JP5593208B2 - Ultrasonic flaw detection apparatus and ultrasonic flaw detection method - Google Patents

Description

The present invention relates to an ultrasonic flaw detector and an ultrasonic flaw detection method using an ultrasonic sensor having an array of ultrasonic transducer elements two-dimensionally.

  As a nondestructive inspection method for solids such as metals, an ultrasonic flaw detection method is generally used. One type of this ultrasonic flaw detection method is a phased array type ultrasonic flaw detection method. A phased array method (also called an electronic scanning method or an electronic scanning method) uses an array sensor in which a plurality of elements capable of oscillating ultrasonic waves, such as piezoelectric elements, are arranged in an array. The flaw detector applies an electrical signal to each element after being delayed by a predetermined time, so that the ultrasonic wave generated from each element forms a focal point in the subject, and further delays the electrical signal to each element. This is an ultrasonic flaw detection method in which a pattern (delay pattern) is changed at high speed so that an ultrasonic transmission / reception angle (refraction angle), a focal position, and the like can be controlled. The reason why this method is regarded as important is to select the angle, position, and focal point that can receive the reflected wave more strongly from the vicinity where the defect is assumed due to the influence of environment, stress, etc. inside the subject. This is because it is easy to detect a defect that is a reflection source. For example, since a defect along the weld line is predicted in the inspection of the welded portion, the defect is formed so as to form a focal point with a refraction angle of 30 degrees or more and a plate thickness or a propagation distance of several times that thickness. An oblique flaw detection method using a phased array method in which a pattern is created and inspected under suitable conditions is effective.

  In recent years, research and development of three-dimensional phased array technology that enables transmission and reception of ultrasonic waves in three dimensions using a matrix array sensor in which elements are arranged in two dimensions has been actively conducted. Volume inspection is possible from cross-sectional inspection by technology (see, for example, Patent Document 1).

  Therefore, the present inventors apply a three-dimensional ultrasonic technique using a matrix array sensor to an ultrasonic inspection of a pipe welded portion that requires a mechanical rotation inspection and an ultrasonic inspection of a thick plate material. Are considering.

  The above-described conventional method is effective, for example, when examining a thin subject. However, in order to inspect defects located in the deep part of the thick plate material by the oblique flaw detection method using the three-dimensional phased array technique, it is necessary to increase the size of the sensor aperture in order to improve the convergence of the ultrasonic wave.

  Here, as a conventional matrix array sensor, a rectangular matrix sensor in which elements having substantially constant sizes are orthogonally arranged, or a rectangular matrix array sensor in which symmetry is improved by changing the arrangement of elements (for example, Patent Document 2) For example).

JP-A-2005-351718 US Pat. No. 6,384,516

  In order to increase the size of the sensor aperture with these matrix array sensors, the number of ultrasonic vibration elements increases in proportion to the square of the sensor aperture. However, there is a technical limit to the total number of elements that can be controlled by the flaw detector, and even if the number of controllable ultrasonic vibration elements can be increased, the apparatus becomes large and expensive.

  Therefore, if it is attempted to increase the size of the sensor aperture while suppressing the total number of elements to a controllable number, the distance (pitch) between the elements increases. When the distance (pitch) between elements increases, in addition to the ultrasonic wave (main lobe) used for original flaw detection, ultrasonic waves (grating lobes) that become interference waves are generated. The occurrence of grating lobes causes a problem that noise increases and the SN ratio decreases.

An object of the present invention, while suppressing the total number of controllable elements, with allows inspection of deep by performing enlargement of the sensor aperture, to provide an ultrasonic flaw detector and an ultrasonic flaw detection method with an improved SN ratio There is.

(1) To achieve the above Symbol object, the present invention is, as a sensor which oscillates an ultrasonic wave, using an ultrasonic sensor having an array of ultrasonic transducer elements which oscillates ultrasonic waves to regularly two-dimensionally, the An ultrasonic flaw detector that transmits ultrasonic waves from the ultrasonic sensor to the inside of the inspection target, receives echoes from the inspection target by the ultrasonic sensors, and evaluates the presence / absence of the defect to be inspected or the size of the defect from the echo a is the number of the ultrasonic transducer elements, said more than the number that can be controlled by the ultrasonic inspection device, among pre-Symbol for the plural ultrasonic transducer elements forming an ultrasonic sensor, used to send and receive ultrasonic When an element use range selection means for selecting an element to be selected and a number of ultrasonic vibration elements larger than the number controllable by the ultrasonic flaw detector are selected by the element use range selection means, a plurality of elements are selected. At the same potential The element short-circuit pattern selection unit that performs short-circuiting is provided.
(2) In order to achieve the above object, the present invention uses an ultrasonic sensor in which ultrasonic vibration elements that oscillate ultrasonic waves are regularly arranged in a two-dimensional manner as a sensor that oscillates ultrasonic waves. An ultrasonic flaw detection method in which ultrasonic waves are transmitted from an ultrasonic sensor to the inside of an inspection object, echoes from the inspection object are received by the ultrasonic sensors, and the presence or absence of the defect or the size of the defect is evaluated from the echo The number of the ultrasonic vibration elements is larger than the number that can be controlled by the ultrasonic flaw detector, and the element used for transmitting and receiving ultrasonic waves among the plurality of ultrasonic vibration elements constituting the ultrasonic sensor. Is selected by the element use range selection means, and when the number of ultrasonic vibration elements larger than the number controllable by the ultrasonic flaw detector is selected by the element use range selection means, the element short-circuit pattern selection unit The number of elements short-circuited to the same potential.

According to the present invention, it is possible to perform a deep inspection by increasing the size of the sensor opening while suppressing the total number of controllable elements, and to improve the SN ratio.

It is a top view which shows the structure of the ultrasonic sensor by the 1st Embodiment of this invention. It is explanatory drawing of the transmission / reception direction of the ultrasonic wave in the ultrasonic sensor by the 1st Embodiment of this invention. It is explanatory drawing of the grating lobe in an array sensor. It is explanatory drawing of the generation direction of the grating lobe in the ultrasonic sensor by the 1st Embodiment of this invention. It is a top view which shows the structure of the ultrasonic sensor by the 2nd Embodiment of this invention. It is a top view which shows the transmission / reception arrangement | positioning by the ultrasonic sensor by the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the ultrasonic flaw detector by the 3rd Embodiment of this invention. It is a flowchart which shows operation | movement of the ultrasonic flaw detector by the 3rd Embodiment of this invention. It is explanatory drawing of the ultrasonic sensor used for the ultrasonic flaw detector by the 3rd Embodiment of this invention. It is explanatory drawing of the ultrasonic sensor used for the ultrasonic flaw detector by the 3rd Embodiment of this invention.

Hereinafter, the configuration and operation of the ultrasonic sensor according to the first embodiment of the present invention will be described with reference to FIGS.
First, the configuration of the ultrasonic sensor according to the present embodiment will be described with reference to FIG.
FIG. 1 is a plan view showing the configuration of the ultrasonic sensor according to the first embodiment of the present invention.

  The ultrasonic sensor 1 of this embodiment is composed of a plurality of ultrasonic vibration elements 1A arranged in an array. The total number of the plurality of elements is within the total number of elements (for example, 256) that can be controlled by the flaw detector. In this example, the plurality of ultrasonic vibration elements 1A are arranged in a staggered manner.

  Here, typical elements constituting the array sensor include a piezoelectric element, a matching layer, a backing, a joint portion, a case, wiring, and the like. Among these elements, the elements are arranged so that the center of gravity R of each element satisfies (n1a1 + n2a2) in the ultrasonic sensor 1 of the present embodiment shown in FIG. n1 and n2 are integers, and a1 and a2 are vectors.

  Here, each ultrasonic vibration element 1A has a rectangular shape as illustrated. A vector from the centroid position of a certain element to the centroid position of another element adjacent to the element in the long side direction (X direction) is defined as a1. Further, a vector from the centroid position of a certain element to the centroid position of another element adjacent to the element in the short side direction (Y direction) is defined as a2. When the centroid position of a certain element is used as a reference, the centroid position R of another element satisfies (n1a1 + n2a2). Note that vector a1> vector a2.

  Further, since the plurality of ultrasonic vibration elements 1A are arranged in a staggered manner, the angle formed by the vector a1 and the vector a2 is other than 90 degrees and satisfies (2a2-a1) · a1 = 0. Here, “·” indicates an inner product.

  Moreover, in this embodiment, in order to be able to test | inspect the defect located in the thick plate material deep part, the sensor opening is enlarged. As a specific example, the length X1 in the X direction is 30 mm, and the length Y1 in the Y direction is 75 mm. The number of elements arranged in an array is 10 in the X direction, 25 in the Y direction, and the total number is 250. In this case, the pitch px1 in the X direction is 3 mm, and the pitch py1 in the Y direction is 3 mm. For example, when a 2 MHz signal is used as the ultrasonic wave, the pitches px1 and py1 are (λ / 2) or more with respect to the wavelength λ of the ultrasonic wave.

Next, the transmission / reception direction of the ultrasonic wave in the ultrasonic sensor according to the present embodiment will be described with reference to FIG.
FIG. 2 is an explanatory diagram of ultrasonic transmission / reception directions in the ultrasonic sensor according to the first embodiment of the present invention. 2A is a perspective view, and FIG. 2B is a top view.

  When transmitting and receiving ultrasonic waves using a sensor in which elements are arranged so that the center-of-gravity position R of other elements satisfies (n1a1 + n2a2), the transmission / reception direction of the ultrasonic waves is expressed as a refraction angle θm and an azimuth angle φm. .

Here, the generation direction of the grating lobe is as follows. First, the vectors a1 and a2 constituting the array sensor are respectively expressed by Equation (1).

And

When the wavelength of the ultrasonic wave is λ and the direction of focusing the ultrasonic wave is a refraction angle θm and an azimuth angle φm, the following equations (2), (3),

Satisfying the expression (4),

Grating lobes are generated.

  From Expression (4), the generation location of the grating lobe is determined by the vectors a1 and a2 for determining the element arrangement and the direction in which the ultrasonic wave is propagated. Therefore, when the generation position of the grating lobe as noise is desired to be shifted, the vectors a1 and a2 It is sufficient to use a sensor as shown in FIG.

Next, the grating lobe in the array sensor will be described with reference to FIG.
FIG. 3 is an explanatory diagram of grating lobes in the array sensor.

  FIG. 3A shows a case where the element spacing (pitch) p is narrower than (λ / 2). In this case, there are only main lobes and no grating lobes are generated.

  On the other hand, as shown in FIG. 3B, when the element interval (pitch) p is wider than (λ / 2), a grating lobe that becomes noise is generated in addition to the main beam. Here, the grating lobe is a sound that strongly propagates in a direction other than the sound collecting direction with respect to the sound collecting direction, that is, the direction to be inspected (45 degrees in the illustrated example).

Next, the generation direction of the grating lobe in the ultrasonic sensor according to the present embodiment will be described with reference to FIG.
FIG. 4 is an explanatory diagram of the generation direction of the grating lobe in the ultrasonic sensor according to the first embodiment of the present invention.

  As shown in FIG. 4A, it is assumed that the ultrasonic wave is focused from the ultrasonic sensor 1 in the direction of the refraction angle θm and the azimuth angle φm to generate the main beam M. At this time, the grating lobe GL is generated in a direction different from the direction in which the main beam M is generated.

  In FIG. 4B, an angle formed by the main beam M and the grating lobe GL is α1 when a plurality of elements are arranged orthogonally (the angle formed by the vector a1 and the vector a2 is 90 degrees).

  4C shows the angle formed by the main beam M and the grating lobe GL when the plurality of elements shown in FIG. 1 are arranged in a staggered arrangement (the angle formed by the vector a1 and the vector a2 is other than 90 degrees). And

  Note that in both FIGS. 4B and 4C, the element spacing is larger than (λ / 2).

  In the case of the present embodiment, the position where the grating lobe is generated is obtained by Expression (4), and the angle α2 at this time is wider than the angle α1 in FIG. Therefore, the influence on flaw detection can be reduced.

  As described above, according to the present embodiment, it is possible to reduce the influence of the noise by increasing the size of the array sensor and causing noise to appear where there is no relation on the flaw detection range. Therefore, the deep inspection can be performed with a good SN ratio.

Next, the configuration and operation of the ultrasonic sensor according to the second embodiment of the present invention will be described with reference to FIGS. 5 and 6.
FIG. 5 is a plan view showing a configuration of an ultrasonic sensor according to the second embodiment of the present invention. FIG. 6 is a plan view showing a transmission / reception arrangement by the ultrasonic sensor according to the second embodiment of the present invention.

  As shown in FIG. 5, the ultrasonic sensor 1 ′ of this embodiment includes a plurality of ultrasonic vibration elements 1 </ b> A arranged in an array. The total number of the plurality of elements is within the total number of elements (for example, 256) that can be controlled by the flaw detector. In this example, the elements are arranged so that the center of gravity R of each element satisfies (n1a1 + n2a2). n1 and n2 are integers, and a1 and a2 are vectors.

  Here, each ultrasonic vibration element 1A has a rectangular shape as illustrated. A vector from the barycentric position of a certain element to the barycentric position of another element adjacent to the element in the long side direction (X direction) is a1. Also, a2 is a vector from the centroid position of a certain element to the centroid position of another element adjacent to the element in the short side direction (Y direction). When the centroid position of a certain element is used as a reference, the centroid position R of another element satisfies (n1a1 + n2a2). Note that vector a1> vector a2.

  Moreover, in this embodiment, in order to be able to test | inspect the defect located in the thick plate material deep part, the sensor opening is enlarged. Then, the pitch px1 in the X direction and the pitch py1 in the Y direction are (λ / 2) or more with respect to the wavelength λ of the ultrasonic wave.

  Also in this embodiment, the position where the grating lobe is generated is obtained by Expression (4), and the angle α2 at this time is wider than the angle α1 in FIG. Therefore, the influence on flaw detection can be reduced.

  Also, as shown in FIG. 6, since the grating lobe generation position can be estimated from the sensor array vectors a1 and a2 and the ultrasonic wave transmission / reception direction, two sensors are prepared, one of which is the transmission sensor 1 ′ ( It is possible to suppress the occurrence of noise by using it as T) and using the other as the receiving sensor 1 ′ (R). At this time, sensors of the same arrangement may be used for each sensor, or different sensors may be used. Further, the sensor having the arrangement shown in FIG. 1 may be used.

  As described above, according to the present embodiment, it is possible to reduce the influence of the noise by increasing the size of the array sensor and causing noise to appear where there is no relation on the flaw detection range. Therefore, the deep inspection can be performed with a good SN ratio.

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.
FIG. 7 is a block diagram showing a configuration of an ultrasonic flaw detector according to the third embodiment of the present invention. FIG. 8 is a flowchart showing the operation of the ultrasonic flaw detector according to the third embodiment of the present invention. 9 and 10 are explanatory diagrams of an ultrasonic sensor used in an ultrasonic flaw detector according to the third embodiment of the present invention.

  As shown in FIG. 7, the ultrasonic flaw detector according to the present embodiment includes a flaw detector 100, an array sensor 1 ″, and a display 10. The flaw detector 100 includes a calculator 110, a memory 120, A data recording unit 130, a delay time control unit 140, an element use range selection unit 150, a pulsar / receiver 160, and a channel box 170. The channel box 170 includes an element short-circuit pattern selection unit 172 and a switch circuit 174. It consists of.

  Here, the array sensor 1 ″ will be described with reference to FIG. 9. The array sensor 1 ″ is composed of a plurality of ultrasonic transducer elements 1A arranged in a matrix. Here, for example, a matrix array sensor of m rows and n columns is used, and the interval between each element is sufficiently narrow ((λ / 2) or less), and no grating lobe is generated. However, the total number of elements is not less than the number that can be controlled by the flaw detector. For example, when the number of flaw detectors that can be controlled is 256, the array sensor 1 ″ has 25 rows and 30 columns and a total of 750.

  FIG. 9 shows a case where the opening area is increased and the deep portion is measured, and FIG. 10 shows a case where the opening area is reduced and wide transmission / reception is possible. In the case of FIG. 9, among all the elements constituting the array sensor 1 ″, the elements are selected using the element use range selection unit 150 shown in FIG. 7 so that the sensor opening is suitable for the selected flaw detection range. (Specifically, the sensor aperture is selected to be large as the entire range from the first row to the m-th row and from the first column to the n-th column), and the channel box 170 shown in FIG. Are divided into a plurality of elements (here, three in the row direction) and set to the same potential, so that the number of elements can be controlled to be equal to or less than the number of elements that can be controlled by the flaw detector. In the figure, an element indicated by a thick black line is used.

  At this time, assuming that the three elements have the same potential, these three elements behave substantially as a single element. In this case, the interval between adjacent elements is tripled, so that (λ / 2) than As a result, the grating lobe is generated. At that time, the selection method of the elements having the same potential by the channel box 170 shown in FIG. 7 is performed. For example, in the m-th row, the third column, the fourth column, and the fifth column are set to the same potential. , When the elements in the 7th and 8th columns have the same potential, the m-1th row has the same potential in the 2nd, 3rd, and 4th elements, the 5th, 6th, The elements in the seventh row are not arranged orthogonally so as to have the same potential. That is, as described with reference to FIG. 5, a vector from the barycentric position of an element having the same potential to the barycentric position of another element having the same potential adjacent to the element in the long side direction (X direction) is represented by a1. And Further, a vector from the centroid position of a certain element to the centroid position of another element adjacent to the element in the short side direction (Y direction) is defined as a2. When the centroid position of a certain element is used as a reference, the centroid position R of another element satisfies (n1a1 + n2a2). Note that vector a1> vector a2. The angle formed by the vector a1 and the vector a2 is other than 90 degrees. As a result, as described with reference to FIG. 4, even when the sensor opening is enlarged to enable deep measurement, the influence of the grating lobe can be reduced and the SN ratio can be improved.

  Further, in order to enable wide transmission / reception, as shown in FIG. 10, among all the elements constituting the array sensor 1 ″, the element use range selection unit 150 shown in FIG. The element is selected so as to have an appropriate sensor opening (specifically, the sensor opening is small in the range from the fifth row to the tenth row and from the third column to the eighth column, and the flaw detector. The channel box 170 shown in Fig. 7 is used, and the elements shown in black in the figure are used.

  Next, the operation of the ultrasonic flaw detector shown in FIG. 7 when flaw detection according to the present embodiment is performed on a plurality of focal points F will be described with reference to FIG.

  When the setting is started, as an initial setting for the array sensor, the computer 110 inputs element information, material information, and the like constituting the array sensor 1 ″ from the memory 120 (step S01).

  Next, the computer 110 sets the inspection range by this sensor (step S02).

Then, the computer 110 determines an element range to be used suitable for the inspection range, sets the element range to be used for the element use range selection unit 150 (step S03), and the calculator 110 also selects the element range. An element pattern to be short-circuited is set for the short-circuit pattern selection unit 172 (step S04). If the element range to be used is determined, generally, the center of the entire sensor is used as the sensor center, and accordingly, the computer 110 sets the sensor center. (Step S05)
Next, the computer 110 calculates a delay time pattern for each element of the array sensor (step S06), and sets the delay time in the delay time control unit 140.

Next, the delay time control unit 140 uses the set delay time and the pattern selected by the element short-circuit pattern selection unit 172 for the element selected by the element use range selection unit 150. In response to this, the switch circuit 174 short-circuits the element to be short-circuited, and then the ultrasonic wave is transmitted from the pulsar 160 to the plurality of focal points F using the array sensor 1 ″. The wave is received by the array sensor 1 ″ and the receiver 160 (step S07).
Data (reflection data) for a plurality of focal points F is recorded in the data recording unit 130 (step S08).

  Further, it is determined whether or not the data recording at all points has been completed (step S09). If the recording has not been completed (NO), the focus F (i) is shifted to the next focus F (i + 1). Then, transmission / reception of ultrasonic waves is performed again, and the recording of reflection data is sequentially repeated until the recording of reflection data in all measurement areas is completed.

  When all the processes are completed (YES), the process ends (step S10).

  Thereafter, generally, a map of pixels and pixel values is created, and the inspection result is visually displayed on the display 10 by image display.

  In order to easily set the combination of the elements used for transmission / reception and the pattern to be short-circuited, a pattern for short-circuiting with the combination of elements to be used is stored in advance in the memory 120 of the apparatus shown in FIG. Can be saved and read at the start of measurement. When inspecting from a deep place to a shallow place, the short-circuit pattern corresponding to the combination of elements to be used is used as shown in FIG. 9 and FIG. 10, and recording is repeated from step S02 regardless of the depth. It becomes possible to inspect.

  The channel box 170 may be inside the flaw detector or may be connected to the original flaw detector from the outside.

  In the example shown in FIG. 9, four elements, for example, the m-th row, the third column, the fourth column, the fifth column, and the sixth column elements have the same potential, and the seventh column and the eighth column. When the elements in the 9th, 9th and 10th columns are set to the same potential, the m−1th row is set so that the elements in the 5th, 6th, 7th and 8th columns have the same potential. If the orthogonal arrangement is not used, the arrangement is the same as described with reference to FIG.

  As described above, according to the present embodiment, it is only necessary to switch the element pattern to be short-circuited with the element pattern used in the channel box, and it is possible to inspect deep and shallow areas with one array sensor.

In addition, the array sensor can be enlarged to reduce the influence of noise even when measuring in a deep place, so that deep inspection can be performed with a high S / N ratio.

DESCRIPTION OF SYMBOLS 1 ... Array sensor 10 ... Display device 100 ... Flaw detector 110 ... Computer 120 ... Memory 130 ... Data recording part 140 ... Delay time control part 150 ... Element use range selection part 160 ... Pulsar receiver 170 ... Channel box 172 ... Element short circuit pattern Selector 174 ... Switch circuit

Claims (2)

As a sensor that oscillates ultrasonic waves, an ultrasonic sensor in which ultrasonic vibration elements that oscillate ultrasonic waves are regularly arranged in a two-dimensional shape is used.
Ultrasonic flaw detection that transmits ultrasonic waves from the ultrasonic sensor to the inside of the inspection target, receives echoes from the inspection target by the ultrasonic sensors, and evaluates the presence / absence of the defect or the size of the defect from the echo A device,
The number of the ultrasonic vibration elements is greater than the number controllable by the ultrasonic flaw detector ,
Among the plurality of ultrasonic transducer elements constituting the front Symbol ultrasonic sensor, an element used range selection means for selecting a device to be used for transmission and reception of ultrasonic waves,
Element short-circuit pattern selection for short-circuiting a plurality of elements to the same potential when the number of ultrasonic vibration elements larger than the number controllable by the ultrasonic flaw detector is selected by the element use range selection means And an ultrasonic flaw detector. As a sensor that oscillates ultrasonic waves, an ultrasonic sensor in which ultrasonic vibration elements that oscillate ultrasonic waves are regularly arranged in a two-dimensional shape is used.
Ultrasonic flaw detection that transmits ultrasonic waves from the ultrasonic sensor to the inside of the inspection target, receives echoes from the inspection target by the ultrasonic sensors, and evaluates the presence / absence of the defect or the size of the defect from the echo A method,
The number of the ultrasonic vibration elements is greater than the number controllable by the ultrasonic flaw detector,
Among the plurality of ultrasonic vibration elements constituting the ultrasonic sensor, an element used for transmission / reception of ultrasonic waves is selected by an element use range selection unit,
When the number of ultrasonic vibration elements larger than the number that can be controlled by the ultrasonic flaw detector is selected by the element use range selection means, the element short-circuit pattern selection unit sets a plurality of elements to the same potential. An ultrasonic flaw detection method characterized by short-circuiting.

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