JP2020201065A - Ultrasonic inspection device - Google Patents

Abstract

To provide an ultrasonic inspection device that can perform a wide-range flaw in a short time, and can achieve improvement in detection sensitivity.SOLUTION: An ultrasonic inspection device comprises: an array probe 2 that has a plurality of piezoelectric elements 1 arranged in line; a wedge 3 that supports the array probe 2; and a control device 4 that controls a transmission timing of a plurality of ultrasonic sound waves from the plurality of piezoelectric elements 1, and executes a sector scan varying a propagation direction of a synthetic wave composed of the plurality of ultrasonic sound waves. The synthetic wave enters a surface of an analyte 20 via the wedge 3, undergoes a mode conversion to a surface wave, and the surface wave propagates along the surface of the analyte 20. The wedge 3 is configured in such a manner that a relative angle β between one side on a piezoelectric element 1 side and one side on an analyte 20 side thereof in each cross section of the wedge 3 vertical to an array direction of the piezoelectric element 1 varies in accordance with a position of each cross section in the array direction of the piezoelectric element 1 so that an incidence angle of the synthetic wave is a prescribed value with respect to the surface of the analyte 20 regardless of the propagation direction of the synthetic wave.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ultrasonic inspection apparatus that detects flaws on the surface layer of a subject using surface waves.

An ultrasonic inspection device that detects a subject using ultrasonic waves is known. In addition to volume waves (longitudinal waves and transverse waves) propagating in the volume of a subject, ultrasonic waves include surface waves (Rayleigh waves) propagating along the surface of the subject. The surface wave propagates along the surface of the subject even when the surface of the subject is a curved surface, and its sound velocity is about 90% of the transverse wave sound velocity.

Non-Patent Document 1 discloses an ultrasonic inspection apparatus that detects flaws on the surface layer of a subject using surface waves. The ultrasonic inspection apparatus of Non-Patent Document 1 supports an array probe having a plurality of piezoelectric elements arranged in a row and an array probe so that the plurality of piezoelectric elements are inclined with respect to the surface of a subject. It includes a wedge and a control device that controls transmission timing of a plurality of ultrasonic waves from a plurality of piezoelectric elements to perform sector scanning that changes the propagation direction of a composite wave composed of the plurality of ultrasonic waves.

In this ultrasonic inspection device, a synthetic wave is incident on the surface of a subject through a wedge and mode-converted into a surface wave, and the surface wave propagates along the surface of the subject. If there is a flaw on the surface of the subject, the reflected wave reflected by the flaw is received by the array probe through the wedge. As a result, scratches on the surface layer of the subject are detected. By executing the sector scan, it is possible to perform a wide range of flaw detection in a short time as compared with the case of performing a mechanical scan in which the probe is moved.

Yoshikazu Ohara, 1 other person, Material of the High Temperature Strength Division Committee of the Japan Society of Materials Science, "Ultrasonic non-destructive measurement using surface waves", [online], Tohoku University, [Search on May 24, 2019], Internet <URL : http://www.material.tohoku.ac.jp/~hyoka/nonlinear04.pdf ＞

However, in the above-mentioned conventional technique, the incident angle of the synthetic wave with respect to the surface of the subject changes according to the propagation direction of the synthetic wave. Depending on the propagation direction of the composite wave, the incident angle of the composite wave is far from the critical angle of the surface wave, so that the intensity of the surface wave is reduced and the detection sensitivity is reduced. In addition, since the intensity of surface waves varies, the detection sensitivity also varies.

The present invention has been made in view of the above matters, and an object of the present invention is to provide an ultrasonic inspection apparatus capable of performing a wide range of flaw detection in a short time and improving the detection sensitivity. It is in.

In order to achieve the above object, the present invention comprises an array probe having a plurality of piezoelectric elements arranged in a row and the array probe so that the plurality of piezoelectric elements are inclined with respect to the surface of a subject. A wedge that supports the above, and a control device that controls the transmission timing of a plurality of ultrasonic waves from the plurality of piezoelectric elements to perform sector scanning that changes the propagation direction of the composite wave composed of the plurality of ultrasonic waves. In an ultrasonic inspection device in which the synthetic wave is incident on the surface of the subject through the wedge and mode-converted into a surface wave, and the surface wave propagates along the surface of the subject, the wedge is the said. Regardless of the propagation direction of the composite wave, with one side of the wedge on each cross section perpendicular to the arrangement direction of the piezoelectric element so that the incident angle of the composite wave with respect to the surface of the subject becomes a predetermined value. The relative angle with one side of the subject side changes according to the position of each cross section in the arrangement direction of the piezoelectric element.

According to the present invention, a wide range of flaw detection can be performed in a short time, and the detection sensitivity can be improved.

It is a figure which shows the structure of the ultrasonic inspection apparatus in one Embodiment of this invention. It is a figure which shows an example of the display screen of the display device in one Embodiment of this invention. It is a figure which shows another example of the display screen of the display device in one Embodiment of this invention. It is a top view which shows the structure of the wedge in one Embodiment of this invention. It is sectional drawing which shows the structure of the wedge in one Embodiment of this invention. It is sectional drawing which shows the structure of the wedge in one Embodiment of this invention. It is a top view which shows the arrangement of the array probe and the wedge in the prior art, and also shows the incident point of the synthetic wave incident on the surface of a subject. It is sectional drawing which shows the incident angle of the synthetic wave propagating in the normal direction of a piezoelectric element and incident on the surface of a subject in the prior art. It is sectional drawing which shows the incident angle of the synthetic wave propagating in the direction inclined with respect to the normal direction of a piezoelectric element in the prior art and incident on the surface of a subject. It is a top view which shows the arrangement of the array probe and the wedge in one Embodiment of this invention, and shows the incident point of the synthetic wave which is incident on the surface of a subject. It is sectional drawing which shows the incident angle of the synthetic wave propagating in the normal direction of a piezoelectric element and incident on the surface of a subject in one Embodiment of this invention. It is sectional drawing which shows the incident angle of the synthetic wave propagating in the direction inclined with respect to the normal direction of a piezoelectric element and incident on the surface of a subject in one Embodiment of this invention. It is a perspective view which shows the synthetic wave propagation direction vector in a wedge and a liquid, and the propagation direction vector of a surface wave in a subject in one Embodiment of this invention. It is sectional drawing which shows the normal vector of the bottom surface of the wedge by the position of the emission point of the synthetic wave in one Embodiment of this invention together with the propagation direction vector of a synthetic wave in a wedge and a liquid. It is a figure which shows the specific example of the relationship between the position of each cross section of a wedge and the relative angle of the upper side and the lower side in each cross section in one Embodiment of this invention. It is a figure which shows the specific example of the relationship between the propagation azimuth of a synthetic wave in a wedge and the propagation azimuth of a surface wave in a subject in one Embodiment of this invention.

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a configuration of an ultrasonic inspection device according to the present embodiment.

The ultrasonic inspection apparatus of this embodiment uses surface waves to detect flaws on the surface layer of a subject 20 (specifically, a solid such as a steel material). This ultrasonic inspection device supports an array probe 2 having a plurality of piezoelectric elements 1 arranged in a row and an array probe 2 so that the plurality of piezoelectric elements 1 are inclined with respect to the surface of the subject 20. A wedge 3, a control device 4, a computer 5, and a display device 6 are provided. The computer 5 is composed of a computer or the like, and the display device 6 is composed of a display or the like.

The plurality of piezoelectric elements 1 oscillate by a plurality of drive signals from the pulsar 7 of the control device 4 described later, transmit a plurality of ultrasonic waves, and combine them into a synthesized wave. This synthetic wave enters the surface of the subject 20 via the wedge 3 and modifies the mode into a surface wave, and the surface wave propagates along the surface of the subject 20. The wedge 3 is made of a resin material such as acrylic, polystyrene, or polyimide, and the space between the wedge 3 and the surface of the subject 20 is filled with a liquid such as water.

When the flaw 21 is present on the surface layer of the subject 20 as shown in FIG. 1, the reflected wave reflected by the flaw 21 is received by the piezoelectric element 1 via the wedge 3. The piezoelectric element 1 converts the received reflected wave into a waveform signal and outputs it to the receiver 8 of the control device 4 described later.

The control device 4 includes a pulsar 7, a receiver 8, a delay control unit 9, and a data recording unit 10. The delay control unit 9 is composed of a processor or the like that executes processing according to a program, and the data recording unit 10 is composed of a memory or the like. The delay control unit 9 outputs a delay pattern corresponding to the propagation direction of the composite wave to the pulsar 7 and the receiver 8 in response to a command from the computer 5.

The pulsar 7 controls the output timing of a plurality of drive signals to be output to the plurality of piezoelectric elements 1 based on the delay pattern. As a result, sector scanning that changes the propagation direction of the composite wave is executed.

The receiver 8 adjusts the input timing of the waveform signal from the piezoelectric element 1 based on the delay pattern, and synthesizes the waveform signal. As a result, the propagation direction of the reflected wave is adjusted so as to correspond to the propagation direction of the composite wave.

The waveform signal synthesized by the receiver is converted into waveform data by an analog-digital converter (not shown) and recorded by the data recording unit 10. The data recording unit 10 records waveform data in association with a delay pattern (or information on propagation directions of synthetic waves and surface waves corresponding thereto). The waveform data consists of a combination of reception time and signal strength.

The computer 5 creates a flaw detection image based on the waveform data recorded by the data recording unit 10 and the information on the propagation directions of the synthetic wave and the surface wave corresponding thereto. Specifically, the reflection position is virtualized based on the information on the propagation direction of the composite wave and the surface wave and the reception time, the pixel position is selected according to the reflection position, and the hue and color saturation of the pixel are selected according to the signal intensity. Create a flaw detection image by varying the degree or brightness.

The display device 6 displays the waveform data recorded by the data recording unit 10, for example, as shown in FIG. This allows the inspector to evaluate the presence and position of scratches. Further, the display device 6 displays the flaw detection image created by the computer 5, for example, as shown in FIG. This allows the inspector to evaluate the size and properties of the flaw.

In the present embodiment, by executing sector scanning (that is, electronic scanning), a wide range of flaw detection can be performed in a short time as compared with the case of performing mechanical scanning in which the probe is moved. That is, the inspection range 22 shown in FIG. 1, for example, can be detected without moving the array probe 2.

Here, in the present embodiment, the center of the plurality of piezoelectric elements 1 is set as the virtual starting point P of the composite wave (see FIGS. 4, 5 (a) and 6 described later), and the virtual starting point P of this composite wave is set. through the axis extending in the array direction of the piezoelectric element 1 is defined as the X ₁ axis (see FIGS. 4 and 6 below) and. An axis extending in the normal direction of the piezoelectric element 1 through the virtual origin P of the composite wave is defined as Z ₁ axis (FIG later. 5 (a) and FIG. 6). The sector scan, which varying along the propagation direction of the composite wave in the wedge 3 in the scanning plane (X ₁ -Z ₁ plane), an axis perpendicular to the scanning plane Y ₁ axis (FIG later 4 and (See FIG. 5 (a)).

Also defines the surface and the Z ₁ axis origin intersections intersects O of the object 20 (see FIG. 1 and described later Figure 13). Is defined as X ₂ axis an axis parallel to the array direction of the piezoelectric element 1 through the origin O on the surface of the subject 20 (see FIG. 1 and described later Figure 13). (In other words, X ₂ axis) array direction of the piezoelectric element 1 through the origin O on the surface of the object 20 perpendicular axis to define a Y ₂ axis (see FIG. 13 of FIG. 1 and described later). (In other _words, X 2 -Y ₂ plane) surface of the subject 20 through the origin O and perpendicular axis to define a _{Z 2} axes (see FIG. 13 of FIG. 1 and described later).

Next, the structure of the wedge 3, which is the main part of the present embodiment, will be described.

FIG. 4 is a top view showing the structure of the wedge 3 in the present embodiment. 5 (a), 5 (b), 5 (c), and 6 are cross-sectional views showing the structure of the wedge 3 in the present embodiment. 5A is a cross-sectional view taken along the middle cross section AA of FIG. 4, FIG. 5B is a cross-sectional view taken along the middle cross section BB of FIG. 4, and FIG. 5C is a cross section CC of FIG. FIG. 6 is a cross-sectional view taken along the line DD in FIG.

The wedge 3 of the present embodiment has a flat surface supporting the array probe 2 (hereinafter, appropriately referred to as an upper surface) and a special curved surface (hereinafter, appropriately referred to as an upper surface) formed on the opposite side (that is, the subject 20 side). has a) and that the bottom surface, in other words the array direction of the piezoelectric element 1 (, X ₁ axis) piezoelectric element 1 side of the side in perpendicular each cross section (hereinafter, appropriately referred to the upper side) and the subject 20 side The relative angle with one side (hereinafter, appropriately referred to as the bottom side) changes according to the position of each cross section in the arrangement direction of the piezoelectric element 1.

More specifically, among the cross sections of the wedges 3 perpendicular to the arrangement direction of the piezoelectric elements 1, the cross section located at the center of the plurality of piezoelectric elements 1 (in other words, X ₁ = 0) is defined as the reference cross section. In the form, as shown in FIG. 5A, the relative angle β ₀ between the upper side E ₀ and the bottom side F ₀ in the reference cross section is zero.

Further, if the cross section of the wedge 3 perpendicular to the arrangement direction of the piezoelectric elements 1 is defined as another cross section different from the reference cross section, in the present embodiment, the relative angle between the upper side and the bottom side in the other cross section is (in other words, the absolute value of X ₁ coordinates) distance from the reference plane to the other cross-section increases, increases. That is, the relative angle β ₁ between the upper side E ₁ and the bottom side F ₁ in the other cross section shown in FIG. 5 (b) is larger than the relative angle β ₀ . The relative angle β ₂ between the upper side E ₂ and the bottom side F ₂ in the other cross section shown in FIG. 5 (c) is larger than the relative angle β ₁ . The fact that the relative angle between the upper side and the bottom side of the cross section of the wedge 3 is increased means that the relative angle between the lower side of the cross section of the wedge 3 and the surface of the subject 20 is reduced.

The wedge 3 has a structure that is line-symmetrical with respect to the reference cross section. Further, as shown in Figure 6, in the cross section of the wedge 3 comprising X ₁ axis and Z ₁ axis, the thickness of the wedge 3 d (hereinafter, referred to as a reference thickness) is constant.

In the present embodiment, due to the structure of the wedge 3 described above, the incident angle γ of the synthetic wave with respect to the surface of the subject 20 is a predetermined value (specifically, the critical angle γ _R of the surface wave is set regardless of the propagation direction of the synthetic wave. Although it is preferable, it may be a predetermined value set within the range of the critical angle γ _R of the surface wave ± the directional angle of the composite wave). As a result, the detection sensitivity can be improved. This effect will be described in comparison with the prior art described in Non-Patent Document 1.

FIG. 7 is a plan view showing the arrangement of the array probe 2 and the wedge 100 in the prior art, and showing the incident point of the synthetic wave incident on the surface of the subject 20. Figure 8 is a sectional view according to FIG. 7 interrupted surfaces VIII-VIII, (in other words, Z ₁ direction) normal direction of the piezoelectric element 1 the incident angle of the synthetic wave incident propagating on the surface of the subject 20 Is shown. FIG. 9 is a cross-sectional view taken along the cross section IX-IX in FIG. 7, showing the incident angle of the synthetic wave propagating in the direction inclined with respect to the normal direction of the piezoelectric element 1 and incident on the surface of the subject 20. FIG. 10 is a plan view showing the arrangement of the array probe 2 and the wedge 3 in the present embodiment and showing the incident point of the synthetic wave incident on the surface of the subject 20. FIG. 11 is a cross-sectional view taken along the cross section XI-XI in FIG. 10, showing the incident angle of the synthetic wave propagating in the normal direction of the piezoelectric element 1 and incident on the surface of the subject 20. FIG. 12 is a cross-sectional view taken along the cross section XII-XII in FIG. 10, showing the incident angle of the synthetic wave propagating in the direction inclined with respect to the normal direction of the piezoelectric element 1 and incident on the surface of the subject 20. In FIGS. 7 and 10, the piezoelectric element 1 is not shown for convenience. Further, in FIGS. 9 and 12, for convenience, the piezoelectric element 1, the array probe 2, and the wedge 3 are not shown. Further, in FIG. 12, for convenience, the virtual starting point P of the composite wave and the composite wave in the wedge 3 are projected onto the cross section.

In the prior art, the wedge 100 has a plane (upper surface) that supports the array probe 2 so that the piezoelectric element 1 is tilted with respect to the surface of the subject 20 at an inclination angle α, and a plane (upper surface) formed on the opposite side thereof. It has a bottom surface). Then, (in other words, X ₁ axis) array direction of the piezoelectric element 1 relative angle of the piezoelectric element 1 side of the side (the upper side) and the object 20 side of one side (lower side) in each cross-section perpendicular wedge 100 is, It is the same regardless of the position of each cross section in the arrangement direction of the piezoelectric elements 1. Further, the bottom surface of the wedge 100 is in contact with the surface of the subject 20. Therefore, as shown in Figure 7, the incident point _G 1, _{G 2} of the composite wave to the surface of the object 20, the scanning surface and the surface of the object 20 _(X 2 -Y ₂ plane) _{(X 1} -Z 1 plane ) is located on the straight line _{(X 2} axis) intersecting.

In the prior art, as shown in FIG. 8, when the propagation direction of the synthetic wave is the normal direction of the piezoelectric element 1, the incident angle γ ₁ of the synthetic wave with respect to the surface of the subject 20 is equal to the inclination angle α described above. Become. If the incident angle γ ₁ of the composite wave is the critical angle γ _R of the surface wave, the intensity of the surface wave can be increased.

However, as shown in FIG. 9, when the propagation direction of the composite wave is inclined with respect to the normal direction of the piezoelectric element 1, the incident angle γ ₂ of the composite wave with respect to the surface of the subject 20 is the incident angle γ _1. Become larger. This is the same as the case where the propagation distance of the synthetic wave in the wedge 100 in the direction perpendicular to the surface of the subject 20 is the same as in the former case, but the propagation of the synthetic wave in the wedge 100 in the direction parallel to the surface of the subject 20. This is because the distance is longer than in the former case (I ₂ > I ₁ as shown in the figure). Then, depending on the propagation direction of the composite wave, the incident angle γ ₂ of the composite wave is largely separated from the critical angle γ _{R of} the surface wave, so that the intensity of the surface wave is reduced and the detection sensitivity is reduced. In addition, since the intensity of surface waves varies, the detection sensitivity also varies.

On the other hand, in the present embodiment, the wedge 3 is on a flat surface (upper surface) that supports the array probe 2 so that the piezoelectric element 1 is inclined with respect to the surface of the subject 20 at an inclination angle α, and on the opposite side thereof. It has a special curved surface (bottom surface) formed. Then, the relative angle between one side (upper side) on the piezoelectric element 1 side and one side (lower side) on the subject 20 side in each cross section of the wedge 100 perpendicular to the arrangement direction of the piezoelectric element 1 is each in the arrangement direction of the piezoelectric element 1. It changes according to the position of the cross section. Further, the space between the bottom surface of the wedge 3 and the surface of the subject 20 is filled with a liquid. Therefore, as shown in Figure 10, the incident point _G 3, _{G 4} of the composite wave to the surface of the object 20, the scanning surface and the surface of the object 20 _(X 2 -Y ₂ plane) _{(X 1} -Z 1 plane ) is not on a straight line (X ₂ axis) crossing, located on a circular arc.

In the present embodiment, the relative angle between the top side and the bottom side in the reference cross section of the wedge 3 is zero. Therefore, as shown in Figure 11, if the propagation direction of the composite wave is a normal direction of the piezoelectric element 1, the composite wave is not refracted when emitted from the emitting point H ₃ of the bottom of the wedge 3. Then, the incident angle γ ₃ of the synthetic wave with respect to the surface of the subject 20 becomes equal to the inclination angle α. If the incident angle γ ₃ of the composite wave is the critical angle of the surface wave, the intensity of the surface wave can be increased.

On the other hand, the relative angle between the upper side and the bottom side in the other cross section of the wedge 3 becomes larger as the distance from the reference cross section to the other cross section increases. Therefore, as shown in Figure 12, if the propagation direction of the composite wave is the direction oblique to the normal direction of the piezoelectric element 1, the composite wave, when emitted from the emitting point H ₄ of the bottom of the wedge 3 , under the influence of the shape of the bottom surface of the wedge 3 it is refracted into and out from the scanning plane (X ₁ -Z ₁ plane). Then, the incident angle γ ₄ of the synthetic wave with respect to the surface of the subject 20 becomes equal to the incident angle γ ₃ . This means that not only the propagation distance of the synthetic wave in the liquid in the direction perpendicular to the surface of the subject 20 but also the propagation distance of the synthetic wave in the liquid in the direction parallel to the surface of the subject 20 is the same as in the former case. (As shown, I ₄ = I ₃ ). Then, regardless of the propagation direction of the composite wave, the incident angle of the composite wave becomes a predetermined value (in the present embodiment, it is the same as the inclination angle α, for example, the critical angle of the surface wave), so that the intensity of the surface wave is increased. Can be enhanced. In addition, variations in surface wave intensity can be suppressed. Therefore, the detection sensitivity can be improved.

Next, a specific example of the angle parameter of the present embodiment will be described.

As described above, the inclination angle α of the upper surface of the wedge 3 of the present embodiment (in other words, the inclination angle α of the upper side of each cross section of the wedge 3) is the same as the incident angle γ of the synthetic wave with respect to the surface of the subject 20. .. Therefore, the inclination angle α is preferably set to the critical angle γ _R of the surface wave calculated by the following equation (1). C _L is the longitudinal wave speed of sound in the liquid in the formula, C _R is the surface wave velocity of sound in the object 20. For example, if the liquid is water between the surface of the wedge 3 and the object 20, the longitudinal wave acoustic velocity C _L in the fluid is 1.48km / s. For example, if the subject 20 is a steel material, the transverse wave sound velocity in the subject 20 is 3.23 km / s, and the surface wave sound velocity is about 0.9 times the transverse wave sound velocity. Therefore, the surface wave sound velocity in the subject 20 C _R is 2.91km / s. In this case, the critical angle γ _R of the surface wave is 30.6 degrees. Therefore, the inclination angle α is preferably set to 30.6 degrees.
γ _R = sin ^-1 ( _CL / _CR ) ・ ・ ・ (1)

The synthetic wave propagating from the array probe 2 toward the surface of the subject 20 has a directivity angle (spread angle) because it spreads spatially. Therefore, the incident angle γ of the synthetic wave with respect to the surface of the subject 20 may be a predetermined value set within the range of the critical angle γ _R of the surface wave ± the directivity angle of the synthetic wave. Therefore, the inclination angle α may be set to a predetermined value set within the range of about 28 degrees to about 33 degrees.

The relative angle β between the upper side and the bottom side of each cross section of the wedge 3 will be described with reference to FIGS. 13 and 14. FIG. 13 is a perspective view representing the propagation direction vector r _W of the synthetic wave in the wedge 3 in the present embodiment, the propagation direction vector r _L of the synthetic wave in the liquid, and the propagation direction vector r _R of the surface wave in the subject 20. It is a figure. 14, (in particular, a cross-section perpendicular to and X ₁ axis includes an exit point H ₅ of the composite wave to be emitted from the bottom of the wedge 3) 13 interrupted surface XIV-XIV a cross-sectional view according to the synthetic wave The normal vector n _W of the bottom surface of the wedge 3 according to the position of the emission point H ₅ is represented together with the propagation direction vector r _W of the composite wave in the wedge 3 and the propagation direction vector r _L of the composite wave in the liquid. In FIG. 14, for convenience, the propagation direction vectors r _W and r _L of the composite wave are projected onto the cross section. Further, each vector is a unit vector having a length of 1.

Propagation direction vector r _R of the surface waves in the object 20 is a vector starting from the incident point G ₆ on the surface of the object 20 is present in the X ₂ -Y ₂ plane (surface of the subject 20). Propagation azimuth ρ of the surface wave in the object 20, the angle of the propagation direction vector r _R of the surface wave to Y ₂ axis.

Propagation direction vector r _W of the composite wave in the wedge 3, the virtual origin P of the composite wave is the vector as a starting point, present in X ₁ -Z ₁ plane (scan surface). Propagation azimuth φ of the composite wave in the wedge 3, the angle of the propagation direction vector r _W of the composite wave with respect to Z ₁ axis.

The exit point H _{5 on} the bottom surface of the wedge 3 exists on a straight line (Z ₁ = d) parallel to the X ₁ axis. The propagation direction vector r _L of the synthetic wave in the liquid is a vector starting from the exit point H ₅ on the bottom surface of the wedge 3, and the following equation (2) (specifically, Snell's law is extended to three dimensions. The relationship given by the light refraction formula) is satisfied. C _W in the equation is the longitudinal wave sound velocity in the wedge 3.
n _W × r _L = ( _CL / C _W ) ・ (n _W × r _W ) ・ ・ ・ (2)

When the above equation (2) is modified, the propagation direction angle φ of the composite wave in the wedge 3, the relative angle β between the top and bottom of the cross section of the wedge 3, the reference thickness d of the wedge 3, and the longitudinal wave in the wedge 3 sound velocity _{C W,} the longitudinal sound velocity _{C L} in the liquid as a variable, _{X 2} direction component _r Lx propagation direction vector _{r L} of the composite wave in the liquid, _{Y 2} direction component _{r Ly,} and the _{Z 2} direction component _{r Lz} The following equation (3) to be calculated can be derived. T in the formula is a transpose symbol.
_{r L (φ, β, d} , C W, C L) = (r Lx, r Ly, r Lz) T ··· (3)

On the other hand, the incident angle γ of the synthetic wave with respect to the surface of the subject 20 can be calculated from the Z _2- direction component r _Lz of the propagation direction vector r _L of the synthetic wave in the liquid (see the following equation (4)). ).
γ = cos ^-1 (r _Lz ) ・ ・ ・ (4)

Therefore, using the above equations (3) and (4), the incident angle γ of the synthetic wave with respect to the surface of the subject 20 is a predetermined value (in the present embodiment, it is the same as the inclination angle α, and the criticality of the surface wave. Although the angle γ _R is preferable, the relative angle between the top side and the bottom side of each cross section of the wedge 3 may be a predetermined value set within the range of the critical angle γ _R of the surface wave ± the directional angle of the composite wave). It is possible to calculate β. As a result, the relationship between the position of each cross section of the wedge 3 and the relative angle β between the upper side and the bottom side in each cross section is acquired. Specific examples (except, for convenience, the positive side only of the _{X 1} axis) is shown in Figure 15. In this specific example, the wedge 3 is made of acrylic, the liquid between the wedge 3 and the surface of the subject 20 is water, and the subject 20 is a steel material. The incident angle γ of the composite wave is the critical angle γ _R of the surface wave, which is 30.6 degrees, the longitudinal wave sound velocity C _W in the wedge 3 is 2.73 km / s, and the longitudinal wave sound velocity in the liquid. C _L is 1.48km / s, reference thickness d of the wedge 3 is 20 mm.

As shown by the following equation (5), the propagation azimuth angle ρ of the surface wave in the subject 20 is the X _two- direction component r _Lx and the Y _two- direction component r _Ly of the propagation direction vector r _L of the synthetic wave in the liquid. It is possible to calculate from. As a result, the relationship between the propagation azimuth φ of the composite wave in the wedge 3 and the propagation azimuth angle of the surface wave in the subject 20 is acquired. A specific example thereof is shown in FIG. 16 (however, the conditions are the same as above). This information is used to create flaw detection images.
ρ = tan ^-1 (r _Lx / r _Ly ) ・ ・ ・ (5)

1 Piezoelectric element 2 Array probe 3 Wedge 4 Control device 20 Subject

Claims (3)

An array probe with multiple piezoelectric elements arranged in a row,
A wedge that supports the array probe so that the plurality of piezoelectric elements are inclined with respect to the surface of the subject.
A control device that controls the transmission timing of a plurality of ultrasonic waves from the plurality of piezoelectric elements and executes sector scanning that changes the propagation direction of the composite wave composed of the plurality of ultrasonic waves.
In an ultrasonic inspection apparatus in which the synthetic wave is incident on the surface of the subject through the wedge and mode-converted into a surface wave, and the surface wave propagates along the surface of the subject.
The wedge is the piezoelectric in each cross section of the wedge perpendicular to the arrangement direction of the piezoelectric elements so that the incident angle of the synthetic wave with respect to the surface of the subject becomes a predetermined value regardless of the propagation direction of the synthetic wave. An ultrasonic inspection apparatus characterized in that the relative angle between one side on the element side and one side on the subject side changes according to the position of each cross section in the arrangement direction of the piezoelectric element. In the ultrasonic inspection apparatus according to claim 1,
The wedge has a reference cross section perpendicular to the arrangement direction of the piezoelectric elements and located at the center of the plurality of piezoelectric elements, and the relative angle between one side on the piezoelectric element side and one side on the subject side is zero. The relative angle between one side of the piezoelectric element side and one side of the subject side in another cross section that is perpendicular to the arrangement direction of the piezoelectric element and different from the reference cross section is the distance from the reference cross section to the other cross section. An ultrasonic inspection device characterized in that the larger the size, the larger the size. In the ultrasonic inspection apparatus according to claim 1,
An ultrasonic inspection apparatus characterized in that the space between the wedge and the surface of the subject is filled with a liquid.

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