Design method and system for flange structure of bolt-connected split casing

Abstract

The invention belongs to the field of aero-engines, relates to a composite material numerical simulation and structural design technology, and provides a design method and system for a split casing flange structure in bolt connection, and the method comprises the steps that a finite element simulation piece of the split casing bolt flange structure is established, and the simulation piece comprises two metal pressing plates and two L-shaped pieces; obtaining an aerodynamic load of the split casing bolt flanging structure under a service condition, and calculating an equivalent load applied to the finite element simulation part by adopting a stress equivalent formula and structural geometric difference according to the aerodynamic load; and performing strength analysis on the finite element simulation part according to the equivalent load, and performing iterative optimization on parameters of the bolt flanging structure according to a strength analysis result until the bolt flanging structure meeting the strength reserve design requirement is obtained. According to the method, the iterative optimization efficiency is improved, support is provided for forward design and engineering application of the flanging structure, and the iteration speed and research and development efficiency of the split casing structure of the bolted connection composite material are improved.

Description

Technical Field

[0001] The present invention belongs to the field of aero-engines, relates to composite material numerical simulation and structural design technologies, and particularly relates to a design method and system for a bolt-connected split casing flanging structure. Background Art

[0002] Due to advantages such as high specific strength, high specific stiffness, strong fatigue resistance and designability, fiber-reinforced composite materials are widely used in aero-engines. Using a composite material casing can significantly reduce the weight of the casing itself, which is of great significance for improving the engine efficiency. Using a composite material casing can greatly improve the efficiency performance of the aircraft and aero-engine, but its connection structure is often a weak link in actual load bearing.

[0003] Currently, the bolt connection structure is a commonly used form for the flanging connection of composite material casings and can transmit high loads. Therefore, targeted design and research are carried out on the bolt connection structure of composite material casings to make the connection position meet the strength design requirements without excessive redundant design. For example, Liu Yulin et al. carried out strength analysis on the bolt connection flanging structure of a resin matrix composite material casing based on test results and established a progressive damage simulation model for the flanging structure (from Liu Yulin, Analysis and Experimental Research on the Connection Strength of the Flanging Structure of a Resin Matrix Composite Material Casing, Nanjing University of Aeronautics and Astronautics); for example, Lei Xianhua et al. used the finite element method to carry out comparative calculations on the strength of the casing with a bolt connection flanging structure, and the results proved that for a split casing, ignoring the front and rear connectors of the casing in strength calculation will cause errors in the calculation results, so the influence of the front and rear connectors (generally connecting casings) should be considered (from Lei Xianhua, Du Wenjun, Gong Mengxian. Stress Analysis of the Casing. Gas Turbine Experiment and Research); for another example, Dong Benhan et al. cited a variety of experimental mechanics methods in the research on the bolt connection flanging structure of the casing, and obtained the connection characteristics of the flanging structure, as well as the laws of deformation, stress, bolt internal force, stress, etc. at the flanging structure of the casing during the loading process (from Dong Benhan, Gao Pengfei, Wang Zhenhua. Hybrid Method for Stress Analysis of the Casing Flanging Structure. Aeroengine).

[0004] It can be seen from the above content that most of the current research is based on the existing typical parts of the bolt connection flanging structure of the casing, establishes the corresponding strength simulation model, and verifies the accuracy of the strength model by comparing with the test results. They explored the influence of the size parameters of the casing flanging structure on the strength, but did not design the typical parts of the flanging according to the actual load-bearing situation and structural form of the full-size parts of the casing flanging, did not establish the connection between the casing flanging structure and its typical parts, and could not directly apply the results of the typical parts to the casing flanging structure; in addition, due to the complex contact between the bolt and nut and the application of the tightening force, it will greatly affect the calculation efficiency during calculation, and even result in non-convergence, which hinders the forward design of the casing flanging structure.

[0005] Therefore, it is necessary to provide a simple, effective and highly applicable method to solve the problems of the lack of a design method for typical parts of the flanging structure of the split casing connected by bolts and the low calculation efficiency at present. Summary of the Invention

[0006] In order to solve the problems of the lack of a design method for typical parts of the flanging structure of the split casing connected by bolts and the low calculation efficiency at present, the present invention discloses a design method for the flanging structure of a split casing connected by bolts, and the method includes the following steps: S1. Establish a finite element simulation part of the flanging structure of the split casing bolts, and the finite element simulation part includes two metal pressing plates and two L-shaped parts, wherein the two L-shaped parts are respectively simplified parts of the upper half casing and the lower half casing; S2. Obtain the aerodynamic load of the flanging structure of the split casing bolts under the service condition, and calculate the equivalent load applied to the finite element simulation part according to the aerodynamic load; S3. Perform a strength analysis on the finite element simulation part according to the equivalent load, and iteratively optimize the parameters of the flanging structure of the split casing bolts according to the strength analysis result until a flanging structure that meets the strength reserve design requirements is obtained.

[0007] Further, in step S1, establishing a finite element simulation part of the flanging structure of the split casing bolts includes: S11. Select the flanging structure of the split casing bolts as a typical part on the split casing, and the typical part includes bolts, metal pressing plates, and a section of the upper half casing and a section of the lower half casing connected by bolts; S12. Simplify the upper half casing and the lower half casing into L-shaped parts respectively, and map the outermost contour lines of the bolts to the longitudinal installation edges of the metal pressing plates and the L-shaped parts respectively to obtain a simplified model including the metal pressing plates and two L-shaped parts; S13. Perform mesh division on the simplified model to obtain a finite element simulation part.

[0008] Further, in step S2, obtaining the aerodynamic load of the flanging structure of the split casing bolts under the service condition and calculating the equivalent load applied to the finite element simulation part according to the aerodynamic load includes: S21. Match the positions of the ends of the L-shaped parts on the split casing, and obtain the aerodynamic load borne by the matched positions under the service condition; S22. Based on the constructed stress equivalent formula, convert the aerodynamic load into a tensile load, and the tensile load includes the lateral load and the vertical load at the matching position; S23. According to the dimensional parameters of the L-shaped part and the dimensional parameters of the split casing, perform a geometric structure difference analysis to convert the tensile load into an equivalent load, where the equivalent load includes a matching position transverse load and a matching position vertical load.

[0009] Further, in step S22, the stress equivalence formula includes the formula and . According to the formula and convert the pneumatic load into a tensile load, where is the matching position transverse load, is the matching position vertical load, Q is the pressure load, R is the radius of the split casing, S is the length of the L-shaped part, and L is the width of the L-shaped part.

[0010] Further, in step S23, according to the dimensional parameters of the L-shaped part and the dimensional parameters of the split casing, perform a geometric structure difference analysis to convert the tensile load into an equivalent load, including: S231. Define that the equivalent load applied to the finite element simulation part includes a simulation part transverse load and a simulation part vertical load; S232. Use the matching position transverse load as the simulation part transverse load; S233. Obtain the distance between the center of the bolt hole on the L-shaped part and the outer edge of the mounting edge, and calculate the simulation part vertical load through the formula , where is the simulation part vertical load, a is the distance between the center of the bolt hole on the L-shaped part and the outer edge of the mounting edge, is a variable, and its value range is ∈ (0, ), d represents the integral of ; X is a variable, and its value range is ∈ (a, ), and dx represents the integral of X.

[0011] Further, in step S3, perform a strength analysis on the finite element simulation part according to the equivalent load, including: S31. For the finite element simulation part, divide the mesh of the metal pressing plate and the mesh of the longitudinal mounting edge of the L-shaped part into a group and bind them with the outermost contour line of the bolt as the boundary; S32. Establish a friction constraint for the unbound meshes in the finite element simulation part, and apply a forced displacement equal to the bolt indentation length to the bound meshes on the outer sides of the two metal pressing plates; S33. Fix one end of the finite element simulation part, apply the equivalent load at the other end to obtain the stress distribution, obtain the current strength reserve according to the stress distribution and the failure criterion, and perform strength analysis according to the current strength reserve and the strength reserve design requirement.

[0012] Further, in step S33, the failure criterion includes the Hashin failure criterion and the maximum stress failure criterion. The Hashin failure criterion is that the current strength reserve ≥ 1.5 times the strength reserve design requirement, and the maximum stress failure criterion is that the current strength reserve ≥ 1.05 times the strength reserve design requirement.

[0013] The embodiment of the present invention also provides a design system for the bolt - connected split - case flanging structure, including a simulation part construction module, an equivalent load calculation module, and a structural parameter iterative optimization module.

[0014] Among them, the simulation part construction module is used to establish a finite element simulation part of the split - case bolt flanging structure. The finite element simulation part includes two metal pressing plates and two L - shaped parts, and the two L - shaped parts are respectively simplified parts of the upper half - case and the lower half - case; The equivalent load calculation module is used to obtain the aerodynamic load of the split - case bolt flanging structure under the service condition, and calculate the equivalent load applied to the finite element simulation part according to the aerodynamic load; The structural parameter iterative optimization module is used to perform strength analysis on the finite element simulation part according to the equivalent load, and iteratively optimize the parameters of the split - case bolt flanging structure according to the strength analysis result until a bolt flanging structure that meets the strength reserve design requirement is obtained.

[0015] Compared with the prior art, the beneficial effects that at least one of the above - mentioned technical solutions adopted in the embodiments of the present specification can achieve at least include: 1. The method of the present invention can quickly design the flanging structure according to the structural characteristics of the composite material case itself and the actual use conditions.

[0016] 2. By converting the aerodynamic load received by the composite material case flanging structure into a tensile load, and converting the tensile load received by the flanging structure into an equivalent load of a typical part according to the structural differences between the case flanging structure and the finite element simulation part, the consistency of the load effect is realized, so that the calculation result of the finite element simulation part can support the strength design of the full - size part; at the same time, the stress distribution calculation model is optimized by grid grouping binding and applying friction constraints, improving the iterative calculation efficiency.

[0017] 3. Compared with the prior art, the present invention takes into account the load changes caused by the differences between the casing flanging structure and the finite element simulation parts, and optimizes the stress distribution calculation model, enabling the forward design of the resin matrix composite material for the split casing flanging structure with different material systems and preparation processes, and improving the iteration speed and R & D efficiency of the composite material casing structure. Description of the Drawings

[0018] To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is a flowchart of the design method for the bolt - connected split casing flanging structure disclosed in the embodiments of the present invention; Figure 2 It is an execution diagram of the design method for the bolt - connected split casing flanging structure disclosed in the embodiments of the present invention; Figure 3 It is a schematic diagram of the finite element simulation part disclosed in the embodiments of the present invention; Figure 4 It is an architecture diagram of the design system for the bolt - connected split casing flanging structure disclosed in the embodiments of the present invention; Among them, 401, simulation part construction module; 402, equivalent load calculation module; 403, structural parameter iteration and optimization module. Detailed Embodiments

[0020] The embodiments of the present application will be described in detail below with reference to the drawings.

[0021] The following illustrates the implementation manners of the present application through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The present application can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, without conflict, the following embodiments and the features of the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.

[0022] An embodiment of the present invention discloses a design method for the flanging structure of a bolt - connected split casing. Taking a resin - matrix composite split casing with a radius of 400 mm and a height of 500 mm, which is subjected to a maximum pressure of 0.4 MPa during use as an example, the parameters of its connection structure (including bolts, nuts, and metal pressing plates, and the material is selected as GH4169) are designed.

[0023] See Figure 1 and Figure 2 As shown, the method includes the following steps: S1. Establish a finite - element simulation model of the bolt - flanging structure of the split casing. The finite - element simulation model includes two metal pressing plates and two L - shaped parts, where the two L - shaped parts are respectively simplified models of the upper half - casing and the lower half - casing. S2. Obtain the aerodynamic load of the bolt - flanging structure of the split casing under service conditions, and calculate the equivalent load applied to the finite - element simulation model according to the aerodynamic load. S3. Conduct a strength analysis on the finite - element simulation model according to the equivalent load, and iteratively optimize the parameters of the bolt - flanging structure of the split casing according to the strength analysis results until a bolt - flanging structure that meets the requirements of strength reserve design is obtained.

[0024] Furthermore, in step S1, establishing a finite - element simulation model of the bolt - flanging structure of the split casing includes: S11. Select the bolt - flanging structure on the split casing as a typical part. The typical part includes bolts, metal pressing plates, and a section of the upper half - casing and a section of the lower half - casing connected by bolts.

[0025] S12. Simplify the upper half - casing and the lower half - casing into L - shaped parts respectively, and map the outermost contour lines of the bolts to the longitudinal installation edges of the metal pressing plates and the L - shaped parts respectively, to obtain a simplified model including metal pressing plates and two L - shaped parts.

[0026] During specific implementation, the length of the L - shaped part needs to meet the clamping requirements of the strength test, generally not less than 100 mm. In the implementation of the present invention, the length of the L - shaped part is set to 100 mm, the width is 50 mm (there are two holes through which bolts pass in its width direction), the flanging height and thickness of the L - shaped part, as well as the dimensions of the metal pressing plate and the bolts are the same as those of the flanging structure of the composite - material split casing. For example, the flanging height and thickness can be set to 37 mm and 4 mm respectively, the width of the metal pressing plate is set to 50 mm, the thickness is 3 mm, M8 bolts are selected for the bolts, and the center distance of the bolt holes from the inner edge of the installation edge is 11 mm.

[0027] When establishing the simplified model, the L - shaped part, the metal pressing plate, and the bolt model can be imported into Ansa software, map the outermost contour line of the nut to the flanging of the metal pressing plate and the longitudinal installation edge, and then delete the bolt and nut structures.

[0028] S13. Mesh the simplified model to obtain a finite element simulation part as shown in Figure 3 the figure.

[0029] Furthermore, in step S2, obtain the aerodynamic load of the split casing bolt flanging structure under the service condition, and calculate the equivalent load applied to the finite element simulation part according to the aerodynamic load, including: S21. Match the position of the end of the L-shaped part on the split casing, and obtain the aerodynamic load borne by the matched position under the service condition; S22. Based on the constructed stress equivalence formula, convert the aerodynamic load into a tensile load, and the tensile load includes the transverse load at the matched position and the vertical load at the matched position; S23. According to the dimensional parameters of the L-shaped part and the dimensional parameters of the split casing, perform geometric structure difference analysis to convert the tensile load into an equivalent load, where the equivalent load includes the transverse load at the matched position and the vertical load at the matched position.

[0030] Even further, in step S22, the stress equivalence formula includes the formula and , and according to the formula and convert the aerodynamic load into a tensile load, where is the transverse load at the matched position, is the vertical load at the matched position, Q is the pressure load, R is the radius of the split casing, S is the length of the L-shaped part, and L is the width of the L-shaped part. According to the parameters provided in step S12 above, F1 can be calculated to be 7762N and F2 to be 1935N.

[0031] Even further, in step S23, according to the dimensional parameters of the L-shaped part and the dimensional parameters of the split casing, perform geometric structure difference analysis to convert the tensile load into an equivalent load, including: S231. Define that the equivalent load applied to the finite element simulation part includes the transverse load of the simulation part and the vertical load of the simulation part; S232. Take the transverse load F1 at the matched position as the transverse load T1 of the simulation part; S233. Obtain the distance between the center of the bolt hole on the L-shaped part and the outer edge of the mounting edge, and calculate the vertical load of the simulation part through the formula , where is the vertical load of the simulation part, a is the distance between the center of the bolt hole on the L-shaped part and the outer edge of the mounting edge, is a variable, and its value range is ∈(0, ), d represents Integral; X is a variable, with a value range ∈ (a, ), dx represents the integral with respect to X. By calculation, the lateral load of the simulation part is 7762 N, and the vertical load of the simulation part is 2515 N.

[0032] Furthermore, in step S3, strength analysis is performed on the finite element simulation part according to the equivalent load, including: S31: For the finite element simulation part, the grids of the metal pressing plate and the longitudinal installation edge of the L-shaped part are divided into a group and bound with the outermost contour line of the bolt as the boundary.

[0033] S32: Frictional constraints are established for the unbound grids in the finite element simulation part, and a forced displacement equal to the bolt indentation length is applied to the bound grids on the outer sides of the two metal pressing plates. In implementation, when an M8 bolt is selected for the bolt, the converted forced displacement is 0.45 mm.

[0034] S33: One end of the finite element simulation part is fixed, and the equivalent load is applied to the other end to obtain the stress distribution. The current strength reserve is obtained according to the stress distribution and the failure criterion, and strength analysis is performed according to the current strength reserve and the strength reserve design requirements.

[0035] Even further, in step S33, the failure criterion includes the Hashin failure criterion and the maximum stress failure criterion. The Hashin failure criterion is that the current strength reserve ≥ 1.5 times the strength reserve design requirement, and the maximum stress failure criterion is that the current strength reserve ≥ 1.05 times the strength reserve design requirement. When the strength reserve requirement is not met, the parameters that can be improved include parameters such as the thickness of the metal pressing plate, the flanging size, the flanging thickness, the bolt hole spacing, and the bolt hole edge distance to form a new bolt flanging structure, and then strength analysis is performed on it.

[0036] The method of the present invention has the following advantages: 1. The method of the present invention can quickly design the flanging structure according to the structural characteristics of the composite material casing itself and the actual use conditions.

[0037] 2. By converting the aerodynamic load received by the flanging structure of the composite material casing into a tensile load, and converting the tensile load received by the flanging structure into the equivalent load of the typical part according to the structural differences between the casing flanging structure and the finite element simulation part, the consistency of the load effect is achieved, so that the calculation result of the finite element simulation part can support the strength design of the full-size part; at the same time, the stress distribution calculation model is optimized by grid grouping and binding and applying frictional constraints, improving the iterative calculation efficiency.

[0038] 3. Compared with the prior art, the present invention takes into account the load changes caused by the differences between the casing flanging structure and the finite element simulation parts, and optimizes the stress distribution calculation model, enabling the forward design of the split casing flanging structure made of resin matrix composites with different material systems and manufacturing processes, and improving the iteration speed and R & D efficiency of the composite casing structure.

[0039] Based on the same inventive concept, an embodiment of the present invention also provides a design system for the split casing flanging structure with bolt connection, as described in the following embodiments. Since the principle of the design system for the split casing flanging structure with bolt connection to solve problems is similar to the design method of the split casing flanging structure with bolt connection disclosed in the above embodiments, the implementation of the design system for the split casing flanging structure with bolt connection can refer to the implementation of the design method of the split casing flanging structure with bolt connection, and the repeated parts will not be described again. Hereinafter, the term "unit" or "module" can be a combination of software and / or hardware that can achieve a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, the implementation in hardware, or a combination of software and hardware, is also possible and contemplated.

[0040] Figure 4 is a structural block diagram of the design system for the split casing flanging structure with bolt connection disclosed in the embodiment of the present invention, as Figure 4 shown. The system includes a simulation part construction module 401, an equivalent load calculation module 402, and a structural parameter iterative optimization module 403. The following will explain this structure.

[0041] Among them, the simulation part construction module 401 is used to establish a finite element simulation part of the split casing bolt flanging structure. The finite element simulation part includes two metal pressing plates and two L-shaped parts, and the two L-shaped parts are respectively simplified parts of the upper half casing and the lower half casing. The equivalent load calculation module 402 is used to obtain the aerodynamic load of the split casing bolt flanging structure under the service condition, and calculate the equivalent load applied to the finite element simulation part according to the aerodynamic load. The structural parameter iterative optimization module 403 is used to perform strength analysis on the finite element simulation part according to the equivalent load, and iteratively optimize the parameters of the split casing bolt flanging structure according to the strength analysis result until a bolt flanging structure that meets the strength reserve design requirements is obtained.

[0042] In this embodiment, a computer device is provided, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, it implements any of the above design methods for the split casing flanging structure with bolt connection to solve the problems of the lack of a typical part design method and low calculation efficiency for the split casing flanging structure made of bolt-connected composite materials.

[0043] Specifically, the computer device may be a computer terminal, a server, or a similar computing device.

[0044] In this embodiment, a computer-readable storage medium is provided, and the computer-readable storage medium stores a computer program for executing the design method of the bolt connection pair opening casing flanging structure described above.

[0045] Specifically, the computer-readable storage medium includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. The information may be computer-readable instructions, data structures, program modules, or other data. Examples of computer-readable storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette tapes, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible by a computing device. As defined herein, computer-readable storage media do not include transitory computer-readable media, such as modulated data signals and carrier waves.

[0046] Obviously, those skilled in the art should understand that the above-mentioned modules or steps of the embodiments of the present invention can be implemented by a general-purpose computing device. They can be concentrated on a single computing device or distributed on a network composed of multiple computing devices. Optionally, they can be implemented by program codes executable by the computing device, so that they can be stored in a storage device and executed by the computing device. And in some cases, the steps shown or described can be executed in a different order than here, or they can be separately fabricated into individual integrated circuit modules, or multiple modules or steps among them can be fabricated into a single integrated circuit module to be implemented. Thus, the embodiments of the present invention are not limited to any specific combination of hardware and software.

[0047] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, various changes and modifications can be made to the embodiments of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A design method for the flanging structure of a bolt-connected split casing, characterized in that, Including: Establish a finite element simulation model for the bolt flanging structure of the split casing. The finite element simulation model includes two metal pressing plates and two L-shaped parts, where the two L-shaped parts are respectively simplified models of the upper half casing and the lower half casing; Obtain the aerodynamic load of the bolt flanging structure of the split casing under service conditions, and calculate the equivalent load applied to the finite element simulation model according to the aerodynamic load; Conduct a strength analysis on the finite element simulation model according to the equivalent load, and iteratively optimize the parameters of the bolt flanging structure of the split casing according to the strength analysis results until a bolt flanging structure that meets the strength reserve design requirements is obtained.

2. The design method of the flanging structure of the split casing with bolt connection according to claim 1, characterized in that Establish a finite element simulation model for the bolt flanging structure of the split casing, including: Select the bolt flanging structure on the split casing as a typical part. The typical part includes bolts, metal pressing plates, and a section of the upper half casing and a section of the lower half casing connected by bolts; Simplify the upper half casing and the lower half casing into L-shaped parts respectively, and map the outermost contour lines of the bolts to the longitudinal installation edges of the metal pressing plates and the L-shaped parts respectively to obtain a simplified model including metal pressing plates and two L-shaped parts; Perform mesh division on the simplified model to obtain a finite element simulation model.

3. The design method of the flanging structure of the split casing connected by bolts according to claim 1, characterized in that, Obtain the aerodynamic load of the bolt flanging structure of the split casing under service conditions, and calculate the equivalent load applied to the finite element simulation model according to the aerodynamic load, including: Match the position of the end of the L-shaped part on the split casing, and obtain the aerodynamic load borne by the matched position under service conditions; Based on the constructed stress equivalence formula, convert the aerodynamic load into a tensile load, and the tensile load includes the lateral load at the matching position and the vertical load at the matching position; According to the dimensional parameters of the L-shaped part and the dimensional parameters of the split casing, conduct a geometric structure difference analysis to convert the tensile load into an equivalent load, where the equivalent load includes the lateral load at the matching position and the vertical load at the matching position.

4. The design method of the flanging structure of the split casing with bolt connection according to claim 3, characterized in that, The stress equivalent formula includes the formula and . According to the formula and , the pneumatic load is converted into a tensile load, where is the lateral load at the matching position, is the vertical load at the matching position, Q is the pressure load, R is the radius of the split casing, S is the length of the L-shaped part, and L is the width of the L-shaped part.

5. The design method of the flanging structure of the split casing with bolt connection according to claim 4, characterized in that, According to the dimensional parameters of the L-shaped part and the dimensional parameters of the split casing, conduct a geometric structure difference analysis to convert the tensile load into an equivalent load, including: Define that the equivalent load applied to the finite element simulation model includes the lateral load of the simulation model and the vertical load of the simulation model; Take the lateral load at the matching position as the lateral load of the simulation model; Obtain the distance between the center of the bolt hole on the L-shaped part and the outer edge of the installation edge, through the formula Calculate the vertical load of the simulated part, where is the vertical load of the simulated part, a is the distance between the center of the bolt hole on the L-shaped part and the outer edge of the installation side, is a variable, and its value range is ∈ (0, ), d represents the integral of ; X is a variable, and its value range is ∈ (a, ), dx represents the integral of X.

6. The design method of the flanging structure of the split casing connected by bolts according to claim 1, characterized in that, Conduct a strength analysis on the finite element simulation model according to the equivalent load, including: For the finite element simulation model, divide the meshes of the metal pressing plate and the longitudinal installation edge of the L-shaped part into a group and bind them with the outermost contour line of the bolt as the boundary; Establish a friction constraint for the unbound meshes in the finite element simulation model, and apply a forced displacement equal to the bolt indentation length on the bound meshes outside the two metal pressing plates; Fix one end of the finite element simulation model, apply the equivalent load at the other end to obtain the stress distribution, obtain the current strength reserve according to the stress distribution and the failure criterion, and conduct a strength analysis according to the current strength reserve and the strength reserve design requirements.

7. The design method of the flanging structure of the split casing with bolt connection according to claim 6, characterized in that The failure criteria include the Hashin failure criterion and the maximum stress failure criterion. The Hashin failure criterion is that the current strength reserve ≥ 1.5 times the design requirement of the strength reserve, and the maximum stress failure criterion is that the current strength reserve ≥ 1.05 times the design requirement of the strength reserve.

8. A design system for the flanging structure of a bolt-connected split casing, characterized in that, including: a simulation component construction module for establishing a finite element simulation component of the bolt flanging structure of the engine case. The finite element simulation component includes two metal pressing plates and two L-shaped components, and the two L-shaped components are respectively simplified components of the upper half engine case and the lower half engine case; an equivalent load calculation module for obtaining the aerodynamic load of the bolt flanging structure of the engine case under the service condition and calculating the equivalent load applied to the finite element simulation component according to the aerodynamic load; a structural parameter iterative optimization module for performing strength analysis on the finite element simulation component according to the equivalent load and iteratively optimizing the parameters of the bolt flanging structure of the engine case according to the strength analysis result until a bolt flanging structure that meets the design requirement of the strength reserve is obtained.

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