Plate bulging method and device based on discrete shielding and local strengthening

Abstract

The invention relates to a plate bulging method based on discrete shielding and local strengthening, which comprises the following steps: determining parameters of a driving coil according to the material and forming specification of a to-be-formed plate, and manufacturing the driving coil; determining size parameters of the shielding ring; determining the size parameter of the reinforcing ring by combining the size parameter of the shielding ring and the forming specification of the plate; manufacturing a shielding ring, a reinforcing ring and a fixing bracket, and arranging the shielding ring and the reinforcing ring on the fixing bracket; a driving coil, a fixing support and a to-be-formed plate are sequentially arranged on the plate forming base and fixed; and the driving coil is connected with a pulse power source through an air switch, the air switch is controlled to supply power to the driving coil, the discharging time of the pulse power source is controlled, and the to-be-formed plate is subjected to electromagnetic bulging. According to the method, the reinforcing ring and the shielding ring are additionally arranged between the driving coil and the plate, so that the plate bulging uniformity is improved, the plate bulging area is smoother after being formed, and the problem that the wall thickness of the plate bulging area is reduced in a traditional plate bulging method is effectively solved.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic forming control of metal workpieces, and in particular relates to a plate bulging method and a bulging device based on discrete shielding and local reinforcement. Background Art

[0002] As a key strategy to alleviate energy shortages and environmental problems, lightweight technology has shown significant advantages, including improving energy efficiency, reducing pollution emissions, and enhancing corrosion resistance. These characteristics have made it widely used in many industrial fields. Studies have shown that reducing the weight of a car can significantly reduce energy consumption and emissions; specifically, for every 10% reduction in car weight, its fuel consumption can be reduced by about 8% and emissions by about 13%. In the aviation field, for every 5 kg reduction in commercial aircraft, the effective payload can be increased by 50 kg. In addition, lightweight technology is also widely used in 3C electronic products, military equipment, large wind turbine blades, aerospace engineering and other fields.

[0003] The development and application of lightweight materials is one of the key ways to achieve lightweight goals. As a mature lightweight material, aluminum alloy has become the focus of lightweight technology research and application in addition to structural optimization design due to its light weight, corrosion resistance and convenient processing. Compared with steel materials, aluminum alloy can reduce weight while maintaining or improving product performance and durability. With the advancement of technology, more new lightweight materials may be developed in the future to meet the specific lightweight needs of different industries.

[0004] Electromagnetic forming technology uses the Lorentz force generated by the driving coil as the driving force to achieve efficient forming of lightweight aluminum alloy materials. Compared with traditional forming methods such as hydraulic, stamping and spinning, electromagnetic forming shows unique advantages. First, since the force generated by the interaction between the pulsed magnetic field and the induced eddy currents in the workpiece is contactless, the friction during the forming process is reduced, thereby maintaining the high quality of the workpiece surface. Secondly, the electroplastic effect caused by the induced eddy currents helps to reduce the strength of the material, making processing easier. In addition, the high speed and high strain rate characteristics of electromagnetic forming can significantly improve the forming limit of lightweight aluminum alloy materials and effectively reduce the springback and surface wrinkling of parts.

[0005] Existing literature on electromagnetic forming mainly focuses on improving the forming performance of workpieces by changing the shape of coils and using magnetic collectors to change the magnetic field distribution. In 2022, Wu Weiye's paper "Analysis of electromagnetic force and formability of electromagnetic bulging of pipes loaded with a new type of coil" [1]"It is proposed to use a new type of coil to replace the original cylindrical coil to improve the forming performance. The new type of coil has more turns at both ends of the coil close to the pipe, and more turns in the middle coil. The new type of coil is used to strengthen the electromagnetic force at both ends and weaken the electromagnetic force in the middle. This method solves the problem of uneven magnetic field forming, but the coil winding is too complicated. In 2023, Shao Zihao's paper "Electromagnetic force and formability analysis of electromagnetic bulging of pipe fittings based on convex magnetic collectors" [2] "It is proposed to use a convex magnetic collector to improve the distribution of electromagnetic force, wherein the protrusion of the convex magnetic collector is adjacent to the driving coil, and the induced eddy current opposite to the driving coil is induced at the protrusion, and the eddy current in the same direction as the driving coil is induced on the outside. At the same time, the induced eddy current on the outside is distributed more evenly, so that the electromagnetic force received by the pipe is more uniform and the overall forming uniformity is higher. However, this new magnetic collector has a complex structure, a high manufacturing cost, and an inflexible control method. In summary, the prior art lacks a method for improving electromagnetic forming performance with flexible control methods and lower costs.

[0006] References: [1] Wu Weiye. Analysis of electromagnetic force and formability of electromagnetic bulging of pipes loaded with new coils[J]. Materials Development and Application, 2022, 37(05): 62-67.

[0007] [2] Shao Zihao, Wu Weiye, Wang Chenxin, et al. Analysis of electromagnetic force and formability of electromagnetic bulging of pipe fittings based on convex magnetic collector[J]. Journal of Plasticity Engineering, 2023, 30(11): 36-44. Summary of the invention

[0008] The purpose of the present invention is to address the above-mentioned problems and to provide a sheet metal bulging method based on discrete shielding and local reinforcement, by introducing a shielding ring and a reinforcement ring between the driving coil and the formed workpiece, using the shielding ring to weaken the local area with excess electromagnetic force, and using the reinforcement ring to strengthen the local area with weak electromagnetic force, ultimately achieving uniform bulging.

[0009] In order to achieve the above object, the technical solution provided by the present invention is: The plate bulging method based on discrete shielding and local reinforcement includes the following steps: Step 1: Determine the drive coil parameters and manufacture the drive coil according to the material and forming specifications of the plate to be formed; Step 2: Determine the size parameters of the shielding ring according to the drive coil parameters and the sheet forming specifications; Step 3: Determine the size parameters of the reinforcement ring based on the size parameters of the shielding ring and the sheet forming specifications; Step 4: Make a shielding ring, a reinforcement ring and a fixing bracket, and place the shielding ring and the reinforcement ring on the fixing bracket; Step 5: Arrange the driving coil, the fixing bracket, and the plate to be formed on the plate forming base in sequence and fix them; Step 6: Connect the drive coil to the pulse power supply via the switch, control the air switch to power the drive coil, control the discharge time of the pulse power supply, and perform electromagnetic bulging on the sheet to be formed; Step 7: Determine whether the bulging effect of the plate meets the forming specifications of the plate. If it meets the forming specifications, end the process; otherwise, execute step 6 to perform electromagnetic bulging on the plate again until the forming specifications of the plate are met.

[0010] Preferably, in step 2, the finite element software COMSOL Multiphysics is used to construct a plate electromagnetic bulging simulation model including a driving coil, a shielding ring and a plate, a pulse current is applied to the driving coil in the plate electromagnetic bulging simulation model, the bulging effect of the plate is simulated, the dimensional parameters of the shielding ring are adjusted so that the bulging effect of the plate meets the requirements of the plate forming specifications, and the dimensional parameters of the shielding ring are determined by simulation.

[0011] Preferably, in step 3, a reinforcement ring is added to the electromagnetic bulging simulation model of the plate, the electromagnetic bulging simulation model of the plate is used again to perform plate bulging simulation, and the size parameters of the reinforcement ring are adjusted so that the plate achieves the optimal bulging effect, thereby obtaining the optimal parameters of the reinforcement ring.

[0012] Preferably, the reinforcement ring is provided with a fracture, and the shielding ring is an integral circular ring.

[0013] Preferably, the cross-sections of the reinforcement ring and the shielding ring are both rectangular.

[0014] Preferably, the shielding ring has a width of 1 mm-30 mm and a thickness of 1 mm-5 mm, and the reinforcing ring has a width of 1 mm-10 mm and a thickness of 1 mm-5 mm.

[0015] Preferably, the spacing between the shielding rings is 1 mm-10 mm.

[0016] Preferably, the distance between the shielding ring and the plate to be formed is 2 mm-8 mm, and the distance between the shielding ring and the driving coil is 1 mm-6 mm.

[0017] Preferably, in step 6, the pulse power supply is a capacitor power supply, the capacitance of the capacitor power supply is 8-800 μF, and the discharge voltage of the capacitor power supply is 5-10 kV.

[0018] Furthermore, the bulging device of the above-mentioned plate electromagnetic bulging method includes a workpiece base, a driving coil, a reinforcing ring, a shielding ring, a fixed bracket and a pulse power supply; the fixed bracket is used to support and fix the reinforcing conductor ring; the driving coil is connected to the pulse power supply via a switch.

[0019] Compared with the prior art, the beneficial effects of the present invention include: 1) The present invention aims to solve the problem that the magnetic field strength at the ends is low while the magnetic field strength in the middle area is high due to the end effect in traditional sheet metal bulging. By adding a reinforcement ring and a shielding ring between the driving coil and the sheet metal, the reinforcement ring improves the magnetic field strength and electromagnetic force at both ends of the sheet metal bulging zone; the shielding ring weakens the magnetic field strength and electromagnetic force in the middle of the sheet metal bulging zone, thereby realizing the regulation of the electromagnetic force in the sheet metal bulging zone during the sheet metal bulging process, improving the uniformity of the sheet metal bulging, making the sheet metal bulging zone smoother after forming, and effectively improving the problem of thinning of the wall thickness of the sheet metal bulging zone in the traditional sheet metal bulging method.

[0020] 2) The cross-section of the shielding ring and the reinforcing ring of the present invention is rectangular, which is easy to manufacture and has low cost. Compared with the method of improving the driving coil, the shielding ring and the reinforcing ring are less difficult and easier to produce than the method of improving the magnetic collector.

[0021] 3) The present invention can achieve different sheet metal bulging effects by replacing reinforcing rings and shielding rings with different size parameters, meet the requirements of various sheet metal forming specifications, and have a high reuse rate of reinforcing rings and shielding rings.

[0022] 4) The present invention can reduce the reaction force of the induced current of the plate on the driving coil during the plate forming process by using a reinforcing ring and a shielding ring, effectively protect the driving coil, and extend the service life of the driving coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0024] Figure 1 It is a schematic diagram of the process of the plate bulging method based on discrete shielding and local reinforcement.

[0025] Figure 2 FIG. 4 is an equivalent circuit diagram of the driving coil and the power supply of the embodiment.

[0026] Figure 3 The figure is a flow chart of modeling and simulation using finite element software in an embodiment of the present invention.

[0027] Figure 4 It is a schematic diagram of the plate bulging device of the first embodiment.

[0028] Figure 5 Schematic diagram of the geometry of the shielding ring and the reinforcement ring of the first embodiment.

[0029] Figure 6 Schematic diagram of the induced eddy current of the shielding ring and the strengthening ring of the first embodiment.

[0030] Figure 7 It is a schematic diagram of the plate bulging device of the second embodiment.

[0031] Figure 8It is a geometric diagram of the shielding ring of the second embodiment.

[0032] Fig. 9 Schematic diagram of the induced eddy current of the shielding ring of the second embodiment.

[0033] Fig.10 This is a schematic diagram of the plate bulging device of Example 3.

[0034] Fig.11 This is a geometric diagram of the reinforcement ring of Example 3.

[0035] Fig.12 Schematic diagram of the induced eddy current of the reinforcement ring of Example 3.

[0036] Fig.13 It is a comparison chart of the forming effects of the plate electromagnetic forming method of Example 1 and the traditional plate bulging method.

[0037] Explanation of the reference numerals: workpiece base 1 , plate to be formed 2 , expansion zone 201 , fixing bracket 3 , reinforcement ring 4 , driving coil 5 , shielding ring 6 . DETAILED DESCRIPTION

[0038] Embodiment 1 By introducing a shielding ring and a reinforcing ring between the driving coil and the forming plate, the shielding ring is used to weaken the local area with excessive electromagnetic force, and the reinforcing ring is used to strengthen the local area with weak electromagnetic force, finally achieving uniform bulging.

[0039] like Figure 1 As shown, the plate bulging method based on discrete shielding and local reinforcement includes the following steps: Step 1: Determine the number of turns and layers of the driving coil and other parameters according to the material and forming specifications of the workpiece to be formed, and wind the driving coil on the reinforcement layer; Step 2: Determine the size parameters of the shielding ring according to the drive coil parameters and the sheet forming specifications; like Figure 3 As shown, the finite element software COMSOL Multiphysics is used to build a plate electromagnetic bulging simulation model including a driving coil, a shielding ring and a plate. A pulse current is applied to the driving coil in the plate electromagnetic bulging simulation model, and the bulging effect of the plate is simulated. The size parameters of the shielding ring are adjusted so that the bulging effect of the plate meets the requirements of the plate forming specifications, and the size parameters of the shielding ring are determined by simulation.

[0040] Step 3: Determine the size parameters of the reinforcement ring based on the size parameters of the shielding ring and the sheet forming specifications; Add a reinforcement ring to the electromagnetic bulging simulation model of the plate, use the electromagnetic bulging simulation model of the plate again to simulate the plate bulging, adjust the size parameters of the reinforcement ring to make the plate achieve the optimal bulging effect, and determine the number and length of the shielding ring and the reinforcement ring, as well as the distance parameters between the shielding ring and the reinforcement ring.

[0041] Step 4: Make a shielding ring, a reinforcement ring and a fixing bracket, and place the shielding ring and the reinforcement ring on the fixing bracket; Step 5: Arrange the driving coil, the fixing bracket, and the plate to be formed on the plate forming base in sequence and fix them; Step 6: Connect the driving coil to the pulse power supply via the air switch, control the air switch to supply power to the driving coil, control the discharge time of the pulse power supply, and perform electromagnetic bulging on the sheet to be formed; Step 7: Determine whether the bulging effect of the plate meets the forming specifications of the plate. If it meets the forming specifications, end the process; otherwise, execute step 6 to perform electromagnetic bulging on the plate again until the forming specifications of the plate are met.

[0042] In the embodiment, the driving coil equivalent circuit is as follows: Figure 3 As shown, after being charged, the capacitor provides a pulse current to the driving coil, and when the air switch is closed, it provides a pulse power supply to the driving coil.

[0043] Sheet metal bulging device based on shielding ring and reinforcing ring Figure 4 As shown, it includes a workpiece base 1, a plate to be formed 2, a fixing bracket 3, a reinforcing ring 4, a driving coil 5, and a shielding ring 6. The workpiece base is used as a fixing device, and the plate to be formed, the fixing bracket, and the driving coil are fixed in sequence from top to bottom. The shielding ring and the reinforcing ring are nested in the fixing bracket at equal intervals. The driving coil is connected to a pulse power supply.

[0044] The length of the plate to be formed in the first embodiment is 80 mm, the number of shielding rings is 3, and the number of reinforcing rings is 1. Because the electromagnetic bulging of the plate is axially symmetrical, the symmetrically distributed shielding rings and reinforcing rings are a whole in the cross-sectional view of the device. The height h of each shielding ring and reinforcing ring is 5 mm, the width is 2 mm, and the spacing d is 5 mm. The geometry of the shielding ring and reinforcing ring in this embodiment is as follows: Figure 5 shown.

[0045] During the electromagnetic bulging process of the plate, the driving coil on the right side of the symmetry axis receives a current perpendicular to the surface and inward. The current directions of the plate to be formed, the driving coil, the shielding ring and the strengthening ring in this embodiment are as follows: Figure 6As shown. The driving coil on the left side of the symmetry axis receives an outward current perpendicular to the surface. The shielding ring is an integral metal cylindrical ring. According to the law of electromagnetic induction, it generates induced eddy currents in the opposite direction to the driving coil, thereby reducing the electromagnetic field of the original driving coil; the strengthening ring generates induced eddy currents in the opposite direction to the pulse magnetic field on the side close to the driving coil. After two reverse rotations on the side close to the plate, it generates induced eddy currents identical to the pulse magnetic field, thereby strengthening the electromagnetic field near the strengthening ring. The introduction of the shielding ring causes the force on the middle of the plate to be less than the electromagnetic force of the traditional electromagnetic bulging of the plate, while the introduction of the strengthening ring causes the force on both ends of the plate to be greater than the electromagnetic force of the traditional electromagnetic bulging. Therefore, the axial electromagnetic force of the traditional electromagnetic bulging of the plate, which is small at both ends and large in the middle, is improved, and the axial electromagnetic force at the intervals between the two ends and the shielding ring is made larger, thereby improving the uniformity and achieving a better forming effect.

[0046] In the embodiment, the plate to be formed is expanded into a basin-shaped member.

[0047] The plate bulging effect of the method of the present invention is compared with the traditional plate bulging method. Fig.13 As shown. It can be seen that the plate bulging method based on discrete shielding and local reinforcement of the present invention solves the problem that the traditional plate bulging method affects the uniformity of plate bulging due to the end effect. The bottom of the basin-shaped part obtained by the plate bulging of the present invention is flatter and more uniform.

[0048] Embodiment 2 The difference between the plate bulging method of the first embodiment and the plate bulging method of the second embodiment is that the plate bulging method of the second embodiment only uses a shielding ring but no reinforcing ring.

[0049] like Figure 7 As shown, the plate bulging device of the second embodiment includes a workpiece base 1, a plate to be formed 2, a fixing bracket 3, a driving coil 5 and a shielding ring 6. The workpiece base is used as a fixing device, and the plate to be formed, the fixing bracket and the driving coil are fixed in sequence from top to bottom. Two shielding rings are nested in the fixing bracket. The driving coil is connected to a pulse power supply.

[0050] The radial length of the plate to be formed in the second embodiment is 80 mm, the number of shielding rings is 2, the cross section of the shielding ring is rectangular, the height h of the shielding ring is 30 mm, and the distance d between the two shielding rings is 8 mm. The geometric shape of the shielding ring is as follows: Figure 8 shown.

[0051] During the electromagnetic bulging process of the plate, the pulse power supply supplies power to the drive coil. The current direction of the drive coil and the shielding ring is as follows: Fig. 9As shown. Each shielding ring is an integral metal cylindrical ring, so according to the law of electromagnetic induction, an induced eddy current opposite to the driving coil is generated. This induced eddy current generates an electromagnetic force opposite to the original driving coil, thereby reducing the electromagnetic force in the middle of the plate. The introduction of the shielding ring causes the force on the middle of the plate to be smaller than the electromagnetic force of the traditional electromagnetic bulging. Therefore, the axial electromagnetic force of the traditional electromagnetic bulging of the plate, which is small at both ends and large in the middle, is improved. Because the electromagnetic forces at both ends are not affected by the shielding ring, the interval in the middle of the shielding ring provides sufficient electromagnetic force for the middle of the plate bulging, avoiding insufficient axial distance of forming. Ultimately, the quality of the plate bulging is better and the overall uniformity is improved.

[0052] Embodiment 3 The difference between the plate bulging method of the first embodiment and the plate bulging method of the third embodiment is that the plate bulging method of the third embodiment only uses a reinforcing ring but no shielding ring.

[0053] like Fig.10 As shown, the plate bulging device of the third embodiment includes a workpiece base 1, a plate to be formed 2, a fixing bracket 3, a reinforcing ring 6, and a driving coil 5. The workpiece base is used as a fixing device, and the plate to be formed, the fixing bracket, and the driving coil are fixed in order from top to bottom. A reinforcing ring is nested in the fixing bracket. The driving coil is connected to a pulse power supply, such as Figure 2 The geometry of the reinforcement ring is shown in Fig.11 shown.

[0054] In the third embodiment, the length of the plate to be formed is 80 mm, the number of the reinforcing ring is 1, the cross section of the reinforcing ring is rectangular, the height h of the reinforcing ring is 5 mm, the width is 2 mm, and the inner diameter of the reinforcing ring is 40 mm.

[0055] During the electromagnetic bulging process, the driving coil on the right side of the symmetry axis receives a current that is perpendicular to the surface and inward. The current flow direction of the driving coil and the strengthening ring is as follows: Fig.12 As shown. The driving coil on the right side of the symmetry axis receives an inward current perpendicular to the surface. The strengthening ring is a metal cylindrical ring with a gap. According to the law of electromagnetic induction, the strengthening ring generates an induced eddy current opposite to the pulse magnetic field on the side close to the driving coil. After two reverse cycles on the side close to the plate, it generates an induced eddy current identical to the pulse magnetic field, which strengthens the magnetic field near the strengthening ring. The introduction of the strengthening ring causes the force on both ends of the plate to be greater than the electromagnetic force of the traditional electromagnetic bulging. Therefore, the radial electromagnetic force at both ends is greater, which improves the axial uniformity and achieves a better forming effect.

Claims

1. A plate bulging method based on discrete shielding and local reinforcement, characterized in that: A shielding ring and a reinforcing ring are added between the driving coil and the plate to be formed, and a fracture is provided on the reinforcing ring. The shielding ring is arranged in the middle of the plate to be formed, and the strengthening ring is arranged at the end of the plate to be formed. The shielding ring is used to weaken the magnetic field strength in the middle of the plate; The reinforcing ring is used to enhance the magnetic field strength at the end of the plate, and the shielding ring and the reinforcing ring are used to achieve uniform bulging of the plate; The plate electromagnetic bulging method comprises the following steps: Step 1: Determine the drive coil parameters and manufacture the drive coil according to the material and forming specifications of the plate to be formed; Step 2: Determine the size parameters of the shielding ring according to the drive coil parameters and the sheet forming specifications; Step 3: Determine the size parameters of the reinforcement ring based on the size parameters of the shielding ring and the sheet forming specifications; Step 4: Make a shielding ring, a reinforcement ring and a fixing bracket, and place the shielding ring and the reinforcement ring on the fixing bracket; Step 5: Arrange the driving coil, the fixing bracket, and the plate to be formed on the plate forming base in sequence and fix them; Step 6: Connect the driving coil to the pulse power supply via the air switch, control the air switch to supply power to the driving coil, control the discharge time of the pulse power supply, and perform electromagnetic bulging on the sheet to be formed; Step 7: Determine whether the bulging effect of the plate meets the forming specifications of the plate. If it meets the forming specifications, end the process; otherwise, execute step 6 to perform electromagnetic bulging on the plate again until the forming specifications of the plate are met.

2. The plate bulging method based on discrete shielding and local reinforcement according to claim 1, characterized in that: In step 2, finite element software is used to construct a plate electromagnetic bulging simulation model including a driving coil, a shielding ring and a plate, a pulse current is applied to the driving coil in the plate electromagnetic bulging simulation model, the bulging effect of the plate is simulated, the dimensional parameters of the shielding ring are adjusted so that the plate bulging effect meets the plate forming specification requirements, and the dimensional parameters of the shielding ring are determined by simulation.

3. The plate bulging method based on discrete shielding and local reinforcement according to claim 2, characterized in that: In step 3, a reinforcement ring is added to the electromagnetic bulging simulation model of the plate, and the plate bulging simulation is performed again using the electromagnetic bulging simulation model of the plate, and the size parameters of the reinforcement ring are adjusted to achieve the optimal bulging effect of the plate, thereby obtaining the optimal parameters of the reinforcement ring.

4. The plate bulging method based on discrete shielding and local reinforcement according to claim 1, characterized in that: The shielding ring has a width of 1-30 mm and a thickness of 1-5 mm.

5. The plate bulging method based on discrete shielding and local reinforcement according to claim 1, characterized in that: The reinforcing ring has a width of 1-10 mm and a thickness of 1-5 mm.

6. The plate bulging method based on discrete shielding and local reinforcement according to claim 1, characterized in that: The spacing between the shielding rings is 1-10 mm.

7. The plate bulging method based on discrete shielding and local reinforcement according to claim 1, characterized in that: The shielding ring has a spacing of 2-8 mm from the plate to be formed, and a spacing of 1-6 mm from the driving coil.

8. The plate bulging method based on discrete shielding and local reinforcement according to claim 1, characterized in that: The number of shielding rings is 3.

9. The plate bulging method based on discrete shielding and local reinforcement according to claim 1, characterized in that: The shielding ring and the strengthening ring are both made of copper.

10. The bulging device of the plate bulging method based on discrete shielding and local reinforcement according to any one of claims 1 to 9, characterized in that: The bulging device comprises a driving coil, a reinforcing ring, a shielding ring, a fixing bracket and a pulse power supply; the fixing bracket is used to support and fix the reinforcing ring and the shielding ring; the driving coil is connected to the pulse power supply via a switch.

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