Sensor device based on Bragg grating and building structure displacement monitoring device

Abstract

The utility model discloses a sensor device based on a Bragg grating and a building structure displacement monitoring device. The sensor device comprises two optical fiber supports, a supporting rod, a signal transmitting optical fiber and a signal receiving optical fiber. Wherein the signal transmitting optical fiber is obtained by arranging an ultrasonic signal transmitting section on a single-mode optical fiber, and the ultrasonic signal transmitting section is formed by stripping a cladding of the single-mode optical fiber and coating a stripping area with a photoacoustic conversion material; the signal receiving optical fiber is a fiber bragg grating; the supporting rod and the signal transmitting optical fiber penetrate through the two optical fiber supports in parallel. The signal receiving optical fiber is fixed to one end faces of the two optical fiber supports and parallel to the signal transmitting optical fiber. And the ultrasonic signal transmitting section of the signal transmitting optical fiber and the Bragg grating of the signal receiving optical fiber are positioned between the two optical fiber brackets. The building structure health monitoring device is simple in structure, small in size, light in weight, good in corrosion resistance, strong in interference resistance and high in sensitivity, can realize real-time continuous monitoring, and can be widely applied to health monitoring of building structures.

Description

Technical Field

[0001] This application belongs to the field of building health monitoring technology, specifically to a sensor device based on a Bragg grating, a building structure displacement monitoring device and method. Background Technology

[0002] Structural displacement is a crucial indicator of a building's stability and safety. Traditional methods for monitoring structural displacement include visual inspection, vibration testing, electrical detection, stress-strain testing, and temperature detection. Visual inspection relies on experience, is highly subjective, and struggles to detect structural problems. Vibration testing is significantly affected by environmental noise and has low sensitivity to minor damage. Electrical detection, stress-strain testing, and temperature detection require the installation of corresponding sensors, necessitating localized modifications or drilling into the structure, thus compromising its integrity. Furthermore, these common methods struggle to simultaneously meet the multiple requirements of high accuracy, real-time performance, and low interference when monitoring complex structures over long periods and at high frequencies.

[0003] Acoustic detection methods can monitor minute displacements in building structures over long periods and at high frequencies without damaging the overall structure. Commonly used acoustic detection methods include acoustic emission (AE) and ultrasonic testing (UT). AE is a damage detection method; its principle is that the sound generated when a solid deforms or breaks is emitted as an elastic wave. This phenomenon is called acoustic emission, and the elastic wave can be detected by an acoustic emission sensor. Small deformations or micro-cracks in building structures are accompanied by acoustic emission, thus displacement caused by structural damage can be detected based on acoustic emission. However, AE relies on acoustic emission caused by existing damage, making it a passive monitoring method. It also suffers from drawbacks such as weak signal strength, susceptibility to noise interference, and limited ability to locate the displacement sound source. Ultrasonic testing, on the other hand, is an active monitoring method. It generates a strong signal, has improved anti-interference capabilities, and can accurately locate displacement.

[0004] However, current ultrasonic testing methods face key challenges in terms of receivers and signal processing equipment, hindering the application of the technology. For ultrasonic testing, the receiver must possess sufficient sensitivity and good resolution to detect and differentiate minute defects. Furthermore, current receivers generally have poor environmental adaptability; their performance is affected by high temperature or high humidity environments. Noise and interference are common challenges in signal processing for ultrasonic testing, thus placing high demands on the performance of the signal processing equipment. Moreover, existing ultrasonic testing methods require a high degree of coordination and compatibility between receivers, signal processing equipment, and other devices; otherwise, poor testing results will occur. Summary of the Invention

[0005] The purpose of the present application is to provide a Bragg grating-based sensor device, a building structure displacement monitoring device and method to solve the technical problems mentioned in the background.

[0006] In one aspect, the present application provides a Bragg grating-based sensor device, comprising two optical fiber supports, a support rod, a signal transmitting optical fiber and a signal receiving optical fiber; wherein the signal transmitting optical fiber is obtained by providing an ultrasonic signal transmitting section on a single-mode optical fiber, the ultrasonic signal transmitting section is formed by stripping the cladding of the single-mode optical fiber and coating photoacoustic conversion material in the stripped area; the signal receiving optical fiber is a fiber Bragg grating; the support rod and the signal transmitting optical fiber are parallel to each other and pass through the two optical fiber supports, the signal receiving optical fiber is fixed to one end surface of the two optical fiber supports and is parallel to the signal transmitting optical fiber; and the ultrasonic signal transmitting section of the signal transmitting optical fiber and the Bragg grating of the signal receiving optical fiber are located between the two optical fiber supports.

[0007] Further, the optical fiber support comprises a support body; the support body is provided with a first through hole and a second through hole parallel to each other, respectively used for inserting the support rod and the signal transmitting optical fiber; a through groove parallel to the first through hole is opened at the top end of the support body, which is used for installing the signal receiving optical fiber.

[0008] Still further, the support body is further provided with an internal threaded hole extending from the side surface of the support body to the first through hole and perpendicular to the first through hole.

[0009] Further, the photoacoustic conversion material is selected from a nano-gold composite material.

[0010] Still further, the nano-gold composite material is prepared by the following method:

[0011] Polydimethylsiloxane and Sylgard 184 curing agent are mixed in a mass ratio of 10:(1-3), stirred and then placed for standby; gold salt HAuCl4·3H2O is ground into powder in a dry box heated to 90-100°C for standby; the gold salt powder is added to the polydimethylsiloxane mixture after standing, stirred to disperse the gold salt powder, and a light yellow gel-like mixture is obtained; wherein the mass of the gold salt powder is 3.75%-7.5% of the polydimethylsiloxane mixture; the light yellow gel-like mixture is placed in an ice-water mixture for ultrasonic water bath, so that the gold salt is reduced to gold nanospheres, i.e. a nano-gold composite material is obtained; the nano-gold composite material is placed in a vacuum device for vacuum degassing.

[0012] In another aspect, the present application provides a building structure displacement monitoring device, comprising a sensor device and a continuous laser, a grating demodulator; the continuous laser is connected to the multi-mode optical fiber in the sensor device, used to emit laser to the multi-mode optical fiber and excite the ultrasonic signal transmitting section to generate ultrasonic signals; the grating demodulator is connected to the signal receiving optical fiber, used to collect the optical signals of the signal receiving optical fiber.

[0013] Further, the sensor device has multiple sensor devices, and the multiple sensor devices are connected by optical fiber strings.

[0014] In another aspect, the building structure displacement monitoring method provided by the application adopts the building structure displacement monitoring device, and comprises the following steps:

[0015] The two optical fiber supports of the sensor device are connected to the wall surface to be measured; the continuous laser is started to emit laser to the multi-mode optical fiber, and the ultrasonic signal emitting section is excited to generate ultrasonic signals; the grating demodulator collects the optical signals of the signal receiving optical fiber; and the displacement of the wall surface to be measured is calculated according to the wavelength change of the optical signals of the signal receiving optical fiber.

[0016] Further, before the continuous laser is started to emit laser to the multi-mode optical fiber, the relative positions of the two optical fiber supports on the support rod are adjusted, so that the distance between the two optical fibers is adjusted to a preset distance; the distance between the two optical fibers is the sensing length, which is related to the displacement monitoring sensitivity, the relationship between the sensing length and the displacement monitoring sensitivity is calibrated in advance, and the distance is preset based on the requirement of the displacement monitoring sensitivity.

[0017] Compared with the prior art, the application has the following advantages and beneficial effects:

[0018] The application has the following advantages and beneficial effects: BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0020] Figure 1 It is a structural schematic diagram of the sensor device in the embodiment;

[0021] Figure 2 It is a structural schematic diagram of the optical fiber support in the embodiment;

[0022] Figure 3 It is a structural schematic diagram of the signal emitting optical fiber in the embodiment;

[0023] Figure 4 This is a schematic diagram of the structure of the signal receiving optical fiber in the embodiment;

[0024] Figure 5 This is a schematic diagram illustrating the application of the sensor device in the embodiment.

[0025] Reference numerals: First fiber optic bracket 1, bracket body 11, first through hole 12, second through hole 13, through groove 14, internal threaded hole 15, second fiber optic bracket 2, support rod 3, signal transmitting fiber 4, ultrasonic signal transmitting segment 41, single-mode fiber core 42, photoacoustic conversion material cladding 43, single-mode fiber cladding 44, signal receiving fiber 5, second single-mode fiber core 51, second single-mode fiber cladding 52, Bragg grating 53, wall surface 6. Detailed Implementation

[0026] The technical solution of this application will be clearly and completely described below with reference to specific embodiments. Obviously, the specific embodiments described are only a part of the specific embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] Example 1

[0028] The sensor device based on a Bragg grating provided in this embodiment has the following specific structure: Figure 1 It includes a first optical fiber support 1, a second optical fiber support 2, a support rod 3, a signal transmitting optical fiber 4, and a signal receiving optical fiber 5; the support rod 3 and the signal transmitting optical fiber 4 pass through the first optical fiber support 1 and the second optical fiber support 2 in parallel; the signal receiving optical fiber 5 is fixed at the top of the first optical fiber support 1 and the second optical fiber support 2 and is parallel to the signal transmitting optical fiber 4.

[0029] The first fiber optic bracket 1 and the second fiber optic bracket 2 have the same structure. Please refer to [link / reference]. Figure 2, the first optical fiber support 1 and the second optical fiber support 2 are shown in the structural schematic diagram of the specific embodiment. The structure of the first optical fiber support 1 and the second optical fiber support 2 both includes a support body 11, in this specific embodiment, the support body 11 is in the shape of a square block, 10mm in length, 10mm in width and 5mm in height; the support body 11 is provided with a first through hole 12 and a second through hole 13 parallel to each other, the first through hole 12 is used for inserting the support rod 3, and the second through hole 13 is used for inserting the signal transmitting optical fiber 4, in this specific embodiment, the aperture of the first through hole 12 is 3mm, and the aperture of the second through hole 13 is 1mm; the top end of the support body 11 is provided with a through groove 14 parallel to the first through hole 12, and the through groove 14 is used for installing the signal receiving optical fiber 5, in this specific embodiment, the width and depth of the through groove 14 are both 1mm.

[0030] The support rod 3 penetrates the first through hole 12 of the two optical fiber supports, the signal transmitting optical fiber 4 penetrates the second through hole 13 of the two optical fiber supports, the signal receiving optical fiber 5 is installed in the through groove 14 at the top end of the two optical fiber supports, and the signal transmitting optical fiber 4 and the signal receiving optical fiber 5 are kept parallel. In this application, the support rod 3 plays a supporting role for the two optical fiber supports, and its material is preferably high-strength, high-toughness, corrosion-resistant and high-temperature-resistant, such as stainless steel, aluminum alloy, engineering plastic, ceramic and titanium alloy.

[0031] Further, the support body 11 is also provided with an internal threaded hole 15 extending from the side surface of the support body 11 to the first through hole 12 and perpendicular to the first through hole 12, and the support body 11 can be fixed on the support rod 3 by rotating the screw into the internal threaded hole 15.

[0032] In this specific embodiment, the first optical fiber support 1 and the second optical fiber support 2 are prepared by taking polycarbonate as the raw material, and a specific preparation method thereof will be provided as follows: first, polycarbonate particles or granules are put into an injection molding machine for heating, and the heated and melted polycarbonate is injected into the injection mold of the optical fiber support, and the molded optical fiber support is obtained after cooling; then, burrs and the like of the optical fiber support are cleaned using a deburring tool to ensure the smooth surface thereof; finally, the internal threaded hole 15 is processed in the direction perpendicular to the first through hole 12 until the internal threaded hole 15 reaches the first through hole 12.

[0033] Please refer to Figure 3Figure 2 shows a structural schematic diagram of the signal transmitting optical fiber 4 in the embodiment, the signal transmitting optical fiber 4 is obtained by setting an ultrasonic signal transmitting section 41 on a single-mode optical fiber, the ultrasonic signal transmitting section 41 is obtained by stripping the cladding of the single-mode optical fiber and coating the stripped area with a photoacoustic conversion material to form a photoacoustic conversion material cladding 43, that is, the ultrasonic signal transmitting section 41 includes a single-mode optical fiber core 42 and the photoacoustic conversion material cladding 43 wrapping the single-mode optical fiber core 42, and the structure of other parts of the single-mode optical fiber is a single-mode optical fiber cladding 44 including the single-mode optical fiber core 42 and wrapping the single-mode optical fiber core 42.

[0034] In the specific embodiment, the photoacoustic conversion material is prepared by mixing polydimethylsiloxane PDMS and Sylgard 184 curing agent in a mass ratio of 10:(1-3), preferably in a mass ratio of 10:3, then stirring with a glass rod for 2 minutes and standing for 1 minute before use; grinding a gold salt HAuCl4·3H2O with a purity of 99.9% into powder in a dry box heated to 90-100°C for standby; adding the gold salt powder into the standing PDMS mixture, fully stirring with a glass rod for 20 minutes to make the gold salt powder fully dispersed, to obtain a light yellow gel-like mixture; wherein the mass of the gold salt powder is 3.75%-7.5% of the PDMS mixture; placing the light yellow gel-like mixture in an ice water mixture for ultrasonic water bath for 30 minutes to reduce the gold salt into gold nanospheres; when the mixture gradually changes from light yellow to ruby red during the reaction process, the photoacoustic conversion material is obtained; placing the photoacoustic conversion material in a vacuum device for vacuum degassing to eliminate bubbles in the photoacoustic conversion material.

[0035] Please refer to Figure 4 Figure 3 shows a structural schematic diagram of the signal receiving optical fiber 5 in the embodiment, the signal receiving optical fiber 5 is obtained by stripping the cladding corresponding to the Bragg grating in the fiber Bragg grating, the fiber Bragg grating includes a second single-mode optical fiber core 51, a second single-mode optical fiber cladding 52 wrapping the second single-mode optical fiber core 51, and a Bragg grating 53 prepared on the second single-mode optical fiber core 51 by a phase mask method.

[0036] Embodiment 2

[0037] The embodiment provides a building structure displacement monitoring device and a monitoring method thereof, the building structure displacement monitoring device in the embodiment includes the sensor device in embodiment 1 and a continuous laser and a grating demodulator; the continuous laser is connected to the multi-mode optical fiber in the sensor device, used to emit laser to the multi-mode optical fiber and excite the ultrasonic signal transmitting section 41 to generate ultrasonic signals; the grating demodulator is connected to the signal receiving optical fiber 5, used to send monitoring laser to the signal receiving optical fiber 5 and collect the light signal reflected by the signal receiving optical fiber 5.

[0038] The following will be combined with Figure 5The specific implementation process of monitoring in this embodiment is provided.

[0039] (1) Adjust the relative position of the first optical fiber support 1 and the second optical fiber support 2 on the support rod 3 to obtain the required sensing length, that is, the distance between the first optical fiber support 1 and the second optical fiber support 2; screw the screw into the internal threaded hole 15 to fix the first optical fiber support 1 and the second optical fiber support 2 on the support rod 3;

[0040] The sensing length value is related to the displacement sensitivity, and different displacement sensitivities can be obtained by adjusting the sensing length. The relationship between the sensing length and the displacement sensitivity is calibrated in advance, and in actual use, the sensing length value is determined according to the requirement of the displacement sensitivity.

[0041] (2) Install the signal receiving optical fiber 5 in the through groove 14 at the top of the first optical fiber support 1 and the second optical fiber support 2, ensure that the Bragg grating 53 is located between the first optical fiber support 1 and the second optical fiber support 2, and use epoxy resin glue to bond the signal receiving optical fiber 5 on the first optical fiber support 1 and the second optical fiber support 2; since the ultrasonic signal emitting section 41 (which can be one or more) is less affected by the working range, the signal emitting optical fiber 4 is not limited to move in the first optical fiber support 1 and the second optical fiber support 2.

[0042] (3) Bond the bottom of the first optical fiber support 1 and the second optical fiber support 2 to the wall surface 6, and unscrew the screw from the internal threaded hole 15 to disassemble the support rod 3;

[0043] (4) Connect the two ends of the signal emitting optical fiber 4 to the continuous laser and the optical power meter respectively, and connect the signal receiving optical fiber 5 to the grating demodulator;

[0044] (5) Start the continuous laser and the grating demodulator, the continuous laser emits laser to excite the ultrasonic signal emitting section 41 to generate ultrasonic waves, the grating demodulator emits laser to monitor the wavelength change of the Bragg grating 53 caused by the ultrasonic waves, and receives reflected light, and according to the wavelength change of the generated light, the displacement of the wall surface 6 can be calculated.

[0045] The working principle of the building structure displacement monitoring device of the present application is:

[0046] The laser emitted by the continuous laser is transmitted into the signal transmitting fiber 4 and propagates, and when it propagates to the ultrasonic signal transmitting section 41, a plasma resonance phenomenon is generated, thereby generating ultrasonic waves. During the propagation of the ultrasonic waves in the wall surface 6, the displacement of the wall surface 6 will disturb the propagation path of the ultrasonic waves, resulting in a change in the wave form. The change in the ultrasonic waves will be monitored by the Bragg grating 53. The ultrasonic waves will cause the signal receiving fiber 5 where the Bragg grating 53 is located to have a slight strain or displacement, thereby affecting the reflection wavelength of the signal receiving fiber 5, i.e., the shift of the Bragg wavelength. The grating demodulator emits laser of a specific wavelength to the signal receiving fiber 5 and detects the wavelength change of the reflected light of the Bragg grating 53, and according to the wavelength change, the displacement degree of the wall surface 6 can be calculated.

[0047] Further, the sensor device can be multiple, and the multiple sensor devices are connected in series through optical fibers. Specifically, the signal transmitting fibers 4 are connected in series through optical fibers, and the signal receiving fibers 5 are connected in series through optical fibers.

[0048] It should be noted that the above are only the preferred embodiments of the present application and the technical principles applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and those skilled in the art can make various obvious changes, re-adjustments and substitutions without departing from the scope of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and all belong to the protection scope of the present application.

Claims

1.A Bragg grating-based sensor device, characterized in that: it comprises two optical fiber holders, a support rod, a signal transmitting optical fiber and a signal receiving optical fiber; the signal transmitting optical fiber is obtained by providing an ultrasonic signal transmitting section on a single-mode optical fiber, the ultrasonic signal transmitting section is formed by stripping the cladding of the single-mode optical fiber and coating photoacoustic conversion material on the stripped area; the signal receiving optical fiber is a fiber Bragg grating; the support rod and the signal transmitting optical fiber are parallel to each other and pass through the two optical fiber holders, the signal receiving optical fiber is fixed to one end surface of the two optical fiber holders and is parallel to the signal transmitting optical fiber; and the ultrasonic signal transmitting section of the signal transmitting optical fiber and the Bragg grating of the signal receiving optical fiber are located between the two optical fiber holders. 2.The Bragg grating-based sensor device according to claim 1, characterized in that: the optical fiber holder comprises a holder main body; the holder main body is provided with a first through hole and a second through hole parallel to each other, respectively used for inserting the support rod and the signal transmitting optical fiber; a through groove parallel to the first through hole is formed at the top end of the holder main body, and the through groove is used for installing the signal receiving optical fiber. 3.The Bragg grating-based sensor device according to claim 2, characterized in that: the holder main body is further provided with an internal threaded hole extending from the side surface of the holder main body to the first through hole and perpendicular to the first through hole. 4.The Bragg grating-based sensor device according to claim 1, characterized in that: the photoacoustic conversion material is selected from a nano-gold composite material. 5.A building structure displacement monitoring device, characterized in that: it comprises the sensor device according to any one of claims 1-4, a continuous laser and a grating demodulator; the continuous laser is connected to the multi-mode optical fiber in the sensor device, used for emitting laser to the multi-mode optical fiber and exciting the ultrasonic signal transmitting section to generate ultrasonic signals; and the grating demodulator is connected to the signal receiving optical fiber, used for collecting the optical signals of the signal receiving optical fiber. 6.The building structure displacement monitoring device according to claim 5, characterized in that: there are multiple sensor devices, and the multiple sensor devices are connected in series by optical fibers; specifically, the signal transmitting optical fibers are connected in series by optical fibers, and the signal receiving optical fibers are connected in series by optical fibers.

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