CN-121978029-A - Fiber bragg grating crevice corrosion early warning system based on chloride ion sensitive hydrogel encapsulation

CN121978029ACN 121978029 ACN121978029 ACN 121978029ACN-121978029-A

Abstract

The invention relates to the technical field of optical fiber sensing and metal corrosion monitoring, and discloses an optical fiber grating crevice corrosion early warning system based on chloride ion sensitive hydrogel encapsulation, which comprises an optical fiber grating sensing subsystem, a metal structure crevice corrosion early warning system and a metal structure crevice corrosion early warning system, wherein the optical fiber grating sensing subsystem is configured to be implanted into the metal structure crevice, and an optical fiber grating in an axial pre-stretching state is anchored in a rigid encapsulation structure by using a gel material sensitive to chloride ions; the corrosion early warning processing subsystem is used for carrying the corrosion early warning processing subsystem. The invention is based on the logic of modulus reduction caused by the reaction of gel material and chloride ions invading into gaps, so that the prestress of the fiber grating is released and wavelength blue shift is generated. The system synchronously quantifies the modulus attenuation and chemical denaturation of gel through the decoupling analysis of the dual-mode resonance characteristics of the inclined grating, solves the problem that the hidden gap area is difficult to monitor in situ, and realizes the early warning of high sensitivity and high confidence of the gap corrosion.

Inventors

Cen Yuanyao
Liao Guangmeng
ZHU YUQIN
LIU CONG
HE QIONGYAO
LI LINGJIE
HE JIANXIN

Assignees

重庆大学
中国兵器装备集团西南技术工程研究所

Dates

Publication Date: 20260505
Application Date: 20260203

Claims (10)

1. Fiber bragg grating crevice corrosion early warning system based on chloride ion sensitive hydrogel encapsulation, which is characterized by comprising: The fiber bragg grating sensing subsystem (10) is used for being implanted into a gap area of a metal structure to be monitored, gel materials sensitive to chloride ions are filled in the gap area, the fiber bragg grating in an axial pre-stretching state is anchored in a rigid packaging structure by the gel materials sensitive to the chloride ions, and the fiber bragg grating sensing subsystem responds to chemical environment and micro-environment changes in the gap area and generates corresponding optical signals; The optical signal demodulation subsystem (20) is used for injecting a broadband excitation optical signal into the fiber grating sensing subsystem (10) and acquiring a spectrum signal which is reflected by the fiber grating sensing subsystem (10) and carries environment characteristic information; And the corrosion early warning processing subsystem (30) is used for inputting the spectrum signal, carrying out characteristic decoupling analysis on the spectrum signal, calculating the prestress release amount of the fiber grating based on a modulus reduction logic caused by the reaction of the gel material sensitive to chloride ions and the chloride ions invading the gap area, and outputting a corrosion early warning result.
2. The fiber grating crevice corrosion warning system based on chloride ion sensitive hydrogel encapsulation of claim 1, wherein the fiber grating sensing subsystem (10) comprises a set of sensing components for performing the anchoring function and responding to the chemical environmental change, the set of sensing components comprising in particular: a tilted grating sensing module (11) comprising, as the fiber grating, a single mode fiber inscribed with a bragg grating structure, the single mode fiber being applied with an axial tension to store elastic potential energy; A rigid encapsulation module (12) made of a corrosion resistant rigid material as the rigid encapsulation structure and having micro-porous channels allowing fluid permeation for providing a reaction force support against the axial tension force; A chloride ion sensitive gel module (13) which is used as the gel material to be filled between the inclined grating sensing module (11) and the rigid packaging module (12), and locks the axial strain of the inclined grating sensing module (11) by utilizing a polymer network structure so as to realize the anchoring function in the sensing assembly set; An environmental response gating module (14) overlaying the microporosity channels for establishing screening channels for acidic fluids.
3. The fiber grating crevice corrosion warning system based on chloride ion sensitive hydrogel encapsulation of claim 2, wherein the tilted grating sensing module (11) comprises a dual mode resonant optical structure for generating the environmental characteristic information, the dual mode resonant optical structure being defined in particular as: The grating surface of the Bragg grating structure is provided with an inclination angle of 4-10 degrees relative to the axis of the optical fiber, so that a fiber core mode formant and a cladding mode formant are excited in the optical signal at the same time; The fiber core mode formants represent the release degree of the elastic potential energy, the cladding mode formants represent the refractive index change of the chloride ion sensitive gel module (13), and the fiber core mode formants and the cladding mode formants jointly form the environment characteristic information generated by the dual-mode resonance optical structure.
4. The fiber bragg grating crevice corrosion warning system based on chloride ion sensitive hydrogel encapsulation of claim 2, wherein the chloride ion sensitive gel module (13) operates based on a chemical coordination dissociation mechanism triggering the modulus decrease, specifically defined as: Polyacrylic acid is used as a high molecular framework, and coordination bonds of silver ions and carboxylate ions are used as physical crosslinking points to form a three-dimensional network structure; when contacting chloride ions, silver ions preferentially combine with chloride ions to form a precipitate, resulting in cleavage of the coordination bond, such that the chloride ion-sensitive gel module (13) is transformed from a high storage modulus solid state to a low modulus mobile state; The transition of the solid state to the rheological state causes the modulus to decrease, thereby releasing the mechanical lock on the tilted grating sensing module (11).
5. The fiber bragg grating crevice corrosion warning system based on chloride ion sensitive hydrogel encapsulation of claim 2, wherein the environmental response gating module (14) is provided with a volume phase change screening mechanism for responding to the micro-environmental changes, the volume phase change screening mechanism being specifically defined as: A pH sensitive hydrogel material with volume phase change characteristic is adopted; when the pH value of the environment is higher than a preset acidity threshold value, the swelling state is kept so as to block the micro pore channel; volume shrinkage occurs to open the microporosity channels when the environmental pH drops below the preset acidity threshold; The pH sensitive hydrogel material responds to the change of the microenvironment through the change of the volume, so that the conduction of the acidic fluid in the gap is realized.
6. The fiber grating crevice corrosion warning system based on chloride ion sensitive hydrogel encapsulation of claim 1, wherein the optical signal demodulation subsystem (20) comprises spectrum acquisition hardware for completely acquiring the spectrum signal, the spectrum acquisition hardware specifically comprising: The light source emission module (21) outputs a spectrum which covers 1520 nm to 1610 nm wave bands so as to cover a fiber core mode formant and a high-order cladding mode formant group in a short wave direction of the fiber bragg grating sensing subsystem (10); A spectrum acquisition module (22) having a picometer-scale spectral resolution for resolving the comb-like structure of the higher-order cladding mode formants; The light source emission module (21) and the spectrum acquisition module (22) work cooperatively to acquire the spectrum signals containing multi-mode resonance information.
7. The fiber bragg grating crevice corrosion warning system based on chloride ion sensitive hydrogel encapsulation of claim 1, wherein the corrosion warning processing subsystem (30) comprises a signal feature extraction module (31) that performs a feature variable extraction procedure for quantifying the spectral signal features, the feature variable extraction procedure specifically comprising: Separating a formant at the longest wavelength from the spectrum signal, and extracting a central wavelength value of the formant as a first characteristic variable for representing a mechanical state; And separating a formant group in a short wave direction from the spectrum signal, and extracting a spectrum envelope form or a cut-off wavelength of the formant group as a second characteristic variable for representing the chemical state.
8. The fiber grating crevice corrosion warning system based on chloride ion sensitive hydrogel packaging of claim 7, wherein the corrosion warning processing subsystem (30) performs parametric decoupling inversion logic for performing the feature decoupling analysis, the parametric decoupling inversion logic specifically comprising: based on the wavelength blue shift of the first characteristic variable, inverting and calculating the release amount of the axial strain of the optical fiber by utilizing the relationship of the optical fiber elasto-optical effect, thereby quantifying the modulus attenuation degree of the gel material; Based on the spectral distortion characteristics of the second characteristic variable, inversion calculation is performed on the effective refractive index change of the medium around the optical fiber by using the cladding mode phase matching condition, so that the chemical denaturation degree of the gel material is quantified; and respectively calculating the release amount of the axial strain of the optical fiber and the effective refractive index change to separate the mechanical parameter from the chemical parameter, thereby completing the characteristic decoupling analysis.
9. The fiber grating crevice corrosion warning system based on chloride ion sensitive hydrogel encapsulation of claim 8, wherein the corrosion warning processing subsystem (30) comprises a corrosion decision warning module (32) executing a dual threshold decision logic for outputting the corrosion warning result, the dual threshold decision logic being specifically defined as: simultaneously monitoring a mechanical retraction criterion and a component denaturation criterion of the parameter decoupling inversion logic output; only when the calculated release amount of the axial strain of the optical fiber exceeds a preset mechanical relaxation threshold value and the calculated effective refractive index change exceeds a preset refractive index fluctuation threshold value, judging that crevice corrosion occurs; and generating and outputting the corrosion early warning result based on the double verification of the mechanical retraction criterion and the component denaturation criterion.
10. The fiber grating crevice corrosion warning system based on chloride ion sensitive hydrogel encapsulation of claim 4, wherein the chloride ion sensitive gel module (13) has gel synthesis parameters for ensuring the anchoring strength, specifically defined as: The polyacrylic acid has a weight average molecular weight of 400000 to 55000; The molar ratio of the silver ions to carboxylate ions on the polyacrylic acid chain is set to be 1:2 to 1:4; the chloride ion-sensitive gel module (13) prepared using the gel synthesis parameters has an initial crosslink density required to maintain the fiber grating pre-stretched state, thereby ensuring the effectiveness of the anchoring.

Description

Fiber bragg grating crevice corrosion early warning system based on chloride ion sensitive hydrogel encapsulation Technical Field The invention relates to the technical field of optical fiber sensing and metal corrosion monitoring, in particular to an optical fiber grating crevice corrosion early warning system based on chloride ion sensitive hydrogel encapsulation. Background Currently, bolting, riveting or structural lamination interfaces are widely available in various large-scale metal facilities such as ocean platforms, oil pipeline networks and aerospace equipment. These sites inevitably form narrow, semi-closed gap areas. In a salt-containing service environment, these small gaps tend to become trapping traps for aggressive anions, especially for localized enrichment of chloride ions. Because the transmission of substances in the gaps is limited, the self-catalytic effect is easy to be initiated and the local acidification is caused, and a corrosion microenvironment which is different from the external macroscopic environment is formed. Such hidden crevice corrosion often causes sudden structural failure when no anomaly is present on the surface of the structure, within which material dissolution or stress corrosion cracking has occurred. Aiming at the monitoring requirement of the hidden area, the existing application technology mainly adopts an electrochemical detection method or a physical quantity optical fiber sensing method. Electrochemical monitoring typically embeds miniature reference electrodes or resistive probes near the connection, which reverse the corrosion tendency by capturing potential drift or changes in polarization resistance. The optical fiber sensing scheme works by utilizing the elasto-optic effect or the thermo-optic effect of the optical fiber grating. The general operation mode is to paste a grating sensor on the surface or the adjacent area of the structure, record the extrusion stress generated by the volume expansion of corrosion products, or monitor the temperature fluctuation caused by heat accumulation accompanied by the corrosion chemical reaction, so as to establish the correlation of the optical signal and the health state of the structure. However, the existing monitoring means still have limitations in practical application. Electrochemical probes are limited by physical dimensions, are difficult to truly penetrate into the micron-sized gap core region, and implantation of the probe itself can change the original geometric space and fluid diffusion dynamics of the gap, resulting in distortion of measurement data. Physical monitoring methods based on corrosion product expansion have time lag, and relying on solid oxide accumulation to trigger the sensor means that substantial loss of matrix material has occurred and zero damage early warning cannot be achieved at the initial stage of chloride ion invasion. In addition, single fiber grating strain measurement faces the cross-sensitivity problem, and the sensor cannot distinguish whether spectrum drift is caused by corrosion expansion or is caused by external mechanical load change or environmental temperature fluctuation, and signal blurring caused by the multi-physical field coupling makes the prior art difficult to provide high-confidence corrosion judgment under complex dynamic working conditions. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a fiber grating gap corrosion early warning system based on chloride ion sensitive hydrogel encapsulation, which solves the technical problems that the prior art cannot go deep into a metal structure to conceal a gap for in-situ monitoring, and mechanical interference and chemical corrosion signals are difficult to distinguish, so that early warning lag and false alarm are caused. In order to achieve the purpose, the invention is realized by the following technical scheme that the fiber grating crevice corrosion early warning system based on chloride ion sensitive hydrogel encapsulation comprises: The optical fiber grating sensing subsystem is implanted into a gap area of a metal structure to be monitored, gel materials sensitive to chloride ions are filled in the optical fiber grating sensing subsystem, the optical fiber grating in an axial pre-stretching state is anchored in the rigid packaging structure by utilizing the gel materials sensitive to the chloride ions, and the optical fiber grating sensing subsystem is used for responding to the chemical environment and micro-environment changes in the gap area and generating corresponding optical signals; The optical signal demodulation subsystem is used for injecting a broadband excitation optical signal into the fiber bragg grating sensing subsystem and acquiring a spectrum signal which is reflected by the fiber bragg grating sensing subsystem and carries environment characteristic information; The corrosion early warning processing subsystem is used for inputting a spectrum signal