JP2012032180A - Eddy current detector, method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide eddy current detection technique with excellent accuracy in detection by performing sensitivity correction in the detection signal of a coil, based on coil traveling information acquired on a subject.SOLUTION: An eddy current detector 1 includes: a traveling control part 10 for traveling a coil 23 on the front surface of a subject U; a transmission part 22 for transmitting an excitation signal J to the coil 23 so as to generate an eddy current in the subject U; a reception part 24 for receiving a detection signal D to be output by the coil 23 where a magnetic field induced by the eddy current is detected; an information acquisition part 12 for acquiring traveling information K of the coil 23 traveling on the front surface of the subject U; a correction part 25 for holding correction information H associated with the traveling information K; and a calculation processing part 26 for calculating a detection signal N of the subject U, based on the excitation signal J and the detection signal D.

Description

  The present invention relates to an eddy current flaw detection technique for detecting a defect such as a crack existing on the surface or inside of a metallic inspection object.

There is an eddy current flaw detector as a technique for detecting a crack existing near the surface of a metal. This apparatus generates a magnetic field from a coil installed on a metal surface, and induces an eddy current near the metal surface by the generated magnetic field.
If there is a crack near the metal surface, the induced eddy current flow changes, and the magnetic field strength distribution formed by the eddy current changes. This coil detects the change in the magnetic field strength distribution and determines the presence or absence of a crack (for example, Patent Document 1).
The sensitivity of the coil detection signal varies depending on the coil operating conditions or operating conditions such as the surface shape and material of the object to be inspected, the temperature around the coil, and the moving speed of the coil.

Japanese Patent No. 3422661

  By the way, in the above-mentioned Patent Document 1, the detection signal actually measured by the coil is compared with reference data registered in advance, and the correction is performed after analyzing the factor of the sensitivity change. However, a plurality of factors have been pointed out as described above for the sensitivity change of the detection signal. For this reason, it is difficult to perform factor analysis in consideration of all of these because the calculation is complicated and difficult, and the technique disclosed in Patent Document 1 has a limit in improving flaw detection accuracy.

  The present invention has been made in view of such circumstances, and performs an eddy current flaw detection technique that performs sensitivity correction of the detection signal of the coil based on the operation information of the coil grasped on the object to be inspected and has excellent flaw detection accuracy. The purpose is to provide.

  The eddy current flaw detector according to the present invention includes an operation control unit that operates a coil on the surface of an object to be inspected, a transmission unit that transmits an excitation signal to the coil to generate an eddy current in the object to be inspected, and the eddy current A receiving unit that receives a detection signal output from the coil that has detected the magnetic field induced by the magnetic field, an information acquisition unit that acquires operation information of the coil that is operating on the surface of the inspected object, and the operation information. And a correction unit that holds the associated correction information, and an arithmetic processing unit that calculates a flaw detection signal of the inspection object based on the correction information, the excitation signal, and the detection signal.

  The present invention provides an eddy current flaw detection technique which performs sensitivity correction of a detection signal of a coil based on the operation information of the coil grasped on the object to be inspected and is excellent in flaw detection accuracy.

(A) shows the block diagram which shows 1st Embodiment of the eddy current flaw detector which concerns on this invention, (B) is the schematic which shows the U-shaped tube (inspection object) which a coil operates. The block diagram which shows 2nd Embodiment of the eddy current flaw detector based on this invention. The top view which shows 3rd Embodiment of the eddy current flaw detector based on this invention. The block diagram which shows 4th Embodiment of the eddy current flaw detector based on this invention. The top view which shows 5th Embodiment of the eddy current flaw detector based on this invention. The block diagram which shows 6th, 7th, 8th embodiment of the eddy current flaw detector based on this invention. The flowchart for demonstrating operation | movement of the eddy current flaw detector in each embodiment.

(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
The eddy current flaw detector 1A according to the first embodiment shown in FIG. 1A includes an operation control unit 10 that operates a coil 23 on the surface of an object U to be inspected, and an excitation signal J transmitted to the coil 23 to be inspected. The transmitter 22 that generates eddy current in the body U, the receiver 24 that receives the detection signal D output from the coil 23 that detects the magnetic field induced by the eddy current, and the surface of the inspected body U are operated. The information acquisition unit 12 that acquires the operation information K of the coil 23, the correction unit 25 that holds the correction information H associated with the operation information K, and the inspection target based on the correction information H, the excitation signal J, and the detection signal D And an arithmetic processing unit 26 for calculating the flaw detection signal N of the body U.

As shown in FIG. 1B, the configuration of the inspected body U in which the coil 23 operates is a case where a curved pipe U2 made of a material different from that of the straight pipe U1 is connected to the straight pipe U1 to take a U shape. Take an example. Further, the curved pipe U2 has a straight portion U3 and a curved portion U4.
In addition, although U-shaped thing was illustrated as to-be-inspected object U, it is not limited to this, A plane board, a spherical board, a wave surface board, an uneven surface board, the board from which surface roughness changes, etc. The surface texture or the material whose material changes can be targeted.

The self-propelled means 11 moves in accordance with a command from the operation control unit 10 along a set operation route in a state where the fixed coil 23 is brought close to or in contact with the surface of the inspection object U.
There are various specific examples of the self-propelled means 11 and its operation control unit 10, but in addition to the case of a wheeled carriage as shown in FIG. 1 (A), a wire pulling device, a pressure gas extrusion device, etc. Can be realized.

The position information acquisition unit 12 (information acquisition unit) acquires position information K1 (operation information K) on the operation route of the coil 23 (or the self-propelled means 11) in the subject U.
This position information K1 (operation information K) is transmitted from the self-propelled means 11 or its operation control unit 10, and if it is a wheeled carriage, the number of rotations of the wheel, if it is a traction device, the length of the wire, In the case of an extrusion apparatus, the measurement value such as the elapsed time after extrusion is converted and guided.
Further, the position information acquisition unit 12 (information acquisition unit) is not limited to the above-described method, and the coil 23 (or the detection is performed by a position detection sensor (not shown) arranged around the object U). In some cases, the position information K1 of the self-propelled means 11) is acquired.

  When an excitation signal J, which is an alternating current, flows through the coil 23, an alternating magnetic field is generated inside and around the coil 23. An eddy current is induced on the surface and inside of the inspection object U by the alternating magnetic field, and a secondary magnetic field due to the eddy current is generated on the front and back surfaces of the inspection object U.

When a magnetic field due to the eddy current is applied to the coil 23, a current is induced in the coil 23 and is received by the receiving unit 24 as the detection signal D.
And if the to-be-inspected object U has a crack, the flow of the magnetic field by an eddy current will change, and the intensity distribution will change. By detecting the change in the intensity distribution with the coil 23, it is possible to detect the presence or absence of a crack in the inspection object U around the coil 23.

  Thus, the coil 23 has a function of inputting the excitation signal J and applying a magnetic field to the object U to be inspected, and a function of detecting the magnetic field due to the eddy current generated in the object U to be inspected and outputting the detection signal D. And have both. Note that the coil 23 may be composed of a coil that receives the excitation signal J and a sensor that outputs the detection signal D, or may be composed of a single coil.

  The condition input unit 21 inputs setting conditions such as the frequency, amplitude, and bias level of the excitation signal J expressed as a sine wave or pulse wave current (or voltage). These setting conditions can be changed as appropriate while referring to the analysis results relating to the presence or absence of defects such as cracks output to the output unit 27.

The transmission unit 22 oscillates an excitation signal J (sine wave or pulse wave) based on the setting condition of the condition input unit 21 and transmits it to the coil 23. The detection signal D output from the coil 23 in response to the input of the excitation signal J is received by the receiving unit 24.
By the way, when the site | part of the to-be-tested body U which the coil 23 passes changes in the straight part U3 of the straight pipe U1, the curved pipe U2, and also the curved part U4 in FIG. Sensitivity also changes.

  In the correction unit 25, sensitivity correction information H associated with the part of the inspection object U is registered in advance based on the mechanical drawing of the inspection object U or the like. And the correction | amendment part 25 will output the corresponding correction information H to the arithmetic processing part 26, if the positional information K1 (operation information K) is received from the coil 23. FIG. The correction information H is obtained in advance by experiment or calculation and is registered in the correction unit 25.

  The arithmetic processing unit 26 derives detection information such as an intensity ratio and a phase shift between both signals from the waveforms of the detection signal D and the excitation signal J. Further, the arithmetic processing unit 26 performs gain adjustment and offset adjustment on the detection information (intensity ratio or phase shift) using the correction information H, and outputs a flaw detection signal N including information on the presence or absence of defects such as cracks. To do.

Here, since the detection signal D represents a change in the complex impedance of the eddy current generated in the inspected object U, the Lissajous can be drawn by being decomposed into a real part and an imaginary part. The presence or absence of defects such as cracks can be determined from the Lissajous waveform.
The flaw detection signal N is used to form visible information necessary for the operator to determine the presence or absence of a defect such as a crack in the output unit 27. The visible information output from the output unit 27 is not particularly limited and is generally used in a flaw detection test.

The operation of the eddy current flaw detector 1 will be described with reference to the flowchart of FIG. 7 (FIG. 1 as appropriate).
The correction information H corresponding to all the position information K1 (operation information K) is obtained from the mechanical drawing of the inspected object U by experiment or calculation in advance, and is registered in the correction unit 25 (S11). Then, setting conditions such as the frequency, amplitude, and bias level of the excitation signal J transmitted to the coil 23 are input to the condition input unit 21 (S12).

  The self-running means 11 to which the coil 23 is fixed is placed on the surface of the inspected body U and moved on a predetermined operation route (S13). Then, an excitation signal J is transmitted to the coil 23 to generate an eddy current in the inspected object U (S14), and a detection signal D output from the coil 23 that detects the magnetic field induced by the eddy current is received (S14). S15).

Further, the position information K1 (operation information K) of the coil 23 operating on the surface of the inspected body U is acquired (S16), and the correction information H stored in association with the position information K1 (operation information K). Is acquired from the correction unit 25 (S17).
Then, the calculation processing unit 26 calculates the flaw detection signal N of the object U to be inspected based on the correction information H, the excitation signal J, and the detection signal D (S18), and determines whether the output unit 27 has a defect such as a crack. Information necessary to do this is displayed (S19).
And the flow from S14 to S19 is repeated until it arrives at the end point of the operation route of the coil 23 (S20).

(Second Embodiment)
The eddy current flaw detector 1B according to the second embodiment shown in FIG. 2 is different from the first embodiment in that it includes a surface shape detection means 30 and a surface shape information acquisition unit 31 (information acquisition unit). 2 that are the same as or correspond to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted. The operation described above with reference to the flowchart of FIG. 7 is used for the operation of the eddy current flaw detector 1B.

The surface shape detection means 30 is fixed to the self-running means 11 together with the coil 23, detects the distance between the surface of the inspected object U and the coil 23 while traveling, and obtains the distance information K2 (operation information K) as a surface shape information acquisition unit. It outputs to 31 (information acquisition part).
Specific examples of the surface shape detection means 30 include a non-contact type sensor using light, sound waves, or the like, or a contact type sensor following the surface shape.

In general, when the surface shape of the inspected object U changes, the distance between the coil 23 moving by the self-running means 11 and the surface of the inspected object U changes, and the sensitivity of the detection signal D changes accordingly. .
And the correction | amendment part 25 has registered beforehand the correction | amendment information H of the sensitivity linked | related with the space | interval (interval information K2) of the surface of the to-be-inspected object U and the coil 23. FIG. And the correction | amendment part 25 will output the corresponding correction information H to the arithmetic process part 26, if the space | interval information K2 (operation information K) is received from the coil 23. FIG. Note that the sensitivity correction information H expected from the distance between the surface of the U to be inspected U and the coil 23 is obtained in advance by experiments or calculations and registered in the correction unit 25.
As described above, by actually measuring the surface shape of the inspected object U, it is possible to obtain an analysis result relating to the presence or absence of defects such as cracks with higher accuracy than when correction is performed using only the drawing information. Further, the data amount of the correction information H registered in the correction unit 25 can be reduced.

(Third embodiment)
FIG. 3 shows the arrangement of the self-running means 11, the surface shape detection means 30, and the coil 23 in the direction facing the surface of the inspection object U in the eddy current flaw detector 1C of the third embodiment. The eddy current flaw detector 1C of the third embodiment is different from the eddy current flaw detector 1B of the second embodiment in that the surface shape detection means 30 is composed of a plurality of distance sensors 30c (three in the figure). Except for the difference, it has the same configuration as FIG.
The operation described above with reference to the flowchart of FIG. 7 is used for the operation of the eddy current flaw detector 1C.

The three distance sensors 30c shown in FIG. 3 are arranged to form a right-angled isosceles triangle when the respective centers are connected. And these distance sensors 30c detect the space | interval with the surface of the to-be-inspected object U in each.
Thus, by comprising the surface shape detection means 30 by the several distance sensor 30c, the surface of the to-be-inspected object U can be measured over a wide range by one operation. Thereby, the complicated change of the surface shape of the to-be-inspected object U can be grasped faithfully, and accurate sensitivity correction can be performed. The plurality of distance sensors 30c are not limited to being arranged at the vertex positions of the right isosceles triangle described above, and can be arbitrarily arranged as long as the arrangement relationship is known. Further, the number of the distance sensors 30c arranged is not particularly limited.

(Fourth embodiment)
The eddy current flaw detector 1D of the fourth embodiment shown in FIG. 4 has the function of a distance sensor for detecting the distance between the surface of the object U to be inspected and the coil 23 combined with the coil 23 itself.
4 that are the same as or correspond to those in FIG. 2 are denoted by the same reference numerals, and redundant description is omitted. The operation described above with reference to the flowchart of FIG. 7 is used for the operation of the eddy current flaw detector 1D.

In addition, although it can use with the excitation signal J as an input signal for outputting the space | interval information K2 (operation information K) from this coil 23 itself, a dedicated signal (not shown) can also be used.
Moreover, although the space | interval information K2 (operation information K) output from the coil 23 is described so that it may be transmitted to the surface shape information acquisition part 31 (information acquisition part) and processed in FIG. Processing may be performed after transmission to 24. In this case, the detection signal D also serves as the interval information K2 (operation information K), and the apparatus configuration is simplified.

(Fifth embodiment)
FIG. 5 shows the arrangement of the self-running means 11 and the coil 23 in the direction facing the surface of the inspected object U in the eddy current flaw detector 1E according to the fifth embodiment. The eddy current flaw detector 1E according to the fifth embodiment is the eddy current according to the fourth embodiment in that it is composed of a plurality of coils 23e (three in the figure) that output the interval information K2 (operation information K) and the detection signal D. Unlike the flaw detection apparatus 1D, it has the same configuration as FIG. 4 except for this difference.
The operation described above with reference to the flowchart of FIG. 7 is used for the operation of the eddy current flaw detector 1E.

Thereby, the surface of the to-be-inspected object U can be measured over a wide range by one operation. Thereby, the complicated change of the surface shape of the to-be-inspected object U can be grasped faithfully, and accurate sensitivity correction can be performed. Furthermore, simplification of the device configuration is achieved.
In addition, the arrangement | positioning relationship of these coils 23 is not limited to what is shown in figure, If the arrangement | positioning relationship is known, arbitrary arrangement | positioning can be taken. Further, the number of coils 23 arranged is not particularly limited.

(Sixth embodiment)
In the eddy current flaw detector 1F of the sixth embodiment shown in FIG. 6, the temperature sensor 40 is provided in the vicinity of the coil 23, and the temperature information K3 (operation information K) output by the temperature sensor 40 is the temperature information acquisition unit 32. (Information acquisition unit).
In addition, as the temperature sensor 40, general things, such as a thermocouple, can be applied.
6 that are the same as or correspond to those in FIG. 1 or FIG. 2 are denoted by the same reference numerals, and redundant description is omitted. Moreover, the description which referred the flowchart of FIG. 7 is used for operation | movement of the eddy current flaw detector 1D.

Generally, when the temperature of the coil 23 changes, the sensitivity of the detection signal D changes.
Therefore, sensitivity correction information H associated with the temperature of the coil 23 is registered in the correction unit 25 in advance. And the correction | amendment part 25 will output the corresponding correction information H to the arithmetic processing part 26, if the temperature information acquisition part 32 receives temperature information K3 (operation information K). Note that the sensitivity correction information H predicted from the temperature of the coil 23 is obtained in advance by experiments or calculations, and is registered in the correction unit 25.
Further, the temperature information K3 (operation information K) does not have to be based on the actually measured value of the temperature sensor 40, and is associated with the position information K1 (operation information K) if the temperature at a predetermined location of the subject U is known. You can also.

(Seventh embodiment)
The seventh embodiment of the present invention is provided with a speed sensor 41 for detecting the moving speed of the coil 23 in the eddy current flaw detector 1F shown in FIG. The speed information K4 (operation information K) output from the speed sensor 41 is transmitted to the speed information acquisition unit 33 (information acquisition unit).

Generally, when the moving speed of the coil 23 changes, the sensitivity of the detection signal D changes.
Therefore, sensitivity correction information H associated with the moving speed of the coil 23 is registered in the correction unit 25 in advance. And the correction | amendment part 25 will output the corresponding correction information H to the arithmetic processing part 26, if the speed information acquisition part 33 receives speed information K4 (operation information K). Note that the sensitivity correction information H predicted from the moving speed of the coil 23 is obtained in advance by experiments or calculations, and is registered in the correction unit 25.

  In addition, the speed information K4 (operation information K) does not need to be based on the actual measurement value of the speed sensor 41. If the moving speed of the inspection subject U at a predetermined location is known, the position information K1 (operation information K) is included. It can also be associated. Further, the speed information K4 can be obtained by time-differentiating the position information K1.

(Eighth embodiment)
In the eighth embodiment of the present invention, in the eddy current flaw detector 1F shown in FIG. 6, an analysis sensor 42 for analyzing the material property of the surface of the object to be inspected is provided. The physical property information K5 (operation information K) output by the analysis sensor 42 is transmitted to the physical property information acquisition unit 34 (information acquisition unit).
Examples of the analysis sensor 42 include a magnetic permeability sensor and a conductivity sensor.

  In general, the sensitivity of the detection signal D changes when the material of the U to be inspected U where the coil 23 is located changes. Therefore, sensitivity correction information H associated with the material of the subject U is registered in the correction unit 25 in advance. And the correction | amendment part 25 will output the corresponding correction information H to the arithmetic processing part 26, if the physical property information acquisition part 34 receives physical property information K5 (operation information K). Note that the correction information H of sensitivity expected from the material of the inspected object U is obtained in advance by experiments or calculations and registered in the correction unit 25.

  Further, the physical property information K5 (operation information K) does not need to be based on the actual measurement value of the analysis sensor 42, and is associated with the position information K1 (operation information K) if the material at a predetermined location of the object U is known. You can also.

  As described above, according to each embodiment of the present invention, the shape and material of the metal surface of the object to be inspected and the ambient temperature and moving speed of the coil that affect the sensitivity of the detection signal in the flaw detection test of the object to be inspected. These factors are analyzed based on management information such as mechanical drawings and actual measurement data at the inspection site. And the eddy current flaw detector which can obtain the analysis result which concerns on the presence or absence of defects, such as a crack, at high speed and with high precision by performing sensitivity correction of detection signal D with correction information H registered beforehand is provided. The

The present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications within the scope of a combination of the embodiments or a common technical idea.
For example, the present invention can be realized as an eddy current flaw detection program that causes each means to function by a computer.

  DESCRIPTION OF SYMBOLS 1 (1A, 1B, 1C, 1D, 1E, 1F) ... Eddy current flaw detector, 10 ... Operation control part, 11 ... Self-propelled means, 12 ... Position information acquisition part (information acquisition part), 21 ... Condition input part, DESCRIPTION OF SYMBOLS 22 ... Transmission part, 23 ... Coil, 24 ... Reception part, 25 ... Correction part, 26 ... Operation processing part, 27 ... Output part, 30 ... Surface shape detection means, 30c ... Distance sensor, 31 ... Surface shape information acquisition part ( Information acquisition unit), 32 ... Temperature information acquisition unit (information acquisition unit), 33 ... Speed information acquisition unit (information acquisition unit), 34 ... Physical property information acquisition unit (information acquisition unit), 40 ... Temperature sensor, 41 ... Speed sensor 42 ... analytical sensor, K1 (K) ... position information (operation information), K2 (K) ... interval information (operation information), K3 (K) ... temperature information (operation information), K4 (K) ... speed information ( Operation information), K5 (K) ... Physical property information (operation information), U ... Inspected object, U ... straight pipe, U2 ... bent tube, U3 ... straight portion, U4 ... curved portion.

Claims (13)

An operation control unit for operating a coil on the surface of the object to be inspected;
A transmitter for transmitting an excitation signal to the coil to generate an eddy current in the inspection object;
A receiving unit that receives a detection signal output by the coil that detects the magnetic field induced by the eddy current;
An information acquisition unit for acquiring operation information of the coil operating on the surface of the inspection object;
A correction unit that holds correction information associated with the operation information;
An eddy current flaw detector comprising: an arithmetic processing unit that calculates a flaw detection signal of the inspection object based on the correction information, the excitation signal, and the detection signal. The eddy current flaw detector according to claim 1,
The eddy current flaw detector according to claim 1, wherein the operation information is based on a position on the operation route of the coil in the inspection object. In the eddy current flaw detector according to claim 1 or 2,
The eddy current flaw detector according to claim 1, wherein the operation information is based on a distance between the surface of the inspection object and the coil. In the eddy current flaw detector according to claim 3,
An eddy current flaw detector according to claim 1, wherein the distance sensor for detecting the interval detects a plurality of intervals. In the eddy current flaw detector according to claim 3 or 4,
An eddy current flaw detector characterized in that the coil also functions as a distance sensor for detecting the interval. In the eddy current flaw detector according to any one of claims 1 to 5,
The eddy current flaw detector according to claim 1, wherein the operation information is based on a temperature of the coil that operates on a surface of the inspection object. In the eddy current flaw detector according to claim 6,
An eddy current flaw detector characterized in that a temperature sensor for detecting the temperature is provided in the vicinity of the coil. In the eddy current flaw detector according to any one of claims 1 to 7,
The eddy current flaw detector according to claim 1, wherein the operation information is based on a moving speed of the coil that operates on the surface of the inspection object. The eddy current flaw detector according to claim 8,
An eddy current flaw detector characterized in that a speed sensor for detecting the moving speed is provided in the vicinity of the coil. In the eddy current flaw detector according to any one of claims 1 to 9,
The eddy current flaw detector according to claim 1, wherein the operation information is based on material properties of the surface of the inspection object. The eddy current flaw detector according to claim 10,
An eddy current flaw detector characterized in that a magnetic permeability sensor or a conductivity sensor for detecting the physical property of the material is provided in the vicinity of the coil. Running a coil on the surface of the object to be inspected;
Transmitting an excitation signal to the coil to generate an eddy current in the inspection object;
Receiving a detection signal output by the coil that has detected a magnetic field induced by the eddy current;
Obtaining operation information of the coil operating on the surface of the object to be inspected;
An eddy current flaw detection method comprising: calculating a flaw detection signal of the object to be inspected based on correction information held in association with the operation information, the excitation signal, and the detection signal. Computer
Means for operating a coil on the surface of the object to be inspected;
Means for generating an eddy current in the inspection object by transmitting an excitation signal to the coil;
Means for receiving a detection signal output by the coil that detects a magnetic field induced by the eddy current;
Means for obtaining operation information of the coil operating on the surface of the inspected object;
Means for holding correction information associated with the operation information;
An eddy current flaw detection program which functions as means for calculating a flaw detection signal of the object to be inspected based on the correction information, the excitation signal, and the detection signal.

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