An electromagnetic detection device, a detection method and a storage medium

Abstract

The embodiment of the application discloses an electromagnetic detection device, a detection method and a storage medium, which are used in the field of nondestructive testing technology and include a coil, a magnet, a signal excitation unit, a data acquisition unit, a detection mode switching unit and a processor. The processor realizes the following steps: when the current detection mode is an electromagnetic tomography detection mode, the signal excitation unit is controlled to output an excitation signal to the first excitation coil; the data acquisition unit is controlled to receive an induced voltage generated by the first detection coil, and a cross-sectional material distribution image of the test piece is generated based on the induced voltage; when the current detection mode is an electromagnetic ultrasonic detection mode, the signal excitation unit is controlled to output an excitation signal to the second excitation coil; the data acquisition unit is controlled to receive an ultrasonic signal collected by the second detection coil, and an axial material distribution image of the test piece is generated based on the ultrasonic signal, realizing defect detection from the cross section to the transverse section, improving the defect detection coverage rate and improving the detection efficiency.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of non-destructive testing, in particular to an electromagnetic detection device, a detection method and a storage medium. BACKGROUND

[0002] Large-span bridges usually use cable bearing systems, including the hangers of suspension bridges, the stay cables of cable-stayed bridges, and the hangers of half-through and through arch bridges. The tension hangers (stay cables, hangers and hangers) are generally arranged outside the beam body and are in a high stress state, and are relatively sensitive to the corrosion environment.

[0003] The cable and anchoring quality of the bridge tension hanger have a major impact on the service life and reliability of the bridge. A comprehensive detection of the anchoring quality, corrosion and broken wires of the anchoring steel wires is required to achieve a complete assessment of the reliability of the bridge. The existing defect detection of the bridge anchoring area and the cable generally detects the surface defects of the bridge cable or the axial surface defects near the sensor. However, the existing defect detection of the bridge anchoring area and the cable may have defects in the interior or surface of the bridge anchoring area and the cable. When detecting defects, only the surface of the bridge cable is detected, which may lead to incomplete detection and inaccurate defect detection results. SUMMARY

[0004] Embodiments of the present application provide an electromagnetic detection device, a detection method and a storage medium, which realize defect detection from cross section to cross section, improve defect detection coverage and detection efficiency.

[0005] Embodiments of the present application provide an electromagnetic detection device, which comprises a coil, a magnet, a signal excitation unit, a data acquisition unit, a detection mode switching unit, a storage and a processor. The storage stores executable program code, and the processor is configured to implement the following steps when executing the executable program code:

[0006] When the detection mode switching unit determines that the current detection mode is an electromagnetic tomography detection mode, the coil comprises a first excitation coil and a first detection coil.

[0007] The signal excitation unit is controlled to output an excitation signal to the first excitation coil, so that the first excitation coil generates a first alternating magnetic field in the test piece.

[0008] The data acquisition unit is controlled to receive an induced voltage generated by the first detection coil, and generate a cross-sectional material distribution image of the test piece based on the induced voltage. The induced voltage is obtained by the first detection coil under the action of the composite magnetic field generated by the test piece under the action of the first alternating magnetic field.

[0009] When the detection mode switching unit determines that the current detection mode is the electromagnetic ultrasonic detection mode, the coils comprise: a second excitation coil and a second detection coil;

[0010] The signal excitation unit is controlled to output an excitation signal to the second excitation coil, so that the second excitation coil generates a second alternating magnetic field in the test piece;

[0011] The data acquisition unit is controlled to receive an ultrasonic signal collected by the second detection coil, and generate an axial material distribution image of the test piece based on the ultrasonic signal, the ultrasonic signal being obtained by the test piece under the action of the second alternating magnetic field and the bias magnetic field generated by the magnet.

[0012] Further, a plurality of coils are distributed around the test piece at a preset interval to obtain a coil array, and the coils and the test piece have a preset distance.

[0013] The magnet is arranged on a side of the coil away from the test piece, and each magnet corresponds to one coil.

[0014] Further, the channel switching circuit is further included.

[0015] When the processor determines that the current detection mode is the electromagnetic tomography detection mode, the channel switching circuit is controlled to determine one coil in the coil array as the first excitation coil and other coils as the first detection coil, and when the data acquisition unit receives an induced voltage collected by the first detection coil, the channel switching circuit is controlled to determine another coil in the coil array as the first excitation coil and other coils as the first detection coil, until the cycle ends.

[0016] When the processor determines that the current detection mode is the electromagnetic ultrasonic detection mode, the channel switching circuit is controlled to determine one coil in the coil array as the second excitation coil and other coils as the second detection coil, and when the data acquisition unit receives an ultrasonic signal collected by the second detection coil, the channel switching circuit is controlled to determine another coil in the coil array as the second excitation coil and other coils as the second detection coil, until the cycle ends.

[0017] Further, the image display is further included.

[0018] The processor is configured to display the cross-sectional material distribution image and the axial material distribution image of the test piece on the image display.

[0019] Further, the processor is configured to generate the axial material distribution image of the test piece based on the ultrasonic signal includes:

[0020] The alternating Lorentz force is generated in the to-be-tested piece under the action of the second alternating magnetic field and the bias magnetic field generated by the magnet;

[0021] The alternating Lorentz force acts on the mass point in the to-be-tested piece to make the mass point vibrate at high frequency, and the ultrasonic signal is generated in the to-be-tested piece;

[0022] An alternating current corresponding to the alternating magnetic field is generated on the side of the second detection coil close to the to-be-tested piece, the voltage signal of the second detection coil is driven by the alternating magnetic field, and the axial material distribution image of the to-be-tested piece is obtained.

[0023] Further, the alternating Lorentz force generated in the to-be-tested piece under the action of the second alternating magnetic field and the bias magnetic field generated by the magnet includes:

[0024] The formula corresponding to the second alternating magnetic field generated by the second excitation coil in the to-be-tested piece is:

[0025]

[0026] Wherein, A is the vector magnetic potential, σ is the conductivity of the to-be-tested piece, J s is the total current density, μ is the magnetic permeability, △ is the Laplace operator, and t is the time unit;

[0027] Under the skin effect and eddy current effect of the second excitation coil, the total current density obtained is:

[0028]

[0029] Wherein, i is the total current; S is the cross-sectional area of the coil conductor;

[0030] It can be obtained that, The eddy current density in the to-be-tested piece is:

[0031] The alternating Lorentz force f L = B0×J e , can be obtained, wherein f L is the alternating Lorentz force, and B0 is the bias magnetic field generated by the magnet.

[0032] Further, the alternating Lorentz force acting on the mass point in the to-be-tested piece to make the mass point vibrate at high frequency to generate the ultrasonic signal in the to-be-tested piece includes:

[0033] The elastic deformation of the mass point in the to-be-tested piece under the alternating Lorentz force obtains the ultrasonic signal, and the motion equation of the elastic deformation is:

[0034]

[0035] Wherein, g is a stress tensor, p is a density, u is a displacement of the mass point in the to-be-tested piece, f L is the alternating Lorentz force, ▽ is a Laplace operator, and t is a time unit.

[0036] Further, the generating of the alternating current on the side of the second detection coil close to the to-be-tested piece according to the ultrasonic signal includes:

[0037] The ultrasonic signal of the to-be-tested piece propagates to the side of the second detection coil close to the to-be-tested piece, and under the action of the bias magnetic field of the magnet, the charged particles in the ultrasonic signal propagation motion generate an alternating current, and the current density J L is:

[0038] J L = σv x B0, wherein, σ is the electrical conductivity of the to-be-tested piece, v is the vibration velocity of the mass point, and B0 is the bias magnetic field generated by the magnet.

[0039] The embodiment of the application further provides an electromagnetic detection method, comprising:

[0040] When it is determined that the current detection mode is an electromagnetic tomography detection mode, driving the first excitation coil to generate a first alternating magnetic field in the to-be-tested piece;

[0041] Receiving an induced voltage generated by the first detection coil, and generating a cross-sectional material distribution image of the to-be-tested piece based on the induced voltage, the induced voltage being obtained by the first detection coil under the action of a composite magnetic field generated by the to-be-tested piece under the action of the excitation magnetic field;

[0042] When it is determined that the current detection mode is an electromagnetic ultrasonic detection mode, driving the second excitation coil to generate a second alternating magnetic field in the to-be-tested piece;

[0043] Receiving an ultrasonic signal collected by the second detection coil, and generating an axial material distribution image of the to-be-tested piece based on the ultrasonic signal, the ultrasonic signal being obtained by the to-be-tested piece under the action of the second alternating magnetic field and a bias magnetic field generated by the magnet.

[0044] The embodiment of the application further provides a computer readable storage medium, characterized in that the computer readable storage medium comprises instructions, when the instructions run on the computer, the computer executes the above-mentioned method.

[0045] From the above technical solutions, the embodiments of the present application have the following advantages:

[0046] The electromagnetic detection device of the embodiments of the present application comprises a coil, a magnet, a signal excitation unit, a data acquisition unit, a detection mode switching unit and a processor. The processor implements the following steps: when the current detection mode is an electromagnetic tomography detection mode, the signal excitation unit is controlled to output an excitation signal to the first excitation coil; the data acquisition unit is controlled to receive an induced voltage generated by the first detection coil, and a cross-sectional material distribution image of the test piece is generated based on the induced voltage; when the current detection mode is an electromagnetic ultrasonic detection mode, the signal excitation unit is controlled to output an excitation signal to the second excitation coil; the data acquisition unit is controlled to receive an ultrasonic signal collected by the second detection coil, and an axial material distribution image of the test piece is generated based on the ultrasonic signal. The cross-sectional defects of the test piece are detected by the obtained cross-sectional material distribution image, and the axial defects of the test piece are detected by the obtained axial material distribution image, which realizes defect detection from the cross section to the transverse section, greatly improves the defect detection coverage rate, and improves the detection efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art according to these drawings.

[0048] Figure 1 A schematic diagram of an electromagnetic detection device disclosed by the embodiments of the present application;

[0049] Figure 2 A system structure diagram of an electromagnetic detection device disclosed by the embodiments of the present application;

[0050] Figure 3 A principle diagram of electromagnetic tomography disclosed by the embodiments of the present application;

[0051] Figure 4 A system structure diagram of electromagnetic tomography disclosed by the embodiments of the present application;

[0052] Figure 5 A signal flow diagram of electromagnetic tomography disclosed by the embodiments of the present application;

[0053] Figure 6 A principle diagram of electromagnetic ultrasonic detection disclosed by the embodiments of the present application;

[0054] Figure 7 An installation schematic diagram of electromagnetic ultrasonic detection disclosed by the embodiments of the present application;

[0055] Figure 8 A flowchart of the electromagnetic detection disclosed in the embodiments of the present application. DETAILED DESCRIPTION

[0056] In order for those skilled in the art to better understand the scheme of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0057] In the description of the embodiments of the present application, it should be noted that the orientations or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and are not intended to indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0058] In the description of the embodiments of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0059] The existing defect detection of bridge anchorage zone and cable generally detects the surface defects of bridge cable or the axial surface defects near the sensor. However, the existing defect detection of bridge anchorage zone and cable may have defects in the inside or surface of the bridge anchorage zone and cable. When defect detection is performed, only the surface of the bridge cable is detected, which can easily lead to incomplete detection and inaccurate defect detection results. Therefore, the embodiments of the present application provide an electromagnetic detection device, which can realize defect detection from cross section to cross section, greatly improve defect detection coverage, and improve detection efficiency, such as Figure 1 and Figure 2 As shown in the specific implementation, the following is provided:

[0060] The electromagnetic detection device provided in this application includes: a coil 101, a magnet 102, a signal excitation unit, a data acquisition unit, a detection mode switching unit, a memory, and a processor. This electromagnetic detection device can be understood as an integrated electromagnetic detection sensor. The sensor is radially and uniformly arranged around the test piece 103 and can be composed of a coil, a strong magnet, and a high-permeability soft magnet, wherein the high-permeability soft magnet is encapsulated together with the coil. The electromagnetic detection device in this application can operate in two detection modes: (1) electromagnetic tomography detection mode: to detect cross-sectional defects in bridge cables; (2) electromagnetic ultrasonic detection mode: to detect axial defects near the sensor. Combining the two modes enables defect detection from the cross-section to the transverse section, greatly improving defect detection coverage and increasing detection efficiency.

[0061] The electromagnetic detection device's memory stores executable program code, and the processor, when executing the executable program code, implements the following steps: When the detection mode switching unit determines that the current detection mode is electromagnetic tomography detection mode, the coil includes: a first excitation coil and a first detection coil; it is understood that when the electromagnetic detection device operates in electromagnetic tomography detection mode, it mainly uses the coils surrounding the test piece to detect the test piece, wherein the test piece can be a bridge anchorage area, a bridge cable, or other ferromagnetic column, and is not specifically limited here. When detecting the test piece, one coil surrounding the test piece can be selected as the first excitation coil, and the other coils as the first detection coils. It is understood that, as Figure 3 As shown, electromagnetic tomography (EMT) is a type of electro-tomographic imaging technology. Based on the principle of electromagnetic induction, it can visualize and measure conductive or magnetic materials within closed pipes or containers. Its working principle is as follows: An alternating excitation magnetic field is used to scan the space containing the conductive or magnetic material from multiple angles. The conductive material generates eddy currents, and the magnetic material generates induced magnetic fields, both of which modulate the original main magnetic field. Detection coils uniformly distributed around the closed pipe or container collect measurement voltage data from various angles, thereby reconstructing the distribution of materials in the measured field. Because EMT is a non-contact, non-invasive, radiation-free, low-cost, and rapid imaging technology, and has the advantage of being sensitive to both conductive and magnetic materials, it has been gradually applied in fields such as non-destructive testing, imaging of cerebral edema in biomedicine, visual monitoring of molten steel, rail flaw detection, and multiphase flow measurement. It is a non-destructive testing technology with great development potential and broad application prospects.

[0062] In the embodiments of the present application, the coils of the electromagnetic detection device are respectively connected with the signal excitation unit and the data acquisition unit. When the current detection mode of the electromagnetic detection device is working in the electromagnetic tomography mode, the detection mode switching unit can control the signal excitation unit (signal generation module) to output excitation signals by the processor (host computer), and the excitation signals generated by the signal excitation unit can be injected into the first excitation coil after passing through the power amplifier, so as to make the first excitation coil generate a first alternating magnetic field (alternating excitation main magnetic field) in the test piece. The data acquisition unit receives the induced voltage generated by the first detection coil, and generates the cross-sectional material distribution image of the test piece based on the induced voltage. The induced voltage is obtained by the first detection coil under the action of the composite magnetic field generated by the test piece under the action of the first alternating magnetic field. The conductive material in the test piece will generate eddy current under the action of the first alternating magnetic field, and the eddy current will induce secondary magnetic field. The magnetically permeable material in the test piece will generate induced magnetic field, which will produce modulation effect with the main magnetic field to produce composite magnetic field. The composite magnetic field acts on the first detection coil to generate boundary induced voltage. The data acquisition unit acquires the induced voltage generated by the first detection coil, so as to obtain the data acquisition of the projection direction corresponding to the first excitation coil. After demodulating the collected data, the material conductivity distribution is calculated by using appropriate iterative or non-iterative image reconstruction algorithm, and finally the cross-sectional material distribution image can be reconstructed. The cross-sectional material distribution image can be understood as the material distribution image obtained at different positions of the corresponding outer periphery of the test piece.

[0063] When the detection mode switching unit determines that the current detection mode is the electromagnetic ultrasonic detection mode, the coil comprises a second excitation coil and a second detection coil; when the electromagnetic detection device works in the electromagnetic ultrasonic detection mode, the coil and the magnet of the electromagnetic detection device are needed. It can be understood that, according to the different excitation principles of electromagnetic ultrasonic waves, electromagnetic ultrasonic transducers can be divided into two types based on the Lorentz force mechanism and the magnetostrictive mechanism. Considering that the material of the test piece is generally ferromagnetic, it is more appropriate to use the electromagnetic ultrasonic detection method based on the Lorentz force mechanism. The electromagnetic ultrasonic transducer based on the Lorentz force mechanism is composed of a coil, a magnet and a non-ferromagnetic test piece. The magnet generally uses a permanent magnet to provide a bias magnetic field, the coil is used to generate an alternating magnetic field, and the test piece is used to generate and propagate ultrasonic waves. Among them, the processor of the electromagnetic detection device can control the signal excitation unit to output an excitation signal to the second excitation coil, so as to make the second excitation coil generate a second alternating magnetic field in the test piece; control the data acquisition unit to receive the ultrasonic signal collected by the second detection coil, and generate an axial material distribution image of the test piece based on the ultrasonic signal. The ultrasonic signal is obtained under the action of the second alternating magnetic field and the bias magnetic field generated by the magnet. The axial material distribution image can be understood as the material distribution image of the extension direction of the test piece. It can be understood that, for the electromagnetic ultrasonic transducer constructed based on the Lorentz force mechanism, the alternating induced eddy current corresponding to the second alternating magnetic field in the skin layer of the test piece will generate an alternating Lorentz force under the action of the bias magnetic field. The alternating Lorentz force acts on the material lattice of the test piece, so that the mass points of the material vibrate at a high frequency, thereby generating ultrasonic signals (ultrasonic waves) in the test piece. When the ultrasonic wave in the test piece propagates below the second detection coil (EMAT receiving coil), under the action of the static bias magnetic field, the charged particles moving with the ultrasonic wave generate an alternating current; the alternating current in the test piece will generate an alternating magnetic field in the test piece and around the test piece. The EMAT receiving coil in the alternating magnetic field will generate an induced electromotive force, that is, the voltage signal received by the electromagnetic ultrasonic transducer. As shown in Figure 6 , a direct current magnetic field bias is realized by a permanent magnet, and an optimal bias point is found, so as to realize optimal alternating magnetic field fluctuation excitation, which is beneficial to realize effective excitation of electromagnetic ultrasonic waves under smaller energy.

[0064] It can be seen that the electromagnetic detection device of the embodiment of the application comprises a coil, a magnet, a signal excitation unit, a data acquisition unit, a detection mode switching unit and a processor, and the processor implements the following steps: when the current detection mode is an electromagnetic tomography detection mode, the signal excitation unit is controlled to output an excitation signal to the first excitation coil; the data acquisition unit is controlled to receive an induced voltage generated by the first detection coil, and a cross-sectional material distribution image of the test piece is generated based on the induced voltage; when the current detection mode is an electromagnetic ultrasonic detection mode, the signal excitation unit is controlled to output an excitation signal to the second excitation coil; the data acquisition unit is controlled to receive an ultrasonic signal collected by the second detection coil, and an axial material distribution image of the test piece is generated based on the ultrasonic signal, the cross-sectional defects of the test piece are detected by the obtained cross-sectional material distribution image, the axial defects of the test piece are detected by the obtained axial material distribution image, the defect detection from the cross section to the transverse section is realized, the defect detection coverage is greatly improved, and the detection efficiency is improved.

[0065] In an implementable manner, on the one hand, the comprehensive detection of defects can be effectively realized, and different types of defect detection can be realized on the same device; on the other hand, the integrated multifunctional detection method can be suitable for detection requirements in different scenes, such as the interface loss of the anchoring section interface steel wire rope interface, the cross-sectional water inflow evaluation, and the detection of defects in the anchoring area embedded in the bridge body. Design and development of an integrated multifunctional bridge anchoring section detection method can greatly improve the nondestructive testing capability of the device, provide an objective basis for comprehensive evaluation of the reliability of the bridge, and ensure the reliable operation of the bridge. The integrated layout design of the electromagnetic detection device realizes the detection of two different forms of defects, which has the following advantages: (1) improves the coverage and efficiency of bridge cable defect detection; (2) can realize cable cross-sectional defects; (3) can simultaneously realize axial transverse defect detection; (4) can realize defect detection in areas that cannot be reached (anchoring area); (5) the device is portable, which is conducive to the realization of automatic detection by a detection robot.

[0066] Further, in the electromagnetic detection device of the embodiment of the application, a plurality of coils are distributed around the test piece at a preset interval to obtain a coil array, the preset interval can be 3 cm or 4 cm, and the specific value is not limited here, that is, the plurality of coils are distributed around the test piece, and the coil and the test piece have a preset distance, which can be 2 cm or 3 cm, and the specific value is not limited here. The magnet is arranged on the side of the coil away from the test piece, and each magnet corresponds to one coil.

[0067] Further, the electromagnetic detection device further comprises a channel switching circuit; the processor is further configured to, when it is determined that the current detection mode is the electromagnetic tomography detection mode, control the channel switching circuit to determine one coil in the coil array as the first excitation coil and other coils as the first detection coil; and when the data acquisition unit receives the induced voltage collected by the first detection coil, control the channel switching circuit to determine another coil in the coil array as the first excitation coil and other coils as the first detection coil, until the cycle ends. Figure 4 and Figure 5 As shown in the figure, the signal excitation unit (signal emission and excitation module) of the host computer generates an excitation signal, which is injected into the first excitation coil selected by the channel switching circuit in the analog switch after being amplified by the power amplifier. The remaining coils except the first excitation coil are sequentially selected as the first detection coil to complete the data collection of one projection direction. The channel switching circuit selects the next coil as the first excitation coil, and the remaining coils are sequentially selected as the first detection coil to complete the data collection of the second projection direction. In this way, the data collection of all projection directions is completed. The collected data is subjected to phase shift and amplitude after phase-amplitude detection, and then subjected to analog-to-digital conversion (A / D). After being processed by the programmable logic unit (FPGA), the data transmission and analysis reconstruct the material distribution image.

[0068] When it is determined that the current detection mode is the electromagnetic ultrasonic detection mode, the channel switching circuit is controlled to determine one coil in the coil array as the second excitation coil and other coils as the second detection coil; and when the data acquisition unit receives the ultrasonic signal collected by the second detection coil, the channel switching circuit is controlled to determine another coil in the coil array as the second excitation coil and other coils as the second detection coil, until the cycle ends. Figure 7 As shown in the figure, the second excitation coil and the magnet can be understood as an electromagnetic ultrasonic array sensor. The electromagnetic ultrasonic array sensor is uniformly distributed circumferentially to the test piece, and each different coil is sequentially excited, and the reflected ultrasonic signal is detected by the second detection coil (signal pickup coil). The defect position information is analyzed from the ultrasonic signal. When the test piece is defect-free, the ultrasonic signal amplitude is small, and when the test piece has a defect, the ultrasonic signal amplitude becomes large, and the axial material distribution image of the test piece can be obtained.

[0069] Further, the electromagnetic detection device further comprises an image display; the image display can be understood as the display of the image reconstruction computer; and the processor is configured to display the cross-sectional material distribution image and the axial material distribution image of the test piece on the image display. It can be understood that the cross-sectional material distribution image and the axial material distribution image displayed on the image display can more clearly and intuitively observe the cross-sectional defects and axial defects of the test piece.

[0070] Further, the process of generating the ultrasonic signal by the test piece involves the coupling of multiple physical fields of static magnetic field, alternating eddy current magnetic field and acoustic field. Among them, the eddy current density, electric field intensity and magnetic field intensity distribution in the conductive material have skin effect, and the amplitude will present exponential decay with the increase in the depth of the conductor, and the skin depth is represented by the penetration depth δ, δ is defined as the depth when the field quantity decays to 1 / e of the surface intensity, where e is the natural constant, then:

[0071] Where f is the frequency of the time-varying field; μ is the magnetic permeability; σ is the electrical conductivity.

[0072] Generating the axial material distribution image of the test piece based on the ultrasonic signal includes: the test piece generates alternating Lorentz force under the action of the second alternating magnetic field and the bias magnetic field generated by the magnet; the alternating Lorentz force acts on the mass point in the test piece to make the mass point vibrate at high frequency, thereby generating an ultrasonic signal in the test piece; an alternating current is generated on the side of the second detection coil close to the test piece according to the ultrasonic signal, and the alternating magnetic field corresponding to the alternating current drives the second detection coil to generate a voltage signal, thereby obtaining the axial material distribution image of the test piece.

[0073] Specifically, in electromagnetic ultrasonic testing, the influence of displacement current can be ignored, and the alternating magnetic field of the EMAT coil corresponds to the following equation, that is, the formula corresponding to the second alternating magnetic field generated by the second excitation coil in the test piece is:

[0074]

[0075] Where A is the vector magnetic potential, σ is the electrical conductivity of the test piece, J s is the total current density, μ is the magnetic permeability, and ∇ is the Laplace operator, t is the time unit.

[0076] Since a pulse current with a frequency of tens of k Hz to several MHz is applied in the EMAT coil, and the distance between the conductors of each turn of the coil and the distance between the coil and the test piece are relatively close, the skin effect and eddy current effect of the EMAT coil need to be considered, that is, under the skin effect and eddy current effect of the second excitation coil, the total current density obtained is:

[0077]

[0078] Where i is the total current; S is the cross-sectional area of the coil conductor;

[0079] It can be obtained that The eddy current density in the test piece is:

[0080] The alternating Lorentz force f L=B0xJ e wherein f L is the alternating Lorentz force, and B0is the bias magnetic field generated by the magnet.

[0081] The alternating Lorentz force acts on the particles in the test piece to cause the particles to vibrate at a high frequency, thereby generating the ultrasonic signal in the test piece. Specifically, the particles in the test piece are elastically deformed under the action of the alternating Lorentz force to obtain the ultrasonic signal. Assuming that the test piece is isotropic and satisfies the conditions of linear elasticity and continuity, the motion equation of the elastic deformation is:

[0082]

[0083] wherein g is a stress tensor, p is a density, u is the displacement of the particles in the test piece, and f L is the alternating Lorentz force, and ▽ is a Laplacian operator, and t is a time unit.

[0084] The ultrasonic signal generates an alternating current on the side of the second detection coil close to the test piece, including: the ultrasonic signal of the test piece propagates to the side of the second detection coil close to the test piece, and under the action of the bias magnetic field of the magnet, the charged particles in the ultrasonic signal propagation motion generate an alternating current, and the current density J L is:

[0085] J L = σv x B0, wherein σ is the electrical conductivity of the test piece, v is the vibration velocity of the particles, and B0is the bias magnetic field generated by the magnet.

[0086] In the embodiments of the present application, the electromagnetic detection device is formed by integrating an electromagnetic tomography and an electromagnetic ultrasonic detection system. The structure is integrated with the structural features of the electromagnetic tomography system and the electromagnetic ultrasonic system. The same points in the structure are comprehensively considered, and the integrated places of the two are improved and optimized to form the final integrated detection sensor. On the basis of considering the characteristics of the two working modes, the interference and signal noise between the two are minimized, and the test piece can be quickly moved axially to obtain the images of different cross sections and the images of axial defects at different positions of the test piece.

[0087] The embodiments of the present application also provide an electromagnetic detection method, as shown in Figure 8 , including:

[0088] 801. When it is determined that the current detection mode is the electromagnetic tomography detection mode, the first excitation coil is driven to generate a first alternating magnetic field in the test piece.

[0089] When the electromagnetic detection device determines that the current detection mode is the electromagnetic tomography detection mode, the first excitation coil is driven to generate a first alternating magnetic field in the test piece.

[0090] 802. The induced voltage generated by the first detection coil is received, and a cross-sectional material distribution image of the test piece is generated based on the induced voltage.

[0091] The electromagnetic detection device can receive the induced voltage generated by the first detection coil, and generate a cross-sectional material distribution image of the test piece based on the induced voltage. The induced voltage is obtained by the first detection coil under the action of the composite magnetic field generated by the test piece under the action of the first alternating magnetic field;

[0092] 803. When it is determined that the current detection mode is the electromagnetic ultrasonic detection mode, the second excitation coil is driven to generate a second alternating magnetic field in the test piece.

[0093] When the electromagnetic detection device determines that the current detection mode is the electromagnetic ultrasonic detection mode, the second excitation coil is driven to generate a second alternating magnetic field in the test piece.

[0094] 804. The ultrasonic signal collected by the second detection coil is received, and an axial material distribution image of the test piece is generated based on the ultrasonic signal.

[0095] The electromagnetic detection device can receive the ultrasonic signal collected by the second detection coil, and generate an axial material distribution image of the test piece based on the ultrasonic signal. The ultrasonic signal is obtained by the test piece under the action of the second alternating magnetic field and the bias magnetic field generated by the magnet.

[0096] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system, device and unit described above can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0097] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interfaces, devices or units, and can be electrical, mechanical or other forms.

[0098] The units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, that is, may be located in one place, or may be distributed to multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0099] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present alone, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0100] The integrated unit, if realized in the form of a software functional unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or the part of the prior art that contributes to the technical solutions or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, read-only memory), a random access memory (RAM, random access memory), a magnetic disk or an optical disk, and various program code storage media.

Claims

1. An electromagnetic detection apparatus, the electromagnetic detection apparatus comprising: The coil, the magnet, the signal excitation unit, the data acquisition unit, the detection mode switching unit, the memory, and the processor, wherein the memory stores executable program code, and the processor is configured to implement the following steps when executing the executable program code: When the detection mode switching unit determines that the current detection mode is the electromagnetic tomography detection mode, the coil comprises: a first excitation coil and a first detection coil; The signal excitation unit is controlled to output an excitation signal to the first excitation coil, so that the first excitation coil generates a first alternating magnetic field in the test piece; The data acquisition unit is controlled to receive an induced voltage generated by the first detection coil, and generate a cross-sectional material distribution image of the test piece based on the induced voltage, wherein the induced voltage is obtained by the first detection coil under the action of a composite magnetic field generated by the test piece under the action of the first alternating magnetic field; When the detection mode switching unit determines that the current detection mode is the electromagnetic ultrasonic detection mode, the coil comprises: a second excitation coil and a second detection coil; The signal excitation unit is controlled to output an excitation signal to the second excitation coil, so that the second excitation coil generates a second alternating magnetic field in the test piece; The data acquisition unit is controlled to receive an ultrasonic signal collected by the second detection coil, and generate an axial material distribution image of the test piece based on the ultrasonic signal, wherein the ultrasonic signal is obtained by the test piece under the action of the second alternating magnetic field and a bias magnetic field generated by the magnet; The generation of the axial material distribution image of the test piece based on the ultrasonic signal comprises: The test piece generates an alternating Lorentz force under the action of the second alternating magnetic field and the bias magnetic field generated by the magnet; The alternating Lorentz force acts on a particle in the test piece, so that the particle vibrates at a high frequency, and the ultrasonic signal is generated in the test piece; According to the ultrasonic signal, an alternating current is generated on the side of the second detection coil close to the test piece, and an alternating magnetic field corresponding to the alternating current drives the second detection coil to generate a voltage signal, thereby obtaining the axial material distribution image of the test piece.

2. The electromagnetic detection apparatus of claim 1, wherein A plurality of coils are distributed around the test piece at a predetermined interval to form a coil array, and the coils are at a predetermined distance from the test piece; The magnet is arranged on the side of the coil away from the test piece, and each magnet corresponds to one coil.

3. The electromagnetic detection apparatus of claim 2, wherein Further comprising: A channel switching circuit; The processor is further configured to, when it is determined that the current detection mode is the electromagnetic tomography detection mode, control the channel switching circuit to determine one coil in the coil array as the first excitation coil and the other coils as the first detection coils; and when the data acquisition unit receives the induced voltage collected by the first detection coil, control the channel switching circuit to determine another coil in the coil array as the first excitation coil and the other coils as the first detection coils, until the cycle ends. When it is determined that the current detection mode is the electromagnetic ultrasonic detection mode, the channel switching circuit is controlled to determine one coil in the coil array as the second excitation coil and other coils as the second detection coils; when the data acquisition unit receives the ultrasonic signal collected by the second detection coils, the channel switching circuit is controlled to determine another coil in the coil array as the second excitation coil and other coils as the second detection coils, until the cycle ends.

4. The electromagnetic detection apparatus of claim 1, wherein Also comprising: an image display; the processor is configured to display the cross-sectional material distribution image and the axial material distribution image of the test piece on the image display.

5. The electromagnetic detection apparatus of claim 1, wherein, the test piece generates an alternating Lorentz force under the action of the second alternating magnetic field and the bias magnetic field generated by the magnet includes: the formula corresponding to the second alternating magnetic field generated by the second excitation coil in the test piece is: where A is the vector magnetic potential, σ is the electrical conductivity of the piece under test, J s is the total current density, μ is the magnetic permeability, ∇ is the Laplace operator, and t is the time unit. under the skin effect and eddy current effect of the second excitation coil, the total current density obtained is: where i is the total current; S is the cross-sectional area of the coil conductor; It is possible to obtain ; the eddy current density within the piece to be tested is: ; The alternating Lorentz force can be obtained, where f L is the alternating Lorentz force and B0is the bias magnetic field generated by the magnet.

6. The electromagnetic detection apparatus of claim 1, wherein, the alternating Lorentz force acts on the particles in the test piece to make the particles vibrate at high frequency, and the ultrasonic signal is generated in the test piece includes: the particles in the test piece elastically deform under the action of the alternating Lorentz force to obtain the ultrasonic signal, and the motion equation of elastic deformation is: where g is the stress tensor, p is the density, u is the displacement of a mass point within the piece to be tested, f L is the alternating Lorentz force, ▽ is the Laplace operator, t is the time unit.

7. The electromagnetic detection apparatus of claim 1, wherein, the alternating current generated by the second detection coil according to the ultrasonic signal includes: The ultrasonic signal of the to-be-tested piece propagates to the side of the second detection coil close to the to-be-tested piece. Under the action of the bias magnetic field of the magnet, the charged particles in the ultrasonic signal propagation motion generate an alternating current, and the current density J of the alternating current is: L is: where σ is the electrical conductivity of the piece under test, v is the particle velocity, and B0is the bias magnetic field produced by the magnet.

8. An electromagnetic detection method, characterized by, including: when it is determined that the current detection mode is the electromagnetic tomography detection mode, the first excitation coil is driven to generate a first alternating magnetic field in the test piece; receive the induced voltage generated by the first detection coil, and generate a cross-sectional material distribution image of the test piece based on the induced voltage, the induced voltage being obtained by the first detection coil under the action of the composite magnetic field generated by the test piece under the action of the first alternating magnetic field; when it is determined that the current detection mode is the electromagnetic ultrasonic detection mode, the second excitation coil is driven to generate a second alternating magnetic field in the test piece; receive the ultrasonic signal collected by the second detection coil, and generate an axial material distribution image of the test piece based on the ultrasonic signal, the ultrasonic signal being obtained by the test piece under the action of the second alternating magnetic field and the bias magnetic field generated by the magnet; the axial material distribution image of the test piece generated based on the ultrasonic signal includes: the test piece generates an alternating Lorentz force under the action of the second alternating magnetic field and the bias magnetic field generated by the magnet; the alternating Lorentz force acts on the particles in the test piece to make the particles vibrate at high frequency, and the ultrasonic signal is generated in the test piece; according to the ultrasonic signal, an alternating current is generated on the side of the second detection coil close to the test piece, and the alternating magnetic field corresponding to the alternating current drives the second detection coil to generate a voltage signal, obtaining the axial material distribution image of the test piece.

9. A computer-readable storage medium, characterized in that, The computer readable storage medium includes instructions that, when executed on a computer, cause the computer to perform the method of claim 8.

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