JP5588918B2 - Ultrasonic inspection method - Google Patents

Description

The present invention relates to an ultrasonic inspection how using ultrasonic sensors, in particular, relates to a preferred ultrasonography how to obtain a low inspection image noise in oblique flaw detection.

  Ultrasonic inspection is used as one of the nondestructive inspection methods in the industrial field and the medical field. Ultrasonic inspection is a method in which ultrasonic waves are applied to an object and the reflected waves are imaged and inspected. In the industrial field, a method for inspecting defects using ultrasonic waves is sometimes called an ultrasonic flaw detection method.

  Among ultrasonic inspection methods, a phased array method is known as one of effective methods (see, for example, Patent Document 1). The phased array method is also called an electronic scanning method or an electronic scanning method, and uses an array sensor in which ultrasonic generating elements capable of oscillating ultrasonic waves, such as piezoelectric elements, are arranged in an array shape. By delaying the electrical signal for a predetermined time, the ultrasonic wave generated from each element forms a focal point in the subject, and furthermore, a pattern (delay pattern) that delays the electrical signal to each element is accelerated. This is a method in which the transmission / reception angle (refraction angle) of the ultrasonic wave into the object to be inspected, the focal position, and the like can be controlled by changing the above.

  The reason why this method is regarded as important is that a defect that is a reflection source is formed by forming a focal point at an angle or position at which the reflected wave can be received more strongly in the vicinity of the inside of the subject, particularly in a range where the defect is expected. This is because it can be easily detected.

  For example, in the inspection of welds, the occurrence of defects is predicted within the range of the heat effect due to welding, so that ultrasonic waves are irradiated from the oblique direction to this range, and the plate thickness or several times that By creating a delay pattern so as to form a focal point with a certain propagation distance, inspection can be performed efficiently. As an array sensor used in the phased array method, a matrix that allows a volume inspection by a linear array sensor that allows a cross-sectional inspection by arranging a large number of elements on a straight line or a curve, and a two-dimensional array of elements. Sensors are known.

JP 2010-276465 A

  When the sensor openings are enlarged while the total number of elements of these sensors is controlled to a controllable number, the distance (pitch) between the elements increases. When the pitch increases, in addition to the ultrasonic wave (main lobe) used for original flaw detection, ultrasonic waves (grating lobes) that become interference waves are generated. For example, the condition of the pitch at which no grating lobe is generated in the linear array sensor is p <λ / (1+ | sin θ |) where the pitch is p, the wavelength in the propagating object is λ, and the propagation direction is θ. It is known that the pitch is limited. It can be seen that in order to perform a wide range of flaw detection, it is necessary to substitute θ = 90 degrees into the above equation and make the pitch p to λ / 2 (half wavelength). At this time, the sensor opening is limited to about pN = λN / 2, where N is the maximum total number of elements that can be controlled, because the total number of elements of the sensor is limited by the apparatus. That is, since there is an upper limit on the sensor opening, there is an upper limit on the resolution and sensitivity of the sensor in the oblique direction.

An object of the present invention, without changing the total number of elements, it is possible to increase in size of the sensor opening, even using the sensor over-pitch, ultrasonography side that can be obtained with low inspection image noise in angle beam To provide a law .

( 1 ) To achieve the above object, the present invention provides an array sensor in which a plurality of ultrasonic oscillating elements that oscillate ultrasonic waves are arranged, and a slant angle incident on the surface to be inspected by giving a delay time to each element. to transmit ultrasonic waves to, to receive a reflected wave from said object, using the apparatus for inspecting the inspection target from the reflected wave, and sets a plurality of focus in the inspection range in the inspection target for each of the plurality of focus, and recording the reflected signals from the interior of the test object, respectively, the reflected signal obtained by thresholding the ultrasonic inspection method for inspecting and imaging the interior of the test object a is said as an array sensor, using an array sensor the pitch of the plurality of ultrasonic wave oscillating elements has greatly toward the oblique incident direction of the ultrasonic wave, the closer to the inspection area of said object Ultrasonic transmitter Wherein the pitch is far side to be larger than the pitch of the ultrasonic wave emitting element, in which the array sensors are located.
With this method, the sensor aperture can be enlarged without changing the total number of elements, and an inspection image with low noise can be obtained in oblique flaw detection even when an over-pitch sensor is used.

(2) In the above (1), preferably, as the array sensor, the pitch of the plurality of first ultrasonic transmission elements used for the first inspection range is in the oblique incident direction of the first ultrasonic wave. An array sensor in which the pitch of the plurality of second ultrasonic transmission elements used for the second inspection range is increased toward the oblique incidence direction of the second ultrasonic wave, A side closer to the second inspection range such that a pitch of the first ultrasonic transmission element closer to the first inspection range is larger than a pitch of the first ultrasonic transmission element closer to the first inspection range. The array sensor is arranged such that the pitch of the second ultrasonic transmission elements is larger than the pitch of the second ultrasonic transmission elements on the far side.

According to the present invention, the sensor aperture can be enlarged without changing the total number of elements, and an inspection image with low noise can be obtained in oblique flaw detection even when an over-pitch sensor is used.

It is explanatory drawing which shows the basic concept of the ultrasonic inspection method by one Embodiment of this invention. It is a perspective view which shows the basic concept of the ultrasonic inspection method by one Embodiment of this invention. It is a top view which shows the 1st structure of the array sensor by one Embodiment of this invention. It is explanatory drawing of the signal obtained by the ultrasonic inspection method by one Embodiment of this invention. It is a top view which shows the 2nd structure of the array sensor by one Embodiment of this invention. It is a block diagram which shows the structure of the ultrasonic inspection apparatus by one Embodiment of this invention. It is a flowchart which shows the content of the inspection method by the ultrasonic inspection apparatus by one Embodiment of this invention. It is explanatory drawing which shows the modification of the ultrasonic inspection method by one Embodiment of this invention. It is a top view which shows the structure of the array sensor by other embodiment of this invention. It is a block diagram which shows the structure of the ultrasonic inspection apparatus by other embodiment of this invention. It is a flowchart which shows the content of the inspection method with the ultrasonic inspection apparatus by other embodiment of this invention.

Hereinafter, the configuration and operation of an ultrasonic inspection apparatus according to an embodiment of the present invention will be described with reference to FIGS.
First, the basic concept of the ultrasonic inspection method according to the present embodiment will be described with reference to FIGS.
FIG. 1 is an explanatory diagram showing the basic concept of an ultrasonic inspection method according to an embodiment of the present invention. 1A is a cross-sectional view, and FIG. 1B is a plan view. FIG. 2 is a perspective view showing the basic concept of the ultrasonic inspection method according to one embodiment of the present invention. FIG. 3 is a plan view showing a first configuration of the array sensor according to the embodiment of the present invention. FIG. 4 is an explanatory diagram of signals obtained by the ultrasonic inspection method according to the embodiment of the present invention. FIG. 5 is a plan view showing a second configuration of the array sensor according to the embodiment of the present invention. 1 to 5, the same reference numerals indicate the same parts.

  As shown in FIG. 1, the subject 10 has a structure in which a first base material MM1 and a second base material MM2 are welded together by a welded portion WP. Such a subject is an example of an examination object that should consider the examination range.

  Since it is affected by heat in the vicinity of the welded portion WP, it is more necessary to inspect than the base materials MM1 and MM2. When the array sensor S is used to inspect the welded portion WP and the vicinity thereof, the element arrangement direction X1 of the array sensor S is inspected at an angle orthogonal to the weld line Y1. The array sensor S detects the assumed defect DE by oblique flaw detection that outputs ultrasonic waves obliquely with respect to the surface of the subject. In this case, when viewed from the array sensor S, the base material (here, the first base material MM1) in the direction opposite to the welded portion WP is no longer affected by heat and the need for inspection is low. Many.

  When the location to be inspected is known in advance (when the position of the assumed defect DE is known in advance), the ultrasonic wave generating elements constituting the array sensor S are oscillated from an element portion far from the inspection site. The ultrasonic wave has a small contribution to focusing because of the directivity per element.

  Therefore, as shown in FIG. 2, when the array sensor S used in the present embodiment is composed of a plurality of ultrasonic generation elements E1,..., En, a place close to the inspection range Ad (such as the ultrasonic generation element E1). ) Has a large pitch, and an array sensor S having a small pitch is used in places far from the inspection range (such as the ultrasonic wave generating element En).

Considering inspection region of the object being examined, by using the array sensor S which eliminates the symmetry element arrangement, it is possible to improve the inspection performance of bevel orientation in view of the inspection range of the inspection Target.

FIG. 3 shows a configuration when the array sensor S is a linear array sensor. Array sensor of the present embodiment is not a size of the element is constant, has the small element and larger elements, towards a fixed direction and are arranged elements such that the larger elements from a small element.

  The array sensor S is composed of n ultrasonic wave generating elements E1, E2,..., E (n−1), En. Here, the width of each element in the ultrasonic wave propagation direction X1 of each ultrasonic wave generation element E1, E2,..., E (n-1), En is We1, We2, ..., We (n-1), Wen, respectively. Then, the width of the element is gradually reduced from one end side to the other end side, that is, We1> We2>...> We (n-1)> Wen.

  In addition, the gaps g of the respective elements should be as narrow as possible, so that they are all equal. In this case, if the pitches, which are the distances between adjacent elements, are Pe1-e2, Pe2-e3,..., Pe (n-2) -e (n-1), Pe (n-1) -en, respectively. , So that the pitch of the elements gradually decreases from one end side to the other end side, that is, Pe1-e2> Pe2-e3>,...> Pe (n-2) -e (n-1 )> Pe (n-1) -en.

  Further, when a line segment passing through the center O of the sensor and orthogonal to the propagation direction X1 is nc, the number of elements E existing in the direction of the propagation direction X1 with respect to the line segment nc is opposite to the propagation direction X1. Less than the number of elements E present.

  Next, with reference to FIG. 4, the intensity of the ultrasonic wave generated by the present embodiment will be described by comparing the intensity of the ultrasonic wave generated by the sensor of the conventional configuration.

  FIG. 4A shows a cross-sectional view when the sensor S is arranged on the subject 10. An ultrasonic wave is output from the array sensor S in the oblique direction toward the focusing point Pf. Here, the center position of the array sensor S is assumed to be O.

  FIG. 4B shows a simulation result of the effect of the present embodiment.

  The solid line in FIG. 4B illustrates the intensity of the ultrasonic wave generated by the array sensor S according to the present embodiment with O being the center position of the sensor S as shown in FIG. An ultrasonic wave (main lobe ML) used for original flaw detection is generated in the vicinity of the focal point Pf, and an ultrasonic wave (grating lobe GL) that becomes an interference wave on the opposite side of the central point O from the focal point Pf. ) Occurs.

  In addition, the alternate long and short dash line in FIG. 4B indicates the strength of the main lobe and the grating lobe when using a conventional array sensor (each element has the same width and the same pitch).

  For example, in the case of a linear array sensor in which elements of 3 MHz are arranged uniformly, the pitch needs to be 1.1 mm or less in order to focus the sound without generating a grating lobe in the direction of 45 degrees in the steel material. If an array sensor is created with an over pitch of 1.5 mm pitch, for example, a grating lobe GL having the same strength as the main lobe ML at the converging point Pf is generated, as shown by a one-dot chain line in FIG. To do.

  On the other hand, an array sensor composed of elements that are changed by 0.1 mm from 2.0 mm to 1.1 mm with the same number of elements and the same sensor opening area, that is, an average 1.5 mm pitch, is used. For example, as indicated by a solid line in FIG. 4B, the intensity of the grating lobe GL can be reduced by about 1/3 of the intensity of the main lobe ML.

  This average pitch is made up of conventional ultrasonic transmission elements having the same pitch, and is equal to the pitch of an array sensor in which grating lobes are generated with the same opening area and the same number of elements.

FIG. 5 shows a configuration when the array sensor S ′ is a matrix array sensor. Array sensor of the present embodiment is not a size of the element is constant, has the small element and larger elements, towards a fixed direction and are arranged elements such that the larger elements El from a small element Es .

  Assuming that a line segment passing through the center O of the sensor S ′ and orthogonal to the first direction is nc, the number of elements E existing in the first direction with respect to this line segment nc (from the line segment nc to the line segment n1) The number of elements in between) is smaller than the number of elements E existing in the direction opposite to the first direction (number of elements between the line segment nc and the line segment n2).

  Further, when a line segment that passes through the center O of the sensor S ′ and is orthogonal to the second direction orthogonal to the first direction is mc, the number of elements E existing in the second direction with respect to this line segment mc. (The number of elements between the line segment mc and the line segment m1) is smaller than the number of elements E existing in the direction opposite to the first direction (the number of elements between the line segment mc and the line segment m2). Become.

  Here, the ultrasonic wave propagation direction X1 is a direction of 45 degrees with respect to the first and second directions. The elements are arranged so that the small element Es becomes the large element El also in the ultrasonic wave propagation direction X1.

  The linear array sensor shown in FIG. 3 and the matrix sensor shown in FIG. 5 are flat, but other than that, the sensor contact surface has a gentle curvature, such as a convex sensor. It can also be applied to what you have.

Next, the configuration of the ultrasonic inspection apparatus according to the present embodiment will be described with reference to FIG.
FIG. 6 is a block diagram showing a configuration of an ultrasonic inspection apparatus according to an embodiment of the present invention.

  The array sensor S has the configuration shown in FIGS. 3 and 5, and is directly or indirectly applied to the surface of the subject 10, and a voltage pulse drive signal is sent from the inspection apparatus body to the ultrasonic sensor. It is done.

A Reisensa S is the cable, which is electrically connected to the main testing device. The inspection apparatus main body includes a transmission / reception unit 102, a control unit 103, and a display unit 104. Details of these will be described later. The drive signal from the transmission / reception unit 102 is transmitted to the piezoelectric element via the electrode of the ultrasonic sensor S and converted into ultrasonic waves. The ultrasonic wave transmitted to the subject 10 propagates in the subject, is reflected at a part having a different acoustic impedance such as a boundary or a different part, and a part of the reflected wave is received by the piezoelectric element of the array sensor S. Here, the reflected wave is again converted into an electric signal by the piezoelectric element and input to the inspection apparatus main body. The input received signal is signal-processed by the control unit 103 of the inspection apparatus body, and is output to the display unit 104 as, for example, a tomographic image.

  As the subject 10, an inspection apparatus can be used for an organic structure such as a living body or an inorganic structure such as a building. Therefore, the ultrasonic sensor according to the present embodiment can be used particularly in various medical fields for performing ultrasonic diagnosis of a subject such as a human body and industrial fields for the purpose of inspecting materials and structures.

  As shown in FIG. 6, the ultrasonic inspection apparatus according to the present embodiment is installed in a subject 10 to be inspected, an array sensor S including an ultrasonic oscillation element that transmits and receives ultrasonic waves to and from the inspection target, and an array A pulsar 102A that gives a delay time to the sensor S and transmits the ultrasonic wave, a transmission / reception unit 102 including a receiver 102 that converts the received ultrasonic wave into an analog-digital signal to obtain a reception signal, and a delay time at the time of transmission / reception A control circuit 103D, a reception signal adding circuit 103Z, and a control unit 103 including a control / processing computer 103A for controlling and recording these received signals and processing, and an element setting input for inputting and displaying various settings The screen 104A and a display unit 104 having a display screen 104Z for displaying a received signal and an inspection image are configured.

  Next, each operation will be described.

  First, when the control / processing computer 103A transmits / receives an ultrasonic wave and records a reflected signal from the inspection object, the ultrasonic wave for focusing / transmitting / receiving the ultrasonic wave through the delay control circuit 103D. A delay time to the oscillation element is given. The transmission delay circuit 102B that has received the transmission signal and the delay time transmits the transmission signal to the transmission amplifier 102E. The transmission amplifier 102E amplifies the transmission signal and applies a driving voltage for transmitting ultrasonic waves to the ultrasonic oscillation elements of the array sensor. The plurality of ultrasonic oscillation elements that have received the amplified transmission signals transmit ultrasonic waves with a time delay corresponding to the delay time due to the piezoelectric effect. When focusing ultrasonic waves, the delay time corresponds to the geometric distance from each ultrasonic oscillation element to the focusing position, that is, the distance considering the ultrasonic velocity of sound in each medium and refraction at the boundary surface. A voltage is applied to each ultrasonic oscillating element, and the ultrasonic wave is focused and transmitted at a predetermined position in the inspection range.

  On the other hand, when the ultrasonic signal is received by the receiver 102Z and the electrical signal generated by the piezoelectric effect is processed, the received signal is amplified by the reception amplifier 102Y corresponding to the ultrasonic wave received by each of the ultrasonic oscillation elements 101A. Then, the analog-to-digital converter 102X converts the received signal that has been analog into a digital signal. The received signal converted into the digital signal and selected is stored in the delay memory 102V. At this time, the delay memory 102V gives the delay time transmitted from the delay control circuit 103D to the received signal from each ultrasonic oscillation element when focusing and receiving the ultrasonic wave as in the case of ultrasonic transmission. Then, it is stored in the storage unit 103B. The addition is performed by the adder circuit 103Z and sent to the control / processing computer 103A. When image processing is performed by the processing device 103 </ b> C, a threshold value or the like is determined, and only a crest value having an intensity equal to or greater than the threshold value is output to the image and displayed on the display unit 104.

Next, the inspection method using the ultrasonic inspection apparatus according to the present embodiment will be described with reference to FIG.
FIG. 7 is a flowchart showing the contents of the inspection method by the ultrasonic inspection apparatus according to the embodiment of the present invention.

  Here, a case where a plurality of focal points F (i) are set in the inspection range and an ultrasonic inspection is performed will be described.

  First, as initial settings for the array sensor, element information, material information, and the like of the ultrasonic oscillation elements constituting the array sensor are input (step S101). Further, based on the information given in step S101, a delay time and a sensor center position serving as a reference for image display are set for these ultrasonic oscillators (step S102). In general, as shown in FIGS. 3 and 5, the center O of the ultrasonic oscillation element is set as the sensor center.

  Next, it is set to which examination range of the subject the ultrasonic wave is focused (step S103). A focus F (i) is set for the inspection range given in step S103, and a delay time is set (step S104). This delay time setting method uses the arrival time from the sensor center to the focus F (i) as a reference, and the arrival time to the focus F (i) based on the element information at the center position of each element given in step S101. Can be set by asking.

  Then, transmission and reception of the ultrasonic waves set as described above are performed (step S105), and data (reflection data) for the focal point F (i) is recorded (step S106). Further, it is determined whether or not the data recording in the entire area has been completed (step S107). If the recording has not been completed (NO), the process proceeds to the next focus F (i + 1), and the ultrasonic transmission / reception is again performed. The reception and recording of the reflection data are sequentially repeated until the recording of the reflection data in all the inspection areas is completed.

  If all the processing has been completed (YES), a map of pixels and pixel values is created (step S108), the image is displayed (step S109), the necessity of image processing is confirmed, and there is no need for image processing. If so, the process ends (step S110).

  When artifacts appear and image processing is necessary, the intensity of the grating lobe can be reduced according to the present invention as shown in FIG. 3. For example, image processing can be performed by providing a threshold value. (Step S111), and the process ends.

Next, a modification of the ultrasonic inspection method according to the present embodiment will be described with reference to FIG.
FIG. 8 is an explanatory view showing a modification of the ultrasonic inspection method according to one embodiment of the present invention. In addition, the same code | symbol as FIGS. 1-5 has shown the same part.

  In the example shown in FIG. 1, the array sensor S is directly installed on the surface of the subject 10. However, as shown in FIG. 8, a shoe SH is arranged between the array sensor S and the subject 10. It may be.

  This configuration is effective when it is desired to reduce the angle of the ultrasonic wave that is obliquely incident on the subject from the surface of the subject and to increase the intensity of the incident ultrasonic wave.

  As described above, according to the present embodiment, the sensor aperture can be enlarged without changing the total number of elements, and an inspection image with low noise can be obtained in oblique flaw detection even when an over-pitch sensor is used. Will be able to.

Next, the configuration and operation of an ultrasonic inspection apparatus according to another embodiment of the present invention will be described with reference to FIGS.
First, the configuration of the array sensor according to the present embodiment will be described with reference to FIG.
FIG. 9 is a plan view showing a configuration of an array sensor according to another embodiment of the present invention.

  The array sensor S ″ shown in FIG. 9 is an array sensor having a part of the structure shown in FIG.

  FIG. 9A shows a plan view and FIG. 9B shows a cross-sectional view. The array sensor S ″ of the present embodiment has a bilaterally symmetric configuration with the line segment nc1 as the center. A large element Es increases from the line segment nc1 toward the line segment n1 on the left end side. Elements El are arranged, and small elements Es to large elements El are arranged in the direction from the line segment nc1 to the line segment n2 on the right end side.

  The array sensor S ″ is also used in the following manner. That is, flaw detection in the oblique direction is performed by using elements arranged on both sides. As nc2, flaw detection is performed using an element disposed between the line segment nc1 and the line segment n1, and in the right oblique direction, the center of the sensor is the line segment nc3 and the line segment nc1 is separated from the line segment n2. Flaw detection is performed using the element to be arranged.

  In the vertical direction, flaw detection is performed using the entire element between the line segment n1 and the line segment n2, or using only the element at the center between the line segment nc2 and the line segment nc3. If the entire device is used, it is possible to detect a deep portion by increasing the aperture diameter. If only the central part is used, it is possible to detect a shallow part. In these cases, the sensor center is the line segment nc1.

  In addition, the sensor contact surface may have a curvature like a convex.

Next, the configuration of the ultrasonic inspection apparatus according to the present embodiment will be described with reference to FIG.
FIG. 10 is a block diagram showing a configuration of an ultrasonic inspection apparatus according to another embodiment of the present invention. The same reference numerals as those in FIG. 6 denote the same parts.

  In this example, in addition to the configuration of FIG. 6, a storage unit 103F for use element range patterns and use element range selection units 102F and 102W are provided on the transmission side and reception side.

  The use element pattern is stored in advance in the storage unit 103F, and in accordance with this pattern, the use element range selection unit 102F and the use element range selection unit 102W select whether to transmit a signal by turning the switch ON / OFF. .

  In addition, in order to display an image drawn in each use element range at a time, the processing device 103C is newly provided with a function of performing an image averaging process.

Next, the inspection method using the ultrasonic inspection apparatus according to the present embodiment will be described with reference to FIG.
FIG. 11 is a flowchart showing the contents of an inspection method using an ultrasonic inspection apparatus according to another embodiment of the present invention. In addition, the same step as FIG. 7 has shown the same content.

  In this example, a used element range pattern setting step S200 is provided, and a process for selecting a used element range and determining its element center is added. Moreover, step S201 which switches this use element range pattern is provided. Furthermore, in order to display the image drawn in each use element range at once, the function which carries out the addition average process of an image is given to step S111.

  As described above, according to the present embodiment, the sensor aperture can be enlarged without changing the total number of elements, and an inspection image with low noise can be obtained in oblique flaw detection even when an over-pitch sensor is used. Will be able to.

  Further, by selecting an element to be used, ultrasonic flaw detection according to a flaw detection location or the like becomes possible.

Claims (2)

An array sensor in which a plurality of ultrasonic oscillation elements that oscillate ultrasonic waves are arranged ;
An apparatus for giving a delay time to each element and transmitting ultrasonic waves so as to be obliquely incident on the surface of the inspection object, receiving a reflected wave from the inspection object, and inspecting the inspection object from the reflected wave using,
Setting a plurality of focus in the inspection range in the inspection Target for each of the plurality of focus, and recording the reflected signals from the interior of the test object, respectively, the reflected signal obtained by threshold processing, the An ultrasonic inspection method for performing an inspection by imaging the inside of an inspection object,
As the array sensor, using an array sensor the pitch of the plurality of ultrasonic wave oscillating elements has greatly toward the oblique incident direction of the ultrasonic wave,
The ultrasonic inspection characterized in that the array sensor is arranged so that the pitch of the ultrasonic transmission elements on the side closer to the inspection range of the inspection object is larger than the pitch of the ultrasonic transmission elements on the far side. Method. The ultrasonic inspection method according to claim 1,
As the array sensor, the pitch of the plurality of first ultrasonic transmission elements used for the first inspection range is larger in the oblique incident direction of the first ultrasonic wave, and the second inspection range Using an array sensor in which the pitch of the plurality of second ultrasonic transmission elements used is increased toward the oblique incident direction of the second ultrasonic wave,
The pitch of the first ultrasonic transmission element on the side closer to the first inspection range is larger than the pitch of the first ultrasonic transmission element on the far side and close to the second inspection range. An ultrasonic inspection method, wherein the array sensor is arranged so that a pitch of the second ultrasonic transmission element on the side is larger than a pitch of the second ultrasonic transmission element on the far side.

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