JP2017167100A - Monitoring system for structure, and method for monitoring structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monitoring system for structures with which it is possible to propagating an elastic wave from a relative wide area among outer faces of a structure to an AE sensor and detect a non-steady elastic wave with excellent sensitivity.SOLUTION: A monitoring system for structures detects a non-steady elastic wave occurring in a structure 10 and thereby monitors destruction such as occurrence of a crack in the structure 10. The monitoring system for structures comprises an AE sensor 20 for converting an elastic wave from the structure 10 into an electric signal, and a contact medium 30 made of metal, interposed between the AE sensor 20 and the structure 10, for propagating the elastic wave from the structure 10 to the AE sensor 20. The area of a structure contact face 36 of the contact medium 30 that is in contact with the structure 10 is larger than the area of a sensor contact face 33 that is in contact with the AE sensor 20.SELECTED DRAWING: Figure 2

Description

  Embodiments described herein relate generally to a technique for monitoring the destruction of a structure.

  When a fracture such as a crack or a defect occurs in a structure, a phenomenon in which an unsteady elastic wave is generated in the structure due to rapid energy release, so-called acoustic emission (hereinafter simply referred to as “AE”) occurs. Sometimes. A technique for monitoring the occurrence of a crack or the like in a structure by detecting an elastic wave generated by such AE, a so-called AE wave (AE wave), and analyzing the waveform has been proposed. For example, a monitoring device that monitors the degree of deterioration due to fatigue of piping or the like has been proposed.

JP-A-10-26613

  For such a monitoring device that monitors the destruction of a structure, a sensor that receives an elastic wave from the structure and converts the elastic wave into an electric signal, a so-called AE sensor, is usually used. The AE sensor is attached to a desired surface of the structure. In order to improve the propagation of elastic waves (ie acoustic energy) to the AE sensor, a couplant is generally provided between the AE sensor and the structure. As the contact medium, for example, a liquid such as oil or glycerin, a relatively soft solid, or the like is used.

  An electrical signal indicating an elastic wave detected by an AE sensor (hereinafter referred to as an AE signal) is generally amplified by an amplifier circuit (so-called amplifier) and subjected to frequency analysis by a processing device or the like, and a frequency spectrum is obtained. Desired. Since the unsteady elastic wave generated from a minute crack or the like is weak, the change in the frequency spectrum is small. In such a case, it is difficult to select the frequency of the elastic wave caused by a crack or the like in the frequency spectrum, that is, to detect and quantify the crack or the like. The AE sensor is required to have high sensitivity in the frequency band of elastic waves caused by cracks and the like.

  The structure which is the monitoring target of the monitoring device described above may be exposed to a high temperature environment or a high radiation environment. For example, a unit constituting the inner surface of a vacuum vessel of a nuclear fusion apparatus is constantly exposed to high-temperature plasma and exposed to radiation such as gamma rays and neutrons. Such units are composed of metals with relatively high corrosion resistance, but are exposed to plasma reacted with hydrogen isotopes (for example, deuterium and tritium), resulting in hydrogen embrittlement and their surfaces and internals. Cracks and defects may occur.

  Such a structure needs to be constantly monitored, for example, during operation of the fusion device, and an AE sensor is coupled to a predetermined surface of the structure via the contact medium described above. For this reason, the AE sensor is also arranged in an environment of high temperature or high radiation, like the structure.

  Generally, commercially available AE sensors cannot operate normally unless they are below a predetermined temperature (for example, 300 ° C.). An AE sensor that can withstand such a harsh environment is not general and has limited applications. Particularly, an AE sensor having a relatively large surface for receiving an elastic wave (hereinafter referred to as a detection surface) It is often difficult to manufacture. Therefore, for the AE sensor coupled to the structure, there is no choice but to use a sensor having a relatively small detection surface for receiving the elastic wave.

  On the other hand, in order for the AE sensor to detect the elastic wave from the structure with a relatively high sensitivity, the contact medium receives the elastic wave from a relatively wide area of the outer surface of the structure and detects the elastic wave by the AE sensor. It must be propagated to the surface.

  The embodiment of the present invention has been made in view of the above circumstances, and an elastic wave from a relatively wide region of the outer surface of the structure is propagated to the AE sensor, thereby providing unsteady elasticity with good sensitivity. An object is to provide a structure monitoring system capable of detecting waves.

  In order to achieve the above-described object, a structure monitoring system according to an embodiment of the present invention is a structure monitoring system that monitors destruction of a structure, and converts an elastic wave from the structure into an electrical signal. An AE sensor; and a metal contact medium that is interposed between the AE sensor and the structure and propagates an elastic wave from the structure to the AE sensor. Among these, the area of the structure contact surface in contact with the structure is larger than the area of the sensor contact surface in contact with the AE sensor.

  The structure monitoring method according to the embodiment of the present invention is a structure monitoring method for monitoring the destruction of the structure, and an AE sensor that converts an elastic wave from the structure into an electric signal and the structure. The metal contact medium that is provided between the two and that propagates the elastic wave from the structure to the AE sensor has an area of the structure contact surface in contact with the structure in contact with the AE sensor. A step of acquiring an electric signal indicating an elastic wave detected by the AE sensor, and extracting a waveform indicating an unsteady elastic wave from the electric signal from the AE sensor. And estimating at least one of the number of cracks generated in the structure and the size of the crack based on the number and amplitude of the waveforms indicating the extracted unsteady elastic waves; , Including It is characterized in.

  According to the embodiment of the present invention, the amplitude of the elastic wave received by the AE sensor, that is, the so-called detection intensity, can be increased as compared with the intensity of the elastic wave incident on the structure contact surface from the structure.

It is a schematic diagram explaining the structure monitoring system of the first embodiment and the structure to be monitored. It is sectional drawing explaining an example of the AE sensor which comprises the monitoring system for structures of 1st Embodiment. It is a perspective view explaining the arrangement | positioning relationship between the shape of the contact medium which comprises the monitoring system for structures of 1st Embodiment, and an AE sensor. It is an end view of the axial direction low temperature side of the structure of the first embodiment. It is a graph explaining the method of extracting the waveform which shows an elastic wave in the structure monitoring method of 1st Embodiment. It is an end elevation of the axial direction low temperature side of the structure of the second embodiment. It is a schematic diagram explaining the monitoring system for structures of 3rd Embodiment, and the structure which is a monitoring object. It is an end elevation of the axial direction low temperature side of the structure of the third embodiment. It is a graph which shows an example of the waveform which shows the elastic wave after difference processing among the structure monitoring methods of a 3rd embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments described below, and various modifications can be made without departing from the scope of the invention.

[First Embodiment]
First, a schematic configuration of a structure monitoring system according to the present embodiment and an example of a structure to be monitored will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram for explaining an example of a structure monitoring system according to the present embodiment and a structure to be monitored. In the drawing, the structure is partially shown in a longitudinal section. FIG. 2 is a cross-sectional view illustrating an example of an AE sensor constituting the structural body monitoring system of the present embodiment.

(Example of structure)
As shown in FIG. 1, the structure 10 of this embodiment is a member which comprises the vacuum vessel (not shown) which surrounds a plasma in a nuclear fusion apparatus as an example, and is inner side from a liner among the said vacuum vessels (FIG. This is a so-called unit that protrudes and extends in the direction of arrow A1. The structure may be a blanket or a diverter that constitutes the vacuum vessel.

  The structure 10 has a substantially cylindrical outer shape whose axis extends in a predetermined direction. The axis of the structure 10 is indicated by a one-dot chain line A in the figure. In the following description, the direction along the alternate long and short dash line A is referred to as “axial direction”. A direction perpendicular to the axial direction is referred to as a “radial direction”, and the outside thereof is indicated by an arrow R1 in the drawing.

  A portion (hereinafter referred to as an outer wall portion) 11 constituting the outer wall of the structure 10 has a substantially cylindrical shape coaxially with the structure 10. The cross section of the outer wall portion 11 has a substantially annular shape. The outer wall portion 11 is exposed to plasma in the vacuum vessel.

  In particular, the end 12 on one side of the outer wall 11 in the axial direction (indicated by an arrow A1 in FIG. 1) receives heat from plasma and becomes particularly high in temperature. One side indicated by an arrow A1 in the axial direction is hereinafter referred to as “high temperature side”, and the opposite side to the high temperature side is hereinafter referred to as “low temperature side”.

  Further, the end portion 12 on the axially high temperature side of the structure 10 is referred to as a “high temperature side end portion 12”. In the present embodiment, the high temperature side end portion 12 has a substantially hemispherical shape with the axial high temperature side convex.

  On the other hand, end surfaces perpendicular to the axis A (hereinafter referred to as low temperature side end surfaces) 16 and 17 are formed on the axially low temperature side (opposite side of the arrow A1) of the structure 10. Among these low-temperature side end faces 16 and 17, the end face 16 on the radially inner side is particularly referred to as “inner end face” 16, and the end face 17 on the radially outer side is particularly referred to as “outer end face”. Between the inner end face 16 and the outer end face 17, an annular opening through which cooling water for cooling the structure 10 flows in or out is formed.

  A passage (hereinafter referred to as a cooling passage) 14 through which a liquid for cooling the structure, that is, cooling water flows, is formed inside the structure 10. The cooling passage 14 of the present embodiment is a passage formed in a metal cooling water pipe. In each drawing, for easy understanding, the cross section of the cooling water pipe defining the cooling passage 14 is omitted, and the cooling passage 14 is schematically shown.

  The cooling passage 14 extends along the outer wall portion 11 of the structure 10. Specifically, the cooling passage 14 extends in the axial direction at a predetermined interval radially inward from the outer wall portion 11, and in the vicinity of the high temperature side end portion 12, a U-shape that protrudes from the high temperature side. I am doing. The cooling water flowing from the outside of the structure 10 into the cooling passage 14 flows in the vicinity of the high temperature side end portion 12 and again flows out of the structure 10 through the opening. Due to the flow of the cooling water, the outer wall portion 11 of the structure 10, particularly the high temperature side end portion 12 is cooled.

  The structure 10 is made of a metal material, and specifically, is made of stainless steel that is a metal having relatively high corrosion resistance. For example, low activation ferritic steel such as F82H is used as the stainless steel constituting the structure 10.

  Among the structures 10, particularly the high-temperature side end 12 is exposed to plasma generated by the reaction of hydrogen isotopes (for example, deuterium and tritium) for a long time, and hydrogen embrittlement occurs. Specifically, cracks 13 and defects are generated on the surface and inside of the high temperature side end portion 12 due to hydrogen embrittlement. For ease of understanding, the crack 13 is indicated by an elliptic symbol in FIG.

  In the structure 10 thus configured, for example, when a crack 13 or a defect is generated at the high temperature side end portion 12 and an elastic wave is emitted, the elastic wave is generated between the outer wall portion 11 and the cooling passage 14. Propagates mainly through the metal between them. The elastic wave propagates to the axially low temperature side (the side opposite to the arrow A1) while being repeatedly reflected and scattered in a pipe (not shown) that defines the outer wall portion 11 and the cooling passage 14. A part of the elastic wave emitted from the crack 13 or the like reaches the outer end face 17 of the structure 10.

(Schematic structure of structure monitoring system)
The structure monitoring system 1 according to the present embodiment, which targets such a structure 10 as a monitoring object, detects and quantifies unsteady elastic waves generated from cracks 13 and defects in the structure 10, so-called AE waves. By doing this, it is a system that monitors the destruction of the structure 10 such as cracks and defects (occurrence of a crack or the like), that is, a system that monitors the soundness of the structure 10. The structure monitoring system 1 is also referred to as a “health monitoring device”.

  The structural monitoring system 1 includes an AE sensor 20 that receives an elastic wave from the structural body 10 on a detection surface 22 (see FIG. 2) and converts the elastic wave into an electric signal, and the structural body 10 and the AE sensor 20. The contact medium 30 is provided so as to propagate the elastic wave from the structure 10 to the AE sensor 20. The contact medium 30 is made of a relatively soft metal (so-called soft metal).

  Further, the structure monitoring system 1 acquires an electric signal indicating an elastic wave detected by the AE sensor 20 and amplified by the amplifier 40 and an amplifier 40 that amplifies the electric signal from the AE sensor 20. And a processing device (hereinafter simply referred to as “processing device”) 50. The processing device 50 according to the present embodiment has a function 52 (hereinafter referred to as a waveform extraction unit) 52 that extracts a waveform indicating an unsteady elastic wave from an electrical signal from the AE sensor 20 and a non-extraction that is extracted by the waveform extraction unit 52. Based on the number and amplitude (crest value) of steady elastic wave waveforms, the number of cracks or defects generated and the function of estimating at least one of the dimensions (hereinafter referred to as an embrittlement estimation unit) 54 Have.

  In the present embodiment, the processing device 50 includes a processor (not shown) that can execute various operations and a memory (not shown) that can store various constants. The processing device 50 can be realized by a general computer. The processing device 50 may be configured using a plurality of electric circuits (processing circuits) or a plurality of computers for each of various functions. Various functions of the processing device 50 will be described later.

(Example of AE sensor)
A configuration of the AE sensor 20 of the present embodiment will be described with reference to FIGS. FIG. 2 is a cross-sectional view for explaining an example of an AE sensor constituting the structural monitoring system of the present embodiment. FIG. 3 is a perspective view for explaining the positional relationship between the shape of the contact medium and the AE sensor constituting the structure monitoring system of the present embodiment.

  The AE sensor 20 of this embodiment is a piezoelectric detector, and includes a piezoelectric element 25 that converts an applied force into a voltage as a conversion element that converts an elastic wave into an electric signal. The piezoelectric element 25 has a substantially plate shape extending along the detection surface 22 that receives the elastic wave from the contact medium 30.

The piezoelectric element 25 includes PZT (lead zirconate titanate), LiNbO ₃ (lithium niobate single crystal), GaPO ₄ (gallium phosphate), AlN (aluminum nitride), La ₃ Ga ₅ SiO ₁₄ (langasite), Ga. ₂ Al ₂ SiO ₇ or the like. In particular, a piezoelectric element composed of LiNbO ₃ , AlN, Ga ₂ Al ₂ SiO ₇ or the like is suitable for those used in a severe environment of high temperature and high radiation.

  The piezoelectric element 25 is sandwiched between two electrodes 26 and 27 for detecting a voltage. These electrodes 26 and 27 are connected to metal wires, so-called signal lines 24 and 28, respectively. The signal lines 24 and 28 are accommodated in the cable 44 and extend outside the AE sensor 20. The cable 44 including the signal lines 24 and 28 is electrically connected to the amplifier 40 (see FIG. 1). The cable 44 may be a general coaxial cable or a so-called MI cable excellent in heat resistance.

  In the AE sensor 20 of the present embodiment, of the two electrodes 26 and 27, the electrode 26 on the contact medium 30 side has a slightly larger area than the electrode 27 and the piezoelectric element 25 on the opposite side. . A surface on the contact medium 30 side of the electrode 26 is a detection surface 22 that receives elastic waves. The elastic wave received by the detection surface 22 propagates to the piezoelectric element 25 through the electrode 26. The piezoelectric element 25 converts acoustic wave acoustic energy into an electrical signal, that is, a voltage. The electrical signal is sent to the amplifier 40.

(Example of contact medium)
As shown in FIGS. 1 and 2, the contact medium 30 is a substance for efficiently propagating the elastic wave generated in the structure 10 to the AE sensor 20. The contact medium 30 is provided between the structure 10 and the AE sensor 20 described above. The contact medium 30 is made of metal. More specifically, the contact medium 30 is made of a metal having a Vickers hardness (HV) of 100 or less, that is, a so-called soft metal.

  Examples of the metal constituting the contact medium 30 include Au (gold), Ag (silver), Cu (copper), and Ni (nickel). Note that the contact medium 30 can also be made of a metal other than these. For example, it is also preferable to use a metal having a relatively low melting point, for example, In (indium).

  As shown in FIG. 2, a surface of the contact medium 30 that contacts the detection surface 22 of the AE sensor 20 is hereinafter referred to as a “sensor contact surface” and denoted by reference numeral 33. In addition, a surface of the contact medium 30 that contacts the structure 10 (specifically, the outer end surface 17) is hereinafter referred to as a “structure contact surface” and denoted by reference numeral 36.

  Of the contact medium 30, the structure contact surface 36 and the sensor contact surface 33 extend substantially in parallel. The contact medium 30 moves from the predetermined surface (outer end surface) 17 of the structure 10 toward the AE sensor 20 (hereinafter referred to as a perpendicular direction) as it goes from the structure contact surface 36 to the sensor contact surface 33. The cross section perpendicular to (indicated by arrow D) is configured to be small.

  As shown in FIG. 3, the contact medium 30 has a frustum shape having the structure contact surface 36 as a lower base and the sensor contact surface 33 as an upper base. The sensor contact surface (upper bottom) 33 and the structure contact surface (lower bottom) 36 extend in parallel with each other at a predetermined interval in a perpendicular direction indicated by an arrow D in FIG. In the present embodiment, the contact medium 30 has a quadrangular pyramid shape, and four surfaces (hereinafter referred to as side surfaces) 34, 34 </ b> B, 35, 35 are provided between the sensor contact surface 33 and the structure contact surface 36. 35B. Specifically, the side surfaces 34, 34 </ b> B, 35, 35 </ b> B connect the outer edge 33 e of the sensor contact surface 33 and the outer edge 36 e of the structure contact surface 36, respectively.

  In the present embodiment, among these side surfaces 34, 34B, 35, and 35B, the side surface 34 and the side surface 34B that face each other in the direction perpendicular to the perpendicular direction have substantially the same area. Similarly, the side surface 35 and the side surface 35B facing each other have substantially the same area.

  As shown in FIGS. 2 and 3, the angle formed between each of the side surfaces 34, 34 </ b> B, 35, 35 </ b> B and the structure contact surface 36 inside the contact medium 30 is in the range of more than 45 degrees and less than 90 degrees. . In other words, inside the contact medium 30, the angle formed between each of the side surfaces 34, 34 </ b> B, 35, 35 </ b> B and the sensor contact surface 33 is in the range of more than 90 degrees and less than 135 degrees. In FIG. 2, the angle formed by the structure contact surface 36 and the side surface 34 is indicated by φ.

  As shown in FIG. 2, the structure contact surface 36 of the contact medium 30 configured as described above is coupled to the structure 10. The contact medium 30 is fixed by welding, brazing, or using a dedicated fixing jig so that no gap is generated between the outer end surface 17 and the structure contact surface 36 of the structure 10. Thereby, the elastic wave from the structure 10 is incident on the structure contact surface 36.

  Further, the contact medium 30 has its sensor contact surface 33 coupled to the detection surface 22 of the AE sensor 20. In the present embodiment, the sensor contact surface 33 is configured to have substantially the same shape and the same area as the detection surface 22. The contact medium 30 is fixed by welding or brazing, or using a dedicated fixing jig so that no gap is generated between the detection surface 22 of the AE sensor 20 and the sensor contact surface 33. Thereby, the detection surface 22 can detect the elastic wave from the structure 10 via the sensor contact surface 33.

  The contact medium 30 configured as described above reflects the elastic waves that have reached the side surfaces 34, 34B, 35, and 35B among the elastic waves incident from the structure contact surface 36 at the side surfaces 34, 34B, 35, and 35B. And propagate toward the sensor contact surface 33. As a result, the contact medium 30 can cause the elastic wave incident from the structure contact surface 36 to converge toward the sensor contact surface 33 and propagate to the detection surface 22 of the AE sensor 20.

(Arrangement of multiple AE sensors and contact medium, FIG. 4)
A plurality of the AE sensors and the contact medium described above are provided in order to estimate the generation position of a crack or a defect, and the details will be described with reference to FIGS. FIG. 4 is an end view of the structure of the present embodiment on the low temperature side in the axial direction. FIG. 4 shows a mode in which an AE sensor is coupled to the structure via a contact medium.

  The AE sensor 20 described above, together with the corresponding contact medium 30, constitutes a device (hereinafter referred to as a detection device) 6 for detecting an elastic wave from the structure 10. The structure monitoring system 1 according to this embodiment includes a plurality of detection devices 6 and 6B. That is, the detection device 6B includes an AE sensor 20B that is substantially the same as the AE sensor 20, and a contact medium 30B that is substantially the same as the contact medium 30.

(Frequency sensitivity characteristic for elastic wave of AE sensor)
The frequency at which the sensitivity coefficient is highest in the AE sensor 20B is (substantially) the same as that of the AE sensor 20, that is, the frequency sensitivity characteristics with respect to elastic waves are substantially the same. For these AE sensors 20, 20B, mass-produced products (commercial products) are used. The contact medium 30B has substantially the same size, shape, and material as the contact medium 30.

  The AE sensor 20B is coupled to the structure 10 via the contact medium 30B. In other words, the plurality of AE sensors 20 and 20B are coupled to the structure 10 via the corresponding contact media 30 and 30B, respectively. Only the arrangement of the detection device 6 and the detection device 6B with respect to the structure 10 is different.

  Specifically, the detection devices 6 and 6B are outside of the end surfaces 16 and 17 on the low temperature side in the axial direction of the structure 10 shown in FIG. Coupled to the end face 17.

  As shown in FIGS. 1 and 4, the detection device 6B (AE sensor 20B and contact medium 30B) includes the inner end surface 16 including the axis A and the cooling passage 14 among the outer end surfaces 17, and the detection device 6B. 6 (AE sensor 20 and contact medium 30) is disposed on the opposite side. That is, the two AE sensors 20 and 20B are arranged to face each other in the radial direction along the outer end surface 17 on the low temperature side in the axial direction of the structure 10 together with the corresponding contact media 30 and 30B.

  By arranging the plurality of AE sensors 20 and 20B at different positions in this way, the elastic waves emitted from the crack 13 and the defects reach the AE sensors 20 and 20B at different timings. The electric signals indicating the elastic waves detected by the AE sensors 20 and 20B are amplified by the amplifier 40, respectively.

  The amplifier 40 of the present embodiment includes a circuit that amplifies a weak electric signal from the piezoelectric element 25 of the AE sensor 20 and performs frequency filtering as necessary. The circuit can be composed of an analog circuit or a digital circuit. The circuit may include a programmable logic device (hereinafter referred to as PLD). For the PLD, for example, a programmable gate array, so-called FPGA (field-programmable gate array) can be used.

  The frequency of the elastic wave generated by the crack 13 or the defect is generally said to be several kHz to several MHz. Therefore, the amplification band in the amplifier 40 is preferably a wide band of approximately several kHz to several tens of MHz. Such frequency filtering processing for amplifying the band can be realized by using a high-pass filter, a low-pass filter, and a band-pass filter. The electric signal indicating the elastic wave from the AE sensors 20 and 20B is amplified by a predetermined amplification band in the amplifier 40 and transmitted to the processing device 50.

(Processing contents of processing equipment)
Various functions of the processing device 50 and details of the processing will be described with reference to FIGS. 1 and 5. FIG. 5 is a graph illustrating a method for extracting a waveform indicating an unsteady elastic wave in the structure monitoring method of the present embodiment. FIG. 5 shows a mode in which a plurality of unsteady elastic waves are extracted.

  The waveform extraction unit 52 of the processing device 50 receives the electrical signal from the amplifier 40 and extracts a waveform indicating an elastic wave from the electrical signal. The function of the waveform extraction unit 52 can be realized by a processing circuit such as an analog circuit or a digital circuit. Such a processing circuit may include a PLD such as the above-described FPGA. Note that the function of the waveform extraction unit 52 can also be realized by software processing of a computer.

  As shown in FIG. 5, the waveform extraction unit 52 sets non-stationary elastic waves 61, 62, 63, 64, 65 by setting a predetermined threshold T <b> 1 to the waveform of the electrical signal from the AE sensors 20, 20 </ b> B. Extract. In the present embodiment, the electrical signals from the AE sensors 20 and 20B are subjected to frequency filtering processing in the amplifier 40. However, the waveform extraction unit 52 may further perform frequency filtering processing.

  The embrittlement estimation unit 54 of the processing device 50 includes the number of unsteady elastic waves 61, 62, 63, 64, and 65 extracted by the waveform extraction unit 52, that is, the number of generated elastic waves, and the peak value of the waveform. That is, the number and size of cracks 13 and defects generated in the structure 10 are estimated based on the amplitude of the elastic wave. The number of elastic waves 61, 62, 63, 64, 65 indicates the number of cracks 13 and the like, and the respective time widths of the elastic waves 61, 62, 63, 64, 65 correspond to the corresponding cracks. There is a correlation with the size of 13.

  Further, in the case of the structure 10 of the present embodiment, the same unsteady elastic wave emitted from the same crack 13 or defect is detected by the AE sensors 20 and 20B having different arrangement locations, thereby causing brittleness. The estimation estimating unit 54 estimates a position where the crack 13 or a defect is generated in the structure 10 (hereinafter referred to as a generation position). Specifically, the embrittlement estimation unit 54 determines the difference between the timing when the unsteady elastic wave from the same crack 13 and the like is detected by the AE sensor 20 and the timing detected by the AE sensor 20B (hereinafter, Based on the acoustic velocity of the elastic wave propagating through the structure, the position where the crack 13 or the defect has occurred is estimated.

  When a large number of elastic waves overlap in time, it may be difficult to determine the number and size of cracks 13 or defects, and the positions where they occur. This is considered to correspond to a case where the crack 13 or the defect is generated, that is, not in the initial stage, but the crack 13 or the like that has progressed further.

As shown in FIG. 1, the structure monitoring system 1 configured as described above generates elastic waves generated at the high temperature side end 12 of the structure 10 and reaching the outer end surface 17 by using two detection devices. 6,6B is detected. In the detection device 6, the contact medium 30 propagates the elastic wave received from the outer end surface 17 of the structure 10 to the detection surface 22 of the AE sensor 20. In the contact medium 30, the area S _L of the structure contact surface 36 in contact with the outer end surface 17 is larger than the area S _U of the sensor contact surface 33 in contact with the detection surface 22. The detection device 6B is the same as the detection device 6.

  In the present embodiment, the structure 10 has a substantially cylindrical shape with a substantially circular cross section and an axial center extending in a predetermined direction. Two detection devices 6 and 6B, that is, AE sensors 20 and 20B, are arranged on the outer end surface 17 on the low temperature side in the axial direction of the structure 10 so as to face each other with the inner end surface 16 and the cooling passage 14 therebetween. Has been. The AE sensors 20 and 20B detect elastic waves generated at the high temperature side end portion 12 and propagated in the vicinity of the outer wall portion 11 to the outer end surface 17 with relatively high sensitivity through the contact media 30 and 30B, respectively. be able to.

  The unsteady elastic wave emitted from the crack 13 or the defect is detected by the two AE sensors 20 and 20B having the same configuration, and the electric signal is amplified by the amplifier 40, respectively. The waveform extraction unit 52 of the processing device 50 extracts an unsteady elastic wave waveform for each of the AE sensors 20 and 20B. The embrittlement estimation unit 54 calculates the average of the number and amplitude of the elastic wave waveforms of the two AE sensors 20 and 20B. As a result, the number of cracks 13 and defects generated and their dimensions can be estimated with higher accuracy.

  Further, the embrittlement estimation unit 54 determines whether or not a plurality of (two) AE sensors 20 and 20B having different arrangement locations have detected cracks based on the measurement time difference detected by the elastic wave generated from the same crack 13 or defect. It is also possible to estimate the generation position such as 13.

  As described above, the structure monitoring system 1 according to this embodiment monitors the occurrence of cracks 13 and the like in the structure 10 by detecting unsteady elastic waves generated in the structure 10. Is. The structural monitoring system 1 is provided with AE sensors 20 and 20B for converting elastic waves from the structural body 10 into electrical signals, and interposed between the AE sensors 20 and 20B and the structural body 10. Metal contact media 30 and 30B for propagating elastic waves from the structure 10 to the AE sensors 20 and 20B are provided. Of the contact media 30 and 30B, the area of the structure contact surface 36 in contact with the structure 10 is larger than the area of the sensor contact surface 33 in contact with the AE sensor 20 (20B).

According to the contact media 30 and 30B of the present embodiment, the amplitude (so-called detection intensity) of the elastic wave received by the AE sensors 20 and 20B is compared with the intensity of the elastic wave incident on the structure contact surface 36 from the structure 10. Can be increased. That is, the intensity of the elastic wave received by the detection surface 22 of the AE sensor 20 (20B) can be approximately S _L / S _U times the intensity of the elastic wave incident on the structure contact surface 36. Thereby, the AE sensors 20 and 20B can detect the elastic wave with relatively high sensitivity, and can detect the elastic wave generated in the initial stage of generation of the crack 13 or the defect.

  In the structural body monitoring system 1 according to the present embodiment, the two AE sensors 20 and 20B are arranged in the radial direction together with the corresponding contact media 30 and 30B on the outer end surface 17 of the structural body 10 on the low temperature side in the axial direction. Although it is assumed that they are arranged to face each other, the arrangement of the AE sensors according to the present invention is not limited to this mode. The plurality of AE sensors and the corresponding contact media can be arranged at various locations on the structure 10 as long as the surfaces are relatively cold.

[Second Embodiment]
The structure monitoring system of this embodiment will be described with reference to FIGS. 1 and 6. FIG. 6 is an end view of the structure of this embodiment on the low temperature side in the axial direction. FIG. 6 shows a mode in which an AE sensor is coupled to the structure via a contact medium. In addition, about the structure substantially common to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 6, a plurality of cooling passages 15 are formed in the structure 10 </ b> C of the present embodiment, and a plurality of openings of the cooling passages 15 are formed on the end surface 18 on the low temperature side in the axial direction. . In this respect, the structure 10C of the present embodiment is different from the structure 10 of the first embodiment (see FIG. 4).

  A plurality (six) of AE sensors 20, 20B, 20C, 20D, 20E, and 20F are coupled to the end surface 18 of the structure 10C through corresponding contact media 30, 30B, 30C, 30D, 30E, and 30F, respectively. Has been.

  The AE sensors 20C, 20D, 20E, and 20F are the same as the AE sensors 20 and 20B described above, except for the arrangement location. That is, the AE sensors 20, 20B, 20C, 20D, 20E, and 20F have substantially the same frequency sensitivity characteristics. Further, the contact media 30C, 30D, 30E, and 30F are configured to have substantially the same dimensions, shapes, and materials as the contact media 30 and 30B described above.

  Each AE sensor 20, 20B, 20C, 20D, 20E, 20F, together with the corresponding contact medium 30, 30B, 30C, 30D, 30E, 30F, constitutes a detection device 6, 6B, 6C, 6D, 6E, 6F, respectively. ing. The plurality of detection devices 6, 6 </ b> B, 6 </ b> C, 6 </ b> D, 6 </ b> E, 6 </ b> F are arranged in the circumferential direction centering on the axis A. It is arranged. The detection devices 6C, 6D, 6E, and 6F differ from the detection devices 6 and 6B described above only in the arrangement with respect to the structure 10C.

  In the structure 10C, for example, when a crack 13 or a defect occurs on the outer side in the radial direction indicated by the arrow R1 in FIGS. 1 and 6 in the high temperature side end portion 12 (see FIG. 1), the AE sensors 20, 20C, 20D. Can detect an unsteady elastic wave from the crack 13 or the like at a relatively early timing, and its amplitude is also relatively large.

  On the other hand, AE sensors 20B, 20E, and 20F detect elastic waves at a later timing than AE sensors 20, 20C, and 20D because their propagation paths from crack 13 and the like are relatively long, and their amplitude is small. For this reason, if the number and size of cracks 13 and defects are determined based on the elastic wave waveforms detected by these AE sensors 20B, 20E, and 20F, the error may be relatively large.

  Therefore, the embrittlement estimation unit 54 (see FIG. 1) of the processing apparatus 50 of the present embodiment detects an elastic wave at a relatively early timing among the six AE sensors 20, 20B, 20C, 20D, 20E, and 20F. Based on the waveform of the elastic wave of some (three) AE sensors 20, 20C, 20D, for example, the number and size of cracks 13 or defects are estimated by performing an averaging process. Note that the elastic wave waveforms of the three AE sensors 20B, 20E, and 20F that have detected the elastic wave at a relatively late timing are not used to estimate the number and size of cracks 13 or defects.

  According to the present embodiment, since the number and size of cracks 13 or defects are estimated based on the elastic wave waveforms detected by the plurality of AE sensors 20, 20C, 20D having relatively large amplitudes, The number of occurrences of cracks 13 and the like and the size thereof can be estimated with higher accuracy than in the case of estimation based on the waveform of the elastic wave detected by the AE sensor.

  In the above-described embodiment, the elastic wave is detected using a plurality of AE sensors 20, 20B, 20C, 20D, 20E, and 20F having substantially the same frequency sensitivity characteristics. However, the AE sensor is not limited to this mode. Each AE sensor may have different frequency sensitivity characteristics, and an example thereof will be described below.

[Third Embodiment]
The structure monitoring system according to this embodiment will be described with reference to FIGS. 2, 7, 8, and 9. FIG. 7 is a schematic diagram for explaining the structure monitoring system of the present embodiment and the structure to be monitored. FIG. 8 is an end view of the structure of this embodiment on the low temperature side in the axial direction. FIG. 9 is a graph showing an example of a waveform indicating an elastic wave after differential processing in the structure monitoring method of the present embodiment. In addition, about the structure substantially common to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIGS. 7 and 8, the structural monitoring system 1E of the present embodiment includes two detection devices 8 and 8B for detecting unsteady elastic waves from the crack 13 and the defect. ing. Only the arrangement of the detection devices 8 and 8B with respect to the structure 10 is different. The detection device 8B is opposed to the detection device 8 in the radial direction across the inner end face 16 through which the axis A passes and the cooling passage 14.

  The detection device 8 includes a plurality (two) of AE sensors 21 and 23 having different frequency sensitivity characteristics. In other words, the frequency at which the AE sensor 23 has the highest sensitivity coefficient is different from the other AE sensors 21. These AE sensors 21 and 23 are coupled to the structure 10 through a common contact medium 30.

  The sensor contact surface 33 (see FIG. 2) of the contact medium 30 is in contact with the respective detection surfaces (see reference numeral 22 in FIG. 2) of the AE sensors 21 and 23. The contact medium 30 propagates the elastic wave from the structure 10 to both the AE sensors 21 and 23.

  On the other hand, the detection device 8B has two AE sensors 21B and 23B having different frequency sensitivity characteristics, like the detection device 8. The AE sensor 21 </ b> B has substantially the same frequency sensitivity characteristics as the AE sensor 21. Similarly, the AE sensor 23B has substantially the same frequency sensitivity characteristics as the AE sensor 23. The two AE sensors 21B and 23B having different frequency sensitivity characteristics are coupled to the structure 10 via a common contact medium 30B. The contact medium 30B has substantially the same size, shape, and material as the contact medium 30 described above. The contact medium 30B propagates the elastic wave from the structure 10 to both the AE sensors 21B and 23B.

  The AE sensors 21, 21B, 23, and 23B are disposed along the outer end surface 17 on the low temperature side in the axial direction together with the contact media 30 and 30B. The AE sensor 21 and the AE sensor 21B are arranged to face each other in the radial direction, and have substantially the same frequency sensitivity characteristic (hereinafter referred to as a first characteristic). The AE sensor 23 and the AE sensor 23B are arranged to face each other in the radial direction, and have substantially the same frequency sensitivity characteristic (hereinafter referred to as a second characteristic). The second characteristic is different from the first characteristic in the frequency at which the sensitivity coefficient is highest.

  In the present embodiment, the AE sensors 21, 21B, 23, and 23B are piezoelectric detectors configured in the same manner as the AE sensor 20 shown in FIG. 2, and a piezoelectric element 25 that converts an elastic wave into an electrical signal (see FIG. 2). In the case of such a piezoelectric AE sensor, the frequency sensitivity characteristic changes according to the dimensions of the piezoelectric element, for example, the thickness indicated by the arrow t in FIG.

The relationship between the frequency f at which the sensitivity coefficient becomes the highest and the thickness t of the piezoelectric element can be expressed by the following equation (1).
f = N / t (1)
In the formula (1), N is a constant. That is, the frequency f at which the sensitivity coefficient is highest has a substantially inversely proportional relationship with the thickness t of the piezoelectric element.

  In the present embodiment, the AE sensors 21 and 21B and the AE sensors 23 and 23B have different piezoelectric element thicknesses, whereby the AE sensors 21 and 21B having the first characteristics and the AE sensors having the second characteristics. 23, 23B can be realized.

  For example, the AE sensor 21 and the AE sensor 21B are arranged to face each other in the radial direction on the outer end face 17, and the length of the propagation path of the elastic wave from the crack 13 is usually different. For this reason, when the AE sensors 21 and 21B having the same frequency sensitivity characteristic respectively detect the elastic waves emitted from the same crack 13 or defect, the waveform of the elastic wave detected by the AE sensor 21 and the The amplitude of the waveform of the elastic wave detected by the AE sensor 21 </ b> B, which is arranged to face the AE sensor 21 in the radial direction and has the same frequency sensitivity characteristic, varies depending on the propagation path.

  Since the AE sensors 21 and 21B have the same configuration except for the arrangement location, the waveforms of the elastic waves detected by the AE sensors 21 and 21B and acquired by the processing device 50E include substantially the same noise. ing. Further, the acoustic wave waveforms detected by the AE sensors 23 and 23B and acquired by the processing device 50E also contain noise, as in the AE sensors 21 and 21B.

  Such noise includes, for example, electrical noise mixed in an electrical signal in the amplifier 40. When such noise is relatively large, it becomes difficult for the above-described waveform extraction unit 52E to extract the unsteady elastic wave waveform from the crack 13, and the embrittlement estimation unit 54E causes the waveform of the elastic wave to be extracted. It is difficult to determine the number of cracks 13 generated and their dimensions based on the number and the crest value.

  In order to remove such noise as much as possible, the processing device 50E according to the present embodiment calculates a difference between waveforms of electric signals from a plurality of (two) AE sensors having substantially the same frequency sensitivity characteristics. , A so-called difference processing function (hereinafter referred to as a difference processing unit) 56 is provided.

  The difference processing unit 56 receives an electrical signal indicating an elastic wave detected by each of the AE sensors 21, 21 </ b> B, 23, and 23 </ b> B via the amplifier 40. The difference processing unit 56 calculates the difference between the waveform of the electrical signal from the AE sensor 21 and the waveform of the electrical signal from the AE sensor 21B. Similarly, the difference processing unit 56 calculates the difference between the waveform of the electrical signal from the AE sensor 23 and the waveform of the electrical signal from the AE sensor 23B.

  When the difference processing unit 56 performs such difference processing, for example, a waveform from which noise is removed can be obtained as shown in FIG. A waveform 5a and a waveform 5b, a waveform 6a and a waveform 6b, and a waveform 7a and a waveform 7b are waveforms of elastic waves caused by the same crack 13 and the like, respectively. For example, the time difference between the waveform 5a and the waveform 5b is that the timing at which the elastic wave from the same crack 13 or the like reaches one AE sensor (for example, the AE sensor 21) and the other AE sensor (for example, the arrangement location is different). , The difference from the timing when the sensor reaches the AE sensor 21B), that is, a so-called measurement time difference. This measurement time difference is due to the difference in the propagation path of the elastic wave.

  The waveform extraction unit 52E of the present embodiment is a non-stationary elastic wave indicating a crack 13 or a defect based on the waveform subjected to the difference processing by the difference processing unit 56, that is, the difference between the electrical signals from the two AE sensors. Is extracted. In this embodiment, it has substantially the same frequency sensitivity characteristics, and based on the difference between the electrical signals of the AE sensor 21 and the AE sensor 21B that are arranged to face each other in the radial direction on the outer end face 17, A waveform indicating an unsteady elastic wave is extracted.

  In addition, the waveform extraction unit 52E extracts a waveform indicating an unsteady elastic wave based on the difference between the electrical signals of the AE sensor 23 and the AE sensor 23B. Since the frequency sensitivity characteristics are different between the AE sensors 21 and 21B and the AE sensors 23 and 23B, waveforms having different shapes and amplitudes are extracted.

  The embrittlement estimation unit 54E is extracted based on the waveform of the elastic wave extracted based on the electrical signals from the AE sensors 21 and 21B thus extracted and the electrical signals from the AE sensors 23 and 23B. Based on at least one of the waveform of the elastic wave, the number of cracks 13 or defects and the size thereof are estimated. The embrittlement estimation unit 54E is based on the elastic wave waveforms of a pair (two) of AE sensors that detect elastic waves having relatively large amplitudes among the AE sensors 21 and 21B and the AE sensors 23 and 23B. It is preferred to estimate the number and size of cracks 13 or defects. Alternatively, the number and size of cracks 13 or defects may be estimated based on the elastic wave waveforms of a pair (two) of AE sensors that detect elastic waves at relatively early timing.

  According to the present embodiment, the difference processing unit 56 has a plurality of AE sensors (for example, the AE sensor 21 and the AE sensor 21B, or the AE sensor 23 and the AE sensor, which have substantially the same frequency sensitivity characteristics and differ only in the arrangement location). The difference between the electrical signals from 23B) is calculated. Even if noise is included in the electrical signal generated by the AE sensor and acquired by the processing device 50E, the noise can be substantially removed.

[Other Embodiments]
In each of the above-described embodiments, the contact medium 30 has the structure contact surface 36 as a lower base, the sensor contact surface 33 as an upper base, and four side surfaces 34, between the sensor contact surface 33 and the structure contact surface 36. Although a quadrangular frustum shape having 34B, 35, and 35B is formed, the shape of the contact medium according to the present invention is not limited to this mode.

  The contact medium according to the present invention may have any shape as long as the area of the structure contact surface is larger than the area of the sensor contact surface. The contact medium may have a truncated cone shape, for example. In particular, it is preferable that the contact medium has an elliptic frustum shape. Further, the shape of the contact medium is not limited to the frustum shape. As the contact medium, various shapes can be used as long as the area of the structure contact surface is larger than the area of the sensor contact surface.

  In each embodiment, the AE sensor is a piezoelectric detector, and the piezoelectric element that converts the force of the elastic wave into an electric signal (voltage) is between the two electrodes 26 and 27 for detecting the voltage. However, the AE sensor according to the present invention is not limited to this mode. The piezoelectric element may be in direct contact with the sensor contact surface of the contact medium and constitute a detection surface that receives elastic waves.

  The AE sensor according to the present invention is not limited to this piezoelectric method. For the AE sensor, it is also preferable to use an electromagnetic ultrasonic transducer (EMAT) that converts acoustic energy into an electric signal (electric vibration) by the interaction between the electromagnetic induction effect and the magnetic field.

  Moreover, in each embodiment, although the structure 10 shall be comprised with the metal material (stainless steel), the material which comprises the structure which concerns on this invention is not limited to this aspect. The structure may be a solid (rigid body). The structure is not limited to a metal material, and may be composed of, for example, concrete, ceramics, or a composite material of these materials.

  Moreover, in each embodiment, although the structure 10 shall be a member which comprises the vacuum vessel of a nuclear fusion apparatus, the structure which concerns on this invention is not limited to this aspect. A structure is good also as what is a member which comprises the turbine of a nuclear fusion plant. The structure may be a member constituting a pressure vessel, a steam generator, or a steam turbine of a nuclear power plant, or may be a member constituting a gas turbine or a steam turbine of a thermal power plant.

  Further, the structure according to the present invention may be a member constituting a petrochemical plant, a food and medical product plant, a water and sewage plant, a steel plant, a power plant, a chemical plant, a bridge, a road, and a building. good. Further, the structure is not limited to the stationary member as described above, and may be a member constituting a moving body such as an airplane, a ship, and an automobile.

  Although several embodiments of the present invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

1,1E Monitoring system for structure 5a, 5b Waveform 6, 6B, 6C, 6D, 6E, 6F Detector 6a, 6b, 7a, 7b Waveform 8, 8B Detector 10, 10C Structure 11 Outer wall (structure)
12 High temperature side end (structure, outer wall)
13 Cracks
14, 15 Cooling passage 16 Low temperature side end face (inner end face)
17 Low temperature side end face (outer end face)
18 Low temperature side end surfaces 20, 20B, 20C, 20D, 20E, 20F AE sensors 21, 21B AE sensor 22 Detection surface (AE sensor)
23, 23B AE sensor 24 Signal line 25 Piezoelectric element 26, 27 Electrode 28 Signal line 30, 30B, 30C, 30D, 30E, 30F Contact medium 33 Sensor contact surface (contact medium)
33e outer edge (contact medium)
34, 34B, 35, 35B Side (contact medium)
36 Structure contact surface (contact medium)
36e outer edge (contact medium)
40 Amplifier 44 Cable 50, 50E, Processing device 52, 52E Waveform extraction unit (processing device)
54,54E Embrittlement estimation unit (processing equipment)
56 Difference processing unit (processing device)
61, 62, 63, 64, 65 Waveform (elastic wave)

Claims (15)

A structure monitoring system for monitoring the destruction of a structure,
An AE sensor that converts an elastic wave from the structure into an electrical signal;
A metal contact medium that is provided between the AE sensor and the structure and propagates an elastic wave from the structure to the AE sensor;
With
The structure monitoring system, wherein an area of a structure contact surface in contact with the structure of the contact medium is larger than an area of a sensor contact surface in contact with the AE sensor. The contact medium is configured so that a cross section perpendicular to a direction from the structure contact surface to the sensor contact surface becomes smaller as it goes from the structure contact surface to the sensor contact surface. The structure monitoring system according to claim 1. 3. The structure according to claim 1, wherein the contact medium has a frustum shape having the structure contact surface as a lower base and the sensor contact surface as an upper base. Monitoring system. The contact medium has at least one side surface between the structure contact surface and the sensor contact surface;
The angle formed between the side surface and the structure contact surface inside the contact medium is in a range of more than 45 degrees and less than 90 degrees. Monitoring system for structure as described in 1. The structure monitoring system according to any one of claims 1 to 4, wherein the contact medium is made of a metal having a Vickers hardness of 100 or less. A processing device for acquiring and processing an electrical signal indicating an elastic wave detected by the AE sensor;
The processing device
Extracting a waveform indicating an unsteady elastic wave from the electrical signal from the AE sensor;
The number of occurrences of cracks generated in the structure and at least one of the dimensions of the cracks are estimated based on the number and amplitude of the waveforms indicating the extracted unsteady elastic waves. The structure monitoring system according to any one of claims 1 to 5. An amplifier for amplifying an electrical signal from the AE sensor;
7. The structural monitoring system according to claim 6, wherein the processing device acquires an electrical signal indicating an elastic wave detected by the AE sensor and amplified by the amplifier. The processing apparatus generates a crack in the structure based on a difference in timing when non-stationary elastic waves from the same crack are detected by the plurality of AE sensors at different locations. The structure monitoring system according to claim 6 or 7, wherein the measured position is estimated. The processing apparatus generates a crack generated in the structure based on the number and amplitude of elastic wave waveforms from a part of the plurality of AE sensors in which the elastic wave is detected at a relatively early timing. The structure monitoring system according to any one of claims 6 to 8, wherein at least one of the number and the size of the crack is estimated. At least some of the plurality of AE sensors are configured to have substantially the same frequency sensitivity characteristics with respect to elastic waves,
The processor is
Calculating a difference between waveforms of electrical signals from the plurality of AE sensors having substantially the same frequency sensitivity characteristics;
The structure monitoring system according to any one of claims 6 to 9, wherein a waveform indicating an unsteady elastic wave is extracted from the difference. The structural monitoring system according to any one of claims 6 to 9, wherein at least one of the plurality of AE sensors has a frequency sensitivity characteristic with respect to an elastic wave different from that of the others. Each of the plurality of AE sensors has a substantially plate shape and has a piezoelectric element that converts an elastic wave force into an electric signal,
12. The structure monitoring system according to claim 11, wherein at least one of the AE sensors has a thickness of the piezoelectric element different from that of the others. The structure monitoring system according to claim 11 or 12, wherein a plurality of AE sensors having different frequency sensitivity characteristics are coupled to the structure via the common contact medium. The structure has a substantially cylindrical outer shape whose axis extends in a predetermined direction,
One end of the outer wall portion constituting the outer wall of the structure body is a high temperature side end portion that receives heat from plasma and becomes high temperature,
The plurality of AE sensors are coupled to the low temperature side end surface on the side opposite to the high temperature side end portion of the outer wall portion via the corresponding contact medium, respectively.
14. The plurality of AE sensors having substantially the same frequency sensitivity characteristics are arranged so as to face each other in a radial direction perpendicular to the axis. The monitoring system for a structure according to one item. A structure monitoring method for monitoring the destruction of a structure,
A metal contact medium that is provided between an AE sensor that converts an elastic wave from the structure into an electric signal and the structure and that propagates the elastic wave from the structure to the AE sensor is provided as follows. The area of the structure contact surface in contact with the structure is larger than the area of the sensor contact surface in contact with the AE sensor,
Obtaining an electrical signal indicating an elastic wave detected by the AE sensor;
Extracting a waveform indicating an unsteady elastic wave from an electrical signal from the AE sensor;
Estimating at least one of the number of cracks generated in the structure and the size of the cracks based on the number and amplitude of waveforms indicating the extracted unsteady elastic waves;
The structure monitoring method characterized by including.

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