Pipe forming method and device using convex pieces to improve magnetic field distribution of trapezoidal magnetic collector

Abstract

The present invention relates to a pipe forming method using convex pieces to improve the magnetic field distribution of a trapezoidal magnetism collector, comprising: determining the longitudinal height of the convex piece of the magnetism collector according to the length of the pipe to be formed; using finite element software to establish a workpiece electromagnetic forming model including a trapezoidal magnetism collector, a driving coil, and the pipe to be formed; applying a pulse current to the driving coil of the workpiece electromagnetic forming model to simulate the magnetic field distribution of the trapezoidal magnetism collector; adjusting the number of convex pieces and the thickness of the convex pieces of the trapezoidal magnetism collector in the workpiece electromagnetic forming model to make the magnetic field distribution of the simulated trapezoidal magnetism collector close to rotational symmetry; according to the parameters of the obtained trapezoidal magnetism collector, making a multi-convex trapezoidal magnetism collector; using the multi-convex trapezoidal magnetism collector to perform compression forming control of the pipe to be formed. The present invention improves the imbalance phenomenon of the electromagnetic field distribution inside the magnetism collector caused by the break, makes the magnetic field distribution inside the annular magnetism collector more close to rotational symmetry, and improves the uniformity of pipe forming.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic forming control of pipe fittings, and in particular relates to a pipe fitting forming method and device which adopts convex pieces to improve the magnetic field distribution of a trapezoidal magnetic collector. Background Art

[0002] Lightweighting is an important technical means to achieve energy conservation and emission reduction in the fields of aerospace, automobile industry, etc. The main way to achieve lightweighting is to use lightweight alloy materials. High-performance aluminum alloys, titanium alloys, and magnesium alloys have become the preferred materials for lightweighting in modern aerospace, automobile industry, etc. However, lightweight alloy materials have low forming plasticity at room temperature, poor local ductility, are prone to cracks, and have large springback. The processing effect using traditional processing technology is not ideal.

[0003] Electromagnetic forming is a high-rate pulse forming technology that can greatly improve the forming performance of metal materials and is one of the effective means to solve the difficulties in forming light alloys. The capacitor power supply discharges the drive coil, generating a strong pulse current in the drive coil and generating induced eddy currents in the metal workpiece; the coil current and its magnetic field interact with the eddy currents and magnetic fields of the workpiece, driving the metal workpiece to accelerate and plastically deform, thereby realizing the forming process of the workpiece. The entire electromagnetic forming process is in milliseconds. Compared with traditional processing technology, electromagnetic forming has two major advantages: one is the high strain rate, which can improve the plastic deformation ability of the material and increase the forming limit of the material by 5-10 times; the second is non-contact force application, high surface quality of the formed part, and only a single mold is required, which can reduce stress concentration during the deformation process.

[0004] In the electromagnetic forming process of pipe fittings, the magnetic collector is placed between the driving coil and the workpiece to adjust the distribution of the magnetic field, thereby changing the distribution of the electromagnetic force, and can better achieve the expected forming effect. Figure 3 As shown, it is used to change the direction of the induced current on the upper and lower surfaces of the magnetic collector, thereby controlling the electromagnetic force. However, due to the structural problem of the fine gap of the magnetic collector itself, there is a problem of uneven distribution of electromagnetic force in the circumferential direction of the workpiece. The closer to the fine gap, the weaker the electromagnetic force. When the magnetic collector of the prior art is used for pipe bulging, compression electromagnetic forming or electromagnetic welding, it is difficult to achieve the ideal forming effect near the fine gap. This structural defect reduces the circumferential uniformity of electromagnetic forming. Summary of the invention

[0005] The purpose of the present invention is to address the above-mentioned problems and to provide a pipe forming method and device that uses protrusions to improve the magnetic field distribution of a trapezoidal magnetic collector. The paired protrusions at the upper and lower ends of the annular magnetic collector are used to improve the uneven magnetic field distribution in the inner ring of the magnetic collector caused by the break in the magnetic collector. When the pipe is formed, the magnetic field distribution of the annular magnetic collector under the action of a driving coil is approximately rotationally symmetrical, so as to improve the uniformity of the pipe forming inside the magnetic collector.

[0006] The technical solution of the present invention is a pipe forming method for improving the magnetic field distribution of a trapezoidal magnetic collector by using convex pieces, comprising the following steps:

[0007] Step 1: Determine the longitudinal height of the convex piece of the magnetic collector according to the length of the pipe to be formed;

[0008] Step 2: Using finite element software to establish an electromagnetic forming model of a workpiece including a trapezoidal magnetic collector, a driving coil, and a pipe to be formed, wherein the workpieces of the trapezoidal magnetic collector and the pipe to be formed are both made of aluminum alloy;

[0009] Step 3: Apply pulse current to the driving coil of the workpiece electromagnetic forming model to simulate the magnetic field distribution of the trapezoidal magnetic collector;

[0010] Step 4: Adjust the number and thickness of the convex pieces of the trapezoidal magnetic collector in the electromagnetic forming model of the workpiece, and execute step 3 to make the magnetic field distribution of the simulated trapezoidal magnetic collector close to rotational symmetry;

[0011] Step 5: According to the parameters of the trapezoidal magnetic flux collector obtained in step 4, a multi-convex trapezoidal magnetic flux collector is manufactured;

[0012] Step 6: Using the multi-convex trapezoidal magnetic collector obtained in step 5 to control the compression forming of the pipe to be formed;

[0013] Step 6.1: Place the pipe to be formed at the inner center of the trapezoidal magnetic collector, with the distance between the pipe to be formed and the trapezoidal magnetic collector being 3 mm;

[0014] Step 6.2: Set a driving coil outside the trapezoidal magnetic collector, and the coil material is copper;

[0015] Step 6.3: Connect the driving coil to the pulse power supply via the discharge switch;

[0016] Step 6.4: Control the discharge switch to power the drive coil, generate radial electromagnetic force and axial electromagnetic force on the pipe to be formed, and the pipe is compressed and formed under the action of the electromagnetic force.

[0017] Furthermore, in step 2, the initial thickness of the protruding piece of the trapezoidal magnetic collector is equal to the width of the fracture, both of which are 1 mm.

[0018] Furthermore, the number of the protrusions of the trapezoidal magnetic collector is 2 pairs, the angle between adjacent protrusions is 120°, the angle between the break and the adjacent protrusion is 120°, the integrity of the forming is good, but reverse displacement occurs in a few areas.

[0019] Preferably, the number of the protrusions of the trapezoidal magnetic collector is 3 pairs, the angle between adjacent protrusions is 90°, and the angle between the break and the adjacent protrusion is 90°. The deformation result is very symmetrical and has good uniformity.

[0020] The pipe forming device using the above-mentioned pipe forming method includes a trapezoidal magnetic collector, a driving coil and a pulse power supply, wherein the trapezoidal magnetic collector is in the shape of a circular ring, the cross-section of the trapezoidal magnetic collector is trapezoidal, the trapezoidal magnetic collector is provided with a break, and a pair of triangular convex pieces are provided on the inner side of the trapezoidal magnetic collector, and the convex pieces and the break of the magnetic collector are evenly distributed in the circumferential direction; the driving coil is arranged on the outer side of the trapezoidal magnetic collector, and the center line of the driving coil is aligned with the center line of the trapezoidal magnetic collector; the driving coil is connected to the pulse power supply via a discharge switch.

[0021] The trapezoidal magnetism collector is in a circular ring shape, has a trapezoidal cross section, is provided with a break, has a pair of triangular convex pieces on the inner side, and the convex pieces and the break of the magnetism collector are evenly distributed in the circumferential direction.

[0022] The beneficial effect of the present invention is that the pipe forming method and device of the present invention utilize the protrusions that are evenly distributed with the gaps in the circumferential direction of the annular magnetic collector to improve the imbalance of the electromagnetic field distribution on the inner side of the magnetic collector caused by the broken seams of the existing annular magnetic collector, so that the magnetic field distribution on the inner side of the annular magnetic collector is more rotationally symmetrical, thereby improving the uniformity of the forming of the pipe inside the magnetic collector; the multi-protrusion trapezoidal magnetic collector of the present invention is easy to produce and manufacture, has low cost, and is convenient for large-scale promotion and use. 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 Schematic diagram of a pipe forming device according to an embodiment of the present invention.

[0025] Figure 2 Schematic diagram of circuit connection of a pipe forming device according to an embodiment of the present invention.

[0026] Figure 3 It is a schematic diagram of a magnetic collector in the prior art.

[0027] Figure 4a Schematic diagram of the structure of the trapezoidal magnetic collector of the first embodiment.

[0028] Figure 4b FIG. 1 is a top view of the trapezoidal magnetic collector of the first embodiment.

[0029] Figure 5a Schematic diagram of the structure of the trapezoidal magnetic collector of the second embodiment.

[0030] Figure 5b It is a top view of the trapezoidal magnetic collector of the second embodiment.

[0031] Figure 6a Schematic diagram of the structure of the trapezoidal magnetic collector of the third embodiment.

[0032] Figure 6b It is a top view of the trapezoidal magnetic collector of the third embodiment. DETAILED DESCRIPTION

[0033] Embodiment 1

[0034] Figure 3 The figure shows a magnetic collector of the prior art, which is a circular ring with a trapezoidal cross section, and there is an extremely narrow crack in the circular ring; and the height of the outer wall of the circular ring is much greater than the height of the inner wall. The capacitor power supply supplies power to the driving coil to generate a counterclockwise pulse current. According to the law of electromagnetic induction, the inner wall of the magnetic collector will generate a clockwise induced current; at the same time, due to the gap in the magnetic collector, the induced current cannot form a closed loop on the inner wall; therefore, when the induced current encounters the gap, it will flow along the gap to the outer wall of the magnetic collector and form a counterclockwise induced current on its outer wall. The induced current on the inner wall of the magnetic collector serves as an excitation source for the workpiece, generates an induced current inside the workpiece, and thus generates a pulse electromagnetic force to drive the workpiece to deform. The electromagnetic force on the part of the workpiece close to the gap is small, and the electromagnetic force on the part of the workpiece closer to the gap is smaller. Due to this defect, the circumferential forming of the workpiece becomes uneven during the electromagnetic forming process.

[0035] The embodiment utilizes triangular convex pieces at the upper and lower ends of the circular trapezoidal magnetic collector to improve the uneven distribution of the magnetic field in the inner ring of the magnetic collector caused by the fracture of the trapezoidal magnetic collector. The convex pieces on the inner side of the trapezoidal magnetic collector and the fracture of the magnetic collector are evenly distributed in the circumferential direction, so that the magnetic field distribution of the trapezoidal magnetic collector is approximately rotationally symmetrical under the action of the driving coil when the pipe is formed. The convex pieces increase the inner wall area of ​​the magnetic collector at the convex piece position, reduce the current density of the magnetic collector at the convex piece position, weaken the electromagnetic field on the inner side of the magnetic collector near the convex piece position, and reduce the electromagnetic force of the workpiece near the convex piece position.

[0036] A pipe forming method for improving the magnetic field distribution of a trapezoidal magnetic collector by using convex pieces comprises the following steps:

[0037] Step 1: Determine the longitudinal height of the convex piece of the magnetic collector according to the length of the pipe to be formed;

[0038] Step 2: Using finite element software to establish an electromagnetic forming model of a workpiece including a trapezoidal magnetic collector, a driving coil, and a pipe to be formed, wherein the workpiece of the trapezoidal magnetic collector and the pipe to be formed are both made of aluminum alloy, and the thickness of the workpiece of the pipe to be formed is 1 mm;

[0039] Step 3: Apply pulse current to the driving coil of the workpiece electromagnetic forming model to simulate the magnetic field distribution of the trapezoidal magnetic collector;

[0040] Step 4: Adjust the number and thickness of the convex pieces of the trapezoidal magnetic collector in the electromagnetic forming model of the workpiece, and execute step 3 to make the magnetic field distribution of the simulated trapezoidal magnetic collector close to rotational symmetry;

[0041] Step 5: According to the parameters of the trapezoidal magnetic flux collector obtained in step 4, a multi-convex trapezoidal magnetic flux collector is manufactured;

[0042] Step 6: Use the multi-convex trapezoidal magnetic collector obtained in step 5 to control the compression forming of the pipe to be formed, such as Figure 1 As shown;

[0043] Step 6.1: Place the pipe to be formed at the inner center of the trapezoidal magnetic collector, with the distance between the pipe to be formed and the trapezoidal magnetic collector being 3 mm;

[0044] Step 6.2: Set a driving coil outside the trapezoidal magnetic collector. The coil material is copper, and the cross-sectional area of ​​the copper wire is 3mm6mm;

[0045] Step 6.3: Connect the driving coil to the pulse power supply via the discharge switch;

[0046] Step 6.4: Control the discharge switch to power the drive coil, generate radial electromagnetic force and axial electromagnetic force on the pipe to be formed, and the pipe is compressed and formed under the action of the electromagnetic force.

[0047] The number of the protrusions 2.2 of the trapezoidal magnetic collector 2 of the embodiment is 3 pairs, the angle between adjacent protrusions 2.2 is 90°, and the angle between the break 2.1 and the adjacent protrusion 2.2 is 90°. Figure 4a , 4b shown.

[0048] like Figure 1 As shown, the pipe forming device of the embodiment includes a trapezoidal magnetism collector 2, a driving coil 1 and a pulse power supply, wherein the trapezoidal magnetism collector 2 is in the shape of a ring, the cross section of the trapezoidal magnetism collector is trapezoidal, the trapezoidal magnetism collector is provided with a break, a pair of triangular convex pieces are provided on the inner side of the trapezoidal magnetism collector, and the convex pieces and the break of the magnetism collector are evenly distributed in the circumferential direction; the driving coil 1 is arranged on the outer side of the trapezoidal magnetism collector 2, and the center line of the driving coil is aligned with the center line of the trapezoidal magnetism collector; the driving coil 1 is connected to the pulse power supply via a pneumatic switch, as shown in FIG. Figure 2 shown.

[0049] Embodiment 2

[0050] The pipe forming method of the embodiment is the same as that of the first embodiment.

[0051] The number of the protrusions 2.2 of the trapezoidal magnetic collector 2 of the embodiment is 2 pairs, the angle between adjacent protrusions 2.2 is 120°, and the angle between the break 2.1 and the adjacent protrusion 2.2 is 120°. Figure 5a , 5b shown.

[0052] Embodiment 3

[0053] The pipe forming method of the embodiment is the same as that of the first embodiment.

[0054] The number of the protruding pieces 2.2 of the trapezoidal magnetic collector 2 of the embodiment is one pair, and the angle between the protruding piece 2.2 and the fracture 2.1 is 180°. Figure 6a , 6b shown.

Claims

1. A pipe forming method using convex pieces to improve the magnetic field distribution of a trapezoidal magnetic collector, characterized in that: The triangular convex piece on the inner side of the circular trapezoidal magnetic collector is used to improve the uneven magnetic field distribution in the inner ring of the magnetic collector caused by the fracture of the trapezoidal magnetic collector. The convex piece on the inner side of the trapezoidal magnetic collector and the fracture of the magnetic collector are evenly distributed in the circumferential direction, so that the magnetic field distribution of the trapezoidal magnetic collector is approximately rotationally symmetrical under the action of the driving coil when the pipe is formed. The method comprises the following steps: Step 1: Determine the longitudinal height of the convex piece of the trapezoidal magnetic collector according to the length of the pipe to be formed; Step 2: Using finite element software to establish an electromagnetic forming model of a workpiece including a trapezoidal magnetic collector, a driving coil, and a pipe to be formed; Step 3: Apply pulse current to the driving coil of the workpiece electromagnetic forming model to simulate the magnetic field distribution of the trapezoidal magnetic collector; Step 4: Adjust the number and thickness of the convex pieces of the trapezoidal magnetic collector in the electromagnetic forming model of the workpiece, and execute step 3 to make the magnetic field distribution of the simulated trapezoidal magnetic collector close to rotational symmetry; Step 5: According to the parameters of the trapezoidal magnetic flux collector obtained in step 4, a multi-convex trapezoidal magnetic flux collector is manufactured; Step 6: Using the multi-convex trapezoidal magnetic collector obtained in step 5 to control the compression forming of the pipe to be formed; Step 6.1: Place the pipe to be formed at the center of the inner side of the trapezoidal magnetic collector; Step 6.2: Arrange a driving coil outside the trapezoidal magnetic collector; Step 6.3: Connect the driving coil to the pulse power supply via the discharge switch; Step 6.4: Control the discharge switch to power the drive coil, generate radial electromagnetic force and axial electromagnetic force on the pipe to be formed, and the pipe is compressed and formed under the action of the electromagnetic force.

2. The pipe forming method according to claim 1, characterized in that: In step 2, the initial thickness of the protruding piece of the trapezoidal magnetic collector is equal to the width of the fracture.

3. The pipe forming method according to claim 2, characterized in that: The number of the convex pieces of the trapezoidal magnetic collector is 2 pairs, the angle between adjacent convex pieces is 120 degrees, and the angle between the break and the adjacent convex piece is 120 degrees.

4. The pipe forming method according to claim 2, characterized in that: The number of the convex pieces of the trapezoidal magnetic collector is 3 pairs, the angle between adjacent convex pieces is 90 degrees, and the angle between the break and the adjacent convex pieces is 90 degrees.

Images