Sensor device based on optical fiber ultrasonic sensing and active steel bar corrosion monitoring device

Abstract

The utility model discloses a sensor device based on optical fiber ultrasonic sensing and an active steel bar corrosion monitoring device. The active steel bar corrosion monitoring device comprises a sensor device, a pulse laser and a signal acquisition device, wherein the pulse laser is used for emitting laser to the multi-mode optical fiber, the laser is transmitted along the multi-mode optical fiber, an ultrasonic signal is generated by the ultrasonic signal emission section, and the ultrasonic signal is transmitted to the fiber bragg grating sensor along the circumference of the surface of the base; the signal acquisition device is used for acquiring a central spectrum of the fiber bragg grating sensor; the sensor device comprises a plurality of sensor units which are connected in series, and each sensor unit comprises a cylindrical base, a multimode optical fiber provided with an ultrasonic signal transmitting section and a fiber bragg grating sensor. According to the utility model, the ultrasonic transmitter and the ultrasonic receiver are designed based on the optical fiber, active monitoring of the corrosion condition of the steel bar is realized, electromagnetic interference can be avoided, the influence of environmental humidity and temperature is avoided, and the reliability and the accuracy are better.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel bar corrosion monitoring, and particularly relates to a sensor device based on optical fiber ultrasonic sensing, an active steel bar corrosion monitoring device and a method. BACKGROUND

[0002] At present, the steel bar corrosion monitoring method based on the optical fiber sensing principle includes an indirect monitoring method and a direct detection method. The indirect monitoring method mainly monitors environmental indexes of the position where the steel bar corrosion occurs, such as water content, chloride ion concentration, iron ion concentration, PH value and the like, and infers the steel bar corrosion state through the change of the environmental indexes. This kind of method is easily disturbed by external factors and has high requirements on the working environment. The direct detection method directly contacts the monitoring target, and the ultrasonic sensing method is one of the common direct detection methods, the principle of which is that ultrasonic waves are generated by exciting medium materials through light energy, and the monitoring target is monitored by using the ultrasonic waves. The monitoring is completed by analyzing the change of the propagation data of the ultrasonic waves through the target. This direct detection method cannot monitor the area not covered by the optical fiber, and its application is limited.

[0003] The Bragg fiber grating sensor can be used for detecting temperature, strain, vibration and the like, and has the advantages of light weight, small volume, corrosion resistance, anti-electromagnetic interference, high sensitivity and high resolution, and has been applied to the field of steel bar corrosion monitoring. For example, the Chinese patent with the application number 2017113685176 discloses a corrosion environment monitoring device and a monitoring method, which uses the FBG temperature sensor and the FBG stress sensor to monitor the temperature and the strain to determine the corrosion condition of the steel bar. However, the method of the patent belongs to passive monitoring and has poor sensitivity. SUMMARY

[0004] The purpose of the application is to provide a sensor device based on optical fiber ultrasonic sensing, an active steel bar corrosion monitoring device and a method. The device structure is simple, easy to arrange, and can actively and real-timely monitor the corrosion state of the steel bar in the concrete structure.

[0005] In one aspect, the application provides a sensor device based on optical fiber ultrasonic sensing, which comprises a plurality of sensor units connected in series, and the plurality of sensor units are arranged to have a decreasing distance from the steel bar to be measured; the sensor unit comprises a cylindrical base, a multimode optical fiber provided with an ultrasonic signal emitting section and a fiber Bragg grating sensor; the base is made of the same material as the steel bar to be measured; the ultrasonic signal emitting section is obtained by stripping the cladding of the multimode optical fiber and coating a photoacoustic conversion material in the stripped area;

[0006] The multimode optical fiber and the fiber Bragg grating sensor are arranged on the surface of the base along the direction parallel to the central axis of the base, and the projection point connecting line of the multimode optical fiber and the fiber Bragg grating sensor on the end face of the base passes through the center of the end face of the base;

[0007] The two sensor units are connected by optical fibers, specifically, the multimode optical fibers of the two sensor units are connected by optical fibers, and the fiber Bragg grating sensors of the two sensor units are connected by optical fibers.

[0008] In some embodiments, the photoacoustic conversion material is selected from a nano-gold composite material.

[0009] In some embodiments, the nano-gold composite material is prepared by the following method:

[0010] Polydimethylsiloxane and Sylgard 184 curing agent are mixed in a mass ratio of 10:(1-3), stirred and then left to stand for use; 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; the mass of the gold salt powder is 3.75%-7.5% of the mass of the polydimethylsiloxane mixture; the light yellow gel-like mixture is placed in an ice-water mixture for ultrasonic water bath to reduce the gold salt into gold nanospheres, i.e. to obtain a nano-gold composite material; the nano-gold composite material is placed in a vacuum device for vacuum degassing.

[0011] In some embodiments, the base is provided with a first through groove and a second through groove in the direction parallel to the central axis of the base, and the projection points of the first through groove and the second through groove on the end face of the base are connected through the center of the end face of the base; the multimode optical fiber and the fiber Bragg grating sensor are respectively installed in the first through groove and the second through groove.

[0012] In some embodiments, the sensor device further comprises a connecting piece, which is a parallelogram-shaped frame structure used to connect the bases of adjacent sensor units; specifically, one short end of the connecting piece is connected to the end face of the base of one sensor unit, and the other short end is connected to the end face of the base of another sensor unit, thereby realizing the connection of the two sensor units.

[0013] Further, the length of the short end of the connecting piece is comparable to the diameter of the end face of the base, and the short end of the connecting piece is connected to the end face of the base along the projection point connection line of the multimode optical fiber and the fiber Bragg grating sensor on the end face of the base.

[0014] On the other hand, the present application provides an active steel bar corrosion monitoring device, which comprises the above-mentioned sensor device, a pulse laser and a signal acquisition device; wherein the pulse laser is used to emit laser to the multimode optical fiber, the laser is transmitted along the multimode optical fiber, and ultrasonic signals are generated by the ultrasonic signal emitting section, the ultrasonic signals propagate along the circumference of the base surface to the fiber Bragg grating sensor; the signal acquisition device is used to acquire the central spectrum of the fiber Bragg grating sensor.

[0015] In still another aspect, the application provides an active steel bar corrosion monitoring method, comprising:

[0016] (1) placing the sensor device in the pouring formwork, pouring concrete, and ensuring that the exposed leads of the multi-mode optical fiber and the fiber Bragg grating sensor are exposed to the concrete structure;

[0017] (2) connecting the exposed leads of the multi-mode optical fiber and the fiber Bragg grating sensor to the pulse laser and the signal acquisition device, respectively;

[0018] (3) starting the pulse laser to emit laser, the laser is transmitted in the multi-mode optical fiber and ultrasonic signals are generated by the ultrasonic signal emitting section, and the signal acquisition device acquires the center spectrum data of the fiber Bragg grating sensor;

[0019] (4) determining whether the center wavelength of the fiber Bragg grating sensor is shifted according to the center spectrum data, determining whether the base where the fiber Bragg grating sensor is located is corroded, and obtaining the corrosion condition of the steel bar to be measured according to the distance between the corroded base and the steel bar to be measured.

[0020] In some embodiments, the sensor device is placed in the pouring formwork, specifically:

[0021] one end of the telescopic positioning rod is fixedly connected with the steel bar to be measured, and the other end is connected with the first sensor unit; the sensor units are connected in series and arranged to have a decreasing distance to the steel bar to be measured; and the length of the positioning rod is adjusted so that the last sensor unit is placed on the steel bar to be measured.

[0022] Compared with the prior art, the application has the following advantages and beneficial effects:

[0023] (1) the ultrasonic transmitter and the ultrasonic receiver are designed based on the optical fiber, active monitoring of the steel bar corrosion condition is realized, electromagnetic interference can be avoided, the reliability and accuracy are better, and the steel bar corrosion condition is not affected by the environmental humidity and temperature;

[0024] (2) the serially connected sensor units are arranged to have a decreasing distance to the steel bar to be measured, the corrosion conditions at different depths in the concrete structure can be monitored, the monitoring area is expanded from one dimension to two dimensions, the precision is high, and the monitoring is more comprehensive.

[0025] (3) the device structure of the application is simple, the operation is simple and convenient, and the monitoring cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only represent some embodiments of the present application, and for those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0027] Figure 1 Structure diagram of the sensor device in the embodiment;

[0028] Figure 2 Structure diagram of the sensor unit in the embodiment;

[0029] Figure 3 Connection diagram of the sensor unit and the connecting piece in the embodiment;

[0030] Figure 4 Connection diagram of the sensor unit and the connecting piece in the embodiment from another angle;

[0031] Figure 5 Application diagram of the active steel bar corrosion monitoring device in the embodiment.

[0032] The accompanying drawings are as follows: base 1, first through groove 11, second through groove 12, multi-mode optical fiber 2, ultrasonic signal emitting section 21, fiber Bragg grating sensor 3, Bragg grating 31, connecting piece 4, positioning rod 5, steel bar to be measured 6, concrete structure 7. DETAILED DESCRIPTION

[0033] The technical solutions of the present application will be described clearly and completely in combination with the specific embodiments of the present application. Obviously, the specific embodiments described are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort are within the scope of protection of the present application.

[0034] Embodiment 1

[0035] The present embodiment is based on a sensor device of optical fiber ultrasonic sensing, and the specific structure is shown in Figure 1The sensor device comprises a plurality of sensor units connected in series, and the plurality of sensor units are arranged in a decreasing distance from the steel bar 6 to be measured; the sensor unit comprises a cylindrical base 1, a multimode optical fiber 2 provided with an ultrasonic signal emitting section 21, and a fiber Bragg grating sensor 3; the base 1 is made of the same material as the steel bar 6 to be measured; the ultrasonic signal emitting section 21 is obtained by stripping the cladding of the multimode optical fiber 2 and coating the stripped area with a photoacoustic conversion material; wherein the multimode optical fiber 2 and the fiber Bragg grating sensor 3 are arranged on the surface of the base 1 along the direction parallel to the central axis of the base 1, and the projection point connecting line of the multimode optical fiber 2 and the fiber Bragg grating sensor 3 on the end face of the base 1 passes through the center of the end face of the base 1; the two sensor units are connected by an optical fiber, specifically, the multimode optical fibers 2 of the two sensor units are connected by an optical fiber, and the fiber Bragg grating sensors 3 of the two sensor units are connected by an optical fiber.

[0036] Please refer to Figure 2 , which shows the structure of the sensor unit in the embodiment. The base 1 is a smooth solid cylinder. The base 1 is provided with a first through groove 11 and a second through groove 12 on the upper and lower surfaces thereof along the direction parallel to the central axis of the base 1. The projection point connecting line of the first through groove 11 and the second through groove 12 on the end face of the base 1 passes through the center of the end face of the base 1. The sizes of the first through groove 11 and the second through groove 12 are matched with those of the multimode optical fiber 2 and the fiber Bragg grating sensor 3, respectively. In this embodiment, the widths of the first through groove 11 and the second through groove 12 are both 4 mm. The multimode optical fiber 2 and the fiber Bragg grating sensor 3 are installed in the first through groove 11 and the second through groove 12, respectively.

[0037] In this embodiment, the sensor device further comprises a connecting piece 4 for connecting the bases 1 of adjacent sensor units. Please refer to Figures 3-4 , which shows the structure of the connecting piece 4. The connecting piece 4 is a frame structure in the shape of a parallelogram. The acute angles of the parallelogram are 45 degrees. One short end of the connecting piece 4 is connected to the end face of the base 1 of one sensor unit, and the other short end of the connecting piece 4 is connected to the end face of the base 1 of another sensor unit, thereby realizing the connection of the two sensor units.

[0038] Further, the length of the short end of the connecting piece 4 is comparable to the diameter of the end face of the base 1, and the short end of the connecting piece 4 is connected to the end face of the base 1 along the projection point connecting line of the first through groove 11 and the second through groove 12 on the end face of the base 1. Specifically, threaded holes are provided at the center of the end face of the base 1 and the midpoint of the end face of the base 1, and the connecting piece 4 is connected to the end face of the base 1 by using bolts to connect the two threaded holes.

[0039] In this embodiment, the sensor device further comprises a length-adjustable positioning rod 5, one end of which is connected to the first sensor unit in the plurality of sensor units connected in series, for supporting and adjusting the height of the first sensor unit. In this application, the materials of the connecting piece 4 and the positioning rod 5 are preferably metals resistant to seawater corrosion, such as stainless steel.

[0040] In the present embodiment, the photoacoustic conversion material is selected as a nanogold composite material, which is prepared by the following method:

[0041] The polydimethylsiloxane (PDMS) and Sylgard 184 curing agent are mixed in a mass ratio of 10:(1-3), preferably in a mass ratio of 10:3; then stirred with a glass rod for 2 minutes and left to stand for 1 minute before use; the gold salt HAuCl4·3H2O with a purity of 99.9% is ground into powder in a dry box heated to 90-100°C for standby; the gold salt powder is added to the PDMS mixture after standing, and stirred thoroughly with a glass rod for 20 minutes to disperse the gold salt powder, obtaining a light yellow gel-like mixture; wherein the mass of the gold salt powder is 3.75%-7.5% of the PDMS mixture; the light yellow gel-like mixture is placed in an ice-water mixture for ultrasonic water bath for 30 minutes to reduce the gold salt into nanogold spheres; when the mixture gradually changes from light yellow to ruby red during the reaction process, the nanogold composite material is obtained; the nanogold composite material is placed in a vacuum device for vacuum degassing to eliminate bubbles in the nanogold composite material.

[0042] The assembly method of the sensor unit in the present embodiment will be provided as follows: first, polish the outer wall of the base 1, and clean the outer wall of the base 1 with acetone to ensure the smoothness and cleanliness of the outer wall of the base 1. Then, peel off the cladding of a section of the multimode optical fiber 2 to expose the core, bond the multimode optical fiber 2 in the first through groove 11, and make the peeled section located in the middle of the first through groove 11, coat the photoacoustic conversion material on the core of the peeled section, and cure at 120°C for 3 days, then coat the entire multimode optical fiber 2 with ultraviolet glue to form a protective layer. Finally, bond the fiber Bragg grating sensor 3 in the second through groove 12, and coat the entire fiber Bragg grating sensor 3 with ultraviolet glue to form a protective layer.

[0043] Embodiment 2

[0044] The active steel bar corrosion monitoring device of the present embodiment includes the sensor device in Embodiment 1, a nanosecond pulse laser, and a signal acquisition device; the nanosecond pulse laser is used to emit incident laser to the multimode optical fiber 2, the incident laser is transmitted in the multimode optical fiber 2, the photoacoustic conversion material of the ultrasonic signal emitting section 21 absorbs the pulse laser energy and generates ultrasonic waves, and the ultrasonic waves propagate along the circumference on the surface of the base 1; the signal acquisition device is used to acquire the center spectrum of the fiber Bragg grating sensor 3.

[0045] The exposed lead of the fiber Bragg grating sensor is connected to a signal acquisition device, which comprises a demodulation laser, a photoelectric detection unit and a data acquisition unit; the demodulation laser is used to emit a detection laser to the fiber Bragg grating sensor, the photoelectric detection unit is used to convert the collected optical signal into an electrical signal and send it to the data acquisition unit, and whether the central wavelength is offset is analyzed through the analysis of the electrical signal collected by the data acquisition unit, so as to calculate whether the base where the fiber Bragg grating sensor is located is corroded.

[0046] In the active steel bar corrosion monitoring device, the multimode optical fiber 2 serves as an ultrasonic wave emitter, and the Bragg grating 31 in the fiber Bragg grating sensor 3 serves as an ultrasonic wave receiver. When the base 1 is corroded, the central wavelength of the fiber Bragg grating sensor 3 will drift, and then the central spectrum of the fiber Bragg grating sensor 3 is collected by using the signal acquisition device, and whether the central wavelength drifts is determined by analyzing the central spectrum, so as to determine whether the base 1 is corroded. In the present application, the sensor unit comprises a plurality of sensor units arranged in decreasing distance from the steel bar 6 to be measured, and by determining the corrosion condition of each base 1, the distance of the corrosion interface from the steel bar 6 to be measured can be determined.

[0047] Please see Figure 5 , which is an application schematic diagram of the active steel bar corrosion monitoring device, and the application method is as follows:

[0048] (1) Place the sensor device in the pouring formwork and pour the concrete, and at the same time ensure that the end lead of the multimode optical fiber 2 and the fiber Bragg grating sensor 3 is exposed to the concrete structure 7.

[0049] Specifically, one end of the positioning rod 5 is fixedly connected with the steel bar 6 to be measured, and the other end is connected with the first sensor unit, which is also the sensor unit farthest from the steel bar 6 to be measured; each sensor unit is connected in series through the connecting piece 4, so that each sensor unit is arranged in decreasing distance from the steel bar 6 to be measured; the length of the positioning rod 5 is adjusted so that the last sensor unit is placed on the steel bar 6 to be measured.

[0050] (2) Connect the exposed leads of the multimode optical fiber 2 and the fiber Bragg grating sensor 3 to the pulse laser and the signal acquisition device respectively;

[0051] When connecting with the exposed leads, only one end of the exposed leads is connected, for example, the pulse laser and the signal acquisition device are connected to the exposed leads of the left end or the right end of the multimode optical fiber 2 and the fiber Bragg grating sensor 3 respectively.

[0052] (3) Start the pulse laser to emit laser, the laser is transmitted in the multimode optical fiber 2 and ultrasonic signals are generated by the ultrasonic signal emitting section 21; the signal acquisition device acquires the central spectrum data of the fiber Bragg grating sensor 3;

[0053] (4) According to the center spectrum data, it is judged whether the center wavelength of the fiber Bragg grating sensor 3 is shifted, whether the base 1 where the fiber Bragg grating sensor 3 is located is corroded, and the corrosion condition of the steel bar 6 to be measured is evaluated according to the distance between the corroded base 1 and the steel bar 6 to be measured.

[0054] When the base 1 where the fiber Bragg grating sensor 3 is located is corroded, the center wavelength of the fiber Bragg grating sensor 3 on the base 1 is shifted, and the distance between the corrosion interface and the steel bar 6 to be measured can be obtained. When the center wavelength of the fiber Bragg grating sensor 3 of the last sensor unit is shifted, it is indicated that the corrosion interface has reached the steel bar 6 to be measured. According to the distance between the corrosion interface and the steel bar 6 to be measured, different remedial measures can be taken.

[0055] Note that the above is only the preferred embodiment of the present application and the technical principle used. 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, readjustments 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 sensor device based on fiber optic ultrasonic sensing, characterized in that: The device includes several sensor units connected in series, arranged at decreasing distances from the steel bar to be measured. Each sensor unit includes a cylindrical base, a multimode optical fiber with an ultrasonic signal transmitting section, and a fiber Bragg grating sensor. The base is made of the same material as the steel bar to be measured. The ultrasonic signal transmitting section is obtained by stripping the cladding of the multimode optical fiber and coating the stripped area with a photoacoustic conversion material. Among them, the multimode fiber and fiber Bragg grating sensor are arranged on the surface of the base along the direction parallel to the central axis of the base, and the line connecting the projection points of the multimode fiber and fiber Bragg grating sensor on the end face of the base passes through the center of the end face of the base. The two sensor units are connected by optical fiber. Specifically, the multimode optical fibers of the two sensor units are connected by optical fiber, and the fiber Bragg grating sensors of the two sensor units are connected by optical fiber.

2. The sensor device based on fiber optic ultrasonic sensing as described in claim 1, characterized in that: The photoacoustic conversion material is selected as a nano-gold composite material.

3. The sensor device based on fiber optic ultrasonic sensing as described in claim 1, characterized in that: The base is provided with a first through groove and a second through groove along the direction parallel to the central axis of the base, and the line connecting the projection points of the first through groove and the second through groove on the end face of the base passes through the center of the end face of the base; the multimode optical fiber and the fiber Bragg grating sensor are respectively installed in the first through groove and the second through groove.

4. The sensor device based on fiber optic ultrasonic sensing as described in claim 1, characterized in that: The sensor device also includes a connector, which is a parallelogram-shaped frame structure used to connect the bases of adjacent sensor units. Specifically, one short end of the connector is connected to the end face of the base of one sensor unit, and the other short end is connected to the end face of the base of another sensor unit, thereby realizing the connection between the two sensor units.

5. The sensor device based on fiber optic ultrasonic sensing as described in claim 4, characterized in that: The short end of the connector is approximately the same length as the diameter of the base end face, and the short end of the connector is connected to the base end face along the line connecting the projection point of the multimode fiber and the fiber Bragg grating sensor on the base end face.

6. An active steel reinforcement corrosion monitoring device, characterized by: The invention includes the sensor device, pulsed laser, and signal acquisition device as described in any one of claims 1-5; wherein the pulsed laser is used to emit laser light into a multimode fiber, the laser light is transmitted along the multimode fiber, and an ultrasonic signal is generated by an ultrasonic signal emission segment, the ultrasonic signal is propagated along the circumference of the base surface to the fiber Bragg grating sensor; the signal acquisition device is used to acquire the center spectrum of the fiber Bragg grating sensor.

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