Real-time detection method for corrosion condition of metal pipeline based on tilted fiber bragg grating

Abstract

The invention relates to the technical field of physical and chemical measurement, in particular to a metal pipeline corrosion condition real-time detection method based on a tilted fiber bragg grating, which comprises the following steps: S1, collecting data; s2, extracting a corrosion distribution area at each moment; s3, obtaining the dimension directivity of the fiber grating sensor arrangement of each type of dimension data at each moment and the dimension directivity of the fiber grating sensor arrangement of the iron ion concentration at each moment; s4, obtaining the dimension direction difference degree of the fiber grating sensor arrangement of the iron ion concentration at each moment; s5, the moments to be adjusted are screened and obtained; s6, acquiring a standard relative proportion of the iron ion concentration at the moment to be adjusted; and S7, acquiring the detection corrosion rate of each position at the moment to be adjusted. According to the invention, the detection precision of the metal corrosion chemical reaction information is improved, and the real-time detection and early warning of the early corrosion of the metal pipeline are realized.

Description

Technical Field

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

[0002] Metal corrosion in metal pipes will cause the pipe wall to become thinner, defects to appear, and fluid leakage in the pipe, which will have a serious impact on personal safety and environmental protection. Early metal corrosion is beyond the range of human naked eye observation. Therefore, timely and accurate detection of early corrosion of metal pipes can effectively prevent corrosion accidents, improve economic benefits, and protect personal property and environmental safety. Traditional metal corrosion detection methods include weight method, gas measurement method and electrochemical method, which can calculate the corrosion rate of metals to a certain extent, but the fundamental trend of the current development of corrosion sensors is to achieve fast, high-sensitivity, non-destructive, in-situ real-time corrosion detection and meet the needs of complex application scenarios. Fiber optic sensors use optical fibers as carriers to detect the changes in optical signal parameters to detect the corrosion of metal pipes to be measured. They have the advantages of small size, light weight, anti-electromagnetic interference, and high resolution, and have attracted the attention of many researchers. The optical fiber itself is both a signal transmission carrier and a signal modulator. Its working principle is that when the external physical quantity changes, the characteristic properties of the transmitted light wave will change accordingly. Therefore, the physical quantity is monitored by monitoring the changes in the light wave.

[0003] At present, fiber optic corrosion sensors are mainly used to detect corrosion displacement, material structure, and changes in physical parameters such as vibration, stress, temperature, humidity cracks, etc. 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 and stable detection, but the internal chemical reaction information of metal corrosion is not clear, and lack the ability to monitor and warn of early corrosion in real time.

[0004] Chinese patent publication number: CN103076391A discloses a method for detecting local corrosion of metal pipelines. A quantitative detection method for local corrosion of metal pipelines, which includes the following steps: Step 1, using ultrasonic guided waves to quickly detect corrosion of the pipeline and mark the suspected local corrosion sites; Step 2, using ultrasonic C scanning to quantitatively detect suspected local corrosion of the pipeline; Step 3, combining the detection results of steps 1 and 2, using probability statistics method to estimate the maximum local corrosion depth: ; Where X: depth of corrosion hole; F(X): probability that the depth of 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 problem that the optical fiber corrosion sensor does not have clear information about the internal chemical reaction of metal corrosion and lacks the ability to detect and warn of early corrosion in real time. Summary of the invention

[0005] To this end, the present invention provides a real-time detection method for the corrosion condition of a metal pipeline based on a tilted fiber grating, so as to overcome the problems in the prior art of low efficiency in real-time detection of the corrosion condition of a metal pipeline, due to the fact that the optical fiber corrosion sensor has unclear information on the internal chemical reaction of metal corrosion, lacks the ability to detect and warn of early corrosion in real time, has a long testing cycle for the metal pipeline corrosion detection technology, cannot adapt to harsh environments, and cannot monitor in real time.

[0006] To achieve the above object, the present invention provides a real-time detection method for metal pipeline corrosion based on tilted fiber Bragg grating, comprising: 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.

[0007] Furthermore, 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.

[0008] Furthermore, 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.

[0009] Further, 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 represent the axial length and 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 time. The axial length of the partition axis, represents 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 directionality of the fiber Bragg grating sensor arrangement of each type of dimensional data at each type of data set as the target time.

[0010] Furthermore, 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.

[0011] Furthermore, 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.

[0012] Further, in step S6, when obtaining the relative proportion combination of 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 taken as the relative proportion at the reference time, and the product of the corrosion change degree at different positions in the metal pipe at the reference time and the relative proportion at the reference time is taken 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 time 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.

[0013] Further, 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:

[0014] 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.

[0015] Further, 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.

[0016] Furthermore, in step S7, when acquiring the detected corrosion rate of each position at the time to be adjusted, it is set:

[0017] 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.

[0018] 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, so that the detection system can make a detailed assessment of the pipeline corrosion situation and ensure the comprehensiveness and accuracy of the data. The method clarifies the corrosion concentration area through step S2, helps to quickly locate the potential problem area, and provides accurate guidance for maintenance and overhaul, thereby saving time and resources. The method optimizes the arrangement and configuration of the sensor through step S3, improves the detection accuracy and response speed, and ensures that the environmental changes in the pipeline can be fully captured. The method improves the understanding of the sensor data through mean and difference analysis through step S4, 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 the external environment or internal factors, ensuring the pertinence of subsequent analysis and adjustment. The method corrects possible measurement errors through accurate proportional calculation through step S6, improves the accuracy of iron ion concentration assessment, and ensures the reliability of corrosion assessment. The method provides accurate corrosion rate information through step S7, supports early maintenance and early warning systems of pipelines, helps reduce sudden failures, and extends the service life of pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of a method for real-time detection of corrosion conditions of metal pipelines based on tilted fiber Bragg gratings according to this embodiment; Figure 2 This is a schematic diagram of the arrangement position of a portion of the tilted fiber Bragg grating in the metal pipe of this embodiment; Figure 3 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; Figure 4 Schematic diagram of the Bragg resonance peak wavelength and stress fitting curve in the tilted fiber Bragg grating sensor of this embodiment. DETAILED DESCRIPTION

[0020] In order to make the objects and advantages of the present invention more clearly understood, the present invention is 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.

[0021] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0022] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely 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. Therefore, it cannot be understood as a limitation on the present invention.

[0023] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] See also Figure 1 As shown, it is a flow chart of a method for real-time detection of metal pipeline corrosion conditions based on tilted fiber Bragg gratings in this embodiment, the method comprising: 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.

[0025] Specifically, the method is set in a real-time detection terminal for the corrosion condition of a metal pipeline, and uses a carbon quantum dot-functionalized tilted fiber Bragg grating that can absorb metallic iron ions to detect the refractive index change in the grating cladding area, and uses the wavelength drift information of the grating cutoff cladding mode to calculate the iron ion concentration, and then evaluates the corrosion rate of the metal pipeline, thereby solving the defects of the detection technology in this field, such as long test cycle, inability to adapt to harsh environments and real-time monitoring, etc. The method has the advantages of smart, in-situ, real-time and highly sensitive early corrosion monitoring and early warning, and is suitable for early corrosion detection of metal pipelines in multiple scenarios such as seawater, oil and sewage. The method provides an accurate data basis for subsequent analysis through step S1, so that the detection system can conduct a detailed evaluation of the pipeline corrosion situation and ensure the comprehensiveness and accuracy of the data. The method clarifies the corrosion concentration area through step S2, helps to quickly locate potential problem areas, and provides maintenance and inspection services. The method provides precise guidance for repair, thereby saving time and resources. The method optimizes the arrangement and configuration of the sensor through step S3, improves the detection accuracy and response speed, and ensures that the environmental changes in the pipeline can be fully captured. The method improves the understanding of the sensor data through mean and difference analysis through step S4, 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 environment or internal factors, to ensure the pertinence of subsequent analysis and adjustment. The method corrects possible measurement errors through precise proportional calculation through step S6, improves the accuracy of iron ion concentration assessment, and ensures the reliability of corrosion assessment. The method provides accurate corrosion rate information through step S7, supports early maintenance and early warning systems of pipelines, helps reduce sudden failures, and extends the service life of pipelines.

[0026] Specifically, the purpose of this embodiment is to detect the initial corrosion of metal pipes in a timely and accurate manner by tilting the fiber grating sensor. The corrosion detection is mainly related to the concentration of iron ions. At the same time, the difference in the detection results at multiple positions is related to the distribution of stress, that is, the stress change at the location of the crack corrosion. When the iron ion concentration is low, that is, in the early stage of corrosion, the influence of other environmental factors will also be greater. In addition to the directional stress distribution, temperature changes will also have different effects on corrosion. It is necessary to obtain two types of dimensional data, temperature and stress, in order to separate the influence weights of different types of dimensional data on the initial corrosion of metal pipes at different times.

[0027] 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.

[0028] Specifically, the manufacturing method of the tilted fiber grating sensor includes: 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.

[0029] 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.

[0030] 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.

[0031] It should be noted that the change in iron ion concentration is strongly correlated with the corrosion position of the metal pipe. The concentration of iron ions is higher at locations with a high degree of corrosion, which means that the location is affected by corrosion areas such as cracks. The closer to the center of the corrosion area, the higher the degree of corrosion change. The corrosion changes at different tilted fiber grating arrangement positions have a directionality distributed along the shape of the corrosion area, and the corresponding temperature and stress data changes have a larger impact area.

[0032] It should be further explained that the actual shape of the corrosion area in the metal pipe is different. Especially for the corrosion caused by cracks, the stress change in the area where the actual cracks exist will gradually decrease along the long axis and short axis of the area, and the diffusion of axial cracks is more obvious than that of circumferential cracks. Therefore, the area affected by iron ions is closer to the actual shape of the corrosion area, while the area affected by other stresses, temperature, etc. is larger.

[0033] Specifically, 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.

[0034] Specifically, the target moment refers to a randomly selected moment. This embodiment does not limit the selection method of the target moment. Technical personnel in this field can freely set it according to actual conditions, and only need to meet the selection requirements of data at the same moment. For example, a random moment can be selected at intervals in time as the target moment. The coverage area of ​​all corrosion coordinate points at the target moment refers to the range set composed of radiation areas where corrosion may exist at each corrosion coordinate point at the target moment. This embodiment does not limit the composition method of the coverage area of ​​all corrosion coordinate points at the target moment. Technical personnel in this field can freely set it according to actual conditions, and only need to meet the extraction requirements of the corrosion distribution area at the target moment. 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 the sum of them is used as the coverage area of ​​all corrosion coordinate points at the target moment. The different positions refer to the sum of the positions of the inclined fiber gratings in the metal pipe.

[0035] Specifically, 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.

[0036] Specifically, in 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 r types 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 represent the axial length and 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 time. The axial length of the partition axis, represents 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 directionality of the fiber Bragg grating sensor arrangement of each type of dimensional data at each type of data set as the target time.

[0037] Specifically, in step S3, when the dimensional directionality of the fiber Bragg grating sensor arrangement of the iron ion concentration at each moment is obtained, 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 target iron ion concentration.

[0038] What needs to be explained is that by analyzing the difference in axial lengths of adjacent partition axes of this type of dimensional data in the corrosion distribution area, the greater the difference in axial lengths of adjacent partition axes, that is, it can be indicated that under this type of dimensional data, the greater the rate of morphological change in the corrosion distribution area is. Then, by quantifying the average change rate, the greater the average change rate, the more compactly this type of dimensional data tends to be distributed in the corrosion distribution area, and the correspondingly greater the dimensional directionality of the fiber grating sensor arrangement of this type of dimensional data is.

[0039] It should be noted that the dimensional directionality distribution of different types of dimensional data reflects the influence range of its dimensional data in the detection process, and the final analysis of the corrosion condition of the metal pipeline is extracted based on the cladding mode resonance peak obtained by the spectrometer; when the iron ion concentration extracted by carbon quantum in different types of dimensional data reflects the corrosion condition more accurately, that is, the dimensional directionality is more significant than the dimensional directionality of other types of dimensional data, it proves that the drift rate of the cutoff mode resonance wavelength is used to reflect the corrosion rate of the metal pipeline, and the effect of initial corrosion detection of the metal pipeline is better; it is necessary to conduct a difference analysis between the dimensional directionality of the iron ion concentration and the dimensional directionality of other types of dimensional data at the same time.

[0040] Specifically, 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.

[0041] It should be noted that the dimensional direction difference 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 characteristic analysis of multi-type dimensional data in the early stage of corrosion. The earlier the corrosion stage of the corresponding pipeline corrosion area, the smaller the iron ion production rate in the corrosion area, the less it combines with carbon quanta, and the smaller the influence of the multi-peak performance of the corresponding spectrum. It is necessary to adjust the corrosion rate of the corrosion distribution area at each moment through the dimensional direction difference, 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 stress, temperature and other types of data to ensure that the drift rate of the cutoff mode resonance wavelength reflects the accuracy of the corrosion rate of the metal pipeline.

[0042] Specifically, in step S5, when the adjustment time is screened and obtained, the dimensional direction difference C of the fiber Bragg grating sensor arrangement of the iron ion concentration at each moment is compared with the preset difference C0, and the adjustment time is screened and obtained according to the comparison result, wherein: When C≥C0, the moment is not the moment to be adjusted; When C<C0, the moment is selected as the moment to be adjusted.

[0043] Specifically, the preset difference C0 refers to a preset difference value that reflects whether the iron ion concentration at each moment corresponds to the detection result. When the iron ion concentration at that moment corresponds to the detection result is inaccurate, the moment is selected as the moment to be adjusted. In this embodiment, C0=0.75.

[0044] It should be noted that for the dimensional directionality of the tilted fiber grating arrangement of each type of dimensional data at the time to be adjusted, the adjustment amplitude is combined and associated with the degree of corrosion change at each arrangement position at the corresponding time; after the dimensional directionality corresponding to the iron ion concentration is combined with the dimensional directionality corresponding to other types of dimensional data at the same time, the more universal it is after combining with the degree of corrosion change at different positions, the less the detection result is affected by other types of dimensional data, and the smaller the corresponding adjustment amplitude.

[0045] Specifically, in step S6, when obtaining the relative proportion combination of 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 pipe 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.

[0046] Specifically, the reference time refers to a time among the times to be adjusted.

[0047] It should be noted that in the ratio quantity histogram, the more the number of relative proportion combinations corresponds to, the more universal the relative proportion combination is. At this time, the changes in factors such as stress and temperature have a relatively stable impact on the estimation of corrosion conditions using iron ions, and the changing trend of the ratio quantity histogram reflects the trend of corrosion conditions under the influence of other factors. The more stable the trend change, the higher the confidence level of the result in calculating the adjustment standard; the calculation results of each relative proportion combination based on the ratio quantity histogram are referenceable.

[0048] Specifically, 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:

[0049] 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, and 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.

[0050] Specifically, the number corresponding to each relative proportion combination refers to the number of relative proportion combinations of the same numerical value, and each relative proportion combination refers to various relative proportion combinations obtained by distinguishing relative proportion combinations of different numerical values.

[0051] It should be noted that through It reflects the trend of the influence of other types of dimensional data before this relative proportion combination. The smaller the value, the more consistent the relative proportion combination is with the influence of other factors under actual conditions. That is, when the relative proportion combination remains unchanged, the fluctuation of other types of dimensional data will not affect the corrosion concentration results of iron ion analysis, and the reference value of this relative proportion combination will be greater.

[0052] Specifically, 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.

[0053] Specifically, in step S7, when acquiring the detected corrosion rate of each position at the time to be adjusted, it is set:

[0054] 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.

[0055] See also Figure 2 As shown, it is a schematic diagram of the arrangement position of part of the tilted fiber Bragg grating in the metal pipe of this embodiment. The tilted fiber Bragg grating is arranged inside the metal pipe, and the corrosion change degree data set and the type dimension data set are collected by the tilted fiber Bragg grating starting from the arrangement of the tilted fiber Bragg grating in the metal pipe. 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, and this embodiment does not make specific limitations. This embodiment does not make specific limitations on the arrangement position of the tilted fiber Bragg grating, such as being set to arrange a tilted fiber Bragg grating at a spacing of 1 cm.

[0056] See also Figure 3 As shown, it is a schematic diagram of the Bragg resonance peak wavelength and temperature fitting curve in the tilted fiber grating sensor of this embodiment, wherein the temperature measurement range is 30-125°C, the Bragg peak (Bragg resonance peak) wavelength change is 0.92nm, the wavelength change is linearly related to the temperature change, and the temperature sensitivity is close to 10pm / °C.

[0057] See also Figure 4 As shown in FIG. 1 , which is a schematic diagram of the Bragg resonance peak wavelength and stress fitting curve in the tilted fiber Bragg grating sensor of this embodiment, when the external strain increases from 0 to When the Bragg resonance peak wavelength changes from 1600.75nm to 1601.632nm, the stress sensitivity is ; The corrosion variation degree at different locations and times, as well as two types of dimensional data, temperature and stress, were obtained.

[0058] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying 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 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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