JPH10197494A - Eddy current flaw detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable highly accurate detection even at a location where the shape of a specimen changes by generating an eddy current flaw detection shape signal only under the influence of the shape alone of the specimen by simulation based on a shape signal of the specimen calculated from a measured value of a displacement gage. SOLUTION: A sensor part is driven by an eddy current flaw detection section 2 to scan the inside of a specimen 5 such as SG piping of a nuclear power piping plant. A displacement meter 11 measures the shape of the inside of the specimen 5 to output a displacement signal 22 to the eddy current flaw detection section 2. A shape detecting section 13 calculates a shape signal of the inside of the specimen based on a position signal 21 and the displacement signal 22 to be outputted to a waveform forming section 14. The waveform forming section 14 calculates an eddy current flaw detection shape signal 23 attributed to changes 8 in the shape of the specimen 5 alone by simulation based on the shape signal of the specimen 5 obtained. An arithmetic section 15 subtracts the eddy current flaw detection shape signal 23 from the eddy current flaw detection coil signal 9 thereby obtaining an eddy current flaw detection defect signal 24 only belonging to a defect 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eddy current flaw detection apparatus for detecting a defect in a subject from a change in eddy current induced by generating a magnetic field in the subject.

[0002]

2. Description of the Related Art Eddy current inspection is a method frequently applied as a nondestructive inspection method, and is widely used, for example, for defect inspection of piping and equipment of nuclear power plants. FIG. 2 shows a conventional eddy current flaw detector. This apparatus comprises an eddy current flaw detection coil 1, an eddy current flaw detection unit 2 for driving the eddy current flaw detection coil 1, and an image display unit 3 for displaying an obtained eddy current flaw detection coil signal 9 in an image. Eddy current testing coil 1
Generates a eddy current 6 in the subject 5. The eddy current inspection coil 1 is detected by the eddy current inspection coil 1, and the obtained eddy current inspection coil signal 9 is signal-processed by the image display unit 3 and displayed in an easily viewable form. Here, when there is a defect 7 in the subject 5, the flow of the eddy current 6 changes at the position of the defect 7 and appears as a change in the eddy current flaw detection coil signal 9. By observing this change, a defect can be detected.

[0003]

In the above-mentioned conventional eddy current flaw detector, when the object 5 has a shape change 8, the eddy current 6
Is affected by both the shape change 8 and the defect 7. If the change of the eddy current 6 due to the effect of the shape change 8 is large, the signal of the defect 7 is buried even if the defect 7 exists, which sometimes makes it difficult to detect the defect. there were.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide an eddy current flaw detection device capable of detecting a defect with high accuracy even in a portion where the shape of an object changes. Is to provide.

[0005]

SUMMARY OF THE INVENTION An eddy current flaw detection apparatus according to the present invention comprises: an eddy current flaw detection coil for generating a magnetic field, detecting a magnetic field due to an eddy current induced in a subject, and outputting the detected magnetic field as an eddy current flaw detection coil signal; A sensor unit including a displacement meter that detects the shape of the subject, an eddy current flaw detection unit that drives the sensor unit, a shape detection unit that calculates a shape signal of the subject based on a measurement value of the displacement meter, A waveform forming section for generating an eddy current flaw detection shape signal affected only by the shape of the subject by simulation based on the shape signal; and subtracting the eddy current flaw detection shape signal from the eddy current flaw detection coil signal to obtain an eddy current flaw detection defect It is characterized by comprising an arithmetic unit for generating a signal, and an image display unit for imaging and displaying the eddy current flaw detection defect signal.

According to the eddy current flaw detector of the present invention, the following operations and effects are obtained. The eddy current testing unit drives the sensor unit. With the driving of the sensor unit, the eddy current inspection coil generates a fluctuating magnetic field, and generates an eddy current in the subject. The displacement meter measures the shape of the subject. The measurement value of this displacement meter is output to the shape detection unit via the eddy current detection unit. When the shape of the subject changes and the vicinity of the location where the defect occurs is scanned, the eddy current fluctuates, and the impedance of the eddy current flaw detection coil changes. This change in impedance is output to the calculation unit via the eddy current detection unit.

The shape detector generates a shape signal representing the shape of the subject based on the input measurement values of the displacement meter, and outputs the shape signal to the waveform generator. The waveform generator is based on this shape signal,
An eddy current flaw detection shape signal that takes into account only the influence of the shape of the subject by simulation analysis is generated and output to the calculation unit.

The arithmetic unit subtracts an eddy current flaw detection shape signal generated by simulation taking only the shape of the object into consideration from an eddy current flaw detection coil signal which is a measurement value including both the shape change and the influence of a defect. Then, an eddy current flaw detection signal indicating the influence of only the defect is calculated and output to the image display unit. The image display unit displays the eddy current flaw detection defect signal waveform,
The observer can detect the presence or absence of a defect from the displayed image.

As described above, by subtracting the eddy current flaw detection shape signal in consideration of only the shape of the subject from the eddy current flaw detection coil signal affected by both the measured shape and the defect, only the defect is obtained. It is possible to generate a flaw detection waveform in consideration of the effect of Accordingly, the accuracy of defect detection is improved without being affected by the change in the shape of the object.

[0010]

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 block diagram showing the overall configuration of the eddy current inspection device according to one embodiment of the present invention. The present apparatus includes an eddy current flaw detection coil 1 for generating a fluctuating magnetic field, a displacement meter 11 for measuring the shape of a subject 5, and a subject 5.
, An eddy current flaw detector 2 for driving the sensor, a position signal 21 and a displacement signal 2 output from the eddy current flaw detector 2
2, a shape signal representing the shape of the subject 5 is detected,
By performing a simulation analysis using the shape detection unit 13 displaying the signal waveform and the shape signal generated by the shape detection unit 13, the eddy current flaw detection shape signal 23 of the eddy current flaw detection coil 1 based on the shape of the subject 5 is obtained. , An arithmetic unit 15 for calculating an eddy current flaw detection signal 24 based on an eddy current flaw shape signal 23 and an eddy current flaw detection coil signal 9, and an image display for displaying the eddy current flaw detection signal 24. It is composed of a unit 3.

The operation of the above embodiment will be described. As shown in FIG. 1, the sensor unit is driven by the eddy current flaw detection unit 2, and an object 5 such as an SG pipe or the like of a nuclear piping plant is driven.
Is scanned along the axial direction of the pipe. The eddy current flaw detection coil 1 constituting the sensor generates a fluctuating magnetic field by excitation. This fluctuating magnetic field induces an eddy current inside the subject 5. The eddy current is constant if the inside of the subject 5 keeps a constant shape with respect to the eddy current flaw detection coil 1 and there is no defect. In addition, with the scanning of the sensor unit, the displacement meter 1
1 measures the shape inside the subject 5 and outputs it to the eddy current flaw detector 2 as a displacement signal 22. Further, the position signal detection unit 12 including, for example, a rotary encoder detects the position of the sensor unit and outputs the position signal 21 to the eddy current flaw detection unit 2.

If there is a defect 7 inside the subject 5, when the sensor section scans the vicinity of the defect 7, the defect 7
As a result, the eddy current induced by the eddy current detection coil 1 is disturbed. This disturbance appears as a change in the impedance of the eddy current inspection coil 1. This change in impedance is output to the eddy current inspection unit 2 as an eddy current inspection coil signal 9.

Further, when there is a shape change 8 inside the object 5, the shape change 8 causes disturbance of the eddy current as in the case where the vicinity of the defect 7 is scanned. Further, the shape is measured by the displacement meter 11 and output to the eddy current flaw detection unit 2.

The eddy current flaw detection unit 2 calculates the eddy current flaw detection coil signal 9 and the position signal 21 sent from the sensor unit by the calculation unit 15.
Then, the position signal 21 and the displacement signal 22 are output to the shape detection unit 13. The shape detection unit 13 calculates a shape signal inside the subject 5 based on the position signal 21 and the displacement signal 22. This shape signal is output to the waveform forming unit 14.

The waveform forming section 14 calculates, based on the obtained shape signal of the subject 5, an eddy current flaw detection shape signal 23 caused by only the shape change 8 of the subject 5 by simulation. That is, if the surface shape of the test object 5 is known, the positional relationship between the eddy current flaw detection coil 1 and the test object 5 can be known. Therefore, their arrangement is simulated, and an eddy current flaw detection shape signal 23 by simulation is generated by analysis. can do. Specifically, a simulation arrangement as shown in the wavy frame of the waveform forming unit 14 in FIG. 1 is performed, and a theoretical eddy current flaw detection shape signal 23 based on this arrangement is calculated.
That is, the calculated eddy current flaw detection shape signal 23 obtained by the simulation is a signal in which the influence of only the shape of the subject 5 is considered, and does not consider the influence of the defect 7 inside the subject 5. The eddy current flaw detection shape signal 23 calculated in this way is output to the calculation unit 15.

The calculating section 15 calculates an eddy current flaw detection signal 24 based on the eddy current flaw detection shape signal 23 obtained by the waveform forming section 14 and the eddy current flaw detection coil signal 9 inputted from the eddy current flaw detecting section 2. I do. Specifically, the operation unit 15 of FIG.
As shown in the frame, the eddy current flaw detection shape signal 23 is subtracted from the eddy current flaw detection coil signal 9. That is, the eddy current flaw detection coil signal 9 is a signal affected by both the shape change 8 and the defect 7, and the eddy current flaw detection shape signal 23 is
Since the signal takes into account only the defect 7, the above-mentioned subtraction results in an eddy current flaw detection defect signal 24 taking only the defect 7 into account. In performing the subtraction, since the positions of the eddy current flaw detection coil 1 and the displacement meter 11 are different, it is necessary to correct the positions. However, since these positional relationships are known, the position signal 21 is used to calculate a known amount. Correction is possible by inputting the shifted value to the calculation unit 15. The eddy current flaw detection signal 24 thus obtained is sent to the image display unit 3 and displayed.

As described above, the shape of the subject 5 is measured by the displacement meter 11, and the waveform forming unit 14 performs a simulation analysis based on the measured values, thereby obtaining an eddy current flaw detection signal due to only the shape. Can be done. Further, by subtracting the influence of only the shape from the eddy current inspection coil signal 9 including the influence of the shape and the defect, an eddy current inspection signal affected by only the defect can be obtained, and the S / N at the time of the defect inspection can be obtained. The ratio is improved, and the defect can be reliably detected even at a location where the shape of the subject 5 changes significantly.

In this embodiment, the nuclear power plant S
Although the G pipe was used as the test object 5, it is a matter of course that the present invention is applicable as long as a defect can be detected by eddy current, for example, equipment of a nuclear power plant.

Also, there has been described a case where the position signal 21 is detected by the position signal detecting section 12 to calculate a shape signal, and a deviation between the eddy current flaw detection coil signal 9 and the eddy current flaw shape signal 23 by simulation is corrected. If the sensor unit is capable of scanning at a constant speed, the shift amount of the eddy current flaw detection shape signal 23 can be obtained without the position signal 21, so that the position signal detection unit 12 can be used. Good.

If the displacement meter 11 does not affect the detection of the eddy current of the eddy current inspection coil 1 such as when the displacement meter 11 measures using light, the eddy current inspection coil 1 and the displacement The total 11 can be provided at the same position. In this case, the position signal
Can be omitted.

[0021]

As described above, according to the present invention, it is possible to remove a signal due to a change in the shape of the object and extract only a signal affected by the defect. However, highly accurate defect detection is possible.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an eddy current inspection device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the overall configuration of a conventional eddy current flaw detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Eddy current flaw detection coil 2 Eddy current flaw detection part 3 Image display part 5 Subject 7 Defect 8 Shape change 9 Eddy current flaw detection coil signal 11 Displacement meter 12 Position signal detection part 13 Shape detection part 14 Waveform formation part 15 Operation part 21 Position signal 22 Displacement signal 23 Eddy current inspection shape signal 24 Eddy current inspection defect signal

Claims (1)

[Claims] 1. A sensor unit comprising: an eddy current inspection coil for generating a magnetic field and detecting a magnetic field due to an eddy current induced in an object to output as an eddy current inspection coil signal; and a displacement meter for detecting the shape of the object. An eddy current flaw detector that drives the sensor unit, a shape detector that calculates a shape signal of the subject based on the measurement value of the displacement meter, and a simulation of only the shape of the subject based on the shape signal. A waveform forming unit for generating an affected eddy current flaw detection shape signal; a calculation unit for subtracting the eddy current flaw detection shape signal from the eddy current flaw detection coil signal to generate an eddy current flaw detection defect signal; An eddy current flaw detection device, comprising: an image display unit that converts a signal into an image and displays the signal.