JP6000158B2 - Flaw detection apparatus and flaw detection method - Google Patents

Description

  The present invention relates to a flaw detection apparatus and a flaw detection method for nondestructively inspecting defects such as cracks generated in a subject such as eddy current flaw detection and ultrasonic flaw detection.

  Conventionally, eddy current testing (ECT: Eddy Current Testing) and ultrasonic testing (UT: Ultrasonic Testing) are known as methods for nondestructively inspecting defects such as cracks generated in an object such as a pipe (for example, Patent Documents 1 and 2).

  Patent Document 1 discloses an apparatus that detects aging of a subject using eddy current flaw detection. Specifically, a first Lissajous waveform as a reference signal obtained by measurement at a first time point, and a second Lissajous waveform as a comparison signal measured at a second time point different from the first time point, It is disclosed that a secular change is inspected by obtaining a difference signal of.

  In Patent Document 2, when flaw detection is performed on a subject having a welded portion extending in one direction, the subject crossing in the extending direction is based on an echo signal when ultrasonic waves are propagated inside the subject. An ultrasonic flaw detector is disclosed that creates a plurality of cross-sectional images of a specimen, corrects the cross-sectional image using a characteristic amount common to the plurality of cross-sectional images, and detects a defect using the corrected cross-sectional image. .

JP 2003-75409 A JP 2008-122187 A

  By the way, when a defect is found by performing such eddy current inspection or ultrasonic inspection, the defect is repaired. For example, as shown in FIG. 15, when a minute crack-like defect is found in a thick portion such as a pipe weld or a nozzle weld, repair may be performed to remove the defect and relieve the surface stress. is there. In this case, there is a possibility that the amplitude of the eddy current flaw detection signal at the end portion of the grinding portion 31 ground for defect removal (hereinafter referred to as “grinding end portion”) becomes large. In such a case, there is a risk of being judged as a defect even if there is no defect, or when a new defect occurs near the end, there is a risk of overlooking the defect signal due to the influence of the signal at the end. There is a risk that the flaw detection performance may deteriorate.

  In particular, the ground end portion 32 shown in FIG. 15 has a two-dimensional distribution unlike the welded portion extending in one direction described in Patent Document 2, and is therefore described in Patent Document 1, for example. As shown, when a technique for detecting a defect based on the difference signal between the reference signal and the comparison signal is applied, if the alignment between the reference signal and the comparison signal is not properly performed, the difference There is a possibility that a large noise is included in the signal and the flaw detection performance is remarkably deteriorated.

That is, since the object surface shape of the grinding end portion 32 changes, local fluctuations are likely to occur in the scanning speed and posture of the sensor. Therefore, just by combining the positions based on the set scanning conditions (positions calculated from the set scanning speed and sampling pitch, positions calculated from encoder signals indicating the sensor movement amount, etc.), the reference signal and the comparison signal There is a possibility that the proper alignment between the two cannot be performed, and the flaw detection performance is significantly deteriorated as described above.
Further, the difference between the position based on the set scanning condition and the actual sensor position differs for each scanning line, and the scanning position also varies among individual scanning lines. Similarly, with respect to the sensor position in the direction orthogonal to the scanning line, there may be a deviation between the set condition and the actual sensor passing position. Therefore, it is difficult to perform proper alignment between the reference signal and the comparison signal by using the known method described above or the existing image processing method.

  The present invention has been made in view of such circumstances, and includes a noise region on the inspection surface where a signal caused by a factor other than a defect is generated. In particular, the noise region has a two-dimensional distribution. It is an object of the present invention to provide a flaw detection apparatus and a flaw detection method that can suppress a decrease in defect detection accuracy even in the case of having it.

  A first aspect of the present invention is a flaw detection apparatus for detecting a defect on a predetermined inspection surface including a noise region where a signal caused by a factor other than a defect is generated, and one or a plurality of sensors are disposed on the inspection surface. First scanning means for storing flaw detection signals of a plurality of scanning lines obtained by moving as a signal to be evaluated, and the scanning line on a non-defective inspection surface in which one or a plurality of sensors have the same shape as the inspection surface Flaw detection signals of a plurality of scanning lines obtained by moving in the same scanning direction, or by moving one or more sensors in the same scanning direction as the scanning lines on the inspection surface without defects in the past The obtained flaw detection signals for a plurality of scanning lines are stored as comparison signals, and for each of the evaluation target signal and the comparison signal, for each scanning line. The evaluation is based on representative value determining means for determining a table value, a difference between a representative value of each of the scanning lines of the signal to be evaluated and a representative value of each of the scanning lines of the comparison signal, and an arrangement order of the scanning lines. Scan line association means for determining the scan line of the comparison signal corresponding to each of the scan lines of the target signal, and the scan line of the evaluation target signal associated by the association means and the comparison signal Positioning the evaluation target signal and the comparison signal in the scanning direction between the scanning lines, generating a subtraction signal by subtracting the signal value of the corresponding positions, the subtraction signal A subtracting signal generating unit that outputs the evaluation target signal in association with scanning line information; and a defect detecting unit that detects a defect using the subtracted signal. It is a flaw detector.

  According to this aspect, the scan lines are associated with each other between the evaluation target signal and the comparison signal, and further, between the associated scan line of the evaluation target signal and the scan line of the comparison signal. The alignment of the evaluation target signal and the comparison signal in the scanning direction is performed, and the subtraction signal corresponding to each scanning line of the evaluation target signal is calculated by subtracting the signal values of the corresponding positions. As described above, since the alignment is performed between the evaluation target signal and the comparison signal in both the direction orthogonal to the scanning direction and the scanning direction, there is a noise region having a two-dimensional distribution on the inspection surface. Even if this is the case, appropriate signals can be associated with each other, and it is possible to suppress a decrease in the calculation accuracy of the subtraction signal.

  The flaw detection apparatus includes: an area specifying unit that specifies an area near a boundary between the noise area and an area outside the noise area; and the scanning line of the evaluation target signal corresponding to the boundary area. The scan line of the comparison signal associated with the scan line and the scan lines on at least both sides sandwiching the scan line of the comparison signal are extracted, and the subtraction signals are respectively generated using the extracted comparison signals of the plurality of scan lines. Further, special processing means for outputting a subtraction signal having the smallest amplitude among them in association with the scanning line of the evaluation target signal may be further provided.

  According to such a configuration, for the scanning line of the evaluation target signal in the boundary vicinity region, the subtraction signal is calculated for the comparison signal scanning line corresponding to the scanning line and at least the scanning line signals existing on both sides thereof. Then, the subtraction signal having the smallest amplitude is identified and used for defect detection. Thereby, the subtraction signal can be calculated using the scanning line of the appropriate comparison signal corresponding to the evaluation target signal corresponding to the boundary vicinity region. As a result, the calculation accuracy of the subtraction signal can be further improved, and it is possible to further suppress a decrease in the accuracy of defect detection in the region near the boundary.

  In the flaw detection apparatus, the first storage unit stores a plurality of evaluation target signals obtained by a plurality of excitation frequencies for each of the scan lines, and the second storage unit stores each of the scan lines. On the other hand, comparison signals relating to the same excitation frequency as the plurality of excitation frequencies are respectively stored, and the association means is configured to output the evaluation target signal at one excitation frequency selected as a representative excitation frequency from the plurality of excitation frequencies. And the comparison signal is used to associate the scanning lines, and the signal generating means associates the scanning lines and the position in the scanning direction by the associating means at other excitation frequencies. It is also possible to reflect and generate a subtraction signal for each scanning line at each excitation frequency.

  For example, when a plurality of evaluation target signals are obtained using a plurality of excitation frequencies during one scan, such as eddy current flaw detection, evaluation target signals and comparison signals corresponding to a plurality of different excitation frequencies, respectively. It is possible to improve the defect detection accuracy by detecting defects using. In addition, the alignment of the evaluation target signal and the comparison signal in both the direction orthogonal to the scanning direction and the scanning direction at the representative excitation frequency is also reflected at other excitation frequencies, so that each excitation frequency is associated individually. Compared to the above, it is possible to maintain a two-dimensional positional correspondence between different excitation frequencies. This makes it possible to maintain the positional relationship of the defect signal characteristics with respect to the amplitude ratio and phase angle difference between the subtraction signals having different excitation frequencies, and defect detection (for example, whether the signal generation factor is a defect). It is possible to improve the accuracy.

  In the flaw detection apparatus, the representative excitation frequency is preferably set to an excitation frequency in which a value obtained by dividing a noise signal amplitude by a flaw signal amplitude takes a relatively large value.

  By using such an excitation frequency as the representative excitation frequency, it is possible to increase the accuracy of the position correspondence between the evaluation target signal and the comparison signal as compared to the case of using another excitation frequency.

  In the flaw detection apparatus, the scanning line association unit performs drift removal processing on the evaluation target signal and the comparison signal in each scanning line, and the evaluation target signal and the comparison signal after the drift removal processing are executed. It is also possible to associate the scanning lines with each other.

  By performing the drift removal process before associating the scan lines, it is possible to associate the scan lines between the evaluation target signal and the comparison signal based on the signal from which the noise factor has been removed. As a result, the scanning line correspondence accuracy can be improved. In addition, by performing drift removal processing when associating scan lines, the above-mentioned region near the boundary can be identified using the signal before drift removal, and the performance of identifying the region near the boundary is improved. Can do.

  According to a second aspect of the present invention, there is provided a flaw detection method for detecting a defect on a predetermined inspection surface including a noise region where a signal caused by a factor other than a defect is generated, wherein one or a plurality of sensors are placed on the inspection surface. A first storage process for storing flaw detection signals of a plurality of scanning lines obtained by moving as evaluation target signals, and the non-defective inspection surface having one or a plurality of sensors having the same shape as the inspection surface as the scanning lines. A flaw detection signal of a plurality of scanning lines obtained by moving in the same scanning direction, or obtained by moving one or more sensors in the same scanning direction as the scanning lines on the inspection surface having no defect in the past. A second storage process of storing the plurality of scanning line flaw detection signals as comparison signals, and each of the evaluation target signal and the comparison signal for each of the scanning lines. The evaluation target signal is determined based on a representative value determination process for determining the difference between a representative value of each of the scanning lines of the evaluation target signal and a representative value of each of the scanning lines of the comparison signal, and an arrangement order of the scanning lines. A scanning line associating process for determining the scanning line of the comparison signal corresponding to each of the scanning lines, and the scanning line of the evaluation target signal and the scanning line of the comparison signal associated in the associating process Between the evaluation target signal and the comparison signal in the scanning direction, a subtraction signal is generated by subtracting signal values of the corresponding positions, and the subtraction signal is converted into the evaluation target A method of flaw detection including a subtraction signal generation process that is output in association with information on a scanning line of a signal, and a defect detection process that detects a defect using the subtraction signal It is.

  According to the present invention, even if a noise region where a signal caused by factors other than defects is generated has a two-dimensional distribution on the inspection surface, it is possible to suppress a decrease in defect detection accuracy. Play.

It is the figure which showed an example of the hardware constitutions of the flaw detection apparatus which concerns on 1st Embodiment of this invention. It is the functional block diagram which expanded and showed the function with which the flaw detection apparatus concerning 1st Embodiment of this invention is provided. It is a figure for demonstrating the acquisition method of the evaluation object signal and comparison signal which are stored in the 1st memory | storage part of FIG. 2, and a 2nd memory | storage part. It is a figure for demonstrating the acquisition method of the evaluation object signal and comparison signal which are stored in the 1st memory | storage part of FIG. 2, and a 2nd memory | storage part. It is a figure for demonstrating the comparison signal stored in the 2nd memory | storage part of FIG. It is a figure for demonstrating zero point correction | amendment. It is the figure which showed an example of the representative value signal. It is a figure for demonstrating a drift removal process. It is a figure for demonstrating an example of matching with the scanning line of an evaluation object signal, and the scanning line of a comparison signal. It is the flowchart shown about a series of processes performed by the flaw detection apparatus which concerns on 1st Embodiment of this invention. It is shown about an example of the evaluation object signal, the comparison signal, and the subtraction signal in the flaw detection apparatus according to the first embodiment of the present invention. It is a figure for demonstrating the problem which the flaw detection apparatus and the flaw detection method which concern on 2nd Embodiment of this invention should solve. It is a functional block diagram of the flaw detection apparatus which concerns on 2nd Embodiment of this invention. It is a figure for demonstrating the boundary vicinity area | region in 2nd Embodiment of this invention. It is the figure shown about an example of the noise area | region in a test | inspection surface. It is a figure explaining the concept of DP matching.

[First Embodiment]
Hereinafter, a flaw detection apparatus and a flaw detection method according to a first embodiment of the present invention will be described with reference to the drawings. The flaw detection apparatus and the flaw detection method according to the present embodiment include a noise region where a signal due to a factor other than a defect is generated, and particularly when the noise region has a two-dimensional distribution on the inspection surface. It is suitable for use in detection. In other words, when the flaw detection apparatus and the flaw detection method according to the present embodiment scan the flaw detection sensor to obtain a flaw detection signal on the inspection surface, the sensor must be scanned across the noise region on the inspection surface. A flaw detection apparatus and a flaw detection method that are suitable for use.

  In the present embodiment, as shown in FIG. 15, an annular grinding end portion 32 is illustrated as a noise region where a signal caused by factors other than defects is generated, and a predetermined inspection surface including the grinding end portion 32 is illustrated. An example in which a defect generated on 30 is detected will be described. Note that a noise region where a signal due to a factor other than a defect is generated is not limited to the grinding end portion 32, such as a joint portion when different materials are joined.

  FIG. 1 is a diagram illustrating an example of a hardware configuration of a flaw detection apparatus 1 according to the first embodiment of the present invention. As shown in FIG. 1, a flaw detection apparatus 1 according to the present embodiment is a computer system (computer system), a CPU (Central Processing Unit) 2, a main storage device 3 such as a RAM (Random Access Memory), and an auxiliary storage. A device 4, an input device 5 including a keyboard and a mouse, a display device 6 for displaying data, a communication device 7 for exchanging information by communicating with external devices, and the like are provided. These units are connected to each other via a bus 8.

  The auxiliary storage device 4 is a computer-readable recording medium, such as a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, or a semiconductor memory. Various programs are stored in the auxiliary storage device 4, and the CPU 2 reads out the programs from the auxiliary storage device 4 to the main storage device 3 and executes them to implement various processes.

  FIG. 2 is a functional block diagram showing the functions provided in the flaw detection apparatus 1 in an expanded manner. As shown in FIG. 2, the flaw detection apparatus 1 includes a first storage unit 11, a second storage unit 12, a representative value determination unit 13, a scanning line association unit 14, a subtraction signal generation unit 15, and a defect detection unit 16. It is provided as a configuration.

In the first storage unit 11, flaw detection signals for a plurality of scanning lines obtained by moving one flaw detection sensor on the inspection surface are stored as evaluation target signals. For example, as shown in FIG. 3, the flaw detection signals of the respective scanning lines b = 1, 2,..., N ₁ when the inspection surface 30 is scanned using one flaw detection sensor 20 are stored as evaluation target signals. ing. Note that the method for acquiring the evaluation target signal is not limited to this example, and for example, as shown in FIG. 4, a flaw detection signal acquired by scanning a sensor array 21 including a plurality of flaw detection sensors 20 may be used.
The flaw detection sensor 20 may be of any type, such as an eddy current flaw detection sensor or an ultrasonic flaw detection sensor. For convenience of explanation, a case where the eddy current flaw detection sensor 20 is used as the flaw detection sensor 20 will be described below.

As shown in FIG. 5, the second storage unit 12 has a plurality of scanning lines when the same inspection surface 30 having no defect is inspected in the past using one or a plurality of eddy current flaw detection sensors (not shown). The flaw detection signals b = 1, 2,..., n ₂ are stored as comparison signals. Here, in addition to the above, the comparison signal is a plurality of scanning lines b = 1, 2, obtained by moving one or more eddy current flaw detection sensors on a non-defective inspection surface having the same shape as the inspection surface 30. ..., n ₂ flaw detection signals may be used.
Here, the scanning direction of the evaluation target signal on the inspection surface and the scanning direction of the comparison signal are parallel to each other, but the scanning position may be shifted, and the number of scanning lines may be different. (That is, n ₁ ≠ n ₂ may be sufficient).

The representative value determination unit 13 determines a representative value for each scanning line for each of the evaluation target signal stored in the first storage unit 11 and the comparison signal stored in the second storage unit 12. Hereinafter, the process executed by the representative value determination unit 13 will be specifically described.
First, the representative value determination unit 13 performs zero point correction on the evaluation target signal and the comparison signal in each scanning line. This process is a process for setting the signal value of the evaluation target signal and the signal value of the comparison signal in a range where there is no significant signal to zero.

For example, as shown in FIG. 3, the scanning direction is a, the direction orthogonal to the scanning direction a is the step direction b, and the two-dimensional signal of eddy current flaw detection is x (a, b) + i ^* y (a, b). Then, the real axis signal x ′ (a, b) of the two-dimensional signal of the eddy current flaw detection after the zero point correction is obtained by the following equation (1).

  For example, by performing the zero point correction expressed by the above equation (1), the evaluation target signal Gm (see FIG. 3) with b = m is corrected as shown in FIG. The zero point correction is not limited to a method of subtracting the signal value of one point signal having no significant signal from the real axis signal x (a, b) to be processed, as in the above equation (1), and is well known. The zero point correction method may be adopted as appropriate. For example, the zero point correction may be performed by specifying two points having no significant signal and subtracting a straight line passing through the two points from the real axis signal x (a, b) to be processed. Here, this step may be omitted when zero point correction is unnecessary, such as when the sensor method is a method in which zero point movement does not occur.

  Here, zero point correction or the like is performed on the imaginary axis signal y (a, b) by the same method, but each process described below performed on the real axis signal is performed on the imaginary axis signal y. Therefore, the description of the imaginary axis signal y will be omitted, and only the real axis signal will be described. When an ultrasonic sensor is used as the flaw detection sensor 20, since the imaginary axis signal y (a, b) = 0, only the real axis signal needs to be considered.

Subsequently, the representative value determining unit 13 uses the evaluation target signal and the comparison signal of each scanning line after the zero point correction to calculate the absolute value average in each scanning line b = _{1 to} n ₁ and b = _{1 to} n ₂ . Each is calculated and this value is set as a representative value. This is expressed by the following equation (2).

FIG. 7 shows an example of the representative value signal when the representative value X ₁ (b) of the real axis signal in each scanning line b = _{1 to} n ₁ of the evaluation target signal is connected by a straight line or a curve. Although illustration is omitted, the representative value signal in the comparison signal is also acquired in the same manner.

The representative value determination unit 13 outputs the representative value signal of the evaluation target signal and the representative value signal of the comparison signal to the scanning line association unit 14.
The scanning line association unit 14 represents the representative value X ₁ (b) of each scanning line b = ₁ to n ₁ of the evaluation target signal and the representative value X ₂ (b) of each scanning line b = 1 to n ₂ of the comparison signal. difference and the scanning line _b = 1 to n 1 and, b = based on order of 1 to n _2, the evaluation of the comparison signal corresponding to each scanning line b = 1 to n ₁ of the target signal scan lines b = 1 to determine the ~n _2.
For example, the scanning line association unit 14 sets the representative value signal of the evaluation target signal as X ₁ (b) + i ^* Y ₁ (b), and the representative value signal of the comparison signal as X ₂ (b) + i ^* Y ₂ (b). The error d (b ₁ , b ₂ ) when the scan line b ₁ of the evaluation target signal is associated with the scan line b _{2 of the} comparison signal is given by the following equation (3), and this error d ( The correspondence between the scanning lines that minimizes the sum of b ₁ and b ₂ ) is acquired by a DP (Dynamic Programming) matching method.

The association of the scanning lines is performed by DP matching in which a maximum score condition that allows the deviation of both end points is designated as a parameter.
In DP matching, as shown in FIG. 16A, the horizontal axis is assigned to the scan lines b = _{1 to} n ₁ of the evaluation target signal, _{and the} vertical axis is assigned to the scan lines b = 1 to n ₂ of the comparison signal. d) at all grid points that pass through the path of the grid points from the left end to the right end of a) (a path that is determined for each grid point on the horizontal axis and does not descend to the right and return to the left). The path that minimizes the sum E or average value E / n _{1 of} (b ₁ , b ₂ ) is determined as the optimal path. Then, the correspondence between the scanning line of the evaluation target signal and the scanning line of the comparison signal associated with each other in the optimum path is selected as the optimum combination.

  In the association of the scanning lines, the following path restrictions may be given. For example, the “width of the vertical axis when the horizontal axis moves one grid point” and “the width of the horizontal axis that moves continuously horizontally without fluctuation” shown in FIG. This corresponds to the ratio of sampling pitch (scanning speed). Accordingly, when J is a value obtained by giving a margin to the maximum ratio of sampling pitch fluctuations assumed from the inspection situation, “vertical movement width when moving one grid point on the horizontal axis” and “vertical axis The path to be searched may be constrained on the condition that “the width continuously moving to the side without fluctuation” does not exceed J. Due to this restriction, the number of cases for obtaining the optimum path is limited, so that the processing can be speeded up and there is no possibility of selecting an unrealistic combination by mistake. However, as shown in FIG. 16 (c), only the end portions (the left end and the right end of association) are shifted due to the difference in the inspection range of the evaluation target signal and the comparison signal in addition to the change in the sampling pitch. The path restriction by J is not applied.

In addition, as shown in FIG. 16C, when the inspection ranges of the evaluation target signal and the comparison signal are different, the end of the correspondence is included only in either the evaluation target signal or the comparison signal. It is not appropriate to include it in the evaluation formula (calculation of E). For this reason, for both ends (left end and right end), “lattice points that move continuously directly to the side without changing the vertical axis” are not included in the error evaluation. In this case, the path that minimizes the value obtained by dividing the error sum E ′ of only the lattice points to be evaluated by the number of grid points n ₁ ′ to be evaluated (average error value per number of evaluation target points) is the optimal combination. You may choose.

The association information by the scanning line association unit 14 is output to the subtraction signal generation unit 15. The subtraction signal generation unit 15 generates a subtraction signal using the evaluation target signal and the comparison signal of each scanning line associated by the scanning line association unit 14, and uses the subtraction signal as the scanning line of each evaluation target signal. b = ₁ to n1 are output in association with information. Hereinafter, the process executed by the subtraction signal generation unit 15 will be specifically described.

First, the subtraction signal generation unit 15 performs drift removal processing of the evaluation target signal and the comparison signal in each scanning line b = _{1 to} n ₁ and b = _{1 to} n ₂ . For example, when the evaluation target signal Gj with b = j is taken as an example, as shown in FIG. 8, the evaluation target signal x ₀ is obtained by applying a median filter to the evaluation target signal Gj = x (a, j) before drift removal. (A, j) is obtained, and this evaluation target signal x ₀ (a, j) is subtracted from the evaluation target signal Gj = x (a, j) before drift removal, whereby the evaluation target signal Gj ′ = after drift removal. x ′ (a, j) is obtained.
At this time, the window width of the median filter is sufficiently longer than the length of the range of the cutting portion 31 (see FIG. 15) assumed in the scanning direction a.

  Subsequently, the signal value of the scanning line of the comparison signal associated with the scanning line is subtracted from the evaluation target signal of each scanning line after drift removal. At this time, the evaluation target signal and the comparison signal of the associated scanning line are processed in the scanning direction between the evaluation target signal and the comparison signal by performing the same processing as in the above-described scanning line association. Associate positions.

For example, as shown in FIG. 9, the scanning line b = m ₁ of the evaluation target signal, if the scan line b = m ₂ of the comparison signal is correlated by the scan line mapping unit 14, the scanning after drift removal line b = evaluation of _{m 1} target signal _{x 1 '(a, m 1} ) and the comparison signal _x 2 scan lines b = _{m 2} after drift removal' (a, _{m 2)} at each position in the scan direction and An association that minimizes the signal error is determined using DP matching, and a signal value at the determined positions is subtracted to generate a subtraction signal. For this DP matching, a known method can be adopted. For example, a method used for associating scan lines may be used.
As a result, a subtraction signal is generated for each scanning line b = ₁ to n ₁ of the evaluation target signal.
A subtraction signal of each of the scanning lines b = _{1 to} n ₁ of the evaluation target signal is output to the defect detection unit 15.

  For example, the defect detection unit 15 detects, as a defect, a position where the signal value is equal to or greater than a predetermined threshold value set in each subtraction signal.

Next, a series of processes executed by the flaw detection apparatus 1 according to the present embodiment will be described with reference to FIG. Here, in a series of processes described below, evaluation target signals in the plurality of scanning lines b = _{1 to} n ₁ on the inspection surface 30 are stored in the first storage unit 11, and evaluation targets are stored in the second storage unit 12. This is executed after the comparison signals in the plurality of scan lines b = 1 to n ₂ to be compared with the signals are stored.

First, for the evaluation target signal of each scanning line b = ₁ to n ₁ stored in the first storage unit 11 and the comparison signal of each scanning line b = 1 to n ₂ stored in the second storage unit 12, zero point correction is performed (step SA1), the comparison signal of each scanning line b = 1 to n ₂ after evaluation target signal and the zero point correction of the scanning lines after the zero point correction, the scanning lines b =. 1 to Representative values at n ₁ and b = _{1 to} n ₂ are calculated (step SA2).
Then, based on the order of the difference and the scanning lines of the representative value of each scan line b = 1 to n ₂ of the comparison signal and the representative value of each scan line b = 1 to n ₁ of the evaluation target signal, evaluated signal The comparison signal scan lines b = ₁ to n ₂ corresponding to the scan lines b = ₁ to n ₁ are determined (step SA3).

Next, the drift removal process is executed for the evaluation target signal and the comparison signal of each associated scan line (step SA4), and the correlation is performed using the evaluation target signal and the comparison signal after the drift removal process. and between the scanning lines (e.g., evaluated signal of the scanning line b = m ₁ and between scan lines b = m ₂ of the comparison signal) positions in the scanning direction in correspondence is performed (step SA5), at mutually corresponding positions By subtracting the signal value of the comparison signal from the signal value of the evaluation target signal, a subtraction signal is calculated for each scanning line b = ₁ to n ₁ of the evaluation target signal (step SA6). Then, defect detection is performed based on the subtraction signal of each scanning line b = ₁ to n ₁ of the evaluation target signal (step SA7).

  As described above, according to the flaw detection apparatus 1 and the flaw detection method according to the present embodiment, the scan lines are associated with each other using DP matching between the evaluation target signal and the comparison signal. Positioning of the evaluation target signal and the comparison signal in the scanning direction is similarly performed using DP matching between the scanning line of the corresponding evaluation target signal and the scanning line of the comparison signal, and the corresponding position By subtracting the signal values of each other, a subtraction signal corresponding to each scanning line of the evaluation target signal is calculated. Thus, since alignment is performed between the evaluation target signal and the comparison signal in both the step direction and the scanning direction, a noise region having a two-dimensional distribution on the inspection surface 30 (for example, in FIG. 15). Even if the grinding end portion 32) exists, it is possible to suppress a decrease in calculation accuracy of the subtraction signal by referring to appropriate signals.

  FIG. 11 shows an example of the subtraction signal obtained by the flaw detection apparatus 1 according to this embodiment. 11A is an evaluation target signal, FIG. 11B is a comparison signal, FIG. 11C is an evaluation target signal shown in FIG. 11A and a comparison signal shown in FIG. The subtraction signal calculated using and is shown. As shown in FIG. 11 (c), the strength of the signal appearing in FIGS. 11 (a) and 11 (b) is offset, and only the defective portion P appears remarkably.

[Second Embodiment]
Next, a flaw detection apparatus and a flaw detection method according to a second embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 12, for example, for the scanning lines b = h and b = j existing near the boundary between the grinding part 31 and the part other than the grinding part 31, the waveform of the flaw detection signal is greatly increased when the scanning line is shifted by one line. On the other hand, except for the vicinity of the boundary, for example, for the scanning line b = i, the waveform of the flaw detection signal does not change much even if the scanning line is shifted by one line. Therefore, in the vicinity of the boundary, it is important to increase the defect detection accuracy that the scan line is appropriately associated between the evaluation target signal and the comparison signal.
Therefore, in the present embodiment, as described above, a region near the boundary that needs to be particularly carefully associated with the scanning line is specified, and the processing in the vicinity of the boundary is performed differently from the other regions. Therefore, the accuracy of the association of the scanning lines between the evaluation target signal and the comparison signal is further improved. Hereinafter, description of points common to the first embodiment described above will be omitted, and different points will be mainly described.

FIG. 13 shows a functional block diagram of the flaw detection apparatus 1 ′ according to the present embodiment. As shown in FIG. 13, the flaw detection apparatus 1 ′ according to the present embodiment includes a region specifying unit 18 and a special processing unit 19 in addition to the functions of the flaw detection apparatus 1 according to the first embodiment described above.
The area specifying unit 18 specifies an area near the boundary located at the boundary between the noise area and the area outside the noise area. For example, the region specifying unit 18 uses the representative value of the evaluation target signal determined by the representative value determination unit 13 to calculate the feature quantity Z (b) in each scanning line b = _{1 to} n ₁ of the evaluation target signal. To do. The feature amount Z (b) is calculated by the following equation (4), for example.

Then, to identify the region of the step direction in which the Z (b) becomes a predetermined threshold value Z ₀ or higher as a noise region. The predetermined threshold value may be a predetermined value set in advance, or may be set using the following equation (5) using the feature value Z (b) as a parameter.

In equation (5), Z ₀ is a threshold value, max (Z (b)) is the maximum value of the feature quantity Z (b), min (Z (b)) is the minimum value of the feature quantity Z (b), and r is 0. It is a constant larger than 1 and indicates the ratio of the threshold value to the maximum change amount.

Next, when the noise region is determined in this way, as shown in FIG. 14, a neighborhood range centered on the boundary of the noise region is specified as the border neighborhood region. Here, it is assumed that the range near the boundary can be appropriately set by design.
Next, the special processing unit 19 processes each scan line of the evaluation target signal corresponding to the boundary vicinity region, thereby calculating a subtraction signal.

  Specifically, the special processing unit 19 scans at least both sides of the scan line of the evaluation target signal corresponding to the boundary vicinity region, the scan line of the comparison signal associated with the scan line, and the scan line of the comparison signal. A subtraction signal is generated by comparing the evaluation target signal and the comparison signal with each scanning line, and the subtraction signal having the smallest amplitude among the subtraction signals is sent to the defect detection unit 16 together with information on the scanning line of the evaluation target signal. Output.

For example, as shown in FIG. 9, the scanning line b = m ₂ scan lines b = m ₁ and the comparison signal of the evaluation target signal by the scanning line mapping unit 14 and is associated, and the evaluation target signal When the scanning line b = m ₁ corresponds to the boundary vicinity region, the special processing unit 19 uses the scanning line b = m _{2 and} the scanning lines on both sides as the scanning line of the comparison signal corresponding to the scanning line b = m _1. b = m ₂ −1 and b = m ₂ +1 are extracted.

Subsequently, the special processing unit 19 compares the evaluation target signal of the scanning line b = m ₁ and the comparison signals of the extracted scanning lines of b = m ₂ −1, b = m ₂ , b = m ₂ +1, respectively. As a result, the subtraction signals are calculated. The subtraction signal calculation method is the same as that in the first embodiment described above. Then, the subtracted signal having the smallest amplitude is extracted from the calculated three subtracted signals, and the subtracted signal is output to the defect detection unit 15 in association with the information of the scanning line b = m ₁ of the evaluation target signal.
Then, when there are other scan lines of the evaluation target signal corresponding to the boundary vicinity region, the special processing unit 19 performs the above-described process for each of the scan lines.

  As described above, according to the flaw detection apparatus 1 ′ and the flaw detection method according to the present embodiment, for the scan line of the evaluation target signal in the boundary vicinity region, the comparison signal scan line corresponding to the scan line and at least the The subtraction signal is calculated for the signals of the scanning lines existing on both sides, and the subtraction signal having the smallest amplitude is identified and used for defect detection. Thereby, the subtraction signal can be calculated using the scanning line of the appropriate comparison signal corresponding to the evaluation target signal corresponding to the boundary vicinity region. As a result, the calculation accuracy of the subtraction signal can be further improved, and it is possible to further suppress a decrease in the accuracy of defect detection in the region near the boundary.

[Third Embodiment]
Next, a flaw detection apparatus and a flaw detection method according to a third embodiment of the present invention will be described.
For example, when an eddy current flaw detection sensor 20 is used as the flaw detection sensor 20, a plurality of flaw detection signals can be obtained for each scanning line by using a plurality of different excitation frequencies. This embodiment is applied when a plurality of flaw detection signals corresponding to a plurality of excitation frequencies are obtained for each scanning line.
Therefore, in the present embodiment, the first storage unit 11 and the second storage unit 12 store flaw detection signals corresponding to a plurality of excitation frequencies for each scanning line, respectively, as evaluation target signals and comparison signals.

In such a state, the various processes described above using the evaluation target signal obtained at a predetermined excitation frequency (hereinafter referred to as “representative excitation frequency”) set in advance and the comparison signal corresponding to the representative excitation frequency. Is executed, a subtraction signal is obtained for each scan line of the evaluation target signal.
Subsequently, each scan line at each excitation frequency is also used by using the evaluation target signal and the comparison signal obtained at other excitation frequencies associating both positions in the step direction and the scanning direction in the evaluation target signal and the comparison signal. Each subtraction signal is calculated.

For example, in the case where a plurality of excitation frequencies are used, if the scan line is associated between the evaluation target signal and the comparison signal for each excitation frequency, a subtraction signal having a different excitation frequency when the subject has a defect. There is a risk that the positional relationship of the defect signal features regarding the amplitude ratio and phase angle difference between them may not be maintained, and the accuracy of defect detection cannot be improved.
In the eddy current flaw detection test, signals are also generated due to factors other than defects (for example, attachments, changes in the shape of the subject surface, changes in the probe posture, changes in the local physical property values of the subject), and so on. It is important to determine what is the cause. In order to determine whether the detected signal is due to a defect or other factors, feature quantities such as the amplitude ratio and phase angle difference of signals obtained with different excitation frequencies are used. Is effective. In such a case, as described above, if the scan line is associated between the evaluation target signal and the comparison signal for each excitation frequency, the correspondence relationship between the two-dimensional positions between the different excitation frequencies is obtained. It becomes impossible to maintain, and it becomes difficult to identify factors other than defects.

  In this regard, as in the present embodiment, the two-dimensional position correspondence between the evaluation target signal and the comparison signal at the representative excitation frequency is reflected in all other excitation frequencies, so that the step direction and the scanning direction are Since the correspondence relationship between the two-dimensional positions is maintained, the accuracy of defect detection can be improved.

Here, it is preferable to use an excitation frequency showing a relatively large value when the noise signal amplitude is divided by the flaw signal amplitude as the representative excitation frequency. The noise signal here is noise that forms a noise region to be reduced by subtraction. For example, in the inspection of the object after cutting as shown in FIG. 15, since the noise factor is a shape change, the amplitude of a predetermined shape change signal and a predetermined defect signal is measured, and the shape is determined for each excitation frequency. It is desirable to calculate the signal amplitude / defect signal amplitude and select an excitation frequency at which this value is large. When the noise region to be reduced by subtraction is a change in physical property value due to welding, it is preferable to select an excitation frequency having a large value of the welding signal amplitude / defect signal amplitude as the representative excitation frequency.
By using such an excitation frequency as the representative excitation frequency, the accuracy of the position correspondence between the evaluation target signal and the comparison signal can be improved compared to the case of using another excitation frequency even when the subject has a defect. It becomes possible.

  Although the flaw detection apparatus and the flaw detection method according to each embodiment of the present invention have been described above, the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the spirit of the invention. Is possible.

DESCRIPTION OF SYMBOLS 1, 1 'flaw detection apparatus 11 1st memory | storage part 12 2nd memory | storage part 13 Representative value determination part 14 Scan line matching part 15 Subtraction signal production | generation part 16 Defect detection part 18 Area | region specific part 19 Special processing part 20 Flaw detection sensor 30 Inspection surface 31 Grinding section 32 Grinding end

Claims (6)

A flaw detection apparatus for detecting a defect on a predetermined inspection surface including a noise region where a signal caused by a factor other than a defect is generated,
First storage means in which flaw detection signals of a plurality of scanning lines obtained by moving one or more sensors on the inspection surface are stored as evaluation target signals;
A flaw detection signal of a plurality of scanning lines obtained by moving one or a plurality of sensors on a non-defective inspection surface having the same shape as the inspection surface in the same scanning direction as the scanning line, or one or a plurality of flaw detection signals in the past A second storage means in which flaw detection signals of a plurality of scanning lines obtained by moving a sensor in the same scanning direction as the scanning lines on the inspection surface having no defect are stored as comparison signals;
Representative value determining means for determining a representative value for each scanning line for each of the evaluation target signal and the comparison signal;
Based on the difference between the representative value of each scanning line of the evaluation target signal and the representative value of each scanning line of the comparison signal and the arrangement order of the scanning lines, the scanning line corresponding to each scanning line of the evaluation target signal Scanning line association means for determining the scanning line of the comparison signal;
The evaluation target signal and the comparison signal are aligned in the scanning direction between the scan line of the evaluation target signal and the scan line of the comparison signal correlated by the correlation unit, and A subtraction signal is generated by subtracting the signal value between the attached positions, and the subtraction signal generation means for outputting the subtraction signal in association with the information of the scanning line of the evaluation target signal; A flaw detection apparatus comprising defect detection means for performing detection. A region specifying means for specifying a region near a boundary between the noise region and a region outside the noise region;
For the scanning line of the signal to be evaluated corresponding to the boundary vicinity region, the scanning line of the comparison signal associated with the scanning line and the scanning lines on at least both sides sandwiching the scanning line of the comparison signal are extracted. And a special processing means for generating the subtraction signals using the extracted comparison signals of the plurality of scanning lines, and outputting the subtraction signal having the smallest amplitude in association with the scanning line of the signal to be evaluated. A flaw detection apparatus according to claim 1. The first storage means stores a plurality of evaluation target signals obtained by a plurality of excitation frequencies for each of the scanning lines,
The second storage means stores a comparison signal relating to the same excitation frequency as the plurality of excitation frequencies for each of the scanning lines, respectively.
The association means associates the scan lines using the evaluation target signal and the comparison signal at one excitation frequency selected as a representative excitation frequency from among the plurality of excitation frequencies,
The signal generation unit reflects the association of the scanning lines by the association unit and the association of the positions in the scanning direction also in the other excitation frequencies, and generates a subtraction signal for each scanning line at each excitation frequency. The flaw detection apparatus according to claim 1 or 2, which is generated respectively.   The flaw detection apparatus according to claim 3, wherein the representative excitation frequency is set to an excitation frequency in which a value obtained by dividing a noise signal amplitude by a flaw signal amplitude takes a relatively large value.   The scanning line association unit performs a drift removal process on the evaluation target signal and the comparison signal in each scan line, and uses the evaluation target signal and the comparison signal after the drift removal process to perform the scanning. The flaw detection apparatus according to any one of claims 1 to 4, wherein line association is performed. A flaw detection method for detecting a defect on a predetermined inspection surface including a noise region where a signal caused by a factor other than a defect is generated,
A first storage step of storing, as evaluation target signals, flaw detection signals of a plurality of scanning lines obtained by moving one or more sensors on the inspection surface;
A flaw detection signal of a plurality of scanning lines obtained by moving one or a plurality of sensors on a non-defective inspection surface having the same shape as the inspection surface in the same scanning direction as the scanning line, or one or a plurality of flaw detection signals in the past A second storage step of storing, as comparison signals, flaw detection signals of a plurality of scan lines obtained by moving a sensor in the same scanning direction as the scan lines on the inspection surface without defects;
For each of the evaluation target signal and the comparison signal, a representative value determination process for determining a representative value for each scanning line;
Based on the difference between the representative value of each scanning line of the evaluation target signal and the representative value of each scanning line of the comparison signal and the arrangement order of the scanning lines, the scanning line corresponding to each scanning line of the evaluation target signal A scan line association process for determining the scan line of the comparison signal;
Positioning the evaluation target signal and the comparison signal in the scanning direction is performed between the scanning line of the evaluation target signal and the scanning line of the comparison signal that are associated in the association process, and A subtracting signal is generated by subtracting the signal value between the attached positions, and the subtracting signal is output in association with information on the scanning line of the evaluation target signal;
A flaw detection method including a defect detection step of detecting a defect using the subtraction signal.

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