JP2005106782A - Ultrasonic flaw detection method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: There is no ultrasonic flaw detector that can easily determine a defect when an inspection result is evaluated in ultrasonic flaw detection by a TOFD method.
SOLUTION: A bottom reflected wave removing device 13 for removing a bottom reflected wave to enhance a defect signal, an ultrasonic signal correcting device 14 for amplifying an ultrasonic echo to emphasize a weak defect signal, and a synthetic aperture process. A synthetic aperture device 15 that amplifies the defect signal, a lateral wave removal device 16 that removes the lateral wave and emphasizes the defect signal, and a wavelet that reconstructs the ultrasonic echo using the wavelet analysis order and emphasizes the defect signal. A processing device 17, and the defect signal is enhanced by any one or a combination of the bottom surface reflected wave removing device 13, the ultrasonic signal correcting device 14, the synthetic aperture device 15, and the lateral wave removing device 16. A measuring device having a function of emphasizing the defect signal by the wavelet processing device 17 is provided.
[Selection] Figure 1

Description

  The present invention relates to an ultrasonic flaw detection method and apparatus for nondestructive inspection of ultrasonic inspection parts such as welded joints, and more particularly to an ultrasonic flaw detection method and apparatus for nondestructive inspection by the TOFD method.

  Conventionally, weld joints and the like have been inspected for defects such as blow holes in order to confirm their reliability. As a means for inspecting the defect of the inspection part in this way, a nondestructive ultrasonic inspection (UT) is known. In this ultrasonic flaw detection inspection, a probe is brought into close contact with the surface of an object to be inspected, and defects are detected by reflected waves or diffracted waves of ultrasonic waves incident on the object to be inspected from the probe, The position of the defect can be known from the time until the reflected wave or diffraction wave of the incident ultrasonic wave is detected.

  FIG. 20 is a diagram showing an example of the ultrasonic flaw detection method. (A) is a schematic diagram of the ultrasonic flaw detection method, and (b) is a schematic diagram of the flaw detection waveform. This ultrasonic flaw detection method is generally called a TOFD (Time of Flight Diffraction) method. The example shown in the figure is an example of inspecting a welded joint part 101 which is an inspected part of the inspected object 100 by the TOFD method, and a transmitting probe 102A and a receiving probe 102B are provided on both sides of the welded joint part 101. The ultrasonic waves are incident on the transmitting probe 102A in a direction orthogonal to the weld line direction of the weld joint 101, and the reflection is received by the receiving probe 102B to perform an ultrasonic flaw inspection.

  In the case of this example, the entire plate thickness direction of the inspected object 100 is inspected by ultrasonic waves transmitted from a position away from the weld joint 101 by a predetermined distance. According to such an ultrasonic flaw detection method, the ultrasonic wave emitted from the transmission probe 102A travels along the surface of the inspection object 100 and is detected by the reception probe 102B, and the bottom surface of the inspection object 100. The reception surface 102B detects the bottom surface reflected wave b reflected by the wave and the upper end wave c and the lower end wave d of the diffracted wave diffracted by the defect 103 between them, and the presence of the defect 103 is detected by this signal. The position of the defect 103 is detected. In the case of this example, the ultrasonic probes 102A and 102B are moved along the weld joint portion 101, so that all lines in the weld line direction of the weld joint portion 101 are subjected to ultrasonic flaw detection.

  However, the TOFD method flaw detection image has a higher noise than the conventional pulse reflection method flaw detection image, and the fact is that the inspector misjudged the noise as a defect or that it took time to determine the defect. is there. As noise (interfering echo), there are a lateral wave propagating on the surface, a bottom reflected wave, a material noise generated in the weld metal, and the like, and it is difficult for an inspector to determine a defect.

  Therefore, in order to facilitate defect determination by the TOFD method, after separating the ultrasonic flaw detection signal from the ultrasonic flaw detection of coarse particles of austenitic steel, the noise echo that does not match the phase is made close to zero. In some cases, the defect part echoes are detected with a high S / N ratio by multiplying and amplifying the defect part echoes having the same phase (see, for example, Patent Document 1).

In addition, wavelet transform is performed on the ultrasonic inspection signal using a directional multidimensional basis, feature extraction is performed from the wavelet transform coefficient, and whether the evaluation target of the ultrasonic signal is a flaw echo or a pseudo echo from the feature amount. Can be discriminated reliably (for example, refer to Patent Document 2), and the ultrasonic echo signal obtained from the object to be inspected is subjected to rotational wavelet transform, thereby reducing pseudo echoes and accurately identifying defective portions. Some of them can be detected (for example, see Patent Document 3).
JP 2002-139479 A (3rd and 5th pages, FIG. 2) JP 2001-165912 A (second page, FIG. 2) JP 2003-66017 A (2nd page, FIG. 1)

  However, in the case of Patent Document 1 described above, an inspection object in which there is no ultrasonic echo from a defect in a plurality of frequency bands is multiplied by a plurality of separated waveforms for inspection, so even one defect signal is generated. If it is 0, the S / N ratio is not improved, but the defect signal may be 0 and the defect signal may not be obtained at all, and there is a possibility that stable defect inspection cannot be performed.

  Further, in the case of this Patent Document 1, it is impossible to remove lateral waves and bottom reflection echoes (both disturbing echoes) that always occur in the TOFD method ultrasonic flaw detection, and defects near the surface and the bottom are easily detected. I can't. Therefore, it may be difficult to improve the S / N ratio of the defect signal only by applying this Patent Document 1.

  Further, Patent Documents 2 and 3 describe that wavelet transform is performed to detect a defective portion with high accuracy, but these are not ultrasonic flaw detection by the TOFD method, and therefore, the TOFD as in the present invention. In this method, it is not possible to easily determine a defect.

  Therefore, an ultrasonic flaw detection method and an ultrasonic flaw detection apparatus that can easily determine a defect when an inspection result is evaluated in ultrasonic flaw detection by the TOFD method are desired.

  Therefore, in order to solve the above-mentioned problem, the ultrasonic flaw detection method of the present invention has a transmitting probe and a receiving probe arranged symmetrically on both sides of the inspection part of the object to be inspected, and In an ultrasonic flaw detection method in which an ultrasonic wave is transmitted to an object and an ultrasonic echo from the body to be inspected is received by a receiving probe and an inspection part of the body to be inspected is scanned, the probe according to the object to be inspected In the vicinity of the position where the bottom reflected wave obtained by geometric calculation from the arrangement of The bottom surface reflected wave is removed by setting the intensity of the ultrasonic echo appearing later than this position to zero.

  In addition, the transmitting probe and the receiving probe are placed symmetrically on both sides of the inspection part of the object to be inspected, ultrasonic waves are transmitted from the transmitting probe to the inspected body, and ultrasonic echoes from the inspected body are received. In the ultrasonic flaw detection method that is received by the probe and scans the inspection portion of the object to be inspected, at each propagation time according to the attenuation of the ultrasonic wave propagating through the object to be inspected and the change in the ultrasonic intensity that decreases due to directivity A weak signal may be emphasized by amplifying ultrasonic echoes measured to have the same intensity.

  Furthermore, the transmission probe and the reception probe are arranged symmetrically on both sides of the inspection part of the object to be inspected, ultrasonic waves are transmitted from the transmission probe into the object to be inspected, and ultrasonic echoes from the object to be inspected are received. In the ultrasonic flaw detection method in which the probe receives and scans the inspection portion of the object to be inspected, the position at which the curved signal generated by the spread of the ultrasonic wave in the scanning direction appears is the transmission probe and the reception probe. Curved defects detected in the scanning direction of the probe by obtaining a curve equation corresponding to each depth of the object to be inspected in advance from the arrangement and the scanning position and performing synthetic aperture processing using the curve equation The signal may be concentrated at the apex and amplified.

  In addition, the transmitting probe and the receiving probe are placed symmetrically on both sides of the inspection part of the object to be inspected, ultrasonic waves are transmitted from the transmitting probe to the inspected body, and ultrasonic echoes from the inspected body are received. In an ultrasonic flaw detection method in which a probe receives and scans an inspection portion of an object to be inspected, an average value of ultrasonic signals obtained at each position in the scanning direction between the transmission probe and the reception probe is calculated. The defect signal may be emphasized by removing the lateral wave by subtracting the average value from the ultrasonic signal obtained at each position.

  Furthermore, the transmission probe and the reception probe are arranged symmetrically on both sides of the inspection part of the object to be inspected, ultrasonic waves are transmitted from the transmission probe into the object to be inspected, and ultrasonic echoes from the object to be inspected are received. In the ultrasonic flaw detection method that is received by the probe and scans the inspection portion of the object to be inspected, after performing wavelet analysis using a basis function similar to a defect signal when a defect exists in the object to be inspected, Only the wavelet analysis order suitable for extracting the defect signal may be used to reconstruct the ultrasonic echo received by the reception probe to enhance the defect signal.

  In addition, an ultrasonic flaw detection method that emphasizes a defect signal by removing the bottom surface reflected wave, an ultrasonic flaw detection method that amplifies the ultrasonic echo to emphasize a weak defect signal, and the synthetic aperture processing generates a defect signal. A defect signal is emphasized by combining an ultrasonic flaw detection method that amplifies by concentrating on a vertex and an ultrasonic flaw detection method that emphasizes a defect signal by removing the lateral wave, and the emphasized defect signal If an ultrasonic flaw detection method based on wavelet analysis is applied to enhance the defect signal, a more preferable image for detecting the defect can be obtained.

  Further, the defect signal emphasized by the ultrasonic flaw detection method based on the wavelet analysis is subjected to threshold processing with a presumed intensity to obtain binarized data, and the defect signal obtained as the binarized data is processed based on the wavelet analysis. The defect signal may be enhanced by multiplying the previous ultrasonic signal.

  Further, if the defect signal is enhanced by performing threshold processing on the defect signal emphasized by the ultrasonic flaw detection method at a predetermined intensity, the defect extraction operation can be automated.

  On the other hand, in the ultrasonic flaw detector according to the present invention, the transmission probe and the reception probe are symmetrically arranged on both sides of the inspection portion of the inspection object, and ultrasonic waves are transmitted from the transmission probe to the inspection object. A measuring device that receives an ultrasonic echo from the body to be inspected by a receiving probe and scans the inspection portion is provided, and the measuring device can be geometrically calculated from the arrangement of the probe according to the object to be inspected. In the vicinity of the position where the bottom surface reflected wave appears, an ultrasonic echo exceeding the preset threshold value of the bottom surface reflected wave is detected, and the intensity of the ultrasonic echo that appears later in time than the rising position of the ultrasonic echo is zero. Thus, a bottom surface reflected wave removing device for removing bottom surface reflected waves is provided.

  In addition, a transmission probe and a reception probe are arranged symmetrically on both sides of the inspection portion of the object to be inspected, and ultrasonic waves are transmitted from the transmission probe into the object to be inspected so that an ultrasonic echo from the object to be inspected is transmitted. A measurement device that receives the reception probe and scans the inspection unit is provided, and the position at which a curved signal generated by the spread of ultrasonic waves in the scanning direction appears on the measurement device is determined by the transmission probe and the reception probe. The scanning direction of the probe is obtained by previously obtaining a curve equation corresponding to each depth of the object to be inspected from the arrangement and scanning position of the child and recording it in the measuring device, and performing synthetic aperture processing using the curve equation. A synthetic aperture device for concentrating and amplifying the curved defect signal detected at the top may be provided.

  Further, a transmission probe and a reception probe are arranged symmetrically on both sides of the inspection part of the object to be inspected, and ultrasonic waves are transmitted from the transmission probe into the object to be inspected so that an ultrasonic echo from the object to be inspected is transmitted. A measurement device that receives the reception probe and scans the inspection unit is provided, and the measurement device has an average value of ultrasonic signals obtained at each position in the scanning direction of the transmission probe and the reception probe. And a lateral wave removing device that emphasizes the defect signal by removing the lateral wave by subtracting the average value from the ultrasonic signal obtained at each position.

  In addition, a transmission probe and a reception probe are arranged symmetrically on both sides of the inspection portion of the object to be inspected, and ultrasonic waves are transmitted from the transmission probe into the object to be inspected so that an ultrasonic echo from the object to be inspected is transmitted. A measurement device that receives a reception probe and scans the inspection unit is provided, and the measurement device performs wavelet analysis using a basis function similar to a defect signal when a defect exists in the inspection object, A wavelet processing device that reconstructs an ultrasonic echo received by the reception probe using only a wavelet analysis order suitable for extracting the defect signal from the result of wavelet analysis and enhances the defect signal; Also good.

  Further, the bottom reflected wave removing device, the synthetic aperture device, the lateral wave removing device, and the wavelet processing device, and any of the bottom reflected wave removing device, the synthetic aperture device, and the lateral wave removing device A measuring device having a function of emphasizing a defect signal by one or a plurality of combinations and emphasizing the emphasized defect signal by the wavelet processing device may be provided. In this case, effective defect detection can be performed by combining a plurality of processes.

  Further, in the ultrasonic flaw detection apparatus, a binarized data processing unit that converts the defect signal emphasized by the ultrasonic flaw detection apparatus based on wavelet analysis to the binarized data by performing threshold processing with an assumed intensity in the measurement apparatus. And a multiplier that multiplies the defect signal as the binarized data by the ultrasonic signal before the processing by the wavelet analysis is performed.

  Further, in this ultrasonic flaw detector, the measurement device may be provided with a threshold control unit that performs threshold processing with a strength assumed in advance for the defect signal emphasized by the ultrasonic flaw detector. In this case, it is possible to automatically detect defects.

  According to the present invention, in the ultrasonic flaw detection by the TOFD method, it is possible to easily evaluate the inspection result and determine the defect by the above means.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an ultrasonic flaw detector according to the TOFD method to which the present invention is applied. Also in the following embodiments, a welded joint part will be described as an example of the part to be inspected.

  As shown in the figure, in this ultrasonic flaw detector 1, a transmission probe 4 and a reception probe 5 are symmetrically arranged on both sides of a welded joint portion 3 that is an inspection portion of an object 2 to be inspected. The ultrasonic wave u is incident from 4 to the direction orthogonal to the scanning direction (indicated by the arrow) of the welded joint portion 3 and the diffraction wave ru is received by the receiving probe 5 to ultrasonically detect the welded joint portion 3. Is configured to do. That is, a continuous ultrasonic signal is generated by transmitting and receiving ultrasonic waves while scanning the transmitting probe 4 and the receiving probe 5 arranged in a certain positional relationship on the surface of the inspection object 2. It is the TOFD method ultrasonic flaw detector 1 to be obtained.

  The transmission probe 4 and the reception probe 5 are connected to an ultrasonic transmitter / receiver 8 provided in the measuring device 7 by wiring 6. The measuring device 7 is provided with an A / D converter 9, and flaw detection result data is recorded in the recording device 10. The data recorded in the recording device 10 is processed by the signal processing device 11 and can be displayed on the display device 12 such as a display. The display device 12 is also connected to the measurement device 7 and is configured to display a signal from the measurement device 7.

  FIG. 2 is a block diagram showing each device provided in the ultrasonic flaw detector according to the first embodiment of the present invention. The ultrasonic flaw detector 1 (FIG. 1) according to the first embodiment includes a bottom reflected wave removing device 13, an ultrasonic signal correcting device 14, a synthetic aperture device 15, a lateral wave removing device 16, a wavelet processing device 17, and an S. An / N ratio enhancement processing device 18 and a defect extraction processing device 19 are provided. In the first embodiment, the bottom surface reflected wave removing device 13, the ultrasonic signal correcting device 14, the synthetic aperture device 15, and the lateral wave removing device 16 are used singly or in combination with a plurality of selectively. The case where the enhanced defect signal is processed by the wavelet processing device 17, the S / N ratio enhancement processing device 18, and the defect extraction processing device 19 is shown.

  FIG. 3 is a block diagram showing each device provided in the ultrasonic flaw detector according to the second embodiment of the present invention. In the ultrasonic flaw detector 1 of the second embodiment (same as FIG. 1), defect signal processing is continuously performed by the devices 13 to 19 in the ultrasonic flaw detector 1 of the first embodiment shown in FIG. Yes. Hereinafter, the flow of signal processing by the devices 13 to 19 of the second embodiment and the processing by each device will be described in detail.

  FIG. 4 is a drawing showing an example of an object to be inspected by the ultrasonic flaw detection method of the present invention, wherein (a) is a plan view, (b) is a side view, and (c) is an AA cross-sectional view. is there. FIG. 5 is a graph showing measurement raw data obtained by ultrasonic flaw detection on the inspection object, and FIG. 6 is a photograph of an image of measurement raw data obtained by ultrasonic flaw detection on the inspection object shown in FIG. FIG. 7 is a graph showing points where the bottom surface reflected wave removal processing is performed on the measurement raw data shown in FIG. 5, and FIG. 8 is a photograph of an image obtained by performing bottom surface reflection wave removal processing on the measurement raw data shown in FIG. . FIG. 9 is a graph showing the relationship between the depth direction of the object to be inspected and the ultrasonic intensity. 10A and 10B are diagrams showing the principle of the synthetic aperture processing, where FIG. 10A is a schematic diagram showing data before the synthetic aperture processing, and FIG. 10B is a schematic diagram showing data after the synthetic aperture processing. FIG. 11 is a drawing showing an example of data acquisition for synthetic aperture processing, (a) is a schematic diagram showing a data acquisition position, and (b) is a drawing of an acquired data list. FIG. 12 is a photograph of an image obtained by performing synthetic aperture processing on the data obtained by performing the bottom surface reflected wave removal processing shown in FIG. FIG. 13 is a photograph of an image obtained by performing lateral wave removal processing on the data subjected to the synthetic aperture processing shown in FIG. FIG. 14 is a photograph of an oscilloscope waveform showing a conversion coefficient obtained as a result of fifth-order wavelet analysis using a basis function, and a result obtained by processing an ultrasonic signal including a defective portion using the conversion coefficient. ~ (E) indicates a conversion coefficient, and (f) ~ (nu) indicate a result. FIG. 15 is a graph showing data in which defects are emphasized using conversion coefficients in the data shown in FIG. 14, and FIG. 16 is a photograph of an image obtained by performing wavelet analysis on the data subjected to the lateral wave removal processing shown in FIG. is there. FIG. 17 is a photograph of an image of wavelet noise processing that has been subjected to threshold processing on the signal of the image that has been subjected to the wavelet analysis shown in FIG. 16 to obtain binarized data, and FIG. FIG. 14 is a photograph of an image that has been subjected to S / N enhancement processing by multiplying the value data by the signal subjected to the lateral wave removal processing shown in FIG. 13. FIG. 19 is a photograph of an image obtained by performing defect extraction processing on the data subjected to S / N enhancement processing shown in FIG.

  Hereinafter, based on these drawings, a specific ultrasonic flaw detection method by the ultrasonic flaw detection apparatus 1 including the devices 13 to 19 will be described.

  As shown in FIG. 4, in the second embodiment, an example will be described in which three artificial defects 51, 52, 53 are provided in advance on the inspected object 2 and these defects 51, 52, 53 are inspected. When ultrasonic inspection is performed on the inspection object 2 as shown in FIG. 4, the defect signal 21 from the defects 51, 52, and 53 existing in the inspection object 2, the lateral wave 64 that propagates on the surface, and the bottom surface reflection from the bottom surface. The measurement raw data of the ultrasonic echo as shown in FIG. When the ultrasonic echo of the measured raw data is displayed on the display with a white color on the plus side and a black side on the minus side of the graph showing strength and weakness on the display, the color is converted into a gray halftone between them. Displayed as an image. Since this image is raw data of the received ultrasonic echoes, the defect images 61, 62, and 63 appearing by the ultrasonic echoes from the defects 51, 52, and 53, and the ultrasonic echoes of noise inherent in the inspected object 2 ( Noise echo), a lateral wave 64 propagating on the surface of the object 2 to be inspected, and a bottom surface reflected wave 65 from the bottom surface of the object 2 to be inspected. Hereinafter, a method for increasing the defect signal intensity in the ultrasonic signal from such measurement raw data and reducing the other signal intensity to improve the S / N ratio and easily determine the defect will be described. To do.

  The bottom surface reflected wave removing device 13 shown in FIG. 3 is a device that removes an indication pattern of bottom surface reflected waves that is harmful to the detection of defects. In the bottom surface reflected wave removing device 13, in the TOFD method, an echo (bottom surface reflected wave) exceeding a preset threshold is generated in the vicinity of the position where the bottom surface reflected wave obtained by geometric calculation from the arrangement of the probes 4 and 5 appears. Detection is performed, and a rising position of the echo (zero cross position of the ultrasonic echo) is obtained. Then, this position is set as the start position of the bottom surface reflected wave, and the bottom surface reflected wave is removed by setting the intensity of the ultrasonic echo that appears later than this position to 0.

  As a specific process by the bottom surface reflected wave removing device 13, as shown in FIG. 7, the flaw detection result is represented by time corresponding to the thickness direction of the inspection object and the intensity of the ultrasonic signal, and the reflected wave echo from the bottom surface. The strength of is very large. Therefore, paying attention to this, the time tb (bottom surface) equivalent to the thickness of the inspection object calculated from the arrangement and thickness of the probe is traced back by a time Δt equivalent to several millimeters (for example, 5 mm). , Tb−Δt and thereafter, a position tc at which the ultrasonic echo exceeds a preset threshold intensity pb is obtained. From this position TC, a position tz where the intensity of the ultrasonic echo intersects with 0 in the surface direction (left direction in the figure) is obtained. Then, the signal from the crossing position tz (zero crossing position) to 0 to the bottom surface direction (the right direction in the figure) is regarded as the bottom surface reflected wave of the inspection object, and all the signals from the tz to the bottom surface direction are set to 0. The reflected wave is removed. When the bottom surface reflected wave removal is performed in this way, as shown in FIG. 8, the bottom surface reflected wave 65 displayed at the bottom of FIG. 6 is removed.

  The ultrasonic signal correction apparatus 14 shown in FIG. 3 is an apparatus that amplifies an ultrasonic signal and emphasizes a weak defect signal in consideration of the directivity of the ultrasonic beam propagating in the inspection object and the distance to the defect. It is. In this ultrasonic signal correction device 14, in the TOFD method, ultrasonic waves measured so as to have the same intensity at each propagation time according to the attenuation of ultrasonic waves propagating through the inspected body and the intensity change of the ultrasonic waves that are reduced by directivity. The signal is amplified.

  As shown in FIG. 9, the specific processing by the ultrasonic signal correcting device 14 is that the ultrasonic signal propagating through the inside of the inspection object 2 is converted into the ultrasonic signal due to its directivity and attenuation within the inspection body. The signal strength is strong in the depth direction before and after the intersection 20 with strong energy (for example, the position of the ultrasonic wave u and the diffracted wave ru shown in FIG. 1), and the shallow portion (left side in the figure) away from the intersection 20 In FIG. 9, the energy is weak, and in the deep part (right side of the figure), the energy is weak and the signal intensity is weakened due to distance attenuation. Therefore, according to the characteristics shown in FIG. By amplifying the low signal intensity portions (shallow and deep portions from the intersection point) so that the intensities are the same, the defect signal from the high attenuation portion in the inspection object 2 can be detected satisfactorily. . Note that the characteristic shown in FIG. 9 is an example, and this characteristic can be obtained by an experiment according to the object 2 to be inspected.

  The synthetic aperture device 15 shown in FIG. 3 is a device that concentrates a curved instruction pattern generated in a defective portion obtained by scanning by a synthetic aperture in consideration of the depth, and emphasizes a signal from the defect. is there. The synthetic aperture device 15 obtains a curve equation for each depth in the TOFD method in advance, and then performs synthetic aperture using the curve equation to concentrate the curved instruction pattern on the defect portion and amplify the defect signal. I am letting. Thereby, the detection accuracy of the defect position is improved and the S / N ratio is improved.

  Specifically, as shown in FIG. 10 (a), the ultrasonic signals from the defects 51, 52, 53 in the inspection object 2 are spatially spread. A position di that is apparently deeper than the depth dr of the actual defects 51, 52, 53 until and after the transmitting probe 4 and the receiving depth probe 5 to be moved reach directly above the defects 51, 52, 53. It is measured as if a defect exists at (slanting direction distance). Therefore, the defect signal obtained by scanning the transmission depth probe 4 and the reception probe 5 on the surface of the inspection object 2 is measured as a curved defect signal 21 as shown in the lower part of FIG. Is done. Therefore, as shown in FIG. 10 (b), synthetic aperture processing is performed as a technique of using the curved defect signal 21 as a defect signal 22 that is concentrated at the apex of the curve. As a method of performing this synthetic aperture processing, there is a method of performing Fourier analysis using a reference curve in general. However, these methods have a constant time (or distance, depth) to a measured defect signal. If the curve shape changes because the distance (depth) to the defect signal is different as in ultrasonic flaw detection, the method of Fourier transform using one reference curve should be applied. I can't. Therefore, as shown in FIG. 11 (a), an ultrasonic wave corresponding to the object 2 to be inspected from the relationship between the amount of deviation from directly above the inspection unit 3 (in this example, -3 mm to +3 mm) and the measurement depth x. The measurement depth x at each sampling of each deviation amount (−3 mm to +3 mm) is calculated in consideration of the propagation speed, etc., and a matrix of a curve equation that changes with distance as shown in FIG. The table is created from the position of the transducer arrangement and signal. Then, by adding signals corresponding to each distance (in this example, −3 mm to +3 mm) to each actually measured defect signal 21, the signals are concentrated at the apex of the curve, and defects having different depths. Even in the case of (reflection source), it is possible to obtain a defect signal 22 in which signals are concentrated well at the synthetic aperture. Such synthetic aperture processing is performed by the synthetic aperture device 15. In FIG. 11A, the numerical values at the positions of x = 0.2 and x = 35.0 are shown. When the ultrasonic signal subjected to the synthetic aperture processing is displayed as an image, an image as shown in FIG. 12 is obtained, and the defect signals 61, 62, and 63 are displayed more clearly.

  The lateral wave removing device 16 shown in FIG. 3 is a device that removes an indication pattern of a lateral wave that propagates on the surface of the inspection object 2 harmful to the detection of defects. In the lateral wave removing device 16, in the TOFD method, the average value of the ultrasonic signals obtained at the respective positions in the scanning direction is subtracted from the ultrasonic signals obtained at the respective positions, thereby preventing the detection of the defect. The lateral wave which becomes becomes.

  As specific lateral wave removal by the lateral wave removal device 16, all the ultrasonic signals obtained by scanning are added, and an average value divided by the number of times of measurement is used as a reference signal. This reference signal is subtracted from the ultrasonic signal obtained at each position to remove the lateral wave. As shown in FIG. 13, the image of the ultrasonic signal from which the lateral wave has been removed is an image in which the lateral wave propagating on the surface of the inspection object displayed in the upper part of FIG. 12 has disappeared.

  The wavelet processing device 17 shown in FIG. 3 is a device that reduces material noise by wavelet analysis and emphasizes defects. In the wavelet processing device 17, in the TOFD method, after performing wavelet transform using a basis function similar to a defect signal, the ultrasonic signal is reconstructed using only the wavelet transform order suitable for extracting the defect signal. The defect signal is emphasized.

  As specific material noise removal for wavelet analysis (time frequency analysis) by the wavelet processing device 17, a basis function (for example, COEF5) similar in shape to a defect signal when a defect exists in the inspection object 2 is used. A fifth-order wavelet analysis is performed using this basis function, and transform coefficients of respective orders are obtained. As the obtained conversion coefficients of the respective orders, for example, oscilloscope waveforms as shown in (a) to (e) of FIG. 14 can be displayed. And the ultrasonic signal containing a defective part is processed using this conversion coefficient. As a result of this processing, it is displayed with an oscilloscope waveform as shown in FIGS. From the oscilloscope waveform displayed in this way, the one having the highest S / N ratio and the defect position appearing at an appropriate position is determined. In this example, the defect signal is displayed at the position closest to the position where the defect is provided in FIG. 14G, and the order d4 shown in FIG. 14B is effective as the conversion coefficient. I understand that. The basis function, the order, the formula for performing the wavelet analysis, and the like may be used according to known means, and may be set according to the object 2 to be inspected.

  Further, in order to remove noise other than defects, the conversion coefficient of the order d4 is subjected to threshold processing with a strength assumed in advance (for example, 20 in the case of FIG. 14) to obtain a new conversion coefficient. The result of emphasizing the defect using this conversion coefficient is the graph shown in FIG. 15, and noise can be reduced while leaving the defect signal clearly. The image obtained as a result of the wavelet analysis as described above is an image in which the portions of the defect signals 61, 62, and 63 are greatly emphasized as shown in FIG.

  In this embodiment, before performing the defect enhancement processing by the wavelet processing device 17, the processing by the bottom surface reflected wave removing device 13, the processing by the ultrasonic signal correction device 14, the processing by the synthetic aperture device 15, and the lateral wave are performed. Since the processing by the removing device 16 is performed, the defect signal is emphasized in the most preferable state. Note that the processing by these devices 13 to 16 can also enhance the defect signal by performing a single process or a combination of a plurality of processes as shown in FIG. The combined processing may be performed, and the wavelet analysis may be performed on the enhanced signal by the wavelet processing device 17 to enhance the defect signal.

  The S / N ratio enhancement processing device 18 shown in FIG. 3 performs threshold processing on the result of the wavelet analysis performed by the wavelet processing device 17 and multiplies the processed signal by the signal before the wavelet analysis. , A device for enhancing the S / N ratio. The S / N ratio enhancement processing device 18 performs threshold processing on the S / N ratio enhanced ultrasonic signal obtained by the wavelet analysis with a presumed intensity, and thus candidates for defects. By multiplying the extracted signal by the ultrasonic signal before performing wavelet analysis, the defect portion is emphasized and the S / N ratio is improved.

  The defect extraction processing device 19 shown in FIG. 3 is a device that performs threshold processing on the result processed by the S / N ratio enhancement processing device 18 and extracts defects. As specific processing by the defect extraction processing device 19, threshold processing is performed with a presumed intensity on the signal processed by the S / N ratio enhancement processing device 18 to improve the S / N ratio. To extract defects. The threshold value may be determined according to the material, thickness, etc. of the device under test 2.

  When the defect signal is emphasized as shown in FIG. 16, there is a portion where the signal other than the defect is emphasized, and a sufficient S / N ratio at the defect portion may not be obtained. Therefore, as a processing method for further improving the S / N ratio, threshold processing is performed on the image shown in FIG. 16 with a presumed intensity to obtain binary data of 1 and 0. An image obtained by displaying the ultrasonic echo subjected to the threshold processing as an image is an image shown in FIG. 17, in which a strong portion and a weak portion of the ultrasonic echo are clearly shown.

  Then, by multiplying the threshold-processed image signal of FIG. 17 and the signal before the wavelet analysis shown in FIG. 13, the binarized portion is shown as a portion having a high ultrasonic echo intensity (FIG. 17 (white portion) can be obtained as an image with an improved S / N ratio. As this enhancement processing, for example, a portion where the ultrasonic echo intensity is high (white portion in FIG. 17) is doubled and a portion where the ultrasonic echo intensity is low (gray portion in FIG. 17) is doubled and displayed. Such processing is performed. In this embodiment, lateral waves and bottom surface reflected waves that interfere with flaw detection are removed, the signal intensity from the defects is increased, and the noise level is lowered by performing this processing, so that the S / N ratio value is about 10 dB. Can be improved. By performing such processing, as shown in FIG. 18, defect images 61, 62, and 63 that can almost determine the sizes of the defects 51, 52, and 53 can be obtained, and the defects 51, 52, and 53 can be obtained. It becomes possible to quickly grasp the position and size.

  As shown in FIG. 19, when threshold processing is performed on the image data shown in FIG. 18 with an assumed intensity in advance, only the portions of the defects 51, 52, and 53 can be clearly displayed as shown in FIG. Therefore, it is possible to automatically detect the presence or absence of the defects 51, 52, 53.

  The devices 13 to 19 are provided in the measuring device 7 described above, and the functions of these devices are provided in a computer or the like constituting the measuring device 7.

  As described above, according to the ultrasonic flaw detector 1 of this embodiment, the bottom reflected wave removal, the signal intensity amplification for attenuation correction, the lateral wave removal, the deletion of the defect end indication pattern by the synthetic aperture processing method, The ultrasonic signal intensity from the defect can be emphasized by the process of removing noise in the material by wavelet diffraction. In this embodiment, the result of processing by combining a plurality of processes for emphasizing the defect in this way is used. Since the S / N ratio is improved by performing threshold processing on the signal and multiplying the signal obtained by extracting only the defect candidate image by the measured ultrasonic signal, the ultrasonic echo of the TOFD method with improved S / N ratio. Since a signal can be obtained, it is not necessary to evaluate even an unnecessary instruction (pseudo instruction), and the inspection time can be shortened. In addition, if only the ultrasonic signal having an intensity higher than that assumed in advance is extracted from the flaw detection image that has been subjected to the above-described processing by threshold processing, defects can be automatically detected.

  In the above-described embodiment, an example in which signal processing is performed by combining all processes has been described. However, as described above, bottom surface reflected wave removal, ultrasonic signal correction, synthetic aperture, and lateral wave removal can be used alone or in combination. You may comprise so that it may process, It is not limited to embodiment mentioned above.

  Further, the above-described embodiment shows an example of the best embodiment, and various modifications can be made without departing from the gist of the present invention, and the present invention is not limited to the above-described embodiment. .

  The present invention can easily determine a defect echo in ultrasonic flaw detection by the TOFD method, and can be used as an ultrasonic flaw detection suitable as a defect extraction technique for flaw detection on a welded joint or the like.

It is a block diagram which shows one Embodiment of the ultrasonic flaw detector which concerns on the TOFD method to which this invention is applied. It is a block diagram which shows each apparatus with which the ultrasonic flaw detector based on 1st Embodiment of this invention was equipped. It is a block diagram which shows each apparatus with which the ultrasonic flaw detector which concerns on 2nd Embodiment of this invention was equipped. BRIEF DESCRIPTION OF THE DRAWINGS It is drawing which shows an example of the to-be-inspected object ultrasonically detected by the ultrasonic flaw detection method of this invention, (a) is a top view, (b) is a side view, (c) is AA sectional drawing. It is a graph which shows the measurement raw data which ultrasonically detected the to-be-inspected object. 6 is a photograph of an image of measurement raw data obtained by ultrasonic flaw detection on the inspection object shown in FIG. 5. It is the graph which showed the point which performs a bottom face reflected wave removal process to the measurement raw data shown in FIG. 6 is a photograph of an image obtained by performing bottom surface reflected wave removal processing on the measured raw data shown in FIG. 5. It is a graph which shows the relationship between the depth direction of a to-be-inspected object, and ultrasonic intensity. It is drawing which shows the principle of a synthetic aperture process, (a) is a schematic diagram which shows the data before a synthetic aperture process, (b) is a schematic diagram which shows the data after a synthetic aperture process. It is drawing which shows the data acquisition example for synthetic | combination aperture processing, (a) is a schematic diagram which shows a data acquisition position, (b) is drawing of the acquired data table. FIG. 9 is a photograph of an image obtained by performing synthetic aperture processing on the data obtained by performing the bottom surface reflected wave removal processing illustrated in FIG. 8. FIG. FIG. 13 is a photograph of an image obtained by performing a lateral wave removal process on the data subjected to the synthetic aperture process illustrated in FIG. 12. It is the photograph of the oscilloscope waveform which shows the conversion coefficient of the result of the fifth-order wavelet analysis using the basis function, and the result of processing the ultrasonic signal including the defect portion using the conversion coefficient. ) Indicates a conversion coefficient, and (f) to (nu) indicate results. It is a graph which shows the data which emphasized the defect using the conversion coefficient to the data shown in FIG. It is the photograph of the image which performed the wavelet analysis to the data which performed the lateral wave removal process shown in FIG. It is the photograph of the image of the wavelet noise process which made the threshold value process and processed the signal of the image which performed the wavelet analysis shown in FIG. 16 into the binarized data. 18 is a photograph of an image obtained by multiplying the binarized data subjected to the wavelet noise processing shown in FIG. 17 by the signal subjected to the lateral wave removal processing shown in FIG. 13 and performing S / N enhancement processing. It is the photograph of the image which performed the defect extraction process to the data which performed the S / N emphasis process shown in FIG. It is drawing which shows the ultrasonic flaw detection method of TOFD method, (a) is a schematic diagram which shows an example of an ultrasonic flaw detection method, (b) is a schematic diagram of the flaw detection waveform.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic flaw detector 2 ... Test object 3 ... Welded joint part 4 ... Transmission probe 5 ... Reception probe 6 ... Wiring 7 ... Measuring device 8 ... Ultrasonic transmitter / receiver 9 ... A / D converter 10 ... Recording device 11 ... Signal processing device 12 ... Display device 13 ... Bottom reflected wave removal device 14 ... Ultrasonic signal correction device 15 ... Synthetic aperture device 16 ... Lateral wave removal device 17 ... Wavelet processing device 18 ... S / N enhancement processing device 19 DESCRIPTION OF SYMBOLS ... Defect extraction processing apparatus 20 ... Interaxial point 21 ... Defect signal 22 ... Defect signal 51, 52, 53 ... Defect 61, 62, 63 ... Defect image 64 ... Lateral wave 65 ... Bottom reflected wave u ... Ultrasonic ru ... Diffraction wave

Claims (15)

The transmitting probe and the receiving probe are arranged symmetrically on both sides of the inspection part of the object to be inspected, ultrasonic waves are transmitted from the transmitting probe to the inspected body, and ultrasonic echoes from the inspected object are received and received. In the ultrasonic flaw detection method in which the child receives and scans the inspection part of the inspection object,
An ultrasonic echo exceeding a preset threshold value of the bottom reflected wave is detected in the vicinity of the position where the bottom reflected wave obtained by geometric calculation from the arrangement of the probe according to the inspection object appears, and the ultrasonic echo is detected. Is the ultrasonic wave flaw detection method in which the bottom reflected wave is removed by setting the intensity of the ultrasonic echo appearing later than this position as zero. The transmitting probe and the receiving probe are arranged symmetrically on both sides of the inspection part of the object to be inspected, ultrasonic waves are transmitted from the transmitting probe to the inspected body, and ultrasonic echoes from the inspected object are received and received. In the ultrasonic flaw detection method in which the child receives and scans the inspection part of the inspection object,
Amplifying the ultrasonic echo measured to have the same intensity at each propagation time according to the attenuation of the ultrasonic wave propagating through the inspected body and the change of the ultrasonic intensity that is reduced by the directivity, so as to emphasize a weak signal Ultrasonic flaw detection method. The transmitting probe and the receiving probe are arranged symmetrically on both sides of the inspection part of the object to be inspected, ultrasonic waves are transmitted from the transmitting probe to the inspected body, and ultrasonic echoes from the inspected object are received and received. In the ultrasonic flaw detection method in which the child receives and scans the inspection part of the inspection object,
The position at which a curved signal generated by the spread of ultrasonic waves in the scanning direction appears is determined in advance as a curve equation corresponding to each depth of the object to be inspected from the arrangement of the transmitting probe and the receiving probe and the scanning position. An ultrasonic flaw detection method in which a curved defect signal detected in the scanning direction of the probe is concentrated at the apex and amplified by performing synthetic aperture processing using the curve equation. The transmitting probe and the receiving probe are arranged symmetrically on both sides of the inspection part of the object to be inspected, ultrasonic waves are transmitted from the transmitting probe to the inspected body, and ultrasonic echoes from the inspected object are received and received. In the ultrasonic flaw detection method in which the child receives and scans the inspection part of the inspection object,
A lateral value is obtained by obtaining an average value of the ultrasonic signals obtained at each position in the scanning direction of the transmission probe and the receiving probe and subtracting the average value from the ultrasonic signals obtained at the respective positions. An ultrasonic flaw detection method that removes waves and emphasizes defect signals. The transmitting probe and the receiving probe are arranged symmetrically on both sides of the inspection part of the object to be inspected, ultrasonic waves are transmitted from the transmitting probe to the inspected body, and ultrasonic echoes from the inspected object are received and received. In the ultrasonic flaw detection method in which the child receives and scans the inspection part of the inspection object,
After performing wavelet analysis using a basis function similar to a defect signal when a defect exists in the inspection object, the receiving probe uses only a wavelet analysis order suitable for extracting the defect signal. An ultrasonic flaw detection method in which a received ultrasonic echo is reconstructed to enhance a defect signal.   An ultrasonic flaw detection method for enhancing a defect signal by removing a bottom reflected wave according to claim 1; an ultrasonic flaw detection method for amplifying an ultrasonic echo according to claim 2 to emphasize a weak defect signal; The ultrasonic flaw detection method for concentrating and amplifying the defect signal at the apex by the synthetic aperture processing according to claim 3 and the ultrasonic flaw detection method for removing the lateral wave and emphasizing the defect signal according to claim 4 alone or An ultrasonic flaw detection method for emphasizing a defect signal by emphasizing a defect signal by combining a plurality of the defect signals and applying the ultrasonic flaw detection method by wavelet analysis to the emphasized defect signals.   6. The defect signal emphasized by the ultrasonic flaw detection method by wavelet analysis according to claim 5 is subjected to threshold processing at a presumed intensity to be binarized data, and the defect signal made into the binarized data is processed by the wavelet analysis. An ultrasonic flaw detection method for emphasizing a defect signal by multiplying an ultrasonic signal before performing.   An ultrasonic flaw detection method for emphasizing a defect signal by performing threshold processing at a predetermined intensity on the defect signal emphasized by the ultrasonic flaw detection method according to claim 7.   A transmitting probe and a receiving probe are arranged symmetrically on both sides of the inspection part of the object to be inspected, and ultrasonic waves are transmitted from the transmitting probe into the object to be inspected to receive ultrasonic echoes from the object to be inspected. Provided with a measurement device that receives the probe and scans the inspection unit, in the measurement device, in the vicinity of the position where the bottom surface reflected wave obtained by geometric calculation from the arrangement of the probe according to the inspection object appears, A bottom surface that detects an ultrasonic echo exceeding a preset threshold value of the bottom surface reflected wave and removes the bottom surface reflected wave by setting the intensity of the ultrasonic echo that appears later than the rising position of the ultrasound echo to zero. An ultrasonic flaw detector provided with a reflected wave removing device.   A transmitting probe and a receiving probe are arranged symmetrically on both sides of the inspection part of the object to be inspected, and ultrasonic waves are transmitted from the transmitting probe into the object to be inspected to receive ultrasonic echoes from the object to be inspected. A measuring device that receives the probe and scans the inspection unit is provided, and the position at which the curved signal generated by the spread of the ultrasonic wave in the scanning direction appears on the measuring device is determined by the transmission probe and the receiving probe. From the arrangement and the scanning position, a curve equation corresponding to each depth of the object to be inspected is obtained in advance and recorded in the measuring device, and synthetic aperture processing is performed using the curve equation to detect in the scanning direction of the probe. An ultrasonic flaw detector provided with a synthetic aperture device for concentrating and amplifying a curved defect signal at the apex.   A transmitting probe and a receiving probe are arranged symmetrically on both sides of the inspection part of the object to be inspected, and ultrasonic waves are transmitted from the transmitting probe into the object to be inspected to receive ultrasonic echoes from the object to be inspected. A measuring device that receives the probe and scans the inspection unit is provided, and an average value of the ultrasonic signals obtained at each position in the scanning direction of the transmitting probe and the receiving probe is obtained in the measuring device. An ultrasonic flaw detector provided with a lateral wave removing device that subtracts the average value from the ultrasonic signal obtained at each position to remove a lateral wave and emphasize a defect signal.   A transmitting probe and a receiving probe are arranged symmetrically on both sides of the inspection part of the object to be inspected, and ultrasonic waves are transmitted from the transmitting probe into the object to be inspected to receive ultrasonic echoes from the object to be inspected. A measurement device that receives a touch with a toucher and scans an inspection unit is provided, and the measurement device performs wavelet analysis using a basis function similar to a defect signal when a defect exists in the inspection object, and the wavelet analysis Ultrasonic flaw detection equipped with a wavelet processing device that reconstructs an ultrasonic echo received by the reception probe using a wavelet analysis order suitable for extracting the defect signal from the result of the inspection, and emphasizes the defect signal apparatus.   An ultrasonic echo exceeding the preset threshold value of the bottom reflected wave is detected near the position where the bottom reflected wave obtained by geometric calculation from the arrangement of the probe according to the object to be inspected, and the rising of the ultrasonic echo The bottom surface reflected wave removal device that removes the bottom surface reflected wave by setting the intensity of the ultrasonic echo that appears later than the position to zero, and the position where the curved signal generated by the spread of the ultrasonic wave in the scanning direction appears. The probe is obtained by previously obtaining a curve equation corresponding to each depth of the object to be inspected from the arrangement and scanning position of the transmission probe and the reception probe, and performing synthetic aperture processing using the curve equation. The synthetic aperture device that concentrates and amplifies the curved defect signal detected in the scanning direction at the apex, and the average of the ultrasonic signals obtained at each position in the scanning direction of the transmitting probe and the receiving probe Find the value and get it at each position 13. The ultrasonic wave flaw detector according to claim 12, further comprising a lateral wave removal device that removes a lateral wave by subtracting the average value from the obtained ultrasonic signal and emphasizes a defect signal, and the bottom surface reflected wave removal device. An ultrasonic flaw detector that has a function of emphasizing a defect signal by any one or a combination of a synthetic aperture device and a lateral wave removing device, and emphasizing the emphasized defect signal by the wavelet processing device. . The ultrasonic flaw detector according to claim 12,
A binarized data processing unit that performs threshold processing on a defect signal emphasized by an ultrasonic flaw detector based on wavelet analysis with the intensity assumed in advance to the binarized data, and the binarized data. An ultrasonic flaw detector comprising: a multiplication unit that multiplies a defect signal by an ultrasonic signal before being subjected to processing by the wavelet analysis. The ultrasonic flaw detector according to claim 14,
An ultrasonic flaw detector in which the measurement device is provided with a threshold control unit that performs threshold processing with a strength assumed in advance for a defect signal emphasized by the ultrasonic flaw detector.