JP6170005B2 - Eddy current flaw detection method and eddy current flaw detection apparatus - Google Patents

Description

  The present invention relates to an eddy current flaw detection method and an eddy current flaw detection apparatus using a mutual induction type standard comparison eddy current flaw probe.

  One of the nondestructive testing methods is an eddy current flaw detection method in which an excitation signal (alternating current) is applied to an excitation coil of an eddy current flaw detection probe to excite it, the probe is brought close to a conductive object to be inspected, and is subjected to electromagnetic induction. In this method, an eddy current is induced in an inspection object, and this eddy current disturbance (or magnetic flux density disturbance associated therewith) is detected by a detection coil of the probe (see, for example, Patent Document 1). Since the eddy current changes depending on the conductivity, magnetic permeability, etc. of the object to be inspected, it is possible to detect a flaw or the like of the object to be inspected. Specifically, for example, a reference detection signal detected for a healthy standard test piece or the like is acquired in advance, and the difference between the detection signal detected for the object to be inspected and the reference detection signal is displayed on the screen. . As one of the display forms of the detection signal, the detection signal (voltage) is decomposed into a voltage having the same component (X component) as the phase of the reference signal (Y component) and a voltage having a component (Y component) that is 90 degrees different from the reference signal. It is known to take a component voltage or a Y component voltage and display the time or probe position on the horizontal axis. Then, for example, when the X component voltage or the Y component voltage is larger than a preset threshold value, it is determined as a flaw.

Japanese Patent Laid-Open No. 2008-8806

  In the eddy current flaw detection method, a lift-off signal due to a change in the distance between the probe and the surface of the object to be inspected is also generated as a signal other than a flaw, and it may be difficult to distinguish it from a flaw signal.

  An object of the present invention is to provide an eddy current flaw detection method and an eddy current flaw detection device capable of discriminating a flaw signal and a lift-off signal.

To achieve the above object, the present invention includes an excitation coil, a first detection coil disposed in a first arrangement direction with respect to the exciting coil, and the first alignment direction with respect to the excitation coil In an eddy current flaw detection method using an eddy current flaw detection probe having second detection coils arranged in intersecting second arrangement directions, a difference between a detection signal of the first detection coil and a detection signal of the second detection coil To generate a differential signal and compare the absolute value of the absolute value of the detection signal of the first detection coil and the absolute value of the detection signal of the second detection coil with the absolute value of the differential signal Then, it is determined that there is a flaw when it is smaller than the absolute value of the difference signal, and it is determined that there is no flaw when it is larger than the absolute value of the difference signal.

To achieve the above object, the present invention includes an excitation coil, a first detection coil disposed in a first arrangement direction with respect to the exciting coil, and the first alignment direction with respect to the excitation coil In an eddy current flaw detector provided with an eddy current flaw detection probe having a second detection coil arranged in the intersecting second arrangement direction, the difference between the detection signal of the first detection coil and the detection signal of the second detection coil A difference calculation unit that generates a difference signal by calculating the difference between the absolute value of the detection signal of the first detection coil and the absolute value of the detection signal of the second detection coil. A comparison / determination unit that determines the presence or absence of a flaw by comparing with an absolute value, and the comparison / determination unit includes an absolute value of a detection signal of the first detection coil and an absolute value of a detection signal of the second detection coil Big of The sale of an absolute value is determined that there flaws is smaller than the absolute value of the difference signal, it is determined that no scratches when the absolute value is greater than said difference signal.

  According to the present invention, a flaw signal and a lift-off signal can be distinguished.

It is the schematic showing the structure of the eddy current flaw detector in one Embodiment of this invention. It is a flowchart showing the procedure of the eddy current flaw detection method in one Embodiment of this invention. It is the top view and side view for explaining operation of one embodiment of the present invention, and shows the case where a flaw signal is detected. It is a figure showing the specific example of detection signal SA of the 1st detection coil, detection signal SB of the 2nd detection coil, and difference signal SC in one embodiment of the present invention, and shows the case where it is a flaw signal. It is a side view for demonstrating operation | movement of one Embodiment of this invention, and shows the case where a lift-off signal is detected. It is a figure showing the specific example of detection signal SA of the 1st detection coil, detection signal SB of the 2nd detection coil, and difference signal SC in one embodiment of the present invention, and shows the case where it is a lift-off signal. It is the schematic showing the structure of the eddy current test probe in the modification of this invention.

  An embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing the configuration of the eddy current flaw detector according to this embodiment.

  The eddy current flaw detector according to the present embodiment is roughly divided into an eddy current flaw probe 1 and a control device 2.

  The eddy current flaw detection probe 1 includes an excitation coil 3, a detection coil 4a disposed in a first alignment direction (left and right direction in the figure) with respect to the excitation coil 3, and a first alignment direction with respect to the excitation coil 3. And a detection coil 4b arranged in the intersecting second arrangement direction (vertical direction in the figure). In the present embodiment, the case where the first arrangement direction and the second arrangement direction are orthogonal to each other is shown as an example, but the present invention is not limited to this. Further, as shown in FIG. 3A described later, the excitation coil 3 and the detection coils 4a and 4b are arranged along the surface of the inspection object 5. Further, the axial directions of the excitation coil 3 and the detection coils 4 a and 4 b are perpendicular to the surface of the inspection object 5.

  The control device 2 includes an excitation signal generation unit 6, detection signal processing units 7 a and 7 b, a difference calculation unit 8, a comparison determination unit 9, a storage unit 10, and a display unit 11 as functional configurations.

  The excitation signal generator 6 applies an excitation signal (alternating current) to the excitation coil 3 of the probe 1. Thereby, the exciting coil 3 is excited, and an eddy current is induced in the inspection object 5 by electromagnetic induction. A change in eddy current (or a change in magnetic flux density associated therewith) due to a flaw or the like is detected by the detection coils 4a and 4b and output as a detection signal.

  The detection signal processing unit 7a performs predetermined processing on the detection signal from the detection coil 4a, and the detection signal processing unit 7b performs predetermined processing on the detection signal from the detection coil 4b. Specifically, for example, it is decomposed into a component (X component) that is the same as the phase of the reference signal and a component (Y component) that is 90 degrees different. Then, the processed data is stored in the storage unit 10 and displayed on the display unit 11. In the display unit 11, as the detection signal SA of the detection coil 4a, one of the X component voltage and the Y component voltage on the vertical axis (specifically, the component voltage on which sensitivity calibration is performed is preferable. Component voltage), and the time or probe position is plotted on the horizontal axis. Similarly, as the detection signal SB of the detection coil 4b, one of the X component voltage and the Y component voltage on the vertical axis (specifically, the component voltage on which sensitivity calibration is performed is preferable. In this embodiment, the Y component voltage ) And display the time or probe position on the horizontal axis.

  The difference calculation unit 8 calculates a difference between the detection signal SA of the detection coil 4a and the detection signal SB of the detection coil 4b to generate a difference signal SC. The comparison determination unit 9 compares the larger absolute value of the absolute value | SA | of the detection signal of the detection coil 4a and the absolute value | SB | of the detection signal of the detection coil 4b with the absolute value | SC | of the difference signal. By doing so, the presence or absence of a flaw is determined. The determination result is stored in association with the data stored in the storage unit 10 and is displayed on the display unit 11.

  FIG. 2 is a flowchart showing the procedure of the eddy current flaw detection method according to this embodiment.

  First, the eddy current flaw detection probe 1 is placed at the inspection position of the inspection object 5 (step 100), and an excitation signal is applied to the excitation coil 3 of the probe 1 to induce an eddy current in the inspection object 5 (step 110). ). Then, a change in eddy current (or a change in magnetic flux density associated therewith) is detected by the detection coils 4a and 4b of the probe 1 to obtain detection signals SA and SB (step 120).

  The difference calculation unit 8 of the control device 2 calculates the difference between the detection signal SA and the detection signal SB to generate a difference signal SC (step 130). The comparison determination unit 9 of the control device 2 uses the larger absolute value of the absolute value | SA | of the detection signal of the detection coil 4a and the absolute value | SB | of the detection signal of the detection coil 4b as the absolute value of the difference signal | Compare with SC | (step 140). Specifically, for example, if the absolute value | SA | of the detection signal is greater than or equal to the absolute value | SB | of the detection signal, whether or not the absolute value | SA | of the detection signal is less than or equal to the absolute value | SC | judge. On the other hand, for example, if the absolute value | SA | of the detection signal is less than the absolute value | SB | of the detection signal, it is determined whether or not the absolute value | SB | of the detection signal is less than or equal to the absolute value | SC | .

  A specific example will be described. For example, as shown in FIG. 3, when the flaw portion of the inspection object 5 is scanned with the probe 1, detection signals SA and SB as shown in FIGS. 4A and 4B are obtained, and FIG. A differential signal SC as shown in c) is obtained. In this case, since the absolute value | SA | of the detection signal is larger than the absolute value | SB | of the detection signal, it is determined whether or not the absolute value | SA | of the detection signal is less than or equal to the absolute value | SC | Since the absolute value | SA | of the detection signal is equal to or smaller than the absolute value | SC | of the difference signal, the determination in step 140 is satisfied, and the routine proceeds to step 150. In step 150, it is determined that the detection signals SA and SB are flaw signals, that is, there are flaws.

  For example, when the distance between the probe 1 and the surface of the inspection object 5 changes as shown in FIG. 5, detection signals SA and SB as shown in FIGS. 6 (a) and 6 (b) are obtained. A differential signal SC as shown in FIG. 6C is obtained. In this case, since the absolute value | SA | of the detection signal is larger than the absolute value | SB | of the detection signal, it is determined whether or not the absolute value | SA | of the detection signal is less than or equal to the absolute value | SC | Since the absolute value | SA | of the detection signal is less than the absolute value | SC | of the difference signal, the determination in step 140 is not satisfied, and the routine proceeds to step 160. In step 160, it is determined that the detection signals SA and SB are lift-off signals, that is, there are no flaws.

  For example, if there is another position on the inspection object 5 to be inspected, the determination at Step 170 is not satisfied, and the probe 1 is moved to the next inspection position (Step 180), and Steps 110 to 140 and Step 150 described above are performed. Alternatively, the procedure of 160 is repeated. On the other hand, if there is no other position to be inspected in the inspection object 5, the determination in Step 170 is satisfied and the inspection is completed.

  As described above, in the present embodiment, the flaw signal and the lift-off signal can be identified, and it is possible to evaluate the presence or absence of flaws, that is, whether the inspected object 5 is healthy.

  In the above-described embodiment, the eddy current flaw detection probe 1 has been described by taking as an example the case of including a pair of exciting coil 3 and detection coils 4a and 4b (that is, three coils). Modifications can be made without departing from the technical idea. That is, for example, as in the modification shown in FIG. 7, the eddy current flaw detection probe 1A may include two or more sets of excitation coils 3 and detection coils 4a and 4b (that is, five or more coils). The combination of the coil 3 and the detection coils 4a and 4b may be switched sequentially. In this modification, the arrangement direction of the excitation coil 3 and the detection coil 4a (the horizontal direction in the figure) and the arrangement direction of the excitation coil 3 and the detection coil 4b (the vertical direction in the figure) are orthogonal (in other words, a plurality of coils). Is shown as an example), but is not limited thereto. That is, for example, a plurality of coils may be arranged in a staggered manner.

  In the above embodiment, the difference calculation unit 8 of the control device 2 calculates the difference between the detection signal SA of the detection coil 4a and the detection signal SB of the detection coil 4b to generate the difference signal SC, and the control device 2, the comparison / determination unit 9 calculates the larger absolute value of the absolute value | SA | of the detection signal of the detection coil 4a and the absolute value | SB | of the detection signal of the detection coil 4b as the absolute value | SC | The case where the presence / absence of a flaw is determined as an example has been described, but modifications can be made without departing from the spirit and technical idea of the present invention. That is, for example, the examiner calculates the difference between the detection signal SA of the detection coil 4a and the detection signal SB of the detection coil 4b to generate the difference signal SC, and the absolute value | SA | of the detection signal of the detection coil 4a The presence / absence of a flaw may be determined by comparing the larger absolute value | SB | of the detection signal of the detection coil 4b with the absolute value | SC | of the difference signal. In such a case, the same effect as described above can be obtained.

DESCRIPTION OF SYMBOLS 1,1A Eddy current test probe 2 Control apparatus 3 Excitation coil 4a, 4b Detection coil 8 Difference calculating part 9 Comparison determination part 11 Display part

Claims (3)

Excitation coil, a first detection coil disposed in a first arrangement direction with respect to the excitation coil, and the placed in a second arrangement direction intersecting with the first arrangement direction with respect to the exciting coil In an eddy current testing method using an eddy current testing probe having two detection coils,
Calculating a difference between the detection signal of the first detection coil and the detection signal of the second detection coil to generate a difference signal;
The larger absolute value of the absolute value of the detection signal of the first detection coil and the absolute value of the detection signal of the second detection coil is compared with the absolute value of the differential signal, and the absolute value of the differential signal is An eddy current flaw detection method characterized in that it is determined that there is a flaw when it is small and that there is no flaw when it is larger than the absolute value of the difference signal. Excitation coil, a first detection coil disposed in a first arrangement direction with respect to the excitation coil, and the placed in a second arrangement direction intersecting with the first arrangement direction with respect to the exciting coil In an eddy current flaw detector provided with an eddy current flaw probe having two detection coils,
A difference calculation unit that calculates a difference between a detection signal of the first detection coil and a detection signal of the second detection coil to generate a difference signal;
The presence / absence of a flaw is determined by comparing the absolute value of the absolute value of the detection signal of the first detection coil and the absolute value of the detection signal of the second detection coil with the absolute value of the difference signal. A comparison judgment unit,
The comparison / determination unit has a flaw when the larger absolute value of the absolute value of the detection signal of the first detection coil and the absolute value of the detection signal of the second detection coil is smaller than the absolute value of the difference signal. The eddy current flaw detector is characterized in that it is determined that there is no flaw when it is larger than the absolute value of the difference signal. The eddy current flaw detector according to claim 2,
An eddy current flaw detector comprising a display unit for displaying a determination result of the comparison determination unit.

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