A Design Method and System for the Flanging Structure of a Bolt-Connected Laminated Composite Split Casing

Abstract

The present invention relates to the technical field of aeroengines, and discloses a design method and system for a bolted connection laminated composite split casing flanging structure. Different laminated composite split casing flanging structure layup schemes are combined according to different thicknesses, layup methods, bolt hole edge distances, and bolt hole spacings, and a three-dimensional finite element analysis model of the split casing structure with bolt holes corresponding to each layup scheme is established. A layup scheme that simultaneously meets the requirements of stable stress concentration coefficient at the bolt hole edge, stable stress concentration coefficient between bolt holes, sealing performance, and strength reserve is obtained through simulation. The present invention comprehensively considers various influencing parameters of the bolted connection laminated composite split casing flanging structure, ensures that the split casing flanging structure can meet the performance requirements without excessive redundant design, provides support for the forward design and engineering application of the bolted connection composite split casing flanging structure, and improves the iteration speed and R & D efficiency of the bolted connection composite split casing structure.

Description

Technical Field

[0001] The present invention relates to the technical field of aeroengines, and discloses a design method and system for a flanging structure of a split casing with bolted connections of laminated composites. Background Art

[0002] Fiber-reinforced composites 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. At present, a large number of studies on composite casings have been carried out at home and abroad.

[0003] The casing using fiber-reinforced composites 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 bolted connection structure is a common form of the flanging connection of the fiber-reinforced composite casing and can be used to transfer high loads. According to statistics, more than 70% of the aircraft structure failures occur at the connection parts. Conducting targeted design and research on the bolted 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 bolted 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 conduct a comparative calculation on the strength of the casing with a bolted 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 (usually connecting casings) should be considered.

[0004] It can be seen that most of the current research is based on the existing bolted 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 bolts, and the bolt hole spacing. Only establishing a strength simulation model is difficult to achieve 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 bolted connection 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:

[0007] A design method for the flanging structure of a bolt-connected laminated composite split casing, comprising:

[0008] 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;

[0009] 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 perform ply design on the flanging structure, obtain ply schemes with different thicknesses, ply patterns, 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 scheme;

[0010] Through simulation analysis of each finite element analysis model, obtain a ply 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;

[0011] 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 ply scheme that satisfies the stability of the stress concentration coefficient at the hole edge and the stress concentration coefficient between holes, analyze and obtain a ply scheme that meets the sealing requirements;

[0012] 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 requirements as the design scheme for the flanging structure of the bolt-connected laminated composite split casing.

[0013] Further, the method for determining that the sealing performance meets the requirements is as follows:

[0014] Based on the maximum pressure load designed for the opening casing and the size parameters of the opening casing as well as the bolt hole spacing in the ply layup scheme, analyze and obtain the pressure-converted tensile load of the opening casing , where is the radius of the casing, is the bolt hole spacing in the

[0015] Based on the pressure-converted tensile load of the opening casing, the distance from the center of the bolt hole in the ply layup scheme to the inner edge of the flanging and 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;

[0016] 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.

[0017] Further, the value range of the radius of the fillet area is , where is the radius of the fillet area, is the thickness of the flanging structure of the opening casing.

[0018] Further, the thickness of the flanging structure of the opening casing has a value range of

[0019] Further, the ply layup method of each ply layup scheme satisfies: the ply angles form a symmetric structure according to 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, 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.

[0020] To achieve the above technical effects, the present invention also provides a bolt-connected ply composite opening casing flanging structure design system, including:

[0021] 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 flanging structure of the opening casing according to the design size requirements of the opening casing; the flanging structure is used to fix the two symmetric split structures of the opening 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;

[0022] A model construction module, which is used to perform ply design on the flanging structure using fiber-reinforced composite materials according to the value ranges of the height, thickness, radius of the fillet area, and thickness of the metal pressing plate of the split casing flanging structure, obtain ply schemes with combinations of 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 of the ply schemes;

[0023] A simulation analysis module, which is used to perform simulation analysis on each finite element analysis model to obtain ply schemes in the ply schemes that satisfy 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;

[0024] A first screening module, which is used to analyze and obtain ply schemes that meet the sealing requirements according to 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 size parameters of the split casing, and the bolt hole spacing in the ply schemes that satisfy the stability of the stress concentration coefficient at the hole edge and the stress concentration coefficient between holes;

[0025] A second screening module, which is used to select a ply scheme with a strength reserve greater than a preset strength reserve threshold and the smallest weight from the ply schemes that meet the sealing requirements as the design scheme for the flanging structure of the split casing with bolt-connected ply composites.

[0026] Furthermore, the first screening module includes:

[0027] A first analysis unit, which 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 scheme, where is the radius of the casing, is the bolt hole spacing in the rd ply scheme;

[0028] A second analysis unit, which is used to analyze and obtain the separation 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 flanging, and the distance from the bolt hole center to the outer edge of the flanging in the ply scheme;

[0029] The sealing performance judgment unit is configured to determine whether the sealing performance meets the requirements based on the numerical values of the bolt tightening force and the separation load in the ply scheme. When the bolt tightening force in the ply scheme is greater than or equal to the separation load, it is determined that the sealing performance meets the requirements; otherwise, it is determined that the sealing performance does not meet the requirements.

[0030] 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, and is the thickness of the flanging structure of the split casing.

[0031] Further, in the value range determination module, the thickness of the flanging structure of the split casing has a value range of

[0032] 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 bolted connection flanging structure of the split casing with laminated composites, ensuring that the flanging structure of the split casing can meet the performance requirements without excessive redundant design, providing support for the forward design and engineering application of the bolted connection composite split casing flanging structure, and improving the iteration speed and R & D efficiency of the bolted connection composite split casing structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is the flowchart of the design method for the bolted connection flanging structure of the split casing with laminated composites in Embodiment 1 or Embodiment 2;

[0034] Figure 2 is the schematic diagram of the split casing structure in Embodiment 1 or Embodiment 2;

[0035] Figure 3 is Figure 2 the enlarged schematic diagram of the partial area A in

[0036] Figure 4 is the block diagram of the design system for the bolted connection flanging structure of the split casing with laminated composites in Embodiment 1;

[0037] 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 DESCRIPTION OF THE EMBODIMENTS

[0038] The present invention will be further described in detail below with reference to the embodiments and the accompanying drawings. However, it should not be understood that the scope of the above-mentioned subject matter of the present invention is limited to the following embodiments. Any technology implemented based on the content of the present invention belongs to the scope of the present invention.

[0039] Example 1

[0040] Refer to Figures 1 - 4 , a design method for the flanging structure of a split compressor casing connected by bolts, including:

[0041] According to the design dimension requirements of the split compressor casing, 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 compressor casing; the flanging structure 2 is used to fix the two symmetric split structures 1 of the split compressor 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;

[0042] 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 compressor casing, use fiber-reinforced composite materials to carry out ply design for the flanging structure 2, obtain ply schemes with different thicknesses, ply patterns, bolt hole edge distances, and bolt hole spacings, and establish a three-dimensional finite element analysis model of the split compressor casing structure with bolt holes obtained for each ply scheme;

[0043] Through simulation analysis of each finite element analysis model, obtain the ply 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;

[0044] 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 compressor casing, the size parameters of the split compressor casing, and the bolt hole spacing in the ply 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 ply scheme that satisfies the sealing requirement;

[0045] Select the ply scheme with a strength reserve greater than the preset strength reserve threshold and the minimum weight from the ply schemes that satisfy the sealing requirement as the design scheme for the flanging structure 2 of the split compressor casing connected by bolts with ply composite materials.

[0046] In this embodiment, a fiber-reinforced composite material is used for the layup design of the flanging structure 2, and different layup schemes are combined according to different thicknesses, layup methods, 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 layup scheme, a layup scheme that simultaneously meets the requirements of stable stress concentration factor at the bolt hole edge, stable stress concentration factor between bolt holes, sealing requirements, and strength reserve requirements is obtained through simulation. All kinds of influencing parameters of the layup composite material on the flanging structure 2 of the split casing are comprehensively considered to ensure 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.

[0047] Based on the same inventive concept, this embodiment also provides a design system for a bolt-connected layup composite split casing flanging structure, including:

[0048] A value range determination module 4, configured to determine the value ranges of the height, thickness, radius of the fillet region 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 through bolts, the fillet region 3 is a corner transition region 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;

[0049] A model construction module 5, configured to perform a layup design on the flanging structure 2 using a fiber-reinforced composite material according to the value ranges of the height, thickness, radius of the fillet region 3, and thickness of the metal pressing plate of the flanging structure 2 of the split casing, obtain layup schemes with different combinations of 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 from each layup scheme;

[0050] A simulation analysis module 6, configured to obtain a layup scheme that meets the requirements of stable stress concentration factor at the hole edge and stable stress concentration factor between holes in the layup scheme through simulation analysis of each finite element analysis model; the basis for judging the stability of the stress concentration factor at the hole edge is that the change rate of the stress concentration factor at the bolt hole edge decreases to less than the first preset change rate limit value as the bolt hole edge distance increases, and the basis for judging the stability of the stress concentration factor between holes is that the change rate of the stress concentration factor between bolt holes decreases to less than the second preset change rate limit value as the bolt hole spacing increases;

[0051] The first screening module 7 is configured to analyze and obtain a ply layup scheme that meets the sealing requirements based on the distance a from the center of the bolt hole to the inner edge of the flange, the distance b 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 ply layup scheme that satisfies the stable hole-edge stress concentration factor and the stable inter-hole stress concentration factor;

[0052] The second screening module 8 is configured to select, from the ply layup schemes that meet the sealing requirements, a ply layup scheme with a strength reserve greater than a preset strength reserve threshold and the minimum weight as the design scheme for the flange structure 2 of the bolt-connected ply composite split casing.

[0053] The first screening module 7 in this embodiment includes:

[0054] The first analysis unit 701 is configured to analyze and obtain the converted tensile load of the split casing pressure based on the maximum design pressure load of the split casing , the size parameters of the split casing, and the bolt hole spacing in the ply layup scheme, where is the radius of the casing, and is the bolt hole spacing in the th ply layup scheme;

[0055] The second analysis unit 702 is configured to analyze and obtain the separating load of the metal pressing plate based on 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 in the ply layup scheme;

[0056] The sealing judgment unit 703 is configured to determine whether the sealing meets the requirements based on the numerical magnitudes of the bolt tightening force and the separating load in the ply layup scheme. When the bolt tightening force in the ply layup scheme 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.

[0057] Embodiment 2

[0058] Referring to Figures 1 - 3 , this embodiment takes the design of the flange structure 2 of a certain aeroengine split casing as an example to illustrate in detail the design method flow of the bolt-connected ply composite split casing flange structure of the present invention, which specifically includes the following steps:

[0059] 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 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 symmetric 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;

[0060] 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 testing area is the position of the fillet area 3 with weak strength. According to the detection results of the defects, the following parameter value ranges are finally determined:

[0061] 1.1. The thickness of the flanging structure 2 is not greater than 4 mm;

[0062] 1.2. The flanging height is not greater than 34 mm;

[0063] 1.3. The radius of the fillet area 3 is determined by 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 determined to be 4 - 5 mm; is 4 - 5 mm;

[0064] 1.4. The thickness of the flanging structure of the split casing has a value range of , and considering the weight factor, the metal pressing plate is first selected with a minimum thickness of 5 mm.

[0065] Step 2. 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, use fiber-reinforced composite materials to carry out ply design on the flanging structure 2 to obtain combined ply schemes with different thicknesses, ply layup methods, bolt hole edge distances , bolt hole spacings , and establish a three-dimensional finite element analysis model of the split casing structure with bolt holes obtained by each ply scheme;

[0066] In this embodiment, the ply layup method of each ply scheme satisfies: the ply angles form a symmetric structure according to the ply sequence, 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 the plies with the same ply angle are not adjacent to two adjacent plies;

[0067] In 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 obtained for each said ply layup scheme is established.

[0068] Step 3: Through simulation analysis of each finite element analysis model, obtain the ply layup scheme in which the stress concentration factor at the hole edge and the stress concentration factor between holes are stable; the basis for judging the stability of the stress concentration factor at the hole edge is that as the bolt hole edge distance 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.

[0069] In this embodiment, the ply layup schemes with stable stress concentration factor at the hole edge and stable stress concentration factor between holes are shown in Table 1 below. The "times" in Table 1 refers to the multiple of the bolt hole edge distance and bolt hole spacing relative to the bolt hole diameter respectively;

[0070] Table 1 Data table of different size combinations of bolt hole edge distance and bolt hole spacing for the flanging structure

[0071]

[0072] 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 pressure load designed for the split casing, the split casing size parameters, and the bolt hole spacing in the ply layup scheme with stable stress concentration factor at the hole edge and stable stress concentration factor between holes, analyze and obtain the ply layup scheme that meets the sealing requirements;

[0073] In this embodiment, first, based on the maximum pressure load designed for the split casing , the split casing size parameters, and the bolt hole spacing in the ply layup scheme, analyze and obtain the converted tensile load of the split casing pressure , where is the casing radius, is the bolt hole spacing in the th ply layup scheme;

[0074] Secondly, based on the converted tensile load of the split casing pressure, the distance from the bolt hole center to the inner edge of the flanging and the distance from the bolt hole center to the outer edge of the flanging in the ply layup scheme, analyze and obtain the separation load of the metal pressing plate;

[0075] According to the layup scheme in Table 1, obtain the distance a from the center of the bolt hole to the inner edge of the flange and the distance b from the center of the bolt hole to the outer edge of the flange for each layup scheme respectively; then obtain the standard tightening force of bolts with different sizes according to HB6586-92 ; the relevant data are shown in Table 2;

[0076] Table 2 Data table of sealing results of bolts with different sizes in the flange structure

[0077]

[0078] In this embodiment, if the bolt tightening force in the 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 flange 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.

[0079] Step Five: 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 layup composite material for the bolt connection to the design scheme of the flange structure 2 of the opening casing

[0080] In this embodiment, for Combination 1 and Combination 2, establish a simulation model of the composite outer casing of different flange structures 2 and apply a pressure load of 0.4MPa. Select the Hashin and Hoffoman strength evaluation criteria, and the strength reserves of different flange structures 2 are shown in Table 3. Then, calculate the weight of the flange 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.

[0081] Table 3 Data table of calculation results of the optimal structure

[0082]

[0083] Finally, the optimal structure can be selected by the ratio of the strength reserve and weight of different structural combinations: as can be seen from Table 3, the strength reserves of the flange structures 2 of the two combinations both meet the strength design requirements, so there is no need to increase the thickness of the metal pressing plate. Among them, the ratio of the strength reserve and weight of Combination 1 is larger, so it is the optimal structure.

[0084] 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 design method for the flanging structure of a bolt - connected laminated composite split - case, characterized in that, Including: According to the design dimension requirements of the split casing, determine the value ranges of the height, thickness, fillet radius of the flanging structure of the split casing, and the thickness of the metal pressing plate; 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 cushion strip arranged between the bolt head and the flanging structure; According to the value ranges of the height, thickness, fillet radius of the flanging structure of the split casing, and the thickness of the metal pressing plate, use fiber-reinforced composite materials to carry out ply design for the flanging structure, obtain different ply combinations of thickness, ply layup method, bolt hole edge distance, and bolt hole spacing, and establish a three-dimensional finite element analysis model of the split casing structure with bolt holes obtained by each ply layup plan; Through simulation analysis of each finite element analysis model, obtain the ply layup plan that satisfies the stability of the stress concentration coefficient at the hole edge and the stress concentration coefficient between holes in the ply layup plan; 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 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 size parameters of the split casing, and the bolt hole spacing in the ply layup plan that satisfies the stability of the stress concentration coefficient at the hole edge and the stress concentration coefficient between holes, analyze and obtain the ply layup plan that meets the sealing requirements; Select the ply layup plan with a strength reserve greater than the preset strength reserve threshold and the minimum weight from the ply layup plans that meet the sealing requirements as the design plan of the flanging structure of the split casing with bolt-connected composite material ply.

2. The bolt connection layup composite material counter-opening casing flange structure design method according to claim 1, characterized in that The method for judging that the sealing meets the requirements is: 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 scheme, the pressure-converted tensile load of the split casing is obtained through analysis , where is the radius of the casing, is the bolt hole spacing in the ply scheme; Convert the pressure of the engine case into tensile load, and determine 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 in the ply layup scheme , and analyze to obtain the separation load of the metal pressing plate ; ; If the bolt tightening force in the ply layup plan is greater than or equal to the separation load, the sealing meets the requirements, otherwise the sealing does not meet the requirements.

3. The design method of the flanging structure of the bolt-connected laminated composite material split casing according to claim 1, characterized in that The radius value range of the fillet area is , where is the radius of the fillet area, is the thickness of the flanging structure of the engine case when starting up.

4. The design method of the flanging structure of the bolt-connected laminated composite split compressor casing according to claim 3, wherein, The thickness of the flanging structure of the engine case takes values in the range of .

5. The design method of the flanging structure of the bolt-connected laminated composite material for the split casing according to claim 1, characterized in that The ply layup method of each ply layup plan satisfies: the ply angles form a symmetric structure according to 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, 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 each other.

6. A bolt - connected laminate composite butt - opening casing flanging structure design system, characterized in that, Including: A value range determination module, which is used to determine the value ranges of the height, thickness, fillet radius of the flanging structure of the split casing, and the thickness of the metal pressing plate according to the design dimension requirements 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 cushion strip arranged between the bolt head and the flanging structure; A model construction module, which is used to perform ply design on the flanging structure by using fiber-reinforced composite materials according to the value ranges of the height, thickness, radius of the fillet area, and thickness of the metal pressing plate of the split casing flanging structure, obtain ply schemes with combinations of 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 of the ply schemes; A simulation analysis module, which is used to obtain the ply schemes that meet the requirements of stable stress concentration factor at the hole edge and stable stress concentration factor between holes in the ply scheme through simulation analysis of each finite element analysis model; the basis for judging that the stress concentration factor at the hole edge is stable is that as the bolt hole edge distance 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 that the stress concentration factor between holes is stable 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 the ply schemes that meet 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, the maximum design pressure load of the split casing, the size parameters of the split casing, and the bolt hole spacing in the ply schemes that meet the requirements of stable stress concentration factor at the hole edge and stable stress concentration factor between holes; A second screening module, which is used to select the 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 requirements as the design scheme of the ply composite split casing flanging structure with bolt connection.

7. The bolted connection layup composite material butt joint casing flanging structure design system according to claim 6, characterized in that The first screening module includes: The first analysis unit is configured to analyze and obtain the pressure-converted tensile load of the split casing 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 scheme , where is the casing radius, is the bolt hole spacing in the ply scheme; A second analysis unit, configured to analyze and obtain the separation load of the metal pressing plate according to the converted tensile load of the casing pressure and the distances from the center of the bolt hole in the ply layup scheme to the inner edge of the flange and the distance from the center of the bolt hole to the outer edge of the flange ; ; 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 separation load in the ply scheme. When the bolt tightening force in the ply 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.

8. The bolted connection layup composite material facing-opening casing flanging structure design system according to claim 6, characterized in that, 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, is the thickness of the flanging structure of the engine casing.

9. The bolt connection layup composite material butt joint casing flanging structure design system according to claim 8, characterized in that In the value range determination module, the thickness of the casing flanging structure has a value range of .

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