Method and device for detecting stress state of reinforced concrete based on magnetic induction chain

Abstract

The invention relates to a reinforced concrete stress state detection method and monitoring device based on a magnetic induction chain, and the device comprises an external magnetic field generation device, a magnetic induction chain detection device and a data processing system, the external magnetic field generation device is placed on the surface of reinforced concrete to be detected and is used for applying a stable magnetic field; the magnetic induction chain detection device is used for detecting the magnetic induction intensity change at a reinforced concrete surface measuring point, the data processing system is used for receiving and processing magnetic intensity data of the magnetic induction chain detection device, and the magnitude of stress (prestress) is analyzed from the magnetic intensity data by establishing a mathematical model of a force-magnetic coupling relationship; therefore, real-time and non-destructive detection of the stress state of the structure is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of civil engineering structure monitoring and evaluation, and relates to a reinforced concrete stress state detection method and monitoring device based on a magnetic induction chain. In particular, it relates to a detection method and monitoring device that utilizes an external magnetic field to load onto steel bars through concrete to form a magnetic induction chain, and measures magnetic field changes on the external concrete surface to detect the stress state (prestress) of reinforced concrete components. Background Art

[0002] The stress state of reinforced concrete is a core indicator for assessing the health and safety of structures. It not only directly impacts structural stability but also plays a crucial role in preventing potential damage. Traditional stress monitoring methods can only measure relative stress states, not absolute stress states. Furthermore, direct measurement of prestress in in-service structures is impossible. Among existing structural monitoring methods, improving the applicability of monitoring sensing technologies, reducing costs, and enabling large-scale deployment have become key challenges in current research and engineering practice.

[0003] At present, there are many different methods for detecting stress in reinforced concrete, which mainly rely on direct measurement of strain values ​​and obtaining stress values ​​through corresponding conversion. Traditional reinforced concrete stress detection methods include resistance strain gauge method, ultrasonic detection method, infrared thermal imaging detection method and fiber Bragg grating detection method. However, these methods all have certain limitations in practical applications. For example, resistance strain gauges are mainly suitable for measuring strain on the surface of concrete and are difficult to detect deeply inside the material. As a new sensing technology, fiber Bragg grating strain gauges have the advantages of high sensitivity, wide measurement bandwidth and strong dynamic responsiveness. However, they have high requirements for the construction environment and require pre-embedded or pasted fiber Bragg gratings in the concrete structure. Ultrasonic detection methods are affected by the characteristics of concrete materials such as cement type, water-cement ratio, aggregate grading, etc., and the accuracy of the measured results is poor. Therefore, the field of concrete stress monitoring urgently needs a new monitoring technology and method that can overcome the above problems.

[0004] This invention proposes a new technology for monitoring the stress state (prestress) of reinforced concrete. The core of this technology lies in using an external magnetic field to load the steel bars through concrete, forming a magnetic induction chain. The magnetic field changes are then measured on the external concrete surface to detect the stress state (prestress) of reinforced concrete components. When the steel bars are subjected to external loads and undergo stress changes or damage, their internal magnetic domain structure adjusts accordingly, resulting in changes in the surrounding magnetic field distribution. By arranging precise magnetic induction elements on the outside of the structure, these subtle magnetic field fluctuations can be captured and converted into quantifiable electrical signals. Combining advanced signal processing techniques with data analysis algorithms, accurate identification and quantitative assessment of the structural stress state can be achieved. By comparing the magnetic induction intensity change data of a designed reference structure during the application of external force with the magnetic induction intensity data of the existing prestressed state of the structure to be measured, the prestress level in the original component can be deduced by calculating the difference in magnetic induction intensity between the two. This technology is expected to achieve long-term and stable measurement of reinforced concrete stress and detection of the prestress magnitude of in-service structures, providing a feasible approach for real-time and accurate structural monitoring. Summary of the Invention

[0005] In view of this, the present invention, in order to solve the above-mentioned problems existing in the use of the above-mentioned existing reinforced concrete stress detection methods, provides a reinforced concrete stress state detection method and monitoring device based on magnetic induction chain. By installing an external magnetic field and a Hall sensor for measuring magnetic induction intensity on the surface of the reinforced concrete, keeping the external magnetic field and the Hall sensor in the same plane and at a constant distance, the external magnetic field penetrates into the concrete, magnetizing the steel bars inside the concrete and forming a magnetic induction chain on the steel bars. By changing the stress applied to the steel bars and using remote magnetic field measurement technology to monitor the changes in the magnetic induction chain, the changes in the induced magnetic field can be measured. By establishing a mathematical model of the force-magnetic coupling relationship, the stress magnitude can be parsed from the change in magnetic induction intensity, thereby achieving real-time, non-destructive detection of the structural stress state.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A reinforced concrete stress state monitoring device based on a magnetic induction chain includes an external magnetic field generating device, a magnetic induction chain detection device, and a data processing system. The external magnetic field generating device is placed on the surface of the reinforced concrete to be detected to apply a stable magnetic field. The magnetic induction chain detection device is used to detect changes in magnetic induction intensity at measuring points on the reinforced concrete surface. The data processing system is used to receive and process magnetic intensity data from the magnetic induction chain detection device. By establishing a mathematical model of the force-magnetic coupling relationship, the stress (prestress) size can be parsed from the magnetic intensity data, thereby realizing real-time, non-destructive detection of the stress state of the reinforced concrete.

[0008] The principles of this basic solution are:

[0009] When an external magnetic field is applied to a steel bar, the atomic magnetic moments within the material rearrange, forming a so-called magnetization effect. This magnetization effect is transmitted step by step within the material through induction, forming a chain conduction. Specifically, the external magnetic field causes the atomic magnetic moments within the material (i.e., the tiny magnetic field of each atom) to tend to align with the direction of the external magnetic field, thereby forming a chain of magnetic moments, i.e., a magnetic chain, between atoms. The formation of this magnetic chain is the basis of the overall magnetization process of the material and the reason why the material exhibits macroscopic magnetism.

[0010] For reinforced concrete components, the stress state of the concrete is usually closely related to the stress condition of the steel bars. As a ferromagnetic material, the stress state of the steel bars (such as tension, compression, bending, etc.) will affect the internal magnetic domain structure and magnetic flux conduction, thereby changing the surface magnetic intensity. This change can be detected by a Hall sensor, thereby indirectly reflecting the stress state and bonding force changes of the steel bars. When reinforced concrete components are subjected to external stress, the steel bars, as the main load-bearing components, will respond first. The external stress will change the stress distribution and strain state inside the steel bars, thereby affecting their magnetic domain structure and magnetic flux conduction. Specifically, areas of stress concentration or large strain will lead to the rearrangement of magnetic domains and local changes in magnetic flux, thereby changing the surface magnetic intensity of the steel bars.

[0011] Furthermore, the external magnetic field generating device is preferably a neodymium iron boron magnet, and the magnetic induction chain detection device is preferably a linear Hall sensor. The linear Hall sensor and the corresponding neodymium iron boron magnet are respectively placed on both sides of the reinforced concrete to be detected and the distance between them is constant.

[0012] The measuring method of the reinforced concrete stress state monitoring device based on the magnetic induction chain comprises the following steps:

[0013] S1: Based on the steel bar arrangement, size and material properties of the reinforced concrete component to be tested, design and manufacture an identical reference structure, place an external magnetic field generator on the surface of the reinforced concrete component to be tested and the reference structure at the same position to apply a stable magnetic field, and place a magnetic induction chain detection device on one side of the external magnetic field generator. The magnetic induction chain detection devices on the reinforced concrete component to be tested and the reference structure are also at the same position and do not contact the corresponding reinforced concrete component to be tested and the reference structure. The external magnetic field generator is preferably a neodymium iron boron magnet, and the magnetic induction chain detection device is preferably a linear Hall sensor;

[0014] S2: Start the magnetic induction chain detection device to monitor the magnetic induction intensity on the surface of the reinforced concrete component in the prestressed state. During this period, the external magnetic field generating device and the magnetic induction chain detection device are kept stationary, and a constant distance is maintained between the external magnetic field generating device and the magnetic induction chain detection device.

[0015] S3: monitoring the magnetic induction intensity of the reference structure in a stress-free state and under an external load condition;

[0016] S4: Analyzing the magnetic intensity data obtained in step S3 using a data processing system to obtain a change in magnetic induction intensity in a trend of magnetic induction chain magnetic intensity change;

[0017] S5: Based on the analysis results of step S4, a mathematical model of the force-magnetic coupling relationship is established to analyze the stress magnitude from the change in magnetic induction intensity. By comparing and analyzing the performance of reinforced concrete components in a free and stress-free state with a reference structure of the same material after being subjected to a preset stress in terms of magnetic induction intensity, the prestress level in the original component can be reversely deduced by calculating the difference in magnetic induction intensity between the two.

[0018] Furthermore, in step S5, the magnetic induction intensity change data of the reference structure during the application of external force is compared with the magnetic induction intensity data of the reinforced concrete component to be tested in the prestressed state, and a specific external stress value is found so that at this stress level, the magnetic induction intensity of the reference structure matches the magnetic induction intensity of the reinforced concrete component to be tested in the prestressed state; when the matching point is found, the external stress value at this time is recorded, that is, the magnitude of the prestress in the reinforced concrete component to be tested.

[0019] Furthermore, in the mathematical model of the magnetomechanical coupling relationship in step S5, after an external magnetic field is applied to the ferromagnetic metal, a magnetic chain effect will be formed inside the ferromagnetic material. This effect manifests itself in the metal as a layer-by-layer transmission characteristic of magnetic intensity changes. It depends on the interlayer magnetic interaction. These magnetic chains are transmitted layer by layer in the metal, and the magnetic intensity changes of each layer of magnetic chains will affect the next layer.

[0020] The mathematical model of magnetomechanical coupling is based on the principle that ferromagnetic materials (such as rebar) undergo changes in their internal magnetic domain structure and flux linkage when subjected to an external magnetic field. This model comprehensively considers the flux linkage effect of ferromagnetic materials, the relationship between stress and magnetic flux intensity, the amplification effect of flux linkage transmission, and comparative analysis of reference structures. This model can be used to derive stress from changes in magnetic flux intensity, enabling real-time, non-destructive testing of the stress state of reinforced concrete.

[0021] Furthermore, the theoretical derivation of magnetic chain effect and the analysis principle of amplification effect are as follows:

[0022] When an external magnetic field is applied to a ferromagnetic metal, the magnetic induction intensity is transmitted layer by layer along a certain direction due to the (virtual) magnetic interaction between layers. Assuming that the interlayer magnetic interaction is the only determining factor for the induction transmission of magnetic field intensity in the magnetic flux linkage, and ignoring the magnetic intensity transmitted by the air, the relationship between the induced magnetic intensity after the external magnetic field passes through a layer, the external magnetic intensity, and the interlayer magnetic interaction force is given as follows:

[0023] B1=B0·f(F m0 ) (1)

[0024] Where B0 is the external magnetic intensity value, B1 is the induced magnetic intensity value of the first layer, F m0 Interlayer magnetic interaction, f(F m0 ) is a continuous function whose variable is the interlayer magnetic interaction force.

[0025] The magnetic intensity of the next layer is induced by the magnetic intensity of the previous layer through the interlayer magnetic interaction force, so:

[0026] B2=B1·f(F m1 ) (2)

[0027] Where B2 is the induced magnetic intensity value of the second layer, F m1 is the interlayer magnetic interaction of the second layer.

[0028] By analogy, we can get:

[0029] B i =B i-1 ·f(F m(i-1) ) (3)

[0030] Among them B i is the induced magnetic intensity value of the i-th layer, F m(i) is the interlayer magnetic interaction of the i-th layer.

[0031] The induced magnetic intensity value of the nth layer (measurement layer) is obtained as follows:

[0032]

[0033] When the average interatomic distance between layers changes due to stress, the interlayer magnetic interaction will change accordingly ΔF mi At this time, the induced magnetic intensity value of the nth layer can be expressed as:

[0034]

[0035] When ΔF mi When we are small, we have:

[0036]

[0037] where f / (Fmi ) means that the function f is in F mi Substituting it into We get:

[0038]

[0039] To B n and Taking the logarithms respectively, we can get:

[0040]

[0041]

[0042] We can get:

[0043]

[0044] Simplifying Equation 10, we can get ΔB n :

[0045]

[0046] Considering that when x is very small, exp(x)≈1+x. Equation 11 can be simplified to:

[0047]

[0048] Since ΔF mi and the change in interatomic distance ΔR i Correlation (ΔF mi =K m ΔR i ), so we can get:

[0049]

[0050] If the entire material is subjected to a uniform force, the change in the distance between atoms in each layer will tend to be consistent, and the magnetic interaction between the layers inside it will also show similar effects. To simplify the derivation, we simply assume that the change in the distance between atoms in each layer (ΔR i ) are equal, that is, ΔR i =ΔR; and the magnetic interaction function f(F mi ) are also equal, that is, f(F mi )=f(F m ).

[0051] Equation 13 can be simplified as:

[0052]

[0053] Note that the same derivation can be used to derive the change in magnetic intensity for any single layer:

[0054]

[0055] Since the distance between atoms does not change much, ΔF C It is also linearly related to ΔR (ΔF C =K c ΔR), substituting the relationship between the interlayer bonding force and the change in the interlayer atomic distance into Equation 14, we can obtain:

[0056] ΔB n =K B ΔF C (16)

[0057] in

[0058] The magnetic intensity ΔB measured by the external Hall sensor H Actually, ΔB n A component of:

[0059] ΔB H =K E ΔB n (17)

[0060] When the measurement distance and environmental factors remain unchanged, K E is a constant.

[0061] We can get:

[0062] ΔB H =K H ΔF C (18)

[0063] where K H =K E K B .

[0064] Furthermore, the analysis principle of the magnetic flux conduction and magnetization process of reinforced concrete is as follows:

[0065] Since stress changes the magnetic domain structure and magnetic flux conduction inside the steel bar, we can assume that there is a stress-related coefficient m(σ), which represents the influence of stress σ on the magnetization intensity M. Therefore, the magnetization intensity can be expressed as:

[0066] M=χB0+m(σ) (19)

[0067] For simplicity, we assume that m(σ) is linearly related to stress σ (this may be an approximation in practice):

[0068]

[0069] Here, k' is a constant that represents the effect of stress on the magnetization intensity.

[0070] Substituting m(σ) into the expression of M, we obtain:

[0071] M=χB0+k'σ (21)

[0072] Substitute B again I =μ0(H+M), we get:

[0073] B I =μ0(μ0B0+χB0+k′σ=(1+χμ0)B0+μ0k′σ (22)

[0074] Let k = 1 + χμ0 and b = μ0k', then:

[0075]

[0076] Or, if we want to I Expressed as a function of B0 and considering the influence of stress, it can be written as:

[0077]

[0078] Among them, k m =k is a constant related to the properties of the material itself, and is a coefficient related to stress.

[0079] The detection method of the reinforced concrete stress state monitoring device based on the magnetic induction chain of the present invention has the following advantages:

[0080] 1) Magnetic induction chain measurement technology does not require physical destruction or invasive operations on reinforced concrete structures. Instead, it monitors stress states using only an applied magnetic field and magnetic induction elements. This avoids the structural damage that traditional detection methods can cause, ensuring structural integrity and safety.

[0081] 2) Magnetic induction chain measurement technology can measure not only relative stress states but also absolute stress states. By comparing the change in magnetic induction intensity of a reference structure during the application of external force with the magnetic induction intensity data of the structure under test under the existing prestress state, the difference in magnetic induction intensity between the two can be used to deduce the prestress level in the original component.

[0082] 3) Magnetic induction chain measurement technology uses precise magnetic induction elements to capture magnetic field fluctuations and convert them into quantifiable electrical signals. Combined with advanced signal processing techniques and data analysis algorithms, this technology can accurately identify and quantitatively assess stress states with high sensitivity and accuracy.

[0083] 4) Magnetic induction chain measurement technology has long-term stable performance and can continuously monitor the stress state of reinforced concrete structures. This is important for assessing the long-term health and safety performance of the structure and helps to promptly identify potential safety hazards.

[0084] 5) Magnetic induction chain measurement technology is not limited by the characteristics of concrete materials, such as cement type, water-cement ratio, aggregate gradation, etc. This makes the technology widely applicable to different types of reinforced concrete structures.

[0085] 6) In addition to reinforced concrete, magnetic induction chain technology can also be applied to stress monitoring of other reinforced concrete structures, such as bridges, dams, and buildings. By deploying magnetic induction elements on the structure, the stress state of the structure can be monitored in real time, providing reliable assurance for its safe operation.

[0086] This method for detecting the stress state (prestress) of reinforced concrete based on a magnetic induction chain utilizes an external magnetic field to excite the magnetic induction chain. By monitoring changes in the magnetic induction chain, the stress state of the reinforced concrete structure is monitored in real time. The magnetic induction intensity change data of a reference structure during the application of an external force is compared with the magnetic induction intensity data of the prestressed structure under test. By calculating the difference in magnetic induction intensity between the two, the prestress level in the original component can be deduced. This method is non-contact, non-destructive, and highly real-time, providing an effective real-time monitoring method for reinforced concrete structures in engineering applications.

[0087] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0089] Figure 1 This is a layout diagram of a reinforced concrete stress state monitoring device based on a magnetic induction chain according to the present invention;

[0090] Figure 2 For the present invention Figure 1 The unloaded state diagram of the reinforced concrete to be tested;

[0091] Figure 3 For the present invention Figure 1 Loading state diagram of the reinforced concrete to be tested;

[0092] Figure 4 This is a diagram of the experimental arrangement of an embodiment of the present invention;

[0093] Figure 5 This is an experimental data diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0094] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0095] like Figure 1 A reinforced concrete stress state monitoring device based on a magnetic induction chain is shown. Its operating principle is to calibrate the prestress using an experimental structure to test the same stress-magnetic intensity relationship as in-service structures. The device comprises an external magnetic field generator, a magnetic induction chain detection device, and a data processing system. The external magnetic field generator is placed on the reinforced concrete surface to apply a stable magnetic field. The magnetic induction chain detection device detects changes in magnetic induction intensity at measuring points on the reinforced concrete surface. The data processing system receives and processes magnetic intensity data from the magnetic induction chain detection device. By establishing a mathematical model of the force-magnetic coupling relationship, the stress (prestress) value can be analyzed from the magnetic intensity data, enabling real-time, non-destructive detection of the reinforced concrete stress state.

[0096] The external magnetic field generating device is a neodymium iron boron magnet, and the magnetic induction chain detection device is a linear Hall sensor. The linear Hall sensor and the corresponding neodymium iron boron magnet are respectively placed on both sides of the reinforced concrete to be detected and the distance between them is constant.

[0097] The measuring method of the reinforced concrete stress state monitoring device based on the magnetic induction chain comprises the following steps:

[0098] S1: Based on the steel bar arrangement, size, and material properties of the reinforced concrete component to be tested, design and manufacture an identical reference structure. Place an external magnetic field generator on the surface of the reinforced concrete component to be tested and the reference structure at the same position to apply a stable magnetic field. Place a magnetic induction chain detection device on one side of the external magnetic field generator. The magnetic induction chain detection devices are also located at the same position on the reinforced concrete component to be tested and the reference structure and are not in contact with the corresponding reinforced concrete component to be tested and the reference structure. The external magnetic field generator is a neodymium iron boron magnet, and the magnetic induction chain detection device is a linear Hall sensor.

[0099] S2: Start the magnetic induction chain detection device to monitor the magnetic induction intensity on the surface of the reinforced concrete component in the prestressed state. During this period, the external magnetic field generating device and the magnetic induction chain detection device are kept stationary, and a constant distance is maintained between the external magnetic field generating device and the magnetic induction chain detection device.

[0100] S3: stress-free state for the reference structure (e.g. Figure 2 ) and the external load state (as shown Figure 3 The magnetic induction intensity under the condition shown in FIG.

[0101] S4: Analyzing the magnetic intensity data obtained in step S3 using a data processing system to obtain a change in magnetic induction intensity in a trend of magnetic induction chain magnetic intensity change;

[0102] S5: Based on the analysis results of step S4, a mathematical model of the force-magnetic coupling relationship is established to analyze the stress magnitude from the change in magnetic induction intensity. By comparing and analyzing the performance of reinforced concrete components in a free and stress-free state with a reference structure of the same material after being subjected to a preset stress in terms of magnetic induction intensity, the prestress level in the original component can be reversely deduced by calculating the difference in magnetic induction intensity between the two.

[0103] In the mathematical model of magnetomechanical coupling, when an external magnetic field is applied to a ferromagnetic metal, a magnetic chain effect is formed inside the ferromagnetic material. This effect manifests itself in the metal as a layer-by-layer transmission of magnetic intensity changes. It relies on interlayer magnetic interactions, and these magnetic chains are transmitted layer by layer in the metal. The changes in magnetic intensity in each layer of magnetic chains affect the next layer.

[0104] The mathematical model of magnetomechanical coupling is based on the principle that ferromagnetic materials (such as rebar) undergo changes in their internal magnetic domain structure and flux linkage when subjected to an external magnetic field. This model comprehensively considers the flux linkage effect of ferromagnetic materials, the relationship between stress and magnetic flux intensity, the amplification effect of flux linkage transmission, and comparative analysis of reference structures. This model can be used to derive stress from changes in magnetic flux intensity, enabling real-time, non-destructive testing of the stress state of reinforced concrete.

[0105] In step S5, the magnetic induction intensity change data of the reference structure during the application of external force is compared with the magnetic induction intensity data of the prestressed state already existing in the reinforced concrete component to be tested, and a specific external stress value is found so that at this stress level, the magnetic induction intensity of the reference structure matches the magnetic induction intensity of the prestressed state of the reinforced concrete component to be tested; when the matching point is found, the external stress value at this time is recorded. Since the reference structure and the reinforced concrete component to be tested have the same steel bar layout and material properties, and the change in magnetic induction intensity is closely related to the stress state inside the steel bar, it is believed that this external stress value is the magnitude of the prestress in the structure to be tested. Through the above steps, we can use the magnitude of the magnetic intensity to calibrate the magnitude of the prestress and realize the measurement of the prestress level in the structure to be tested.

[0106] Specifically, we need to prepare a reference structure with the same reinforcement layout and dimensions as the reinforced concrete component under test. We measure the magnetic field of this reference structure in its stress-free state. In this stress-free state, the magnetic domain structure within the reinforcement is relatively stable, and the flux linkage is relatively uniform. We then use Hall sensors to measure the magnetic flux density on the reinforced concrete surface and record the magnetic flux density data in this state as a baseline. We then apply a gradually increasing external force to this reference structure to simulate the prestressing process. This can be achieved using specialized loading equipment to ensure uniform and controllable application of the external force. As the external force increases, the stress distribution and strain state within the reinforcement change, affecting its magnetic domain structure and flux linkage. These changes cause changes in the magnetic flux density on the reinforcement surface. By continuously monitoring the changes in magnetic flux density, we can observe a trend of increasing magnetic flux density with increasing applied stress. We need to find a specific applied stress level at which the magnetic flux density of the reference structure is the same as the magnetic flux density of the prestressed structure under test. When the magnetic induction intensity of the reference structure under a certain applied stress matches the magnetic induction intensity of the structure under test in its prestressed state, we can assume that this applied stress value is the magnitude of the prestress in the structure under test. This is because, given the same reinforcement layout and material properties, the change in magnetic induction intensity is closely related to the stress state within the reinforcement. Therefore, by comparing the magnetic induction intensity performance of the two structures, we can indirectly infer the prestress level in the structure under test.

[0107] Magnetic induction chain detection can detect the stress state (prestress) of reinforced concrete. This method has the advantages of high sensitivity, strong reliability, easy digital output, and the ability to solve the problem of material dispersion. It can also intuitively display the changes in steel bars under different stress states, providing a feasible approach for real-time and accurate structural monitoring.

[0108] In the mathematical model of the magnetomechanical coupling relationship in step S5, after an external magnetic field is applied to the ferromagnetic metal, a magnetic chain effect will be formed inside the ferromagnetic material. This effect manifests itself in the metal as a layer-by-layer transmission of magnetic intensity changes. It depends on the interlayer magnetic interaction. These magnetic chains are transmitted layer by layer in the metal, and the magnetic intensity changes of each layer of magnetic chains will affect the next layer.

[0109] Furthermore, the theoretical derivation of magnetic chain effect and the analysis principle of amplification effect are as follows:

[0110] When an external magnetic field is applied to a ferromagnetic metal, the magnetic induction intensity is transmitted layer by layer along a certain direction due to the (virtual) magnetic interaction between layers. Assuming that the interlayer magnetic interaction is the only determining factor for the induction transmission of magnetic field intensity in the magnetic flux linkage, and ignoring the magnetic intensity transmitted by the air, the relationship between the induced magnetic intensity after the external magnetic field passes through a layer, the external magnetic intensity, and the interlayer magnetic interaction force is given as follows:

[0111] B1=B0·f(F m0 ) (1)

[0112] Where B0 is the external magnetic intensity value, B1 is the induced magnetic intensity value of the first layer, F m0 Interlayer magnetic interaction, f(F m0 ) is a continuous function whose variable is the interlayer magnetic interaction force.

[0113] The magnetic intensity of the next layer is induced by the magnetic intensity of the previous layer through the interlayer magnetic interaction force, so:

[0114] B2=B1·f(F m1 ) (2)

[0115] Where B2 is the induced magnetic intensity value of the second layer, F m1 is the interlayer magnetic interaction of the second layer.

[0116] By analogy, we can get:

[0117] B i =B i-1 ·f(F m(i-1) ) (3)

[0118] Among them B i is the induced magnetic intensity value of the i-th layer, F m(i) is the interlayer magnetic interaction of the i-th layer.

[0119] The induced magnetic intensity value of the nth layer (measurement layer) is obtained as follows:

[0120]

[0121] When the average interatomic distance between layers changes due to stress, the interlayer magnetic interaction will change accordingly ΔF mi At this time, the induced magnetic intensity value of the nth layer can be expressed as:

[0122]

[0123] When ΔF mi When we are small, we have:

[0124]

[0125] where f / (F mi ) means that the function f is in F mi Substituting it into We get:

[0126]

[0127] To B n and Taking the logarithms respectively, we can get:

[0128]

[0129]

[0130] We can get:

[0131]

[0132] Simplifying Equation 10, we can get ΔB n :

[0133]

[0134] Considering that when x is very small, exp(x)≈1+x. Equation 11 can be simplified to:

[0135]

[0136] Since ΔF mi and the change in interatomic distance ΔR i Correlation (ΔF mi =K m ΔR i ), so we can get:

[0137]

[0138] If the entire material is subjected to a uniform force, the change in the distance between atoms in each layer will tend to be consistent, and the magnetic interaction between the layers inside it will also show similar effects. To simplify the derivation, we simply assume that the change in the distance between atoms in each layer (ΔRi ) are equal, that is, ΔR i =ΔR; and the magnetic interaction function f(F mi ) are also equal, that is, f(F mi )=f(F m ).

[0139] Equation 13 can be simplified as:

[0140]

[0141] Note that the same derivation can be used to derive the change in magnetic intensity for any single layer:

[0142]

[0143] Since the distance between atoms does not change much, ΔF C It is also linearly related to ΔR (ΔF C =K c ΔR), substituting the relationship between the interlayer bonding force and the change in the interlayer atomic distance into Equation 14, we can obtain:

[0144] ΔB n =K B ΔF C (16)

[0145] in

[0146] The magnetic intensity ΔB measured by the external Hall sensor H Actually, ΔB n A component of:

[0147] ΔB H =K E ΔB n (17)

[0148] When the measurement distance and environmental factors remain unchanged, K E is a constant.

[0149] We can get:

[0150] ΔB H =K H ΔF C (18)

[0151] where K H =K E K B .

[0152] Furthermore, the analysis principle of the magnetic flux conduction and magnetization process of reinforced concrete is as follows:

[0153] Since stress changes the magnetic domain structure and magnetic flux conduction inside the steel bar, we can assume that there is a stress-related coefficient m(σ), which represents the influence of stress σ on the magnetization intensity M. Therefore, the magnetization intensity can be expressed as:

[0154] M=χB0+m(σ) (19)

[0155] For simplicity, we assume that m(σ) is linearly related to stress σ (this may be an approximation in practice):

[0156] m(σ)=k'σ (20)

[0157] Here, k' is a constant that represents the effect of stress on the magnetization intensity.

[0158] Substituting m(σ) into the expression of M, we obtain:

[0159] M=χB0+k'σ (21)

[0160] Substitute B again I =μ0(H+M), we get:

[0161] B I =μ0(μ0B0+χB0+k′σ)=(1+χμ0)B0+μ0k′σ (22)

[0162] Let k = 1 + χμ0 and b = μ0k', then:

[0163] B I =kB0+bσ (23)

[0164] Or, if we want to I Expressed as a function of B0 and considering the influence of stress, it can be written as:

[0165]

[0166] Among them, k m =k is a constant related to the properties of the material itself, and is a coefficient related to stress.

[0167] Example

[0168] Field test equipment (such as Figure 4The equipment (shown in the figure) includes: an external magnetic field generator, a linear Hall effect sensor, a pressure sensor, a hydraulic jack, a magnetic field collector, and a multifunctional static strain testing system. This test used a 150mm × 150mm × 300mm C40 reinforced concrete rectangular specimen. Before the test, strain gauges were attached to the concrete surface. To reduce errors and prevent disturbances in the instrument position during compression from affecting data acquisition, the Hall effect sensor did not fully adhere to the concrete surface during the test, leaving a gap of approximately five millimeters. The sensor and related software program were used to read force, strain, and magnetic induction intensity data. The load was scaled at 20kN, and five loading cycles were performed. The strain load data and magnetic induction intensity data were read using a magnetic field collector and a computer.

[0169] To ensure the accuracy and reliability of the test results, we applied the same loading conditions, using 20 kN increments, to unreinforced plain concrete for five repeated loading cycles. During these comparative tests, we observed and recorded the magnetic induction chain's performance data during each loading cycle. No significant changes were observed in the magnetic induction chain's performance across the five loading cycles, indicating that the plain concrete did not affect the performance of the magnetic induction chain.

[0170] Depend on Figure 5 The experimental data shown here demonstrates a close and strong correlation between the mechanical properties of reinforced concrete structures and their magnetic properties. This finding confirms our theoretical hypothesis. During the experiment, the applied magnetic field successfully penetrated the concrete, effectively magnetizing the rebar and forming a clear magnetic induction chain. As different levels of load were applied to the reinforced concrete specimens, we observed significant changes in the magnetic flux data of the magnetic induction chain, which were highly consistent with the stress state within the reinforced concrete.

[0171] The experimental data demonstrates a particularly strong magnetomechanical coupling relationship, revealing the inherent connection between changes in steel bar stress and magnetic induction intensity. Specifically, as the stress on the steel bar increases, the magnetic induction intensity around it also changes accordingly, and this change exhibits a linear trend. By analyzing the magnetic flux data and reinforced concrete stress, we found a significant linear relationship between the two. This discovery further enhances our understanding of the magnetomechanical coupling effect and provides strong support for subsequent mathematical modeling and data analysis.

[0172] Our detection method, based on a magnetic induction chain, is not only highly sensitive and accurate, but also enables non-destructive testing of the stress state of reinforced concrete structures. By measuring magnetic field variations on the external concrete surface, we can effectively capture changes in the stress state within the steel bars, thereby achieving precise measurement of stress and prestress in reinforced concrete structures. The successful application of this technology not only provides a new means for monitoring and evaluating civil engineering structures, but is also expected to play a significant role in the future field of structural health monitoring.

[0173] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A reinforced concrete stress state monitoring device based on magnetic induction chain, characterized in that: The invention comprises an external magnetic field generating device, a magnetic induction chain detecting device and a data processing system. The external magnetic field generating device is placed on the surface of reinforced concrete to be detected to apply a stable magnetic field. The magnetic induction chain detecting device is used to detect the change of magnetic induction intensity at the measuring point on the surface of reinforced concrete. The data processing system is used to receive and process the magnetic intensity data of the magnetic induction chain detecting device. By establishing a mathematical model of the force-magnetic coupling relationship, the stress magnitude can be parsed from the magnetic intensity data, thereby realizing real-time and non-destructive detection of the stress state of reinforced concrete.

2. The reinforced concrete stress state monitoring device based on magnetic induction chain according to claim 1 is characterized in that: The external magnetic field generating device is preferably a neodymium iron boron magnet, and the magnetic induction chain detection device is preferably a linear Hall sensor. The linear Hall sensor and the corresponding neodymium iron boron magnet are respectively placed on both sides of the reinforced concrete to be detected and the distance between them is constant.

3. A detection method for a reinforced concrete prestressed stress state monitoring device based on the magnetic induction chain of claim 1 or 2, characterized in that: The following steps are involved: S1: According to the steel bar arrangement, size and material properties of the reinforced concrete component to be tested, design and manufacture a completely identical reference structure, place the external magnetic field generating device on the surface of the reinforced concrete component to be tested and the reference structure at the same position to apply a stable magnetic field, and place the magnetic induction chain detection device on one side of the external magnetic field generating device. The magnetic induction chain detection devices on the reinforced concrete component to be tested and the reference structure are also at the same position and are not in contact with the corresponding reinforced concrete component to be tested and the reference structure. The external magnetic field generating device is preferably a neodymium iron boron magnet, and the magnetic induction chain detection device is preferably a linear Hall sensor; S2: Start the magnetic induction chain detection device to monitor the magnetic induction intensity on the surface of the reinforced concrete member in the prestressed state, during which the external magnetic field generating device and the magnetic induction chain detection device are kept stationary, and a constant distance is maintained between the external magnetic field generating device and the magnetic induction chain detection device; S3: monitoring the magnetic induction intensity of the reference structure in a stress-free state and under an external load condition; S4: Analyze the magnetic intensity data obtained in step S3 using a data processing system to obtain a change in magnetic induction intensity in the magnetic induction chain magnetic intensity change trend; S5: According to the analysis results of step S4, a mathematical model of the force-magnetic coupling relationship is established to analyze the stress from the change in magnetic induction intensity. By comparing the performance of reinforced concrete components in a free and stress-free state with the reference structure of the same material after being subjected to a preset stress in terms of magnetic induction intensity, the prestress level in the original component can be reversely deduced by calculating the difference in magnetic induction intensity between the two.

4. The detection method of the reinforced concrete stress state monitoring device of the magnetic induction chain according to claim 3 is characterized in that: In step S5, the magnetic induction intensity change data of the reference structure during the external force application process is compared with the magnetic induction intensity data of the reinforced concrete component to be tested in the prestressed state, and a specific applied stress value is found so that at this stress level, the magnetic induction intensity of the reference structure matches the magnetic induction intensity of the reinforced concrete component to be tested in the prestressed state; When the matching point is found, the applied stress value at that time is recorded, that is, the magnitude of the prestress in the reinforced concrete component to be tested.

5. The detection method of the reinforced concrete stress state monitoring device of the magnetic induction chain according to claim 3 is characterized in that: In the mathematical model of magnetomechanical coupling relationship in step S5, after an external magnetic field is applied to the ferromagnetic metal, a magnetic flux linkage effect is formed inside the ferromagnetic material. This effect is manifested in the metal as a layer-by-layer transmission of magnetic intensity changes. It depends on the interlayer magnetic interaction. These magnetic flux linkages are transmitted layer by layer in the metal, and the magnetic intensity changes of each layer of magnetic flux linkages will affect the next layer. The mathematical model of magnetomechanical coupling is based on the principle that the internal magnetic domain structure and magnetic flux conduction of ferromagnetic materials will change when subjected to an external magnetic field. The model comprehensively considers the magnetic flux effect of ferromagnetic materials, the relationship between stress and magnetic induction intensity, the amplification effect in the magnetic flux transfer process, and the comparative analysis of the reference structure. Through this model, the stress magnitude can be analyzed from the change in magnetic induction intensity, thereby realizing real-time, non-destructive detection of the stress state of reinforced concrete.

6. The detection method of the reinforced concrete stress state monitoring device of the magnetic induction chain according to claim 5 is characterized in that: The theoretical derivation of magnetic chain effect and the analysis principle of amplification effect are as follows: When an external magnetic field is applied to a ferromagnetic metal, the magnetic induction intensity is transmitted layer by layer along a certain direction due to the (virtual) magnetic interaction between layers. Assuming that the magnetic interaction between layers is the only determining factor for the induction transmission of magnetic field intensity in the magnetic flux chain, and ignoring the magnetic intensity of the external magnetic field transmitted by the air, the relationship between the induced magnetic intensity value after the external magnetic field passes through a layer and the external magnetic intensity value and the magnetic interaction force between layers is given: B1=B0·f(F m0 ) (1) Where B0 is the external magnetic intensity value, B1 is the induced magnetic intensity value of the first layer, F m0 Interlayer magnetic interaction, f(F m0 ) is a continuous function of the interlayer magnetic interaction force; The magnetic strength of the next layer is induced by the magnetic strength of the previous layer through the interlayer magnetic interaction force, so: <h2 style=";text-align:left;direction:ltr">B2=B1·f(F<h2 style=";text-align:left;direction:ltr"> m1 <h2 style=";text-align:left;direction:ltr"> ) (2) Where B2 is the induced magnetic intensity value of the second layer, F m1 is the interlayer magnetic interaction of the second layer; By analogy, we get: B i =B i-1 ·f(F m(i-1) ) (3) Among them B i is the induced magnetic intensity value of the i-th layer, F m(i) is the interlayer magnetic interaction of the i-th layer; The induced magnetic intensity value of the nth layer (measurement layer) is obtained as follows: When the average interatomic distance between layers changes due to stress, the magnetic interaction between the layers will change accordingly ΔF mi ; At this time, the induced magnetic intensity value of the nth layer is expressed as: When ΔF mi Very small: f(F mi +ΔF mi )≈f(F mi )+f / (F mi )·ΔF mi (6) where f / (F mi ) means that the function f is in F mi Substituting it into In the result: To B n and Taking the logarithms respectively, we get: get: Simplifying Equation 10, we can get ΔB n : Considering that when x is very small, exp(x)≈1+x; Equation 11 is simplified to: Since ΔF mi The change in the interatomic distance between layers ΔR i Correlation (ΔF mi =K m ΔR i ),get: If the entire material is subjected to a uniform force, the change in the distance between atoms in each layer tends to be consistent, and the magnetic interaction between the layers inside it will also show similar effects. In order to simplify the derivation, it is simply assumed that the change in the distance between atoms in each layer (ΔR i ) are equal, that is, ΔR i =ΔR; and the magnetic interaction function f(F mi ) are also equal, that is, f(F mi )=f(F m ); Equation 13 is simplified to: Note that the same derivation gives the change in magnetic intensity for any single layer: Since the distance between atoms does not change much, ΔF C It is also linearly related to ΔR (ΔF C =K c ΔR), substituting the relationship between the interlayer bonding force and the change in the interlayer atomic distance into formula 14, we get: ΔB n =K B ΔF C (16) in The magnetic intensity ΔB measured by the external Hall sensor H Actually, ΔB n A component of: ΔB H =K E ΔB n (17) When the measurement distance and environmental factors remain unchanged, K E is a constant; get: ΔB H =K H ΔF C (18) Where K H =K E K B .

7. The detection method of the reinforced concrete stress state monitoring device of the magnetic induction chain according to claim 6 is characterized in that: The analysis principle of magnetic flux conduction and magnetization process of reinforced concrete is: Since stress will change the magnetic domain structure and magnetic flux conduction inside the steel bar, it is assumed that there is a stress-related coefficient m(σ), which represents the influence of stress σ on the magnetization intensity M; therefore, the magnetization intensity is expressed as: M=XB0+m(σ) (19) For simplicity, it is assumed that m(σ) is linearly related to stress σ: m(σ)=k'σ (20) Among them, k' is a constant that represents the influence of stress on magnetization intensity; Substituting m(σ) into the expression of M, we obtain: M=χB0+k'σ (21) Substitute into B I =μ0(H+M), we get: B I =μ0(μ0 B0+χB0+k′σ=(1+χμ0)B0+μ0kσ' (22) Let k = 1 + χμ0 and b = μ0 k', then: B I =kB0+bσ (23) Or, if you want to change B I Expressed as a function of B0 and considering the influence of stress, it can be written as: Among them, k m = k is a constant related to the properties of the material itself, and is a coefficient related to stress.

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