JPH1164294A - Eddy current testing sensor and method for detecting flaw using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recognize a direction and shape of depth of a flaw by forming spiral thin film coils on an insulating film of a sensor board, superposing AC voltages having different frequencies on the respective thin film coils of an eddy current testing sensor covered with a protective film to be applied, and detecting changes of impedances with respect to the respective frequencies. SOLUTION: Thin film coils 1 are formed by forming an insulating film 18 on a sensor board 10, and forming the coils 1 on the film 18 by lithography or the like. Leader wires 2 are connected to the coils 1, and then connected to an eddy current tester 3. AC currents having two frequencies FA1 and FA2 are superposed on the coil 1a and supplied. And, AC currents having two frequencies FB1 and FB2 are superposed on the coil 1b and supplied. The tester 3 senses changes of impedances of the AC currents of the respective frequencies. The current having low frequency brings about a deep eddy current and the current having high frequency brings about a shallow eddy current. Accordingly, if the changes of the impedances with respect to the respective frequencies are detected, not only a direction of a flaw but also a depth of the flaw can be sensed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eddy current detection sensor for non-destructively detecting defects and cracks in component materials of nuclear power equipment and aeronautical equipment.

[0002]

2. Description of the Related Art In an eddy current flaw detection sensor, an electric current is applied to a coil to bring it close to a component material, to form an induced eddy current on the surface of the component material. This is to detect flaws. Eddy current flaw sensors currently on the market are of the probe type using hand-wound work coils, but it is difficult to miniaturize the sensor shape to detect minute defects and mass-produce coils with uniform characteristics. There is such a problem. The applicant of the present application has filed a utility model registration application (Japanese Utility Model Application No. 5-7) to solve the above problem.
567 (filing date: February 26, 1993).

FIGS. 4 to 6 are drawings of the eddy current sensor disclosed in the above application. FIG. 4 is a schematic perspective view of the above-described device, and the surface of the sensor substrate 10 is provided with a flaw detection unit 1 composed of thin-film coils 11 arranged in a zigzag pattern.
2 and a connection cord 13 for connecting to a detection circuit (not shown).

As shown in FIG. 5, a thin-film coil 11 includes an induction current generating coil 14 for generating an eddy current on the surface of a component material and a signal detection coil 15, and the induction current generating coil 14 is formed in a spiral shape. The signal detection coil 15 is
It is formed in a ring shape so as to be located on the outer periphery of the induced current generating coil 14, and extraction electrodes 16 and 17 are integrally connected to ends of the coils 14 and 15, respectively.

As shown in FIG. 6, the thin-film coil 11 is formed by first forming an insulating film 18 of, for example, SiO ₂ on the sensor substrate 10, and forming an induction current generating coil 14 and a signal on the insulating film 18. Thin-film coil 1 consisting of detection coil 15
1 and the extraction electrodes 16 and 17 are formed by lithography or the like.
In this case, the extraction electrode 1 inside the induction current generating coil 14
6a intersects the induction current generating coil 14, so that an insulating layer 18a is interposed therebetween so that the two do not come into contact with each other.

After the thin-film coil 11 and the extraction electrodes 16 and 17 are formed, they are covered with a protective film 19 made of an insulating material such as SiO ₂ . Lead wires 20 are connected to the extraction electrodes 16 and 17.
Are connected, and the lead wire 20 is connected to the connection cord 13 shown in FIG. In this case, the lead wire 20 is provided so as to pass through the inside of the sensor substrate 10 although not shown in the drawing.

[0007]

The eddy current sensor described above is effective in detecting the presence or absence of a flaw because the shape of the flaw detection unit is circular. It was difficult to recognize the depth).

The present invention has been devised in view of the above-mentioned problems of the prior art, and an eddy current flaw detection sensor capable of recognizing not only the presence or absence of a flaw but also the shape and direction of a flaw and a flaw detection using the same The aim is to provide a method.

[0009]

In order to achieve the above object, in the eddy current flaw detection sensor according to the first aspect of the present invention, a spiral thin film coil is formed on an insulating film of a sensor substrate, and the thin film coil is covered with a protective film. An eddy-current flaw detection sensor comprising two thin-film coils formed in a rectangular or elliptical shape and laminated such that their longitudinal directions are substantially orthogonal to each other.

The eddy current detection sensor preferably has a size of about 5 mm square.

A plurality of the eddy current detection sensors may be arranged in a straight line or in a staggered manner to form a flaw detection probe.

Further, in the flaw detection method using the eddy current flaw detection sensor according to the second invention of the present application, the eddy current flaw detection sensor is connected to an eddy current flaw detector, and an AC voltage having a different frequency is superimposed and applied to each thin-film coil. The flaw detection is performed by detecting a change in impedance or a change in electromotive force at the frequency of.

Next, the operation of the present invention will be described. Since the spiral thin film coil is formed in a rectangular or elliptical shape,
The eddy current generated on the surface of the test object also becomes rectangular or elliptical. In that case, the flaws parallel to the longitudinal direction of the eddy current do not affect the eddy current, and thus are hardly detected, whereas the flaws perpendicular to the longitudinal direction have a large effect on the eddy current, and are clearly detected. In the present invention, the thin-film coils are formed by laminating them so that their longitudinal directions are orthogonal to each other, so that any one of the thin-film coils can detect a flaw in any direction, and thereby the direction of the flaw is also reduced. Recognize.

It is known that the skin effect of the AC voltage applied to the thin-film coil depends on the frequency. That is, a low-frequency alternating current causes a deep eddy current in the device under test, and a high-frequency alternating current causes a shallow eddy current in the device under test. Therefore, the depth of the flaw can be detected by applying an AC voltage having a different frequency to the thin-film coil and detecting a change in impedance or a change in electromotive force at each frequency.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a drawing of the eddy current detection sensor of the present invention, FIG. 1 (A) is a plan view, and FIG. 1 (B) is a cross-sectional view taken along line BB of FIG. 1 (A). In these figures, the same parts as those described with reference to FIGS. 3 to 5 are denoted by the same reference numerals, and redundant description will be omitted. In FIG. 1, reference numeral 1 denotes a rectangular thin-film coil, which is formed by laminating a thin-film coil 1b on a thin-film coil 1a so that their longitudinal directions are substantially orthogonal to each other. The thin-film coil 1 is formed by forming an insulating film 18 of, for example, SiO ₂ on the sensor substrate 10 and applying the high aspect ratio processing technology to the thin-film coil 1 on the insulating film 18 by lithography or the like. I do. The thin-film coil 1 has, for example, a wire having a width of about 50 μm and a thickness of about 1 μm, and has a DC resistance of about 5Ω and a reactance of about 50Ω. It is preferable that the thin film coil 1 has a size of about 5 mm square.

A lead wire 2 is connected to the thin film coil 1 and is connected to an eddy current flaw detector 3. The eddy current flaw detector 3 has an oscillator 3a. An AC current having two different frequencies FA1 and FA2 is superimposed and flows through the thin film coil 1a, and two different frequencies FB1 and FB2 are flown through the thin film coil 1b. Are superimposed and flow. The eddy current flaw detector 3 detects a change in impedance with respect to an alternating current of each frequency, and has various principles. For example, there is an eddy current flaw detector having a circuit shown in FIG.

In general, the signal generated by a flaw changes abruptly, but many of the signals generated by factors other than the flaw often change moderately. Therefore, by adjusting the response speed of the auto-balancing device, it is not possible to follow a sudden change, but to select a speed that responds only to a gentle change, thereby removing unnecessary factors and facilitating defect detection. be able to.

FIG. 2 shows the most basic circuit. The automatic balancer detects the signal of the amplifier by the detection circuit, and operates the servomotors Mx and My according to the signal from the detection circuit.
It automatically removes the imbalance of the bridge to mild changes.

Next, the operation of the present embodiment will be described. FIG. 3 shows an eddy current generated on the surface of the component material by the thin film coil 1. 4 indicates an eddy current, and X and Y indicate flaws. The eddy current 4 has a shape similar to that of the thin-film coil 1. Since the thin-film coil 1 has a rectangular or elliptical shape, the eddy current 4 also has a rectangular or elliptical anisotropic shape. I have. Therefore, as shown by X in FIG. 3, when the flaw is oriented in a direction perpendicular to the longitudinal direction, the eddy current 4 has a large effect, so that the flaw appears on the eddy current flaw detector 3 as a change in impedance and the length of the flaw is reduced. Can be detected and the scratch is Y
As shown in (1), when it is parallel to the longitudinal direction, there is almost no effect on the eddy current 4, and therefore, no change in impedance appears in the eddy current flaw detector 3, so that the presence of a flaw cannot be detected. In the present invention, since the thin-film coils 1a and 1b are formed by lamination so that the longitudinal directions are orthogonal to each other, the length of the flaw X is detected by the eddy current flaw detector 3 connected to the thin-film coil 1a. Since the length of the flaw Y is detected by the eddy current flaw detector 3 connected to the thin film coil 1b, a flaw in any direction can be detected by either of them. Further, since the oblique scratch appears as a change in the impedance of both the thin film coils 1a and 1b, it can be seen that the oblique scratch is oblique.

The alternating current applied to the thin-film coils 1a and 1b has a low frequency (FA1 or FB1) and a high frequency (FA2
Or FB2) is applied in a superimposed manner. In general, a low-frequency alternating current causes a deep eddy current 4 in the device under test, and a high-frequency alternating current causes a shallow eddy current 4 in the device under test. For example, the depths of the flaws X and Y can be detected.

The present invention is not limited to the embodiment described above, and various changes can be made without departing from the gist of the invention. For example, the thin-film coil 1 has been described as having the excitation coil and the detection coil integrated with each other, but may be formed separately as shown in FIG. In this case, a change in the electromotive force of the detection coil may be detected. In addition, one eddy current detection sensor may be provided in the probe, but a large number may be arranged in a staggered manner as shown in FIG. By using such a probe, a long flaw can be detected at once. Furthermore, they may be arranged in a straight line instead of in a staggered manner.

[0022]

As described above, the eddy current flaw detection sensor according to the present invention has the anisotropic thin-film coils stacked so that their longitudinal directions are orthogonal to each other, so that the direction and length of the flaw can be detected. In the flaw detection method of the present invention, alternating currents of different frequencies are applied to the thin-film coil to detect a change in impedance for each frequency, so that not only the direction of the flaw but also the depth of the flaw is detected. It has excellent effects such as being able to.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an eddy current detection sensor according to the present invention;
(A) is a plan view, and (B) is a cross-sectional view taken along the line BB of (A).

FIG. 2 is a circuit diagram of the eddy current flaw detector.

FIG. 3 is an explanatory diagram of an eddy current.

FIG. 4 is a perspective view of a conventional eddy current sensor.

FIG. 5 is a plan view of a conventional eddy current sensor.

FIG. 6 is a sectional view of a conventional eddy current sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thin-film coil 3 Eddy current flaw detector 10 Sensor board 18 Insulating film 19 Protective film

Claims (4)

[Claims] An eddy current flaw detection sensor in which a spiral thin film coil is formed on an insulating film of a sensor substrate and the thin film coil is covered with a protective film, wherein two rectangular or elliptical shapes are formed. An eddy current flaw detection sensor comprising thin-film coils stacked so that their longitudinal directions are substantially orthogonal to each other. 2. The eddy current detection sensor according to claim 1, wherein the eddy current detection sensor has a size of about 5 mm square. 3. The eddy current detection sensor according to claim 1, wherein a plurality of the eddy current detection sensors are arranged in a linear or staggered arrangement. 4. The eddy current flaw detection sensor is connected to an eddy current flaw detector, an AC voltage having a different frequency is superimposed and applied to each thin-film coil, and a change in impedance or a change in electromotive force is detected for each frequency. A flaw detection method using an eddy current flaw detection sensor, which performs flaw detection.