Method for skin-drawing and liquid-filling composite forming of double-layer plate of double-curvature part

Abstract

The invention relates to the technical field of pressure forming, in particular to a skin drawing and liquid filling composite forming method for a double-layer plate of a double-curvature part, and aims to solve the problems that according to an existing aircraft skin forming process, the part is broken and wrinkled, the surface quality is poor, and the part with the complex shape and the large curvature change is difficult to manufacture. The method comprises the following steps that double-layer plate materials comprise a first plate material and a second plate material which are made of different materials; skin stretching forming is conducted, specifically, the double-layer plate is placed on a skin stretching forming die to be subjected to skin stretching forming; and liquid filling forming is conducted, specifically, the double-layer plate obtained after surface drawing forming is placed in a bulging mold, liquid is injected for pressurization, and therefore the first plate forms a final part. The friction maintaining effect between the second plate and the first plate is utilized, the plasticity of the second plate is larger than that of the first plate, deformation of the first plate is more sufficient, the forming limit of a part formed by the first plate is improved, and the problems that the part is broken, wrinkled, poor in surface quality, difficult to manufacture and the like are solved.

Description

Technical Field

[0001] The invention relates to the technical field of pressure forming, and in particular to a method for composite forming of double-layer plates of double-curvature parts by drawing and liquid filling. Background Art

[0002] With the rapid development of military industries such as aerospace, ships, and weapons, the demand for lightweight, low energy consumption, and high stability in high-end equipment is increasing. High-performance thin-walled components have been widely used because they meet this demand. Aircraft skin parts, as an important part of the aircraft structure, are mainly used to bear part of the limited aerodynamic load and reduce aircraft resistance. Their manufacturing quality directly affects the overall performance and safety of the aircraft. Aluminum alloys have become the preferred material for aircraft skin parts due to their high specific strength, specific stiffness, good corrosion resistance, and low temperature performance. With the development of the new generation of carrier equipment towards large-scale, lightweight, long life, and high reliability, a class of high-performance complex skin thin-walled components has emerged, whose outstanding features are overall structure, large curvature, complex shape, small features, high precision, and difficult material deformation. These characteristics coexist, making the manufacture of such components extremely difficult.

[0003] Traditional aircraft skins are mainly manufactured through drop-pressing and stretch-forming processes. The forming process can cause problems such as cracking, wrinkling and poor surface quality in parts. It is also difficult to manufacture skin parts with complex shapes and large curvature changes, which greatly affects the performance of the aircraft skin. Summary of the invention

[0004] The purpose of the present invention is to provide a method for double-layer plate drawing and liquid filling composite forming of double-curvature parts to solve the problems of part cracking, wrinkling, poor surface quality and difficulty in manufacturing parts with complex shapes and large curvature changes in existing aircraft skin forming processes.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is: A method for composite forming of double-layer plates of a double-curvature part by drawing and liquid filling, comprising the following steps; A double-layer plate material is used, wherein the double-layer plate material comprises a first plate material and a second plate material of different materials, and the plasticity of the first plate material is lower than the plasticity of the second plate material; Skin stretch forming: placing the double-layer sheet material on a skin stretching die for skin stretching forming, with one side of the second sheet material in contact with the skin stretching die and the other side in contact with the first sheet material; Liquid forming: the double-layer sheet material after the Monstrance forming is placed in a bulging die and liquid is injected for pressurization so that the first sheet material is formed into a final part.

[0006] Furthermore, the bulging die includes a bulging concave die and a bulging convex die; In the liquid filling forming step, the double-layer sheet material after Monel forming is placed in the bulging die, one side of the first sheet material contacts the bulging die, and the other side contacts the second sheet material, then the bulging punch and the bulging die are closed and mechanically extruded, and finally liquid is injected for pressurization, and the liquid pressure makes the first sheet material adhere to the bulging die.

[0007] Furthermore, the bulging die also includes a sealing ring, which is installed on the bulging convex die, and the bulging convex die is provided with a water inlet for injecting liquid for pressurization; After the mold is closed, the sealing ring abuts against the second sheet material, and the second sheet material, the sealing ring and the bulging punch form a pressurizing cavity, and liquid enters the pressurizing cavity through the water inlet for pressurization.

[0008] Optionally, in the leather stretching forming step, the jaws of the leather stretching machine clamp the double-layer sheet material, the skin stretching die applies a thrust to the double-layer sheet material to perform skin stretching forming, and then punches part positioning holes on the double-layer sheet material; In the liquid filling forming step, the bulging die is provided with a die positioning hole, and when the double-layer sheet material after the Monogram forming is placed in the bulging die, it is positioned through the part positioning hole and the die positioning hole.

[0009] Furthermore, the ends of the double-layer sheet material along the length direction are folded in half so as to be clamped by the jaws of the lathe.

[0010] Furthermore, in the skin stretch forming step, after drilling the part positioning hole, the first sheet material formed by skin stretching is taken out and quenched.

[0011] Furthermore, during quenching, the first sheet material formed by skin stretching is placed in a limiting frame to prevent deformation caused by quenching.

[0012] Furthermore, the first sheet material and the second sheet material have the same length, and the width of the first sheet material is smaller than the width of the second sheet material; When clamping the double-layer sheet material, both ends along the length direction are clamped.

[0013] Furthermore, the deformation amount of the first sheet material is e, e∈[3%, 5%].

[0014] Based on the above technical solutions, the technical effects that can be achieved by the present invention are: The method for composite forming of double-layer plates of a double-curvature part by drawing and liquid filling provided by the present invention comprises the following steps: A double-layer plate material is used, wherein the double-layer plate material comprises a first plate material and a second plate material of different materials, and the plasticity of the first plate material is lower than the plasticity of the second plate material; Skin stretch forming: Place the double-layer sheet on the skin stretching die for skin stretching forming, with one side of the second sheet in contact with the skin stretching die and the other side in contact with the first sheet; Liquid forming: The double-layer sheet after Monel forming is placed in a bulging mold and liquid is injected for pressurization to form the first sheet into the final part.

[0015] The method for composite forming of double-layer plates of double-curvature parts by stretching and liquid filling provided by the present invention adopts a first plate material and a second plate material of different materials to stack into a double-layer plate material and perform stretching and liquid filling forming, thereby eliminating the problems of thinning, cracking, wrinkling, poor surface quality at the deformation part of the part due to the plasticity of the material of the formed part itself in the existing forming, as well as the difficulty in manufacturing parts with complex shapes and large curvature changes.

[0016] Specifically, during processing, the first sheet material is the part material, and the second sheet material is the auxiliary material. Usually, the first sheet material is aluminum alloy, and the second sheet material can be steel. During the Monel forming, since the forming effect of steel is better than that of aluminum alloy, when the sheet material is lifted and deformed by the mold, the second steel sheet material deforms more evenly, and it is not easy to be excessively thinned at the deformed convex part to cause uneven thickness. Since the first sheet material and the second sheet material are attached, the second sheet material deforms first during deformation, and the second sheet material deforms evenly, so the deformation pressure is transmitted to the first sheet material through the second sheet material so that the first sheet material is evenly stressed; at the same time, friction is generated between the two during forming and pressurization, and the friction between the second steel sheet material and the first sheet material made of aluminum alloy guides and restricts the deformation of the first sheet material. That is, the first sheet material deforms with the second sheet material under the action of friction, and since the deformation of the second sheet material is uniform, the first sheet material is also more evenly formed. Similarly, the same effect can be achieved during liquid forming; thus, the problem of excessive thinning of the first sheet material at the top deformation part leading to cracking and wrinkling and poor surface quality caused by uneven deformation is avoided. At the same time, since the deformation of the first sheet material is more uniform, it is also easier to manufacture parts with complex shapes and large curvature changes.

[0017] In short, the present invention utilizes the friction retaining effect between the second sheet material and the first sheet material. The plasticity of the second sheet material is greater than that of the first sheet material, so that the deformation of the part formed by the first sheet material is more complete, the forming limit of the part formed by the first sheet material is improved, and the problems of thinning, cracking, wrinkling, poor surface quality, and difficulty in manufacturing at the deformed parts of the parts are solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic diagram of a method for combined forming of double-layer plates of a double-curvature part by forming a double-layer plate ...curvature part by a method according to an embodiment of the present invention; Figure 2 Schematic diagram of the structure of the bulging die Figure 3 It is a schematic diagram of the structure of the bulging die; Figure 4 It is a structural schematic diagram of the bulging punch; Figure 5 It is a schematic diagram of the structure of the bulging die during liquid filling forming; Figure 6 It is a schematic diagram of the structure of the double-layer sheet after Monel forming; Figure 7 This is the main view of the double-layer sheet after Monel forming; Figure 8 This is a top view of the double-layer sheet after Monel forming; Fig. 9 It is a schematic diagram of the structure of the double-layer sheet after liquid forming; Fig.10 This is the main view of the double-layer sheet after liquid forming; Fig.11 This is a top view of the double-layer sheet after liquid forming.

[0020] Icons: 100, double-layer sheet; 110, first sheet; 120, second sheet; 101, part positioning hole; 200, skin drawing mold; 310, bulging die; 320, bulging punch; 330, sealing ring; 321, water inlet; 410, jaws. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0023] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0024] Traditional aircraft skins are mainly manufactured through drop-pressing and stretch-forming processes. The forming process can cause problems such as cracking, wrinkling and poor surface quality in parts. It is also difficult to manufacture skin parts with complex shapes and large curvature changes, which greatly affects the performance of the aircraft skin.

[0025] In view of this, the present invention provides a method for composite forming of double-layer plates for hyperbolic parts by stretching and liquid filling, comprising the following steps: using a double-layer plate 100, the double-layer plate 100 includes a first plate 110 and a second plate 120 of different materials, the plasticity of the first plate 110 is lower than the plasticity of the second plate 120; stretch forming: placing the double-layer plate 100 on a skin stretching mold 200 for skin stretching forming, one side of the second plate 120 is in contact with the skin stretching mold 200, and the other side is in contact with the first plate 110; liquid filling forming: placing the double-layer plate 100 after stretching into a bulging mold and injecting liquid for pressurization to form the first plate 110 into a final part.

[0026] The method for composite forming of double-layer plates of double-curvature parts by stretching and liquid filling provided by the present invention adopts a first plate 110 and a second plate 120 of different materials to stack into a double-layer plate 100 and perform stretching and liquid filling forming, thereby eliminating the problems of thinning, cracking, wrinkling, poor surface quality at the deformation part of the part due to the plasticity of the material of the formed part itself in the existing forming, and difficulty in manufacturing parts with complex shapes and large curvature changes.

[0027] Specifically, during processing, the first sheet material 110 is a part material, and the second sheet material 120 is an auxiliary material. In this embodiment, the first sheet material 110 is an aluminum alloy, and the second sheet material 120 is selected as steel. During the Monstration forming, since the forming effect of steel is better than that of aluminum alloy, when the sheet material is lifted and deformed by the mold, the second steel sheet material 120 deforms more evenly, and it is not easy to be excessively thinned at the deformed protruding part to cause uneven thickness. Since the first sheet material 110 and the second sheet material 120 are attached, the second sheet material 120 deforms first during deformation, and the second sheet material 120 deforms evenly, so the deformation pressure is transmitted to the first sheet material 110 through the second sheet material 120 so that the first sheet material 110 is evenly stressed; at the same time, friction is generated between the two during forming and pressurization, and the friction between the second steel sheet material 120 and the first sheet material 110 made of aluminum alloy guides and restricts the deformation of the first sheet material 110. That is, the first sheet material 110 deforms along with the second sheet material 120 under the action of friction, and since the second sheet material 120 deforms evenly, the first sheet material 110 is also formed more evenly. Similarly, the same effect can be achieved during liquid filling forming; thus, the problem of excessive thinning of the first sheet material 110 at the top deformation part leading to cracking and wrinkling and poor surface quality caused by uneven deformation is avoided. At the same time, since the first sheet material 110 deforms more evenly, it is also easier to manufacture parts with complex shapes and large curvature changes.

[0028] In short, the present invention utilizes the friction retaining effect between the second sheet material and the first sheet material. The plasticity of the second sheet material is greater than that of the first sheet material, so that the deformation of the part formed by the first sheet material is more complete, the forming limit of the part formed by the first sheet material is improved, and the problems of thinning, cracking, wrinkling, poor surface quality, and difficulty in manufacturing at the deformed parts of the parts are solved.

[0029] The following combination Figure 1-Figure 11 The method for double-layer plate forming by stretching and liquid filling for double-curvature parts provided in this embodiment is described in detail: The method for double-layer plate forming by double curvature parts provided in this embodiment includes the following steps: S100 Sheet material cutting: cutting two sheets of different materials into a first sheet 110 and a second sheet 120, which are stacked to form a double-layer sheet 100. The first sheet 110 is formed into a final part.

[0030] In this embodiment, the first plate material 110 is made of aluminum alloy, and the second plate material 120 is made of steel, and the two materials are selected according to processing requirements. The forming effect of the second plate material 120 is better than that of the first plate material 110, so as to improve the forming effect of the first plate material 110.

[0031] S200: The double-layer sheet material 100 is placed on the skin stretching die 200 for skin stretching forming. One side of the second sheet material 120 contacts the skin stretching die 200, and the other side contacts the first sheet material 110. Figure 1 Specifically, the steps include: S210 Skin stretching: from top to bottom, the first sheet 110, the second sheet 120 and the skin stretching mold 200 are arranged in order, and the protruding part of the skin stretching mold 200 faces upward; the first sheet 110 and the second sheet 120 have the same length, and the width of the first sheet 110 is smaller than the width of the second sheet 120. Specifically, the width of the first sheet 110 is D1, and D1 depends on the shape of the part and the plasticity of the material; the width of the second sheet 120 is D2, and D2=D1+supplemental profile size, such as Figure 1 shown.

[0032] In this embodiment, the jaws 410 of the laminating machine clamp the two ends of the double-layer sheet 100 along the length direction, that is, the two ends of the first sheet 110 and the second sheet 120 that are flush with each other. Figure 1 As shown, after clamping, the ejector cylinder of the skin stretching machine drives the skin stretching die 200 to be ejected upward to complete the skin stretching forming.

[0033] To increase the friction between the jaws 410 and the double-layer sheet 100, the ends of the double-layer sheet 100 along the length direction are folded in half to facilitate the clamping of the jaws 410 and prevent slipping during forming. Specifically, the ends are folded in half with a length of 30mm-50mm, that is, the ends with a width of 30mm-50mm are folded upward by 180°.

[0034] S220: Punching positioning holes: When the jaws 410 clamp the double-layer sheet 100 and the skin-drawing mold 200 is lifted, punch the part positioning holes 101 on the double-layer sheet 100. Specifically, at least two part positioning holes 101 are provided to ensure the positioning effect; the part positioning holes 101 can be arranged along the width direction of the double-layer sheet 100.

[0035] In this embodiment, two part positioning holes 101 with a diameter of 10 mm are punched on the double-layer sheet 100 by using a drilling press plate to prevent the double-layer sheet 100 from rebounding or shrinking at both ends after pressure relief, which may cause misalignment of the double-layer sheet 100 in the next process. The drilling press plate is a drilling mold, which is used to locate the punching position to prevent the part positioning hole 101 from being inaccurately positioned.

[0036] S230 Part quenching: After the part positioning hole 101 is drilled, the first sheet material 110 formed by skin stretching is taken out for quenching. During quenching, the first sheet material 110 formed by skin stretching is placed in a limiting frame, and the first sheet material 110 is fixed by the limiting frame to prevent deformation caused by quenching. The internal space surrounded by the limiting frame is consistent with the shape of the first sheet material 110 formed by skin stretching to limit the first sheet material 110, and the frame structure does not affect the quenching process.

[0037] S300 Liquid filling forming: the double-layer sheet material 100 after the Monstrance forming is placed in a bulging mold and liquid is injected for pressurization so that the first sheet material 110 is formed into a final part.

[0038] In this embodiment, the bulging die includes a bulging die 310, a bulging die 320 and a sealing ring 330. Figure 2 , Figure 4 As shown, the sealing ring 330 is an annular structure and is installed on the bulging convex mold 320. The bulging convex mold 320 is provided with a water inlet 321, and the water inlet 321 is arranged in the area surrounded by the sealing ring 330.

[0039] First, the double-layer sheet material 100 after the Monstration forming is placed in the bulging die 310, and one side of the first sheet material 110 contacts the bulging die 310, and the other side contacts the second sheet material 120. Figure 5 As shown. That is, from top to bottom, they are the second sheet material 120, the first sheet material 110 and the bulging die 310. The bulging die 310 is provided with a die positioning hole. When the double-layer sheet material 100 after the Monstration Forming is placed into the bulging die 310, it is positioned through the part positioning hole 101 and the die positioning hole. The two positioning holes are aligned with the positioning pins through the holes. The positioning pins are simultaneously inserted into the die positioning hole and the part positioning hole 101 to ensure that the double-layer sheet material 100 is accurately positioned in the bulging die 310. The drilling platen can ensure that the position of the part positioning hole 101 is consistent with the position of the die positioning hole.

[0040] The location of the positioning hole is outside the area surrounded by the sealing ring 330 to ensure the sealing performance. In addition, the positioning hole can ensure that the relative position of the first plate material 110 and the second plate material 120 remains unchanged when they are re-overlapped after quenching.

[0041] Then, the bulging punch 320 and the bulging die 310 are molded together and mechanically extruded. After the molds are closed, the sealing ring 330 abuts against the second sheet material 120. The second sheet material 120, the sealing ring 330 and the bulging punch 320 form a pressurized cavity, and the water inlet 321 is connected to the pressurized cavity.

[0042] Finally, the liquid enters the pressurizing chamber through the water inlet 321 for pressurization. The pressure exerted by the liquid is transmitted from the second sheet material 120 to the first sheet material 110, so that the first sheet material 110 is attached to the bulging die 310. The finally formed first sheet material 110 is the required part. The pressure is unloaded, and the mold is opened to take out the part.

[0043] In this embodiment, the deformation of the first sheet material 110 is e, e∈[3%, 5%]. If the deformation is too large, rupture may occur easily. If the deformation is too small, springback, wrinkling and inadequate forming may occur due to insufficient plastic deformation.

[0044] The method for double-layer plate stretching and liquid filling composite forming of double-curvature parts provided in this embodiment utilizes the friction effect between the double-layer plates to improve the forming limit of aluminum alloy materials, fully utilizes the characteristics of stretching and liquid filling composite forming, and forms a preformed part by skin stretching. By changing the mold tonnage and the pressure of the liquid chamber to control the deformation of the part, the purpose of forming high-precision parts is achieved, while reducing manual intervention and shortening the part manufacturing cycle. This method is particularly suitable for the processing and forming of large-size parts with double curvature, which can effectively avoid problems such as springback and wrinkling, facilitate direct forming of parts and obtain a higher yield rate.

[0045] The method for double-layer sheet drawing and liquid filling composite forming of double-curvature parts provided in this embodiment uses double-layer sheet for skin deep drawing to make the material deform evenly and improve the forming limit of aluminum alloy; using double-layer sheet for liquid filling stretch forming can largely suppress the occurrence of wrinkling, cracking and other defects in the suspended area of ​​the sheet. Compared with the mold directly acting on the first sheet 110, the second sheet 120 is located on the inner wall of the curved surface after the first sheet 110 is formed, and the second sheet 120 and the first sheet 110 are always in a fitting state, the two are in uniform contact and the first sheet 110 is deformed with the second sheet 120. Since the second sheet 120 deforms evenly, it applies uniform force to the first sheet 110, which helps the first sheet 110 to deform evenly; at the same time, since the second sheet 120 has a good forming effect, it is not easy to have wrinkles, uneven deformation, etc., which ensures the uniform force on the first sheet 110 and guides the first sheet 110 to be uniformly thinned with the second sheet 120 through friction.

[0046] Specifically, when the aluminum alloy part becomes thinner, if it continues to deform and thin, it will continue to thin in the place where the thinning is the largest. The function of the double-layer plate is to use the friction between the first plate 110 and the second plate 120 to make the first plate 110 thinner evenly by taking advantage of the forming advantage of the second plate 120, and to a certain extent inhibit further thinning in the weakest place; at the same time, the second plate 120 is used to form a pressurized cavity, so that the liquid pressure is applied to the first plate 110 through the second plate 120, and the first plate 110 is uniformly formed by taking advantage of the forming advantage of the second plate 120.

[0047] This method is aimed at the forming of aluminum alloy parts with low elongation, especially the forming of parts with double curvature and large chord height ratio. It fully utilizes the advantages of composite forming of stretching and liquid filling, controls the forming accuracy of parts, solves the problems of cracking and uneven thickness caused by material plasticity and wrinkling and cracking caused by insufficient deformation during aluminum alloy forming, realizes efficient and high-performance manufacturing of aircraft skin parts, obtains aluminum alloy parts with high forming accuracy, excellent surface quality and uniform wall thickness distribution, and greatly improves work efficiency while saving costs.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for composite forming of double-layer plates of double-curvature parts by stretching and liquid filling, characterized in that: The method comprises the following steps: A double-layer plate material (100) is used, wherein the double-layer plate material (100) comprises a first plate material (110) and a second plate material (120) of different materials, and the plasticity of the first plate material (110) is lower than the plasticity of the second plate material (120); Skin stretch forming: placing the double-layer sheet material (100) on a skin stretching die (200) to perform skin stretch forming, with one side of the second sheet material (120) in contact with the skin stretching die (200) and the other side in contact with the first sheet material (110); Liquid filling forming: the double-layer sheet material (100) after the Monstretch forming is placed in a bulging die and liquid is injected for pressurization so that the first sheet material (110) is formed into a final part.

2. The method for double-layer plate forming by double curvature parts by double-layer plate forming and liquid filling according to claim 1, characterized in that: The bulging die comprises a bulging concave die (310) and a bulging convex die (320); In the liquid filling forming step, the double-layer sheet material (100) after the Monogram forming is placed in the bulging die (310), one side of the first sheet material (110) contacts the bulging die (310), and the other side contacts the second sheet material (120), then the bulging punch (320) and the bulging die (310) are molded together and mechanically extruded, and finally liquid is injected for pressurization, and the liquid pressure makes the first sheet material (110) adhere to the bulging die (310).

3. The method for composite forming of double-layer plates of double-curvature parts by stretching and liquid filling according to claim 2 is characterized in that: The bulging die further comprises a sealing ring (330), wherein the sealing ring (330) is mounted on the bulging convex die (320), and the bulging convex die (320) is provided with a water inlet (321) for injecting liquid for pressurization; After the mold is closed, the sealing ring (330) abuts against the second plate material (120), and the second plate material (120), the sealing ring (330) and the bulging punch (320) form a pressurizing cavity, and liquid enters the pressurizing cavity through the water inlet (321) for pressurization.

4. The method for double-layer plate forming by double curvature parts by double-layer plate drawing and liquid filling according to claim 2, characterized in that: In the stretch forming step, the jaws (410) of the stretch machine clamp the double-layer sheet material (100), the skin stretching die (200) applies a thrust to the double-layer sheet material (100) to perform skin stretch forming, and then a part positioning hole (101) is punched on the double-layer sheet material (100); In the liquid filling forming step, a die positioning hole is provided on the bulging die (310), and when the double-layer sheet material (100) after the Monogram forming is placed in the bulging die (310), it is positioned through the part positioning hole (101) and the die positioning hole.

5. The method for composite forming of double-layer plates of double-curvature parts by lamination and liquid filling according to claim 4, characterized in that: The double-layer sheet material (100) is folded in half at the end along the length direction so as to be clamped by the jaws (410) of the laminating machine.

6. The method for composite forming of double-layer plates of double-curvature parts by forming a double-layer plate ... according to claim 4, characterized in that: In the skin stretch forming step, after the part positioning hole (101) is punched, the first sheet material (110) formed by skin stretching is taken out and quenched.

7. The method for composite forming of double-layer plates of double-curvature parts by stretching and liquid filling according to claim 6, characterized in that: During quenching, the first sheet material (110) formed by skin stretching is placed in a limiting frame to prevent deformation caused by quenching.

8. The method for composite forming of double-layer plates of double-curvature parts by lamination and liquid filling according to claim 1, characterized in that: The first plate material (110) and the second plate material (120) have the same length, and the width of the first plate material (110) is smaller than the width of the second plate material (120); and when the double-layer plate material (100) is clamped, both ends along the length direction are clamped.

9. The method for composite forming of double-layer plates of double-curvature parts by forming a double-layer plate ... according to claim 1, characterized in that: The deformation amount of the first sheet material (110) is e, e∈[3%, 5%].

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