JP2011247649A - Method and program for identifying surface shape of ultrasonic wave flaw detection test piece, aperture synthesis processing program, and phased array flaw detection program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grasp the shape of a surface of a test piece by using a reflection wave from the surface when an ultrasonic wave is made incident to the test piece.SOLUTION: A phased array is arranged on the surface of the test piece along the surface shape of a test piece having a shape change part whose surface shape has changed, with a medium whose configurations may change intervening in between; an ultrasonic wave is projected to the test piece for each oscillator of the phased array to receive a surface echo; a reflection wave from the surface of the test piece obtained for each oscillator is detected to acquire a beam path from each oscillator to the surface of the test piece and to assume a circle having each oscillator as the center and the beam path acquired for each oscillator as the radius; a common circumscribing line of the circles having the adjacent oscillators as the respective centers is acquired; points on the common circumscribing line are two-dimensionally interpolated and identified as a test piece surface in a section where the common circumscribing line is acquired; a gap between the oscillators is determined to be a boundary of shape change in a section where a common circumscribing line cannot be acquired, and the points on the common circumscribing lines obtained in the respective sections are two-dimensionally interpolated; and the two-dimensionally interpolated point is extrapolated to identify as a surface shape of the boundary and acquire a test piece surface shape.

Description

  The present invention relates to a method for identifying a surface shape of a specimen to which an ultrasonic flaw detection method is applied, an identification program, an aperture synthesis processing program, and a phased array flaw detection program. More specifically, the present invention relates to a method for identifying a surface shape of a test specimen suitable for ultrasonic flaw detection using a phased array, an identification program, an aperture synthesis processing program, and a phased array flaw detection program.

  In the flaw detection of the pipe welded portion, since the mechanical scanning of the ultrasonic probe is limited by the welding surplus, flaw detection in the surface area of the shape change portion becomes difficult. When the access of the probe is poor as described above, a one-time reflection method is effective in which an ultrasonic beam is reflected on the inner back surface of the pipe for flaw detection. However, in this single reflection method, the flaw detection accuracy is lower than that in the direct irradiation method due to the influence of ultrasonic diffusion and attenuation, ultrasonic scattering due to the back surface shape, and change in propagation direction.

  On the other hand, high-chromium steel is used in high-temperature and high-pressure piping in thermal power generation facilities, and it has been confirmed that type IV damage due to creep occurs in the heat-affected zone fine-grained area of weld joints of the same material. This type IV damage is an important issue in ensuring the structural integrity of thermal power generation facilities. Type IV damage is a form of damage caused by creep that occurs in the heat-affected zone fine-grained area from inside the wall, occurs along the heat-affected zone fine-grained area, and proceeds in the surface layer area below the weld toe There is. For this reason, as shown in FIG. 15, in the flaw detection in the surface layer area below the weld toe, the mechanical scanning of the probe is limited due to the approach limit, and the incident ultrasonic wave is almost all depending on the inclination of the type IV damage. It may not return. Further, at the stage where creep voids before the occurrence of type IV cracks begin to be dense, detection is difficult because the signal intensity obtained by ultrasonic flaw detection is weak.

  For this reason, there is a demand for the development of a phased array method and an aperture synthesis method that can detect flaws by a direct method from a shape change portion such as a surplus. In particular, at the stage where creep voids before Type IV cracks start to gather, detection is difficult because the signal intensity obtained by ultrasonic flaw detection is weak, but signal amplification, azimuth resolution, and SN ratio are improved. Improvement of detection performance can be expected by applying a possible aperture synthesis method.

  Conventionally, as a technique for performing ultrasonic flaw detection by direct irradiation method from above the shape change part, a local water that uses a medium that can change its form along the surface shape of the specimen, for example, a medium such as water or gel, instead of a wedge. The immersion method is common. However, the phased array method and the aperture synthesis method are premised on being applied to a specimen having a flat surface shape (Patent Documents 1 to 3, Non-Patent Documents 1 to 3). Therefore, even if flaw detection by the phased array method is simply applied to this local water immersion method, etc., in the delay control assuming a flat specimen surface shape, the ultrasonic beam does not converge due to the extra shape, or the set direction May not propagate to The same applies to the case where the aperture synthesis method is simply applied. Therefore, prior to the ultrasonic test, the surface shape of the test specimen was grasped in advance by mechanical measurement using a general mold as a surface shape measurement technique, laser displacement measurement, etc. It is necessary to calculate the propagation path of the ultrasonic wave, control the delay time of each transducer, and match the phase of the received waveform.

  In addition, recently, there has been proposed one in which the transducer groups of the phased array probe are supported one by one so as to be vertically movable and are always urged toward the surface of the specimen (non-patent document). 4). According to this phased array probe, each of the transducers is moved along the shape changing portion, and the excitation of each transducer is controlled with delay while mechanically measuring the surface shape with this movable amount. Thus, the ultrasonic beam can be focused from above the complicated shape portion.

JP-A-8-201569 JP-A-10-142201 JP 2008-122209 A

H. Karasawa, M. Izumi, T. Suzuki, S. Nagai, M. Tamura and S. Fujimori, “Development of under sodium 3D visual inspection technique by using matrix-arrayed ultrasonic transducer”, Journal of Nuclear Science and Technology, 37 (2000), pp. 769-779. Motohisa Abe and Hirokazu Kurosawa “Portable Type 3D Ultrasound Inspection System Matrixey” Toshiba Review Vol.60 No.4, 48-51, 2005 Karasawa Hirokazu, Isobe Hideo, Hamashima Takayuki "3D Aperture Synthesis (3D-SAFT) Arrays and 9 Applications" Non-destructive inspection Vol.56 No.10, 520-524, 2007 S. Chatillon, G. Cattiaux, M. Serre and O. Roy, “Ultrasonic non-destructive testing of pieces of complex geometry with flexible phased array transducer”, Ultrasonics, Vol. 38, pp. 131-134, 2007.

  However, prior to the ultrasonic test, in order to grasp the surface shape in advance, when performing mechanical measurement using a mold, laser displacement measurement, etc., inspect after installing other measurement equipment of the flaw detector Therefore, there is a problem that a lot of inspection time is required and the cost is increased because other measuring instruments for the flaw detector are required.

  Further, in the method proposed in Non-Patent Document 4, since the vibrator itself is brought into contact by being individually displaced along the surface shape of the test body, the transverse wave cannot be incident by Snell's law, There is a problem that it is limited to longitudinal wave oblique angle flaw detection. Since shear waves are generally superior in resolution compared to longitudinal waves, it is possible to detect flaws with weak signal strength obtained by ultrasonic flaw detection, for example, the stage where creep voids before the occurrence of type IV cracks begin to crowd. It is desirable to be able to perform shear wave oblique angle flaw detection.

  Therefore, the present invention provides a method for identifying the surface shape of an ultrasonic flaw detection test body and an identification program that make it possible to grasp the surface shape of the test body using reflected waves from the surface when ultrasonic waves are incident on the test body. Another object is to provide an aperture synthesis processing program and a phased array flaw detection program.

  As a result of various studies conducted by the present inventors in order to achieve such an object, it is possible to reproduce the surface of the specimen by specifying the coordinates at which reflection occurs on the surface of the specimen due to the spread of the beam. As a result, it has been found that the surface shape can be identified by using the reflected wave from the surface when the sample is incident on the specimen. The present invention has been made on the basis of such knowledge, and the surface shape is measured using a reflected wave from the surface when ultrasonic waves are incident on the test body.

  That is, the method for identifying the surface shape of a test body according to the first aspect of the present invention is a medium that can change the shape along the surface shape of the test body on the surface of the test body having a shape changing portion whose surface shape has changed. A phased array is arranged via each of the phased arrays, ultrasonic waves are emitted toward the test body for each transducer of the phased array, and a surface echo is received from the surface of the test body acquired for each transducer. Adjacent transducers are assumed by detecting a reflected wave and calculating a beam path from each transducer to the surface of the test body, and assuming a circle with a radius of the beam path determined for each transducer centered on each transducer. A common tangent line of the circle centered at the center is obtained, and in the section where the common tangent line is obtained, a point on the common tangent line is subjected to quadratic interpolation, and this is identified as the surface of the specimen, and the common tangent line is obtained. In the interval that is not It is determined that the boundary change, the curve that is obtained by the secondary interpolation in each section extrapolated identified as the surface shape of the boundary, and to obtain the specimen surface shape.

  According to a second aspect of the present invention, there is provided a program for identifying a surface shape of a test specimen, wherein the medium can change a shape along the surface shape of the test specimen on the surface of the test specimen having a shape changing portion whose surface shape has changed. A step of receiving a surface echo by emitting an ultrasonic wave toward the test body for each transducer of the phased array disposed via the antenna, and a reflected wave from the surface of the test body acquired for each transducer Detecting a beam path from each transducer to the surface of the specimen, and assuming a circle having a radius of the beam path centered on each transducer and having a radius determined for each transducer, A step of obtaining a common tangent of the circle as a center, and a section where the common tangent is obtained, quadratic interpolation is performed on the contact points of the circles to specify the surface of the specimen, and the common tangent is identified as the surface of the specimen. Step And a curve created by extrapolating a quadratic interpolation of the points on the common tangent line obtained in each section in the section where the common tangent line is not obtained is determined as a shape change boundary between the vibrators. The step of identifying the surface shape at the boundary is executed by a computer so as to obtain the surface shape of the specimen.

  According to a third aspect of the present invention, there is provided an aperture composition processing program, on a surface of a test body having a shape changing portion whose surface shape is changed, via a medium whose form can be changed along the surface shape of the test body. A step of receiving a surface echo by emitting an ultrasonic wave toward the test body for each transducer of the arranged phased array, and detecting a reflected wave from the surface of the test body obtained for each transducer. Assuming a step of obtaining a beam path from each transducer to the surface of the specimen, and a circle centered on each transducer and having a radius of the beam path obtained for each transducer, and centering on adjacent transducers Obtaining a common outer tangent of the circle, and interpolating the contact points of the circles in a section in which the common outer tangent is obtained, specifying the surface as a test specimen, and identifying the common outer tangent as a specimen surface; ,in front In a section where a common tangent line is not found, the boundary between these transducers is determined as a shape change boundary, and a curve created by extrapolating the points on the common tangent line obtained in each section is extrapolated to the boundary. And a step of calculating for each transducer that receives the propagation distance of the ultrasonic wave from any section of the flaw detection range inside the specimen to the transducer using the identified specimen surface shape. Then, the phase of the waveform is shifted so as to correct the delay of the A scope waveform signal received by each receiving element based on the propagation path of the ultrasonic wave for each transducer, and the phase of the wave is aligned and superimposed. The aperture synthesis process and the step of causing the display to draw the flaw detection image after the phase operation are executed by a computer.

  Furthermore, the phased array flaw detection program according to the invention of claim 4 is provided on a surface of a test body having a shape changing portion whose surface shape is changed via a medium whose form can be changed along the surface shape of the test body. A step of receiving a surface echo by emitting an ultrasonic wave toward the test body for each transducer of the arranged phased array, and detecting a reflected wave from the surface of the test body obtained for each transducer. Assuming a step of obtaining a beam path from each transducer to the surface of the specimen, and a circle centered on each transducer and having a radius of the beam path obtained for each transducer, and centering on adjacent transducers A step of obtaining a common outer tangent of the circle, and a step of interpolating the contact points of the circles in a section in which the common outer tangent is obtained, specifying the surface as a specimen, and identifying the common tangent as a specimen surface. In the section where the common tangent is not found, it was determined that the boundary between these transducers was the shape change boundary, and the points on the common tangent obtained in each section were extrapolated and extrapolated. A step of identifying a curve as a surface shape at the boundary, and a step of calculating a propagation distance of ultrasonic waves from any section of a flaw detection range inside the test body to all transducers using the identified test body surface shape Calculating a delay time of each transducer based on an ultrasonic wave propagation path for each transducer, performing a phased array flaw detection by controlling the transducer based on the delay time, and flaw detection And causing the computer to execute the step of rendering the image on the display.

  According to the surface shape identification method and identification program for an ultrasonic flaw detector of the present invention, the surface shape is calculated by calculation by a central processing unit using an ultrasonic beam transmitted and received for each transducer of the flaw detector. Therefore, since the time required for the inspection hardly changes and the measurement can be performed using the phased array, no separate measuring device or instrument is required, and the equipment cost is hardly required.

  Further, according to the aperture synthesis processing program of the present invention, the surface shape is calculated by the calculation by the central processing unit using the ultrasonic beam transmitted and received for each transducer of the flaw detector, and the surface shape data is used. An aperture that shifts the phase of the waveform so as to correct the delay of the A scope waveform signal received by each receiving element based on the propagation path of the ultrasonic wave for each transducer to be received, and superimposes the wave phases in an aligned state. Since the synthesizing process can be executed, a weak echo can be detected and a weak echo can be detected while maintaining a high azimuth resolution by performing weak signal intensity amplification, azimuth resolution and SN ratio improvement over the entire flaw detection area inside the specimen. Therefore, it is possible to detect flaws in the surface area of the shape change portion such as welding surplus. In addition, an ultrasonic beam having a large spread that is not focused is made incident, so that the lower side of the weld toe as shown in FIG. 15 is generated in the heat-affected zone fine grain region in the weld joint of the high-temperature high-pressure pipe in which high-chromium steel is used. Even when the type IV damage in the surface layer of the surface layer, that is, the propagation direction of ultrasonic waves and the type IV damage are parallel to each other, it is possible to detect defects at the stage where creep voids before the occurrence of type IV cracks begin to condense. I can expect.

  Further, according to the phased array flaw detection program of the present invention, the surface shape is calculated by the calculation by the central processing unit using the ultrasonic beam transmitted and received for each transducer of the flaw detector, and the surface shape data is used. The delay time of each transducer can be calculated by calculating the propagation distance of the ultrasonic waves from any section of the flaw detection range inside the specimen to all transducers. Can be controlled to perform phased array flaw detection. Therefore, since the transmission and reception are repeated so that the ultrasonic beam is successively focused in accordance with the surface shape obtained in advance in the entire flaw detection area, flaw detection can be performed with high accuracy. This phased array flaw detection also enables flaw detection equivalent to the above-described aperture synthesis process.

It is a principle figure of the identification method of the surface shape of the ultrasonic testing specimen concerning this invention. It is a principle figure at the time of carrying out an aperture synthetic process using the surface shape data of the test body identified by the identification method of the surface shape of an ultrasonic flaw detection test body. It is explanatory drawing which shows the state of the ultrasonic beam reflected from the test body surface, (a) shows a normal flat surface, (b) shows the reflection by an inclined surface. It is explanatory drawing which shows the determination method of the test body surface shape by a common tangent, (a) is a figure which shows the relationship between a test body and a vibrator | oscillator, (b) is a figure which shows the common external tangent between vibrator | oscillators. It is explanatory drawing which shows the approximation of the surface shape by a quadratic function. It is explanatory drawing which shows the determination method of the path | route between two points. It is explanatory drawing which shows the determination method of the path | route between a probe position and a converging point. It is explanatory drawing which shows the calculation method of an aperture synthetic method. It is the top view and side view of the test body which has a horizontal hole in the complicated shape part used for verification of the effectiveness of the surface shape identification method, (a) The test body which simulated the shape of butt welding, (b) Shape discontinuity The test body which simulated the shape of the part welding part is shown. It is a surface shape measurement model, (a) shows the vertical flaw detection in the butt welding model, (b) shows the oblique flaw detection in the butt welding model, and (c) shows the oblique flaw detection in the shape discontinuity welding model. It is a graph which shows the measurement result of the test body surface shape shown to (a)-(c) of FIG. 10, (a) is the vertical flaw detection in a butt welding model, (b) is an oblique flaw detection in a butt welding model, (c ) Shows the results of oblique flaw detection in the shape discontinuity welding model. It is a B scope image in a butt welding model, (a) shows a phased array method, (b) shows what is based on the aperture synthesis method of the present invention. It is a B scope image in a shape discontinuity part welding model, (a) echo from a horizontal hole by a transverse wave component and a longitudinal wave component by a phased array method, (b) is a horizontal hole by a transverse wave component by the aperture synthesis method of the present invention. (C) shows the echo from a horizontal hole by a longitudinal wave component by the aperture synthesis method of the present invention. It is explanatory drawing which shows refraction | bending of the ultrasonic beam in a shape change part. It is explanatory drawing which shows the flaw detection of a welding surplus shape change part surface layer area. It is a flowchart which shows the whole procedure of opening synthetic | combination processing. It is a flowchart which shows the procedure of surface shape identification. It is a flowchart which shows an opening synthetic | combination process procedure.

  Hereinafter, the configuration of the present invention will be described in detail based on embodiments.

  A part of the ultrasonic beam 4 transmitted from the probe 1 propagates inside the test body 2, and a part is reflected by the surface of the test body 2. Usually, the ultrasonic probe is designed so that echoes from the surface of the specimen are absorbed in the wedge and not detected by the probe, and only echoes from inside the specimen are detected. . The method for identifying the surface shape of a specimen having a shape changing portion according to the present invention identifies the surface shape by actively using echoes from the surface of the specimen.

  Here, the ultrasonic beam 4 is detected by the probe 1 as a reflected wave perpendicular to the surface of the specimen 2. Therefore, in the case of a spreading ultrasonic wave, as shown in FIG. 1, when the surface of the test body 2 and the surface of the vibrator 1 are parallel to each other, it is directly below the vibrator perpendicular to both the test body surface and the vibrator surface. An echo from the surface of the test body is detected, and an echo perpendicular to the surface of the test body is detected when the surface of the test body and the transducer surface are not parallel. However, it cannot be determined from the detection signal alone whether the ultrasonic wave is reflected on the surface of the test body immediately below the transducer or is reflected at a point away from directly below the transducer. For this reason, it is presumed that what is reflected by the inclined surface is reflected by the point A 'in FIG. 1, and an error occurs between the point A and the point A on the surface of the test body 2 directly under the vibrator. For this reason, even if the shape is specified by simply connecting the beam path derived from the surface echo of the specimen, an error occurs in the surface shape.

  That is, as shown in FIG. 3A, when the propagation direction of the ultrasonic beam and the normal direction of the specimen surface are parallel, the beam up to the reception echo of the surface reflected wave can be calculated by calculating the beam path as the actual distance. The path length is the distance from the transducer surface to the specimen surface. However, when the beam propagation direction and the normal direction of the specimen surface are tilted as shown in Fig. 3 (b), the reflected wave is received by the wave incident perpendicularly to the surface (indicated by the solid arrow in the figure). If the distance between the transducer surface and the specimen surface is calculated using this, an error is generated by Δy in the figure. When the surface of the test specimen is flat, it is easy to correct Δy because the incident angle is uniform, but it is difficult to correct the test specimen whose surface shape changes midway. Therefore, it was considered to reconstruct the surface of the specimen by specifying the coordinates at which surface reflection occurs due to beam expansion.

  As shown in FIG. 4, if it is assumed that the surface of the test specimen from which the reflected wave is obtained is a straight line between adjacent transducers, a circle is formed with the radius of the beam path r where the echo from the surface appears, centering on the transducer. Considering, the tangent to the circle drawn by the adjacent vibrator is the surface of the specimen. In the present invention, the contact point between the tangent line and the circle is considered as the coordinate of the surface of the specimen. In this method, a reflected wave can be obtained from the surface of the specimen having a large inclination by using a beam having a large spread. However, in the adjacent transducers A and B shown in FIG. If the beam path difference Δr where the echo appears is large, a common tangent cannot be created. This occurs when there is a significant change in the shape of the surface to be measured between the vibrators. For example, it occurs when the shape of the molten metal rises from the base metal, such as a surplus in butt welding. Therefore, in the present invention, it is considered that the gradient of the shape change becomes discontinuous at the point where such a common tangent cannot be created. And it assumed that the surplus shape of butt-welding can be approximated by a quadratic function, was divided at the boundary, and the surface coordinates in each section were subjected to quadratic interpolation.

Hereinafter, the procedure of the surface shape identification method will be described more specifically based on FIG. 16 and FIG.
First, the phased array 1 is arranged on the surface of the test body 2 having the shape changing portion whose surface shape has changed via the medium 3 whose form can be changed along the surface shape of the test body. At this time, the array probe 1 is fixed by the jig 5 or the like, and the distance from the surface of the specimen is maintained. Here, the medium 3 interposed between the phased array 1 of the flaw detector and the test body 2 is preferably a liquid such as water or a semi-solid body such as gel. When water is used as a medium, a phased array is used in a flaw detection method generally called a local water immersion method.

  Next, the ultrasonic flaw detector detects the amplitude resulting from the surface reflection of the specimen at each probe position by linear electronic scanning using one element (S1). That is, surface echoes are acquired by emitting ultrasonic waves toward the test body for each transducer of the phased array. For example, when a 64-element phased array is used, transmission / reception of one element is repeated in order from 1 element to 64 elements, and a surface echo for each transducer is acquired.

Next, the beam path length until the amplitude due to the surface reflection acquired for each transducer appears, that is, the beam path length from each transducer to the surface of the test body where the reflection occurs is obtained ( _S3-1 ).

Then, assuming a circle whose radius is the beam path obtained for each transducer centering on each transducer, a common outer tangent of the circles centering on adjacent transducers is obtained by calculation (S _3-2 ). The common tangent of two circles can be calculated if the radius (beam path) of the two circles and the center distance (transducer spacing) of the two circles are determined, and the common tangent is already calculated. Since the equation is derived and known, the description is omitted.

Next, it is determined whether or not a common tangent line is obtained in the section between the two vibrators ( _S3-3 ). When the common tangent line is obtained, a process for obtaining a common tangent line for all vibrators is further performed. It is determined whether or not (S _3-5 ). That is, a boundary where a common tangent cannot be created is searched while sequentially creating a common outer tangent. When the common circumscribing line cannot be obtained, it is determined that the transducer section is a boundary and a flag j is set or 1 is added to the flag j to identify the transducer section as a boundary ( _S3-4 ). Jump to step _S3-5 . When the process for obtaining the common tangent line is not added for all the vibrators, 1 is added to the vibrator flag i (S _3-6 ), the process jumps to step S _3-2 , and the next Steps S _{3-2 to} S _3-5 are repeated for the vibrator. And when the process which calculates | requires a common circumscribed line about all the vibrators is completed, it moves to step _S3-7 .

Next, in step _S3-7 , the initial value is k = 1, the group of points on the common tangent line in the sections k and k + 1 determined to be the boundary is subjected to quadratic interpolation, and these quadratic interpolated ones are tested. Identify as surface. Then, for all the sections it is determined as a boundary to determine whether the secondary interpolation (S3 _-8), adds 1 to the flag k in step S3 _-9 If not completed, step S3 _- Jump to ₇ , and quadratic interpolation is performed on the group of points on the common tangent line in the corresponding section.

Next, a surface shape is identified by extrapolating the quadratic curves of each group to the intersection of each other. Corresponding quadratic curves between the intersections become surface coordinates between the intersections (x coordinates) ( _S3-10 ). As for the surface shape data of the test body, for example, considering the xy plane with the position of the first transducer as the origin, the direction in which the transducers are arranged is the x-axis direction, the beam path direction is the y-axis direction, and secondary the curve is stored in memory as ^{y = ax 2 + bx + c} (S3 -11). Specifically, the coefficients a, b, and c of two quadratic curves in a group of sections in which two common circumscribed lines with the boundary as a boundary are obtained are stored in the memory. If necessary, an image is displayed on the display of the PC, or used for aperture synthesis processing or phased array flaw detection. Of course, the surface shape data of the specimen may be temporarily stored in a work memory or the like and used for the aperture synthesis processing in the next process or the arithmetic processing for the phased array flaw detection.

  The above calculation and identification of the surface shape and the like are executed by a personal computer by a program stored in a storage medium such as a ROM of a personal computer (PC). Here, the ultrasonic flaw detector and the PC process the surface echo data acquired by the flaw detector into the PC and then process it offline in the PC and display the image on the PC display. It is not particularly limited.

If the surface shape of the specimen is identified by the above procedure, the path until the ultrasonic beam radiated from the vibrator reaches the point in the specimen can be calculated using the surface shape data.
For example, a propagation path can be calculated according to Fermat's principle that a wave travels a path that takes the minimum time to propagate between two points. Now, as shown in FIG. 6, an orthogonal coordinate system xy is defined, and the media 1 and 2 are divided by a boundary line described by y = ax ² + bx + c. At this time, considering the propagation path between the point P (x _t , 0) of the medium 1 and the point Q (x _t + x ₁ + x ₂ , y ₁ + y ₂ ) of the medium 2, the following geometrically: The formula holds.
y ₁ tan θ ₁ + (y−y ₁ ) tan θ ₂ = x−x _t (3-1)
C ₂ sin (θ ₁ + θ ₀ ) = C ₁ sin (θ ₂ + θ ₀ ) (3-2)
tanθ ₀ = 2a (x _t + x ₁ ) + b (3-3)
y ₁ = a (x _t + x _i ) ² + b (x _t + x ₁ ) + c (3-4)
Here, C ₁ and C ₂ are sound speeds of the media 1 and 2. Since the above equation is non-linear, it is necessary to determine the angle by successive approximation or the like. Differentiating and organizing the formula gives the following formula.
(3-5)
By applying successive approximation to the above equation so that δx = 0, θ ₀ , θ ₁ , θ ₂ , y ₁ can be calculated. In this method, the surface of the specimen is approximated by a plurality of quadratic curves, and there are a plurality of paths. Therefore, it is necessary to determine a curve that gives an initial value when performing sequential calculation.

In the following, a method for determining an ultrasonic beam propagation path including how to assign an initial value will be described. The xy orthogonal coordinate system shown in FIG. 7 is defined.
1) Divide the surface of the test body into n pieces, and let the division point be S _i (i = 1, n).
2) starting from the arbitrary point Q of the test body to the point reaching through the points S _i on the specimen surface according to Fermat's principle flaw detection surface and _{X i (i = 1, n} ).
3) The points X _i and X _{i + 1} sandwiching the transducer P are searched, and the distances in the x-axis direction between P and the points X _i and X _{i + 1} are set to Δx _i and Δx _{i + 1} , respectively.
4) Considering the point R on the surface of the specimen, the distances in the x-axis direction between R and the points S _i and S _{i + 1} are respectively Δ
When s _i and Δs _{i + 1} are set, an x coordinate satisfying Δs _i : Δs _{i + 1} = Δx _i : Δx _{i + 1} is set as an x coordinate of the point R.
5) Using the point R as the initial value, determine the coordinates that satisfy Fermat's principle from the sequential calculation of Equation (3-5).
6) Check if the line segments PR and QR intersect the surface approximation curve other than the surface where R exists, and determine the propagation path.

Then, if the above procedure is executed by a computer and the propagation path of the ultrasonic wave incident on the shape changing portion is determined, the amplitude of an arbitrary point can be calculated by the following method. That is, the aperture synthesis process can be performed on a test body having a shape changing portion whose surface shape has changed.
As shown in FIG. 8, the amplitude value E (x _i , y _i ) of the pixel Q (x _i , y _i ) of interest in the B scope image was obtained at the transducer position P (x _k , 0). Using the A scope waveform S (x _k , t), the following equation is used.
(3-6)
here,
c ₁ and c ₂ : sound speeds of the media 1 and 2 N: total number of elements r ₁ (x _i , y _i , x _k ): ultrasonic waves from the transducer position P (x _k , 0) to the pixel Q (x _i , The distance r ₂ (x _i , y _i ,) from P (x _k , 0) to a point on the boundary between the medium 1 and the medium 2 on the path to reach y _i ) so as to satisfy Fermat's principle x _k ): a distance from a point on the boundary to the pixel Q (x _i , y _i ) in the path.

Specifically, the aperture synthesis processing program causes the following procedure shown in FIG. 16 to be executed in the central processing unit of each of the ultrasonic transmitter and the PC connected thereto.
1) A linear scan using one element for transmission / reception is executed by an ultrasonic flaw detector to acquire surface reflection data for each transducer (S1).
2) The coordinates of the surface shape of the specimen are determined from the received surface reflected wave by computer processing (S3). Specifically, the steps (S1, S3) of the above 1) and 2) are performed based on the surface echo data (S1) of the specimen taken from the ultrasonic flaw detector as shown in FIG. by executing the identification processing _(S3 -1 _{~S3 -12)} computer to calculate the surface shape data of the specimen represented by quadratic curve of ^{y = ax 2 + bx + c} .
3) Further, the inside of the test body is detected with an ultrasonic flaw detector, and a received waveform is acquired (S2). For example, a linear scan in which a plurality of vibration elements are simultaneously transmitted is performed to acquire internal echo data of a flaw detection area for flaw detection inside the specimen.
4) Then, from the surface shape coordinates determined in step (S3) of the above 2), a propagation path of the ultrasonic wave passing through the surface R from the element P and reaching the point Q in the test body is determined (S4). That is, the flaw detection range inside the specimen is divided into meshes, and the propagation distance of ultrasonic waves from each mesh to each vibrator to be received is calculated based on the identified specimen surface shape.
5) The amplitude of the received waveform corresponding to the path determined in 4) above is added to the amplitude of the Q point (S5 _-1 ).
6) Move the Q point of the test body while repeating the above 4 and 5 _(S5 -2). In other words, the phase of the waveform is shifted so as to correct the delay of the A scope waveform signal received by each receiving element based on the ultrasonic wave propagation path for each transducer for all sections of the flaw detection range. Aperture synthesis processing is performed in which the phases are aligned (S5).
In this embodiment, the surface echo data and the internal echo data are continuously taken into the PC, and then the surface shape is calculated using the surface echo for each transducer in the off-line PC (personal computer). Then, using this identified surface shape data, find the propagation path of the ultrasonic wave to any point inside the specimen for each transducer that receives the internal echo, and according to the propagation path The phase of the waveform is shifted so as to correct the delay of the A scope waveform signal received for each transducer, and aperture synthesis processing is performed in which the phases of the waves are aligned. Then, the flaw detection image generated by the aperture synthesis process is displayed on the display of the PC (S6).

  In the present embodiment, both the surface echo and the internal echo are acquired in steps 1 and 2, but the surface echo is used in step 1 and the echo inside the specimen is used in step 2. Therefore, if the echo from the internal crack can be received in the echo inside the specimen by transmission by one element in step 1, the surface shape of the specimen is identified by the echo data acquired in one scan, Therefore, the data acquisition in step 2 is not necessary. That is, in this embodiment, the linear scan using one vibration element for identifying the surface shape of the test specimen and the linear scan for simultaneously transmitting a plurality of vibration elements for flaw detection inside the test specimen are separate steps. However, the present invention is not particularly limited to this, and may be processed in one step as necessary. For example, when using a large vibrator, by transmitting from a single vibrator, it is possible to receive an echo from the surface of the specimen and an echo large enough for flaw detection from within the specimen, Both echoes can be acquired simultaneously by only a linear scan using one vibration element. However, since ultrasonic waves with only one element with a small transducer size are weak in energy and may not receive echoes large enough for flaw detection, the number of simultaneously transmitted elements must be set to collect echoes inside the specimen. It is preferable to increase the energy of ultrasonic waves. In some cases, a linear scan using one vibration element for identifying the surface shape of the test object may be executed after the linear scan for simultaneously transmitting a plurality of vibration elements for flaw detection inside the test object. good. In any case, when the surface echo acquired by the ultrasonic flaw detector and the echo data inside the specimen are once stored in the memory of the PC and then processed by the central processing unit of the offline PC. The data acquisition context is irrelevant.

The effectiveness of the identification method and identification program of the surface shape of the ultrasonic testing specimen of the present invention was verified.
A test specimen simulating the shape of the butt weld and the discontinuous part weld shown in Fig. 9 was produced, and a number of 1 mm diameter horizontal holes that assumed type IV damage were introduced at positions that assumed a fine grain region of the weld heat affected zone. did. Here, the material of the test body is SUS304. Then, water immersion testing was performed using a phased array probe having a frequency of 5 MHz, 64 elements, an opening area of each element of 0.6 mm × 10 mm, and a pitch of 0.7 mm. At this time, if the flaw detection surface is parallel, a jig capable of maintaining an angle at which a transverse wave is incident at a refraction angle of 45 degrees is attached to the probe. The jig is one channel of the array probe and has a height of 8 mm. For data acquisition, a three-dimensional aperture synthetic array inspection device (Matrixeye EX (registered trademark) manufactured by Toshiba Electric Power Systems Co., Ltd.) was used, and electronic scanning was linear scanning using one element for transmission and reception. Matrixeye performs aperture synthesis processing at high speed by using a parallel arithmetic circuit and four A / D converters that incorporate the amplitude values of the pixels in the B scope image from the A scope waveform received by each element, and generates the B scope image in real time. Can be displayed.

  First, the specimen surface shape was measured by the method for identifying the surface shape of the specimen according to the present invention. Regarding the surface shape measurement, as shown in FIG. 10, vertical flaw detection was also performed using a jig capable of holding the flaw detection surface and a height of 20 mm. In FIG. 11, Method 1 (Method 1) is used to calculate the surface coordinates of the test specimen based on the beam path of the reflected echo from the surface, and Method 2 (Method 2) is used as the surface coordinates reconstructed by the method of the present invention. The surface coordinates of are also shown as a reference. 11 (a) and 11 (b), there is an error between the reference and method 2 in the portion surrounded by the dotted line. In this part, since the refraction angle of the ultrasonic main beam exceeds the critical angle and does not enter the specimen, it is considered that it does not contribute much to the result after the aperture synthesis method. Further, the portions other than the portion surrounded by the dotted line in FIG. 11 are in good agreement with the actual surface shape, and it has been found that the surface shape can be reproduced by the method of the present invention.

  Next, flaw detection results are shown. In electronic scanning, seven elements were used for simultaneous transmission, and 15 element groups having the same center as the transmitting element group were set for reception. As a comparison, an ultrasonic phased array flaw detector (Omniscan) was used to perform a transverse wave oblique water immersion flaw detection that does not take into account changes in the ultrasonic propagation path due to surface shape changes. Electronic scanning was linear scanning, the number of simultaneous transmitting and receiving elements was 16, and delay control was set so that the beam converged near the side hole when a flat plate was assumed. B scope images obtained by flaw detection of the butt welding simulated test specimen and the shape discontinuity weld simulated specimen are shown in FIGS. 12 and 13, respectively. FIGS. 12A and 13A are the results obtained by the phased array method without considering the shape change, and FIG. 12B is the flaw detection result to which the aperture synthesis method according to the present invention is applied. The vertical axis indicates the beam path length. Here, the beam path length is calculated based on the sound speed of water. In FIG. 12, T indicates an echo from a lateral hole caused by a transverse wave. Further, in the result of FIG. 12B, correction is performed by post-processing so that the actual coordinates are displayed in the test body so as to facilitate the analysis. The focusing of the echo by the aperture synthesis method is similar to the flaw detection result of the phased array method focused by using 16 elements, but the echo positional relationship is clearer in the result of the aperture synthesis method.

  In FIG. 13, L indicates an echo from a horizontal hole due to a longitudinal wave component. As shown in FIG. 14, in the ultrasonic beam radiated from the vibrator, the transverse wave that has undergone mode conversion after being incident on the specimen surface A reaches the horizontal hole, and after incident on the surface B, the longitudinal wave reaches the horizontal hole. In FIG. 13A showing the flaw detection result of the phased array method, T and L are displayed together. In FIG. 13B in which the aperture synthesis method processing is performed based on the transverse wave, it is surrounded by a broken line. L becomes thinner and only T is focused. Further, in FIG. 13C in which the aperture synthesis method processing is performed on the basis of the longitudinal wave, T disappears and only L is focused. In addition, for L, instructions from three horizontal holes are obtained, whereas for T, only two are obtained. This is because, as shown in FIG. 14, the transverse wave reaching the lateral hole near the surface has a smaller amplitude than the transverse wave reaching the other lateral hole, so that the obtained echo is also smaller than the other lateral holes and is hardly visible. Conceivable. As described above, by applying the aperture synthesis method in consideration of the propagation path of the ultrasonic beam due to the shape change, it is possible to remove the mixture of the longitudinal wave component and the transverse wave component of the echo and facilitate the flaw detection.

  As a result, it was verified that the surface shape of the test specimen can be identified using only the received waveform of the surface reflected wave. In addition, in the conventional phased array method, echoes due to both longitudinal and transverse modes were mixed due to the influence of the shape change part and analysis after flaw detection was difficult, but based on the identified specimen surface shape, According to the aperture synthesis method of the present invention that calculates the propagation path of the ultrasonic beam and controls the phase of the received waveform so as to be focused on all points in the test body, it is possible to amplify the signal intensity, improve the azimuth resolution, and the SN ratio. In addition, the longitudinal wave mode and the transverse wave mode can be selectively displayed, so that the identification accuracy of the reflection source position is improved.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, the present invention has mainly been described with respect to aperture synthesis processing using a phased array. However, the present invention is not particularly limited to this. Identification of the surface shape of a specimen and determination of the propagation path of ultrasonic waves taking the surface shape into consideration. The steps up to here are common in setting the delay time for each transducer in the phased array flaw detection, and therefore can be easily applied to the phased array flaw detection.

  That is, when the surface shape of the test body having a shape change portion such as a weld surplus is specified by the above-described surface shape identification method of the test body, the flaw detection range inside the test body is meshed from the surface shape of the test body. Since the ultrasonic propagation distance to all transducers can be calculated for each mesh, the delay time of each transducer can be obtained based on the ultrasonic propagation path for each transducer. it can. Therefore, phase array flaw detection can be performed by inputting the delay time for each vibrator calculated by the computer to the flaw detector and controlling the transmission of each vibrator. As a result, the ultrasonic waves are focused at an arbitrary position in the flaw detection area inside the specimen by transmitting the ultrasonic waves with a unique delay time for every transducer. Since the ultrasonic waves transmitted from all the transducers gather at the focal point, the flaw detection accuracy increases. Similarly, since the transmission and reception are repeated so that the ultrasonic beam is sequentially focused in accordance with the surface shape obtained in advance in the entire flaw detection area, flaw detection can be performed with high accuracy. Then, a flaw detection image of the entire flaw detection area is depicted on the display.

Specifically, the phased array flaw detection program causes the following procedure to be executed in the central processing unit of each of the ultrasonic transmitter and the PC connected online thereto.
1) A linear scan using one element for transmission / reception is executed by an ultrasonic flaw detector to acquire surface reflection data for each transducer (S1).
2) Further, the inside of the specimen is detected by linear electronic scanning using one or several elements with an ultrasonic flaw detector, and a received waveform is acquired (S2). The surface echo data and the internal echo data acquired in steps 1 and 2 are taken into the PC, respectively.
3) Based on the acquired surface echo data, the coordinates of the surface shape of the specimen are determined by calculation processing on the PC (S3).
4) Then, from the surface shape coordinates determined in step (S3), the propagation path of the ultrasonic wave passing through the surface R from the element P and reaching the point Q in the test body is determined (S4).
5) Next, based on the propagation path of the ultrasonic wave calculated in step 4, the delay time during which the ultrasonic waves of all the transducers are focused at an arbitrary position in the flaw detection area inside the test body is calculated (S5 ′). ). Here, for example, UltraVision 3 (registered trademark) manufactured by Zetec Corporation in the United States is known as PC software that implements a function of calculating delay control of a phased array in accordance with the shape change portion. Therefore, if the surface shape of the specimen can be identified, the delay control of the phased array can be easily calculated with existing software.
6) The delay time for each transducer calculated by the central processing unit of the PC is input to the ultrasonic flaw detector to perform phased array flaw detection (S6 ′).
7) The flaw detection image is displayed on the display of the PC (S7 ′).

Claims (4)

A phased array is arranged on the surface of a test body having a shape change portion whose surface shape has changed via a medium whose shape can be changed along the surface shape of the test body, and each phased array has a super A beam path from each transducer to the surface of the specimen is detected by emitting a sound wave toward the specimen and receiving a surface echo and detecting a reflected wave from the surface of the specimen obtained for each transducer. Assuming a circle centered on each transducer and having a radius of the beam path obtained for each transducer, a common tangent of the circles centered on adjacent transducers is obtained, and the common tangent is determined. In the section, a point obtained by quadratic interpolation of the points on the common outer tangent is identified as the surface of the test body, and in the section where the common outer tangent is not obtained, it is determined that the boundary between the vibrators is a shape change boundary. Extrapolate curve obtained by quadratic interpolation Surface shape identification method of the specimen having a shape changing unit, characterized in that identified as the surface shape of the boundary, determining the specimen surface shape Te. Ultrasonic wave is applied to each of the transducers of the phased array arranged on the surface of the test body having the shape changing portion whose surface shape has been changed via a medium whose shape can be changed along the surface shape of the test body. And receiving a surface echo and detecting a reflected wave from the surface of the specimen obtained for each transducer to determine a beam path from each transducer to the surface of the specimen. Assuming a circle centered on each transducer and having a radius that is the beam path obtained for each transducer, obtaining a common tangent of the circle centered on adjacent transducers, and the common tangent In the obtained section, the step of identifying the contact point of these circles by quadratic interpolation to identify the surface of the test body and identifying the common outer tangent line as the surface of the test body, and in the section where the common outer tangent line is not obtained, the shape between the vibrators is formed. Boundary of change Determining and extrapolating a quadratic interpolated point on the common tangent line obtained in each section and identifying it as a surface shape at the boundary, and obtaining a specimen surface shape by executing the computer A surface shape identification program for a specimen having a shape change portion. Ultrasonic wave is applied to each of the transducers of the phased array arranged on the surface of the test body having the shape changing portion whose surface shape has been changed via a medium whose shape can be changed along the surface shape of the test body. And receiving a surface echo and detecting a reflected wave from the surface of the specimen obtained for each transducer to obtain a beam path length from each transducer to the surface of the specimen. Assuming a circle centered on each transducer and having a radius that is the beam path obtained for each transducer, obtaining a common tangent of the circle centered on adjacent transducers, and the common tangent In the obtained section, the step of specifying the interpolated points of the circles as the test body surface and identifying the common outer tangent as the test body surface, and in the section where the common outer tangent is not obtained, between the vibrators The shape change Identifying a curve created by extrapolating a quadratic interpolation of points on the common tangent line obtained in each section as a boundary, and identifying the surface shape of the specimen as identified Using the step of calculating for each transducer that receives the propagation distance of the ultrasonic wave from any section of the flaw detection range inside the specimen to the transducer, and each receiving element based on the propagation path of the ultrasonic wave for each transducer The phase of the waveform is shifted so as to correct the delay of the A-scope waveform signal received at, and the aperture synthesis processing is performed to superimpose the waves in a state where the phases of the waves are aligned, and the flaw detection image after the phase operation is drawn on the display An aperture synthesis processing program for causing a computer to execute steps. Ultrasonic wave is applied to each of the transducers of the phased array arranged on the surface of the test body having the shape changing portion whose surface shape has been changed via a medium whose shape can be changed along the surface shape of the test body. And receiving a surface echo and detecting a reflected wave from the surface of the specimen obtained for each transducer to obtain a beam path length from each transducer to the surface of the specimen. Assuming a circle centered on each transducer and having a radius that is the beam path obtained for each transducer, obtaining a common tangent of the circle centered on adjacent transducers, and the common tangent In the interval obtained, the step of interpolating the contact points of these circles to specify the surface of the test body and identifying the common outer tangent as the surface of the test body, and in the interval where the common outer tangent is not obtained, between the vibrators Boundary of shape change A step of identifying a curve created by extrapolating a point obtained by quadratic interpolation of points on the common tangent line obtained in each section as a surface shape at the boundary, and using the identified specimen surface shape Calculate the propagation distance of ultrasonic waves from any section of the flaw detection range inside the specimen to all transducers, and calculate the delay time of each transducer based on the ultrasonic propagation path for each transducer. A phased array flaw detection program for causing a computer to execute a step, a step of performing phase array flaw detection by controlling the transducer based on the delay time, and a step of drawing a flaw detection image on a display.