Device and method for assisting in reducing bending springback of magnesium alloy plate through electric pulse

Abstract

The invention relates to the technical field of non-ferrous metal bending springback experiments, and discloses a device and a method for reducing bending springback of a magnesium alloy plate under the assistance of an electric pulse, the device comprises a high-power pulse power supply device and a universal testing machine, and the universal testing machine is arranged on one side of the high-power pulse power supply device; and an insulating base is arranged at the bottom in the universal testing machine. According to the device and the method for reducing the bending springback of the magnesium alloy plate under the assistance of the electric pulse, the insulating base and the insulating pressure head are made of high-hardness resin materials, so that a testing machine can be effectively prevented from being damaged, and meanwhile, the springback amount of a test piece is obviously reduced relative to the springback amount of the test piece at normal temperature and participation of pulse current; in the parameters selected by the experiment, the rebound amount of the test piece tends to be gradually reduced along with the increase of the electrical parameters, and in order to control the rebound, under the condition that the same electrical parameter is used, the electrifying effect in the unloading process of the test piece is almost the same as the electrifying effect in the whole process.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal bending springback experiments, and in particular to a device and method for reducing the bending springback of a magnesium alloy plate by using electric pulses. Background Art

[0002] With the increasing demands for large capacity, low energy consumption and long life in high-end aerospace equipment, the requirements for lightweight structural parts have become more urgent. Magnesium alloy is currently the lightest engineering metal material. It has the advantages of high specific strength, high specific stiffness, good damping and shock absorption, good thermal conductivity, strong electromagnetic shielding capability and easy cutting. In addition, it has large reserves and low cost, which makes it have huge application potential in industrial production. It is a popular material for lightweight weight reduction and energy saving.

[0003] The main reason why electric pulses reduce the bending springback of magnesium alloy sheets is that electric pulses can significantly reduce the flow stress of the material, thereby reducing the amount of springback. Electric pulse assisted forming technology can effectively reduce the deformation resistance of the material, improve the plasticity of the material, and thus reduce the springback phenomenon by applying current during the material deformation process.

[0004] Based on the above requirements, in order to meet the parameters of the electric pulse under which the rebound amount of the test piece can be clearly understood, as well as the effects of power-on during the unloading process and power-on throughout the process of the test piece under the same parameters.

[0005] Based on this, it is necessary to propose a device and method for reducing the bending springback of magnesium alloy sheets with the assistance of electric pulses. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a device and method for reducing the bending springback of magnesium alloy plates with the assistance of electric pulses. The device and method have the advantage of being able to understand the springback amount of the test piece under electrical parameters of 220V-300Hz-60us, 250V-300Hz-60us, and 280V-300Hz-60us, thereby solving the problems raised in the background technology.

[0007] The present invention provides the following technical solution: a device for reducing the bending springback of a magnesium alloy plate by electric pulse assistance, comprising a high-power pulse power supply device and a universal testing machine:

[0008] A universal testing machine is provided on one side of the high-power pulse power supply device;

[0009] An insulating base is provided at the inner bottom of the universal testing machine, and triangular bearing blocks are slidably connected to both sides of the upper surface of the insulating base. Electrode connecting rods are installed on the upper surface of the triangular bearing blocks, one group of the electrode connecting rods is connected to the negative electrode connecting piece, and the other group of the electrode connecting rods is connected to the positive electrode connecting piece, and the positive electrode connecting piece and the negative electrode connecting piece are connected to the positive and negative electrodes of the high-power pulse power supply device through wires.

[0010] Preferably, a limiting bolt is threadedly connected to the surface of the electrode connecting rod, and the upper surfaces of the positive electrode connecting sheet and the negative electrode connecting sheet abut against the lower surfaces of the limiting bolt.

[0011] Preferably, the insulating base and the insulating pressure head are both made of high-hardness resin material.

[0012] A method for reducing the bending springback of a magnesium alloy plate with the aid of electric pulses, characterized in that it comprises a high-power pulse power supply device and a universal testing machine: the positive and negative electrodes of the high-power pulse power supply device are connected to the positive and negative electrodes of the universal testing machine through wires, and the electric pulse parameters are 220V-300Hz-60us, 250V-300Hz-60us, and 280V-300Hz-60us. The specific method comprises the following steps:

[0013] Step 1: Place the magnesium alloy plate to be tested on a triangular bearing block;

[0014] Step 2: Set up the universal testing machine program. The universal testing machine moves the indenter downward at a rate of 1 mm / min. When the displacement of the indenter reaches 2.84 mm, the testing machine unloads the indenter at the same rate as the loading process.

[0015] Step 3: When the pressure head position reaches 2.84mm, turn on the high-power pulse power supply device at the same time until the pressure head of the universal testing machine is unloaded and then turn off the power supply.

[0016] Preferably, the experiment is repeated three times according to the provided parameters: 220V-300Hz-60us, 250V-300Hz-60us, 280V-300Hz-60us.

[0017] Preferably, before the experiment, the bending sample is polished with 200# or 400# sandpaper to make the surface smooth, the bending specimen is preloaded with about 10N, and each experiment is set to stop when the force drops to 50% of the maximum load.

[0018] Preferably, the span of the lower pressure head is 18 mm; the diameters of the upper and lower pressure heads are both 3 mm, the bending rate is 1 mm / min, and the size of the bending sample is 30×10×1.5 (length×width×thickness / mm).

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This device and method for reducing the bending springback of magnesium alloy plates with the assistance of electric pulses can effectively prevent damage to the testing machine by setting the materials of the insulating base and the insulating pressure head to high-hardness resin materials. At the same time, compared with the rebound amount of the test piece at room temperature, the participation of the pulse current makes the rebound amount of the test piece significantly reduced. In the parameters selected in the experiment, as the electrical parameters increase, the rebound amount of the test piece shows a trend of gradually decreasing. In order to control the rebound, when the same electrical parameters are used, the effects of energizing the test piece during the unloading process and energizing the test piece throughout the whole process are almost the same, and energizing only during the unloading process also saves more electricity. At the same time, when the same parameters are applied during the unloading process with different energization durations, the rebound amount of the bending of the test piece is reduced, and as the energization duration increases, the rebound amount of the test piece gradually decreases. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of the overall structure of the device of the present invention;

[0023] Figure 2 It is a partial structural schematic diagram of the universal testing machine of the present invention;

[0024] Figure 3 This is a schematic diagram of the electric pulse assisted bending of magnesium alloy according to the present invention;

[0025] Figure 4 Schematic diagram of the load-displacement curve of the pressure head under different power-on parameters of the present invention;

[0026] Figure 5 It is a statistical schematic diagram of the rebound amount under different electrical parameters of the present invention;

[0027] Figure 6 This is a schematic diagram of industrial production of the present invention;

[0028] Figure 7 The same power-on parameters but different power-on time of the present invention are used to illustrate the rebound of the test piece. Figure 1 ;

[0029] Figure 8 The same power-on parameters but different power-on time of the present invention are used to illustrate the rebound of the test piece. Figure 2 .

[0030] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0031] 1. High power pulse power supply device;

[0032] 2. Universal testing machine; 210. Insulating base; 220. Triangular bearing block; 230. Insulating pressure head; 240. Electrode connecting rod; 250. Negative connecting piece; 260. Limit bolt; 270. Positive connecting piece. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] See also Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 , a device for reducing the bending springback of a magnesium alloy plate with electric pulse assistance, comprising a high-power pulse power supply device 1 and a universal testing machine 2:

[0035] A universal testing machine 2 is provided on one side of the high-power pulse power supply device 1;

[0036] An insulating base 210 is provided at the inner bottom of the universal testing machine 2, and triangular bearing blocks 220 are slidably connected to both sides of the upper surface of the insulating base 210. Electrode connecting rods 240 are installed on the upper surface of the triangular bearing blocks 220, one group of electrode connecting rods 240 is connected to the negative electrode connecting piece 250, and the other group of electrode connecting rods 240 is connected to the positive electrode connecting piece 270. The positive electrode connecting piece 270 and the negative electrode connecting piece 250 are connected to the positive and negative electrodes of the high-power pulse power supply device 1 through wires.

[0037] As a preferred technical solution of the present invention, the surface of the electrode connecting rod 240 is threadedly connected with the limiting bolt 260 , and the upper surfaces of the positive electrode connecting plate 270 and the negative electrode connecting plate 250 abut against the lower surface of the limiting bolt 260 .

[0038] As a preferred technical solution of the present invention, the insulating base 210 and the insulating pressure head 230 are both made of high-hardness resin material.

[0039] A method for reducing the bending springback of a magnesium alloy plate by electric pulse assistance includes a high-power pulse power supply device 1 and a universal testing machine 2: the positive and negative electrodes of the high-power pulse power supply device 1 are connected to the positive and negative electrodes of the universal testing machine 2 through wires, and the electric pulse parameters are 220V-300Hz-60us, 250V-300Hz-60us, and 280V-300Hz-60us. The specific method includes the following steps:

[0040] Step 1: placing the magnesium alloy plate to be tested on the triangular bearing block 220;

[0041] Step 2: Set up the universal testing machine 2 program. The universal testing machine 2 moves the indenter downward at a rate of 1 mm / min. When the displacement of the indenter reaches 2.84 mm, the testing machine unloads the indenter at the same rate as the loading process.

[0042] Step 3: When the pressure head position reaches 2.84 mm, turn on the high-power pulse power supply device 1 at the same time, and turn off the power until the pressure head of the universal testing machine 2 is unloaded.

[0043] As a preferred technical solution of the present invention, the experiment was repeated three times according to the above method according to the provided parameters: 220V-300Hz-60us, 250V-300Hz-60us, and 280V-300Hz-60us.

[0044] The influence of pulse current on the bending mechanical properties of AZ31 magnesium alloy sheet can be seen in the following figure: Figure 3 .

[0045] As a preferred technical solution of the present invention, the bending sample is polished with 200# and 400# sandpaper to make the surface smooth before the experiment. The bending specimen is preloaded with about 10N, and each experiment is set to stop when the force drops to 50% of the maximum load.

[0046] As a preferred technical solution of the present invention, the span of the lower pressure head is 18 mm; the diameters of the upper and lower pressure heads are both 3 mm, the bending rate is 1 mm / min, and the size of the bending sample is 30×10×1.5 (length×width×thickness / mm).

[0047] Compared with the springback of the specimen at room temperature, the participation of pulse current significantly reduces the springback of the specimen. In addition, among the parameters selected in the experiment, as the electrical parameters increase, the springback of the specimen shows a trend of gradually decreasing. This may indicate that choosing a suitable electrical parameter in industrial production will greatly reduce the bending springback of the specimen. The figure below shows the load-displacement curve of the indenter under different power-on parameters. Figure 4 .

[0048] Attached Figure 5Statistics of springback under different electrical parameters.

[0049] Comparison of the same electrical parameters when powered on during loading and unloading and when powered on during unloading:

[0050] Referring to the electrical parameters in the electric pulse assisted bending process, when the parameters are 250V-300Hz-60us, a stronger plasticity phenomenon appears, so it is selected as the parameters of this experiment. One object is powered on at the beginning of loading. For comparison, the other object is powered on at the same time when the pressure head displacement reaches 2.84mm and the pressure head starts to unload under the changed parameters. Each experiment is repeated three times to avoid contingency (see the figure below for details). It can be seen from the figure that compared with only powering on during the unloading process, continuous powering on only reduces the bending load on the specimen during the loading process, and the curves of the elastic stage of the specimen are almost the same. In the unloading process, the unloading curve of the electrical parameters only powered on during the unloading process is almost the same as the unloading curve of the loading and unloading process. The experiment shows that in order to control the rebound, when the same electrical parameters are used, the effect of powering on during the unloading process of the specimen is almost the same as that of powering on throughout the whole process, and powering on only during the unloading process also saves more electricity. This result can provide a reference for industrial production. Figure 6 .

[0051] The influence of the same power-on parameters but different power-on time on the springback of the specimen

[0052] In order to study the effect of the power-on time of the same electrical parameter on the rebound during the unloading process, the program was set to keep the test machine for 30 seconds when the displacement of the indenter reached 2.84mm, and apply pulse currents of the same power-on parameter with different durations during this 30s. After the specimen was kept for 30s, it was unloaded at the same rate as the loading process, and the power-on time was selected to be 2s, 5s, 10s, 20s, and 30s. The experimental results are as follows Figure 7 and Figure 8 shown.

[0053] The results show that when the same parameters but different power-on durations are applied during the unloading process, the springback of the specimen bending is reduced, and as the power-on duration increases, the springback of the specimen gradually decreases. In the results of this experiment, the downward gradient is largest when the power-on duration is between 2s and 5s, but after the duration exceeds 20s, the reduction in springback is not obvious.

[0054] In the description of the present invention, it is necessary to understand that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0055] In the present invention, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "screw-on" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0056] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A device for reducing the bending springback of a magnesium alloy plate by electric pulse assistance, comprising a high-power pulse power supply device (1) and a universal testing machine (2), characterized in that: A universal testing machine (2) is provided on one side of the high-power pulse power supply device (1); An insulating base (210) is provided at the inner bottom of the universal testing machine (2), and triangular bearing blocks (220) are slidably connected to both sides of the upper surface of the insulating base (210), and electrode connecting rods (240) are installed on the upper surface of the triangular bearing blocks (220), wherein one group of the electrode connecting rods (240) is connected to a negative electrode connecting piece (250), and another group of the electrode connecting rods (240) is connected to a positive electrode connecting piece (270), and the positive electrode connecting piece (270) and the negative electrode connecting piece (250) are connected to the positive and negative electrodes of the high-power pulse power supply device (1) through wires.

2. The device for reducing the bending springback of magnesium alloy sheet with electric pulse assistance according to claim 1 is characterized in that: The surface of the electrode connecting rod (240) is threadedly connected to a limiting bolt (260), and the upper surfaces of the positive electrode connecting piece (270) and the negative electrode connecting piece (250) are in contact with the lower surface of the limiting bolt (260).

3. The device for reducing the bending springback of magnesium alloy sheet with electric pulse assistance according to claim 2 is characterized in that: The insulating base (210) and the insulating pressure head (230) are both made of high-hardness resin material.

4. A method for reducing the bending springback of a magnesium alloy sheet with the aid of electric pulses, characterized in that: The invention comprises a high-power pulse power supply device (1) and a universal testing machine (2): the positive and negative electrodes of the high-power pulse power supply device (1) are connected to the positive and negative electrodes of the universal testing machine (2) through wires, the electric pulse parameters are 220V-300Hz-60us, 250V-300Hz-60us, and 280V-300Hz-60us, and the specific method comprises the following steps: Step 1: placing the magnesium alloy plate to be tested on a triangular bearing block (220); Step 2: Set up the universal testing machine (2) program. The universal testing machine (2) moves the indenter downward at a rate of 1 mm / min. When the displacement of the indenter reaches 2.84 mm, the testing machine unloads the indenter at the same rate as the loading process. Step 3: When the pressure head position reaches 2.84 mm, turn on the high-power pulse power supply device (1) at the same time until the pressure head of the universal testing machine (2) is unloaded and then turn off the power.

5. The method for reducing the bending springback of a magnesium alloy sheet with electric pulse assistance according to claim 3, characterized in that: The experiment was repeated three times according to the provided parameters: 220V-300Hz-60us, 250V-300Hz-60us, 280V-300Hz-60us.

6. The method for reducing the bending springback of a magnesium alloy sheet with electric pulse assistance according to claim 3, characterized in that: Before the experiment, the bending sample was polished with 200# and 400# sandpaper to make the surface smooth. The bending specimen had a preload of about 10N. Each experiment was set to stop when the force dropped to 50% of the maximum load.

7. The method for reducing the bending springback of a magnesium alloy sheet with electric pulse assistance according to claim 13, characterized in that: The span of the lower pressure head is 18 mm; the diameters of the upper and lower pressure heads are both 3 mm, the bending rate is 1 mm / min, and the size of the bending sample is 30×10×1.5 (length×width×thickness / mm).

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