A device for precise measurement of magnetic properties of submarine hull steel material

Abstract

The application provides a device for precise measurement of magnetic characteristics of submarine body steel material, which comprises a sample, an excitation system, a stress application system, a zero magnetic field environment realization system and a measurement system; the sample is in a circular ring structure, and its cross section is approximately a cylindrical structure, which is similar to the structure of a submarine; the excitation system provides a magnetic field acting on the sample; the stress application system simulates the extrusion effect of seawater on the submarine; the zero magnetic field environment realization system is used for shielding the environmental magnetic field to avoid the influence of the weak magnetic field magnetization on the measurement results; the measurement system is used for measuring the B and H signals of the sample under the action of different excitation and pressure, constructing a J-A magnetic hysteresis model, calculating the parameters of the J-A model, carrying out numerical analysis on the magnetic field distribution of the ship, and finally adopting a conventional finite element method to analyze the magnetic field of the ship. The measurement results are applied to the magnetic field analysis of the submarine, and the consistency of the magnetic field analysis and the measurement results of the submarine is improved.

Description

Technical Field

[0001] This invention relates to the field of magnetic property measurement technology for steel materials, and in particular to a precise measuring device for the magnetic properties of steel materials used in submarine hulls. Background Technology

[0002] With the deepening development of marine resources, more and more submarine equipment is being deployed in the marine environment. During operation, submarine equipment is magnetized by the Earth's magnetic field, generating its own additional magnetic field. This alters the surrounding magnetic field, causing magnetic anomalies that can interfere with scientific detection equipment and reveal the location information of important targets such as submarines. Therefore, in-depth exploration of the dynamic magnetization mechanism and magnetic field distribution of marine ferromagnetic equipment is of great significance.

[0003] To fully understand the variation patterns of magnetic and magnetic fields in submarine equipment, precise calculations of the magnetic field distribution are needed to meet design requirements such as target detection and magnetic stealth. However, current analysis and measurement results for the magnetic field of submarine equipment show significant discrepancies. One major reason is the lack of magnetic property parameters for the steel used in submarine equipment; approximations are generally made using saturation hysteresis loops or magnetization curves, leading to substantial errors. However, the specific factors preventing accurate measurement of the magnetic property parameters of the steel used in submarine equipment remain undetermined. Summary of the Invention

[0004] This invention identifies the factors that prevent accurate measurement of the magnetic properties of steel in submarine equipment, and provides a precise measuring device for the magnetic properties of submarine hull steel. The precise measuring device for the magnetic properties of submarine hull steel includes a sample, an excitation system, a stress application system, a zero magnetic field environment realization system, and a measurement system.

[0005] The sample has a ring structure, and its cross-section is approximately cylindrical, similar to the structure of a submarine.

[0006] The excitation system includes an excitation coil wound on the sample, and the magnetic field passes through the sample to form a complete magnetic circuit.

[0007] The stress application system includes two arc-shaped clamps that match the circular structure of the sample; a set of screws and nuts are provided on both sides of the clamps, and a force sensor is provided between the nuts and the clamps; the clamps are in contact with the sample surface, and stress is applied to the sample by the compression of the screws and nuts;

[0008] The zero magnetic field environment realization system consists of three sets of large coils covering the outside of the sample, excitation system and stress loading system, used to control the magnetic field in three orthogonal directions;

[0009] The measurement system includes a sensor and a computer; the sensor includes a B coil wound on the sample for acquiring the induced electromotive force.

[0010] The computer is used to construct the JA hysteresis model and calculate the parameters of the JA model, perform numerical analysis of the magnetic field distribution of the submarine, and finally use the conventional finite element method to analyze the submarine's magnetic field.

[0011] Furthermore, the magnetic field strength in the sample is calculated using Ampere's circuital law from the excitation coil. Ampere's circuital law is shown in formula (1):

[0012]

[0013] In the formula, This indicates the number of turns in the excitation coil. Indicates the excitation current. It represents the effective magnetic circuit length, which is approximately equal to the circumference of the ring;

[0014] The Calculation of induced electromotive force from coil measurement as follows:

[0015]

[0016] express The cross-sectional area of ​​the coil, express The number of turns of the coil, express The induced electromotive force measured on the coil.

[0017] Furthermore, the JA hysteresis model is used to describe the relationship between the magnetic field strength H and the magnetization M, and the magnetic flux density is expressed as... ,in, ;

[0018] The magnetization M of the ferromagnetic material is divided into reversible magnetization. and irreversible magnetization :

[0019]

[0020] at the same time:

[0021]

[0022]

[0023] in, The magnetic field strength; The magnetization intensity; It is a hysteresis-free magnetization intensity; These are coupling parameters, in A / m. This is the direction coefficient, which can be 1 or -1; These are the internal coupling parameters of the magnetic domains;

[0024] By combining the improved Langevin function, the following formula can be derived:

[0025]

[0026]

[0027] in, Indicates the effective magnetic field strength. Saturation magnetization Shape parameters of the nonhysteresis magnetization curve Domain wall bending constant;

[0028] The five parameters of the JA model were calculated and solved using the measured hysteresis loop data, which are as follows: Saturation magnetization Shape parameters of the nonhysteresis magnetization curve Coupling parameters, Internal coupling parameters of magnetic domains By obtaining the domain wall bending constant, the parameters of the JA model can be derived, allowing for numerical analysis of the submarine's magnetic field distribution.

[0029] Furthermore, the finite element analysis includes ship modeling, setting excitation boundary conditions, defining material parameters, mesh generation, solving, and post-processing.

[0030] First, a three-dimensional ship model is constructed based on the ship's actual geometry and dimensions;

[0031] After the 3D ship model is completed, material parameters and constraints are defined, and the magnetic properties of the steel plate are characterized using the JA hysteresis model.

[0032] Then, mesh partitioning is performed to discretize the variational problem;

[0033] Finally, a system of equations containing the variables to be solved is constructed.

[0034] Furthermore, the functional form of the constant magnetic field in the system of equations is:

[0035]

[0036] in, It represents the reciprocal of the permeability. Represents magnetic flux density, Represents the integration field. Indicates vector magnetic potential. Indicates current density, The infinitesimal element representing the integration path, Indicates the third type of boundary condition;

[0037] With the functional form, and based on discretization, we can write out the extremum problem of the functional in each region, i.e.

[0038]

[0039] in, Describes a functional. Represents the vector magnetic potential within a discrete unit;

[0040] Finally, using matrices to represent the functional extremum problem for each discrete region above, we get the following formula:

[0041]

[0042] In the formula, This is called the stiffness matrix. Represents the variable to be solved. Indicates boundary conditions.

[0043] The beneficial effects achieved by this invention are:

[0044] This invention discovers that the immense pressure exerted by seawater on submarine equipment causes stress anisotropy in magnetic materials, thereby altering their magnetic properties. Furthermore, the Earth's magnetic field is a weak magnetic signal, typically on the order of microtesla. Therefore, this invention, by simulating the magnetization characteristics of ship steel under high pressure and weak magnetic field magnetization, identifies factors that prevent accurate measurement of the magnetic field of marine equipment.

[0045] This invention uses a circular ring sample to simulate the cylindrical structure of a submarine, and employs a novel stress loading mechanism to apply pressure inward to the outer surface of the ring, simulating the squeezing effect of seawater on a submarine in the deep sea. This solves the problem that conventional magnetic property measurement devices that consider stress can only apply stress in a single direction or two orthogonal directions and cannot fully simulate the pressure effect of seawater.

[0046] This invention achieves excitation through an excitation coil and calculates the magnetic field strength H using Ampere's circuital law. The magnetic flux density B is then calculated by measuring the induced voltage using a coil B wound around the sample. Six large coils, each 1m in diameter, are used to dynamically compensate for the Earth's magnetic field. This active magnetic field compensation technology dynamically cancels out the environmental magnetic field in real time, eliminating the influence of ambient noise on the measurement results. This enables the measurement of magnetic properties under weak magnetic fields, providing the necessary magnetic characteristic parameters for the analysis of marine equipment exposed to the Earth's magnetic field during weak magnetic field magnetization. It also completes the measurement of the hysteresis characteristics of steel plates under micro-level weak magnetic fields.

[0047] This invention ultimately achieves the measurement of the magnetic properties of submarine steel under the influence of seawater pressure and geomagnetic field, and applies the measurement results to the magnetic field analysis of submarines, effectively improving the consistency between the submarine magnetic field analysis and measurement results, and providing theoretical guidance for marine target detection and magnetic stealth technology.

[0048] The measuring device proposed in this invention has a simple structure, low cost, is easy to transport, and can be used on a large scale. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of a device for accurately measuring the magnetic properties of steel materials used in submarine hulls.

[0050] Figure 2 This is a schematic diagram of the sample structure in an embodiment of a precision measuring device for the magnetic properties of submarine hull steel.

[0051] Figure 3 This is a schematic diagram of the structure of a magnetic property measuring device in an embodiment of a precision measuring device for the magnetic properties of submarine hull steel.

[0052] Figure 4 This is a schematic diagram of the stress loading mechanism in an embodiment of a precision measurement device for the magnetic properties of submarine hull steel.

[0053] Figure 5 This is a schematic diagram of a coil constructed in a zero magnetic field environment, as described in an embodiment of a precision measurement device for the magnetic properties of submarine hull steel.

[0054] Figure 6 This is a schematic diagram of the test system in an embodiment of a precision measurement device for the magnetic properties of submarine hull steel.

[0055] Figure 7 This is an example of a device for accurately measuring the magnetic properties of submarine hull steel, showing the results of measuring the magnetic properties of steel plates under different pressures.

[0056] Figure 8 This is an example of a device for accurately measuring the magnetic properties of submarine hull steel, illustrating the distribution of the ship's magnetic field. Detailed Implementation

[0057] The technical solution of the present invention will be described in more detail below with reference to the accompanying drawings. The present invention includes, but is not limited to, the following embodiments.

[0058] like Figure 1As shown, this invention proposes a precise measuring device for the magnetic properties of submarine hull steel. The device includes a sample, an excitation system, a stress application system, a zero-magnetic-field environment realization system, and a measurement system. The measurement in this patent serves for precise magnetic field analysis, and the overall scheme is detailed below.

[0059] like Figure 2 As shown, the present invention designs the sample as a ring structure with a cross-section approximately cylindrical, similar to that of a submarine. This arc structure can simulate the squeezing effect of seawater on a submarine in the deep sea, where pressure compresses the hull radially inward from the outer surface of the submarine.

[0060] like Figure 3 As shown, the excitation system includes an excitation coil and a power amplifier. In fact, all important magnetic material parameters, such as power loss, permeability, and hysteresis, depend on the magnetic flux density. and magnetic field strength Measuring the magnetic properties of silicon steel involves measuring the magnetic field strength of the material under the influence of an external magnetic field. With magnetic flux density The relationship between them is represented by the hysteresis loop, and the magnetic flux density is expressed as a magnetic flux density. and magnetic field strength The relationship between these changes is crucial. Therefore, when measuring the magnetic properties of silicon steel, an external magnetic field needs to be applied to the sample, and this external magnetic field is generated by the excitation system.

[0061] An excitation coil is wound around the specimen, and the magnetic field forms a complete magnetic circuit through one turn of the specimen. The excitation coil is made of 100 turns of enameled wire with a diameter of 1 mm. The excitation coil is connected to the output terminal of a power amplifier, and a magnetic field is generated when energized. Since the magnetic permeability of the specimen is much greater than that of air, the magnetic field forms a complete toroidal magnetic circuit within the toroidal specimen. The magnetic field strength in the specimen can be calculated using Ampere's circuital law. Ampere's circuital law is shown in formula (1):

[0062] (1)

[0063] In the formula, This indicates the number of turns in the excitation coil. This represents the excitation current, which is measured by an ammeter connected in series in the circuit. It represents the effective magnetic circuit length, which is approximately equal to the circumference of the ring.

[0064] During actual excitation, the excitation voltage waveform is generated by a computer, and then the generated waveform is input to a power amplifier through a data acquisition card. After being amplified by the power amplifier, the excitation voltage waveform is applied to the excitation coil to excite the test sample.

[0065] like Figure 4 As shown, the stress loading system is used to simulate the effects of real seawater pressure. The system includes two arc-shaped clamps that match the circular structure of the sample. A set of screws and nuts are located on each side of the clamps, and a force sensor is placed between the nuts and the clamps. When applying stress, the screws are tightened with a wrench, causing the two clamps to come closer together. Because the clamps are in contact with the sample surface, the sample surface is subjected to compression, achieving a pressure simulation range of -50 MPa to +50 MPa. The pressure magnitude can be read by the force sensor fixed to the screw, and the stress reading is transmitted to a computer for real-time display via a data acquisition card. Compared to the commonly used method of measuring the magnetic properties of silicon steel materials, which involves stress in a single direction or two orthogonal directions, the stress loading method proposed in this invention can better simulate the effects of seawater pressure on submarines, obtaining the magnetic properties of submarine steel plate materials considering deep-sea pressure.

[0066] To avoid the influence of the background magnetic field in the environment on the measurement results, especially since the measurement results under weak magnetic field magnetization are greatly affected by the ambient magnetic field, a zero magnetic field environment realization system was designed to realize the active magnetic field compensation device.

[0067] like Figure 5-6 As shown, the zero-magnetic-field environment realization system employs three sets of large coils positioned outside the sample, excitation system, and stress loading system to control the magnetic field in three orthogonal directions. During operation, the system first measures the magnetic field of the target area using a giant magnetoresistive sensor. This magnetic field data is then transmitted to the controller, which uses a PID control algorithm to generate the voltage required to counteract the magnetic field in the target area. This voltage is applied to the coils, and real-time feedback control continuously adjusts the voltage to achieve a zero-magnetic-field environment in the target area. This actively counteracts the influence of the ambient magnetic field, including the Earth's magnetic field, enabling the system to dynamically compensate for the ambient magnetic field in real time. The measurement results of the magnetic properties of the steel plate material under different pressures are shown below. Figure 7 As shown.

[0068] The measurement system primarily measures the sample under different excitation and pressure conditions. , The signal consists of a sensor, preamplifier, data acquisition card, and computer. The signal acquired by the sensor is amplified by the preamplifier and then transmitted to the computer via the data acquisition card. The computer analyzes and plots the signal to generate the magnetic property curve of the sample. Magnetic field strength. Magnetic flux density is measured by an ammeter connected in series with the excitation coil. The measurement is based on the law of electromagnetic induction, by measuring the amount of electromagnetic induction applied to the sample. The induced voltage of the coil, coils Figure 2As shown, it is made by winding 200 turns of enameled wire with a diameter of 0.5mm. Calculating magnetic flux density from induced electromotive force measured by coil as follows:

[0069] (2)

[0070] express The cross-sectional area of ​​the coil, express The number of turns of the coil, express The induced electromotive force measured on the coil. Magnetic field strength. The result is calculated using Ampere's circuital law, as shown in formula (1). Another advantage of using a circular ring sample is that it allows for convenient calculation. The coil coefficient is determined because the circular specimen allows for a tight fit between the coil and the specimen; therefore, the sum of the specimen's diameter and the wire diameter is the coil's diameter, making it easier to calculate the cross-sectional area compared to other specimen shapes. During data acquisition, the signal needs to be averaged and filtered to suppress noise.

[0071] The magnetic properties of the steel plates of ships are modeled by solving the JA model parameters through the measured material hysteresis loop data. After obtaining the JA model parameters, the JA model is used to characterize the magnetic properties of the steel plate material required for numerical analysis. That is, the relationship between the change of magnetic flux density and magnetic field strength is characterized by the JA model.

[0072] The JA hysteresis model is a hysteresis model based on the principle of energy balance within ferromagnetic materials. It describes the relationship between magnetic field strength H and magnetization M, therefore the magnetic flux density is expressed as... Converting magnetic flux density into magnetization ,in, Magnetization of ferromagnetic materials It consists of two parts, namely, reversible magnetization. and irreversible magnetization :

[0073] (3)

[0074] at the same time:

[0075] (4)

[0076] (5)

[0077] in, The magnetic field strength; The magnetization intensity; It is a hysteresis-free magnetization intensity; These are coupling parameters, in A / m. This is the direction coefficient, which can be 1 or -1; These are the internal coupling parameters of the magnetic domains.

[0078] By combining the improved Langevin function, the following formula can be derived:

[0079] (6)

[0080] (7)

[0081] in, Denotes the hyperbolic cotangent function. Indicates the effective magnetic field strength. Saturation magnetization Shape parameters of the nonhysteresis magnetization curve Domain wall bending constant;

[0082] Based on the above relationships, the five parameters of the JA model can be calculated using the measured hysteresis loop data, which are as follows: Saturation magnetization Shape parameters of the nonhysteresis magnetization curve Coupling parameters, Internal coupling parameters of magnetic domains Domain wall bending constant. By obtaining the parameters of the JA model, numerical analysis of the submarine's magnetic field distribution can be performed.

[0083] The measurement system then performs a final analysis and calculation of the ship's magnetic field.

[0084] This invention provides more accurate material parameters, enabling the influence of seawater pressure on the magnetic properties of steel plates to be considered in the magnetic field analysis of ships. This more closely approximates the actual ship environment and improves the accuracy of ship magnetic field analysis. The conventional finite element method is used for ship magnetic field analysis, which mainly includes ship modeling, setting excitation boundary conditions, defining material parameters, mesh generation, solving, and post-processing. The material parameter modeling utilizes a calculated JA hysteresis model.

[0085] When performing finite element analysis of a magnetic field, a three-dimensional geometric model is first constructed based on the actual geometry and dimensions of the ship, typically using geometric modeling software. After the geometric model is completed, material parameters and constraints can be defined. Here, the magnetic properties of the steel plate are characterized using the JA hysteresis model, and the constraints are set according to the actual analysis scenario, such as zero tangential magnetic field, given tangential component values ​​of magnetic field H, etc. Then, spatial discretization is performed, which is mesh generation, and is actually the discretization of the variational problem. After discretization, a system of equations containing the variables to be solved can be constructed.

[0086] The functional form of the constant magnetic field is:

[0087] (8)

[0088] in, It represents the reciprocal of the permeability. Represents magnetic flux density, Represents the integration field. Indicates vector magnetic potential. Indicates current density, The infinitesimal element representing the integration path, Indicates the third type of boundary condition;

[0089] Based on discretization, the extremum problem of the functional in each region can be written out, that is...

[0090] (9)

[0091] in, Describes a functional. Represents the vector magnetic potential within a discrete unit;

[0092] Finally, using matrices to represent the functional extremum problem for each discrete region above, we get the following formula:

[0093] (10)

[0094] In the formula, This is called the stiffness matrix. Represents the variable to be solved. Indicates boundary conditions.

[0095] Solving the above system of equations using the conjugate gradient method yields the solution to the problem. Then, the obtained magnetic field data is presented in the form of graphs, tables, etc., which constitutes post-processing of the calculation results. The final generated ship magnetic field analysis calculation results are as follows: Figure 8 As shown.

[0096] The invention is not limited to the specific embodiments described above. Those skilled in the art can implement the invention using other specific embodiments based on the disclosed content of the embodiments and accompanying drawings. Therefore, any design that adopts the design structure and concept of the invention and makes some simple changes or modifications falls within the protection scope of the invention.

Claims

1. A device for precise measurement of magnetic properties of submarine hull steel material, characterized in that, The device for precise measurement of magnetic properties of submarine hull steel material comprises a sample, an excitation system, a stress application system, a zero magnetic field environment realization system and a measurement system; The sample is in a circular ring structure, and its cross section is approximately cylindrical, similar to the structure of a submarine; The excitation system comprises an excitation coil, which is wound on the sample, and a magnetic field forms a complete magnetic circuit through one turn of the sample; The stress application system comprises two arc-shaped clamping pieces, which are matched with the circular ring structure of the sample; a set of screw rods and nuts are arranged on both sides of the clamping pieces, and a force sensor is further arranged between the nuts and the clamping pieces; the clamping pieces are attached to the surface of the sample, and stress is applied to the sample by extrusion through the screw rods and nuts; The zero magnetic field environment realization system is three groups of large coils wrapped outside the sample, the excitation system and the stress loading system, which are used to realize the regulation and control of the magnetic field in three orthogonal directions; The measurement system comprises a sensor and a computer; the sensor comprises a B coil wound on the sample, which is used to obtain induced electromotive force; The computer is used to construct a J-A magnetic hysteresis model, calculate the parameters of the J-A model, perform numerical analysis on the magnetic field distribution of the submarine, and finally use the conventional finite element method to analyze the magnetic field of the submarine.

2. The device for precise measurement of magnetic properties of submarine hull steel material according to claim 1, characterized in that, The magnetic field intensity in the sample is calculated by Ampere's loop theorem Ampere's loop theorem is shown in equation (1): ； wherein denotes the number of turns of the field coil, denotes the field current, denotes the effective magnetic path length, which is approximately equal to the circumference of the circular ring; The Induced electromotive force calculation of coil measurement As follows: ； denotes cross-sectional area of the coil, denotes number of turns of the coil, denotes induced electromotive force measured across the coil.

3. The device for precise measurement of magnetic properties of submarine hull steel material according to claim 2, characterized in that, The J-A magnetic hysteresis model is used to describe the relationship between the magnetic field strength H and the magnetization M, the magnetic flux density is expressed as wherein, ; and the magnetization M of the ferromagnetic body is divided into the reversible magnetization and the irreversible magnetization : ； Meanwhile: ； ； wherein is the magnetic field strength; is the magnetization; is the anhysteretic magnetization; is the coupling parameter in A / m; is the direction coefficient, which takes the value 1 or -1 ; is the intra-domain coupling parameter; The improved Langmuir function can be used to derive the following formula: ； ； wherein, represents the effective magnetic field strength, saturation magnetization, non-hysteresis magnetization curve shape parameter, domain wall bending constant; The five parameters of J-A model are calculated by the measured hysteresis loop data, which are saturation magnetization, non-hysteresis magnetization curve shape parameter, coupling parameter, magnetic domain internal coupling parameter, magnetic domain wall bending constant. The parameters of J-A model are obtained, and the magnetic field distribution of submarine can be analyzed numerically.

4. The device for precise measurement of magnetic properties of submarine hull steel material according to claim 3, characterized in that, The finite element analysis comprises ship modeling, excitation boundary condition setting, material parameter definition, mesh division, solution, post-processing; First, a three-dimensional ship model is constructed according to the actual geometric structure and size of the ship; After the three-dimensional ship modeling is completed, the material parameters and constraint conditions are defined, and the JA magnetic hysteresis model is used to represent the magnetic properties of the steel plate; Then, mesh division is performed, and the variational problem is discretized; Finally, an equation group containing the variables to be solved is constructed.

5. The device for precise measurement of magnetic properties of submarine hull steel material according to claim 4, characterized by, The constant magnetic field functional form in the equation group is: ； wherein, denotes the inverse of the magnetic permeability, denotes the magnetic flux density, denotes the integration domain, denotes the vector magnetic potential, denotes the current density, denotes an infinitesimal of the integration path, denotes a third kind of boundary condition; With the functional form, on the basis of discretization, the extremum problem of the functional of each region can be written as ； wherein denotes the functional, denotes the vector magnetic potential within the discrete element; Finally, the extremum problem of the functional of each discrete region is represented by a matrix, and the following formula is obtained: ； In the formula, is called the stiffness matrix, denotes the variable to be solved, denotes the boundary conditions.

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