CN108007935B - On-line monitoring system for buried cracks based on distributed optical fiber sensing technology structure - Google Patents
On-line monitoring system for buried cracks based on distributed optical fiber sensing technology structure Download PDFInfo
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- CN108007935B CN108007935B CN201711104271.1A CN201711104271A CN108007935B CN 108007935 B CN108007935 B CN 108007935B CN 201711104271 A CN201711104271 A CN 201711104271A CN 108007935 B CN108007935 B CN 108007935B
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Abstract
The invention provides an on-line monitoring system for a structure buried crack based on a distributed optical fiber sensing technology, which comprises an on-line monitoring module, a loss mechanism research module, a multi-scale dynamic analysis module, a damage characteristic extraction module, a damage intelligent identification module and a damage evaluation module, wherein the on-line monitoring module carries out external excitation on a hoisting equipment structure, adopts the distributed optical fiber sensing technology to carry out real-time monitoring on the hoisting equipment structure, detects surface and internal cracks, captures the crack state in real time, and carries out tracking monitoring on crack formation, crack propagation and critical damage to obtain a monitoring signal.
Description
Technical Field
The invention relates to an on-line monitoring system for a structural buried crack based on a distributed optical fiber sensing technology.
Background
In spite of the current development situation of distributed optical fiber sensing technology at home and abroad, the current distributed optical fiber sensing technology can be applied to long-term online monitoring of cracks on the surface of a structure. Meanwhile, the common and conventional static nondestructive detection method for the structural cracks has the advantages and disadvantages of visual inspection, permeation, eddy current, magnetic powder, ultrasound, ray and the like, but the common method needs to stop the operation of the structure and carry out the static detection and needs to carry out comprehensive detection. The detection positions and intervals are required to be based on the statistical characteristics of defects in the prior use of the structure, cracks which are not found in the first detection often occur, and the cracks are long in the next detection interval, so that the structure is required to be disassembled to perform fracture analysis to determine the crack formation life in a reverse thrust manner.
The optical fiber sensing technology has the advantages of light weight, electromagnetic interference resistance, high humidity resistance, electric insulation, signal attenuation reduction and the like, and is widely applied to the fields of engineering monitoring, industrial and agricultural production, life science and the like. In particular, the optical fiber can be used as both the sensing element and the transmission element, and the distributed optical fiber sensor can be formed by connecting the sensing units of the transmission optical fiber in series. Compared with a point sensor, the point sensor has the obvious advantages that the point sensor can be used for continuously monitoring the detected member in a distributed manner, the problem of a monitoring blind area of the point sensor is solved, a major leakage detection dangerous case is avoided, and the monitoring reliability of the detected member is improved.
Disclosure of Invention
The invention provides an on-line monitoring system for a structure buried crack based on a distributed optical fiber sensing technology, which comprises an on-line monitoring module, a loss mechanism research module, a multi-scale dynamic analysis module, a damage characteristic extraction module, a damage intelligent identification module and a damage evaluation module, wherein the on-line monitoring module carries out external excitation on a hoisting equipment structure, adopts the distributed optical fiber sensing technology to carry out real-time monitoring on the hoisting equipment structure, detects surface and internal cracks, captures the crack state in real time, and carries out tracking monitoring on crack formation, crack propagation and critical damage to obtain a monitoring signal.
The invention adopts advanced distributed optical fiber sensing network technology, belongs to dynamic crack monitoring, can make up the defects of conventional nondestructive detection, captures the crack state in real time, and can trace and monitor the crack formation, crack propagation and critical damage after the main key part is determined.
The invention aims at the high-speed online monitoring and evaluation of mechanical equipment for various types of defects (surface/internal cracks, stress strain and deformation), mainly structural surface and near-surface cracks. Mainly aiming at 2 aspects of scientific and technical problems: the on-line monitoring technology for the fatigue crack damage and defect evolution of the structural material; the intelligent identification and risk assessment technology of structural damage.
The invention can solve the problems of inspection monitoring of the structure cracks, the evolution mechanism of the structure crack defects, the evaluation of the remaining service life of the structure and the like, is suitable for the requirements of the application difficulties of system maintenance and service life evaluation based on the service state, and realizes the in-service nondestructive monitoring and evaluation of major mechanical equipment such as a movable pressure container, a large-scale amusement facility or hoisting equipment.
Drawings
FIG. 1 is a schematic diagram of a distributed optical fiber arrangement; FIG. 2 is a technical route and layout;
FIG. 3 is a distributed optical fiber sensing network remote monitoring system;
FIG. 4 is a linear interpolation of the global strain field from the monitored local strain;
FIG. 5 is a quadratic interpolation of the global strain field from the monitored local strains.
Detailed Description
When the macrocracks appear on the structure and the macrocracks are expanded on the cracks, the stress strain field around the cracks can be changed (outer surface), the inner surface and the outer surface of the complex combination body are connected with an external component through rivets and bolts, the force of the whole structure is transferred in a multi-path transfer mode under the action of external load, and when the large macrocracks appear on the internal component, the surface stress strain field closest to the cracks and the external component fixed with the macroscopic racks can also be changed. Thus, distributed fiber sensing technology can be used to detect surface and internal cracks. Distributed fiber optic sensing wiring is shown in fig. 1.
The structural fatigue damage accumulation criterion is judged by adopting the following formula:
ith optical fiber monitoring value
Monitoring value without crack initially
If it is satisfied with
It is assumed that a crack has occurred at or near the site at least at the ith measurement, where D is the systematic error.
The technical route and the plan are shown in fig. 2. In order to establish a structural crack damage distributed optical fiber sensing network remote monitoring system, the occurrence, the position and the degree of structural damage are intelligently identified in a structural operation state by combining international leading theories and technologies from progressive levels of damage mechanisms, damage models, damage characteristic identification, online intelligent monitoring, risk assessment, safety early warning and the like, and online emergency early warning is realized. The monitoring system comprises an online monitoring module, a loss mechanism research module, a multi-scale dynamic analysis module, a damage characteristic extraction module, a damage intelligent identification module and a damage evaluation module, wherein the online monitoring module carries out external excitation on a hoisting equipment structure, carries out real-time monitoring on the hoisting equipment structure by adopting a distributed optical fiber sensing technology, detects surface and internal cracks, captures crack states in real time, carries out tracking monitoring on crack formation, crack propagation and critical damage and obtains monitoring signals.
The key core technology A: establishing a cross-scale crack damage evolution model of a major equipment structure
The solution is as follows: according to the characteristics of structural deterioration on two different-magnitude space scales, namely an overall structure scale, a local micro scale and a microscopic scale, and by combining the analysis processing of the existing monitoring data, an efficient and accurate structure cross-scale damage fine analysis model is established. Based on the established refined model and the nonlinear damage accumulation criterion, the generation and evolution rules of the structure cross-scale damage are researched, the structure degradation process of multi-factor coupling is analyzed, and the structure damage initiation-expansion mechanism is further disclosed.
The key core technology B: establishing a structure (including damage) multi-scale dynamic model
The solution is as follows: dividing a complex structure into more easily processed and smaller substructures by using a substructure method in a finite element method, and finely simulating concerned local details by adopting a microscopic scale unit in the substructures; the substructure is connected with the finite element model of the whole structure as only one unit under the integral macroscopic scale to form a full-scale-construction-scale-local fine three-scale multi-scale finite element model. The overall characteristics of the structure can be obtained by solving the multi-scale finite element model under the macro scale, and then the mechanical characteristics of local details under the small scale can be obtained by expanding and solving the interior of the substructure, so that the structure (including damage) multi-scale numerical calculation method is formed.
The key core technology C: technology for extracting wavelet-fractal multi-scale singular spectrum damage features in noise environment
The solution is as follows: and analyzing the compatibility of fractal and wavelet transformation based on multi-scale mathematics. On the basis, a new structural damage detection mode of 'wavelet suppression measurement noise and fractal reinforcement damage characteristics' is established, and structural damage characteristic quantity suitable for a low signal-to-noise ratio environment is established in mode implementation: wavelet-fractal multi-scale singular spectra. The characteristic quantity comprises two basic elements of wavelet suppression measurement noise and fractal reinforcement damage characteristics: (1) wavelet packet transformation algorithm of wavelet inhibition measurement noise, newly-built frequency-time order and no 'down sampling', decomposes structural dynamic response into a group of multi-scale wavelets, and the multi-scale characteristics of the wavelets can decompose the damage characteristics of the structure and the measurement noise on different scales, thereby effectively realizing signal-noise separation; (2) fractal strengthening damage characteristics, namely, correlation dimensions and Katz waveform dimensions are adopted as singularity detection operators, singularity analysis is carried out on the multi-scale wavelet level, and the structural damage effect is represented by the mutation of the fractal dimensions.
The structure trans-scale damage evolution model adopts multiple times of experimental research, and multiple times of judgment are carried out according to the following judgment, wherein the expression of the structure trans-scale damage variable D is as follows:
in the formula: eta is the residual strain coefficient;0is unit principal strain;ris the unit residual strain;uin the form of a unit of ultimate strain,maxthe maximum tensile strain value corresponding to a certain load value during loading.
When in usemax<0Time cell damage does not occur;0<max<rwhen the 1 st stage damage of partial unit occurs,r<max<uwhen part of the cells are damaged in stage 2,max〉uthe cell is completely destroyed.
When D is 0, the material has no initial damage, and when D is 1, fatigue damage occurs and cracks form.
By adopting the structure trans-scale damage evolution model, the damage mechanism can be rapidly analyzed, and the reasonable and accurate crack condition can be obtained.
As shown in fig. 3, a distributed optical fiber sensing network remote monitoring system, a mobile pressure vessel, a large amusement facility or a hoisting device and other major equipment are constructed, the equipment performs data transmission and instruction reception with an embedded wireless transceiving and remote monitoring integrated unit, transmits all data to a safety monitoring and emergency management and safeguard center in real time, and the safety monitoring and emergency management and safeguard center performs timed transmission of typical data or temporary transmission of abnormal data with the embedded wireless transceiving and remote monitoring integrated unit, so as to realize communication with the mobile pressure vessel, the large amusement facility or the hoisting device and other major equipment.
The optical fiber distributed sensing technology is adopted, the optical fiber is used as a signal pickup device, and the monitoring work of the disturbance of a tiny strain field is realized by adopting the characteristics of being passive, resisting electromagnetic interference, needing no power supply at the front end, being light in size, easy to install and the like. The following aspects can be considered:
A. a high-sensitivity grating sensing network monitors disturbance of a tiny strain field A, and a structure of a white light interference system is to be adopted.
B. The two-path interference signal output structure is adopted, so that the noise brought by the optical path system is effectively reduced, and meanwhile, an ideal working point with high sensitivity is provided for the system.
C. By adopting a single-core feedback structure, as shown in the previous figure, light input into the fiber grating sensor is reflected by the reflection unit and then returns to the fiber interference module in the original path. This configuration may allow the structural sensitivity of the system to be unaffected by the monitoring distance. Moreover, due to the reflection effect, the optical signal passes through the same sensing optical fiber twice, so that the signal is multiplied, and the pick-up sensitivity is increased.
D. And analyzing and designing the structural parameters of the all-fiber interference module and the fiber grating sensor.
E. Because the optical fiber light path is easily influenced by the polarization of the optical fiber, the influence of the polarization on the system is reduced by adopting a polarization control technology according to the specific structure of the light path and the characteristics of white light interference.
Based on the arrangement mode of the fiber bragg grating sensing network, the whole strain field is obtained through the monitored local strain.
(a) The global strain field, a linear interpolation, is derived from the monitored local strain, as shown in figure 4,
wherein
NiIs a shape function, which is a function of local coordinates. The shape function satisfies the following conditions
The local strain field of the cell is written as
And assembling all the monitoring points to obtain the strain field of the whole surface field.
(b) The global strain field, quadratic interpolation, is obtained from the monitored local strains, as shown in figure 5,
in the formula
The interpolation of the displacement is of the form
And assembling all the monitoring points to obtain the strain field of the whole surface field.
The invention can be applied to important equipment such as movable pressure vessels, large amusement facilities or hoisting equipment. The invention carries out high-speed online monitoring and evaluation aiming at important equipment with complex shape surface and various defects (surface/internal cracks, stress strain and deformation), and is a novel measurement method which is a breakthrough; it is helpful to understand the micro-to macro-evolution mechanism of the major equipment defect. The system can solve the problems of fatigue and crack damage routing inspection monitoring, defect evolution mechanism, equipment residual life assessment and the like, meets the application difficulty requirements of service state-based system maintenance and life assessment, and realizes the integrated detection and monitoring of in-service nondestructive detection and assessment and structure health monitoring of major equipment.
Claims (5)
1. An on-line monitoring system for a structural buried crack based on a distributed optical fiber sensing technology comprises an on-line monitoring module, a loss mechanism research module, a multi-scale dynamic analysis module, a damage characteristic extraction module, a damage intelligent identification module and a damage evaluation module, the on-line monitoring module is characterized in that the on-line monitoring module carries out external excitation on the hoisting equipment structure, adopts the distributed optical fiber sensing technology to carry out real-time monitoring on the hoisting equipment structure, detects surface and internal cracks, captures the crack state in real time, tracking and monitoring crack formation, crack propagation and critical damage to obtain a monitoring signal, wherein the loss mechanism research module comprises a structure trans-scale damage evolution model and a structure fatigue damage accumulation criterion, the structure trans-scale damage evolution model adopts multiple times of experimental research to perform multiple times of judgment, wherein the expression of the structure trans-scale damage variable D is as follows:
in the formula: eta is residual strainA coefficient;0is unit principal strain;ris unit residual strain； uIn the form of a unit of ultimate strain,maxis the maximum tensile strain value corresponding to a certain load value during loading,
when in usemax<0Time cell damage does not occur;0<max<rwhen the 1 st stage damage of partial unit occurs,r<max<uwhen part of the cells are damaged in stage 2,max〉uwhen the unit is completely destroyed,
when D is 0, the material has no initial damage, and when D is 1, fatigue damage occurs and cracks form;
the structural fatigue damage accumulation criterion is judged by adopting the following formula:
ith optical fiber monitoring value
Monitoring value without crack initially
If it is satisfied with
It is assumed that a crack has occurred at or near the site at least at the ith measurement, where D is the systematic error.
2. The online monitoring system of claim 1, wherein the multi-scale kinetic analysis model comprises a structure multi-scale kinetic model and a cross-scale sensitivity of structural damage.
3. The on-line monitoring system of claim 2, wherein the structural multi-scale dynamic model employs a substructure method in a finite element method, the substructure being connected as only one unit with the finite element model of the overall structure at the overall macro-scale to form a full-scale-build-scale-locally refined "three-scale" finite element model.
4. The on-line monitoring system of claim 1, wherein the damage feature extraction module comprises wavelet-fractal multi-scale singular spectrum extraction structure damage features, structural local damage factor characterization structure nonlinear damage features, and wavelet neural network damage identification and intelligent identification.
5. The on-line monitoring system of claim 1, wherein the distributed fiber sensing technology employs a network arrangement to obtain an overall strain field from the monitored local strain.
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| 《基于桥梁健康监测的有限元模型修正研究现状与发展趋势》;梁鹏等;《长安大学学报（自然科学版）》;20141231;第34卷(第4期);第52-60页 * |
| 《大跨斜拉桥有限元模型修正与结构损伤监测方法研究》;范哲;《万方数据知识服务平台》;20140714;正文第2-138页 * |
| 范哲.《大跨斜拉桥有限元模型修正与结构损伤监测方法研究》.《万方数据知识服务平台》.2014,正文第2-138页. * |
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Effective date of registration: 20211209 Address after: Room 710, block a, building 2, Xiyuan, Heping Street, Chaoyang District, Beijing 100020 Patentee after: BEIJING ZHONGJIAN HOPES TECHNOLOGY CO.,LTD. Address before: 100029 No.2 Xiyuan, Heping Street, Chaoyang District, Beijing Patentee before: CHINA SPECIAL EQUIPMENT INSPECTION AND Research Institute Patentee before: Beijing Zhongjian hope Technology Co., Ltd |
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Address after: Room 710, block a, building 2, Xiyuan, Heping Street, Chaoyang District, Beijing 100020 Patentee after: China Merchants zhongtezhi inspection (Beijing) Technology Co.,Ltd. Address before: Room 710, block a, building 2, Xiyuan, Heping Street, Chaoyang District, Beijing 100020 Patentee before: BEIJING ZHONGJIAN HOPES TECHNOLOGY CO.,LTD. |