CN110899452B - Metal plate attraction type forming method adopting double coil groups - Google Patents

Metal plate attraction type forming method adopting double coil groups Download PDF

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CN110899452B
CN110899452B CN201911303862.0A CN201911303862A CN110899452B CN 110899452 B CN110899452 B CN 110899452B CN 201911303862 A CN201911303862 A CN 201911303862A CN 110899452 B CN110899452 B CN 110899452B
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forming
metal plate
coil group
sheet metal
generating circuit
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CN110899452A (en
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熊奇
杨猛
刘馨
闫佳颖
宋先祺
李哲
邱立
江进波
余坤
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China Three Gorges University CTGU
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D26/00—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces
    • B21D26/14—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces applying magnetic forces

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  • Shaping Metal By Deep-Drawing, Or The Like (AREA)

Abstract

The invention discloses a sheet metal suction type forming method adopting a double-coil group, which comprises the steps of applying pressure to the edge of a formed sheet metal to fix the sheet metal, controlling a first pulse generating circuit to generate a background magnetic field in a forming area, determining the size of induced eddy current in the sheet metal required in the forming process, controlling a second pulse generating circuit to generate short-pulse-width current in a second coil group, so that the induced eddy current required by forming is generated in the sheet metal and is subjected to upward Lorentz force, and the forming area is deformed upwards. The invention also discloses a metal plate forming device. The forming of the metal plate is controlled through the two groups of coil groups, the first coil group forms a background magnetic field in a forming area, the second coil group generates induction eddy currents required by forming in the metal plate, and the background magnetic field and the induction eddy currents are controlled through the first coil group and the second coil group respectively, so that the efficient and accurate forming of the metal plate is realized.

Description

Metal plate attraction type forming method adopting double coil groups
Technical Field
The invention belongs to the field of metal forming and manufacturing, and particularly relates to a metal plate attraction type forming method and a metal plate attraction type forming device adopting double coils.
Background
The light alloy is widely applied to the manufacturing of various high-precision products such as airplanes, rockets, automobiles and the like, so the light alloy has great purpose and significance for the dent repair of the light alloy. The existing methods for forming the attraction type plate include gradient magnetic field force method, metal screen method and hot forming method. As shown in the literature, "Pulsed electromagnetic absorption of sheet metals-metals and passive applications", the gradient magnetic field force method adopts a metal plate made of a coil magnetized magnetic material based on low-frequency current, and generates stronger gradient magnetic field force between the coil and a workpiece so as to realize plate attraction forming; as shown in the document "Pulsed electromagnetic absorption of non-magnetic sheet metals", the metal screen method adds a good metal conductor between the coil and the metal plate, and pulse current is introduced into the coil to generate induced eddy currents in the same direction in the metal conductor and the plate, so as to realize attractive force shaping; the thermoforming method is to heat the plate by using high-temperature gas or liquid and then perform drawing forming by using a specific tool, such as drawing forming and top warping forming mainly in the automobile dent repairing technology.
Disclosure of Invention
The technical problem of the invention is that the existing forming method of the metal plate comprises a gradient magnetic field force method, a metal screen method and a hot forming method, which have the disadvantages of undesirable effect, low efficiency and uncontrollable forming quality.
The present invention is directed to solve the above problems, and an object of the present invention is to provide a method and an apparatus for forming a sheet metal member by attraction using a dual coil, in which a background magnetic field is generated in a sheet metal member forming area by a first coil group, and an induced eddy current is generated in the sheet metal member forming area by a second coil group, so that the sheet metal member forming area is deformed by an upward lorentz force, thereby achieving the sheet metal member forming specification.
The technical scheme of the invention is that a sheet metal attraction type forming method of a double-coil group is adopted, a first coil group and a second coil group are respectively adopted to generate a background magnetic field and an induced eddy current in a forming area of a formed sheet metal, the forming area of the sheet metal is subjected to an upward Lorentz force to enable the forming area to deform upward, the sheet metal forming method comprises the following steps,
step 1: applying pressure to the edge of the metal plate to fix the metal plate, placing a first coil group above the metal plate, and arranging a second coil group above a forming area of the metal plate;
step 2: connecting the first coil group to a first pulse generating circuit, controlling the first pulse generating circuit, generating a long pulse width current in the first coil group, and generating a background magnetic field in a forming area;
and step 3: determining the size of the induced eddy current in the metal plate required in the forming process according to the size of the background magnetic field and the forming specification of the formed metal plate;
and 4, step 4: connecting the second coil group to a second pulse generating circuit, controlling the second pulse generating circuit, and generating short-pulse-width current in the second coil group to generate induced eddy current required by forming in the metal plate, wherein the forming area of the metal plate generating the induced eddy current is subjected to upward Lorentz force under the action of a background magnetic field, and the forming area is deformed upwards;
and 5: judging whether the forming of the formed metal plate in the step 4 reaches the forming specification of the metal plate or not;
step 5.1: if the molding specification is not met, executing the step 2;
step 5.2: if the molding specification is reached, the process is terminated.
The attraction forming method for the sheet metal part adopting the double-coil group further comprises the step of annealing pretreatment on the sheet metal part before the step 1.
Further, the formed sheet metal piece is an alloy sheet piece for automobile skins.
Preferably, the first pulse generating circuit is a capacitor bank, and the capacitance is 2880-3200 muF.
Preferably, the second pulse generating circuit is a capacitor bank, and the capacitance is 40-160 muF.
The metal plate forming device comprises a first coil group, a second coil group, a first pulse generating circuit, a second pulse generating circuit and a blank pressing device, wherein the first coil group is connected with the first pulse generating circuit through a switch tube VT1, the second coil group is connected with the second pulse generating circuit through a switch tube VT2, and the blank pressing device is used for fixing the edge of a metal plate.
Preferably, the first coil set is connected with a freewheeling diode VD1 in parallel.
Preferably, the second coil group is connected with a freewheeling diode VD2 in parallel.
Compared with the prior art, the invention has the beneficial effects that:
1) the forming of the metal plate is controlled through two groups of coil groups, a background magnetic field is formed in a forming area by a first coil group, induced eddy current required by forming is generated in the formed metal plate by a second coil group, the forming area of the formed metal plate is subjected to upward Lorentz force under the action of the background magnetic field, the forming area is deformed upwards, and the background magnetic field and the induced eddy current are respectively controlled through the first coil group and the second coil group, so that the efficient and accurate forming of the metal plate is realized;
2) controlling the pulse current of the second coil group by controlling the voltage and the capacitance of the capacitor group connected with the second coil group, and further controlling the forming quality of the metal plate;
3) controlling the pulse current of the first coil group by controlling the voltage and the capacitance of the capacitor group connected with the first coil group, and controlling the background magnetic field formed by the metal plate;
4) the method of the invention realizes the accurate control of the forming effect of the metal plate, and can repeatedly carry out forming adjustment on the forming area of the metal plate for many times.
Drawings
The invention is further illustrated by the following figures and examples.
Fig. 1 is a flowchart of a metal plate suction type forming method using a double coil.
Fig. 2 is a schematic view of a sheet metal member forming apparatus of the present invention.
Fig. 3 is a schematic structural diagram of the coil assembly of the embodiment.
Fig. 4 is a waveform diagram of currents in the first coil assembly and the second coil assembly.
Fig. 5 is a schematic diagram of magnetic induction lines of the first coil assembly and the second coil assembly.
FIG. 6 is a schematic illustration of induced eddy currents and Lorentz forces generated on a sheet metal piece.
Fig. 7 is a diagram showing simulation results of the forming of the metal plate member.
Description of reference numerals: the device comprises a first coil group 1, a second coil group 2, a first pulse generation circuit 3, a second pulse generation circuit 4, a blank pressing device 5 and a metal plate 6.
Detailed Description
As shown in fig. 1, a sheet metal suction type forming method using a double coil group is adopted, after annealing pretreatment is performed on an alloy sheet metal used for automobile skin, a hydraulic mechanism of a blank holder is utilized to fix the sheet metal from the edge, a first coil group and a second coil group are adopted to respectively generate a background magnetic field and an induced eddy current in a forming area of the formed sheet metal, the forming area of the sheet metal is subjected to an upward lorentz force to enable the forming area to deform upward, the forming method comprises the following steps,
step 1: applying pressure to the edge of the formed metal plate to fix the metal plate, placing a first coil group above the formed metal plate, and arranging a second coil group above a forming area of the formed metal plate;
step 2: connecting the first coil group to a first pulse generating circuit, controlling the first pulse generating circuit, generating a long pulse width current in the first coil group, and generating a background magnetic field in a forming area;
and step 3: determining the size of the induced eddy current in the formed metal plate required in the forming process according to the size of the background magnetic field and the forming specification of the formed metal plate;
and 4, step 4: connecting the second coil group to a second pulse generating circuit, controlling the second pulse generating circuit, and generating short-pulse-width current in the second coil group to generate induced eddy current required by forming in the formed sheet metal part, wherein the forming area of the formed sheet metal part generating the induced eddy current is subjected to upward Lorentz force under the action of a background magnetic field, and the forming area is deformed upwards;
and 5: judging whether the forming of the formed metal plate in the step 4 reaches the forming specification of the formed metal plate;
step 5.1: if the molding specification is not met, executing the step 2;
step 5.2: if the molding specification is reached, the process is terminated.
In one embodiment, the first pulse generating circuit is a capacitor bank having a capacitance of 3200 μ F. The second pulse generating circuit is a capacitor bank with a capacitance of 120 muF.
Are respectively paired by computerThe first pulse generating circuit and the second pulse generating circuit are controlled, and the first coil group generates a long pulse width current I under the time sequence regulation of the first pulse generating circuitLGenerating a large background magnetic field B in the shaping regionL12T and a smaller counter-clockwise induced eddy current JL＝9.11×104A/m2(ii) a The second coil group generates a short-pulse width current I under the time sequence control of the second pulse generating circuitSWhen the long pulse width current reaches the peak value, the second pulse generating circuit is conducted to generate short pulse width current; less magnetic induction B is generated on the metal plateS1.5T and larger clockwise induced eddy current JS＝4.38×108A/m2(ii) a According to the left-hand rule, the plate is subjected to a large axially upward Lorentz force FZ. Long pulse width current ILShort pulse width current ISAs shown in fig. 4. Fig. 5 shows the magnetic induction lines of the first coil group and the second coil group.
The stress analysis is carried out on the metal plate,
Figure GDA0003216364120000041
analyzing the induced eddy current density on the sheet metal part, when t1＞＞t2-t1When the current is over;
induced eddy current density
JS＞＞JL
And ILmax＞＞ISmax，
Figure GDA0003216364120000042
Further obtain
Fz≈-JS×BL-R；
In the formula FZAs axial Lorentz force, FRIs the radial lorentz force; j. the design is a squareeThe induced eddy current density on the metal plate is positive in the clockwise direction; b isZ、BRAre respectively a shaftA radial magnetic field component; j. the design is a squareLInduced eddy currents, J, generated on sheet metal elements for long pulse width currentsSInduced eddy currents generated on the metal plate for short pulse width currents; b isL-RRadial magnetic field generated in the forming zone of the sheet metal element for long pulse width current, BS-RA radial magnetic field generated in a metal plate forming area for short pulse width current; t represents time, t1The time when the long pulse width current reaches the peak value, t2The time when the short pulse width current reaches the peak value; i isLmaxFor a long pulse width current ILPeak value of (1)SmaxFor short pulse width current ISPeak value of (a). Induced eddy currents, lorentz forces, generated on the sheet metal piece are shown in fig. 6.
In the embodiment, the first coil group 1 has 45 turns and a cross section of 1mm × 4mm, the second coil group 2 has 12 turns and a cross section of 1mm × 4mm, a bobbin adapted to the geometric shape of the coil is manufactured, high-strength fibers are used for inter-layer reinforcement and external fixation of the coil, and the first coil group 1 and the second coil group 2 are assembled into a whole, as shown in fig. 3.
As shown in fig. 2, in the embodiment, the sheet metal forming apparatus includes a first coil group 1, a second coil group, a first pulse generating circuit 3, a second pulse generating circuit 4, and a blank pressing device 5, where the first coil group 1 is connected to the first pulse generating circuit 3 through a switching tube VT1, the second coil group 2 is connected to the second pulse generating circuit 4 through a switching tube VT2, and the blank pressing device 2 is used to fix an edge of the sheet metal 3. The first coil group 1 is connected in parallel with a freewheeling diode VD 1. The second coil group 2 is connected in parallel with a freewheeling diode VD 2. The inductor Ls is a line inductor of the first coil assembly 1, and the resistor Rs is a line resistor of the first coil assembly 1. The inductance Lf is the line inductance of the second coil assembly 2, and the resistance Rf is the line resistance of the second coil assembly 2.
The finite element software COMSOL5.4a is adopted to simulate the forming of the sheet metal, the discharge voltage of the first coil group is set to be 11kV, the capacitor value of the first pulse generation circuit is set to be 3200uF, the discharge voltage of the second coil group is set to be 6.8kV, the capacitor value of the second pulse generation circuit is set to be 120uF, and the simulation result shows that the maximum axial displacement of the center point of the sheet metal is 3.12mm, as shown in FIG. 7.

Claims (5)

1. The attracted forming method of the sheet metal by adopting the double coil group is characterized in that a first coil group and a second coil group are respectively adopted to generate a background magnetic field and an induced eddy current in a forming area of the formed sheet metal, the forming area of the sheet metal is subjected to an upward Lorentz force to deform the forming area upwards, the forming method of the sheet metal comprises the following steps,
step 1: applying pressure to the edge of the metal plate to fix the metal plate, placing a first coil group above the metal plate, and arranging a second coil group above a forming area of the metal plate;
step 2: connecting the first coil group to a first pulse generating circuit, controlling the first pulse generating circuit, generating a long pulse width current in the first coil group, and generating a background magnetic field in a forming area;
and step 3: determining the size of the induced eddy current in the metal plate required in the forming process according to the size of the background magnetic field and the forming specification of the metal plate;
and 4, step 4: connecting the second coil group to a second pulse generating circuit, controlling the second pulse generating circuit, generating short-pulse-width current in the second coil group, generating induced eddy current required by forming in the metal plate, and enabling a forming area of the metal plate generating the induced eddy current to be subjected to upward Lorentz force under the action of a background magnetic field, so that the forming area is deformed upwards;
and 5: judging whether the forming of the metal plate in the step 4 reaches the forming specification of the metal plate;
step 5.1: if the molding specification is not met, executing the step 2;
step 5.2: if the molding specification is reached, the process is terminated.
2. The attraction type forming method for a sheet metal element using a double coil assembly as claimed in claim 1, further comprising an annealing pretreatment for the sheet metal element before step 1.
3. The sheet metal element attraction-type forming method using a double coil group as claimed in claim 1, wherein the formed sheet metal element is an alloy sheet element for an automobile skin.
4. The attraction type forming method for metal plate with the double coil sets as claimed in claim 1, wherein the first pulse generating circuit is a capacitor set, and the capacitance is 2880-3200μF。
5. The attraction type forming method for metal plates by using double coil groups as claimed in claim 1, wherein the second pulse generating circuit is a capacitor group, and the capacitance is 40-160%μF。
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CN112387845A (en) * 2020-11-16 2021-02-23 湖北继扬电力科技有限公司 Large-size pipe fitting electromagnetic flanging device and method based on magnetic collector
CN112389119A (en) * 2020-11-16 2021-02-23 湖北继扬电力科技有限公司 Plate embossing forming method and device based on single pulse power supply
CN112775257B (en) * 2020-12-14 2022-10-04 三峡大学 Plate embossing forming device and method based on pulse electromagnetic force
CN112719022B (en) * 2020-12-14 2022-11-18 三峡大学 Auxiliary electromagnetic forming device and method for coil surrounding plate

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