A stress detection method for pipelines

Abstract

The present invention provides a stress detection method for pipelines. An indoor test platform for pipeline stress detection is designed, a large-diameter three-dimensional pipeline used for oil and gas transportation is adopted, and stress concentration, defect, stress concentration and defect superposition, soil covering, equal-thickness girth weld and unequal-thickness girth weld working conditions are set to simulate the actual in-service oil and gas transportation pipeline environment. Based on the indoor test platform, weak magnetic detection technology is used to detect the spatial distribution data of magnetic field signals that vary with pipeline length, and the spatial distribution law of the magnetic field on the oil and gas transportation pipeline under different working conditions is obtained, thereby determining the stress distribution on the oil and gas transportation pipeline under different working conditions, and improving the accuracy of stress detection on the oil and gas transportation pipeline.

Description

Technical Field

[0001] The invention relates to the technical field of nondestructive testing of oil and gas pipelines, and in particular to a stress detection method for pipelines. Background Art

[0002] Pipeline transportation is the main way to transport oil and natural gas. However, stress concentration is very likely to occur during the operation of the pipeline. When the stress on the pipeline exceeds the yield limit of the pipeline material, plastic deformation or cracks may occur on the pipeline, seriously affecting the safe operation of the pipeline. Therefore, effective detection of pipeline stress is a necessary measure to avoid safety accidents.

[0003] At present, the stress distribution on the pipeline can be detected based on weak magnetic detection technology. That is, the stress state of the pipeline material is evaluated by using the natural magnetomechanical relationship of the stress concentration area to make early predictions and assessments of the pipeline stress concentration area.

[0004] However, since the weak magnetic detection signal is weak and easily interfered by external signals, and the signal stability is poor, there is great interference and uncertainty in the process of detecting the stress distribution on the pipeline based on the weak magnetic stress detection technology, which reduces the accuracy of pipeline stress detection. Summary of the invention

[0005] The present invention provides a pipeline stress detection method, which can improve the accuracy of pipeline stress detection.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] In a first aspect, the present invention provides a stress detection method for a pipeline, the method comprising steps S101-S114:

[0008] S101: Build a detection platform. The detection platform includes a shell, a pipeline, a loader, and a probe slide. The inside of the shell is filled with covering soil. The pipeline is a hollow structure, and both ends of the pipeline are closed. The pipeline is located at a preset depth of the covering soil. The loader is set on the outer wall of the pipeline to apply stress to the pipeline. The probe slide is parallel to the pipeline and is set just above the axis of the pipeline along the length of the pipeline. It is used to carry the detection probe to detect the magnetic field space data of the corresponding position through the detection probe. Welds and defects are set on the pipeline.

[0009] S102: Setting a first stress concentration point on the pipeline, applying stress on the first stress concentration point based on a loader. The first stress concentration point does not coincide with any defect on the pipeline.

[0010] S103: Setting a second stress concentration point on the pipeline, and applying stress on the second stress concentration point based on a loader; a second stress concentration point coincides with a defect on the pipeline.

[0011] S104: Mounting a detection probe on the probe slide rail.

[0012] S105: Measure the magnetic field spatial data from the detection starting point to the detection end point by using the detection probe. The detection starting point is from one end of the pipeline to the point at the second preset distance away from the pipeline. The detection end point is from the other end of the pipeline to the point at the second preset distance away from the pipeline. The line between the detection starting point and the detection end point is parallel to the pipeline.

[0013] S106: Based on the magnetic field spatial data measured from the detection start point to the detection end point, the characteristic vectors of the target position are obtained, and the characteristic values ​​corresponding to each characteristic vector are obtained. The target position includes the position of the defect on the pipeline that does not coincide with the second stress concentration point, the position of the first stress concentration point, the position of the second stress concentration point, and the position of the weld.

[0014] S107: increasing the thickness of the soil covering the pipeline and the elastic modulus of the soil covering in geometric proportion, repeating S105-S106, and obtaining the attenuation of the magnetic field signal at each target position when the soil covering the pipeline has different thicknesses based on the eigenvectors of each target position and the eigenvalues ​​corresponding to each eigenvector;

[0015] S108: For any soil cover thickness on the pipeline, perform summing and averaging processing on the attenuation of the magnetic field signal at each target position under any soil cover thickness to obtain the average attenuation of the magnetic field signal under any soil cover thickness.

[0016] S109: Based on the average attenuation of the magnetic field signal at each soil cover thickness, a functional relationship between the soil cover thickness and the average attenuation of the magnetic field signal is obtained.

[0017] S110: Based on the functional relationship between the soil cover thickness and the average attenuation of the magnetic field signal, a first distribution relationship corresponding to the magnetic field signal on the pipeline is obtained. The first distribution relationship is a functional relationship of the magnetic field signal on the pipeline with the length of the pipeline under different soil cover thicknesses.

[0018] S111: reducing the soil covering the pipeline to a state without soil covering, increasing the stress applied by the loader to the pipeline in equal proportion, and measuring the magnetic field spatial data within a preset detection range through the detection probe. The preset detection range includes a range between the third preset distances extending from the first stress concentration point to both ends of the pipeline on the pipeline.

[0019] S112: Based on the magnetic field spatial data measured within the preset detection range, a second distribution relationship corresponding to the magnetic field signal on the pipeline is obtained. The second distribution relationship is a functional relationship between the magnetic field signal on the pipeline and the length of the pipeline when stress is concentrated on the pipeline.

[0020] S113: Based on the modified model, the Jiles-Atherton hysteresis formula is modified; wherein the modified model is:

[0021] ;

[0022] ;

[0023] ;

[0024] ;

[0025] ;

[0026] ;

[0027] ;

[0028] in, is the actual magnetization intensity, is the Earth's magnetic field strength, is the hysteresis-free magnetization, is the direction coefficient, is the material saturation magnetization, is the equivalent magnetic field, α is the magnetic coupling parameter, is the vacuum permeability, is the reversible component, is the irreversible component, c is the reversible component coefficient, is the demagnetization factor, is Poisson's ratio, E is the elastic modulus, σ is the applied stress, is the initial stress constant, is the angle between the direction of the external stress and the direction of the external magnetic field, is the saturation magnetic induction intensity, k is the pinning coefficient, is the initial pinning coefficient, is the relative pinning coefficient, For coercive force.

[0029] S114: Based on the first distribution relationship, the second distribution relationship and the modified Jiles-Atherton hysteresis formula, a stress space forward modeling is performed on the pipeline to be inspected to obtain stress distribution information on the pipeline to be inspected.

[0030] Based on the above technical solution, the present invention can also be improved as follows.

[0031] Further, the detection probe includes four three-axis magnetic sensors. Two three-axis magnetic sensors are arranged in the horizontal direction, and another two three-axis magnetic sensors are arranged in the vertical direction to obtain the detection probe. The connection line between the two three-axis magnetic sensors arranged in the horizontal direction intersects with the connection line between the other two three-axis magnetic sensors arranged in the vertical direction. The detection probe is mounted on the probe slide rail.

[0032] Further, S201: among the eigenvalues ​​corresponding to the eigenvectors, determine the eigenvector corresponding to the maximum eigenvalue. S202: based on the direction of the eigenvector corresponding to the maximum eigenvalue, adjust the layout of the four three-axis magnetic sensors. S203: repeat S201-S202 until the maximum eigenvalue is greater than the characteristic threshold.

[0033] Further, the loader comprises a bolt and a pressure device, wherein the pressure device contacts the outer wall of the pipeline, and the bolt is used to tighten the pressure device to apply stress to the pipeline through the pressure device.

[0034] Furthermore, the welds on the pipeline include equal-thickness girth welds and unequal-thickness girth welds. The pipeline wall thickness on both sides of the equal-thickness girth weld is consistent, while the pipeline wall thickness on both sides of the unequal-thickness girth weld is inconsistent.

[0035] Furthermore, the defects on the pipeline are volume defects, which include porosity defects and / or slag inclusion defects.

[0036] Furthermore, there are two defects on the pipeline, one defect is located at the top of the pipeline, and one defect is located at the bottom of the pipeline; the line between the two defects is not perpendicular to the axis of the pipeline along the length direction of the pipeline.

[0037] Furthermore, the distance between the first stress concentration point and the second stress concentration point and any weld on the pipeline is greater than a first preset distance.

[0038] The beneficial effects of the present invention are as follows: an indoor test platform for pipeline stress detection is designed, and a large-diameter three-dimensional pipeline used for oil and gas transportation is adopted, and the actual in-service oil and gas transportation pipeline environment is simulated by setting stress concentration, defects, stress concentration and defect superposition, soil covering, equal-thickness girth welds and unequal-thickness girth welds working conditions; based on the indoor test platform, weak magnetic detection technology is used to detect the spatial distribution data of the magnetic field signal that changes with the length of the pipeline, and the spatial distribution law of the magnetic field on the oil and gas transportation pipeline under different working conditions is obtained, thereby determining the stress distribution on the oil and gas transportation pipeline under different working conditions, which can improve the accuracy of stress detection on the oil and gas transportation pipeline.

[0039] In a second aspect, the present invention provides an electronic device, comprising: a memory, one or more processors; the memory and the processor are coupled; wherein the memory stores computer program code, the computer program code includes computer instructions, and when the computer instructions are executed by the processor, the electronic device executes the stress detection method for a pipeline as described in any one of the above-mentioned first aspects.

[0040] In a third aspect, a computer-readable storage medium is provided, comprising computer instructions. When the computer instructions are executed on an electronic device, the electronic device executes the stress detection method for a pipeline as described in any one of the first aspects.

[0041] It can be understood that the beneficial effects that can be achieved by the electronic device of the second aspect and the computer-readable storage medium of the third aspect provided above can be referred to the beneficial effects of the first aspect and any possible design thereof, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of a process flow of a stress detection method for a pipeline provided by the present invention;

[0043] Figure 2 A schematic diagram of the structure of the detection platform provided by the present invention;

[0044] Figure 3 A schematic diagram of the structure of the loader provided by the present invention;

[0045] Figure 4 This is a schematic structural diagram of the detection probe provided by the present invention. DETAILED DESCRIPTION

[0046] The technical solution in the embodiment of the present application will be described below in conjunction with the drawings in the embodiment of the present application. Among them, in the description of the present application, unless otherwise specified, " / " indicates that the objects associated before and after are in an "or" relationship, for example, A / B can represent A or B; "and / or" in the present application is only a description of the association relationship of the associated objects, indicating that there can be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. And, in the description of the present application, unless otherwise specified, "multiple" refers to two or more than two. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, c can be single or multiple. In addition, in order to facilitate the clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, the words "first", "second" and the like are used to distinguish between the same items or similar items with substantially the same functions and effects. Those skilled in the art will understand that the words "first", "second" and the like do not limit the quantity and execution order, and the words "first", "second" and the like do not necessarily limit the differences. At the same time, in the embodiments of the present application, the words "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or design.

[0047] The present invention provides a stress detection method for a pipeline. Figure 1 The method comprises the following steps S101-S114:

[0048] S101: Build a testing platform.

[0049] Among them, see Figure 2 The detection platform includes a shell 201, a pipe 202, a loader 203, and a probe slide 204. The shell 201 is a hollow cuboid with a missing top surface, the bottom surface of the shell 201 is a rectangle, and the inside of the shell 201 is filled with covering soil 205. The pipe 202 is a hollow structure, and both ends of the pipe 202 are closed. The pipe 202 is located at a preset depth of the covering soil 205. The loader 203 is arranged on the outer wall of the pipe 202, and is used to apply stress to the pipe 202. The probe slide 204 is parallel to the pipe 202, and is arranged directly above the axis 206 of the pipe 202 along the length direction of the pipe, and is used to carry a detection probe to detect the magnetic field spatial data of the corresponding position through the detection probe. A weld 207 and a defect 208 are arranged on the pipe 202.

[0050] It should be noted that those skilled in the art can set the preset depth based on actual needs, for example, setting the preset depth to 0.3 meters, which is not limited in the embodiments of the present application.

[0051] In some embodiments, the pipeline can be a seamless steel pipe, which is not pressure-bearing and sealed at both ends to ensure that there is no scattered spatial magnetic field around the detection platform.

[0052] In some embodiments, the defect position should be set to avoid spatial interference between defect signals. The simulation software Ansoft Maxwell can be used to establish a pipeline model, set a volume defect on the model, set the external magnetic field to the size of the geomagnetic field, and perform visual simulation analysis. According to the simulation results, the change curve of the magnetic field signal above the pipeline axis within the pipeline length range under the condition of no covering soil is obtained; if there is signal superposition on the curve, the defect spacing is changed, and the visual simulation analysis is performed again until the minimum spacing between the defect signals that do not affect each other is found, which serves as a theoretical reference for setting the defect position on the actual pipeline.

[0053] In some embodiments, see Figure 3 The loader includes a bolt 301 and a pressure device 302, and the pressure device 302 is in contact with the outer wall 303 of the pipeline. The pressure device 302 can be tightened by rotating the bolt 301, so that the pressure device 302 applies stress to the outer wall 303 of the pipeline.

[0054] In some embodiments, the welds on the pipeline include equal-thickness girth welds and unequal-thickness girth welds. The pipeline wall thicknesses on both sides of the equal-thickness girth welds are consistent, while the pipeline wall thicknesses on both sides of the unequal-thickness girth welds are inconsistent.

[0055] For example, the length of the pipeline on one side of the unequal thickness girth weld can be 18m, and a pipe with a pipe diameter of De219×6.5mm is selected, that is, the outer diameter of the pipe is 219mm and the wall thickness is 6.5mm. The pipe on the other side of the unequal thickness girth weld can be a pipe with a pipe diameter of De219×8mm, that is, the outer diameter of the pipe is 219mm and the wall thickness is 8mm. Among them, the equal thickness girth weld can be set at 12m of the pipeline, and the unequal thickness girth weld can be set at 18m of the pipeline.

[0056] In some embodiments, the defects on the pipeline are volume defects, which include porosity defects and / or slag inclusion defects.

[0057] In some embodiments, the number of defects on the pipeline is 2, 1 defect is located at the top of the pipeline, and 1 defect is located at the bottom of the pipeline; the line between the 2 defects is not perpendicular to the axis of the pipeline along the length direction of the pipeline.

[0058] Exemplarily, the two defects may be set at the 12 o'clock direction at 1m of the pipeline and at the 6 o'clock direction at 29m.

[0059] S102: Setting a first stress concentration point on the pipeline, and applying stress on the first stress concentration point based on a loader.

[0060] The first stress concentration point does not coincide with any defect on the pipeline.

[0061] In some embodiments, the distance between the first stress concentration point and any weld on the pipeline is greater than the first preset distance. Those skilled in the art may set the first preset distance based on actual needs, for example, setting the first preset distance to 6 meters, which is not limited in the embodiments of the present application.

[0062] Exemplarily, the first stress concentration point may be set at 6 m of the pipeline to distinguish the effects of different working conditions on the spatial magnetic field signal.

[0063] S103: Setting a second stress concentration point on the pipeline, and applying stress on the second stress concentration point based on a loader.

[0064] Among them, a second stress concentration point coincides with a defect on the pipeline.

[0065] In some embodiments, the distance between the second stress concentration point and any weld on the pipeline is greater than the first preset distance.

[0066] Exemplarily, the second stress concentration point may be set at 24 m of the pipeline, and defects may be set at 6 points of the pipeline at 24 m, so as to distinguish the effects of different working conditions on the spatial magnetic field signal.

[0067] S104: Mounting a detection probe on the probe slide rail.

[0068] In some embodiments, the detection probe includes four three-axis magnetic sensors. Figure 4 , two three-axis magnetic sensors (for example, three-axis magnetic sensor 401 and three-axis magnetic sensor 402) may be arranged in the horizontal direction, and another two three-axis magnetic sensors (for example, three-axis magnetic sensor 403 and three-axis magnetic sensor 404) may be arranged in the vertical direction to obtain a detection probe. The line between the two three-axis magnetic sensors arranged in the horizontal direction intersects the line between the other two three-axis magnetic sensors arranged in the vertical direction.

[0069] In some embodiments, the stepping distance of the detection probe carried on the probe slide rail can be controlled by a single chip microcomputer and a computer program.

[0070] S105: Measure the magnetic field spatial data from the detection starting point to the detection end point through the detection probe.

[0071] The detection starting point is from one end of the pipeline to the point at the second preset distance away from the pipeline direction. The detection end point is from the other end of the pipeline to the point at the second preset distance away from the pipeline direction. The line between the detection starting point and the detection end point is parallel to the pipeline.

[0072] For example, it is possible to start from both ends of the pipeline and extend 3m outward along the axis respectively. The extended length coordinates are used as the detection starting point and detection end point respectively. The detection probe is mounted on the probe slide rail, and the measurement is made from the detection starting point to the detection end point along the axial direction of the pipeline, and the magnetic field spatial data measured by the detection probe is recorded. Each time the detection probe reaches the detection end point, a measurement is completed. After that, the probe slide rail carries the detection probe back to the detection starting point.

[0073] S106: Based on the magnetic field spatial data measured from the detection starting point to the detection end point, obtain the characteristic vector of the target position, and obtain the characteristic value corresponding to each characteristic vector.

[0074] The target position includes the position of the defect on the pipeline that does not coincide with the second stress concentration point, the position of the first stress concentration point, the position of the second stress concentration point, and the position of the weld.

[0075] In some embodiments, the magnetic field spatial data measured from the detection starting point to the detection end point is obtained, and the obtained magnetic field spatial data can also be preprocessed, for example, data cleaning, denoising, screening, sorting, etc. Then, based on the preprocessed magnetic field spatial data, the characteristic vector of the target position is obtained, and the characteristic values ​​corresponding to each characteristic vector are obtained.

[0076] In some embodiments, the following steps S201 - S203 may also be performed to optimize the layout of the three-axis magnetic sensors included in the detection probe.

[0077] S201: Determine the eigenvector corresponding to the maximum eigenvalue among the eigenvalues ​​corresponding to the eigenvectors.

[0078] S202: Adjust the layout of the four three-axis magnetic sensors based on the direction of the eigenvector corresponding to the maximum eigenvalue.

[0079] S203: Repeat S201-S202 until the maximum eigenvalue is greater than the eigenvalue threshold.

[0080] For example, a sensitivity analysis can be performed on the axial magnetic sensors and magnetic field directions that have the greatest impact on target positions such as the position of the defect that does not coincide with the second stress concentration point, the position of the first stress concentration point, the position of the second stress concentration point, and the position of the weld, that is, to find the eigenvector with the largest eigenvalue, and the direction of the eigenvector is the direction in which the magnetic field has the greatest impact on the axial magnetic sensor; according to this method, the layout of each three-axis sensor included in the detection probe is optimized; after optimization, steps S105-S106 can be repeated to test the optimized probe layout, obtain the reliability of the eigenvalue of the data, and determine the optimal layout of each three-axis sensor. Based on the optimal layout of each three-axis sensor, the pipeline is inspected.

[0081] S107: Increase the thickness of the soil covering the pipeline and the elastic modulus of the soil covering in equal proportion, repeat S105-S106, and obtain the attenuation of the magnetic field signal at each target position when the soil covering the pipeline has different thicknesses based on the eigenvectors of each target position and the eigenvalues ​​corresponding to each eigenvector.

[0082] Exemplarily, proportionally increasing the thickness of the soil covering the pipeline may be sequentially changing the thickness of the soil covering the pipeline to 0.6 m, 0.9 m, 1.2 m, etc. Proportionally increasing the elastic modulus of the soil covering the pipeline may be sequentially changing the elastic modulus of the soil covering the pipeline to 0.3 m, 0.5 m, 0.7 m, etc.

[0083] In some embodiments, the pipeline length can be used as the horizontal axis. , the magnetic field space data is the vertical coordinate , use MATLAB software to interpolate the data and draw the values ​​of the soil cover depth used in all experiments on the same two-dimensional coordinate axis. - The different colors of the curve represent different soil cover depths. The image is analyzed to calculate the attenuation of the magnetic field signal at each target position at the same defect at different soil cover depths, and the attenuation degree of the magnetic field signal at each target position at different soil cover depths is qualitatively analyzed.

[0084] In some embodiments, the elastic modulus of the covering soil may not be adjusted during the first test, and the elastic modulus of the covering soil may be adjusted starting from the second test.

[0085] S108: For any soil cover thickness on the pipeline, perform summing and averaging processing on the attenuation of the magnetic field signal at each target position under any soil cover thickness to obtain the average attenuation of the magnetic field signal under any soil cover thickness.

[0086] S109: Based on the average attenuation of the magnetic field signal at each soil cover thickness, a functional relationship between the soil cover thickness and the average attenuation of the magnetic field signal is obtained.

[0087] For example, after obtaining the average attenuation of the magnetic field signal under any soil cover thickness, the soil cover thickness can be used as the horizontal coordinate. , the average attenuation of the magnetic field signal is the vertical coordinate , draw a scatter plot. The fitting function form can be determined according to the scatter plot image, and MATLAB can be used to fit the scattered data to obtain the functional relationship between the average attenuation of the magnetic field signal and the thickness of the covering soil, and quantitatively analyze the relationship between the covering soil depth and the attenuation of the magnetic field signal.

[0088] S110: Based on the functional relationship between the soil cover thickness and the average attenuation of the magnetic field signal, a first distribution relationship corresponding to the magnetic field signal on the pipeline is obtained.

[0089] The first distribution relationship is a functional relationship between the magnetic field signal on the pipeline and the length of the pipeline under different cover soil thicknesses.

[0090] Combined with the above S107-S110, it can be seen that due to the lift-off effect, that is, the disturbance magnetic field generated by the defect is rapidly attenuated in the air, and the difference in the signals detected by the sensor at different heights is large, so the weak magnetic detection method used is indicative, and does not allow quantification of defects, nor does it allow quantification of the relationship between the magnetic field signal generated by the defect and the depth of the covering soil. Therefore, only the semi-quantitative relationship between the depth of the covering soil and the magnetic field signal can be determined. The specific method is as follows:

[0091] The pipe length can be used as the horizontal axis , the magnetic field space data is the vertical coordinate , use MATLAB software to interpolate the data and draw the values ​​of the soil cover depth used in all experiments on the same two-dimensional coordinate axis. - The different colors of the curve represent different soil cover depths. The image is analyzed to calculate the attenuation of the magnetic field signal at each target position at the same defect at different soil cover depths, and the attenuation degree of the magnetic field signal at each target position at different soil cover depths is qualitatively analyzed.

[0092] The attenuation of magnetic field signals at all defects at the same soil covering depth was summed and averaged to obtain the average attenuation at different soil covering depths. The soil covering depth was taken as the horizontal coordinate x and the average attenuation was taken as the vertical coordinate y. The data was fitted using MATLAB to obtain the functional relationship between the magnetic field signal and the soil covering depth, and the attenuation relationship between the soil covering depth and the magnetic field signal was quantitatively analyzed.

[0093] By combining qualitative analysis with quantitative analysis, a semi-quantitative relationship between the soil cover depth and the magnetic field signal is obtained, and the first distribution relationship can be obtained.

[0094] S111: reducing the soil covering the pipeline to a state without soil covering, proportionally increasing the stress applied by the loader to the pipeline, and measuring the magnetic field spatial data within a preset detection range through the detection probe.

[0095] The preset detection range includes a range on the pipeline, with the first stress concentration point as the center, and extending to the two ends of the pipeline between third preset distances.

[0096] It should be noted that those skilled in the art may set the third preset distance based on actual needs, for example, setting the third preset distance to 6 meters, which is not limited in the embodiments of the present application.

[0097] In some embodiments, the stress applied by the loader to the pipe through the bolt can be based on Hooke's law Determine the stress exerted by the bolt on the pipe. In this case, within the elastic range of the pipe, the elastic coefficient k of the pipe is a constant, and the screw-in depth of the bolt is It is linearly positively correlated with the applied load F and is controlled by the screwing depth of the bolt. , which can quantitatively control the stress applied to the pipeline .

[0098] S112: Based on the magnetic field spatial data measured within a preset detection range, a second distribution relationship corresponding to the magnetic field signal on the pipeline is obtained.

[0099] The second distribution relationship is a functional relationship between the magnetic field signal on the pipeline and the length of the pipeline when the stress on the pipeline is concentrated.

[0100] For example, the screwing depth of the bolt can be increased proportionally. Repeat S105-S106 within the measurement range. The length of the pipeline within the measurement range is the horizontal coordinate. , the magnetic field space data is the vertical coordinate , use MATLAB to interpolate the data and plot the values ​​of the precession depths used in all experiments on the same two-dimensional coordinate axis. - The different colors of the curve represent different precession depths. By analyzing the image, the spatial distribution law of the magnetic field signal changing with the pipeline length under the condition of quantitative stress concentration is obtained, that is, the second distribution relationship is obtained.

[0101] S113: Based on the modified model, the Jiles-Atherton hysteresis formula is modified; wherein the modified model is:

[0102] ;

[0103] ;

[0104] ;

[0105] ;

[0106] ;

[0107] ;

[0108] ;

[0109] in, is the actual magnetization intensity, is the Earth's magnetic field strength, is the hysteresis-free magnetization, is the direction coefficient, is the material saturation magnetization, is the equivalent magnetic field, α is the magnetic coupling parameter, is the vacuum permeability, is the reversible component, is the irreversible component, c is the reversible component coefficient, is the demagnetization factor, is Poisson's ratio, E is the elastic modulus, σ is the applied stress, is the initial stress constant, is the angle between the direction of the external stress and the direction of the external magnetic field, is the saturation magnetic induction intensity, k is the pinning coefficient, is the initial pinning coefficient, is the relative pinning coefficient, For coercive force.

[0110] It should be noted that the directional coefficient δ can be taken according to the following rules: When ,δ=1; when ,δ= -1.

[0111] S114: Based on the first distribution relationship, the second distribution relationship and the modified Jiles-Atherton hysteresis formula, a stress space forward modeling is performed on the pipeline to be inspected to obtain stress distribution information on the pipeline to be inspected.

[0112] In some embodiments, the accuracy of the method provided by the present invention can be verified by:

[0113] An excavated pipe section is selected on the pipeline to be inspected, and the magnetic field signal data of the pipe section is measured along the axial direction of the pipeline to be inspected using a weak magnetic detection method; after the measurement is completed, the pipe section is excavated on site, the cover depth above the pipe section is measured, the type, location and size of the defect are determined, and the defect is detected using other non-destructive testing methods; the data measured by this method are compared and analyzed with the data measured by other non-destructive testing methods, so as to verify the accuracy of the deduction of the stress distribution on the pipeline to be inspected based on the first distribution relationship, the second distribution relationship and the Jiles-Atherton correction model in this method.

[0114] It can be seen that the stress detection method for pipelines provided by the present invention designs an indoor test platform for pipeline stress detection, adopts a large-diameter three-dimensional pipeline used for oil and gas transportation, and simulates the actual environment of oil and gas transportation pipelines in service by setting stress concentration, defects, stress concentration and defect superposition, covering, equal-thickness girth welds and unequal-thickness girth welds. Based on the indoor test platform, weak magnetic detection technology is used to detect the spatial distribution data of the magnetic field signal that changes with the length of the pipeline, and the spatial distribution law of the magnetic field on the oil and gas transportation pipeline under different working conditions is obtained, thereby determining the stress distribution on the oil and gas transportation pipeline under different working conditions, which can improve the accuracy of stress detection on the oil and gas transportation pipeline.

[0115] In some schemes, multiple embodiments of the present application can be combined, and the combined scheme can be implemented. Optionally, some operations in the process of each method embodiment are optionally combined, and / or the order of some operations is optionally changed. In addition, the execution order between the steps of each process is only exemplary and does not constitute a restriction on the execution order between the steps. There can also be other execution orders between the steps. It is not intended to indicate that the execution order is the only order in which these operations can be performed. A person of ordinary skill in the art will think of a variety of ways to reorder the operations described herein. In addition, it should be noted that the process details involved in a certain embodiment of this article are also applicable to other embodiments in a similar manner, or different embodiments can be used in combination.

[0116] In addition, some steps in the method embodiment may be equivalently replaced by other possible steps. Alternatively, some steps in the method embodiment may be optional and may be deleted in certain usage scenarios. Alternatively, other possible steps may be added to the method embodiment. Furthermore, the method embodiments may be implemented separately or in combination.

[0117] In the several embodiments provided in this application, it should be understood that the disclosed method can be implemented in other ways. The technical solution of the embodiment of this application is essentially or the part that makes the contribution or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions to enable a device (which can be a single-chip microcomputer, chip, etc.) or a processor to execute all or part of the steps of the method described in each embodiment of this application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk and other media that can store program code.

[0118] The above contents are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application shall be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A stress detection method for a pipeline, characterized in that: include: S101: Build a detection platform; the detection platform includes a shell, a pipeline, a loader, and a probe slide rail; the shell is filled with covering soil; the pipeline is a hollow structure, and both ends of the pipeline are closed; the pipeline is located at a preset depth of the covering soil; the loader is arranged on the outer wall of the pipeline, and is used to apply stress to the pipeline; the probe slide rail is parallel to the pipeline, and is arranged just above the axis of the pipeline along the length direction, and is used to carry a detection probe, so as to detect the magnetic field space data of the corresponding position through the detection probe; the pipeline is provided with welds and defects; S102: Setting a first stress concentration point on the pipeline, and applying stress to the first stress concentration point based on the loader; the first stress concentration point does not overlap with any defect on the pipeline; S103: setting a second stress concentration point on the pipeline, and applying stress to the second stress concentration point based on the loader; one of the second stress concentration points coincides with a defect on the pipeline; S104: Mounting a detection probe on the probe slide rail; S105: measuring the magnetic field spatial data from the detection starting point to the detection end point by the detection probe; wherein the detection starting point is from one end of the pipeline to a point at a second preset distance away from the pipeline direction; the detection end point is from the other end of the pipeline to a point at a second preset distance away from the pipeline direction; and the line connecting the detection starting point to the detection end point is parallel to the pipeline; S106: based on the magnetic field spatial data measured from the detection starting point to the detection end point, obtaining the characteristic vectors of the target position, and obtaining the characteristic values ​​corresponding to each characteristic vector; the target position includes the position of the defect on the pipeline that does not overlap with the second stress concentration point, the position of the first stress concentration point, the position of the second stress concentration point, and the position of the weld; S107: increasing the thickness of the soil covering the pipeline and the elastic modulus of the soil covering in equal proportion, repeating S105-S106, and obtaining the attenuation of the magnetic field signal at each target position when the soil covering the pipeline has different thicknesses based on the feature vectors of each target position and the feature values ​​corresponding to each feature vector; S108: for any soil cover thickness on the pipeline, performing summing and averaging processing on the attenuation of the magnetic field signal at each target position under the any soil cover thickness to obtain an average attenuation of the magnetic field signal under the any soil cover thickness; S109: obtaining a functional relationship between the soil cover thickness and the average attenuation of the magnetic field signal based on the average attenuation of the magnetic field signal at each soil cover thickness; S110: based on the functional relationship between the soil cover thickness and the average attenuation of the magnetic field signal, obtaining a first distribution relationship corresponding to the magnetic field signal on the pipeline; the first distribution relationship is a functional relationship of the magnetic field signal on the pipeline with the length of the pipeline under different soil cover thicknesses; S111: reducing the soil covering the pipeline to a state without soil covering, increasing the stress applied by the loader to the pipeline in equal proportion, and measuring the magnetic field spatial data within a preset detection range through the detection probe; the preset detection range includes a range on the pipeline, with the first stress concentration point as the center, and extending to the two ends of the pipeline by a third preset distance respectively; S112: based on the magnetic field spatial data measured within the preset detection range, obtaining a second distribution relationship corresponding to the magnetic field signal on the pipeline; the second distribution relationship is a functional relationship between the magnetic field signal on the pipeline and the length of the pipeline when stress concentration is present on the pipeline; S113: Based on the correction model, the Jiles-Atherton hysteresis formula is corrected; wherein the correction model is: ； ； ； ； ； ； ； in, is the actual magnetization intensity, is the Earth's magnetic field strength, is the hysteresis-free magnetization, is the direction coefficient, is the material saturation magnetization, is the equivalent magnetic field, α is the magnetic coupling parameter, is the vacuum permeability, is the reversible component, is the irreversible component, c is the reversible component coefficient, is the demagnetization factor, is Poisson's ratio, E is the elastic modulus, σ is the applied stress, is the initial stress constant, is the angle between the direction of the external stress and the direction of the external magnetic field, is the saturation magnetic induction intensity, k is the pinning coefficient, is the initial pinning coefficient, is the relative pinning coefficient, is the coercive force; S114: Based on the first distribution relationship, the second distribution relationship and the modified Jiles-Atherton hysteresis formula, perform stress space forward modeling on the pipeline to be inspected to obtain stress distribution information on the pipeline to be inspected.

2. The method according to claim 1, characterized in that The detection probe includes four three-axis magnetic sensors; the detection probe is mounted on the probe slide rail and includes: Two three-axis magnetic sensors are arranged in the horizontal direction, and another two three-axis magnetic sensors are arranged in the vertical direction to obtain the detection probe; a line between the two three-axis magnetic sensors arranged in the horizontal direction intersects a line between the other two three-axis magnetic sensors arranged in the vertical direction; The detection probe is mounted on the probe slide rail.

3. The method according to claim 2, characterized in that Before increasing the thickness of the soil covering the pipeline and the elastic modulus of the soil covering in equal proportion, the method further comprises: S201: Determine, among the eigenvalues ​​corresponding to the eigenvectors, an eigenvector corresponding to the maximum eigenvalue; S202: adjusting the layout of the four three-axis magnetic sensors based on the direction of the eigenvector corresponding to the maximum eigenvalue; S203: Repeat S201-S202 until the maximum eigenvalue is greater than the eigenvalue threshold.

4. The method according to claim 3, characterized in that: The loader comprises a bolt and a pressure device, wherein the pressure device is in contact with the outer wall of the pipeline; the bolt is used to tighten the pressure device so as to apply stress to the pipeline through the pressure device.

5. The method according to claim 4, characterized in that The welds on the pipeline include equal-thickness girth welds and unequal-thickness girth welds; the pipeline wall thicknesses on both sides of the equal-thickness girth welds are consistent, and the pipeline wall thicknesses on both sides of the unequal-thickness girth welds are inconsistent.

6. The method according to claim 5, characterized in that The defects on the pipeline are volume defects; the volume defects include porosity defects and / or slag inclusion defects.

7. The method according to claim 6, characterized in that There are two defects on the pipeline, one defect is located at the top of the pipeline, and one defect is located at the bottom of the pipeline; the connecting line between the two defects is not perpendicular to the axis of the pipeline along the length direction of the pipeline.

8. The method according to claim 7, characterized in that The distance between the first stress concentration point and the second stress concentration point and any weld on the pipeline is greater than a first preset distance.

9. An electronic device, characterized in that: include: A memory and one or more processors; the memory is coupled to the processor; wherein the memory stores computer program code, the computer program code includes computer instructions, and when the computer instructions are executed by the processor, the electronic device executes the stress detection method for a pipeline as described in any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that: It comprises computer instructions, and when the computer instructions are executed on an electronic device, the electronic device executes the stress detection method for a pipeline as described in any one of claims 1 to 8.

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