Intelligent FRP reinforcement and its manufacturing method, performance monitoring method and system

Abstract

The present invention relates to an intelligent FRP bar and a manufacturing method, a performance monitoring method and a system thereof, and belongs to the technical field of structural health monitoring for construction engineering, wherein the intelligent FRP bar comprises: an FRP bar; an ultrasonic transducer optical fiber is embedded in the center of the FRP bar; and an ultrasonic detection optical fiber is wound between the ribs of the FRP bar. The present invention utilizes the ultrasonic transducer optical fiber embedded in the center to convert light energy and heat energy to excite ultrasonic waves, and utilizes the ultrasonic detection optical fiber wound between the ribs to collect ultrasonic signals. This ultrasonic sensing method can directly characterize and excite the FRP bar body, thereby realizing real-time monitoring of the stress state of the FRP bar during the service life of the engineering structure, and effectively solves the problem that the detection technology for exciting ultrasonic signals in the prior art is easily affected by the complex environment of concrete and electromagnetic interference.

Description

Technical Field

[0001] The present invention relates to the technical field of structural health monitoring for construction engineering, and in particular to an intelligent FRP reinforcement with an embedded all-fiber ultrasonic sensing system, a manufacturing method thereof, and a performance monitoring method and system thereof. Background Art

[0002] FRP (Fiber Reinforced Polymer) is a composite material composed of resin-coated fibers. Due to its light weight, high strength and excellent corrosion resistance, it has been gradually used as a substitute for traditional metal reinforcement materials in actual engineering. Among them, for engineering structures that are greatly affected by chloride ion corrosion and carbonization, the use of FRP bars to replace steel bars in concrete has become a very effective solution. However, existing studies have shown that with the increase of service age, the high alkaline environment of ordinary concrete will cause debonding of the fiber-resin interface inside the FRP bars and slight hydrolysis of the resin on the surface of the bars, which will eventually manifest as the degradation of the mechanical properties of the FRP bars and the deterioration of the bonding properties of the FRP bars / concrete interface, thereby causing the resistance degradation of the FRP reinforced concrete structure and posing potential safety hazards. Therefore, it is of great engineering significance to develop a long-term and effective monitoring technology for the mechanical properties of FRP bars and the bonding properties of the FRP bars / concrete interface during the service life of the project.

[0003] At present, most of the monitoring of FRP bars is still focused on the strain field monitoring under long-term loads, and the monitoring research on its damage and mechanical performance degradation is not sufficient. Relevant scholars have tried to use ultrasonic sensing and other technical means to identify the damage and predict the performance of FRP bars, but the traditional piezoelectric and electromagnetic surface-attached sensors used cannot directly characterize and excite the FRP bars in the concrete environment. At the same time, the detection technology based on the piezoelectric effect to excite ultrasonic signals is also easily affected by the complex environment of concrete and electromagnetic interference, and the signal-to-noise ratio is relatively low. Summary of the invention

[0004] The purpose of the present invention is to provide an intelligent FRP bar and its manufacturing method, performance monitoring method and system, which adopts the ultrasonic sensing method of central optical fiber transducer excitation and outer edge optical fiber detection and reception to directly characterize and excite the FRP bar body, effectively solving the problem that the detection technology of exciting ultrasonic signals in the prior art is easily affected by the complex environment of concrete and electromagnetic interference.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] An intelligent FRP rib, comprising: an FRP rib, an ultrasonic transducer optical fiber and an ultrasonic detection optical fiber;

[0007] The ultrasonic transducer optical fiber is embedded in the center of the FRP rib;

[0008] The ultrasonic detection optical fiber is wound between the ribs of the FRP bar.

[0009] In some embodiments, packaging glue is provided on the surface of the ultrasonic detection optical fiber.

[0010] A method for manufacturing an intelligent FRP reinforcement, comprising:

[0011] Pre-install an ultrasonic transducer optical fiber at the center of the FRP rib;

[0012] Ultrasonic detection optical fibers are wound between the ribs of the FRP bar.

[0013] In some embodiments, before pre-placing the ultrasonic transducer optical fiber at the center of the FRP rib, the method further includes:

[0014] removing the cladding of the optical fiber at a specific point along the axis of the optical fiber;

[0015] The photoacoustic conversion material is coated on the portion where the cladding is removed to obtain an ultrasonic transducer optical fiber.

[0016] In some embodiments, the photoacoustic conversion material includes: one of a metal film, a graphite-epoxy composite material, and a gold nano-PDMS composite material.

[0017] In some embodiments, before winding the ultrasonic detection optical fiber between the ribs of the FRP tendon, the method further comprises:

[0018] FBGs with different central wavelengths are inscribed along the axial direction of the optical fiber to obtain an ultrasonic detection optical fiber.

[0019] In some embodiments, when the ultrasonic detection optical fiber is wound between the ribs of the FRP rib, it is ensured that the position of the FBG corresponds to the position of the specific point on the ultrasonic transducer optical fiber.

[0020] A method for monitoring performance of an intelligent FRP reinforcement bar, comprising:

[0021] Acquiring the ultrasonic signal generated by the ultrasonic transducer optical fiber by using the ultrasonic detection optical fiber;

[0022] The mechanical properties of the FRP bars are monitored according to the amplitude, wave velocity, arrival time and energy index of the ultrasonic signal.

[0023] In some embodiments, before using the ultrasonic detection optical fiber to obtain the ultrasonic signal generated by the ultrasonic transducer optical fiber, the method further includes:

[0024] An external nanosecond laser is used to introduce pulsed laser into the ultrasonic transducer fiber.

[0025] An intelligent FRP reinforcement performance monitoring system, comprising:

[0026] A signal acquisition unit, used for acquiring an ultrasonic signal generated by an ultrasonic transducer optical fiber using an ultrasonic detection optical fiber;

[0027] The performance analysis unit is used to monitor the mechanical properties of the FRP reinforcement according to the amplitude, wave velocity, arrival time and energy index of the ultrasonic signal.

[0028] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0029] The present invention provides an intelligent FRP bar and a manufacturing method, a performance monitoring method and a system thereof, wherein the intelligent FRP bar comprises: an FRP bar; an ultrasonic transducer optical fiber is embedded in the center of the FRP bar; and an ultrasonic detection optical fiber is wound between the ribs of the FRP bar. The present invention uses the ultrasonic transducer optical fiber embedded in the center to perform central optical fiber transduction excitation, and uses the ultrasonic detection optical fiber wound between the ribs to receive. This ultrasonic sensing method can directly characterize and excite the FRP bar body, thereby realizing real-time monitoring of the stress state of the FRP bar during the service life of the engineering structure, and effectively solves the problem that the detection technology of exciting ultrasonic signals in the prior art is easily affected by the complex environment of concrete and electromagnetic interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 This is a schematic diagram of the intelligent FRP reinforcement structure provided in Example 1 of the present invention.

[0032] Figure 2 This is a schematic diagram of the structure of an ultrasonic transducer optical fiber provided in Example 1 of the present invention.

[0033] Figure 3 This is a schematic diagram of the structure of an ultrasonic detection optical fiber provided in Example 1 of the present invention.

[0034] Figure 4 This is a schematic diagram of the implementation process of the performance monitoring method of the intelligent FRP reinforcement provided in the third embodiment of the present invention.

[0035] Figure 5 This is a connection diagram of the ultrasonic excitation system provided in Example 3 of the present invention.

[0036] Figure 6 This is a connection diagram of the ultrasonic detection system provided in Embodiment 3 of the present invention.

[0037] Explanation of symbols:

[0038] 1—FRP tendon, 2—ultrasonic transducer fiber, 3—ultrasonic detection fiber, 4—photoacoustic conversion material, 5—ultrasonic signal, 6—fiber cladding, 7—fiber core, 8—FBG, 9—debonding of FRP tendon / concrete interface or damage of FRP tendon body. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The purpose of the present invention is to provide an intelligent FRP bar and its manufacturing method, performance monitoring method and system, which adopts the ultrasonic sensing method of central optical fiber transducer excitation and outer edge optical fiber detection and reception to directly characterize and excite the FRP bar body, effectively solving the problem that the detection technology of exciting ultrasonic signals in the prior art is easily affected by the complex environment of concrete and electromagnetic interference.

[0041] The present invention relates to a structural design and specific use method of an intelligent fiber reinforcement (FRP reinforcement). An ultrasonic sensing method with central optical fiber transducer excitation and outer optical fiber detection reception is adopted to realize damage detection and deterioration monitoring of FRP reinforcement and evaluation of the bonding state of the FRP reinforcement / concrete interface. The long-term stable monitoring of the long-term performance degradation and structural damage of FRP reinforcement during the service life of FRP reinforced concrete structures can be realized, and the method is mainly used in the field of structural health monitoring of construction projects.

[0042] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] Embodiment 1:

[0044] like Figure 1 As shown, this embodiment provides an intelligent FRP rib, including: an FRP rib 1, an ultrasonic transducer optical fiber 2, and an ultrasonic detection optical fiber 3.

[0045] The ultrasonic transducer optical fiber 2 is embedded in the center of the FRP rib 1 ; and the ultrasonic detection optical fiber 3 is wound between the ribs of the FRP rib 1 .

[0046] The surface of the ultrasonic detection optical fiber 3 is provided with packaging glue.

[0047] This embodiment embeds the ultrasonic transducer fiber 2 and the ultrasonic detection fiber 3 in the FRP bar 1 to form an all-fiber ultrasonic sensing system, which can actively monitor the degradation of the mechanical properties of the FRP bar and the degradation of the bonding properties of the FRP bar / concrete interface caused by corrosion damage during the service life of the engineering structure. Figure 2 As shown, the fiber cladding 6 at a specific point is removed by chemical corrosion or mechanical stripping, and the photoacoustic conversion material 4 is coated on the surface of the fiber core 7. The photoacoustic conversion material 4 can generate an ultrasonic signal 5 after being excited to prepare an ultrasonic transducer fiber 2. A fiber grating (FBG) is used as an ultrasonic receiving element and is placed at the edge of the FRP rib 1 or in a prefabricated groove on the surface. The ultrasonic transducer fiber 2 is fixed to the center of the FRP rib, and the intelligent FRP rib is prepared by pultrusion, spiral winding and other processes. Then, the ultrasonic detection fiber 3 is spirally wound in the low groove between the ribs of the FRP rib 1, and then fixed by an epoxy resin-based adhesive, and finally an intelligent FRP rib with an embedded all-fiber ultrasonic sensor system is formed.

[0048] During the service life of engineering structures, FRP bars may be subjected to the coupling of various environmental factors and long-term loads, resulting in corrosion damage including fiber-resin matrix debonding, FRP bar surface resin hydrolysis leading to pores and voids, FRP bar / concrete interface debonding, etc., which will cause changes in physical and mechanical indicators such as material density and stiffness in some areas, affecting the ultrasonic propagation speed and path. Therefore, by monitoring the ultrasonic propagation speed, arrival time, and energy attenuation before and after FRP bar corrosion damage, it is possible to achieve a quantitative evaluation of the degradation degree of various mechanical properties of FRP bars to a certain extent.

[0049] By removing the cladding at different points of the ultrasonic transducer optical fiber 2 and coating the photoacoustic conversion material 4, distributed ultrasonic excitation along the optical fiber axis can be achieved; the ultrasonic detection optical fiber 3 is continuously wound in the low grooves between the FRP ribs, and FBG8 with different central wavelengths are respectively engraved at the corresponding ultrasonic transducer points to obtain the ultrasonic detection optical fiber 3, as shown in FIG. Figure 3As shown, combined with time division multiplexing or wavelength division multiplexing technology, distributed detection of ultrasonic waves can be achieved. Traditional ultrasonic sensing technology based on piezoelectric materials requires piezoelectric ceramic sheets (PZT) or piezoelectric probes to be attached to the surface as signal excitation sources. However, piezoelectric materials have the disadvantages of narrow response frequency band, large volume (millimeter level), susceptibility to electromagnetic interference, poor signal transmission stability, and poor reusability. In particular, for engineering structures that require multi-point distributed monitoring, each piezoelectric transducer needs to be connected separately, which requires a large amount of engineering and unstable signal transmission. In contrast, the present invention uses an all-optical fiber-based ultrasonic transducer device, which can realize multi-point distributed ultrasonic excitation and signal reception along the axial direction of the optical fiber, and has many advantages such as wide response frequency band, small volume (micrometer level), no electromagnetic interference, long signal transmission distance, good reusability, and corrosion resistance; at the same time, the optical fiber sensor device is embedded in the inside and surface of the FRP bar, realizing direct monitoring of the FRP bar body.

[0050] Embodiment 2:

[0051] This embodiment provides a method for manufacturing an intelligent FRP bar, comprising:

[0052] First, the cladding of the optical fiber is removed at a specific point along the axis of the optical fiber, and a photoacoustic conversion material is coated on the portion where the cladding is removed to obtain an ultrasonic transducer optical fiber. The photoacoustic conversion material includes: one of a metal film, a graphite-epoxy resin composite material, and a gold nano-PDMS composite material.

[0053] Then, an ultrasonic transducer optical fiber is preset at the center of the FRP rib.

[0054] Then, FBGs with different central wavelengths are inscribed along the axial direction of the optical fiber to obtain an ultrasonic detection optical fiber.

[0055] Finally, the ultrasonic detection optical fiber is wound between the ribs of the FRP bar. During the winding, the position of the FBG is ensured to correspond to the position of the specific point on the ultrasonic transducer optical fiber.

[0056] In this embodiment, an ultrasonic transducer optical fiber is prepared using a material having a photoacoustic effect. By means of optical fiber side wheel polishing, optical fiber side arc groove block polishing, chemical etching and other technical means, the cladding at a specific position of the optical fiber is removed and the photoacoustic conversion material is coated to form a sidewall optical fiber ultrasonic transducer. The photoacoustic conversion material used includes but is not limited to metal film, graphite-epoxy resin composite material, gold nano-PDMS composite material, etc. When the pulsed laser propagates along the fiber core to the photoacoustic conversion material, part of the energy will be coupled from the fiber core to the photoacoustic conversion material and absorbed and deposited as a heat source to generate thermal expansion. The instantaneous thermoelastic effect will excite ultrasonic waves on the surface of the optical fiber.

[0057] According to the radiation beam theory in the absorption medium, the absorption of the pulsed laser by the photoacoustic conversion material is calculated. The radiation intensity of the beam is described by the Beer-Lambert law, and the radiation transmission equation is established as follows:

[0058]

[0059] Among them, I i It represents the power density of the i-th pulse laser injected into the photoacoustic conversion material, in W / m 2 .e i represents the direction of the i-th pulse laser. κ represents the absorption coefficient of the photoacoustic conversion material, with the unit of 1 / m.

[0060] Radiation heat source (after the photoacoustic conversion material absorbs the laser energy, it can be regarded as a heat source according to the absorption medium radiation beam theory) Qr (unit: W / m 3 ) corresponds to the energy deposited by the pulsed laser beam and is defined as:

[0061]

[0062] Therefore, when the pulsed laser excitation acts on the ultrasonic transducer fiber, the heat absorption process in the photoacoustic conversion material can be expressed as ：

[0063]

[0064] Q r (t) = κβI(t) (4)

[0065] Among them, K i represents the thermal conductivity of the medium (the medium in this embodiment is the photoacoustic conversion material) (unit: W / (m·K)), T represents the temperature (referring to the temperature of the photoacoustic conversion material, without considering the temperature distribution difference along the thickness direction) (unit: K), ρ i Indicates the medium density (unit: kg / m 3 ), C i Indicates the heat capacity of the medium (unit: J / (kg·K)), represents the thermal conductivity of the photoacoustic conversion material (unit: m / s), t represents the time when the laser pulse starts to act on the photoacoustic conversion material (unit: s), β represents the laser energy coupling coefficient (obtained by analyzing the light field distribution between the fiber core and the photoacoustic conversion material, with a value between 0 and 1), I(t) represents the pulsed laser power density (unit: W / m 2 ), Q r (t) represents a heat source, and the above formulas (1) and (2) are explanations of formula (3).

[0066] It should be noted that all the formulas listed here are only explanations of the principles, not for a specific example. If a specific calculation is to be performed, it is necessary to assume multiple specific parameters such as laser power density, and the actual calculation process is often performed through numerical simulation.

[0067] According to (3) and (4), the temperature distribution of the photoacoustic conversion material due to transient thermal expansion is calculated and used as input to calculate the thermal strain:

[0068] ε th =α(TT ref ) (5)

[0069] Among them, ε th represents thermal strain, α represents the secant thermal expansion coefficient of the medium, T ref Indicates the initial temperature when no laser is irradiated (unit: K).

[0070] Meanwhile, the geometric equation of the material in solid mechanics is:

[0071]

[0072] Among them, ε x represents strain, u represents displacement (unit: m), and x represents displacement along the x direction.

[0073] The instantaneous thermal expansion of the photoacoustic material layer will excite ultrasonic waves and propagate in the FRP material. Considering the anisotropy of the FRP material, its scalar wave equation can be expressed as:

[0074]

[0075] in, Indicates the effective bulk modulus of FRP material (unit: Pa), p t Indicates the total sound pressure (unit: kg / m 3 ), ρ represents the density of FRP material (unit: kg / m 3 ), is the Hamiltonian operator.

[0076] At the same time, the following boundary conditions are met at the interface between the photoacoustic material layer and the FRP material:

[0077]

[0078] Where n represents the interface normal, ρ represents the FRP material density, Indicates structural degree (unit: m / s 2 ).

[0079] By solving (5)-(8), the ultrasonic sound pressure distribution in the FRP bar can be obtained. However, due to the different relative densities of the FRP constituent materials, the acoustic impedance at the fiber-resin matrix interface is different, resulting in obvious irregularities in the FRP material, which is manifested as large scattering and absorption of ultrasonic waves. Therefore, FRP materials are usually regarded as high-attenuation waveguide materials, and it is necessary to further consider the attenuation of ultrasonic waves during propagation, including diffusion attenuation, absorption attenuation, and scattering attenuation.

[0080] Since the length dimension of the photoacoustic material coating is much larger than the wavelength of the sound wave, and its radial dimension is much smaller than the wavelength, it can be regarded as a cylindrical sound source that generates cylindrical waves, which will cause the diffusion and attenuation of the beam. The wavefront of the cylindrical wave is a coaxial cylindrical surface, and the beam spreads in all directions. The sound pressure is inversely proportional to the square root of the distance, and the sound pressure attenuation equation is:

[0081]

[0082] Where P1 represents the sound pressure at a distance of 1 from the wave source (unit: Pa), P x represents the sound pressure at a distance x from the wave source (unit: Pa), x represents the distance to the wave source (unit: m), and α represents the attenuation coefficient.

[0083] When ultrasonic waves propagate, internal friction (i.e., viscosity) and heat conduction between particles in the medium will cause absorption attenuation, and scattering attenuation will occur due to the scattering of sound waves at interfaces with different acoustic impedances. Generally, these two situations are considered by introducing an attenuation coefficient. Medium attenuation is closely related to the properties of the medium. In actual testing, the medium attenuation coefficient is often determined experimentally. According to the apparent attenuation coefficient determination method recommended by ASTM E664, an A-Scan test is performed on the FRP sample, and two groups of backscattering peaks are selected to calculate the medium apparent attenuation coefficient α of the FRP material. apparent .

[0084]

[0085] Among them, A m and A n They represent the mth and nth backscattering peak values ​​converted in percentage respectively (n>m), and T represents the sample thickness.

[0086] Based on (9) and (10), the sound pressure value of the ultrasonic wave excited by the side wall of the optical fiber at the center of the FRP rib when it propagates to the surface of the FRP rib is calculated.

[0087] When the ultrasonic wave is attenuated and propagates to the surface of the FRP rib, the FBG on the spirally wound ultrasonic detection optical fiber can effectively receive the ultrasonic signal. FBGs with different central wavelengths are engraved along the axial direction of the optical fiber by methods such as phase mask and double-wave interference (in this embodiment, multiple FBGs are actually engraved on a single-mode optical fiber, and each FBG has a different central wavelength, so it has multiplexing capability. When the ultrasonic wave acts on the FBG, its central wavelength will drift). The ultrasonic detection optical fiber is wound on the surface of the FRP rib and encapsulated for protection to ensure that each FBG point corresponds to each ultrasonic excitation point on the ultrasonic transducer optical fiber at the center of the FRP. Distributed ultrasonic detection can be achieved by combining wavelength division multiplexing and time division multiplexing technology. The principle of FBG detecting ultrasonic waves is acoustic induced λ B Drift mainly involves the effect of ultrasonic sound pressure on the FBG grating period and effective refractive index. FBG center wavelength drift value Δλ B It can be expressed as:

[0088] Δλ B =2n eff ΔΛ+2ΛΔn eff (11)

[0089] Among them, n eff represents the effective refractive index of FBG, Λ represents the FBG period, λ B Indicates the central wavelength of the light reflected by the FBG (unit: nm).

[0090] According to the photoelastic effect, the refractive index change caused by the sound pressure acting on the FBG is expressed as:

[0091]

[0092]

[0093] Among them, p 11 ,p 12 represents the strain optical tensor, S j represents the strain tensor, ε represents the longitudinal wave sound pressure, and v represents the Poisson's ratio.

[0094] The periodic change of FBG caused by ultrasonic wave can be expressed as:

[0095] ΔΛ=εΛ (14)

[0096] According to (11)-(14), the center wavelength drift of FBG caused by ultrasound is:

[0097]

[0098] Therefore, by measuring the degree of drift of the central wavelength of the FBG reflected light, the change of the ultrasonic sound pressure amplitude can be quantitatively characterized to a certain extent, thereby realizing the effective detection of ultrasonic signals.

[0099] In this embodiment, an intelligent self-sensing FRP rib is prepared by embedding an ultrasonic transducer fiber and an ultrasonic detection fiber in the FRP rib. An ultrasonic transducer fiber is preset at the center of the FRP rib, and an ultrasonic detection fiber is wound between the ribs on the surface of the FRP rib. The surface-wound fiber needs to be evenly coated with packaging glue for protection. The embedded fiber optic ultrasonic sensing system can excite ultrasonic waves inside the FRP rib and receive ultrasonic waves on the surface of the FRP rib. The real-time status of the FRP material can be identified based on the characteristic changes in the time and frequency domains of the ultrasonic signal. Due to the small size of the optical fiber, it will not have a significant effect on the mechanical properties of the FRP rib itself. At the same time, since the optical fiber is wrapped by the resin matrix in the FRP material, it is guaranteed that the sensor can work stably for a long time.

[0100] Embodiment three:

[0101] like Figure 4 As shown, this embodiment provides a method for monitoring the performance of an intelligent FRP tendon. First, an external nanosecond laser is used to introduce pulsed laser into an ultrasonic transducer optical fiber.

[0102] like Figure 5 As shown, the nanosecond laser, high-power erbium-doped fiber amplifier, optical isolator, and ultrasonic transducer fiber are connected in sequence to form an ultrasonic excitation system. With pulsed laser as input, when the laser beam propagates to the photoacoustic conversion material, the interface refractive index between the fiber core and the photoacoustic material (a type of material with thermoelastic effect, including graphite-epoxy resin mixture, nano-gold particles-PDMS, etc., after the cladding of the optical fiber is removed and the photoacoustic conversion material is coated, the leaked laser energy can be converted into thermal energy, and the instantaneous thermal expansion will generate ultrasonic waves, so it is called photoacoustic conversion material) no longer meets the total reflection condition, so that part of the laser energy is coupled into the photoacoustic material and absorbed, and ultrasonic waves are generated through the thermoelastic effect and propagated in the FRP ribs.

[0103] according to Figure 6 According to the connection sequence shown, a tunable laser, a circulator, an ultrasonic detection optical fiber, a photodetector and an oscilloscope are combined into an ultrasonic detection system to collect the ultrasonic signal generated by the ultrasonic transducer optical fiber and propagating radially along the FRP reinforcement to the surface.

[0104] The specific monitoring process includes:

[0105] Using ultrasonic detection optical fiber to obtain ultrasonic signals generated by ultrasonic transducer optical fiber;

[0106] The mechanical properties of the FRP bars are monitored according to the amplitude, wave velocity, arrival time and energy index of the ultrasonic signal.

[0107] For FRP reinforced concrete structures, under the coupling of environmental erosion and long-term loads, FRP materials will inevitably suffer a certain degree of damage and degradation, which is manifested in the degradation of the mechanical properties of the reinforcement material. For FRP reinforcement in actual engineering structures, changes in its tensile properties, shear properties, and bonding properties with concrete are of great significance for structural safety assessment and service life prediction. The all-fiber ultrasonic sensing intelligent FRP reinforcement developed above can realize damage detection of engineering structures and quantitative evaluation of related mechanical properties. The specific implementation process is as follows: Figure 4 As shown, Figure 4 The 9 in the figure indicates debonding of the FRP bar / concrete interface or damage to the FRP bar itself.

[0108] Through external optical devices such as second lasers, pulsed lasers are introduced into the ultrasonic transducer fiber at the center of the intelligent FRP rib. When the laser beam propagates to the ultrasonic excitation point, part of the energy will be coupled to the photoacoustic conversion material and produce instantaneous thermal expansion, thereby exciting ultrasonic waves; the ultrasonic signal propagates radially along the FRP rib to the surface area, and is received by the FBG on the ultrasonic detection fiber spirally wound along the surface of the FRP rib, and finally converted into an electrical signal through a photoelectric converter.

[0109] For FRP materials that have been in a high alkaline environment of concrete for a long time, the resin matrix on its surface may be hydrolyzed and damaged, and moisture may penetrate into the interface between FRP bars and concrete to produce microcracks and voids. Due to the difference in thermal expansion coefficients between FRP materials and concrete, interfacial stress will be caused. These factors will lead to the degradation of the bonding performance between FRP bars and concrete. Due to material degradation, the physical properties of FRP materials such as sound velocity and density change. The bonding slip under long-term load will change the geometric shape of FRP bars. Both will affect the propagation process of ultrasonic waves. By monitoring the ultrasonic signal received by the FBG on the surface of the intelligent FRP bars and analyzing the amplitude, wave velocity, arrival time and energy indicators of the ultrasonic wave, the bonding state of the FRP bar / concrete interface can be quantitatively evaluated to a certain extent.

[0110] The high alkaline environment of concrete will also have an adverse effect on the mechanical properties of the reinforcement material itself. Long-term wet and alkaline environment will cause the fiber-resin matrix in the FRP reinforcement to debond, produce micro-voids and cavities, aggravate water intrusion, and cause the degradation of the tensile and shear mechanical properties of the FRP reinforcement. Corrosion degradation will change the physical properties of the FRP material such as sound velocity and density, thereby affecting the ultrasonic propagation process. By monitoring the ultrasonic signals received by each FBG on the surface of the intelligent FRP reinforcement and analyzing the amplitude, wave velocity, arrival time and energy indicators of the ultrasonic wave, the long-term mechanical properties of the FRP reinforcement can be quantitatively evaluated to a certain extent.

[0111] Embodiment 4:

[0112] This embodiment provides a performance monitoring system for intelligent FRP bars, including:

[0113] A signal acquisition unit, used for acquiring an ultrasonic signal generated by an ultrasonic transducer optical fiber using an ultrasonic detection optical fiber;

[0114] The performance analysis unit is used to monitor the mechanical properties of the FRP reinforcement according to the amplitude, wave velocity, arrival time and energy index of the ultrasonic signal.

[0115] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0116] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An intelligent FRP bar, characterized in that: Including: FRP ribs, ultrasonic transducer optical fiber and ultrasonic detection optical fiber; The ultrasonic transducer optical fiber is embedded in the center of the FRP rib; The ultrasonic detection optical fiber is wound between the ribs of the FRP tendon; During the process of preparation, the ultrasonic transducer optical fiber is fixed at the center of the FRP rib.

2. The intelligent FRP reinforcement according to claim 1, characterized in that: The surface of the ultrasonic detection optical fiber is provided with packaging glue.

3. A method for manufacturing an intelligent FRP bar, characterized in that: include: An ultrasonic transducer optical fiber is pre-placed at the center of the FRP rib; Ultrasonic detection optical fibers are wound between the ribs of the FRP bar.

4. The method for manufacturing the intelligent FRP bar according to claim 3, characterized in that: Before pre-setting the ultrasonic transducer optical fiber at the center of the FRP rib, the method further comprises: removing the cladding of the optical fiber at a specific point along the axis of the optical fiber; The photoacoustic conversion material is coated on the portion where the cladding is removed to obtain an ultrasonic transducer optical fiber.

5. The method for manufacturing the intelligent FRP bar according to claim 4, characterized in that: The photoacoustic conversion material comprises: one of a metal film, a graphite-epoxy resin composite material and a gold nano-PDMS composite material.

6. The method for manufacturing the intelligent FRP bar according to claim 4, characterized in that: Before winding the ultrasonic detection optical fiber between the ribs of the FRP bar, the method further comprises: FBGs with different central wavelengths are inscribed along the axial direction of the optical fiber to obtain an ultrasonic detection optical fiber.

7. The method for manufacturing the intelligent FRP reinforcement according to claim 6, characterized in that: When the ultrasonic detection optical fiber is wound between the ribs of the FRP rib, it is ensured that the position of the FBG corresponds to the position of the specific point on the ultrasonic transducer optical fiber.

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