KR101966168B1 - Eddy Current Inspection Apparatus for Nondestructive Test - Google Patents

Abstract

An eddy current inspection apparatus for non-destructive inspection is disclosed. This apparatus is a bobbin type coil inserted inside the test specimen to be inspected for the nondestructive inspection to apply an induction current to the inner wall of the specimen and inserted into the defectless specimen as a reference of the specimen to induce an induced current in the inner wall of the defect- A bobbin type coil and a cylindrical Hall sensor array disposed in the bobbin type coil and including a row and a column and a plurality of frequencies are selected to apply an alternating current power to the bobbin type coil and the reference coil, And a control module for controlling the first and second multipliers so that the applied signal and the square wave signal are multiplied by a first multiplication factor, wherein the control module controls the drive power source to sequentially select arrays in the arcuate direction among the plurality of arrays of the cylindrical hall sensor array, And the square wave having the different phase difference generated in the applied signal is multiplied by the second time And control, but based on the first multiplied signal and the second multiplied signal, it is possible to use the magnitude and distribution of the phase difference between the signals to detect defects on the specimen. Thus, defect detection can be accurately performed.

Description

[0001] Eddy Current Inspection Apparatus for Nondestructive Test [

This disclosure relates to an eddy current testing apparatus for non-destructive testing.

The heat exchanger installed in the power plant performs the function of heating, cooling, and condensing by causing the heat of the fluid to transfer heat through the heat transfer surface of the heat transfer tube. Heat exchanger tubes that have been used for a long time under high temperature, high pressure, vibration and hydrochemical environment are used for corrosion, denting, erosion, formulation, wear, thinning, fatigue cracking, stress corrosion cracking (SCC) and irradiation assisted stress corrosion cracking It can be damaged. Failure to perform the function of the heat exchanger due to such damage may interfere with normal operation of the power plant. Therefore, non-destructive testing for the integrity of the heat exchanger tube is periodically performed during the planning, prevention and maintenance of the power plant. For this purpose, a probe for an eddy current test can be inserted into the heat transfer tube and a non-destructive inspection can be performed.

However, in the prior art, nondestructive inspection was performed using a bobbin type probe, an annular array probe, and a rotary type probe. However, the inspection speed, the defect inspection capability and the durability are further improved as compared with the prior art, and the nondestructive inspection device performing the quantitative evaluation function is required.

Open Patent Publication No. 10-2012-0054419 (Published May 22, 2012)

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an embodiment of the present invention proposes an eddy current testing apparatus for measuring the amplitude and phase difference distribution of an eddy current in real time.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, unless further departing from the spirit and scope of the invention as defined by the appended claims. It will be possible.

In order to accomplish the above object, an eddy current inspection apparatus for non-destructive inspection according to an embodiment of the present invention includes: a bobbin type coil inserted into a test piece to be inspected of the nondestructive inspection and applying an induced current to the inner wall of the test piece; A reference coil inserted into the defect-free test piece, which is a reference of the test piece, for applying an induced current to the inner wall of the defect-free test piece; A cylindrical Hall sensor array disposed within the bobbin type coil and including rows and columns; And a control unit for controlling the bipolar coil and the reference coil to apply an AC power to the bobbin type coil and the reference coil to generate a square wave signal having a different phase difference and to control the applied signal and the square wave signal to be first multiplied Wherein the control module switches and applies a drive power source so that arrays in the circumferential direction are successively selected from a plurality of columns of the cylindrical hall sensor array, and a rectangular wave having a different phase difference generated in the applied signal And a defect of the test piece can be detected based on the first multiplied signal and the second multiplied signal and using the distribution of the amplitude and the phase difference of the signal.

According to various embodiments of the present invention, the following effects can be obtained.

First, an eddy current inspecting apparatus which is not a rotating body structure but which is simple and mechanically excellent in durability can be provided.

Also, by providing the eddy current inspecting apparatus, it is possible to visually display the amplitude and phase difference distribution of the eddy current in real time which is not realized in the conventional equipment.

Further, by providing the eddy current inspection apparatus, advantages such as a bobbin type probe, a rotary type probe, and an annular array type probe can be realized.

Further, by providing the eddy current inspecting apparatus, defects in the small diameter heat exchanger heat transfer pipe can be automatically detected.

Further, by providing the eddy current inspection apparatus, the position, shape, size, etc. of defects can be automatically evaluated.

Further, by providing the eddy current inspection apparatus, the distortion distribution of the electromagnetic field due to the presence of defects can be quantitatively measured as compared with the conventional bobbin eddy current probe, and corrosion, wear and cracks can be discriminated and quantitatively evaluated .

Further, by providing the eddy current inspecting apparatus, it is possible to quantitatively measure the distortion distribution of the electromagnetic field at a high speed, despite the structure not including the rotating body, as compared with the conventional rotary eddy current transducer, and the corrosion, Can be discriminated, quantitatively evaluated and excellent durability can be provided.

Further, by providing the eddy current inspecting apparatus, it is possible to quantitatively measure the distortion distribution of the electromagnetic field at a high speed and to detect corrosion, wear and cracks at a high speed with a low heat generation and a high spatial resolution as compared with the conventional annular eddy current transducer , A quantitative evaluation can be performed.

Further, by providing the eddy current inspecting apparatus, it is possible to quantitatively evaluate the position of the defect, either internally or externally, as compared with the conventional annular magnetic sensor array transducer, The distortion distribution can be measured quantitatively, and it is easy to discriminate between corrosion, wear and cracks, and can be evaluated quantitatively.

Lastly, by providing the eddy current inspecting apparatus, it is possible to quantitatively evaluate the position of a defect, either internally or externally, as compared with a conventional cylindrical magnetic sensor array transducer, and the distortion distribution of the electromagnetic field according to the frequency can be quantitatively measured , Corrosion, wear and cracks can be easily identified and quantitatively evaluated.

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description will be.

1 shows a probe of an eddy current inspecting apparatus inserted into a test piece according to an embodiment of the present invention.
FIG. 2 is a partially enlarged view of a part of the probe shown in FIG. 1. FIG.
Fig. 3 shows a reference coil corresponding to the bobbin type coil shown in Fig.
4 shows a multi-frequency AC power supply circuit according to an embodiment of the present invention.
5 shows a circuit for acquiring an eddy current signal using a bobbin type coil and a reference coil according to an embodiment of the present invention.
6 shows a circuit for acquiring an eddy current signal using a cylindrical Hall sensor arrangement according to an embodiment of the present invention.
7 is a block diagram showing the configuration of an eddy current testing apparatus according to an embodiment of the present invention.
Figures 8 (a) and 8 (b) show test specimens comprising various defects according to an embodiment of the present invention.
9 to 12 show amplitude distribution and phase difference distribution according to multiple frequencies using the test piece shown in Fig.
FIG. 13 is a graph of the RISAS diagram based on the output of the sensor passing the center of the defect in FIGS. 11 and 12 when a frequency of 50 kHz is applied.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, Various changes and modifications will be possible.

Various embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Fig. 1 shows an example in which a probe 30 of the present eddy current inspection apparatus (Figs. 7 and 100) is inserted into a test piece 10. Fig. In the following description, the reference numerals of FIG. 7 will be borrowed.

The nondestructive inspection can be performed without destroying the test piece 10 by using ultrasonic waves, eddy currents, etc., defects such as pores and cracks in the test piece 10. The eddy current is an induction current induced by an alternating magnetic field applied to the surface of a conductor. The eddy current testing apparatus measures the eddy current induced in the test piece 10 to perform a nondestructive inspection. Also, a probe 30 called a probe corresponds to a search unit for performing a nondestructive inspection.

In this specification, a heat transfer tube (heat transfer tube) for transferring heat of a fluid used in a heat exchanger of a nuclear power plant is described as an example of a test piece 10, but various objects that are objects of nondestructive inspection are used as a test piece 10 .

The transducer 30 may be formed in a cylindrical shape and the transducer 30 may include a transducer mechanism 33, a bobbin type coil 110 wound on the transducer mechanism 33, a bobbin type coil 110 disposed inside the bobbin type coil 110 (Not shown). The probe unit 33 may be configured in various shapes, but when the probe unit 10 is inserted into the test piece 10, it may detect an obstacle and transmit it to the control module 115 (FIG. 7).

Hereinafter, the specific portion u of the probe 30 shown in FIG. 1 will be described in more detail with reference to FIG. 2, which is an enlarged view.

According to Fig. 2, the test piece 10 may include a defective portion 13. The defective portion 13 may be caused by corrosion, abrasion, cracks, or the like, and may be caused by a defective volume property.

The eddy current inspecting apparatus 100 is provided with a bobbin type coil 110 and a cylindrical hole sensor array 120. The eddy current inspecting apparatus 100 includes a bobbin type coil 110, The region 13 can be accurately detected.

The bobbin type coil 110 is a wide bobbin type coil having a radius r and can be inserted into a small-diameter pipe test piece 10 made of a metal. Although the test piece 10 is described as a small-diameter small-diameter test piece, the test piece 10 may have a large diameter and a medium diameter.

The AC voltage of the following formula (1) may be applied to the bobbin type coil 110.

[Equation 1]

Here, the frequency can be derived by the equation ω = 2πf, and the eddy current testing apparatus (FIGS. 7 and 100) can apply the alternating voltage of multiple frequencies to the bobbin type coil 110. For example, the eddy current testing apparatus 100 can apply a frequency of 30 KHz to the bobbin type coil 110, apply a frequency of 50 KHz to the bobbin type coil 110, But the embodiment is not limited thereto. A separate multi-frequency ac power application circuit may be included to apply multiple frequencies.

At this time, when an alternating voltage is applied to the bobbin type coil 110, an induction current may flow in the inner diameter of the test piece 10. If the resistance and inductance of the bobbin type coil 110 are R and L, respectively, in the radial direction r, the circular direction?, And the axial direction z as the cylindrical coordinate system, the exciting current is derived as shown in the following equation . The excitation current of the bobbin type coil 110 generates a magnetic flux in the z-axis direction as shown in Equation (3).

&Quot; (2) "

&Quot; (3) "

If there is no defect in the test piece 10, an induction current of Equation (4) occurs along the direction of the Φ of the test piece 10 in the direction opposite to the bobbin type coil 110. In addition, such an induced current generates a magnetic flux as shown in Equation (5) in the -z direction. Where d is the thickness of the specimen (10, specimen).

&Quot; (4) "

&Quot; (5) "

Therefore, the magnetic flux of Equation (6) can be applied to the bobbin type coil 110.

&Quot; (6) "

The cylindrical Hall sensor array 120 may be disposed inside the bobbin type coil 110. A plurality of Hall sensors can be arranged in a row and a column along a cylindrical shape. Further, when the heat exchanger heat transfer tube has a shape of a curved tube portion and the total length of the sensor is to be shortened, the heat exchanger tube can be arranged in a single row and arranged in an annular shape. The cylindrical Hall sensor array 120 is fixed without rotating, and the durability of the eddy current testing apparatus is excellent.

When the induced current of the test piece 10 is distorted, the time-varying magnetic field (time-varying magnetic field) is also distorted. A plurality of Hall sensors can be used to measure the distortion of a time-varying magnetic field with a semiconductor-based passive magnetic sensor configured in an annular or cylinder shape. Accordingly, the plurality of Hall sensors can measure the intensity of the time-varying magnetic field as well as the presence of defects in the test piece 10. [ This is smaller than the case of using an active type coil sensor, and there is no need to drive the sensor at an intersection as well as a spatial resolution because there is no dryness between sensors. Also, in implementation, the plurality of hall sensors may be replaced by giant magnetoresistance (GMR) sensors.

FIG. 3 shows a reference coil 110r corresponding to the bobbin type coil 110 shown in FIG.

The test piece 20 shown in Fig. 3 is a defect-free test piece 20. The defect-free test piece 20 is the same material as the test piece 10 and is a reference of the test piece 10 and is free from defects. The reference coil 110r may be disposed inside the defect-free test piece 20. [ The magnetic flux according to Equation (7) can be applied to the reference coil 110r.

&Quot; (7) "

4 shows a multi-frequency AC power supply circuit according to an embodiment of the present invention.

The output of the reference coil 110r interpolated into the bobbin type coil 110 and the defectless test piece 20 interpolated in the measurement test piece 10 can be differentially connected as shown in Fig. Specifically, the bobbin type coil 110 is disposed at one end of the bridge circuit of the multi-frequency AC power source application unit 107, and the reference coil 110r is disposed at the other end thereof.

The multi-frequency AC power applying unit 107 can be applied with AC power at a selected frequency among a plurality of frequencies under the control of a control module 115, which will be described later. At this time, when the outputs of the bobbin type coil 110 and the reference coil 110r are differentially connected, the output signal can be expressed as shown in the following equation (8) using the following equations (6) have. Here, reference represents a reference coil 110r, and specimen represents a bobbin type coil 110.

&Quot; (8) "

If there is no defect in the test piece 10, the output current according to? In [Equation 8] is zero. However, when there is a defect in the test piece 10,? Is not 0, and the impedance and the phase difference expressed by Equations (9) and (10) change depending on the position and size of the defect.

&Quot; (9) "

&Quot; (10) "

For convenience, the output current may be derived using Equation (9) and Equation (10) as Equation (11) below. Here, crack indicates a defect.

 &Quot; (11) "

5 shows a circuit for acquiring an eddy current signal using the bobbin type coil 110 and the reference coil 110r according to an embodiment of the present invention. However, at the time of implementation, the reference coil 110r may be omitted from the circuit, and the defect-free test piece 20 may be omitted.

The eddy current testing apparatus 100 may amplify the differential signal line between the bobbin type coil 110 and the reference coil 110r to a sufficient signal level by connecting the differential signal line to the coil amplifier output AC amplifying circuit 130. The eddy current inspection apparatus 100 can branch the amplified signal level by the coil sensor output branch circuit 135. [ When the eddy current testing apparatus 100 multiplies each of the branch signals by the signal 105a of the phase delay square wave circuit 105 by using the coil sensor output multiplying circuit 140, Can be derived from the following equations (12) and (13). Here, the phase-delayed square wave circuit 105 can provide a signal having a phase difference of 90 degrees to the coil sensor output multiplication circuit 140.

&Quot; (12) "

&Quot; (13) "

The eddy current testing apparatus 100 can integrate each of the multiplied signals by an integration circuit 145 for coil sensor output. The eddy current testing apparatus 100 may express a signal as a real part and an imaginary part of a complex plane in performing a signal operation of the bobbin type coil 110 using the control module 115. [

That is, when the sides of Equations (12) and (13) are squared and then the square root operation is performed, a difference in impedance as shown in the following Equation (14) can be derived. If there is a defect in the test piece 10, the impedance of the induced current is increased.

&Quot; (14) "

Further, when performing the division operation, the phase difference as shown in the following equation (15) can be derived. It can be detected based on the phase difference whether a defect has occurred in the inner diameter (ID), outer diameter (OD) or outer diameter (OD) of the test piece 10.

&Quot; (15) "

Thus, the eddy current testing apparatus 100 can detect the position of the test piece 10 where the defect is generated based on the difference in impedance and the phase difference.

Meanwhile, FIG. 6 shows a circuit for acquiring an eddy current signal using the cylindrical Hall sensor array 120 according to an embodiment of the present invention.

The eddy current testing apparatus 100 can acquire a signal using the cylindrical hall sensor array 120. [ The eddy current inspection apparatus is constructed such that when a wide bobbin type coil 110 having a radius r is inserted into a small-diameter pipe test piece 10 made of a metal and an AC voltage is applied at a frequency derived by the formula ω = 2πf, The induced current is distorted in the vicinity of the defect. Therefore, an alternating magnetic field in the r direction is generated together with the alternating magnetic field in the z direction. Here, the alternating magnetic field refers to a magnetic field which is increased or decreased in the positive or negative direction and does not change its direction along with three device times.

In order to measure such an alternating magnetic field, the eddy current testing apparatus 100 operates the magnetic sensor driving power supply switching circuit 190 so that one column 120-1 to 120-4 in the? Direction of the cylindrical hall sensor array 120 ). The cylindrical hall sensor array 120 may include more columns than the four columns 120-1 to 120-4 shown in FIG. 6, and when the overall length of the sensor is to be shortened, As shown in FIG.

Further, the eddy current testing apparatus 100 connects the signal lines of the respective sensor arrays in the z direction to the parallel AC amplifier circuit 160 for magnetic sensor output, amplifies the signals to a sufficient signal level, 165).

The eddy current testing apparatus 100 may multiply the square wave signal 105a and the branch signal of the phase delay square wave circuit 105 by using the respective branch signals by the magnetic sensor output multiplying circuit 170. [ Accordingly, the eddy current testing apparatus 100 can measure the amplitude and the phase difference of the alternating magnetic field in the r direction due to the presence of defects as in the above-described [Expressions 12 to 15]. At this time, the respective amplitudes and phase differences can be calculated in software by the annular array magnetic sensor signal arithmetic operation unit 115b2, and can also be calculated in hardware at the time of implementation.

According to Fig. 6, it can be evaluated whether the defects of the test piece 10 are defective or defective, so that the risk of leakage due to rupture of the heat transfer pipe during the normal output operation of the power plant can be solved. In addition, even if the cylindrical hall sensor array 120 is inserted and stopped, the distribution of the time-varying magnetic field can be measured without mechanical rotation, thereby preventing deterioration of the equipment. In addition, defect detection and evaluation speed can be accelerated by electronic scanning. In addition, since the cylindrical hole sensor array 120 is formed of a plurality of columns and each column is annular, only one column is selected, and the defect is scanned in the axial direction, so that it can be used for the determination of defect existence and quantitative evaluation at a high speed. In addition, since the hall sensor itself is not an active coil sensor and is small in size, mutual interference of sensors is not a problem, cost can be reduced, and spatial resolution is excellent. In addition, the scan can be performed only in a part of the axial direction of the test piece 10, and if the observer's magnetic field due to the defect is distorted, the presence or absence of the defect, the shape and size of the defect, etc. can be quantitatively accurately evaluated. Further, since it is possible to detect defects using multiple frequencies, an excellent effect can be obtained in quantitative evaluation of defects.

Hereinafter, referring to FIG. 7, a block diagram illustrating a configuration of an eddy current testing apparatus 100 according to an embodiment of the present invention will be described. The eddy current inspection apparatus 100 can provide both defect detection based on the coils 110 and 110r sensing and defect detection using the cylindrical hole sensor array 120. [

First, the sensing of the coils 110 and 110r will be described first.

The eddy current testing apparatus 100 may include a multi-frequency AC power applying unit 107 for applying multiple frequencies. The control module 115 of the eddy current testing apparatus 100 may control the multiple frequency AC power applying unit 107 to apply a plurality of frequencies.

The eddy current testing apparatus 100 applies a signal output from the coil sensor output AC amplifier circuit 130 and the coil sensor output branch circuit 135 to the applied AC current and a square wave signal having a phase difference of 90 degrees from the phase delay square wave circuit 105 May be multiplied by the coil sensor output multiplication circuit (140).

The multiplied signal can be converted into a digital signal by the AD conversion circuit 155 via the coil sensor output integration circuit 145 and the coil sensor output DC amplification circuit 150.

At this time, the bobbin type coil sensor signal operating unit 115b1 of the control module 115 can calculate the amplitude and the phase difference according to the presence or absence of the defect and the position by combining the two signals output from the coil amplifier sensor output DC amplification circuit 150. [

Next, the detection of defects using the cylindrical Hall sensor array 120 following the sensing of the coils 110 and 110r will be described.

The eddy current testing apparatus 100 includes a magnetic sensor driving power source switching unit 120 for selectively applying driving power to the columns 120-1, 120-2, 120-3, and 120-4 of the cylindrical Hall sensor array 120, Power can be sequentially applied in the axial direction through the circuit 190. [ In the implementation, it is not limited to the axial direction, but power may be sequentially applied back and forth with respect to a defect detection region.

The eddy current inspection apparatus 100 can control so that the applied signal is outputted through the AC amplifier circuit 160 for magnetic sensor output and the parallel type branch circuit 165 for magnetic sensor output.

At this time, the signal output from the branch circuit 165 can be multiplied by the square wave signal of the phase delay square wave circuit 105 and the multiplier circuit 170 for magnetic sensor output. The square wave signal may be a rectangular wave signal used in the coil sensors 110 and 110r and has a phase difference of 90 degrees.

The multiplied signal can be converted into a digital signal by the AD conversion circuit 155 via the magnetic sensor output integration circuit 175, the magnetic sensor output DC amplification circuit 180, and the like.

At this time, the annular array type magnetic sensor signal calculator 115b2 of the control module 115 combines signals corresponding to twice the number of column direction sensors output from the magnetic sensor output DC amplifier circuit 180, The distribution of the amplitude and the phase difference can be calculated.

The bobbin type coil sensor signal computing unit 115b1 and the annular array type magnetic sensor signal computing unit 115b2 are respectively connected to a coil sensor output integrating circuit 145 for amplifying two integral signals, A DC amplifier circuit 180 for magnetic sensor output for amplifying two integrated signals per sensor output through the circuit 150 and the integration circuit 175 for magnetic sensor output, 180 and the analog signal output from the coil amplifier sensor output DC amplifying circuit 150 to an AD conversion circuit 155 for converting the analog signal into a digital signal.

The cylinder array type magnetic sensor signal calculator 115b3 sequentially selects each column of the cylindrical Hall sensor array 120 in the arcuate direction while selecting a specific frequency of the multiple frequency AC power source 107, A signal corresponding to twice the number of the column direction sensors output from the magnetic sensor output DC amplifying circuit 180 may be combined to calculate the distribution of amplitudes and phase differences depending on the presence or absence of the defect and the position.

The control module 115 controls the frequency selection of the multi-frequency ac power application unit 107, the amplification ratio conversion of the coil amplification circuit 130 for the coil sensor output and the amplification circuit 150 for the coil sensor output, Conversion of the magnetic sensor output AC amplification circuit 160 and the DC amplification circuit 180, the drive of the AD conversion circuit 155, the bobbin type coil sensor signal calculation unit 115b1, the annular array type magnetic sensor The signal calculation unit 115b2, and the cylinder arrangement type magnetic sensor signal calculation unit 115b3.

Figures 8 (a) and 8 (b) show test specimens comprising various defects according to an embodiment of the present invention.

According to Fig. 7 (a), the total length of the test piece 10 is 500 mm, and various defects appear. In addition, there is no defect of the test piece 10 in the case of the defect-free test piece 20 apart from the test piece 10.

The outer wall (OD) is 15.87, the circumferential inner diameter (ID) is 13.33, the thickness is 1.27, and the material is SS304. The TSP (tube support plate) may be made of carbon steel, but the dimensions of the test piece 10 may vary in various ways during implementation.

A table corresponding to the defect for each point in Fig. 8 (a) is shown in Fig. 8 (b).

A flat bottomed hole (FBH) is a flat bottom hole, and a through wall hole (TWH) is a through hole. TSP (tube support plate) is also observed.

9 shows the amplitude distribution of each defect when a frequency of 30 KHz is applied.

9, when a frequency of 30 kHz is applied to the bobbin type coil 110, a distribution of a time-varying magnetic field amplitude measured in a selected one of the cylindrical hall sensor arrays 120 is shown. The abscissa represents the distance, and the ordinate represents the position of the sensor arranged in the 360 degree direction. Continuous defects in the circumferential direction of the test specimen, such as ID groove, OD groove, and TSP, are continuous in all the sensors, so they show a continuously changing magnetic field distribution along the longitudinal axis. FBH 20% -4 indicates that four FBH defects are annularly arranged at intervals of 90 degrees, and defects are arranged at intervals of 90 degrees through the amplitude distribution. And, FBH 40 ~ 100% shows defects whose diameters and depths are different from each other. The eight three-dimensional graphs in total, four in each of the upper and lower sides, show the distribution of the amplitude of the time-varying magnetic field that can be obtained when the cylindrical Hall sensor array 120 is placed at the central position of the defect, . That is, it is possible to measure the amplitude distribution in a specific region without the mechanical driving necessarily accompanied by the conventional technique.

10 shows the phase difference distribution of each defect when a frequency of 30 KHz is applied.

Fig. 10 shows the distribution of the phase difference of the time-varying magnetic field measured under the same conditions as those in Fig. 9, but the results of FBH 20% -4 are clearly different. That is, the sensor probe does not maintain a constant lift-off (distance between the sensor and the measurement surface) on the inner wall of the pipe, and when the sensor probe is shifted to one side, the intensity of the amplitude changes as shown in FIG. 9, It is difficult to distinguish whether the off is large. However, as shown in Fig. 10, since the phase difference distribution is not largely affected by the lift-off, it exhibits the same phase difference distribution in defects of the same size.

11 shows the distribution of amplitudes when a frequency of 50 KHz is applied.

If the frequency is high, penetration depth of the eddy current becomes shallow. That is, the defect near the sensor is easy to measure, but the output from the defect at the position far from the sensor is small. This principle can distinguish TSP signals. In FIG. 9, the TSP signal is very large, indicating a larger signal than a defect of ID groove 10% and OD groove 20%. However, when a high frequency such as 50 kHz is applied, the induced current is concentrated only on the surface of the test piece 110 and does not reach the TSP located outside the test piece. That is, by comparing the signals of 30 kHz and 50 kHz at the same time, it is possible to distinguish between TSP and groove. However, according to the conventional technique, in order to measure the distribution of the time-varying magnetic field while inputting a plurality of frequencies, a first method of scanning multiple times while changing frequencies, and a first method of alternately performing multiple scans The second method must be used. In the first method, the inspection time increases to the number of times of the frequency, so that it takes twice or more time to input two frequencies and eight times or more to input eight frequencies. The second method complicates the signal processing circuit and becomes expensive. However, according to the present invention, when a sensor probe is placed in the vicinity of a defect and an electronic scan is operated, a time-varying magnetic field distribution can be observed in real time in the corresponding region. That is, it is only necessary to change the input frequency.

12 shows the phase difference distribution of each defect when a frequency of 50 KHz is applied.

12 shows the phase difference distribution of the time-varying magnetic field measured under the same conditions as those of FIG. Although there may not be a large difference on the graph, referring to FIG. 13 below, the difference can be more clearly derived.

FIG. 13 is a graph of the RISAS diagram based on the output of the sensor passing the center of the defect in FIGS. 11 and 12 when a frequency of 50 kHz is applied.

In the eddy current test, the lithography is used to identify the presence and location of defects, and the curved pattern represents each defect. And, the curved pattern rotates counterclockwise as the depth of the coordinate defect deepens from 20% to 100%. The position and magnitude of the defect can be determined through this rotational direction and degree. That is, it can be determined whether the defect is inside or outside the test piece 10.

9 to 13, it is possible to measure the defects of the test piece 10 at multiple frequencies, so that the quantitative evaluation can be performed effectively.

The present invention described above can be embodied as computer-readable codes on a medium on which a program is recorded. The computer readable medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of the computer readable medium include a hard disk drive (HDD), a solid state disk (SSD), a silicon disk drive (SDD), a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, , And may also be implemented in the form of a carrier wave (e.g., transmission over the Internet). The computer may also include a control module 400 of the system 1000 for providing content. Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

Claims (11)

1. An eddy current inspection apparatus for nondestructive inspection,
A bobbin type coil inserted into a test piece to be inspected for the nondestructive inspection and applying an induction current to the inner wall of the test piece;
A reference coil inserted into the defect-free test piece, which is a reference of the test piece, for applying an induced current to the inner wall of the defect-free test piece;
A cylindrical Hall sensor array disposed within the bobbin type coil and including rows and columns; And
A control module for selecting one or more frequencies among multiple frequencies and applying an AC power to the bobbin type coil and the reference coil to generate a square wave signal having a different phase difference and for controlling the applied signal and the square wave signal to be first multiplied, ≪ / RTI >
The control module includes:
A driving power source is switched and applied so that arrays in the arcuate direction are successively selected from among a plurality of columns of the cylindrical hall sensor array, and a square wave having a different phase difference generated in the applied signal is controlled to be second multiplied,
Wherein the defect of the test piece is detected based on the first multiplied signal and the second multiplied signal using a distribution of the amplitude and phase difference of the signal. 1. An eddy current inspection apparatus for nondestructive inspection,
A bobbin type coil inserted into a test piece to be inspected for the nondestructive inspection and applying an induction current to the inner wall of the test piece;
A cylindrical Hall sensor array disposed within the bobbin type coil and including rows and columns; And
And a control module for selecting at least one frequency among the multiple frequencies to apply an AC power to the bobbin type coil, generating a square wave signal having a different phase difference, and controlling the applied signal and the square wave signal to be first multiplied ,
The control module includes:
A driving power source is switched and applied so that arrays in the arcuate direction are successively selected from among a plurality of columns of the cylindrical hall sensor array, and a square wave having a different phase difference generated in the applied signal is controlled to be second multiplied,
Wherein the defect of the test piece is detected based on the first multiplied signal and the second multiplied signal using a distribution of the amplitude and phase difference of the signal. 1. An eddy current inspection apparatus for nondestructive inspection,
A bobbin type coil inserted into a test piece to be inspected for the nondestructive inspection and applying an induction current to the inner wall of the test piece;
A reference coil inserted into the defect-free test piece, which is a reference of the test piece, for applying an induced current to the inner wall of the defect-free test piece;
An annular array of Hall sensors arranged in the bobbin type coil and consisting of one row; And
A control module for selecting one or more frequencies among multiple frequencies and applying an AC power to the bobbin type coil and the reference coil to generate a square wave signal having a different phase difference and for controlling the applied signal and the square wave signal to be first multiplied, ≪ / RTI >
The control module includes:
Applying driving power to the annular Hall sensor array and controlling a square wave having a different phase difference generated in the applied signal to be multiplied by a second time,
Wherein the defect of the test piece is detected based on the first multiplied signal and the second multiplied signal using a distribution of the amplitude and phase difference of the signal. 1. An eddy current inspection apparatus for nondestructive inspection,
A bobbin type coil inserted into a test piece to be inspected for the nondestructive inspection and applying an induction current to the inner wall of the test piece;
An annular array of Hall sensors arranged in the bobbin type coil and consisting of one row; And
And a control module for selecting at least one frequency among the multiple frequencies to apply an AC power to the bobbin type coil, generating a square wave signal having a different phase difference, and controlling the applied signal and the square wave signal to be first multiplied ,
The control module includes:
Applying driving power to the annular Hall sensor array and controlling a square wave having a different phase difference generated in the applied signal to be multiplied by a second time,
Wherein the defect of the test piece is detected based on the first multiplied signal and the second multiplied signal using a distribution of the amplitude and phase difference of the signal. A method of driving an eddy current inspecting apparatus,
At least one frequency of multiple frequencies is selected from a bobbin type coil inserted into a test piece to be tested for non-destructive testing and a reference coil inserted into a defect-free test piece which is a reference of the test piece to induce an induced current, And multiplying the applied signal by a first multiplication, the outputs of the bobbin type coil and the reference coil being differentially connected;
Wherein the driving power is switched and applied so that arrays in the arcuate direction are successively selected from among a plurality of rows of the cylindrical Hall sensor array inserted into the bobbin type coil, and a square wave having the different phase difference generated in the applied signal is applied to the second Multiplying; And
And detecting a defect of the test piece based on the first multiplied signal and the second multiplied signal using a distribution of amplitude and phase difference of a signal. A non-transitory computer-readable recording medium having recorded thereon a program for execution on a computer, the program comprising:
At least one frequency of multiple frequencies is selected from a bobbin type coil inserted into a test piece to be tested for non-destructive testing and a reference coil inserted into a defect-free test piece which is a reference of the test piece to induce an induced current, And multiplying the applied signal by a first multiplication, the outputs of the bobbin type coil and the reference coil being differentially connected;
Wherein the driving power is switched and applied so that arrays in the arcuate direction are successively selected from among a plurality of rows of the cylindrical Hall sensor array inserted into the bobbin type coil, and a square wave having the different phase difference generated in the applied signal is applied to the second Multiplying; And
And detecting a defect of the test piece based on the first multiplied signal and the second multiplied signal using a distribution of the amplitude and phase difference of the signal. 5. The method according to any one of claims 1 to 4,
Wherein the phase difference of the rectangular wave having the different phase difference is 90 degrees. 6. The method of claim 5,
Wherein the phase difference of the rectangular wave having the different phase difference is 90 degrees. The method according to claim 6,
Wherein the phase difference of the rectangular wave having the different phase difference is 90 degrees. 5. The method according to any one of claims 1 to 4,
Further comprising a display,
The control module includes:
Wherein the amplitude and phase difference of the signal are quantitatively displayed on the display for each defective part based on the selected one or more frequencies. 3. The method according to claim 1 or 2,
The control module includes:
And a driving circuit for driving the circuit for converting an analog signal into a digital signal, the method comprising: determining an amplification ratio of the AC amplification circuit and the DC amplification circuit, switching the driving power source to rows and columns included in the cylindrical Hall sensor array, Inspection device.

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