Inverse finite element-based large storage tank fiber bragg grating visual monitoring method and device and storage medium

Abstract

The invention discloses a large storage tank fiber bragg grating visual monitoring method and device based on an inverse finite element and a storage medium. The method comprises the steps that the tank wall of a storage tank is divided into units, monitoring points are selected at equal intervals in combination with the requirements of storage tank foundation design specifications, and grating strain sensors are arranged in the divided units; the collected real-time data are preprocessed, and gross errors generated in the monitoring process are eliminated; and according to the preprocessed grating strain sensor data, reconstructing by using an inverse finite element method to obtain the overall real-time strain and displacement data of the storage tank, and visualizing the overall real-time strain and displacement data. According to the method, guidance can be provided for measuring point setting and arrangement, the system building cost is reduced, the overall working condition of the storage tank can be rapidly and accurately monitored for a long time, the visual detection function is provided, in addition, the calculated amount for calibrating forward finite elements can be greatly reduced, and the system reliability is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of large storage tank health status monitoring, and relates to a large storage tank fiber grating visualization monitoring method, equipment and storage medium based on inverse finite element, and specifically relates to a method for reconstructing and real-time monitoring of the health status of the storage tank using an inverse finite element algorithm. Background Art

[0002] Oil is an important pillar of the world's energy, with many advantages such as easy storage, transportation and development. As the basic device for oil storage, large vertical steel storage tanks have the characteristics of good reliability, convenient maintenance and low construction cost, and have always been the focus of research and construction in countries around the world.

[0003] In actual operation, storage tanks will be affected by natural disasters such as typhoons and earthquakes, and the foundations of large storage tanks are also prone to settlement and deformation. Therefore, it is of great engineering significance to carry out tank health inspection. At present, in order to ensure the normal operation of storage tanks, a series of tank inspection standards have been established at home and abroad, stipulating the implementation specifications of many projects such as settlement inspection. Some enterprises and institutions have established a tank deformation detection system using fiber gratings, but the traditional grating detection system can only obtain discrete detection data, and cannot directly obtain the overall state of the tank, and cannot fully guarantee reliability. In addition, the setting and arrangement of grating detection points are highly random, lacking scientific guidance, and are not conducive to cost control.

[0004] In addition, although the traditional finite element calculation method can reconstruct the overall stress, strain, and displacement state of the tank based on the measurement data, the calculation amount is extremely large, the calculation cost is high, and the stability cannot be guaranteed. It is not conducive to long-term real-time detection, and it is even more unfavorable to establish a visualization system for the overall state of the tank. Summary of the invention

[0005] In order to solve the many problems mentioned in the prior art, the present invention provides a large-scale storage tank fiber Bragg grating visualization monitoring method, equipment and storage medium based on inverse finite element, which can effectively solve the problems existing in traditional detection and simulation methods. The present invention can provide guidance for the setting and arrangement of measurement points, reduce the cost of system construction, can quickly and accurately monitor the overall working condition of the storage tank for a long time, provide a visualized detection function, and can also greatly reduce the amount of calculation used for calibration of forward finite elements and improve system reliability.

[0006] The technical solution adopted by the present invention is:

[0007] A fiber Bragg grating visualization monitoring method for large storage tanks based on inverse finite element, comprising:

[0008] First, the tank wall is divided into units, and according to the requirements of the tank foundation design specification, monitoring points are selected at equal intervals, and grating strain sensors are arranged in the divided units;

[0009] Pre-process the collected real-time data to eliminate gross errors generated during the monitoring process;

[0010] According to the grating strain sensor data obtained after preprocessing, the inverse finite element method is used to reconstruct the real-time strain and displacement data of the entire tank and visualize them.

[0011] In the above technical solution, further, the selection of the monitoring points satisfies: the monitoring points are distributed on the bottom of the tank wall, i.e., the first layer of steel plate, the top of the tank wall, i.e., the uppermost layer of steel plate, and any steel plate in the middle of the tank wall, and grating strain sensors are arranged equidistantly on the outer walls of the corresponding steel plates along the circumference of the tank.

[0012] Furthermore, the preprocessing includes: performing error analysis on the real-time data, using the sliding average method to eliminate the gross errors generated during the monitoring process; specifically, grouping the data obtained by the sensor, calculating the mean and variance of each group of data, and when the number in this group of data meets:

[0013] X≥A+3D or X≤A-3D

[0014] If it is an outlier, it needs to be removed, otherwise it does not need to be processed. X is the number within the range of this group of data, A is the average of all numbers, and D is the standard deviation.

[0015] Furthermore, the inverse finite element method is used to calculate the theoretical strain from the theoretical displacement through the geometric relationship between the structural strain and the displacement. Finally, the error function of the theoretical strain and the measured strain is constructed, and the theoretical displacement that minimizes the error function is solved as the displacement solution.

[0016] Furthermore, for the four-node plate inverse finite element unit, the displacement of any point in the plate is:

[0017]

[0018] where u = u(x, y) and v = v(x, y) are the corresponding displacements of the mid-plane in the x and y directions, θ x =θ x (x,y) and θ y =θ y (x, y) is the corresponding rotation angle along the negative x direction and the positive y direction; w = w(x, y) is the deflection component, which does not change along the thickness direction z of the shell; the linear strain ε of the plate element surface along the x-axis and the y-axis is obtained by derivation xx With ε yy , and the shear strain γ of the plate element xy , γ xz and γ yz ;

[0019] The strain is divided into film strain e(u e), bending strain k(u e ), and transverse shear y(u e ) three categories, u e is the unit displacement matrix containing four nodes, then the strain at any position is obtained:

[0020]

[0021] According to the above division method, the least square error function between the strain measurement value and the theoretical value is constructed to achieve structural deformation reconstruction:

[0022] Δ e (u e )=w e ||e(u e )-e ε || 2 +w k ||k(u e )-k ε || 2 +w γ ||γ(u e )-γ ε || 2

[0023] In the formula, e(u e )、k(u e ),γ(u e ) is the theoretical strain, e ε , k ε , γ ε is the measured strain value, w e 、w k 、w γ is the dimensionless weighting coefficient; for u e By minimizing the local coordinates, we can get the unit stiffness equation:

[0024] k e u e =f e

[0025] Through coordinate transformation, the overall stiffness equation of the structure is obtained:

[0026] KU=F

[0027] By introducing boundary conditions using the direct substitution method, the measured strain obtained at the monitoring point can be used as the load input equation to solve the corresponding displacement solution, and finally the structural deformation reconstruction can be achieved.

[0028] Furthermore, based on the measurement and calculation results, post-processing software and traditional finite element models are used to construct a three-dimensional cloud map of the tank's stress, strain, and displacement, thereby achieving visual real-time monitoring of the tank's working status.

[0029] A large storage tank fiber Bragg grating visualization monitoring system based on inverse finite element is used to implement the method described in any one of the above items.

[0030] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements any of the methods described above.

[0031] An electronic device, comprising:

[0032] one or more processors;

[0033] A memory for storing one or more programs;

[0034] When the one or more programs are executed by the one or more processors, the one or more processors implement any of the methods described above.

[0035] The beneficial effects of the present invention are:

[0036] Compared with the traditional detection method, the inverse finite element tank detection scheme proposed in this invention has the following advantages:

[0037] 1. The overall information of the tank can be obtained: Compared with the traditional grating detection method, the inverse finite element method can reconstruct the overall working status information of the tank, such as stress, strain, displacement, etc., with a limited number of measurement points and detection data. It has good reliability and is also conducive to a comprehensive assessment of the health status of the tank;

[0038] 2. Low system cost: Based on the inverse finite element algorithm and engineering practice, the grating monitoring points can be designed quantitatively and fixed-point, which solves the problem of blind and disorderly traditional grating layout schemes, provides a scientific measurement point layout guidance scheme, and is conducive to reducing the system layout cost;

[0039] 3. Easy to visualize: Compared with the traditional finite element calculation method, the inverse finite element calculation does not require huge calculations, has low cost, small data volume, reduces the system usage load, and can quickly obtain the three-dimensional stress, strain, and displacement cloud map of the storage tank to further realize visualization.

[0040] 4. Low-loss detection: Using the inverse finite element method for detection, it is only necessary to fix the grating sensor at a specific position outside the tank to collect the settlement and strain data of the tank, without causing obvious damage to the target tank;

[0041] 5. Data driven: The inverse finite element method is centered on the calculation of mathematical models, with high stability and reliability. The model parameters can be adjusted at any time according to the actual situation of the tank and measured data, thereby improving the adaptability to different environments and different target tanks;

[0042] 6. Less preparation in advance and low application threshold: Different from traditional testing methods, the inverse finite element method does not need to know the actual stress conditions of the tank, material and other information. Only through the measured strain and basic dimensions of the tank, the overall stress state of the tank can be inferred, and the application threshold is low;

[0043] 7. Scalability: The obtained inverse finite element calculation results can be combined with high-precision finite element calculation, three-dimensional laser detection and other solutions to achieve more accurate detection of the working status of the storage tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic diagram of an arrangement of grating strain sensors on the tank wall;

[0045] Figure 2 It is a schematic diagram of the process of the present invention;

[0046] Figure 3 It is a schematic diagram of the inverse finite element unit structure of a four-node plate in the present invention;

[0047] Figure 4 This is a cloud diagram of the radial displacement of the tank wall predicted in an example of the present invention, and the unit in the diagram is m;

[0048] Figure 5 This is a cloud diagram of the equivalent stress on the tank wall predicted in an example of the present invention, with the unit in the diagram being Pa. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0050] According to a specific example of the present invention, a large storage tank fiber Bragg grating visualization monitoring method based on inverse finite element includes the following steps:

[0051] 1. According to the actual situation of the target tank project and the requirements of the inverse finite element algorithm for input data, the tank wall is divided into units. Combined with the requirements of GB50473-2008 "Design Specifications for Foundations of Steel Tanks" and other documents, monitoring points are selected at equal intervals and grating strain sensors are arranged in the divided units.

[0052] Uneven settlement of the tank will directly affect the stress and strain of the bottom plate; uneven settlement will also cause additional stress on the tank wall, causing it to ellipse; in addition, for floating roof tanks, the radial displacement of the top tank mouth will also affect the normal rise and fall of the floating roof. Therefore, the bottom, top and middle of the tank wall are important areas for sensor layout, and the sensors arranged circumferentially at the bottom of the tank need to focus on detecting the settlement of the tank.

[0053] Taking a 110,000 cubic meter storage tank whose tank wall is welded by nine layers of steel plates as an example, according to the engineering experience related to inverse finite element analysis, such as Figure 1 As shown in the figure, 16 grating strain sensors can be installed equidistantly around the center of the first, fourth and ninth steel plates on the outer wall of the tank. In addition, a temperature monitoring sensor can be arranged at 45° intervals on each layer to compensate for the stress caused by temperature. Optical fiber is used to connect the sensors, and then carbon fiber glue is used to fix them to the paint surface. After installation, another layer of carbon fiber glue is applied, and a 20mm wide carbon fiber cloth strip is installed on the outer layer to increase the service life.

[0054] After obtaining the measured data, the following subsequent steps are performed on it, as follows: Figure 2 shown.

[0055] 2. Perform error analysis and use the sliding average method to eliminate gross errors generated during the monitoring process. Group the sensor data and calculate the mean and variance of each group of data. When the number in this group of data meets the following conditions:

[0056] X≥A+3D or X≤A-3D (1)

[0057] If it is an outlier, it needs to be removed, otherwise it does not need to be processed. X is the number within the range of this group of data, A is the average of all numbers, and D is the standard deviation.

[0058] 3. Based on the data measured by different grating strain sensors, the strain and displacement data of the entire tank are reconstructed through the inverse finite element algorithm.

[0059] Using the inverse finite element method, the theoretical strain can be calculated from the theoretical displacement through the geometric relationship between the structural strain and displacement. Finally, the error function of the theoretical strain and the measured strain is constructed, and the theoretical displacement that minimizes the error function is solved as the displacement solution.

[0060] Take the four-node plate inverse finite element unit as an example, Figure 3 , the displacement of any point in the plate is:

[0061]

[0062] where u = u(x, y) and v = v(x, y) are the corresponding displacements of the mid-plane in the x and y directions, θ x =θ x (x,y) and θ y =θ y (x, y) is the corresponding rotation angle along the negative x direction and the positive y direction; w = w(x, y) is the deflection component, which does not change along the thickness direction z of the shell, and 2h is the thickness of the entire shell, which is equivalent to the thickness of the steel plate. The linear strain ε of the plate element along the surface along the x-axis and the y-axis is obtained by derivation xx With ε yy , and the shear strain γ of the plate element xy , γ xz and γyz

[0063] The strain is divided into film strain e(u e ), bending strain k(u e ), and transverse shear y(u e ) three categories, u e is the unit displacement matrix containing four nodes, then the strain at any position can be obtained

[0064]

[0065] According to the above division method, the least square error function between the strain measurement value and the theoretical value can be constructed to achieve structural deformation reconstruction.

[0066] Δ e (u e )=w e ||e(u e )-e ε || 2 +w k ||k(u e )-k ε || 2 +w γ ||γ(u e )-γ ε || 2 (5)

[0067] In the formula, e(u e )、k(u e ),γ(u e ) is the theoretical strain, e ε , k ε , γ ε is the measured strain value, w e 、w k 、w γ is the dimensionless weighting coefficient. e By minimizing the local coordinates, we can get the unit stiffness equation:

[0068] k e u e =f e (6)

[0069] Through coordinate transformation, the overall stiffness equation of the structure can be obtained:

[0070] KU=F (7)

[0071] When calculating, the boundary conditions are introduced by direct substitution method, and the surface strain can be input as the load into the equation to solve it, and the corresponding displacement solution is obtained, and finally the structural deformation reconstruction is realized.

[0072] 4. Based on the results of measurement and calculation, post-processing software such as tecplot and ParaView are used in combination with traditional finite element models to construct a three-dimensional cloud map of tank stress, strain, and displacement to achieve visual real-time monitoring of the tank's working status.

[0073] like Figure 4 for Figure 1 The radial displacement cloud map of the tank wall predicted by the method of the present invention is reconstructed by the finite element method, that is, the displacement data obtained by inverse finite element calculation is brought into the traditional finite element model to reconstruct the stress data of the tank, and the stress cloud map is obtained as shown in FIG. Figure 5 As shown in the figure, it can be seen that through the displacement data obtained from several measurements, a relatively complete overall stress distribution of the tank can be reconstructed, which has a lower application threshold than traditional simulation methods.

[0074] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0075] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in this application (but not limited to) by each other.

Claims

1. A fiber Bragg grating visualization monitoring method for large storage tanks based on inverse finite element, It is characterized in that include: First, the tank wall is divided into units, and monitoring points are selected at equal intervals according to the requirements of the tank foundation design specifications, and grating strain sensors are arranged in the divided units; Pre-process the collected real-time data to eliminate gross errors generated during the monitoring process; According to the grating strain sensor data obtained after preprocessing, the inverse finite element method is used to reconstruct the real-time strain and displacement data of the entire tank and visualize them.

2. According to the inverse finite element-based large storage tank fiber Bragg grating visualization monitoring method according to claim 1, It is characterized in that The selection of the monitoring points satisfies the following conditions: the monitoring points are distributed on the bottom of the tank wall, i.e., the first steel plate, the top of the tank wall, i.e., the uppermost steel plate, and any steel plate in the middle of the tank wall, and grating strain sensors are arranged equidistantly on the outer walls of the corresponding steel plates along the circumference of the tank.

3. According to claim 1, the fiber Bragg grating visualization monitoring method for large storage tanks based on inverse finite element, It is characterized in that The preprocessing includes: performing error analysis on real-time data, using the sliding average method to eliminate gross errors generated during the monitoring process; specifically, grouping the data obtained by the sensor, calculating the mean and variance of each group of data, and when the number in this group of data meets: X≥A+3D or X≤A-3D If it is an outlier, it needs to be removed, otherwise it does not need to be processed. X is the number within the range of this group of data, A is the average of all numbers, and D is the standard deviation.

4. According to claim 1, the fiber Bragg grating visualization monitoring method for large storage tanks based on inverse finite element, It is characterized in that The inverse finite element method is used to calculate the theoretical strain from the theoretical displacement through the geometric relationship between the structural strain and the displacement. Finally, the error function of the theoretical strain and the measured strain is constructed, and the theoretical displacement that minimizes the error function is solved as the displacement solution.

5. According to claim 4, the fiber Bragg grating visualization monitoring method for large storage tanks based on inverse finite element, It is characterized in that For the four-node plate inverse finite element unit, the displacement of any point in the plate is: where u = u(x, y) and v = v(x, y) are the corresponding displacements of the mid-surface in the x and y directions, θ x =θ x (x,y) and θ y =θ y (x, y) is the corresponding rotation angle along the negative x direction and the positive y direction; w = w(x, y) is the deflection component, which does not change along the thickness direction z of the shell; the linear strain ε of the plate element surface along the x-axis and the y-axis is obtained by derivation xx With ε yy , and the shear strain γ of the plate element xy , γ xz and γ yz ; The strain is divided into film strain e(u e ), bending strain k(u e ), and transverse shear y(u e ) three categories, u e is the unit displacement matrix containing four nodes, then the strain at any position is obtained: According to the above division method, the least square error function between the strain measurement value and the theoretical value is constructed to achieve structural deformation reconstruction: D e (u e )=w e ||e(u e )-e ε || 2 +w k ||k(u e )-k ε || 2 +w γ ||γ(u e )-c ε || 2 In the formula, e(u e )、k(u e ),γ(u e ) is the theoretical strain, e ε , k ε , γ ε is the measured strain value, w e 、w k 、w γ is the dimensionless weighting coefficient; for u e By minimizing the local coordinates, we can get the unit stiffness equation: k e u e =f e Through coordinate transformation, the overall stiffness equation of the structure is obtained: KU=F By introducing boundary conditions using the direct substitution method, the measured strain obtained at the monitoring point can be used as the load input equation to solve the corresponding displacement solution, and finally the structural deformation reconstruction can be achieved.

6. The fiber Bragg grating visualization monitoring method for large storage tanks based on inverse finite element according to claim 1, It is characterized in that Based on the measurement and calculation results, post-processing software and traditional finite element models are used to construct a three-dimensional cloud map of the tank's stress, strain, and displacement, realizing visual real-time monitoring of the tank's working status.

7. A fiber Bragg grating visualization monitoring system for large storage tanks based on inverse finite element, It is characterized in that Used to implement the method according to any one of claims 1 to 6.

8. A computer-readable storage medium having a computer program stored thereon, It is characterized in that When the program is executed by a processor, the method according to any one of claims 1 to 6 is implemented.

9. An electronic device, It is characterized in that The device comprises: one or more processors; A memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method according to any one of claims 1 to 6.

Images