Optimization design method for circular opening reinforced enclosure bulkhead of pressure-bearing cylindrical shell

Abstract

The invention discloses an optimization design method for a reinforced enclosure bulkhead of a circular opening of a pressure-bearing cylindrical shell. The method comprises the following steps: determining fixed parameters which need to be defined before the reinforced optimization design of the opening of the cylindrical shell according to constraint conditions; calculating the total height coefficient xi of the enclosure bulkhead; setting a plurality of groups of enclosure bulkhead height related parameter schemes c1 and c2, and respectively calculating a corresponding enclosure bulkhead short-end height coefficient eta 1 and a corresponding enclosure bulkhead long-end height coefficient eta 2; calculating the effective height coefficient zeta of the enclosure bulkhead corresponding to each scheme; calculating the effective area Aeff of the enclosure bulkhead corresponding to each scheme; calculating a stress concentration extreme value sigma max of a cylindrical shell trepanning area corresponding to each scheme; judging whether the sigma max is smaller than the allowable stress [sigma s] of the material or not; various design schemes of the trepanning reinforced enclosure bulkhead are listed, and the optimal scheme meeting the trepanning function requirement, the constraint condition and the strength requirement is preferably selected from the various design schemes of the trepanning reinforced enclosure bulkhead. According to the method, the key height parameters of the reinforced enclosure bulkhead can be accurately designed by a designer according to the requirements of different sizes of circular holes in the pressure-bearing cylindrical shells with various curvatures, and multiple schemes can be rapidly iterated at the initial stage of design for the designer to select preferentially.

Description

Technical Field

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

[0002] Cylindrical shell structures are widely used in pressure vessels, underwater vehicles and other fields due to their good pressure-bearing performance. The structural conformal design and opening design derived from them are customized works that serve the engineering, reflecting the coordinated symbiosis of overall functions and structural mechanics. Generally speaking, for pressure-bearing cylindrical shell structures, shell openings usually have stress concentration problems, which will destroy the local strength of the structure and reduce the overall pressure-bearing capacity. However, in order to achieve specific functions, a small number of openings are always unavoidable. For this contradiction, the engineering generally adopts the equal area method, the limit pressure method, the finite element method, etc., and sets a ring-section reinforced 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 product function. The limit 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 be a failure. The corresponding load at this time is called the limit 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 opening reinforcement area of ​​the cylindrical shell, 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 the openings in pressure-bearing cylindrical shells, the parameters related to the shell and the openings are all fixed values, so the main factors affecting the strengthening effect of the wall 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, which 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 underwater vehicle penetration parts. With the diversified development 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 limit 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 reinforced walls with openings.

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

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

[0008] S1. Determine the fixed parameters that need to be clarified before optimizing the design of the cylindrical shell opening reinforcement according to the constraint conditions, wherein the constraint conditions include the size limit of the opening of the pressure-bearing cylindrical shell, the space limit of the reinforcement surrounding wall, and the weight limit of the reinforcement surrounding wall;

[0009] S2, calculate the total height coefficient ξ of the surrounding wall;

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

[0011] S4, calculating the effective height coefficient ζ of the surrounding wall corresponding to the above-mentioned schemes;

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

[0013] S6. Calculate the extreme value of 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 of the surrounding wall l, and the surrounding wall thickness δ.

[0016] In the above scheme, 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 scheme, 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 scheme, 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 scheme, in step S5, the effective area A of the surrounding wall is 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 shell thickness in the opening area.

[0030] In the above scheme, in step S6, the stress concentration extreme value σ in the opening area of ​​the cylindrical shell 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 opening radius, δ is the wall thickness, 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 optimization design method for the reinforced surrounding wall of a cylindrical shell with a circular opening. According to the requirements for circular openings of different sizes on pressure-bearing cylindrical shells with various curvatures, the method S1-S7 steps can enable the designer to accurately design key height parameters of the reinforced surrounding wall, and a variety of schemes can be quickly iterated in the early stage of design for the designer to select the best one. The method is simple and effective, which makes up for the shortcomings of the traditional equal area method and the limit pressure method, such as the large errors in the design results, the high usage conditions of the finite element method and the inability to quickly iterate the 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 briefly introduces 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 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 surrounding wall;

[0040] Figure 3 It 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 It 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 It is the finite element calculation result of the stress concentration value of the opening reinforcement area in the third embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with 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 used to limit the present invention.

[0044] It should be noted that the illustrations provided in the embodiments of the present invention are only used to illustrate the basic concept of the present invention in a schematic manner. Therefore, the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout type may also be more complicated.

[0045] In the present invention, it is also necessary to explain that, if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, if the terms "first" and "second" appear, they are only used for description and distinction purposes, and cannot be understood as indicating or implying relative importance.

[0046] According to the plate and shell opening theory, increasing the effective height coefficient of the surrounding wall is a key means to reduce the stress concentration coefficient at the hole edge. The present invention provides an optimization design method for strengthening the surrounding wall of a circular opening of a pressure-bearing cylindrical shell, which can refine the key height parameters of the surrounding wall in accordance with the opening strengthening requirements. 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 clarified 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 thickness of the wall 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 and is used to simplify the formula to facilitate the programming of this method.

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

[0052]

[0053] Among them, 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 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 surrounding wall shown is used to quickly calculate the effective height coefficient ζ of the surrounding wall during multi-scheme optimization to reduce the calculation time.

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

[0061]

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

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

[0064]

[0065] in:

[0066]

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

[0068] The extreme value of stress concentration appears at the farthest point of the opening along the axial direction of the cylindrical shell. This method introduces the correction value of the curvature of the cylindrical shell based on the extreme value of stress concentration at the edge of the flat plate opening and strengthening the surrounding wall structure. The analytical solution of the extreme value of stress concentration on the wall surrounding the opening of a cylindrical shell 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 solution 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, it is necessary to design a reinforced wall to reinforce the pressure-bearing boundary of the opening area. Due to the constraints of the internal and external space of the cylindrical shell, the total height of the wall is l≤40 mm, the thickness of the wall 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 surrounding wall is made of the same steel material as the cylindrical shell. According to the method described in the present invention, the key height parameters c1 and c2 of the strengthened surrounding wall are designed, the extreme values ​​of each stress concentration are calculated, and a better design scheme is sought.

[0072] First, according to 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 = 30mm; c1 = 15mm; c2 = 15mm

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

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

[0077]

[0078] According to step S7, among the above-mentioned schemes, only scheme 2 and scheme 3 meet the strength requirements of the cylindrical shell circular opening reinforced wall, but the total height of the wall corresponding to scheme 3 is higher, and the corresponding weight and space cost are greater. From the results, scheme 2 is obviously better than scheme 3. Designers can design and select the most reasonable scheme according to 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, and 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 order of execution of each step in the above embodiment does not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment 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 these 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 the fixed parameters that need to be clarified before optimizing the design of the cylindrical shell opening reinforcement according to the constraint conditions, wherein the constraint conditions include the size limit of the opening of the pressure-bearing cylindrical shell, the space limit of the reinforcement surrounding wall, and the weight limit of the reinforcement surrounding wall; S2, calculate the total height coefficient ξ of the surrounding wall; S3, setting multiple sets of wall height related parameters c1, c2 schemes, where c1 is the height of the shorter side of the wall protruding from the opening area, c2 is the height of the higher side of the wall protruding from the opening area, and c1+c2=l, l is the total height of the wall, and respectively calculating the corresponding short end height coefficient η1 and long end height coefficient η2 of the wall; S4, calculating the effective height coefficient ζ of the surrounding wall corresponding to the above-mentioned schemes; S5. Calculate the effective area A of the surrounding wall corresponding to each scheme eff ; S6. Calculate the extreme value of stress concentration σ in the cylindrical shell opening area corresponding to each scheme max ; 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.

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

3. The optimization design method for the circular opening reinforced surrounding wall of a pressure-bearing cylindrical shell according to claim 1 is characterized in that: In step S2, the calculation method of the total height coefficient ξ of the surrounding wall is: 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, 4. The method for optimizing the design of a circular opening reinforced surrounding wall of a pressure-bearing cylindrical shell according to claim 1, characterized in that: 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: Where a is the opening radius, δ is the wall thickness, ν is the Poisson’s ratio of the wall material, 5. The optimization design method for the circular opening reinforced surrounding wall of a pressure-bearing cylindrical shell according to claim 1 is characterized in that: In step S4, the calculation method of the effective height coefficient ζ of the surrounding wall is as follows: in: 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, 6. The optimization design method for the circular opening reinforced surrounding wall of a pressure-bearing cylindrical shell according to claim 1 is characterized in that: In step S5, the effective area A of the surrounding wall eff The calculation method is as follows: 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 shell thickness in the opening area.

7. The method for optimizing the design of a circular opening reinforced wall of a pressure-bearing cylindrical shell according to claim 1, characterized in that: In step S6, the stress concentration extreme value σ in the opening area of ​​the cylindrical shell max The calculation method is as follows: in: 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 opening radius, δ is the wall thickness, and ν is the Poisson's ratio of the wall material.

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