JP2001041942A - Ultrasonic inspection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic inspection apparatus by which the sound velocity of leakage surface acoustic waves can be calculated with high accuracy without measur ing a water temperature. SOLUTION: The focus of an acoustic lens 3 is made to agree with the surface of an object S to be inspected (Procedure S1). Ultrasonic waves are transmitted from a vibrator 2, the propagation time tL0 of the ultrasonic waves passing an oblique route is measured, the propagation time tV0 of the ultrasonic waves passing a vertical route is measured. In addition, the output value Z0 of a Z-axis slider 18 to which an ultrasonic probe 1 is attached is read out (Procedure S2). The ultrasonic probe is brought close to the object S, to be inspected, until the leakage surface acoustic waves are detected (Procedures S3, S4). The ultrasonic waves are transmitted from the probe, the propagation time tL1 of the ultrasonic waves passing the oblique route is measured, and the propagation time tV1 of the ultrasonic waves passing the vertical route is measured. In addition, the output value Z1 of the Z-axis slider 18 is read out (Procedure S5). A time difference ΔtL(=tL0-tL1) and a time difference ΔtV (=tV0-tV1) as well as the defocus amount ΔZ(=Z0-Z1) of the acoustic lens 3 are calculated (Procedure S6). On the basis of their calculated values, the sound velocity of the leakage surface acoustic waves is found by using VL=2.ΔZ.(ΔtV2-ΔtL2)-1/2.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic inspection apparatus applied to a nondestructive inspection of a subject.

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 10-3189
As described in Japanese Unexamined Patent Publication No. 95, etc., the change in sound velocity of leaky surface acoustic waves, which is one of the ultrasonic modes, is used to determine the stress distribution and fracture toughness of the specimen, as well as materials such as thermal embrittlement and intergranular corrosion. A technique for non-destructively evaluating the degree of deterioration is known.
FIG. 13 is a sectional view and a plan view of an essential part showing an example of an ultrasonic probe conventionally applied to this type of nondestructive inspection. As is clear from these figures, the ultrasonic probe 101 of this example is Has a configuration including a single-type vibrator 102 having a circular planar shape, and a concave lens-type acoustic lens 103 that converges ultrasonic waves transmitted from the vibrator 102 and enters the subject S. In general, a damper member 101a is provided around the vibrator 102 in order to suppress the occurrence of unnecessary vibration. The vibrator 102
It is composed of a piezoelectric thin film provided with electrodes on both front and back surfaces. On the other hand, the acoustic lens 103 is made of a material having a high ultrasonic wave propagation speed, such as aluminum, and
The second setting surface 103a is formed in a flat shape, and the lens curvature surface 103b opposed thereto is formed in a spherical shape. The vibrator 102 is mounted on the acoustic lens 1 by means such as bonding.
03 is fixed to the transducer setting surface 103a. When evaluating the degree of deterioration of the subject, the ultrasonic probe 101 is fixed to a mechanical scanner (not shown) that moves in a three-dimensional direction, and is arranged to face the subject S in water. The height position is adjusted so that the focal point P of the acoustic lens 103 is slightly below the surface of the subject S, as shown in FIG. The symbol ΔZ in the figure indicates the focal point P from the surface of the subject S.
Are shown. In this state, when a drive voltage is supplied from a control unit (not shown) to the electrodes of the vibrator 102, the vibrator 102 is driven, and the ultrasonic waves transmitted from the vibrator 102 pass through the acoustic lens 103 and the water, and the subject S Incident on. Further, the reflected wave and the leaked wave from the subject S pass through the water and the acoustic lens 103, and the vibrator 102
Is received. Among the ultrasonic waves transmitted from the transducer 102, the oblique incident wave incident on the surface of the subject S at the Rayleigh critical angle θ _L through the oblique path A → B → C is converted into a leaky surface acoustic wave. Proceed along the surface of the subject S. This leaky surface acoustic wave leaks at the Rayleigh critical angle θ _L while propagating from the incident point C to the surface of the subject S, and the D
The leaked wave leaked at the point is received by the vibrator 102 through the route D → E → F. On the other hand, of the ultrasonic waves transmitted from the transducer 102, the subject S passes through the vertical path G → H → I.
The vertical incident wave incident on the surface of is reflected by the subject S, and the reflected wave (vertical reflected wave) is transmitted through the vertical path I → H → G.
And is received by the transducer 2. The receiving timing of the leaked wave and the vertically reflected wave by the vibrator 102
2, there is a time difference based on the stroke difference of each wave from the transmission of the oblique incident wave and the normal incident wave to the reception of the leaky wave and the vertical reflected wave by the vibrator 102, and this time difference Δt;
From the sound velocity V _{W of the} ultrasonic wave propagating in the water, which is an ultrasonic medium interposed between the ultrasonic probe 101 and the subject S, and the defocus amount ΔZ of the acoustic lens 103, The sound velocity _VL can be calculated, and the degree of deterioration of the subject S can be evaluated from the change in the sound velocity _VL of the leaky surface acoustic wave.

(Equation 1) FIG. 14 shows an echo waveform L of a leaky wave and an echo waveform V of a vertically reflected wave received by the transducer 102. The time difference Δt is obtained by measuring a time difference between the peaks of the echo waveform L of the leaky wave and the echo waveform V of the vertical reflection wave. In addition, the speed of sound V of ultrasonic waves transmitted in water
_W can also be determined by measurement. Further, the defocus amount ΔZ of the acoustic lens 103 can be obtained from the position of the surface of the subject S, the set position of the ultrasonic probe 101, and the focal length of the acoustic lens 103. In addition,
As a method of obtaining the sound velocity _VL of the leaky surface acoustic wave, in addition to the above-described method, the leak wave and the vertically reflected wave are positively interfered with each other by using the incident wave from the oscillator 102 as a burst wave, and the interference wave Although there is a method of obtaining the change curve (V (z) curve) from the dip cycle, the description is omitted because it is not directly related to the present invention.

By the way, in order to obtain the sound velocity _VL of the leaky surface acoustic wave from the above equation (1) and to evaluate the degree of deterioration of the subject S, the received signal of the transducer 102 must be determined. It is premised that the echo waveform L of the leaky wave and the echo waveform V of the vertical reflected wave can be clearly separated from each other, and the time difference Δt can be measured. Generally, when the defocus amount ΔZ of the acoustic lens 103 is increased, the propagation distance of the leaky surface acoustic wave is increased, and the path A → B → C → D → E → F and the path G → H
The stroke difference of → I → H → G increases, and as shown in FIG. 14, the echo waveform L of the leaky wave and the echo waveform V of the vertical reflected wave are separated on the time axis, and the time difference Δt can be measured. However, according to a study by the inventors of the present application, for a subject whose base material is coated with a coating such as a sprayed coating that easily attenuates leaky surface acoustic waves, the defocus amount ΔZ of the acoustic lens 103 is variously changed. However, it was found that the echo waveform L of the leaky wave and the echo waveform V of the vertical reflection wave could not be clearly separated, and the time difference Δt could not be obtained. That is, the inventors of the present application performed an experiment on a test object in which a sprayed coating made of a WC-based sprayed material having a thickness of 0.1 mm was applied to the surface of the base material, and found that the defocus amount Δ
When Z is increased, the attenuation of the leaky surface acoustic wave increases, and it becomes difficult to detect the echo waveform L of the leaky wave. Conversely, when the defocus amount ΔZ of the acoustic lens 103 is reduced, the echo waveform V of the vertical reflected wave is reduced. In this case, the echo waveform L of the leaky wave is buried, and the two cannot be clearly separated, and the time difference Δt cannot be obtained. When theoretical analysis is added to this, the above-mentioned subject has a throat thickness (FIG. 13).
(Between GH in (a)) 5 mm aluminum (sound speed = 6)
When a 10 MHz ultrasonic pulse is transmitted from a 400 m / s acoustic lens with a defocus amount ΔZ of 0.2 mm, the sound velocity _VL of a leaky surface acoustic wave propagating through the WC-based thermal spray coating is about 2300 m / s (the surface 13 (a), and the Rayleigh critical angle is about 41 degrees. Therefore, the path G → H shown in FIG.
While the propagation time of a vertically incident wave and a vertically reflected wave propagating in → I → H → G is 10.05 μs, FIG.
The propagation time of the oblique incident wave, the leaky surface acoustic wave and the leaky wave propagating along the route A → B → C → D → E → F shown in FIG. 10A is 10.1 μs, and the difference is 50 ns. Therefore, even if a weak leaky wave is received, the time difference Δt cannot be obtained even if only half of the period of the used frequency (100 ns) is used. Further, in order to obtain the sound velocity _VL of the leaky surface acoustic wave from the above equation (1) and to evaluate the degree of deterioration of the subject S, for example, an intervening probe is provided between the ultrasonic probe 101 and the subject S. It is necessary to specify the sound velocity V _W of the ultrasonic wave propagating in water, but as is well known, the sound velocity V _W of the ultrasonic wave propagating in water changes depending on the water temperature. Since s also changes, it is necessary to measure the water temperature for each test in order to accurately determine the sound velocity _VL of the leaky surface acoustic wave by the equation (1). For this reason, in the conventional ultrasonic inspection apparatus, a temperature sensor for measuring the water temperature is required, which complicates the structure and measures the water temperature every time the sound velocity _VL of the leaky surface acoustic wave is measured. Since it is necessary to go through a complicated procedure such as finding the sound velocity of water, there is a disadvantage that it is difficult to efficiently measure the sound velocity _VL of the leaky surface acoustic wave, and furthermore, to inspect the degree of deterioration of the subject.
In the above description, the stress distribution and fracture toughness value of the test object and the degree of deterioration of the material such as thermal embrittlement and intergranular corrosion have been described as examples. Similar inconveniences arise when assessing the soundness of the surface of the subject, such as the presence or absence of peeling of the coating. The present invention has been made in order to solve the deficiencies of the related art, and an object thereof is to provide an ultrasonic inspection apparatus capable of calculating the sound velocity of a leaky surface acoustic wave with high accuracy without measuring the water temperature. Further, to provide an ultrasonic inspection apparatus capable of calculating the sound velocity of the leaky surface acoustic wave with high accuracy without measuring the water temperature even for a subject having a large leaky surface acoustic wave attenuation. is there.

According to the present invention, there is provided an ultrasonic scanning section having an ultrasonic probe and a mechanical scanner for transferring the ultrasonic probe to a subject. In an ultrasonic inspection apparatus including a driving unit of an ultrasonic scanning unit and an arithmetic processing unit that controls the ultrasonic scanning unit via the driving unit and performs a desired ultrasonic inspection, a focus of the ultrasonic probe Is set to the first depth position of the subject, and the transmission time of the oblique incident wave and the leaky surface acoustic wave when the ultrasound is transmitted and the propagation time of the leaky wave and the focal point of the ultrasound probe are set to the second position of the subject. The difference between the oblique incident wave and the leaky surface acoustic wave and the propagation time of the leaky wave when the ultrasonic wave is set at the depth position of 2, and the focus of the ultrasonic probe are set to the first position of the subject. Ultrasound was transmitted at the depth position Kino second focal point of the subject of the propagation time of the vertical incident wave and vertical reflected wave and the ultrasonic probe
Based on the difference between the propagation time of the vertically incident wave and the vertically reflected wave when transmitting the ultrasonic wave at the depth position, the arithmetic processing unit calculates the sound velocity of the leaky surface acoustic wave. did. In the ultrasonic inspection apparatus having the above configuration, the first
The depth position may be a surface of the subject, and the second depth position may be a position where a leaky surface acoustic wave is generated in the subject by ultrasonic waves transmitted from the ultrasonic probe. Can be. As shown in FIG. 11, when the focal position of the acoustic lens 3 matches the surface of the subject S, the propagation time t of the ultrasonic wave passing through the path A → B → C → D → E → F
_L0 and the path A → B → C → when the focal position of the acoustic lens 3 is shifted inward from the surface of the subject S as shown in FIG.
The time difference Δt from the propagation time t _{L1 of the} ultrasonic wave passing through D → E → F
_L is, when the defocus amount of the acoustic lens 3 is ΔZ, the Rayleigh critical angle is θ _L , the sound velocity of water is V _W , and the sound velocity of the leaky surface acoustic wave is _VL ,

(Equation 2) The following equation (3) is obtained by eliminating θ _L from equation (2) using the fact that V _W = V _L sin θ _L according to Snell's law.

(Equation 3) On the other hand, when the focal position of the acoustic lens 3 matches the surface of the subject S, the propagation time t of the ultrasonic wave passing through the route G → I → G
_{When V0} and the focal position of the acoustic lens 3 are shifted from the surface of the subject S, the propagation time t _{V1 of the} ultrasonic wave passing through the path G → I → G
Time difference Delta] t _V with is expressed by the following equation (4).

(Equation 4) From this equation (4), the sound velocity V _W of the water is obtained by the following equation (5).

(Equation 5) Here, if the equation (5) is substituted into the equation (3), the sound velocity V of the water
_{The following} equation (6) for obtaining the sound velocity _VL of the leaky surface acoustic wave that does not include _W as a variable can be obtained.

(Equation 6) Therefore, the oblique incident wave and the leaked surface acoustic wave, which are measured with the focus of the ultrasonic probe coincident with the surface of the subject S, and the propagation time of the leaky wave, and the focus of the ultrasonic probe are set inside the subject and measured. The difference Δt _L between the oblique incident wave and the leaked surface acoustic wave and the propagation time of the leaked wave, the propagation time of the vertically incident wave and the vertically reflected wave measured by matching the focal point of the ultrasonic probe to the surface of the subject S. The sound velocity of the leaky surface acoustic wave is calculated from the difference Δt _V between the propagation time of the vertical incident wave and the vertical reflected wave measured by setting the focus of the ultrasonic probe inside the subject and the defocus amount of the acoustic lens 3 from ΔZ. The calculation can be performed, and the configuration of the ultrasonic inspection apparatus can be simplified and the efficiency of the calculation can be increased. In addition, as shown in FIG. 13 described above, as the ultrasonic probe, the propagation speed of the ultrasonic wave in the propagation path (G → H and H → G) of the vertically incident wave and the vertically reflected wave, the oblique incident wave, and the leakage A device having a uniform acoustic lens 103 having the same ultrasonic wave propagation velocity in the wave propagation path (A → B and E → F) can be used. For example, as shown in FIG. The propagation speed of the ultrasonic wave in the propagation path of the wave and the vertically reflected wave (G → I and I → G) and the propagation velocity of the ultrasonic wave in the propagation path of the oblique incident wave and the leaky wave (A → B and E → F) However, it is also possible to use a lens provided with an acoustic lens 3 having a different shape. In the ultrasonic probe of FIG. 13, the attenuation of the leaky surface acoustic wave is small, the echo waveform V of the vertically reflected wave and the echo waveform L of the leaky wave can be separated on the time axis, and the time difference Δt _{L in the} equation (6) and The present invention is applied to an examination of a subject in which Δt _V can be calculated. On the other hand, the ultrasonic probe illustrated in FIG. 3 has a large attenuation of the leaky surface acoustic wave as well as this type of subject, for example, a subject on which a thermal spray coating is formed.
With the ultrasonic probe of 0, the echo waveform V of the vertically reflected wave and the echo waveform L of the leaky wave cannot be separated on the time axis, and therefore, the time difference Δt _L and Δt _V in the equation (6) cannot be calculated. It can also be applied to inspections. As means for making the propagation speed of the ultrasonic wave in the propagation path of the normal incident wave and the vertically reflected wave of the acoustic lens different from the propagation speed of the ultrasonic wave in the propagation path of the oblique incident wave and the leaky wave of the acoustic lens, (A) A through hole is formed in a propagation path of a normal incident wave and a vertical reflected wave of the acoustic lens from a setting surface of the vibrator to a lens curvature surface facing the setting surface. (B) A depression in a lens curvature surface of the acoustic lens. (C) Propagation of ultrasonic waves in a through-hole formed in the acoustic lens, or in a recess formed in the vibrator setting surface or lens curvature surface of the acoustic lens, as compared with the material constituting the acoustic lens. Filling a filling made of slow material,
(D) A material having a higher ultrasonic wave propagation speed than a material constituting the acoustic lens in a through-hole formed in the acoustic lens, or in a recess formed in a vibrator setting surface or a lens curvature surface of the acoustic lens. Means for filling a filling consisting of As a specific example of the above (c), an acoustic lens made of aluminum in which a resin is filled in a through hole or a hollow can be cited. Further, as a specific example of the above (d), an acoustic cylindrical lens is press-fitted into a through hole or a hollow of an acoustic lens made of resin, or resin is outsert molded around a core material made of aluminum to form an acoustic lens. Can be mentioned. There is no limitation on the shapes of the acoustic lens and the vibrator, and a concave-type lens having a spherical curvature surface and a single-type vibrator having a circular planar shape can be provided. The lens may be provided with a single type or array type transducer. When the propagation speed of the ultrasonic wave in the propagation path of the normal incident wave and the vertically reflected wave of the acoustic lens and the propagation speed of the ultrasonic wave in the propagation path of the oblique incident wave and the leaky wave of the acoustic lens are different,
Defocus amount Δ due to large attenuation of leaky surface acoustic waves
Even when Z cannot be increased, the reception timing of the vertically reflected wave and the reception timing of the leaked wave by the vibrator can be shifted, so that the echo waveform V of the vertically reflected wave and the echo waveform L of the leaked wave are plotted on the time axis. Thus, it is possible to clearly separate the signals, and it is possible to obtain the propagation time of each echo.
Therefore, the sound velocity _VL of the leaky surface acoustic wave can be easily obtained by using the above equation (6). So from this,
For specimens with a coating that easily attenuates leaky surface acoustic waves such as thermal spray coating on the surface of the base metal, the stress distribution, fracture toughness, material degradation such as thermal embrittlement and intergranular corrosion, Non-destructive evaluation of the soundness of the subject such as the presence or absence of cracks on the surface of the sample and the presence or absence of peeling of the coating provided on the surface of the sample can be performed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an overall configuration of an ultrasonic inspection apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of an ultrasonic inspection apparatus, and FIG. 2 is a partially sectional perspective view of an ultrasonic probe setting unit in the ultrasonic inspection apparatus. As shown in these drawings, the ultrasonic inspection apparatus of the present example includes an ultrasonic scanning unit 10 that two-dimensionally scans an ultrasonic wave along the surface of a subject S, and a driving unit 2 of the ultrasonic scanning unit 10.
0, the ultrasonic scanning unit 10 is controlled via the driving unit 20 to calculate desired test results such as a stress distribution, a fracture toughness value, and a degree of deterioration of the subject from the reception waveform of the ultrasonic wave. It mainly comprises a unit 30 and a display unit 40 for displaying the results of the ultrasonic inspection obtained by the arithmetic processing unit 30. As shown in FIG. 2, the ultrasonic scanning unit 10 includes an ultrasonic probe 1, a water tank 11 that stores the ultrasonic probe 1 and water W that stores the subject S, and the ultrasonic probe 1 in a three-dimensional direction. Driven mechanical scanner 12
Consists of The mechanical scanner 12 includes a pair of Y-axis guides 13 arranged along two parallel sides of the water tank 11 in the Y-Y direction, and a Y-axis slider guided by the Y-axis guides 13 in the Y-Y direction. 14 and an X-axis guide 1 fixed at both ends to the Y-axis slider 14 and arranged in the XX direction.
5, an X-axis slider 16 guided in the X-X direction by the X-axis guide 15, a Z-axis guide 17 fixed vertically to the X-axis slider 16, and the ultrasonic probe 1
And a Z-axis slider 18 guided in the Z-Z direction by the Z-axis guide 17. Each of the sliders 14, 16, 18 has three motors M 1 to M 1 shown in FIG.
Driven by M3. Each of these motors is provided with a position signal output device such as a rotary encoder, and the arithmetic processing unit 30 can detect coordinate signals of the sliders 14, 16, and 18. The driving unit 20 includes a pulsar / receiver 21 for transmitting an ultrasonic wave from the ultrasonic probe 1 and receiving an ultrasonic wave by the ultrasonic probe 1, and an A / D for digitally converting a reception signal of the pulsar / receiver 21. A converter 22 and a motor driver 23 for driving three motors M1 to M3 provided in the mechanical scanner 12 are provided. The arithmetic processing unit 30 includes a CPU 31, input means 32 such as a keyboard and a mouse, a trigger 33 driven by a command from the input means 32, and a motor controller 34.
And the A / D-converted received signals are transmitted to the motors (M1 to M1) via the motor driver 23 and the motor controller 34.
3) a first memory 35 that stores together with the coordinate signals taken in from the memory, a timer 36 that is activated by a signal from the trigger 33 to set a gate for signal processing by the CPU 31, and a second memory that stores the procedure of signal processing by the CPU 31. Memory 37 is provided. Therefore, the ultrasonic inspection apparatus of the present example operates the motors M1 to M3 provided in the mechanical scanner 12 by operating the input unit 32.
Can be driven, and the ultrasonic probe 1 can be positioned with respect to the subject S set in the water tank 11. The coordinate signal of the ultrasonic probe 1 at this time is taken into the first memory 35 via the motor driver 23 and the motor controller 34. By operating the input means 32 from this state, the pulsar / receiver 21 and the motor controller 34 can be driven, and the ultrasonic probe 1 is moved two-dimensionally along the surface of the subject S, The transmission of the ultrasonic wave from the ultrasonic probe 1 and the reception of the ultrasonic wave by the ultrasonic probe 1 can be performed. Ultrasonic waves received by the ultrasonic probe 1 are A / D converted by the A / D converter 22 and are stored in the first memory together with coordinate signals taken in from the motors M1 to M3 via the motor driver 23 and the motor controller 34. 35. The CPU 31 fetches the signal stored in the first memory 35 for each gate set in the timer 36, performs the signal processing based on the signal processing procedure stored in the second memory 37, and executes the processing result. Is displayed on the display device 40 in color tone. Hereinafter, the configuration of the ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described. <First Example of Ultrasonic Probe> First, a first example of an ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described with reference to FIGS. 3A and 3B are a sectional view and a plan view of a main part showing a first example of an ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention, and FIG. It is an echo waveform diagram of a reflected wave.
As is clear from FIGS. 3A and 3B, the ultrasonic probe 1A of the present example has the same basic configuration as the ultrasonic probe 101 according to the conventional example, and has a simple planar shape circular. One type of vibrator 2 and a cylindrical acoustic lens 3 that converges the ultrasonic wave transmitted from the vibrator 2 and enters the subject S
It is configured to have: Ultrasonic probe 1 of this example
A is characterized in that a through hole 4 penetrating from the setting surface 3a of the vibrator 2 to the lens curvature surface 3b is formed in the center of the acoustic lens 3 as the acoustic lens 3. It is sufficient if the diameter of the through hole 4 is set to be equal to or larger than the propagation range of the vertically incident wave and the vertically reflected wave. However, in order to suppress the reception of noise as much as possible, it is possible to prevent the propagation of the obliquely incident wave and the leaky wave. It is preferable to make it as large as possible. Other components are the same as those of the ultrasonic probe 101 according to the conventional example, and therefore, description thereof will be omitted to avoid duplication. As described above, the ultrasonic probe is
When the subject S is evaluated, the subject S is placed in water together with the subject S. Therefore, when the ultrasonic probe 1A of the present embodiment in which the through hole 4 is formed in the center of the acoustic lens 3 is used, as shown in FIG.
Between the B → C and D → E → F and the subject S, an aluminum acoustic lens 3 (sound velocity =
Water (about 6400 m / s) having a low ultrasonic wave propagation velocity (19
C., about 1480 m / s at 26 ° C., and about 1500 m / s at 26 ° C., whereas ultrasonic waves are transmitted between the vertical path G → I and I → G of the vibrator 2 and the subject S. Route A → B → C → D
→ The propagation time of the vertical incident wave and the vertical reflected wave passing through the route G → I → G is longer than the propagation time of the oblique incident wave, leaky surface acoustic wave and leaky wave passing through E → F. As shown, an echo waveform V of a vertically reflected wave and an echo waveform L of a leaky wave are shown.
And a received signal in which the echo waveform L of the leaky wave precedes the echo waveform V of the surface reflected wave.
Accordingly, the time difference Δt between the echo waveform L of the leaky wave and the echo waveform V of the surface reflected wave can be obtained, and the sound velocity _VL of the leaky surface acoustic wave can be obtained from the above equation (6). From the change in sound speed of the leaky surface acoustic wave, for example, the stress distribution and fracture toughness of the specimen S, the degree of deterioration of the material such as thermal embrittlement and intergranular corrosion, the presence or absence of cracks on the specimen surface, and the coating provided on the specimen surface The non-destructive evaluation of the soundness of the surface of the subject such as the presence or absence of peeling of the sample As described above, the thickness of the base material is 0.1 mm.
Thickness of the specimen and lens with WC sprayed coating of 5
mm aluminum acoustic lens, defocus amount ΔZ is 0.2 mm, operating frequency is 10 MHz, sound velocity _VL of leaky surface acoustic wave is 2300 m / s, Rayleigh critical angle is 41 degrees, vertical wave V and leaky elastic surface Time difference Δ of wave L
When t is obtained, while the propagation time of the ultrasonic wave propagating along the route A → B → C → D → E → F is about 10 μs, the propagation time of the ultrasonic wave propagating along the route G → I → G is It is about 15 μs, and the difference is 5 μs (50 times the period of the used frequency), and it can be seen that both waves can be separated even in the test object having the thermal spray coating. In addition, in the previous example, the used frequency was set to 10 MHz, but similar results were obtained when the frequency was changed in the range of 5 to 20 MHz. <Second Example of Ultrasonic Probe> Next, a second example of the ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described with reference to FIG. FIG. 5 is a sectional view of a main part of an ultrasonic probe according to a second example. The ultrasonic probe 1B of the second example has an acoustic lens 3 instead of a configuration in which a through-hole 4 is formed in the center of the acoustic lens 3 (propagation path of a vertically incident wave and a vertically reflected wave).
A concave portion 5 is formed at the center of the lens curvature surface 3b. In the case where the ultrasonic probe 1B is used, similarly to the ultrasonic probe 1A according to the first example, the path A
→ B → C → D → E → F Since the propagation time of the ultrasonic wave propagating through the path G → I → G can be relatively delayed from the propagation time of the ultrasonic wave passing through F, the echo waveform V of the vertical reflected wave can be obtained. And the echo waveform L of the leaky wave can be separated. Further, the acoustic lens 3 of the present embodiment has an effect that the vibrator 2 can be easily and reliably set because the vibrator setting surface 3a is closed. <Third Example of Ultrasonic Probe> Next, a third example of the ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described with reference to FIG. FIG. 6 is a sectional view of a main part of an ultrasonic probe according to a third example. The ultrasonic probe 1 </ b> C of the third example is formed by simply forming a through hole 4 in the center of the acoustic lens 3.
In place of the configuration in which the material is used, the filling material 6 made of a material having a different ultrasonic wave propagation speed from the material forming the acoustic lens 3 is filled in the opened through hole 4 or the formed recess 5. Features. FIG. 6A shows a case where the filler 6 is filled in the through hole 4 formed in the center of the acoustic lens 3, and FIG. 6B shows a depression 5 formed on the vibrator setting surface 3 a of the acoustic lens 3. FIG. 6 (c) shows a depression 5 formed in the lens curvature surface 3b of the acoustic lens 3 when the filling material 6 is filled therein.
The figure shows a case where the filling material 6 is filled in the inside. The material of the acoustic lens 3 and the filling 6 are preferably as large as the difference in the propagation speed of the ultrasonic wave. When the acoustic lens 3 is made of aluminum (sound speed = 6400 m / s), the filling 6 is used. Is preferably made of a resin material such as an acrylic resin (sound speed = 2000 to 2500 m / s). Conversely, when the acoustic lens 3 is made of a resin material, aluminum is preferably used as the filler 6. When a resin is used as the filling portion 6, the acoustic lens 3 can be manufactured by potting the resin as the filling material into the opened through hole 4 or the formed recess 5. In the case where a solid is used as the filling portion 6, the acoustic lens 3 can also be formed by press-fitting a solid as a filling material into the opened through hole 4 or the formed recess 5.
Can be manufactured. Further, when the acoustic lens 3 is made of a resin material, a desired acoustic lens 3 can be manufactured by outsert molding a resin around a filler 6 such as aluminum. Of course, when the filling material 6 whose ultrasonic wave propagation speed is lower than the material forming the acoustic lens 3 is filled, the route A → B → C → D →
The propagation time of the ultrasonic wave propagating along the route G → I → G is relatively slower than the propagation time of the ultrasonic wave passing through E → F, and FIG.
As shown in the figure, the echo waveform L of the leaky wave has a shape preceding the echo waveform V of the vertically reflected wave, and conversely, the filling material 6 having a higher ultrasonic wave propagation speed than the material forming the acoustic lens 3 is used. In the case of filling, the propagation time of the ultrasonic wave propagating along the route G → I → G becomes relatively faster than the propagation time of the ultrasonic wave passing through the route A → B → C → D → E → F. As shown in FIG. 11, the echo waveform V of the vertically reflected wave has a shape preceding the echo waveform L of the leaky wave. Ultrasonic probe 1 of this example
C has a sound velocity between the propagation paths G → I and I → G of the vertically incident wave and the vertically reflected wave in the acoustic lens 3 and the propagation paths A → B → C and D → E → F of the obliquely incident wave and the leaky wave. Since they are made of different materials, the difference between the propagation times of the ultrasonic waves passing through the respective paths becomes large, so that the echo waveform V of the vertically reflected wave and the echo waveform L of the leaky wave can be separated, and the acoustic lens 3
Since the vibrator setting surface is closed, the vibrator 2 can be set easily and reliably. <Fourth Example of Ultrasonic Probe> Next, a fourth example of the ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention is shown in FIG.
A description will be given based on (a) and (b). FIG. 7 (a),
(B) is the principal part perspective view seen from the plane direction of the ultrasonic probe concerning a 4th example, and the principal part perspective view seen from the bottom direction.
As shown in FIG. 7A, the ultrasonic probe 1D of the fourth example uses a cylindrical lens as the acoustic lens 3 and a plurality of transducers 2a to 2n are adjacently arranged in one direction as the transducer 2. An array-type transducer is provided. As shown in FIG. 7B, a through hole 4 is formed in the propagation path of the vertically incident wave and the vertically reflected wave on the bottom surface of the cylindrical lens. In addition, it is also possible to form a depression instead of the configuration in which the through hole 4 is formed in the bottom surface of the cylindrical lens, and further, the oblique incident wave and the leakage wave are formed in the formed through hole or the formed depression. Of course, it is also possible to fill the filler with a different propagation speed of the ultrasonic wave from the propagation path. Ultrasonic probe 1 of this example
D uses a cylindrical lens as the acoustic lens 3 and an array-type vibrator as the vibrator 2, so that the surface of the subject S can be traced in a plane.
Inspection efficiency of the subject S can be increased as compared with a case where a cylindrical acoustic lens is provided with a single-type vibrator having a circular planar shape. <Fifth Example of Ultrasonic Probe> Next, a fifth example of the ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described with reference to FIG. FIG. 8 is a perspective view of a main part of an ultrasonic probe according to a fifth example viewed from a plane direction. As shown in FIG. 8, the ultrasonic probe 1E of the fifth example is characterized in that a cylindrical lens is used as the acoustic lens 3 and a single-type vibrator is provided as the vibrator 2. As shown in FIG. 7B, a through hole 4 is formed in the propagation path of the vertically incident wave and the vertically reflected wave on the bottom surface of the cylindrical lens. Of course, a through hole 4 is provided on the bottom of the cylindrical lens.
Instead of forming a recess, a recess may be formed by filling the opened through-hole or formed recess with a filling material having a different propagation speed of ultrasonic waves from the propagation path of the oblique incident wave and the leaky wave. It is also possible. Ultrasonic probe 1 of this example
D uses a cylindrical lens as the acoustic lens 3 and a single-type vibrator as the vibrator 2, so that the surface of the subject S can be irradiated with an ultrasonic beam in a linear manner. Inspection efficiency of the subject S can be improved as compared with the case where the acoustic lens of the above is provided with a single-type vibrator having a circular planar shape. <Sixth Example of Ultrasonic Probe> Next, a sixth example of the ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described with reference to FIG. FIG. 9 is a sectional view of a main part of an ultrasonic probe according to a sixth example. The ultrasonic probe 1F of the sixth example has the same configuration as the ultrasonic probe 101 described in the conventional example, and as the acoustic lens 3, a through-hole or a hollow is formed in a propagation path of a vertically incident wave and a vertically reflected wave, and a filling material is provided. Is not provided, and the whole is configured homogeneously.
When the ultrasonic probe 1F of this example is used, the echo waveform V of the vertically reflected wave and the echo waveform L of the leaky wave cannot be separated, so that, for example, a leaky elastic surface such as an object provided with a thermal spray coating is provided. Although it is difficult to apply the method to a subject having a large attenuation of a wave, it is possible to perform a desired ultrasonic inspection without measuring a water temperature for a subject having a small attenuation of a leaky surface acoustic wave. <Seventh Example of Ultrasonic Probe> Next, a seventh example of the ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described with reference to FIG. FIG. 10 is a sectional view of a main part of an ultrasonic probe according to a seventh example. Ultrasound probe 1G of seventh example
Is characterized in that a vibrator 2 having a circular planar shape on a concave surface 1b formed on a probe main body 1a is provided without an acoustic lens. Even when the ultrasonic probe 1 of the present example is used, the echo waveform V of the vertically reflected wave and the echo waveform L of the leaky wave cannot be separated as in the case of using the ultrasonic probe 1 according to the fifth example. For example, it is difficult to apply to a subject having a large leaky surface acoustic wave attenuation such as a subject provided with a thermal spray coating, but for a subject having a small leaky surface acoustic wave attenuation, the water temperature is measured. A desired ultrasonic inspection can be performed without any need. Hereinafter, an example of an ultrasonic inspection method using the ultrasonic inspection apparatus according to the present invention,
This will be described with reference to FIG. 3A and FIGS. This test method does not measure the water temperature,
The sound velocity _VL of a leaky surface acoustic wave can be calculated. FIG. 11 is an explanatory diagram showing the arrangement of the ultrasonic probe when the focal point of the acoustic lens coincides with the surface of the subject, and FIG. 12 is a flowchart showing the procedure of the ultrasonic inspection method. The procedure of the ultrasonic inspection method shown in FIG. 12 is stored in the second memory 37 shown in FIG.
First, in step S1, the Z-axis slider 18 of the mechanical scanner 12 is driven to move the ultrasonic probe 1 in a direction to approach the subject S or in a direction away from the subject S, as shown in FIG. The focal point of the acoustic lens 3 is matched with the surface of the subject S. When the focus of the acoustic lens 3 matches the surface of the subject S, the echo level of the leaked wave becomes maximum, so that it can be known that the focus of the acoustic lens 3 matches the surface of the subject S. In step S2, an ultrasonic wave is transmitted from the transducer 2, and a propagation time t _{L0 of the} ultrasonic wave passing through the route A → B → C (D) → E → F and a propagation of the ultrasonic wave passing through the route G → I → G. Time t
Measure _V0 . Further, the output value Z ₀ of the Z-axis slider 18 is read. Next, in steps S3 and S4, the ultrasonic probe 1 is brought close to the subject S until a leaked surface acoustic wave is detected. The stop position of the ultrasonic probe 1 does not necessarily need to be a position where the echo level of the leaky surface acoustic wave is maximized, and can be set arbitrarily within a range where the leaky surface acoustic wave can be detected. When a leaky surface acoustic wave is detected, the ultrasonic probe 1 is at the position shown in FIG. 3A, and the focal position of the acoustic lens 3 is shifted from the surface of the subject S by the defocus amount Δ
Only Z is inside. In step S5, an ultrasonic wave is transmitted from the transducer 2, and the propagation time t _{L1 of the} ultrasonic wave passing through the path A → B → C → D → E → F and the propagation time of the ultrasonic wave passing through the path G → I → G Measure t _V1 . Also, the output value Z ₁ of the Z-axis slider 18
To read Next, the process proceeds to step S6, and step S2
The propagation time t _{L0 of the} ultrasonic wave passing through the route A → B → C (D) → E → F measured in step A and the route A → B → measured in step S5
The time difference Δt _L (= t _L0 −t _L1 ) from the propagation time t _{L1 of the} ultrasonic wave passing through C → D → E → F, and the path G measured in step S2
The time difference Δt _V between the propagation time t _{V0 of the} ultrasonic wave passing through I → G and the propagation time t _{V1 of the} ultrasonic wave passing through the path G → I → G measured in step S5 (= t _V0 −t _V1 ) and the procedure The difference between the output value Z ₀ of the Z-axis slider 18 measured in S2 and the output value Z ₁ of the Z-axis slider 18 measured in step S5, that is, the defocus amount ΔZ of the acoustic lens 3 (= Z ₀ −Z ₁ ). Is calculated. Finally, from these calculated values, the sound velocity _VL of the leaky surface acoustic wave is obtained by using the above equation (6). Since the equation (6) does not include the sound velocity V _W of the water as a variable, the sound velocity V _L of the leaky surface acoustic wave can be calculated based on this equation without measuring the sound velocity V _W of the water. Although the description is omitted in the above description, when the above-described inspection method is performed, the Y-axis slider 14 and / or the X-axis slider 16 of the mechanical scanner 12 are appropriately driven to move along the surface of the subject S. Needless to say, the ultrasonic probe 1 is scanned. In addition,
In the ultrasonic inspection method of FIG. 12, the focus of the acoustic lens 3 is matched with the surface of the subject S in step S1, but the focus of the acoustic lens 3 must be completely matched with the surface of the subject S in this procedure. This does not mean that the required ultrasonic inspection cannot be performed, and the focal point of the acoustic lens 3 can be positioned slightly inside the surface of the subject S. In this case, in steps S3 and S4, the focal position of the acoustic lens 3 is moved further inside the subject S than the focal position of the acoustic lens 3 set in step S1.

According to the ultrasonic inspection apparatus of the present invention, the oblique incident wave, the leaky surface acoustic wave, the propagation time of the leaky wave, and the propagation time of the ultrasonic probe measured with the focus of the ultrasonic probe coincident with the surface of the subject are measured. The difference between the oblique incident wave, the leaky surface acoustic wave, and the propagation time of the leaky wave measured with the focus set inside the subject, and the normal incidence measured with the focus of the ultrasonic probe matched to the surface of the subject Calculates the sound velocity of leaky surface acoustic waves based on the difference between the propagation times of waves and vertically reflected waves and the propagation times of vertically incident waves and vertically reflected waves measured with the focus of the ultrasonic probe set inside the subject. Therefore, it is not necessary to measure the water temperature for each test, and the temperature sensor can be omitted, so that the configuration of the ultrasonic inspection apparatus can be simplified and the calculation can be performed more efficiently.

[Brief description of the drawings]

FIG. 1 is a block diagram of an ultrasonic inspection apparatus.

FIG. 2 is a configuration diagram of an ultrasonic scanning unit in the ultrasonic inspection apparatus.

FIG. 3 is a sectional view and a plan view of a main part of the ultrasonic probe according to the first embodiment.

FIG. 4 is an echo waveform of a leaky wave and a vertically reflected wave received by a vibrator.

FIG. 5 is a sectional view of a main part of an ultrasonic probe according to a second embodiment.

FIG. 6 is a sectional view of a main part of an ultrasonic probe according to a third embodiment.

FIGS. 7A and 7B are a perspective view of a main part viewed from a plane direction and a perspective view of a main part viewed from a bottom direction of an ultrasonic probe according to a fourth embodiment.

FIG. 8 is a perspective view of a main part of an ultrasonic probe according to a fifth embodiment.

FIG. 9 is a sectional view of an essential part of an ultrasonic probe according to a sixth embodiment.

FIG. 10 is a sectional view of an essential part of an ultrasonic probe according to a seventh embodiment.

FIG. 11 is an explanatory diagram when the focal point of the acoustic lens matches the surface of the subject.

FIG. 12 is a flowchart illustrating a procedure of an ultrasonic inspection method.

FIG. 13 is a sectional view and a plan view of a main part of a conventionally known ultrasonic probe.

FIG. 14 is an echo waveform of a leaky wave and a vertically reflected wave received by the vibrator.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 ultrasonic probe 1A ultrasonic probe according to first example of implementation 1B ultrasonic probe according to second example of implementation 1C ultrasonic probe according to third example of implementation 1D ultrasonic probe according to fourth example of implementation 1E implementation Ultrasonic probe according to the fifth example 1F Ultrasonic probe according to the sixth example 1G Ultrasonic probe according to the seventh example 2 Vibrator 3 Acoustic lens 3a Vibrator setting surface 3b Lens curvature surface 4 Through hole 5 Hollow 6 filling

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[Procedure amendment]

[Submission date] August 3, 1999 (1999.8.3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

[Title of the Invention] Ultrasonic inspection device

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic inspection apparatus applied to a nondestructive inspection of a subject.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 10-3189
As described in Japanese Unexamined Patent Publication No. 95, etc., the change in sound velocity of leaky surface acoustic waves, which is one of the ultrasonic modes, is used to determine the stress distribution and fracture toughness of the specimen, as well as materials such as thermal embrittlement and intergranular corrosion. A technique for non-destructively evaluating the degree of deterioration is known.

FIG. 13 is a sectional view and a plan view of an essential part showing an example of an ultrasonic probe conventionally applied to this type of nondestructive inspection. The acoustic probe 101 includes a single-type vibrator 102 having a circular planar shape, and a concave lens-type acoustic lens 103 that converges the ultrasonic wave transmitted from the vibrator 102 and enters the subject S. In general, a damper material 101a is provided around the vibrator 102 in order to suppress the occurrence of unnecessary vibration. The vibrator 102 is configured by a piezoelectric thin film having electrodes provided on both front and back surfaces. On the other hand, the acoustic lens 103 is made of a material having a high ultrasonic wave propagation speed such as aluminum,
A setting surface 103a of the vibrator 102 is formed in a planar shape, and a lens curvature surface 103b opposed thereto is formed in a spherical shape. The vibrator 102 is fixed to the vibrator setting surface 103a of the acoustic lens 103 by means such as bonding.

When evaluating the degree of deterioration of a subject, the ultrasonic probe 101 is fixed to a mechanical scanner (not shown) that moves in a three-dimensional direction, and is arranged in water to face the subject S. The height position is as shown in FIG.
The focal point P of the acoustic lens 103 is adjusted to be slightly below the surface of the subject S. The symbol ΔZ in the figure indicates the defocus amount from the surface of the subject S to the focal point P. In this state, when a drive voltage is supplied from a control unit (not shown) to the electrodes of the vibrator 102, the vibrator 102 is driven,
The ultrasonic wave transmitted from the transducer 102 is transmitted to the acoustic lens 1
03 and water and enter the subject S. Further, the reflected wave and the leaked wave from the subject S
And is received by the vibrator 102.

[0005] Among the ultrasonic waves transmitted from the transducer 102, the oblique incident wave incident on the surface of the subject S at a Rayleigh critical angle θ _L through the oblique path A → B → C is a leaky surface acoustic wave. And travels along the surface of the subject S. This leaky surface acoustic wave leaks at the Rayleigh critical angle θ _L while propagating from the incident point C to the surface of the subject S, and the D
The leaked wave leaked at the point is received by the vibrator 102 through the route D → E → F. On the other hand, of the ultrasonic waves transmitted from the transducer 102, the subject S passes through the vertical path G → H → I.
The vertical incident wave incident on the surface of is reflected by the subject S, and the reflected wave (vertical reflected wave) is transmitted through the vertical path I → H → G.
And is received by the transducer 2.

At the reception timing of the leaked wave and the vertically reflected wave by the oscillator 102, the oblique incident wave and the vertically incident wave are transmitted from the oscillator 102, and then the leaked wave and the vertically reflected wave are received by the oscillator 102. There is a time difference based on the stroke difference of each wave until the time difference Δt and the ultrasonic probe 10
From the sound velocity V _{W of the} ultrasonic wave propagating in the water, which is the ultrasonic medium interposed between the sample surface 1 and the subject S, and the defocus amount ΔZ of the acoustic lens 103, the sound velocity V _{L of the} leaky surface acoustic wave is calculated by the following equation. Can be calculated, and the degree of deterioration or the like of the subject S can be evaluated from the change in the sound speed _VL of the leaky surface acoustic wave.

[0007]

(Equation 1)

FIG. 14 shows an echo waveform L of a leaky wave and an echo waveform V of a vertically reflected wave received by the vibrator 102. The time difference Δt is obtained by measuring a time difference between the peaks of the echo waveform L of the leaky wave and the echo waveform V of the vertical reflection wave. Further, the sound speed V _{W of the} ultrasonic wave transmitted in water can also be obtained by measurement. Further, the defocus amount ΔZ of the acoustic lens 103 can be obtained from the position of the surface of the subject S, the set position of the ultrasonic probe 101, and the focal length of the acoustic lens 103.

As a method for obtaining the sound velocity _VL of the leaky surface acoustic wave, in addition to the above-described method, the leaky wave and the vertically reflected wave are positively interfered with each other by using the incident wave from the vibrator 102 as a burst wave. There is also a method of obtaining from the dip period of the variation curve (V (z) curve) of the interference wave, but the description is omitted because it is not directly related to the present invention.

[0010]

By the way, in order to obtain the sound velocity _VL of the leaky surface acoustic wave from the above equation (1) and to evaluate the degree of deterioration of the subject S, the received signal of the transducer 102 must be determined. It is premised that the echo waveform L of the leaky wave and the echo waveform V of the vertical reflected wave can be clearly separated from each other, and the time difference Δt can be measured. Generally, when the defocus amount ΔZ of the acoustic lens 103 is increased, the propagation distance of the leaky surface acoustic wave is increased, and the path A → B → C → D → E → F and the path G → H
The stroke difference of → I → H → G increases, and as shown in FIG. 14, the echo waveform L of the leaky wave and the echo waveform V of the vertical reflected wave are separated on the time axis, and the time difference Δt can be measured. However, according to a study by the inventors of the present application, for a subject whose base material is coated with a coating such as a sprayed coating that easily attenuates leaky surface acoustic waves, the defocus amount ΔZ of the acoustic lens 103 is variously changed. However, it was found that the echo waveform L of the leaky wave and the echo waveform V of the vertical reflection wave could not be clearly separated, and the time difference Δt could not be obtained. That is, the inventors of the present application performed an experiment on a test object in which a sprayed coating made of a WC-based sprayed material having a thickness of 0.1 mm was applied to the surface of the base material, and found that the defocus amount Δ
When Z is increased, the attenuation of the leaky surface acoustic wave increases, and it becomes difficult to detect the echo waveform L of the leaky wave. Conversely, when the defocus amount ΔZ of the acoustic lens 103 is reduced, the echo waveform V of the vertical reflected wave is reduced. In this case, the echo waveform L of the leaky wave is buried, and the two cannot be clearly separated, and the time difference Δt cannot be obtained.

When a theoretical analysis is added to this, the thickness of the throat (between GH in FIG. 13A) is 5 mm
From an aluminum (acoustic velocity = 6400 m / s) acoustic lens with a defocus amount ΔZ of 0.2 mm and 10 MHZ
When the ultrasonic pulse of z is transmitted, the sound velocity _VL of the leaky surface acoustic wave propagating through the WC sprayed coating is about 2300 m / s.
(Value measured in advance using the same kind of thermal sprayed coating whose surface has been polished), and the Rayleigh critical angle is about 41 degrees, so the path G → H → I → H → G shown in FIG. Propagation time of propagating normal incident wave and vertical reflected wave is 10.05μs
In contrast, the route A → B → shown in FIG.
The propagation time of the oblique incident wave, the leaky surface acoustic wave and the leaky wave propagating in the C → D → E → F path is 10.1 μs, and the difference is 50 ns, and the period of the used frequency (100 ns)
, The time difference Δt cannot be determined even if a weak leaky wave is received.

Further, in order to obtain the sound velocity _VL of the leaky surface acoustic wave from the above equation (1), and to evaluate the degree of deterioration of the subject S, the distance between the ultrasonic probe 101 and the subject S must be determined. It is necessary to specify the sound speed V _W of the ultrasonic wave propagating in the intervening water, but as is well known, the sound speed V _{W of the} ultrasonic wave propagating in the water is known.
Varies depending on the water temperature, and varies by several m / s with a difference of 1 ° C. in a normally used range. Therefore, in order to accurately obtain the sound velocity _VL of the leaky surface acoustic wave by the equation (1), the water temperature must be changed for each test. Need to measure. For this reason, the conventional ultrasonic inspection apparatus requires a temperature sensor for measuring the water temperature, which complicates the structure and the sound velocity V _{L of the} leaky surface acoustic wave.
Measurement of the water temperature and the sound velocity of the water every time it is measured, it is necessary to efficiently measure the sound velocity _VL of the leaky surface acoustic wave and, consequently, to inspect the degree of deterioration of the subject. Is difficult to perform.

In the above description, the stress distribution and fracture toughness of the specimen and the degree of deterioration of the material such as thermal embrittlement and intergranular corrosion have been described as examples. Similar inconveniences arise when evaluating the soundness of the surface of the subject, such as the presence or absence of peeling of the provided coating.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned deficiencies of the prior art, and an object thereof is to provide a supersonic wave capable of calculating the sound velocity of a leaky surface acoustic wave with high accuracy without measuring the water temperature. To provide an ultrasonic inspection apparatus, and further to provide an ultrasonic inspection apparatus capable of calculating the sound velocity of a leaky surface acoustic wave with high accuracy without measuring the water temperature even for a subject having a large attenuation of the leaky surface acoustic wave. Is to do.

[0015]

According to the present invention, there is provided an ultrasonic scanning section having an ultrasonic probe and a mechanical scanner for transferring the ultrasonic probe to a subject. In an ultrasonic inspection apparatus including a driving unit of an ultrasonic scanning unit and an arithmetic processing unit that controls the ultrasonic scanning unit via the driving unit and performs a desired ultrasonic inspection, a focus of the ultrasonic probe Is set to the first depth position of the subject, and the transmission time of the oblique incident wave and the leaky surface acoustic wave when the ultrasound is transmitted and the propagation time of the leaky wave and the focal point of the ultrasound probe are set to the second position of the subject. The difference between the oblique incident wave and the leaky surface acoustic wave and the propagation time of the leaky wave when the ultrasonic wave is set at the depth position of 2, and the focus of the ultrasonic probe are set to the first position of the subject. Ultrasound was transmitted at the depth position Kino second focal point of the subject of the propagation time of the vertical incident wave and vertical reflected wave and the ultrasonic probe
Based on the difference between the propagation time of the vertically incident wave and the vertically reflected wave when transmitting the ultrasonic wave at the depth position, the arithmetic processing unit calculates the sound velocity of the leaky surface acoustic wave. did.

In the ultrasonic inspection apparatus having the above-mentioned configuration, the first depth position may be a surface of the subject,
The second depth position may be a position where a leaked surface acoustic wave is generated in the subject by an ultrasonic wave transmitted from the ultrasonic probe.

When the focal position of the acoustic lens 3 matches the surface of the subject S as shown in FIG.
The propagation time t _{L0 of the} ultrasonic wave passing through D → E → F and the path A → B → C → D when the focal position of the acoustic lens 3 is shifted inward from the surface of the subject S as shown in FIG. The time difference Δt _{L from} the propagation time t _{L1 of the} ultrasonic wave passing through → E → F is represented by ΔZ for the defocus amount of the acoustic lens 3 and θ _{L for the} Rayleigh critical angle,
When the sound velocity of water is V _W and the sound velocity of leaky surface acoustic waves is _VL ,

[0018]

(Equation 2)

From the Snell's law, V _W = V _L si
Eliminating θ _L from equation (2) using nθ _L yields equation (3) below.

[0020]

(Equation 3)

On the other hand, the focal position of the acoustic lens 3 is set
When the ultrasonic wave propagation time t _V0 passing through the path G → I → G is matched with the surface of the subject S, and the focal position of the acoustic lens 3 is shifted from the surface of the subject S, the ultrasonic wave passes through the path G → I → G. The time difference Δt _V from the sound wave propagation time t _V1 is represented by the following equation (4).

[0022]

(Equation 4)

From the equation (4), the sound velocity V _W of the water is obtained by the following equation (5).

[0024]

(Equation 5)

Here, if the equation (5) is substituted into the equation (3), the following equation (6) for obtaining the sound velocity _VL of the leaky surface acoustic wave which does not include the sound velocity V _W of the water as a variable can be obtained. it can.

[0026]

(Equation 6)

Accordingly, the oblique incident wave and the leaked surface acoustic wave and the propagation time of the leaked wave and the focal point of the ultrasonic probe, which are measured with the focus of the ultrasonic probe coincident with the surface of the subject S, are set inside the subject. And the difference Δt _L between the oblique incident wave and the leaky surface acoustic wave and the propagation time of the leaky wave measured, and the normal incident wave and the vertical reflected wave measured by adjusting the focus of the ultrasonic probe to the surface of the subject S. The difference Δt _V between the propagation time and the propagation time of the vertically incident wave and the vertically reflected wave measured by setting the focal point of the ultrasonic probe inside the subject and the defocus amount of the acoustic lens 3 from the ΔZ Can be calculated, and the configuration of the ultrasonic inspection apparatus can be simplified and the calculation can be performed more efficiently.

As the ultrasonic probe, as shown in FIG. 13 described above, the propagation speed of the ultrasonic wave in the propagation path (G → H and H → G) of the vertically incident wave and the vertically reflected wave and the oblique incidence One having a uniform acoustic lens 103 having the same ultrasonic wave propagation velocity in the propagation path of the wave and the leaky wave (A → B and E → F) can be used. For example, as shown in FIG. , The propagation velocity of the ultrasonic wave in the propagation path (G → I and I → G) of the vertically incident wave and the vertically reflected wave, and the propagation velocity of the ultrasonic wave in the propagation path (A → B and E → F) of the oblique incident wave and the leaky wave A lens provided with an acoustic lens 3 having a different propagation speed can also be used.

In the ultrasonic probe shown in FIG. 13, the attenuation of the leaky surface acoustic wave is small, and the echo waveform V of the vertically reflected wave and the echo waveform L of the leaky wave can be separated on the time axis. The present invention is applied to an examination of a subject in which Δt _L and Δt _V can be calculated. On the other hand, the ultrasonic probe illustrated in FIG. 3 has a large attenuation of the leaky surface acoustic wave as well as this type of subject, for example, a subject on which a thermal spray coating is formed. In the ultrasonic probe of the above, the echo waveform V of the vertically reflected wave and the echo waveform L of the leaky wave cannot be separated on the time axis, and therefore, the time difference Δ
The present invention can also be applied to an examination of a subject for which t _L and Δt _V cannot be calculated.

Means for making the propagation speed of the ultrasonic wave in the propagation path of the vertical incident wave and the vertically reflected wave of the acoustic lens different from the propagation velocity of the ultrasonic wave in the propagation path of the oblique incident wave and the leaky wave of the acoustic lens. (A) a through hole is formed in the propagation path of a normal incident wave and a vertical reflected wave of the acoustic lens from a setting surface of the vibrator to a lens curvature surface opposed thereto, and (b) a lens curvature of the acoustic lens. (C) in a through-hole formed in the acoustic lens,
Alternatively, a filling made of a material whose ultrasonic wave propagation speed is lower than that of the material forming the acoustic lens is filled in a recess formed on the transducer setting surface or the lens curvature surface of the acoustic lens. In the through-hole opened in, or in the recess formed in the vibrator setting surface or lens curvature surface of the acoustic lens, a filler made of a material having a higher ultrasonic wave propagation speed than the material constituting the acoustic lens is filled. There is a means of filling.

As a specific example of the above (c), an acoustic lens made of aluminum in which a resin is filled in a through hole or a hollow can be cited. Further, as a specific example of the above (d), an acoustic cylindrical lens is press-fitted into a through hole or a hollow of an acoustic lens made of resin, or resin is outsert molded around a core material made of aluminum to form an acoustic lens. Can be mentioned.

The shapes of the acoustic lens and the vibrator are not limited at all, and a single-type vibrator having a circular planar shape formed on a concave lens having a spherical curvature surface may be provided. However, the cylindrical lens may be provided with a single or array type transducer.

If the propagation speed of the ultrasonic wave in the propagation path of the normal incident wave and the vertically reflected wave of the acoustic lens differs from the propagation speed of the ultrasonic wave in the propagation path of the oblique incident wave and the leaky wave of the acoustic lens, the leakage Even when the amount of defocus ΔZ cannot be increased due to the large attenuation of the surface acoustic wave, the reception timing of the vertical reflected wave and the reception timing of the leaky wave by the vibrator can be shifted, so that the echo waveform V of the vertical reflected wave And the echo waveform L of the leaky wave can be clearly separated on the time axis, and the propagation time of each echo can be obtained. Therefore, the sound velocity _VL of the leaky surface acoustic wave can be easily obtained by using the above equation (6). Therefore, from this fact, even for specimens with a coating that easily attenuates leaky surface acoustic waves such as a thermal spray coating on the surface of the base material, the stress distribution, fracture toughness, thermal embrittlement and intergranular corrosion The non-destructive evaluation of the degree of deterioration of the specimen, the presence or absence of cracks on the specimen surface, and the presence or absence of peeling of the coating provided on the specimen surface can be performed without destruction.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an overall configuration of an ultrasonic inspection apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of an ultrasonic inspection apparatus, and FIG. 2 is a partially sectional perspective view of an ultrasonic probe setting unit in the ultrasonic inspection apparatus.

As shown in these figures, the ultrasonic inspection apparatus according to the present embodiment includes an ultrasonic scanning unit 10 for two-dimensionally scanning an ultrasonic wave along the surface of a subject S, and a drive of the ultrasonic scanning unit 10. Unit 20 and the ultrasonic scanning unit 1 via the driving unit 20
0, an arithmetic processing unit 30 that obtains desired inspection results such as stress distribution, fracture toughness value, and degree of deterioration of the subject from the received waveform of the ultrasonic wave by calculation, It mainly comprises a display unit 40 for displaying the results of the ultrasonic inspection.

As shown in FIG. 2, the ultrasonic scanning unit 10
The ultrasonic probe 1 includes a water tank 11 in which water W that stores the ultrasonic probe 1 and the subject S is stored, and a mechanical scanner 12 that drives the ultrasonic probe 1 in a three-dimensional direction. The mechanical scanner 12 is provided with two parallel
A pair of Y-axis guides 1 arranged in the YY direction along the side
3, a Y-axis slider 14 guided by the Y-axis guide 13 in the Y-Y direction, and an X-axis guide 15 fixed at both ends to the Y-axis slider 14 and arranged in the XX direction.
An X-axis slider 16 guided in the X-X direction by the X-axis guide 15, a Z-axis guide 17 fixed perpendicular to the X-axis slider 16, and the ultrasonic probe 1, It has a Z-axis slider 18 guided in a Z-Z direction by a shaft guide 17, and each of the sliders 14, 16, 18 has three motors M1 to M shown in FIG.
3 driven. Each of these motors is provided with a position signal output device such as a rotary encoder, and the arithmetic processing unit 30 can detect coordinate signals of the sliders 14, 16, and 18.

The driving unit 20 includes a pulsar / receiver 21 for transmitting an ultrasonic wave from the ultrasonic probe 1 and receiving an ultrasonic wave by the ultrasonic probe 1, and digitally converts a signal received by the pulsar / receiver 21. An A / D converter 22 and a motor driver 23 for driving three motors M1 to M3 provided in the mechanical scanner 12 are provided.

The arithmetic processing unit 30 includes a CPU 31
Input means 32 such as a keyboard and a mouse; a trigger 33 and a motor controller 34 driven by a command from the input means 32; and an A / D-converted received signal transmitted to the motor via the motor driver 23 and the motor controller 34. A first memory 35 that accumulates together with the coordinate signals fetched from (M1 to M3), a timer 36 that is activated by a signal from the trigger 33 to set a gate for signal processing by the CPU 31, and stores a procedure of signal processing by the CPU 31. The second memory 37 is provided.

Accordingly, the ultrasonic inspection apparatus of this embodiment operates the mechanical scanner 12 by operating the input means 32.
Can drive the motors M1 to M3 provided in the
The ultrasonic probe 1 can be positioned with respect to the subject S set in the water tank 11. The coordinate signal of the ultrasonic probe 1 at this time is taken into the first memory 35 via the motor driver 23 and the motor controller 34. By operating the input means 32 from this state, the pulsar / receiver 21 and the motor controller 34 can be driven, and the ultrasonic probe 1 is moved two-dimensionally along the surface of the subject S, The transmission of the ultrasonic wave from the ultrasonic probe 1 and the reception of the ultrasonic wave by the ultrasonic probe 1 can be performed. Ultrasonic probe 1
The ultrasonic wave received by the A / D converter 22 is A / D converted by the A / D converter 22 and is stored in the first memory 35 together with coordinate signals taken in from the motors M1 to M3 via the motor driver 23 and the motor controller 34. You. CP
U31 is the first for each gate set in the timer 36.
The signal stored in the memory 35 is fetched, the signal processing is performed based on the signal processing procedure stored in the second memory 37, and the processing result is displayed on the display device 40 in color tone.

Hereinafter, the configuration of an ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described.

<First Example of Ultrasonic Probe> First, a first example of an ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described with reference to FIGS. FIG. 3 (a),
FIG. 4B is a sectional view and a plan view of a main part showing a first example of an ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention. FIG. It is.

As is apparent from FIGS. 3A and 3B,
The ultrasonic probe 1A of the present example has the same basic configuration as the ultrasonic probe 101 according to the conventional example, and is a single-type vibrator 2 having a circular planar shape and transmitted from the vibrator 2. And a cylindrical acoustic lens 3 for converging the ultrasonic waves and entering the subject S. The ultrasonic probe 1A of this example is characterized in that a through hole 4 is formed in the center of the acoustic lens 3 so as to penetrate from the setting surface 3a of the vibrator 2 to the lens curvature surface 3b. It is sufficient if the diameter of the through hole 4 is set to be equal to or larger than the propagation range of the vertically incident wave and the vertically reflected wave. However, in order to suppress the reception of noise as much as possible, it is possible to prevent the propagation of the obliquely incident wave and the leaky wave. It is preferable to make it as large as possible. Other components are the same as those of the ultrasonic probe 101 according to the conventional example, and therefore, description thereof will be omitted to avoid duplication.

As described above, the ultrasonic probe is placed in the water together with the subject S when the subject S is evaluated. Therefore, when the ultrasonic probe 1A of the present embodiment in which the through hole 4 is opened in the center of the acoustic lens 3 is used,
As shown in FIG. 3A, the oblique path A → B →
C and D → E → F and the subject S, an aluminum acoustic lens 3 (sound speed = about 6) having a high ultrasonic wave propagation speed.
400 m / s) and water having a low ultrasonic propagation speed (about 1480 m / s at 19 ° C. and about 1500 m / s at 26 ° C.), whereas the vertical paths G → I and I →
Since only water having a low ultrasonic wave propagation speed is interposed between G and the subject S, the route A → B → C → D → E
→ The propagation time of the normal incident wave and the vertical reflected wave passing through the route G → I → G is longer than the propagation time of the oblique incident wave, leaky surface acoustic wave and leaky wave passing through F, as shown in FIG. To
An echo waveform V of the vertically reflected wave and an echo waveform L of the leaky wave are separated, and a received signal in which the echo waveform L of the leaky wave precedes the echo waveform V of the surface reflected wave is obtained. Therefore, the time difference Δt between the echo waveform L of the leaky wave and the echo waveform V of the surface reflected wave can be obtained, and the above (6)
Since the sound velocity _VL of the leaky surface acoustic wave can be obtained from the equation, for example, the stress distribution and fracture toughness value of the specimen S and the degree of deterioration of the material such as thermal embrittlement and intergranular corrosion can be obtained from the change in sound speed of the leaky surface acoustic wave. In addition, the soundness of the surface of the subject, such as the presence or absence of cracks on the surface of the subject and the presence or absence of peeling of the coating provided on the surface of the subject, can be evaluated nondestructively.

As described above, the surface of the base material has a thickness of 0.1 m.
m and a lens having a throat thickness of 5 mm, an aluminum acoustic lens having a thickness of 5 mm, a defocus amount ΔZ of 0.2 mm, an operating frequency of 10 MHz, and a sound velocity _VL of a leaky surface acoustic wave of 2300 m. / S, the Rayleigh critical angle is 41 degrees, and the time difference Δt between the vertical wave V and the leaky surface acoustic wave L is obtained. The propagation time of the ultrasonic wave propagating along the route A → B → C → D → E → F is about 10 μs. On the other hand, the propagation time of the ultrasonic wave propagating along the route G → I → G is about 15 μs.
And the difference is 5 μs (50 times the period of the used frequency)
Thus, it can be seen that both waves can be separated even in a test object having a thermal spray coating.

In the previous example, the frequency used was 10
MHz, but similar results were obtained when the frequency was changed in the range of 5 to 20 MHz.

<Second Example of Ultrasonic Probe> Next, a second example of the ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described with reference to FIG. FIG. 5 is a sectional view of a main part of an ultrasonic probe according to a second example.

The ultrasonic probe 1B of the second example has a central portion of the acoustic lens 3 (propagation path of a vertically incident wave and a vertically reflected wave).
Instead of the configuration in which the through hole 4 is formed, a recess 5 is formed at the center of the lens curvature surface 3b of the acoustic lens 3.

When the ultrasonic probe 1B is used, similarly to the ultrasonic probe 1A according to the first example, the path A
→ B → C → D → E → F Since the propagation time of the ultrasonic wave propagating through the path G → I → G can be relatively delayed from the propagation time of the ultrasonic wave passing through F, the echo waveform V of the vertical reflected wave can be obtained. And the echo waveform L of the leaky wave can be separated. Further, the acoustic lens 3 of the present embodiment has an effect that the vibrator 2 can be easily and reliably set because the vibrator setting surface 3a is closed.

<Third Example of Ultrasonic Probe> Next, a third example of the ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described with reference to FIG. FIG. 6 is a sectional view of a main part of an ultrasonic probe according to a third example.

The ultrasonic probe 1C of the third example is different from the configuration in which the hollow 5 for simply forming the through hole 4 is formed in the center portion of the acoustic lens 3 in the inside of the opened through hole 4 or the formed hollow. 5 is characterized by being filled with a filling material 6 made of a material having a different ultrasonic wave propagation speed from the material constituting the acoustic lens 3. FIG. 6A shows a case where the filler 6 is filled in the through hole 4 formed in the center of the acoustic lens 3.
FIG. 6B shows a case where the filler 6 is filled in the recess 5 formed on the transducer setting surface 3 a of the acoustic lens 3. FIG. 6C shows the inside of the recess 5 formed on the lens curvature surface 3 b of the acoustic lens 3. Shows a case in which the filling material 6 is filled.

The material constituting the acoustic lens 3 and the filler 6 are preferably as large as the difference in the propagation speed of the ultrasonic wave. If the acoustic lens 3 is made of aluminum (sound speed = 6400 m / s), A resin material such as an acrylic resin (sound speed = 2000 to 2500 m / s) is preferably used as the material 6, and conversely, when the acoustic lens 3 is made of a resin material, aluminum is preferably used as the filler 6. Used. When a resin is used as the filling portion 6, the acoustic lens 3 can be manufactured by potting the resin as the filling material into the opened through hole 4 or the formed recess 5. When a solid is used as the filling portion 6, the acoustic lens 3 can also be manufactured by press-fitting a solid as a filling material into the opened through hole 4 or the formed recess 5. Further, when the acoustic lens 3 is made of a resin material, a desired acoustic lens 3 can be manufactured by outsert molding a resin around a filler 6 such as aluminum.

Of course, when the filling material 6 whose ultrasonic wave propagation speed is lower than that of the material forming the acoustic lens 3 is filled,
The propagation time of the ultrasonic wave propagating through the route G → I → G is relatively slower than the propagation time of the ultrasonic wave passing through the route A → B → C → D → E → F, and as shown in FIG. When the echo waveform L of the wave has a shape preceding the echo waveform V of the vertically reflected wave, and conversely, when the filling material 6 having a higher ultrasonic wave propagation speed than the material forming the acoustic lens 3 is filled, , Route A →
The propagation time of the ultrasonic wave propagating through the route G → I → G becomes relatively faster than the propagation time of the ultrasonic wave passing through B → C → D → E → F, and as shown in FIG. Echo waveform V
Has a shape preceding the echo waveform L of the leaky wave.

The ultrasonic probe 1C of the present example has a propagation path G → I of a vertical incident wave and a vertical reflected wave in the acoustic lens 3.
And I → G and propagation path A → B → of oblique incident wave and leaky wave
Since C and D → E → F are made of materials having different sound velocities, the difference between the propagation times of the ultrasonic waves passing through the respective paths becomes large, and the echo waveform V of the vertically reflected wave and the echo waveform L of the leaky wave become large.
Can be separated, and the vibrator setting surface of the acoustic lens 3 has a closed shape, so that the vibrator 2 can be set easily and reliably.

<Fourth Example of Ultrasonic Probe> Next, a fourth example of the ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described with reference to FIGS. 7 (a) and 7 (b). FIG.
(A), (b) is the principal part perspective view seen from the plane direction of the ultrasonic probe which concerns on the 4th example, and the principal part perspective view seen from the bottom face direction.

The ultrasonic probe 1D of the fourth example is shown in FIG.
As shown in FIG. 1A, a cylindrical lens is used as the acoustic lens 3, and an array type vibrator in which a plurality of vibrators 2a to 2n are adjacently arranged in one direction is provided as the vibrator 2. Features. As shown in FIG. 7B, a through hole 4 is formed in the propagation path of the vertically incident wave and the vertically reflected wave on the bottom surface of the cylindrical lens. In addition, it is also possible to form a depression instead of the configuration in which the through hole 4 is formed in the bottom surface of the cylindrical lens,
Furthermore, in the opened through-hole or formed hollow,
Of course, it is also possible to fill the filling material having a different propagation speed of the ultrasonic wave from the propagation path of the oblique incident wave and the leaky wave.

The ultrasonic probe 1D of this embodiment uses a cylindrical lens as the acoustic lens 3 and an array type vibrator as the vibrator 2, so that the surface of the subject S can be traced in a plane. As compared with the case where a cylindrical acoustic lens is provided with a single-type vibrator having a circular planar shape, the inspection efficiency of the subject S can be improved.

<Fifth Example of Ultrasonic Probe> Next, a fifth example of the ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described with reference to FIG. FIG. 8 is a perspective view of a main part of an ultrasonic probe according to a fifth example viewed from a plane direction.

As shown in FIG. 8, the ultrasonic probe 1E according to the fifth example is characterized in that a cylindrical lens is used as the acoustic lens 3 and a single-type vibrator is provided as the vibrator 2. FIG. 7B shows a propagation path of a vertical incident wave and a vertical reflected wave on the bottom surface of the cylindrical lens.
In the same manner as shown in FIG. Of course, instead of the configuration in which the through-hole 4 is formed in the bottom surface of the cylindrical lens, a depression may be formed, and the propagation path of the oblique incident wave and the leaky wave in the opened through-hole or the formed depression may be superfluous. It is also possible to fill the filling with different sound wave propagation speeds.

The ultrasonic probe 1D of this embodiment uses a cylindrical lens as the acoustic lens 3 and a single type of vibrator as the vibrator 2, so that the ultrasonic beam is linearly applied to the surface of the subject S. Since the irradiation can be performed, the inspection efficiency of the subject S can be increased as compared with a case where the cylindrical acoustic lens is provided with a single-type vibrator having a circular planar shape.

<Sixth Example of Ultrasonic Probe> Next, a sixth example of the ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described with reference to FIG. FIG. 9 is a sectional view of a main part of an ultrasonic probe according to a sixth example.

The ultrasonic probe 1F of the sixth example has the same configuration as the ultrasonic probe 101 of the conventional example. The acoustic lens 3 has through holes and dents in the propagation paths of the vertically incident wave and the vertically reflected wave. It is characterized in that it is not provided with a filling material and is entirely homogeneous.

When the ultrasonic probe 1F of this embodiment is used, an echo waveform V of a vertically reflected wave and an echo waveform L of a leaky wave are used.
Preparative separation can a bur, the subject attenuation is small LSAW is not possible to measure the water temperature, it is possible to perform the desired ultrasound.

<Seventh Example of Ultrasonic Probe> Next, a seventh example of the ultrasonic probe provided in the ultrasonic inspection apparatus of the present invention will be described with reference to FIG. FIG. 10 is a sectional view of a main part of an ultrasonic probe according to a seventh example.

The ultrasonic probe 1G of the seventh example is characterized in that the transducer 2 is not provided with an acoustic lens, but is provided with a vibrator 2 having a circular planar shape formed on a concave surface 1b formed on the probe main body 1a.

In the case where the ultrasonic probe 1 of this embodiment is used, the echo waveform V of the vertically reflected wave and the echo waveform L of the leaky wave are also determined similarly to the case where the ultrasonic probe 1F of the fifth embodiment is used. For a subject that can not be separated but has a small attenuation of leaky surface acoustic waves, a desired ultrasonic inspection can be performed without measuring the water temperature.

Hereinafter, an example of an ultrasonic inspection method using the ultrasonic inspection apparatus according to the present invention will be described with reference to FIG. 3A, FIG. 11 and FIG. This inspection method
Without measuring the water temperature, the sound velocity V _{L of the} leaky surface acoustic wave
Can be calculated. FIG. 11 is an explanatory diagram showing the arrangement of the ultrasonic probe when the focal point of the acoustic lens coincides with the surface of the subject, and FIG. 12 is a flowchart showing the procedure of the ultrasonic inspection method. FIG.
The procedure of the ultrasonic inspection method shown in FIG.
Is stored in the memory 37.

First, in step S1, the Z-axis slider 18 of the mechanical scanner 12 is driven to move the ultrasonic probe 1 in a direction to approach the subject S or in a direction away from the subject S, as shown in FIG. In this way, the focal point of the acoustic lens 3 is matched with the surface of the subject S. The focus of the acoustic lens 3 is the subject S
Since the echo level of the leaked wave becomes maximum when the surface of the subject S is matched, it is possible to know that the focal point of the acoustic lens 3 matches the surface of the subject S.

In step S2, an ultrasonic wave is transmitted from the vibrator 2, and the propagation time t _{L0 of the} ultrasonic wave passing through the path A → B → C (D) → E → F and the ultrasonic wave passing through the path G → I → G Sound propagation time t
Measure _V0 . Further, the output value Z ₀ of the Z-axis slider 18 is read.

Next, in steps S3 and S4, the ultrasonic probe 1 is brought close to the subject S until a leaky surface acoustic wave is detected. The stop position of the ultrasonic probe 1 does not necessarily need to be a position where the echo level of the leaky surface acoustic wave is maximized, and can be set arbitrarily within a range where the leaky surface acoustic wave can be detected. When a leaky surface acoustic wave is detected, the ultrasonic probe 1 is at the position shown in FIG. 3A, and the focal position of the acoustic lens 3 is inside the surface of the subject S by the defocus amount ΔZ.

In step S5, an ultrasonic wave is transmitted from the vibrator 2, and the propagation time t _{L1 of the} ultrasonic wave passing through the path A → B → C → D → E → F and the ultrasonic wave passing through the path G → I → G Propagation time t _V1
Is measured. Further, it reads the output value Z ₁ of the Z-axis slider 18.

Then, the process proceeds to step S6, where the propagation time t _{L0 of the} ultrasonic wave passing through the route A → B → C (D) → E → F measured in step S2 and the route A → B → measured in step S5. C → D
→ E → Time difference Δt _{L from} ultrasonic wave propagation time t _L1 passing through F
(= T _L0 −t _L1 ), the route G → I → measured in step S2
The time difference Δt _V (= t _V0 −t _V1 ) between the propagation time t _{V0 of the} ultrasonic wave passing through G and the propagation time t _{V1 of the} ultrasonic wave passing through the path G → I → G measured in step S5 and measured in step S2 The difference between the output value Z ₀ of the Z-axis slider 18 thus obtained and the output value Z ₁ of the Z-axis slider 18 measured in step S5, that is, the defocus amount ΔZ (= Z ₀ −Z ₁ ) of the acoustic lens 3 is calculated. .

Finally, from these calculated values, the sound velocity _VL of the leaky surface acoustic wave is obtained by using the above equation (6).

Since equation (6) does not include the sound velocity V _W of water as a variable, the sound velocity V _L of leaky surface acoustic waves can be calculated without measuring the sound velocity V _W of water based on this equation. . Although the description is omitted in the above description, when the above-described inspection method is performed, the Y
It goes without saying that the ultrasonic probe 1 is scanned along the surface of the subject S by appropriately driving the axis slider 14 and / or the X-axis slider 16.

In the ultrasonic inspection method shown in FIG. 12, the focus of the acoustic lens 3 is matched with the surface of the subject S in step S1, but the focus of the acoustic lens 3 is set on the surface of the subject S in this procedure. It is not that the required ultrasonic inspection cannot be performed unless they completely match.
May be positioned slightly inside the surface of the subject S. In this case, in steps S3 and S4, the focal position of the acoustic lens 3 is moved further inside the subject S than the focal position of the acoustic lens 3 set in step S1.

[0075]

According to the ultrasonic inspection apparatus of the present invention, the oblique incident wave, the leaky surface acoustic wave, the propagation time of the leaky wave, and the propagation time of the ultrasonic probe measured with the focus of the ultrasonic probe coincident with the surface of the subject are measured. The difference between the oblique incident wave, the leaky surface acoustic wave, and the propagation time of the leaky wave measured with the focus set inside the subject, and the normal incidence measured with the focus of the ultrasonic probe matched to the surface of the subject Calculates the sound velocity of leaky surface acoustic waves based on the difference between the propagation times of waves and vertically reflected waves and the propagation times of vertically incident waves and vertically reflected waves measured with the focus of the ultrasonic probe set inside the subject. Therefore, it is not necessary to measure the water temperature for each test, and the temperature sensor can be omitted, so that the configuration of the ultrasonic inspection apparatus can be simplified and the calculation can be performed more efficiently.

[Brief description of the drawings]

FIG. 1 is a block diagram of an ultrasonic inspection apparatus.

FIG. 2 is a configuration diagram of an ultrasonic scanning unit in the ultrasonic inspection apparatus.

FIG. 3 is a sectional view and a plan view of a main part of the ultrasonic probe according to the first embodiment.

FIG. 4 is an echo waveform of a leaky wave and a vertically reflected wave received by a vibrator.

FIG. 5 is a sectional view of a main part of an ultrasonic probe according to a second embodiment.

FIG. 6 is a sectional view of a main part of an ultrasonic probe according to a third embodiment.

FIGS. 7A and 7B are a perspective view of a main part viewed from a plane direction and a perspective view of a main part viewed from a bottom direction of an ultrasonic probe according to a fourth embodiment.

FIG. 8 is a perspective view of a main part of an ultrasonic probe according to a fifth embodiment.

FIG. 9 is a sectional view of an essential part of an ultrasonic probe according to a sixth embodiment.

FIG. 10 is a sectional view of an essential part of an ultrasonic probe according to a seventh embodiment.

FIG. 11 is an explanatory diagram when the focal point of the acoustic lens matches the surface of the subject.

FIG. 12 is a flowchart illustrating a procedure of an ultrasonic inspection method.

FIG. 13 is a sectional view and a plan view of a main part of a conventionally known ultrasonic probe.

FIG. 14 is an echo waveform of a leaky wave and a vertically reflected wave received by the vibrator.

[Description of Signs] 1 Ultrasonic probe 1A Ultrasonic probe according to first example of implementation 1B Ultrasound probe according to second example of implementation 1C Ultrasound probe according to third example of implementation 1D According to fourth example of implementation Ultrasonic probe 1E Ultrasonic probe according to fifth embodiment 1F Ultrasonic probe according to sixth embodiment 1G Ultrasonic probe according to seventh embodiment 2 Vibrator 3 Acoustic lens 3a Vibrator setting surface 3b Lens curvature Surface 4 through-hole 5 hollow 6 filling

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 10

[Procedure amendment 3]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 13

Claims (8)

[Claims] An ultrasonic scanning unit having an ultrasonic probe and a mechanical scanner for transferring the ultrasonic probe to a subject; a driving unit of the ultrasonic scanning unit; and the ultrasonic scanning unit via the driving unit. An ultrasonic inspection apparatus having an arithmetic processing unit that controls an ultrasonic wave scanning unit and performs a desired ultrasonic inspection, wherein the ultrasonic probe is set at a first depth position of the subject, The oblique incident wave and the leaky surface acoustic wave when transmitting the acoustic wave and the propagation time of the leaky wave and the ultrasonic probe when transmitting the ultrasonic wave with the focal point of the ultrasonic probe set to the second depth position of the subject The difference between the oblique incident wave, the leaky surface acoustic wave, and the propagation time of the leaky wave, and the normal incidence when the ultrasonic probe is set at the first depth position of the subject and the ultrasonic wave is transmitted. Time of Wave and Vertically Reflected Wave and the Ultrasonic Wave Move the focus of the probe to the second
Based on the difference between the propagation time of the vertically incident wave and the vertically reflected wave when transmitting the ultrasonic wave at the depth position, calculating the sound velocity of the leaky surface acoustic wave in the arithmetic processing unit. Ultrasonic inspection equipment. 2. The ultrasonic inspection apparatus according to claim 1, wherein the first depth position is a surface of the subject, and the second depth position is an ultrasonic wave transmitted from the ultrasonic probe. An ultrasonic inspection apparatus, wherein a position where a leaked surface acoustic wave is generated in the subject by a sound wave is provided. 3. The ultrasonic inspection apparatus according to claim 1, wherein the ultrasonic probe includes a vibrator and an acoustic lens that converges ultrasonic waves transmitted from the vibrator and enters the object. The ultrasonic wave is configured such that the propagation velocity of the ultrasonic wave in the propagation path of the normal incident wave and the vertical reflection wave of the acoustic lens is different from the propagation velocity of the ultrasonic wave in the propagation path of the oblique incident wave and the leaky wave of the acoustic lens. An ultrasonic inspection apparatus characterized by using: 4. The ultrasonic inspection apparatus according to claim 3, wherein the acoustic lens penetrates a propagation path of a vertically incident wave and a vertically reflected wave from a transducer setting surface to a lens curvature surface opposed thereto. An ultrasonic inspection apparatus characterized in that a concave portion is formed in a propagation path of a vertical incident wave and a vertical reflected wave of the lens curvature surface. 5. The ultrasonic inspection apparatus according to claim 3, wherein the acoustic lens penetrates a propagation path of a vertically incident wave and a vertically reflected wave from a transducer setting surface to a lens curvature surface opposed thereto. Or a hollow is formed in the propagation path of the normal incident wave and the vertical reflected wave on the transducer setting surface or the lens curvature surface, and the material constituting the acoustic lens in these through holes or the hollow is an ultrasonic wave. An ultrasonic inspection apparatus characterized by using a material filled with a filler made of a material having different propagation speeds. 6. The ultrasonic inspection apparatus according to claim 3, wherein a concave lens having a lens curvature surface formed in a spherical shape is used as the acoustic lens. . 7. The ultrasonic inspection apparatus according to claim 3, wherein a cylindrical lens is used as the acoustic lens. 8. The ultrasonic inspection apparatus according to claim 1, wherein an ultrasonic probe having a transducer setting surface formed in a spherical shape is used as the ultrasonic probe.