Plate wave detector, plate wave detection device, and composite plate wave detection device

Abstract

To provide a method for a measurement and a measurement device which can increase the degree of freedom of a measurement target object, a measurement range, or a measurement environment in which a generation source of an elastic wave is located.SOLUTION: The plate wave detector of an embodiment includes a base board and a thin layer on the surface of the base board, the thin layer being thinner than the base board. The layer has a first layer having a first side and a second side, the first side extending along a lateral direction perpendicular to the direction of detection in a first position in the direction of detection parallel to the surface of the base board and the second side extending along the lateral direction in a second position away from the first position in the direction of detection, the length of the first side in the lateral direction and the length of the second side in the lateral direction being different from each other.SELECTED DRAWING: Figure 18

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The embodiments of the present invention relate to a plate wave detector, a plate wave detection device, and a hybrid plate wave detection device. [Background technology]

[0002] In structures made of thin plates such as tanks and piping, plate waves are generated by stress or damage. The vibration direction and vibration plane of Lamb waves, which are a type of plate wave, are perpendicular to the surface of the plate material, and Lamb waves have a certain vibration component in the propagation direction. The thinner the plate material, the stronger the Lamb waves are. By detecting mainly Lamb waves as plate waves generated in thin plates, it is possible to grasp the state of a structure made of thin plates and the presence or absence of damage, and to determine the need for reinforcement work or repair work. As plate wave detectors capable of detecting plate waves and the position of their generation source, for example, plate wave detectors made of piezoelectric bodies having a shape that satisfies a certain condition and multi-channel type piezoelectric acoustic sensors having a shape that imitates and realizes the function of a basement membrane are known. However, it was difficult for the above-mentioned plate wave detectors to determine the propagation direction of the input plate wave. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-275570 A [Non-patent literature]

[0004] [Non-Patent Document 1] Youngdo Jung, et al.; “Development of a Multi-Channel Piezoelectric Acoustic Sensor Based on an Artificial Basilar Membrane”, Sensors 2014,14,117-128. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a plate wave detector, a plate wave detection device, and a hybrid plate wave detection device that can easily detect the propagation direction of an incident plate wave. [Means for solving the problem]

[0006] The plate wave detector of the embodiment has a base and a layer provided on a surface of the base and thinner than the base. The layer has a first layer having a first side extending along a lateral direction perpendicular to the detection direction at a first position in the detection direction parallel to the surface of the base and a second side extending along the lateral direction at a second position away from the first position in the detection direction. The lateral length of the first side and the lateral length of the second side are different from each other. The base is composed of a first base and a second base arranged to be spaced apart from the first base in the detection direction. The layer further includes a third layer provided on a surface of the first base and connected to the first layer by a first side, and a fourth layer provided on a surface of the second base and connected to the first layer by a second side. Alternatively, the length of the first layer in the detection direction is LM, and the velocity of the plate wave is V. p When the detection time of the plate wave propagating from the first position to the first layer in the detection direction is (LM / V p The present invention further includes an analysis device that calculates the signal strength by the above equation. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a side view of the plate wave detector according to the first embodiment. [Diagram 2] FIG. 1 is a perspective view of a plate wave detector according to a first embodiment. [Diagram 3] FIG. 2 is a perspective view of a calculation model of the plate wave detector according to the first embodiment. [Figure 4] FIG. 4 is a perspective view showing the results of a simulation of the movement of the calculation model shown in FIG. 3 when a driving force is applied thereto. [Diagram 5] 4 is another perspective view showing the results of a simulation of the movement when a driving force is applied to the calculation model shown in FIG. 3. [Figure 6] FIG. 4 is a perspective view of another calculation model of the plate wave detector according to the first embodiment. [Figure 7] 7 is a graph showing the results of calculating the change in volumetric strain of the first layer over time when an input signal is input to the calculation model shown in FIG. 6. [Figure 8] FIG. 4 is a perspective view of a plate wave detector according to a modified example of the first embodiment. [Figure 9] FIG. 11 is a plan view of a plate wave detection device according to a second embodiment. [Figure 10] FIG. 11 is a side view showing the positional relationship between a plate wave detection device and a generation source according to a second embodiment. [Figure 11] FIG. 11 is a plan view of a plate wave detecting device according to a third embodiment. [Figure 12] FIG. 13 is a plan view of a plate wave detecting device according to a modified example of the third embodiment. [Figure 13] FIG. 13 is a plan view of a plate wave detecting device according to a fourth embodiment. [Figure 14] FIG. 13 is a plan view of a plate wave detector according to a fifth embodiment. [Figure 15] FIG. 13 is a side view of a plate wave detector according to a fifth embodiment. [Figure 16] FIG. 13 is a side view illustrating a state in which a plate wave is input to a plate wave detector of a fifth embodiment. [Figure 17] FIG. 13 is another side view illustrating a state in which a plate wave is input to the plate wave detector of the fifth embodiment. [Figure 18] 13 is yet another side view illustrating a state in which a plate wave is input to the plate wave detector of the fifth embodiment. FIG. [Figure 19] FIG. 13 is a schematic diagram of an electrical signal detected by a plate wave detector according to a fifth embodiment. [Figure 20] FIG. 13 is a plan view of a plate wave detector according to a sixth embodiment. [Figure 21] FIG. 13 is a side view of a plate wave detector according to a sixth embodiment. [Figure 22] FIG. 13 is a plan view of a plate wave detector according to a seventh embodiment. [Figure 23] FIG. 23 is a plan view of a plate wave detector according to a first modified example of the seventh embodiment. [Figure 24] FIG. 23 is a plan view of a plate wave detector according to a second modified example of the seventh embodiment. [Diagram 25] FIG. 23 is a plan view of a plate wave detector according to a third modified example of the seventh embodiment. [Figure 26] FIG. 13 is a plan view of a plate wave detector according to an eighth embodiment. [Figure 27] FIG. 23 is a plan view of a plate wave detector according to a first modified example of the eighth embodiment. [Figure 28] FIG. 23 is a plan view of a plate wave detector according to a second modified example of the eighth embodiment. [Figure 29] FIG. 23 is a plan view of a plate wave detector according to a third modified example of the eighth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the plate wave detector, plate wave detection device, and composite plate wave detection device of the embodiment will be described with reference to the drawings. In the following description, components having the same or similar functions are given the same reference numerals. Also, duplicated descriptions of components having the same or similar functions may be omitted.

[0009] [First embodiment] As shown in FIG. 1, the plate wave detector 111 of the first embodiment is used in a structure T composed of a thin plate W, such as a tank or a pipe. The interior or inner region of the thin plate W is hollow. The plate wave detector 111 is provided on a surface a of the thin plate W. The surface a is the surface of the thin plate W that is exposed to the outside of the structure T, and is the surface opposite to the surface exposed to the hollow. Note that, in FIG. 1, the surface a in the range where the plate wave detector 111 is provided is a flat surface, but the shapes of the thin plate W and the surface a are not limited to a specific shape.

[0010] In the following description and in each drawing, two directions parallel to the surface a of the thin plate W and perpendicular to each other are defined as the X direction and the Y direction. A direction perpendicular to each of the X direction and the Y direction is defined as the Z direction. In each of the X direction, the Y direction, and the Z direction, a position on one side is relatively described as a +X side position, a +Y side position, or a +Z side position, and the opposite side to the one side is described as a -X side, a -Y side, or a -Z side. The Z direction is parallel to the thickness direction of the plate wave detector 111.

[0011] As shown in FIGS. 1 and 2, the plate wave detector 111 includes a base 12 and a layer 22 . The base 12 of the first embodiment is composed of a single base. The bottom surface 12b of the base 12 is in contact with the surface a of the thin plate W. The surface 12a and the bottom surface 12b of the base 12 are formed in a trapezoid shape, similar to the surface 40a and the bottom surface 40b of the first layer 40 described below. The base 12 is a polyhedron having a trapezoidal surface 12a and bottom surface 12b. The thickness of the base 12 is constant in the XY plane including the X direction and the Y direction, and is at least thinner than the thickness of a silicon (Si) substrate that is commonly used in semiconductor technology.

[0012] The thickness of the base 12 is set to be larger than the maximum amplitude of the oscillation from the surface 40a to the -Z side in the Z direction among the multiple second layers 50 so that the multiple second layers 50 do not come into contact with the surface a of the thin plate W when the multiple second layers 50 described later vibrate in the Z direction due to the propagation of the plate wave PW1. The base 12 is made of a material capable of transmitting the plate wave from the thin plate W to the layer 22 described next, for example, a film material or resin having high heat resistance and adhesiveness.

[0013] An adhesive film (not shown) is provided on the bottom surface 12b of the base 12. That is, in a state where the plate wave detector 111 is disposed on the surface a of the thin plate W, the adhesive film exists between the base 12 and the thin plate W in the Z direction. The adhesive film (not shown) is detachable from the surface a of the thin plate W, and is made of a material that does not prevent the plate wave generated in the thin plate W from propagating to the base 12 and the layer 22 when it exists between the base 12 and the thin plate W as described above. The adhesive film is, for example, an adhesive film made of resin.

[0014] The layer 22 of the first embodiment includes a first layer 40 and a second layer 50. The first layer 40 is provided on the surface 12a of the base 12 and overlaps with the surface 12a when viewed from the Z direction. The bottom surface 40b of the first layer 40 and the surface 12a of the base 12 are in direct contact with each other. An adhesive (not shown) that does not impede the propagation of plate waves may be provided between the bottom surface 40b of the first layer 40 and the surface 12a of the base 12. The surface 40a and the bottom surface 40b of the first layer 40 have a trapezoidal shape. The first layer 40 includes the surface 40a, the bottom surface 40b, and a first end surface e1, a second end surface e2, a first side surface s1, and a second side surface s2 as surfaces that connect the peripheries of the surface 40a and the bottom surface 40b in the height direction.

[0015] Here, an axis J101 overlapping with the detection direction D1 of the plate wave in the plate wave detector 111 and the reverse direction D2 opposite to the detection direction D1 is assumed. The axis J101 is parallel to the detection direction D1, and is parallel to the surface 12a of the base 12 and the surface 40a of the first layer 40. The axis J101 in the first embodiment is parallel to the Y direction. The first end face e1 is at a position (first position) P1 of the axis J101 in the detection direction D1, and extends parallel to the horizontal direction D3 perpendicular to the detection direction D1. The horizontal direction D3 in the first embodiment is parallel to the X direction. The second end face e2 is at a position (second position) P2 away from the position P1 on the axis J101, and extends parallel to the horizontal direction D3. The length L2 of the horizontal direction D3 of the second end face e2 is different from at least the length L1 of the horizontal direction D3 of the first end face e1, and is longer than the length L1 in the first embodiment. Position P2 is on the -Y side of position P1 in the Y direction.

[0016] In the following description and drawings, a position on one side in the horizontal direction D3 is referred to as a position on the +D3 side, and a position on the opposite side to the one side is referred to as a position on the -D3 side. The first side surface s1 connects an end on the -D3 side (first side) of the first end surface e1 to an end on the -D3 side of the second end surface e2. The second side surface s2 connects an end on the +D3 side (second side) opposite to the -D3 side of the first end surface e1 to an end on the +D3 side of the second end surface e2.

[0017] A side (first side) W1 parallel to the direction D3 on the first end face e1 constitutes the upper base of the trapezoidally formed front face 40a or bottom face 40b. A side (second side) W2 parallel to the lateral direction D3 on the second end face e2 constitutes the lower base of the front face 40a or bottom face 40b. In the first embodiment, the detection direction D1 and the reverse direction D2 are directions passing through the midpoint of the side W1 and the midpoint of the side W2.

[0018] Since the length L1 of the side W1 and the length L2 of the side W2 are different from each other, the shape and volumetric strain of the first layer 40 when the plate wave PW1 propagating through the first layer 40 along the detection direction D1 is inputted is different from the shape and volumetric strain of the first layer 40 when the plate wave PW2 propagating through the first layer 40 along the reverse direction D2 is inputted. Specifically, since L1>L2, when the plate wave PW1 propagating through the first layer 40 along the detection direction D1 is inputted, the first layer 40 vibrates largely and the plate wave PW1 is detected. Conversely, even if the plate wave PW2 propagating through the first layer 40 along the reverse direction D2 is inputted, the first layer 40 does not vibrate as compared to when the plate wave PW1 propagating through the first layer 40 along the detection direction D1 is inputted. The propagation direction of the plate waves PW1 and PW2 is parallel to the surface 40a of the first layer 40, and is parallel to the Y direction and the axis J101. The vibration direction of the plate waves PW1 and PW2 is parallel to the Z direction and the thickness direction of the layer 22, and extends to the space on the ±Z side with respect to the surface 40a of the first layer 40.

[0019] If the change in shape and volumetric strain of the first layer 40 when a plate wave PW1 propagating through the first layer 40 along the detection direction D1 is input is grasped in advance, then when a plate wave is input from an arbitrary position and a shape and volumetric strain of the first layer 40 similar to the change in shape and volumetric strain of the first layer 40 grasped as described above are detected, it is possible to detect that a plate wave PW1 propagating in the detection direction D1 is occurring in the thin plate W on which the plate wave detector 111 is provided.

[0020] The larger the ratio (L2 / L1) of the length L1 of the side W1 to the length L2 of the side W2, the larger the difference between the shape and volumetric strain of the first layer 40 when the plate wave PW1 is input and the shape and volumetric strain of the first layer 40 when the plate wave PW2 is input. Therefore, the ratio (L2 / L1) is determined according to the sensitivity of the plate wave detector 111 to detect the plate wave PW1 within the range of manufacturability of the plate wave detector 111, and is appropriately set in consideration of the accuracy of a device (not shown) that detects the shape and volumetric strain of the first layer 40. In view of this, in order to obtain a good sensitivity for detecting the plate wave PW1, it is preferable that the ratio (L2 / L1) is 2 or more. The larger the ratio (L2 / L1), the higher the sensitivity of the plate wave detector 111.

[0021] The length L5 of the first layer 40 in the Y direction, i.e., the detection direction D1, is longer than at least the wavelength of the plate wave that can be incident on the plate wave detector 111, i.e., the wavelength of the plate wave that can be generated in the thin plate W of the structure T. The length L5 of the first layer 40 is set to a length that satisfactorily generates the arrival time difference between the plate wave PW1 propagating in the detection direction D1 at any position on the axis J101 of the first layer 40 and the plate wave PW2 that is detected weaker than the plate wave PW1 in the reverse direction D2. The length L5 of the first layer 40 is preferably, for example, twice or more the wavelength of the input plate wave, and more preferably five times or more the wavelength of the input plate wave. In the first embodiment, since a large structure T including a tank is assumed, the frequency of the plate wave that can be generated in the thin plate W is several [kHz] to several hundreds [kHz]. Therefore, the wavelength of the plate wave that can be generated in the thin plate W is several [mm] to several [cm]. For example, the length L5 of the first layer 40 is more preferably 50 mm or more and 500 mm or less. When the length L5 is shorter than the wavelength of the plate wave incident on the first layer 40, the entire first layer 40 vibrates regardless of the directionality of the plate wave. When the entire first layer 40 vibrates, it becomes difficult to distinguish the detection direction D1 and the reverse direction D2 of the plate wave in the plate wave detector 111, that is, to distinguish between the plate waves PW1 and PW2, and the sensitivity of the plate wave detector 111 in the detection direction D1 and the detection accuracy of the plate wave PW1 are reduced.

[0022] The side (third side) W3 parallel to the XY plane in the first side surface s1 constitutes one of the pair of legs of the surface 40a or the bottom surface 40b. The side (fourth side) W4 parallel to the XY plane in the second side surface s2 constitutes the other of the pair of legs of the surface 40a or the bottom surface 40b. The lengths of the sides W3 and W4 are equal to each other. The interior angle formed by the sides W2 and W3 of the surface 40a or the bottom surface 40b in the XY plane is equal to the interior angle formed by the sides W2 and W4. That is, the shape of the surface 40a is an isosceles trapezoid. The first layer 40 is preferably thinner than the base 12 and is made of a piezoelectric material or an electret, and may be made of a metal thin enough to vibrate in response to the plate wave PW1.

[0023] The plate wave detector 111 of the first embodiment includes a plurality of second layers 50. The plurality of second layers 50 of the first embodiment are, for example, configured by four types of second layers 51A-54A and second layers 51B-54B. In the plate wave detector 111, the second layers 51A-54A are connected to the first side surface s1 of the first layer 40. The second layers 51A-54A are sequentially arranged at positions spaced apart from a predetermined position on the +Y side of the first side surface s1 along the side W3 to the -Y side, that is, at positions spaced apart from a position closer to the first end surface e1 than the second end surface e2 along the side W3 to the second end surface e2. The second layers 51B-54B are connected to the second side surface s2 of the first layer 40. The second layers 51B-54B are sequentially arranged at positions spaced apart from a predetermined position on the +Y side of the second side surface s2 along the side W4 on the -Y side, i.e., positions approaching the second end face e2 at an interval along the side W4 from a position closer to the first end face e1 than the second end face e2. In the detection direction D1, each of the second layers 51A-54A and each of the second layers 51B-54B are arranged at the same positions as each other.

[0024] The lengths of the second layers 51A to 54A in the horizontal direction D3 are different from each other. The four types of second layers 51A to 54A and the four types of second layers 51B to 54B are the second layers 50 having four different lengths in the horizontal direction D3. The lengths of the second layers 51A and 51B in the horizontal direction D3 are equal to each other. The lengths of the second layers 52A and 52B in the horizontal direction D3 are equal to each other. The lengths of the second layers 53A and 53B in the horizontal direction D3 are equal to each other. The lengths of the second layers 54A and 54B in the horizontal direction D3 are equal to each other. The widths of the second layers 51A to 54A and the second layers 51B to 54B in the detection direction D1 are equal to each other. The thicknesses in the Z direction of the second layers 51A to 54A and the second layers 51B to 54B are equal to each other and are equal to the thickness in the Z direction of the first layer 40.

[0025] The second layers 51A-54A and 51B-54B are made of the same material as the first layer 40 and are formed integrally with the first layer 40. The plate wave detector 111 is a sheet-like detector formed to be thinner than the general-purpose Si substrate described above. The plate wave detector 111 is formed using printing or nanoimprint technology.

[0026] The length in the horizontal direction D3 of the second layers 51A to 54A in the first embodiment is successively shorter. The length in the horizontal direction D3 of each of the second layers 51A to 54A is a predetermined length determined by the frequency of the detection target included in the frequency range of the plate wave PW1 propagating along the detection direction D1, and differs from one another depending on the difference in the frequency of the detection target. As the length in the horizontal direction D3 of the second layer 50 is longer, the second layer 50 vibrates in response to a plate wave of a relatively lower frequency, and therefore, a plate wave of a relatively lower frequency can be detected.

[0027] The lowest frequency of the frequency domain of plate waves PW1 and PW2 is ω MIN and the highest frequency is ω MAX and the number of types of lengths in the horizontal direction D3 of the second layers 50 connected to each of the first side surfaces s1 and s2 is m, the length in the horizontal direction D3 of the second layer 50 having the longest length in the horizontal direction D3 among the m types of second layers 50 is, for example, the minimum frequency ω MINThe length in the horizontal direction D3 of the second layer 50 having the shortest length in the horizontal direction D3 among the m types of second layers 50 is set to a predetermined length determined by, for example, the maximum frequency ω MAX The length in the horizontal direction D3 of the second layer 50 other than the second layer 50 having the shortest length in the horizontal direction D3 is set to a predetermined length determined by the difference ω P . That is, the length in the horizontal direction D3 of each second layer 50 is inversely proportional to the square root of the resonance frequency of each second layer 50, and the resonance frequency of each second layer 50 is inversely proportional to the square of the length in the horizontal direction D3. The above-mentioned resonance frequency may be simply referred to as frequency in this specification, and is synonymous with the natural frequency in Table 1 shown later. As a result, the kth longest second layer 50 has a frequency {ω MIN -(k-1)·ω P When a plate wave PW1 having a frequency {ω MIN -(k-1)·ω P}, the occurrence of a plate wave PW1 having the following characteristics is detected.

[0028] Applying the above-mentioned settings, the length of the second layer 51A in the horizontal direction D3 is set to the minimum frequency ω MIN The length of the second layer 52A in the horizontal direction D3 is a predetermined length determined by a frequency (ω MIN +ω P The length of the second layer 53A in the horizontal direction D3 is a predetermined length determined by a frequency approximately equal to the frequency (ω MIN +2×ω P The length of the second layer 54A in the horizontal direction D3 is a predetermined length determined by a frequency approximately equal to the maximum frequency ω MAX The length of the second layers 52A to 54A in the lateral direction D3 is a predetermined length determined by a frequency that is approximately equal to the difference ω P It is inversely proportional to the square root of .

[0029] The vibration and volumetric strain of each layer when the plate wave PW1 propagates through the first layer 40 and the plurality of second layers 51A-54A and second layers 51B-54B are output as an electric signal to an analysis device (not shown). The electric signal corresponding to the vibration and volumetric strain of each layer may be output to the analysis device via electrodes or electric wires (not shown), or may be output to the analysis device by wireless spatial propagation. The analysis device receives the electric signal from the first layer 40 and the electric signal from each of the plurality of second layers 51A-54A and second layers 51B-54B individually.

[0030] When the level of the electric signal output from the first layer 40 is greater than a predetermined value, the analyzer determines that the plate wave PW1 propagating in the detection direction D1 has been generated, and calculates the amplitude of the plate wave PW1, which is approximately proportional to the level of the electric signal output from the first layer 40. Furthermore, the analyzer specifies the three-dimensional position of the source of the plate wave PW1 on the surface a of the thin plate W based on the calculated amplitude of the plate wave PW1. The analyzer calculates the intensity of each frequency that determines the lateral direction D3 of each of the plurality of second layers 51A-54A and second layers 51B-54B based on the level of the electric signal output from each of the plurality of second layers 51A-54A and second layers 51B-54B, and calculates the frequency distribution of the plate wave PW1. The analyzer obtains the strain at the position of the source of the thin plate W and the stress distribution of the thin plate W from the information including the position of the source of the plate wave PW1 specified as described above and the frequency distribution, and quantitatively analyzes the state of the structure T and the presence or absence of damage. The analysis device is composed of wiring, an integrated circuit, or a control board (not shown), and a calculator or computer having a built-in program for carrying out the above-mentioned calculation and analysis processes.

[0031] In order to confirm the detection of the plate waves PW1, PW2 by the plurality of second layers 51A to 54A and second layers 51B to 54B of the plate wave detector 111, a simulation was performed using a calculation model MD1 shown in FIG.

[0032] The first layer 40 of the calculation model MD1 is connected to the fixed member SL and the interlocking member VL. Each of the fixed member SL and the interlocking member VL is composed of a rectangular thin plate and has a thickness equivalent to that of the first layer 40. The first end face e1 of the first layer 40 is parallel to the XZ plane including the X direction and Z direction of the fixed member SL and is in contact with the end face on the -Y side. The size of the fixed member SL in the X direction is set to be equivalent to that of the first end face e1. The fixed member SL does not vibrate and is immovable.

[0033] The second end face e2 of the first layer 40 is parallel to the XZ plane of the interlocking member VL and is in contact with the end face on the +Y side. The size of the interlocking member VL in the X direction is set to be equal to that of the second end face e2. The interlocking member VL is not fixed to or connected to another member, but is interlocked with the first layer 40.

[0034] In the calculation model MD1, the second layers 51A-54A are sequentially arranged at positions spaced apart from a predetermined position on the -Y side of the first side surface s1 along the side W3 toward the +Y side, that is, at positions spaced apart from a position closer to the second end surface e2 than the first end surface e1 along the side W3 toward the first end surface e1. As described above, the calculation model MD1 has a similar configuration to the above-mentioned plate wave detector 111, except that the arrangement order of the four types of 51A-54A on the side W3 is reversed. Therefore, the arrangement order of the four types of 51A-54A on the side W4 is reversed from that of the plate wave detector 111, and the second layers 51B-54B are sequentially connected to positions spaced apart from a predetermined position on the -Y side of the second side surface s2 along the side W3 toward the +Y side.

[0035] Table 1 shows the length in the horizontal direction D3, the length in the detection direction D1, and the thickness in the Z direction of each of the four types of elements 51A to 54A used in the calculation model MD1.

[0036] [Table 1]

[0037] In the first simulation, as shown in FIG. 3, a driving force F was applied to the first layer 40 from the +Z side at a position P1 in the driving direction D1 in a direction parallel to and opposite to the Z direction. The driving force F was set to a volume force of 1 [g] to simulate the plate waves PW1 and PW2. Specifically, the driving force F was applied to the boundary between the first layer 40 and the interlocking member VL. The minimum frequency ω MIN is set to 20 [kHz], and the maximum frequency of the driving force F is ω MAX is 400 [kHz], and the difference ω P The resonance frequency of the primary vibration mode of the first layer 40 having a trapezoidal shape when viewed from the Z direction was 355 kHz.

[0038] 4(a) to (f) are diagrams showing three-dimensional behavior of the calculation model MD1 when the frequency of the driving force F is set to 20 [kHz], 30 [kHz], 80 [kHz], 110 [kHz], 255 [kHz], and 400 [kHz] in the first simulation. In each of FIG. 4(a) to (f), the thickness of the calculation model MD1 in the Z direction is omitted. In the first simulation, as described above, the driving force F is applied to the second end face e2 of the first layer 40, and therefore the driving force F propagates from the -Y side portion of the first layer 40 to the +Y side portion.

[0039] As shown in (a) to (c) of FIG. 4, when the frequency of the driving force F was 20 [kHz], 30 [kHz], or 80 [kHz], the second layers 51A to 54A and the second layers 51B to 54B did not vibrate at all, and the tips of the second layers 54A and 54B vibrated slightly. As shown in (d) of FIG. 4, when the frequency of the driving force F was 110 [kHz], the second layers 51A, 52A, 54A and the second layers 51B, 52B, 54B did not vibrate at all, and the second layers 53A and 53B vibrated. When the frequency of the driving force F was 110 [kHz], the amplitude in the Z direction of each of the second layers 53A and 53B was larger than the amplitude in the Z direction of each of the second layers 54A and 54B when the frequency of the driving force F was 20 [kHz], 30 [kHz], or 80 [kHz].

[0040] As shown in (e) of FIG. 4, when the frequency of the driving force F was 255 [kHz], the second layers 51A and 51B did not vibrate at all, and the second layers 52A-54A and the second layers 52B-54B vibrated. When the frequency of the driving force F was 255 [kHz], the amplitude in the Z direction of each of the second layers 52A-54A and the second layers 52B-54B was smaller than the amplitude in the Z direction of each of the second layers 53A and 53B when the frequency of the driving force F was 110 [kHz]. As shown in (f) of FIG. 4, when the frequency of the driving force F was 400 [kHz], the second layers 51A, 53A, 54A and the second layers 51B, 53B, 54B vibrated slightly, and the second layers 52A and 52B vibrated more than the other second layers. The Z-direction amplitude of each of second layers 52A, 52B when the frequency of driving force F was 400 [kHz] was smaller than the Z-direction amplitude of each of second layers 53A, 53B when the frequency of driving force F was 110 [kHz], and was larger than the Z-direction amplitude of each of second layers 52A-54A and second layers 52B-54B when the frequency of driving force F was 255 [kHz].

[0041] Next, in the second simulation, the fixed member SL and the interlocking member VL in the first simulation were replaced with an interlocking member and a fixed member, and a driving force F was applied to the first layer 40 from the +Z side to position P2 in the driving direction D1 in a direction parallel to and opposite to the Z direction. More specifically, the driving force F was applied to the boundary between the first layer 40 and the interlocking member. The characteristics, frequency, and conditions for applying the driving force F in the second simulation were set in the same way as in the first simulation.

[0042] 5(a) to (f) are diagrams showing three-dimensional behavior of the calculation model MD1 when the frequency of the driving force F is set to 20 [kHz], 30 [kHz], 80 [kHz], 110 [kHz], 255 [kHz], and 400 [kHz] in the second simulation. In each of FIG. 5(a) to (f), the thickness of the calculation model MD1 in the Z direction is also omitted. In the second simulation, as described above, the driving force F is applied to the first end face e1 of the first layer 40, and therefore the driving force F propagates from the +Y side portion of the first layer 40 to the -Y side portion.

[0043] As shown in (a) and (b) of FIG. 5, when the frequency of the driving force F was 20 [kHz] or 30 [kHz] in the second simulation, each of the second layers 51A and 51B vibrated, and the second layers 52A to 54A and the second layers 52B to 54B hardly vibrated. When the frequency of the driving force F was 20 [kHz] or 30 [kHz] in the second simulation, the amplitudes in the Z direction of each of the second layers 51A and 51B were approximately equal to each other, and were at least greater than the amplitudes in the Z direction of each of the second layers 54A and 54B when the frequency of the driving force F was 20 [kHz] in the first simulation. When the frequency of the driving force F was 30 [kHz] in the second simulation, the direction of the vibration in the Z direction of each of the second layers 51A and 51B was opposite to the direction of the vibration in the Z direction of each of the second layers 51A and 51B when the frequency was 20 [kHz] in the second simulation.

[0044] 5(c), when the frequency of the driving force F was 80 [kHz] in the second simulation, all of the second layers 51A-54A and 51B-54B vibrated. The Z-directional amplitude of each of the second layers 51A-53A and 51B-53B when the frequency of the driving force F was 80 [kHz] in the second simulation was greater than the Z-directional amplitude of each of the second layers 54A, 54B when the frequency was 80 [kHz] in the second simulation, and was approximately equal to the Z-directional amplitude of each of the second layers 51A, 51B when the frequency of the driving force F was 20 [kHz] or 30 [kHz] in the second simulation. In the second simulation, when the frequency of driving force F was 80 kHz, the direction of Z-direction vibration of each of second layers 51A, 53A and second layers 51B, 53B was opposite to the direction of Z-direction vibration of each of second layers 52A, 52B when the frequency was 80 kHz in the same second simulation.

[0045] 5(d), when the frequency of the driving force F was 110 [kHz] in the second simulation, the second layers 51A, 52A, 54A and the second layers 51B, 52B, 54B did not vibrate at all, but the second layers 53A, 53B vibrated, as in the case when the frequency of the driving force F was 110 [kHz] in the first simulation. The Z-directional amplitude of each of the second layers 53A, 53B when the frequency of the driving force F was 110 [kHz] in the second simulation was approximately equal to the Z-directional amplitude of each of the second layers 53A, 53B when the frequency of the driving force F was 110 [kHz] in the first simulation. In the second simulation, the direction of vibration of each of the second layers 53A, 53B when the frequency of the driving force F was 110 [kHz] was the same as the direction of vibration of each of the second layers 53A, 53B when the frequency of the driving force F was 110 [kHz] in the first simulation.

[0046] 5(e), when the frequency of the driving force F was 255 [kHz] in the second simulation, the second layers 51A, 51B did not vibrate at all, and the second layers 52A-54A and the second layers 52B-54B vibrated, similarly to when the frequency of the driving force F was 255 [kHz] in the first simulation. The Z-direction amplitude of each of the second layers 52A-54A and the second layers 52B-54B when the frequency of the driving force F was 255 [kHz] in the second simulation was at least greater than the Z-direction amplitude of each of the second layers 52A-54A and the second layers 52B-54B when the frequency of the driving force F was 255 [kHz] in the first simulation, and was slightly smaller than the Z-direction amplitude of each of the second layers 53A, 53B when the frequency of the driving force F was 110 [kHz] in the second simulation. The direction of vibration of each of the second layers 52A-54A and second layers 52B-54B when the frequency of driving force F was 255 [kHz] in the second simulation was the same as the direction of vibration of each of the second layers 52A-54A and second layers 52B-54B when the frequency of driving force F was 255 [kHz] in the first simulation.

[0047] 5(f), when the frequency of the driving force F was 400 [kHz] in the second simulation, the second layers 51A, 52A and the second layers 51B, 52B vibrated in a wavy manner in the horizontal direction D3, i.e., in the X direction, and the second layers 53A, 54B and the second layers 54A, 54B did not vibrate at all. When the frequency of the driving force F was 400 [kHz] in the second simulation, the amplitude in the Z direction of each of the second layers 51A, 52A and the second layers 51B, 52B was greater than the amplitude in the Z direction of each of the second layers 51A, 52A and the second layers 51B, 52B when the frequency of the driving force F was 400 [kHz] in the first simulation.

[0048] From the results of the first and second simulations, it was confirmed that even if the frequency of the driving force F is the same, the direction of vibration, shape during vibration, and amplitude in the Z direction of each of the second layers 51A-54A and second layers 51B-54B differ depending on the position at which the driving force F is applied and whether the direction in which the driving force F propagates in the first layer 40 is the detection direction D1 or the reverse direction D2.

[0049] Furthermore, from the results of the first simulation, when driving force F was applied to position P2 of first layer 40 and propagated in detection direction D1 from the -Y side portion to the +Y side portion of first layer 40, second layers 52A and 52B vibrated and deformed significantly when the frequency of driving force F was 400 [kHz], which is closest to 355 [kHz], the resonant frequency of first layer 40. In the first simulation, when the frequency of driving force F was a frequency far from the resonant frequency of first layer 40, such as any of 20 [kHz], 30 [kHz], 80 [kHz], and 255 [kHz], second layers 51A-54A and second layers 51B-54B hardly vibrated or deformed.

[0050] On the other hand, from the results of the second simulation, when driving force F is applied to position P1 of first layer 40 and propagates in reverse direction D2 from the +Y side portion to the -Y side portion of first layer 40, the Z-direction amplitude of each of second layers 51A, 51B to second layers 54A, 54B increases sequentially as the frequency of driving force F increases. Therefore, by measuring the Z-direction amplitude and the shape during vibration of each of second layers 51A-54A and second layers 51B-54B, it is possible to detect the frequency of driving force F by back-calculating.

[0051] Next, in the third simulation, an ultrasonic analysis was performed using a calculation model MD2 shown in Fig. 6. The calculation model MD2 includes a first layer 40 made of a polyhedron having a trapezoidal surface and a bottom surface similar to the first layer 40 of the plate wave detector 111 of the first embodiment, and a third layer 61 and a fourth layer 62 connected to the first layer 40. In the third simulation, the length L1 of the side W1 of the first layer 40 was set to 1 [mm], the length L2 of the side W2 was set to 4 [mm], and the length L5 was set to 120 [mm].

[0052] 6, the thicknesses of the first layer 40, the third layer 61, and the fourth layer 62 are omitted. The first layer 40, the third layer 61, and the fourth layer 62 are assumed to have the same thickness and are integrated with each other as thin metal plate members. In the third simulation, the thicknesses of the first layer 40, the second layer 50, the third layer 61, and the fourth layer 62 are assumed to be 1 mm.

[0053] The third layer 61 is connected to the first end face e1 of the first layer 40. The surface 61a and the bottom face 61b of the third layer 61 are rectangular in shape. The four sides of the surface 61a and the bottom face 61b of the third layer 61 are at least longer than the side W1 and are further longer than the side W2. The fourth layer 62 is connected to the second end face e2 of the first layer 40. The surface 62a and the bottom face 62b of the fourth layer 62 are rectangular in shape. The four sides of the surface 62a and the bottom face 62b of the fourth layer 62 are longer than the side W2 and are equal to the four sides of the surface 61a and the bottom face 61b of the third layer 61. In FIG. 6, the first end face e1 and the second end face e2 are omitted.

[0054] In the third simulation, a wavelet having a frequency of 150 [kHz] was input as an input signal simulating a plate wave PW1 to a position P11 near the side W1 of the first layer 40 in the detection direction D1 on the surface 61a of the third layer 61, and the volumetric strain of the first layer 40 was calculated. The wavelet sampling rate was set to 300 [MHz]. Then, the same signal as the input signal input to the position P11 as described above was input to a position P12 near the side W2 of the first layer 40 in the detection direction D1 on the surface 62a of the fourth layer 62.

[0055] FIG. 7 shows the results of calculating the change in volumetric strain over time in the first layer 40 when the above-mentioned input signal is input to each of the positions P11 and P12. The solid line in the graph of FIG. 7 represents the calculation result of the volumetric strain in the first layer 40 when the input signal is input to the position P11 and the propagation direction of the input signal is from the side W1 to the side W2, i.e., the reverse direction D2. The dashed line in the graph of FIG. 7 represents the calculation result of the volumetric strain in the first layer 40 when the input signal is input to the position P12 and the propagation direction of the input signal is from the side W2 to the side W1, i.e., the detection direction D1. As shown in FIG. 7, when the input signal is input to the position P12, the volumetric strain in the first layer 40 is larger than the volumetric strain in the first layer 40 when the input signal is input to the position P11.

[0056] From the results of the third simulation, it was confirmed that when an input signal is input from a position near side W2, which is longer than side W1, the volumetric strain of the first layer 40 increases compared to when the input signal is input from a position near side W1. Therefore, it is understood that by measuring the volumetric strain of the first layer 40, it is possible to determine along which of the detection direction D1 and reverse direction D2 the input signal is propagating through the first layer 40, and thereby detect the input position and propagation direction of the input signal.

[0057] The plate wave detector 111 of the first embodiment described above includes a base 12 and a layer 22 that is thinner than the base 12. The layer 22 includes a first layer 40 provided on a surface 12a of the base 12. The first layer 40 has a side W1 extending along a horizontal direction D3 at a position P1 in a detection direction D1 parallel to the surface 40a, and a side W2 extending along the horizontal direction D3 at a position P2 away from the position P1 in the detection direction D1. In the plate wave detector 111 of the first embodiment, a length L1 of the side W1 in the horizontal direction D3 and a length L2 of the side W2 in the horizontal direction D3 are different from each other. According to the plate wave detector 111 of the first embodiment, the behavior of the first layer 40 is made different between the case where the plate wave PW1 propagates along the detection direction D1 from side W2 to side W1 perpendicular to the horizontal direction D3 and the case where the plate wave PW2 propagates along the detection direction D1 from side W1 to side W2 perpendicular to the horizontal direction D3. According to the plate wave detector 111 of the first embodiment, not only can it detect whether or not a plate wave is input, but it can also determine the propagation direction of the plate wave input to the plate wave detector 111 from the thin plate W of the structure T from the difference in the behavior of the first layer 40 described above.

[0058] In the plate wave detector 111 of the first embodiment, the first layer 40 is formed in a trapezoid shape having sides W1 to W4. The side W3 connects the end of the side W1 on the -D3 side in the horizontal direction D3 to the end of the side W2 on the -D3 side. The side W4 connects the end of the side W1 on the +D3 side in the horizontal direction D3 to the end of the side W2 on the +D3 side. According to the plate wave detector 111 of the first embodiment, it is possible to increase the detection sensitivity of the plate wave PW1 propagating in the first layer 40 along the detection direction D1 from the longer side W2 of the sides W1 and W2 toward the shorter side W1. Also, according to the plate wave detector 111 of the first embodiment, it is possible to easily realize the trapezoidal first layer 40 having a piece formed of a straight line as the first layer 40 capable of increasing the detection sensitivity of the plate wave PW1 propagating in parallel to the detection direction D1 in the first layer 40.

[0059] In the plate wave detector 111 of the first embodiment, the ratio (L2 / L1) of the length L1 of the side W1 of the first layer 40 to the length L2 of the side W2 is set according to the detection sensitivity of the plate wave PW1 and is proportional to the signal-to-noise (SN) ratio regarding the detection of the plate wave PW1. The SN ratio regarding the detection of the plate wave PW1 means the ratio of the detection sensitivity of the plate wave PW2 to the detection sensitivity of the plate wave PW1. The plate wave PW2 propagates in the first layer 40 in the opposite direction to the plate wave PW2.

[0060] In the plate wave detector 111 of the first embodiment, the length L5 of the first layer 40 in the detection direction D1 is at least longer than the wavelength of the plate wave WP1, for example, 5 times or more the wavelength of the plate wave WP1. By ensuring the length L5 of the first layer 40 as described above, the detection sensitivity and the SN ratio of the plate wave PW1 are improved. The length L5 of the first layer 40 is set according to the detection intensity of the plate wave WP1 required when detecting the plate wave PW1, and is proportional to the magnitude of the amplitude in the Z direction for obtaining the detection intensity of the plate wave WP1.

[0061] The plate wave detector 111 of the first embodiment further includes a plurality of second layers 51A to 54A and a plurality of second layers 51B to 54B. The length in the horizontal direction D3 of each of the second layers 51A to 54A and 51B to 54B is set to a value smaller than the frequency domain (ω MAX -ω MIN ) The length in the horizontal direction D3 of the second layers 51A and 51B, the length in the horizontal direction D3 of the second layers 52A and 52B, the length in the horizontal direction D3 of the second layers 53A and 53B, and the length in the horizontal direction D3 of the second layers 54A and 54B are different from one another.

[0062] In the plate wave detector 111 of the first embodiment, four types of second layers 51A to 54A and four types of second layers 51B to 54B are provided, so that the frequency domain (ω MAX -ω MINWhen the plate wave PW1 having a frequency included in the frequency range of 1000 to 2000 Hz propagates, at least one of the second layers 51A-54A, 51B-54B having a predetermined length determined by a frequency close to the frequency of the plate wave PW1 among the frequencies corresponding to the predetermined lengths of the second layers 51A-54A, 51B-54B vibrates relatively strongly. According to the plate wave detector 111 of the first embodiment, the frequency of the plate wave PW1 can be detected by detecting at least one of the second layers 51A-54A, 51B-54B vibrating relatively strongly.

[0063] In the plate wave detector 111 of the first embodiment, the second layers 51A-54A are connected to the first side surface s1 having the side W3 of the first layer 40 at intervals, and the second layers 51B-54B are connected to the second side surface s2 having the side W4 of the first layer 40 at intervals. The length of the horizontal direction D3 of each of the second layers 51A-54A is a dimension that increases as the connection position between each of the second layers 51A-54A and the first layer 40 moves from the second layer 51A closer to the side (one of the first and second sides) W1 to the second layer 54A closer to the side (the other of the first and second sides) W2 in the detection direction D1. Specifically, the predetermined length of the horizontal direction D3 of the longest second layer 51A, 51B of the four types of second layers 50 is a length that is longer than the minimum frequency ω MIN Equal to or the lowest frequency ω MIN The predetermined length in the lateral direction D3 of the second layers 54A and 54B, which are the shortest among the four types of second layers 50, is determined by the frequency close to the maximum frequency ω MAX Equal to or the highest frequency ω MAX The predetermined length of the second layers 52A and 52B in the horizontal direction D3 is determined by the frequency close to the lowest frequency ω MIN Higher than the highest frequency ω MAX The predetermined length of the second layers 53A and 53B in the horizontal direction D3 is determined by a frequency lower than the lowest frequency ω MIN Higher than the highest frequency ω MAX and is a length determined by a frequency that is lower than the frequency that determines the predetermined length of the second layers 52A, 52B in the lateral direction D3.

[0064] In the plate wave detector 111 of the first embodiment, the frequency of the plate wave PW1 propagating from the first layer 40 is in the frequency domain (ω MAX -ω MIN ) the vibrating second layer 50 changes in sequence from the second layers 51A, 51B to the second layers 54A, 54B. Therefore, according to the plate wave detector 111 of the first embodiment, the high and low frequency of the plate wave PW1 propagating from the first layer 40 can be easily detected.

[0065] In the plate wave detector 111 of the first embodiment, the second layer 50 is formed of a piezoelectric material or an electret. According to the plate wave detector 111 of the first embodiment, when a plate wave PW1 having a frequency equal to or close to a frequency that determines a predetermined length in the horizontal direction D3 is input to the second layer 50, the second layer 50 having the predetermined length vibrates, so that an electric signal corresponding to the vibration and the amplitude in the Z direction can be detected well from the second layer 50. In addition, when the first layer 40 and the second layer 50 are integrally formed of the same piezoelectric material or electret, as described above, in addition to being able to detect an electric signal corresponding to the vibration and the amplitude in the Z direction from the second layer 50 well, the first layer 40 and the second layer 50 having a large area can be easily formed using a printing or nanoimprinting technique.

[0066] Furthermore, according to the plate wave detector 111 of the first embodiment, it is formed in a sheet shape and has an adhesive film (not shown) provided on the bottom surface 12b opposite the surface 12a of the base 12, so that it can be easily attached to either the flat surface a or the curved surface a of the thin plate W regardless of the shape of the structure T.

[0067] In the plate wave detector 111 of the first embodiment, an adhesive film (not shown) is provided between the first layer 40 of the layer 22 and the base 12. According to the plate wave detector 111 of the first embodiment, the first layer 40 and the base 12 can be easily bonded together using the adhesive film.

[0068] As a modification of the first embodiment, the layer 22 of the plate wave detector 111 may include only the first layer 40, and may not include the second layer 50. By including at least the first layer 40 in the plate wave detector 111, it is possible to detect the presence or absence of the plate wave PW1 propagating along the detection direction D1 as described above, that is, the directionality of the plate wave input to the first layer 40.

[0069] As a modification of the first embodiment, the first side surface s1 and the second side surface s2 of the first layer 40 of the plate wave detector 111 are not necessarily limited to flat surfaces, and may be curved surfaces. The shape of the first layer 40 when viewed from the Z direction is not necessarily limited to an isosceles trapezoid, and may be any shape as long as it has sides W1 and W2 and the size of the lateral direction D3 of the first layer 40 increases from the position P1 of the side W1 to the position P2 of the side W2 in the detection direction D1.

[0070] 1 and 2, four types of second layers 51A to 54A and second layers 51B to 54B are illustrated as the multiple second layers 50, but as a modification of the first embodiment, the number m of types of second layers 50 is not limited to 4, and may be any of 1 to 3, or a natural number equal to or greater than 5. MIN and the highest frequency is ω MAX If is constant, the frequency of the plate waves PW1 and PW2 becomes smaller as the number of meters increases. MAX -ω MIN In other words, the number m is set to match the conditions of the frequency band of the plate waves PW1 and PW2 to be detected, the frequency interval required during detection, and the frequency fluctuation range.

[0071] In addition, the difference ω between the frequencies of the plate waves PW1 and PW2 determines the length in the lateral direction D3 of the second layers 50 adjacent to each other in the detection direction D1 among the plurality of second layers 50. P may or may not be constant. The lowest frequency is MIN The highest frequency from ω MAX In the frequency domain up to ω P In the second layers 50 having a predetermined length determined by a relatively small frequency, the difference ω PIn comparison with the plurality of second layers 50 having a predetermined length determined by a relatively large frequency, the frequencies of the plate waves PW1 and PW2 are detected with high resolution.

[0072] As a modification of the first embodiment, the second layers 51A-54A may be connected in sequence to predetermined positions on the first side surface s1 closer to the second end surface e2 in the detection direction D1 at intervals along the side W3. The second layers 51B-54B may be connected in sequence to predetermined positions on the second side surface s2 closer to the first end surface e1 at intervals along the side W4 from predetermined positions on the second side surface s2 closer to the second end surface e2 in the detection direction D1. That is, in the plate wave detector 112 shown in FIG. 8, the order in which the second layers 51A-54A and the second layers 51B-54B are arranged in the detection direction D1 may be reversed to that of the plate wave detector 111. In other words, the horizontal length D3 of each of the multiple second layers 50 may be a dimension that increases as the connection position between each of the multiple second layers 50 and the first side surface s1 of the first layer 40 moves from the second layer 50 closer to side W2 to the second layer 50 closer to side W1 in the detection direction D1.

[0073] However, when the plate wave PW1 is incident on the first layer 40 from the thin plate W through the base 12 and propagates along the detection direction D1, the higher the frequency of the component included in the plate wave PW1, the greater the attenuation amount with respect to the propagation distance in the detection direction D1. That is, the higher the frequency of the component included in the plate wave PW1, the greater the attenuation and disappearance in the shorter distance from the side W2 in the detection direction D1. In the plate wave detector 111, the longest second layers 51A and 51B among the four types of second layers 51A to 54A and second layers 51B to 54B are arranged at a position (predetermined position) closer to the side W2 than the other second layers 52A to 54A and second layers 52B to 54B in the detection direction D1. This allows the second layers 51A and 51B to detect the high-frequency plate wave PW1 well.

[0074] The positions where each of the multiple second layers 50 is connected to the first layer 40 in the detection direction D1 are included in a range where the Lamb wave PW1 having the frequency to be detected can reach, not disappear due to attenuation, and vibrate the second layer 50. Within the above-mentioned range in the detection direction D1, the positions where each of the multiple second layers 50 is connected to the first layer 40 can be changed, and the arrangement order of the four types of second layers 51A to 54A and the arrangement order of the second layers 51B to 54B in the detection direction D1 can be appropriately changed.

[0075] As a modification of the first embodiment, as shown in FIG. 8, the base 12 of the plate wave detector 112 may be provided in the region on the -Z side of the plurality of second layers 50. In the plate wave detector 112, when viewed from the Z direction, the base 12 has a shape similar to that of the layer 22 and overlaps with the layer 22. As described above, the base 12 is formed of a material that smoothly propagates the plate wave PW1 input from the thin plate W to the layer 22, and is formed of, for example, a film material or resin having high heat resistance and adhesiveness. According to the plate wave detector 112, since not only the first layer 40 but also the plurality of second layers 50 are supported by the base 12 from the -Z side, the plurality of second layers 50, which are longer in the lateral direction D3 than the detection direction D1 and formed in layers, do not break at the connection position with the first layer 40, and the durability of the plurality of second layers 50 can be improved.

[0076] [Second embodiment] Next, a second embodiment of the present disclosure will be described. In each of the following embodiments, components common to the upper embodiment are given the same reference numerals as the corresponding components of the upper embodiment, and detailed description of the components will be omitted. In each embodiment, even if there is no protrusion, a modified example of the related upper garment embodiment can be applied.

[0077] As shown in Fig. 9, the plate wave detection device 121 of the second embodiment includes a plurality of plate wave detectors 111, for example, six plate wave detectors 111A to 111F. In the plate wave detection device 121, the plate wave detectors 111A to 111F are arranged concentrically around a predetermined position PC. An axis J101 of each of the plate wave detectors 111A to 111F spreads radially from the position PC. In the second embodiment, the detection direction D1 of each of the plate wave detectors 111A to 111F overlaps with a radial direction centered around the position PC. The detection direction D1 of each of the plate wave detectors 111A to 111F is directed toward the position PC.

[0078] When the plate wave detecting device 121 is disposed on the surface a of the thin plate W of the structure T, a plate wave PW1 propagating in at least one of the detection directions D1 of the six plate wave detectors 111A to 111F is detected by the plate wave detector 111 having at least one detection direction D1. An analysis device (not shown) of the plate wave detecting device 121 individually receives electrical signals from the first layer 40 and each of the multiple second layers 50 for each of the six plate wave detectors 111A to 111F.

[0079] The analysis device of the plate wave detection device 121 judges whether or not the plate wave PW1 is detected by each of the six plate wave detectors 111A-111F based on the level of the electric signal output from each of the plurality of second layers 51A-54A and second layers 51B-54B for each of the six plate wave detectors 111A-111F as described in the first embodiment. Next, the analysis device of the plate wave detection device 121 calculates the three-dimensional position of the source of the plate wave PW1 in the thin plate W and the frequency distribution of the plate wave PW1 based on the electric signal from the plate wave detector 111 judged to have detected the plate wave PW1 among the six plate wave detectors 111A-111F, and obtains the strain at the position of the source of the thin plate W and the stress distribution of the thin plate W. The analysis device of the plate wave detection device 121 quantitatively analyzes the state of the structure T and the presence or absence of damage.

[0080] As shown in Fig. 10, the analysis device of the plate wave detection device 121 can calculate the distance LA, the distance LL, and the angles θ1 and θ2 based on the arrangement between two plate wave detectors 111, 111 among the six plate wave detectors 111A to 111F that detect the propagation direction of the plate wave PW1 with higher sensitivity than the other four plate wave detectors 111 to 111 and the directionality of the plate wave PW1 detected by each plate wave detector 111. In Fig. 10, the plate wave detectors 111A and 111D are illustrated as the two plate wave detectors 111, 111 that detect the propagation direction of the plate wave PW1 with high sensitivity. The distance LA represents the distance between the position XS on the surface a directly above the source SS of the plate wave PW1 in the thin plate W on the +Z side and the center point of the area where one plate wave detector 111A and the surface a contact each other. The distance LL represents the distance between the center points of the area where the two plate wave detectors 111, 111 and the surface a contact each other. Angle θ1 represents an angle formed on the YZ plane including the Y direction and the Z direction between a line L12 connecting the generation source SS and one of the two plate wave detectors 111, 111, and the surface a. Angle θ2 represents an angle formed on the YZ plane between a line L13 connecting the generation source SS and the other of the two plate wave detectors 111, 111, and the surface a.

[0081] 10, plate wave detectors 111A and 111B are illustrated as two plate wave detectors 111. The plate wave detector 111 corresponds to, for example, the plate wave detector 111A. The other plate wave detector 111 corresponds to, for example, the plate wave detector 111B.

[0082] When performing two-dimensional location, the analysis device of the plate wave detection device 121 can identify the three-dimensional position of the generation source SS by the following equations (1) and (2).

[0083]

number

[0084] The analysis device of the plate wave detection device 121 can calculate the position of the source SS using vector calculations based on the distance between two of the multiple plate wave detectors 111, 111 and the angles θ1, θ2 between the lines L12, L13 connecting each of the plate wave detectors 111 to the source SS of the plate wave PW1 and the surface a of the thin plate W on which the multiple plate wave detectors 111 are installed.

[0085] The plate wave detection device 121 includes an analyzer (not shown) provided in each of the six plate wave detectors 111A-111F, and a second analyzer (not shown) that quantitatively analyzes the state of the structure T and the presence or absence of damage by collecting information on the determination result of whether the plate wave PW1 in the detection direction D1 calculated for the six plate wave detectors 111A-111F is detected or not, and information on the position of the source of the plate wave PW1 and the frequency distribution of the plate wave PW1. The plate wave detection device 121 may be capable of collecting the electric signals from the first layer 40 and the plurality of second layers 50 for each of the six plate wave detectors 111A-111F individually and collectively, and may include a device that serves both as the above-mentioned analyzer (not shown) and the second analyzer.

[0086] The plate wave detection device 121 of the second embodiment described above includes six plate wave detectors 111A to 111F. In the plate wave detector 121 of the second embodiment, the plate wave detectors 111A to 111F are arranged in the circumferential direction centered on a predetermined position PC. The plate wave detectors 111A to 111F are arranged with their respective detection directions D1 facing a predetermined position. According to the plate wave detection device 121 of the second embodiment, the same action and effect as the plate wave detector 111 of the first embodiment can be obtained, and the plate wave PW1 propagating along six different detection directions D11 to D16 in the XY plane parallel to the surface a of the thin plate W can be detected using the plate wave detectors 111A to 111F. This makes it possible to specify the angle of the plate wave PW1 input from the thin plate W in the XY plane. Each of the detection directions D11 to D16 corresponds to the detection direction D1 of each of the plate wave detectors 111A to 111F.

[0087] As a modified example of the plate wave detecting device 121 of the second embodiment, although not shown, the plate wave detecting device of the second embodiment may include two or more, five or less, or seven or more plate wave detectors 111. That is, the plate wave detector 121 of the second embodiment includes plate wave detectors 111 equal to or more than the number of types of propagation directions of the plate wave PW1 to be detected in the XY plane.

[0088] In the plate wave detection device of the second embodiment, the axis J101 parallel to each detection direction D1 of the plate wave detectors 111 is arranged at equal angular intervals in the circumferential direction centered on the position PC. As a modified example of the plate wave detection device 121 of the second embodiment, although not shown, the plate wave detectors 111 are arranged so that the axis J101 parallel to each detection direction D1 is arranged at arbitrary angular intervals in the circumferential direction centered on the position PC, in such a manner that the axis J101 is aligned with an arbitrary propagation direction of the plate wave PW1 to be detected in the XY plane. For example, the plate wave detection device of the second embodiment may include only one or more and five or less arbitrary plate wave detectors 111 among the six plate wave detectors 111A, 111B, and 111D shown in FIG. 9, and may further include a plate wave detector 111 between the plate wave detectors 111, 111 adjacent to each other in the circumferential direction centered on the position PC among the six plate wave detectors 111A to 111F.

[0089] In the plate wave detection device of the second embodiment, the six plate wave detectors 111A to 111F are arranged at substantially equal positions in the radial direction centered on the position PC. As a modified example of the plate wave detection device 121 of the second embodiment, although not shown, the positions in the radial direction of the plate wave detectors 111 may be different from each other and can be freely adjusted as long as the axis J101 coincides with the same direction as the propagation direction of the plate wave PW1 to be detected in the XY plane.

[0090] Each of the plate wave detectors 111 included in the plate wave detection device of the second embodiment may be inverted about an axis (not shown) perpendicular to the axis J101, and the second end face e2 (not shown) of each of the plate wave detectors 111 may be disposed closer to the position PC in the radial direction centered on the position PC than the first end face e1. In such a configuration, the detection direction D1 of each of the plate wave detectors 111 spreads radially from the position PC.

[0091] Moreover, all the modifications described in the first embodiment are applicable to the plate wave detector 111 included in the plate wave detecting device 121 of the second embodiment and the plate wave detecting device of the above-mentioned modifications.

[0092] [Third embodiment] Next, a third embodiment of the present disclosure will be described.

[0093] 11, a plate wave detecting device 122 of the third embodiment includes two plate wave detectors 111A and 111B. In the plate wave detecting device 122, the plate wave detector 111B is disposed at a position on the -X side of the plate wave detector 111A. In the plate wave detecting device 122, a side W2 of the plate wave detector 111A and a side W1 of the plate wave detector 111B are aligned substantially in a straight line and overlap each other in the Y direction. A side W1 of the plate wave detector 111A and a side W2 of the plate wave detector 111B are aligned substantially in a straight line and overlap each other in the Y direction.

[0094] In the plate wave detecting device 122, the detection direction D1 of the plate wave detector 111A is the same as the Y direction, whereas the detection direction D1 of the plate wave detector 111B is parallel to the Y direction and directed opposite to the Y direction.

[0095] The plate wave detection device 122 of the third embodiment described above includes two plate wave detectors 111A and 111B. In the plate wave detection device 122 of the third embodiment, the detection directions D1 of the plate wave detectors 111A and 111B are parallel to each other, and the detection directions D1 from the side W1 to the side W2 of the plate wave detectors 111A and 111B adjacent to each other in the X direction are arranged opposite to each other. According to the plate wave detection device 121 of the third embodiment, in addition to obtaining the same action and effect as the plate wave detector 111 of the first embodiment, it is possible to detect not only the plate wave PW1 having the propagation direction of the detection direction D1 of the plate wave detector 111A, but also the plate wave PW1 having the propagation direction of the detection direction D1 of the plate wave detector 111B. That is, according to the plate wave detection device 121 of the third embodiment, it is possible to detect the plate wave PW1 having the same propagation direction as the detection direction D21 and the plate wave PW1 having the propagation direction of the detection direction D22 opposite to the detection direction D21. The detection direction D21 corresponds to the detection direction D1 of the plate wave detector 111A, and the detection direction D22 corresponds to the detection direction D1 of the plate wave detector 111B.

[0096] In the plate wave detecting device 122 of the third embodiment, the relative arrangement of the plate wave detectors 111A and 111B may be inverted in the X direction. That is, in the plate wave detecting device 122, the plate wave detector 111B may be disposed in an area on the +X side of the plate wave detector 111A.

[0097] As a modification of the plate wave detection device 122 of the third embodiment, the detection directions D1 of the plate wave detectors 111A and 111B may be directed in any direction in the XY plane parallel to the surface a of the thin plate W, as long as the detection directions D1 of the plate wave detectors 111A and 111B are parallel to each other. For example, as shown in FIG. 12, in the plate wave detection device 123 of the modification of the third embodiment, the detection direction D1 of the plate wave detector 111A is the same as the X direction. The plate wave detector 111B is disposed at a position on the +Y side of the plate wave detector 111A. In the plate wave detection device 123, the side W2 of the plate wave detector 111A and the side W1 of the plate wave detector 111B are aligned substantially on a straight line and overlap each other in the X direction. The side W1 of the plate wave detector 111A and the side W2 of the plate wave detector 111B are aligned substantially on a straight line and overlap each other in the X direction. In the plate wave detecting device 123, the detection direction D1 of the plate wave detector 111B is parallel to the X direction and is opposite to the X direction. According to the plate wave detecting device 123 of the modification of the third embodiment, it is possible to detect the plate wave PW1 having the same propagation direction as the detection direction D23 and the plate wave PW1 having the propagation direction of the detection direction D24 opposite to the detection direction D23.

[0098] In the plate wave detecting device 123 according to the modification of the third embodiment, the relative arrangement of the plate wave detectors 111A and 111B may be inverted in the Y direction. That is, in the plate wave detecting device 123, the plate wave detector 111B may be disposed in an area on the -Y side of the plate wave detector 111A.

[0099] Moreover, all the modifications described in the first embodiment are applicable to the plate wave detector 111 provided in the plate wave detecting device 122 of the third embodiment and the plate wave detecting device 123 of the above-mentioned modifications.

[0100] [Fourth embodiment] Next, a fourth embodiment of the present disclosure will be described.

[0101] As shown in Fig. 13, the plate wave detecting device 124 of the fourth embodiment includes a plurality of plate wave detectors 111, similar to the plate wave detecting device 121 of the second embodiment. In Fig. 13, for example, ten plate wave detectors 111A to 111J are illustrated as the plurality of plate wave detectors 111 included in the plate wave detecting device 124. Note that the second layers 51A to 54A and 51B to 54B of each of the plate wave detectors 111A to 111J are illustrated as a second layer 50.

[0102] In the plate wave detection device 124, the plate wave detectors 111A to 111J are arranged at intervals in the circumferential direction centered on a predetermined position PC. In the plate wave detection device 124, unlike the plate wave detection device 121, the plate wave detectors 111A and 111B adjacent to each other in the circumferential direction centered on the position PC form a pair. The plate wave detectors 111C and 111D adjacent to each other in the circumferential direction form a pair. The plate wave detectors 111E and 111F adjacent to each other in the circumferential direction form a pair. The plate wave detectors 111G and 111H adjacent to each other in the circumferential direction form a pair. The plate wave detectors 111I and 111J adjacent to each other in the circumferential direction form a pair.

[0103] In the plate wave detecting device 124, similarly to the plate wave detecting device 122 of the third embodiment, the detection directions D1 of the plate wave detectors 111A and 111B are opposite to each other. The detection directions D1 of the plate wave detectors 111C and 111D are opposite to each other. The detection directions D1 of the plate wave detectors 111E and 111F are opposite to each other. The detection directions D1 of the plate wave detectors 111G and 111H are opposite to each other. The detection directions D1 of the plate wave detectors 111I and 111J are opposite to each other.

[0104] In the plate wave detection device 124, the center line (not shown) between the respective axes J101 of the plate wave detectors 111A and 111B, the center line (not shown) between the respective axes J101 of the plate wave detectors 111C and 111D, the center line (not shown) between the respective axes J101 of the plate wave detectors 111E and 111F, the center line (not shown) between the respective axes J101 of the plate wave detectors 111G and 111H, and the center line (not shown) between the respective axes J101 of the plate wave detectors 111I and 111J intersect at a position PC. That is, in the plate wave detection device 124, as described above, the center lines of the two pairs of plate wave detectors 111A, 111B, plate wave detectors 111C, 111D, plate wave detectors 111E, 111F, plate wave detectors 111G, 111H, and plate wave detectors 111I, 111J each extend radially around the position PC.

[0105] The analyzer of the plate wave detection device 124 judges whether or not the plate wave PW1 is detected by each of the plate wave detectors 111A-111J as described in the first embodiment, based on the level of the electric signal output from each of the plurality of second layers 50 for each of the ten plate wave detectors 111A-111J. Next, the analyzer of the plate wave detection device 124 calculates the directionality of the plate wave PW1 in the thin plate W, the three-dimensional position of the source, and the frequency distribution of the plate wave PW1 based on the electric signal from the plate wave detector 111 that is judged to have detected the plate wave PW1 among the ten plate wave detectors 111A-111J, and obtains the strain at the position of the source of the thin plate W and the stress distribution of the thin plate W. The analyzer of the plate wave detection device 124 quantitatively analyzes the state of the structure T and the presence or absence of damage.

[0106] The plate wave detection device 124 of the fourth embodiment described above includes ten plate wave detectors 111A to 111J in total, five pairs. In the plate wave detection device 124 of the fourth embodiment, the ten plate wave detectors 111A to 111J are arranged in the circumferential direction with the position PC as the center, and the center lines of the axes 101 of the paired plate wave detectors 111, 111 radially extend from the position PC. In the plate wave detection device 124 of the fourth embodiment, the plate wave detectors 111, 111 that are adjacent to each other in the circumferential direction with the position PC as the center are arranged with the detection directions D1 opposite to each other. According to the plate wave detection device 124 of the fourth embodiment, the same action and effect as the plate wave detector 111 of the first embodiment, the plate wave detection device 121 of the second embodiment, and the plate wave detection device 122 of the third embodiment can be obtained, and the plate wave PW1 propagating along ten different detection directions D31A to D35B and the detection directions D31B to D35B in the XY plane can be detected by using the plate wave detection device 124 of the fourth embodiment. Each of the detection directions D31A to D35A corresponds to the detection direction D1 of each of the plate wave detectors 111A, 111C, 111E, 111G, and 111I. Each of the detection directions D31B to D35B corresponds to the detection direction D1 of each of the plate wave detectors 111B, 111D, 111F, 111H, and 111J, and is the opposite direction to each of the detection directions D31A to D35A. By using the plate wave detection device 124 of the fourth embodiment, the above-mentioned action and effect can be achieved to identify the angle that the directivity and propagation direction of the plate wave PW1 in the XY plane make with respect to a reference direction (not shown), and to easily determine whether the source of the plate wave PW1 (not shown) is located inside or outside the area surrounded by the ten plate wave detectors 111A to 111J in the XY plane.

[0107] As a modification of the plate wave detection device 124 of the fourth embodiment, the total number of plate wave detectors 111 and the number of pairs are not limited to a specific number as long as the detection directions D1 of the plate wave detectors 111, 111 that are adjacent to each other in the circumferential direction with the position PC as the center are opposite to each other. Also, in the plate wave detection device 124 of the fourth embodiment, each of the plurality of plate wave detectors 111 can be disposed at any position on the axis J101.

[0108] Moreover, all the modified examples described in the first embodiment are applicable to the plate wave detector 111 included in the plate wave detection device 124 of the fourth embodiment. Furthermore, the configurations and modified examples described in the second and third embodiments are applicable to the plate wave detection device 124 of the fourth embodiment.

[0109] [Fifth embodiment] Next, a fifth embodiment of the present disclosure will be described.

[0110] 14 and 15 , the plate wave detector 116 of the fifth embodiment includes a base 12 and a layer 22, similar to the plate wave detector 111 of the first embodiment. However, in the plate wave detector 116 of the fifth embodiment, the base 12 includes a first base 14 and a second base 15. The layer 22 includes a first layer 40, a plurality of second layers 50, a third layer 61, and a fourth layer 62.

[0111] In the plate wave detector 116, four types of second layers 51A-54A, 51B-54B constituting the plurality of second layers 50 are provided on the surface 40a of the first layer 40. The second layers 51A, 51B are integrally formed with each other. The second layers 52A, 52B are integrally formed with each other. The second layers 53A, 53B are integrally formed with each other. The second layers 54A, 54B are integrally formed with each other. The length in the horizontal direction D3 from the side W3 to each tip of the second layers 51A-54A is equal to the length in the horizontal direction D3 of the second layers 51A-54A of the plate wave detector 111 of the first embodiment, and is determined according to the frequency of the plate wave PW1 to be detected in the same manner as the second layers 51A-54A of the plate wave detector 111 of the first embodiment. The length in the horizontal direction D3 from the side W4 to each tip of the second layers 51B to 54B is equivalent to the length in the horizontal direction D3 of the second layers 51B to 54B of the plate wave detector 111 of the first embodiment, and is determined according to the frequency of the plate wave PW1 to be detected, in the same manner as the second layers 51B to 54B of the plate wave detector 111 of the first embodiment.

[0112] In the plate wave detector 116, the third layer 61 is connected to a first end face e1 of the first layer 40, and is connected to the first layer 40 at a position of a side W1 in the Y direction and the detection direction D1. The fourth layer 62 is connected to a second end face e2 of the first layer 40, and is connected to the first layer 40 at a position of a side W2 in the Y direction and the detection direction D1. The third layer 61 and the fourth layer 62 are formed in a rectangular shape, have a thickness equivalent to that of the first layer 40, and are formed integrally with the first layer 40. The length of each of the four sides of the third layer 61 and the fourth layer 62 is longer than the length of the side W2 in the horizontal direction D3.

[0113] In the plate wave detector 116, the third layer 61 is provided on the surface 14a of the first base 14. The third layer 61 and the first base 14 are either in direct contact with each other as described in the first embodiment, or are bonded with an adhesive (not shown) that does not impede vibration. The fourth layer 62 is provided on the surface 15a of the second base 15. The fourth layer 62 and the second base 15 are bonded with an adhesive film (not shown). As shown in FIG. 16, the first base 14 and the second base 15 are spaced apart from each other in the Y direction and the detection direction D1, and are arranged in a non-connected state. In this specification, the term "unconnected state" means that the first base 14 and the second base 15 are not simply arranged apart from each other in the Y direction and the detection direction D1, but are not connected to each other by any other member than the first base 14 and the second base 15 among the members constituting the plate wave detector 116, and the movement of one of the first base 14 and the second base 15 is not restricted by the movement of the other base at all. The base 12 is not provided in the region on the -Z side in the Z direction from the first layer 40. The bottom surface 14b of the first base 14 and the bottom surface 15b of the second base 15 are in contact with the surface a of the thin plate W.

[0114] As shown in Fig. 16, when the plate wave QW propagates in the Y direction in the thin plate W, when the plate wave QW arrives at the area overlapping with the second table 15 in the Y direction as shown in Fig. 17, the plate wave (part of the plate wave) PW1 from the plate wave QW propagates from the second end face e2 to the first layer 40 through the second table 15 and the fourth layer 62. After a time difference according to the length L5 in the Y direction and the detection direction D1 of the first layer 40 has elapsed, when the plate wave QW arrives at the area overlapping with the first table 14 in the Y direction as shown in Fig. 18, the plate wave (the remaining part of the plate wave) PW2 from the plate wave QW propagates from the first end face e1 to the first layer 40 through the first table 14 and the third layer 61. Since the first layer 40 is formed in a trapezoidal shape, the maximum amplitude of the first layer 40 differs depending on the propagation direction of the plate wave PW1, i.e., the detection direction D1, and the propagation direction of the plate wave PW2, i.e., the reverse direction D2.

[0115] As shown in Fig. 17, in a time period t1 when only the plate wave PW1 propagates in the first layer 40, the amplitude caused by the plate wave PW1 is detected as information on the plate wave PW1. As shown in Fig. 18, in a time period (second time period) t2 when both the plate waves PW1 and PW2 propagate in the first layer 40, the information on the plate wave PW1 and the information on the plate wave PW2 are superimposed, and the amplitude caused by the superimposed plate waves PW1 and PW2 is obtained. As shown in Fig. 19, the amplitude and the level of the electric signal detected from the first layer 40 and the plurality of second layers 50 in the time period t2 are increased compared to the time period t1. An analysis device (not shown) of the plate wave detector 116 can detect the amplitude in the time period t1 and detect the generation and directionality of the plate wave PW1 after determining the start time of the time period t2 from the difference between the amplitude in the time period t1 and the amplitude in the time period t2. In addition, the analyzer of the plate wave detector 116 calculates the frequency components of the plate wave PW1 based on the electrical signals from the second layers 50 having different lengths in the horizontal direction D3, and quantitatively calculates the amplitude and strength of the plate wave PW1, which are proportional to the level of the electrical signals from at least one or more second layers 50.

[0116] The analysis device (not shown) sets the acquisition time of the first electric signal reflecting information on the amplitude of the plate wave PW1 (i.e., a part of the plate wave) in the detection direction D1 as described above, as a time window dt from the time when the plate wave PW1 arrives at the position P2 to the time when the plate wave PW2 (i.e., the remaining part of the plate wave) arrives at the position P1. The analysis device (not shown) defines the length of the first layer 40 in the detection direction D1 as LM and the velocities of the plate waves PW1 and PW2 as V. p When the time window dt is (LM / V p ) The length LM of the first layer 40 is equal to the length L5 of the first layer 40 described in the first embodiment and the length L5 of the first layer 40 shown in FIG. 1. This makes it possible to specify the detection time and propagation direction of the Plate wave PW1 without needing to measure the difference between the amplitude and the level of the electric signal detected in the time period t1 and the amplitude and the level of the electric signal detected in the time period t2.

[0117] The plate wave detector 116 of the fifth embodiment described above includes, as the base 12, the first base 14 and the second base 15 spaced apart from the first base 14 in the detection direction D1. The plate wave detector 116 of the fifth embodiment further includes, as the layer 22, a third layer 61 and a fourth layer 62 in addition to the first layer 40 and the plurality of second layers 50. The third layer 61 is provided on the surface 14a of the first base 14 and is connected to the first layer 40 at a position P1 of the side W1 in the detection direction D1. The fourth layer 62 is provided on the surface 15a of the second base 15 and is connected to the first layer 40 at a position P2 of the side W2 in the detection direction D1. In the plate wave detector 116 of the fifth embodiment, in addition to obtaining the same effects as those of the plate wave detector 111 of the first embodiment, the first base 14 and the second base 15 are separated from each other in the detection direction D1, and a space exists between the first layer 40 and the thin plate W in the Z direction. The plate wave detector 116 of the fifth embodiment includes an analyzer that acquires a first electric signal in a time period t1 reflecting information on the amplitude of the plate wave PW1 and a second electric signal in a time period t2 reflecting information on the amplitude of the plate wave PW1 and the amplitude of the plate wave PW2, and determines the propagation direction of the plate waves PW1 and QW based on the level difference between the first electric signal and the second electric signal and the length of each of the time periods t1 and t2. That is, the plate wave detector 116 of the fifth embodiment includes an analyzer that determines the length of the first layer 40 in the detection direction D1 as LM, the speed of the plate waves PW1 and PW2 as V, p When the time window (detection time) dt for detecting the plate wave PW1 propagating from the position (first position) P2 in the detection direction D1 on the first layer 40 is set as (LM / V p ) according to the plate wave detector 116 of the fifth embodiment. The plate wave detector 116 of the fifth embodiment can increase the difference between the amplitude detected in the time period t1 and the amplitude detected in the time period t2 compared with the plate wave detector 111 of the first embodiment, and can improve the discrimination sensitivity between the plate waves PW1 and PW2 and the detection sensitivity of the directionality of the plate waves QW and PW1. The plate wave detector of the other embodiments described in this specification may be appropriately equipped with the analysis device equipped in the plate wave detector 116 of the fifth embodiment.

[0118] In the plate wave detector 116 of the fifth embodiment, the same modified example as that of the plate wave detector 111 of the first embodiment is applied with respect to the shape of each of the first layer 40 and the plurality of second layers 50 and the number of the second layers 50. In the plate wave detector 116 of the fifth embodiment, the third layer 61 and the fourth layer 62 are formed in a rectangular shape, and the first base 14 and the second base 15 are formed in a hexahedron having rectangular surfaces 14a, 15a and bottom surfaces 14b, 15b. As a modified example of the plate wave detector 116 of the fifth embodiment, although not shown, the shapes of the third layer 61 and the fourth layer 62 can be changed to any shape as long as they can support the first layer 40 in the detection direction D1, and may be formed, for example, in a circular shape or a hexagonal shape. It is preferable that the shapes of the first base 14 and the second base 15 are appropriately set to a shape that overlaps with the third layer 61 and the fourth layer 62 when viewed from the Z direction.

[0119] For the operation of the plate wave detector 116 of the fifth embodiment, the third simulation described in the first embodiment and the calculation model MD2 shown in FIG. 6 can be referred to.

[0120] [Sixth embodiment] Next, a sixth embodiment of the present disclosure will be described.

[0121] 20 and 21, the plate wave detector 118 of the sixth embodiment includes a base 12 and a layer 22, similar to the plate wave detector 116 of the fifth embodiment. The base 12 includes a first base 14 and a second base 15. However, in the plate wave detector 118 of the sixth embodiment, the layer 22 includes a first layer 40, a plurality of electrodes 70, a third layer 61, and a fourth layer 62. That is, the plate wave detector 118 of the sixth embodiment includes a plurality of electrodes 70 instead of the plurality of second layers 50 of the plate wave detector 116 of the fifth embodiment, and includes the same components as the plate wave detector 116 of the fifth embodiment except for the plurality of second layers 50.

[0122] The multiple electrodes 70 in the sixth embodiment are configured by, for example, four electrodes 71 to 74. The electrodes 71 to 74 are provided on the surface 40a of the first layer 40. The bottom surface 70b of each of the electrodes 71 to 74 may be in direct contact with the surface 40a of the first layer 40, or may be in contact with the surface 40a of the first layer 40 via an adhesive (not shown).

[0123] The electrodes 71-74 are sequentially arranged at positions spaced apart from a predetermined position on the +Y side of the first layer 40 toward the -Y side in the opposite direction to the detection direction D1, that is, at positions spaced apart from a position closer to the first end face e1 than the second end face e2 along the detection direction D1 toward the second end face e2. Each of the electrodes 71-74 is formed in a substantially rectangular shape. The four sides of each of the electrodes 71-74 are equal to each other and are equal to or shorter than the side W1. The electrodes 71-74 are made of a conductive material, for example, aluminum (Al), gold (Au), or copper (Cu).

[0124] The positions of the electrodes 71-74 in the Y direction, i.e., the detection direction D1, correspond to the frequency of the frequency component of the detection target included in the plate wave PW1 of each of the electrodes 71-74. As described in the fifth embodiment with reference to Figs. 16 to 18, when at least the plate wave PW1 propagates from the plate wave QW to the first layer 40, the positions in the Y direction and the detection direction D1 where the first layer 40 largely vibrates in the Z direction due to the plate wave PW1 differ depending on the frequency of the detection target included in the plate wave PW1. For example, if the frequency of the detection target detected by the electrode 71 is ω1, the electrode 71 is disposed at the position in the Y direction where the first layer 40 vibrates most and the maximum amplitude appears due to the component of the frequency ω1 of the plate wave PW1 inputted from the second end face e2 to the first layer 40 and propagating in the detection direction D1. Similarly, if the frequencies to be detected by the electrodes 72, 73, and 74 are ω2, ω3, and ω4, the electrodes 72, 73, and 74 are disposed at positions in the Y direction where the first layer 40 vibrates most and the maximum amplitude appears due to the components of the frequencies ω2, ω3, and ω4 of the plate wave PW1. MIN and the highest frequency ω MAX is included between.

[0125] Of the sides and lateral faces of the electrodes 71 and 73 that are substantially parallel to the Y direction and the detection direction D1, the side W11 and the first side face s11 located on the -X side are disposed near the side W3 and the first side face s1 of the first layer 40 when viewed along the Z direction. Of the sides and lateral faces of the electrodes 72 and 74 that are substantially parallel to the Y direction and the detection direction D1, the side W12 and the second side face s2 located on the +X side are disposed near the side W4 and the second side face s2 of the first layer 40 when viewed along the Z direction. That is, the four electrodes 71 to 74 are disposed alternately at positions on the -X side and the +X side in the X direction with respect to the axis J101. By arranging the electrodes 71 to 74 as described above, the accuracy of distinguishing the electrical signals output from each of the electrodes 70 adjacent to each other in the Y direction and detection direction D1 is improved compared to when the electrodes 71 to 74 are arranged overlapping each other in the X direction on the axis J101 or when the electrodes 71 to 74 are arranged overlapping each other on the same side of either the ±X side relative to the axis J101 and at approximately the same position in the X direction.

[0126] The plate wave detector 118 of the sixth embodiment described above includes, as the base 12, the first base 14 and the second base 15 arranged apart from the first base 14 in the detection direction D1. The plate wave detector 118 of the sixth embodiment includes, as the layer 22, the first layer 40, the third layer 61, and the fourth layer 62. The plate wave detector 118 of the sixth embodiment further includes four electrodes 71-74 provided on the surface 40a of the first layer 40, instead of the four types of second layers 51A-54A, 51B-54B described in the fifth embodiment. The four electrodes 71-74 are provided at different positions in the Y direction and the detection direction D1, and are provided at positions where the maximum amplitude of the first layer 40 occurs due to the frequency component of the plate wave PW1 to be detected. According to the plate wave detector 118 of the sixth embodiment, in addition to obtaining the same effect as the plate wave detector 116 of the fifth embodiment, the electrodes 71-74 for detecting the frequency component of the plate wave PW1 are arranged in a region overlapping with the first layer 40 in the Z direction, and the components for detecting information about the plate wave PW1 provided between the third layer 61 and the fourth layer 62 in the detection direction D1 can be made smaller than that of the plate wave detector 116. The aforementioned components refer to the first layer 40 and the plurality of electrodes 70, and include the first layer 40 and the plurality of second layers 50 in the other embodiments.

[0127] In the plate wave detector 118 of the sixth embodiment, the same modified examples as those of the plate wave detector 111 of the first embodiment are applied to the configurations common to the plate wave detector 111 of the first embodiment, and the same modified examples as those of the plate wave detector 116 of the fifth embodiment are applied to the configurations common to the plate wave detector 111 of the fifth embodiment.

[0128] Further, the plate wave detector 118 of the sixth embodiment includes four electrodes 71 to 74. However, as a modified example of the plate wave detector 118 of the sixth embodiment, the plate wave detector of the sixth embodiment may include electrodes 70 equal to or more than the number of frequency components of the plate wave PW1 to be detected. Therefore, the plate wave detector of the sixth embodiment may include two or three electrodes 70, or may include five or more electrodes 70. Regardless of the total number, the electrodes 70 are provided at positions where the maximum amplitude of the first layer 40 occurs according to the frequency of the plate wave PW1 to be detected by the electrodes 70. Note that the positions where the maximum amplitude of the first layer 40 occurs according to the frequency components of the plate wave PW1 to be detected by each electrode 70 can be calculated in advance at the time of designing the plate wave detector 118 by using a numerical calculation based on a frequency analysis or a simulation similar to the second simulation of the first embodiment.

[0129] [Seventh embodiment] Next, a seventh embodiment of the present disclosure will be described.

[0130] As shown in Fig. 22, the plate wave detector 126 of the seventh embodiment includes two plate wave detectors 116A and 116B having the same configuration as the plate wave detector 116 of the fifth embodiment. However, in the plate wave detector 126, the plate wave detector 116B is disposed at a position on the -X side of the plate wave detector 118A. In the plate wave detector 126, the side W2 of the plate wave detector 116A and the side W1 of the plate wave detector 116B overlap each other in the Y direction. The side W1 of the plate wave detector 116A and the side W2 of the plate wave detector 116B overlap each other in the Y direction. In the plate wave detector 126, the detection direction D1 of the plate wave detector 116A is the same as the Y direction, whereas the detection direction D1 of the plate wave detector 116B is parallel to the Y direction and is opposite to the Y direction. The plate wave detector 126 has two axes J111 and J112. The axis J111 corresponds to the axis J101 of the plate wave detector 118A, and passes through the centers of the sides W1 and W2 of the first layer 40 in the detection direction D11 that is disposed on the +X side in the X direction of the two first layers 40. The axis J112 corresponds to the axis J101 of the plate wave detector 118B, and passes through the centers of the sides W1 and W2 of the first layer 40 in the detection direction D12 that is disposed on the -X side in the X direction of the two first layers 40.

[0131] In the plate wave detecting device 126, the third layer 61 of the plate wave detector 116A and the fourth layer 62 of the plate wave detector 116B are disposed in a region on the +Y side of the center (not shown) of the plate wave detecting device 126 in the detection direction D1. The third layer 61 of the plate wave detector 116A and the fourth layer 62 of the plate wave detector 116B are integrally formed with each other in a common fifth layer (layer) 65. The fourth layer 62 of the plate wave detector 116A and the third layer 61 of the plate wave detector 116B are disposed in a region on the -Y side of the center of the plate wave detecting device 126 in the detection direction D1. The fourth layer 62 of the plate wave detector 116A and the third layer 61 of the plate wave detector 116B are integrally formed with each other in a common sixth layer (layer) 66.

[0132] The first base 14 of the plate wave detector 116A and the second base 15 of the plate wave detector 116B are disposed in a region on the +Y side of the center (not shown) of the plate wave detecting device 126 in the detection direction D1. In the plate wave detecting device 126, the first base 14 of the plate wave detector 116A and the second base 15 of the plate wave detector 116B are integrally formed with each other in a common third base 17. The second base 15 of the plate wave detector 116A and the first base 14 of the plate wave detector 116B are disposed in a region on the -Y side of the center of the plate wave detecting device 126 in the detection direction D1. The second base 15 of the plate wave detector 116A and the first base 14 of the plate wave detector 116B are integrally formed with each other in a common fourth base 18.

[0133] The plate wave detection device 126 of the seventh embodiment described above includes two plate wave detectors 116A and 116B. In the plate wave detection device 126 of the seventh embodiment, the third layer 61 and the first base 14 of one plate wave detector 116 of the two plate wave detectors 116 and the fourth layer 62 and the second base 15 of the other plate wave detector 116 are integrated into a common fifth layer 65 and third base 17. According to the plate wave detection device 126 of the seventh embodiment, it is possible to reduce the size of the device and shorten the installation work time compared to a case where the two plate wave detectors 116 are spaced apart from each other in the X direction and arranged in a non-connected state, although not shown.

[0134] In addition, in the plate wave detection device 126 of the seventh embodiment, the fourth layer 62 and the second base 15 of one plate wave detector 116 of the two plate wave detectors 116, 116 and the third layer 61 and the first base 14 of the other plate wave detector 116 are integrated into a common sixth layer 66 and fourth base 18. The first end face e1 of the first layer 40 of the plate wave detector (one plate wave detector) 116A and the second end face e2 of the first layer 40 of the plate wave detector (the other plate wave detector) 116B are connected to the fifth layer 65. The second end face e2 of the first layer 40 of the plate wave detector 116A and the first end face e1 of the first layer 40 of the plate wave detector 116B are connected to the sixth layer 66. In the plate wave detection device 126 of the seventh embodiment, the two first layers 40 are arranged apart from the thin plate W in the Z direction. According to the lamb wave detection device 126 of the seventh embodiment, similarly to the lamb wave detector 116 of the fifth embodiment, the difference between the amplitude of the electrical signal detected in each of the lamb wave detectors 116A and 116B in the time period when only the lamb wave PW1 propagates and the amplitude of the electrical signal detected in the time period when the lamb waves PW1 and PW2 (not shown) are superimposed is enlarged compared to the lamb wave detection device 122 of the third embodiment, and the sensitivity of discrimination between the lamb wave PW1 and the lamb wave PW2, i.e., the detection sensitivity of the directionality of the lamb wave PW1 can be improved.

[0135] In addition, in the plate wave detection device 126 of the seventh embodiment, the detection directions D1 of the plate wave detectors 116A and 116B are parallel to each other, and the detection directions D1 from the side W1 to the side W2 of the plate wave detectors 116A and 116B adjacent to each other in the X direction are arranged opposite to each other. According to the plate wave detection device 126 of the seventh embodiment, not only the plate wave PW1 having the propagation direction of the detection direction D1 of the plate wave detector 116A but also the plate wave PW1 having the propagation direction of the detection direction D1 of the plate wave detector 116B can be detected. That is, according to the plate wave detection device 126 of the seventh embodiment, the plate wave PW1 having the same propagation direction as the detection direction D21 and the plate wave PW1 having the propagation direction of the detection direction D22 opposite to the detection direction D21 can be detected. The detection direction D21 corresponds to the detection direction D1 of the plate wave detector 116A. The detection direction D22 corresponds to the detection direction D1 of the plate wave detector 116B.

[0136] In the plate wave detecting device 126 of the seventh embodiment, the relative arrangement of the first layer 40 and the plurality of second layers 50 of the plate wave detector 116A and the first layer 40 and the plurality of second layers 50 of the plate wave detector 116B may be reversed in the X direction. That is, in the plate wave detecting device 126, the plate wave detector 116B may be disposed in an area on the +X side of the plate wave detector 116A.

[0137] As a first modification of the plate wave detection device 126 of the seventh embodiment, the detection directions D1 of the plate wave detectors 116A and 116B may be directed to any direction in the XY plane, as long as the detection directions D1 of the plate wave detectors 116A and 116B are parallel to each other. For example, as shown in FIG. 23, in a plate wave detection device 127 of the modification of the seventh embodiment, the detection direction D1 of the plate wave detector 116A is the same as the X direction. The plate wave detector 116B is disposed at a position on the +Y side of the plate wave detector 116A. In the plate wave detection device 127, the side W2 of the plate wave detector 116A and the side W1 of the plate wave detector 116B overlap each other in the X direction. The side W1 of the plate wave detector 116A and the side W2 of the plate wave detector 116B overlap each other in the X direction. In the plate wave detection device 127, the detection direction D1 of the plate wave detector 116B is parallel to the X direction and is opposite to the X direction. According to the plate wave detecting device 127 of the modification of the seventh embodiment, the same action and effect as the plate wave detecting device 126 of the seventh embodiment can be obtained, and the plate wave PW1 having the same propagation direction as the detection direction D23 and the plate wave PW1 having the propagation direction of the detection direction D24 opposite to the detection direction D23 can be detected. The detection direction D23 corresponds to the detection direction D1 of the plate wave detector 116A. The detection direction D24 corresponds to the detection direction D1 of the plate wave detector 116B.

[0138] In the plate wave detecting device 127 of the modified example of the seventh embodiment, the relative arrangement of the first layer 40 and the plurality of second layers 50 of the plate wave detector 116A and the first layer 40 and the plurality of second layers 50 of the plate wave detector 116B may be reversed in the Y direction. That is, in the plate wave detecting device 127, the plate wave detector 116B may be disposed in an area on the -Y side of the plate wave detector 116A.

[0139] As a second modification of the plate wave detecting device 126 of the seventh embodiment, plate wave detectors 118A and 118B may be provided instead of the plate wave detectors 116A and 116B. For example, as shown in FIG. 24, the plate wave detecting device 128 of the modification of the seventh embodiment is equipped with two plate wave detectors 118A and 118B, and is a device in which the four types of second layers 51A-54A and 51B-54B in the plate wave detecting device 126 of the seventh embodiment are replaced with four electrodes 71-74. According to the plate wave detecting device 128 of the modification of the seventh embodiment, the same action and effect as the plate wave detecting device 126 of the seventh embodiment can be obtained, and the plate wave PW1 having the same propagation direction as the detection direction D21 and the plate wave PW1 having the propagation direction of the detection direction D22 can be detected. In this modification, the detection direction D21 corresponds to the detection direction D1 of the plate wave detector 118A. The detection direction D22 corresponds to the detection direction D1 of the plate wave detector 118B. Furthermore, according to the plate wave detecting device 128 of the modified example of the seventh embodiment, the components of the plate wave detectors 118A and 118B that detect information regarding the plate wave PW1 can be made smaller than those of the plate wave detecting device 126.

[0140] As a third modification of the plate wave detection device 126 of the seventh embodiment, in the plate wave detection device 128 of the modification of the seventh embodiment, the detection direction D1 of the plate wave detectors 118A, 118B may be directed to any direction in the XY plane. For example, as shown in FIG. 25, the plate wave detection device 129 of the modification of the seventh embodiment is a device including two plate wave detectors 118A, 118B, and replacing the four types of second layers 51A-54A, 51B-54B in the plate wave detection device 127 of the modification of the seventh embodiment with four electrodes 71-74. According to the plate wave detection device 129 of the modification of the seventh embodiment, the same action and effect as the plate wave detection device 127 of the seventh embodiment can be obtained, and the plate wave PW1 having the same propagation direction as the detection direction D23 and the plate wave PW1 having the propagation direction of the detection direction D24 can be detected. In this modification, the detection direction D23 corresponds to the detection direction D1 of the plate wave detector 118A. The detection direction D24 corresponds to the detection direction D1 of the plate wave detector 118B. According to the plate wave detecting device 129 of the modified example of the seventh embodiment, each of the components of the plate wave detectors 118A and 118B that detect information related to the plate wave PW1 can be made smaller than that of the plate wave detecting device 127.

[0141] In addition, all of the modifications described in the first embodiment can be applied to the plate wave detector 116 provided in the plate wave detection device 126 of the seventh embodiment and the plate wave detection device 127 of the above-mentioned modified example, and the plate wave detector 118 provided in the plate wave detection devices 128, 129 of the above-mentioned modified examples.

[0142] [Eighth embodiment] Next, an eighth embodiment of the present disclosure will be described.

[0143] As shown in Fig. 26, the plate wave detection device 131 of the eighth embodiment includes a plurality of plate wave detectors 116. In Fig. 22, for example, four plate wave detectors 116A to 116D are extracted and illustrated from the plurality of plate wave detectors 116. In the plate wave detection device 131, the plurality of plate wave detectors 116 are arranged so as to spread radially from a predetermined position PC. An axis J101 of each of the plurality of plate wave detectors 116 spreads radially from the position PC and intersects with each other at the position PC. A detection direction D1 of each of the plurality of plate wave detectors 116 overlaps with a radial direction centered on the position PC. The direction of the detection direction D1 of each of the plurality of plate wave detectors 116 is a direction toward the position PC.

[0144] In the plate wave detection device 131, the third layer 61 of the plurality of plate wave detectors 116 is constituted by a common seventh layer (center layer) 67. The centers of the top and bottom surfaces of the seventh layer 67 overlap with the position PC. The first bases 14 of the plurality of plate wave detectors 116 are constituted by a common fifth base (center base) 19. The fourth layer 62 and the second base 15 of the plurality of plate wave detectors 116 are arranged concentrically around the position PC, and are spaced apart in the circumferential direction around the position PC.

[0145] In addition, when the total number of plate wave detectors 116 is four and the axes J101 of the four plate wave detectors 116A to 116D are arranged at intervals of 90 [deg.] in the circumferential direction centered on the position PC as shown in Fig. 22, the third layer 61 and the seventh layer 67 are formed in a rectangular shape. Even if the total number of plate wave detectors 116 is two or three, when two or three plate wave detectors 116 are arranged at positions overlapping any two or three of the four plate wave detectors 116A to 116D shown in Fig. 22 and the axes J101 are arranged at angular intervals of an integral multiple of 90 [deg.] in the circumferential direction centered on the position PC, the third layer 61 and the seventh layer 67 are formed in a rectangular shape.

[0146] When the total number of plate wave detectors 116 is a natural number B of 2 or more, and the angle between the axes J101 of the B plate wave detectors 116 in the circumferential direction centered on the position PC, i.e., the angle difference between the axes J101, is an angle other than an integer multiple of 90 degrees, the seventh layer 67 is formed in a polygonal shape including all the sides W1 of the B plate wave detectors 116. In the plate wave detecting device 131 including the four plate wave detectors 116A to 116D shown in Fig. 22, the seventh layer 67 is formed in a rectangular shape including the sides W1 of the plate wave detectors 116A to 116D as its four sides. Although not shown, for example, when the total number of plate wave detectors 116 is three and the angular differences between the axes J101 of the three plate wave detectors 116 are equal to each other and are 120 degrees, the seventh layer 67 is formed in a triangular shape including the sides W1 of the three plate wave detectors 116 as three sides. When the total number of plate wave detectors 116 is B, the angular differences between the axes J101 of the B plate wave detectors 116 do not have to be equal to each other and are set at any angle, and the seventh layer 67 is formed in a polygonal shape including the sides W1 of the B plate wave detectors 116 on the periphery.

[0147] When the plate wave detecting device 131 is disposed on the surface a of the thin plate W of the structure T, the plate wave PW1 propagating in at least one or more detection directions D1 of the detection directions D11, ..., D14, ... of the plurality of plate wave detectors 116 is detected by the plate wave detector 116 having at least one detection direction D1. An analysis device (not shown) of the plate wave detecting device 131 receives electrical signals from the first layer 40 and each of the plurality of second layers 50 for each of the plurality of plate wave detectors 116 individually.

[0148] The analyzer of the plate wave detection device 121 judges whether or not the plate wave PW1 is detected by each of the plate wave detectors 116 as described in the first embodiment, based on the level of the electric signal output from each of the second layers 51A-54A and the second layers 51B-54B for each of the plate wave detectors 116. Next, the analyzer of the plate wave detection device 131 calculates the three-dimensional position of the source of the plate wave PW1 in the thin plate W and the frequency distribution of the plate wave PW1 based on the electric signal from the plate wave detector 116 that is judged to have detected the plate wave PW1 among the plate wave detectors 116, and obtains the strain at the position of the source of the thin plate W and the stress distribution of the thin plate W. The analyzer of the plate wave detection device 131 quantitatively analyzes the state of the structure T and the presence or absence of damage.

[0149] The plate wave detection device 131 includes an analyzer (not shown) provided in each of the plate wave detectors 116, and a second analyzer (not shown) that quantitatively analyzes the state of the structure T and the presence or absence of damage by collecting information on the determination result of whether the plate wave PW1 is detected or not calculated for each plate wave detector 116 from the analyzers, and information on the position of the source of the plate wave PW1 and the frequency distribution of the plate wave PW1. Note that, like the plate wave detection device 121 of the second embodiment, the plate wave detection device 131 may be capable of collecting the electric signals from the first layer 40 and the plurality of second layers 50 for each of the plurality of plate wave detectors 116 individually and collectively, and may include a device that serves both as the above-mentioned analyzer (not shown) and the second analyzer.

[0150] The plate wave detection device 131 of the eighth embodiment described above includes a plurality of plate wave detectors 116. In the plate wave detector 131 of the eighth embodiment, the plate wave detectors 116 are arranged so as to radiate from a predetermined position PC as a center. The detection directions D1 of the plurality of plate wave detectors 116 are directed to a common position PC. According to the plate wave detection device 131 of the eighth embodiment, the same action and effect as the plate wave detector 121 of the second embodiment can be obtained, and the plate wave PW1 propagating along the detection directions D11, ..., D14, ... which are different from each other in the XY plane parallel to the surface a of the thin plate W and the number of the detection directions D11, ..., D14, ... is the same as the total number of the plate wave detectors 116, can be detected by using the plurality of plate wave detectors 116. This makes it possible to specify the angle of the plate wave PW1 input from the thin plate W in the XY plane. Each of the detection directions D11, ..., D14, ... corresponds to the detection direction D1 of each of the plurality of plate wave detectors 116A, ..., 116D, ....

[0151] In the plate wave detection device 131 of the eighth embodiment, the third layer 61 of the plurality of plate wave detectors 116 is integrated into a common seventh layer 67. According to the plate wave detection device 131 of the eighth embodiment, it is possible to reduce the space of the entire device and shorten the installation work time, compared to a case in which the plurality of plate wave detectors 116 are arranged in a non-connected state at intervals from each other in the circumferential direction centered on the position PC (not shown).

[0152] In addition, in the plate wave detection device 131 of the eighth embodiment, the first unit 14, the fifth unit 19 and the second unit 15 of the plate wave detectors 116 are arranged in a non-connected state, separated from each other. Therefore, in the plate wave detection device 126 of the eighth embodiment, the first layer 40 of each of the plate wave detectors 116 is arranged in a Z direction separated from the thin plate W. Therefore, according to the plate wave detection device 131 of the eighth embodiment, similarly to the plate wave detector 116 of the fifth embodiment, the difference between the amplitude of the electric signal detected in the time period when only the plate wave PW1 propagates in each of the plate wave detectors 116 and the amplitude of the electric signal detected in the time period when the plate waves PW1 and PW2 (not shown) are superimposed is enlarged compared to the plate wave detection device 121 of the second embodiment, and the sensitivity of discrimination between the plate wave PW1 and the plate wave PW2, that is, the detection sensitivity of the directionality of the plate wave PW1 can be improved.

[0153] The total number of the plate wave detectors 116 included in the plate wave detection device 131 of the eighth embodiment is appropriately set to be equal to or more than the number of types of propagation directions of the plate wave PW1 to be detected in the XY plane. The propagation direction of the plate wave PW1 to be detected in the XY plane is not limited to a specific direction. In the plate wave detection device 131 of the eighth embodiment, the axis lines J101 parallel to the detection direction D1 of each of the plate wave detectors 116 are arranged at equal angular intervals in the circumferential direction centered on the position PC. As a modified example of the plate wave detection device 121 of the second embodiment, although not shown, the axis lines J101 of the multiple plate wave detectors 116 may be arranged at different angular intervals in the circumferential direction centered on the position PC, or may be arranged at any angular interval. The multiple plate wave detectors 116 are arranged with their respective axis lines J101 parallel to any propagation direction of the plate wave PW1 to be detected in the XY plane.

[0154] Moreover, all of the modifications described in the first and fifth embodiments can be applied to the plate wave detector 116 included in the plate wave detecting device 131 of the eighth embodiment and the plate wave detecting device of the above-mentioned modifications.

[0155] As a first modification of the plate wave detection device 131 of the eighth embodiment, a plurality of plate wave detectors 118 may be provided instead of the plurality of plate wave detectors 116. For example, as shown in FIG. 27, the plate wave detection device 132 of the modification of the eighth embodiment is a device including a plurality of plate wave detectors 118, and replacing the four types of second layers 51A-54A, 51B-54B in the plate wave detection device 131 of the eighth embodiment with four electrodes 71-74. According to the plate wave detection device 132 of the modification of the eighth embodiment, the same action and effect as the plate wave detection device 131 of the eighth embodiment can be obtained, and the plate wave PW1 propagating along the same number of detection directions D11, ..., D14, ... as the total number of the plate wave detectors 118 can be detected. This allows the angle of the plate wave PW1 input from the thin plate W in the XY plane to be well specified. In addition, each of the detection directions D11, ..., D14, ... in this modification corresponds to the detection direction D1 of each of the plurality of plate wave detectors 118A, ..., 118D, .... In addition, according to the plate wave detecting device 132 of the modification of the eighth embodiment, each component of the plurality of plate wave detectors 118 that detects information related to the plate wave PW1 can be made smaller than that of the plate wave detecting device 131.

[0156] As a second modification of the plate wave detection device 131 of the eighth embodiment, a plurality of plate wave detection devices 126 may be provided instead of the plurality of plate wave detectors 116. For example, as shown in Fig. 28, a plate wave detection device (composite plate wave detection device) 133 of the modification of the eighth embodiment includes a plurality of plate wave detection devices 126. In Fig. 28, for example, four plate wave detection devices 126A to 126D are extracted and illustrated from the plurality of plate wave detection devices 126. In the plate wave detection device 133, a center line C101 between two axes J111, J112 of each of the plurality of plate wave detection devices 126 spreads radially from a position PC and intersects at the position PC. The detection directions D21, D22 of each of the plurality of plate wave detection devices 126 are parallel to a radial direction centered on the position PC.

[0157] In the plate wave detection device 133, the third layer 61 of the plurality of plate wave detection devices 126 is constituted by a common seventh layer (center layer) 67. The centers of the front and bottom surfaces of the seventh layer 67 overlap the position PC. The first base 14 of the plurality of plate wave detection devices 126 is constituted by a common fifth base (center base) 19. The fourth layer 62 and the second base 15 of the plurality of plate wave detection devices 126 are concentrically arranged around the position PC, and are arranged at intervals in the circumferential direction around the position PC. The seventh layer 67 is formed in a rectangular shape including, as its four sides, the sides W1 and W2 of the two first layers 40 of each of the plate wave detection devices 126A to 126D, which are arranged closer to the position PC in the radial direction around the position PC. When the total number of plate wave detection devices 126 included in the plate wave detection device 133 is any natural number E equal to or greater than 2, the angular differences between the center lines C101 of the E plate wave detection devices 126 in the circumferential direction about the position PC do not have to be equal to each other and are set to any angle. The seventh layer 67 of the plate wave detection device 133 is formed in a polygonal shape including, on its periphery, the sides W1 and W2 of the E plate wave detection devices 126 that are located closer to the position PC in the radial direction about the position PC.

[0158] When the plate wave detecting device 133 is disposed on the surface a of the thin plate W of the structure T, the plate wave PW1 propagating in at least one or more detection directions D31A, ... or the plate wave PW1 propagating in detection directions D31B, ... of the detection directions of the plurality of plate wave detecting devices 126 is detected by one or more plate wave detecting devices 126. An analysis device (not shown) of the plate wave detecting device 133 individually receives an electric signal from each of the first layer 40 and the plurality of second layers 50 in the detection direction D31A, ... and an electric signal from each of the first layer 40 and the plurality of second layers 50 in the detection direction D31B, ... for each of the plurality of plate wave detecting devices 126.

[0159] The analysis device of the plate wave detection device 133 performs the same processing as the analysis device of the plate wave detection device 131, and calculates the three-dimensional position of the source of the plate wave PW1 in the thin plate W and the frequency distribution of the plate wave PW1 based on the electric signal from the plate wave detection device 126 that is determined to have detected the plate wave PW1 among the multiple plate wave detection devices 126, and obtains the strain at the position of the source of the thin plate W and the stress distribution of the thin plate W. The analysis device of the plate wave detection device 133 quantitatively analyzes the state of the structure T and the presence or absence of damage.

[0160] The plate wave detection device 133 includes an analyzer (not shown) provided in each of the plate wave detection devices 126, and a second analyzer (not shown) that quantitatively analyzes the state of the structure T and the presence or absence of damage by collecting information on the determination result of whether the plate wave PW1 is detected in either of the two opposite detection directions calculated for each plate wave detection device 126 from these analyzers, and information on the position of the source of the plate wave PW1 and the frequency distribution of the plate wave PW1. Note that the plate wave detection device 133 may be capable of individually and collectively collecting and processing electric signals from each of the first layer 40 and the multiple second layers 50, which have the opposite detection directions D21 and D22 as the directionality of the detection target, in each of the multiple plate wave detection devices 126, and may include a device that serves as the above-mentioned analyzer and the second analyzer (not shown).

[0161] According to the plate wave detection device 133 of the modification of the eighth embodiment, the same action and effect as the plate wave detection device 131 of the eighth embodiment can be obtained, and the plate wave PW1 propagating along the detection directions D31A, ... of the same number as the total number of the plate wave detection devices 126, and the plate wave PW1 propagating along the detection directions D31B, ... opposite to the detection directions D31A, ... can be detected. This makes it possible to well specify the angle and directivity in the XY plane of the plate wave PW1 input from the thin plate W, and to easily determine whether the source of the plate wave PW1 (not shown) exists in the area surrounded by the fourth layer 62 of the plurality of plate wave detection devices 126 or outside the area in the XY plane. Each of the detection directions D31A, ... in this modification corresponds to one of the detection directions D21, D22 of each of the plurality of plate wave detection devices 126. Each of the detection directions D31B, . . . in this modification corresponds to the other of the detection directions D21, D22 of each of the plurality of plate wave detecting devices 126.

[0162] As a third modification of the plate wave detection device 131 of the eighth embodiment, a plurality of plate wave detectors 128 may be provided instead of the plurality of plate wave detectors 126 of the plate wave detection device 132 described above. For example, as shown in Fig. 29, a plate wave detection device (composite plate wave detection device) 134 of the modification of the eighth embodiment is a device that includes a plurality of plate wave detectors 128 and replaces the plurality of second layers 50 in the plate wave detection device 133 of the second modification of the eighth embodiment with the same number of electrodes 70. According to the plate wave detection device 134 of the modification of the eighth embodiment, the same action and effect as the plate wave detection device 133 of the eighth embodiment can be obtained, and the plate waves PW1 propagating along the same number of detection directions D31A, ... as the total number of the plate wave detection devices 128, and the plate waves PW1 propagating along the detection directions D31B, ... opposite to the detection directions D31A, ... can be detected. This allows the angle of the plate wave PW1 input from the thin plate W in the XY plane to be well specified, and allows easy determination as to whether the source of the plate wave PW1 (not shown) is present in the area surrounded by the fourth layer 62 of the plate wave detection devices 126 or outside the area in the XY plane. Each of the detection directions D31A, ... in this modification corresponds to one of the detection directions D21, D22 of each of the plate wave detection devices 128. Each of the detection directions D31B, ... in this modification corresponds to the other of the detection directions D21, D22 of each of the plate wave detection devices 128. In addition, according to the plate wave detection device 134 of the modification of the eighth embodiment, each component of the plate wave detector 128 that detects information related to the plate wave PW1 can be made smaller than that of the plate wave detection device 133.

[0163] According to at least one of the embodiments described above, plate waves that generate stress and volumetric strain in a thin plate W of a hollow structure T made of the thin plate W can be detected easily and with high sensitivity.

[0164] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0165] 111,111A,111B,111C,111D,111E,111F,111G,111H,111I,111J,112,116,116A,11 6B,118,118A,118B...plate wave detector, 12...base, 12a...surface, 22...layer, 40...first layer, 50...second layer, D1...detection direction, D3...horizontal direction

Claims

1. A base, a layer provided on a surface of the base and thinner than the base; Equipped with the layer includes a first layer having a first side extending along a lateral direction perpendicular to the detection direction at a first position in the detection direction parallel to the surface, and a second side extending along the lateral direction at a second position in the detection direction away from the first position; a length of the first side in the horizontal direction and a length of the second side in the horizontal direction are different from each other, The base is The first one, a second unit disposed apart from the first unit in the detection direction; It is composed of The layer comprises: a third layer provided on a surface of the first base and connected to the first layer at the first side; a fourth layer provided on a surface of the second platform and connected to the first layer at the second side; Further comprising Plate wave detector.

2. A base, a layer provided on a surface of the base and thinner than the base; Equipped with the layer includes a first layer having a first side extending along a lateral direction perpendicular to the detection direction at a first position in the detection direction parallel to the surface, and a second side extending along the lateral direction at a second position in the detection direction away from the first position; a length of the first side in the horizontal direction and a length of the second side in the horizontal direction are different from each other, The length of the first layer in the detection direction is LM, and the velocity of the plate wave is V ｐ When the detection time of the plate wave propagating in the detection direction from the first position in the first layer is expressed as (LM / V ｐ ) An analysis device for calculating the Plate wave detector.

3. the first layer is formed in a trapezoidal shape having the first side, the second side, a third side connecting an end of the first side in the horizontal direction of the first side and an end of the second side in the horizontal direction of the first side, and a fourth side connecting an end of the second side opposite to the first side in the horizontal direction of the first side and an end of the second side opposite to the first side in the horizontal direction of the second side, 3. The plate wave detector according to claim 1 or 2.

4. the layer further comprises a plurality of second layers connected to the first layer; each of the plurality of second layers has a predetermined length in the lateral direction; The predetermined length of each of the plurality of second layers is determined by a frequency of a detection target included in a frequency range of a plate wave propagating through the first layer. A plate wave detector according to any one of claims 1 to 3.

5. the layer further comprises a plurality of second layers connected to the first layer; the second layers are connected at intervals along each of the third side and the fourth side; the lateral length of the plurality of second layers is longer as the connection position with the first layer is closer to one of the first side and the second side; 4. The plate wave detector according to claim 3.

6. An electrode is provided on a surface of the first layer, The position of the electrode in the detection direction is determined by a frequency of the detection target included in a frequency range of the plate wave propagating through the first layer. A plate wave detector according to any one of claims 1 to 3.

7. The layer is formed of a piezoelectric material or an electret. A plate wave detector according to any one of claims 1 to 6.

8. An adhesive film is provided on a bottom surface of the base opposite to the surface. A plate wave detector according to any one of claims 1 to 7.

9. A plate wave detection device having a plurality of plate wave detectors according to any one of claims 1 to 8, Further, an analysis device is provided for calculating the position of the source of the plate wave based on the distance between two plate wave detectors among the plurality of plate wave detectors that detect the propagation direction of the plate wave with higher sensitivity than the other plate wave detectors, and the angle between a line connecting each of the two plate wave detectors and the source of the plate wave and the surface of the thin plate on which the plate wave detection device is installed. Plate wave detector.

10. A plate wave detection device comprising: a base; and a layer provided on a surface of the base and thinner than the base, the layer having a first side extending along a lateral direction perpendicular to a detection direction at a first position in the detection direction parallel to the surface, and a second side extending along the lateral direction at a second position in the detection direction away from the first position, the plate wave detection device having a plurality of plate wave detectors in which the lateral length of the first side and the lateral length of the second side are different from each other, Further, an analysis device is provided for calculating the position of the source of the plate wave based on the distance between two plate wave detectors among the plurality of plate wave detectors that detect the propagation direction of the plate wave with higher sensitivity than the other plate wave detectors, and the angle between a line connecting each of the two plate wave detectors and the source of the plate wave and the surface of the thin plate on which the plate wave detection device is installed. Plate wave detector.

11. A plate wave detector according to any one of claims 1 to 8, A plurality of plate wave detectors are arranged concentrically around a predetermined position, The detection directions of the plurality of plate wave detectors are radially expanded from the predetermined position or directed toward the predetermined position. Plate wave detector.

12. A plurality of plate wave detectors according to claim 1 are provided, A plurality of plate wave detectors are arranged radially around a predetermined position, The detection directions of the plurality of plate wave detectors are radially expanded from the predetermined position or directed toward the predetermined position; Either one of the first and second units of the plurality of plate wave detectors is configured with a common center unit, and one of the third and fourth layers of the plurality of plate wave detectors provided on one of the units is configured with a common center unit. Plate wave detector.

13. A plate wave detector according to any one of claims 1 to 8, The detection directions of the plurality of plate wave detectors are parallel to each other; The detection directions of two adjacent plate wave detectors in the horizontal direction among the plurality of plate wave detectors are opposite to each other. Plate wave detector.

14. A plate wave detector comprising: a base; and a layer provided on a surface of the base and thinner than the base, the layer having a first side extending along a lateral direction perpendicular to a detection direction at a first position in the detection direction parallel to the surface, and a second side extending along the lateral direction at a second position in the detection direction away from the first position; the plate wave detector comprising a plurality of plate wave detectors, the lateral length of the first side and the lateral length of the second side being different from each other; The detection directions of the plurality of plate wave detectors are parallel to each other; The detection directions of two adjacent plate wave detectors in the horizontal direction among the plurality of plate wave detectors are opposite to each other. Plate wave detector.

15. A plurality of plate wave detectors according to claim 1 are provided, The detection directions of the plurality of plate wave detectors are parallel to each other; The detection directions of two adjacent plate wave detectors in the lateral direction among the plurality of plate wave detectors are opposite to each other, The third layer or the fourth layer arranged in a region on one side of the center in the detection direction of the plurality of plate wave detectors is composed of a fifth layer in common with each other, and the fourth layer or the third layer arranged in a region on the other side of the center is composed of a sixth layer in common with each other, The first or second units arranged in the region on one side of the plurality of plate wave detectors are constituted by a common third unit, and the first or second units arranged in the region on the other side are constituted by a common fourth unit. Plate wave detector.

16. A plate wave detection device according to claim 15, A plurality of plate wave detection devices are arranged radially around a predetermined position, Either one of the third and fourth units of the plurality of plate wave detectors is configured as a common center unit, and one of the fifth and sixth layers of the plurality of plate wave detectors provided on one of the units is configured as a common center unit. Composite plate wave detector.

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