JP7258792B2 - Laser ultrasonic measuring device and laser ultrasonic measuring method - Google Patents

Description

An embodiment of the present invention relates to a laser ultrasonic measuring device and a laser ultrasonic measuring method.

Ultrasonic testing (UT) is a technology that can non-destructively check the soundness of the surface and interior of structural materials, and has become an indispensable inspection technology in various fields.

A contact-type UT that transmits and receives ultrasonic waves by bringing a piezoelectric element into contact with an object to be inspected, and small piezoelectric elements for transmitting and receiving ultrasonic waves are arranged. Waveformable phased array ultrasonic testing (PAUT) is widely used in industrial applications. A method such as laser ultrasonic testing (LUT) is also used, in which ultrasonic waves are excited by irradiating a pulsed laser and micro-vibrations on the surface of an object to be inspected are measured using a separate laser and a laser interferometer. Since the laser ultrasonic method enables non-contact inspection, it is also applied to inspections during welding work.

Various forms have been proposed for ultrasonic signal processing methods and devices and methods for imaging the inside of an object to be inspected. Since the speed of sound differs depending on the tissue, methods such as measuring ultrasonic waves assuming the speed of sound in a specific area of the inspection target and analyzing from the difference between the obtained detection result and the expected result, etc. is also proposed.

Japanese Patent No. 5651533 Japanese Patent No. 4632517 Japanese Patent No. 5528083

Ultrasonic surface waves are used to detect defects such as scratches and cracks on the surface of the object to be measured during periodic inspections of power plants and quality inspections of welded parts of welded structures. Is possible. In order to generate surface waves, a method using an ultrasonic probe is conceivable, but it is difficult to install a piezoelectric element in a site that is difficult to access. In the laser ultrasonic method, surface waves are excited by irradiating a pulsed laser for transmitting ultrasonic waves, and a separate receiving laser and a laser interferometer are used to measure minute vibrations on the surface of the inspection object, making it possible to detect defects. However, when the surface of the object to be measured has deposits or the surface roughness is large, there is a problem that the amount of reflected light from the reception laser is reduced and sufficient reception sensitivity cannot be obtained.

As another method, when performing ultrasonic surface inspection underwater, the surface wave excited by the transmitting laser propagates into the water as a leaky wave due to defects, and the leaky wave vibrates a separately installed thin plate such as a metal. A method of measuring the is also proposed using a receiving laser. However, in the case of this method, the depth from the surface of the defect is determined by arranging the excitation point and the reception point of the ultrasonic wave so as to straddle the defect, and analyzing the frequency of the leaky wave generated from the surface wave that has passed through the defect. However, a signal processing PC with a frequency analysis function is required as a device, and a frequency analysis step is required as a method.

Moreover, even if the leaky wave is received by a piezoelectric sensor instead of a laser, only the leaky wave close to the sensor's peculiar center frequency is detected, so the depth of the defect cannot be obtained.

Accordingly, an object of an embodiment of the present invention is to acquire information about the depth of a surface defect without performing frequency analysis in laser ultrasonic flaw detection.

In order to achieve the above-described object, the laser ultrasonic measurement apparatus according to the present embodiment includes a laser ultrasonic generator that excites a surface wave having a broadband frequency in a measurement target in a liquid , and a plurality of ultrasonic waves having different center frequencies. and a defect estimating unit for estimating the scale of the defect in the measurement object based on the ultrasonic signals received by the plurality of piezoelectric elements.

Further, the laser ultrasonic measurement method according to the present embodiment includes a generator installation step of installing a laser ultrasonic generator that generates ultrasonic waves to a measurement target in a liquid , and a plurality of piezoelectric elements having different center frequencies. After the first piezoelectric element installation step of installing at the first position, and the generator installation step and the first piezoelectric element installation step, an ultrasonic wave having a broadband frequency is generated on the object to be measured by a laser ultrasonic wave generator. and acquiring signals from the plurality of piezoelectric elements in the first ultrasonic wave generating step, comparing the levels of the signals, and measuring the scale of the defect in the object to be measured. and a first defect estimation step of estimating
Further, the laser ultrasonic measurement method according to the present embodiment includes a generator installation step of installing a laser ultrasonic generator that generates ultrasonic waves to a measurement target, and a plurality of piezoelectric elements having different center frequencies from each other at a first position. After the first piezoelectric element installation step, and the generator installation step and the first piezoelectric element installation step, the laser ultrasonic generator generates ultrasonic waves having a broadband frequency to the measurement target. A first ultrasonic wave generation step, and a first signal from the plurality of piezoelectric elements in the first ultrasonic wave generation step, comparing levels of the first signal, and detecting a defect in the object to be measured. and a first defect estimation step of estimating the scale of the first defect estimation step, wherein the first signal from the plurality of piezoelectric elements is a transmitted surface wave or a reflected surface wave a second piezoelectric element installation step of moving the plurality of piezoelectric elements to positions according to the result of the determination step and installing the piezoelectric elements at a second position; After the piezoelectric element installation step, a second ultrasonic wave generating step of generating ultrasonic waves having a broadband frequency to the object to be measured by a laser ultrasonic wave generator, and the plurality of piezoelectric elements in the second ultrasonic wave generating step a second defect estimation step of obtaining a second signal from and comparing the level of the second signal to estimate the size of the defect in the measurement object; the first defect estimation step and the and a defect position estimation step of estimating the position of the defect from the result of the second defect estimation step.

1 is a block diagram showing the configuration of a laser ultrasonic measuring device according to a first embodiment; FIG. It is a block diagram which shows the structure of the modification of the laser ultrasonic measuring device which concerns on 1st Embodiment. It is a conceptual block diagram explaining the operation|movement in the case of the 1st defect of the laser ultrasonic measuring device which concerns on 1st Embodiment. It is a conceptual block diagram explaining the operation|movement in the case of the 2nd defect of the laser ultrasonic measuring device which concerns on 1st Embodiment. It is a conceptual block diagram explaining the operation|movement in the case of the 3rd defect of the laser ultrasonic measuring device which concerns on 1st Embodiment.

FIG. 3 is a flowchart showing the procedure of a laser ultrasonic measurement method according to the first embodiment; FIG. 2 is a block diagram showing the configuration when a transmitted surface wave is used in the laser ultrasonic measuring device according to the first embodiment; FIG. 4 is a waveform diagram showing waveforms received by the piezoelectric element when using a transmitted surface wave in the laser ultrasonic measurement method according to the first embodiment; FIG. 4 is a graph waveform diagram showing the relationship between defect depth and echo intensity when a transmitted surface wave is used in the laser ultrasonic measurement method according to the first embodiment; FIG. 2 is a block diagram showing the configuration of the laser ultrasonic measurement apparatus according to the first embodiment when using reflected surface waves; FIG. 4 is a waveform diagram showing waveforms received by the piezoelectric element when using reflected surface waves in the laser ultrasonic measurement method according to the first embodiment; FIG. 4 is a graph waveform diagram showing the relationship between defect depth and echo intensity when using reflected surface waves in the laser ultrasonic measurement method according to the first embodiment; It is a block diagram which shows the structure of the laser ultrasonic measuring device which concerns on 2nd Embodiment. It is a block diagram which shows the structure of the laser ultrasonic measuring device which concerns on 3rd Embodiment. It is a block diagram which shows the structure of the laser ultrasonic measuring device which concerns on 4th Embodiment.

Hereinafter, a laser ultrasonic measuring device and a laser ultrasonic measuring method according to embodiments of the present invention will be described with reference to the drawings. Here, portions that are the same or similar to each other are denoted by common reference numerals, and overlapping explanations are omitted.

[First embodiment]
FIG. 1 is a block diagram showing the configuration of a laser ultrasonic measuring device according to the first embodiment.

The laser ultrasonic measurement device 100 has a laser ultrasonic generator 10 , a piezoelectric element 20 and a defect estimator 30 .

The laser ultrasonic wave generator 10 has a pulse laser light source 11 , an optical fiber injection mechanism 12 , an irradiation probe 13 and an optical fiber 15 . The ultrasonic waves generated by the laser ultrasonic generator 10 have a frequency range, that is, a wide band of frequencies from low frequencies to high frequencies. As for the specific frequency range, the range including the crack is selected according to the size of the defect 2 (FIG. 3) including the crack to be detected, specifically the depth from the surface.

Lasers used as the pulse laser light source 11 include, for example, Nd:YAG lasers, CO2 lasers, Er:YAG lasers, titanium sapphire lasers, alexandrite lasers, ruby lasers, dye lasers and excimer lasers. may be the case. The pulse laser light source 11 may be composed of not only one unit but also a plurality of units.

A pulsed laser beam oscillated from a pulsed laser light source 11 is introduced into an optical fiber 15 via an optical fiber injection mechanism 12 and is irradiated from an irradiation probe 13 onto a measurement object 1 .

The piezoelectric element 20 has three piezoelectric elements, a first piezoelectric element 21 , a second piezoelectric element 22 and a third piezoelectric element 23 . The piezoelectric element is called an ultrasonic probe, and although not shown, it generally includes a mechanism for generating ultrasonic waves, a damping material for damping ultrasonic waves, and an ultrasonic wave oscillation surface. It becomes the structure which consists of any structure or the combination with the front board. The piezoelectric element 20 need not have an ultrasonic wave generating mechanism. The center frequency, which is the natural frequency of the piezoelectric element, is determined by the rigidity of the front plate and its supporting portion.

Here, the first piezoelectric element 21, the second piezoelectric element 22, and the third piezoelectric element 23 have different center frequencies. Although the piezoelectric element 20 has three piezoelectric elements, the number may be two or four or more.

The defect estimator 30 detects the liquid in the container 3 based on the ultrasonic signals received by the plurality of piezoelectric elements, that is, the first piezoelectric element 21, the second piezoelectric element 22, and the third piezoelectric element 23. A defect 2 in a measurement object 1 immersed in 4 is estimated. In addition, the specific content of estimation is mentioned later.

FIG. 2 is a block diagram showing the configuration of a modified example of the laser ultrasonic measuring device according to the first embodiment.

In this modification, the laser ultrasonic wave generator 10a has the pulse laser light source 11, the reflecting mirror 14, and the optical lens 16, and the optical path of the pulse laser light emitted from the pulse laser light source 11 is obtained without using an optical fiber. is reflected by the reflecting mirror 14 to change the direction, condensed by the optical lens 16, and irradiated onto the measurement target 1. For example, such a configuration may be used.

FIG. 3 is a conceptual block diagram for explaining the action of the laser ultrasonic measuring apparatus according to the first embodiment for the first defect, and FIG. 4 is a conceptual block diagram for explaining the action for the second defect. A block diagram, and FIG. 5, is a conceptual block diagram explaining the operation in the case of the third defect.

3 to 5, A, B, and C schematically show three types of waves contained in the surface wave Us propagating on the surface of the measurement object 1 generated by the irradiation by the laser ultrasonic generator 10. , which will be called surface waves A, surface waves B, and surface waves C, respectively. The surface waves A, B, and C have wavelengths λA, λB, and λC, respectively, where λA<wavelength λB<wavelength λC. Also, the frequencies corresponding to these are assumed to be frequency fA, frequency fB, and frequency fC, respectively. Therefore, frequency fA>frequency fB>frequency fC.

A surface wave Us generated in the object 1 to be measured propagates on the surface of the object 1 to be measured. Defect 2 reflects.

That is, a surface wave Us whose wavelength is shorter than the depth of the defect 2 is reflected by the defect. The ultrasonic wave reflected by this defect is called a reflected surface wave Ur. A surface wave Us, whose wavelength is longer than the depth of the defect 2, propagates through the defect. This surface wave is called a transmitted surface wave Ut.

Taking FIGS. 3 to 5 as an example, FIG. 3 shows the case where the depth of the defect 2 is larger than the wavelength λA of the surface wave A and smaller than the wavelength λB of the surface wave B. In this case, the surface Wave A is reflected at defect 2 and surface waves B and C are transmitted. FIG. 4 shows the case where the depth of the defect 2 is greater than the wavelength λB of the surface wave B and less than the wavelength λC of the surface wave C. In this case, the surface waves A and B are reflected at the defect 2. , and only the surface wave C is transmitted. 5 shows the case where the depth of the defect 2 is larger than the wavelength λC of the surface wave C. In this case, the surface waves A, B and C are all reflected at the defect 2. .

Now, as shown in FIGS. 3 to 5, the object 1 to be measured is immersed in a liquid 4 in a container 3, and ultrasonic waves are transmitted and received in the liquid 4. FIG. In such a state, part of the surface wave Us, the reflected surface wave Ur, and the transmitted surface wave Ut propagating on the surface of the object 1 leaks into the water. The leaky waves resulting from leakage of the reflected surface wave Ur and the transmitted surface wave Ut into water are hereinafter referred to as the reflected leaky wave Urw and the transmitted leaky wave Utw, respectively. The piezoelectric element 20 receives the reflected leaky wave Urw and the transmitted leaky wave Utw at positions where they can be received. For example, in the case of FIG. 4, the reflected leaky wave Urw is mainly caused by the surface waves A and B, and the transmitted leaky wave Utw is mainly caused by the surface wave C.

FIG. 6 is a flowchart showing the procedure of the laser ultrasonic measurement method according to the first embodiment.

First, the laser ultrasonic generator 10 for generating ultrasonic waves is installed on the object 1 to be measured (step S10).

Next, the first measurement is performed (step S20). The first measurement step S20 has three steps.

First, a first piezoelectric element 21, a second piezoelectric element 22, and a third piezoelectric element 23 are installed at a first position P1 (FIG. 7) as a plurality of piezoelectric elements having different frequencies (step S21).

FIG. 7 is a block diagram showing the configuration of the laser ultrasonic measurement apparatus according to the first embodiment when a transmitted surface wave is used.

The first position P1 where the first piezoelectric element 21, the second piezoelectric element 22, and the third piezoelectric element 23 are installed is measured by the laser ultrasonic wave generator 10 across the defect 2 of the measurement target 1. It is on the opposite side of the irradiated position P0. However, at this stage, the relationship between the first position P1 and the position of the defect 2 is unknown.

Next, the laser ultrasonic wave generator 10 generates ultrasonic waves having a wide band of frequencies in the measurement object 1 (step S22). As a result, a surface wave Us is generated on the surface of the object 1 to be measured. At position P1, mainly transmitted leaky waves Utw are received.

Next, signals are obtained from each of the first piezoelectric element 21, the second piezoelectric element 22, and the third piezoelectric element 23, and their signal levels are compared (step S23).

FIG. 8 is a waveform diagram showing a waveform received by the piezoelectric element when using a transmitted surface wave in the laser ultrasonic measurement method according to the first embodiment. In the vertical direction, the waveforms of the high frequency from the first piezoelectric element 21, the high frequency from the second piezoelectric element 22, and the high frequency from the third piezoelectric element 23 are shown from top to bottom. ing. Further, the case of the first defect is shown on the left side of the waveform diagrams arranged horizontally, and the case of the second defect is shown on the right side.

Comparing the waveform for the first defect and the waveform for the second defect, the strength of the high-frequency waveform from the first piezoelectric element 21 is small and there is no difference. The intensity of the high-frequency waveform from the second piezoelectric element 22 is smaller in the case of the first defect than in the case of the second defect on the right side. Moreover, there is no significant difference in the intensity of the high-frequency waveform from the third piezoelectric element 23 .

First, in both the case of the first defect and the case of the second defect, the center frequency fC is low, i.e., the strength of the waveform of the high frequency from the third piezoelectric element 23, which has a long corresponding wavelength λC, is strong, which means that the position P1 is the position where the transmitted surface wave Utw is measured. It means the position on the opposite side of the position P0. Therefore, it can be seen that defect 2 is between position P0 and position P1.

In the case of the second defect on the right side, since only the high frequency from the third piezoelectric element 23 is transmitted, the depth of the crack is the wavelength corresponding to the center frequency fB of the second piezoelectric element 22. It can be seen that it is deeper than λB and shallower than the wavelength λC corresponding to the center frequency fC of the third piezoelectric element 23 .

In the case of the first defect on the left side, since only the high frequency wave from the first piezoelectric element 21 is reflected, the depth of the crack is the wavelength corresponding to the center frequency fA of the first piezoelectric element 21. It can be seen that it is deeper than λA and shallower than the wavelength λB corresponding to the center frequency fB of the second piezoelectric element 22 .

In this way, a rough estimate of the depth and location of the defect 2 can be estimated.

FIG. 9 is a graph waveform diagram showing the relationship between defect depth and echo intensity when using a transmitted surface wave in the laser ultrasonic measurement method according to the first embodiment. The horizontal axis is the depth of the defect 2 formed in the measurement object 1. FIG. The vertical axis is the echo intensity when the transmitted surface wave transmitted through the defect is measured by the piezoelectric element. Regarding the piezoelectric elements, the dashed line indicates the first piezoelectric element 21 , the dashed line indicates the second piezoelectric element 22 , and the solid line indicates the third piezoelectric element 23 .

The respective transmitted surface wave Utw decreases monotonically with successively increasing defect depths to be formed. In particular, the slope of the decrease becomes greater when the defect sizes are in the vicinity of the respective wavelengths.

By preparing in advance a reduction characteristic diagram of this transmitted surface wave, the relative ratio of echo signal levels from the first piezoelectric element 21, the second piezoelectric element 22 and the third piezoelectric element 23 is obtained. By comparing with this decrease characteristic diagram, the depth of the defect 2 can be estimated with higher accuracy.

After the above first measurement, the second measurement is performed (step S30). The second measurement step S30 also has three steps.

First, a first piezoelectric element 21, a second piezoelectric element 22, and a third piezoelectric element 23 are installed at a second position P2 (FIG. 10) as a plurality of piezoelectric elements having different center frequencies (step S31). ).

FIG. 10 is a block diagram showing the configuration when using reflected surface waves in the laser ultrasonic measurement apparatus according to the first embodiment.

A second position P2 where the first piezoelectric element 21, the second piezoelectric element 22, and the third piezoelectric element 23 are installed is on the opposite side of the position P1 across the defect 2 of the measurement target 1. . This is because, in step S23 of the first measurement, the first position P1 is the position on the opposite side of the position P0 across the defect 2, that is, the defect 2 is between the positions P0 and P1. depending on what i found out. In this case, a position P2 is set between the positions P0 and P1 in order to further improve the accuracy of estimating the position of the defect 2. FIG. For convenience of explanation, the position P2 is assumed to be a position where the leakage reflected wave Urw can be detected.

Next, the laser ultrasonic wave generator 10 generates ultrasonic waves having a wide band of frequencies in the measurement object 1 (step S32). As a result, a surface wave Us is generated on the surface of the object 1 to be measured. At the position P2, mainly reflected leaky waves Urw are received.

Next, signals are acquired from each of the first piezoelectric element 21, the second piezoelectric element 22, and the third piezoelectric element 23, and their signal levels are compared (step S33).

FIG. 11 is a waveform diagram showing waveforms received by the piezoelectric element when using reflected surface waves in the laser ultrasonic measurement method according to the first embodiment. In the vertical direction, the waveforms of the high frequency from the first piezoelectric element 21, the high frequency from the second piezoelectric element 22, and the high frequency from the third piezoelectric element 23 are shown from top to bottom. ing. Further, the case of the first defect is shown on the left side of the waveform diagrams arranged horizontally, and the case of the second defect is shown on the right side.

Comparing the waveform for the first defect and the waveform for the second defect, the strength of the high-frequency waveform from the first piezoelectric element 21 is high in both cases, but the strength of the waveform in the first defect is higher than that of the first defect. is large. The strength of the high-frequency waveform from the second piezoelectric element 22 is smaller than the strength of the high-frequency waveform from the first piezoelectric element 21, and in the case of the first defect, the second defect on the right side larger than the case. In addition, the intensity of the high-frequency waveform from the third piezoelectric element 23 is small and there is no difference.

First, in both the case of the first defect and the case of the second defect, the intensity of the high-frequency waveform from the first piezoelectric element 21 having a high center frequency fA, that is, having a short wavelength λA corresponding to the center frequency The fact that fC is low, ie, that the corresponding wavelength λC is greater than the intensity of the high-frequency waveform from the third piezoelectric element 21, means that the position P1 is the position where the reflected surface wave Urw is measured, that is, the defect 2 and the position P0 It means that the position is between Therefore, it can be seen that defect 2 is between position P2 and position P1.

In addition, in the case of the second defect on the right side, since there is almost no high-frequency reflection from the third piezoelectric element 23 and little high-frequency reflection from the second piezoelectric element 22, the first piezoelectric element It can be seen that it is deeper than the wavelength λA corresponding to the center frequency fA of the element 21 and shallower than the wavelength λB corresponding to the center frequency fB of the second piezoelectric element 22 .

In the case of the first defect on the left side, only the reflection of the high frequency from the third piezoelectric element 23 is small. It can be seen that it is deeper than λB and shallower than the wavelength λC corresponding to the center frequency fC of the third piezoelectric element 23 .

In this way, a rough estimate of the depth and location of the defect 2 can be estimated.

FIG. 12 is a graph waveform diagram showing the relationship between defect depth and echo intensity when using reflected surface waves in the laser ultrasonic measurement method according to the first embodiment. The horizontal axis is the depth of the defect formed in the object 1 to be measured. The vertical axis is the echo intensity when the reflected surface wave reflected by the defect is measured by the piezoelectric element. Regarding the piezoelectric elements, the dashed line indicates the first piezoelectric element 21 , the dashed line indicates the second piezoelectric element 22 , and the solid line indicates the third piezoelectric element 23 .

By preparing a reduction characteristic diagram of the reflected surface wave in advance, the relative ratio of echo signal levels from the first piezoelectric element 21, the second piezoelectric element 22, and the third piezoelectric element 23 is obtained. By comparing with this decrease characteristic diagram, the depth of the defect 2 can be estimated with higher accuracy.

It should be noted that if the result of step S20 of the first measurement is such that the position of the defect 2 can be sufficiently grasped, step S30 of the second measurement is unnecessary. In addition, if the result of step S30 of the second measurement is the same as the result of step S20 of the first measurement, that is, for example, if both detect transmitted leaky waves, the distance of position P2 from position P0 is If is still large, further measurements may be performed by moving the piezoelectric element 20 between positions P2 and P0.

After the second measurement in step S30, the surface defect size and position are evaluated and determined (step S40). That is, comprehensive confirmation is made including the consistency of the results of the first and second measurements, and the estimation of the depth and position of the defect 2 is ensured.

As described above, according to this embodiment, in laser ultrasonic flaw detection, information about the depth of surface defects can be obtained without performing frequency analysis.

[Second embodiment]
FIG. 13 is a block diagram showing the configuration of the laser ultrasonic measuring device according to the second embodiment. This embodiment is a modification of the first embodiment. The laser ultrasonic measurement apparatus 100 according to this embodiment further has a transmission/reception position adjusting section 40 .

The transmission/reception position adjustment section 40 has a transmission/reception unit housing 41 and a transmission/reception unit driving section 42 .

The transmission/reception unit housing 41 accommodates the irradiation probe 13 and the piezoelectric element 20 . The transmission/reception unit driving section 42 drives the transmission/reception unit housing 41 to move.

The installation positions of the irradiation probe 13 and the piezoelectric element 20 need to be adjusted according to the surface shape of the object 1 to be measured, for example, if the defect 2 is a crack, the direction in which the crack propagates. Therefore, a transmission/reception position adjusting unit 40 is provided to adjust the positions of the irradiation probe 13 and the piezoelectric element 20 . For example, in addition to adjusting the vertical, horizontal, and anteroposterior three-axis position, it is possible to adjust the irradiation direction of the irradiation probe 13 with respect to the measurement object 1, the direction of the sensor surface of the piezoelectric element 20, and the like. For example, by using a robot arm or the like for the transmission/reception position adjustment unit 40, it is possible to easily inspect a predetermined position even if the shape of the measurement object 1 is complicated.

[Third embodiment]
FIG. 14 is a block diagram showing the configuration of a laser ultrasonic measuring device according to the third embodiment.

In this embodiment, the piezoelectric element 20 has a plurality of first piezoelectric elements 21 and a plurality of second piezoelectric elements 22 . Two types of piezoelectric elements having different center frequencies, the first piezoelectric element 21 and the second piezoelectric element 2, are alternately arranged on the same circumference. The circumference on which the piezoelectric elements 20 are arranged includes the position P0 irradiated with the pulsed laser light and is centered on a straight line L0 perpendicular to the surface of the object 1 to be measured.

When the piezoelectric element is installed in this manner, the surface wave Us excited on the surface of the measurement target 1 by the pulsed laser beam propagates outward in the radial direction around the irradiation point P0 of the pulsed laser beam. As for the underwater leaky wave Utw reaching the piezoelectric element 20, since the ultrasonic waves of a plurality of modes can take different paths, for example, the underwater leaky wave generated from the defect position, the underwater leaky wave from the surface wave transmitted through the defect, etc. is detected. By arranging the piezoelectric elements 20 in an annular shape, it is possible to analyze the ultrasonic waveform detected by each piezoelectric element 20 and to know the presence or absence of defects within the measurement range. Furthermore, it is possible to obtain information on the position and depth of the defect depending on the difference in the time at which the echo from the defect is obtained and whether or not the transmitted surface wave is detected. Note that the number of piezoelectric element groups and the order in which the piezoelectric elements are arranged are not limited to this. Also, an elliptical, semicircular, or other arrangement form may be employed.

[Fourth embodiment]
FIG. 15 is a block diagram showing the configuration of a laser ultrasonic measuring device according to the fourth embodiment.

In this embodiment, a cylindrical lens 17 is provided on the irradiation side of the pulse laser. Also, the piezoelectric element 20 has a plurality of first piezoelectric elements 21 and a plurality of second piezoelectric elements 22 . The plurality of first piezoelectric elements 21 and the plurality of second piezoelectric elements 22 are arranged alternately in a straight line radially outward from the cylindrical lens 17 . are distributed. Although the piezoelectric element 20 is arranged only on one side when viewed from the cylindrical lens 17, it may be arranged on both sides.

A surface wave Us excited on the surface of the object 1 to be measured by the pulsed laser beam propagates from the irradiation point P0 in the horizontal direction in the figure. On the other hand, by arranging the piezoelectric elements 20 in a row, it is possible to receive the signal of the underwater leaky wave Uw from the range in which the surface wave Us has propagated.

[Other embodiments]
Although the embodiments of the present invention have been described above, the embodiments are presented as examples and are not intended to limit the scope of the invention.

Moreover, you may combine the characteristic of each embodiment. In addition, the embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention.

The embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and its equivalents.

DESCRIPTION OF SYMBOLS 1... Measurement object, 2... Defect, 3... Container, 4... Liquid, 10, 10a... Laser ultrasonic generator, 11... Pulse laser light source, 12... Optical fiber injection mechanism, 13... Irradiation probe, 14... Reflecting mirror, DESCRIPTION OF SYMBOLS 15... Optical fiber, 16... Optical lens, 17... Cylindrical lens, 20... Piezoelectric element, 21... First piezoelectric element, 22... Second piezoelectric element, 23... Third piezoelectric element, 30... Defect estimation unit, 40... Transmission/reception position adjustment part, 41... Transmission/reception unit housing, 42... Transmission/reception unit driving part, 100... Laser ultrasonic measuring device

Claims (9)

a laser ultrasonic generator that excites a surface wave having a broadband frequency in a measurement target in a liquid ;
a plurality of piezoelectric elements having different center frequencies;
a defect estimator for estimating the scale of a defect in the measurement object based on the ultrasonic signals received by the plurality of piezoelectric elements;
A laser ultrasonic measurement device comprising: The laser ultrasonic generator is
a pulsed laser light source that generates pulsed laser light;
an illumination probe;
an optical fiber that transmits the pulsed laser light;
an optical fiber injection mechanism for injecting the pulsed laser light into the optical fiber;
The laser ultrasonic measuring device according to claim 1, characterized by comprising : The laser ultrasonic generator is
a pulsed laser light source that generates pulsed laser light;
an optical mirror for changing the optical path of the pulsed laser light;
an optical lens for condensing the pulsed laser light;
The laser ultrasonic measuring device according to claim 1, characterized by comprising: 4. The defect estimator according to claim 1, wherein the defect estimating unit estimates the scale of the defect in the object to be measured based on the intensity of each of the ultrasonic signals received by the plurality of piezoelectric elements. The laser ultrasonic measurement device according to any one of the items . 5. The laser ultrasonic wave according to claim 1, further comprising a transmitting/receiving position control mechanism for individually adjusting installation positions of the plurality of piezoelectric elements and the laser ultrasonic wave generator. measuring device. 6. The laser ultrasonic measurement apparatus according to claim 1 , wherein the plurality of piezoelectric elements are arranged linearly . 6. The laser ultrasonic measurement apparatus according to claim 1 , wherein the plurality of piezoelectric elements are arranged in a ring . A generator installation step of installing a laser ultrasonic generator that generates ultrasonic waves to a measurement target in a liquid;
a first piezoelectric element installation step of installing a plurality of piezoelectric elements having different center frequencies at a first position;
a first ultrasonic wave generating step of generating ultrasonic waves having a broadband frequency to a measurement target by a laser ultrasonic wave generator after the generator installation step and the first piezoelectric element installation step;
A first defect estimation step of acquiring signals from the plurality of piezoelectric elements in the first ultrasonic wave generation step, comparing the signal levels, and estimating the scale of the defect in the measurement object;
A laser ultrasonic measurement method comprising : A generator installation step of installing a laser ultrasonic generator that generates ultrasonic waves to a measurement target;
a first piezoelectric element installation step of installing a plurality of piezoelectric elements having different center frequencies at a first position;
a first ultrasonic wave generating step of generating ultrasonic waves having a broadband frequency to a measurement target by a laser ultrasonic wave generator after the generator installation step and the first piezoelectric element installation step;
A first step of obtaining a first signal from the plurality of piezoelectric elements in the first ultrasonic wave generating step, comparing levels of the first signal, and estimating the scale of the defect in the measurement object a defect estimation step;
has
The first defect estimation step includes a determination step of determining whether the first signal from the plurality of piezoelectric elements is a transmitted surface wave or a reflected surface wave,
a second piezoelectric element installation step of moving the plurality of piezoelectric elements to positions according to the result of the determining step and installing them at a second position;
After the second piezoelectric element installation step, a second ultrasonic wave generating step of generating ultrasonic waves having a broadband frequency to the object to be measured by a laser ultrasonic generator;
A second step of obtaining a second signal from the plurality of piezoelectric elements in the second ultrasonic wave generating step, comparing the levels of the second signal, and estimating the scale of the defect in the measurement object a defect estimation step;
a defect position estimation step of estimating the position of the defect from the results of the first defect estimation step and the second defect estimation step;
A laser ultrasonic measurement method comprising:

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