A device and method for forming a marble-type deformable elastic cushion multi-point press for complex-profile hard-to-deform alloy sheet

Abstract

The present invention discloses a device and method for forming a complex-shaped and difficult-to-deform alloy sheet with a marble-type variant elastic cushion multi-point press. The method combines the self-resistance heating characteristics of the sheet with the flexible technology of the multi-point forming marble cushion. The forming device includes: an alloy sheet to be formed, an electrode, a low-voltage and high-current pulse power supply, a marble-type elastic cushion, a tool head, a support plate, and a servo hydraulic cylinder. The present invention utilizes the softening characteristics of the alloy material in a heated state to improve its plasticity, thereby reducing the forming force; the multi-point press forming of the marble-type variant elastic cushion can maintain the rigidity of the elastic cushion while distributing the load of the tool head more evenly to the surface of the sheet, so as to realize the flexible mold processing process of the workpiece and higher surface forming quality. In addition, the metal marbles of each unit body are made of cemented carbide materials with different resistivities, and the elastic cushion can achieve different temperature rises in different areas, so that the sheet can be heated at different zones.

Description

Technical Field

[0001] The present invention belongs to the technical field of multi-point progressive and numerically controlled hot progressive composite forming, in particular to an electrically assisted marble-type variant elastic cushion multi-point press forming device and a forming method for a difficult-to-deform alloy sheet with a complex profile. Background Art

[0002] Metal-based titanium alloys, magnesium alloys, aluminum-lithium alloys, etc. have been widely used in high-tech fields, especially in aerospace, due to their advantages of high strength and low density. However, these materials have poor plasticity at room temperature and are difficult to deform at room temperature. It is difficult to form the materials using traditional processes. Usually, these materials need to be heated to a certain hot forming temperature to complete the deformation process. A large number of experiments have shown that under heating conditions, these materials show significantly improved plastic deformation capabilities. Therefore, warm or hot stamping processes that can effectively improve the forming properties of these difficult-to-form materials at room temperature are bound to be widely used.

[0003] Multi-point forming technology has been applied in many fields such as aviation, shipbuilding, high-speed rail, and construction. The principle is to form a mold surface through multiple regularly arranged, highly adjustable basic units, and to form curved parts of different shapes with one set of devices. However, multi-point forming will have very common forming defects such as indentation and wrinkling. Adding a polyurethane pad between the basic unit and the plate of the multi-point forming device can disperse the concentrated load generated by the basic unit on the plate and suppress the generation of indentations, but adding the polyurethane pad will reduce the forming accuracy, and the thicker the polyurethane pad, the more obvious the impact on the forming accuracy.

[0004] After searching, it was found that the Chinese invention patent: Multi-point forming method of aluminum alloy aircraft integral wall panel, authorization number: CN207971263 U, application number: 201720754135.6, the invention discloses a composite elastic pad for multi-point forming using a multi-layer steel pad, the composite elastic pad is composed of two or more layers of multiple steel pads and polyurethane pads arranged in an interlaced manner, the steel pads are selected with different thicknesses and cross-sectional shapes, each layer of multiple steel pads are connected to each other as a whole, or are discrete from each other, and different layers of steel pads are selected with the same or different connection methods. The invention effectively disperses the concentrated load applied by the basic unit of the multi-point forming device through the steel pad, so that the formed die surface has better continuity, the stress and strain in the sheet forming process are more uniform, the generation of indentations and wrinkles is suppressed, and the surface quality of the workpiece is improved. However, the polyurethane pad will affect the accuracy of multi-point forming and hinder the combination of multi-point forming technology and electric-assisted heating forming, increasing the difficulty of forming large-size sheets with poor plasticity and high resistance at room temperature such as titanium alloys.

[0005] The use of a marble-type variant elastic cushion can effectively disperse the concentrated load generated by the basic body unit, making the formed die surface more continuous, the stress and strain of the sheet metal during forming more uniform, suppressing the generation of indentations and wrinkles, and improving the surface quality and forming accuracy of the workpiece. In addition, the marble-type variant elastic cushion can be connected to an electrode to heat the sheet metal, which can not only achieve the function of the cushion to disperse the concentrated load, but also complete the electrically assisted processing process. The metal marbles of each unit body can be made of cemented carbide materials with different resistivities. After the pulse current is passed through the marble-type variant elastic cushion, the temperature rise in different areas can be achieved, and the sheet metal can be heated and deformed in different areas, which is conducive to reducing the difficulty of forming complex surface difficult-to-deform alloy sheets. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention proposes a multi-point press forming device and method with a marble-type variant elastic cushion layer for complex-shaped and difficult-to-deform alloy sheets, which combines the progressive forming of a multi-point press with an elastic cushion layer with the self-resistance heating technology of the sheet under electric pulses, and utilizes the softening and creep properties of the alloy material in a heated state to improve its plasticity, thereby reducing the forming force and improving the formability, reducing the springback of parts and simplifying the processing route. Multi-point press forming with a marble-type variant elastic cushion layer can fully utilize the flexible advantages of multi-point forming, dispersing the concentrated load of the tool head to multiple marbles, which can not only reduce the number of tool heads per unit area and avoid sheet cracking, but also achieve the rigidity and high-precision requirements that polyurethane pads cannot achieve. For large-size, multi-variety, multi-curvature complex surface parts in alloy sheets, the production and manufacturing costs can be greatly reduced.

[0007] The object of the present invention is achieved through the following technical scheme: a marble-type variant elastic cushion multi-point press forming device for complex-profile hard-to-deform alloy sheet material comprises:

[0008] The sheet material to be formed is in the middle layer between the upper and lower marble-type variant elastic cushion layers, and the marble-type variant elastic cushion layers are clamped and fixed by the pressure blocks on both sides; the first tool head group is installed on the upper support plate, and the second tool head group is installed on the lower support plate, and the rigid tool heads of the first tool head group and the second tool head group can feed and move along their axial directions; the left end of the upper marble-type variant elastic cushion layer is connected to the left electrode, and the right end of the upper marble-type variant elastic cushion layer is connected to the right electrode, the left electrode is connected to the positive pole of the low-voltage and high-current pulse power supply through a wire and a power switch, and the right electrode is connected to the negative pole of the low-voltage and high-current pulse power supply through a wire, forming The circuit is closed, and the current flows through the marble-type variant elastic cushion layer, which heats up the elastic cushion layer to heat the sheet to be formed; the forming control system controls the feeding movement of the rigid tool heads of the first tool head group and the second tool head group according to a pre-set program, and the rigid tool heads disperse the concentrated load to the marble-type variant elastic cushion layer, and the marbles then load the forming force to the sheet to be formed more evenly, and the sheet deforms under the high temperature and forming force until the forming is completed; after the forming is completed, the sheet to be formed is removed, and the rigid tool head continues to feed the movement to restore the marble-type variant elastic cushion layer to its initial state for reuse next time.

[0009] Optionally, the two tool head groups each include: N×M groups of rigid tool heads and N×M groups of servo hydraulic cylinders; wherein each rigid tool head is connected to the support plate via a corresponding servo hydraulic cylinder, and the feed motion power of the tool head is provided by the servo hydraulic cylinder.

[0010] Optionally, the marble-type variant elastic cushion layer adopts a mesh structure composed of multiple groups of unit grids, each unit grid contains a×b×c rigid marbles, the values ​​of a, b and c are determined by the thickness and size of the plate, generally speaking, a≤20, b≤20, c≤6; the diameter of the marbles is 2-5mm, and the specific size is determined by the precision requirements and material properties of the plate to be formed; the metal marble material should be an alloy material with good red hardness, and the marbles can maintain high stiffness and hardness when heated by electricity, and YW1 cemented carbide and YG8 cemented carbide can be selected as manufacturing materials; the metal marbles of each unit body can be made of cemented carbide materials with different resistivities. After the pulse current is passed through the marble-type variant elastic cushion layer, the temperature rise in different areas can be achieved, and the plate can be heated and deformed in different areas, which is beneficial to reduce the difficulty of forming complex surface difficult-to-deform alloy plates.

[0011] Optionally, it also includes: electrodes, wires, a curved surface forming control system and a high-current low-voltage pulse power supply;

[0012] The left end of the upper marble-type variant elastic cushion is connected to the left electrode, and the right end of the upper marble-type variant elastic cushion is connected to the right electrode. The left electrode is connected to the positive pole of the low-voltage and high-current pulse power supply through a wire, and the right electrode is connected to the negative pole of the low-voltage and high-current pulse power supply through a wire.

[0013] The curved surface forming control system is connected with the low-voltage and high-current pulse power supply and the first and second tool head groups. The discharge intensity of the pulse power supply and the feeding movement of the tool head are controlled and realized by the curved surface forming control system.

[0014] Optionally, it also includes: a power switch;

[0015] The power switch is arranged on the wire connecting the left electrode and the low-voltage and high-current pulse power supply. When the power switch is closed, a closed circuit loop can be formed on the elastic cushion layer, and the elastic cushion layer heats the sheet to be formed under the thermal resistance effect.

[0016] The present invention also discloses a titanium alloy integral wall panel electrically assisted multi-point press forming method, comprising:

[0017] The sheet material to be formed is located in the middle layer between the upper and lower marble-type variant elastic cushion layers, and the marble-type variant elastic cushion layers are clamped and fixed by the pressing blocks on both sides;

[0018] The first tool head group is installed on the upper support plate, and the second tool head group is installed on the lower support plate. Each adjustable tool head group includes N×M groups of servo hydraulic cylinders and N×M groups of rigid tool heads. The rigid tool heads of the first tool head group and the second tool head group can be fed and moved along their axis directions.

[0019] The left end of the upper marble-type variant elastic cushion is connected to the left electrode, and the right end of the upper marble-type variant elastic cushion is connected to the right electrode. The left electrode is connected to the positive electrode of the low-voltage and high-current pulse power supply through a wire and a power switch, and the right electrode is connected to the negative electrode of the low-voltage and high-current pulse power supply through a wire, forming a closed circuit loop. Current flows through the marble-type variant elastic cushion, and the elastic cushion heats up to heat the sheet to be formed; the size of the pulse current is determined by the forming temperature of the sheet to be formed and controlled by the forming control system.

[0020] The forming control system controls the feeding movement of the rigid tool heads of the first tool head group and the second tool head group according to a preset program. The rigid tool heads disperse the concentrated load to the marble-type variant elastic cushion layer, and the marbles then load the forming force to the sheet to be formed more evenly. The sheet is deformed under the high temperature and forming force until the forming is completed. After the forming is completed, the sheet to be formed is removed, and the rigid tool heads continue to feed the movement to restore the marble-type variant elastic cushion layer to its initial state for reuse next time.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) The present invention discloses a device and method for forming complex-surface difficult-to-deform alloy sheets with a marble-type variant elastic cushion layer and a multi-point press. The adopted marble-type variant elastic cushion layer can disperse the concentrated force of the tool head to the multiple marbles thereunder, and the marbles then distribute the load more evenly on the surface of the formed sheet, thereby improving the surface quality of the sheet and avoiding problems such as large pits and cracks on the surface of the sheet.

[0023] (2) The present invention discloses a multi-point press forming device and method for a marble-type variant elastic cushion layer of a complex-shaped, difficult-to-deform alloy sheet. Electrodes can be connected on both sides of the marble-type variant elastic cushion layer, and the electrodes are connected to a low-voltage, high-current pulse power supply through wires and a power switch. When the power switch is closed, a closed current loop is formed, the marble-type variant elastic cushion layer heats up, and the sheet to be formed is heated.

[0024] (3) The present invention discloses a multi-point press forming device and method for a marble-type variant elastic cushion layer of a complex-shaped and difficult-to-deform alloy plate. During the forming process, the metal marbles are in direct contact with the plate, the marbles have good rigidity, and small vertical compression deformation, and have higher forming accuracy than polyurethane pads.

[0025] (4) The present invention discloses a multi-point press forming device and method for a marble-type variant elastic cushion layer of a complex-shaped, difficult-to-deform alloy sheet. The metal marbles of each unit body can be made of hard alloy materials with different resistivities. After a pulse current is passed through the marble-type variant elastic cushion layer, the temperature rise in different areas can be achieved, and the sheet can be heated and deformed in different areas, which is beneficial to reducing the difficulty of forming complex-shaped, difficult-to-deform alloy sheets.

[0026] (5) The present invention discloses a multi-point press forming device and method for a marble-type variant elastic cushion layer of a complex-surface difficult-to-deform alloy sheet. The outer mesh layer of the marble-type variant elastic cushion layer adopts a Ni-Ti-based recoverable memory alloy. After the multi-point progressive forming of the sheet is completed, the elastic cushion layer can be restored to its original shape by adjusting the position of the tool head, thereby realizing the reuse of the elastic cushion layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the structure of a marble-type variant elastic cushion multi-point press forming device for a complex-shaped hard-to-deform alloy sheet of the present invention (before sheet forming);

[0028] Figure 2 This is a structural schematic diagram of a marble-type variant elastic cushion multi-point press forming device for a complex-shaped, difficult-to-deform alloy sheet of the present invention (after the sheet is formed);

[0029] Figure 3 It is a unit structure diagram of a marble-type variant elastic cushion;

[0030] Figure 4It is a marble-type variant elastic cushion structure composed of two units;

[0031] Figure 5 A top view of the marble-type variant elastic cushion layer of the present invention;

[0032] Figure 6 It is the outer network layer structure of a single unit body;

[0033] Figure 7 A saddle-shaped surface with double curvature that can be formed by the method;

[0034] In the figure: 1. lower support plate; 2. second tool head group; 3. pressing block; 4. lower layer of marble-type variant elastic cushion; 5. power switch; 6. left electrode; 7. upper layer of marble-type variant elastic cushion; 8. low-voltage and high-current pulse power supply; 9. wire; 10. upper support plate; 11. first tool head group; 12. servo hydraulic cylinder; 13. rigid tool head; 14. right electrode; 15. sheet to be formed; 16. forming control system; 101. inner partition; 102. metal marbles; 103. outer mesh layer. DETAILED DESCRIPTION

[0035] The following will refer to the attached Figures 1 to 3 Specific embodiments of the present invention are described in detail. Although specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0036] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0038] Example 1

[0039] The present invention discloses a marble-type variant elastic cushion multi-point press forming device for complex-shaped and difficult-to-deform alloy sheets, which combines electric pulse assisted forming technology with multi-point press forming technology with an elastic cushion. The forming object involved is a difficult-to-deform alloy sheet with a complex surface. The alloy material used has the characteristics of high room temperature deformation resistance, poor plasticity and difficulty in deformation.

[0040] Reference Figure 1 , which is a structural schematic diagram of a multi-point press forming device with a marble-type variant elastic cushion layer for a complex-surface difficult-to-deform alloy sheet in the present invention. The electrically assisted multi-point press forming device includes: a sheet to be formed, a first tool head group, a second tool head group, an upper support plate, a lower support plate, an upper layer of marble-type variant elastic cushion layer, a lower layer of marble-type variant elastic cushion layer, a low-voltage and high-current pulse power supply, an electrode, a power switch, and a pressing block.

[0041] The sheet material to be formed is in the middle layer between the upper and lower marble-type variant elastic cushion layers, which are clamped and fixed by pressure blocks on both sides; the first tool head group is installed on the upper support plate, and the second tool head group is installed on the lower support plate, and the rigid tool heads of the first tool head group and the second tool head group can feed and move along their axial directions; the left end of the upper marble-type variant elastic cushion layer is connected to the left electrode, and the right end of the upper marble-type variant elastic cushion layer is connected to the right electrode, the left electrode is connected to the positive pole of a low-voltage and high-current pulse power supply through a wire, and the right electrode is connected to the negative pole of the low-voltage and high-current pulse power supply through a wire, forming a closed circuit loop, and current flows through the marble-type variant elastic cushion layer, and the elastic cushion layer heats up to heat the sheet material to be formed.

[0042] The forming control system controls the feeding movement of the rigid tool heads of the first tool head group and the second tool head group according to the pre-set program. The rigid tool heads disperse the concentrated load to the marble-type variant elastic cushion layer, and the marbles then load the forming force to the sheet to be formed more evenly. The sheet deforms under the high temperature and forming force until the forming is completed. After the forming is completed, the sheet to be formed is removed, and the rigid tool heads continue to feed and restore the marble-type variant elastic cushion layer to its initial state for reuse next time.

[0043] In the present invention, if Figure 1, the first tool head group and the second tool head group both include: N×M groups of rigid tool heads and N×M groups of servo hydraulic cylinders. Among them, the servo hydraulic cylinder of the first tool head group is connected and fixed to the upper support plate, the servo hydraulic cylinder of the second tool head group is connected and fixed to the lower support plate, and the feeding power of the rigid tool head is provided by the servo hydraulic cylinder. Preferably, the number N×M of rigid tool heads and servo hydraulic cylinders can be set according to the marble size and the condition of the dispersed load of the marble-type variant elastic cushion layer and the size and forming accuracy of the sheet to be formed. Generally, for relatively large-sized sheets to be formed, the value of N×M should be larger; for some sheets with relatively complex surfaces and high surface forming accuracy requirements, the distance between each adjacent pair of tool heads should be smaller, and the corresponding value of N×M should be larger.

[0044] In the present invention, if Figure 2 , the marble-type variant elastic cushion layer includes: rigid metal marbles, an outer mesh layer and an inner interlayer structure. The rigid metal marbles need to play the role of intermediate force dispersion under high temperature and pressure. The marbles should be made of metal materials with good red hardness. The marbles can maintain high rigidity and hardness when heated by electricity. YW1 hard alloy and YG8 hard alloy can be selected as manufacturing materials; the marbles are in direct contact with the plate during the forming process of the marble-type variant elastic cushion layer. The marbles have good rigidity and small compression deformation in the vertical direction. Compared with the polyurethane pad, the forming accuracy is high; the diameter of the rigid metal marbles is 2-5mm, and the size of the marbles can be selected according to the forming accuracy and deformation of the plate; the contact area between the marbles is small, the resistance is large, the temperature rise of the variant elastic cushion layer is fast, and the plate can be heated quickly. Generally, the greater the required forming force, the larger the diameter of the marbles to avoid marble breakage and severe deformation; the higher the forming accuracy requirement of the plate surface, the smaller the diameter of the marbles to more evenly disperse the concentrated load to the surface to be formed. Therefore, the size of the metal marbles needs to consider the two factors that affect the forming force and the required forming accuracy of the sheet. While ensuring the surface accuracy of the sheet to be formed, the marbles should be prevented from being crushed during the forming process due to excessive force. In addition, the metal marbles of each unit body can be made of cemented carbide materials with different resistivities. After the pulse current is passed through the marble-type variant elastic cushion layer, different temperature rises can be achieved in different areas, and the sheet can be heated at different zones. The unit body in contact with the area with large deformation can be made of high-resistance material, and the unit body in contact with the area with small deformation can be made of low-resistance material. In order to prevent the resistance difference from being too large and too much current from flowing into the low-resistance unit body, it can be subjected to certain insulation treatment to achieve zoned variable temperature heating of the sheet to be formed in contact with the unit body, thereby reducing the difficulty of forming complex surface and difficult-to-deform alloy sheet.

[0045] The outer mesh layer is made of Ni-Ti based alloy material, which is a recoverable variant metal material. This material can ensure that the marble-type variant elastic cushion layer can recover to a relatively straight state before deformation under the feeding action of the rigid tool head after forming, so as to be used for the next forming; this structure can clamp the rigid metal marbles, and one-third of the outermost metal marbles are exposed from the circular gap of the mesh structure, the exposed part of the upper marbles contacts the tool head, the exposed part of the lower marbles contacts the plate, and the middle marbles are sealed inside to transfer the load.

[0046] The inner partition structure also adopts Ni-Ti based alloy material. This material can make the marble-type variant elastic cushion layer recover to a relatively straight state before deformation under the feeding action of the rigid tool head after forming, so as to be used for the next forming; the inner partition divides the marble-type variant elastic cushion layer into multiple elastic cushion layer units, which can ensure the overall strength of the elastic cushion layer, avoid large displacement of the metal marble in the horizontal direction, and prevent large scratches on the surface of the plate.

[0047] Example 2

[0048] The present invention also discloses a multi-point press forming method for a marble-type variant elastic cushion layer of a complex-shaped and difficult-to-deform alloy sheet material, which is characterized in that it comprises: a sheet material to be formed, a first tool head group, a second tool head group, an upper support plate, a lower support plate, an upper layer of a marble-type variant elastic cushion layer, a lower layer of a marble-type variant elastic cushion layer, a low-voltage and high-current pulse power supply, an electrode, a power switch, and a pressing block; the sheet material to be formed is located in the middle layer between the upper and lower marble-type variant elastic cushion layers, and the marble-type variant elastic cushion layer is clamped and fixed by the pressing blocks on both sides; the first tool head group is mounted on the upper support plate, the second tool head group is mounted on the lower support plate, and the first tool head group is mounted on the lower support plate. The rigid tool heads of the tool head group and the second tool head group can feed and move along their axial direction; the left end of the upper marble-type variant elastic cushion layer is connected to the left electrode, and the right end of the upper marble-type variant elastic cushion layer is connected to the right electrode. The left electrode is connected to the positive pole of the low-voltage and high-current pulse power supply through a wire, and the right electrode is connected to the negative pole of the low-voltage and high-current pulse power supply through a wire, forming a closed circuit loop, and the elastic cushion layer heats up to heat the sheet to be formed; when the sheet to be formed reaches the forming temperature, the rigid tool head of the tool head group feeds and moves, dispersing the forming force to the surface to be formed through the marble-type variant elastic cushion layer, and the sheet begins to form under the action of high temperature and pressure. In addition, the metal marbles of each unit body can be made of hard alloy materials with different resistivities. After the pulse current is passed through the marble-type variant elastic cushion layer, different temperature rises can be achieved in different areas, and the plate can be heated at different zones. The unit body in contact with the area with large deformation can be made of high-resistance materials, and the unit body in contact with the area with small deformation can be made of low-resistance materials. In order to prevent the resistance difference from being too large and too much current from flowing into the low-resistance unit body, a certain insulation treatment can be performed on it to achieve zoned variable temperature heating of the plate to be formed in contact with the unit body, thereby reducing the difficulty of forming complex-surface difficult-to-deform alloy plates.

[0049] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A marble-type deformable elastic cushion multi-point press forming device for complex-shaped and difficult-to-deform alloy sheets, characterized in that: include: Sheet material to be formed, a first tool head group, a second tool head group, an upper support plate, a lower support plate, an upper layer of marble-type variant elastic cushion layer, a lower layer of marble-type variant elastic cushion layer, a low-voltage and high-current pulse power supply, an electrode, a power switch, and a pressing block; the sheet material to be formed is located in the middle layer between the upper and lower marble-type variant elastic cushion layers, and the marble-type variant elastic cushion layers are clamped and fixed by pressing blocks on both sides; the first tool head group is mounted on the upper support plate, and the second tool head group is mounted on the lower support plate, and the rigid tool heads of the first tool head group and the second tool head group are fed and moved along their axial directions; the left end of the upper layer of marble-type variant elastic cushion layer is connected to the left electrode, and the right end of the upper layer of marble-type variant elastic cushion layer is connected to the right electrode, the left electrode is connected to the positive electrode of the low-voltage and high-current pulse power supply through a wire, and the right electrode is connected to the negative electrode of the low-voltage and high-current pulse power supply through a wire, forming a closed circuit loop; The marble-type variant elastic cushion layer adopts a mesh structure composed of multiple groups of units. The metal marbles of each unit body are made of hard alloy materials with different resistivities. After the pulse current is passed through the marble-type variant elastic cushion layer, different temperature rises are achieved in different areas, and the plate is heated at different zones. The units in contact with the area with large deformation are made of high-resistance materials, and the units in contact with the area with small deformation are made of low-resistance materials. In order to prevent the resistance difference from being too large and too much current from flowing into the low-resistance units, they are insulated to achieve zoned variable temperature heating of the plate to be formed in contact with the units, thereby reducing the difficulty of forming complex-surface difficult-to-deform alloy plates.

2. According to the marble-type variant elastic cushion multi-point press forming device for complex-surface difficult-to-deform alloy sheets as described in claim 1, the object to be formed is a large-sized alloy sheet that is difficult to deform at room temperature and easy to rebound after deformation, including a titanium alloy sheet.

3. According to the multi-point press forming device of a marble-type variant elastic cushion layer for complex-surface difficult-to-deform alloy sheet material as described in claim 1, each unit body contains a×b×c rigid marbles, and the values ​​of a, b and c are determined by the thickness and size of the sheet material. Generally speaking, a≤20, b≤20, c≤6.

4. According to the multi-point press forming device of a marble-type variant elastic cushion layer of a complex-surface difficult-to-deform alloy sheet material as described in claim 1, the diameter of the marbles of the marble-type variant elastic cushion layer is 2-5mm, and the specific size is determined by the precision requirements and material properties of the sheet to be formed; the metal marble material is an alloy material with good red hardness, and the marbles maintain high stiffness and hardness when electrically heated, and YW1 cemented carbide and YG8 cemented carbide are selected as manufacturing materials.

5. According to the multi-point press forming device of a marble-type variant elastic cushion layer of a complex-surface difficult-to-deform alloy sheet material as described in claim 1, the outer mesh layer of the marble-type variant elastic cushion layer adopts a Ni-Ti based recoverable memory alloy. After completing the multi-point progressive forming of the sheet material, the elastic cushion layer is restored to its original shape by adjusting the position of the rigid tool head. The elastic cushion layer is reusable, and flexible production can be achieved.

6. According to the multi-point press forming device of a marble-type variant elastic cushion layer of a complex-surface difficult-to-deform alloy sheet material as described in claim 1, the left end of the upper marble-type variant elastic cushion layer is connected to the left electrode, and the right end of the upper marble-type variant elastic cushion layer is connected to the right electrode. The left electrode is connected to the positive pole of a low-voltage, high-current pulse power supply through a wire, and the right electrode is connected to the negative pole of the low-voltage, high-current pulse power supply through a wire. The power switch is arranged on the wire connecting the left electrode and the low-voltage, high-current pulse power supply. When the power switch is closed, a closed circuit loop can be formed on the elastic cushion layer, and the elastic cushion layer heats the sheet to be formed under the thermal resistance effect, thereby reducing the deformation resistance and forming difficulty of the sheet to be formed, and reducing the cracking phenomenon of the sheet during the forming process.

7. According to claim 1, in the marble-type variant elastic cushion multi-point press forming device for complex-surface difficult-to-deform alloy sheets, the feeding movement of the rigid tool heads of the first tool head group and the second tool head group is controlled by the forming control system; the discharge intensity of the low-voltage and high-current pulse power supply is also completed by the forming control system.

8. According to the marble-type variant elastic cushion multi-point press forming device for complex-surface difficult-to-deform alloy sheets as described in claim 1, the rigid tool head and the pressing block need to be insulated to ensure the stability and singularity of the closed circuit.

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