Method and system for designing flanged edge structure of split casing of bolt-connected laminated composite material

Abstract

The invention relates to the technical field of aero-engines, and discloses a method and a system for designing a flanged structure of a split casing of a bolted connection laying composite material, and different laying schemes of the flanged structure of the fiber reinforced composite material are combined according to different thicknesses, laying modes, bolt hole edge distances and bolt hole distances. And establishing a three-dimensional finite element analysis model of the split casing structure with the bolt holes corresponding to each layering scheme, and simulating to obtain the layering scheme which simultaneously meets the stability of the stress concentration coefficient of the edge of the bolt holes, the stability of the stress concentration coefficient between the bolt holes, the sealing performance requirement and the strength reserve requirement. According to the method, various influence parameters of the split casing bolt connection flanging structure of the layering composite material are comprehensively considered, it is ensured that the split casing flanging structure can meet the performance without excessive redundant design, and a support is provided for forward design and engineering application of the split casing flanging structure of the bolt connection composite material; and the iteration speed and the research and development efficiency of the bolt connection composite material split casing structure are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of aeroengines, and discloses a design method and system for a bolt-connected laminated composite split casing flanging structure. Background Art

[0002] Fiber-reinforced composite materials have been widely used in aeroengines due to their advantages such as high specific strength, high specific stiffness, fatigue resistance, and strong designability. Using a composite casing can significantly reduce the weight of the casing itself, which is of great significance for improving the engine efficiency. Currently, a large number of studies on composite casings have been carried out at home and abroad.

[0003] The casing using fiber-reinforced composite materials can greatly improve the efficiency performance of the aircraft and aeroengine, but its connection structure is often a weak link in actual load-bearing. The bolt connection structure is a common form of the flanging connection of the fiber-reinforced composite casing and can be used to transfer higher loads. According to statistics, more than 70% of the structural failures of aircraft occur at the connection parts. Carrying out targeted design and research on the bolt connection structure of the composite casing, so that the connection position meets the strength design requirements without excessive redundant design, has important practical significance for promoting the application of composite materials in aeroengines in China and the development of composite material structure design technology. In the prior art, through the strength analysis of the bolt connection flanging structure of the resin matrix composite casing, Liu Yulin of Nanjing University of Aeronautics and Astronautics established a progressive damage simulation model of the flanging structure in "Analysis and Experimental Research on the Connection Strength of the Flanging Structure of Resin Matrix Composite Casings"; another scholar used the finite element method to compare and calculate the strength of the casing with a bolt connection flanging structure. The results show that for a split casing, not considering 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.

[0004] It can be seen that most of the current research is based on the existing bolt connection flanging structure of the casing, establishing a corresponding strength simulation model, and verifying 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 discuss how to design the connection structure of the casing flanging structure, did not consider the influence of the process level, the characteristics of the material itself, and the geometric structure of the casing on the value range of the connection structure parameters of the flanging structure, and could not judge the rationality of parameters such as the thickness of the flanging structure, the size of the bolt, and the bolt hole spacing. Only establishing a strength simulation model is difficult to realize the forward design of the casing flanging structure. Therefore, it is necessary to provide a simple, effective, and highly applicable method to solve the problem of the lack of forward design of the bolt-connected composite split casing flanging structure at present. Summary of the Invention

[0005] The object of the present invention is to provide a design method and system for the flanging structure of a bolt-connected laminated composite split casing, which can ensure that the flanging structure of the split casing can meet the performance requirements without excessive redundant design, provide support for the forward design and engineering application of the bolt-connected composite material split casing flanging structure, and improve the iteration speed and R & D efficiency of the bolt-connected composite material split casing structure.

[0006] In order to achieve the above technical effects, the technical solution adopted by the present invention is: A design method for the flanging structure of a bolt-connected laminated composite split casing, comprising: According to the design dimension requirements of the split casing, determine the value ranges of the height, thickness, radius of the fillet area and thickness of the metal pressing plate of the flanging structure of the split casing; the flanging structure is used to fix the two symmetric split structures of the split casing through bolts, the fillet area is the corner transition area between the flanging structure and the corresponding split structure, and the metal pressing plate is a gasket strip arranged between the bolt head and the flanging structure; According to the value ranges of the height, thickness, radius of the fillet area and thickness of the metal pressing plate of the flanging structure of the split casing, use fiber-reinforced composite materials to carry out layup design for the flanging structure, obtain layup schemes with different thicknesses, layup methods, bolt hole edge distances and bolt hole spacings, and establish a three-dimensional finite element analysis model of the split casing structure with bolt holes obtained by each layup scheme; Through simulation analysis of each finite element analysis model, obtain the layup scheme in which the stress concentration coefficient at the hole edge and the stress concentration coefficient between holes are stable; the basis for judging the stability of the stress concentration coefficient at the hole edge is that as the bolt hole edge distance increases, the change rate of the stress concentration coefficient at the hole edge decreases to less than the first preset change rate limit value, and the basis for judging the stability of the stress concentration coefficient between holes is that as the bolt hole spacing increases, the change rate of the stress concentration coefficient between holes decreases to less than the second preset change rate limit value; According to the distance from the center of the bolt hole to the inner edge of the flange, the distance from the center of the bolt hole to the outer edge of the flange, the maximum design pressure load of the split casing, the size parameters of the split casing, and the bolt hole spacing in the layup scheme that satisfies the stability of the stress concentration coefficient at the hole edge and the stress concentration coefficient between holes, analyze and obtain the layup scheme that meets the sealing requirements; Select the layup scheme with a strength reserve greater than the preset strength reserve threshold and the minimum weight from the layup schemes that meet the sealing requirements as the design scheme for the flanging structure of the bolt-connected laminated composite split casing.

[0007] Further, the method for judging that the sealing is satisfied is: According to the maximum design pressure load of the split casing , analyze the size parameters of the split casing and the bolt hole spacing in the ply layup scheme to obtain the converted tensile load of the split casing pressure , where is the casing radius, is the bolt hole spacing in the According to the converted tensile load of the split casing pressure, the distance from the center of the bolt hole to the inner edge of the flange and the distance from the center of the bolt hole to the outer edge of the flange , analyze to obtain the separation load of the metal pressing plate; If the bolt tightening force in the ply layup scheme is greater than or equal to the separation load, the sealing performance meets the requirements; otherwise, the sealing performance does not meet the requirements.

[0008] Further, the radius of the fillet area has a value range of where is the radius of the fillet area and

[0009] Further, the thickness of the flanged structure of the split casing has a value range of

[0010] Further, the ply layup method of each ply layup scheme satisfies: the ply angles form a symmetric structure in the ply layup order, the number of plies with a ply angle of 45° is greater than or equal to one-third of the total number of plies, the plies with a ply angle of 45° are on the upper and lower surfaces of the flanged structure, the plies with a ply angle of 90° are not used as intermediate plies, and the plies with the same ply angle are not adjacent to two adjacent plies.

[0011] To achieve the above technical effects, the present invention also provides a bolt - connected ply composite split casing flanged structure design system, including: A value range determination module, configured to determine the value ranges of the height, thickness, fillet area radius, and metal pressing plate thickness of the flanged structure of the split casing according to the design size requirements of the split casing; the flanged structure is used to fix the two symmetric split structures of the split casing through bolts, the fillet area is the corner transition area between the flanged structure and the corresponding split structure, and the metal pressing plate is a gasket strip arranged between the bolt head and the flanged structure; A model construction module, configured to perform ply layup design on the flanged structure using fiber - reinforced composite materials according to the value ranges of the height, thickness, fillet area radius, and metal pressing plate thickness of the flanged structure of the split casing, obtain ply layup schemes with different thicknesses, ply layup methods, bolt hole margins, and bolt hole spacings, and establish a three - dimensional finite element analysis model of the split casing structure with bolt holes obtained for each ply layup scheme; A simulation analysis module, which is used to perform simulation analysis on each finite element analysis model to obtain a ply layup plan in the ply layup plan that satisfies the stability of the stress concentration factor at the hole edge and the stress concentration factor between holes; the basis for judging the stability of the stress concentration factor at the hole edge is that as the distance from the bolt hole edge increases, the change rate of the stress concentration factor at the hole edge decreases to less than the first preset change rate limit value, and the basis for judging the stability of the stress concentration factor between holes is that as the bolt hole spacing increases, the change rate of the stress concentration factor between holes decreases to less than the second preset change rate limit value; A first screening module, which is used to analyze and obtain a ply layup plan that meets the sealing requirements according to the distance from the bolt hole center to the inner edge of the flange, the distance from the bolt hole center to the outer edge of the flange in the ply layup plan that satisfies the stability of the stress concentration factor at the hole edge and the stress concentration factor between holes, as well as the maximum pressure load designed for the split casing, the size parameters of the split casing, and the bolt hole spacing; A second screening module, which is used to select a ply layup plan with a strength reserve greater than the preset strength reserve threshold and the smallest weight from the ply layup plans that meet the sealing requirements as the design plan for the ply composite split casing flange structure of the bolt connection.

[0012] Further, the first screening module includes: A first analysis unit, which is used to analyze and obtain the converted tensile load of the split casing pressure according to the maximum pressure load designed for the split casing , the size parameters of the split casing, and the bolt hole spacing in the ply layup plan , where is the radius of the casing, is the bolt hole spacing in the th ply layup plan; A second analysis unit, which is used to analyze and obtain the separating load of the metal pressing plate according to the converted tensile load of the split casing pressure, the distance from the bolt hole center to the inner edge of the flange in the ply layup plan, and the distance from the bolt hole center to the outer edge of the flange ;

[0013] A sealing judgment unit, which is used to judge whether the sealing meets the requirements according to the numerical magnitudes of the bolt tightening force and the separating load in the ply layup plan. When the bolt tightening force in the ply layup plan is greater than or equal to the separating load, it is determined that the sealing meets the requirements; otherwise, it is determined that the sealing does not meet the requirements. Further, in the value range determination module, the value range of the radius of the fillet area is , where is the radius of the fillet area,

[0014] and The value range is .

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention comprehensively considers various influencing parameters of the laminated composite material on the flanging structure of the bolt connection of the engine casing, ensuring that the flanging structure of the engine casing can meet the performance requirements without excessive redundant design, providing support for the forward design and engineering application of the bolt connection composite material engine casing flanging structure, and improving the iteration speed and R & D efficiency of the bolt connection composite material engine casing structure. Description of the Drawings

[0016] Figure 1 It is a flowchart of the design method for the flanging structure of the bolt connection laminated composite material engine casing in Embodiment 1 or Embodiment 2; Figure 2 It is a schematic diagram of the engine casing structure in Embodiment 1 or Embodiment 2; Figure 3 is Figure 2 an enlarged schematic diagram of the local part A in Figure 4 It is a block diagram of the design system for the flanging structure of the bolt connection laminated composite material engine casing in Embodiment 1; Among them, 1. Split structure; 2. Flanging structure; 3. Fillet area; 4. Value range determination module; 5. Model construction module; 6. Simulation analysis module; 7. First screening module; 701. First analysis unit; 702. Second analysis unit; 703. Sealing performance judgment unit; 8. Second screening module. Detailed Embodiments

[0017] The present invention will be further described in detail below in conjunction with the embodiments and the drawings. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments. All technologies implemented based on the content of the present invention belong to the scope of the present invention.

[0018] Embodiment 1 Refer to Figures 1 - 4 , a design method for the flanging structure of the bolt connection laminated composite material engine casing, including: According to the design dimension requirements of the engine casing, determine the value ranges of the height, thickness, radius of the fillet area 3 and the thickness of the metal pressing plate of the flanging structure 2 of the engine casing; the flanging structure 2 is used to fix the two symmetrical split structures 1 of the engine casing through bolts, the fillet area 3 is the corner transition area between the flanging structure 2 and the corresponding split structure 1, and the metal pressing plate is a gasket strip arranged between the bolt head and the flanging structure 2; According to the value ranges of the height, thickness, radius of the fillet region 3, and the thickness of the metal pressing plate of the split casing flanging structure 2, a ply design is carried out on the flanging structure 2 using fiber-reinforced composite materials, obtaining different ply schemes with combinations of thickness, ply arrangement, bolt hole edge distance, and bolt hole spacing, and establishing a three-dimensional finite element analysis model of the split casing structure with bolt holes obtained for each of the ply schemes; Through simulation analysis of each finite element analysis model, a ply scheme that satisfies stable hole edge stress concentration factor and stable inter-hole stress concentration factor in the ply scheme is obtained; the basis for judging the stability of the hole edge stress concentration factor is that as the bolt hole edge distance increases, the change rate of the hole edge stress concentration factor decreases to less than the first preset change rate limit value, and the basis for judging the stability of the inter-hole stress concentration factor is that as the bolt hole spacing increases, the change rate of the inter-hole stress concentration factor decreases to less than the second preset change rate limit value; According to the distance from the bolt hole center to the inner edge of the flange, the distance from the bolt hole center to the outer edge of the flange, the maximum design pressure load of the split casing, the size parameters of the split casing, and the bolt hole spacing in the ply scheme that satisfies stable hole edge stress concentration factor and stable inter-hole stress concentration factor, a ply scheme that meets the sealing requirement is analyzed and obtained; Select a ply scheme with a strength reserve greater than the preset strength reserve threshold and the minimum weight from the ply schemes that meet the sealing requirement as the design scheme of the flanging structure 2 of the split casing with bolt-connected composite materials.

[0019] In this embodiment, a ply design is carried out on the flanging structure 2 using fiber-reinforced composite materials, and different ply schemes are combined according to different thicknesses, ply arrangements, bolt hole edge distances, and bolt hole spacings. By establishing a three-dimensional finite element analysis model of the split casing structure with bolt holes corresponding to each ply scheme, a ply scheme that simultaneously satisfies stable bolt hole edge stress concentration factor, stable bolt hole inter-stress concentration factor, sealing requirement, and strength reserve requirement is obtained through simulation; all kinds of influencing parameters of the bolt-connected flanging structure 2 of the split casing with composite materials are comprehensively considered, ensuring that the flanging structure 2 of the split casing can meet the performance requirements without excessive redundant design, providing support for the forward design and engineering application of the bolt-connected composite split casing flanging structure 2, and improving the iteration speed and R & D efficiency of the bolt-connected composite split casing structure.

[0020] Based on the same inventive concept, this embodiment also provides a design system for the flanging structure of a split casing with bolt-connected composite materials, including: The value range determination module 4 is used to determine the value ranges of the height, thickness, radius of the fillet area 3, and thickness of the metal pressing plate of the flanging structure 2 of the split casing according to the design dimension requirements of the split casing; the flanging structure 2 is used to fix the two symmetric split structures 1 of the split casing by bolts, the fillet area 3 is the corner transition area between the flanging structure 2 and the corresponding split structure 1, and the metal pressing plate is a cushion strip arranged between the bolt head and the flanging structure 2; The model construction module 5 is used to perform ply design on the flanging structure 2 with fiber-reinforced composite materials according to the value ranges of the height, thickness, radius of the fillet area 3, and thickness of the metal pressing plate of the flanging structure 2 of the split casing, obtain ply combination schemes with different thicknesses, ply laying methods, bolt hole edge distances, and bolt hole spacings, and establish a three-dimensional finite element analysis model of the split casing structure with bolt holes obtained for each ply combination scheme; The simulation analysis module 6 is used to perform simulation analysis on each finite element analysis model to obtain the ply combination scheme that satisfies the stability of the stress concentration coefficient at the hole edge and the stress concentration coefficient between holes; the basis for judging the stability of the stress concentration coefficient at the hole edge is that as the bolt hole edge distance increases, the change rate of the stress concentration coefficient at the hole edge decreases to less than the first preset change rate limit value, and the basis for judging the stability of the stress concentration coefficient between holes is that as the bolt hole spacing increases, the change rate of the stress concentration coefficient between holes decreases to less than the second preset change rate limit value; The first screening module 7 is used to analyze and obtain the ply combination scheme that satisfies the sealing requirement according to the distance a from the bolt hole center to the inner edge of the flanging, the distance b from the bolt hole center to the outer edge of the flanging, the maximum design pressure load of the split casing, the size parameters of the split casing, and the bolt hole spacing in the ply combination scheme that satisfies the stability of the stress concentration coefficient at the hole edge and the stress concentration coefficient between holes; The second screening module 8 is used to select the ply combination scheme with a strength reserve greater than the preset strength reserve threshold and the minimum weight from the ply combination schemes that satisfy the sealing requirement as the design scheme of the flanging structure 2 of the split casing with bolt-connected laminated composites.

[0021] The first screening module 7 in this embodiment includes: The first analysis unit 701 is used to analyze and obtain the converted tensile load of the split casing pressure according to the maximum design pressure load of the split casing 、the size parameters of the split casing, and the bolt hole spacing in the ply combination scheme, where where is the radius of the casing, is the bolt hole spacing in the th ply combination scheme; The second analysis unit 702 is used to analyze and obtain the converted tensile load of the split casing pressure according to the converted tensile load of the split casing pressure, the distance from the bolt hole center to the inner edge of the flanging in the ply combination scheme, distance from the center of the bolt hole to the outer edge of the flanging , analyze and obtain the separation load of the metal pressing plate ; Sealing judgment unit 703, which is used to judge whether the sealing meets the requirements according to the numerical magnitudes of the bolt tightening force and the separation load in the laying scheme. When the bolt tightening force in the laying scheme is greater than or equal to the separation load, it is determined that the sealing meets the requirements; otherwise, it is determined that the sealing does not meet the requirements.

[0022] Embodiment 2 Refer to Figures 1 - 3 , in this embodiment, taking the flanging structure 2 of the split casing of a certain aero-engine as an example, the design method flow of the bolt-connected laminated composite split casing flanging structure of the present invention is described in detail, which specifically includes the following steps: Step 1: According to the design dimension requirements of the split casing, determine the value ranges of the height, thickness, radius of the fillet area 3 and the thickness of the metal pressing plate of the flanging structure 2 of the split casing; the flanging structure 2 is used to fix the two symmetrical split structures 1 of the split casing through bolts, the fillet area 3 is the corner transition area between the flanging structure 2 and the corresponding split structure 1, and the metal pressing plate is a gasket strip arranged between the bolt head and the flanging structure 2. In this embodiment, according to the design dimension requirements of the split casing, the split flanging structure 2 with different thickness and height parameters is manufactured by the autoclave process. Then, non-destructive testing is carried out on the flanging structure 2 by means of ultrasonic A-scan, C-scan, etc. The detection area is the position of the fillet area 3 where the strength is weak. According to the detection results of the defects, the following parameter value ranges are finally determined: 1.1. The thickness of the flanging structure 2 is not greater than 4 mm; 1.2. The flanging height is not greater than 34 mm; 1.3. The radius of the fillet area 3 is determined according to analysis, where is the radius of the fillet area 3, is the thickness of the flanging structure 2 of the split casing, and finally the radius of the fillet area 3 is 4 - 5 mm; 1.4. The thickness of the flanging structure of the split casing has a value range of

[0023] Step 2: According to the value ranges of the height, thickness, radius of the fillet area 3 and the thickness of the metal pressing plate of the flanging structure 2 of the split casing, use fiber-reinforced composite materials to carry out layer design on the flanging structure 2, and obtain different thicknesses, layer laying methods, bolt hole edge distances , bolt hole spacings Combined ply layup schemes are developed, and a three-dimensional finite element analysis model of the split casing structure with bolt holes is established for each of the said ply layup schemes; In this embodiment, the ply layup method for each ply layup scheme satisfies the following: the ply angles form a symmetric structure in the ply layup order, the number of plies with a ply angle of 45° is greater than or equal to one-third of the total number of plies, the plies with a ply angle of 45° are on the upper and lower surfaces of the flanging structure 2, the plies with a ply angle of 90° are not used as intermediate plies, and plies with the same ply angle are not adjacent to each other; For each ply layup scheme, different bolt hole diameters, bolt hole edge distances, and bolt hole spacing parameters are set, and a three-dimensional finite element analysis model of the split casing structure with bolt holes is established for each of the said ply layup schemes.

[0024] Step 3: Through simulation analysis of each finite element analysis model, ply layup schemes in which the stress concentration coefficient at the hole edge is stable and the stress concentration coefficient between holes is stable are obtained; the basis for judging the stability of the stress concentration coefficient at the hole edge is that as the bolt hole edge distance increases, the change rate of the stress concentration coefficient at the hole edge decreases to less than the first preset change rate limit value, and the basis for judging the stability of the stress concentration coefficient between holes is that as the bolt hole spacing increases, the change rate of the stress concentration coefficient between holes decreases to less than the second preset change rate limit value.

[0025] In this embodiment, the ply layup schemes with a stable stress concentration coefficient at the hole edge and a stable stress concentration coefficient between holes are shown in Table 1 below. In Table 1, "times" refers to the multiples of the bolt hole edge distance and bolt hole spacing relative to the bolt hole diameter respectively; Table 1 Data table of different size combinations of bolt hole edge distance and bolt hole spacing for the flanging structure

[0026] Step 4: Based on the distance from the bolt hole center to the inner edge of the flanging, the distance from the bolt hole center to the outer edge of the flanging, the maximum design pressure load of the split casing, the split casing size parameters, and the bolt hole spacing in the ply layup scheme with a stable stress concentration coefficient at the hole edge and a stable stress concentration coefficient between holes, a ply layup scheme that meets the sealing requirements is analyzed and obtained; In this embodiment, first, based on the maximum design pressure load of the split casing , the split casing size parameters, and the bolt hole spacing in the ply layup scheme, the pressure-converted tensile load of the split casing is analyzed and obtained , where is the casing radius, is the th bolt hole spacing in the ply layup scheme; Secondly, based on the pressure-converted tensile load of the split casing and the distance from the bolt hole center to the inner edge of the flanging in the ply layup scheme , the distance from the center of the bolt hole to the outer edge of the flanging , analyze and obtain the separation load of the metal pressing plate ; According to the ply layup scheme in Table 1, obtain the distance a from the center of the bolt hole to the inner edge of the flanging and the distance b from the center of the bolt hole to the outer edge of the flanging in each ply layup scheme respectively; then obtain the standard tightening force of bolts with different sizes according to HB6586-92 ; the relevant data is shown in Table 2; Table 2 Data table of sealing results of bolts with different sizes in the flanging structure

[0027] In this embodiment, if the bolt tightening force in the ply layup scheme is greater than or equal to the separation load , the sealing performance meets the requirements; otherwise, the sealing performance does not meet the requirements. From the relevant data in Table 2, it can be seen that the bolt combination with a diameter of 6mm does not meet the sealing requirements. Therefore, the structural combination of the flanging structure 2 is excluded, and only two groups of combinations that meet the conditions are left, which are named Combination 1 and Combination 2 respectively.

[0028] Step Five: Select the ply layup scheme with a strength reserve greater than the preset strength reserve threshold and the minimum weight from the ply layup schemes that meet the sealing requirements as the ply composite for the bolt connection to the design scheme of the flanging structure 2 of the engine casing In this embodiment, for Combination 1 and Combination 2, establish a simulation model of the composite outer casing of different flanging structures 2 and apply a pressure load of 0.4 MPa. Select the Hashin and Hoffoman strength evaluation criteria, and the strength reserves of different flanging structures 2 are shown in Table 3. Then, calculate the weight of the flanging structure 2 by multiplying the volume by the density, and the total weight of different structural combinations is obtained by adding the weights of the bolts and nuts.

[0029] Table 3 Data table of calculation results of the optimal structure

[0030] Finally, the optimal structure can be selected by the ratio of the strength reserve to the weight of different structural combinations. As can be seen from Table 3, the strength reserves of the flanging structures 2 of the two combinations both meet the strength design requirements. Therefore, it is not necessary to increase the thickness of the metal pressing plate. Among them, the ratio of the strength reserve to the weight of Combination 1 is larger, so it is the optimal structure.

[0031] The above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for designing a bolt-connected laminated composite casing flange structure, characterized in that: include: According to the design dimension requirements of the split receiver, the value ranges of the height, thickness, radius of the rounded area and thickness of the metal pressure plate of the split receiver flange structure are determined; the flange structure is used to fix the two symmetrical petal structures of the split receiver by bolts, the rounded area is the corner transition area between the flange structure and the corresponding petal structure, and the metal pressure plate is a gasket arranged between the bolt head and the flange structure; According to the range of values ​​of the height, thickness, radius of the rounded area and thickness of the metal pressing plate of the split-casing flange structure, a fiber-reinforced composite material is used to perform a layup design on the flange structure, and a layup scheme with different thicknesses, layup methods, bolt hole margins and bolt hole spacings is obtained, and a three-dimensional finite element analysis model of the split-casing structure with bolt holes obtained by each of the layup schemes is established; By performing simulation analysis on each finite element analysis model, a plying scheme that satisfies the requirements of stable hole edge stress concentration coefficient and stable inter-hole stress concentration coefficient is obtained in the plying scheme; the basis for judging the stability of the hole edge stress concentration coefficient is that the change rate of the hole edge stress concentration coefficient decreases to less than a first preset change rate limit value as the bolt hole margin increases, and the basis for judging the stability of the inter-hole stress concentration coefficient is that the change rate of the inter-hole stress concentration coefficient decreases to less than a second preset change rate limit value as the bolt hole spacing increases; According to the distance from the center of the bolt hole to the inner edge of the flange, the distance from the center of the bolt hole to the outer edge of the flange in the layup scheme that satisfies the stable stress concentration coefficient at the hole edge and the stable stress concentration coefficient between holes, as well as the maximum design pressure load of the split receiver, the size parameters of the split receiver, and the bolt hole spacing, the layup scheme that meets the sealing requirements is analyzed and obtained; From the layup schemes that meet the sealing requirements, a layup scheme with a strength reserve greater than a preset strength reserve threshold and a minimum weight is selected as the design scheme for the bolted layup composite split receiver flange structure.

2. The bolt-connected laminated composite split casing flange structure design method according to claim 1 is characterized in that: The method to judge whether the sealing meets the requirements is: Design maximum pressure load based on split case , the size parameters of the split casing and the bolt hole spacing in the ply scheme, and the pressure conversion tensile load of the split casing is obtained by analysis ,in is the casing radius, For the Bolt hole spacing in each layup solution; Calculate the tensile load based on the split casing pressure and the distance from the center of the bolt hole to the inner edge of the flange in the layup plan , Distance from the center of the bolt hole to the outer edge of the flange , analyze and obtain the separation load of the metal plate ; If the bolt tightening force in the ply plan is greater than or equal to the separation load, the sealing meets the requirement, otherwise the sealing does not meet the requirement.

3. The bolt-connected laminated composite split casing flange structure design method according to claim 1 is characterized in that: The radius of the rounded area ranges from ,in is the radius of the rounded area, It is the thickness of the flange structure of the split receiver.

4. The bolt-connected laminated composite split casing flange structure design method according to claim 3 is characterized in that: Thickness of the flange structure of the split receiver The value range is .

5. The bolt-connected laminated composite split casing flange structure design method according to claim 1 is characterized in that: The layup method of each layup scheme meets the following requirements: the layup angle forms a symmetrical structure according to the layup sequence, the number of layups with a layup angle of 45° is greater than or equal to one third of the total number of layups, the layups with a layup angle of 45° are on the upper and lower surfaces of the flange structure, the layups with a layup angle of 90° are not used as intermediate layers, and the layups with the same layup angle are not two adjacent layups.

6. A bolt-connected laminated composite split casing flange structure design system, characterized in that: include: A value range determination module is used to determine the value range of the height, thickness, radius of the rounded area and thickness of the metal pressure plate of the split receiver according to the design size requirements of the split receiver; the flanging structure is used to fix the two symmetrical petal structures of the split receiver by bolts, the rounded area is the corner transition area between the flanging structure and the corresponding petal structure, and the metal pressure plate is a gasket arranged between the bolt head and the flanging structure; A model building module is used to design the layup of the flange structure using fiber-reinforced composite materials according to the value range of the height, thickness, radius of the rounded area and the thickness of the metal pressure plate of the split-casing flange structure, obtain combined layup schemes of different thicknesses, layup methods, bolt hole margins, and bolt hole spacings, and establish a three-dimensional finite element analysis model of the split-casing structure with bolt holes obtained by each of the layup schemes; A simulation analysis module is used to obtain a plying scheme that satisfies the stability of the hole edge stress concentration coefficient and the stability of the inter-hole stress concentration coefficient in the plying scheme by performing simulation analysis on each finite element analysis model; the basis for judging the stability of the hole edge stress concentration coefficient is that the change rate of the hole edge stress concentration coefficient decreases to less than a first preset change rate limit value as the bolt hole margin increases, and the basis for judging the stability of the inter-hole stress concentration coefficient is that the change rate of the inter-hole stress concentration coefficient decreases to less than a second preset change rate limit value as the bolt hole spacing increases; The first screening module is used to analyze and obtain a plying scheme that meets the sealing requirements according to the distance from the center of the bolt hole to the inner edge of the flange, the distance from the center of the bolt hole to the outer edge of the flange, the maximum design pressure load of the split receiver, the size parameters of the split receiver, and the bolt hole spacing in the plying scheme that meets the requirements of stable hole edge stress concentration coefficient and stable inter-hole stress concentration coefficient, as well as the split receiver size parameters and bolt hole spacing. The second screening module is used to select a layup scheme with a strength reserve greater than a preset strength reserve threshold and a minimum weight from the layup schemes that meet the sealing requirements as a bolt-connected layup composite split casing flange structure design scheme.

7. The bolted laminated composite split casing flanging structure design system according to claim 6 is characterized in that: The first screening module comprises: The first analysis unit is used to design the maximum pressure load according to the split receiver , the size parameters of the split casing and the bolt hole spacing in the ply scheme, and the pressure conversion tensile load of the split casing is obtained by analysis ,in is the casing radius, For the Bolt hole spacing in each layup solution; The second analysis unit is used to convert the tensile load and the distance from the center of the bolt hole to the inner edge of the flange in the layup scheme according to the pressure of the split receiver. , Distance from the center of the bolt hole to the outer edge of the flange , analyze and obtain the separation load of the metal plate ; The sealing judgment unit is used to judge the sealing performance meets the requirements according to the values ​​of the bolt tightening force in the laying scheme and the separation load when the bolt tightening force in the laying scheme is greater than or equal to the separation load, otherwise, it is judged that the sealing performance does not meet the requirements.

8. The bolt-connected laminated composite split casing flanging structure design system according to claim 6 is characterized in that: In the value range determination module, the radius of the rounded area has a value range of ,in is the radius of the rounded area, It is the thickness of the flange structure of the split receiver.

9. The bolted laminated composite split casing flanging structure design system according to claim 8 is characterized in that: The value range determines the thickness of the flange structure of the split receiver in the module The value range is .

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