JPH0833375B2 - Surface wave probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a surface wave probe for measuring a propagation velocity, a propagation time and the like when a surface wave of an ultrasonic wave is propagated on the surface of an elastic member. It is about.

[Prior Art] FIG. 10 is a cross-sectional view illustrating an example of a usage state of a conventional surface acoustic wave probe in the above-described field of use. As shown in the figure, the conventional surface wave probe 1, 1 ′ has transducers 1 a, 1 ′ a.
And the delay material (generally acrylic resin) 1b, 1'b, and the mode conversion is caused by the difference between the speed of the ultrasonic wave propagating through the delay material 1b, 1b 'and the speed of the ultrasonic wave propagating through the test body 3. , Which transmits and receives surface waves of ultrasonic waves.

In the example of FIG. 10, ultrasonic waves are transmitted from the oscillator 1a of the surface wave probe 1 on the transmission side, propagated through the delay material 1b, and propagated to the test body 3. The test body 3 has a contact medium 4
When a sound wave is incident at a certain angle or more through the, the surface wave propagates in the direction of arrow A on the surface portion of the test body 3 due to the mode conversion of the sound wave. Then, in the surface acoustic wave probe 1'on the receiving side, the acoustic wave is received by the transducer 1'a after propagating through the contact medium 4'and the delay material 1'b.

The above-mentioned conventional surface wave probe 1, 1'is generally widely used, but it is insufficient for accurate measurement of the propagation speed and propagation time of sound waves.

That is, referring to the example in FIG. 10, first, since the contact surfaces 1c and 1'c of the probes 1 and 1'have a width in the traveling direction A of the sound wave, when the distance L is to be set. An accurate reference point cannot be obtained. Further, since 1c and 1'c are flat surfaces, even if the contact state with the test body 3 is slightly different due to, for example, the unevenness of the surface of the test body 3 or the parallel relationship with the surface of the test body 3, Variation occurs in the incident position of the sound wave to and the receiving position from the test body 3.

Further, the amount of transmitted and received surface waves varies depending on the material, characteristics, thickness, etc. of the contact medium 4, 4 '. As a result, the propagation time and the propagation distance L of the sound wave fluctuate, and accurate measurement becomes impossible.

In order to solve the above-mentioned problems, we previously invented a surface wave probe in Japanese Patent Application No. 61-15402, which enables accurate measurement of the propagation speed and propagation time of sound waves. Then, using the probe, it is possible to non-destructively measure the stress value acting on the surface of the object, the depth of the crack occurring on the surface of the object, and the like.

The above application was obtained by interposing a surface wave transmitter 2 between a conventional surface wave probe 1 and a test body 3, as shown in FIGS. 8 and 9. And the
In order to eliminate the problem when the conventional surface probe 1 shown in FIG. 10 is directly contacted with the test body 3, as shown in FIGS. 8 and 9, the tip of the surface wave transmitter 2 is The portion 2a was made to abut linearly. Although the drawing looks like a dot because it is drawn in a sectional view, it actually makes a linear contact due to the thickness in the direction perpendicular to the paper surface. Contact with the test body 3
Although point contact is ideal, the attenuation of ultrasonic waves becomes significant and the ultrasonic waves are not sufficiently transmitted. Therefore, in consideration of practicality, it is preferable to approach a point and make a linear contact within a range where the output of ultrasonic waves is allowed.

By doing so, the ultrasonic wave transmitted from the surface acoustic wave probe 1 propagates on the surface 2b of the transmitting body 2, is transmitted to the surface of the test body 3 at the tip 2a, and propagates in the direction of arrow B. .
Further, since the tip portion is in 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 wave propagated in the opposite direction of the arrow in the case of transmitting is received, and the same effect can be obtained.

It should be noted that, as shown in FIG.
When the contact surface 1c of the probe 1 is brought into contact with the surface 2b, if there is a sharp corner in the traveling direction (arrow D) of the surface wave, the surface wave is greatly attenuated. In this case, the radius of curvature of the roundness may be larger than the wavelength of the surface wave used, but it is preferable to make it as large as possible.

In the case of the receiving probe as well, the surface wave is prevented from being attenuated by similarly providing the roundness.

FIG. 11 and FIG. 12 are diagrams for explaining an application example in which the velocity when a surface wave propagates, that is, the sound velocity is measured using the above probe.

As shown in FIG. 11, the transmitting probes 1 and 2 and the receiving probes 1'and 2'are applied to the surface of the test body 3 at arbitrary intervals M. When a pulse current is supplied from the ultrasonic transmitter / receiver (not shown) to the transmitting probe 1, the surface wave of the ultrasonic wave propagates on the surface of the test body 3 in the direction of arrow J, and the receiving probe 1 ' It is converted into an electrical signal and amplified by the ultrasonic transceiver. Then, a sound velocity measuring device (not shown) calculates the distance M between the contact position 2a of the transmitting probe and the contact position 2'a of the receiving probe from the propagation time of the ultrasonic waves propagated, and the sound is calculated. Speed is obtained.

FIG. 12 shows, as another application example, transmitting / receiving probes 5 and 2 having both transmitting and receiving functions are applied to the surface of the test body 3 and a reflecting metal is placed at an arbitrary distance N from the contact position 2a. In this example, the body 6 is attached and the measurement is performed. When a pulse current is supplied from the ultrasonic transmitter / receiver (not shown) to the transmitting / receiving probe 5, the ultrasonic surface wave propagates on the surface of the test body 3 and arrives at the reflecting metal body 6. A part of the surface wave is reflected at the reflecting metal body 6 and returns to the transmitting / receiving probes 2 and 5. In the figure, arrow K indicates the propagation direction of the surface wave.
The returned surface wave is converted into an electric signal by the transmission / reception probe 5 and amplified by the ultrasonic transmitter / receiver. One round trip distance N × 2 between the contact position 2a of the probe and the reflecting metal body 6
And sound velocity measurement device (not shown)
The sound velocity is calculated and obtained by.

By accurately measuring the sound velocity of the surface wave as described above, it is possible to determine the material of the surface of the test body and the stress value acting on the surface of the test body. That is, the test body has a sound velocity value peculiar to the material. The sound velocity increases linearly with increasing compressive stress, and the sound velocity decreases linearly with increasing tensile stress. Therefore, if the relationship between the sound velocity and the stress of the same or similar material as the test body is obtained in advance, the material and the generated stress value can be determined nondestructively by measuring the sound velocity of the test body. is there. The relationship between the sound velocity and the stress can be obtained by measuring the sound velocity of the test piece while applying a compressive load or a tensile load to the test piece of the same or similar material as the test piece.

FIG. 13 is a front view for explaining an example using the depth of fatigue precrack of a fracture toughness test piece as another application example of the above application.

The test piece 7 is supported by fulcrums R and S and a load T is applied 3
For point bending test. The surface wave emitted from the linear contact position 2a of the transmitting probe 1 and the transmitter 2 propagates on the surface 7a of the test piece as indicated by an arrow U, and the linear contact position 2'a
Are received by the probe 1'and the transmitter 2 '. the first,
The velocity at which the surface wave propagates, that is, the velocity of sound, the propagation distance (which is known), and the propagation time in the state where no crack is generated in the groove bottom 7b are obtained. Next, after the fatigue pre-crack 7c is generated, when the same measurement is performed, the surface wave bypasses the tip of the crack 7c, and the propagation time becomes longer accordingly. At this time, the sound velocity is already known and the propagation time is measured, so that the depth of the crack 7c can be known.

[Problems to be Solved by the Invention] The surface acoustic wave probe shown in Japanese Patent Application No. 61-15402 described above is applied to the surface of the test body 3 to measure the speed of sound as shown in FIG. 11, for example. In this case, when a pulse current is supplied from the ultrasonic transmitter / receiver (not shown) to the transmitting probe 1, the surface wave of the ultrasonic wave propagates on the surface of the transmitter 2 in the directions D, E, F, and , The surface of the test body 3 is propagated in the direction J, the surface of the transmitter 2'is propagated in the directions G, H, Q, and is converted into an electric signal by the receiving probe 1 '. Is amplified by. The propagation path of the surface wave of the ultrasonic wave is the contact positions 2a and 2'as described above.
There is a problem in that the reception strength becomes weak because of the large bending at a.

An object of the present invention is to provide a surface wave probe having high reception intensity and capable of accurately and nondestructively measuring the stress value acting on the surface of an object, the depth of a crack occurring on the surface of the object, and the like. To provide.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a surface acoustic wave probe having an ultrasonic wave and a delay member in contact with a surface acoustic wave transmitter, The tip of the surface wave transmitter that comes into contact with the test body is formed into a linear shape or a narrow band, and the rear end portion of the surface wave transmitter in the direction opposite to the traveling direction or the receiving direction of the surface wave is provided with a roundness. The surface wave probe is characterized in that the surface facing the surface of the test body that connects the rear end portion and the tip is made to form an angle of 0.2 ° to 1.2 ° with the surface of the test body. .

And, the radius of curvature of the roundness at the rear end of the surface wave transmitter is
It is desirable that the wavelength is larger than the wavelength of the surface wave used.

[Operation] The shape of the surface wave transmitter of the surface wave probe is as described above, and since there is no large bending of the surface wave at the contact position with the surface of the test body, the attenuation of ultrasonic waves is prevented, and as a result, the reception intensity is increased. Can be increased.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

1 to 5 are sectional views for explaining an embodiment of the present invention,
FIG. 7 is a front view for explaining another embodiment. In each drawing, the same portions as those in FIGS. 8 to 13 described above are designated by the same reference numerals.

As shown in FIG. 1, the contact surface 1c of the probe 1 and the transmitter 2
The surface 2b is fixed with an adhesive (not shown).
In these cases, the adhesive acts as a medium. By doing so, the mode conversion of the sound wave emitted from the oscillator 1a and propagated through the delay member 1b into the surface wave is stabilized.

Since a sound wave is attenuated when there is a sharp corner in the sound wave propagation direction (arrow D) on the surface of the transmitter 2, the probe of the present invention has a corner 2d.
It has a rounded shape. The radius of curvature of the corner 2d may be larger than the wavelength of the propagating sound wave.

When the tip 2a of the transmission body 2 of the probe 1 is brought into contact with the surface of the test body 3 in a linear or narrow strip shape, the surface wave propagates in the directions of arrows D, E, F from the 2b plane and is tested. It is 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 transmitter 2 is made small, and the corners 2c, 2d of the transmitter 2 are provided with roundness to prevent sound wave attenuation. It is possible to measure the narrow part and the concave part.

FIG. 3 and FIG. 4 are diagrams for explaining an application example in which the velocity when a surface wave propagates, that is, the sound velocity is measured 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 body 3 at arbitrary intervals M. When a pulse current is supplied from the ultrasonic transmitter / receiver (not shown) to the transmitting probe 1, the surface wave of the ultrasonic wave becomes D,
Propagate on the surface of the test body 3 via E in the directions of arrows F, L, and G,
After passing through Q, it is converted into an electric signal by the receiving probe 1'and amplified by the ultrasonic transmitter / receiver. Then, a sound velocity measuring device (not shown) calculates the distance M between the contact position 2a of the transmitting probe and the contact position 2'a of the receiving probe from the propagation time of the ultrasonic waves propagated, and the sound is calculated. Speed is obtained.

FIG. 4 shows another example of application, in which the transmitting and receiving probes 5 and 2 having both transmitting and receiving functions are applied to the surface of the test body 3 and a reflecting metal is placed at an arbitrary distance N from the contact position 2a. In this example, the body 6 is attached and the measurement is performed. When a pulse current is supplied from the ultrasonic transmitter / receiver (not shown) to the transmitting / receiving probe 5, the surface wave of the ultrasonic wave propagates through the surface F of the test body 3 via D and E and reaches the reflection metal body 6. arrive. A part of the surface wave is reflected at the reflecting metal body 6, passes through F, E, and D and returns to the transmitting and receiving probes 2 and 5. In the figure, arrow K indicates the propagation direction of the surface wave. The returned surface wave is converted into an electric signal by the transmission / reception probe 5 and amplified by the ultrasonic transmitter / receiver. The sound velocity is calculated by a sound velocity measuring device (not shown) from one reciprocating distance N × 2 between the contact position 2a of the probe and the reflecting metal body 6 and the time of one reciprocating ultrasonic wave. .

By accurately measuring the sound velocity of the surface wave as described above, it is possible to determine the material of the surface of the test body and the stress value acting on the surface of the test body. That is, the test body has a sound velocity value peculiar to the material. The sound velocity increases linearly with increasing compressive stress, and the sound velocity decreases linearly with increasing tensile stress. Therefore, if the relationship between the sound velocity and the stress of the same or similar material as the test body is obtained in advance, the material and the generated stress value can be determined nondestructively by measuring the sound velocity of the test body. is there. The relationship between the sound velocity and the stress can be obtained by measuring the sound velocity of the test piece while applying a compressive load or a tensile load to the test piece of the same or similar material as the test piece.

As shown in FIG. 5, a surface of the transmission body 2 fixed to the probe 1 and having a rounded corner portion 2d facing the surface of the test body changes the corner α formed with the surface of the test body 3. , A transducer 1a of the probe 1'transmits ultrasonic waves from the transducer 1a of the probe 1
Received waveform height (%) when received at a And a plot of the received waveform height (%) (•) when ultrasonic waves are transmitted from the transducer 1′a of the probe 1 ′ and received by the transducer 1a of the probe 1 Is FIG. 6.

From FIG. 6, the height (%) of the received waveform is high because the angle α
It can be seen that the received waveform height (%) becomes low in the range of 0.2 ° or more and 1.2 ° or less if the contact is made outside this range.

FIG. 7 is a front view illustrating another example of application of the present invention for measuring the depth of fatigue precrack of a fracture toughness test piece.

The test piece 7 is supported by fulcrums R and S and a load T is applied 3
For point bending test. The surface wave emitted from the linear contact position 2a of the transmitting probe 1 and the transmitter 2 propagates on the surface 7a of the test piece as indicated by an arrow U, and the linear contact position 2'a
Are received by the probe 1'and the transmitter 2 '. the first,
The velocity at which the surface wave propagates, that is, the velocity of sound, the propagation distance (which is known), and the propagation time in the state where no crack is generated in the groove bottom 7b are obtained. Next, after the fatigue pre-crack 7c is generated, when the same measurement is performed, the surface wave bypasses the tip of the crack 7c, and the propagation time becomes longer accordingly. At this time, the sound velocity is already known and the propagation time is measured, so that the depth of the crack 7c can be known.

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

Then, although the residual stress and the highly accurate measurement of the crack depth and the like can be measured by using the surface wave of the ultrasonic wave, the use is not limited to these examples.
Whatever the condition of the test object, such as the assembled machine or structure member, is that it is generated on the surface by measuring the speed at which the ultrasonic surface wave propagates (sound speed). It enables non-destructive measurement of the stress value and crack depth, and is applicable to all objects as long as it is an elastic body in which surface waves propagate.

As described above, the probe of the present invention is simple and exhibits a wide range of effects in managing industrial products.

[Brief description of drawings]

1 and 2 are cross-sectional views for explaining the probe of the present invention, and FIGS. 3, 4, and 5 show the propagation velocity of surface waves using the probe of the present invention. FIG. 6 is a cross-sectional view for explaining a measuring method, FIG. 6 is a view showing a relationship between an angle α and a height (%) of a received waveform of ultrasonic waves when a transmitter comes into contact with a test body, and FIG. The front view for explaining the method of measuring the crack depth of a toughness test piece using the probe of the present invention.
FIGS. 9 and 10 are cross-sectional views for explaining a conventional probe, and FIGS. 10, 11 and 12 show a method for measuring the propagation velocity of surface waves using the conventional probe. FIG. 13 is a cross-sectional view for explaining, and FIG. 13 is a front view for explaining a method for measuring the crack depth of a fracture toughness test piece using a conventional probe. 1,1 '... Probe, 1a, 1'a ... Transducer, 1b, 1'b ...
Delay material, 2,2 '... Transmitter, 3 ... Test body, 5 ... Transmission / reception probe.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-180456 (JP, A) JP-A-62-172260 (JP, A)

Claims (2)

[Claims] 1. A surface acoustic wave probe is provided in contact with an ultrasonic surface acoustic wave probe having a vibrator and a delay member, and a tip of the surface acoustic wave transducer that comes into contact with a test body is linear or wide. A narrow band is formed, and a rounded portion is provided at the rear end of the surface wave transmitter in the direction opposite to the traveling direction or the receiving direction of the surface wave, and the surface of the test body connecting the rear end and the front end. The surface wave probe is characterized in that the opposing surfaces are formed at an angle of 0.2 ° to 1.2 ° with the surface of the test piece. 2. The surface wave probe according to claim 1, wherein the radius of curvature of the rear end portion of the surface wave transmitter is larger than the wavelength of the surface wave used.