Electromagnetic bulging method and bulging device for sheet metal based on layered magnetic field transformer

Abstract

The application relates to a layered magnetic field transformer-based plate electromagnetic bulging method, the cross section of the layered magnetic field transformer is trapezoidal, the layered magnetic field transformer comprises an end surface conductor layer, a middle insulating layer and a bottom surface conductor layer; a through gap is arranged on the layered magnetic field transformer, the end surface conductor layer and the bottom surface conductor layer are electrically connected at the gap; the layered magnetic field transformer is arranged between a driving coil and a plate to be formed, and the end surface conductor layer is close to an end bulging area of the plate; when the driving coil is electrified, axial electromagnetic force is generated under the superimposed magnetic field of the current of the driving coil and the induced current of the layered magnetic field transformer, the axial electromagnetic force on the end bulging area of the plate is greater than that on the middle bulging area, and the induced magnetic flux of the middle bulging area of the plate is uniformly distributed, thereby improving the flatness of the middle bulging area of the plate. The application improves the electromagnetic force distribution characteristics on the bulging plate, can realize uniform deformation of the plate, and improves the bulging effect of the plate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metal forming manufacturing, and particularly relates to a plate electromagnetic bulging method and bulging device based on a layered magnetic field transformer. BACKGROUND

[0002] Electromagnetic forming as a high-speed pulse forming technology can significantly improve the forming limit and surface quality of materials. In recent years, lightweight alloys have been widely used in the field of metal manufacturing due to their low carbon and environmental protection characteristics. Therefore, improving the uniformity of electromagnetic forming of lightweight alloys has great significance to the metal manufacturing industry. The document "Study of a topology for Plate Electromagnetic Forming Based on Inner Reverse and Outer Positive Double Coil Loading" adopts a double-coil plate electromagnetic forming technology of inner reverse and outer positive. By applying opposite currents to the small coil inside the large coil, the axial electromagnetic force on the middle part of the pipe is weakened, and finally the profile of the formed plate is more uniform. However, this method uses a double-coil structure which is relatively complex, and most of the energy is consumed in the coil, which makes the energy utilization rate of the forming system too low, and the disadvantages are obvious.

[0003] The Chinese invention "Plate electromagnetic forming method based on conductor circular ring" with publication number CN116833297A provides a plate uniform forming method based on conductor circular ring. By setting multiple metal conductor circular rings between the driving coil and the plate to be formed, opposite direction induced currents are generated on the conductor circular rings, the magnetic flux density and induced eddy current in the middle part of the plate are weakened, so as to improve the electromagnetic force distribution on the plate and make it more uniform, and the uniformity of plate forming is improved. The invention makes full use of the skin effect of current, and the use of conductor circular ring can accurately realize the uniform forming of plate. However, this method uses multiple conductor circular rings, and the forming system is too complex and cannot be applied to various processing scenes. SUMMARY

[0004] The application aims at the above problems, and provides a plate electromagnetic bulging method based on a layered magnetic field transformer, a layered magnetic field collector is introduced between a driving coil and a forming plate, the layered magnetic field transformer comprises an end surface conductor layer, an intermediate insulating layer and a bottom surface conductor layer, the end surface conductor layer is electrically connected with the bottom surface conductor layer, the end surface conductor layer is close to an end bulging area of the plate, an axial electromagnetic force is generated on the plate under a superimposed magnetic field of a current of the driving coil and an induced current of the layered magnetic field transformer, the axial electromagnetic force on the end bulging area of the plate is greater than that on a middle bulging area of the plate, and the induced magnetic flux of the middle bulging area of the plate is uniformly distributed, so that the flatness of the middle bulging area is improved; the induced current distribution on the plate is forcedly regulated by the layered magnetic field collector, the distribution characteristics of the electromagnetic force are improved, and then the uniform deformation of the plate is realized.

[0005] In order to achieve the above object, the technical scheme provided by the application is as follows:

[0006] The plate electromagnetic bulging method based on the layered magnetic field transformer comprises the following steps.

[0007] Step 1: according to the forming specification of the plate, the parameters of the driving coil are determined, and the driving coil is made;

[0008] Step 2: according to the parameters of the driving coil and the forming specification of the plate, the shape of the layered magnetic field transformer and the material and size parameters of the end surface conductor layer, the intermediate insulating layer and the bottom surface conductor layer are determined;

[0009] Step 3: according to the result obtained in step 2, the layered magnetic field transformer is made;

[0010] Step 4: the edges of the plate to be formed are fixed by using a blank holder die, and the layered magnetic field transformer is arranged on the other side of the plate in the bulging direction of the plate, so that the end surface conductor layer of the layered magnetic field transformer is close to the end bulging area of the plate;

[0011] Step 5: the driving coil is placed on one side of the bottom surface conductor layer of the layered magnetic field transformer, and the driving coil is connected to the pulse power supply through an air switch;

[0012] Step 6: the air switch is controlled to supply power to the driving coil, and the discharge time of the pulse power supply is controlled, so that the plate to be bulged is subjected to electromagnetic bulging;

[0013] Step 7: whether the bulging effect of the plate meets the forming specification of the plate is judged, if yes, the process is ended, otherwise, step 6 is executed to perform electromagnetic bulging on the plate again.

[0014] Preferably, in step 1, a workpiece electromagnetic forming model containing the driving coil and the plate to be formed is established by using finite element software, a pulse current is applied to the driving coil of the workpiece electromagnetic forming model, the bulging effect of the plate is simulated and compared with the forming specification of the plate, the parameters of the driving coil are adjusted so that the bulging effect of the plate meets the needs of the forming specification of the plate, and the parameters of the driving coil are determined by simulation.

[0015] Preferably, in step 2, a layered magnetic field transformer is added to the workpiece electromagnetic forming model, the bulging simulation of the plate is performed again by using the workpiece electromagnetic forming model, the shape, material and size parameters of the layered magnetic field transformer are adjusted so that the flatness of the middle bulging area of the plate after forming is best, and the shape of the layered magnetic field transformer and the material and size parameters of the end conductor layer, the middle insulating layer and the bottom conductor layer are determined by simulation.

[0016] Preferably, the cross section of the layered magnetic field transformer is a right trapezoid.

[0017] Preferably, the length of the lower base of the cross section trapezoid of the layered magnetic field transformer is greater than twice the length of the upper base.

[0018] Preferably, the end conductor layer and the bottom conductor layer of the layered magnetic field transformer are made of red copper material.

[0019] Preferably, the middle insulating layer of the layered magnetic field transformer is made of insulating material mica.

[0020] Preferably, the distance between the layered magnetic field transformer and the plate to be formed is not greater than 2 mm.

[0021] Preferably, the distance between the layered magnetic field transformer and the driving coil is not greater than 1.5 mm.

[0022] Preferably, the driving coil is powered by a pulse power supply, and the discharge pulse width of the pulse power supply is 50-1000 μs.

[0023] As another object of the application, a plate electromagnetic bulging device comprises a layered magnetic field transformer, a driving coil and a pulse power supply, and the driving coil is connected with the pulse power supply through an air switch.

[0024] The layered magnetic field transformer is in the shape of a circular ring, the cross section of the layered magnetic field transformer is a trapezoid, the layered magnetic field transformer comprises an end conductor layer, a middle insulating layer and a bottom conductor layer, the layered magnetic field transformer is provided with a gap penetrating through the end conductor layer, the middle insulating layer and the bottom conductor layer, and the end conductor layer and the bottom conductor layer are electrically connected at the gap.

[0025] Compared with the prior art, the application has the following beneficial effects:

[0026] 1) The present application sets a layered magnetic field transformer between the driving coil and the bulging plate member, uses the layered magnetic field transformer to regulate the induced current distribution on the plate member, improves the electromagnetic force distribution characteristics on the bulging plate member, and can realize uniform deformation of the plate member and improve the bulging effect of the plate member.

[0027] 2) The present application uses a trapezoidal cross-section magnetic field transformer, the induced current intensity of the end face of the layered magnetic field transformer is greater than that of the bottom of the layered magnetic field transformer, the end face of the layered magnetic field transformer is close to the end bulging area of the plate member, the axial electromagnetic force received by the end bulging area of the plate member is greater than that received by the middle bulging area of the plate member, and the induced magnetic flux of the middle bulging area of the plate member is uniformly distributed, so that the end bulging area of the plate member deforms preferentially, drives the middle bulging area of the plate member to deform, and improves the flatness of the middle bulging area of the plate member.

[0028] 3) The present application uses the layered magnetic field transformer whose end face is close to the end bulging area of the plate member, in the bulging process, the induced current of the end face of the layered magnetic field transformer flows to the bottom of the layered magnetic field transformer through the gap, a pulse strong magnetic field is generated at the end of the bulging plate member, the energy generated by the driving coil is concentrated in the end deformation of the bulging plate member, thereby driving the middle deformation of the plate material, reducing the electric energy loss, and improving the electric energy utilization rate.

[0029] 4) The present application can manufacture different specifications of bulging plate members by replacing magnetic field transformers of different sizes and parameters, without replacing the driving coil, which can meet the production needs of bulging plate members of different forming specifications, reduce the bulging processing difficulty of multi-specification plate members, and improve the bulging processing production efficiency of plate members.

[0030] 5) The plate bulging device provided by the present application improves the bulging effect and production efficiency of the plate, reduces the electric energy loss in the plate bulging process, and is more energy-saving and environmentally friendly.

[0031] 6) The layered magnetic field transformer of the present application is easy to manufacture, has low cost, can meet the production needs of bulging plate members of different forming specifications through magnetic field transformers of different sizes and parameters, can reduce the reaction force generated by the induced current on the bulging plate member on the driving coil in the plate bulging process, thereby protecting the driving coil and prolonging the service life of the driving coil. BRIEF DESCRIPTION OF DRAWINGS

[0032] The present application will be further described below in combination with the drawings and examples.

[0033] Figure 1 It is a circuit connection schematic diagram of the plate electromagnetic bulging method of the embodiment of the present application.

[0034] Figure 2 It is a schematic diagram of the plate electromagnetic bulging device of Example 1.

[0035] Figure 3 Schematic diagram of the electromagnetic bulging device for plates in the second embodiment.

[0036] Figure 4 Schematic diagram of the structure of the layered magnetic field converter of Example 2.

[0037] Figure 5 A comparison chart of the plate induced current and magnetic flux density between the present invention and the traditional plate bulging method.

[0038] Figure 6 This is a comparison diagram of the axial electromagnetic force on the plate by the present invention and the traditional plate bulging method.

[0039] Figure 7 This is a comparison chart of the plate bulging effects of the present invention and the traditional plate bulging method.

[0040] Explanation of reference numerals: driving coil 1 , layered magnetic field converter 2 , end surface conductor layer 201 , middle insulating layer 202 , bottom surface conductor layer 203 , fracture 204 , plate 3 , middle bulging area 301 , end bulging area 302 . DETAILED DESCRIPTION

[0041] Example 1

[0042] like Figure 2 As shown, the plate to be formed is circular, the layered magnetic field converter 2 is in the shape of a ring, the cross section of the layered magnetic field converter is trapezoidal, and the layered magnetic field converter 2 includes an end conductor layer 201, an intermediate insulating layer 202, and a bottom conductor layer 203; the layered magnetic field converter 2 is provided with a break 204 that passes through the end conductor layer, the intermediate insulating layer, and the bottom conductor layer, and the end conductor layer 201 and the bottom conductor layer 203 are electrically connected at the break; the layered magnetic field converter is arranged between the driving coil 1 and the plate to be formed, and the end conductor layer 201 is in close contact with the end bulging area 302 of the plate. When the driving coil is energized, an axial electromagnetic force is generated under the superimposed magnetic field of the current of the driving coil and the induced current of the layered magnetic field converter. The axial electromagnetic force on the end bulging area 302 of the plate is greater than the axial electromagnetic force on the middle bulging area 301 of the plate, and the induced magnetic flux in the middle bulging area 301 of the plate is evenly distributed. The driving coil is connected to a pulse power supply, as shown in FIG. Figure 1 shown.

[0043] The electromagnetic bulging method of a plate based on a layered magnetic field converter comprises the following steps:

[0044] Step 1: Determine the drive coil parameters according to the sheet metal forming specifications;

[0045] The finite element software is used to establish a workpiece electromagnetic forming model containing a driving coil and a plate to be formed, a pulse current is applied to the driving coil of the workpiece electromagnetic forming model, the bulging effect of the plate is simulated, and the bulging effect of the plate is compared with the forming specification of the plate, the parameters of the driving coil are adjusted, so that the bulging effect of the plate meets the needs of the forming specification of the plate, and the parameters of the driving coil are determined through simulation;

[0046] The driving coil is manufactured.

[0047] Step 2: According to the driving coil parameters and the plate forming specification, the shape of the layered magnetic field transformer and the material and size parameters of the end surface conductor layer, the middle insulating layer and the bottom surface conductor layer are determined;

[0048] The layered magnetic field transformer is added to the workpiece electromagnetic forming model, and the plate bulging simulation is performed again by using the workpiece electromagnetic forming model, the shape, material and size parameters of the layered magnetic field transformer are adjusted, so that the flatness of the plate middle bulging area after forming is best, and the shape of the layered magnetic field transformer and the material and size parameters of the end surface conductor layer, the middle insulating layer and the bottom surface conductor layer are determined through simulation.

[0049] Step 3: According to the results obtained in step 2, the layered magnetic field transformer is manufactured;

[0050] Step 4: The edges of the plate to be formed are fixed by using a blank holder die, and the layered magnetic field transformer is arranged on the other side of the plate bulging direction, so that the end surface conductor layer of the layered magnetic field transformer tightly abuts the end bulging area of the plate;

[0051] Step 5: The driving coil is placed on one side of the bottom surface conductor layer of the layered magnetic field transformer, and the driving coil is connected to the pulse power supply through an air switch;

[0052] Step 6: The air switch is controlled to supply power to the driving coil, and the discharge time of the pulse power supply is controlled, so as to perform electromagnetic bulging on the plate to be bulged;

[0053] Step 7: It is judged whether the bulging effect of the plate meets the forming specification of the plate, if yes, the process is ended, otherwise, step 6 is executed to perform electromagnetic bulging on the plate again.

[0054] In the embodiment, the discharge pulse width of the pulse power supply is 100 μs.

[0055] As shown in Figure 4 The end surface conductor layer 201 and the bottom surface conductor layer 203 of the layered magnetic field transformer are made of red copper conductor material, and the middle insulating layer 202 is made of insulating material Chailong. The height of the end surface conductor layer 201 and the bottom surface conductor layer 203 is equal and less than the height of the middle insulating layer; at the joint, the end surface conductor layer and the bottom surface conductor layer are connected to each other to form a loop.

[0056] Example Two

[0057] The main difference between the plate electromagnetic bulging device of the second embodiment and the first embodiment is that the cross-sectional area of the layered magnetic field transformer is a right trapezoid, and the length of the lower base of the trapezoid is about 3 times the length of the upper base.

[0058] As shown in Figure 3 , the plate electromagnetic bulging device comprises a layered magnetic field transformer 2, a driving coil 1 and a capacitor power supply. The outer diameter of the end conductor layer 201 of the layered magnetic field transformer is equal to the outer diameter of the bottom conductor layer 203. The driving coil 1 is connected to the capacitor power supply through an air switch. When the air switch is turned on, a pulse current is generated in the driving coil 1. The discharge pulse width of the capacitor power supply is 100 μs.

[0059] The plate electromagnetic bulging method of the second embodiment is the same as the first embodiment.

[0060] In the embodiment, the plate to be formed is processed into a basin-shaped part through bulging.

[0061] As shown in Figure 5 , the plate electromagnetic bulging method based on the layered magnetic field transformer, i.e. the method of the present application, and the conventional plate electromagnetic forming method without a magnetic field transformer are simulated and compared. The simulation voltage is set to 1.5 kV, and the circuit parameters are the same. As shown in Figure 5 , the layered magnetic field transformer forcibly changes the current distribution in the magnetic field transformer, greatly enhances the current intensity at the end surface, and increases the induced current and the magnetic flux density in the bulging area at the end of the plate. The plate stress conditions of the method of the present application and the conventional plate bulging method without a magnetic field transformer at 50 μs after the driving coil is energized are simulated and compared, as shown in Figure 6 . As shown, due to the effect of the layered magnetic field transformer, the induced current is forcibly distributed at the end surface of the magnetic field transformer, the axial electromagnetic force in the bulging area at the end of the plate is much greater than that at the middle of the plate, the end of the plate deforms preferentially, drives the middle part with less constraint to deform, and improves the uniformity of plate forming. The final plate bulging three-dimensional effect of the present application and the plate electromagnetic bulging method without a magnetic field transformer is shown in Figure 7 . The diameter of the middle part, i.e. the bottom of the basin, of the basin-shaped workpiece obtained by the present application is 64 mm, and the bottom of the basin is very flat. The diameter of the bottom of the basin-shaped workpiece obtained by the conventional plate electromagnetic bulging method without a magnetic field transformer is less than 30 mm. It can be seen that the bulging method of the present application greatly improves the flatness and uniformity of plate bulging.

Claims

1. A plate electromagnetic bulging method based on a layered magnetic field converter, characterized in that: The plate to be formed is circular, the layered magnetic field converter is in the shape of a circular ring, and the cross-section of the layered magnetic field converter is trapezoidal, and the layered magnetic field converter includes an end surface conductor layer, an intermediate insulating layer and a bottom surface conductor layer; the layered magnetic field converter is provided with a fracture penetrating the end surface conductor layer, the intermediate insulating layer and the bottom surface conductor layer, and the end surface conductor layer and the bottom surface conductor layer are electrically connected at the fracture; the layered magnetic field converter is arranged between the driving coil and the plate to be formed, and the end surface conductor layer is in close contact with the end expansion zone of the plate; when the driving coil is energized, an axial electromagnetic force is generated under the superimposed magnetic field of the current of the driving coil and the induced current of the layered magnetic field converter, and the axial electromagnetic force on the end expansion zone of the plate is greater than the axial electromagnetic force on the middle expansion zone of the plate, and the induced magnetic flux in the middle expansion zone of the plate is evenly distributed, thereby improving the flatness of the middle expansion zone of the plate; The plate electromagnetic bulging method comprises the following steps: Step 1: Determine the drive coil parameters according to the sheet metal forming specifications and manufacture the drive coil; Step 2: Based on the drive coil parameters and sheet metal forming specifications, determine the shape of the layered magnetic field converter and the material and size parameters of the end conductor layer, middle insulation layer, and bottom conductor layer; Step 3: Based on the results obtained in step 2, a layered magnetic field converter is fabricated; Step 4: Use a clamping die to fix the edge of the sheet to be formed, and arrange a layered magnetic field converter on the other side of the sheet in the bulging direction, so that the end surface conductor layer of the layered magnetic field converter is in close contact with the end bulging area of ​​the sheet; Step 5: Place a drive coil on one side of the bottom conductor layer of the layered magnetic field converter and connect the drive coil to the pulse power supply via an air switch; Step 6: Control the air switch to power the drive coil, control the discharge time of the pulse power supply, and perform electromagnetic bulging on the plate to be bulged; 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.

2. The plate electromagnetic bulging method based on a layered magnetic field converter according to claim 1, characterized in that: In step 1, finite element software is used to establish an electromagnetic forming model of the workpiece including a driving coil and a plate to be formed. A pulse current is applied to the driving coil of the electromagnetic forming model of the workpiece, and the bulging effect of the plate is simulated and compared with the plate forming specifications. The parameters of the driving coil are adjusted so that the bulging effect of the plate meets the requirements of the plate forming specifications, and the parameters of the driving coil are determined by simulation.

3. The plate electromagnetic bulging method based on a layered magnetic field converter according to claim 2, characterized in that: In step 2, a layered magnetic field converter is added to the electromagnetic forming model of the workpiece, and the electromagnetic forming model of the workpiece is used again to simulate the sheet metal expansion. The shape, material and size parameters of the layered magnetic field converter are adjusted to ensure the best flatness of the middle expansion area of ​​the sheet metal after forming. The shape of the layered magnetic field converter and the material and size parameters of the end conductor layer, the middle insulation layer and the bottom conductor layer are determined by simulation.

4. The electromagnetic bulging method for sheet metal based on a layered magnetic field converter according to claim 1, 2 or 3, characterized in that: The cross section of the layered magnetic field converter is a right-angled trapezoid, and the length of the lower base of the trapezoid is greater than twice the length of the upper base.

5. The plate electromagnetic bulging method based on a layered magnetic field converter according to claim 1, 2 or 3, characterized in that: The end surface conductor layer and the bottom surface conductor layer of the layered magnetic field converter are both made of copper material.

6. The electromagnetic bulging method for sheet metal based on a layered magnetic field converter according to claim 1, 2 or 3, characterized in that: The distance between the layered magnetic field converter and the plate to be formed is no more than 2 mm.

7. The plate electromagnetic bulging method based on a layered magnetic field converter according to claim 1, 2 or 3, characterized in that: The distance between the layered magnetic field converter and the driving coil is no more than 1.5 mm.

8. The electromagnetic bulging method for sheet metal based on a layered magnetic field converter according to claim 1, 2 or 3, characterized in that: In step 6, the discharge pulse width of the pulse power supply is 50-1000 μs.

9. A layered magnetic field converter for electromagnetic bulging of sheet metal, characterized in that: The layered magnetic field converter is in the shape of a ring, and the cross-section of the layered magnetic field converter is trapezoidal. The layered magnetic field converter includes an end conductor layer, an intermediate insulating layer and a bottom conductor layer; the layered magnetic field converter is provided with a fracture penetrating the end conductor layer, the intermediate insulating layer and the bottom conductor layer, and the end conductor layer and the bottom conductor layer are electrically connected at the fracture; the layered magnetic field converter is arranged between the driving coil and the plate to be formed, and the end conductor layer is close to the end expansion area of ​​the plate. When the driving coil is energized, an axial electromagnetic force is generated under the superimposed magnetic field of the current of the driving coil and the induced current of the layered magnetic field converter, and the axial electromagnetic force on the end expansion area of ​​the plate is greater than the axial electromagnetic force on the middle expansion area of ​​the plate.

Images