A method of forming an ellipsoidal container

Abstract

This invention relates to the field of advanced plastic forming technology, and specifically discloses a method for forming an ellipsoidal container, comprising the following steps: forming an ellipsoidal shape by hydraulically bulging a metal original shell without a mold; constraining the end face and filling the metal original shell with a pressure medium for one-time forming; after the one-time forming is completed, releasing the constraint and filling the pressure medium again for a second-time forming; emptying the pressure medium to form the ellipsoidal shape; the ellipsoidal container formed according to the above method includes an original shell and a supporting structure, the original shell being composed of side bodies and welded end faces, and the interior of the original shell being composed of microshells containing the supporting structure. This method for forming an ellipsoidal container avoids wrinkling and instability during the forming process by first forming the side bodies and then forming the end faces in a second-time forming. The use of lobes with supporting structures and external constraints makes it easier to obtain complex structural shapes such as large curvatures, resulting in high surface quality.

Description

Technical Field

[0001] This invention relates to the field of advanced plastic forming technology, specifically to a method for forming an ellipsoidal container. Background Technology

[0002] Ellipsoidal shell structures, due to their ability to meet the special functional requirements of liquid transportation and ultra-high pressure, are widely used in strategic and core fields such as spacecraft fuel tanks and liquefied natural gas storage tanks. However, the curvature of ellipsoidal shell structures often changes continuously along meridians and parallels, and traditional stamping or forging splicing processes suffer from stress concentration and poor sealing, making manufacturing difficult. The use of moldless bulging technology, with its three core advantages of flexible forming, lightweight design, and high-precision control, is becoming a key process in high-end equipment manufacturing.

[0003] As is well known, spherical containers undergoing membrane-free bulging have relatively low technical difficulty due to their high geometric symmetry and uniform circumferential expansion of the blank. They also have a low risk of local necking due to overall deformation. The process is simple and the molding efficiency is high, making them suitable for mass production of symmetrical structures. In contrast, ellipsoidal containers have lower geometric symmetry, with differences between the major and minor axes. Deformation is more significant along the major axis, and cracking often begins in areas of stress concentration. Due to the anisotropy and non-uniform deformation capacity of the material, they are prone to local excessive thinning or obvious orange peel texture. Therefore, the process of ellipsoidal shell containers is highly complex and requires precise control of deformation path and stress distribution.

[0004] The current challenges in moldless bulging manufacturing of ellipsoidal shells include difficulties in controlling forming limits and defects (wrinkling and instability caused by compressive stress) and controlling process parameters (stress concentration leading to uneven pressure distribution, complex boundary conditions, and multi-field coupling effects). There is an urgent need to innovate a method to avoid wrinkling and instability during the moldless bulging process of ellipsoidal shells. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides the following technical solution: a method for forming an ellipsoidal container, comprising the following steps: An ellipsoidal shape is formed by hydraulically expanding the original metal shell without molds. The end face is constrained and the pressure medium is filled into the original metal housing in a single molding process; After the first molding is completed, release the constraint and refill the pressure medium for a second molding. The pressure medium is emptied to form the ellipsoidal shape; The ellipsoidal container formed according to the above method includes an original shell and a supporting structure. The original shell is composed of side bodies and end faces welded together, and the interior of the original shell is composed of microshells containing the supporting structure.

[0006] Preferably, the pressure medium includes at least one of liquid, gas, or particles; The liquid includes at least one of water or oil, the gas includes at least one of air, nitrogen or argon, and the particles include at least one of ceramic balls, steel balls, silica sand or polymer particles.

[0007] Preferably, the material of the original shell includes at least one of aluminum alloy, magnesium alloy, titanium alloy, low carbon steel, stainless steel, high strength steel or copper.

[0008] Preferably, the support structure includes at least one level of support unit, the support unit is distributed along the axial or circumferential direction, and the support structure adjusts the support stiffness according to the bulging pressure or temperature to match the deformation rate or gradient; The cross-sectional shape of the support unit includes at least one of the following: circular, square, polygonal, wavy, spiral, and fractal structure.

[0009] Preferably, the support unit further includes biodegradable inserts at both ends, which are removed by chemical etching to form internal functional channels.

[0010] Preferably, the thickness of the original shell is set based on the finite element stress distribution or the equivalent curvature.

[0011] Preferably, the ellipsoidal container further includes a dynamic adjustment mechanism, which monitors the expansion pressure or temperature in real time, and the pressure or temperature signal and the shape of the ellipsoidal body establish an input-output correspondence prediction relationship through a neural network.

[0012] Preferably, the training of the neural network is based on the results of the signal and shape calculations in the finite element model.

[0013] Preferably, the side body has at least one microshell, and the microshell includes at least one of a melon petal or a ring shell, and the shape of the microshell on the side body is different from that on the end face.

[0014] Preferably, the constraint includes at least limiting the displacement of the end face.

[0015] It has the following beneficial effects: By first forming the side body and then forming the end face in a secondary molding process, wrinkling and instability during the forming process are avoided. The use of supporting structures and external constraints makes it easier to obtain complex structural shapes with large curvatures and high surface quality. Biodegradable inserts at both ends of the support unit can be removed by chemical etching, ensuring the connectivity of the internal cavity. A dynamic adjustment mechanism can adjust the support stiffness to match the deformation rate. A neural network is used to establish a matching deformation rate with pressure or temperature signals as input and shape as output. The neural network is trained using the results of the signals and shape calculations in the finite element method. This invention provides an ellipsoidal container forming method that solves the problems of difficult high-precision ellipsoid manufacturing and easy wrinkling and instability. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the original shell structure of the present invention.

[0017] In the diagram: 1. End face; 2. Side body; 3. Weld. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] For the first embodiment, please refer to... Figure 1 The present invention provides a technical solution: a method for forming an ellipsoidal container, which forms an ellipsoidal shape by hydraulically expanding a metal original shell without a mold, including at least the original shell, a support and a pressure medium. The original shell is composed of side bodies and end faces welded together. The interior of the original shell is composed of petals containing the support structure. The end faces are constrained and the pressure medium is filled into the metal original shell for one-time forming. After the one-time forming is completed, the constraint is released and the pressure medium is filled again for a second forming. The pressure medium is then emptied to form the ellipsoidal shape.

[0020] Moldless hydraulic bulging is a plastic processing technology that uses internal pressure or external action to form an ellipsoidal shape from sheet (shell) or tube without the constraint of a rigid mold. Its core lies in using material flowability and precise mechanical control to achieve the target shape.

[0021] It should be noted that during the one-time forming of the end face, the material is plastically deformed under bidirectional stress by filling the cavity of the original shell with a pressure medium and cooperating with constraints (external boundary constraints).

[0022] In this embodiment of the invention, wrinkling and instability during the forming process are avoided by first forming the side body and then forming the end face in a secondary forming process. The use of a microshell with a supporting structure and external constraints makes it easier to obtain complex structural shapes with large curvatures and high surface quality. Biodegradable inserts at both ends of the supporting unit can be removed by chemical etching, ensuring the connectivity of the internal cavity. A dynamic adjustment mechanism can adjust the support stiffness to match the deformation rate. A neural network is used to establish a matching deformation rate with pressure or temperature signals as input and shape as output. The neural network is trained using the results of the signals and shape calculations in the finite element method. This invention provides an ellipsoidal container forming method that solves the problems of difficulty in manufacturing high-precision ellipsoids and their susceptibility to wrinkling and instability.

[0023] The pressure medium includes at least one of liquid, gas, or particles; the liquid includes at least one of water or oil; the gas includes at least one of air, nitrogen, or argon; and the particles include at least one of ceramic balls, steel balls, silica sand, or polymer particles.

[0024] In the hydraulic bulging embodiment of the present invention, a high-viscosity medium is partially filled and a low-viscosity liquid is filled in other areas to form a pressure gradient. The high-viscosity medium transmits pressure to uniformly support the thin wall, while the low-viscosity medium has strong fluidity and is filled quickly to reduce wrinkling or cracking.

[0025] Mixed media (such as liquid + gas) can achieve dynamic pressure changes by adjusting the gas volume. In the initial stage of expansion, low-pressure gas is used for rapid filling, and in the later stage, hydraulic pressure is used for precise molding.

[0026] It should be noted that high-viscosity media can easily lead to uneven material rebound or uneven local deformation. Mixing with low-viscosity media (such as water) can wash away the adhesive layer and improve surface quality.

[0027] Mixed media include components with large differences in thermal conductivity, and local heating or cooling can be achieved by controlling the temperature of the media; for example, in bulging high-temperature alloys, the outer layer of heat-conducting oil dissipates heat quickly to prevent overheating, while the inner layer of water maintains stable pressure.

[0028] Mixed media (such as particles + liquid) can disperse localized stress concentrations through particle flow and rearrangement.

[0029] It should be noted that the hybrid medium significantly optimizes the pressure distribution, friction control, temperature management, and deformation uniformity of moldless bulging by synergistically leveraging the advantages of different media.

[0030] The original metal casing material includes at least one of aluminum alloy, magnesium alloy, titanium alloy, low carbon steel, stainless steel, high strength steel, or copper.

[0031] The copper mentioned refers to substances containing the element copper, such as copper alloys.

[0032] The support includes at least one level of support units, which are distributed along the axial or circumferential direction and have different / same stiffness to match the deformation gradient of the bulging member; When shaping a complex curved ellipsoid, a first-level support unit is used to provide overall support stiffness. The second-level support is designed with different shapes and sizes of local supports according to the curvature of the part surface to accurately fit the part surface and avoid excessive or insufficient local deformation.

[0033] The cross-sectional shape of the support unit includes at least one of the following: circular, square, polygonal, wavy, spiral, and fractal structure. The cross-sectional shapes of different groups of support units can be different, and the cross-sections of the same group along the length direction can also be different. This setting is determined based on the final formed shape calculated by finite element method.

[0034] It should be noted that if the support unit contains multiple sets, the cross-sectional area or shape of the support between the sets can be different or the same.

[0035] It should be noted that the support structure is not a single, simple whole, but is composed of one or more support units with specific functions. The hierarchical design can be flexibly adjusted and optimized according to different bulging requirements and part shapes.

[0036] Preferably, when the internal support structure includes multiple levels of support units, the support units at each level have a certain cooperative working relationship in order to achieve a more complex and precise support effect.

[0037] The materials of the support unit also include shape memory alloys (which recover a preset shape upon heating to compensate for expansion and rebound) or magnetorheological fluids (which dynamically adjust the support force by controlling the annual growth through an external magnetic field).

[0038] Optionally, it also includes a dynamic adjustment mechanism that monitors the bulging pressure or temperature in real time, and the support adjusts the support stiffness according to the bulging pressure or temperature to match the deformation rate.

[0039] Optionally, the side body has at least one microshell, and the microshell includes at least a melon petal or a ring shell. The shape of the microshell on the side body is different from that on the end face.

[0040] The melon petals are formed by uniformly dividing the side body along the warp direction, except for the end face; The annular shell is formed by dividing the side body along the latitudinal direction, except for the end face; The ring shell is in the shape of a ring cone.

[0041] The shape of the melon lobes on the side body is different from that on the end face; the shape of the melon lobes on the side body is the same; the shape of the melon lobes on the end face is the same.

[0042] The number of lobes on the lateral body of the melon is determined based on the curvature, preferably not less than 8 lobes.

[0043] The end face segments are located on both sides of the side body segments, and the minimum number of segments on both end faces with regular shapes is no less than 2 segments.

[0044] Optionally, the constraint includes at least limiting the displacement of the outer side of the end face.

[0045] When displacement is restricted on the outer side of the end face, external tooling is used to restrict the outward expansion of the end face displacement.

[0046] Optionally, the support unit may further include biodegradable inserts at both ends, which are removed by chemical etching to form internal functional channels.

[0047] By adding biodegradable inserts at both ends of the support unit, selective separation from the cavity can be achieved, thereby adjusting the shape of the cavity and increasing the internal channels.

[0048] Optionally, the thickness of the original shell is set based on an equivalent finite element stress distribution or curvature.

[0049] By applying different temperatures or pressures through finite element analysis, specific shapes can be obtained, and then the necessary shape predictions can be obtained by applying finite element conditions in experiments.

[0050] Preferably, the pressure or temperature signal and the shape of the ellipsoid are used to establish an input-output prediction relationship through a neural network, and the training of the neural network is based on the results of the signal and the shape calculation in the finite element model.

[0051] For shapes modeled by finite element method, finite element analysis can be used for prediction. Based on the large amount of data results established by finite element analysis, neural networks can be used for training, so that the shape of the shape can be predicted without finite element modeling. The shape can be curvature, major or minor axis, or other necessary shape parameters.

[0052] Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art and related fields based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described and explained in the present invention, unless otherwise specified or limited, shall be implemented according to conventional means in the art.

Claims

1. A method for forming an ellipsoidal container, characterized in that, Includes the following steps: An ellipsoidal shape is formed by hydraulically expanding the original metal shell without molds. The end face is constrained and the pressure medium is filled into the original metal housing in a single molding process; After the first molding is completed, release the constraint and refill the pressure medium for a second molding. The pressure medium is emptied to form the ellipsoidal shape; The ellipsoidal container formed according to the above method includes an original shell and a supporting structure. The original shell is composed of side bodies and end faces welded together, and the interior of the original shell is composed of microshells containing the supporting structure.

2. The method for forming an ellipsoidal container according to claim 1, characterized in that: The pressure medium includes at least one of liquid, gas, or particles; The liquid includes at least one of water or oil, the gas includes at least one of air, nitrogen or argon, and the particles include at least one of ceramic balls, steel balls, silica sand or polymer particles.

3. The method for forming an ellipsoidal container according to claim 1, characterized in that: The material of the original shell includes at least one of aluminum alloy, magnesium alloy, titanium alloy, low carbon steel, stainless steel, high strength steel or copper.

4. The method for forming an ellipsoidal container according to claim 1, characterized in that: The support structure includes at least one level of support unit, which is distributed along the axial or circumferential direction. The support structure adjusts the support stiffness according to the bulging pressure or temperature to match the deformation rate or gradient. The cross-sectional shape of the support unit includes at least one of the following: circular, square, polygonal, wavy, spiral, and fractal structure.

5. The method for forming an ellipsoidal container according to claim 4, characterized in that: The support unit also includes biodegradable inserts at both ends, which are removed by chemical etching to form internal functional channels.

6. The method for forming an ellipsoidal container according to claim 1, characterized in that: The thickness of the original shell is set based on the finite element stress distribution or the equivalent curvature.

7. The method for forming an ellipsoidal container according to claim 1, characterized in that: The ellipsoidal container also includes a dynamic adjustment mechanism, which monitors the expansion pressure or temperature in real time. The pressure or temperature signal and the shape of the ellipsoidal body are used to establish an input-output prediction relationship through a neural network.

8. The method for forming an ellipsoidal container according to claim 7, characterized in that: The training of the neural network is based on the results of the signal and shape calculations in the finite element model.

9. The method for forming an ellipsoidal container according to claim 1, characterized in that: The side body has at least one microshell, and the microshell includes at least one of a melon petal or a ring shell. The shape of the microshell on the side body is different from that on the end face.

10. The method for forming an ellipsoidal container according to claim 1, characterized in that: The constraint includes at least limiting the displacement of the end face.

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