Workpiece electromagnetic forming method and device based on eddy current attraction

Abstract

The invention belongs to the field of metal electromagnetic forming manufacturing, particularly relates to a workpiece electromagnetic forming method and device based on vortex attraction, and aims to solve the problem of axial non-uniformity of a pipe fitting or the problem of radial non-uniformity of a plate in a traditional electromagnetic forming technology. A conductor is introduced into the middle of a driving coil, eddy current induced in the conductor and eddy current in a to-be-formed metal workpiece mutually generate electromagnetic attraction force according to the eddy current attraction principle, the electromagnetic attraction force is opposite to electromagnetic force for workpiece forming machining in direction, and the deformation amount of the middle of the workpiece is reduced; uniform deformation of the pipe fitting in the axial direction or uniform deformation of the plate piece in the radial direction is achieved. According to the method, the quality and precision of the formed workpiece are improved, and new possibility is provided for further application of the electromagnetic forming technology in the field of high-precision manufacturing.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal electromagnetic forming manufacturing, and in particular relates to a workpiece electromagnetic forming method and device based on eddy current attraction. Background Art

[0002] Electromagnetic forming (EMF) is an advanced manufacturing technology that uses pulsed electromagnetic forces to rapidly deform conductive materials. Its core principle is to generate a transient, strong magnetic field through a drive coil, inducing eddy currents in the workpiece, which in turn generates electromagnetic force to deform the material. This technology, with its advantages of high efficiency, contactlessness, high precision, and adaptability to complex shape processing, has led to its widespread application in a variety of technical fields, including aerospace, automotive manufacturing, and electronics and electrical appliances. In aerospace, EMF is commonly used to manufacture lightweight, high-strength metal components, such as aircraft skins, titanium alloy plates, and complex curved structures, to meet the lightweight and high-performance requirements of aircraft. In automotive manufacturing, the technology is used to manufacture body panels, aluminum alloy pipes, and special-shaped connectors, contributing to vehicle lightweighting and improved fuel efficiency. In the electronics and electrical industry, EMF is suitable for the precision machining of micro-metal components, such as mobile phone casings or conductive tubing, to meet the requirements of high precision and miniaturization. In recent years, with the increasing demand for high-strength, corrosion-resistant metal materials, the technology has also shown promising application prospects in areas such as shipbuilding and energy equipment.

[0003] Compared with traditional processing methods such as mechanical stamping and hydraulic forming, electromagnetic forming technology has significant advantages. First, it does not require physical molds, avoiding the complexity and high cost of mold design and manufacturing, and is particularly suitable for small-batch, high-variety production models. Second, electromagnetic forming can achieve high-speed processing and a short forming cycle, significantly improving production efficiency. In addition, because the electromagnetic force acts directly on the interior of the workpiece, the material is evenly stressed, and the rebound and residual stress generated during the forming process are relatively small, which helps to improve the geometric accuracy and mechanical properties of the formed parts. These characteristics make electromagnetic forming a competitive technology in modern manufacturing.

[0004] However, existing electromagnetic forming technology still faces some challenges in practical applications, especially in the processing of plates and pipes. For plate forming, the electromagnetic force generated by the driving coil is usually concentrated in the middle of the plate, resulting in uneven deformation in the radial direction, which is specifically manifested as excessive bulge in the middle and insufficient deformation in the edge area. This unevenness not only affects the dimensional accuracy of the formed part, but may also cause material cracks or strength loss in the excessively deformed area, limiting the application of this technology in the field of high-precision manufacturing. For pipe forming, the electromagnetic force in traditional methods is unevenly distributed along the axial direction, the deformation in the middle area of ​​the pipe is large, and the deformation at both ends is insufficient, forming a "waist drum-shaped" defect, which also affects the forming quality and the accuracy of subsequent assembly. These problems are particularly prominent when processing high-strength materials or complex geometric shapes, and have become a bottleneck restricting the development of electromagnetic forming technology.

[0005] To solve these defects, researchers have tried a variety of improvement methods. For example, by optimizing the design of the driving coil, adjusting the shape, number of turns and position of the coil to improve the uniformity of the distribution of the electromagnetic force; or by adjusting the discharge parameters, such as the discharge voltage and current waveform, to control the magnitude and action time of the electromagnetic force. These methods have alleviated the problem of deformation unevenness to a certain extent, but the effect is limited and has not fundamentally solved the problem. In recent years, some studies have begun to explore the introduction of auxiliary magnetic fields or changing the relative position of the workpiece and the coil to further optimize the distribution of electromagnetic force. However, these solutions often increase the complexity and operational difficulty of the production and manufacturing system, and their practicality in actual production is limited. In addition, existing improvement measures are mostly focused on adjusting the distribution of electromagnetic repulsion, and less attention is paid to balancing the deformation process by introducing new force mechanisms.

[0006] In view of the shortcomings of traditional electromagnetic forming technology, there is an urgent need for an innovative method and device that can solve the problem of uneven deformation of plates and pipes from a physical mechanism perspective. Summary of the Invention

[0007] The present invention addresses the aforementioned issues by providing a method and apparatus for electromagnetic forming of workpieces based on eddy current attraction. By introducing eddy current attraction-based electromagnetic forming technology, the electromagnetic attraction generated by eddy currents induced in a conductor and in the metal workpiece to be formed is utilized to improve the uniformity of the electromagnetic repulsive force distribution in existing electromagnetic forming methods, achieving uniform radial deformation of sheet metal parts and uniform axial deformation of pipes. This improves the quality of the formed workpieces and opens new possibilities for the further application of electromagnetic forming technology in high-precision manufacturing.

[0008] In order to achieve the above object, the technical solution provided by the present invention is: A workpiece electromagnetic forming method based on eddy current attraction, wherein the workpiece is a pipe, and a driving coil for providing an electromagnetic field for pipe forming includes a first coil group and a second coil group connected in series, an eddy current induction conductor is provided between the first coil group and the second coil group, and the first coil group and the second coil group are symmetrical in vertical direction with the center line of the pipe expansion zone as the symmetry axis. During the pipe forming process, under the action of the electromagnetic field generated by the first coil group and the second coil group, eddy currents with the same direction as the current in the pipe to be formed are formed in the eddy current induction conductor, thereby generating mutual attraction. The attraction applied to the middle of the pipe expansion zone is opposite to the expansion direction of the pipe, so that the pipe is uniformly expanded in the axial direction during the forming process. The workpiece electromagnetic forming method comprises the following steps: Step 1: Determine the parameters of the drive coil and the size parameters of the eddy current induction conductor according to the pipe forming specifications, and manufacture the drive coil and eddy current induction conductor; Step 2: Use the mold to fix the tube to be formed, and coaxially place the first coil group, the eddy current induction conductor, and the second coil group inside the tube in sequence. The center line of the eddy current induction conductor is aligned with the center line of the tube expansion area, and the distances between the first coil group, the second coil group, and the eddy current induction conductor are equal; Step 3: After connecting the first coil group and the second coil group in series, connect the driving coil to the power system via the discharge switch; Step 4: Close the discharge switch to power the drive coil; pulse current is generated in the first coil group and the second coil group, forming an electromagnetic field; induced eddy current is generated in the pipe fitting. Under the action of the electromagnetic field of the drive coil, the pipe fitting is subjected to a radially outward electromagnetic force, which causes the pipe wall of the expansion zone of the pipe fitting to deform outward; At the same time, an eddy current induction conductor is formed in the same direction as that in the pipe, thereby generating an electromagnetic force that attracts the pipe. The electromagnetic force of attraction is opposite to the direction of the radially outward electromagnetic force, thereby suppressing the outward deformation of the middle part of the pipe expansion zone and reducing the deformation of the middle part of the pipe expansion zone. Step 5: Turn off the discharge switch and determine whether the bulging effect of the bulging zone of the tube meets the tube forming specifications. If so, the process ends; otherwise, execute step 4 to bulge the tube again.

[0009] Furthermore, the first coil assembly and the second coil assembly have the same material, parameters and size.

[0010] Preferably, the eddy current induction conductor is a cylinder made of copper material.

[0011] In another preferred solution, the eddy current inducing conductor comprises a plurality of cylinders of equal height made of metal material, and the cylinders of equal height are coaxially stacked to form the eddy current inducing conductor.

[0012] In another preferred solution, the eddy current inducing conductor comprises a plurality of cylinders of unequal heights made of metal material, and the plurality of cylinders of unequal heights made of metal material are symmetrical up and down along the center line of the eddy current inducing conductor.

[0013] Preferably, in step 1, a tube bulging simulation model including a driving coil, an eddy current induction conductor and a tube is constructed using finite element software, a pulse current is applied to the driving coil in the tube bulging simulation model, and the bulging effect of the tube is simulated and obtained. The parameters of the driving coil and the dimensional parameters of the eddy current induction conductor as well as the relative positions of the driving coil, the eddy current induction conductor and the tube are repeatedly adjusted to obtain the optimal parameters of the driving coil and the dimensional parameters of the eddy current induction conductor, compared with the tube forming specifications.

[0014] Preferably, the power supply system adopts a capacitor power supply, the capacitance of the capacitor power supply is 160-1600 μF, and the voltage of the capacitor power supply is 5-25 kV.

[0015] The pipe forming device of the above method includes an eddy current induction conductor, a drive coil, a power supply system and a mold for fixing the pipe to be formed. The drive coil includes a first coil group and a second coil group. After the first coil group and the second coil group are connected in series, they are connected to the power supply system through a discharge switch.

[0016] On the other hand, the present invention provides an electromagnetic forming method for workpieces used for sheet metal expansion processing, which adopts a hollow driving coil and a coaxial eddy current induction conductor in the middle of the driving coil. During the sheet metal forming process, under the action of the electromagnetic field, eddy currents with the same direction as the current in the sheet metal are formed in the eddy current induction conductor, thereby generating mutual attraction. The attraction exerted on the middle part of the sheet metal forming area is opposite to the expansion direction of the sheet metal, so that the sheet metal is uniformly expanded axially during the forming process.

[0017] The workpiece electromagnetic forming method comprises the following steps: Step 1: Determine the parameters of the drive coil and the size parameters of the eddy current induction conductor according to the sheet metal forming specifications, and manufacture the drive coil and eddy current induction conductor; Step 2: Place the driving coil, eddy current induction conductor and the plate to be formed coaxially in sequence, and use the edge clamping die to fix the edge of the plate to be formed. Step 3: Connect the drive coil to the power system via the discharge switch; Step 4: Close the discharge switch to power the drive coil. A pulse current is generated in the drive coil, forming an electromagnetic field. Induced eddy currents are generated in the plate. Under the action of the electromagnetic field of the drive coil, the plate is subjected to an axial outward electromagnetic force, which causes the bulging area of ​​the plate to deform outward. At the same time, an eddy current induction conductor generates an eddy current in the same direction as that in the plate, thereby generating an axially inward electromagnetic force on the plate. The axially inward electromagnetic force suppresses the outward deformation of the middle part of the plate bulging zone, thereby reducing the deformation of the middle part of the plate bulging zone; Step 5: Turn off the discharge switch and determine whether the bulging effect of the bulging zone of the plate meets the plate forming specifications. If so, end; otherwise, execute step 4 to bulge the plate again.

[0018] The sheet metal bulging device of the above method includes an eddy current induction conductor, a drive coil, a power supply system, and a clamping die for fixing the edge of the sheet metal to be formed. The eddy current induction conductor is arranged in the middle of the drive coil and is coaxial with it. The drive coil is connected to the power supply system via a discharge switch.

[0019] Furthermore, the eddy current induction conductor of the plate bulging device is a cylinder made of copper.

[0020] In another preferred solution, the eddy current inducing conductor includes a plurality of conductor rings of equal width made of metal material, and the conductor rings of equal width are nested to form the eddy current inducing conductor.

[0021] In another preferred solution, the eddy current inducing conductor includes a plurality of conductor rings of unequal widths made of metal materials, and the conductor rings of unequal widths are nested to form the eddy current inducing conductor.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1) By introducing eddy current induction conductors and utilizing the principle of eddy current attraction, this invention effectively addresses the radial non-uniformity issues of sheet metal parts and axial non-uniformity of pipes encountered in traditional electromagnetic forming technology, significantly improving forming quality and consistency. This invention not only improves the quality and precision of formed workpieces but also opens new possibilities for the further application of electromagnetic forming technology in high-precision manufacturing, thus possessing significant theoretical and practical value.

[0023] 2) The forming quality is significantly improved; In traditional electromagnetic forming processes, sheet metal often exhibits radial non-uniformity with excessive deformation in the middle and insufficient deformation at the edges, while tubes exhibit axial non-uniformity with excessive deformation in the middle and insufficient deformation at both ends. The present invention introduces a conductor into the middle of the driving coil of the sheet metal forming device or the middle of the driving coil of the tube forming device, and utilizes the interaction between the conductor and the induced eddy currents in the part to be formed to generate electromagnetic attraction, thereby effectively suppressing excessive deformation in the middle of the tube expansion zone or the sheet metal forming zone. At the same time, the electromagnetic attraction and the electromagnetic repulsion generated by the driving coil work together to achieve uniform radial deformation of the sheet metal and uniform axial deformation of the tube. This uniformity improves the dimensional accuracy, mechanical properties and surface quality of the formed parts, meeting the requirements of high-precision forming.

[0024] 3) Outstanding technological innovation; This invention introduces the principle of eddy current attraction into the field of electromagnetic forming for the first time, breaking through the limitations of conventional techniques that rely solely on electromagnetic repulsion. By regulating deformation distribution through eddy current-sensing conductors, precise control of the forming process is achieved, eliminating the need for complex molds or multi-step processes, streamlining the process and improving efficiency. The innovative application of eddy current-sensing conductors not only expands research in electromagnetic forming but also provides new insights into addressing uniformity issues, possessing significant theoretical and practical value.

[0025] 4) Easy to operate and promote; The device of the present invention adopts an axisymmetric structure and coaxial assembly design, with low manufacturing and maintenance costs. During the forming process, the power supply system is controlled by a discharge switch to supply power to the drive coil, which is simple to operate and easy to realize the automation of the workpiece processing process.

[0026] The forming device provided by the present invention has wide adaptability to a variety of conductive materials and formed part shapes, and is particularly suitable for the high-precision requirements of aerospace, automobile manufacturing and other fields. Its simplicity and universality give it great potential for promotion in industry.

[0027] 5) The forming process is highly controllable; By adjusting the eddy current induction conductor parameters, such as the thickness of the conductor ring in plate parts or the height of the conductor in pipe parts, the distribution and intensity of the electromagnetic attraction can be flexibly controlled, precisely controlling deformation. This modular design enhances the device's flexibility, allowing users to customize parameters based on workpiece characteristics, improving process adaptability and stability.

[0028] 6) Significant economic benefits and good application prospects; This invention reduces scrap rates, minimizes material waste, shortens production cycles, and improves efficiency, significantly boosting economic returns. It has broad application prospects in aerospace (e.g., fuselage components), automotive manufacturing (e.g., body panels), and electronics (e.g., precision housings), meeting the modern manufacturing industry's demand for high-precision, lightweight parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below with reference to the accompanying drawings.

[0030] Figure 1 Schematic diagram of the structure of the pipe forming device of embodiment 1.

[0031] Figure 2 Schematic diagram of the structure of the eddy current induction conductor of the second embodiment.

[0032] Figure 3 Schematic diagram of the structure of the eddy current induction conductor of Example 3.

[0033] Figure 4 This is a schematic structural diagram of the plate forming device of Example 4.

[0034] Figure 5 Schematic diagram of the structure of the eddy current induction conductor of the fifth embodiment.

[0035] Figure 6 This is a structural diagram of the eddy current induction conductor of Example 6. DETAILED DESCRIPTION

[0036] Example 1 like Figure 1 As shown, the electromagnetic forming method of pipe fittings based on eddy current attraction includes: Step 1: According to the pipe forming specifications, determine the parameters of the drive coil and the size parameters of the eddy current induction conductor, and make the drive coil and eddy current induction conductor. The eddy current induction conductor is a cylinder made of copper material.

[0037] The finite element software COMSOL Multiphysics was used to construct a tube bulging simulation model including a driving coil, an eddy current induction conductor, and a tube. A pulse current was applied to the driving coil in the tube bulging simulation model to simulate the bulging effect of the tube. Compared with the tube forming specifications, the parameters of the driving coil, the dimensional parameters of the eddy current induction conductor, and the relative positions of the driving coil, eddy current induction conductor, and tube were repeatedly adjusted to obtain the optimal parameters of the driving coil and the dimensional parameters of the eddy current induction conductor.

[0038] Step 2: Use the mold to fix the tube to be formed, and coaxially place the first coil group, eddy current induction conductor and second coil group inside the tube in sequence. The center line of the eddy current induction conductor is aligned with the center line of the tube expansion area, so that the distance between the first coil group, the second coil group and the eddy current induction conductor is equal.

[0039] Step 3: After connecting the first coil group and the second coil group in series, connect the driving coil to the power supply system via the discharge switch.

[0040] The power supply system in the embodiment adopts a capacitor power supply, the capacitance of the capacitor power supply is 640 μF, and the voltage of the capacitor power supply is 20 kV.

[0041] Step 4: Close the discharge switch to power the drive coil; a pulse current is generated in the first coil group and the second coil group, forming an electromagnetic field; induced eddy currents are generated in the pipe fitting. Under the action of the electromagnetic field of the drive coil, the pipe fitting is subjected to a radially outward electromagnetic force Fa, which causes the pipe wall in the expansion zone of the pipe fitting to deform outward.

[0042] At the same time, an eddy current induction conductor forms an eddy current in the same direction as that in the pipe, thereby generating a radially inward electromagnetic force Fe on the pipe. The radially inward electromagnetic force suppresses the outward deformation of the middle part of the pipe expansion zone, thereby reducing the deformation of the middle part of the pipe expansion zone.

[0043] Step 5: Turn off the discharge switch and determine whether the bulging effect of the bulging zone of the tube meets the tube forming specifications. If so, the process ends; otherwise, execute step 4 to bulge the tube again.

[0044] The pipe forming device of the above method includes an eddy current induction conductor 1, a drive coil 2, a power supply system 4, and a mold for fixing the pipe 5 to be formed. The drive coil includes a first coil group 201 and a second coil group 202. After the first coil group and the second coil group are connected in series, they are connected to the power supply system through a discharge switch 3. The axis of the eddy current induction conductor 1 is aligned with the center line of the pipe expansion zone 501. Figure 1 shown.

[0045] Example 2 The difference between the pipe forming device of this embodiment and the pipe forming device of the first embodiment is that the eddy current induction conductor 1 is composed of a plurality of cylinders 101 of equal height made of copper material. Figure 2 As shown, these cylinders 101 of equal height are coaxially stacked to form the eddy current induction conductor 1 .

[0046] The method of this embodiment is the same as that of the first embodiment.

[0047] Example 3 The difference between the pipe forming device of this embodiment and the pipe forming device of the first embodiment is that the eddy current induction conductor 1 is composed of a plurality of cylinders 102 of unequal heights made of copper material. Figure 3 As shown, these cylinders 102 of different heights are coaxially stacked to form the eddy current induction conductor 1 .

[0048] The method of this embodiment is the same as that of the first embodiment.

[0049] Example 4 In the embodiment, the plate to be formed is expanded into a basin-shaped member.

[0050] like Figure 4 As shown, the electromagnetic forming method of a sheet metal part based on eddy current attraction includes: Step 1: Determine the parameters of the drive coil and the size parameters of the eddy current induction conductor according to the sheet metal forming specifications, and then manufacture the drive coil and eddy current induction conductor. The eddy current induction conductor is a cylindrical copper material.

[0051] The finite element software COMSOL Multiphysics is used to construct a sheet metal bulging simulation model including a driving coil, an eddy current induction conductor and a sheet metal. A pulse current is applied to the driving coil in the sheet metal bulging simulation model to simulate the bulging effect of the sheet metal. Compared with the sheet metal forming specifications, the parameters of the driving coil and the dimensional parameters of the eddy current induction conductor, as well as the relative positions of the driving coil, eddy current induction conductor and sheet metal are repeatedly adjusted to obtain the optimal parameters of the driving coil and the dimensional parameters of the eddy current induction conductor.

[0052] Step 2: Place the driving coil, eddy current induction conductor and the plate to be formed coaxially in sequence, and use a clamping die to fix the edge of the plate to be formed.

[0053] Step 3: Connect the drive coil to the power system through the discharge switch.

[0054] The power supply system in the embodiment adopts a capacitor power supply, the capacitance of the capacitor power supply is 480 μF, and the voltage of the capacitor power supply is 10.04 kV.

[0055] Step 4: Close the discharge switch to power the drive coil; a pulse current is generated in the drive coil to form an electromagnetic field; induced eddy currents are generated in the plate. Under the action of the electromagnetic field of the drive coil, the plate is subjected to an axial outward electromagnetic force Fa, which causes the bulging area of ​​the plate to deform outward.

[0056] At the same time, an eddy current induction conductor forms an induced eddy current in the same direction as that in the plate, thereby generating an axially inward electromagnetic force Fe on the plate. The axially inward electromagnetic force suppresses the outward deformation of the middle part of the plate bulging zone, reducing the deformation amount of the middle part of the plate bulging zone.

[0057] Step 5: Turn off the discharge switch and determine whether the bulging effect of the bulging zone of the plate meets the plate forming specifications. If so, end; otherwise, execute step 4 to bulge the plate again.

[0058] The plate forming device of the above method includes an eddy current induction conductor 1, a driving coil 2, a power supply system 4 and a clamping die 6 for fixing the edge of the plate 7 to be formed. The eddy current induction conductor is arranged in the middle of the driving coil and is coaxial with it. The driving coil is connected to the power supply system 4 via a discharge switch 3.

[0059] The distance between the driving coil 2 and the plate 7 to be formed is 4 mm.

[0060] Example 5 The difference between the plate forming device of this embodiment and the plate forming device of the fourth embodiment is that the eddy current induction conductor 1 is composed of a plurality of conductor rings 103 of equal width made of copper material, such as Figure 5 As shown, these conductor rings 103 of equal width are nested to form an eddy current induction conductor 1 .

[0061] The method of this embodiment is the same as that of the fourth embodiment.

[0062] Example 6 The difference between the plate forming device of this embodiment and the plate forming device of the fourth embodiment is that the eddy current induction conductor 1 is composed of a plurality of conductor rings 104 of unequal width made of copper material, such as Figure 5 As shown, these conductor rings 104 of unequal width are nested to form an eddy current induction conductor 1 .

[0063] The method of this embodiment is the same as that of the fourth embodiment.

[0064] Implementation results demonstrate that this invention improves the quality and precision of formed workpieces. By adjusting eddy current induction conductor parameters, such as the conductor loop width for sheet metal forming or the cylindrical height for tube forming, the distribution and intensity of the electromagnetic attraction can be flexibly controlled, precisely controlling the workpiece forming effect. By utilizing drive coils of varying specifications and corresponding eddy current induction conductors, this method can meet the diverse sheet and tube forming and manufacturing needs of industries such as aerospace, automotive manufacturing, and electronics.

Claims

1. A workpiece electromagnetic forming method based on eddy current attraction, characterized in that: The workpiece is a pipe, and the driving coil includes a first coil group and a second coil group that are symmetrically connected in series, with an eddy current induction conductor provided between the first coil group and the second coil group. When the pipe is formed, an eddy current in the eddy current induction conductor is formed under the action of the electromagnetic field of the driving coil in the same direction as the current in the pipe, thereby generating a mutual attraction. The attraction applied to the pipe is opposite to the direction of the pipe expansion. The workpiece electromagnetic forming method comprises the following steps: Step 1: Determine the parameters of the drive coil and the size parameters of the eddy current induction conductor according to the pipe forming specifications, and manufacture the drive coil and eddy current induction conductor; Step 2: Fix the tube to be formed, and coaxially place the first coil group, the eddy current induction conductor, and the second coil group inside the tube in sequence, with the center line of the eddy current induction conductor aligned with the center line of the tube expansion area; Step 3: Connect the drive coil to the power system via the discharge switch; Step 4: Close the discharge switch to power the drive coil. A pulse current is generated in the drive coil, forming an electromagnetic field. Eddy currents are induced in the pipe. Under the electromagnetic field of the drive coil, the pipe is subjected to a radially outward electromagnetic force, causing it to bulge outward. The eddy current induction conductor simultaneously generates an eddy current in the same direction as that in the pipe, thereby generating a radially inward electromagnetic force on the pipe, reducing the deformation of the middle part of the pipe expansion zone; Step 5: Turn off the discharge switch and determine whether the bulging effect of the bulging zone of the tube meets the tube forming specifications. If so, the process ends; otherwise, execute step 4 to bulge the tube again.

2. The workpiece electromagnetic forming method based on eddy current attraction according to claim 1, characterized in that: The first coil group and the second coil group have the same material, parameters and size.

3. The workpiece electromagnetic forming method based on eddy current attraction according to claim 2, characterized in that: The eddy current induction conductor is a cylinder made of copper material.

4. The workpiece electromagnetic forming method based on eddy current attraction according to claim 2, characterized in that: The eddy current induction conductor includes a plurality of cylinders of equal height made of metal material, and the cylinders of equal height are coaxially stacked to form the eddy current induction conductor.

5. The workpiece electromagnetic forming method based on eddy current attraction according to claim 2, characterized in that: The eddy current induction conductor includes a plurality of cylinders of unequal heights made of metal material, and the plurality of cylinders of unequal heights made of metal material are symmetrical up and down along the center line of the eddy current induction conductor.

6. The workpiece electromagnetic forming method based on eddy current attraction according to claim 3, 4 or 5, characterized in that: In step 1, a tube bulging simulation model including a driving coil, an eddy current induction conductor, and a tube is constructed using finite element software. A pulse current is applied to the driving coil in the tube bulging simulation model to simulate the bulging effect of the tube. The parameters of the driving coil and the dimensional parameters of the eddy current induction conductor, as well as the relative positions of the driving coil, the eddy current induction conductor, and the tube are repeatedly adjusted to obtain the optimal parameters of the driving coil and the dimensional parameters of the eddy current induction conductor.

7. The workpiece electromagnetic forming method based on eddy current attraction according to claim 6, characterized in that: The power supply system adopts a capacitor power supply, the capacitance of the capacitor power supply is 160-1600 μF, and the voltage of the capacitor power supply is 5-25 kV.

8. The device for electromagnetic forming of a workpiece according to claim 2, 3, 4, 5 or 7, used for bulging of pipes, characterized in that: The invention comprises an eddy current induction conductor (1), a driving coil (2), a power supply system (4), and a mold for fixing a pipe to be formed (5). The driving coil comprises a first coil group (201) and a second coil group (202). The first coil group and the second coil group are connected in series and then connected to the power supply system via a discharge switch (3).

9. A method for electromagnetic forming of a workpiece based on eddy current attraction, characterized in that: The workpiece is a plate, and the electromagnetic forming method for the workpiece uses a hollow drive coil and an eddy current induction conductor coaxially provided in the middle of the drive coil. During the plate forming process, eddy currents in the eddy current induction conductor are formed under the action of the electromagnetic field in the same direction as the current in the plate, thereby generating mutual attraction. The attraction in the middle of the plate forming area is opposite to the direction of plate expansion, so that the plate is uniformly expanded in the axial direction during the forming process. The workpiece electromagnetic forming method comprises the following steps: Step 1: Determine the parameters of the drive coil and the size parameters of the eddy current induction conductor according to the sheet metal forming specifications, and manufacture the drive coil and eddy current induction conductor; Step 2: Place the driving coil, eddy current induction conductor and the plate to be formed coaxially in sequence, and use the edge clamping die to fix the edge of the plate to be formed. Step 3: Connect the drive coil to the power system via the discharge switch; Step 4: Close the discharge switch to power the drive coil. A pulse current is generated in the drive coil, forming an electromagnetic field. Induced eddy currents are generated in the plate. Under the action of the electromagnetic field of the drive coil, the plate is subjected to an axial outward electromagnetic force, which causes the bulging area of ​​the plate to deform outward. At the same time, an eddy current induction conductor generates an eddy current in the same direction as that in the plate, thereby generating an axially inward electromagnetic force on the plate. The axially inward electromagnetic force suppresses the outward deformation of the middle part of the plate bulging zone, thereby reducing the deformation of the middle part of the plate bulging zone; Step 5: Turn off the discharge switch and determine whether the bulging effect of the bulging zone of the plate meets the plate forming specifications. If so, end; otherwise, execute step 4 to bulge the plate again.

10. The device for electromagnetic forming of a workpiece according to claim 9, used for bulging of a plate, characterized in that: The invention comprises an eddy current induction conductor (1), a driving coil (2), a power supply system (4), and a pressing die (6) for fixing the edge of a plate to be formed (7), wherein the eddy current induction conductor is arranged in the middle of the driving coil and is coaxial with the driving coil, and the driving coil is connected to the power supply system via a discharge switch (3).

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