Sheet metal bulging method and bulging device based on discrete shielding and local reinforcement

Abstract

The present application relates to a plate bulging method based on discrete shielding and local reinforcement, wherein the parameters of a driving coil are determined according to the material and forming specification of a plate to be formed, and the driving coil is manufactured; the size parameters of a shielding ring are determined; the size parameters of a reinforcing ring are determined in combination with the size parameters of the shielding ring and the forming specification of the plate; the shielding ring and the reinforcing ring and a fixing support are manufactured, and the shielding ring and the reinforcing ring are arranged on the fixing support; the driving coil, the fixing support and the plate to be formed are sequentially arranged on a plate forming base and fixed; 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 discharge time of the pulse power source is controlled, and the plate to be formed is subjected to electromagnetic bulging. The present application improves the uniformity of plate bulging by additionally arranging a reinforcing ring and a shielding ring between the driving coil and the plate, makes the plate bulging area more flat after forming, and effectively improves the problem of wall thickness thinning of the plate bulging area in the traditional plate bulging method.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electromagnetic forming control of metal workpieces, and particularly relates to a plate bulging method and a bulging device based on discrete shielding and local reinforcement. BACKGROUND

[0002] Lightweight technology has shown significant advantages as a key strategy to alleviate energy shortages and environmental problems, including improving energy efficiency, reducing pollution emissions, and enhancing corrosion resistance, which makes 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, fuel consumption can be reduced by about 8%, and emissions can be reduced by about 13%. In the aviation field, every 5 kg of weight reduction of a commercial aircraft can increase the effective commercial load by 50 kg. In addition, lightweight technology is also widely used in 3C electronic products, military equipment, large wind turbine blades, and aerospace engineering fields.

[0003] The development and application of lightweight materials is one of the key ways to achieve the goal of lightweight. 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 lightweight, corrosion resistance, and processing convenience. Compared with steel materials, aluminum alloy can not only reduce weight, but also maintain or improve the performance and durability of products. With the advancement of technology, more new lightweight materials may be developed in the future to meet the specific needs of different industries for lightweight.

[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 hydraulic, stamping and spinning forming methods, electromagnetic forming exhibits unique advantages. First, the force generated by the interaction of the pulsed magnetic field and the induced eddy current in the workpiece is non-contact, reducing friction during the forming process and maintaining the high quality of the workpiece surface. Second, the electroplastic effect caused by the induced eddy current helps to reduce the strength of the material, making it easier to process. 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 electromagnetic forming related literature mainly focuses on changing the shape of the coil and using a magnetic concentrator to change the magnetic field distribution to improve the forming performance of the workpiece. In 2022, Wu Weiyeh's paper "Analysis of Electromagnetic Force and Formability of Tube Electromagnetic Bulging with New Coil Loading" [1]"Put forward to use new type of coil to replace the original cylindrical coil to improve the forming performance, the new type of coil is that the number of turns of the two ends is close to the pipe, the number of turns of the middle coil is close to the coil, the electromagnetic force of the two ends is strengthened by using the new type of coil, and the electromagnetic force of the middle part is weakened. This method solves the problem of uneven magnetic field forming, but the coil winding is too complex. In 2023, the paper "Analysis of electromagnetic force and forming performance of pipe electromagnetic bulging based on convex magnetic concentrator [2] "Put forward to use convex magnetic concentrator to improve the electromagnetic force distribution, wherein the convex of the convex magnetic concentrator is adjacent to the driving coil, the induction eddy current opposite to the driving coil is induced at the convex, the eddy current with the same direction as the driving coil is induced outside, and the eddy current distribution outside is uniform, so that the electromagnetic force received by the pipe is uniform, and the overall forming uniformity is higher. But this new type of magnetic concentrator has complex structure, high manufacturing cost, and flexible control mode. In summary, there is a lack of method for improving the electromagnetic forming performance in the prior art, which has flexible control mode and lower cost.

[0006] Reference:

[0007] [1] Wu Weiy, New type of coil loading pipe electromagnetic bulging electromagnetic force and forming performance analysis [J]. Materials development and application, 2022, 37 (05): 62-67.

[0008] [2] Shao Zihao, Wu Weiy, Wang Chenxin, et al. Analysis of electromagnetic force and forming performance of pipe electromagnetic bulging based on convex magnetic concentrator [J]. Journal of plastic engineering, 2023, 30 (11): 36-44. SUMMARY

[0009] The purpose of the present application is to solve the above problems, and provide a plate bulging method based on discrete shielding and local reinforcement. By introducing a shielding ring and a reinforcement ring between the driving coil and the forming workpiece, the shielding ring is used to weaken the local area of excessive electromagnetic force, and the reinforcement ring is used to strengthen the local area of weak electromagnetic force. Finally, uniform bulging is achieved.

[0010] In order to achieve the above purpose, the technical scheme provided by the present application is as follows:

[0011] The plate bulging method based on discrete shielding and local reinforcement comprises the following steps:

[0012] Step 1: according to the material and forming specification of the plate to be formed, determine the driving coil parameters, and make the driving coil;

[0013] Step 2: according to the driving coil parameters and the plate forming specification, determine the size parameters of the shielding ring;

[0014] Step 3: combine the size parameters of the shielding ring and the plate forming specification to determine the size parameters of the reinforcement ring;

[0015] Step 4: making the shielding ring and the reinforcing ring and the fixing support, and arranging the shielding ring and the reinforcing ring coaxially on the fixing support;

[0016] Step 5: arranging the driving coil, the fixing support and the plate to be formed in sequence on the plate forming base and fixing them;

[0017] Step 6: connecting the driving coil with the pulse power source through the switch, controlling the air switch to supply power to the driving coil, controlling the discharge time of the pulse power source, and performing electromagnetic bulging on the plate to be formed;

[0018] Step 7: judging whether the bulging effect of the plate meets the forming specification of the plate, and if so, ending, otherwise, performing electromagnetic bulging on the plate again in step 6 until the forming specification of the plate is met.

[0019] Preferably, in step 2, a plate electromagnetic bulging simulation model containing the driving coil, the shielding ring and the plate is constructed by using the finite element software COMSOL Multiphysics, 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 size parameters of the shielding ring are adjusted so that the bulging effect of the plate meets the needs of the forming specification of the plate, and the size parameters of the shielding ring are determined by simulation.

[0020] Preferably, in step 3, the reinforcing ring is added to the plate electromagnetic bulging simulation model, and the plate bulging simulation is performed again by using the plate electromagnetic bulging simulation model, the size parameters of the reinforcing ring are adjusted so that the plate achieves the optimal bulging effect, and the optimal parameters of the reinforcing ring are obtained.

[0021] Preferably, the reinforcing ring is provided with a split, and the shielding ring is a whole ring.

[0022] Preferably, the cross sections of the reinforcing ring and the shielding ring are both rectangular.

[0023] Preferably, the width of the shielding ring is 1-30 mm, the thickness is 1-5 mm, the width of the reinforcing ring is 1-10 mm, and the thickness is 1-5 mm.

[0024] Preferably, the distance between the shielding rings is 1-10 mm.

[0025] Preferably, the distance between the shielding ring and the plate to be formed is 2-8 mm, and the distance between the shielding ring and the driving coil is 1-6 mm.

[0026] Preferably, in step 6, the pulse power source is a capacitor power source, the capacitance of the capacitor power source is 8-800 μF, and the discharge voltage of the capacitor power source is 5-10 kv.

[0027] Further, the bulging device of the above-mentioned plate electromagnetic bulging method comprises a workpiece base, a driving coil, a reinforcing ring, a shielding ring, a fixed support and a pulse power supply; the fixed support is used for supporting and fixing the reinforcing conductor ring; the driving coil is connected with the pulse power supply through a switch.

[0028] Compared with the prior art, the beneficial effects of the present application include:

[0029] 1) The present application is aimed at the problem that the magnetic field strength of the end part is low and the magnetic field strength of the middle part is high due to the end effect of the traditional plate bulging. By additionally arranging a reinforcing ring and a shielding ring between the driving coil and the plate, the reinforcing ring increases the magnetic field strength and the electromagnetic force at both ends of the plate bulging area, and the shielding ring weakens the magnetic field strength and the electromagnetic force in the middle part of the plate bulging area, thereby realizing the regulation of the electromagnetic force in the plate bulging area during the plate bulging process, improving the uniformity of the plate bulging, making the plate bulging area more flat after forming, and effectively improving the problem of wall thickness thinning in the plate bulging area of the traditional plate bulging method.

[0030] 2) The cross section of the shielding ring and the reinforcing ring of the present application is rectangular, which is easy to manufacture and low in cost, and has less difficulty compared with the way of improving the driving coil and is easier to produce and manufacture compared with the way of improving the magnetic collector.

[0031] 3) The present application can realize different plate bulging effects by replacing reinforcing rings and shielding rings with different size parameters, meet the needs of various plate forming specifications, and has high reuse rate of the reinforcing ring and the shielding ring.

[0032] 4) The present application can reduce the reaction force generated by the induced current of the plate in the plate forming process on the driving coil by using the reinforcing ring and the shielding ring, effectively protect the driving coil, and prolong the service life of the driving coil. BRIEF DESCRIPTION OF DRAWINGS

[0033] The present application will be further described below in combination with the drawings and examples.

[0034] Figure 1 It is a flowchart of the plate bulging method based on discrete shielding and local reinforcement.

[0035] Figure 2 It is an equivalent circuit diagram of the connection between the driving coil and the power supply in the example.

[0036] Figure 3 It is a flowchart of modeling and simulation using finite element software in the example of the present application.

[0037] Figure 4 It is a schematic diagram of the plate bulging device of Example 1.

[0038] Figure 5 It is a geometric schematic diagram of the shielding ring and the reinforcing ring of Example 1.

[0039] Figure 6 Schematic diagram of the induced eddy current of the shielding ring and the reinforcement ring in Example 1.

[0040] Figure 7 Schematic diagram of the plate bulging device of the second embodiment.

[0041] Figure 8 This is a geometric diagram of the shielding ring of the second embodiment.

[0042] Figure 9 Schematic diagram of the induced eddy current of the shielding ring in the second embodiment.

[0043] Figure 10 Schematic diagram of the plate bulging device of Example 3.

[0044] Figure 11 This is a geometric diagram of the reinforcement ring of Example 3.

[0045] Figure 12 Schematic diagram of the induced eddy current of the reinforcement ring of Example 3.

[0046] Figure 13 3 is a comparison chart of the forming effects of the electromagnetic forming method of the plate in Example 1 and the traditional plate bulging method.

[0047] Description of the accompanying drawings: workpiece base 1, plate to be formed 2, expansion area 201, fixing bracket 3, reinforcement ring 4, driving coil 5, shielding ring 6. DETAILED DESCRIPTION

[0048] Example 1

[0049] By introducing a shielding ring and a reinforcement ring between the driving coil and the plate to be formed, the shielding ring is arranged in the middle of the plate to be formed in the vertical direction, and the reinforcement ring is arranged at the end of the plate to be formed in the vertical direction. The shielding ring and the reinforcement ring are coaxially arranged inside the fixed bracket. The shielding ring is used to weaken the local area with excess electromagnetic force; the reinforcement ring is used to strengthen the local area with weak electromagnetic force; and finally uniform expansion is achieved.

[0050] like Figure 1 As shown, the plate bulging method based on discrete shielding and local reinforcement includes the following steps:

[0051] Step 1: Determine the number of turns and layers of the drive coil and other parameters based on the material and forming specifications of the workpiece to be formed, and wind the drive coil on the reinforcement layer;

[0052] Step 2: Determine the size parameters of the shielding ring based on the drive coil parameters and sheet metal forming specifications;

[0053] like Figure 3As shown in the figure, 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 to simulate the bulging effect of the plate. 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.

[0054] Step 3: Determine the size parameters of the reinforcement ring based on the size parameters of the shielding ring and the sheet metal forming specifications;

[0055] Add a reinforcement ring to the electromagnetic bulging simulation model of the plate, and use the electromagnetic bulging simulation model of the plate to simulate the plate bulging again. Adjust the size parameters of the reinforcement ring to achieve the optimal bulging effect of the plate, 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.

[0056] Step 4: Make the shielding ring, reinforcement ring and fixing bracket, and place the shielding ring and reinforcement ring on the fixing bracket;

[0057] Step 5: Arrange the driving coil, the fixing bracket, and the panel to be formed on the panel forming base in sequence and fix them;

[0058] Step 6: Connect the driving coil to the pulse power supply through the air switch, control the air switch to power the driving coil, control the discharge time of the pulse power supply, and perform electromagnetic bulging on the sheet to be formed;

[0059] Step 7: Determine whether the bulging effect of the plate meets the forming specifications of the plate. If it meets the forming specifications, end; otherwise, execute step 6 to perform electromagnetic bulging on the plate again until the plate forming specifications are met.

[0060] In the embodiment, the equivalent circuit of the driving coil 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.

[0061] Sheet metal bulging device based on shielding ring and reinforcement ring Figure 4 As shown, the system comprises a workpiece base 1, a sheet to be formed 2, a fixing bracket 3, a reinforcing ring 4, a driving coil 5, and a shielding ring 6. The workpiece base serves as a fixture, while the sheet to be formed, the fixing bracket, and the driving coil are fixed in sequence from top to bottom. The shielding ring and reinforcing ring are nested within the fixing bracket at equal intervals. The driving coil is connected to a pulse power supply.

[0062] The length of the plate to be formed in the embodiment one is 80mm, the number of the shielding rings is 3, and the number of the reinforcing rings is 1. Since the electromagnetic bulging of the plate is distributed symmetrically, the symmetrically distributed shielding ring and reinforcing ring are an integral whole on the cross-sectional view of the device. The height h of each shielding ring and reinforcing ring is 5mm, the width is 2mm, and the interval d is 5mm. The geometry of the shielding ring and the reinforcing ring in the embodiment is shown in Figure 5 .

[0063] During the electromagnetic bulging of the plate, the driving coil on the right side of the symmetric axis obtains the current inward the vertical surface. The current direction of the plate to be formed, the driving coil, the shielding ring and the reinforcing ring in the embodiment is shown in Figure 6 . The driving coil on the left side of the symmetric axis obtains the current outward the vertical surface. The shielding ring is an integral whole metal cylindrical ring. According to the electromagnetic induction law, the induced eddy current in the opposite direction of the driving coil is generated, so that the electromagnetic field of the original driving coil is reduced. The reinforcing ring generates the induced eddy current opposite to the pulsed magnetic field near the driving coil, and generates the induced eddy current same to the pulsed magnetic field after reversing twice near the plate, so that the electromagnetic field near the reinforcing ring is strengthened. The introduction of the shielding ring leads to that the force on the middle part of the plate is smaller than the electromagnetic force in the conventional plate electromagnetic bulging, and the introduction of the reinforcing ring leads to that the force on the two ends of the plate is larger than the electromagnetic force in the conventional electromagnetic bulging. Therefore, the axial electromagnetic force of the conventional plate electromagnetic bulging is improved, the axial electromagnetic force between the two ends and the shielding ring is larger, so that the uniformity is improved and the forming effect is better.

[0064] In the embodiment, the plate to be formed is bulged into a basin-shaped part.

[0065] The bulging effect of the plate in the method of the present application is compared with that of the conventional plate bulging method, which is shown in Figure 13 . It can be seen that the plate bulging method based on discrete shielding and local reinforcement solves the problem that the uniformity of the plate bulging is affected by the end effect in the conventional plate bulging method. The bottom of the basin-shaped part obtained by the plate bulging is more flat and the uniformity is better.

[0066] Embodiment two

[0067] The difference between the plate bulging method of the embodiment one and the plate bulging method of the embodiment two is that the plate bulging method of the embodiment two only uses the shielding ring but not the reinforcing ring.

[0068] As shown in Figure 7 , the plate bulging device of the embodiment two includes a workpiece base 1, a plate to be formed 2, a fixed support 3, a driving coil 5 and a shielding ring 6. The workpiece base is a fixing device, and the plate to be formed, the fixed support and the driving coil are fixed in order from top to bottom. Two shielding rings are nested in the fixed support. The driving coil is connected with a pulse power supply.

[0069] The radial length of the plate to be formed in Example Two 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 shielding ring geometry is as shown in Figure 8 .

[0070] During the electromagnetic bulging of the plate, the pulse power supplies power to the drive coil, and the current directions of the drive coil and the shielding ring are as shown in Figure 9 . Each shielding ring is a whole metal cylindrical ring, so according to the law of electromagnetic induction, an induced eddy current opposite to the drive coil is generated, which generates an electromagnetic force opposite to the original drive coil, thereby reducing the electromagnetic force in the middle of the plate. The introduction of the shielding ring causes the force received by the middle of the plate to be less than the electromagnetic force of the conventional electromagnetic bulging, thus improving the conventional plate electromagnetic bulging of the two ends small and the middle large axial electromagnetic force. The electromagnetic force at both ends is not affected by the shielding ring, and the interval in the middle of the shielding ring provides sufficient electromagnetic force for the bulging middle of the plate, avoiding insufficient forming axial distance. Finally, the plate bulging quality is better, and the overall uniformity is improved.

[0071] Example Three

[0072] The difference between the plate bulging method of Example One and the plate bulging method of Example Three is that the plate bulging method of Example Three only uses a reinforcing ring without a shielding ring.

[0073] As shown in Figure 10 , the plate bulging device of Example Three includes a workpiece base 1, a plate to be formed 2, a fixed support 3, a reinforcing ring 6, and a drive coil 5. The workpiece base serves as a fixing device, and the plate to be formed, the fixed support, and the drive coil are fixed in order from top to bottom. One reinforcing ring is nested in the fixed support. The drive coil is connected to the pulse power supply, as shown in Figure 2 . The geometry of the reinforcing ring is as shown in Figure 11 .

[0074] In Example Three, the length of the plate to be formed is 80 mm, the number of reinforcing rings 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.

[0075] During the electromagnetic bulging, the drive coil on the right side of the symmetry axis obtains a current facing inward, and the current flow directions of the drive coil and the reinforcing ring are as shown in Figure 12The driving coil on the right side of the symmetry axis gets the vertical surface inward current, and the reinforcement ring is a metal cylindrical ring with a broken seam. According to the electromagnetic induction law, the reinforcement ring generates the induced eddy current opposite to the pulsed magnetic field near the driving coil side, and generates the induced eddy current same as the pulsed magnetic field after reversing twice near the plate piece side, so as to strengthen the magnetic field near the reinforcement ring. The introduction of the reinforcement ring causes the force received by the two ends of the plate piece to be greater than the electromagnetic force of the traditional electromagnetic bulging. Therefore, the radial electromagnetic force of the two ends is greater, the axial uniformity is improved, and the forming effect is better.

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. The reinforcing ring is provided with a fracture. The shielding ring is arranged in the middle of the plate to be formed in the vertical direction, and the strengthening ring is arranged at the end of the plate to be formed in the vertical direction. The shielding ring and the strengthening ring are coaxially arranged inside the fixed bracket. 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 panel to be formed; Step 2: Determine the size parameters of the shielding ring based on the drive coil parameters and sheet metal forming specifications; Step 3: Determine the size parameters of the reinforcement ring based on the size parameters of the shielding ring and the sheet metal forming specifications; Step 4: Make the shielding ring, reinforcement ring and fixing bracket, and place the shielding ring and reinforcement ring on the fixing bracket; Step 5: Arrange the driving coil, the fixing bracket, and the panel to be formed on the panel forming base in sequence and fix them; Step 6: Connect the driving coil to the pulse power supply through the air switch, control the air switch to power 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; otherwise, execute step 6 to perform electromagnetic bulging on the plate again until the plate forming specifications 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. The size parameters of the reinforcement ring are adjusted to achieve the optimal bulging effect of the plate and obtain 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 distance between the shielding ring and the plate to be formed is 2-8 mm, and the distance between the shielding ring and the driving coil is 1-6 mm.

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 reinforcement ring are both made of copper.

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