Optimization design method for the reinforced wall of a pressure-bearing cylindrical shell with a circular opening

Abstract

The present invention discloses a method for optimizing the design of a reinforced wall of a cylindrical shell with a circular opening, comprising: determining fixed parameters that need to be clarified before optimizing the design of the cylindrical shell opening reinforcement according to constraint conditions; calculating the total height coefficient ξ of the wall; setting multiple sets of wall height-related parameter c1 and c2 schemes, and respectively calculating the corresponding short-end height coefficient η1 and long-end height coefficient η2 of the wall; calculating the effective height coefficient ζ of the wall corresponding to each scheme; and calculating the effective area A of the wall corresponding to each scheme. eff ; Calculate the extreme value of stress concentration σ in the cylindrical shell opening area corresponding to each scheme max ; judge σ max Is it less than the allowable stress of the material [σ s [The text then abruptly shifts topics.] A variety of opening reinforcement wall design options are listed, and the optimal solution that meets the opening's functional requirements, constraints, and strength requirements is selected. This invention addresses the requirements for circular openings of varying sizes on pressure-bearing cylindrical shells of various curvatures, enabling designers to precisely design the key height parameters of the reinforcement wall. Multiple solutions can be rapidly iterated and selected from the initial design stages.

Description

Technical Field

[0001] The present invention relates to the technical field of ship structure design, and in particular to a method for optimizing the design of a reinforced wall of a pressure-bearing cylindrical shell with a circular opening. Background Art

[0002] Cylindrical shell structures are widely used in pressure vessels, underwater vehicles, and other fields due to their excellent pressure-bearing performance. The structural conformal design and opening design derived from them are customized works that serve the engineering purpose, reflecting the coordinated symbiosis of overall function and structural mechanics. Generally speaking, for pressure-bearing cylindrical shell structures, shell openings often cause stress concentration problems, which will destroy the local strength of the structure and reduce the overall pressure-bearing capacity. However, to achieve specific functions, a small number of openings are always unavoidable. To address this contradiction, engineering generally adopts the equal area method, the ultimate pressure method, the finite element method, etc., and sets an annular cross-section reinforcement wall in the opening area to compensate for the local strength.

[0003] The equal area reinforcement method is a design method based on the theory of flat plate openings, which requires that the cross-sectional area of ​​the reinforced wall should not be less than the cross-sectional area of ​​the shell plate opening. Its disadvantage is that the design result has a large error. In some cases, the volume of the reinforced structure is too large, which will affect the function of the product. The ultimate pressure method adopts the plastic failure criterion, which believes that the initial yield of the structure does not mean the loss of bearing capacity. It is only when the entire cross-section of a certain area of ​​the cylindrical shell enters the plastic state, so that plastic flow occurs, that it is considered to have failed. The corresponding load at this time is called the ultimate load. Since this principle takes a large stress allowable value for stress concentration near the opening, the calculation result is dangerous and is almost only applicable to the reinforcement of large openings in pressure vessels. The finite element method can more accurately calculate the overall stress distribution in the reinforced area of ​​the cylindrical shell opening, but its calculation results are severely restricted by the unit form and mesh division results, and the workload for complex models is huge.

[0004] Generally speaking, for the problem of strengthening openings in pressure-bearing cylindrical shells, the parameters related to the shell and the opening are all fixed values. Therefore, the main factors affecting the wall reinforcement effect are the wall thickness and wall height. Among them, the wall thickness is often restricted by the product function and the design range is limited. Therefore, how to design a reasonable wall height is the key to condensing a fast, accurate and refined wall optimization design method. This is also a technical problem that needs to be solved urgently in related engineering fields. Summary of the Invention

[0005] The main purpose of the present invention is to address the design problems of reinforced walls of pressure cylindrical shells with openings, such as the design of penetration parts for underwater vehicles. With the diversification of product functionality, the integrated design of structure and equipment has gone deeper. An efficient and refined optimization design method for reinforced walls of pressure cylindrical shells with circular openings is proposed to make up for the shortcomings of large errors in the design results of traditional equal area method and ultimate pressure method, high usage conditions of finite element method, and inability to quickly iterate solutions for complex models, and to guide designers to accurately design key height parameters of the reinforced walls with openings.

[0006] The technical solution adopted in the present invention is:

[0007] A method for optimizing the design of a reinforced wall of a pressure-bearing cylindrical shell with a circular opening comprises the following steps:

[0008] S1. Determine fixed parameters that must be determined before optimizing the design of the cylindrical shell opening reinforcement based on the constraints, wherein the constraints include the size limit of the opening of the pressure-bearing cylindrical shell, the space limit of the reinforcement wall, and the weight limit of the reinforcement wall;

[0009] S2. Calculate the total height coefficient ξ of the surrounding wall;

[0010] S3. Set multiple sets of wall height related parameters c1 and c2, where c1 is the height of the shorter side of the wall protruding from the opening area, c2 is the height of the taller side of the wall protruding from the opening area, and c1 + c2 = l, where l is the total height of the wall. Calculate the corresponding short end height coefficient η1 and long end height coefficient η2 of the wall respectively.

[0011] S4. Calculate the effective height coefficient ζ of the surrounding wall corresponding to each of the above schemes;

[0012] S5. Calculate the effective area A of the wall corresponding to each scheme eff ;

[0013] S6. Calculate the extreme stress concentration σ in the cylindrical shell opening area corresponding to each scheme max ;

[0014] S7. Determine the extreme value of stress concentration σ at the opening max Is it less than the allowable stress of the material [σ s ], whether it meets the strength requirements; then repeat steps S3 to S6 multiple times, list a variety of opening reinforcement wall design schemes, and select the best scheme that meets the opening function requirements, constraints, and strength requirements.

[0015] In the above scheme, in step S1, the fixed parameters that need to be determined before the optimization design of the cylindrical shell opening reinforcement include the opening radius a, the total height l of the surrounding wall, and the surrounding wall thickness δ.

[0016] In the above solution, in step S2, the calculation method of the total height coefficient ξ of the surrounding wall is:

[0017]

[0018] Where: l is the total height of the wall, a is the radius of the opening, δ is the thickness of the wall, ν is the Poisson's ratio of the wall material,

[0019] In the above solution, in step S3, the calculation method of the short end height coefficient η1 and the long end height coefficient η2 of the surrounding wall is as follows:

[0020]

[0021] Where a is the opening radius, δ is the wall thickness, ν is the Poisson's ratio of the wall material,

[0022] In the above solution, in step S4, the calculation method of the effective height coefficient ζ of the surrounding wall is as follows:

[0023]

[0024] in:

[0025]

[0026] l is the total height of the wall, a is the radius of the opening, δ is the thickness of the wall, ν is the Poisson's ratio of the wall material,

[0027] In the above solution, in step S5, the effective area of ​​the wall A eff The calculation method is as follows:

[0028]

[0029] Where: ζ is the effective height coefficient of the surrounding wall, a is the radius of the opening, δ is the thickness of the surrounding wall, and h is the thickness of the shell plate in the opening area.

[0030] In the above scheme, in step S6, the extreme stress concentration value σ in the opening area of ​​the cylindrical shell is max The calculation method is as follows:

[0031]

[0032] in:

[0033]

[0034] R is the radius of the cylindrical shell, p is the external pressure, h is the thickness of the shell plate in the opening area, A eff is the effective area of ​​the wall, a is the radius of the opening, δ is the thickness of the wall, and ν is the Poisson's ratio of the wall material.

[0035] The beneficial effects produced by the present invention are:

[0036] The present invention provides an efficient and refined method for optimizing the design of reinforced walls of cylindrical shells with circular openings. Aiming at the requirements for circular openings of different sizes on pressure-bearing cylindrical shells with various curvatures, the method, using steps S1-S7, enables the designer to accurately design key height parameters of the reinforced walls. In the early stages of design, multiple schemes can be quickly iterated for the designer to select the best one. The method is simple and effective, and overcomes the shortcomings of the traditional equal area method and the ultimate pressure method, such as large errors in the design results, and the high usage conditions of the finite element method and the inability to quickly iterate schemes for complex models. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are 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.

[0038] Figure 1 It is a schematic diagram of the reinforced wall of a cylindrical shell with a circular opening;

[0039] Figure 2 It is a quick calculation chart of the effective height coefficient of the wall;

[0040] Figure 3 This is the finite element calculation result of the stress concentration value of the opening reinforcement area in the first embodiment of the present invention;

[0041] Figure 4 This is the finite element calculation result of the stress concentration value of the opening reinforcement area in the second embodiment of the present invention;

[0042] Figure 5 This is the finite element calculation result of the stress concentration value in the opening reinforcement area in the third embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0044] It should be noted that the illustrations provided in the embodiments of the present invention are only schematic illustrations of the basic concept of the present invention. Therefore, the drawings only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0045] In the present invention, it should also be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like are used to indicate positions or locations based on those shown in the accompanying drawings. These terms are intended solely to facilitate the description of the present application and to simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present application. Furthermore, the terms "first" and "second" are used solely for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0046] According to the theory of plate and shell openings, increasing the effective height coefficient of the surrounding wall is a key means to reduce the stress concentration factor at the hole edge. The present invention provides an optimization design method for the reinforced surrounding wall of a pressure-bearing cylindrical shell with a circular opening. This method can refine the key height parameters of the surrounding wall according to the requirements of the opening reinforcement. The design method includes the following steps:

[0047] S1. According to the design constraints such as the opening size limit of the pressure-bearing cylindrical shell, the space limit of the reinforced wall, and the weight limit of the reinforced wall, the fixed parameters that need to be determined before the optimization design of the cylindrical shell opening reinforcement are determined, such as the opening radius a, the total height of the wall l, and the wall thickness δ. Figure 1 .

[0048] S2. Calculate the total height coefficient of the surrounding wall ξ:

[0049]

[0050] Where: l is the total height of the wall, a is the radius of the opening, δ is the thickness of the wall, ν is the Poisson's ratio of the wall material, It is the process value of solving the equation, which is used to simplify the formula and facilitate the programming of this method.

[0051] S3. Set multiple sets of wall height related parameters c1 and c2, and calculate the corresponding wall short end height coefficient η1 and long end height coefficient η2 respectively:

[0052]

[0053] Wherein, c1 is the height of the lower side of the protruding opening area of ​​the surrounding wall, c2 is the height of the higher side of the protruding opening area of ​​the surrounding wall, and c1+c2=1.

[0054] S4. Calculate the effective height coefficient ζ of the surrounding wall corresponding to each of the above schemes:

[0055]

[0056] in:

[0057]

[0058] The effective height coefficient of the enclosure wall represents the height of the truly "useful" part of the enclosure wall. Its solution process equates the cylindrical enclosure wall subjected to linear load to a uniformly compressed enclosure wall, thereby obtaining the truly effective reinforcement height of the enclosure wall.

[0059] According to steps S1-S4, the following Figure 2 The fast calculation diagram of the effective height coefficient of the wall shown is used to quickly calculate the effective height coefficient ζ of the wall during multi-scheme optimization, thereby reducing calculation time.

[0060] S5. Calculate the effective area A of the wall corresponding to each scheme eff :

[0061]

[0062] Where: h is the shell thickness in the opening area.

[0063] S6. Calculate the extreme value σ of the stress concentration in the cylindrical shell opening area (mid-surface stress) corresponding to each scheme max :

[0064]

[0065] in:

[0066]

[0067] R is the radius of the cylindrical shell, and p is the external pressure.

[0068] The extreme stress concentration value appears at the farthest point of the opening along the axial direction of the cylindrical shell. This method introduces the correction value of the cylindrical shell curvature based on the extreme stress concentration value of the hole edge of the flat plate opening reinforced wall structure. The analytical solution of the extreme stress concentration on the wall of a cylindrical shell with an opening is obtained.

[0069] S7. Determine the extreme value of stress concentration σ at the opening max Is it less than the allowable stress of the material [σ s ], whether it meets the strength requirements; then repeat steps S3 to S6 multiple times, list a variety of opening reinforcement wall design schemes, and select the best scheme that meets the opening function requirements, constraints, and strength requirements.

[0070] The following is a specific embodiment of the present invention:

[0071] Assume that a cylindrical shell with an external pressure of p = 1.0 MPa has a radius of R = 2000 mm and a shell plate thickness of h = 12 mm. Due to the functional requirements of the equipment in the cabin, a circular hole with a radius of a = 60 mm is now to be opened on it. Therefore, a reinforced wall is required to reinforce the pressure-bearing boundary of the opening area. Due to the space constraints inside and outside the cylindrical shell, the total height of the wall is l ≤ 40 mm, the wall thickness is δ = 12 mm, the material of the cylindrical shell is Q235B, and the allowable stress [σ s ]=235MPa, Poisson's ratio is ν=0.3, and the wall is made of the same steel as the cylindrical shell. According to the method described in the present invention, the key height parameters c1 and c2 of the reinforced wall are designed, the extreme values ​​of each stress concentration are calculated, and a better design scheme is sought.

[0072] First, based on the design constraints, the fixed parameters in step S1 are clarified and brought into step S2. Then, according to step S3, the following initial solutions can be proposed:

[0073] Solution 1: l = 30 mm; c1 = 10 mm; c2 = 20 mm

[0074] Solution 2: l = 30 mm; c1 = 15 mm; c2 = 15 mm

[0075] Option 3: l = 40mm; c1 = 13mm; c2 = 27mm

[0076] Repeat steps S3 to S6 to design the following types of opening-reinforced walls:

[0077]

[0078] According to step S7, among the above-mentioned solutions, only Solution 2 and Solution 3 meet the requirements for strengthening the surrounding wall strength of the cylindrical shell with a circular opening. However, Solution 3 corresponds to a higher total height of the surrounding wall, and the corresponding weight and space costs are greater. From the results, Solution 2 is obviously better than Solution 3. Designers can design and select the most reasonable solution based on this method.

[0079] The design method of the present invention can be verified by finite element simulation calculation. Abaqus statics module is used for modeling. The parameters of the cylindrical shell model are consistent with the case. The extreme value of the stress concentration (mid-surface stress) in the opening area of ​​the cylindrical shell in schemes 1, 2 and 3 is obtained. max ,See Figure 3 、 Figure 4 and Figure 5 , the calculation results of the design method of the present invention are compared with the finite element calculation results as follows:

[0080]

[0081] It can be seen that the calculation results of the design method of the present invention have a smaller relative error than the finite element calculation results. This method can meet the relevant requirements of the design of the opening reinforced wall in engineering.

[0082] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0083] The size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0084] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for optimizing the design of a circular opening reinforced wall of a pressure-bearing cylindrical shell, characterized in that: The following steps are involved: S1. Determine fixed parameters that must be determined before optimizing the design of the cylindrical shell opening reinforcement based on the constraints, wherein the constraints include the size limit of the opening of the pressure-bearing cylindrical shell, the space limit of the reinforcement wall, and the weight limit of the reinforcement wall; S2. Calculate the total height coefficient of the surrounding wall ; S3. Set multiple sets of wall height related parameters c 1、 c 2 options, among which, c 1 is the height of the shorter side of the protruding opening area of ​​the wall, c 2 is the height of the higher side of the wall protruding from the opening area, and there is , is the total height of the wall, and the corresponding short end height coefficient of the wall is calculated respectively , long end height coefficient ; S4. Calculate the effective height coefficient of the wall corresponding to each of the above schemes , the calculation method is as follows: (4) in: ； is the total height of the wall, is the opening radius, is the wall thickness, is the Poisson's ratio of the wall material, ; S5. Calculate the effective area of ​​the wall corresponding to each scheme ; S6. Calculate the extreme stress concentration in the cylindrical shell opening area corresponding to each scheme ; S7. Determine the extreme value of stress concentration at the opening Is it less than the allowable stress of the material? , whether the strength requirements are met; then repeat steps S3 to S6 multiple times, list a variety of openings to strengthen the surrounding wall design scheme, from which the best solution that meets the opening function requirements, constraints, and strength requirements is selected.

2. The optimization design method for the circular opening reinforced wall of a pressure-bearing cylindrical shell according to claim 1 is characterized in that: In step S1, the fixed parameters that need to be determined before optimizing the cylindrical shell opening reinforcement include the opening radius , total height of the wall , wall thickness .

3. The optimization design method for the circular opening reinforced wall of a pressure-bearing cylindrical shell according to claim 1 is characterized in that: In step S2, the total height coefficient of the surrounding wall The calculation method is: (1) in: is the total height of the wall, is the opening radius, is the wall thickness, is the Poisson's ratio of the wall material, .

4. The optimization design method for the circular opening reinforced wall of a pressure-bearing cylindrical shell according to claim 1 is characterized in that: In step S3, the short end height coefficient of the wall , long end height coefficient The calculation method is as follows: (2) (3) in, is the opening radius, is the wall thickness, is the Poisson's ratio of the wall material, .

5. The optimization design method for the circular opening reinforced wall of a pressure-bearing cylindrical shell according to claim 1 is characterized in that: In step S5, the effective area of ​​the wall The calculation method is as follows: (5) in: is the effective height coefficient of the wall, is the opening radius, is the wall thickness, is the shell thickness in the opening area.

6. The optimization design method for the circular opening reinforced wall of a pressure-bearing cylindrical shell according to claim 1 is characterized in that: In step S6, the stress concentration extreme value in the cylindrical shell opening area The calculation method is as follows: (6) in: is the radius of the cylindrical shell, is external pressure, is the shell thickness in the opening area, is the effective area of ​​the wall, is the opening radius, is the wall thickness, is the Poisson's ratio of the wall material.

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