Figure-eight trajectory detection program, eddy current flaw detection apparatus, and method

Abstract

To provide means that can quantitatively detect a "figure-of-eight trajectory" of the Lissajous curve, and can thereby determine the presence or absence of a flaw without individual differences.SOLUTION: A figure-of-eight trajectory detection program receives an X signal and a Y signal each periodically changing centered on the same definite point, and detects a figure-of-eight trajectory drawn by the Lissajous curve R obtained by overlapping the X signal and Y signal each other. An eddy current flaw detection device comprises a probe, an eddy current flaw detector, and a figure-of-eight trajectory detection device. An eddy current flaw detection method has a figure-of-eight detection step of detecting the figure-of-eight trajectory drawn by the Lissajous curve R obtained by overlapping the X signal and Y signal each other. In the figure-of-eight detection step, the figure-of-eight trajectory detection device calculates in real time a momentary phase difference Z that is the difference between the phase angle of the X signal and the phase angle of the Y signal, and when the difference between the maximum value and the minimum value of the momentary phase difference Z exceeds a predetermined threshold, detects the figure-of-eight trajectory drawn by the Lissajous curve R.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a figure-eight trajectory detection program, an eddy current flaw detection apparatus, and a method for detecting the figure-eight trajectory of a Lissajous curve. [Background technology]

[0002] Eddy current testing is applicable to conductive materials such as steel, non-ferrous metals, and graphite. It utilizes the property that eddy currents induced in a material change with the presence of cracks (defects) to detect cracks. An eddy current testing device is a device that places a coil on the material and passes an AC power supply through the coil to perform eddy current testing.

[0003] In eddy current testing (ET), eddy currents are generated within the test specimen by the probe's input coil, and the output signal from the detection coil resulting from these eddy currents is detected. The eddy current detector also outputs ET signals (X signal and Y signal) that change periodically around the same fixed point from the output signal. Furthermore, a Lissajous curve is drawn by superimposing the X and Y signals, and the presence or absence of defects is determined based on the shape of this trajectory.

[0004] In eddy current testing, it is known that the Lissajous curve traces a "figure-eight closed curve" as the probe passes through a defect. Hereafter, this "figure-eight closed curve" will be referred to as the "figure-eight locus." The "figure-eight locus" in Lissajous curves is disclosed, for example, in Patent Documents 1 and 2.

[0005] Paragraph 0029 of Patent Document 1 states, "When the detection coil 19a reaches the position of the vertical scratch 32, a change in eddy current due to the vertical scratch 32 is detected, and an eight-figure Lissajous waveform appears on the monitor."

[0006] Paragraph 0019 of Patent Document 2 states, "Since the basic oscillation pattern of the ECT signal is that it starts from the origin and returns to the origin, the waveform of the Lissajous 23 takes the shape of a circle or a figure eight."

[0007] In addition, an invention related to the present invention is disclosed in Patent Document 3.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] As described above, in the eddy current flaw detection test, when the probe passes over a flaw, the Lissajous curve traces an "8-shaped locus", so the presence or absence of a flaw can be determined from the "8-shaped locus".

[0010] However, such conventional flaw determination means have the following problems. (1) In the determination of small flaws or flaws in complex-shaped parts, individual differences occur. (2) Although automatic determination means based on pattern recognition are known, the determination criteria are black-boxed, so the determination criteria cannot be explained. (3) There is no method for quantitatively judging the "8-shaped locus", and the objectivity of the judgment is not ensured. (4) The visual determination of the "8-shaped locus" requires frequent shifting of the viewing point among the probe in hand, the test piece, and the Lissajous curve, which places a burden on the inspector.

[0011] The present invention was devised to solve the above-described problems. That is, an object of the present invention is to provide an "eight-shaped locus detection program", an eddy current flaw detection device, and a method that can quantitatively detect the "8-shaped locus" of the Lissajous curve, and thereby determine the presence or absence of a flaw without individual differences.

Means for Solving the Problem

[0012] According to the present invention, there is provided an eight-shaped locus detection program that receives an X signal and a Y signal that each periodically change around the same fixed point, and detects an eight-shaped locus drawn by a Lissajous curve obtained by overlapping the X signal and the Y signal, causing a computer to calculate in real time an instantaneous phase difference that is the difference between the phase angle of the X signal and the phase angle of the Y signal; and output a detection signal of the eight-shaped locus when the difference between the maximum value and the minimum value of the instantaneous phase difference exceeds a predetermined threshold value.

[0013] Further, according to the present invention, there is provided a probe that generates an eddy current in a test object by an input coil and detects an output signal of a detection coil due to the eddy current, an eddy current flaw detector that outputs an X signal and a Y signal that each periodically change around the same fixed point from the output signal, and an eight-shaped locus detection device that detects an eight-shaped locus drawn by a Lissajous curve obtained by overlapping the X signal and the Y signal, wherein the eight-shaped locus detection device calculates in real time an instantaneous phase difference that is the difference between the phase angle of the X signal and the phase angle of the Y signal from the X signal and the Y signal, and outputs a detection signal of the eight-shaped locus when the difference between the maximum value and the minimum value of the instantaneous phase difference exceeds a predetermined threshold value.

[0014] Furthermore, according to the present invention, there are provided: a first step of generating an eddy current in a test object by an input coil of a probe and detecting an output signal of a detection coil due to the eddy current; a second step of outputting an X signal and a Y signal that each periodically change around the same fixed point from the output signal; and a third step of detecting an eight-shaped locus drawn by a Lissajous curve obtained by overlapping the X signal and the Y signal. In the third step above, From the X signal and the Y signal, the instantaneous phase difference, which is the difference between the phase angle of the X signal and the phase angle of the Y signal, is calculated in real time. An eddy current testing method is provided, which outputs a detection signal for the figure-eight trajectory when the difference between the maximum and minimum values ​​of the instantaneous phase difference exceeds a predetermined threshold. [Effects of the Invention]

[0015] In eddy current testing, it has long been known that the Lissajous curve traces a "figure-eight trajectory" as the probe passes through a defect. Furthermore, when a Lissajous curve traces a "figure-eight" shape, the frequencies of the X and Y signals, which change periodically around the same fixed point, are in a ratio of approximately 2:1.

[0016] Furthermore, the inventors of this invention have obtained a new finding that when the frequencies of the X signal and the Y signal are in a ratio of approximately 2:1, the instantaneous phase difference, which is the difference between the phase angle of the X signal and the phase angle of the Y signal, becomes large at a certain point in time. This invention is based on these new findings.

[0017] According to the present invention, the instantaneous phase difference, which is the difference between the phase angle of the X signal and the phase angle of the Y signal, is calculated in real time from the X signal and the Y signal, and when the difference between the maximum and minimum values ​​of the instantaneous phase difference exceeds a predetermined threshold, a figure-eight trajectory detection signal is output. Therefore, the present invention makes it possible to quantitatively detect the "figure-eight locus" of the Lissajous curve, thereby enabling the determination of the presence or absence of defects without individual differences. [Brief explanation of the drawing]

[0018] [Figure 1] This is a diagram illustrating the principle of the present invention. [Figure 2] This is an explanatory diagram of the Synchro-PRIMO method. [Figure 3] This is an explanatory diagram of a computer screen with a post-analysis application installed. [Figure 4]This is an overall configuration diagram of the eddy current flaw detection apparatus according to the present invention. [Figure 5] This is a circuit diagram of an eddy current flaw detector. [Figure 6] This figure shows specific examples of examination images. [Figure 7] This is an overall flowchart of the eddy current testing method according to the present invention. [Figure 8] These are specific examples of ET signals, with (A) showing a damaged signal and (B) showing an undamaged signal. [Figure 9] These are specific examples of the ET signal after DC component removal, corresponding to Figures 8(A) and 8(B). [Figure 10] These are Lissajous curves corresponding to Figures 8(A) and 8(B). [Figure 11] This is an enlarged view of Figure 10(A)(B). [Figure 12] This is an example (calculation example) of instantaneous amplitude extraction using the SPRIMO method, corresponding to Figures 8(A) and 8(B). [Figure 13] This is an example (calculation example) of instantaneous frequency extraction using the SPRIMO method, corresponding to Figures 8(A) and 8(B). [Figure 14] This is an example (calculation example) of instantaneous phase difference extraction using the SPRIMO method, corresponding to Figures 8(A) and 8(B). [Figure 15] This figure shows the ET signal with scratches, the ET signal after DC component removal, and the instantaneous phase difference. [Figure 16] This figure shows the ET signal in the case of no damage, the ET signal after DC component removal, and the instantaneous phase difference. [Figure 17] This diagram shows the differences in the workflow during flaw detection. [Modes for carrying out the invention]

[0019] Embodiments of the present invention will be described below with reference to the drawings. In each figure, common parts are denoted by the same reference numerals, and redundant explanations are omitted.

[0020] This invention relates to a Lissajous curve obtained by superimposing X and Y signals that change periodically around the same fixed point. As mentioned above, when the Lissajous curve traces a "figure-eight" shape, the frequencies of the X and Y signals are in a ratio of approximately 2:1.

[0021] (Principle of the invention) Figure 1 is an explanatory diagram of the principle of the present invention. Below, the amplitude and frequency of the X signal are defined as the first amplitude A and the first frequency ω X The amplitude and frequency of the Y signal are defined as the second amplitude B and the second frequency ω Y Let φ be the phase difference between the two. In this case, the X and Y signals of the ET signal at a certain time t can be expressed by the following equations. X(t) = A·sin(ω X ·t+φ)···(1) Y(t) = B·sin(ω Y ·t)···(2)

[0022] Figure 1(A) shows the phase difference φ=0, ω X :ω Y This shows the case where the ratio is 2:1. In this figure, the horizontal axis represents time t, and the vertical axis represents the values ​​of the X and Y signals (voltage [V] in this example). In this figure, ω X :ω Y Due to the 2:1 relationship, while the Y signal completes one cycle from 0 to 360°, the X signal completes two cycles from 0 to 360°. In this case, as mentioned above, the Lissajous curve traces a "figure-eight locus".

[0023] Figure 1(B) shows the relationship between time t and phase angle [deg] in Figure 1(A), where the horizontal axis represents time t and the vertical axis represents the phase angle between the X and Y signals. Since the phase angle repeats between 0 and 360° during one cycle, the X signal rises from 0° to 360° in the first cycle, and then rises again from 0° to 360° in the next cycle. In other words, the X signal reaches its maximum phase angle of 360° in the first cycle and becomes its minimum phase angle of 0° at the next moment (at the start of the next cycle). On one hand, when the X signal reaches the maximum phase angle of 360° in the first cycle, the phase angle of the Y signal is 180°, and the X signal continues to rise to the maximum phase angle of 360°.

[0024] In FIG. 1(B), let the phase angle of the X signal and the phase angle of the Y signal be the first phase angle θ X and the second phase angle θ Y respectively. Then, the first phase angle θ X and the second phase angle θ Y at a certain time t can be expressed by the following equations. θ X = ω X ·t1 ···(3) θ Y = ω Y ·t2 ···(4) Here, t1 and t2 are the elapsed times from the respective minimum phase angles of 0°.

[0025] FIG. 1(C) is a relationship diagram of the time t and the instantaneous phase difference Z in FIG. 1(B), where the horizontal axis is the time t and the vertical axis is the instantaneous phase difference Z. Note that the "instantaneous phase difference" means the difference between the phase angle of the X signal and the phase angle of the Y signal, that is, the difference between the first phase angle θ X and the second phase angle θ Y . From this figure, it can be seen that during one cycle of the Y signal with a relatively long period in this example (in this example, at the 0.5 cycle point of the Y signal), the instantaneous phase difference Z becomes large, that is, it reaches the maximum value or the minimum value. Therefore, by detecting that the difference between the maximum value and the minimum value of the instantaneous phase difference Z exceeds a predetermined threshold, an eight-shaped trajectory can be detected.

[0026] In the above example, the values of the X signal and the Y signal at time t are shown as sine waves, but the same results can be obtained even if they are shown as cosine waves respectively. Also, although the phase difference φ = 0 is set, even if the phase difference φ ≠ 0, the instantaneous phase difference Z becomes large during one cycle of the Y signal with a relatively long period. Also, an example where ω X : ω Y = 2:1 is shown, but even if ω X : ω YThe ratio can also be 1:2. Furthermore, this ratio is not strictly defined and may vary as long as the Lissajous curve traces a "figure-eight" shape.

[0027] (Synchro-PRIMO method) Figure 2 is an explanatory diagram of the Synchro-PRIMO method (hereinafter referred to as the SPRIMO method). The SPRIMO method is a calculation method that calculates the basic parameters of a sine wave composed of discrete data using a simple mathematical formula. If the frequency ω, amplitude A, and phase difference φ are known, the time-series waveform can be easily synthesized as X(t) = A·sin(ωt+φ). If we consider this as the "forward problem," the mathematics of the SPRIMO method is an equation that finds the frequency ω, amplitude A, and phase difference φ from the time-series waveform obtained by measurement (= solving the "inverse problem"). The mathematical principles of the SPRIMO method are disclosed, for example, in Patent Document 3.

[0028] In Figure 1, the X and Y signals are the values ​​of the time-series waveforms obtained by measurement at time t. Therefore, the frequencies ω of the X and Y signals are calculated using the SPRIMO method. X ,ω Y The amplitudes A and B, and the phase difference φ can be determined. Furthermore, between the X signal and the Y signal, the first phase angle θ is determined within the period of the one with the relatively longer period. X and the second phase angle θ Y The difference (i.e., the instantaneous phase difference Z) can be calculated in real time. Therefore, by using the SPRIMO method to detect when the difference between the maximum and minimum values ​​of the instantaneous phase difference Z exceeds a predetermined threshold, the figure-eight trajectory can be detected.

[0029] (Program for detecting figure-eight trajectories) The present invention's figure-eight trajectory detection program receives X and Y signals that change periodically around the same fixed point, and detects the figure-eight trajectory drawn by the Lissajous curve formed by superimposing the X and Y signals.

[0030] In other words, this figure-eight trajectory detection program is installed on a computer's storage medium and is a program that causes the computer to execute an instantaneous phase difference calculation means and a detection signal output means.

[0031] The instantaneous phase difference calculation means uses the SPRIMO method described above to determine the phase angle of the X signal (first phase angle θ) from the X signal and the Y signal. X ) and the phase angle of the Y signal (second phase angle θ) Y The instantaneous phase difference Z, which is the difference between ( ) and ( ), is calculated in real time. Furthermore, in the instantaneous phase difference calculation means, it is preferable to calculate the change in instantaneous phase difference Z in real time during the period of the one with the relatively longer period among the X signal and the Y signal.

[0032] The detection signal output means outputs a detection signal for the figure-eight trajectory when the difference between the maximum and minimum values ​​of the instantaneous phase difference Z exceeds a predetermined threshold. It is best to pre-set the specified threshold values ​​and input them into the computer.

[0033] The figure-eight trajectory detection program described above can be used as a post-analysis application (hereinafter referred to as the post-analysis application) to read previously acquired flaw detection data (i.e., X and Y signals), display it on a computer screen, and perform flaw detection.

[0034] Figure 3 is an explanatory diagram of a computer screen with the post-analysis application installed. As shown in Figure 3(A), when a file of previously acquired flaw detection data is loaded, the loaded flaw signals (i.e., X and Y signals) and Lissajous curves are displayed on the screen. Furthermore, as shown in Figure 3(B), when the focus cursor on the screen is aligned with the scratch signal, the internal processing detects a figure-eight trajectory, and the Lissajous trajectory within the cursor turns red. Furthermore, as shown in Figure 3(C), the intensity of the preprocessing and the threshold setting for detecting the figure-eight trajectory can be freely changed.

[0035] (Eddy current flaw detection device) Figure 4 is an overall diagram of the eddy current flaw detection apparatus 100 according to the present invention. In this figure, the eddy current flaw detection apparatus 100 comprises a probe 10, an eddy current flaw detector 20, and a figure-eight trajectory detection device 30.

[0036] The probe 10 has an input coil 10a and a detection coil 10b. The input coil 10a generates eddy currents within the test specimen, and the probe detects the output signal from the detection coil 10b due to these eddy currents.

[0037] The probe 10 is preferably a differential probe. This is because probes other than differential probes do not show differential indications for defects, and the Lissajous curve does not trace a figure-eight trajectory. Furthermore, by differentiating (differentially analyzing) the output using digital signal processing, it is possible to simulate differential indication even with a single probe. Therefore, the probe 10 is not limited to a differential probe, and may be of any other type as long as it can output X and Y signals using the eddy current flaw detector 20.

[0038] The eddy current flaw detector 20 outputs ET signals (X signal and Y signal) that change periodically around the same fixed point, based on the output signal of the probe 10.

[0039] Figure 5 is a circuit diagram of the eddy current flaw detector 20. As shown in this figure, the eddy current flaw detector 20 consists of an oscillator that supplies alternating current to the coil of the probe 10, a bridge for measuring the impedance of the coil, an amplifier, a synchronous detector, a phase shifter, and the like.

[0040] The signal processing in the eddy current flaw detector 20 is as follows: The AC signal (reference signal) generated by the oscillator is supplied to the bridge via a power amplifier. The bridge is adjusted to produce the minimum output when the test specimen is sound. As the probe passes over a defect, the impedance of the coil changes in accordance with the change in eddy currents, and a voltage is output that is amplitude-modulated by the defect signal, with the reference signal as the carrier wave. On the other hand, the phase shifter outputs reference signal 1, which is shifted in phase from 0° to 360° from the reference signal, and the 90° phase shifter outputs reference signal 2, which is shifted in phase from reference signal 1 by another 90°. Synchronous detector X detects (demodulates) the signal from the amplifier while synchronizing with reference signal 1, and extracts the flawed signal X. Similarly, synchronous detector Y detects (demodulates) the signal while synchronizing with reference signal 2, and extracts the flawed signal Y. The filter removes the flawed signal and noise with different frequency components. The flawed signals X and Y, after the noise has been removed, are the ET signal (X signal and Y signal).

[0041] As mentioned above, the ET signal (X signal and Y signal) originates from the change in the impedance of the coil. Therefore, the Lissajous curve can be described as a projection of the trajectory of the coil's impedance change onto the XY plane, which is likened to an impedance plane.

[0042] In Figure 4, the figure-eight trajectory detection device 30 detects the figure-eight trajectory drawn by the Lissajous curve, which is formed by superimposing the X and Y signals output from the eddy current flaw detector 20.

[0043] In the example shown in Figure 4, the probe 10 is electrically connected to the eddy current flaw detector 20 via the signal cable 12, and the output signal from the detection coil 10b is input to the eddy current flaw detector 20. In this example, the figure-eight trajectory detection device 30 is a control tablet 32, which has a built-in computer (PC) and receives X and Y signals from the eddy current flaw detector 20 via wired or wireless connection.

[0044] Preferably, the computer of the figure-eight trajectory detection device 30 has the figure-eight trajectory detection program described above installed. The figure-eight trajectory detection device 30 performs the following (1) and (2). (1) From the X signal and the Y signal, the phase angle of the X signal (first phase angle θ) X ) and the phase angle of the Y signal (second phase angle θ) Y The instantaneous phase difference Z, which is the difference between ( ) and ( ), is calculated in real time. (2) When the difference between the maximum and minimum values ​​of the instantaneous phase difference Z exceeds a predetermined threshold, a figure-eight trajectory detection signal is output.

[0045] The control tablet 32 ​​is, for example, a tablet PC for control and displaying flaw detection results, and displays inspection images 34 based on the inspection results on its display screen. Furthermore, the figure-eight trajectory detection device 30 (control tablet 32) has a detection sound output device 35 that outputs a detection sound in response to the detection signal.

[0046] Figure 6 shows a specific example of the examination image 34. In this example, the figure-eight trajectory detection device 30 has a Lissajous curve display unit 36 ​​and a plurality of history display units 37 on a display screen. The Lissajous curve display unit 36 ​​displays the Lissajous curve R in real time. Multiple (six in this example) history display units 37 each display the history of multiple Lissajous curves R. In this figure, reference numeral 38 denotes the X signal display unit, and reference numeral 39 denotes the Y signal display unit.

[0047] (Eddy current testing method) Figure 7 is an overall flow diagram of the eddy current testing method according to the present invention. In this diagram, the eddy current testing method has steps (processes) S1 to S6.

[0048] In step S1, the ET signal from the eddy current flaw detector 20 is acquired as digital data. A / D conversion is performed as needed. Step S1 consists of a detection signal output step SA and an ET signal output step SB. In the detection signal output step SA, the input coil 10a of the probe 10 generates eddy currents within the test body, and the output signal from the detection coil 10b due to these eddy currents is detected. In the ET signal output step SB, the X signal and Y signal, which change periodically around the same fixed point, are output from the output signal of the detection coil 10b.

[0049] Figure 8 shows specific examples of ET signals, where (A) is an example with a defect and (B) is an example without a defect.

[0050] The digital data to be acquired is sampled data at equal intervals. For example, it is good practice to sample the ET signal at 1 kHz. Furthermore, the sampling frequency should be sufficiently large compared to the frequencies of the constituent components of the analysis target (ET signal). For example, the frequencies of the constituent components of the ET signal are around 20 Hz. Furthermore, it is advisable to set the bit resolution during A / D conversion to a sufficiently large value. For example, a bit resolution of 12 bits is recommended.

[0051] In step S2 of Figure 7, the DC component contained in the ET signal is removed using a high-pass filter or the like. The SPRIMO method described above does not support the analysis of signals containing DC components. However, if the DC component is removed in step S1, or if zero balance is achieved during calibration, step S2 can be omitted.

[0052] Figures 9(A) and 9(B) show specific examples of the ET signal after DC component removal, corresponding to Figures 8(A) and 8(B).

[0053] In this invention, the Lissajous curve R is displayed in real time on the Lissajous curve display unit 36 ​​in Figure 6. Figures 10(A) and 10(B) show the Lissajous curve R corresponding to Figures 8(A) and 8(B), and Figures 11(A) and 11(B) are enlarged views of Figures 10(A) and 10(B). Figures 10 and 11 show that when there is damage, the Lissajous curve R follows a figure-eight pattern, while when there is no damage, it does not follow a figure-eight pattern.

[0054] Furthermore, the present invention includes an eight-shaped trajectory detection step SC for detecting the eight-shaped trajectory traced by the Lissajous curve R obtained by superimposing the X signal and the Y signal. The eight-shaped trajectory detection step SC consists of steps S3 to S5 in Figure 7.

[0055] In step S3, the instantaneous phase difference Z is calculated using the SPRIMO method for the acquired ET signal. That is, from the X signal and the Y signal, the phase angle of the X signal (first phase angle θ) X ) and the phase angle of the Y signal (second phase angle θ) Y The instantaneous phase difference Z, which is the difference between ( ) and ( ), is calculated in real time. This calculation is valid if there are five or more sampled data points. Furthermore, increasing the window width improves calculation accuracy due to the averaging effect. "Window width" refers to the calculation interval for each calculation when calculating instantaneous phase difference continuously along the time axis. Another example of the use of the term "window width" is "window width of the time window in the Short-Time Fourier Variation (STFT)." By plotting instantaneous phase differences while shifting the window (window width), a graph of instantaneous phase differences is obtained. Note that if the window width is larger than 5 points, the number of combinations of 5 points within the window increases, allowing for multiple instantaneous phase difference calculations and providing an averaging effect (noise immunity). Therefore, the window width should ideally be 5 or more sample points, and at most about 1 / 4 of the approximate period of the ET signal.

[0056] Figures 12(A) and 12(B) show examples of instantaneous amplitude extraction (calculation examples) using the SPRIMO method, corresponding to Figures 8(A) and 8(B). Note that instantaneous amplitude refers to the amplitude at each time point t. Figures 13(A) and 13(B) show examples of instantaneous frequency extraction (calculation examples) using the SPRIMO method, corresponding to Figures 8(A) and 8(B). Note that instantaneous frequency refers to the frequency at each time point t. Furthermore, calculating instantaneous amplitude and instantaneous frequency is not mandatory and may be omitted.

[0057] In step S4, noise components of the feature are removed based on the amplitude values ​​of the X and Y signals. This is to prevent miscalculations and over-detections by not performing calculations outside of the interval where the ET signal is generated.

[0058] In step S5, we determine whether or not a figure-eight trajectory is observed. For example, if the difference between the maximum and minimum values ​​of the instantaneous phase difference Z exceeds a predetermined threshold, a figure-eight trajectory detection signal is output. Figures 14(A) and 14(B) show examples of instantaneous phase difference Z extraction (calculation examples) using the SPRIMO method, corresponding to Figures 8(A) and 8(B). In Figure 14(A), the instantaneous phase difference Z is larger than in Figure 14(B), and it can be seen that the presence or absence of a figure-eight trajectory can be detected by comparing the difference between the maximum and minimum values ​​of the instantaneous phase difference Z with a predetermined threshold.

[0059] If there is no figure-eight trajectory in step S5 (NO), repeat steps 1-5.

[0060] In step S5, if an eight-shaped trajectory is detected (YES), in step S6, a detection sound (Beep sound) is output from the detection sound output device 35 based on the detection signal. Furthermore, multiple Lissajous curves R generated when a detection signal with a figure-eight trajectory is output are displayed as history on the Lissajous curve display unit 36.

[0061] Figures 15 and 16 are representative diagrams of examples with and without scratches. Figure 15 shows the case with scratches, and Figure 16 shows the case without scratches, respectively: (A) original signal (ET signal), (B) after pre-processing (ET signal after DC component removal), and (C) instantaneous phase difference. A comparison of Figure 15 and Figure 16 shows that the instantaneous phase difference Z in Figure 15 is larger than in Figure 16. By comparing the difference between the maximum and minimum values ​​of the instantaneous phase difference Z with a predetermined threshold, it is possible to detect the presence or absence of a figure-eight trajectory.

[0062] Figure 17 shows the differences in the workflow during flaw detection. In this figure, (A) shows the conventional example, and (B) shows the case of the present invention. Both (A) and (B) are the same in that the "probe operation" is performed manually by the examiner.

[0063] In the conventional example shown in Figure 17(A), the inspector visually checks the Lissajous figure (Lissajous curve) while manipulating the probe and visually detects the "figure-eight trajectory." If the "figure-eight trajectory" is not present, the "probe operation" is repeated. Furthermore, if the "figure-eight trajectory" is visually detected, the presence or absence of a defect is determined. In conventional methods, visually determining the "figure-eight trajectory" is burdensome for the inspector because it requires frequent shifts of the viewpoint between the probe, the test specimen, and the Lissajous curve. Furthermore, individual differences can arise in the detection of small defects or defects in complex shapes.

[0064] In the present invention shown in Figure 17(B), the "figure-eight trajectory" is automatically detected, and an audible signal (e.g., a beep) and its history are displayed on the screen. The inspector visually checks the Lissajous figure (Lissajous curve) based on the beep, for example, and determines whether or not there are any defects. In this invention, there is no need to frequently move the viewpoint of the probe, test specimen, and Lissajous curve; the Lissajous curve can be confirmed based on the beep sound. Furthermore, since the "figure-eight trajectory" is detected quantitatively, the judgment criteria are clear and individual differences can be eliminated.

[0065] As described above, the inventors of the present invention have found that when the frequencies of the X signal and the Y signal are in a ratio of approximately 2:1, the phase angle of the X signal (first phase angle θ) X ) and the phase angle of the Y signal (second phase angle θ) Y We gained a new insight: the instantaneous phase difference Z, which is the difference between ) and , becomes large at a certain point in time. The present invention described above is based on these new findings.

[0066] According to the embodiment of the present invention described above, from the X signal and the Y signal, the phase angle of the X signal (first phase angle θ) is obtained. X ) and the phase angle of the Y signal (second phase angle θ) Y The instantaneous phase difference Z, which is the difference between ( ), is calculated in real time, and when the difference between the maximum and minimum values ​​of the instantaneous phase difference Z exceeds a predetermined threshold, a figure-eight trajectory detection signal is output. Therefore, the present invention makes it possible to quantitatively detect the "figure-eight locus" of the Lissajous curve, thereby enabling the determination of the presence or absence of defects without individual differences.

[0067] It should be noted that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit of the invention. [Explanation of symbols]

[0068] A 1st amplitude, B 2nd amplitude, R Lissajous curve, Z instantaneous phase difference, θ X First phase angle, θ Y second phase angle, ω X 1st frequency, ω Y Second frequency, φ phase difference, 10 probe, 10a input coil, 10b detection coil, 12 signal cable, 20 eddy current flaw detector, 30 figure-eight trajectory detection device, 32 control tablet, 34 inspection image, 35 detection sound output device, 36 Lissajous curve display unit, 37 history display unit, 38 X signal display unit, 39 Y signal display unit, 100 eddy current flaw detector

Claims

1. A figure-eight trajectory detection program that receives X and Y signals that change periodically around the same fixed point, and detects the figure-eight trajectory drawn by the Lissajous curve obtained by superimposing the X and Y signals, On the computer, An instantaneous phase difference calculation means that calculates in real time the instantaneous phase difference, which is the difference between the phase angle of the X signal and the phase angle of the Y signal, A detection signal output means for outputting a figure-eight trajectory detection signal when the difference between the maximum and minimum values ​​of the instantaneous phase difference exceeds a predetermined threshold, and a figure-eight trajectory detection program for causing this program to run.

2. The figure-eight trajectory detection program according to claim 1, wherein the instantaneous phase difference calculation means calculates the change in the instantaneous phase difference Z in real time between the period of the X signal and the Y signal which has a relatively longer period.

3. A probe that generates eddy currents within a test specimen using an input coil and detects the output signal of a detection coil caused by these eddy currents, An eddy current flaw detector that outputs X and Y signals that change periodically around the same fixed point from the output signal, The system includes a figure-eight trajectory detection device that detects the figure-eight trajectory traced by the Lissajous curve obtained by superimposing the X signal and the Y signal, The aforementioned figure-eight trajectory detection device is From the aforementioned X signal and the Y signal, the instantaneous phase difference, which is the difference between the phase angle of the X signal and the phase angle of the Y signal, is calculated in real time. An eddy current flaw detection device that outputs a detection signal for the figure-eight trajectory when the difference between the maximum and minimum values ​​of the instantaneous phase difference exceeds a predetermined threshold.

4. The figure-eight trajectory detection device includes a Lissajous curve display unit that displays the Lissajous curve in real time, A detection sound output device that outputs a detection sound based on the aforementioned detection signal, The eddy current flaw detection apparatus according to claim 3, comprising a plurality of history display units for displaying the history of a plurality of Lissajous curves.

5. A detection signal output step involves generating eddy currents within the test body using the probe's input coil and detecting the output signal of the detection coil due to these eddy currents. An ET signal output step outputs X and Y signals that change periodically around the same fixed point from the output signal, The system includes a figure-eight trajectory detection step that detects the figure-eight trajectory traced by the Lissajous curve obtained by superimposing the X signal and the Y signal, In the figure-eight trajectory detection step, From the aforementioned X signal and the Y signal, the instantaneous phase difference, which is the difference between the phase angle of the X signal and the phase angle of the Y signal, is calculated in real time. An eddy current testing method that outputs a detection signal for the figure-eight trajectory when the difference between the maximum and minimum values ​​of the instantaneous phase difference exceeds a predetermined threshold.

6. The eddy current flaw detection method according to claim 5, wherein a detection sound is output based on the detection signal.

7. The eddy current testing method according to claim 5, wherein the Lissajous curve is displayed in real time.

8. The eddy current testing method according to claim 5, wherein a plurality of Lissajous curves at the time of output of the detection signal are displayed as a history.

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