A real-time detection method for the corrosion condition of metal pipelines based on tilted fiber Bragg gratings

Abstract

The present invention relates to the technical field of physical and chemical measurement, and in particular to a real-time detection method for the corrosion condition of metal pipelines based on tilted fiber Bragg gratings, including: Step S1, collecting data; Step S2, extracting the corrosion distribution area at each moment; Step S3, obtaining the dimensional directivity of the fiber Bragg grating sensors arranged for each type of dimensional data at each moment and the dimensional directivity of the fiber Bragg grating sensors arranged for the iron ion concentration at each moment; Step S4, obtaining the dimensional direction difference degree of the fiber Bragg grating sensors arranged for the iron ion concentration at each moment; Step S5, screening and obtaining the moment to be adjusted; Step S6, obtaining the standard relative ratio of the iron ion concentration at the moment to be adjusted; Step S7, obtaining the detected corrosion rate at each position at the moment to be adjusted. The present invention improves the detection accuracy of metal corrosion chemical reaction information and realizes real-time detection and early warning of early corrosion of metal pipelines.

Description

Technical Field

[0001] The present invention relates to the technical field of physical and chemical measurement, and in particular to a real-time detection method for the corrosion condition of metal pipelines based on tilted fiber Bragg gratings. Background Art

[0002] The corrosion of metal inside metal pipelines can cause the pipe wall to become thinner, develop defects, and result in leakage of the fluid inside the pipeline, which has a serious impact on various aspects such as personal safety and environmental protection. Early-stage metal corrosion is beyond the scope of human visual observation. Therefore, timely and accurate detection of the initial corrosion of metal pipelines can effectively prevent corrosion accidents, improve economic efficiency, and ensure personal property and environmental safety. Traditional metal corrosion detection methods include the gravimetric method, gas determination method, and electrochemical method, which can calculate the corrosion rate of metals to a certain extent. However, the fundamental trend in the development of current corrosion sensors is to achieve fast, highly sensitive, non-destructive, in-situ real-time corrosion detection and meet the requirements of complex application scenarios. Fiber optic sensors use optical fibers as carriers and detect the corrosion of the metal pipeline to be measured by detecting changes in optical signal parameters. They have the advantages of small size, light weight, anti-electromagnetic interference, and high resolution, and have received the attention of many research scholars. The optical fiber itself is both a signal transmission carrier and a signal modulator. Its working principle is that when an external physical quantity changes, the characteristic properties of the transmitted light wave will change accordingly. Therefore, the physical quantity is monitored by monitoring the change in the light wave.

[0003] Currently, fiber optic corrosion sensors are mainly used to detect changes in physical parameters such as corrosion displacement, material structure, and vibration, stress, temperature, humidity, and cracks related to corrosion, so as to reflect or predict the occurrence and degree of corrosion. Fiber optic corrosion sensors can work in harsh environments for long-term stable detection, but the internal chemical reaction information of metal corrosion is not clear, and they lack the ability of real-time monitoring and early warning of early corrosion.

[0004] Chinese Patent Publication No.: CN103076391A discloses a detection method for local corrosion of metal pipelines. A quantitative detection method for local corrosion of metal pipelines includes the following steps: Step 1, using ultrasonic guided waves to quickly detect the corrosion of the pipeline and mark the suspected parts of local corrosion; Step 2, using ultrasonic C-scan to quantitatively detect the suspected local corrosion of the pipeline; Step 3, combining the detection results of Steps 1 and 2, and using probability statistics to calculate the maximum local corrosion depth: ; where X: the depth of the corrosion hole; F(X): the probability that the depth of the corrosion hole is less than or equal to X; α: statistical parameter (size parameter); λ: statistical parameter (position parameter). However, this solution does not solve the problems that the internal chemical reaction information of metal corrosion by fiber optic corrosion sensors is not clear and the lack of real-time detection and early warning ability for early corrosion. Summary of the Invention

[0005] To this end, the present invention provides a real-time detection method for the corrosion condition of metal pipelines based on tilted fiber Bragg gratings, so as to overcome the problems in the prior art that the fiber optic corrosion sensor is not clear about the internal chemical reaction information of metal corrosion, lacks the ability of real-time detection and early warning of corrosion, the test period of the metal pipeline corrosion detection technology is long, it cannot adapt to harsh environments and cannot be monitored in real time, resulting in low efficiency of real-time detection of the corrosion condition of metal pipelines.

[0006] To achieve the above object, the present invention provides a real-time detection method for the corrosion condition of metal pipelines based on tilted fiber Bragg gratings, including:

[0007] Step S1, collecting the corrosion change degree data set and the type dimension data set through tilted fiber Bragg gratings;

[0008] Step S2, extracting the corrosion distribution area at each moment according to the corrosion change degree at different positions in the metal pipeline at the same moment in the corrosion change degree data set;

[0009] Step S3, obtaining the dimensional directivity of the fiber Bragg grating sensors arranged for each type dimension data at each moment and the dimensional directivity of the fiber Bragg grating sensors arranged for the iron ion concentration at each moment according to the corrosion distribution area at each moment and the type dimension data set;

[0010] Step S4, obtaining the mean value of the dimensional directivity of the fiber Bragg grating sensors arranged for each type dimension data at each moment, and obtaining the dimensional direction difference degree of the fiber Bragg grating sensors arranged for the iron ion concentration at each moment according to the mean value of the dimensional directivity of the fiber Bragg grating sensors arranged for each type dimension data at each moment;

[0011] Step S5, screening and obtaining the moment to be adjusted according to the dimensional direction difference degree of the fiber Bragg grating sensors arranged for the iron ion concentration at each moment;

[0012] Step S6, obtaining the relative proportion combination of the iron ion concentration at each position at the moment to be adjusted according to the dimensional directivity of the fiber Bragg grating sensors arranged for each type dimension data at the moment to be adjusted, the dimensional directivity of the fiber Bragg grating sensors arranged for the iron ion concentration at the moment to be adjusted, and the corrosion change degree at different positions in the metal pipeline at the moment to be adjusted, and obtaining the standard relative proportion of the iron ion concentration at the moment to be adjusted according to the relative proportion combination of the iron ion concentration at each position at the moment to be adjusted;

[0013] Step S7, obtaining the detected corrosion rate at each position at the moment to be adjusted according to the relative proportion combination of the iron ion concentration at each position at the moment to be adjusted and the standard relative proportion of the iron ion concentration at the moment to be adjusted.

[0014] Further, in the step S2, when extracting the corrosion sub-regions at each moment according to the corrosion change degree of different positions in the metal pipeline at the same moment in the corrosion change degree dataset by the corrosion distribution region extraction method, the corrosion distribution region extraction method includes:

[0015] Step S20, obtaining the mean value of the corrosion change degree at the arrangement positions of each inclined fiber Bragg grating in the metal pipeline at the target moment in the corrosion change degree dataset, and taking it as the standard level of the iron ion concentration at the target moment;

[0016] Step S21, constructing a two-dimensional sample space of the metal pipeline, where the horizontal axis of the two-dimensional sample space is the axial direction of the metal pipeline, the vertical axis of the two-dimensional sample space is the circumferential direction after the two-dimensional expansion of the metal pipeline, and the arrangement positions of each inclined fiber Bragg grating correspond to the coordinate points on the two-dimensional sample space;

[0017] Step S22, comparing the corrosion change degree H of the coordinate points in the two-dimensional sample space of the metal pipeline with the standard level H0 of the iron ion concentration at the target moment, and identifying the corrosion coordinate points at the target moment according to the comparison result, where:

[0018] When H ≤ H0, it is identified that this coordinate point is not the corrosion coordinate point at the target moment;

[0019] When H > H0, it is identified that this coordinate point is the corrosion coordinate point at the target moment;

[0020] Extract the coverage area of all corrosion coordinate points at the target moment, take it as the corrosion distribution area at the target moment, and take the set of the corrosion distribution areas at each moment as the corrosion distribution area at each moment.

[0021] Further, in the step S3, the dimensional directionality of the fiber Bragg grating sensors arranged for each type of dimensional data at each moment is obtained by the type-dimensional directionality obtaining method, and the type-dimensional directionality obtaining method includes:

[0022] Step S31, obtaining the dimensional data of each coordinate point in the corrosion distribution area at the target moment for this type;

[0023] Step S32, performing PCA principal component analysis on the dimensional data of each coordinate point for this type, obtaining the two principal component directions with the largest eigenvalues for this type, and connecting the coordinate points passed by the two principal component directions with the largest eigenvalues for this type in the corrosion distribution area at the target moment to obtain the major axis and the minor axis of the dimensional data for this type;

[0024] Step S33: Divide the area between the major axis of the type of dimensional data and the minor axis of each piece of the type of dimensional data according to a preset partitioning angle, to obtain the type of dimensional data partitioning, the axis of the type of dimensional data partitioning, and the axial lengths of the axes of each partition of the type of dimensional data.

[0025] Step S34: Obtain the difference in axial lengths between adjacent partition axes among the axes of each partition of the type of dimensional data, take it as the adjacent axial difference, and obtain the dimensional directivity of the fiber Bragg grating sensor arrangement for each type of dimensional data at the target moment according to the adjacent axial difference, and use the set of the dimensional directivities of the fiber Bragg grating sensor arrangement for each type of dimensional data at each moment as the dimensional directivity of the fiber Bragg grating sensor arrangement for each type of dimensional data at each moment.

[0026] Further, in step S34, when obtaining the dimensional directivity of the fiber Bragg grating sensor arrangement for each type of dimensional data at the target moment according to the adjacent axial difference, calculate the dimensional directivity of the fiber Bragg grating sensor arrangement for the r-th type of dimensional data at the target moment , set , where N is the total number of axes of the type of dimensional data partitioning, and respectively represent the axial length of the i-th partition axis of the r-th type of dimensional data in the corrosion distribution area at the target moment and the axial length of the -th partition axis, represents the absolute value function, represents the sigmoid function, and use the dimensional directivity of the fiber Bragg grating sensor arrangement for the r-th type of dimensional data at the target moment in each type of data set as the dimensional directivity of the fiber Bragg grating sensor arrangement for each type of dimensional data at the target moment.

[0027] Further, in step S3, when obtaining the dimensional directivity of the fiber Bragg grating sensor arrangement for the iron ion concentration at each moment, perform PCA principal component analysis on the degree of corrosion change of all coordinate points in the two-dimensional sample space of the metal pipeline in the corrosion distribution area at the target moment, and use the analysis result as the dimensional directivity of the fiber Bragg grating sensor arrangement for the iron ion concentration at the target moment.

[0028] Further, in step S4, when obtaining the dimensional direction difference degree of the fiber Bragg grating sensor arrangement for the iron ion concentration at each moment, take the absolute value of the difference between the mean value of the dimensional directivity of the fiber Bragg grating sensor arrangement of the type of dimensional data at the target moment and the dimensional directivity of the fiber Bragg grating sensor arrangement for the iron ion concentration at the target moment as the dimensional direction difference degree of the fiber Bragg grating sensor arrangement for the iron ion concentration at the target moment.

[0029] Further, in step S6, when obtaining the relative proportion combination of ferric ion concentrations at each position at the moment to be adjusted, the ratio of the mean of the dimensional directivity of the fiber Bragg grating sensors arranged for the ferric ion concentration at the reference moment to the dimensional directivity of the fiber Bragg grating sensors arranged for the type dimension data is used as the relative proportion at the reference moment. The product of the corrosion change degree at different positions in the metal pipe at the reference moment and the relative proportion at the reference moment is used as the relative proportion combination of ferric ion concentrations at each position at the reference moment. Each moment in the moment to be adjusted is sequentially used as the reference moment to obtain the relative proportion combination of ferric ion concentrations at each position at each reference moment, and it is used as the relative proportion combination of ferric ion concentrations at each position at the moment to be adjusted.

[0030] Further, in step S6, when obtaining the standard relative proportion of ferric ion concentration at the moment to be adjusted, a quantity statistics is performed on the relative proportion combination of ferric ion concentrations at each position at the reference moment, and a ratio quantity histogram is constructed in ascending order. The abscissa is the numerical value of the relative proportion combination of ferric ion concentrations at each position arranged from small to large, the ordinate is the quantity corresponding to each relative proportion combination, and the result referenceability of the k-th relative proportion combination at the reference moment is calculated, and it is set that:

[0031] wherein, represents the value of the k-th relative proportion combination at the reference moment, represents the quantity corresponding to the k-th relative proportion combination at the reference moment, k represents the order value of the k-th relative proportion combination arranged from small to large at the reference moment, represents the weight normalization function;

[0032] According to each relative proportion combination at the reference moment and the result referenceability of the k-th relative proportion combination at the reference moment , the standard relative proportion of ferric ion concentration at the reference moment is obtained.

[0033] Further, in step S6, when obtaining the standard relative proportion of ferric ion concentration at the reference moment, according to the result referenceability of the k-th relative proportion combination at the reference moment and the value of the k-th relative proportion combination in each relative proportion combination at the reference moment, the standard relative proportion of ferric ion concentration at the reference moment is calculated, and it is set ;

[0034] Take each moment in the moments to be adjusted as the reference moment in turn, and obtain the standard relative ratio of the iron ion concentration at each reference moment, and use it as the standard relative ratio of the iron ion concentration at the moment to be adjusted.

[0035] Further, in step S7, when obtaining the detected corrosion rate at each position at the moment to be adjusted, it is set that:

[0036]

[0037] Among them, represents the detected corrosion rate at the m-th position at the j-th moment to be adjusted, represents the degree of corrosion change at the m-th position at the j-th moment to be adjusted, represents the relative ratio combination of the iron ion concentration at the m-th position at the j-th moment to be adjusted, represents the standard relative ratio of the iron ion concentration at the j-th moment to be adjusted, represents the absolute value function.

[0038] Compared with the prior art, the beneficial effects of the present invention are that the method provides an accurate data basis for subsequent analysis through step S1, enables the detection system to conduct a detailed assessment of the pipeline corrosion situation, ensures the comprehensiveness and accuracy of the data. The method clarifies the corrosion concentration area through step S2, helps quickly locate potential problem areas, and provides accurate guidance for maintenance and repair, thereby saving time and resources. The method optimizes the arrangement and configuration of sensors through step S3, improves the detection accuracy and response speed, and ensures that the environmental changes inside the pipeline can be comprehensively captured. The method improves the understanding of sensor data through step S4 by mean and difference analysis, ensures the stability and consistency of the data, and identifies possible abnormal signals. The method effectively identifies abnormal time points through step S5, which may be affected by external environments or internal factors, and ensures the pertinence of subsequent analysis and adjustment. The method corrects possible measurement errors through step S6 by precise ratio calculation, improves the accuracy of iron ion concentration evaluation, and ensures the reliability of corrosion evaluation. The method provides accurate corrosion rate information through step S7, supports the early maintenance and warning system of the pipeline, helps reduce sudden failures, and extends the service life of the pipeline. Description of the Drawings

[0039] Figure 1 is a schematic flowchart of the real-time detection method for the corrosion condition of a metal pipeline based on an inclined fiber Bragg grating in this embodiment;

[0040] Figure 2 is a schematic diagram of the arrangement positions of some inclined fiber Bragg gratings in a metal pipeline in this embodiment;

[0041] Figure 3 Schematic diagram of the fitting curve between the wavelength of the Bragg resonance peak and temperature in the tilted fiber Bragg grating sensor of this embodiment;

[0042] Figure 4 Schematic diagram of the fitting curve between the wavelength of the Bragg resonance peak and stress in the tilted fiber Bragg grating sensor of this embodiment. Detailed implementation manners

[0043] In order to make the objectives and advantages of the present invention clearer and more understandable, the present invention will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] The preferred implementation manners of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these implementation manners are only used to explain the technical principle of the present invention and do not limit the protection scope of the present invention.

[0045] It should be noted that in the description of the present invention, the terms indicating the direction or positional relationship such as "upper", "lower", "left", "right", "inner", "outer", etc. are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0046] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0047] Please refer to Figure 1 as shown, which is a schematic flow diagram of the method for real-time detection of the corrosion condition of a metal pipeline based on a tilted fiber Bragg grating. The method includes:

[0048] Step S1, collecting the corrosion change degree dataset and the type dimension dataset through the tilted fiber Bragg grating;

[0049] Step S2, extracting the corrosion distribution area at each moment according to the corrosion change degrees at different positions in the metal pipeline at the same moment in the corrosion change degree dataset;

[0050] Step S3, obtain the dimensional directivity of the fiber Bragg grating sensors for each type dimension data at each moment and the dimensional directivity of the fiber Bragg grating sensors for the iron ion concentration at each moment according to the corrosion distribution area and type dimension data set at each moment;

[0051] Step S4, obtain the mean value of the dimensional directivity of the fiber Bragg grating sensors for each type dimension data at each moment, and obtain the dimensional direction difference degree of the fiber Bragg grating sensors for the iron ion concentration at each moment according to the mean value of the dimensional directivity of the fiber Bragg grating sensors for each type dimension data at each moment;

[0052] Step S5, screen and obtain the moment to be adjusted according to the dimensional direction difference degree of the fiber Bragg grating sensors for the iron ion concentration at each moment;

[0053] Step S6, obtain the relative proportion combination of the iron ion concentration at each position at the moment to be adjusted according to the dimensional directivity of the fiber Bragg grating sensors for each type dimension data at the moment to be adjusted, the dimensional directivity of the fiber Bragg grating sensors for the iron ion concentration at the moment to be adjusted, and the corrosion change degree at different positions in the metal pipeline at the moment to be adjusted, and obtain the standard relative proportion of the iron ion concentration at the moment to be adjusted according to the relative proportion combination of the iron ion concentration at each position at the moment to be adjusted;

[0054] Step S7, obtain the detected corrosion rate at each position at the moment to be adjusted according to the relative proportion combination of the iron ion concentration at each position at the moment to be adjusted and the standard relative proportion of the iron ion concentration at the moment to be adjusted.

[0055] Specifically, the method is set in the real-time detection terminal for the corrosion condition of metal pipelines. It uses carbon quantum dot-functionalized tilted fiber Bragg gratings that can absorb metal iron ions to detect the change in the refractive index of the grating cladding region, calculates the iron ion concentration using the wavelength drift information of the grating cutoff cladding mode, and then evaluates the corrosion rate of the metal pipeline. It solves the defects in the detection technology in this field, such as long test cycle, inability to adapt to harsh environments, and lack of real-time monitoring. It has the advantages of being flexible, in-situ, real-time, and highly sensitive for early corrosion monitoring and warning, and is applicable to the initial corrosion detection of metal pipelines in multiple scenarios such as seawater, oil, and sewage. Among them, the method provides an accurate data basis for subsequent analysis through step S1, enabling the detection system to conduct a detailed assessment of the pipeline corrosion situation and ensuring the comprehensiveness and accuracy of the data. The method clarifies the corrosion-concentrated area through step S2, helps quickly locate potential problem areas, and provides accurate guidance for maintenance and repair, thus saving time and resources. The method optimizes the arrangement and configuration of sensors through step S3, improves the detection accuracy and response speed, and ensures that environmental changes inside the pipeline can be comprehensively captured. The method improves the understanding of sensor data through step S4 by means of mean and difference analysis, ensures the stability and consistency of the data, and identifies possible abnormal signals. The method effectively identifies abnormal time points through step S5, which may be affected by external environments or internal factors, ensuring the pertinence of subsequent analysis and adjustment. The method corrects possible measurement errors through step S6 by means of accurate ratio calculation, improves the accuracy of iron ion concentration evaluation, and ensures the reliability of corrosion assessment. The method provides accurate corrosion rate information through step S7, supports the early maintenance and warning system of the pipeline, helps reduce sudden failures, and extends the service life of the pipeline.

[0056] Specifically, the purpose of this embodiment is to detect the initial corrosion of metal pipelines in a timely and accurate manner through tilted fiber Bragg grating sensors. Corrosion detection is mainly related to the concentration of iron ions, and at the same time, the differences in detection results at multiple positions are related to the stress distribution, that is, the stress changes at the positions of crack corrosion. When the iron ion concentration is low, that is, in the initial stage of corrosion, the influence of other environmental factors is also relatively large. In addition to the directional stress distribution, temperature changes will also have different effects on corrosion. Therefore, it is necessary to obtain two types of dimensional data, namely temperature and stress, to separate the influence weights of different types of dimensional data on the initial corrosion of metal pipelines at different times.

[0057] It should be noted that the spectral performance of fiber Bragg gratings is the combined influence of multiple types of dimensional data, that is, the multi-peak shift characteristics of the spectral data are affected by multiple factors such as corrosion rate, temperature, and stress. Especially in the early stages of metal pipe corrosion, the carbon quantum dot-functionalized tilted fiber Bragg grating that can absorb metallic iron ions is less sensitive to iron ions in metal pipe corrosion with lower concentrations, and is easily affected by the regional structure of the corrosion location. Dimensional data such as temperature and stress have a wider range of influence, resulting in large errors in the analysis of corrosion conditions.

[0058] Specifically, the manufacturing method of the tilted fiber grating sensor includes:

[0059] Step N1, writing a tilted fiber grating with a grating plane at a certain angle to the fiber axis: using a phase mask to write a tilted fiber grating with an angle of 6 to 12 degrees, and the grating area length is 1 cm; Step N2, deposition of carbon quantum dots on the grating surface: using a silane coupling method; first, using a piranha solution to hydroxylate the grating area of ​​the tilted fiber grating; immersing the hydroxylated tilted fiber grating in an ethanol solution of 3-aminopropyl-trimethoxysilane (APTMS); then, using ethanol and ultrapure water to rinse the tilted fiber grating multiple times to remove excess APTMS solution on the surface, and vacuum drying the cleaned tilted fiber grating; dissolving carbon quantum dots in a phosphate buffer solution, using EDC-NHS to activate the surface groups of the carbon quantum dots, and then immersing the tilted fiber grating in a phosphate buffer solution of carbon quantum dots with activated groups to complete the self-assembly of carbon quantum dots on the side surface of the tilted fiber grating.

[0060] It should be further explained that the iron ion concentration is obtained by utilizing the linear relationship between the cutoff cladding mode wavelength and the refractive index of the tilted fiber Bragg grating. The iron ion concentration in the metal pipe is proportional to the corrosion rate, that is, the iron ion concentration at different arrangement positions of the tilted fiber Bragg grating is represented by detecting the drift rate of the cutoff mode resonance wavelength; at the same time, the Bragg resonance peak in the tilted fiber Bragg grating can measure the ambient temperature and stress, thereby detecting multi-type dimensional data of the metal pipe through the tilted fiber Bragg grating.

[0061] Specifically, in step S1, the corrosion change degree data set refers to a collection of corrosion change degree data of metal pipelines at different locations and at different times, and the type dimension data set refers to several types of dimensional data related to corrosion in metal pipelines, such as dimension and stress.

[0062] It should be noted that the change in the concentration of iron ions is strongly correlated with the corrosion location of the metal pipeline. That is, the concentration of iron ions is higher at the location with a higher degree of corrosion. That is, affected by corrosion areas such as cracks, the degree of corrosion change is higher closer to the center of the corrosion area. Therefore, the corrosion changes at different inclined fiber Bragg grating arrangement positions have a directionality following the shape of the corrosion area, and the degree of change in data of types such as corresponding temperature and stress has a larger influence area.

[0063] Furthermore, it should be noted that the actual shape of the corrosion area in the metal pipeline is different. Especially for the corrosion caused by cracks, the stress change in the actual area where the crack exists will gradually decrease along the long axis and short axis of the area to the outside of the area, and the diffusion condition of the axial crack is more obvious than that of the circumferential crack. Therefore, the influence area of iron ions is closer to the actual shape of the corrosion area, while the influence areas of other stresses, temperatures, etc. are larger.

[0064] Specifically, in the step S2, when extracting the corrosion distribution area by the corrosion distribution area extraction method according to the corrosion change degree of different positions in the metal pipeline at the same moment in the corrosion change degree dataset, the corrosion distribution area extraction method includes:

[0065] Step S20, obtaining the average value of the corrosion change degree of each inclined fiber Bragg grating arrangement position in the metal pipeline at the target moment in the corrosion change degree dataset, and taking it as the standard level of the iron ion concentration at the target moment;

[0066] Step S21, constructing a two-dimensional sample space of the metal pipeline, where the horizontal axis of the two-dimensional sample space is the axial direction of the metal pipeline, and the vertical axis of the two-dimensional sample space is the circumferential direction after the two-dimensional expansion of the metal pipeline. Each inclined fiber Bragg grating arrangement position corresponds to a coordinate point on the two-dimensional sample space;

[0067] Step S22, comparing the corrosion change degree H of the coordinate point in the two-dimensional sample space of the metal pipeline with the standard level H0 of the iron ion concentration at the target moment, and identifying the corrosion coordinate point at the target moment according to the comparison result, where:

[0068] When H ≤ H0, it is identified that this coordinate point is not the corrosion coordinate point at the target moment;

[0069] When H > H0, it is identified that this coordinate point is the corrosion coordinate point at the target moment;

[0070] Extract the coverage area of all corrosion coordinate points at the target moment, and take it as the corrosion distribution area at the target moment. The set of corrosion distribution areas at each moment of the target moment is used as the corrosion distribution area at each moment.

[0071] Specifically, the target moment refers to a randomly selected moment. In this embodiment, the selection method of the target moment is not limited, and those skilled in the art can freely set it according to the actual situation, as long as the requirement for selecting data at the same moment is met. For example, a random moment can be selected at a regular time interval as the target moment. The coverage area of all corrosion coordinate points at the target moment refers to the range set composed of the radiation areas where corrosion may exist at each corrosion coordinate point at the target moment. In this embodiment, the composition method of the coverage area of all corrosion coordinate points at the target moment is not limited, and those skilled in the art can freely set it according to the actual situation, as long as the requirement for extracting the corrosion distribution area at the target moment is met. For example, the area with each corrosion coordinate point as the center and a preset radiation distance of 10 cm as the radius at the target moment can be set as the radiation area where corrosion may exist at each corrosion coordinate point, and their sum is used as the coverage area of all corrosion coordinate points at the target moment. The different positions refer to the sum of the arrangement positions of each tilted fiber Bragg grating in the metal pipeline.

[0072] Specifically, in step S3, the dimensional directionality of the fiber Bragg grating sensor arrangement for each type of dimensional data at each moment is obtained through the type-dimensional directionality acquisition method. The type-dimensional directionality acquisition method includes:

[0073] Step S31, obtaining the coordinate points in the corrosion distribution area at the target moment in the dimensional data of this type;

[0074] Step S32, performing PCA principal component analysis on the dimensional data of each coordinate point in this type to obtain the two principal component directions with the largest eigenvalues in this type. Connect the coordinate points passed by the two principal component directions with the largest eigenvalues in this type in the corrosion distribution area at the target moment to obtain the major axis and minor axis of the dimensional data of this type;

[0075] Step S33, dividing the area between the major axis of the dimensional data of this type and each minor axis of the dimensional data of this type according to the preset partition angle to obtain the dimensional data partition of this type, the dimensional data partition axis of this type, and the axial lengths of the respective partition axes of the dimensional data of this type;

[0076] Step S34, obtaining the difference in axial lengths between adjacent partition axes in the respective partition axes of the dimensional data of this type, taking it as the adjacent axial difference, and obtaining the dimensional directionality of the fiber Bragg grating sensor arrangement for each type of dimensional data at the target moment according to the adjacent axial difference. The set of the dimensional directionality of the fiber Bragg grating sensor arrangement for each type of dimensional data at the target moment at each moment is used as the dimensional directionality of the fiber Bragg grating sensor arrangement for each type of dimensional data at each moment.

[0077] Specifically, in the step S34, when obtaining the dimensional directivity of the fiber Bragg grating sensors for each type of dimensional data at the target moment according to the adjacent axial differences, calculate the dimensional directivity of the fiber Bragg grating sensors for r types of dimensional data at the target moment , set , where N is the total number of partition axes of this type of dimensional data, and respectively represent the axial length of the i-th partition axis and the axial length of the -th partition axis of the r-th type of dimensional data in the corrosion distribution area at the target moment, represents the absolute value function, represents the sigmoid function, and use the dimensional directivity of the fiber Bragg grating sensors for the r-th type of dimensional data at the target moment as the dimensional directivity of the fiber Bragg grating sensors for each type of dimensional data at the target moment in each type of data set.

[0078] Specifically, in the step S3, when obtaining the dimensional directivity of the fiber Bragg grating sensors for the iron ion concentration at each moment, perform PCA principal component analysis on the corrosion change degree of all coordinate points in the two-dimensional sample space of the metal pipeline in the corrosion distribution area at the target moment, and use the analysis result as the dimensional directivity of the fiber Bragg grating sensors for the target iron ion concentration.

[0079] It should be noted that by analyzing the difference in the axial lengths of the adjacent partition axes of this type of dimensional data in the corrosion distribution area, the greater the difference change in the axial lengths of the adjacent partition axes, that is, the greater the morphological change rate of the corrosion distribution area under this type of dimensional data. Then, by quantifying the average change rate, the greater the average change rate, the more compact the distribution of this type of dimensional data on the corrosion distribution area, and the greater the dimensional directivity of the fiber Bragg grating sensors for this type of dimensional data.

[0080] It should be noted that the dimensional directivity distribution of different types of dimensional data reflects the influence range of their dimensional data during the detection process, and the final analysis of the corrosion condition of the metal pipeline is based on the cladding mode resonance peak condition obtained by the spectral analyzer; when among different types of dimensional data, the iron ion concentration extracted by carbon quantum reflects the corrosion condition more accurately, that is, the dimensional directivity is more significant than the dimensional directivity of other types of dimensional data, it proves that using the cut-off mode resonance wavelength drift rate to reflect the metal pipeline corrosion rate and achieving the effect of early corrosion detection of the metal pipeline is better; then it is necessary to perform a difference analysis on the dimensional directivity of the iron ion concentration at the same moment and the dimensional directivity of other types of dimensional data.

[0081] Specifically, in step S4, when obtaining the dimensional direction difference degree of the fiber Bragg grating sensors arranged for the iron ion concentration at each moment, the absolute value of the difference between the mean of the dimensional directionality of the fiber Bragg grating sensors arranged for the target moment type dimension data and the dimensional directionality of the fiber Bragg grating sensors arranged for the iron ion concentration at the target moment is used as the dimensional direction difference degree of the fiber Bragg grating sensors arranged for the iron ion concentration at the target moment.

[0082] It should be noted that the dimensional direction difference degree actually reflects the credibility of the corrosion rate in the corrosion distribution area analyzed by iron ions, that is, the accuracy of the corrosion rate under the influence range characteristics analysis of multi-type dimension data at the initial stage of corrosion. Correspondingly, the earlier the corrosion stage of the pipeline corrosion area is, the smaller the generation rate of iron ions in the corrosion area is, the less combined with carbon quantum, and the smaller the influence on the multi-peak performance of the corresponding spectrum is; then it is necessary to adjust the corrosion rate of each corrosion distribution area through the dimensional direction difference degree, so as to improve the accuracy of the metal corrosion rate obtained by the tilted fiber Bragg grating, that is, it is necessary to adjust the influence of data of types such as stress and temperature to ensure that the cut-off mode resonance wavelength drift rate reflects the accuracy of the metal pipeline corrosion rate.

[0083] Specifically, in step S5, when screening and obtaining the moment to be adjusted, the dimensional direction difference degree C of the fiber Bragg grating sensors arranged for the iron ion concentration at each moment is compared with the preset difference degree C0, and the moment to be adjusted is screened and obtained according to the comparison result, where:

[0084] When C≥C0, screen that this moment is not the moment to be adjusted;

[0085] When C<C0, screen that this moment is the moment to be adjusted.

[0086] Specifically, the preset difference degree C0 refers to the preset value of the difference degree reflecting whether the detection results corresponding to the iron ion concentration at each moment are accurate. When the detection results corresponding to the iron ion concentration at this moment are inaccurate, screen that this moment is the moment to be adjusted. In this embodiment, C0 = 0.75.

[0087] It should be noted that for the dimensional directionality of the tilted fiber Bragg grating arranged for each type of dimension data at the moment to be adjusted, its adjustment amplitude is combined and correlated with the corrosion change degree at each arrangement position; after the dimensional directionality corresponding to the iron ion concentration at the same moment is combined with the dimensional directionality corresponding to other types of dimension data, the more universal it is after combining the corrosion change degree at different positions, the smaller the influence of other types of dimension data on the detection results, and the smaller the corresponding adjustment amplitude.

[0088] Specifically, in step S6, when obtaining the relative proportion combination of iron ion concentrations at each position at the moment to be adjusted, the ratio of the mean of the dimensional directivity of the fiber Bragg grating sensors arranged for iron ion concentration at the reference moment to the dimensional directivity of the fiber Bragg grating sensors arranged for the type dimension data is used as the relative proportion at the reference moment. The product of the corrosion change degree at different positions in the metal pipeline at the reference moment and the relative proportion at the reference moment is used as the relative proportion combination of iron ion concentrations at each position at the reference moment. Each moment in the moment to be adjusted is sequentially used as the reference moment to obtain the relative proportion combination of iron ion concentrations at each position at each reference moment, and it is used as the relative proportion combination of iron ion concentrations at each position at the moment to be adjusted.

[0089] Specifically, the reference moment refers to one moment in the moment to be adjusted.

[0090] It should be noted that in the ratio quantity histogram, the more the quantity corresponding to the relative proportion combination, the more universal this relative proportion combination is. At this time, the influence of changes in factors such as stress and temperature on estimating the corrosion status with iron ions is relatively stable, and the change trend of the ratio quantity histogram reflects the trend of the corrosion status under the influence of other factors. The more stable the trend change, the higher the confidence level of the result that can be used to calculate the adjustment standard; then the reference of the calculation result for each relative proportion combination is based on the ratio quantity histogram.

[0091] Specifically, in step S6, when obtaining the standard relative proportion of iron ion concentration at the moment to be adjusted, the quantity statistics are performed according to the relative proportion combination of iron ion concentrations at each position at the reference moment, and the ratio quantity histogram is constructed by ascending order. Among them, the abscissa is the numerical value of the relative proportion combination of iron ion concentrations at each position arranged from small to large, the ordinate is the quantity corresponding to each relative proportion combination, and the result reference of the k-th relative proportion combination at the reference moment is calculated, and it is set that:

[0092]

[0093] Among them, represents the value of the k-th relative proportion combination at the reference moment, represents the quantity corresponding to the k-th relative proportion combination at the reference moment, k represents the order value of the k-th relative proportion combination arranged from small to large at the reference moment, represents the weight normalization function;

[0094] According to each relative proportion combination at the reference moment and the result reference of the k-th relative proportion combination at the reference moment , the standard relative proportion of iron ion concentration at the reference moment is obtained.

[0095] Specifically, the quantity corresponding to each relative proportion combination refers to the quantity of relative proportion combinations of the same value, and each relative proportion combination refers to various relative proportion combinations obtained by differentiating according to the relative proportion combinations of different values.

[0096] It should be noted that through reflect the trend affected by other types of dimensional data before this relative proportion combination. The smaller the value, the more this relative proportion combination conforms to the influence of other factors in the actual situation. That is, when the relative proportion combination remains unchanged, the fluctuating changes of other types of dimensional data will not affect the result of the iron ion analysis corrosion concentration. Then, the reference of this relative proportion combination is greater.

[0097] Specifically, in step S6, when obtaining the standard relative proportion of the iron ion concentration at the reference time, according to the reference of the k-th relative proportion combination at the reference time and the value of the k-th relative proportion combination in each relative proportion combination at the reference time calculate the standard relative proportion of the iron ion concentration at the reference time , set ;

[0098] Take each moment in the moment to be adjusted as the reference time in turn, obtain the standard relative proportion of the iron ion concentration at each reference time, and take it as the standard relative proportion of the iron ion concentration at the moment to be adjusted.

[0099] Specifically, in step S7, when obtaining the detected corrosion rate at each position at the moment to be adjusted, set:

[0100]

[0101] where represents the detected corrosion rate at the m-th position at the j-th moment to be adjusted, represents the degree of corrosion change at the m-th position at the j-th moment to be adjusted, represents the relative proportion combination of the iron ion concentration at the m-th position at the j-th moment to be adjusted, represents the standard relative proportion of the iron ion concentration at the j-th moment to be adjusted, represents the absolute value function.

[0102] Please refer to Figure 2As shown, it is a schematic diagram of the arrangement position of a partial tilted fiber Bragg grating in a metal pipe in this embodiment. The tilted fiber Bragg grating is arranged inside the metal pipe, and starting from the arrangement of the tilted fiber Bragg grating in the metal pipe, the corrosion change degree data set and the type dimension data set are collected through the tilted fiber Bragg grating. As of the current moment, the sampling interval for collecting the corrosion change degree data set and the type dimension data set is determined by the tilted fiber Bragg grating, which is not specifically limited in this embodiment. The arrangement position of the tilted fiber Bragg grating is not specifically limited in this embodiment. For example, a tilted fiber Bragg grating can be arranged at an interval of 1 cm.

[0103] Please refer to Figure 3 As shown, it is a schematic diagram of the fitting curve of the Bragg resonance peak wavelength and temperature in the tilted fiber Bragg grating sensor of this embodiment. The temperature measurement range is 30 - 125 °C, the wavelength change amount of the Bragg peak (Bragg resonance peak) is 0.92 nm, the wavelength change amount has a linear relationship with the temperature change amount, and the temperature sensitivity is close to 10 pm / °C.

[0104] Please refer to Figure 4 As shown, it is a schematic diagram of the fitting curve of the Bragg resonance peak wavelength and stress in the tilted fiber Bragg grating sensor of this embodiment. When the external strain increases from 0 to the wavelength of the Bragg resonance peak changes from 1600.75 nm to 1601.632 nm, and the stress sensitivity is ; thus, the corrosion change degrees at different positions and different times, as well as the dimensional data of two types, namely temperature and stress, are obtained.

[0105] So far, the technical solution of the present invention has been described in combination with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims

1. A real-time detection method for metal pipeline corrosion based on tilted fiber Bragg grating, characterized in that: include: Step S1, collecting a corrosion variation degree data set and a type dimension data set by tilting the fiber Bragg grating; Step S2, extracting the corrosion distribution area at each moment according to the corrosion change degree at different positions in the metal pipeline at the same moment in the corrosion change degree data set; Step S3, acquiring the dimensional directionality of the fiber Bragg grating sensor arrangement of each type of dimensional data at each moment and the dimensional directionality of the fiber Bragg grating sensor arrangement of the iron ion concentration at each moment according to the corrosion distribution area and type dimensional data set at each moment; Step S4, obtaining the mean value of the dimensional directionality of the fiber Bragg grating sensor arrangement of the type dimensional data at each moment, and obtaining the dimensional direction difference of the fiber Bragg grating sensor arrangement of the iron ion concentration at each moment according to the mean value of the dimensional directionality of the fiber Bragg grating sensor arrangement of the type dimensional data at each moment; Step S5, screening and acquiring the time to be adjusted according to the dimensional direction difference of the fiber Bragg grating sensor arrangement of the iron ion concentration at each moment; Step S6, acquiring a relative ratio combination of the iron ion concentration at each position at the time to be adjusted according to the dimensional directionality of the fiber grating sensor arrangement of each type of dimensional data at the time to be adjusted, the dimensional directionality of the fiber grating sensor arrangement of the iron ion concentration at the time to be adjusted, and the degree of corrosion change at different positions in the metal pipeline at the time to be adjusted, and acquiring a standard relative ratio of the iron ion concentration at the time to be adjusted according to the relative ratio combination of the iron ion concentration at each position at the time to be adjusted; Step S7, acquiring the detected corrosion rate of each position at the time to be adjusted according to the relative ratio combination of the iron ion concentration at each position at the time to be adjusted and the standard relative ratio of the iron ion concentration at the time to be adjusted.

2. The real-time detection method for metal pipeline corrosion based on tilted fiber Bragg grating according to claim 1 is characterized in that: In step S2, when extracting the corrosion sub-regions at each moment according to the corrosion change degree at different positions in the metal pipeline at the same moment in the corrosion change degree data set by using the corrosion distribution area extraction method, the corrosion distribution area extraction method includes: Step S20, obtaining the average value of the corrosion change degree of each inclined fiber grating arrangement position in the metal pipeline at the target time in the corrosion change degree data set, and using it as the standard level of iron ion concentration at the target time; Step S21, constructing a two-dimensional sample space of the metal pipe, wherein the horizontal axis of the two-dimensional sample space is the axial direction of the metal pipe, the vertical axis of the two-dimensional sample space is the circumferential direction of the metal pipe after two-dimensional expansion, and each inclined fiber grating arrangement position corresponds to a coordinate point on the two-dimensional sample space; Step S22, comparing the corrosion change degree H of the coordinate point in the two-dimensional sample space of the metal pipeline with the standard level H0 of the iron ion concentration at the target time, and identifying the corrosion coordinate point at the target time according to the comparison result, wherein: When H ≤H0, it is identified that the coordinate point is not the corrosion coordinate point at the target time; When H > H0, the coordinate point is identified as the corrosion coordinate point at the target time; The coverage area of ​​all corrosion coordinate points at the target time is extracted and used as the corrosion distribution area at the target time, and the set of the corrosion distribution area at the target time at each time is used as the corrosion distribution area at each time.

3. The real-time detection method for metal pipeline corrosion based on tilted fiber Bragg grating according to claim 2 is characterized in that: In step S3, the dimensional directionality of the fiber Bragg grating sensor arrangement of each type of dimensional data at each moment is acquired by a type dimensional directionality acquisition method, and the type dimensional directionality acquisition method includes: Step S31, obtaining the dimension data of each coordinate point in the corrosion distribution area at the target time; Step S32, performing PCA principal component analysis on the dimensional data of the type for each coordinate point to obtain the two principal component directions with the largest eigenvalues ​​of the type, connecting the coordinate points that the two principal component directions with the largest eigenvalues ​​of the type pass through in the corrosion distribution area at the target time to obtain the major axis of the dimensional data of the type and the minor axis of the dimensional data of the type; Step S33, dividing the area between the major axis of the type dimensional data and the minor axes of each type dimensional data according to a preset partitioning angle, to obtain the type dimensional data partition, the type dimensional data partition axis and the axial length of each partition axis of the type dimensional data; Step S34, obtaining the axial length difference between adjacent partition axes in each partition axis of the type of dimensional data, taking it as the adjacent axial length difference, and obtaining the dimensional directionality of the fiber Bragg grating sensor arrangement of each type of dimensional data at the target moment based on the adjacent axial length difference, and taking the set of the dimensional directionality of the fiber Bragg grating sensor arrangement of each type of dimensional data at the target moment at each moment as the dimensional directionality of the fiber Bragg grating sensor arrangement of each type of dimensional data at each moment.

4. The real-time detection method for metal pipeline corrosion based on tilted fiber Bragg grating according to claim 3 is characterized in that: In the step S34, when the dimensional directivity of the fiber Bragg grating sensor arrangement of each type of dimensional data at the target time is obtained according to the adjacent axial differences, the dimensional directivity of the fiber Bragg grating sensor arrangement of the rth type of dimensional data at the target time is calculated. ,set up , where N is the total number of axis partitions for this type of dimension data. and They respectively represent the axial length of the i-th partition axis and the axial length of the i-1-th partition axis of the r-th type of dimensional data in the corrosion distribution area at the target time, representing the absolute value function, represents the sigmoid function, which is the dimensional directionality of the fiber Bragg grating sensor arrangement of the r-th type dimensional data at the target time. The dimensional directivity of the fiber Bragg grating sensor arrangement of each type of dimensional data at each type of data set as the target time.

5. The real-time detection method for metal pipeline corrosion based on tilted fiber Bragg grating according to claim 3 is characterized in that: In step S3, when acquiring the dimensional directionality of the fiber Bragg grating sensor arrangement of the iron ion concentration at each moment, a PCA principal component analysis is performed on the corrosion change degree of all coordinate points in the two-dimensional sample space of the metal pipeline in the corrosion distribution area at the target moment, and the analysis result is used as the dimensional directionality of the fiber Bragg grating sensor arrangement of the iron ion concentration at the target moment.

6. The real-time detection method for metal pipeline corrosion based on tilted fiber Bragg grating according to claim 2 is characterized in that: In step S4, when obtaining the dimensional direction difference of the fiber Bragg grating sensor arrangement of the iron ion concentration at each moment, the absolute value of the difference between the mean of the dimensional directionality of the fiber Bragg grating sensor arrangement of the type dimensional data at the target moment and the dimensional directionality of the fiber Bragg grating sensor arrangement of the iron ion concentration at the target moment is taken as the dimensional direction difference of the fiber Bragg grating sensor arrangement of the iron ion concentration at the target moment.

7. The real-time detection method for metal pipeline corrosion based on tilted fiber Bragg grating according to claim 1 is characterized in that: In step S6, when obtaining the relative proportion combination of the iron ion concentration at each position at the time to be adjusted, the ratio of the dimensional directionality of the fiber grating sensor arrangement of the iron ion concentration at the reference time to the average of the dimensional directionality of the fiber grating sensor arrangement of the type dimensional data is used as the relative proportion at the reference time, and the product of the corrosion change degree at different positions in the metal pipeline at the reference time and the relative proportion at the reference time is used as the relative proportion combination of the iron ion concentration at each position at the reference time, and each moment in the time to be adjusted is taken as the reference moment in turn, and the relative proportion combination of the iron ion concentration at each position at each reference time is obtained, and it is used as the relative proportion combination of the iron ion concentration at each position at the time to be adjusted.

8. The real-time detection method for metal pipeline corrosion based on tilted fiber Bragg grating according to claim 7 is characterized in that: In step S6, when the standard relative ratio of the iron ion concentration at the time to be adjusted is obtained, the relative ratio combination of the iron ion concentration at each position at the reference time is counted, and the ratio quantity histogram is constructed in ascending order, wherein the abscissa is the value of the relative ratio combination of the iron ion concentration at each position arranged from small to large, and the ordinate is the quantity corresponding to each relative ratio combination, and the result of the kth relative ratio combination at the reference time is referenced. To perform the calculation, set: ； in, represents the value of the kth relative proportion combination at the reference time, represents the number corresponding to the kth relative proportion combination at the reference time, k represents the order value of the kth relative proportion combination at the reference time from small to large, represents the weight normalization function; The result reference of each relative proportion combination at the reference time and the kth relative proportion combination at the reference time , obtain the standard relative ratio of iron ion concentration at the reference time.

9. The real-time detection method for metal pipeline corrosion based on tilted fiber Bragg grating according to claim 8 is characterized in that: In step S6, when obtaining the standard relative ratio of the iron ion concentration at the reference time, the reference value is obtained according to the result of the kth relative ratio combination at the reference time. and the value of the kth relative proportion combination in each relative proportion combination at the reference time Calculate the standard relative ratio of iron ion concentration at the reference time ,set up ; Each moment in the time to be adjusted is taken as a reference moment in turn, and the standard relative ratio of the iron ion concentration at each reference moment is obtained, and it is used as the standard relative ratio of the iron ion concentration at the time to be adjusted.

10. The real-time detection method for metal pipeline corrosion based on tilted fiber Bragg grating according to claim 1, characterized in that: In step S7, when acquiring the detected corrosion rate of each position at the time to be adjusted, it is set: ; in, represents the detected corrosion rate of the mth position at the jth time to be adjusted, Indicates the degree of corrosion change at the mth position at the jth time to be adjusted, It represents the relative proportion combination of the iron ion concentration at the mth position at the jth time to be adjusted, represents the standard relative proportion of iron ion concentration at the jth time to be adjusted, represents the absolute value function.

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