JP5841027B2 - Inspection apparatus and inspection method - Google Patents

Description

  The present invention relates to an inspection apparatus and an inspection method, and more particularly to a nondestructive inspection apparatus and method using elastic waves.

  Long members such as constituent members, building members, and construction members of various machines may be disposed deep in the machine, or may be embedded in a building or soil. In such a case, even if cracks, wear, corrosion, etc. occur due to changes over time and the like, and the cross-sectional area or cross-sectional shape changes, it is difficult to directly check the change visually. Therefore, conventionally, by transmitting an elastic wave that travels to the axis of the long member from a place where the long member can be directly accessed, and receiving an elastic wave (echo) reflected from the portion where the shape has changed, An elastic wave pulse echo method for detecting existence, position, degree, and the like has been proposed (see, for example, Non-Patent Document 1). In this method, the distance to the defect is evaluated by the time from when the elastic wave is transmitted until the reflected echo is received, and the degree of the defect is evaluated by the amplitude of the echo.

Shunpei Kameyama, others, guided wave flaw detection system, Japan Nondestructive Inspection Association, Nondestructive Inspection, Vol. 52, No. 12, 672-678, issued on December 1, 2003

  However, in the above-described method, the change is detected based on the echo from the part where the shape has changed. Therefore, although a change in shape that is abrupt in space can be detected to some extent, the cross-sectional shape is gradually lowered in the axial direction. The case of change could not be detected. For this reason, it has been desired that even if the cross-sectional shape changes gently, the change can be detected.

  Therefore, an object of the present invention is to provide an inspection apparatus and an inspection method capable of detecting whether or not the shape of the long member has changed even when the cross-sectional shape changes gently. To do.

In order to solve the above-described problems, an inspection apparatus according to the present invention includes a transmission unit that transmits an elastic wave to an inspection target member, a reception unit that receives an elastic wave propagated through the inspection target member, and the reception unit. Detected by the detection unit, a detection unit for detecting the frequency characteristic of the average group velocity of the elastic wave received by the unit, a storage unit for previously storing the frequency characteristic of the average group velocity of the elastic wave propagating through the comparison target member, and the detection unit The frequency characteristic of the average group velocity of the elastic wave propagating through the inspection target member is compared with the frequency characteristic of the average group velocity of the elastic wave propagating through the comparison target member stored in the storage unit. A determination unit that determines whether or not the shape of the target member is the same as the shape of the comparison target member; and a known frequency at which the average group velocity is constant regardless of the shapes of the inspection target member and the comparison target member Use elastic wave And a measuring unit for measuring the length of said object member Te, the frequency characteristic of the average group velocity is characterized in that the frequency dependence of the average group velocity.

In the inspection apparatus, the sending unit sends an elastic wave having a frequency at which a difference in average group velocity between the inspection target member and the comparison target member is maximum to the inspection target member, and the receiving unit is the inspection target receiving the acoustic waves propagating member, the detecting unit, the receiving unit detects the propagation time at the time of receiving the elastic wave, said measuring section, the shape of said object member and said comparison member Regardless of whether the average group velocity is constant, an elastic wave having a known frequency is transmitted from the sending unit to the inspection target member and received, and the average group velocity of the known frequency is measured. Based on the propagation time, the length of the inspection target member is measured, and the storage unit generates an elastic wave having a frequency at which a difference in average group velocity between the inspection target member and the comparison target member is maximum. in comparison member Storing the propagation time of the acoustic wave propagating when issued in advance, the determining unit includes a propagation time of the acoustic wave propagating through said object member detected by the detecting unit, which is stored in the storage unit the comparison member is compared with the propagation time of the acoustic wave propagating, it is characterized in that the shape of said object member to determine whether or not the same as the shape of the comparison member.

Further, in the inspection method according to the present invention, the transmission unit transmits the elastic wave to the inspection target member, the reception unit receives the elastic wave propagated through the inspection target member, and the detection unit includes A detecting step for detecting the frequency characteristic of the average group velocity of the elastic wave received by the receiving unit; and a storage step for storing in advance the frequency characteristic of the average group velocity of the elastic wave propagating through the comparison target member; The frequency characteristic of the average group velocity of the elastic wave propagating through the inspection target member detected by the detection unit and the average group velocity of the elastic wave propagating through the comparison target member stored in the storage unit A determination step of determining whether or not the shape of the inspection target member is the same as the shape of the comparison target member, and a measuring unit that compares the frequency characteristics of the inspection target member and the comparison target member form A measurement step of measuring the length of the member to be inspected using an elastic wave having a known frequency at which the average group velocity is constant regardless of the frequency characteristic of the average group velocity is the frequency of the average group velocity. It is characterized by dependency .

In the inspection method, the sending step sends an elastic wave having a frequency that maximizes the difference in average group velocity between the inspection target member and the comparison target member to the inspection target member, and the receiving step includes The elastic wave propagated through the inspection target member is received, and the detection step detects a propagation time when the receiving unit receives the elastic wave, and the measurement step includes the inspection target member and the comparison target member. Measures the propagation time from when the elastic wave having a known frequency at which the average group velocity is constant regardless of the shape is sent to the inspection target member by the sending unit to receive it, and the average group velocity at the known frequency And measuring the length of the inspection object member based on the propagation time, and the storing step has a maximum difference in average group velocity between the inspection object member and the comparison object member. The propagation time of the elastic wave propagating when the elastic wave of the frequency to be sent to the comparison target member is stored in advance, and the determination step includes the propagation time of the elastic wave propagating through the inspection target member detected by the detection unit And the propagation time of the elastic wave propagating through the comparison target member stored in the storage unit to determine whether the shape of the inspection target member is the same as the shape of the comparison target member It is characterized by this.

  According to the present invention, the cross-sectional shape seems to change gently by comparing the frequency characteristics of the average group velocity of the elastic wave propagating through the inspection target member with the frequency characteristics of the average group velocity propagating through the comparison target member. Even in this case, it is possible to inspect whether or not the shape of the inspection target member has changed.

FIG. 1 is a block diagram showing a configuration of an inspection apparatus according to the first embodiment of the present invention. FIG. 2 is a front view showing an example of a long member. FIG. 3 is a diagram showing the measurement results of the frequency characteristics of the group velocity. FIG. 4 is a flowchart showing the inspection operation of the inspection apparatus according to the first embodiment of the present invention. FIG. 5 is a block diagram showing a configuration of an inspection apparatus according to the second embodiment of the present invention. FIG. 6 is a diagram for explaining that the group velocity of the elastic wave at a predetermined frequency is used as the frequency characteristic of the group velocity from the measurement result of FIG. FIG. 7 is a flowchart showing the inspection operation of the inspection apparatus according to the second embodiment of the present invention.

[First Embodiment]
First, a first embodiment according to the present invention will be described.

<Configuration of inspection device>
As shown in FIG. 1, the inspection apparatus 1 according to the present embodiment includes a transmission / reception unit 11, a signal processing unit 12, a storage unit 13, a determination unit 14, and an output unit 15.

  As shown in FIG. 2, the transmitter / receiver 11 drives a probe 111 fixed at an arbitrary position of the long member 10 to be measured, and drives the probe 111 and is detected by the probe 111. And a transmission / reception circuit 112 for outputting the received signal to the signal processing unit 12.

  The probe 111 can be realized by, for example, an array of piezoelectric elements that transmit and receive ultrasonic waves. The probe 111 is attached to, for example, a portion exposed on the surface of a metal bar embedded in the soil, and is fixed to the long member 10 based on an instruction from the signal processing unit 12 described later. A wave packet of an elastic wave propagating in the extending direction of the long member is transmitted, and an echo reflected by the end E of the long member is received.

  The transmission / reception circuit 112 includes a waveform generator that generates an arbitrary waveform based on an instruction from the signal processing unit 12 to be described later, a power amplification circuit that drives a piezoelectric element of the probe 111 based on the waveform, a probe And a receiving amplifier that amplifies the elastic wave signal received by the touch element 111.

The signal processing unit 12, the storage unit 13, the determination unit 14, and the output unit 15 are an arithmetic device such as a CPU (Central Processing Unit), a storage device such as a memory and an HDD (Hard Disc Drive), a keyboard, a mouse, and a pointing device. , Buttons, touch panels and other input devices that detect information input from the outside, I / F (Interface) devices that send and receive information to and from the outside, LCD (Liquid Crystal Display), organic EL (Electro Luminescence), etc. It is comprised from the computer provided with the display apparatus. Such an inspection apparatus 1 is configured such that the hardware resources as described above are controlled by a program installed in the computer, and the hardware apparatus and the software cooperate to generate a signal processing unit 12, a storage unit 13, and a determination. The unit 14 and the output unit 15 are realized.

The signal processing unit 12 gives data of a predetermined waveform to the transmission / reception unit 11 and drives to send an elastic wave to the long member, while processing a signal received by the probe 111 to process the long member. The frequency characteristic of the average group velocity of the elastic wave that propagated through is detected.
In the present embodiment, the signal processing unit 12 detects a frequency distribution profile indicating the frequency dependence of the average group velocity as indicated by symbols a and b in FIG. In FIG. 3, the vertical axis represents average group velocity [m / sec], and the horizontal axis represents frequency [kHz].
Detection of such frequency characteristics is performed as follows. First, the time from sending an elastic wave to receiving it is measured, and the average group velocity of the elastic wave is calculated from the distance traveled by the elastic wave. Thereby, the average group velocity at one point in FIG. 3 is calculated. A frequency distribution profile as shown in FIG. 3 can be obtained by repeatedly calculating such an average group velocity over a predetermined frequency range.

For example, when an elastic wave is transmitted to a cylindrical rod whose material is iron and whose cross-sectional shape is a circle having a diameter of 20 [mm] at any position, a frequency profile of a group velocity as indicated by symbol a in FIG. 3 is obtained. Similarly, when the material is iron and the cross-sectional shape is a cylinder having a diameter of 10 [mm] at any position, a frequency profile of the group velocity as shown by symbol b in FIG. 3 can be obtained.
Here, the long round bar member shown in FIG. 2, that is, the material is iron, the length is 10 [m], the diameter is almost 20 [mm], and the range indicated by the symbol L (length r [ Consider a cylinder that is 10 [mm] for most of m]). The average group velocity Vaverage at each frequency is obtained by averaging the group velocity V20 for a round bar with a diameter of 20 [mm] and the group velocity V10 for a round bar with a diameter of 10 [mm] based on the ratio of their lengths. As shown in equation (1).

Vaverage = 10 ・ V10 ・ V20 / ((10-r) ・V 10 + r ・ V20) (1)

By performing such an evaluation on an acoustic wave packet having a plurality of frequencies, it is possible to obtain a frequency profile of an average group velocity that falls between the characteristics represented by the symbols a and b in FIG.
In this way, if the cross-sectional shape or cross-sectional area is different even in part, the frequency profile of the average group velocity changes. Therefore, in the present embodiment, a member having a known shape such as a shape before use of a long member to be inspected (hereinafter referred to as “inspection member”) is referred to as a comparison target (hereinafter referred to as “comparison target member”). ), The frequency profile of the average group velocity is acquired in advance, and the frequency profile of the comparison target member is compared with the frequency profile of the inspection target member. I am inspecting. FIG. 3 shows a measurement result when a guide wave in the L (0, 1) mode is transmitted as an elastic wave. Here, the L mode means a mode in which the long member vibrates axisymmetrically, but the elastic wave mode to be used is not limited thereto.

  The memory | storage part 13 memorize | stores beforehand the frequency dependence of the average group velocity of the elastic wave which propagates a comparison object member. In the present embodiment, a frequency profile is stored as the frequency characteristics of the average group velocity. Here, as described above, the comparison target member is a comparison target for detecting whether or not the inspection target member is deformed. For example, the inspection target member before use or the inspection target member before use is used. It consists of a member etc. which have the same shape. The frequency profile of the comparison target member can be acquired by a method equivalent to the method in which the signal processing unit 12 detects the frequency profile of the long member.

  The determination unit 14 compares the frequency characteristic of the average group velocity of the elastic wave propagating through the inspection target member detected by the signal processing unit 12 with the frequency characteristic of the average group velocity of the comparison target member stored in the storage unit 13. Then, it is determined whether or not the shape of the inspection target member is the same as the shape of the comparison target member. In the present embodiment, the frequency profile of the member to be inspected is compared with the frequency profile of the member to be compared, and whether or not the member to be inspected has been deformed is determined based on whether or not they are the same. This determination result is output to the output unit 15.

  The output unit 15 outputs the determination result by the determination unit 14 to a monitor or the like.

<Operation of inspection device>
Next, the inspection operation by the inspection apparatus 1 according to the present embodiment will be described.

  First, the inspection apparatus 1 stores in advance the frequency profile of the average group velocity of elastic waves propagating through the comparison target member in the storage unit 13 (step S1). In the frequency profile, the signal processing unit 12 gives data of a predetermined waveform to the transmission / reception unit 11, drives the comparison target member to send an elastic wave, and processes the signal received by the probe 111. Then, it can be obtained by detecting the frequency profile of the average group velocity of the elastic wave propagated through the comparison target member.

  Next, the signal processing unit 12 detects the frequency profile of the average group velocity of the elastic wave propagating through the inspection target member (step S2). Specifically, the transmitter / receiver 11 is supplied with data having the same predetermined waveform as when the frequency profile of the comparison target member is detected, and is driven to send an elastic wave to the inspection target member. The frequency profile of the average group velocity of the elastic wave propagated through the inspection target member is detected by processing the received signal. The detected frequency profile of the inspection object member is output to the determination unit 14.

  When the frequency profile of the inspection target member is input, the determination unit 14 acquires the frequency profile of the comparison target member from the storage unit 13, compares the inspection target and the frequency profile of the comparison target, and determines whether these are the same. Is determined (step S3). This comparison is performed, for example, by overlapping frequency characteristic profiles as shown in FIG. 3 and confirming whether or not they match.

  When the frequency profiles of the inspection target member and the comparison target member are the same (step S3: YES), the determination unit 14 determines that the inspection target member is not deformed (step S4).

  On the other hand, when the frequency profiles of the inspection target member and the comparison target member are not the same (step S3: NO), the determination unit 14 determines that the inspection target member is deformed (step S5).

  When the determination is made by the determination unit 14, the output unit 15 outputs the determination result to a monitor or the like (step S6). Thereby, the user can confirm whether the inspection object member is deformed by confirming the monitor screen.

  As described above, according to the present embodiment, the inspection is conventionally performed by comparing the frequency profile of the elastic wave propagating through the inspection target member with the frequency profile of the elastic wave propagating through the comparison target member. It is possible to inspect whether or not the shape of the member to be inspected has changed even when the cross-sectional shape that has been difficult to change gradually changes.

[Second Embodiment]
Next, a second embodiment according to the present invention will be described. In the present embodiment, the average group velocity of elastic waves having a predetermined frequency is used as the frequency characteristic of the average group velocity. Therefore, components equivalent to those in the first embodiment described above are denoted by the same names and reference numerals, and description thereof is omitted as appropriate.

<Configuration of inspection device>
As shown in FIG. 5 , the inspection apparatus 2 according to the present embodiment includes a transmission / reception unit 11 and a signal processing unit 2.
2, a storage unit 23, a determination unit 24, an output unit 15, and a measurement unit 26.

  Here, the signal processing unit 22 gives data of a predetermined waveform to the transmission / reception unit 11 and drives to send an elastic wave to the long member, while processing a signal received by the probe 111. The frequency characteristic of the average group velocity of the elastic wave propagated through the long member is detected. In the present embodiment, the average group velocity of elastic waves having a predetermined frequency is used as the frequency characteristic. Specifically, a propagation time from when an acoustic wave having a specific frequency is transmitted by the probe 111 to when the probe 111 receives an echo is used as a frequency characteristic. The reason for this will be described below.

  Since the frequency profile of the average group velocity as shown by reference symbols a and b in FIG. 6 differs depending on the shape of the long member, the average group velocity is different at almost all frequencies. For this reason, when an elastic wave having a specific frequency whose average group velocity differs depending on the shape of the long member is transmitted to the long member having a different shape, the propagation time from when the elastic wave is transmitted to when the echo is received. On the other hand, when transmitted to a long member of the same shape, the propagation time is the same. Note that the frequency profiles indicated by symbols a and b in FIG. 6 are the same as the frequency profiles indicated by symbols a and b in FIG. 3.

  For example, for a long member having a frequency profile of 10 [m] having a frequency profile indicated by symbol a in FIG. 6 and a long member having a frequency profile indicated by symbol b of FIG. 6 having a frequency of 10 [m], Consider a case where an elastic wave having a frequency f1 (165 [kHz]) at which the average group velocity difference is maximum is transmitted. As for the propagation time of the long member denoted by a, the average group velocity when the frequency is 165 [kHz] is about 1960 [m / sec], and the traveling distance of the elastic wave is 20 [m]. The time until is about 10.2 [msec]. Further, the propagation time of the long member denoted by reference symbol b is about 4.3 [msec] because the average group velocity when the frequency is 165 [kHz] is about 4670 [m / sec].

  Further, regarding the propagation time of the long round bar member shown in FIG. 2, if the section L having a diameter of 10 [mm] is effectively 1 [m], the distance of 18 [m] is set to a speed of 1960 [m]. m / sec] and a distance of 2 [m] travel at a speed of 4670 [m / sec], so the propagation time is about 9.6 [msec]. Thus, if the shape of the long member is different, the propagation time of the elastic wave is also different.

In addition, the propagation time difference t (propagation time difference depending on whether or not the cross-sectional area is changed) in the section where the cross-sectional area is changed can be calculated by the following equation (2). In the following equation (2), l is the distance of the travel distance of the elastic wave in the section where the cross-sectional area has changed (when it is evaluated by echo, it is a reciprocation and is twice the actual length), and ν ₀ is the cross-sectional area The group velocity when ν is not changed, and ν ₁ mean the group velocity when the cross-sectional area is changed.

l · (1 / ν ₀ −1 / ν ₁ ) = t (2)

  Therefore, in the present embodiment, the frequency at which the difference in the average group velocity between the inspection target member and the comparison target member is maximized is detected in advance from the frequency profile and experience as shown by reference symbols a and b in FIG. Whether or not the shape of the object to be inspected has changed by measuring the propagation time from the time when the elastic wave of this frequency is transmitted to the member to be inspected and the member to be compared until the echo is received, and comparing this time Determine whether.

  The memory | storage part 23 memorize | stores propagation time beforehand after transmitting a specific frequency to a comparison object member, and receiving an echo. The propagation time of the comparison target member can be obtained by a method equivalent to the method in which the signal processing unit 22 detects the propagation time of the inspection target member.

  The determination unit 24 compares the propagation time of the inspection target member detected by the signal processing unit 22 with the propagation time of the comparison target member stored in the storage unit 23 in advance, so that the shape of the inspection target member is compared. It is determined whether or not the shape of the member is the same. This determination result is output to the output unit 15.

  When the length of the member to be inspected is not known, the measuring unit 26 causes the signal processing unit 22 to transmit an elastic wave having a specific frequency whose average group velocity is known to the member to be inspected until receiving an echo. The propagation time is measured, and the length of the inspection object is measured from this time and the known average group velocity.

  As shown in FIG. 6, the group velocities near the frequency f2 (10 to 30 [kHz]) have the same value in both the profiles a and b. This means that an elastic wave having a frequency of 10 to 30 [kHz] has a constant group velocity regardless of the shape of the long member when the cross-sectional diameter is in the range of 10 [mm] to 20 [mm]. Therefore, if the propagation time from transmitting an elastic wave of that frequency to a member to be inspected whose length is unknown and receiving an echo is measured, the object to be inspected can be determined from this propagation time and the average group velocity of the elastic waves of that frequency. The length can be measured regardless of whether or not the diameter of the cross section of the member changes. Based on such a principle, the measuring unit 26 measures the length of the inspection target member.

<Operation of inspection device>
Next, the inspection operation by the inspection apparatus 2 according to the present embodiment will be described.

  First, the inspection device 2 stores the propagation time of the comparison target member in the storage unit 23 in advance (step S11). The propagation time is the time from when the elastic wave having a specific frequency set in advance based on the shape of the comparison target member is transmitted to the comparison target member by the signal processing unit 22 until the echo of the elastic wave is received. It can be acquired by measuring.

  Next, when the length of the inspection target member is unknown, the measuring unit 26 measures the length (step S12).

  Next, the signal processing unit 22 detects the propagation time of the inspection target member (step S13). Specifically, the detection is performed by measuring the time from when an elastic wave having the same specific frequency as the elastic wave transmitted to the comparison target member is transmitted to the inspection target member until the echo of the elastic wave is received. The detected propagation time of the inspection target member is output to the determination unit 24.

  When the propagation time of the inspection target member is input, the determination unit 24 acquires the propagation time of the comparison target member from the storage unit 23 and determines whether the propagation time of the inspection target member and the comparison target member is the same. (Step S14).

  When the propagation times of the inspection target member and the comparison target member are the same (step S14: YES), the determination unit 24 determines that the inspection target member is not deformed (step S15).

  On the other hand, when the propagation times of the inspection target member and the comparison target member are not the same (step S14: NO), the determination unit 24 determines that the inspection target member is deformed (step S16).

  When the determination is made by the determination unit 24, the output unit 15 outputs the determination result to a monitor or the like (step S17). Thereby, the user can confirm whether the inspection object member is deformed by confirming the monitor screen.

  As described above, according to the present embodiment, the inspection is conventionally performed by comparing the propagation time of the elastic wave propagating through the inspection target member and the propagation time of the elastic wave propagating through the comparison target member. It is possible to inspect whether or not the shape of the member to be inspected has changed even when the cross-sectional shape that has been difficult to change gradually changes.

  In this embodiment, the case where an elastic wave having a frequency at which the difference in average group velocity is the maximum is described as an example. However, if the average group velocity is different depending on the shape of the long member, what is the frequency? You may make it transmit the elastic wave of a various frequency.

  Further, in the first embodiment, the measurement unit 26 in the present embodiment may be further provided. Thereby, also in the first embodiment, the length of the long member can be measured.

  In the first and second embodiments, the case where the elastic wave is transmitted from an arbitrary position of the long member and the echo reflected from the end of the long member is received is described as an example. A probe may be further provided between the arbitrary position and the end, and the frequency characteristic of the average group velocity of the elastic wave propagating through the long member detected by the probe may be detected.

  Further, in the first and second embodiments, the case of inspecting whether or not the long member is deformed has been described as an example, but if it is a member that can propagate an elastic wave, its shape is It is not limited to a long member, It can test | inspect whether it deform | transforms about various shapes.

  Further, FIG. 3 shows the measurement result when a guide wave is transmitted, but the elastic wave is not limited to the guide wave, and a bulk wave is used if the average group velocity can be evaluated by the received wave. It may be. Here, the bulk wave means a plane wave in a material that is infinitely large (which can be regarded as having no boundary for the wave), and generally has no frequency dependence of the sound velocity (group velocity, phase velocity). is there. On the other hand, a guide wave means a wave defined by the boundary condition in a situation where a boundary exists for the wave, and generally has a frequency dependence of sound speed. Note that when evaluating changes in the member shape, it is necessary that the frequency characteristics of the average group velocity change depending on the shape. Therefore, when using a bulk wave, generally at least part of the path is used. It must be a guide wave. Further, when evaluating the length of the inspection target member, it is necessary that the frequency characteristics of the group velocity do not change depending on the shape.

  INDUSTRIAL APPLICABILITY The present invention can be applied to various inspection apparatuses that inspect whether a long member embedded and installed in the ground or a structure is deformed.

  DESCRIPTION OF SYMBOLS 1, ... Inspection apparatus, 10 ... Long member, 11 ... Transmission / reception part, 12, 22 ... Signal processing part, 13, 23 ... Memory | storage part, 14, 24 ... Determination part, 15 ... Output part, 26 ... Measurement part, 111: Probe; 112: Transmission / reception circuit.

Claims (4)

A sending section for sending an elastic wave to the inspection target member;
A receiving unit for receiving an elastic wave propagated through the inspection target member;
A detecting unit for detecting frequency characteristics of an average group velocity of the elastic wave received by the receiving unit;
A storage unit that stores in advance the frequency characteristics of the average group velocity of the elastic waves propagating through the comparison target member;
The frequency characteristic of the average group velocity of the elastic wave propagating through the inspection target member detected by the detection unit and the frequency characteristic of the average group velocity of the elastic wave propagating through the comparison target member stored in the storage unit In comparison, a determination unit that determines whether the shape of the inspection target member is the same as the shape of the comparison target member ;
A measuring unit that measures the length of the inspection target member using an elastic wave having a known frequency at which the average group velocity is constant regardless of the shapes of the inspection target member and the comparison target member ;
The frequency characteristic of the average group velocity is frequency dependency of the average group velocity. The sending section sends an elastic wave having a frequency at which a difference in average group velocity between the inspection target member and the comparison target member is maximum to the inspection target member ;
The receiving unit receives the acoustic wave propagated through said object member,
Wherein the detection unit detects the propagation time for the receiver receives the acoustic wave,
The measuring unit transmits an elastic wave having a known frequency at which the average group velocity is constant regardless of the shapes of the inspection target member and the comparison target member to the reception target member after receiving the elastic wave by the transmission unit. And measuring the length of the member to be inspected based on the average group velocity of the known frequency and the propagation time,
The storage unit stores in advance a propagation time of an elastic wave that is propagated when an elastic wave having a frequency that maximizes the difference in average group velocity between the inspection target member and the comparison target member is sent to the comparison target member. ,
The determination unit compares the propagation time of the acoustic wave propagating through said object member detected by the detecting unit, and a propagation time of the acoustic wave propagating through the comparison member stored in the storage unit an inspection apparatus according to claim 1, wherein the shape of said object member and judging whether or not the same as the shape of the comparison member. A sending step for sending an elastic wave to the inspection target member;
A receiving step for receiving an elastic wave propagated through the inspection target member; and
A detecting step for detecting a frequency characteristic of an average group velocity of the elastic wave received by the receiving unit;
A storage step in which the storage unit stores in advance the frequency characteristics of the average group velocity of the elastic waves propagating through the comparison target member;
The determination unit has a frequency characteristic of an average group velocity of the elastic wave propagating through the inspection target member detected by the detection unit, and an average group velocity of the elastic wave propagating through the comparison target member stored in the storage unit. A determination step of comparing the frequency characteristics and determining whether or not the shape of the inspection target member is the same as the shape of the comparison target member;
A measurement step in which the measurement unit measures the length of the inspection target member using an elastic wave having a known frequency at which the average group velocity is constant regardless of the shapes of the inspection target member and the comparison target member;
Have
The frequency characteristic of the average group velocity, the inspection method, which is a frequency dependence of the average group velocity. The sending step sends an elastic wave having a frequency at which the difference in average group velocity between the inspection target member and the comparison target member is maximum to the inspection target member;
The receiving step receives an elastic wave propagated through the inspection target member,
The detecting step detects a propagation time when the receiving unit receives the elastic wave,
In the measurement step, an elastic wave having a known frequency at which the average group velocity is constant regardless of the shapes of the inspection target member and the comparison target member is transmitted to the inspection target member by the transmission unit and then received. And measuring the length of the member to be inspected based on the average group velocity of the known frequency and the propagation time,
The storing step stores in advance a propagation time of an elastic wave that propagates when an elastic wave having a frequency that maximizes the difference in average group velocity between the inspection target member and the comparison target member is sent to the comparison target member. ,
The determination step compares the propagation time of the elastic wave propagating through the inspection target member detected by the detection unit with the propagation time of the elastic wave propagating through the comparison target member stored in the storage unit. 4. The inspection method according to claim 3 , wherein it is determined whether or not the shape of the inspection target member is the same as the shape of the comparison target member .

Images