JP2009281805A - Ultrasonic flaw detecting method and ultrasonic flaw detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flaw detecting method which enables the rapid acquisition of a flaw detection result in a high SN ratio with high resolving power, and an ultrasonic flaw detector. <P>SOLUTION: The original signal, which is transmitted by one element set to a pixel forming and setting part 102F among the elements constituting an array type ultrasonic sensor 101 and received by one element, is recorded. A calculator 102G synthesizes the original signal by the delay time based on the focal position set by a delay time setting part 102E with respect to a plurality of sensor center positions to synthesize a plurality of flaw detecting images focused by all of pixels and an image of a further high SN ratio is obtained. Further, a pixel position is locally changed to more rapidly obtain an ultrasonic flaw detection result of high resolving power and a high SN ratio. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrasonic flaw detection method and apparatus which is one of non-destructive inspection methods, and particularly suitable for defect imaging by a full waveform sampling method using an array type ultrasonic sensor (ultrasonic array probe). The present invention relates to an ultrasonic inspection method and apparatus.

  In the ultrasonic flaw detection method using various structural materials as inspection targets, conventionally, an ultrasonic sensor consisting of a single element is used for transmission and reception of ultrasonic waves, and ultrasonic signals reflected by defects inside the inspection target are used. The defect is detected based on the propagation time and the position of the ultrasonic sensor.

  At this time, move the ultrasonic sensor to find the position where the reflected wave from the defect can be obtained, and receive the reflected wave from the bottom surface (distant boundary surface) or surface (closer boundary surface) to be inspected. The dimension of the defect is identified by the integration of the difference between the two and the sound speed of the material (the speed of sound in the material to be inspected).

  This method is simple and clear in principle, and is relatively easy to use. Therefore, this method is often used for general defect inspection. However, the ultrasonic reflected wave is measured and the defect is detected only from the reception time of the reflected wave. Since it must be evaluated, a highly accurate inspection requires a skilled inspector and much time is required for measurement.

  On the other hand, in recent years, as known as a phased array method, an aperture synthesis method, or the like, a flaw detection method has been developed for imaging and inspecting the inside of an inspection object with high accuracy (for example, see Non-Patent Document 1). .

  The phased array method uses a so-called ultrasonic array probe in which a plurality of piezoelectric vibration elements are arranged, and the wavefronts of ultrasonic waves transmitted from the piezoelectric vibration elements interfere to form a composite wavefront and propagate. It is based on the principle. Therefore, by delay controlling the ultrasonic transmission timing of each piezoelectric vibration element and shifting the timing, the incident angle of the ultrasonic wave can be controlled and the ultrasonic wave can be focused.

  In addition, when receiving ultrasonic waves, the reflected ultrasonic waves received by each piezoelectric vibration element are shifted and added to control the reception angle of the ultrasonic waves as in the case of transmission, or the ultrasonic waves are focused and focused. Can be received.

  As the phased array method, a linear scan method that linearly scans a piezoelectric vibrator and a sector scan method that changes the transmission and reception directions of ultrasonic waves in a fan shape are generally known. In any method, the ultrasonic wave can be scanned at high speed without moving the ultrasonic sensor, or the ultrasonic incident angle and focusing depth position can be arbitrarily controlled without replacing the ultrasonic sensor. Therefore, it can be said that this is a technique capable of high-speed and high-precision inspection.

  On the other hand, in the aperture synthesis method, when the ultrasonic wave is transmitted so that the wave is widely diffused in the inspection object and the reflected ultrasonic signal is received, the position of the defect serving as the sound source of the received reflected ultrasonic wave is A circular arc centered on the position of the piezoelectric vibration element that transmitted and received the sound wave and the propagation distance of the reflected ultrasonic wave as the radius (or if the transmitting and receiving piezoelectric vibrators are different, the transmitting piezoelectric vibrator And on the elliptical arc with the receiving piezoelectric vibrator as the focal position). For this reason, ultrasonic transmission and reception are performed by sequentially changing the position of the piezoelectric vibration element, and the received signal at each position is calculated on an electronic computer and spread in an arc shape (or elliptic arc shape), thereby reflecting the ultrasonic waves. The intersections of the arcs are concentrated at the position where the source defect exists, and the position of the defect is specified.

  In practice, this is a technology that uses the position of the ultrasonic sensor and the ultrasonic waveform signal at that position to perform high-resolution imaging processing on an electronic computer. Is described in Non-Patent Document 1.

  Furthermore, while changing the incident angle of the ultrasonic wave oscillated from the ultrasonic array probe and flawing the inside of the inspection object by sector scanning, the ultrasonic wave transmission / reception position is sequentially moved, and the acquired flaw detection image is moved. A technique is known in which video is synthesized from a plurality of images by adding or averaging while shifting only the transmission / reception position (see, for example, Patent Document 1).

JP 2006-30566 A Co-authored by Masamasa Kondo, Yoshimasa Ohashi, and Akio Mimori, Digital Signal Processing Series, Volume 12 “Digital Signal Processing in Measurements and Sensors”, May 20, 1993, published by Shorindo, pages 143-186

  First of all, in the case of the phased array method in the above prior art, there is an advantage that the ultrasonic incident angle and the focusing position can be arbitrarily controlled by a plurality of piezoelectric vibration elements, and high-speed and high-precision inspection can be performed. Since the focal point is focused only on the focal depth position, the focal point is not focused at the unfocused depth position. As a result, there is a problem in that the spatial resolution is lowered at the focal position where the focal point is not focused.

  In addition, using this phased array method, if an ultrasonic scan is to be performed by sequentially focusing on all depth positions to be inspected, the procedure of flaw detection is performed while changing the focal position setting little by little. There is a problem that it is necessary and enormous time is required for the inspection and its evaluation, which is not realistic.

  Next, in the above-described prior art, in the case of the aperture synthesis method, the waveform of each of the transmission point and the reception point of the ultrasonic wave is processed on the electronic computer, so that high-resolution imaging is possible. Although there is an advantage, generally, it is necessary to determine a range to be imaged and its pitch (spatial resolution) in advance before imaging and to perform advanced arithmetic processing on an electronic computer. Therefore, in order to visualize a video with a better resolution, a very large amount of computation is required. For example, there is a problem that it is difficult to evaluate a flaw detection image in a short time at the inspection site.

  Moreover, in the thing of patent document 1, since the signal used as the origin of imaging is the image obtained by the normal phased array method (sector scan method), the essential subject of the phased array method, ie, Because the focus is only on the set focus depth position, the focus is not focused at the unfocused depth position, and the spatial resolution is lowered at the unfocused depth position. It remains.

  An object of the present invention is to provide an ultrasonic flaw detection method and apparatus capable of quickly obtaining flaw detection results having a high resolution and a high S / N ratio.

(1) In order to achieve the above object, the present invention uses an ultrasonic array probe composed of a plurality of piezoelectric elements to transmit ultrasonic waves to a subject, and from the surface or inside of the subject. An ultrasonic flaw detection apparatus that inspects the inside of a subject with reflected waves (echoes), wherein the ultrasonic array probe includes N piezoelectric elements, and the i th of the N piezoelectric elements. An element switching means for transmitting by the jth element and receiving by the jth element, a recording means for recording a total of up to N × N elementary signals obtained by switching the transmission / reception elements by the switching means, Receiving element setting for setting the sensor center position, K (1 ≦ K ≦ N) transmitting elements used for transmission, and L (1 ≦ L ≦ N) receiving elements used for reception Means, pixel position setting means for setting a pixel position for image display, and On the other hand, the transmitting and receiving elements set by the receiving element setting means, and a calculation means for synthesizing signals by giving a delay time with reference to the sensor center position and the focal position, and A display unit for displaying a synthesized signal synthesized by the computing means, and adding or averaging the synthesized signal with respect to the plurality of sensor center positions as a reference, thereby displaying the interior of the subject; The image is displayed on the display unit.
With this configuration, a flaw detection result having a high resolution and a high S / N ratio can be obtained quickly.

  (2) In the above (1), preferably, the pixel position for video display has position size setting means for setting the position or size of the pixel.

(3) Further, in order to achieve the above object, the present invention transmits an ultrasonic wave to a subject using an ultrasonic array probe including a plurality of piezoelectric elements, and the surface or the inside of the subject. An ultrasonic flaw detection method for inspecting the inside of the subject by reflected waves (echoes) from the N-piezoelectric elements constituting the ultrasonic array probe, transmitted by the i-th element, Received by the jth element and records a total of up to N × N elementary signals, a plurality of sensor center positions, a transmitting element used for transmission, a receiving element used for reception, and an image display By adding or averaging the pixel signals to the pixel position while shifting the prime signal by the delay time with respect to the sensor center position, using the delay time with reference to the pixel position for the inside of the subject. Is made into a video.
By this method, a flaw detection result having a high resolution and a high S / N ratio can be obtained quickly.

  (4) In the above (3), preferably, with respect to a specimen having a known thickness and sound velocity, the shape changing portion of the inside or the surface of the specimen or the bottom surface of the specimen is a reflection source, and the i th After performing the process of measuring the characteristics of the piezoelectric element using one or more elementary signals for calibration (reference signals) received by the i-th element that is the same as the transmission and compensating for the characteristics. In addition, a maximum of N × N elementary signals obtained by flaw detection of the subject are imaged.

  (5) In the above (3), preferably, in the partially selected region, the pixel position interval or size for video display is displayed with a pixel position interval or size different from the periphery of the selected region. It is what you do.

  According to the present invention, a flaw detection result having a high resolution and a high S / N ratio can be obtained quickly.

Hereinafter, the configuration and operation of the ultrasonic flaw detector according to the first embodiment of the present invention will be described with reference to FIGS.
First, the configuration of the ultrasonic flaw detector according to the present embodiment will be described with reference to FIG.
FIG. 1 is a block diagram showing the configuration of the ultrasonic flaw detector according to the first embodiment of the present invention.

  The ultrasonic flaw detection apparatus according to this embodiment includes an ultrasonic array probe 101, a transmission / reception unit 102, and a display unit 103 that displays a flaw detection image. The ultrasonic array probe 101 makes an ultrasonic wave incident on the subject 100 to be inspected. The transmission / reception unit 102 uses the reflected wave from the subject 100 to detect the reflection source 110 such as a defect, a crack, or a crack in or on the subject 100 by imaging.

  As shown in the figure, the ultrasonic array probe 101 basically includes a plurality of piezoelectric vibrating elements 104 that generate and receive ultrasonic waves. The ultrasonic array probe 101 is installed on the testing surface of the subject 100 via a contact medium (liquid such as water or glycerin) or a shoe (made of synthetic resin such as acrylic). The ultrasonic array probe 101 generates an ultrasonic wave 105 by a drive signal supplied from the transmission / reception unit 102, propagates the ultrasonic wave 105 into the subject 100, and detects and receives a reflected wave (echo) 106 appearing thereby. The signal is input to the transmission / reception unit 102.

  The transmission / reception unit 102 performs transmission / reception of ultrasonic waves by the ultrasonic array probe 101. The transmission / reception unit 102 includes a pulsar 102A, a receiver 102B, a data recording unit 102C, an element switching unit 102D, a delay time setting unit 102E, an imaging setting unit 102F, a computer 102G, and a storage unit 102H. The pulsar 102A supplies drive vibration to the ultrasonic array probe 101, and the receiver 102B processes the reception signal input from the ultrasonic array probe 101.

  At this time, the computer 102G controls the pulser 102A, the receiver 102B, the data recording unit 102C, the element switching unit 102D, the delay time setting unit 102E, and the imaging setting unit 102F so as to obtain necessary operations. In addition, the computer 102G synthesizes the signals received by the data recording unit 102C and visualizes them.

  First, the element switching unit 102D switches elements used for transmission and reception. For example, when the ultrasonic array probe 101 is composed of N piezoelectric vibrating elements 104, the operation of transmitting by the i-th element and receiving by the j-th element is repeated, and N patterns and reception are performed by transmission. The elements to be connected to the pulsar 102A and the receiver 102B are sequentially switched with respect to a combination of transmission and reception of N patterns and a maximum of N × N patterns in total.

  Next, the data recording unit 102C performs AD conversion or the like on the maximum N × N received signals (elementary signals) corresponding to the maximum N × N pattern described above, and records the received signal.

  Here, in the description of the present embodiment, the most basic received signal obtained by transmitting with one i-th element and receiving with one j-th element is referred to as an elementary signal φij. .

  The delay time setting unit 102E also shifts the amount of timing to be given to the received signal based on the values determined by the pixel position setting unit, the sensor center position setting unit, and the transmission / reception position setting unit in the imaging setting unit 102F ( (Delay time) is calculated, and processing for shifting the time axis to plus or minus for each of the maximum N × N elementary signals is performed. Although the maximum number of elementary signals is N × N, when K out of N is used for transmission and L out of N is used for reception, the number of elementary waveforms φij is K × L. Become.

Here, the calculation method of the delay time in the ultrasonic flaw detector according to the present embodiment will be described with reference to FIG.
FIG. 2 is an explanatory diagram of a delay time calculation method in the ultrasonic flaw detector according to the first embodiment of the present invention.

  Here, it is assumed that K elements are used for transmission and L elements are used for reception. Further, the following description will be made assuming that the point F (201) is set as the pixel position for imaging in the pixel position setting unit of the imaging setting unit 102F illustrated in FIG.

  The transmission / reception position setting unit of the imaging setting unit 102F sets the i-th element for transmission and the j-th element for reception. The position of the transmitting element is point I (reference numeral 202 in FIG. 2), and the position of the receiving element is point J (reference numeral 203 in FIG. 2). In addition, the sensor center position setting unit of the imaging setting unit 102F sets the sensor center as a point C (reference numeral 101A in FIG. 2). In this case, so that the elementary signal transmitted from the i-th element and received by the j-th element can be regarded as equivalent to being transmitted and received from the sensor center position C (reference numeral 202 in FIG. 2), The delay time is set by the delay time setting unit 102E.

  Hereinafter, for easy understanding, it is assumed that there is a reflection source that reflects ultrasonic waves at the pixel position F (reference numeral 201 in FIG. 2). Considering the sensor center position C as a reference, the signal transmitted to the pixel position F, reflected at the point F, and received again at the sensor center position C is the CF signal for the transmission path and FC for the reception path. Can be schematically written as a waveform indicated by reference numeral 210 shown in (1) path CF → FC at the bottom of FIG. Here, for example, T (CF) represents a propagation time during which ultrasonic waves travel along the path CF.

  Next, an ultrasonic wave is transmitted from the i-th transmission element, reflected at the point F, and received by the j-th reception element, since the transmission path is IF and the reception path is FJ, φij can be schematically written as a waveform indicated by reference numeral 211A shown in (2) path IF → FJΦij at the bottom of FIG.

  It is assumed that the delay time when the transmission is the i-th element and the reception is the j-th element is written as ΔT (i, j). The value of the delay time ΔT (i, j) is a conversion for assuming that the elementary signal when the reception is the i-th element and the j-th element is transmitted / received at the sensor center C. Therefore, the delay time ΔT (I, j) can be written as equation (1).

  When the delay time ΔT (i, j) is defined in this way, an elementary signal having a transmission path of IF and a reception path of FJ is taken into account as shown in Φij at the bottom of FIG. It can be written as 211B, and it can be seen that the propagation time is equal to the elementary signal 210 when transmitting and receiving at the sensor center C. In this way, setting the delay time with reference to the pixel position F means that the elementary signal has the same phase at the pixel position F, so that the pixel position F can be regarded as the focal position. In the method according to the present embodiment, It is possible to obtain a high-resolution flaw detection result that focuses at all pixel positions to be visualized.

Next, a specific example of the delay time in the ultrasonic flaw detector according to the present embodiment will be described with reference to FIGS.
3-6 is explanatory drawing of the specific example of the delay time in the ultrasonic flaw detector by the 1st Embodiment of this invention.

  For example, as shown in FIG. 3, the pixel positions are actually set in a spatial distribution. Therefore, as seen from the center of the sensor, as in the pixel positions F1 (reference numeral 301 in FIG. 3), F2 (reference numeral 302 in FIG. 3), and F3 (reference numeral 303 in FIG. 3), the diagonally lower left (F1), directly below (F2) ), In the case of diagonally lower right (F3), the delay time is specifically calculated.

  FIG. 4 shows the delay time calculated for the pixel position F1 in FIG. FIG. 5 shows the delay time calculated for the pixel position F2 in FIG. FIG. 6 shows the delay time calculated for the pixel position F3 in FIG.

  4 to 6, the ultrasonic array probe is composed of eight elements, the ultrasonic velocity of the subject is 5900 m / second (for example, carbon steel), the sensor center C and each pixel position ( The distance from F1 to F3) is 30 mm, and the element pitch is 1 mm. At this time, FIGS. 4 to 6 summarize the delay time ΔT (i, j) in a table with the number of transmitting elements (T) on the horizontal axis and the number of receiving elements (R) on the vertical axis. Is. The unit is ns.

  When the pixel position (point F), sensor center position (point C), and transmission / reception position (point I and point J) are set by the imaging setting unit 102F as shown in FIGS. 102E can specifically determine the delay time ΔT (i, j) from the sound speed of the subject.

Next, a procedure for visualizing K × L elementary signals in consideration of the delay time ΔT (i, j) in the ultrasonic flaw detector according to the present embodiment will be described with reference to FIG.
FIG. 7 is an explanatory diagram of a procedure for visualizing K × L elementary signals in consideration of the delay time ΔT (i, j) in the ultrasonic flaw detector according to the first embodiment of the present invention.

  Eventually, the pixel position F and the sensor center position C are also set at a plurality of positions. First, a case where the pixel position F and the sensor center position C are fixed at one position will be described. Regarding the position F, finally, a plurality of sensor center positions C will be described.

  First, a case where an imaging result is obtained for a certain pixel position F (reference numeral 201 in FIG. 7) will be described. An elementary signal obtained by shifting the delay time ΔT (i, j) with respect to the elementary signal φij (t) obtained by transmitting by the i-th element and receiving by the j-th element is written as Φij.

  For example, the i-th element is set for transmission, and the reception elements are sequentially changed from 1 to L. With this as one set, the transmitting element is set to the (i + 1) th element, and similarly, the receiving element is sequentially changed from 1 to L.

  By repeating this procedure from 1 to K for the transmitting elements, a total of K × L elementary signals are received. With respect to these elementary signals, the delay time setting unit 102E applies a shift corresponding to the delay time assuming the sensor center position C and the pixel position F to the elementary signals, and the storage unit 102H stores the elementary waveforms Φij (K × L). ) Is recorded.

  For these elementary waveforms Φij, the amplitude corresponding to the round trip propagation time t (i, j) = T (IF) + T (FJ) −ΔT (i, j) from the sensor center position C and the pixel position F to the pixel position F. The value Φij (t (i, j)) is obtained, and the amplitude value of the elementary signal is repeatedly calculated and added for the elements i and j as shown in the equation (2), and the resultant value A (F of the amplitude of the elementary waveform is added. ) Is calculated.

  The pixel position F (reference numeral 201 in FIG. 2) is visualized based on the composite value A (F) of the amplitude of the elementary waveform obtained in this way. For example, the pixels are displayed using black and white or color according to the magnitude of the amplitude value of the composite value A (F).

Next, the contents of the imaging process when the pixel position F in the ultrasonic flaw detector according to the present embodiment is changed will be described with reference to FIGS.
FIGS. 8-11 is explanatory drawing of the content of the imaging process at the time of changing the pixel position F in the ultrasonic flaw detector by the 1st Embodiment of this invention.

  The procedure described in FIG. 7 is an explanation of the imaging process for the sensor center position C fixed at one place and the pixel position F fixed at one place. In contrast, a situation in which the pixel position F is changed will be described with reference to FIGS.

  In order to non-destructively inspect the inside of the subject for the presence or absence of a reflection source such as a crack or a defect, a wide region inside the subject can also be visualized in this embodiment. For example, as a distribution of pixel positions, there is a method in which pixel positions F801 are distributed two-dimensionally at equal intervals within a range 802 designated by a rectangle as shown in FIG. For example, if the pitch of the pixel position in the horizontal direction is ΔY and the pitch of the pixel position in the vertical direction is ΔZ, the YZ coordinates of F (m, n) are expressed using the indices m and n with respect to the pixel position. (MΔY, nΔZ).

  By synthesizing an elementary waveform considering delay time with respect to a sensor center position as described above for a certain pixel position F (m, n) 801, the pixel position F (m, n) at each pixel position F (m, n) is synthesized. A composite value A (F (m, n)) can be obtained. A map obtained by spatially displaying the composite value A thus obtained with respect to the pixel position F is referred to as a flaw detection image.

  As the distribution of the pixel positions F, the pixel positions F901 are distributed in a grid shape within the sector-shaped range 902 as shown in FIG. It may be.

  10 and 11 relate to the simple display mode described with reference to FIGS. 17 and 18, and this point will be described later together with FIGS. 17 and 18.

Next, a situation in which the sensor center position C in the ultrasonic flaw detector according to the present embodiment is changed will be described with reference to FIGS.
12 and 13 are explanatory diagrams of a situation where the sensor center position is changed in the ultrasonic flaw detector according to the first embodiment of the present invention.

  In the above description, the sensor center position C is fixed at one place and the pixel positions F are spatially distributed. However, in the present embodiment, the sensor center position C is moved to perform imaging. .

  FIG. 12 shows an example in which the sensor center is moved when a flaw detection image is drawn with pixel positions distributed in a rectangular shape with respect to the sensor center position C shown in FIG. The sensor center position is set to point C (p−1) 1201. In this situation, using K elements for transmission and L elements for reception, K × L elements per pixel position for pixel positions F (m, n) distributed in space. The waveform is synthesized, and a synthesized value A (C (p−1); F (m, n)) is calculated in the rectangular area 1204. Next, the sensor center position is set to a point C (p) 1202, and similarly, a composite signal A (C (p); F (m, n)) is calculated in the rectangular area 1205. Thereafter, while sequentially moving the sensor center position, the combined value A (C (p); F (m, n)) for the pixel position F (m, n) is similarly calculated in each rectangular area. . With respect to the index p representing the number of sensor center positions, if p = 1 to Q, a total of Q rectangular flaw detection images are obtained.

  FIG. 13 shows a case where the sensor center position is moved in the example of drawing in a fan shape with respect to the sensor center position shown in FIG. 9. Similar to the case of FIG. 12, the composite value A (C (p−1); F (m, n)) is calculated in the area of the sector 1304, and then the point C (p) 1302 is obtained as the sensor center position. Similarly, the combined waveform A (C (p); F (m, n)) is calculated within the sector 1305 region. Thereafter, the same processing is performed while sequentially moving the sensor center position. When the sensor center position moves in Q places in total, Q pieces of rectangular flaw detection images are obtained.

Next, a method for synthesizing Q flaw detection images in the ultrasonic flaw detection apparatus according to the present embodiment will be described with reference to FIG.
FIG. 14 is an explanatory diagram of a method for synthesizing Q flaw detection images in the ultrasonic flaw detection apparatus according to the first embodiment of the present invention.

  FIG. 14 is an explanatory diagram for the case where pixel positions are distributed in a rectangular shape with respect to one sensor center position, as described in FIGS. 8 and 12, but the pixel position distribution is a sector or the like. Even so, the procedure is the same.

  As shown in FIG. 14, when the sensor center position is set to C (p−1) 1201, a plurality of elementary signals taking delay time into account are added (see Expression 2), so that in the imaging region 1204. A composite value A (C (p−1); F (m, n)) for imaging for each pixel position F (m, n) is obtained, and a flaw detection image (p−1) 1204 is drawn. Can do.

  Here, when attention is paid to a specific pixel position F ′, the combined value when the sensor center position is C (p−1) is A (C (p−1); F ′). Next, when the sensor center position is moved to C (p), the combined value of the pixel position F ′ is similarly A (C (p); F ′), and it is assumed that the sensor center position has moved Q places. For example, Q values from A (C (1); F ′) to A (C (Q); F ′) are obtained as the combined values for a specific pixel position F ′.

  For these Q composite values A (C; F ′), the final processing value S (F ′) for the pixel position F ′ can be obtained by performing the averaging process shown in Expression (3). .

  Here, Np in Expression (3) is the number of composite values A for the pixel position F ′ to be imaged. For example, a plurality of three composite values A (p− When the averaging process is performed for 1) to A (p + 1), Np = 3. Generally, if the sensor center position moves Q places, Np = Q. However, there may be a case where an area where the flaw detection image does not overlap when the sensor center moves appears at the end of the flaw detection image, such as the imaging area 1212. In such a case, the number of flaw detection images contributing to the imaging area is set as the value of Np.

  The processed image 1210 can be obtained by spatially drawing the map for the pixel position F with the processing value S (F) averaged in this way, and the processed image is displayed on the display unit 103 in FIG. The

Next, a processing method for flaw detection image synthesis by the ultrasonic flaw detection apparatus according to the present embodiment will be described with reference to FIG.
FIG. 15 is a flowchart showing the content of a processing method for flaw detection image synthesis by the ultrasonic flaw detection apparatus according to the first embodiment of the present invention.

  An ultrasonic array probe 101 composed of N piezoelectric elements is set on the subject 100. The initial steps of the process are composed of two processes of recording an elementary waveform (steps S1501 to S1502) and initial setting (steps S1511 to 1513).

  First, an ultrasonic wave is transmitted from the i-th element among the N piezoelectric elements, and an ultrasonic signal is received as an elementary signal by the j-th element. This elementary signal is repeated for i and j to obtain a maximum of N × N signals (step S1501). These elementary signals are once recorded in the storage unit 102H (step S1502). For example, when the ultrasonic array probe is composed of 64 piezoelectric elements, 64 × 64 = 4096 elementary signals are recorded.

  As another process, the imaging condition is set. First, a pixel position to be visualized is set (step S1511). For example, assuming that the depth direction of the subject is 50 mm, the direction orthogonal to the depth direction is 100 mm, and the pixel size is 0.5 mm pitch, 100 × 200 = 20000 pixel positions are set. Next, a sensor center position and a transmission / reception position are set (steps S1512 and S1513). For example, when the ultrasonic array probe is composed of 64 piezoelectric elements, the first to 24th elements are considered as one group, and the initial value of the sensor center position is the center of 1 to 24 elements. Set to. At this time, for the initial sensor center position, the transmission position is virtually set as a position corresponding to each of the 1st to 24th elements, and the reception position is set as a position corresponding to each of the 1st to 24th elements.

  Next, the process proceeds to the imaging process (steps S1521 to S1527). As the start of the imaging process, a certain pixel position is set (step S1521). Next, the sensor center position is set (step S1522), the delay time ΔT for the pixel position is calculated from the initial values of the sensor center position and the transmission / reception position by Equation 1, and the first recorded elementary signal is shifted by the time. The elementary signal Φij is calculated (step S1523).

  Next, this prime signal Φij is processed in accordance with Equation 2 to calculate a composite value A (C; F) (step S1524). Since this is a composite value for a certain sensor center position, calculation is repeatedly performed for the sensor center position. Specifically, as in the previous example, when the ultrasonic array probe is composed of 64 piezoelectric elements, the 2nd to 25th elements are considered as the next group, and the sensor center is 2 Set to the center of the 25th element. For the sensor center position, the transmission position is set as the 2nd to 25th elements, and the reception position is set as the 2nd to 25th elements. By moving the sensor center position, a combined value A (C; F) for each sensor center position is calculated, and a processing value S (F) for a certain pixel position F is calculated according to the above-described equation (3) (step) S1525).

  Since the above processing is a processing value for a certain pixel position, steps S1521 to S1525 are repeated for the pixel position.

  Finally, a map of the processing value S with respect to the pixel position F is created (step S1526) and displayed as a processed image on the display unit 103 (step S1527).

Next, an example of a processed image obtained by the ultrasonic flaw detector according to the present embodiment will be described with reference to FIG.
FIG. 16 is an explanatory diagram of an example of a processed image obtained by the ultrasonic flaw detector according to the first embodiment of the present invention.

  FIG. 16 schematically shows a case where the sensor center position changes from C (p−1) to C (p + 1) as an example of the processed image obtained by the present embodiment. The target of ultrasonic flaw detection is the reflection source 110 existing inside or on the surface of the subject 100. The flaw detection image 1204 at a certain sensor center position includes a reflected wave (bottom echo 1601) from the bottom surface of the subject, a reflected wave from the tip of the reflection source (defect tip echo 1602), and an opening to the bottom surface of the reflection source. The reflected wave (defect corner echo 1603) from is imaged. This flaw detection image is a video with improved resolution and SN ratio because the delay time is taken into consideration for all the pixels in the imaging region.

  However, in addition to these signals, noise signals due to the material characteristics of the specimen (ultrasonic scattering echoes in the material generated when the crystal grains are large or in the case of welds) and electrical noise are inherently noise for flaw detection. There is also a possibility that the signal 1610A which becomes

  When the sensor center position is moved, the bottom echo 1601, the defect tip echo 1602, the defect corner echo 1603, and noise are imaged, but the signal caused by the bottom and the defect is because the position of the reflection source is constant. The feature is that the coordinates at which they are imaged are almost the same. On the other hand, material noise and electrical noise 1610A, 1610B, and 1610C are characterized in that the positions to be imaged are random.

  In the present invention, a final processed image 1210 shown at the bottom of FIG. 16 is synthesized by performing an averaging process on a plurality of flaw detection images having different sensor center positions. By doing this, for signals whose coordinates do not change much during imaging, the signal is strengthened by averaging, whereas for noise whose coordinates change randomly, the intensity is obtained by averaging. Becomes weaker. By this averaging process, the bottom echo 1601 and the defect corner echo 1603 are imaged at the depth position 1605 and the defect tip echo 1602 is imaged at the depth position 1604, respectively.

  Therefore, the processed image obtained in the present embodiment can obtain a video with a higher SN ratio by the averaging process.

  As described above, according to the present embodiment, among the N piezoelectric elements, the ultrasonic array probe is transmitted by the i-th element and received by the j-th element, and the maximum is N × N in total. By recording a plurality of elementary signals, a delay time based on a plurality of sensor center positions, a transmission element used for transmission, a reception element used for reception, and a pixel position for image display, First, an image is displayed by visualizing the inside of the subject by adding or averaging the pixel signal while shifting the elementary signal by a delay time with respect to the sensor center position. A high-resolution flaw detection image focused on all pixel positions in the region can be obtained, and second, by adding or averaging the flaw detection images, an image with a high S / N ratio can be obtained.

Next, the configuration and operation of an ultrasonic flaw detector according to the second embodiment of the present invention will be described with reference to FIGS. The configuration of the ultrasonic flaw detector according to the present embodiment is the same as that shown in FIG.
FIGS. 17 and 18 are flowcharts showing the contents of a processing method for flaw detection image synthesis by the ultrasonic flaw detection apparatus according to the second embodiment of the present invention. FIG. 19 is an explanatory diagram of setting a detailed imaging range in the ultrasonic flaw detector according to the second embodiment of the present invention.

  In the flowchart shown in FIG. 17, processing related to the simple display mode (step S1701) is added to the flowchart shown in FIG.

  FIG. 18 is a flowchart showing details of the processing in the simple display mode in step S1701 of FIG. First, as an initial setting for visualization in the simple mode, a pixel position, a sensor center position, and a transmission / reception position are set (step S1801). For example, in the example of imaging a rectangular area, the pixel position F is set as shown in FIG. 8 in the first embodiment, but in the simple mode in the second embodiment, as shown in FIG. In addition, the pixel positions F are set so as to have a coarse interval.

  Next, the pixel position is set (step S1802), and the sensor center position is set (step S1803). Here, regarding the setting of the sensor center position, in the simple mode, it is not always necessary to move the sensor center position, and the sensor center position may be set at one or more places. A delay time is calculated for the sensor center position C and the pixel position F (step S1804), and a combined value A (C; F) is calculated (step S1805). Thereafter, iterative calculation for the pixel position is executed (step S1806).

  Next, a map (simple process image) of F with the process value S (F) by the simple process is created (step S1807). Next, this simplified processing image is displayed (step S1808), and a range to be visualized in the detailed mode is set (step S1809).

  Here, the setting of the detailed imaging range will be described in detail with reference to FIGS. 10 (A), 10 (B), 19 (A), and 19 (B).

  FIG. 10A shows a setting example of the pixel position F in the simple mode in the case of the sensor center C as described above. In the simple mode, since the pixel position F1001A is set with a rough pitch, an image inside the subject can be obtained quickly and easily with a short calculation time and a small calculation resource, although the resolution is rough. Here, it is assumed that when a simple processed image is displayed, some reflected waves are visualized from the inside of the subject in the region 1003. The detailed mode is a mode in which a region desired to be focused can be visualized in more detail. For example, if it is desired to look in detail in the region 1003, the pixel positions F1001B may be set and imaged at finer intervals within the range. For example, assume that an image as shown in FIG. 19A is obtained in the simple mode. From the simple image, it is expected that the signal 1910 is a signal from the bottom surface of the subject and the signals 1911 and 1912 are signals due to defects. Therefore, the range to be visualized in detail is designated by the horizontal cursor (1901S, 1901E) and the vertical cursor (1902S, 1902E). A plurality of ranges to be specified in detail may be specified. When the user manually sets the range, the range including the pixel position F of the simple processing such that the processing value S (F) exceeds a certain threshold value is automatically detailed. Any of automatic processing to be set as the imaging range may be used. For pixel positions within the detailed imaging range, for example, the pixel size (interval between pixel positions) is set using an input unit as shown in FIG.

  In this way, after designating the range and pixel size of the detailed visualization in the simple display mode, as shown in FIG. 17, as in the first embodiment, the processed image is displayed for the range to be visualized in detail. Ask.

  In addition, when displaying the simplified processing image, in addition to using a process of setting the interval between the pixel positions roughly as shown in FIG. 10A, the simpler processing image shown in FIG. 11A and FIG. A method may be used. In the simple mode, when the pixel position F1101A is set and the composite value A (F) at the pixel position 1101A is obtained, the direction is the same as the line segment CF, and the distance from the sensor center point C is R. Assuming that a pixel position is virtually at a point F0 (reference numeral 1104 in FIG. 11A) on the arc 1103, the delay time ΔT is obtained according to Equation 1, and the composite value A (F0) is calculated according to Equation 2. To do. This corresponds to simulating a signal from a focus type ultrasonic sensor whose focal position is F0, and uses a delay time function and a composite value substituted for the pixel position F0. Although the ratio is reduced, it is possible to meet the purpose of the simple mode of obtaining information on where the signal of interest is. As described above, after obtaining the simplified processing image instead of the pixel position on the sector 1103, the pixel position 1101B is set in the detailed imaging range 1105 as shown in FIG. Can be made.

  According to the present embodiment, in the partially selected region, the interval or size of the pixel position for video display is displayed with the interval or size of the pixel position different from the periphery of the selected region, thereby enabling more Only a region where a highly accurate flaw detection image is required can be selectively imaged, and a flaw detection image with a high resolution and a high S / N ratio can be obtained quickly.

  As described above, according to the present embodiment, among the N piezoelectric elements, the ultrasonic array probe is transmitted by the i-th element and received by the j-th element. Record N elementary signals, and delay time based on multiple sensor center positions, transmitting elements used for transmission, receiving elements used for reception, and pixel positions for image display First, an image is displayed by visualizing the inside of the subject by adding or averaging the pixel signals while shifting the elementary signal by a delay time with respect to the sensor center position. A high-resolution flaw detection image focused on all the pixel positions in the region to be processed can be obtained, and secondly, an image with a high S / N ratio can be obtained by adding or averaging the flaw detection images. .

Next, the configuration and operation of an ultrasonic flaw detector according to the third embodiment of the present invention will be described with reference to FIGS. The configuration of the ultrasonic flaw detector according to the present embodiment is the same as that shown in FIG.
20 and 21 are flowcharts showing the contents of a processing method for flaw detection image synthesis by the ultrasonic flaw detection apparatus according to the third embodiment of the present invention. FIG. 22 is an explanatory diagram of correction processing for sensitivity variations between elements of the ultrasonic array probe in the ultrasonic flaw detector according to the third embodiment of the present invention. FIG. 23 and FIG. 24 are explanatory diagrams of another correction process of sensitivity variation between elements of the ultrasonic array probe in the ultrasonic flaw detector according to the third embodiment of the present invention.

  In the flowchart shown in FIG. 20, step S2001 for processing the reference signal is added between step S1502 and step S1521 with respect to the flowchart shown in FIG. In the present embodiment, the same effect can be obtained by adding step S2001 between step S1502 and step S1521 in the flowchart of FIG. 17 of the second embodiment.

  FIG. 21 is a flowchart showing details of reference signal processing in step S2001 of FIG.

  First, the elements used for transmission and reception are set to the same one, and a reflection source (for example, a slit or a drill hole) on the surface or bottom surface of the test body or a reflected wave on the bottom surface of the test body is received (step S2101). At least one reference signal transmitted by the i-th element and received by the same i-th element is recorded in the recording unit (step S2102). Note that elements used for transmission / reception may be repeated from the first to the Nth, and a maximum of N reference signals may be recorded.

  Next, it is confirmed whether or not to perform waveform processing (details will be described later) (step S2103). If waveform processing is to be performed, the waveform processing content is selected (step S2104), and the maximum N before considering the delay time is selected. Waveform processing is performed on the × N elementary signals (step S2105).

  After the processing of the reference signal is completed, the normal imaging procedure is resumed. If waveform processing is selected, a maximum of N × N elementary signals are replaced with a set of elementary signals that have undergone waveform processing and stored in the storage unit, and then a combined value calculation and processing is performed. An image calculation procedure is performed.

  Examples of the contents of waveform processing include the following. One is correction processing for sensitivity variations between elements of the ultrasonic array probe 101.

  Details of correction processing for sensitivity variations between elements of the ultrasonic array probe 101 will be described with reference to FIG. First, an ultrasonic array probe is installed on a test body 2201 whose thickness and sound velocity are known, the bottom surface reflected wave 2202 of the test body 2201 is received, and the amplitude value S (i) of the bottom surface reflected wave is recorded. Note that the specimen 2201 may be a subject. In addition, the reflected wave from the shape changing portion of the specimen or the subject or an artificial reflection source (slit or drill hole) may be used instead of the bottom reflected wave.

  For each element, the amplitude P (i) is recorded, the average value S0 of the amplitude P (i) is obtained, and the square root of the ratio between the average values S0 and P (i) is set as the weight W (i). By multiplying the prime signal φij transmitted by the i-th element and received by the j-th element by W (i) × W (j), the sensitivity variation of each element can be corrected. . Note that N reference signals are required to perform sensitivity variation correction processing.

  Next, another correction process for frequency characteristics using a transfer function will be described with reference to FIG. First, an ultrasonic array sensor is installed on a test body 2301 whose thickness and sound speed are known, the bottom surface reflected wave 2302 of the test body 2201 is received, and the bottom surface reflected wave r (t) is recorded. Note that the specimen 2201 may be a subject. In this process, r (t) may be recorded for each element in order to correct the frequency characteristic. However, when there is no variation in the frequency characteristic, the bottom surface reflected wave for the i-th element is used as a representative. Good. The bottom surface reflected wave r (t) can be regarded as a reflection of transmission characteristics due to transmission / reception of ultrasonic waves when the impulse function δ (t) is used as an input signal. In addition, as a reflection source other than the bottom surface reflection wave, a reflection wave from a reflection source whose shape is known in advance, such as a drill hole, may be used.

  If the transfer characteristic by ultrasonic transmission / reception is written as τ (t), r (t) can be written in the form of convolution integral of δ (t) and τ (t), so the component of Fourier transform (R (ω ), I (ω), T (ω)) can be written as shown in Equation (4).

  By using a transmission / reception transfer function T (ω), an elementary signal φ′ij () obtained by correcting a frequency characteristic (transfer characteristic) of transmission / reception with respect to an elementary signal φij (t) obtained when a subject is flawed. t) can be determined.

  Here, details of the corrected elementary signal φ′ij (t) will be described with reference to FIG. The elementary signal φij (t), when δ (t) is regarded as an input signal, is regarded as an output signal affected by transmission / reception characteristics (τ (t)) and reflection source characteristics (g (t)). be able to. As in the case of the bottom reflected wave r (t), ψij (ω), which is the Fourier transform of φij (t), is the product of Fourier transform components (I (ω), T (ω), G (ω)). It can be shown. Of these, by removing transmission / reception transfer characteristics, it is possible to obtain a signal φ′ij (t) that is purely influenced by the characteristics of the reflection source as shown in equation (5).

  The delay time ΔT is calculated for the elementary signal φ′ij (t) whose transmission / reception frequency characteristics are corrected, and Φ′ij (t) is obtained. Based on this, the combined value A (F) and the processed value S (F ), The influence of the transmission and reception transfer characteristics is corrected, and the received ultrasonic signal is reduced in the number of vibrations and approaches an impulse waveform, resulting in improved time resolution. it can.

  As described above, according to the present embodiment, with respect to a specimen having a known thickness and sound speed, the shape change portion of the inside or the surface of the specimen or the bottom surface of the specimen is used as a reflection source, and the i th After performing the process of measuring the characteristics of the piezoelectric element using one or more elementary signals for calibration (reference signals) received by the i-th element that is the same as the transmission and compensating for the characteristics. In addition, by imaging a maximum of N × N elementary signals obtained by flaw detection of the subject, signal processing for correcting sensitivity variations and frequency characteristics of the elements is performed on the elementary signals. By doing so, a highly accurate flaw detection image can be obtained. In other words, it is possible to visualize in more detail only in an area in the subject where there is a notable reflection source such as a defect or a crack, and it is possible to reduce time and memory required for imaging.

As described above, according to the present embodiment, among the N piezoelectric elements, the ultrasonic array probe is transmitted by the i-th element and received by the j-th element. Record N elementary signals, and delay time based on multiple sensor center positions, transmitting elements used for transmission, receiving elements used for reception, and pixel positions for image display First, an image is displayed by visualizing the inside of the subject by adding or averaging the pixel signals while shifting the elementary signal by a delay time with respect to the sensor center position. A high-resolution flaw detection image focused on all the pixel positions in the region to be processed can be obtained, and secondly, an image with a high S / N ratio can be obtained by adding or averaging the flaw detection images. .

1 is a block diagram showing a configuration of an ultrasonic flaw detector according to a first embodiment of the present invention. It is explanatory drawing of the calculation method of the delay time in the ultrasonic flaw detector by the 1st Embodiment of this invention. It is explanatory drawing of the specific example of the delay time in the ultrasonic flaw detector by the 1st Embodiment of this invention. It is explanatory drawing of the specific example of the delay time in the ultrasonic flaw detector by the 1st Embodiment of this invention. It is explanatory drawing of the specific example of the delay time in the ultrasonic flaw detector by the 1st Embodiment of this invention. It is explanatory drawing of the specific example of the delay time in the ultrasonic flaw detector by the 1st Embodiment of this invention. It is explanatory drawing of the procedure which visualizes the KxL elementary signal in consideration of delay time (DELTA) T (i, j) in the ultrasonic flaw detector by the 1st Embodiment of this invention. It is explanatory drawing of the content of the imaging process at the time of changing the pixel position F in the ultrasonic flaw detector by the 1st Embodiment of this invention. It is explanatory drawing of the content of the imaging process at the time of changing the pixel position F in the ultrasonic flaw detector by the 1st Embodiment of this invention. It is explanatory drawing of the content of the imaging process at the time of changing the pixel position F in the ultrasonic flaw detector by the 1st Embodiment of this invention. It is explanatory drawing of the content of the imaging process at the time of changing the pixel position F in the ultrasonic flaw detector by the 1st Embodiment of this invention. It is explanatory drawing of the condition which changes the sensor center position in the ultrasonic flaw detector by the 1st Embodiment of this invention. It is explanatory drawing of the condition which changes the sensor center position in the ultrasonic flaw detector by the 1st Embodiment of this invention. It is explanatory drawing of the synthetic | combination method of the Q flaw detection image in the ultrasonic flaw detection apparatus by the 1st Embodiment of this invention. It is a flowchart which shows the content of the processing method of the flaw detection image synthesis | combination by the ultrasonic flaw detector by the 1st Embodiment of this invention. It is explanatory drawing of the example of the process image obtained by the ultrasonic flaw detector by the 1st Embodiment of this invention. It is a flowchart which shows the content of the processing method of the flaw detection image synthesis | combination by the ultrasonic flaw detector by the 2nd Embodiment of this invention. It is a flowchart which shows the content of the processing method of the flaw detection image synthesis | combination by the ultrasonic flaw detector by the 2nd Embodiment of this invention. It is explanatory drawing of the setting of the detailed imaging range in the ultrasonic flaw detector by the 2nd Embodiment of this invention. It is a flowchart which shows the content of the processing method of the flaw detection image synthesis | combination by the ultrasonic flaw detector by the 3rd Embodiment of this invention. It is a flowchart which shows the content of the processing method of the flaw detection image synthesis | combination by the ultrasonic flaw detector by the 3rd Embodiment of this invention. It is explanatory drawing of the correction process of the sensitivity variation between the elements of the ultrasonic array probe in the ultrasonic flaw detector by the 3rd Embodiment of this invention. It is explanatory drawing of other correction | amendment processes of the sensitivity variation between the elements of the ultrasonic array probe in the ultrasonic flaw detector by the 3rd Embodiment of this invention. It is explanatory drawing of other correction | amendment processes of the sensitivity variation between the elements of the ultrasonic array probe in the ultrasonic flaw detector by the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Ultrasonic array probe 102 ... Transmission / reception part 103 ... Display part 100 ... Subject 104 ... Piezoelectric vibration element 102A ... Pulser 102B ... Receiver 102C ... Data recording part 102D ... Element switching part 102E ... Delay time setting part 102F ... Image | video Setting unit 102G ... computer 102H ... storage unit

Claims (5)

Using an ultrasonic array probe composed of a plurality of piezoelectric elements, an ultrasonic wave is transmitted to the subject, and the inside of the subject is inspected by a reflected wave (echo) from the surface or inside of the subject. An acoustic flaw detector,
The ultrasonic array probe includes N piezoelectric elements,
Among the N piezoelectric elements, element switching means for transmitting by the i-th element and receiving by the j-th element;
Recording means for recording a maximum of N × N elementary signals in total obtained by switching transmission / reception elements by the switching means;
A receiving element for setting a plurality of sensor center positions, K (1 ≦ K ≦ N) transmitting elements used for transmission, and L (1 ≦ L ≦ N) receiving elements used for receiving Setting means;
Pixel position setting means for setting a pixel position for image display;
Arithmetic means for synthesizing signals by giving a delay time with respect to the elementary signal based on the sensor center position and the focus position, and the transmitting and receiving elements set by the receiving element setting means When,
A display unit for displaying the synthesized signal synthesized by the computing means;
An ultrasonic flaw detection apparatus characterized in that an image of the inside of the subject is imaged on the display unit by adding or averaging signals based on the plurality of sensor center positions as the synthesized signal. The ultrasonic flaw detector according to claim 1,
An ultrasonic inspection apparatus comprising position size setting means for setting the pixel position or size for the pixel position for video display. Using an ultrasonic array probe composed of a plurality of piezoelectric elements, an ultrasonic wave is transmitted to the subject, and the inside of the subject is inspected by a reflected wave (echo) from the surface or inside of the subject. An acoustic flaw detection method,
Of the N piezoelectric elements constituting the ultrasonic array probe, the i-th element transmits and the j-th element receives, and a total of up to N × N elementary signals are recorded.
Based on a plurality of sensor center positions, a transmission element used for transmission, a reception element used for reception, and a pixel position for image display, the elementary signal is converted into the sensor center. An ultrasonic flaw detection method characterized in that the inside of the subject is visualized by adding or averaging the pixel positions while shifting the position by a delay time. The ultrasonic flaw detection method according to claim 3,
For a test specimen whose thickness and sound speed are known, the inside of the test specimen or the shape change part of the surface or the bottom surface of the specimen is used as a reflection source, transmitted by the i-th element, and the same i-th transmission. After measuring the characteristics of the piezoelectric element using one or more calibration source signals (reference signals) received by the element, and performing processing for compensating the characteristics, the maximum N × obtained by flaw detection of the subject An ultrasonic flaw detection method comprising imaging N elementary signals. The ultrasonic flaw detection method according to claim 3,
An ultrasonic flaw detection method comprising: displaying a pixel position interval or size for video display in a partially selected region at a pixel position interval or size different from the periphery of the selected region.

Images