Die-free forming method and system for thin-wall curved-surface shell component

Abstract

The invention discloses a thin-wall curved-surface shell component die-free forming method, which relates to the technical field of thin-wall curved-surface shell forming, and comprises the following steps: determining the characteristics of a closed shell according to the characteristics of a target curved-surface shell; determining a strength calculation model of the selected blank under bidirectional stress during bulging; calculating the characteristics of the prefabricated closed shell according to the strength calculation model and the characteristics of the closed shell; forming the prefabricated closed shell according to the characteristics of the prefabricated closed shell; bulging the prefabricated closed shell to obtain a closed shell; and the closed shell is cut, and the target curved-surface shell is obtained. According to the die-free forming method for the thin-wall curved-surface shell component, the forming process is simple, implementation is easy, no die needs to be used during forming, the method is suitable for manufacturing large-size thin-wall containers on site, and the size and strength of the target curved-surface shell are controllable and adjustable. The invention further provides a die-free forming system for the thin-wall curved-surface shell component.

Description

Technical Field

[0001] The present invention relates to the technical field of thin-walled curved shell forming, and in particular to a dieless forming method and system for a thin-walled curved shell component. Background Art

[0002] Large thin-walled curved shells (such as Figure 1 As a key structure in aerospace, aviation, navigation, and nuclear fusion, it usually has the characteristics of ultra-high strength (1000MPa), ultra-large size (10m level), ultra-thinness (1-3mm), and bidirectional variable curvature. In addition, its complex surface and very high dimensional accuracy requirements have led to huge challenges in its manufacturing process.

[0003] Currently, thin-walled curved components are primarily formed using die stamping, which primarily involves deep drawing, pressing, spinning, and roll bending. The use of die forming methods for the production of large, complex curved shells is associated with high mold manufacturing costs, long manufacturing cycles, and large-scale forming equipment. Furthermore, the strength of the formed part is related to the amount of deformation, and in die stamping methods, the amount of deformation is related to both the initial slab shape and the die shape, making it difficult to regulate the amount of deformation and uniformity. That is, once the initial slab shape and die shape are determined, the strength distribution of the formed part obtained by die stamping is essentially determined, making it difficult to regulate the strength of the formed part. Summary of the Invention

[0004] The purpose of the present invention is to provide a moldless forming method and system for thin-walled curved shell components to solve the problems existing in the above-mentioned prior art. The thin-walled curved shell forming process is simple and easy to implement. No mold is required during forming. It is suitable for on-site manufacturing of large-sized thin-walled containers, and the size and strength of the target curved shell are controllable and adjustable.

[0005] To achieve the above object, the present invention provides the following solutions: The present invention provides a dieless forming method for a thin-walled curved shell component, comprising the steps of: Determine the closed shell: determine the characteristics of the closed shell based on the characteristics of the target surface shell; Determine the strength characteristics of the blank: determine the strength calculation model of the selected blank under biaxial stress during bulging; Determining a prefabricated closed shell: inferring the characteristics of the prefabricated closed shell according to the strength calculation model and the characteristics of the closed shell; Forming a prefabricated enclosure: forming the prefabricated enclosure according to the characteristics of the prefabricated enclosure; Forming a closed shell: bulging the prefabricated closed shell to obtain the closed shell; Forming a target curved surface shell: cutting the closed shell to obtain the target curved surface shell.

[0006] Preferably, in the step of determining a closed shell, the target curved shell is hemispherical or spherical, and correspondingly, the closed shell is a spherical shell; or, the target curved shell is semi-ellipsoidal, and correspondingly, the closed shell is an ellipsoidal shell; and the closed shell can form two of the target curved shells.

[0007] Preferably, in the step of forming the closed shell, the prefabricated closed shell is expanded at room temperature or ultra-low temperature according to the design strength of the target curved shell to obtain the closed shell.

[0008] Preferably, in the step of determining the strength characteristics of the blank, the blank is selected from stainless steel plates; The strength calculation model of stainless steel plates at room temperature:

[0009] Where, is the design strength of the target curved shell; is the initial yield strength of the stainless steel plate at room temperature, obtained by performing a uniaxial or biaxial tensile test on the initial slab at room temperature; H is the tangent modulus of the stainless steel plate at room temperature, which is obtained by fitting the true stress-strain data of the initial slab in single tension at room temperature; It is the equivalent strain caused by the deformation of the stainless steel plate; Strength calculation model of stainless steel plates at ultra-low temperatures:

[0010] Where, is the ultra-low temperature initial yield strength of the stainless steel plate, obtained by performing a uniaxial or biaxial tensile test on the initial slab at ultra-low temperature; A, B and C is the hardening coefficient of the stainless steel plate at ultra-low temperature, which is obtained by fitting the true stress-strain data of the initial slab under ultra-low temperature single tension; It is the equivalent strain caused by the deformation of the stainless steel plate.

[0011] Preferably, in the step of determining the strength characteristics of the blank, the blank is selected from stainless steel plates; The strength calculation model of stainless steel plates at room temperature can be replaced by the true stress and strain data of single tension of 304L stainless steel plates at room temperature; the strength calculation model of stainless steel plates at ultra-low temperature can be replaced by the true stress and strain data of single tension of 304L stainless steel plates at liquid nitrogen temperature.

[0012] Preferably, the step determines the relationship between the diameter of the prefabricated enclosed shell and the equivalent strain:

[0013] Where, d is the diameter of the closed shell; d 0 is the diameter of the prefabricated closed shell; ε i is equivalent strain; the diameter of the prefabricated closed shell is smaller than the diameter of the closed shell; The relationship between the wall thickness expression of the prefabricated closed shell and the equivalent strain is:

[0014] Where, t is the wall thickness of the closed shell, which is the same as the wall thickness of the target curved shell; t 0 is the wall thickness of the prefabricated closed shell; ε i is equivalent strain; the wall thickness of the prefabricated closed shell is greater than the wall thickness of the closed shell.

[0015] Preferably, in the step of forming the prefabricated closed shell, the component structure of the prefabricated closed shell is first determined, and the component structure includes an intermediate shell and two top covers, the intermediate shell has openings on both sides, the two top covers are respectively placed in the two openings, and are fixedly connected to the intermediate shell to form the prefabricated closed shell.

[0016] Preferably, in the step of forming the closed shell, the forming internal pressure and the forming volume increment required for forming the closed shell are determined, the bulging pressure and the volume increment in the prefabricated closed shell are monitored, and when the volume increment of the prefabricated closed shell reaches the forming volume increment, the bulging of the prefabricated closed shell is stopped; The expression of forming internal pressure is:

[0017] Where, p is the forming internal pressure; t 0 is the wall thickness of the prefabricated closed shell; σ i The strength of the closed shell is not less than the design strength of the target curved shell; d 0 is the diameter of the prefabricated closed shell; d is the diameter of the closed shell; The expression of forming volume increment is: Δ V=VV 0 Where, V is the volume of the closed shell after forming; V 0 is the volume of the prefabricated closed shell.

[0018] The present invention also provides a moldless forming system for thin-walled curved shell components, comprising an environmental box and a pressurizing component; the environmental box has a accommodating cavity, which is used to place a prefabricated closed shell; the pressurizing component is connected to the interior of the prefabricated closed shell and the interior of the environmental box, and the pressurizing component can pass fluid into the prefabricated closed shell to achieve pressurized expansion of the prefabricated closed shell, and the pressurizing component can also pass fluid into the environmental box to regulate the environmental information outside the prefabricated closed shell.

[0019] Preferably, it also includes a volume measuring component, a displacement measuring component, a temperature measuring component and a control component; the volume measuring component is used to monitor the flow rate information of the fluid filled into the environmental box and the prefabricated closed shell by the charging component, and is also used to monitor the weight information of the fluid in the prefabricated closed shell; the displacement measuring component is used to monitor the deformation information of the prefabricated closed shell during the expansion process; the temperature measuring component is used to monitor the temperature information in the environmental box; the control component is communicated with the temperature measuring component and is used to obtain the temperature information; the control component is also communicated with the volume measuring component and is used to receive the flow rate information and weight information of the fluid to obtain the volume of the fluid in the prefabricated closed shell; the control component is also communicated with the displacement measuring component and is used to receive the deformation information to obtain the real-time size of the prefabricated closed shell during the expansion process; the control component is communicated with the charging component and is used to control the action of the charging component.

[0020] Compared with the prior art, the present invention has achieved the following technical effects: The present invention provides a dieless forming method for thin-walled curved shell components, which determines the characteristics of a closed shell according to the characteristics of a target curved shell; determines a strength calculation model of a selected blank under bidirectional stress during bulging; infers the characteristics of a prefabricated closed shell according to the strength calculation model and the characteristics of the closed shell; forms a prefabricated closed shell according to the characteristics of the prefabricated closed shell; bulges the prefabricated closed shell to obtain a closed shell; cuts the closed shell to obtain a target curved shell; compared with existing mold stamping forming, the forming process is simple and easy to implement. After selecting a blank, the characteristics of the prefabricated closed shell are determined according to the strength calculation model of the blank under bidirectional stress during bulging so that it meets the requirements of bulging forming. The closed shell can be obtained by calculation and the characteristics of the prefabricated closed shell can be adjusted according to the required size and strength of the target curved shell. No mold is needed during bulging. After the bulging parameters are determined according to the characteristic size of the prefabricated closed shell, the closed shell that meets the requirements can be obtained by directly pressurizing and bulging the interior of the prefabricated closed shell. The target curved shell can then be obtained by cutting the closed shell. It is suitable for on-site manufacturing of large-sized thin-walled curved containers. It only needs to form the prefabricated closed shell on-site and bulge it. The size and strength of the target curved shell can be adjusted on-site according to the strength calculation model to adjust the forming characteristics of the prefabricated closed shell to meet the forming of the target curved shell.

[0021] The moldless forming system for thin-walled curved shell components provided by the present invention places a prefabricated closed shell in an environmental chamber, and introduces fluid into the environmental chamber through a charging component to adjust the environmental information required for expansion, such as temperature, and then introduces fluid into the prefabricated closed shell through the charging component to perform pressurized expansion, so as to form the closed shell without using a mold. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 is a schematic diagram of the target surface shell parts; Figure 2 A dieless forming method for thin-walled curved shell components provided in Embodiments 1 and 2; Figure 3 A schematic diagram of a closed housing provided in Example 1; Figure 4 A schematic diagram of a prefabricated closed shell provided in Example 1; Figure 5 Another schematic diagram of the prefabricated closed shell provided in Example 1; Figure 6 Another schematic diagram of the prefabricated closed shell provided in Example 1; Figure 7 for Figure 4 Schematic diagram of the dimensions of the provided prefabricated enclosure; Figure 8 for Figure 4 A schematic axial view of the prefabricated enclosure shell is provided; Figure 9 A schematic axial view of the closed housing provided in this embodiment; Figure 10 A schematic structural diagram of a dieless forming system for a thin-walled curved shell component provided in Example 3.

[0024] In the figure: 1-enclosed shell; 2-target curved shell; 3-prefabricated enclosed shell; 31-intermediate shell; 32-top cover; 33-intermediate cone section; 34-equatorial cone section; 4-environmental chamber; 41-accommodation chamber; 5-charging component; 51-hydraulic pump; 52-first solenoid valve; 53-second solenoid valve; 54-first overflow valve; 55-second overflow valve; 6-volume measurement component; 61-flow monitoring component; 62-weight monitoring component; 7-displacement measurement component; 71-displacement sensor; 8-temperature measurement component; 9-control component. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] The purpose of the present invention is to provide a moldless forming method and system for thin-walled curved shell components to solve the problems existing in the above-mentioned prior art. The thin-walled curved shell forming process is simple and easy to implement. No mold is required during forming. It is suitable for on-site manufacturing of large-sized thin-walled containers, and the size and strength of the target curved shell are controllable and adjustable.

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Example 1 This embodiment provides a die-free forming method for thin-walled curved shell components. Figure 2 , including the steps of: Determine the closed shell 1: determine the characteristics of the closed shell 1 based on the characteristics of the target curved shell 2, where the characteristic information includes diameter, wall thickness, strength, etc.; Determine the strength characteristics of the blank: determine the strength calculation model of the selected blank under biaxial stress during bulging; Determine the prefabricated closed shell 3: infer the characteristics of the prefabricated closed shell 3 based on the strength calculation model and the characteristics of the closed shell 1; Forming the prefabricated closed shell 3: forming the prefabricated closed shell 3 according to the characteristics of the prefabricated closed shell 3; Forming the closed shell 1: bulging the prefabricated closed shell 3 to obtain the closed shell 1; Forming the target curved surface shell 2: cutting the closed shell 1 to obtain the target curved surface shell 2.

[0029] Compared with the existing mold stamping forming, the forming process is simple and easy to implement. After the blank is selected, the characteristics of the prefabricated closed shell 3 are determined according to the strength calculation model of the blank under bidirectional stress during expansion so that it meets the closed shell 1 required for expansion forming. These can be achieved through calculation, and the characteristics of the prefabricated closed shell 3 can be adjusted according to the required size and strength of the target curved shell 2. No mold is required during expansion. After the expansion parameters are determined according to the characteristic size of the prefabricated closed shell 3, the closed shell 1 that meets the requirements can be obtained by directly pressurizing and expanding the inside of the prefabricated closed shell 3. Then, the closed shell 1 can be cut to obtain the target curved shell 2; it is suitable for on-site manufacturing of large-sized thin-walled curved containers. It is only necessary to form the prefabricated closed shell 3 on-site and expand it. The size and strength of the target curved shell 2 can be adjusted on-site according to the strength calculation model to adjust the forming characteristics of the prefabricated closed shell 3 to meet the forming requirements of the target curved shell 2.

[0030] In the optional scheme of this embodiment, it is more preferred that the step determines that in the closed shell 1, the target curved shell 2 is hemispherical or spherical, and correspondingly, the closed shell 1 is a spherical shell; or, the target curved shell 2 is hemispherical, and correspondingly, the closed shell 1 is an ellipsoidal shell; and the closed shell 1 includes two target curved shells 2; this embodiment is explained by taking the target curved shell 2 as a hemispherical or spherical as an example, and correspondingly, the closed shell 1 is a spherical shell; it can be seen that the diameter and wall thickness of the target curved shell 2 are the same as the curvature radius and wall thickness of the closed shell 1, such as Figure 2 As shown, the curvature radius R of the target curved shell 2 is set to 250 mm and the wall thickness t is set to 1.5 mm. Correspondingly, as Figure 3 and Figure 7 , diameter d is 500mm and wall thickness t is 1.5mm.

[0031] In the optional scheme of this embodiment, it is more preferred that in the step of forming the closed shell 1, the prefabricated closed shell 3 is expanded at room temperature or ultra-low temperature according to the design strength of the target curved shell 2 to obtain the closed shell 1, wherein the room temperature is 20°C and the ultra-low temperature is -60°C~-196°C; specifically, when the design strength When forming, both room temperature bulging and ultra-low temperature bulging can be used, and room temperature bulging is preferred. The room temperature bulging process mainly causes the prefabricated closed shell 3 to undergo deformation and strengthening, and the closed shell 1 reaches the designed strength and target size by controlling the expansion amount.

[0032] In the optional solution of this embodiment, it is more preferred that in the step of determining the strength characteristics of the blank, the blank is a stainless steel plate, and the strength calculation model of the stainless steel plate at room temperature is: (1) Where, is the design strength of the target curved shell 2; is the initial yield strength of the stainless steel plate at room temperature, obtained by performing a uniaxial or biaxial tensile test on the initial slab at room temperature; H is the tangent modulus of the stainless steel plate at room temperature, which is obtained by fitting the true stress-strain data of the initial slab in single tension at room temperature; It is the equivalent strain caused by the deformation of the stainless steel plate.

[0033] Specifically, 304L stainless steel plate can be selected. Under room temperature conditions, the Take 286MPa, H Take 1839MPa; when determining the design strength After that, the equivalent strain can be determined according to the above calculation model .

[0034] In the optional scheme of this embodiment, it is more preferred that, in order to facilitate actual production use, the real stress-strain data of 304L stainless steel plate at room temperature can be directly used instead of the strength calculation model of the plate under bidirectional stress, as shown in Table 1. The values ​​between the data can be obtained by linear interpolation; the design strength of the target curved shell 2 is set. If the strength of the closed shell 1 is 600 MPa, it is determined that the strength of the closed shell 1 is greater than or equal to 600 MPa; the equivalent strain (true strain) can be obtained by matching the strength of the target curved shell 2 to the equivalent stress (true stress) in Table 1. ε i It is 0.159.

[0035] Table 1 is the room temperature uniaxial tensile mechanical properties of 304L stainless steel

[0036] In the optional scheme of this embodiment, it is more preferred to convert the complex biaxial strain state into the equivalent strain of uniaxial tension through equivalent strain. When the strain increment increases proportionally, the longitudinal strain and the latitudinal strain of the spherical shell bulging are equal. ,in, ε φ is the meridional strain, εθ is the latitudinal strain. According to the condition of constant volume of plastic deformation, the equivalent strain calculation formula is: (2) Through the prefabricated closed shell 3 diameter d 0 with a closed shell diameter of 1 d The calculated latitudinal strain is: (3) in, d is the diameter of the closed shell 1, d 0 is the diameter of the prefabricated closed shell 3, η is the expansion rate of the spherical shell, where the expansion rate η The expression is as follows: (4) Therefore, according to formulas (2), (3) and (4), the relationship between the diameter of the prefabricated closed shell (3) and the equivalent strain can be determined by deducing the steps: (5) Where, d is the diameter of the closed shell 1; d 0 is the diameter of the prefabricated closed shell 3; is the equivalent strain; the diameter of the prefabricated enclosure 3 is smaller than the diameter of the enclosure 1; specifically, the target diameter d of the enclosure 1 is 500 mm and the target strength is 600 MPa. By corresponding the strength of the enclosure formed part to the equivalent stress (true stress) in Table 1, the equivalent strain (true strain) can be obtained. is 0.159, and the diameter of the prefabricated closed shell 3 is calculated d 0 The actual diameter of the prefabricated closed shell 3 is 461.8 mm. d 0 The design is rounded to 460 mm. The equivalent strain (true strain) of the actual closed shell 1 is verified by formula (5): is 0.167. According to the data in Table 1, the equivalent stress (strength) of the closed shell 1 is 626 MPa according to linear interpolation, which meets the target strength requirement. In addition, in order to adjust the actual equivalent stress (strength) of the closed shell 1, the diameter of the prefabricated closed shell 3 is obtained according to the design strength calculation. d 0 After that, the diameter of the prefabricated closed shell 3 can be further adjusted d 0 value to adjust the intensity to better meet your needs.

[0037] Further preferably, the wall thickness expression of the prefabricated closed shell 3 is the same as the equivalent strain The relationship: (6) The derivation process is: Expressing through-thickness strain through slab thickness ε t , whose expression is: , Combined with the volume invariance condition of plastic deformation, , the through-thickness strain can be obtained ε t The expression is , we can get the above formula (6); Where, t is the wall thickness of the closed shell 1, which is the same as the wall thickness of the target curved shell 2; t 0 is the wall thickness of the prefabricated closed shell 3; ε i The wall thickness of the prefabricated closed shell 3 is greater than the wall thickness of the closed shell 1; specifically, the wall thickness t of the closed shell 1 is 1.5 mm, the equivalent strain of the aforementioned known prefabricated closed shell 3 ε i is 0.167, according to formula (6) t 0=1.77mm, and a plate with a thickness of 1.91mm is actually selected to prepare the prefabricated closed shell 3. The thickening is selected to cope with the problem of thinning of the wall thickness after bulging.

[0038] In the optional solution of this embodiment, it is more preferred that in the step of forming the prefabricated closed shell 3, the component structure of the prefabricated closed shell 3 is first determined, and the component structure includes an intermediate shell 31 and two top covers 32. The intermediate shell 31 has openings on both sides, and the two top covers 32 are respectively placed at the two openings and fixedly connected to the intermediate shell 31 to form the prefabricated closed shell 3; specifically, see Figure 4-6 , which are different types of combinations of top covers 32 and intermediate shells 31, Figure 4 It is a combination of a double-curvature top cover (top cover 32) and a single-curvature cone shell (intermediate shell 31). Figure 5 It is a combination of a flat plate, i.e., the top cover 32, and a single-curvature melon-shaped structure, i.e., the middle shell 31. Figure 6 It is a combination of a double-curvature top cover, i.e., the top cover 32, and a double-curvature melon-shaped structure, i.e., the middle shell 31. Figure 4 The combination of the double-curvature top cover and the single-curvature cone shell is explained; Figure 7 and Figure 8 As shown, the single curvature cone shell consists of four symmetrical segments with the largest diameter d 0 is 460mm, the dihedral angle between the cone shells α 1. α 2. α3 are all greater than 155°. The larger the dihedral angle is, the more conducive it is to flattening the weld during the bulging process, making the deformation more uniform.

[0039] Specifically, half of the prefabricated closed shell 3 is composed of three shell plate parts, namely, a hyperbolic top cover 32, an intermediate cone section 33, and an equatorial cone section 34. Conventional three-dimensional design software is used to unfold the three shell plate parts to obtain the slabs required for forming. The top cover 32 can be formed by deep drawing, and the intermediate cone section 33 and the equatorial cone section 34 are formed by bending. The formed parts are connected by argon arc welding to form a prefabricated closed shell 3.

[0040] In the optional scheme of this embodiment, it is more preferred that in the step of forming the closed shell 1, the forming internal pressure and forming volume increment required for forming the closed shell 1 are determined, the expansion pressure and volume increment in the prefabricated closed shell 3 are monitored, and after the expansion pressure in the prefabricated closed shell 3 reaches the forming internal pressure and the volume increment of the prefabricated closed shell 3 reaches the forming volume increment, the expansion of the prefabricated closed shell 3 is stopped, so as to perform precise forming of the closed shell 1 according to the characteristics determined by the strength calculation model.

[0041] The expression of forming internal pressure is: (7) Where, p is the forming internal pressure; t 0 is the wall thickness of the prefabricated closed shell 3; σ i The strength of the closed shell 1 is not less than the design strength of the target curved shell 2; d 0 is the diameter of the prefabricated closed shell 3; d Specifically, the wall thickness of the prefabricated closed shell 3 is known t 0 is 1.91mm, the strength of the closed shell 1 σ i is 626MPa, the diameter of the closed shell 1 d The diameter of the prefabricated enclosure 3 is 500 mm. d 0 is 460 mm, and the forming internal pressure is obtained according to formula (7): p It is 8.1MPa.

[0042] The expression of forming volume increment is: Δ V=VV 0 (8) Where, V is the volume of the closed shell 1 after forming; V 0 is the volume of the prefabricated closed shell 3; the volume of the prefabricated closed shell 3 before forming V 0 is 49L, the volume of the closed shell 1 after forming V is 65.1 L, and the volume increment Δ is calculated by formula (8): VThe volume of the prefabricated closed shell 3 can be estimated based on an ideal sphere, or measured by three-dimensional modeling software, or the prefabricated sphere can be directly filled with water and the mass of the water can be measured to indirectly obtain the volume of the prefabricated closed shell 3 by calculation.

[0043] Further preferably, the prefabricated closed shell 3 is filled with liquid before the room temperature bulging, and the prefabricated closed shell 3 is continuously filled with liquid during the room temperature bulging while monitoring the internal pressure. p With liquid volume V , when the liquid volume increases ∆V When it reaches 16.1L, stop pressurizing and the internal pressure at the end of the forming p The prefabricated closed shell 3 undergoes deformation strengthening during the room temperature bulging process, obtaining a closed shell 1 with a strength of 626 MPa and a diameter of 500 mm. Figure 9 shown.

[0044] In the optional solution of this embodiment, it is more preferred that in the step of forming the target curved shell 2, the closed shell 1 is cut to obtain the target curved shell 2. Specifically, the cutting method mainly includes laser cutting, CNC milling and wire cutting; see Figure 1 and Figure 3 If a hemispherical target curved shell 2 is required, two target curved shells can be obtained by cutting from the middle cross section of the closed shell 1. H The spherical cap-shaped target curved shell 2 is translated from both sides of the middle cross section of the closed shell 1 h Cutting can obtain two target surface shells 2, where R = H+h.

[0045] Example 2 This embodiment provides a die-free forming method for a thin-walled curved shell component. The difference from the die-free forming method for a thin-walled curved shell component provided in the first embodiment is that: In the step of forming the closed shell 1, the prefabricated closed shell 3 is expanded at ultra-low temperature according to the design strength of the target curved shell 2 to obtain the closed shell 1, the ultra-low temperature is -60℃~-196℃; specifically, when the design strength When the pressure is greater than 700 MPa, ultra-low temperature expansion is adopted, mainly to make the prefabricated closed shell 3 undergo phase change strengthening, and the closed shell 1 reaches the designed strength and target size by controlling the expansion amount.

[0046] In the step of determining the strength characteristics of the blank, the blank is selected from stainless steel plates. The strength calculation model of stainless steel plates at ultra-low temperatures is as follows: , In the formula, in the formula, is the design strength of the target curved shell member; is the ultra-low temperature initial yield strength of the stainless steel plate, obtained by performing a uniaxial or biaxial tensile test on the initial slab at ultra-low temperature; A, B and C is the hardening coefficient of stainless steel plate at ultra-low temperature; It is the equivalent strain caused by the deformation of the stainless steel plate.

[0047] Specifically, 304L stainless steel plate can be selected. Under ultra-low temperature, the Take 480MPa, A Take -3590MPa, B Take 57120MPa, C Take -91340MPa; when determining the design strength After that, the equivalent strain can be determined according to the above calculation model .

[0048] In the optional scheme of this embodiment, it is more preferred that, in order to facilitate actual production use, the true stress-strain data of 304L stainless steel plate under liquid nitrogen temperature can be directly used to replace the strength calculation model of the plate under bidirectional stress, as shown in Table 2. The values ​​between the data can be obtained by linear interpolation; the design strength of the target curved shell 2 is set If the strength of the closed shell 1 is 1000 MPa, the strength of the closed shell 1 is determined to be greater than or equal to 1000 MPa; other design dimensions remain unchanged relative to the first embodiment, and the equivalent strain (true strain) can be obtained by corresponding the strength of the target curved shell 2 to the equivalent stress (true stress) in Table 1. ε i is 0.165.

[0049] Table 2 shows the uniaxial tensile mechanical properties of 304L stainless steel at ultra-low temperature (liquid nitrogen temperature)

[0050] Specifically, the target diameter d of the closed shell 1 is 500 mm and the target strength is 1000 MPa. By comparing the strength of the closed shell formed part with the equivalent stress (true stress) in Table 1, the equivalent strain (true strain) can be obtained. is 0.165, and the diameter of the prefabricated closed shell 3 is calculated d 0 The actual diameter of the prefabricated closed shell 3 is 460.4 mm. d 0 The design is rounded to 460 mm. The equivalent strain (true strain) of the actual closed shell 1 is verified by formula (5): is 0.167. According to the data in Table 1, the equivalent stress (strength) of the closed shell 1 is 1015 MPa according to linear interpolation, which meets the target strength requirement. In addition, in order to adjust the actual equivalent stress (strength) of the closed shell 1, the diameter of the prefabricated closed shell 3 is obtained according to the design strength calculation. d 0 After that, the diameter of the prefabricated closed shell 3 can be further adjusted d 0 value to adjust the intensity to better meet your needs.

[0051] Specifically, the wall thickness of the prefabricated enclosure 3 is known to be t 0 is 1.91mm, the strength of the closed shell 1 σ i is 1015MPa, the diameter of the closed shell 1 d The diameter of the prefabricated enclosure 3 is 500 mm. d 0 is 460 mm, and the forming internal pressure is obtained according to formula (7): p It is 13.1MPa.

[0052] Further preferably, before the ultra-low temperature bulging, the accommodating cavity 41 of the low temperature environment box 4 of the prefabricated closed shell 3 is first filled with a low temperature liquid, wherein the low temperature liquid used is liquid nitrogen, and the ambient temperature of the low temperature environment box is lowered to a temperature close to that of the low temperature liquid (the ambient temperature corresponding to liquid nitrogen should be lower than -190°C), and kept warm for 5-20 minutes to ensure that the environment in which the prefabricated closed shell 3 is located is an ultra-low temperature environment; then, during the low temperature bulging, the low temperature liquid is continuously filled into the prefabricated closed shell 3, while the internal pressure is monitored. p With liquid volume V , when the liquid volume increases ∆V When it reaches 16.1L, stop pressurizing and the internal pressure at the end of the forming p The prefabricated closed shell 3 undergoes phase change and deformation strengthening during the ultra-low temperature bulging process, obtaining a closed shell 1 with a strength of 1015 MPa and a diameter of 500 mm.

[0053] Further preferably, during ultra-low temperature bulging, an exhaust port is provided in the prefabricated enclosure 3. During ultra-low temperature bulging, the gas generated by the prefabricated enclosure 3 (cryogenic liquid vaporization) is discharged while the cryogenic liquid is being filled into the prefabricated enclosure 3, thereby ensuring the accuracy of the liquid volume measurement. The exhaust port is provided at the top to facilitate gas discharge, and an exhaust pipe is provided at the exhaust port. A switch valve is provided on the exhaust pipe. During the filling process, the switch valve is opened to exhaust gas. After the liquid is fully filled, the switch valve on the exhaust pipe is closed to close the exhaust port, and then the liquid is filled and pressurized. In addition, other configurations can be provided, such as the exhaust port can be shared with the liquid outlet. During the filling process, the exhaust port is provided at the top and connected to the liquid outlet pipe. The gas is exhausted through the liquid outlet pipe, while the liquid is introduced from the bottom. After the filling is completed, the liquid outlet pipe is closed to pressurize the liquid. When liquid needs to be discharged later, the prefabricated enclosure 3 can be flexibly flipped so that the liquid outlet is at the bottom to achieve liquid discharge.

[0054] The other contents of the dieless forming method of the thin-walled curved shell component provided in this embodiment are the same as those in the first embodiment and will not be elaborated here.

[0055] Example 3 This embodiment provides a die-free forming system for thin-walled curved shell components. Figure 10 , specifically including an environmental box 4 and a charging component 5; the environmental box 4 has a accommodating cavity 41, and the accommodating cavity 41 is used to place the prefabricated closed shell 3; the charging component 5 is connected to the interior of the prefabricated closed shell 3 and the interior of the environmental box 4, and the charging component 5 can pass fluid into the prefabricated closed shell 3 to achieve pressurized expansion of the prefabricated closed shell 3, and the charging component 5 can also pass fluid into the environmental box 4 to regulate the environmental information outside the prefabricated closed shell 3.

[0056] The prefabricated closed shell 3 is placed in an environmental box 4, and fluid is introduced into the environmental box 4 through the charging component 5 to adjust the environmental information required for expansion, such as temperature. Then, fluid is introduced into the prefabricated closed shell 3 through the charging component 5 for pressurized expansion, so that the closed shell 1 can be formed without using a mold.

[0057] Further preferably, the thin-walled curved shell component moldless forming system provided in this embodiment also includes a volume measuring component 6, a displacement measuring component 7, a temperature measuring component 8 and a control component 9; the volume measuring component 6 is used to monitor the fluid flow information filled into the environmental box 4 and the prefabricated closed shell 3 by the charging component 5, and is also used to monitor the weight information of the fluid in the prefabricated closed shell 3; the displacement measuring component 7 is used to monitor the deformation information of the prefabricated closed shell 3 during the expansion process; the temperature measuring component 8 is used to monitor the temperature information in the environmental box 4; the control component 9 is communicated with the temperature measuring component 8 and is used to obtain temperature information; the control component 9 is also communicated with the volume measuring component 6 and is used to receive the flow information and weight information of the fluid to obtain the volume of the fluid in the prefabricated closed shell 3; the control component 9 is also communicated with the displacement measuring component 7 and is used to receive deformation information to obtain the real-time size of the prefabricated closed shell 3 during the expansion process; the control component 9 is communicated with the charging component 5 and is used to control the action of the charging component 5.

[0058] Specifically, the pressure charging assembly 5 includes a hydraulic pump 51, a first solenoid valve 52, a second solenoid valve 53, a first relief valve 54 and a second relief valve 55, wherein the inlet of the hydraulic pump 51 is connected to the liquid storage tank, and the liquid storage tank stores room temperature liquid or ultra-low temperature liquid nitrogen. The outlet of the hydraulic pump 51 is connected to the first solenoid valve 52 through a liquid outlet pipeline, and a first relief valve 54 is provided on the liquid outlet pipeline. The first solenoid valve 52 can be connected to the environmental box 4 and the prefabricated closed shell 3, and the second solenoid valve 53 can be connected to the environmental box 4, The prefabricated closed shell 3 and the liquid storage tank, a second overflow valve 55 is provided on the top of the environmental box 4, and the first overflow valve 54 and the second overflow valve 55 are both connected to the liquid storage tank; the control component 9 is configured as a control cabinet, which is in communication with the hydraulic pump 51, the first solenoid valve 52 and the second solenoid valve 53. Through the action of the first solenoid valve 52, the hydraulic pump 51 is connected to the environmental box 4 or the prefabricated closed shell 3 for liquid injection, and through the action of the second solenoid valve 53, the liquid storage tank is connected to the environmental box 4 or the prefabricated closed shell 3 for liquid drainage.

[0059] Furthermore, the temperature measuring component 8 is configured as a temperature sensor for monitoring the temperature of the prefabricated closed shell 3 so that the control component 8 controls the filling action of the charging component 5 according to the temperature information.

[0060] Furthermore, the volume measurement component 6 includes a flow monitoring component 61 such as a flow meter and a weight monitoring component 62 such as a force sensor, which are both communicatively connected to the control component 9. The flow monitoring component 61 is arranged on the pipeline connecting the hydraulic pump 51 and the prefabricated closed shell 3 to monitor the liquid filling volume. The weight monitoring component 62 is arranged outside the environmental box 4. When the environmental box 4 is filled with liquid, the weight information is obtained once as the zero position, and then the process of continuously filling the prefabricated closed shell 3 with liquid is summarized. The value change of the weight monitoring component 62 is the weight of the liquid in the prefabricated closed shell 3. In this way, the control component 9 obtains the liquid volume in the prefabricated closed shell 3 according to the monitoring information, so that∆V Stop injection when the target value is reached.

[0061] Furthermore, the displacement measurement component 7 includes two displacement sensors 71, which are arranged on the environmental chamber 4 and are used to monitor the lateral and vertical deformation displacements of the prefabricated closed shell 3. In this way, the control component 9 can timely obtain the real-time external dimensions of the prefabricated closed shell 3 during the expansion process based on the displacement information, and compare it with the target dimension of the closed shell 1 to confirm when the dimension reaches the target value.

[0062] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A dieless forming method for a thin-walled curved shell component, characterized in that: Including steps: Determining the closed shell (1): determining the characteristics of the closed shell (1) according to the characteristics of the target curved shell (2); Determine the strength characteristics of the blank: determine the strength calculation model of the selected blank under biaxial stress during bulging; Determining the prefabricated closed shell (3): inferring the characteristics of the prefabricated closed shell (3) based on the strength calculation model and the characteristics of the closed shell (1); Forming a prefabricated closed shell (3): forming the prefabricated closed shell (3) according to the characteristics of the prefabricated closed shell (3); Forming the closed shell (1): bulging the prefabricated closed shell (3) to obtain the closed shell (1); Forming a target curved shell (2): cutting the closed shell (1) to obtain the target curved shell (2).

2. The dieless forming method of a thin-walled curved shell member according to claim 1, characterized in that: The step determines that in a closed shell (1), the target curved shell (2) is hemispherical or spherical, and correspondingly, the closed shell (1) is a spherical shell; or, the target curved shell (2) is hemispherical, and correspondingly, the closed shell (1) is an ellipsoidal shell; and the closed shell (1) is capable of forming two target curved shells (2).

3. The dieless forming method of a thin-walled curved shell member according to claim 2, characterized in that: In the step of forming the closed shell (1), the prefabricated closed shell (3) is expanded at room temperature or ultra-low temperature according to the design strength of the target curved shell (2) to obtain the closed shell (1).

4. The dieless forming method of a thin-walled curved shell member according to claim 3, characterized in that: In the step of determining the strength characteristics of the blank, the blank is selected from stainless steel plates; The strength calculation model of stainless steel plates at room temperature: Where, is the design strength of the target curved shell (2); is the initial yield strength of the stainless steel plate at room temperature, obtained by performing a uniaxial or biaxial tensile test on the initial slab at room temperature; H is the tangent modulus of the stainless steel plate at room temperature, which is obtained by fitting the true stress-strain data of the initial slab in single tension at room temperature; It is the equivalent strain caused by the deformation of the stainless steel plate; Strength calculation model of stainless steel plates at ultra-low temperatures: Where, is the ultra-low temperature initial yield strength of the stainless steel plate, obtained by performing a uniaxial or biaxial tensile test on the initial slab at ultra-low temperature; A, B and C is the hardening coefficient of the stainless steel plate at ultra-low temperature, which is obtained by fitting the true stress-strain data of the initial slab under ultra-low temperature single tension; It is the equivalent strain caused by the deformation of the stainless steel plate.

5. The dieless forming method of a thin-walled curved shell member according to claim 3, characterized in that: In the step of determining the strength characteristics of the blank, the blank is selected from stainless steel plates; The strength calculation model of stainless steel plates at room temperature can be replaced by the true stress and strain data of single tension of stainless steel plates at room temperature; the strength calculation model of stainless steel plates at ultra-low temperature can be replaced by the true stress and strain data of single tension of stainless steel plates at liquid nitrogen temperature.

6. The dieless forming method of a thin-walled curved shell member according to claim 4 or 5, characterized in that: The step is to determine the relationship between the diameter of the prefabricated closed shell (3) and the equivalent strain: Where, d is the diameter of the closed shell (1); d 0 is the diameter of the prefabricated closed shell (3); ε i is equivalent strain; the diameter of the prefabricated closed shell (3) is smaller than the diameter of the closed shell (1); The relationship between the wall thickness expression of the prefabricated closed shell (3) and the equivalent strain is: Where, t is the wall thickness of the closed shell (1), which is the same as the wall thickness of the target curved shell (2); t 0 is the wall thickness of the prefabricated closed shell (3); ε i is equivalent strain; the wall thickness of the prefabricated closed shell (3) is greater than the wall thickness of the closed shell (1).

7. The dieless forming method of a thin-walled curved shell member according to claim 1, characterized in that: In the step of forming a prefabricated closed shell (3), the component structure of the prefabricated closed shell (3) is first determined, and the component structure includes an intermediate shell (31) and two top covers (32). The intermediate shell (31) has openings on both sides, and the two top covers (32) are respectively placed in the two openings and fixedly connected to the intermediate shell (31) to form the prefabricated closed shell (3).

8. The dieless forming method of a thin-walled curved shell member according to claim 6, characterized in that: In the step of forming the closed shell (1), the forming internal pressure and the forming volume increment required for forming the closed shell (1) are determined, the bulging pressure and the volume increment in the prefabricated closed shell (3) are monitored, and after the volume increment of the prefabricated closed shell (3) reaches the forming volume increment, the bulging of the prefabricated closed shell (3) is stopped; The expression of forming internal pressure is: Where, p is the forming internal pressure; t 0 is the wall thickness of the prefabricated closed shell (3); σ i The strength of the closed shell (1) is not less than the design strength of the target curved shell (2); d 0 is the diameter of the prefabricated closed shell (3); d is the diameter of the closed shell (1); The expression of forming volume increment is: D V=VV 0 Where, V is the volume of the closed shell (1) after forming; V 0 is the volume of the prefabricated closed shell (3).

9. A dieless forming system for thin-walled curved shell components, characterized in that: include: An environmental chamber (4) having a receiving chamber (41), wherein the receiving chamber (41) is used to place the prefabricated closed shell (3); and A pressure-charging component (5) is in communication with the interior of the prefabricated closed shell (3) and the interior of the environmental box (4). The pressure-charging component (5) can pass fluid into the prefabricated closed shell (3) to achieve pressurized expansion of the prefabricated closed shell (3), and the pressure-charging component (5) can also pass fluid into the environmental box (4) to regulate environmental information outside the prefabricated closed shell (3).

10. The dieless forming system for thin-walled curved shell components according to claim 9, characterized in that: Also includes: A volume measurement component (6) is used to monitor the flow rate of the fluid filled into the environmental chamber (4) and the prefabricated closed shell (3) by the pressure charging component (5), and is also used to monitor the weight of the fluid in the prefabricated closed shell (3); A displacement measuring component (7) for monitoring deformation information of the prefabricated closed shell (3) during the expansion process; A temperature measuring component (8) for monitoring temperature information in the environmental chamber (4); The control component (9) is connected in communication with the temperature measuring component (8) and is used to obtain the temperature information; the control component (9) is also connected in communication with the volume measuring component (6) and is used to receive the flow rate information and weight information of the fluid to obtain the volume of the fluid in the prefabricated closed shell (3); the control component (9) is also connected in communication with the displacement measuring component (7) and is used to receive the deformation information to obtain the real-time size of the prefabricated closed shell (3) during the expansion process; the control component (9) is connected in communication with the charging component (5) and is used to control the action of the charging component (5).

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