Electromagnetic ultrasonic transducer wiring structure and application thereof

Abstract

This invention discloses a wiring structure for an electromagnetic ultrasonic transducer and its application, belonging to the field of ultrasonic nondestructive testing technology. The wiring structure includes independent transmitting-side and receiving-side switch groups, allowing independent switching of the coil's topology connection during transmission and reception. Combined with a novel coil group structure design, it achieves both high-efficiency excitation and high-sensitivity reception. This invention integrates the above wiring structure into the transducer and constructs a semi-closed peripheral magnetic circuit to enhance the signal and meet the excitation energy and reception sensitivity requirements of different test pieces. This invention solves the problems of existing transducers, such as topology binding, poor adaptability, and weak detection signals. It can flexibly adapt to different testing scenarios, improve the detection signal strength and signal-to-noise ratio, and has a wide range of applications.

Description

Technical Field

[0001] This invention belongs to the field of nondestructive testing technology, and particularly relates to an electromagnetic ultrasonic transducer wiring structure and its application. Background Technology

[0002] An electromagnetic ultrasonic transducer (EMAT) is a non-contact ultrasonic transducer that operates based on the Lorentz force mechanism or magnetostriction effect. It can excite and receive ultrasonic waves in conductive or ferromagnetic materials, and is applied in the non-destructive testing of metal components such as steel pipes, steel plates, and forgings. The basic structure of a traditional electromagnetic ultrasonic transducer typically consists of a permanent magnet, a coil, and the test piece. The permanent magnet generates a static bias magnetic field on the surface of the test piece, and the coil is energized with a high-frequency alternating current to excite ultrasonic waves or receive ultrasonic echo signals propagating within the test piece.

[0003] However, existing electromagnetic ultrasonic technology faces the following technical problems: First, most existing electromagnetic ultrasonic transducers only utilize the permanent magnet itself to generate a bias magnetic field, lacking an effective external magnetic circuit structure. This results in a large amount of magnetic field lines dissipating outside the permanent magnet, failing to be sufficiently concentrated on the surface of the test piece, leading to a low effective magnetic field strength, which in turn limits the excitation and reception amplitude of the ultrasonic signal. Second, existing electromagnetic ultrasonic transducers generally use a single coil to simultaneously perform both transmission and reception functions. For the transmission function, to obtain a larger excitation current, the coil impedance should not be too high, i.e., the number of turns should not be too many; while for the reception function, to obtain a higher induced voltage, it is desirable to have as many coil turns as possible. These two requirements are contradictory, and a single coil cannot simultaneously meet the requirements of efficient transmission and high-sensitivity reception. Third, existing electromagnetic ultrasonic transducers usually use a fixed wiring method, lacking the ability to reconfigure operating modes. In actual testing, different test pieces (such as thick-walled steel pipes and thin-walled aluminum plates) have significantly different requirements for excitation energy and reception sensitivity: thick-walled, high-attenuation test pieces require the maximum excitation current, while thin-walled, low-noise scenarios require higher reception sensitivity. Fixed wiring methods cannot meet the needs of different scenarios, thus limiting the applicability of transducers.

[0004] Therefore, there is an urgent need in the current technology for a signal-enhanced electromagnetic ultrasonic transducer that can balance efficient excitation and high-sensitivity reception. Summary of the Invention

[0005] Objectives of this invention: The first objective is to provide an electromagnetic ultrasonic transducer wiring structure and its topology control method, introducing a dual-coil combined working mode and providing a novel dual-coil structure. This solves the problems of mutual constraints between the transmission and reception performance of a single coil and the inability of a fixed working mode to adapt to diverse detection needs. The second objective is to apply the electromagnetic ultrasonic transducer wiring structure to electromagnetic ultrasonic transducer applications, providing a signal-enhancing electromagnetic ultrasonic transducer. This optimizes the magnetic circuit structure surrounding the permanent magnet. Furthermore, by using the aforementioned electromagnetic ultrasonic transducer wiring structure, the problem of low magnetic field utilization in existing technologies is solved, further improving the signal-to-noise ratio and sensitivity of electromagnetic ultrasonic signals. The third objective is to provide a detection method based on the aforementioned signal-enhancing electromagnetic ultrasonic transducer.

[0006] Technical solution: According to a first aspect of the present invention, the wiring structure of the electromagnetic ultrasonic transducer includes: a first coil, a second coil, and a switch control module;

[0007] The switch control module has two sets of connection terminals. The first connection terminal includes an independent transmitting interface and a receiving interface. The transmitting interface is electrically connected to the output terminal of the excitation circuit of the detection instrument, and the receiving interface is electrically connected to the input terminal of the receiving circuit of the detection instrument. The second connection terminal is electrically connected to the two terminals of the first coil and the two terminals of the second coil, respectively.

[0008] The switch control module has built-in transmitter-side switch group and receiver-side switch group. The transmitter-side switch group is connected to the current path between the transmitter interface and the second connection terminal, and is used to independently switch the topology connection mode of the first coil and the second coil in the transmission timing. The receiver-side switch group is connected to the signal path between the receiver interface and the second connection terminal, and is used to independently switch the topology connection mode of the first coil and the second coil in the reception timing.

[0009] Based on the above structure, the present invention can achieve complete decoupling between the transmitting-side topology and the receiving-side topology.

[0010] Optionally, the first coil includes terminal A and terminal B, and the second coil includes terminal C and terminal D;

[0011] The transmitting interface includes a TX+ port and a TX- port, which are electrically connected to the TX+ and TX- terminals of the excitation circuit, respectively; the receiving interface includes an RX+ port and an RX- port, which are electrically connected to the RX+ and RX- terminals of the receiving circuit, respectively.

[0012] The transmitting-side switch group includes single-pole single-throw switches T1, T1r, T2, T2r, T3, T4, T4r, T5, and T5r; wherein, switches T1, T2, and T4 are connected in parallel in the path between the TX+ port and terminal A, and are used to selectively connect the transmission channel from the TX+ port to terminal A; switches T1r and T4r are connected in parallel in the path between terminal B and the TX- port, and are used to selectively connect the transmission channel from terminal B to the TX- port; switch T3 is a switch located between terminal B and terminal C, and is used to allow current to flow from the first coil to the second coil; switch T5 is a switch located between the TX+ port and terminal C; switches T2r and T5r are parallel switches located in the path between terminal D and the TX- port, and are used to selectively connect the transmission channel from terminal D to the TX- port.

[0013] The receiving-side switch group includes single-pole single-throw switches R1, R1r, R2, R3, and R3r; wherein, switches R1r and R3r are connected in parallel in the path between the RX- port and terminal A, and are used to selectively conduct the transmission channel between the RX- port and terminal A; switch R1 is a switch located between terminal B and the RX+ port; switch R3 is a switch located between terminal D and the RX+ port; switch R2 is a switch located between terminal B and terminal C, and is used to allow the induced current to flow from the first coil to the second coil for superposition.

[0014] Optionally, the single-pole single-throw (SPST) switch is a mechanical switch or a solid-state electronic switch.

[0015] Optionally, the transmitter-side switch group forms three excitation channels, including:

[0016] A separate excitation channel for the first coil is formed by the cooperation of switches T1 and T1r, which is used to separately supply excitation current to the first coil;

[0017] Switches T2, T3 and T2r work together to form a series excitation channel for the first and second coils, which is used to sequentially supply excitation current to the two coils connected in series.

[0018] Switches T4, T4r, T5, and T5r work together to form a parallel excitation channel for the first and second coils, which is used to supply excitation current to the two parallel coils in parallel.

[0019] By independently controlling the on / off state of three sets of switches, interference-free independent switching of the topology connection mode for three transmission working sequences can be achieved.

[0020] Optionally, the receiving-side switch group forms two receiving channels, including:

[0021] A separate receiving channel for the first coil is formed by the cooperation of switch R1r and R1, wherein switch R1r serves as the channel entrance for the separate receiving of the first coil.

[0022] A receiving channel for the first and second coils is formed by the cooperation of switches R3r, R2 and R3, wherein switch R3r serves as the channel entrance for the two coils to receive data in series.

[0023] By independently controlling the on / off state of two sets of switches, interference-free independent switching between two receiving timing topology connection modes can be achieved.

[0024] Meanwhile, the on / off control of the transmitting-side switch group and the receiving-side switch group is independent of each other, realizing complete decoupling of the transmitting-side topology and the receiving-side topology.

[0025] Optionally, the first coil and the second coil are enameled wire coils with the same parameters. They are arranged in a double-wire parallel winding pattern in the same plane, forming a concentric spiral shape. The wires are arranged alternately and wound synchronously from the center outward. Alternatively, they can be arranged in an overlapping pattern, with the first coil located on the lower side near the test piece and the second coil located on the upper side. The two coils have the same planar dimensions and their central axes are aligned. An insulating layer is provided between the coils.

[0026] Optionally, the first coil and the second coil, which are two independently wound helical coils, are both wound with enameled wire with a diameter of 0.05 to 0.3 mm. Each coil has 10 to 60 turns and a coil diameter of 5 to 20 mm.

[0027] According to a second aspect of the present invention, a topology control method for an electromagnetic ultrasonic transducer wiring structure is provided. This method, based on the aforementioned electromagnetic ultrasonic transducer wiring structure, includes:

[0028] Select the corresponding topology connection method for the transmission and reception timing according to the detection requirements, control the corresponding single-pole single-throw switch to close and the other switches to open, forming a unique conducting excitation circuit and reception circuit;

[0029] The topology connection method for the launch timing includes the following three independent modes:

[0030] Transmission mode ①: The first coil is excited alone. Switches T1 and T1r are closed, and the other transmitting side switches are opened. The transmitting current flows into the first coil through the TX+ port, switch T1, and terminal A, and then flows back to the excitation circuit through terminal B, switch T1r, and TX- port, forming a closed channel.

[0031] Transmission mode ②: The first coil and the second coil are connected in series for excitation. Switches T2, T3, and T2r are closed, and the other transmitting side switches are open. The transmitting current flows into the first coil through the TX+ port, switch T2, and terminal A, then into the second coil through terminal B, switch T3, and terminal C, and finally flows back to the excitation circuit through terminal D, switch T2r, and TX- port, forming a closed channel.

[0032] Transmission mode ③: The first coil and the second coil are excited in parallel. When switches T4, T4r, T5, and T5r are closed, the other transmitting side switches are opened. The transmitting current is output from the TX+ port and then splits into two independent loops. The first loop flows into the first coil through switch T4 and terminal A, and then returns through terminal B, switch T4r, and the TX- port. The second loop flows into the second coil through switch T5 and terminal C, and then returns through terminal D, switch T5r, and the TX- port, thus forming a parallel excitation channel.

[0033] The topology connection method for receiving working timing includes the following two independent modes:

[0034] Receive mode The first coil receives signals independently. Switches R1 and R1r are closed, while the other receiving side switches are open. Switch R1r is the channel entrance for the first coil to receive signals independently. The induced signal flows into the first coil through the RX- port, switch R1r, and terminal A, and then is transmitted to the receiving circuit through terminal B, switch R1, and RX+ port, forming a transmission channel.

[0035] Receive mode The first and second coils are connected in series to receive signals. Switches R3r, R2, and R3 are closed, and the other receiving side switches are open. Switch R3r is the channel entrance for the two coils connected in series to receive signals. The induced signal flows into the first coil through the RX- port, switch R3r, and terminal A, then into the second coil through terminal B, switch R2, and terminal C, and finally to the receiving circuit through terminal D, switch R3, and RX+ port, forming a transmission channel.

[0036] In summary, the legal combinations of the topology connection methods for the transmission and reception timing include the following five: Transmission mode ① combined with reception mode ②. Transmit mode ① combined with receive mode Transmit mode ② combined with receive mode Transmit mode ③ combined with receive mode Transmit mode ③ combined with receive mode .

[0037] According to a third aspect of the present invention, a signal-enhancing electromagnetic ultrasonic transducer is provided, comprising: a housing, terminals, a permanent magnet, a magnetic sheet, a magnetic cavity, a coil assembly, a switch control module, and a non-magnetic insulating support.

[0038] One side of the switch control module is electrically connected to the external excitation circuit and the receiving circuit, and the other side is electrically connected to the wiring terminal of the coil group through the wiring terminal, which is used to switch the topology connection mode of the transmitting operation timing and the receiving operation timing of the coil group.

[0039] The bottom plate of the outer shell has an opening, and the non-magnetic insulating support is embedded in the opening, forming a closed bottom surface of the outer shell together with the bottom plate. The coil group, magnetic conductive sheet, and permanent magnet are stacked on the non-magnetic insulating support from bottom to top. The magnetic conductive cavity is also sleeved on the radial outer side of the permanent magnet. The magnetic conductive cavity is a hollow rectangular frame, and its bottom end is fixed to the bottom plate of the outer shell, forming a semi-closed peripheral magnetic circuit. The semi-closed peripheral magnetic circuit is used to constrain the scattered magnetic lines of force of the permanent magnet and guide the magnetic lines of force to concentrate through the working area of ​​the coil group.

[0040] By cooperating with the semi-closed peripheral magnetic circuit and the equipped coil group, the electromagnetic ultrasonic conversion efficiency of the coil group can be improved, and the ultrasonic detection signal enhancement can be achieved by switching the topological connection mode of the transmission and reception working sequences.

[0041] Optionally, the magnetic cavity is made of a high-permeability magnetic material, and the outer shell is made of a non-magnetic material (such as aluminum alloy or engineering plastic).

[0042] Optionally, the coil group and the switch control module may adopt any of the transducer wiring structures described above.

[0043] According to a fourth aspect of the present invention, a method for detecting a signal-enhanced electromagnetic ultrasonic transducer is provided, comprising the following steps:

[0044] (1) Place the transducer on the surface of the test piece, and complete the electrical connection between the excitation circuit, the receiving circuit and the switch control module through the wiring terminals. Confirm that all single-pole single-throw switches of the switch control module are in the initial open state.

[0045] (2) Based on the material, thickness and attenuation characteristics of the test piece, the topology connection method of the appropriate transmission working sequence and the topology connection method of the receiving working sequence are selected through the switch control module, and the on / off state of the corresponding single-pole single-throw switch is controlled to complete the transmission and receiving topology configuration of the coil group.

[0046] (3) Start the excitation circuit and apply a high-frequency alternating excitation current to the coil group through the switch control module. Under the magnetic field constraint of the semi-closed peripheral magnetic circuit, electromagnetic ultrasonic waves are generated in the test piece. At the same time, the electromagnetic ultrasonic echo signal induced by the coil group is collected through the receiving channel switched by the switch control module to complete the thickness measurement or internal defect detection of the test piece.

[0047] (4) After the test is completed, reset all single-pole single-throw switches of the switch control module to the initial open state, disconnect the circuit connection, and remove the transducer.

[0048] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0049] (1) Separate optimization of transmit and receive performance: By introducing a dual-coil design, the transmit and receive coils can be independently optimized for their respective performance requirements—a low-impedance connection is used during transmission to obtain a large current, and a high number of turns is used in series during reception to obtain a high induced voltage, thus resolving the contradiction between transmit and receive performance in traditional single-coil designs. Experiments have verified that using a dual-coil series receiver (transmit mode ① + receive mode ②) is effective. Compared to a single-coil transceiver, the received signal amplitude is increased by approximately 47.8%.

[0050] (2) Flexible and reconfigurable working modes: The switch control module supports the rapid switching of 5 legal working modes. One transducer can adapt to diverse testing scenarios such as different test pieces, thicknesses, and attenuation characteristics. There is no need to replace the transducer or rewire, which significantly improves testing efficiency and reduces usage costs.

[0051] (3) Significant magnetic field enhancement effect: By adding a magnetically conductive cavity outside the permanent magnet and a magnetically conductive sheet below the permanent magnet, a complete peripheral magnetic circuit is constructed, which effectively reduces the dissipation of magnetic lines of force and significantly improves the static bias magnetic field strength on the surface of the test piece, thereby improving the excitation and reception amplitude of the electromagnetic ultrasonic signal. Experimental verification shows that compared with the structure without a peripheral magnetic circuit, the received signal amplitude is increased by about 17.3% after adding the magnetically conductive cavity and magnetically conductive sheet. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the wiring structure of an electromagnetic ultrasonic transducer.

[0053] Figure 2 This is a schematic diagram of a signal-enhancing electromagnetic ultrasonic transducer.

[0054] Figure 3 This is a schematic diagram of a single coil structure of the electromagnetic ultrasonic transducer in the comparative example;

[0055] Figure 4 This is a schematic diagram of the series connection of the double-wire parallel winding structure of the coil group of the present invention;

[0056] Figure 5 This is a schematic diagram of the parallel connection of the double-wire winding structure of the coil group in this invention;

[0057] Figure 6 This is a schematic diagram of the lower series connection of the coil group's upper and lower stacked winding structure of the present invention;

[0058] Figure 7 This is a schematic diagram of the parallel connection of the upper and lower coil stacked structure of the present invention;

[0059] Figure 8 is a comparison of experimental results of the magnetic circuit modification to enhance the received signal of the present invention. In Figure 8(a), the received signal waveform is when a single coil structure is used, and in Figure 8(b), the received signal waveform is when a signal enhancement electromagnetic ultrasonic transducer is used under the same conditions of coil and permanent magnet.

[0060] Figure 9 is a comparison of the signal enhancement experimental results of the present invention with the change of coil wiring method. In Figure 9(a), the received signal waveform is when a single spiral coil transceiver structure is used. In Figure 9(b), the received signal waveform is when the same single coil is used for transmission and two identical coils are stacked in series for reception. Detailed Implementation

[0061] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0062] Example 1

[0063] like Figure 1 As shown, it illustrates a schematic diagram of the wiring structure of an electromagnetic ultrasonic transducer.

[0064] The wiring structure of the electromagnetic ultrasonic transducer includes: a first coil, a second coil, and a switch control module;

[0065] The switch control module has two sets of connection terminals. The first connection terminal includes an independent transmitting interface and a receiving interface. The transmitting interface is electrically connected to the output terminal of the excitation circuit of the detection instrument, and the receiving interface is electrically connected to the input terminal of the receiving circuit of the detection instrument. The second connection terminal is electrically connected to the two terminals of the first coil and the two terminals of the second coil, respectively.

[0066] The switch control module has built-in transmitter-side switch group and receiver-side switch group. The transmitter-side switch group is connected to the current path between the transmitter interface and the second connection terminal, and is used to independently switch the topology connection mode of the first coil and the second coil in the transmission timing. The receiver-side switch group is connected to the signal path between the receiver interface and the second connection terminal, and is used to independently switch the topology connection mode of the first coil and the second coil in the reception timing.

[0067] Furthermore, the present invention also discloses a topology control method for the wiring structure of an electromagnetic ultrasonic transducer, a signal-enhanced electromagnetic ultrasonic transducer including the wiring structure of the electromagnetic ultrasonic transducer, and a detection method based on the transducer.

[0068] The topology control method for the electromagnetic ultrasonic transducer wiring structure is based on the above-mentioned electromagnetic ultrasonic transducer wiring structure and includes:

[0069] Select the corresponding topology connection method for the transmission and reception timing according to the detection requirements, control the corresponding single-pole single-throw switch to close and the other switches to open, forming a unique conducting excitation circuit and reception circuit;

[0070] The topology connection method for the launch timing includes the following three independent modes:

[0071] Transmission mode ①: The first coil is excited alone. Switches T1 and T1r are closed, and the other transmitting side switches are opened. The transmitting current flows into the first coil through the TX+ port, switch T1, and terminal A, and then flows back to the excitation circuit through terminal B, switch T1r, and TX- port, forming a closed channel.

[0072] Transmission mode ②: The first coil and the second coil are connected in series for excitation. Switches T2, T3, and T2r are closed, and the other transmitting side switches are open. The transmitting current flows into the first coil through the TX+ port, switch T2, and terminal A, then into the second coil through terminal B, switch T3, and terminal C, and finally flows back to the excitation circuit through terminal D, switch T2r, and TX- port, forming a closed channel.

[0073] Transmission mode ③: The first coil and the second coil are excited in parallel. When switches T4, T4r, T5, and T5r are closed, the other transmitting side switches are opened. The transmitting current is output from the TX+ port and then splits into two independent loops. The first loop flows into the first coil through switch T4 and terminal A, and then returns through terminal B, switch T4r, and the TX- port. The second loop flows into the second coil through switch T5 and terminal C, and then returns through terminal D, switch T5r, and the TX- port, thus forming a parallel excitation channel.

[0074] The topology connection method for receiving working timing includes the following two independent modes:

[0075] Receive mode The first coil receives signals independently. Switches R1 and R1r are closed, while the other receiving side switches are open. Switch R1r is the channel entrance for the first coil to receive signals independently. The induced signal flows into the first coil through the RX- port, switch R1r, and terminal A, and then is transmitted to the receiving circuit through terminal B, switch R1, and RX+ port, forming a transmission channel.

[0076] Receive mode The first and second coils are connected in series to receive signals. Switches R3r, R2, and R3 are closed, and the other receiving side switches are open. Switch R3r is the channel entrance for the two coils connected in series to receive signals. The induced signal flows into the first coil through the RX- port, switch R3r, and terminal A, then into the second coil through terminal B, switch R2, and terminal C, and finally to the receiving circuit through terminal D, switch R3, and RX+ port, forming a transmission channel.

[0077] The signal-enhancing electromagnetic ultrasonic transducer includes: a housing, terminals, a permanent magnet, a magnetic sheet, a magnetic cavity, a coil group, a switch control module, and a non-magnetic insulating support.

[0078] One side of the switch control module is electrically connected to the external excitation circuit and the receiving circuit, and the other side is electrically connected to the wiring terminal of the coil group through the wiring terminal, which is used to switch the topology connection mode of the transmitting operation timing and the receiving operation timing of the coil group.

[0079] The coil assembly, magnetic sheet, and permanent magnet are stacked on the non-magnetic insulating support from bottom to top. The magnetic cavity is also sleeved on the radial outer side of the permanent magnet. The magnetic cavity is a hollow rectangular frame with its bottom end fixed to the bottom plate of the outer shell, forming a semi-closed peripheral magnetic circuit. The semi-closed peripheral magnetic circuit is used to constrain the scattered magnetic lines of force of the permanent magnet and guide the magnetic lines of force to concentrate through the working area of ​​the coil assembly.

[0080] The detection method for the signal-enhanced electromagnetic ultrasonic transducer includes the following steps:

[0081] (1) Place the transducer on the surface of the test piece, and complete the electrical connection between the excitation circuit, the receiving circuit and the switch control module through the wiring terminals. Confirm that all single-pole single-throw switches of the switch control module are in the initial open state.

[0082] (2) Based on the material, thickness and attenuation characteristics of the test piece, the topology connection method of the appropriate transmission working sequence and the topology connection method of the receiving working sequence are selected through the switch control module, and the on / off state of the corresponding single-pole single-throw switch is controlled to complete the transmission and receiving topology configuration of the coil group.

[0083] (3) Start the excitation circuit and apply a high-frequency alternating excitation current to the coil group through the switch control module. Under the magnetic field constraint of the semi-closed peripheral magnetic circuit, electromagnetic ultrasonic waves are generated in the test piece. At the same time, the electromagnetic ultrasonic echo signal induced by the coil group is collected through the receiving channel switched by the switch control module to complete the thickness measurement or internal defect detection of the test piece.

[0084] (4) After the test is completed, reset all single-pole single-throw switches of the switch control module to the initial open state, disconnect the circuit connection, and remove the transducer.

[0085] Example 2

[0086] The switch control module of the electromagnetic ultrasonic transducer wiring structure is used for flexible topology configuration of the coil group. All switches in the switch control module are single-pole single-throw (SPST) mechanical switches or equivalent electronic switches, with only two states: open (0) and closed (1), and no transition state.

[0087] The switch control module is electrically connected to the transducer switch circuit and the coil group via two sets of connection terminals, respectively. In this embodiment, the transducer switch circuit includes two independent branches: an excitation circuit and a receiving circuit. The coil group includes two independent coils: a first coil and a second coil (hereinafter referred to as coil 1 and coil 2). Figure 1 As shown, the specific configuration is as follows:

[0088] 1. Circuit endpoint definition

[0089] Excitation circuit: TX+ (excitation positive terminal) and TX- (excitation loop terminal) are both connected to the output terminal of the excitation circuit of the detection instrument.

[0090] Receiving circuit: RX+ (positive signal terminal) and RX- (signal loop terminal) are both connected to the input terminal of the receiving circuit of the testing instrument.

[0091] First coil: A terminal (input terminal), B terminal (output terminal).

[0092] Second coil: C terminal (input terminal), D terminal (output terminal).

[0093] 2. Transmitter-side switch group definition (9 SPST switches in total)

[0094] T1: Located on the connection line from TX+ to end A of coil 1, used for the separate excitation channel entrance of coil 1 (Note: T1, T2, and T4 are all connected from TX+ to end A of coil 1, belonging to three independent excitation channels, and are used mutually exclusively).

[0095] T1r: Located on the connection line from the B end of coil 1 to TX-, used for the separate excitation channel outlet of coil 1 (r represents the loop end).

[0096] T2: Located on the connection line from TX+ to the A end of coil 1, used as the entrance to the series excitation channel of coil 1 and coil 2.

[0097] T2r: Located on the connection line from the D end of coil 2 to TX-, used as the outlet of the series excitation channel of coil 1 + coil 2.

[0098] T3: Set on the bridging line from the B end of coil 1 to the C end of coil 2, it is a bridging switch (bridge) for the series excitation channel, so that the current flows from coil 1 to coil 2.

[0099] T4: Located on the connection line from TX+ to the A end of coil 1, used as the entrance for the parallel excitation channel of coil 1.

[0100] T4r: Located on the connection line from the B end of coil 1 to TX-, used for the parallel excitation channel outlet of coil 1.

[0101] T5: Located on the connection line from TX+ to the C end of coil 2, used as the entrance for the parallel excitation channel of coil 2.

[0102] T5r: Located on the connection line from the D end of coil 2 to TX-, used for the parallel excitation channel outlet of coil 2.

[0103] 3. Receiver-side switch group definition (5 SPST switches in total)

[0104] R1: Located on the connection line from the B end of coil 1 to RX+, used for the separate receiving channel output of coil 1.

[0105] R1r: Located on the connection line from RX- to end A of coil 1, used for the separate receiving channel entrance of coil 1.

[0106] R2: Located on the bridging wire from terminal B of coil 1 to terminal C of coil 2, it serves as a bridging switch (bridge) for the series receiving channel, allowing the induced electromotive force to flow from coil 1 to coil 2 and be superimposed. This switch is shared by all series receiving modes to reduce the total number of switches on the receiving side.

[0107] R3: Located on the connection line from the D end of coil 2 to RX+, used for series connection of the receiving channel output.

[0108] R3r: Located on the connection line connecting RX- to end A of coil 1, used for series connection of the receiving channel entrance.

[0109] Therefore, a topology control method for the wiring structure of an electromagnetic ultrasonic transducer is provided, including:

[0110] Select the corresponding transmission and reception topology connection methods according to the detection requirements, control the corresponding single-pole single-throw switch to close and the other switches to open, forming a unique conducting excitation circuit and reception circuit.

[0111] The topology connection method of the transmission timing includes three transmission modes, and the topology connection method of the reception timing includes two reception modes, as detailed below.

[0112] Transmission mode ①: Coil 1 is excited alone. In this case, when switches T1 and T1r are closed, the transmission current path is: TX+ → T1 → Terminal A of coil 1 → Coil 1 → Terminal B of coil 1 → T1r → TX-.

[0113] Transmission mode ②: Coil 1 and coil 2 are excited in series. At this time, when switches T2, T3 and T2r are closed, the transmission current path is: TX+ → T2 → terminal A of coil 1 → coil 1 → terminal B of coil 1 → T3 → terminal C of coil 2 → coil 2 → terminal D of coil 2 → T2r → TX-.

[0114] Transmission mode ③: Coil 1 and coil 2 are excited in parallel. At this time, when switches T4, T4r, T5 and T5r are closed, the transmission current path includes two parallel independent branches 1 and 2 that do not cross-connect. Among them, branch 1 is: TX+→T4→A terminal of coil 1→coil 1→B terminal of coil 1→T4r→TX-; branch 2 is: TX+→T5→C terminal of coil 2→coil 2→D terminal of coil 2→T5r→TX-.

[0115] Receive mode : Coil 1 receives signals alone. At this time, when switches R1 and R1r are closed, the signal path is: RX- → R1r → Terminal A of Coil 1 → Coil 1 → Terminal B of Coil 1 → R1 → RX+.

[0116] Receive mode : Coil 1+2 connected in series for reception (signal enhancement reception). At this time, when switches R3r, R2 and R3 are closed, the received signal path is: RX- → R3r → A terminal of coil 1 → coil 1 → B terminal of coil 1 → R2 → C terminal of coil 2 → coil 2 → D terminal of coil 2 → R3 → RX+.

[0117] Therefore, by establishing the legal pairing relationships between the three transmission modes and the two reception modes, five legal operating modes can be obtained, namely:

[0118] Operating mode 1: Coil 1 is excited alone + Coil 1 is received alone

[0119] The transmitting side switch group is configured with switches T1 and T1r closed, and the rest open; the receiving side switch group is configured with switches R1 and R1r closed, and the rest open. The transmitting current path is: TX+ → T1 → terminal A of coil 1 → coil 1 → terminal B of coil 1 → T1r → TX-; the receiving signal path is: RX- → R1r → terminal A of coil 1 → coil 1 → terminal B of coil 1 → R1 → RX+. In this mode, only coil 1 participates in excitation and reception. The coil impedance and excitation current are moderate, and the receiving sensitivity is average, making it suitable for benchmark testing scenarios to evaluate the basic performance of the transducer.

[0120] Operating mode 2: Coil 1 is excited individually + coil group is received in series

[0121] The transmitting side switch group is configured the same as in operating mode one (only switches T1 and T1r are closed); the receiving side switch group is configured with switches R3r, R2, and R3 closed, and switches R1 and R1r open. The received signal path is: RX- → R3r → terminal A of coil 1 → coil 1 → terminal B of coil 1 → R2 → terminal C of coil 2 → coil 2 → terminal D of coil 2 → R3 → RX+. This mode is one of the core preferred modes of this invention: during transmission, only coil 1 is involved, with moderate impedance and moderate excitation current; during reception, coils 1 and 2 are connected in series, and the induced electromotive forces are superimposed, resulting in a received signal amplitude approximately twice that of a single coil, high receiving sensitivity, and achieving functional separation of efficient excitation by a single coil and enhanced reception by dual coils.

[0122] Operating Mode 3: Series Excitation of Coil Groups + Series Reception of Coil Groups

[0123] The transmitting side switch group is configured with switches T2, T3, and T2r closed, and the remaining transmitting side switches open; the receiving side switch group is configured the same as in operating mode two. The transmitting current path is: TX+ → T2 → terminal A of coil 1 → coil 1 → terminal B of coil 1 → T3 → terminal C of coil 2 → coil 2 → terminal D of coil 2 → T2r → TX-. In this mode, the two coils are connected in series during transmission, with a total impedance approximately twice that of a single coil, resulting in minimal excitation current; during reception, the two coils are connected in series, leading to high receiving sensitivity, making it suitable for detection scenarios requiring a balance between excitation coverage and receiving sensitivity.

[0124] Operating Mode 4: Parallel excitation of coil groups + individual reception of coil 1

[0125] The transmitting-side switch group is configured such that switches T4, T4r, T5, and T5r are closed, while the remaining transmitting-side switches are open; the receiving-side switch group is configured such that switches R1 and R1r are closed, while the remaining receiving-side switches are open. The transmitting current path consists of two parallel, independent, and non-overlapping branches. Branch 1 is: TX+ → T4 → Terminal A of Coil 1 → Coil 1 → Terminal B of Coil 1 → T4r → TX-; Branch 2 is: TX+ → T5 → Terminal C of Coil 2 → Coil 2 → Terminal D of Coil 2 → T5r → TX-. In this mode, the two coils are connected in parallel during transmission, and the total impedance is approximately half that of a single coil, resulting in the maximum excitation current and generating the strongest ultrasonic excitation, suitable for detecting thick-walled components or highly attenuated materials.

[0126] Operating Mode 5: Parallel excitation of coil groups + series reception of coil groups

[0127] The transmitting-side switch group is configured the same as in operating mode four (T4, T4r, T5, T5r closed); the receiving-side switch group is configured with switches R3r, R2, and R3 closed, and switches R1 and R1r open. This mode is another core preferred mode of the invention: during transmission, the two coils are connected in parallel, resulting in the minimum total impedance and the maximum excitation current; during reception, the two coils are connected in series, resulting in high receiving sensitivity. Combining maximum excitation energy and highest receiving sensitivity, it achieves the optimal signal-to-noise ratio, making it particularly suitable for applications involving remote defect detection or severe signal attenuation.

[0128] The performance characteristics of the five legal operating modes are summarized in Table 1.

[0129] Table 1. Correspondence between Transmit / Receive Operating Modes

[0130]

[0131] Note 1: The transmission path is marked according to the current direction (TX+→…→TX-); the reception path is marked according to the direction of the induced signal flow (RX-→…→RX+).

[0132] Note 2: In transmit mode ① (coil 1 is energized alone) combined with receive mode When receiving in series with coil groups, coil 2 only participates in inductive reception and is not excited, realizing single-excitation-dual-coil enhanced reception, which can effectively increase the amplitude of the received signal.

[0133] Example 3

[0134] The coil assembly can be constructed using a two-wire parallel winding method; this embodiment details its structure and connection method. (Refer to...) Figure 4 and Figure 5Coil 1 and coil 2 are wound side by side in the same plane, coplanar, and form a concentric spiral. The wires of the two coils are arranged alternately and wound synchronously from the center outwards. The two ends of coil 1 are defined as end A (input end) and end B (output end), and the two ends of coil 2 are defined as end C (input end) and end D (output end).

[0135] (a) Series connection

[0136] like Figure 4 As shown, when the coils are connected in series, terminal B of coil 1 is directly connected to terminal C of coil 2. The current direction is sequentially through terminal A → coil 1 → terminal B → terminal C → coil 2 → terminal D. Series connection requires the two coils to be wound in the same direction to ensure that the current direction in both coils is the same and the resulting magnetic field direction is superimposed and enhanced. After series connection, the total number of turns is the sum of the number of turns of the two coils, and the total impedance is approximately twice the impedance of a single coil. When used in receiving mode (receiving mode B), the induced electromotive forces generated by the two coils are superimposed, and the total induced voltage is approximately twice the induced voltage of a single coil, which can significantly improve the receiving sensitivity.

[0137] (ii) Parallel connection

[0138] like Figure 5 As shown, when the coil groups are connected in parallel, terminal A of coil 1 is electrically connected to terminal C of coil 2 as the parallel input terminal, and terminal B of coil 1 is electrically connected to terminal D of coil 2 as the parallel output terminal. Parallel connection requires that the current flows in the two coils in the same direction so that the magnetic fields they generate are in the same direction. After parallel connection, the total impedance is approximately half the impedance of a single coil, and under the same excitation voltage, approximately twice the total excitation current of a single coil can be obtained, which is beneficial for increasing the ultrasonic excitation amplitude.

[0139] Example 4

[0140] The coil group can also be stacked vertically; this embodiment describes its structure and connection method in detail. See also... Figure 6 and Figure 7 Coil 1 is located below (closer to the device under test), and coil 2 is located above (closer to the magnetic sheet). They are spatially stacked, one above the other. The two coils have the same planar dimensions and their central axes are aligned. An insulating film separates the two coils to prevent short circuits between the wires. The advantages of this stacked structure are: the centers of the two coils completely coincide, occupying roughly the same space as a single coil; simultaneously, coil 1, closer to the device under test, is in an optimal position for both excitation and reception, which helps improve transduction efficiency.

[0141] (a) Series connection

[0142] like Figure 6As shown, when the coil groups are stacked and connected in series, the connection method is the same as that of two parallel-wound coils connected in series: connect the B end of coil 1 to the C end of coil 2 to ensure that the current directions of the two coils are consistent and the magnetic fields are superimposed. The total induced voltage in series is approximately the sum of the two coils, which is suitable for high-sensitivity receiving applications.

[0143] (ii) Parallel connection

[0144] like Figure 7 As shown, when the coil groups are stacked and connected in parallel, the connection method is the same as that of the two-wire parallel winding: terminals A and C are connected as input, and terminals B and D are connected as output, ensuring that the current directions of the two coils are consistent. After parallel connection, the total impedance is reduced, and a larger excitation current can be obtained under the same excitation voltage, which is suitable for high-efficiency emission applications.

[0145] Example 5

[0146] This embodiment provides the overall assembly structure of the signal-enhancing electromagnetic ultrasonic transducer.

[0147] Reference Figure 2 The signal-enhancing electromagnetic ultrasonic transducer includes, from top to bottom: a terminal block 34, a housing assembly 1, a permanent magnet 22, a magnetic conductive sheet 23, a coil group (including a first coil 31 and a second coil 32), a non-magnetic insulating support 4, and a magnetic conductive cavity 21 provided on the outside of the permanent magnet 22, the bottom end of which is connected to the bottom plate 13 of the housing.

[0148] The outer casing assembly consists of three parts: a top cover 11, a side portion 12, and a bottom plate 13, all made of non-magnetic materials (such as aluminum alloy or engineering plastics). The bottom plate has an opening, and the non-magnetic insulating support 4 is embedded within this opening, thus forming a closed cavity together with the outer casing assembly for mechanical protection and structural support, fixing the internal components of the transducer as a single unit. In a specific embodiment, the embedding is achieved as follows: the size of the opening is slightly larger than the diameter of the non-magnetic insulating support 4, by an equivalent amount of 0.1mm to 1mm, and then the edge of the non-magnetic insulating support is tightly connected to the edge of the opening. This tight connection can be achieved using a liquid colloid.

[0149] Terminal 34 is located above the top cover 11 of the housing and is used for electrical connection between the internal coil group of the transducer and the external switch control module 5. The terminals (A, B, C, and D) of the coil group are led out to the outside through wires and then connected to the switch control module 5 through wires. The other side of the switch control module 5 is connected to the excitation circuit wiring port 61 and the receiving circuit wiring port 62 of the detection instrument through wires.

[0150] The permanent magnet 22 is located inside the transducer and can be made of neodymium iron boron (NdFeB) or similar strong magnetic materials. It is used to generate a high-intensity static bias magnetic field on the surface of the test piece 7, providing the necessary static magnetic field conditions for the electromagnetic ultrasonic transduction mechanism. The typical dimensions of the permanent magnet 22 are 30 mm × 20 mm × 30 mm, and the magnetization direction is vertical (perpendicular to the surface of the test piece 7).

[0151] The magnetic guide plate 23 is located directly below the permanent magnet 22 and is made of a soft magnetic material with high permeability. The magnetic guide plate 23 guides the magnetic field lines to concentrate and penetrate into the surface area of ​​the test piece 7, reducing magnetic flux dissipation and increasing the effective magnetic field strength. The thickness of the magnetic guide plate 23 is 0.25–3 mm, and its planar dimensions match the bottom surface of the permanent magnet 22.

[0152] The magnetically conductive cavity 21 is fitted around the permanent magnet 22 and is made of a high-permeability magnetic material, forming a semi-closed peripheral magnetic circuit. The magnetically conductive cavity 21 is a hollow rectangular frame with inner wall dimensions adapted to the shape of the permanent magnet 22, and a wall thickness of 1–5 mm. The bottom end of the magnetically conductive cavity 21 is connected to the bottom plate 13 of the transducer housing, allowing magnetic lines of force to originate from the permanent magnet 22, pass through the side wall of the magnetically conductive cavity 21 and the bottom plate 13 of the housing, and ultimately form a more concentrated and uniform magnetic field distribution on the surface of the test piece 7, significantly improving the effective magnetic field strength.

[0153] The non-magnetic insulating support 4 is located below the coil assembly, closely attached to the inner side of the outer casing base plate 13. The non-magnetic insulating support can be made of yttrium-stabilized zirconia ceramic material with a thickness of 0.1–1 mm. The function of the non-magnetic insulating support is twofold: firstly, to provide sufficient hardness and toughness to support and protect the coil assembly. Hardness is for wear resistance, ensuring the support does not thin or deform after repeated sliding, while toughness ensures it is not easily broken upon impact. Secondly, the ceramic sheet has good insulation properties, preventing short circuits between the coil assembly and the outer casing base plate 13, and also preventing the generation of ultrasonic waves due to the shielding of eddy currents generated by the coil on the surface of the workpiece being inspected.

[0154] The coil assembly is located below the magnetic sheet 23, and the entire effective winding area is attached to the surface of the coaxially placed non-magnetic insulating support 4. The coil assembly includes two independently wound helical coils, a first coil 31 and a second coil 32.

[0155] In electromagnetic ultrasonic testing, the effective acoustic field area generated by the coil in the test piece is related to the coil diameter as follows: the larger the coil diameter, the wider the acoustic field coverage area, but the spatial resolution and detection sensitivity for small-sized local defects decrease accordingly. Considering both the requirements for excitation intensity and detection sensitivity, the coil diameter range is determined to be 5–20 mm: an upper limit of 20 mm to ensure sufficient sensitivity, and a lower limit of 5 mm to meet the minimum excitation area requirement, while also taking into account the feasibility of manufacturing processes.

[0156] Regardless of whether the excitation is AC or DC, when the conductor diameter is small (d < 0.05 mm), the coil resistance increases significantly, leading to a decrease in the transducer's transmission efficiency, a reduction in power transmission efficiency, and a deterioration in the signal-to-noise ratio of the received signal. Therefore, 0.05 mm is selected as a reasonable lower limit for the conductor diameter.

[0157] The wire diameter is also coupled with the coil size and number of turns. With a fixed number of turns N, increasing the wire diameter d will directly lead to an increase in the coil's outer diameter Dc. When d > 0.3 mm and the number of turns N ≥ 10, the coil's outer diameter will exceed the design range of 5–20 mm, or force a significant reduction in the number of turns, thus affecting the magnetic flux intensity generated by the coil. Therefore, d = 0.3 mm is set as the upper limit for the wire diameter.

[0158] Therefore, based on the relationship between the wire diameter, the number of turns, and the coil diameter, the coil groups are all wound with enameled wire with a diameter of 0.05 to 0.3 mm, each coil has 10 to 60 turns, and the coil diameter is 5 to 20 mm. The leads of each coil are led out through coil leads 33 and connected to terminals 34.

[0159] Comparative Example 1

[0160] This comparative example verifies, through comparative experiments, the enhancement effect of the peripheral magnetic circuit formed by the magnetic cavity 21 and the magnetic sheet 23 on the electromagnetic ultrasonic receiving signal.

[0161] The experimental conditions are as follows: Test piece 7 is a carbon steel specimen with a thickness of 10 mm and dimensions of 100 mm × 100 mm; a single tightly wound spiral coil with a diameter of 15 mm is used; permanent magnet 22 is a neodymium iron boron permanent magnet with dimensions of 30 mm × 20 mm × 30 mm. The EMAT excitation frequency is 4 MHz, and the operating mode is mode one (single coil transceiver).

[0162] Adopting such Figure 3 The single-coil structure shown in the figure acquires the received signal without an external magnetic circuit (i.e. without the magnetic cavity 21 and the magnetic sheet 23). The waveform of the received signal is shown in Figure 8(a): the peak-to-peak value of the first bottom surface echo 81 is 0.81 V, and the second bottom surface echo 82 is visible.

[0163] Under the same conditions of coil and permanent magnet, the received signal waveform obtained by using the signal-enhancing electromagnetic ultrasonic transducer of the present invention (after adding the magnetic cavity 21 and the magnetic circuit around the magnetic sheet 23) is shown in Figure 8(b): the peak-to-peak value of the primary bottom echo 81 is increased to 0.95 V, and the secondary bottom echo 82 is also visible. The signal amplitude is increased by about 17.3%, and the signal-to-noise ratio is improved.

[0164] The above experimental results show that by constructing a complete peripheral magnetic circuit (magnetic cavity 21 + magnetic sheet 23), the magnetic field line dissipation of permanent magnet 22 can be effectively reduced, and more magnetic flux can be concentrated on the surface of the test piece 7, thereby increasing the static bias magnetic field strength and increasing the excitation and reception amplitude of electromagnetic ultrasonic signals, thus verifying the effectiveness of the magnetic circuit improvement scheme of the present invention.

[0165] Comparative Example 2

[0166] This comparative example uses a comparative experiment: under the same transmission mode①, different reception modes are used respectively. and receiving mode To verify the signal enhancement effect of the dual-coil series receiving mode compared to the single-coil transceiver mode, the experimental conditions are as follows, referring to Figure 9: no new magnetic circuit structure was used; the effect of changing the coil wiring method on the received signal amplitude was verified independently; the coil parameters and magnet parameters were the same as those in Comparative Example 1; the test piece 7 was an aluminum alloy specimen with a thickness of 10 mm and dimensions of 100 mm × 100 mm. The EMAT excitation frequency was 4 MHz.

[0167] Figure 9(a) shows a transceiver structure using a single helical coil (corresponding to transmission mode ① + reception mode). The received signal waveform at that time is shown. The peak-to-peak value of the first bottom echo 81 is 1.59 V, and the second bottom echo 82 can be seen.

[0168] Figure 9(b) shows a transmission using the same single coil (coil 1) and a reception using two identical coils stacked in series (corresponding to transmission mode ① + reception mode). The received signal waveform shows that the peak-to-peak value of the first bottom echo 81 is increased to 2.35 V, the signal amplitude is increased by about 47.8%, and the receiving sensitivity is greatly improved.

[0169] The above experimental results show that the working mode of using single-coil excitation and dual-coil series reception (transmit mode ① + receive mode ②) is effective. Without changing the excitation conditions, the received signal amplitude can be increased to 1.48 times its original value by superimposing the induced electromotive forces of the two coils in series. This result fully verifies the effectiveness of the dual-coil operating mode design of this invention.

[0170] Example 6

[0171] This embodiment provides a specific implementation method for the detection of a signal-enhanced electromagnetic ultrasonic transducer, which combines peripheral magnetic circuit enhancement (magnetic cavity 21 + magnetic sheet 23) with a dual-coil parallel excitation-series receiving mode (transmit mode ③ + receiving mode). This combination enables typical application scenarios for comprehensive signal enhancement, suitable for thick-walled steel pipes, high-attenuation ferromagnetic materials, etc.

[0172] The specific operating procedure is as follows:

[0173] The first step is to check the surface condition of the test piece 7 (such as a steel pipe or steel plate), remove the severely rusted areas (generally, oxide layers with a rust thickness greater than 0.5 mm need to be polished, while rust less than 0.5 mm does not need to be polished and can be directly tested by electromagnetic ultrasound), and place the signal-enhancing electromagnetic ultrasound transducer on the surface of the test piece 7 (such as a steel pipe or steel plate).

[0174] The second step is to connect terminal 34 to switch control module 5 via wires. Switch control module 5 is then connected to the excitation circuit of the testing instrument via excitation circuit terminal 61 and to the receiving circuit of the testing instrument via receiving circuit terminal 62. After connection, confirm that all switches are in the off state (initial state of all 0s).

[0175] The third step is to select the working mode according to the testing requirements: For thick-walled steel pipes (wall thickness not less than 20 mm) or ferromagnetic materials with severe signal attenuation, the working mode five (parallel excitation + series reception) should be selected first to obtain the maximum excitation current and the highest receiving sensitivity; for steel plates of general thickness (wall thickness 3 to 15 mm), the working mode two (single coil excitation + series reception) can be selected to improve the receiving sensitivity while maintaining the maximum excitation current.

[0176] The fourth step is to configure the switch states according to the switch state truth table shown in Table 2 via the switch control module 5 to complete the working mode switching. During switching, the principle of "disconnect before connecting" must be followed: first disconnect all closed switches of the previous mode, and then close the switch corresponding to the new mode to avoid short circuits or false triggering in the intermediate state.

[0177] Table 2 Truth Table of Switch States (1 = Closed, 0 = Open)

[0178]

[0179] In the table, 1 indicates that the switch is closed, and 0 indicates that the switch is open.

[0180] It should be noted that in the transmitter-side switch group, switches T1 and T1r, switches T2, T2r and T3, and switches T4, T4r, T5 and T5r each constitute a transmission mode switch group. These mode switches are mutually exclusive, and only one group is active at any given time. Similarly, in the receiver-side switch group, the two groups of mode switches R1 and R1r and R2, R3 and R3r are mutually exclusive.

[0181] The fifth step involves applying a high-frequency alternating current (typically 0.5–10 MHz, with an excitation pulse width of 1–5 sine cycles) to the coil group via the excitation circuit of the testing instrument, thereby generating ultrasonic waves in the test piece 7. The receiving circuit of the testing instrument acquires the induced signal from the coil group in real time, and displays the ultrasonic wave pattern after A / D conversion and signal processing. By analyzing the arrival time and amplitude of the bottom echo, thickness measurement and internal defect detection are achieved.

[0182] Step 6: After the test is completed, reset all switches to the off state (all 0 initial state), then disconnect the connecting wires between the transducer and the switch control module, and finally remove the transducer and store it properly.

[0183] Compared with traditional single-coil electromagnetic ultrasonic transducers without external magnetic circuits, the signal-enhancing electromagnetic ultrasonic transducer of this invention can improve the overall signal amplitude by more than 50%, effectively improving the detection signal-to-noise ratio and enhancing the reliability of non-destructive testing.

Claims

1. A wiring structure for an electromagnetic ultrasonic transducer, characterized in that, The structure includes: a first coil, a second coil, and a switch control module; The switch control module has two sets of connection terminals. The first connection terminal includes an independent transmitting interface and a receiving interface. The transmitting interface is electrically connected to the output terminal of the excitation circuit of the detection instrument, and the receiving interface is electrically connected to the input terminal of the receiving circuit of the detection instrument. The second connection terminal is electrically connected to the two terminals of the first coil and the two terminals of the second coil, respectively. The switch control module has built-in transmitter-side switch group and receiver-side switch group. The transmitter-side switch group is connected to the current path between the transmitter interface and the second connection terminal, and is used to independently switch the topology connection mode of the first coil and the second coil in the transmission timing. The receiver-side switch group is connected to the signal path between the receiver interface and the second connection terminal, and is used to independently switch the topology connection mode of the first coil and the second coil in the reception timing.

2. The wiring structure of the electromagnetic ultrasonic transducer according to claim 1, characterized in that, The first coil includes terminal A and terminal B, and the second coil includes terminal C and terminal D; The transmitting interface includes a TX+ port and a TX- port, which are electrically connected to the TX+ and TX- terminals of the excitation circuit, respectively; the receiving interface includes an RX+ port and an RX- port, which are electrically connected to the RX+ and RX- terminals of the receiving circuit, respectively. The transmitting-side switch group includes single-pole single-throw switches T1, T1r, T2, T2r, T3, T4, T4r, T5, and T5r; wherein, switches T1, T2, and T4 are connected in parallel in the path between the TX+ port and terminal A, and are used to selectively connect the transmission channel from the TX+ port to terminal A; switches T1r and T4r are connected in parallel in the path between terminal B and the TX- port, and are used to selectively connect the transmission channel from terminal B to the TX- port; switch T3 is a switch located between terminal B and terminal C, and is used to allow current to flow from the first coil to the second coil; switch T5 is a switch located between the TX+ port and terminal C; switches T2r and T5r are parallel switches located in the path between terminal D and the TX- port, and are used to selectively connect the transmission channel from terminal D to the TX- port. The receiving-side switch group includes single-pole single-throw switches R1, R1r, R2, R3, and R3r; wherein, switches R1r and R3r are connected in parallel in the path between the RX- port and terminal A, and are used to selectively conduct the transmission channel between the RX- port and terminal A; switch R1 is a switch located between terminal B and the RX+ port; switch R3 is a switch located between terminal D and the RX+ port; switch R2 is a switch located between terminal B and terminal C, and is used to allow the induced current to flow from the first coil to the second coil for superposition.

3. The wiring structure of the electromagnetic ultrasonic transducer according to claim 2, characterized in that: The transmitter-side switch group forms three excitation channels, including: A separate excitation channel for the first coil is formed by the cooperation of switches T1 and T1r, which is used to separately supply excitation current to the first coil; Switches T2, T3 and T2r work together to form a series excitation channel for the first and second coils, which is used to sequentially supply excitation current to the two coils connected in series. Switches T4, T4r, T5, and T5r work together to form a parallel excitation channel for the first and second coils, which is used to supply excitation current to the two parallel coils in parallel.

4. The wiring structure of the electromagnetic ultrasonic transducer according to claim 2, characterized in that: The receiving-side switch group forms two receiving channels, including: A separate receiving channel for the first coil is formed by the cooperation of switch R1r and R1, wherein switch R1r serves as the channel entrance for the separate receiving of the first coil. A receiving channel for the first and second coils is formed by the cooperation of switches R3r, R2 and R3, wherein switch R3r serves as the channel entrance for the two coils to receive data in series.

5. The wiring structure of the electromagnetic ultrasonic transducer according to claim 1, characterized in that, The first coil and the second coil are enameled wire coils with the same parameters. They are arranged in a double-wire parallel winding method in the same plane, in a concentric spiral shape, with the wires arranged alternately and wound synchronously from the center outward; or they are arranged in an overlapping manner, with the first coil located on the lower side near the test piece and the second coil located on the upper side. The two coils have the same plane size and their central axes are aligned, and an insulating layer is provided between the coils.

6. The wiring structure of the electromagnetic ultrasonic transducer according to claim 5, characterized in that, The first and second coils are two independently wound helical coils, both wound with enameled wire with a diameter of 0.05 to 0.3 mm. Each coil has 10 to 60 turns and a diameter of 5 to 20 mm.

7. A topology control method based on the wiring structure of an electromagnetic ultrasonic transducer according to any one of claims 1 to 6, characterized in that, include: Select the corresponding topology connection method for the transmission and reception timing according to the detection requirements, control the corresponding single-pole single-throw switch to close and the other switches to open, forming a unique conducting excitation circuit and reception circuit; The topology connection method for the launch timing includes the following three independent modes: Transmission mode ①: The first coil is excited alone. Switches T1 and T1r are closed, and the other transmitting side switches are opened. The transmitting current flows into the first coil through the TX+ port, switch T1, and terminal A, and then flows back to the excitation circuit through terminal B, switch T1r, and TX- port, forming a closed channel. Transmission mode ②: The first coil and the second coil are connected in series for excitation. Switches T2, T3, and T2r are closed, and the other transmitting side switches are open. The transmitting current flows into the first coil through the TX+ port, switch T2, and terminal A, then into the second coil through terminal B, switch T3, and terminal C, and finally flows back to the excitation circuit through terminal D, switch T2r, and TX- port, forming a closed channel. Transmission mode ③: The first coil and the second coil are excited in parallel. When switches T4, T4r, T5, and T5r are closed, the other transmitting side switches are opened. The transmitting current is output from the TX+ port and then splits into two independent loops. The first loop flows into the first coil through switch T4 and terminal A, and then returns through terminal B, switch T4r, and the TX- port. The second loop flows into the second coil through switch T5 and terminal C, and then returns through terminal D, switch T5r, and the TX- port, thus forming a parallel excitation channel. The topology connection method for receiving working timing includes the following two independent modes: Receive mode The first coil receives signals independently. Switches R1 and R1r are closed, while the other receiving side switches are open. Switch R1r is the channel entrance for the first coil to receive signals independently. The induced signal flows into the first coil through the RX- port, switch R1r, and terminal A, and then is transmitted to the receiving circuit through terminal B, switch R1, and RX+ port, forming a transmission channel. Receive mode The first and second coils are connected in series to receive signals. Switches R3r, R2, and R3 are closed, and the other receiving side switches are open. Switch R3r is the channel entrance for the two coils connected in series to receive signals. The induced signal flows into the first coil through the RX- port, switch R3r, and terminal A, then into the second coil through terminal B, switch R2, and terminal C, and finally is transmitted to the receiving circuit through terminal D, switch R3, and RX+ port, forming a transmission channel.

8. A signal-enhancing electromagnetic ultrasonic transducer, characterized in that, include: Housing, terminals, permanent magnet, magnetic sheet, magnetic cavity, coil assembly, switch control module, and non-magnetic insulating support; The wiring terminals are fixedly installed on the top of the housing; One side of the switch control module is electrically connected to the external excitation circuit and the receiving circuit, and the other side is electrically connected to the wiring terminal of the coil group through the wiring terminal, which is used to switch the topology connection mode of the transmitting operation timing and the receiving operation timing of the coil group. The bottom plate of the outer shell has an opening, and the non-magnetic insulating support is embedded in the opening, forming a closed bottom surface of the outer shell together with the bottom plate. The coil group, magnetic conductive sheet, and permanent magnet are stacked on the non-magnetic insulating support from bottom to top. The magnetic conductive cavity is also sleeved on the radial outer side of the permanent magnet. The magnetic conductive cavity is a hollow rectangular frame, and its bottom end is fixed to the bottom plate of the outer shell, forming a semi-closed peripheral magnetic circuit. The semi-closed peripheral magnetic circuit is used to constrain the scattered magnetic lines of force of the permanent magnet and guide the magnetic lines of force to concentrate through the working area of ​​the coil group.

9. The signal-enhancing electromagnetic ultrasonic transducer according to claim 8, characterized in that, The coil group and the switch control module adopt the transducer wiring structure described in any one of claims 1 to 6.

10. A detection method based on the signal-enhancing electromagnetic ultrasonic transducer according to any one of claims 8 to 9, characterized in that, Includes the following steps: (1) Place the transducer on the surface of the test piece, and complete the electrical connection between the excitation circuit, the receiving circuit and the switch control module through the wiring terminals. Confirm that all single-pole single-throw switches of the switch control module are in the initial open state. (2) Based on the material, thickness and attenuation characteristics of the test piece, the topology connection method of the appropriate transmission working sequence and the topology connection method of the receiving working sequence are selected through the switch control module, and the on / off state of the corresponding single-pole single-throw switch is controlled to complete the transmission and receiving topology configuration of the coil group. (3) Start the excitation circuit and apply a high-frequency alternating excitation current to the coil group through the switch control module. Under the magnetic field constraint of the semi-closed peripheral magnetic circuit, electromagnetic ultrasonic waves are generated in the test piece. At the same time, the electromagnetic ultrasonic echo signal induced by the coil group is collected through the receiving channel switched by the switch control module to complete the thickness measurement or internal defect detection of the test piece. (4) After the test is completed, reset all single-pole single-throw switches of the switch control module to the initial open state, disconnect the circuit connection, and remove the transducer.

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