JPH102883A - Eddy current flaw detection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily sense the direction of defects existing in an objective metal to be inspected, obtain a large quantity of information of the defects, and make it possible to repair precisely and remarkably shorten the repairing time. SOLUTION: A probe comprises two detection coils 2, 3 installed at right angles to each other and an excitation coil 103 installed at 45 deg. to respective coils 2, 3. The signal of the voltage difference induced by respective detection coils 2, 3 is processed by a flaw detection apparatus 120 and when the detection coils 2, 3 and the excitation coil 103 are placed on a sound part of an objective metal 110 to be inspected, the effect of the eddy current generated in the metal affects evenly the two detection coils 2, 3 and no signal is generated and the direction of a defect can be therefore detected based on generation of signals different depending on the direction of the defect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eddy current testing device for checking the soundness of, for example, a flat metal plate.

[0002]

2. Description of the Related Art Generally, an eddy current flaw detector is used to determine the presence or absence of a defect near the surface of a metal object such as a metal flat plate and to confirm its soundness. As shown in FIG. 5, this conventional eddy current flaw detector uses a flaw detector including a detection coil 101, a dummy coil 102, and an excitation coil 103, a flaw detector 120 having a display screen 121, and a connection cable 130 connecting between them. It is configured.

FIG. 6 shows an electrical connection state of the eddy current flaw detector having such a configuration. This eddy current flaw detector is
The presence or absence of a defect near the surface of the metal object is determined, and is used for confirming the soundness. 5 and 6, reference numeral 110 denotes a target metal to be tested, 111 denotes a defect near the surface of the target metal, 131 denotes a magnetic field generated by the exciting coil 103,
Reference numeral 132 denotes an eddy current flowing in the metal body due to a magnetic field 131 generated by the exciting coil 103, 133 denotes a magnetic field generated by the eddy current 132, and 141 denotes an oscillator built in the flaw detector 120.

A connection cable 130 is connected to the exciting coil 103.
, An alternating current having a constant amplitude and a constant frequency flows from the oscillator 141. When an alternating current flows through the exciting coil 103, the magnetic field 13
1 occurs. This magnetic field 131 is applied to the detection coil 101,
An eddy current 132 is generated in the test object metal 110 by interlinking with the dummy coil 102 and the test object metal 110. This eddy current 132 is generated when the metal 110 is healthy.
It occurs concentrically with 03. The eddy current 132 also generates a magnetic field 133, and this magnetic field 133 is also generated by the detection coil 1
Link with 01.

When the alternating magnetic fields 131 and 133 are linked to the detection coil 101, the detection coil 1
At 01, an AC voltage is induced. Since the alternating magnetic field 131 interlinks with the dummy coil 102, an alternating voltage is also induced in the dummy coil 102.

[0006] Detection coil 101 and dummy coil 102
Constitutes a bridge circuit inside the flaw detector 120, so that when the flaw detector is in a healthy part of the subject metal 110, the voltages induced in the detection coil 101 and the dummy coil 102 cancel each other out so that no output is generated. Adjusted.

The arrow 151 in FIG. 5 indicates the scanning direction X of the flaw detector, and the arrow 152 indicates the scanning direction Y of the flaw detector.
The flaw detector is scanned on the surface of the subject in the directions of these arrows X and Y to detect the flaw of the subject metal 110.

When the defect 111 exists in the metal 110 to be inspected, the flow of the eddy current 132 changes as compared with the case where there is no defect. At this time, the magnetic field 13 generated by the eddy current 132
3 also changes as compared with the case where there is no defect, the voltage induced in the detection coil 101 also changes, and this change in the voltage is processed by the flaw detector 120 and displayed on the screen 121 of the flaw detector 120. When actually applied, the flaw detector is connected to the object metal 11.
The surface 0 is scanned in the directions of arrows 151 and 152, and a signal waveform 123 appearing on the screen 121 of the flaw detector 120 at this time, that is, a signal waveform 123 obtained by processing a voltage induced in the detection coil 101 is observed. Flaw detector is object metal 1
10, the voltage induced in the detection coil 101 and the dummy coil 102 is adjusted so as to cancel each other out, so that the signal waveform 123 on the screen 121 of the flaw detector 120 has a dot. And it is determined that there is no defect.

Therefore, the screen 121 of the flaw detector 120 is moved while the flaw detector is moved on the test object metal 110 as described above.
By observing, the presence or absence of a defect can be determined, and the soundness of the test metal 110 can be known.

[0010]

However, in the above-described flaw detector using the conventional flaw detector, since the eddy current in the metal to be tested flows concentrically with the exciting coil of the flaw detector, a signal due to the defect is not detected. There is a problem that the defect occurs regardless of the direction and the direction of the defect is not known.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can easily detect the direction of a defect existing in a metal to be inspected, and can obtain a great deal of information on the defect, thereby enabling accurate repair. It is an object of the present invention to provide an eddy current flaw detector capable of greatly shortening the period.

[0012]

An eddy current flaw detector according to the present invention comprises two detection coils provided orthogonally to each other;
A flaw detector having an excitation coil provided at an angle of 45 ° with respect to each of them, and a flaw detector that generates a signal by performing signal processing on a voltage difference induced by each of the detection coils. When the detection coil and the excitation coil are placed in a healthy part of the test object metal, the influence of the eddy current in the metal acts equally on the two detection coils and no signal is generated, and the direction of the defect is not detected. Therefore, the direction of the defect can be known by generating different signals.

(Operation) An excitation coil is provided at an angle of 45 ° to each of the two detection coils provided orthogonal to each other as described above, and generated by the excitation coil in the subject metal. Eddy currents are generated equally in the two detection coils, and when there is no defect, the induced voltages of the two detection coils become equal. When there is a defect, the detection is affected by the direction of the defect. Since the coils are limited and the flaw detector is configured to output the difference between the detection coils, the direction of the defect can be detected by the polarity of the signal.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an eddy current inspection device according to an embodiment of the present invention. In FIG. 1, 10
Reference numeral 3 denotes an exciting coil of a flaw detector formed in a rectangular shape, for example.
An alternating current from the flaw detector 120 generates an alternating magnetic field. Outside the excitation coil 103, for example, a first detection coil 2 and a second detection coil 3 formed in a rectangular shape are arranged so as to be orthogonal to each other. In this case, the excitation coil 103 includes the first detection coil 2 and the second detection coil 3
Are set to be at an angle of 45 ° with respect to each of. The flaw detector configured as described above is connected to the flaw detector 120 via the cable 130. The first detection coil 2 and the second detection coil 3 include an excitation coil 1
The induced voltage changes due to the change in the magnetic field and the like due to the change in the magnetic field 03 and the eddy current in the test object metal 110. The change in the induced voltage of the detection coils 2 and 3 is processed by the internal circuit of the flaw detector 120 in the same manner as the conventional one, and
The signal waveform 52 is displayed on the screen 121 of FIG. An arrow 151 indicates the scanning direction X of the flaw detector, and an arrow 152 indicates the scanning direction Y of the flaw detector.

Next, the operation of the above embodiment will be described with reference to FIGS. 2, 3 and 4. FIG. 2 is a diagram for explaining the operation of the flaw detector according to the present invention. FIG. 3 is a diagram for explaining a signal waveform when there is no defect of the flaw detector according to the present invention. Reference numeral 125 denotes a signal waveform when there is no defect observed on the screen 121 of the flaw detector 120. FIG. 4 is a diagram for explaining the direction of the defect and the direction of the signal waveform.
Reference numeral 126 denotes a signal waveform when the first detection coil 2 crosses a defect in a direction parallel to the coil 2 and FIG.
Reference numeral 127 indicates a signal waveform when the second detection coil 3 crosses a defect in a direction parallel to the coil 3.

FIG. 2 explains how the flow of the eddy current 132 flowing in the test metal 110 changes depending on the direction of the defect 111. FIG. 2A illustrates how an eddy current flows when a flaw detector is present on a healthy (no defect) metal body. When the flaw detector is on a healthy metal body, the eddy current 132 tends to flow immediately below the excitation coil 103 in parallel with the excitation coil 103, and as shown in FIG. Flows symmetrically around the center. Since the exciting coil 103 is provided at 45 ° with the first detection coil 2 and the second detection coil 3, the magnetic field generated by the eddy current 132 is equal to the first detection coil 2 and the second detection coil 3.
Acts on the detection coil 2 and the second detection coil 3 in the same manner, and generates the same induced voltage. On the other hand, as described above, the inside of the flaw detector 120 performs signal processing on the difference between the voltages induced in the two detection coils 2 and 3. Therefore, when the flaw detector is on a healthy metal body, the two Since the voltages induced by the detection coils 2 and 3 are the same, nothing is generated as the output of the flaw detector 120, and no vibration occurs in the screen 121 of the flaw detector as shown by the signal waveform 125 in FIG.

FIG. 2B shows the first detection coil 2 and the defect 1
11 is a diagram showing a case where the directions coincide with each other (excitation coil omitted), and when the flaw detector is on a defect 111 in a direction parallel to the first detection coil 2, the eddy current 132 in the metal body is , Does not flow across the defect, as shown
A component flowing in parallel with the detection coil 2 is generated. The magnetic field generated by the eddy current flowing in parallel with the first detection coil 2 acts only on the detection coil 2 and does not act on the second detection coil 3. For this reason, a difference occurs between the voltages induced by the respective detection coils 2 and 3, and a defect 11 parallel to the first detection coil 2 is generated.
When a flaw detector is scanned over the flaw detector 1, the flaw detector 120 processes the flaw detector 120 to output the difference between the induced voltages of the respective detection coils 2 and 3, and as shown in FIG. A signal waveform 126 having a shake therein is displayed.

FIG. 2C shows the second detection coil 3 and the defect 1
11 is a diagram showing a case where the directions coincide with each other (excitation coil is omitted), but when the flaw detector is on a defect 111 in a direction parallel to the second detection coil 3, eddy currents in the metal body The component 132 does not flow across the defect 111, but generates a component flowing in parallel with the second detection coil 3 as shown in the figure. The magnetic field generated by the eddy current flowing in parallel with the second detection coil 3 acts only on the second detection coil 3 and does not act on the first detection coil 2, contrary to FIG. That is, a difference occurs between the voltages induced by the respective detection coils 2 and 3 due to a phenomenon opposite to that of FIG. 2B described above. When the flaw detector scans over the defect 111 parallel to the second detection coil 3, the voltage induced on each of the detection coils 2 and 3 depends on the flaw detector 1.
At step 20, the difference between the induced voltages of the detection coils 2 and 3 is output. Since the difference between the induced voltages is caused by a phenomenon opposite to that of FIG. 2B, as shown in FIG. Flaw detector screen 12
1, a signal waveform 127 having a polarity opposite to that of the case of FIG.
Is displayed.

As described above, according to the present invention, the waveform of the obtained signal differs depending on the direction of the defect, and the direction of the defect can be known from the direction of the signal. Although the present embodiment has been described using a rectangular coil, the present method is not limited to the coil shape, and the same effect can be obtained regardless of whether the coil is circular or triangular.

[0020]

As described above, according to the present invention,
It is possible to easily detect the direction of the defect existing in the test object metal, and the information on the repairs required in the next step is increased, and the accuracy of the repairs etc. is greatly improved in terms of the accuracy period etc. Will be.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an eddy current inspection device according to an embodiment of the present invention.

FIG. 2 is a view for explaining the operation of the flaw detector in the embodiment.

FIG. 3 is an exemplary view for explaining a signal waveform of the flaw detector in the embodiment.

FIG. 4 is a view for explaining a direction of a defect and a direction of a signal waveform in the embodiment.

FIG. 5 is an explanatory view showing a conventional flaw detector and an eddy current flaw detector.

FIG. 6 is a diagram illustrating an electrical connection state of a conventional flaw detector and flaw detector.

[Explanation of Symbols] 2 First detection coil 3 Second detection coil 52 Signal waveform 103 Excitation coil 110 Metal to be tested 111 Defects existing in metal body 120 Flaw detector 121 Flaw detector screen 125 Signal without defect Waveform 126 Signal waveform when the first detection coil crosses the defect 127 Signal waveform when the second detection coil crosses the defect 130 Connection cable 132 Eddy current flowing through the metal body 133 Magnetic field where eddy current is generated 151 Flaw detection scanning direction X 152 Flaw detector scanning direction Y

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naomi Araki 2-1-1, Shinhama, Arai-machi, Takasago City, Hyogo Prefecture Inside the Takasago Research Laboratory, Mitsubishi Heavy Industries, Ltd. No. 1-1, Mitsubishi Heavy Industries, Ltd., Kobe Shipyard

Claims (1)

[Claims] 1. A flaw detector having two detection coils provided at right angles to each other, an excitation coil provided at an angle of 45 ° to each of the detection coils, and each of the detection coils A signal detector for processing the difference in voltage induced by the sensor and generating a signal. When the detection coil and the excitation coil are placed in a healthy part of the test object metal, the influence of the eddy current in the metal is reduced to 2 above. An eddy current flaw detection device characterized in that a signal is not generated by acting evenly on the detection coils, and a different signal is generated depending on the direction of the defect so that the direction of the defect can be known.