Data processing method and data processing device for eddy current flaw detection

Abstract

To provide a data processing method for an eddy current flaw detection system capable of accurately evaluating changes in slit signal intensity even when a scan starting position in each time deviates in a case of probe-scanning a magnetic material multiple times.SOLUTION: A multi-coil type probe 51 is placed on an inspection object 1 made of a magnetic material having a slit 4, and a portion including the slit is scanned by the probe to acquire an initial waveform and an evaluation waveform multiple times. A movement amount of the evaluation waveform in a case where the evaluation waveform is moved toward the initial waveform is calculated so that the deviation between the initial waveform and the evaluation waveform becomes minimal. A correction value for the evaluation waveform is calculated on the basis of position information of each channel in the probe and the movement amount of the evaluation waveform. A new evaluation waveform is generated by moving the evaluation waveform in accordance with the correction value. A difference in peak values between the initial waveform and the new evaluation waveform is calculated.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a method and apparatus for processing eddy current flaw detection data.

Background Art

[0002] Eddy current flaw detection is a non-destructive inspection for inspecting a test object using an eddy current flaw detection probe (hereinafter simply referred to as a probe) having at least one electrical induction coil (hereinafter simply referred to as a coil). More specifically, when the probe is brought close to the test object and an alternating magnetic field is generated by the coil (excitation coil) of the probe, eddy currents are generated at the skin depth determined by the conductivity and magnetic permeability of the test object. If there is a defect in the test object, the eddy currents are disturbed so as to avoid the defect, and the presence or absence of the defect is evaluated by detecting the impedance change caused by the disturbance of the eddy currents with a coil (detection coil).

[0003] Patent Document 1 relates to an eddy current inspection signal analysis apparatus that analyzes an eddy current inspection signal obtained by eddy current inspection for detecting fluctuations in eddy currents generated in a test object, removes a low-frequency component from the eddy current inspection signal, and compares it with a predetermined threshold value to extract a first signal section in which there is a high possibility of damage in the test object. It is explained that this reduces the influence of the drift of the eddy current inspection signal and enables accurate extraction of a signal section in which there is a high possibility of damage in the test object.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] From the viewpoint of ensuring the reliability of eddy current flaw detection inspection, it is preferable to confirm that there are no abnormalities in the equipment and probes constituting the eddy current flaw detection system before and after the inspection. For example, in this confirmation operation, a probe is brought close to a test piece (comparison test piece) provided with a slit of a constant depth, and the probe is scanned by a scanning device from a predetermined starting position in a predetermined direction and at a predetermined speed, and the intensity (for example, voltage value) of a signal (hereinafter sometimes referred to as a slit signal) detected as a peak when passing through the slit is acquired. Then, when the deviation of the slit signal intensity acquired before and after the inspection is within a predetermined range, the eddy current flaw detection system is determined to be normal.

[0006] By the way, the magnetic permeability distribution in a magnetic material is non-uniform, and the magnetic permeability of the magnetic material varies depending on the position. Therefore, when scanning a magnetic material with a probe, even if there are no defects, the penetration depth of the eddy current changes and a signal (hereinafter sometimes referred to as a magnetic signal) is detected. Also, in a normal eddy current flaw detection system, the signal intensity at the starting position of probe scanning is set to 0 (0 V). That is, a signal based on the magnetic permeability at the scanning start position is detected. This means that when measuring the slit signal intensity twice for a test piece made of a magnetic material, if the first and second scanning start positions are not exactly the same, different-intensity slit signals can be detected even when the probe is scanned in the same direction and at the same speed. That is, if the scanning start position shifts between the first and second measurements, it is impossible to determine whether the cause of the change in the intensity of the slit signal is an abnormality in the eddy current flaw detection system. Note that, for example, a scanning device with high position accuracy tends to be large-sized, but when spatial restrictions are severe and it is difficult to introduce such a device, the above-mentioned problem of position shift is likely to occur.

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to provide a data processing method and an eddy current flaw detection system for an eddy current flaw detection system that can accurately evaluate a change in slit signal intensity even when the scanning start position shifts each time a magnetic material is scanned with a probe multiple times.

Means for Solving the Problem

[0008] This application includes multiple means for solving the above problems. For example, in a data processing method of an eddy current flaw detection system, a multi-coil probe having a plurality of channels that are combinations of an excitation coil and a detection coil is installed on a magnetic inspection object provided with a slit, and the part including the slit is scanned with the probe to obtain an initial waveform and an evaluation waveform for each channel. For each channel, the amount of movement of the evaluation waveform when the evaluation waveform is moved toward the initial waveform so that the deviation between the initial waveform and the evaluation waveform is minimized is calculated. Based on the position information of each channel in the probe and the amount of movement of the evaluation waveform of each channel, a correction value for the evaluation waveform of each channel is calculated, and a new evaluation waveform for each channel is generated by moving the evaluation waveform of each channel according to the correction value of each channel. The difference between the peak values of the initial waveform and the new evaluation waveform is calculated for each channel.

Advantages of the Invention

[0009] According to the present invention, even if the starting position of each scan shifts when the magnetic inspection object is scanned with the probe multiple times, the change in the slit signal intensity can be accurately evaluated.

Brief Description of the Drawings

[0010]

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0012] FIG. 1 is a configuration diagram of an eddy current flaw detection system 100 according to an embodiment of the present invention. The eddy current flaw detection system 100 in this figure includes a probe (eddy current flaw detection probe) 51 incorporating a plurality of coils, a scanning device 52 for scanning the probe 51, an eddy current flaw detector 53 connected to the probe 51, a computer 54 connected to the scanning device 52 and the eddy current flaw detector 53, and a monitor 55 connected to the computer 54.

[0013] The probe 51 is a multi-coil type probe having a plurality of channels 11 (see FIGS. 2, 3, etc.) which are combinations of at least one excitation coil and at least one detection coil. When the probe is scanned by the scanning device 52, waveforms are obtained by each channel 11. Each coil in the probe 51 can function as at least one of an excitation coil and a detection coil. That is, one coil may function as either an excitation coil or a detection coil (mutual induction coil), or one coil may function as both an excitation coil and a detection coil (self-induction coil).

[0014] The scanning device 52 is a device that scans the probe 51 based on a control signal input from the computer 54, and can output its position as a signal (position signal) to the computer 54. In the control signal, the scanning speed and scanning direction of the probe 51 can be specified, and the probe 51 can be scanned at a predetermined speed in a predetermined direction.

[0015] The eddy current flaw detector 53 can supply an exciting current (alternating current) to the coil in the probe 51 and operate the coil as an exciting coil. Further, the induced voltage detected by the coil (detection coil) in the probe 51 can be input, and the detection signal can be output to the computer 54.

[0016] The computer 54 includes at least one processor 54a and a storage device 54b that stores various data including programs executed by the processor 54a. The computer 54 may be provided with an input device for inputting operations and data from an operator and a communication device for communicating with other terminals. The computer 54 can set scanning conditions such as the scanning speed and scanning range of the scanning device 52, and can also set flaw detection conditions such as the frequency of the exciting current of the eddy current flaw detector 53. Further, the computer 54 can process the position signal from the scanning device 52 and the detection signal of the detection coil from the eddy current flaw detector 53 to generate flaw detection data (waveform), and can display the flaw detection data on the monitor 55 or store it in the storage device 54b.

[0017] By the way, a magnetic material may be used as the object to be inspected in the eddy current flaw detection system 100 as described above. When the object to be inspected is a magnetic material, due to the property of the magnetic material that the magnetic permeability is unevenly distributed, even in a non-defective part, a change may occur in the penetration depth of the eddy current generated by the exciting coil. The distribution of the magnetic permeability in the magnetic material can be changed to a different distribution when a magnetic field larger than the external one is applied, but it cannot be changed with a coil magnetic field level generally used in eddy current flaw detection. That is, when inspecting a magnetic material by eddy current, a magnetic signal is generated even in a non-defective part of the object to be inspected, but it is a reproducible signal. That is, in other words, it shows that the same magnetic signal can be obtained even when the same part of the magnetic material is inspected multiple times.

[0018] The problems in the case of inspecting a magnetic material by a magnetic signal are described below. As described above, the eddy current flaw detection system applies an alternating magnetic field to the object to be inspected by an excitation coil, and a detection coil captures changes in the impedance of the coil and the induced voltage due to the flaw at that time. At this time, the probe detection voltage (signal intensity) at the scanning start position (starting point) is set to a reference (0 V). In the case of a magnetic material, a magnetic signal is generated even in a sound part, so there is a problem with the reproducibility of the flaw signal. For example, assume that in an object to be inspected made of a magnetic material, a signal caused by a flaw exceeding the level of the magnetic signal is generated from the first measurement. When the second measurement is carried out for confirmation, unless the scanning starts exactly from the same starting point of the probe scan as the first time, the peak value of the flaw signal will change. For this reason, there is a problem that it is impossible to distinguish whether the reason for the signal change is due to factors affecting the test itself, such as equipment or probe malfunction, or lift-off between the probe and the object to be inspected.

[0019] FIG. 2 is a side view of the probe 51 and the object to be inspected 1 according to the present embodiment, and FIG. 3 is a top view thereof. The object to be inspected 1 is formed of a magnetic material and has a slit 4 with a constant depth at the center. The position of the left end of the object to be inspected 1 is set to zero, the scanning start position (starting point) of the probe 51 is set to Ln (n = 0, 1), and the position of the slit 4 is set to K.

[0020] In order to confirm that there is no abnormality in the equipment and probe of the eddy current flaw detection system, for example, before and after the eddy current flaw detection inspection, the part including the slit 4 is scanned by the probe 51, and thereby an initial waveform and an evaluation waveform are acquired at each channel 11 of the probe 51. When acquiring the waveform, the probe 51 is arranged on the surface of the object to be inspected 1 and moved in a predetermined scanning direction 5 at a predetermined scanning speed from the position Ln. It is preferable to acquire the initial waveform before the inspection, and it is preferable to acquire the evaluation waveform after the inspection. However, when the operator manually installs the probe 51 at the scanning start position Ln, the start position Ln may shift each time. Note that the object to be inspected 1 is also referred to as a reference test piece.

[0021] FIG. 4 is a diagram showing an example of an initial waveform (change in flaw signal) 70 obtained in a certain channel 11 by scanning the inspection object 1 with the probe 51. The horizontal axis in FIG. 4 represents the position in the inspection object 1, and the vertical axis represents the intensity of the flaw detection signal (for example, voltage [V]). Data is recorded such that the signal intensity at the start position L0 of the probe scan becomes a predetermined reference value (0 V). In the illustrated initial waveform 70, a magnetic signal 6 is generated throughout, and a slit signal 7 when passing through the slit 4 is generated at the position K. It is preferable to adjust the setting of the eddy current flaw detector 53 so that the peak value (peak of the slit signal 7) of the initial waveform of each channel 11 becomes a predetermined value (1 V in the illustrated example).

[0022] FIG. 5 is a diagram showing an evaluation waveform 80 obtained by performing flaw detection in the same manner as in the case of FIG. 4 with the start point of the probe scan being L1 different from L0. The evaluation waveform 80 shown by the solid line has the start point of the probe scan as L1, and the signal 70 shown by the broken line is the same initial waveform as FIG. 4 with the start point of the probe scan being L0. Since the start point of the probe scan is based on the 0 V reference and the magnetic permeability of the inspection object 1 varies depending on the location, the peak value of the slit signal of the signal 80 is different from the slit signal 7 of the initial waveform 70 by the amount of the arrow 9.

[0023] FIG. 6 shows a probe output signal group (flaw detection signal) 12 which is a set of initial waveforms obtained in each channel 11 of the probe 51. The horizontal axis represents the position, and the vertical axis represents the flaw detection signal intensity. Data is recorded with the signal intensity at the start position L0 of the probe scan being the 0 V reference. A magnetic signal 13 is generated throughout in all channels 11, and a slit signal 14 of the slit 4 is generated at the position k in all channels 11. For example, at this time, the setting value of the eddy current flaw detector 53 is adjusted so that the peak values of the slit signals in all channels 11 become the same value (1 V in the illustrated example).

[0024] FIG. 7 shows a probe output signal group (flaw detection signal) 15, which is a set of evaluation waveforms obtained at each channel 11 of the probe 51, with the starting point of the probe scan being L1, which is different from L0. Since the signal intensity at the starting point L1 of the signal group 15 of the probe scan is based on the 0 V reference, the magnetic signal affects the peak value of the slit signal and changes as shown by the arrow 16. That is, the signal intensity is not unified to the reference value of 1 V. The eddy current flaw detection probe 51 incorporating a plurality of coils can flaw the width in the coil arrangement direction at once, but such a phenomenon occurs because the magnetic permeability at the starting position L1 of each channel 11 is different and the magnetic signals are different.

[0025] Therefore, in the present embodiment, in the data processing of the initial waveform and the evaluation waveform related to the system 100, the following procedures S101-105 are to be performed. FIG. 8 is a flowchart summarizing the procedures performed in the data processing of the initial waveform and the evaluation waveform according to the present embodiment.

[0026] (S101) A multi-coil type probe 51 having a plurality of channels 11, which is a combination of at least one excitation coil and at least one detection coil, is installed on the magnetic test object 1 provided with the slit 4, and the initial waveform and the evaluation waveform are acquired at each channel 11 by scanning the portion including the slit 4 with the probe 51.

[0027] (S102) At each channel 11, calculate the amount of movement of the evaluation waveform when the evaluation waveform is moved toward the initial waveform so that the deviation between the initial waveform and the evaluation waveform is minimized.

[0028] (S103) Based on the position information of each channel 11 in the probe 51 and the amount of movement of the evaluation waveform of each channel 11 calculated in (S102) above, calculate the correction value of the evaluation waveform of each channel 11.

[0029] (S104) Generate a new evaluation waveform for each channel 11 by moving the evaluation waveform of each channel 11 according to the correction value of each channel 11 calculated in (S103) above.

[0030] (S105) Calculate the difference in peak values between the initial waveform and the new evaluation waveform generated in the above (S104) for each channel 11.

[0031] In addition, in the above S101, it is preferable to perform the scanning of the probe 51 at least twice in order to acquire the initial waveform and the evaluation waveform. Although the starting position of the scanning of the probe 51 is different each time, the scanning direction and the scanning speed are the same. Also, as shown in FIG. 4 and the like, the initial waveform and the evaluation waveform can be represented on a two-dimensional plane composed of a horizontal axis indicating the position and a vertical axis indicating the signal intensity.

[0032] The magnitude of the "deviation" in the above S102 can be evaluated, for example, by moving the evaluation waveform so that the evaluation waveform overlaps the initial waveform, calculating the absolute value of the difference in signal intensity between the two waveforms after the movement for each position, and evaluating by the magnitude of the integrated value of these. That is, the amount of movement of the evaluation waveform at which the integrated value becomes minimum is calculated in S102. When the evaluation waveform is plotted on a two-dimensional plane composed of a horizontal axis indicating the position and a vertical axis indicating the signal intensity, the amount of movement of the evaluation waveform can be defined by the change amount ΔK of the position of the evaluation waveform which is the horizontal axis and the change amount ΔV of the signal intensity which is the vertical axis.

[0033] The "position information of each channel 11 in the probe 51" used in the above S103 is, for example, the arrangement of each channel 11 at the scanning start position of the probe 51 when the evaluation waveform is acquired. In the arrangement of the channels in the probe 51 exemplified in this embodiment, as shown in FIG. 3, a plurality of channels 11 are arranged linearly at substantially equal intervals. In the case of such a probe 51, the position of each channel 11 in the scanning direction can change depending on the inclination of the probe 51 at the scanning start position when the evaluation waveform is acquired. For example, if the longitudinal direction of the probe 51 is parallel to the depth direction of the object to be inspected 1 (the vertical direction in FIG. 3), the scanning start positions of each channel 11 coincide.

[0034] The "correction value for each channel 11" in S103 above can be a value approximated based on the amount of movement of the evaluation waveform of each channel 11 plotted on a two-dimensional plane, based on the arrangement of each channel 11 at the scanning start position of the probe 51 when the evaluation waveform was acquired.

[0035] Also, the "correction value for each channel 11" in S103 above can be a value approximated by a straight line having the same slope as the straight line (the first straight line) when each channel 11 is arranged along a straight line (the first straight line) at the scanning start position of the probe 51 when the evaluation waveform was acquired, for the amount of movement of the evaluation waveform of each channel 11 plotted on a two-dimensional plane.

[0036] Also, after S105 above, the difference in peak values between the initial waveform and the new evaluation waveform of each channel 11 calculated in S105 may be displayed on the monitor 55.

[0037] Next, an example of a specific procedure according to the flow of FIG. 8 will be described with reference to FIGS. 9-14.

[0038] FIG. 9 shows the scanning start positions of the probe 51 when two waveform measurements of the initial waveform and the evaluation waveform are performed on the same slit 4 (test object 1). The start position 20 when the first initial waveform was measured is designated as L0, and the start position 21 when the second evaluation waveform was measured is designated as L1. As previously described, when the scanning start position of the probe 51 is different, the peak value of the slit signal changes due to the influence of the permeability distribution. This change may seem to result in measurements with low reproducibility due to equipment dependence, even though there is no failure of the probe 51 or change in the settings of the eddy current flaw detector 53. Hereinafter, a method for correcting the evaluation waveform obtained in the second measurement to a state where it is scanned from the same position as the scanning position of the probe 51 in the first measurement will be described.

[0039] First, obtain the position information of each channel 11 from the arrangement structure and drive information of the multiple coils built into the probe 51. Since eddy current flaw detection uses the signal intensity at the start point of probe scanning as a reference (0 V), the coil arrangement is utilized in this adjustment. Here, as shown in FIG. 3, the case where the probe 51 in which each coil is linearly arranged at equal intervals along the longitudinal direction of the probe 51 is used will be described.

[0040] Next, scan the test object 1 twice with the probe 51 and measure the initial waveform and the evaluation waveform at each channel 11 (S101). Then, when the evaluation waveform is moved from the initial position and fitted to the initial waveform at each channel 11, the amount of movement of the evaluation waveform is represented by two parameters (the position ΔK of the evaluation waveform and the signal intensity (DC bias voltage) ΔV). The two waveforms are fitted, and the values of the parameters (the position ΔKmin and the DC bias voltage ΔVmin) at which the deviation between the two waveforms (the method of evaluating the "deviation" is as described above) is minimized are calculated. The same process is performed for the initial waveforms and evaluation waveforms obtained at all channels 11 to calculate ΔKmin and ΔVmin (the amount of movement of the evaluation waveform) (S102).

[0041] The details of the calculation of ΔKmin and ΔVmin (the amount of movement of the evaluation waveform) will be described with reference to FIG. 10. FIG. 10 is a diagram showing the initial waveform 22 and the evaluation waveform 23 obtained at a certain channel 11 in a two-dimensional plane with the horizontal axis being the scanning position and the vertical axis being the signal intensity (V). The dashed line indicates the first initial waveform 22, and the solid line indicates the evaluation waveform 23. Here, since the magnetic waveform is reproducible, the evaluation waveform 23 and the initial waveform 22 will coincide if there is no damage to the probe 51 or change in the device settings. Therefore, as shown in FIG. 11, the evaluation waveform is shifted by ΔK on the horizontal axis and ΔV on the vertical axis to calculate the deviation between the two waveforms. The ΔK and ΔV at which this deviation is minimized are taken as ΔKmin and ΔVmin, and these are written together with the channel number (Ch number) of that channel into the memory (storage device 54b) of the computer 54.

[0042] Next, for the combination of the Ch number written in the memory and ΔKmin (the amount of movement in the horizontal axis direction), a relational expression between the Ch number and the correction value ΔKcrc corresponding to the channel of that number is created using the approximation formula determined by the coil array in the probe 51 (that is, the correction value ΔKcrc in the horizontal axis direction for each Ch is calculated) (S103). This procedure will be described in detail with reference to FIG. 12.

[0043] FIG. 12 shows the result of plotting the calculation results of the Ch number and ΔKmin in a two-dimensional plane with the vertical axis being the Ch number and the horizontal axis being ΔKmin. In the present embodiment, as shown in FIG. 9, the probe 51 has a plurality of coils (channels) linearly arranged along the depth direction of the object under inspection 1. Considering that the probe 51 does not rotate (the rotation angle is zero) in each measurement round, by creating an approximation formula with a straight line (regression line) 25 where ΔKmin = constant, it is possible to derive the correction value ΔKcrc with high accuracy for each channel 11 taking into account the coil arrangement of the probe 51. That is, when the angle of the probe 51 is held as shown in FIG. 9 both times, an approximation formula can be created with a straight line (regression line) 25 where ΔKmin = constant, and the correction value for each channel 11 is ΔKcrc. The calculated correction value ΔKcrc may be written in the memory (storage device 54b) of the computer 54 in association with the Ch number.

[0044] Next, after moving the evaluation waveform of each channel 11 in the direction of the horizontal axis according to the correction value ΔKcrc of each channel 11, it is moved in the direction of the vertical axis to a position overlapping with the initial waveform of each channel 11 to generate a new evaluation waveform for each channel 11. That is, the position of the evaluation waveform is corrected by ΔKcrc obtained from the Ch number and ΔKmin of each channel 11, and the evaluation waveform is moved so as to add a DC bias current of ΔV so that the position corresponding to the probe scan start point of the initial waveform becomes 0V. In this way, for all channels 11, the evaluation waveform is shifted to generate a new evaluation waveform (S104). Since the information on the arrangement structure of the coils in the probe 51 is taken into account in the process of generating the new evaluation waveform as described above, it is difficult to include the operator's arbitrariness and high-precision waveform position correction can be realized.

[0045] Next, the difference in peak values between the initial waveform and the new evaluation waveform is calculated for each channel 11 (S105). The difference may be displayed on the monitor 55. By evaluating the difference, it is possible to promptly consider the presence or absence of a system abnormality and the necessity of calibration. That is, according to the present embodiment, even when the scanning start position shifts in each of multiple probe scans of the magnetic material, the change in the slit signal intensity can be accurately evaluated.

[0046] In the above description, the case where the starting points L0 and L1 of the two probe scans are shifted in the horizontal axis direction (Fig. 9) was mentioned. However, in reality, the case where the posture of the probe 51 at the start of the second scan is rotated as shown in Fig. 13 is also conceivable. In Fig. 13, the dashed rectangle labeled 30 indicates the posture of the probe 51 at the scan start position when the initial waveform of the first time was measured (when the rotation angle of the probe 51 is zero), and the rectangle labeled 31 indicates the posture of the probe 51 at the scan start position when the evaluation waveform of the second time was measured (when the probe 51 is rotated θ degrees counterclockwise). In this case as well, the correction value ΔKcrc can be calculated in the same manner as in the case of Fig. 9. That is, as described above, after obtaining the movement amount ΔKmin for each channel 11 in S102, in S103, the ΔKmin of each channel 11 is plotted on a two-dimensional plane with the vertical axis being the Ch number and the horizontal axis being ΔKmin, and a linear approximation formula (regression line) 32 is created based on the result and the channel position information of the probe 51 (that is, each channel 11 is arranged linearly). When the scan start point of the probe 51 when the evaluation waveform is acquired is rotated, as shown in Fig. 14, each point of ΔKmin on the two-dimensional plane is plotted corresponding to the rotation of the probe 51, and the approximation formula is also generated as a line having a slope. That is, since the relational expression (approximation formula) between the Ch number and the correction values (ΔKcrc1, ΔKcrc2, ΔKcrc3, ΔKcrc4, ΔKcrc5) corresponding to each Ch reflects the inclination θ of the probe 51, it can be said that the correction value can be calculated in the same procedure as above, and furthermore, the difference in the peak values between the initial waveform and the new evaluation waveform can be evaluated. When the rotation angle θ of the probe 51 is known, the accuracy of each correction value ΔKcrc1, ΔKcrc2, ΔKcrc3, ΔKcrc4, ΔKcrc5 can be improved by making the slope of the approximation formula 32 coincide with θ.

[0047] In addition, each procedure including S101 - 105 described above may be executed by the processor 54a of the computer 54 in the system 100. In this case, the computer 54 functions as a data processing device in the system 100.

[0048] <Second Embodiment> Next, a second embodiment of the present invention will be described. As shown in FIG. 9, this embodiment can be applied when the postures (rotation angles) of the probe 51 at the first and second scanning start positions are the same but the scanning start positions are shifted.

[0049] In this embodiment, in the data processing of the initial waveform and the evaluation waveform related to the system 100, the following procedures of S101, S112 - 115 are performed. FIG. 15 is a flowchart summarizing the procedures performed in the data processing of the initial waveform and the evaluation waveform according to this embodiment. Note that the hardware configuration of the system 100 is the same as that of the first embodiment, and S101 in FIG. 15 is the same as that in FIG. 8.

[0050] (S101) A multi - coil type probe 51 having a plurality of channels 11, which is a combination of at least one excitation coil and at least one detection coil, is installed on a magnetic test object 1 provided with a slit 4, and the part including the slit 4 is scanned with the probe 51 to obtain an initial waveform and an evaluation waveform in each channel 11.

[0051] (S112) On a two - dimensional plane composed of a horizontal axis indicating position and a vertical axis indicating signal intensity, a plurality of evaluation waveforms obtained in each channel 11 are arranged, and reference points Pm (m = 0, 1, 2, 3, ···, n) arranged at predetermined intervals on the horizontal axis are set.

[0052] (S113) One reference point is selected from among the plurality of reference points Pm, and the plurality of evaluation waveforms on the two - dimensional plane are respectively translated in the direction of the vertical axis so that the signal intensity at the selected reference point becomes zero, and the variation in the peak values of the plurality of translated evaluation waveforms is calculated. This is repeated until all the reference points of the plurality of reference points Pm are selected.

[0053] (S114) Among the plurality of translated evaluation waveforms, the one with the smallest variation in the peak values calculated in (S113) is taken as the new evaluation waveform for each channel 11.

[0054] (S115) In each channel 11, calculate the difference between the peak values of the new evaluation waveform generated in (S114) and the initial waveform.

[0055] Note that, in the above (S112), when a plurality of reference points are arranged on the horizontal axis at a predetermined interval, if the evaluation waveform is composed of point group data, it is preferably the pitch of the points constituting the point group data.

[0056] Also, the plurality of reference points may be set at positions closer to the origin of the two-dimensional plane than the peak positions in the evaluation waveforms of each channel 11. By limiting the range for setting the reference points in this way, the number of times of calculating the variation in (S113) can be reduced, so the time required to generate a new evaluation waveform can be shortened.

[0057] Also, the magnitude of the "variation" calculated in (S113) can be evaluated by the variance or standard deviation of the peak values of the plurality of evaluation waveforms after translation.

[0058] Also, when arranging the plurality of evaluation waveforms acquired in each channel 11 in the two-dimensional plane in (S112), it is preferable to set the position of the left end of each evaluation waveform to the scanning start position when the evaluation waveform is acquired. Then, it is preferable to set the first reference point P0 at the scanning start position, and set the remaining reference points P1, P2, P3,... from there to the right on the horizontal axis.

[0059] Next, an example of the procedure performed in S113 in the flow of FIG. 15 will be described with reference to FIGS. 16-18. Here, the interval between each reference point Pm is ΔK.

[0060] FIG. 16 is a diagram showing a state in which each evaluation waveform is translated in the vertical axis direction so that the signal intensity of each evaluation waveform becomes zero at the reference point P1. The set 40 of a plurality of illustrated evaluation waveforms is after translation, and in S113, the variation (for example, standard deviation or variance) of the peak values 41 of the set 40 of a plurality of evaluation waveforms after translation is calculated. The set 40 of evaluation waveforms is arranged on a two-dimensional plane in S112 before reaching the state of FIG. 16 such that the left ends of the plurality of evaluation waveforms acquired by each channel 11 are located on the scanning start position L1.

[0061] FIG. 17 is a diagram showing a state in which each evaluation waveform 40 is translated in the vertical axis direction so that the signal intensity becomes zero at the reference point P2, and the variation of the peak value 42 is calculated in this state. FIG. 18 is a diagram showing a state in which each evaluation waveform 40 is translated in the vertical axis direction so that the signal intensity becomes zero at the reference point Pn, and the variation of the peak value 43 is calculated in this state. The calculated variation of the peak value may be associated with the code (which may be a number) of the selected reference point and the position of each evaluation waveform after translation and stored in the storage device 54b of the computer 54.

[0062] For the set of evaluation waveforms translated so that the signal intensity becomes zero at all the reference points Pm in this way, the variation of each peak value is calculated, and the one with the smallest variation among them is used as a new set of evaluation waveforms (that is, the new evaluation waveforms of each channel 11). For example, if the variation of the peak value 42 of the set 40 of evaluation waveforms in FIG. 17 is the smallest, the reference point P2 is regarded as the scanning start position of the initial waveform and the evaluation waveform, and the difference between the peak value of each evaluation waveform on FIG. 17 and the corresponding initial waveform is calculated in S115. That is, even when using this embodiment, when the scanning start position shifts each time a magnetic body is probed multiple times, the change in the slit signal intensity can be accurately evaluated.

[0063] Before quickly determining a new evaluation waveform from the set of evaluation waveforms with the smallest peak value variation as described above, the correlation coefficient indicating the degree of coincidence between each evaluation waveform and the corresponding initial waveform may be evaluated, and after confirming that the correlation coefficient is greater than a predetermined value and a desired degree of coincidence is ensured, the evaluation waveform may be determined as the new evaluation waveform.

[0064] In addition, each procedure including S101 and S112-115 described above may be executed by the processor 54a of the computer 54 in the system 100. In this case, the computer 54 functions as a data processing device in the system 100.

[0065] Furthermore, the present invention is not limited to the above-described embodiments, and various modifications within the scope not departing from the gist thereof are included. For example, the present invention is not limited to those having all the configurations described in the above embodiments, and those in which a part of the configuration is deleted are also included. Also, a part of the configuration according to one embodiment can be added to or replaced with the configuration according to another embodiment.

[0066] In addition, each configuration related to the above computer 54, the functions of each configuration, the execution processing, etc. may be realized in part or in whole by hardware (for example, designing the logic for executing each function with an integrated circuit). Also, the configuration related to the above computer 54 may be a program (software) in which each function related to the configuration of the computer 54 is realized by being read and executed by the processor 54a (for example, CPU). Information related to the program can be stored in, for example, a semiconductor memory (flash memory, SSD, etc.), a magnetic storage device (hard disk drive, etc.), and a recording medium (magnetic disk, optical disk, etc.).

[0067] <Supplementary Note> The above-described embodiments include the following features.

[0068] (1) Install a multi-coil type probe having a plurality of channels, which is a combination of an excitation coil and a detection coil, on a magnetic inspection object provided with a slit, and scan the part including the slit with the probe to obtain an initial waveform and an evaluation waveform in each channel. In each channel, calculate the movement amount of the evaluation waveform when the evaluation waveform is moved toward the initial waveform so that the deviation between the initial waveform and the evaluation waveform is minimized. Based on the position information of each channel in the probe and the movement amount of the evaluation waveform of each channel, calculate the correction value of the evaluation waveform of each channel. Generate a new evaluation waveform for each channel by moving the evaluation waveform of each channel according to the correction value of each channel. A data processing method for an eddy current flaw detection system, characterized by calculating the difference between the peak values of the initial waveform and the new evaluation waveform in each channel.

[0069] (2) In the data processing method of the eddy current flaw detection system in (1) above, The correction value of each channel is a value approximated based on the movement amount of the evaluation waveform of each channel plotted on a two-dimensional plane and the arrangement of each channel at the scanning start position of the probe when the evaluation waveform is obtained. A data processing method for an eddy current flaw detection system, characterized by this.

[0070] (3) In the data processing method of the eddy current flaw detection system in (1) above, When each channel at the scanning start position of the probe when the evaluation waveform is obtained is arranged along a first straight line, The correction value of each channel is a value approximated by a straight line having the same slope as the first straight line based on the movement amount of the evaluation waveform of each channel plotted on a two-dimensional plane. A data processing method for an eddy current flaw detection system, characterized by this.

[0071] (4) In the data processing method of the eddy current flaw detection system in (1) above, The initial waveform and the evaluation waveform are represented on a two-dimensional plane composed of a horizontal axis indicating position and a vertical axis indicating signal intensity. For each channel, calculate the amount of movement of the evaluation waveform in the two-dimensional plane toward the initial waveform so that the deviation between the initial waveform and the evaluation waveform is minimized. Based on the position information of each channel in the probe and the amount of movement of the evaluation waveform of each channel in the direction of the horizontal axis among the amounts of movement of the evaluation waveforms of each channel, calculate the correction value in the direction of the horizontal axis of the evaluation waveform of each channel. After moving the evaluation waveform of each channel in the direction of the horizontal axis according to the correction value of each channel, move it in the direction of the vertical axis to a position overlapping the initial waveform to generate the new evaluation waveform of each channel, which is a data processing method of an eddy current flaw detection system.

[0072] (5) In the data processing method of an eddy current flaw detection system according to any one of (1)-(4) above, Monitor and display the difference in peak values between the initial waveform and the new evaluation waveform of each calculated channel, which is a data processing method of an eddy current flaw detection system.

[0073] (6) Install a multi-coil type probe having a plurality of channels that are combinations of excitation coils and detection coils on a magnetic inspection object provided with a slit, and scan the portion including the slit with the probe to obtain an initial waveform and an evaluation waveform for each channel. Arrange the plurality of evaluation waveforms obtained for each channel on a two-dimensional plane composed of a horizontal axis indicating position and a vertical axis indicating signal intensity, and set a plurality of reference points arranged at predetermined intervals on the horizontal axis. Select one reference point from among the plurality of reference points, and parallelly move each of the plurality of evaluation waveforms on the two-dimensional plane in the direction of the vertical axis so that the signal intensity at the selected reference point becomes zero, and calculate the variation in peak values of the plurality of evaluation waveforms after the parallel movement. Repeat this until all of the plurality of reference points are selected. Among the plurality of evaluation waveforms after the translation, the one with the smallest variation in peak values is used as the new evaluation waveform for each channel. A data processing method for an eddy current flaw detection system, characterized by calculating the difference in peak values between the initial waveform and the new evaluation waveform for each channel.

[0074] (7) In the data processing method of the eddy current flaw detection system described in (6) above, The evaluation waveform is composed of point cloud data, A data processing method for an eddy current flaw detection system, characterized in that the predetermined interval is the pitch of the points constituting the point cloud data.

[0075] (8) In the data processing method of the eddy current flaw detection system described in (6) or (7) above, A data processing method for an eddy current flaw detection system, characterized in that the plurality of reference points are set at positions closer to the origin of the two-dimensional plane than the peak positions in the evaluation waveform of each channel.

[0076] (9) In the data processing method of the eddy current flaw detection system according to any one of (6)-(8) above, A data processing method for an eddy current flaw detection system, characterized in that the magnitude of the variation is evaluated by variance or standard deviation.

[0077] (10) An eddy current flaw detection system comprising a multi-coil probe having a plurality of channels which are combinations of an excitation coil and a detection coil, a storage device storing the initial waveform and the evaluation waveform obtained for each channel by scanning a magnetic test object provided with a slit with the probe, a processor, and a monitor, The processor Calculates the amount of movement of the evaluation waveform when the evaluation waveform is moved toward the initial waveform so that the deviation between the initial waveform and the evaluation waveform is minimized for each channel, Calculates a correction value for the evaluation waveform of each channel based on the position information of each channel in the probe and the amount of movement of the evaluation waveform of each channel. Generating a new evaluation waveform for each channel by moving the evaluation waveform of each channel according to the correction value of each channel, Calculating the difference in peak values between the initial waveform and the new evaluation waveform for each channel, An eddy current flaw detection system characterized by displaying the difference in peak values on the monitor.

[0078] (11) A multi-coil type probe having a plurality of channels which are combinations of an excitation coil and a detection coil, a storage device storing an initial waveform and an evaluation waveform acquired for each channel by scanning a magnetic inspection object provided with a slit with the probe, a processor, and a monitor, and an eddy current flaw detection system comprising: The processor: Arranging a plurality of the evaluation waveforms acquired for each channel on a two-dimensional plane composed of a horizontal axis indicating position and a vertical axis indicating signal intensity, setting a plurality of reference points arranged at predetermined intervals on the horizontal axis, Selecting one reference point from among the plurality of reference points, moving each of the plurality of evaluation waveforms on the two-dimensional plane parallel to the vertical axis direction so that the signal intensity at the selected reference point becomes zero, and calculating the variation in peak values of the plurality of evaluation waveforms after the parallel movement, repeating this until all of the plurality of reference points are selected, Regarding the one with the smallest variation in peak values among the plurality of evaluation waveforms after the parallel movement as the new evaluation waveform for each channel, Calculating the difference in peak values between the initial waveform and the new evaluation waveform for each channel, An eddy current flaw detection system characterized by displaying the difference in peak values on the monitor.

Explanation of Signs

[0079] 1…Inspected object, 2…Scanning device, 4…Slit, 5…Scanning direction, 6…Magnetic signal, 7…Slit signal, 11…Channel, 12…Probe output signal group, 13…Magnetic signal, 14…Slit signal, 15…Signal group, 15…Probe output signal group, 20…Start position, 21…Start position, 22…Initial waveform, 23…Evaluation waveform, 25…Straight line (regression line), 32…Straight line (regression line), 40…Evaluation waveform, 41…Peak value, 42…Peak value, 43…Peak value, 51…Probe (eddy current flaw detector probe), 52…Scanning device, 53…Eddy current flaw detector, 54…Computer, 54a…Processor, 54b…Storage device (memory), 55…Monitor, 70…Initial waveform, 80…Evaluation waveform, 100…Eddy current flaw detection system, Pm…Reference point, ΔKcrc…Correction value, ΔKmin…Movement amount of the horizontal axis, ΔVmin…Movement amount of the vertical axis, θ…Rotation angle of probe 51

Claims

1. A multi-coil type probe having a plurality of channels that are combinations of an excitation coil and a detection coil is installed on a magnetic inspection object provided with a slit, and each channel acquires an initial waveform and an evaluation waveform by scanning a portion including the slit with the probe. For each channel, calculate the amount of movement of the evaluation waveform when the evaluation waveform is moved toward the initial waveform so that the deviation between the initial waveform and the evaluation waveform is minimized. Based on the position information of each channel in the probe and the amount of movement of the evaluation waveform of each channel, calculate a correction value for the evaluation waveform of each channel. Generate a new evaluation waveform for each channel by moving the evaluation waveform of each channel according to the correction value of each channel. A data processing method for an eddy current flaw detection system, characterized by calculating the difference between the peak values of the initial waveform and the new evaluation waveform for each channel.

2. In the data processing method for an eddy current flaw detection system according to Claim 1, the correction value for each channel is a value approximated based on the amount of movement of the evaluation waveform of each channel plotted on a two-dimensional plane and the arrangement of each channel at the scanning start position of the probe when the evaluation waveform is acquired. A data processing method for an eddy current flaw detection system, characterized by this.

3. In the data processing method for an eddy current flaw detection system according to Claim 1, when each channel at the scanning start position of the probe when the evaluation waveform is acquired is arranged along a first straight line, the correction value for each channel is a value approximated by a straight line having the same slope as the first straight line based on the amount of movement of the evaluation waveform of each channel plotted on a two-dimensional plane. A data processing method for an eddy current flaw detection system, characterized by this.

4. In the data processing method for an eddy current flaw detection system according to Claim 1, the initial waveform and the evaluation waveform are represented on a two-dimensional plane composed of a horizontal axis indicating position and a vertical axis indicating signal intensity. For each channel, calculate the amount of movement of the evaluation waveform when the evaluation waveform is moved toward the initial waveform on the two-dimensional plane so that the deviation between the initial waveform and the evaluation waveform is minimized. Based on the position information of each channel in the probe and the amount of movement in the direction of the horizontal axis among the amounts of movement of the evaluation waveforms of each channel, calculate a correction value in the direction of the horizontal axis of the evaluation waveform of each channel. A data processing method for an eddy current flaw detection system, characterized in that after moving the evaluation waveform of each channel in the direction of the horizontal axis according to the correction value of each channel, it is moved in the direction of the vertical axis to a position overlapping the initial waveform to generate the new evaluation waveform of each channel.

5. In the data processing method of the eddy current flaw detection system according to Claim 1, A data processing method for an eddy current flaw detection system, characterized in that the difference in peak values between the initial waveform and the new evaluation waveform of each calculated channel is displayed on a monitor.

6. A multi-coil type probe having a plurality of channels which are combinations of an excitation coil and a detection coil is installed on a magnetic inspection object provided with a slit, and the initial waveform and the evaluation waveform are obtained for each channel by scanning the portion including the slit with the probe. A plurality of the evaluation waveforms obtained for each channel are arranged on a two-dimensional plane composed of a horizontal axis indicating position and a vertical axis indicating signal intensity, and a plurality of reference points arranged at predetermined intervals on the horizontal axis are set. One reference point is selected from among the plurality of reference points, and the plurality of evaluation waveforms on the two-dimensional plane are each translated in the direction of the vertical axis so that the signal intensity at the selected reference point becomes zero, and the variation in peak values of the plurality of evaluation waveforms after the translation is calculated. This is repeated until all of the plurality of reference points are selected. The one with the smallest variation in peak values among the plurality of evaluation waveforms after the translation is used as the new evaluation waveform for each channel. A data processing method for an eddy current flaw detection system, characterized in that the difference in peak values between the initial waveform and the new evaluation waveform is calculated for each channel.

7. In the data processing method of the eddy current flaw detection system according to Claim 6, The evaluation waveform is composed of point group data. A data processing method for an eddy current flaw detection system, characterized in that the predetermined interval is the pitch of the points constituting the point group data.

8. In the data processing method of the eddy current flaw detection system according to Claim 6, A data processing method for an eddy current flaw detection system, characterized in that the plurality of reference points are set at positions closer to the origin of the two-dimensional plane than the peak positions in the evaluation waveform of each channel.

9. In the data processing method of the eddy current flaw detection system according to Claim 6, A data processing method for an eddy current flaw detection system, characterized in that the magnitude of the variation is evaluated by variance or standard deviation.

10. An eddy current flaw detection system comprising: a multi-coil type probe having a plurality of channels which are combinations of an excitation coil and a detection coil; a storage device which stores an initial waveform and an evaluation waveform acquired in each channel by scanning a magnetic inspection object provided with a slit with the probe; a processor; and a monitor, wherein the processor calculates, for each channel, the amount of movement of the evaluation waveform when the evaluation waveform is moved toward the initial waveform so that the deviation between the initial waveform and the evaluation waveform is minimized, calculates a correction value for the evaluation waveform of each channel based on the position information of each channel in the probe and the amount of movement of the evaluation waveform of each channel, generates a new evaluation waveform for each channel by moving the evaluation waveform of each channel according to the correction value of each channel, calculates the difference in peak values between the initial waveform and the new evaluation waveform for each channel, and displays the difference in peak values on the monitor. An eddy current flaw detection system characterized by the above.

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