JPS63131058A - Surface wave probe - Google Patents

Abstract

PURPOSE:To enable non-destructive measurement of a stress value working accurately on the surface of an object, depth or the like of a crack thereon, by making a surface wave transmitting body linear or a strip with a narrow width at the tip thereof contacting a test object and rounding the body at the rear end thereof. CONSTITUTION:A surface wave transmitting body 2 is provided abutting an ultrasonic surface wave probe 1 having a vibrator 1a and a delay material 1b. The transmitting body 2 is made linear or as strip with a narrow width at the tip 2a thereof contacting a test object 3 and a surface wave is transmitted to the surface of the test object 3 propagating in the directions of the arrows D, E and F from the surface 2b the probe 1 contacts. The rear end 2d of the transmitting body 2 in the ongoing direction of the surface wave is made round and the surface thereof facing the surface of the test object 3 connecting the rear end 2d and the tip 2a thereof is set at 0.2-1.2 deg. with the surface of the test object. Here, it is desirable that the radius of curvature of the roundness at the rear end 2d of the transmitting body 2 is larger than the wavelength of the surface wave. As there is no large bending of the surface wave at a contact position with the surface of a test object, the attenuation of the ultrasonic wave is prevented, resulting in a greater intensity of reception.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a surface wave probe for measuring the propagation velocity, propagation time, etc. when an ultrasonic surface wave is propagated on the surface of an elastic member. It is related to.

[Prior Art] FIG. 10 is a sectional view illustrating an example of how a conventional surface wave probe is used in the above field of application. As shown in the figure, the conventional surface wave probe 1°1' has a vibrator 1a,
1'a and delay material (generally acrylic resin) 1b, 1'
b, causing mode conversion due to the difference in the speed of the ultrasonic waves propagating through the delay materials 1b and 1b' and the speed of the ultrasonic waves propagating through the test specimen 3, and transmitting an ultrasonic surface wave,
It is something to receive (ffi).

Using the example shown in FIG. 10, an ultrasonic wave is transmitted from the transducer 1a of the surface wave probe 1 on the transmitting side, and the surface wave is propagated through the delay material 1b to the test specimen 3.

When a sound wave is incident on the test body 3 at a certain angle or more through the couplant 4, a surface wave propagates on the surface of the test body 3 in the direction of arrow A due to mode conversion of the sound wave. Then, at the surface wave probe 1' on the receiving side, contact is made! I! The sound wave propagates through the waveguide 4' and the delay material 1'b and is received by the vibrator 1'a.

The above-mentioned conventional surface wave probe 1.1', which is generally widely used, has a propagation velocity of 8 waves.

This was insufficient when trying to accurately measure propagation time, etc.

That is, using the example shown in Fig. 10, first, since the contact surfaces 1C and 1'C of the probes 1 and 1' have a width in the direction A of the sound wave, when trying to set the distance, An accurate reference point cannot be obtained.

In addition, since 1C and 1'c are flat surfaces, even slight differences in the state of contact with the test piece 3 based on, for example, unevenness on the surface of the test piece 3, parallel relationship with the surface of the test piece, etc. This causes fluctuations in the incident position of the sound wave and the reception position from the test object 3.

Further, the amount of surface waves transmitted and received varies depending on the material, characteristics, thickness, etc. of the couplant material 4.4'. With these, the propagation time and propagation distance of sound waves! ! Fluctuations occur in IL, making accurate measurement impossible.

In order to solve the above-mentioned problems, we previously invented a surface wave probe in Japanese Patent Application No. 15402/1983 that enables accurate measurement of the propagation velocity, propagation time, etc. of sound waves. Using this probe, it has become possible to non-destructively measure the value of stress acting on the surface of an object, the depth of cracks occurring on the surface of the object, etc.

The above-mentioned application was obtained by interposing a surface wave transmitting body 2 between a conventional surface wave probe 1 and a test specimen 3, as shown in FIGS. 8 and 9. And the first
In order to solve the problem when the conventional surface probe 1 shown in FIG. The portion 2a is arranged to abut linearly. Since the drawing is a cross-sectional view, it looks like a point, but in reality, there is a thickness in the direction perpendicular to the plane of the paper, so there is a linear contact. Ideally, the contact with the test object 3 is point-like contact, but the attenuation of the ultrasonic waves becomes significant and the ultrasonic waves are not transmitted sufficiently.

Therefore, considering practicality, it is preferable to make linear contact as close to the point as the ultrasonic output allows.

By doing this, the ultrasonic waves emitted from the surface wave probe 1 propagate on the surface 2b of the transmitting body 2, are transmitted to the surface of the test specimen 3 at the tip 2a, and are propagated in the direction of arrow B. . Since the tip makes linear contact as described above, a stable contact state and contact position can be obtained.

Although the case of the transmitting probe has been described above, in the case of the receiving probe, the sound waves propagated in the opposite direction of the arrow in the case of transmitting are received, and the same effect can be obtained.

In addition, as shown in FIG. 9, 2 of the wedge-shaped transmitting body 2
When the contact surface 1C of the probe 1 is brought into contact with the b-plane, if there is a sharp corner in the traveling direction of the surface wave (arrow D), the attenuation of the surface wave will be large, so this problem was solved by providing a roundness 2d. In this case, the radius of curvature of the roundness only needs to be larger than the wavelength of the surface wave used, but it is preferable to make it as large as possible.

Incidentally, in the case of the reception probe, attenuation of surface waves is also prevented by providing a roundness.

FIGS. 11 and 12 are diagrams for explaining an application example of measuring the velocity when a surface wave propagates, that is, the speed of sound, using the above-mentioned probe.

As shown in FIG. 11, the transmitting probes 1 and 2 and the receiving probes 1' and 2' are placed on the surface of the test specimen 3 at an arbitrary interval M. When a pulse current is supplied from an ultrasonic transceiver (not shown) to the transmitting probe 1, the surface waves of the ultrasonic waves propagate on the surface of the test specimen 3 in the direction of arrow J, and
' is converted into an electrical signal and amplified by an ultrasonic transceiver. Then, using a sound velocity measuring device (not shown), the contact position 1t2a of the transmitting probe and the contact position 2'a of the receiving probe are determined.
The speed of sound can be calculated from the propagation time of the ultrasonic wave that has propagated the distance M from the point.

FIG. 12 shows another application example in which transmitting/receiving probes 5 and 2, which have both transmitting and receiving functions, are placed on the surface of a test object 3, and a reflective metal is placed at an arbitrary distance N from the contact position 2a. body 6
This is an example of attaching and measuring. When a pulsed current is supplied from an ultrasonic transceiver (not shown) to the transceiver probe 5, the surface waves of the ultrasonic waves propagate on the surface of the test specimen 3 and reach the reflective metal body 6. A part of the surface wave is reflected by the reflective metal body 6 and returns to the transmitting/receiving probes 2 and 5. In the figure, arrows indicate the propagation direction of surface waves. The returned surface waves are converted into electrical signals by the transmitting/receiving probe 5 and amplified by the ultrasonic transmitting/receiving device. One round trip distance between the contact position 2a of the probe and the reflective metal body 6: 111N
The sonic velocity type is obtained by calculating the sonic velocity type using a sonic velocity measuring device (not shown) from the time that X2 and the ultrasonic wave make one round trip.

By measuring the sonic velocity of surface waves with high accuracy in this way, the material quality of the surface of the test piece can be determined.

This makes it possible to determine the stress value acting on the surface of the specimen. In other words, the test specimen has a sonic velocity displacement unique to its material. The sonic type increases linearly as the compressive stress increases, and the sonic type decreases linearly as the tensile stress increases. Therefore, if the relationship between the sonic profile and stress of the same or similar material as the test piece is determined in advance, the material and the stress value generated can be determined non-destructively by measuring the sonic profile of the test piece. be. The relationship between the sonic type and stress can be obtained by measuring the sonic type of a test piece while applying a compressive load or tensile load to a test piece made of the same or similar material as the test piece.

FIG. 13 is a front view illustrating an example in which the depth of fatigue pre-crack in a fracture toughness test piece is used as another application example of the above application.

Test piece 7 is for a three-point bending test in which a load T is applied while being supported at fulcrums R and S. Transmission probe 1 and transmitter 2
The surface wave emitted from the linear contact position 2a propagates on the surface 7a of the test piece as shown by arrow U, and reaches the linear contact position 21.
The signal is received by the probe 1' and the transmitter 2' at point a. Initially, the speed at which the surface wave propagates when no cracks occur in the groove bottom 7b, that is, the sound speed, and the propagation distance (known)
.

Find the propagation time. Next, when similarly measured after the fatigue pre-crack 7C has occurred, the propagation time becomes longer as the surface waves detour around the tip of the crack 7C.

At this time, since the sonic type is already known and the propagation time is measured, the depth of the crack 7c can be known.

[Problems to be Solved by the Invention] The surface wave probe shown in the above-mentioned Japanese Patent Application No. 15402/1982 is applied to the surface of the test specimen 3, as shown in FIG. 11, for example, to measure the sound velocity. In this case, when a pulse current is supplied from an ultrasonic transceiver (not shown) to the transmitting probe 1, the surface wave of the follow-up sound propagates along the surface of the transmitting body 2 in the directions E and F, and further , propagates in the J direction on the surface of the test object 30, propagates in the G, H, and Q directions on the surface of the transmitting body 2', and is converted into an electrical signal by the receiving probe 1', and is converted into an electric signal by the ultrasonic transceiver. amplified. Since the propagation path of the ultrasonic surface wave is largely bent at the contact positions ff2a and 2'a as described above, there is a problem in that the reception intensity becomes weak.

An object of the present invention is to provide a surface wave probe that has high reception strength and is capable of accurately and non-destructively measuring the stress value acting on the surface of an object, the depth of cracks occurring on the surface of the object, etc. Our goal is to provide the following.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a surface wave transmitting body that is provided in contact with an ultrasonic surface wave probe having a vibrator and a delay material. The tip of the surface wave transmitter that comes into contact with the test specimen is shaped like a line or a narrow band, and the rear end of the surface wave transmitter, which is in the opposite direction to the traveling direction or receiving direction of the surface wave, is rounded. A surface wave characterized in that the surface facing the surface of the specimen connecting the rear end portion and the tip is formed at an angle of 0.2” to 1.2° with the surface of the specimen. It is a probe.

The radius of curvature of the rear end of the surface wave transmitter is preferably larger than the wavelength of the surface wave used.

[Function] The shape of the surface wave transmitter of the surface wave probe is as described above,
Since there is no large bend in the surface waves at the point of contact with the surface of the test object, attenuation of the ultrasonic waves is prevented, and as a result, the reception intensity can be increased.

[Example] Embodiments of the present invention will be described below based on the drawings.

1 to 5 are cross-sectional views explaining the present invention in detail;
The figure is a front view for explaining another embodiment. In each figure, the same parts as in the above-mentioned FIGS. 8 to 13 are given the same reference numerals.

As shown in FIG. 1, the contact surface 1C of the probe 1 and the transmitting body 2
It is fixed to the 2b side with an adhesive (not shown). In these cases, the adhesive serves as the medium. By doing this, the signal transmitted from the vibrator 1a and the delay material 1
This stabilized the mode conversion of the sound waves propagating through b into surface waves.

If there is a sharp corner in the sound wave propagation direction (arrow D) on the surface of the transmitter 2, the sound wave will be attenuated.
It is rounded. The radius of curvature of this corner 2d only needs to be larger than the wavelength of the propagating sound wave.

When the tip 2a of the transmitting body 2 of the probe 1 is brought into contact with the surface of the test specimen 3 in a linear or narrow band shape, the surface waves propagate from the surface 2b in the directions of arrows E and F to perform the test. transmitted to the surface of the body 3.

FIG. 2 shows an embodiment of a contactor in which the width of the lower part of the transmitting body 2 is reduced, and the corner portion 2c of the transmitting body 2.

Each 2d is rounded to prevent sound waves from attenuating.
Narrow portions and concave portions of the test specimen 3 can also be measured.

FIGS. 3 and 4 are diagrams for explaining an application example of measuring the velocity of surface waves propagating, that is, sonic dust, using the probe of the present invention.

As shown in FIG. 3, the transmitting probes 1 and 2 and the receiving probes 1' and 2' are applied to the surface of the test specimen 3 at an arbitrary interval M. When a pulse current is supplied from an ultrasonic transceiver (not shown) to the transmitting probe 1, the surface wave of the ultrasonic wave is generated.
It propagates on the surface of the test object 3 in the directions of arrows F, J, and G via E, and is converted into an electrical signal by the receiving probe 1' via H and Q, and is amplified by the ultrasonic transceiver. Then, using a sound velocity measuring device (not shown), the distance M between the contact position 2a of the transmitting probe and the contact position 2'a of the receiving probe is calculated from the propagation time of the ultrasonic wave, and the sound velocity is determined. You get dust.

FIG. 4 shows another application example in which transmitting/receiving probes 5 and 2, which have both transmitting and receiving functions, are placed on the surface of a test object 3, and a reflective metal is placed at an arbitrary distance N from the contact position 2a. This is an example in which a body 6 is attached and measured.

When a pulse current is supplied from an ultrasonic transceiver (not shown) to the transceiver probe 5, an ultrasonic surface wave is generated.

E, the metal body 6 for reflection propagates through the surface F of the test specimen 3.
arrive at. A part of the surface wave is reflected at the reflective metal body 6 and passes through F, E, and D to the transmitting/receiving probes 2 and 5.
come back to. In the figure, arrows indicate the propagation direction of surface waves. The returned surface waves are converted into electrical signals by the transmitting/receiving probe 5 and amplified by the ultrasonic transmitting/receiving device.

The sonic velocity dust is obtained by calculating the sonic velocity dust using a sonic velocity measuring device (not shown) from the one-round reciprocating distance NX2 between the contact position 2a of the probe and the reflective metal 3-hook 6 and the time for one reciprocating of the ultrasonic wave.

By measuring the sonic dust of surface waves with high precision in this way, the material quality of the surface of the test piece can be determined.

This makes it possible to determine the stress value acting on the surface of the specimen. In other words, the test specimen has a sonic velocity displacement unique to its material. Then, as the compressive stress increases, the sonic dust increases linearly, and as the tensile stress increases, the sonic dust decreases linearly. Therefore, if the relationship between sonic dust and stress of the same or similar material as the test piece is determined in advance, the material and the stress value generated can be determined non-destructively by measuring the sonic dust of the test piece. be. The relationship between sonic dust and stress can be obtained by measuring the sonic dust of a specimen made of the same or similar material as the test specimen while applying a compressive load or tensile load.

As shown in FIG. 5, the surface of the transmitter 2 fixed to the probe 1 and having a rounded corner 2d facing the surface of the specimen 3 forms a corner α with the surface of the specimen 3. , the ultrasonic wave is emitted from the transducer 1a of the probe 1, and the transducer 1 of the probe 1'
' Received waveform height when received at a (%) (O mark)
and the received waveform height (%) (marked with *) when an ultrasonic wave is emitted from transducer 1'a of probe 1' and received by transducer 1a of probe 1. FIG.

From Figure 6, the received waveform height (%) is high when the angle α is between 0.2' and 1.2°, and when contact is outside this range, the received waveform height (%) becomes low. I understand that.

FIG. 7 is a front view illustrating another application example of the present invention in which the present invention is used to measure the depth of fatigue pre-crack in a fracture toughness test piece.

Test piece 7 is for a three-point bending test in which a load ff1T is applied while supporting at support points R and S. The surface waves transmitted from the linear contact position 2a of the transmitting probe 1 and the transmitting body 2 are indicated by arrow U.
It propagates on the surface 7a of the test piece as follows, and is received by the probe 1' and the transmitter 2' at the linear contact position 2'a. Initially, the speed at which the surface wave propagates when no cracks occur in the tM bottom 7b, that is, the sound speed, and the propagation distance (known).

Find the propagation time. Next, when similarly measured after the fatigue pre-crack 7C has occurred, the propagation time becomes longer as the surface waves detour around the tip of the crack 7C.

At this time, the sound speed is already known and the propagation time is measured, so the depth of the crack 7C can be known.

[Effects of the Invention] According to the present invention, since the propagation efficiency of ultrasonic waves is improved, the reception strength is increased, the signal is captured more clearly, and the measurement accuracy is improved.

Although this embodiment makes it possible to measure residual stress, crack depth, etc. with high precision using ultrasonic surface waves, the present invention is not limited to just these embodiments. No matter what condition the test object is in, such as the parts of an assembled machine or structure, we can measure the propagation speed (sound velocity) of ultrasonic surface waves to determine the speed at which ultrasonic surface waves are generated on the surface. It makes it possible to non-destructively measure stress values and crack depths, etc., and can be applied to any elastic object in which surface waves propagate.

As described above, the probe of the present invention is simple and effective in controlling a wide range of industrial products.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views for explaining the present invention in detail, and Figures 3, 4, and 5 are for measuring the propagation velocity of surface waves using the probe of the present invention. A cross-sectional view for explaining the method, FIG. 6 is a diagram showing the relationship between the angle α when the transmitting body comes into contact with the test object and the received waveform height (%) of the ultrasonic wave,
Figure 7 is a front view for explaining the method of measuring the crack depth of a fracture toughness test piece using the probe of the present invention, and Figures 8 and 9 are for explaining conventional probes, respectively. Figures 10, 11, and 12 are cross-sectional views for explaining the method of measuring the propagation velocity of surface waves using conventional probes. Figure 13 is a fracture toughness test piece. FIG. 2 is a front view illustrating a method for measuring a crack depth using a conventional probe. 1.1'... Probe, 1a, 1' a... Camera element, lb, 1' b... Delay material, 2.2'... Transmitter, 3... Test object , 5... Transmitting/receiving probe. Fig. 3 Fig. 4 Fig. 5 1a 1g 6 Fig. Angle irises Fig. 7 Fig. 8 Fig. 119 Fig. 10 Fig. 11 Fig. 13

Claims (2)

[Claims] (1) A surface wave transmitter is provided in contact with an ultrasonic surface wave probe having a transducer and a delay material, and the tip of the surface wave transmitter that contacts the test specimen is linear or narrow strip-shaped. west,
Further, the rear end of the surface wave transmitting body in the direction opposite to the traveling direction or receiving direction of the surface wave is rounded, and the surface facing the test specimen surface connecting the rear end and the tip is rounded. A surface wave probe characterized in that the angle formed with the surface of a test specimen is 0.2° to 1.2°. (2) The surface wave probe according to claim 1, wherein the radius of curvature of the roundness of the rear end of the surface wave transmitter is larger than the wavelength of the surface wave used.