Equal-wall-thickness storage tank diaphragm structure with reinforcing ribs and capable of improving local rigidity of structure and design method of equal-wall-thickness storage tank diaphragm structure

Abstract

The invention relates to an equal-wall-thickness storage tank diaphragm structure with reinforcing ribs for improving structural local rigidity and a design method, the equal-wall-thickness storage tank diaphragm structure with the reinforcing ribs comprises a spherical crown section, the spherical crown section is connected with a pre-bent edge through a conical column section, the end of the pre-bent edge is a welding section, and the reinforcing ribs are arranged at the position, with insufficient local rigidity, of a storage tank diaphragm (the conical column section); the design method comprises the following steps: preliminarily determining geometric parameters of a diaphragm according to the mounting size and drainage volume requirements of a spaceflight storage tank; performing turnover process simulation on the basis of the material attributes and the geometric parameters of the diaphragm, and judging whether working requirements are met or not; if yes, completing the design, and if not, carrying out local reinforcing rib design; geometric parameters of the reinforcing ribs are designed, the diaphragm structure with the reinforcing ribs is simulated, and whether the working requirements are met or not is judged; if yes, completing the design, and if not, continuing to carry out the geometric parameter iterative design of the reinforcing rib to obtain the structural parameters meeting the working requirements; the local structural rigidity of the storage tank diaphragm is improved, the design technological process of the storage tank diaphragm is simplified, and the cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of manufacturing of diaphragm for flight equipment storage tank, and particularly relates to a diaphragm structure with ribs and equal wall thickness for enhancing local stiffness of the structure and a design method thereof. Background Art

[0002] The diaphragm of the storage tank is a key component installed inside the propellant storage tank of a spacecraft. The interior of the storage tank is divided into a gas chamber and a liquid chamber by the diaphragm. The diaphragm is made of a metal material and has good elastoplastic deformation ability, and can be turned over under the action of high-pressure gas. During operation, high-pressure gas is introduced into the gas chamber of the storage tank, and the gas pressure acts on the surface of the diaphragm, causing the diaphragm to deform and turn towards the liquid chamber; as the diaphragm turns over, the propellant in the liquid chamber is gradually squeezed into the downstream delivery pipeline of the storage tank, thereby providing fuel and oxidant for the engine. As the core component of the storage tank, the diaphragm of the storage tank needs to undergo large-range non-linear deformation and turning during operation, which makes the stability of the diaphragm of the storage tank poor and the design difficult.

[0003] In the prior art, the diaphragm of the storage tank usually adopts a variable wall thickness design. For example, in the patent application named "A Variable Thickness Large Flow Metal Diaphragm for Spacecraft Storage Tank" (publication number CN207000833U), the thickness t of the diaphragm changes with the height. However, for such large-sized and variable-curvature thin-walled components, due to the gradual change of the diaphragm thickness and the relatively thin overall wall thickness, the processing accuracy requirements are extremely high, and the traditional process is difficult to meet its high-precision requirements; in addition, compared with the equal wall thickness diaphragm, the variable wall thickness diaphragm is more likely to have eccentricity during the processing process, which not only increases the processing difficulty, but also may cause problems such as instability during the turning of the diaphragm. Therefore, developing new structures and manufacturing processes to improve the processing accuracy and quality of the variable wall thickness diaphragm while reducing the probability of eccentricity is a technical problem that needs to be solved urgently at present. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a diaphragm structure with ribs and equal wall thickness for enhancing local stiffness of the structure and a design method thereof. The diaphragm structure is easy to process, has good anti-wrinkling and anti-eccentricity capabilities, and can well meet the requirements of diaphragm turning; at the same time, the design cost of the diaphragm structure of the storage tank is reduced.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A diaphragm structure with ribs and equal wall thickness for enhancing local stiffness of the structure, including a spherical crown section, the spherical crown section is connected through a conical column section and a pre-bent edge, the end of the pre-bent edge is a welding section, and ribs are arranged at the conical column section where the local stiffness of the storage tank diaphragm is insufficient.

[0007] The number of the stiffeners is 2 - 4; the shapes of the stiffeners are shallow circular arcs, trapezoids, sine shapes or cosine shapes.

[0008] A design method for a diaphragm structure of an equal - wall - thickness storage tank with stiffeners to enhance the local stiffness of the structure, comprising the following steps:

[0009] Step 1: Obtain the installation geometric dimension information of the space storage tank, and determine the maximum dimension information of the storage tank diaphragm according to the design requirements.

[0010] Step 2: Obtain the drainage volume requirement of the space storage tank, and preliminarily determine the geometric parameters of the storage tank diaphragm according to the turnover volume requirement of the storage tank diaphragm and the maximum dimension information.

[0011] Step 3: Obtain the material property parameters of the storage tank diaphragm, and perform a simulation of the turnover process of the storage tank diaphragm according to the geometric parameters and material property parameters to judge whether the turnover process of the storage tank diaphragm meets the working requirements.

[0012] Step 4: If so, the design is completed; if not, local stiffener design is carried out.

[0013] Step 5: Design the geometric parameters of the stiffeners according to the instability phenomenon occurring during the turnover process, and obtain the structure information of the storage tank diaphragm with stiffeners based on the geometric parameters of the stiffeners.

[0014] Step 6: Perform a simulation based on the storage tank diaphragm structure and material property parameters to judge whether the storage tank diaphragm with stiffeners meets the working requirements.

[0015] Step 7: If so, the design is completed; if not, continue the iterative design of the geometric parameters of the stiffeners to obtain the structural parameters that meet the working requirements.

[0016] The turnover volume of the storage tank diaphragm in Step 2 is the cavity volume V formed before and after the turnover of the storage tank diaphragm; the geometric parameters of the storage tank diaphragm include the diaphragm diameter D1, height H1, spherical crown section radius R1, pre - bent edge radius R2, welding section height H2, and diaphragm wall thickness t.

[0017] The material property parameters of the storage tank diaphragm in Step 3 include material density, Young's modulus, Poisson's ratio, and plastic constitutive; the simulation of the turnover process of the storage tank diaphragm is to create a structure model of the storage tank diaphragm based on the geometric parameters and material property parameters of the storage tank diaphragm, apply boundary conditions and acting forces, divide the shell element tetrahedral mesh, and obtain the simulation results of the turnover process of the storage tank diaphragm; set the boundary conditions of the storage tank diaphragm based on the boundary connection method between the storage tank and the storage tank diaphragm, and design the internal and external pressure difference as the driving force for the diaphragm turnover based on the working principle of the storage tank diaphragm.

[0018] If there is no obvious wrinkling phenomenon during the flipping process of the tank diaphragm; if the maximum plastic strain of the tank diaphragm is less than the limit strain value; if the maximum radial displacement of the diaphragm is less than the design requirement; if the drainage rate and flipping rate of the tank diaphragm reach the design requirements; then it is judged that the tank diaphragm meets the design requirements and the design is completed; if the above judgment conditions are not all met, it is judged that local stiffeners should be added to the tank diaphragm; the drainage rate of the tank diaphragm is V / Vz, and the flipping rate is Dd / Dz; where V is the effective flipping volume of the tank diaphragm, Vz is the propellant volume; Dd is the vertex displacement before and after the flipping of the tank diaphragm, and Dz is the distance from the vertex of the diaphragm before flipping to the vertex of the tank.

[0019] The instability phenomena occurring during the flipping process described in step 5 include wrinkling, eccentricity, and rupture;

[0020] The geometric parameters of the stiffeners include the shape of the stiffeners, the number of stiffeners n, the number of passes of the stiffeners x, the position h, the spacing a, the height l, the height increment b, the radius r1, and the radius increment c; where:

[0021] The shape of the stiffeners is a shallow circular arc;

[0022] The number of passes of the stiffeners x <= n, and they are arranged in order from top to bottom according to the layout of the stiffeners;

[0023] The position of each pass of the stiffeners is h(x) = h(1) + (x - 1) * a;

[0024] The radius of each pass of the stiffeners is r1(x) = r1(1) + (x - 1) * b;

[0025] The height of each pass of the stiffeners is l(x) = l(1) + (x - 1) * c;

[0026] The structural information of the tank diaphragm includes the geometric information of the tank diaphragm, the geometric information of the stiffeners, and the fillet radius r2 of the stiffeners, the fillet radius increment d of the stiffeners, where:

[0027] The fillet radius of each pass of the stiffeners is r2(x) = r2(1) + (x - 1) * d.

[0028] During the simulation of the flipping process of the tank diaphragm with stiffeners in step 6, the mesh of the stiffener part needs to be refined.

[0029] In step 7, if there is no obvious wrinkling phenomenon during the flipping process of the tank diaphragm; if the maximum plastic strain of the tank diaphragm is less than the limit strain value; if the maximum radial displacement of the diaphragm is less than the design requirement; if the drainage rate and flipping rate of the tank diaphragm reach the design requirements; then it is judged that the tank diaphragm meets the design requirements and the design is completed. If the above judgment conditions are not all met, the structural parameters of the stiffeners are designed and checked again, and it is rejudged whether the tank diaphragm with stiffeners meets the design requirements.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] The present invention proposes an integrated structure with a fascia sheet, and for the first time proposes a design method for a diaphragm structure of an equal-wall-thickness storage tank with stiffeners to enhance the local stiffness of the structure. The method obtains the installation dimensions and volume information of the storage tank, and determines the initial geometric parameters of the storage tank diaphragm based on the design requirements. It can be understood that the diaphragm structure of the storage tank needs to establish a basic three-dimensional model based on the initial geometric parameters of the diaphragm in advance, perform simulations by inputting the material model, obtain the flipping process and working parameters of the storage tank diaphragm, and compare them with the flipping process and parameters required by the design requirements. If the design requirements are not met, a stiffener structure is designed on the basis of the initial diaphragm geometric model, the material model is input again for simulation, the flipping process and working parameters of the diaphragm with the fascia sheet are obtained, and the verification is continued. If the design requirements are not met, the iterative verification is continued, and at the same time, the number, radius, height, position, spacing, and fillet radius of the stiffeners are redesigned. The diaphragm structure of the storage tank designed by this method realizes the integration of the diaphragm and the stiffener structure. Compared with the variable-wall-thickness storage tank diaphragm and the variable-wall-thickness ribbed storage tank diaphragm of the same size, it has a smaller weight, and compared with the overall diaphragm structure, the stiffener structure is smaller, which is convenient for realizing the integrated processing and shaping verification of the storage tank diaphragm, and through model simulation calculation, the design process of the storage tank diaphragm and the stiffener structure can be simplified, and the material, structure design, and processing technology costs of the storage tank diaphragm can be reduced. Brief Description of the Drawings

[0032] Figure 1 is a schematic diagram of the existing equal-wall-thickness storage tank diaphragm structure.

[0033] Figure 2 is a schematic sectional view of the existing equal-wall-thickness storage tank diaphragm.

[0034] Figure 3 is a geometric parameter diagram of the existing equal-wall-thickness storage tank diaphragm.

[0035] Figure 4 is a schematic diagram of the equal-wall-thickness storage tank diaphragm structure with stiffeners according to an embodiment of the present invention.

[0036] Figure 5 is a schematic sectional structure diagram of the equal-wall-thickness storage tank diaphragm with stiffeners and a partial sectional view of the stiffeners according to an embodiment of the present invention.

[0037] Figure 6 is a schematic diagram of the geometric parameters of the stiffeners of the equal-wall-thickness storage tank diaphragm with stiffeners according to an embodiment of the present invention.

[0038] Figure 7 is a flowchart of the design method for the diaphragm structure of an equal-wall-thickness storage tank with stiffeners to enhance the local stiffness according to an embodiment of the present invention.

[0039] Figure 8It is a comparison diagram of the diaphragm flipping results of an equal-wall-thickness storage tank without stiffeners and with stiffeners in the embodiment of the present invention.

[0040] Figure 9 It is a comparison diagram of the axial displacement during the diaphragm flipping process of an equal-wall-thickness storage tank without stiffeners and with stiffeners in the embodiment of the present invention.

[0041] Figure 10 It is a comparison diagram of the radial displacement during the diaphragm flipping process of an equal-wall-thickness storage tank without stiffeners and with stiffeners in the embodiment of the present invention. Detailed implementation manners

[0042] The present invention will be described in detail below in conjunction with embodiments and drawings.

[0043] Refer to Figures 1 - 3 , the existing equal-wall-thickness storage tank diaphragm includes a spherical crown section 1, the spherical crown section 1 is connected through a conical column section 2 and a pre-bent edge 3, and the end of the pre-bent edge 3 is a welding section 4. During actual use, it is welded to the storage tank connection structure through the welding section 4. The inside of the storage tank diaphragm is filled with propellant, and high-pressure gas is charged outside the storage tank diaphragm. The storage tank diaphragm starts to flip under the action of the internal and external pressure difference. During the flipping process of the storage tank diaphragm, due to the small wall thickness of the storage tank diaphragm, the storage tank diaphragm is continuously in the buckling and post-buckling states during the flipping process, and it is easy to produce wrinkling (low local stiffness), incomplete liquid drainage (the storage tank diaphragm does not achieve complete flipping), and eccentricity (the circumferential deformation speed of the storage tank diaphragm is inconsistent during the flipping process of the storage tank diaphragm), resulting in the failure of the storage tank diaphragm. In order to solve the above problems, the traditional storage tank diaphragm is designed as a variable-wall-thickness structure, which has a certain effect of improving the local stiffness of the storage tank diaphragm and is widely used in the aerospace industry. However, this structure has obvious disadvantages. The thin-walled curved surface variable-wall-thickness structure often needs to first use a high-precision grinding process to process the metal plate to form a variable-thickness circular diaphragm blank, and then perform stamping, spinning and other processes to form the shape of the storage tank diaphragm. The process is complex, and the material and process costs are high.

[0044] In order to solve the above problems, this embodiment proposes a stiffener-added equal-wall-thickness storage tank diaphragm structure for improving the local stiffness of the structure. As Figures 4 - 6 shown, stiffeners 5 are provided for the part with insufficient local stiffness of the storage tank diaphragm (conical column section 2). These stiffeners 5 can effectively improve the local stiffness of the structure, improve the liquid drainage rate of the diaphragm, and prevent the diaphragm from being eccentric during the flipping process.

[0045] In addition, in the prior art, there is no applicable method to systematically determine whether the diaphragm of the storage tank with stiffeners can meet the working requirements of the storage tank diaphragm. When locally strengthening the stiffness of the storage tank diaphragm, the structural form of the stiffeners is single, resulting in limited stiffness and strength of the storage tank diaphragm, complex diaphragm structure design process, and higher material and structure design costs. Based on this, this embodiment proposes a design method for a diaphragm structure of an equal-wall-thickness storage tank with stiffeners to improve the local stiffness of the structure.

[0046] Referring to Figures 1 - 7 , a design method for a diaphragm structure of an equal-wall-thickness storage tank with stiffeners to improve the local stiffness of the structure includes the following steps:

[0047] Step 1: Obtain the installation geometric dimension information of the aerospace storage tank, and determine the maximum dimension information of the storage tank diaphragm according to the design requirements;

[0048] The installation geometric dimension information of the aerospace storage tank includes the number of storage tanks installed, the distribution of storage tanks, the reserved space height and width of the storage tanks; the maximum dimension information of the storage tank diaphragm includes the diameter and maximum height of the metal storage tank diaphragm;

[0049] Step 2: Obtain the drainage volume requirement of the aerospace storage tank, and preliminarily determine the geometric parameters of the storage tank diaphragm according to the turnover volume requirement of the storage tank diaphragm and the maximum dimension information;

[0050] Based on the volume constraint of the storage tank diaphragm, this embodiment designs other geometric parameters on the premise that the diameter of the storage tank diaphragm and the maximum height of the storage tank diaphragm are determined; it should be noted that the turnover volume of the storage tank diaphragm is the cavity volume V formed before and after the turnover of the storage tank diaphragm; the geometric parameters of the storage tank diaphragm include the diaphragm diameter D1, height H1, spherical crown section radius R1, pre-bending edge radius R2, welding section height H2, and diaphragm wall thickness t; a set of initial geometric parameters are determined on the premise that the storage tank volume V, diaphragm diameter D, and maximum height H of the storage tank diaphragm are determined; the height H2 of the storage tank diaphragm is less than the maximum height H of the storage tank diaphragm, and 3D modeling software such as SolidWorks and NX can be used for modeling; after modeling, the volume of the storage tank diaphragm is preliminarily checked. If the volume of the storage tank diaphragm is less than the design requirements, the geometric parameters are redesigned and modeled again; if not, step 3 is executed;

[0051] Step 3: Obtain the material property parameters of the storage tank diaphragm, and perform a simulation of the turnover process of the storage tank diaphragm according to the geometric parameters and material property parameters to determine whether the turnover process of the storage tank diaphragm meets the working requirements;

[0052] In this embodiment, a three-dimensional model is imported into numerical simulation software such as ABAQUS or ANSYS, and material property parameters of diaphragm materials such as aluminum alloy and titanium alloy are input. It should be noted that the material property parameters of the tank diaphragm include material density, Young's modulus, Poisson's ratio, and plastic constitutive relation. The simulation of the flipping process of the tank diaphragm is to create a structural model of the tank diaphragm based on the geometric parameters and material property parameters of the tank diaphragm, apply boundary conditions and acting forces, divide the shell element tetrahedral mesh, and obtain the simulation results of the flipping process of the tank diaphragm. The boundary conditions of the tank diaphragm are set based on the boundary connection mode between the tank and the diaphragm, and the internal and external pressure difference is designed as the driving force for the diaphragm to flip based on the working principle of the tank diaphragm. In this step, if there is no obvious wrinkling phenomenon during the flipping process of the tank diaphragm; if the maximum plastic strain of the tank diaphragm is less than the limit strain value; if the maximum radial displacement of the diaphragm is less than the design requirement; if the drainage rate and flipping rate of the tank diaphragm reach the design requirements; then it is judged that the tank diaphragm meets the design requirements, the design is completed, and relevant parameters are output. It should be noted that the drainage rate of the tank diaphragm is V / Vz; the flipping rate is Dd / Dz; where V is the effective volume of the flipping of the tank diaphragm, Vz is the volume of the propellant; Dd is the vertex displacement of the tank diaphragm before and after flipping, and Dz is the distance from the vertex of the diaphragm before flipping to the vertex of the tank. If there is an obvious wrinkling phenomenon during the flipping process of the tank diaphragm; if the maximum plastic strain of the tank diaphragm is greater than or equal to the limit strain value; if the maximum radial displacement of the diaphragm is greater than or equal to the design requirement; if the drainage rate and flipping rate of the tank diaphragm do not reach the design requirements; then it is judged that local stiffening rib structures should be added to the tank diaphragm, and step 4 is executed;

[0053] Step 4: If so, the design is completed; if not, local stiffening rib design is carried out;

[0054] If there is no obvious wrinkling phenomenon during the flipping process of the tank diaphragm; if the maximum plastic strain of the tank diaphragm is less than the limit strain value; if the maximum radial displacement of the diaphragm is less than the design requirement; if the drainage rate and flipping rate of the tank diaphragm reach the design requirements; if so, it is judged that the tank diaphragm meets the design requirements and the design is completed. If all the above judgment conditions are not met, it is judged that the local stiffness of the tank diaphragm is insufficient; add a stiffening rib structure with smooth transition to the wall surface of the tank diaphragm to improve the local stiffness of the tank diaphragm;

[0055] Step 5: Design the geometric parameters of the stiffening ribs according to the instability phenomena occurring during the flipping process, and obtain the structural information of the tank diaphragm with stiffening ribs based on the geometric parameters of the stiffening ribs;

[0056] The instability phenomena occurring during the flipping process include wrinkling, eccentricity, and rupture;

[0057] The geometric parameters of the stiffening ribs include the shape of the stiffening ribs, the number of stiffening ribs n, the number of passes of the stiffening ribs x, the position h, the spacing a, the height l, the height increment b, the radius r1, and the radius increment c; where:

[0058] The shape of the stiffener is a shallow circular arc;

[0059] The number of passes of the stiffener x <= n, and they are arranged in sequence from top to bottom according to the layout of the stiffeners;

[0060] The position of each pass of the stiffener is h(x) = h(1) + (x - 1) * a;

[0061] The radius of each pass of the stiffener is r1(x) = r1(1) + (x - 1) * b;

[0062] The height of each pass of the stiffener is l(x) = l(1) + (x - 1) * c;

[0063] The structural information of the tank diaphragm includes the geometric information of the tank diaphragm, the geometric information of the stiffeners, and the fillet radius r2 of the stiffeners, and the fillet radius increment d of the stiffeners, where:

[0064] The fillet radius of each pass of the stiffener is r2(x) = r2(1) + (x - 1) * d;

[0065] Step 6: Perform simulations based on the structure and material property parameters of the tank diaphragm to determine whether the tank diaphragm with stiffeners meets the working requirements;

[0066] Substitute the material property parameters in Step 3 into this step. It should be noted that in this step, when simulating the flipping process of the tank diaphragm with stiffeners, the mesh of the stiffener part needs to be refined; obtain the working process of the diaphragm through the flipping process simulation. If obvious wrinkling occurs during the flipping process of the tank diaphragm; if the maximum plastic strain of the tank diaphragm is greater than or equal to the limit strain value; if the maximum radial displacement of the diaphragm is greater than or equal to the design requirement; if the drainage rate and flipping rate of the tank diaphragm do not meet the design requirements; it is determined that the setting of the stiffener parameters does not meet the design requirements;

[0067] Step 7: If so, the design is completed; if not, continue with the iterative design of the geometric parameters of the stiffeners to obtain the structural parameters that meet the working requirements.

[0068] If so, correct the initial parameters of the stiffeners and re - judge whether the flipping performance of the tank diaphragm meets the design requirements.

[0069] If no obvious wrinkling occurs during the flipping process of the tank diaphragm; if the maximum plastic strain of the tank diaphragm is less than the limit strain value; if the maximum radial displacement of the diaphragm is less than the design requirement; if the drainage rate and flipping rate of the tank diaphragm meet the design requirements; if so, it is determined that the tank diaphragm meets the design requirements and the design is completed. If the above judgment conditions are not all met, perform the design and verification of the stiffener structure parameters again and re - judge whether the diaphragm with fascia meets the design requirements.

[0070] It should be noted that the limit value of the number of stiffeners can be 2, 3, 4, etc., and 3 is preferred. Too many stiffeners will not significantly improve the flipping performance of the tank diaphragm, and too many stiffeners will increase the process difficulty and production cost. Other parameters are also designed and adjusted according to the instability performance of the tank diaphragm. The height l of the stiffener is as small as possible under the premise of meeting the design requirements to facilitate the demolding of the tank diaphragm after processing.

[0071] It should be noted that the above-mentioned shape of the stiffener is only exemplified by a shallow circular arc, but is not limited to the shallow circular arc, and can also be trapezoidal, sinusoidal, cosine-shaped, etc., and still belongs to the scope covered by the present invention.

[0072] It should be noted that the size of the stiffener is related to the number of passes of the stiffener, the initial stiffener parameters, and the size increment of the stiffener. For example, when the number of stiffeners n is 1, a feasible solution can be that the position of the first pass of the stiffener h(1) = 30 mm, the radius of the first pass of the stiffener r1(1) = 15 mm, the height of the first pass of the stiffener l(1) = 1 mm, and the fillet radius of the first pass of the stiffener r2(1) is 10 mm; for example, when the number of stiffeners n is 3, first set the initial parameters and increment parameters of the first pass of the stiffener. The position of the first pass of the stiffener h(1) = 30 mm, the spacing between the stiffeners a = 30 mm, the radius of the first pass of the stiffener r1(1) = 15 mm, the radius increment of the stiffener b = 2 mm, the height of the first pass of the stiffener l(1) = 1 mm, the height increment of the stiffener c = 0.5 mm, the fillet radius of the first pass of the stiffener r2(1) is 10 mm, and the fillet radius increment of the stiffener d = 2 mm; then the parameters of the second pass of the stiffener are h(2) = 60 mm, r1(2) = 17 mm, l(2) = 1.5 mm, r2(2) = 12 mm; the parameters of the third pass of the stiffener are h(3) = 90 mm, r1(2) = 19 mm, l(2) = 2 mm, r2(2) = 14 mm.

[0073] Compared with the prior art, the above-mentioned embodiments have the following beneficial effects:

[0074] The design method and the stiffener structure of this embodiment can effectively improve the local stiffness of the diaphragm and prevent wrinkling and eccentricity; referring to Figures 8 - 10 , Figure 8 For the comparison of the flipping results of the tank diaphragm without stiffeners and the tank diaphragm with stiffeners, both the tank diaphragm without stiffeners and the tank diaphragm with stiffeners have achieved complete flipping, but the tank diaphragm with stiffeners obviously will not wrinkle, and has good anti-wrinkle ability and stiffness improvement effect; Figure 9Axial displacement comparison during the flipping process of the tank diaphragm without stiffeners and the tank diaphragm with stiffeners. Under the same flipping pressure difference and flipping time, compared with the tank diaphragm without stiffeners, the axial displacement Dd of the tank diaphragm with stiffeners is smaller. When the flipping time is 0.2 s, the axial displacement of the tank diaphragm with stiffeners is reduced by 32.37 mm compared with that of the tank diaphragm without stiffeners, a decrease of 13.06%. This shows that the stiffeners delay the flipping time and improve the local stiffness of the tank diaphragm well. Figure 10 Radial displacement comparison during the flipping process of the tank diaphragm without stiffeners and the tank diaphragm with stiffeners. Compared with the tank diaphragm without stiffeners, the radial displacement of the tank diaphragm with stiffeners is smaller. The maximum radial displacement is reduced by 0.4 mm, a decrease of 25.36%, showing a good anti-eccentric effect. In addition, the maximum plastic strain of the tank diaphragm without stiffeners reaches 0.286, while the maximum plastic strain of the tank diaphragm with stiffeners is only 0.174, effectively reducing the tearing risk of the tank diaphragm during the flipping process. Through simulation analysis, the design and manufacturing process of the tank diaphragm and stiffener structure is simplified, reducing material and processing costs.

[0075] The present invention has been described in detail above in conjunction with the embodiments, but the above content is only the preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the present invention application should still fall within the scope covered by the present invention.

Claims

1. A diaphragm structure of a tank with equal wall thickness and with reinforcing ribs for improving local structural rigidity, comprising a spherical crown section, the spherical crown section is connected to a pre-bent edge via a conical column section, the end of the pre-bent edge is a welding section, and is characterized in that: Reinforcing ribs are provided in the conical column section, i.e., the part where the local rigidity of the tank diaphragm is insufficient.

2. The diaphragm structure of a tank with equal wall thickness and with reinforcing ribs according to claim 1, characterized in that: The number of the reinforcing ribs is 2-4; the shape of the reinforcing ribs is shallow arc, trapezoid, sine or cosine.

3. A design method for a tank diaphragm structure with reinforcing ribs and equal wall thickness for improving local structural rigidity according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step 1: Obtain the installation geometric dimension information of the aerospace tank and determine the maximum dimension information of the tank diaphragm according to the design requirements; Step 2: Obtain the liquid discharge volume requirement of the aerospace tank, and preliminarily determine the tank diaphragm geometric parameters according to the tank diaphragm turnover volume requirement and maximum size information; Step 3: Obtain the material property parameters of the tank diaphragm, simulate the tank diaphragm flipping process according to the geometric parameters and material property parameters, and determine whether the tank diaphragm flipping process meets the working requirements; Step 4: If yes, complete the design; if no, proceed with local reinforcement design; Step 5: Design the geometric parameters of the reinforcement ribs according to the instability phenomenon occurring during the overturning process, and obtain the structural information of the tank diaphragm with the reinforcement ribs based on the geometric parameters of the reinforcement ribs; Step 6: Perform simulation based on the tank diaphragm structure and material property parameters to determine whether the tank diaphragm with reinforcement ribs meets the working requirements; Step 7: If yes, the design is completed; if no, the iterative design of the stiffener geometry parameters is continued to obtain the structural parameters that meet the work requirements.

4. The method according to claim 3, characterized in that: The tank diaphragm flip volume in step 2 is the cavity volume V formed before and after the tank diaphragm flips; the tank diaphragm geometric parameters include diaphragm diameter D1, height H1, spherical crown segment radius R1, pre-bending edge radius R2, welding segment height H2, and diaphragm wall thickness t.

5. The method according to claim 3, characterized in that: The material property parameters of the tank diaphragm in step 3 include material density, Young's modulus, Poisson's ratio, and plastic constitutive property; the simulation of the tank diaphragm flipping process is to create a tank diaphragm structure model based on the tank diaphragm geometric parameters and material property parameters, apply boundary conditions and forces, divide the shell unit tetrahedral grid, and obtain the simulation results of the tank diaphragm flipping process; set the tank diaphragm boundary conditions based on the boundary connection mode of the tank and the tank diaphragm, and design the internal and external pressure difference as the diaphragm flipping driving force based on the working principle of the tank diaphragm.

6. The method according to claim 3, characterized in that: In step 3, if no obvious wrinkling occurs during the tank diaphragm flipping process; if the maximum plastic strain of the tank diaphragm is less than the limit strain value; if the maximum radial displacement of the diaphragm is less than the design requirement; if the discharge rate and flipping rate of the tank diaphragm meet the design requirements; then it is judged that the tank diaphragm meets the design requirements and the design is completed; if the above judgment conditions are not all met, then it is judged that the tank diaphragm should be added with a local reinforcing rib structure; the tank diaphragm discharge rate is V / Vz, and the flipping rate is Dd / Dz; wherein V is the flipping effective volume of the tank diaphragm, and Vz is the propellant volume; Dd is the vertex displacement of the tank diaphragm before and after flipping, and Dz is the distance from the diaphragm vertex to the tank vertex before flipping.

7. The method according to claim 3, characterized in that: The instability phenomena occurring during the flipping process in step 5 include wrinkling, eccentricity, and rupture; The rib geometric parameters include rib shape, rib number n, rib pass x, position h, spacing a, height l, height increment b, radius r1, radius increment c; where: The shape of the reinforcing rib is a shallow arc; The number of reinforcement ribs is x <= n, and they are arranged from top to bottom according to the reinforcement rib arrangement; The position of each reinforcement rib is h(x)=h(1)+(x-1)*a; The radius of each reinforcing rib is r1(x)=r1(1)+(x-1)*b; The height of each reinforcement rib is l(x)=l(1)+(x-1)*c; The tank diaphragm structural information includes tank diaphragm geometric information, rib geometric information, rib fillet radius r2, and rib fillet radius increment d, wherein: The fillet radius of each reinforcement rib is r2(x)=r2(1)+(x-1)*d.

8. The method according to claim 3, characterized in that: When simulating the flipping process of the tank diaphragm with reinforcement ribs in step 6, the mesh of the reinforcement rib part needs to be encrypted.

9. The method according to claim 3, characterized in that: In step 7, if no obvious wrinkling occurs during the flipping process of the tank diaphragm; if the maximum plastic strain of the tank diaphragm is less than the limit strain value; if the maximum radial displacement of the diaphragm is less than the design requirement; if the liquid discharge rate and flipping rate of the tank diaphragm meet the design requirements; then it is judged that the tank diaphragm meets the design requirements and the design is completed. If the above judgment conditions are not all met, the rib structure parameter design and verification are performed again to re-judge whether the tank diaphragm with ribs meets the design requirements.

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