JP2014178289A - Plate wave inspection method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a plate wave inspection device executing a long distance inspection even in a plate to be inspected having an R part and a step part and capable of improving a detection sensitivity.SOLUTION: A probe 3 is moved up above the upper part of a test part 1 for calibration having the same shape and quality of material as an object 10 to be inspected, and a rotating stage 5 is adjusted. The probe 3 scans a reflection source of the test part 1 for calibration, calculates a relationship between a propagation time and a defect position and the relationship between the propagation time and a detection sensitivity, and corrects data obtained by inspecting the object 10 to be inspected using the calculated relationships. Thereby, even the object 10 to be inspected having the R part and the step part can be subjected to a long distance inspection, and a water immersion plate wave inspection device for executing a plate wave inspection capable of improving detection sensitivity can be achieved.

Description

  The present invention relates to an inspection method and an inspection apparatus for a thin metal plate or a processed product thereof.

  Ultrasonic inspection is used as one of the typical nondestructive inspection methods in the industrial field. Ultrasonic inspection oscillates ultrasonic waves by applying a voltage to a piezoelectric element (vibrator) with electromechanical conversion efficiency provided inside the ultrasonic sensor (probe), and propagates this vibration into the inspection object. This is a method that uses the property that ultrasonic waves are reflected at the interface of substances, etc., and converts some of the reflected waves to voltage by a vibrator again, and records, graphs, or visualizes them for inspection. .

  When detecting defects by performing ultrasonic flaw detection on a production line of a relatively thin metal plate or a product made from a thin metal plate, in addition to longitudinal and transverse waves, a plate that is a type of guide wave A flaw detection method using waves is generally used. As a defect detection method inside a metal structure, a vertical or oblique flaw detection method using a longitudinal wave or a transverse wave has been generally used.

  Since these methods have a narrow inspection range, a subject having a wide inspection area needs to scan the probe over a wide range, and the inspection time and labor become enormous.

  On the other hand, a plate wave can propagate over a wide range in a relatively thin metal plate or its structure, and has less diffusion loss due to propagation than a longitudinal wave or a transverse wave. Therefore, the inspection method using plate waves is expected as a non-destructive inspection method capable of inspecting steel plates and piping in a wide area.

  In the industrial field, for example, an apparatus for inspecting a long-distance section of a fuel transport pipe in a lump has been put into practical use.

  As an ultrasonic flaw detector using a plate wave flaw detector, there is a technique described in Patent Document 1. The technique described in Patent Document 1 is a technique in which SSP (divided spectrum processing) parameters are stored for a plurality of types of inspection objects, and the parameters are changed each time the object changes.

Japanese Patent Laid-Open No. 2001-074703

  However, in the conventional technology, the process in which the plate wave is generated from the process of multiple reflection and propagation is not clear, so when a reflected signal from the vicinity of the incident point is obtained, it is accurate using theoretical calculations. It was difficult to estimate the defect location.

  Moreover, when setting a test | inspection area | region and implementing a plate wave test | inspection, it was difficult to set a test | inspection area | region appropriately.

  When conducting a plate wave inspection in the air, the acoustic impedance of the metal-air is greatly different, so the energy of the wave once incident on the subject is less likely to leak and can be propagated over a long distance as a plate wave. It can be realized.

  Therefore, the inspection may be performed using a region sufficiently far from the incident point where energy of waves other than the plate wave is sufficiently lost.

  However, if the subject needs to scan a probe that crosses the stepped portion or a scan that contacts the R portion with respect to a prismatic object having a stepped portion or an R portion, The contact with the inspection surface is deteriorated, high-accuracy flaw detection inspection cannot be performed, and inspection automation is difficult.

  In order to solve the contact problem, it is conceivable to perform a plate wave inspection in a liquid such as water or glycerin.

  However, in water, since the difference in acoustic impedance is smaller than in the air, wave energy leaks, making it difficult to propagate over long distances compared to the air. Therefore, in order to inspect a wide area, it is necessary to use an area near the incident point as an inspection area.

  As described above, when the plate wave inspection is performed in the liquid, in addition to the problem that the accuracy of indicating the defect position is lowered, there is a problem that the sensitivity to the defect is greatly different between the vicinity of the incident point and the distance.

  Moreover, when it is going to apply the technique of patent document 1 about the level | step-difference part to which welding is performed, or the site | part where a plate | board thickness changes gradually, calculation of a parameter is difficult for such a site | part, and apply. I could not.

  An object of the present invention is to realize a plate wave inspection method and apparatus for performing a plate wave inspection capable of performing a long distance inspection and improving detection sensitivity even for a subject having an R portion or a step portion. It is to be.

  In order to achieve the above object, the present invention is configured as follows.

  In the plate wave flaw detection method, a calibration test body in a liquid, which has the same shape and the same material as a part of the subject and has a reflection source formed at a predetermined position, is subjected to ultrasonic waves from the probe. Receiving and scanning, the relationship between the propagation time of the ultrasonic wave from the probe to the reflection source and the position of the reflection source, the propagation time of the ultrasonic wave and the reflection intensity of the calibration specimen And the first correction data for converting the propagation time of the ultrasonic wave to the defect position, and the second correction data for correcting the propagation time of the ultrasonic wave and the reflection intensity from the defect position. calculate.

  Then, an ultrasonic wave is transmitted / received from the probe to scan the object in the liquid, and object data indicating the relationship between the propagation time of the ultrasonic wave from the probe and the reflection intensity for the object is obtained. Calculate and correct the subject data using the first correction data and the second correction data.

  In a plate wave flaw detection apparatus, a liquid that supports a specimen and a calibration test body that has the same shape and the same material as a part of the specimen and has a reflection source formed at a predetermined position in the liquid. A storage tank, a probe, a probe driving unit, a support stage for the probe, and a stage control unit that rotates, horizontally moves, and vertically moves the probe.

  Further, the plate wave flaw detection apparatus controls the operation of the flaw detector driving unit and the stage control unit, and scans the calibration test body by transmitting and receiving ultrasonic waves using the probe. And calculating the relationship between the propagation time of the ultrasonic wave from the probe to the reflection source and the position of the reflection source and the relationship between the propagation time of the ultrasonic wave and the reflection intensity. First correction data for converting the time into the defect position, and second correction data for correcting the propagation time of the ultrasonic wave and the reflection intensity from the defect position are calculated, and the ultrasonic wave is calculated from the probe. The object data indicating the relationship between the propagation time and the reflection intensity of the ultrasonic wave from the probe for the object is calculated, and the object data is The first correction data and the second correction data are There comprises a calculation control unit for correcting.

  According to the present invention, a plate wave inspection method and apparatus for performing a plate wave inspection capable of performing a long-distance inspection and improving detection sensitivity even for a subject having an R portion or a step portion is realized. Can do.

It is a schematic block diagram of the water immersion plate wave inspection apparatus by one Example of this invention. It is an operation | movement flowchart of the said inspection method in one Example of this invention. It is a figure explaining the positional relationship of the test body for a calibration in one Example of this invention, a reflection source, and a probe. It is a graph which shows the peak value and propagation time of the signal from the reflection source of the test body for a calibration in one Example of this invention. It is a flowchart which shows preparation of the correction data in one Example of this invention. It is explanatory drawing of the subject with R part and level | step difference part. It is a figure explaining formation of the reflective source in R section. It is a figure which shows the example of the scanning direction of the reflective source in a level | step-difference part. It is a figure which shows the example of the scanning direction of the reflection source in a R part and a level | step difference part. It is a graph showing the relationship between a propagation distance and a crest value. It is a graph which shows the relationship between a Y direction distance and a sensitivity correction value. It is a sensitivity correction flowchart in a case where the far field is also set as a detection region and sensitivity correction is performed. It is explanatory drawing of a plate wave test | inspection.

  An embodiment of the present invention will be described with reference to the accompanying drawings. Prior to that, a plate wave inspection will be described below.

  FIG. 13 is a schematic diagram for explaining how a plate wave is generated on a thin flat plate 200 installed in water 100.

  In FIG. 13, generally, a plate wave is incident on a flat plate at a certain angle, refracted and transmitted into the flat plate, and is repeatedly reflected on the front and back surfaces of the flat plate (multiple reflection). Is known to occur. There are two types of plate waves, a symmetric wave and an asymmetric wave, each of which is referred to as an S wave or an A wave.

  Further, various modes (0th order, 1st order, 2nd order,...) Exist for the S wave and the A wave, and S0, S1, S2... (S wave), A0, A1, A2. A wave) is generally written. These various modes have dispersibility in which the sound speed varies depending on the plate thickness and frequency.

  Since the plate wave is highly dispersible, the propagation speed includes a phase speed that is the traveling speed of the wave phase and a group speed that is the traveling speed of the wave packet (energy). In order to theoretically and experimentally examine which mode the plate wave is inspected, it is necessary to obtain a dispersion curve indicating the relationship between sound speed and frequency.

In order to obtain an incident angle suitable for generating a plate wave, a phase velocity is used. An expression for determining an incident angle suitable for generating a plate wave is as follows. When the longitudinal sound velocity in the incident angle water is V _W , the incident angle to the subject is θ _W , and the phase velocity of the plate wave is V _Phase , the following expression (1 ).

sin θ _W = sin ⁻¹ (V _W / V _Phase ) (1)

  Therefore, in order to perform plate wave inspection, a pedestal on which a transducer called a wedge (wedge, shoe) made of polystyrene, polyimide, or the like is placed, or a contact medium such as water is used, and the transducer is covered. It is necessary to place it at an appropriate angle with respect to the specimen.

For example, when a Zircaloy thin plate structure having a thickness of about 3 mm is immersed in a plate wave inspection, for example, the phase velocity of the A1 mode plate wave is about 2360 m / s, and the underwater sound velocity is about 1480 m / s at room temperature (20 ° C.). is there. By substituting this speed of sound into equation (1), the incident angle θ _W becomes 38.8 °, and it can be seen that it is preferable to tilt the transducer by about 39 ° with respect to the subject.

  In the plate wave inspection, the difference between the signal position (defect indication position) and the actual defect position is a problem, and it is difficult to reflect the sound velocity of the contact medium (reference: piping by a guide wave propagating in the circumferential direction of the pipe) Nondestructive evaluation, Hisashi Nagamizo Mitsubishi Chemical Engineering Co., Ltd. Morimasa Murase, Non-destructive Inspection Vol. 52, No. 12 (2003), Graduate School of Engineering, Nagoya Institute of Technology.

  Even if the sound velocity of the contact medium is known accurately, it is very difficult to reflect the sound velocity in the vicinity of the incident point because the plate wave is generated by multiple wave reflection and wave interference on the thin object surface. .

  Let us consider plate wave inspection for a Zircaloy thin plate structure in water, taking water as an example of a contact medium that clearly shows the speed of sound. The underwater sound velocity C depends on the temperature (T) and can be obtained with high accuracy using the following equation (2) (Reference: N. Bilaniuk and GSKWong (1993), Speed of sound in pure water as a function of temperature, J. Acoust. Aoc. Am. 93 (3) pp 1609-1612).

C (T) = 1.40238744 * 10 ³ + 5.03836361 * T- 5.81172916 * 10 ⁻² * T ² + 3.3346181117 * 10 ⁻⁴ * T ³ −1.48259672 * 10 ⁻⁶ * T ⁴ +3 .16585020 * 10 ^-9 * T ⁵
(Range of validity: 0-100 ° atmospheric pressure) (2)

  When the inspection result is displayed as a plate wave inspection, the underwater sound velocity is 1482 m / s (water temperature is 20 ° C.) using the above equation (2), and the sound velocity of the plate wave is 2330 m / s of the group velocity (the phase velocity is 2360 m / s). However, since the ultrasonic wave propagates in water with a spread (including side lobes), and the phase velocity and the transverse wave velocity (2350 m / s) are almost the same, even if the probe position is the same, In a region relatively close to the incident point position, a transverse wave having an incident angle of about 36 to 37 ° and a refraction angle of about 70 to 75 ° propagates relatively strongly as multiple reflections due to the influence of reflection efficiency. Further, since the shear wave critical angle is close to 39.0 °, surface waves are also generated.

  For this reason, the detected waveform component due to the multiple reflection of the transverse wave is a plate wave or surface having a sound velocity of 2350 × sin 70 ° m / s = 2208 to 2350 × sin 75 ° = 2270 m / s if the propagation velocity vector is projected onto the subject surface. The detected waveform component due to the wave appears as if it is a plate wave of 2350 × 0.9 = 2215 m / s.

  The underwater propagation distance at an incident angle of 36 to 37 ° is different from the underwater propagation distance at an incident angle of 39 ° for generating a plate wave.

  As described above, it can be seen that, due to the difference in the group velocities of the transverse wave, the surface wave, and the plate wave propagating through the subject and the difference in the underwater propagation distance, a deviation from the value set as the plate wave inspection occurs in the inspection by multiple reflection.

  In view of this, in the present invention, in consideration of the occurrence of the above-described shift, the detected defect position is corrected so that the defect position detection accuracy can be improved even at a distance.

  Examples of the present invention will be described below. For simplicity, the liquid to be used will be described as water.

  FIG. 1 is a schematic configuration diagram of a water immersion plate wave inspection apparatus according to an embodiment of the present invention. In FIG. 1, a water immersion plate wave inspection apparatus according to an embodiment of the present invention includes a calibration test specimen 1 prepared for creating correction data, a water tank 2 for placing a subject 10 in water, A probe 3 for transmitting and receiving ultrasonic waves and a flaw detector (probe drive unit) 4 for applying a voltage to the probe 3 are provided.

  Further, the immersion plate wave inspection apparatus supports the probe 3 and controls the rotation stage 5 and the XYZ stage 6 for controlling, holding, and scanning the attitude of the probe 3, and the rotation stage 5 and the XYZ stage 6. PC (Personal Computer (Computation Control Unit)) that gives instructions to the stage control device 7 that controls the operation of the above, the flaw detector 4 and the stage control device 7, and displays, corrects and records the results of the obtained waveform data 8 and. The rotation stage 5 and the XYZ stage 6 are collectively used as a support stage.

  The subject 10 is supported by subject jigs 11a and 11b in water in a water tank (liquid storage tank). Then, the posture of the subject 10 is controlled by causing the subject posture control device 17 to operate the subject jigs 11a and 11b.

  Since the phase velocity of the plate wave differs depending on the plate thickness and density of the subject 10, a calibration test body 1 having a plate thickness and density substantially the same as the subject 10 is prepared. Further, in order to easily create the correction data, for example, when the propagation direction of the plate wave is the Y direction, the calibration specimen 1 is arranged so that the reflected wave from the reflection source is exactly in the -Y direction. As the reflection source, a material obtained by processing the end portion of the calibration specimen 1 to be flat or a circular through hole is preferable.

  The probe 3 may be a probe having a single transducer, a plurality of probes having a single transducer, or an array probe having a plurality of transducers. You may use a child. The flaw detector 4 is selected according to the probe 3 to be used.

  The XYZ stage 6 mainly determines the center position of the probe 3 and the distance (water height) in the Z direction (vertical direction) to the calibration specimen 1 and the subject 10 while maintaining the water height. The moving mechanism for scanning in the XY direction (horizontal direction) shown in FIG.

  The rotary stage 5 is mainly for rotating in the YZ plane shown in FIG. 1 and placing the probe 3 at an angle with respect to the surfaces of the calibration test body 1 and the subject 10. The rotary stage 5 may have a function of rotating in the XY plane in order to change the propagation direction of the plate wave. A thermometer 9 may be provided in an environment where the water temperature changes greatly. If there is no need to change the posture of the subject 10, the subject posture control device 17 can be omitted.

  Next, an inspection method for performing a plate wave inspection with improved defect position accuracy and detection sensitivity at a distance using the water immersion plate wave inspection apparatus shown in FIG. 1 will be described.

  FIG. 2 is an operation flowchart of the inspection method in one embodiment of the present invention.

  In step S000 in FIG. 2, the surface of the calibration specimen 1 and the surface of the subject 10 are arranged so as to be parallel to the XY plane (horizontal plane), and the inspection is started.

  Next, in step S001, the probe 3 is moved to the upper part of the calibration specimen 1, and in step S002, the rotary stage 5 is adjusted so that the reflected wave from the surface of the calibration specimen 1 shows the maximum value. To do.

In step S003, the rotation stage 5 is rotated in the XZ plane by the plate wave generation incident angle θ _W derived from the plate wave phase velocity in the subject calculated using the plate thickness, frequency, and density as input values (incident angle). Is θ _W ).

  Next, in step S004, the reflection source of the calibration test body 1 is scanned by transmitting and receiving ultrasonic waves from the probe 3 in at least one axial direction, and in step S005, the propagation time and reflection intensity to the reflection source are obtained. In step S006, correction data for converting the propagation time into the actual defect position is created. In step S007, correction data for correcting the propagation time and the intensity of the reflected wave from the reflection source is created.

  Subsequently, in step S008, the probe 3 is moved to the examination start position above the subject 10, and in step S009, the probe 3 is scanned in parallel with the examination region of the subject 10, and the subject 10 is scanned. Inspection data indicating the relationship between the propagation time of the ultrasonic wave and the reflected wave is acquired, and for the acquired data, the relationship between the propagation time of the ultrasonic wave obtained using the calibration specimen 1 and the defect position, and Correction processing is performed using the relationship between the propagation time of ultrasonic waves and the reflection source intensity (detection sensitivity). In step S010, it is determined whether or not the input scanning range is completed. If the scanning is not completed, the process returns to step S009 to scan the probe 3 again. When the input scanning range is completed in step S010, the flaw detection result is displayed on the display unit (display) of the PC 8, and the inspection is completed in step S011.

  Preferably, in step S000, they are arranged so that the positional relationship between the surface of the calibration specimen 1 and the surface of the subject 10 in the Z direction is the same. If the positional relationship in the Z direction is different, it is preferable to place and scan the probe 3 so that the water height is the same in step S000, using the difference in the Z direction (water height) as input information.

In step S003, when the rotary stage 5 is rotated, for example, in the situation shown in FIG. 1, when a plate wave is propagated in the Y-axis direction, the plate wave is propagated counterclockwise by θ _{W in} the −Y direction. It can be rotated by θ _W clockwise when. When there is a temperature variation, calculated water sound speed using the values read from the thermometer 9, when the rotary stage 5 in the XZ plane in search of a wave generation incident angle theta _W may. The angle theta _W of the rotary stage 5, the reflected wave intensity from the reflected source may be finely adjust the angle.

  Next, the creation of correction data in steps S006 and S007 shown in FIG. 2 will be described in detail. Here, a simple calibration method using a calibration specimen 1 having a plurality of reflection sources (FH1, FH2, FH3, FH4...) Whose positions are predetermined as shown in FIG. 3 will be described as an example. To do.

  If the calibration specimen 1 is used to scan the probe 3 in the X-axis direction at a constant water height, as shown in FIGS. 3 and 4, the first reflection source FH1 is scanned when the distance X0 is scanned. The reflection signal from the second reflection source FH2 is obtained when the distance X1 is further scanned. Further, when the distance X2 is scanned, the reflected signal from the third reflection source FH3 is obtained along different paths.

As a step of generating correction data using these reflected signals, YW (distance in the Y direction from the ultrasonic wave generation point to the calibration test specimen 1) = WH (distance in the Z direction from the ultrasonic wave generation point to the calibration test specimen 1 ( Since the water height)) × tan θ _W , the correction data can be created if the distance YT to FH1 is known.

  That is, correction data generation is started in step S100 in the correction data flow shown in FIG. 5, and in step S101, the propagation time YON (N = 1, 2, 3,...) And the actual defect position YW + YT + YN (N = 1, 2, 3,...) (Time, distance).

  Specifically, it is preferable to plot (YO1, YW + YT), (YO2, YW + YT + Y1), (YO3, YW + YT + Y1 + Y2),.

  Next, in step S102, the relationship between the propagation time YON (N = 1, 2, 3,...) And the reflected signal height (peak value) OIN (N = 1, 2, 3,...). (Propagation time, peak value) is obtained.

  Specifically, (YO1, IO1), (YO2, IO2), (YO3, IO3),... Are plotted on the graph and fitted, and the relationship between the propagation time and the peak value (detection sensitivity) is shown. It is good to ask.

  Next, in step S103, the relationship between the propagation time obtained in step S102 and the detection sensitivity is converted into a relationship between the propagation time and the signal amplification factor.

  Next, in step S104, using the above two relationships (the relationship between the propagation time and the defect position, the relationship between the propagation time and the signal amplification factor), after the inspection of the object 10, when the defect detection data is displayed or the data After recording, correct the data and finish.

  It is also possible to form a single reflection source on the calibration specimen 1 and scan the probe 3 in the same direction as the plate wave propagation direction to obtain the above two relationships. However, when the probe 3 is scanned in the same Y-axis direction as the plate wave propagation direction for a certain reflection source to obtain these relationships, for example, if there is a bent portion or a step in the inspection region, the application is difficult. It is. Also in the correction of the detection sensitivity, when the direction of the probe 3 on the XY plane is slightly different, the detection sensitivity is largely shifted far away.

  Therefore, it is necessary to form a plurality of reflection sources in the calibration specimen 1.

  The distance (YW + YT) of the reflection source FH1 closest to the probe 3 is preferably at or before the start position of the region to be inspected. The distance YT is preferably YT ≧ ZT × tan 70 ° × 2 where ZT is the thickness of the test specimen 1 for calibration. For example, when ZT = 3 mm, YT ≧ 16.4. This is based on the assumption that the back surface of the 70-degree incident component is reflected once more than once, and by taking such a distance, inspection is performed using both multiple reflection and plate waves efficiently. It becomes possible.

  Further, the other one reflection source FH3 is preferably at the final position of the region to be inspected or beyond. FH2 located in the middle between FH1 and FH3 and FH4 located farther than FH3 are effective when it is desired to make correction more accurate, and may be arranged with an appropriate distance XN in the X-axis direction.

  Further, as shown in FIGS. 6 and 7, a rectangular metal plate-like metal structure having flat portions 13 a, 13 b, 13 c, 13 d, 15 a, 15 b, 15 c, 15 d, welded portion (stepped portion) 12, and R portion 16. The case of inspecting not only the plane portions 13a to 13d and 15a to 15d but also the R portion 16 and the welded portion (stepped portion) 12 of the object 14 will be described.

  The welded portion 12 is a portion that connects the first prismatic portion 14a having a plate thickness Amm and the second prismatic portion (plate thickness Bmm) having a plate thickness smaller than that of the first prismatic portion 14b, The outer surface of the connecting portion 12 has a shape that inclines from the first prism portion 14a toward the second prism portion 14b, and has a shape in which the plate thickness decreases in an inclined manner. As described above, the various modes of the S wave and the A wave have dispersibility in which the sound speed varies depending on the plate thickness. When the plate thickness changes in an inclined manner, it is difficult to calculate the sound speed.

  For this reason, it reflects in the predetermined position of the welding part 12 of the test body 1 for calibration (thin sheet metal structure 14) of the same shape and the same material as a part of the subject 10 (including the R part and the welding part). Sources FHa, FHb, and FHc are formed, and reflection sources FH1, FH2, and FH3 are formed at predetermined positions of the R portion 16.

  In the welded portion 12, the reflection sources FHa and FHc are formed on both sides of the welded portion 12 (a flat portion near the start point of the inclined portion and a flat portion near the end point), and the reflection source FHb is formed at an intermediate position between FHa and FHc. To do. In the R portion 16, FH2 is formed in the central portion of the R portion, and FH1 and FH3 are formed on both sides of the FH2. In the illustrated example, FHa to FHc and FH1 to FH3 are through holes.

  As for the stepped portion 12, as shown in FIG. 8, the reflection sources FHa and FHc formed so as to straddle the stepped portion 12 have different thicknesses at the formed positions, so that FHa → FHb → FHc and FHc → In order to scan and perform inspection in two orders of FHb → FHa, it is preferable to create correction data from two directions.

  FIG. 9 is a diagram illustrating an example of the scanning direction of the probe 3 in the R portion (curved surface portion) 16 and the welded portion (stepped portion) 12.

  In FIG. 9, circles 1 and 2 indicate scanning lines in the circumferential direction of the calibration specimen 1 with respect to the welded portion 12, and circles 3 and 4 indicate scanning lines in the axial direction of the calibration specimen 1 with respect to the welded portion 12. Indicates. Circles 5 and 6 indicate scanning lines in the axial direction of the calibration specimen 1 with respect to the R portion 16.

  By scanning the probe 3 as shown in FIG. 9, it is possible to carry out the immersion plate wave inspection with sufficiently good positional accuracy and sensitivity.

  FIG. 10 is a graph showing the relationship between the propagation distance and the peak value, where the vertical axis indicates the peak value (%) and the horizontal axis indicates the distance in the Y direction. In FIG. 10, the influence of multiple reflection or the like appears strongly in the vicinity of the incident point of the ultrasonic wave, and the amplitude fluctuates greatly. On the other hand, the plate wave component is mainly present at a distance YR or more that is considered to be reflected a plurality of times. Attenuation is gently attenuated by two factors: diffusion attenuation in which the wave spreads in a direction perpendicular to the propagation direction.

  Since the detection sensitivity is relatively high in the vicinity of the ultrasonic incident point, the detection sensitivity does not pose a problem in determining the presence or absence of a defect. Obviously, if it is desired to perform sensitivity correction near the incident point with high accuracy, the calibration specimen 1 should be provided with a large number of reflection sources.

  When using a distant area where the detection sensitivity is lowered as an inspection area, it is necessary to perform sensitivity correction. At this time, it is preferable to obtain an attenuation constant in a sufficiently far plate wave region and use the reciprocal thereof as a sensitivity correction value.

  FIG. 11 is a graph showing the relationship between the Y-direction distance and the sensitivity correction value. The vertical axis represents the sensitivity correction value (%), and the horizontal axis represents the distance in the Y direction. In FIG. 11, an exponential correction coefficient is present beyond YR, and noise may be amplified when sensitivity is corrected far away.

  For this reason, when the far field is also set as the detection region and sensitivity correction is performed, the background data (the subject has a defect in the operation of step S004 shown in FIG. 2) at the initial position in the X-axis direction of the flaw detector 3 shown in FIG. Step S004A for recording (data obtained when there is no data) is added. Then, steps S200 to S204 shown in FIG. 12 are added between step S009 and step S010 in FIG.

  That is, in step S200, sensitivity correction is started on the data recorded in the inspection, and in step S201, the recorded data is corrected using the relationship between the propagation time and the signal amplification factor. In step S202, the background data of the calibration specimen 1 is corrected using the relationship between the propagation time and the signal amplification factor. In step S203, the difference between the corrected recorded data and the corrected background data is obtained. . By taking the difference, it can be determined that there is a defect in a portion where a large difference has occurred. In step S204, the difference result is displayed on the display of the PC 8. Then, the process proceeds to step S010 in FIG.

  As described above, if the background data of the calibration specimen 1 is recorded, the detection sensitivity can be improved even in the case where the distance from the subject 10 is set as the detection region.

  As described above, according to the present invention, the probe for ultrasonic waves in the R portion (curved surface portion) or the step portion is obtained by using the calibration test body 1 having the same shape and the same material as the subject 10. The relationship between the propagation time from the defect position to the defect position and the defect position and the relationship between the propagation time of the ultrasonic wave and the detection sensitivity are calculated, and the data obtained by inspecting the subject 10 is corrected using the calculated relationship. Since it is configured as described above, a submerged plate wave inspection method and apparatus for performing a plate wave inspection capable of performing a long distance inspection and improving detection sensitivity even for a subject having an R portion or a stepped portion. Can be realized.

  The present invention is a plate wave inspection, and is preferably applied to a subject having a thin plate thickness, for example, 5 mm or less.

  The calibration specimen 1 preferably has the same shape and the same material as the subject 10, but the size is smaller than the subject 10 and can be a part including the R portion and the welded portion.

  DESCRIPTION OF SYMBOLS 1 ... Test body for calibration, 2 ... Water tank, 3 ... Flaw detector, 4 ... Flaw detector, 5 ... Rotation stage, 6 ... XYZ stage, 7 ... Stage control device 8 ... Personal computer (calculation control unit), 9 ... Thermometer, 10 ... Test object, 11a, 11b ... Jig for test object, 12 ... Welded part (step part), 13a to 13d, 15a to 15d ... flat plate portion, 14 ... thin metal structure, 14a ... first prism portion, 14b ... second prism portion, 16 ... R portion (curved surface) Part)

Claims (10)

It is the same shape and the same material as a part of the subject, and scans the calibration test body in the liquid in which the reflection source is formed at a predetermined position by transmitting and receiving ultrasonic waves with a probe,
For the calibration specimen, calculate the relationship between the propagation time of the ultrasonic wave from the probe to the reflection source and the position of the reflection source, and the relationship between the propagation time of the ultrasonic wave and the reflection intensity, Calculating first correction data for converting the propagation time of the ultrasonic wave to the defect position, and second correction data for correcting the propagation time of the ultrasonic wave and the reflection intensity from the defect position;
Ultrasound is transmitted / received from the probe to scan the object in the liquid, and object data indicating the relationship between the propagation time of the ultrasonic wave from the probe and the reflection intensity for the object is calculated. ,
A plate wave flaw inspection method, wherein the subject data is corrected using the first correction data and the second correction data. In the plate wave flaw inspection method according to claim 1,
2. The plate wave flaw inspection method according to claim 1, wherein the calibration specimen is formed with two or more reflection sources having different positional relationships with respect to the propagation direction of the ultrasonic wave. The plate wave flaw detection method according to claim 2,
A plate wave flaw inspection method, wherein the calibration specimen has a curved surface portion, and a plurality of reflection sources are formed with the curved surface portion interposed therebetween. The plate wave flaw detection method according to claim 2,
A plate wave flaw inspection method characterized in that the calibration specimen has a stepped portion, and a plurality of reflection sources are formed with the stepped portion in between. In the plate wave flaw inspection method according to claim 1,
The first correction data and the second correction data are calculated, and the position of the portion of the calibration test body where the generation source is not formed from the probe and the reflection intensity of the ultrasonic wave Get background data to show the relationship
After correcting the object data using the first correction data and the second correction data, the reflection intensity of the background data is corrected using the second correction data, and the corrected object is corrected. A plate wave flaw inspection method, comprising: calculating a difference between the data and the reflection-corrected background data and determining the presence or absence of a defect in the subject. A specimen, a liquid storage tank for supporting a calibration test body in which a reflection source is formed at a predetermined position in a liquid, the same shape and the same material as a part of the specimen;
A probe that transmits and receives ultrasound,
A flaw detector driving unit that applies voltage to the probe and drives the probe;
A support stage for supporting the probe;
A stage controller that moves the support stage to rotate, horizontally, and vertically move the probe;
The operation of the flaw detector driving unit and the stage control unit is controlled, the calibration test body is scanned by transmitting and receiving ultrasonic waves by the probe, and the calibration test specimen is scanned from the probe to the above. Calculate the relationship between the propagation time of the ultrasonic wave to the reflection source and the position of the reflection source, and the relationship between the propagation time of the ultrasonic wave and the reflection intensity, and convert the propagation time of the ultrasonic wave to the defect position. The first correction data and the second correction data for correcting the propagation time of the ultrasonic wave and the reflection intensity from the defect position are calculated, and the ultrasonic wave is transmitted and received from the probe, thereby the object in the liquid. , The object data indicating the relationship between the propagation time of the ultrasonic wave from the probe and the reflection intensity for the object is calculated, and the object data is converted into the first correction data and the first correction data. An arithmetic control unit for correcting using the correction data of 2;
A plate wave flaw inspection apparatus characterized by comprising: In the plate wave flaw detection apparatus according to claim 6,
2. The plate wave flaw inspection apparatus according to claim 1, wherein the calibration specimen is formed with two or more reflection sources having different positional relationships with respect to the propagation direction of the ultrasonic wave. In the plate wave flaw detection apparatus according to claim 7,
The plate wave flaw inspection apparatus characterized in that the calibration specimen has a curved surface portion, and a plurality of reflection sources are formed with the curved surface portion interposed therebetween. In the plate wave flaw detection apparatus according to claim 7,
The plate wave flaw detection apparatus according to claim 1, wherein the calibration specimen has a stepped portion, and a plurality of reflection sources are formed with the stepped portion in between. In the plate wave flaw detection apparatus according to claim 6,
The arithmetic control unit is
The first correction data and the second correction data are calculated, and the position of the portion of the calibration test body where the generation source is not formed from the probe and the reflection intensity of the ultrasonic wave Get background data to show the relationship
After correcting the object data using the first correction data and the second correction data, the reflection intensity of the background data is corrected using the second correction data, and the corrected object is corrected. A plate wave flaw inspection apparatus characterized by calculating a difference between data and the background data corrected for reflection intensity and determining the presence or absence of a defect in the subject.

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