length or width of the excitation coils C21 to C24 is This is the length of the coil surface in the length direction of the detection coil C1, or the outer diameter of the excitation coils C21 to C24.

As shown in Fig. 4, the multi-Θ probe MP is installed in a so-called vertical position where the coil surface of the detection coil C1 is perpendicular to the inspection surface of the inspection object T, and the coil surfaces of the excitation coils C21 to C24 are As shown in FIG. 2, it is arranged on the inspection object T so as to be parallel to the inspection surface of the inspection object T.

Although the multi-Θ probe MP shown in FIGS. 2 to 4 has been described with an example in which four excitation coils are arranged, one or more probes may be used. When one excitation coil is used, the range that can be detected by one scan of the multi-probe MP is narrow !, but shallow! It does not change whether the number is one or more.

Next, an eddy current flaw detector using the multi-probe according to the present invention will be described. As shown in FIG. 7, the eddy current flaw detection device includes an excitation signal generation unit 11 and a flaw detection evaluation unit 12.

The excitation signal generator 11 constituting the eddy current flaw detector applies excitation signals to the four excitation coils C21 to C24 of the multi-probe MP sequentially, for example, in the order of C21, C22, C23, and C24. Since the excitation coils C21 to C24 are arranged close to each other, if excitation signals are applied to the adjacent excitation coils C21 to C24 at the same time, interference occurs. In order to avoid the interference, excitation signals are sequentially applied to each of the excitation coils C21 to C24 with a time lag. When an excitation signal is applied to the excitation coils C21 to C24, an eddy current is generated in the test object T corresponding to each excitation coil as described later. If the inspection object T has a flaw, an eddy current is generated due to the flaw, and a flaw detection signal is generated in the detection coil C1. The flaw detection evaluation section 12 detects the flaw detection signal generated in the detection coil C1, and flaw-detects and evaluates the presence / absence, position, depth, etc., of the test object T.

Instead of applying excitation signals one by one in the order of C21, C22, C23, and C24, for example, the excitation coils C21 to C24 are divided into two groups every other excitation coil C21 to C24, and the excitation signals are grouped. May be configured so that excitation signals are applied in group units by switching the supply lines. The number of groups of the exciting coils is not limited to two, and may be further increased. When the excitation coils are divided into groups, the excitation signal generation unit 11 has a small number of switching switches for the excitation coils, thereby simplifying the configuration.

Since the multi-Θ probe MP has only one detection coil C1, it is not necessary to provide a detection coil switching switch in the flaw detection evaluation unit 12. Therefore, the configuration of the flaw detection evaluation unit 12 is simpler than a configuration in which a plurality of conventional eddy current flaw detection probes are arranged in parallel.

The multi-probe MP to which the present invention is applied scans along the inspection surface of the inspection object T in the direction of the arrow X perpendicular to the flaw F as shown in FIG. When the multi-Θ probe MP moves over the flaw F of the test object T, when an excitation signal is applied to the exciting coil C22 located above the flaw F, the flaw F is generated around the flaw F as described later. An eddy current is generated, and the eddy current induces a flaw detection signal in the detection coil C1.

When an excitation signal is applied to the four excitation coils C21 to C24, the inspection surface of the inspection object T An eddy current is generated at a position corresponding to the exciting coils C21 to C24. Therefore, the multi-Θ probe MP can detect a range of four exciting coils in one scan.

When the excitation signal is applied by sequentially switching to the excitation coils C21 to C24, a flaw detection signal is generated in the detection coil C1 when the excitation signal closest to the flaw F, for example, the excitation signal is applied to the excitation coil C22. Therefore, the position of the flaw can be specified by specifying any one of the excitation coils C21 to C24 when the flaw detection signal is generated.

Here, the state of the eddy current generated in the test object T by the multi- マルチ probe MP is shown in FIGS. 9A to 9C.

9A shows a state where the multi-Θ probe MP is placed on the specimen T, FIG. 9B shows an eddy current when the specimen T has no flaw, and FIG. 9C shows a state where the specimen T has flaw. It shows the eddy current in the case. Note that only one excitation coil is shown.

As shown in FIG. 9A, when the multi-Θ probe MP is placed on the test object T and an excitation signal (excitation current) is supplied to the excitation coil C21, if the test object T has no flaw, FIG. As shown in (1), an eddy current I is generated and flows along the winding of the exciting coil C21. On the other hand, when the specimen T has a flaw, as shown in FIG. 9C, the eddy currents i, i, i, i, i

1 2 3 occurs. The eddy current generated due to the flaw F is on both sides of the flaw F (Fig. 9C).

Four

The eddy currents, which are widely distributed on both sides of the top and bottom and the ends of the flaw F, contribute most to the generation of the flaw detection signal, and are the eddy currents i, i, i, i generated around the flaw F.

1 2 3 4

When there is no flaw in the inspection object T, no signal is induced in the detection coil C1 because there is no eddy current flowing along the winding of the detection coil C1 as shown in Fig. 9Β. That is, if there is no flaw in the inspection body 傷, no flaw detection signal is generated. On the other hand, when the specimen F has a flaw F, as shown in FIG. 9C, a flaw detection signal is induced to the detection coil CI by the eddy currents i and i.

1 2

Wake up. That is, when the inspection object T has the flaw F, a flaw detection signal is generated.

If there is no flaw in the test object T, no signal is induced in the detection coil C1. Therefore, during the scanning of the multi-probe MP, the distance between the multi-probe MP and the test object T ( Does not cause lift-off noise. The same applies to the other excitation coils C22 to C24.

10A to 10C show an example of detecting a flaw parallel to the detection coil. The specimen T Is not shown. The eddy currents i, i, i, i shown in FIGS.10A to 10C are shown in FIG.

1 2 3 4

Eddy currents i, i, i, i

Same as 1 2 3 4.

FIG. 10A shows a state in which the multi-probe MP scans the test object T (not shown) in the direction of the arrow X, and the detection coil C1 is in front of the flaw F.

When an excitation signal is applied to the excitation coil, eddy currents i, i, i, i are generated around the wound F.

1 2 3 4

Therefore, a signal is induced in the detection coil C1 by the eddy currents i, i. In that case, the eddy current i

1 2 1

, i flow in opposite directions, so the detection coil C1 is induced by both currents.

2

Signal (differential signal) is generated. That is, a flaw detection signal is generated. The flaw detection signal increases as the detection coil C1 approaches the flaw F, and becomes maximum at the position where the detection coil C1 comes closest to the flaw F of the test object T as shown in FIG. 10A. The flaw detection signal is more eddy current i than the signal induced by eddy current i.

Since the signal induced by 2 is larger, the polarity of the flaw detection signal is

Depends on 2.

FIG. 10B shows a state in which the detection coil C1 is located directly above the flaw F of the test object T. When the detection coil C1 is located directly above the flaw F of the test object T, the detection coil is detected by the currents i and i.

1 2

The signals induced in the coil C1 are equal in magnitude but opposite in direction, and are canceled out, so that no detection signal is generated in the detection coil C1.

FIG. 10C shows a state immediately after the detection coil C1 has passed the flaw F of the test object T.

In the case of Fig. 10C, a differential signal (detection signal) is induced in the detection coil C1 by the eddy currents i and i.

1 2

Wake up. As in the case shown in FIG. 1 OA, the detection coil C1 is located closest to the flaw F of the test object T, so that the flaw detection signal becomes maximum. In that case, the signal induced by eddy current i is eddy current i

2, the polarity of the flaw detection signal is

1 and opposite to the flaw detection signal shown in Fig. 10A.

FIG. 11A shows a signal pattern of a flaw detection signal generated when the multi-probe MP scans the inspection object T as shown in FIGS. 10A to 10C described above.

FIG. 11B shows a signal pattern of a flaw detection signal generated when the above-described conventional eddy current flaw detection probe P scans the inspection object T for comparison with the multi-probe of the present invention.

11A and 11B, the horizontal axis shows the flaw detection signal component (unit: V) in phase with the excitation signal. The vertical axis shows the flaw detection signal component (unit: V) whose phase differs from that of the excitation signal by 90 degrees. There are three types of flaw depth: 20%, 60% and 80% of the thickness of the specimen.

Here, the signal pattern whose depth of the flaw is 20% of the thickness of the test object T is indicated by S, the signal pattern of 60% is indicated by S, and the signal pattern of 80% is indicated by S.

twenty three

The signal patterns S 1, S 2, S 3 shown in FIG. 11A and the signal patterns S 1, S 2, S 3 shown in FIG.

Comparing 1 2 3 1 2, the signal patterns S 1, S 2, and S 3 shown in FIG.

3 1 2 3

Like S, S, S, draw a stable 8-character signal pattern for each depth of the

one two Three

The phase changes in accordance with the depth of. That is, since the multi-Θ probe MP does not generate lift-off noise as in the conventional eddy current probe P, the phase of the flaw detection signal changes according to the depth of the flaw without being affected by the lift-off noise. .

The signal patterns S 1, S 2, and S 3 shown in 11 A have a large amplitude even when the scratch is shallow.

one two Three

It is fixed. That is, when the depth of the flaw is 20% of the thickness of the specimen T, the amplitude of the signal pattern S shown in FIG. 11B is a force that rapidly decreases.The change in the amplitude of the signal pattern S shown in FIG. 11A is shown in FIG. 11B. It is smaller than the signal pattern S shown. Therefore, the multi-Θ probe MP to which the present invention is applied can detect flaws with higher sensitivity and higher precision than the conventional eddy current flaw detection probe P even when the scratch is shallow.

Here, the size of the multi-probe MP according to the present invention used for measuring the flaw detection signal pattern is such that the detection coil has a length of 50 mm, a height of 9 mm, a winding cross-sectional area of 1 X lmm ² , and an excitation coil of outer diameter 9 mm, a winding cross-sectional area 1. 5 X 1. 5mm ^2. The specimen used was a 1.5 mm thick brass plate, and the brass plate had slits with a length of 15 mm, a width of 0.5 mm, and a depth of 20%, 40%, 60%, and 80% of the plate thickness. Was formed and scratched. The excitation signal was set to 20 kHz and the lift-off was set to 0.2 mm.

FIG. 12 shows the relationship between the depth of a flaw and the amplitude of a flaw detection signal in a multi-Θ probe MP to which the present invention is applied and a conventional eddy current flaw detection probe P. FIG. 12 shows the peaks of the signal patterns S 1, S 2 and S 3 at the respective depths of the flaws shown in FIGS. 11A and 11B.

one two Three

It is a lot. Note that FIG. 11A and FIG. 1 IB do not show a signal pattern when the depth of the flaw is 40% of the plate thickness.

In FIG. 12, the horizontal axis indicates the depth (%) of the flaw with respect to the plate thickness, and the vertical axis indicates the flaw detection signal. The depth of the flaw with respect to the plate thickness is 80% and the amplitude is normalized.

A comparison of the characteristics of the multi-Θ probe MP shown by the solid line in FIG. 12 with the characteristics of the conventional eddy current inspection probe P shown by the broken line in FIG. 12 shows that if the depth of the flaw is the same, the amplitude of the flaw detection signal is The force of the multi-Θ probe MP according to the invention is larger than that of the conventional eddy current inspection probe P, and becomes larger even when the scratch is shallow. Therefore, the multi-layer probe MP according to the present invention has higher flaw detection sensitivity than the conventional eddy current flaw detection probe P, and can detect and evaluate the presence / absence, position, and depth of flaw even with a shallow flaw with high accuracy. .

13A to 13C show an example of detecting a flaw perpendicular to the detection coil. The test object T is not shown.

Figure 13A shows the multi-Θ probe MP scanned in the direction of the arrow X against the specimen T (not shown).

2

This shows a state in which the detection coil C1 is in front of the flaw F.

When the excitation signal is applied to the excitation coil, the eddy currents i, i, i, i, i

Since 1 2 3 4 is generated, a flaw detection signal is induced in the detection coil C1 by the eddy current i3. The flaw detection signal increases as the detection coil C1 approaches the flaw F, and becomes maximum at the position where the detection coil C1 comes closest to the flaw F as shown in FIG. 13A.

FIG. 13B shows a state where the detection coil C1 is located between the flaws F of the test object T. When the detection coil C1 is located between the flaws F, no flaw detection signal is generated because there is no eddy current flowing along the winding of the detection coil C1. That is, eddy currents i and i

Since 12 flows in a direction orthogonal to the winding of the detection coil C1, it does not contribute to the generation of a flaw detection signal.

FIG. 13C shows a state immediately after the detection coil C1 has passed the flaw F of the test object T.

In the case of FIG. 13C, a flaw detection signal is induced in the detection coil C1 by the eddy current i4. As in the case shown in FIG. 13A, the detection coil C1 is located closest to the flaw F of the test object T, so that the flaw detection signal becomes maximum. Eddy current i

4 indicates that the flowing direction is eddy current i

Because it's the opposite of 3

The polarity of the flaw detection signal is opposite to that of the flaw detection signal shown in FIG. 13A.

FIG. 14A shows a signal pattern of a flaw detection signal generated when the multi-probe MP according to the present invention is scanned on the inspection object T as shown in FIGS. 13A to 13C described above. FIG. 14B shows a signal pattern of a flaw detection signal generated when the above-described conventional eddy current flaw detection probe P scans the inspection object T for comparison with the multi-probe of the present invention. Show.

14A and 14B, the horizontal axis shows the flaw detection signal component (unit V) in phase with the excitation signal, and the vertical axis shows the flaw detection signal component (unit V) 90 degrees out of phase with the excitation signal. There are three types of flaw depth: 20%, 60% and 80% of the thickness of the specimen.

twenty three

Here, the signal patterns S 1, S 2 and S 3 shown in FIG. 14A and the signal patterns S 1 and S 2 shown in FIG.

1 2 3 1

Comparing S 1 and S 2, the signal patterns S 1, S 2 and S 3 shown in FIG.

2 3 1 2 3

However, the signal patterns S, S, and S shown in FIG.

one two Three

A stable 8-character signal pattern is drawn for each depth, and the phase changes according to the depth of the flaw. That is, it is difficult for the conventional eddy current inspection probe P to detect flaws perpendicular to the detection coil, but the multi-Θ probe MP according to the present invention detects flaws perpendicular to the detection coil with high sensitivity and high accuracy. it can.

The excitation coil used in the above-mentioned multi-probe MP and the eddy current inspection device using the multi-probe MP has been described as a pancake-shaped coil, but may be a rectangular or other quadrangular coil. Further, the detection coil is not limited to a rectangular shape, and may be a polygon other than a rectangle, such as a quadrangle or a triangle.

The present invention is not limited to the above-described embodiment described with reference to the drawings.

It will be apparent to those skilled in the art that various modifications, substitutions, or equivalents can be made without departing from the scope of the appended claims and their spirit. Industrial applicability

The eddy current inspection device provided with the eddy current inspection probe according to the present invention can inspect the inspection object for the presence or absence of flaws without contacting the inspection object.

Claims

The scope of the claims

[1] 1. One polygonal detection coil,

An excitation coil disposed in the detection coil,

An eddy current flaw detection probe, wherein the detection coil and the excitation coil are arranged with their coil surfaces crossing each other.

2. The eddy current inspection probe according to claim 1, wherein the detection coil is longer than the excitation coil.

3. The eddy current flaw detection probe according to claim 1, wherein the excitation coil has a pancake shape.

4. The eddy current flaw detection probe according to claim 1, wherein the detection coil has a rectangular shape.

5. The eddy current inspection probe according to claim 1, wherein two or more exciting coils are arranged in parallel along a winding of the detection coil.

[6] 6. Two or more excitation coils are arranged in a polygonal detection coil so as to be juxtaposed along the winding of the detection coil, and the detection coil and the excitation coil are connected to each other. An eddy current probe arranged to intersect the

An excitation signal generator for sequentially switching to the two or more excitation coils and applying an excitation signal;

A flaw detection evaluation unit that detects a flaw detection signal from the detection coil to detect and evaluate flaws on the test object;

An eddy current flaw detection device comprising: