A curved fiber metal cylindrical shell, an optimization design method and model thereof

Abstract

This invention discloses a curved fiber metal cylindrical shell, its optimization design method, and model. This invention relates to the field of composite material rotation modeling, design, and manufacturing technology. The specific steps of the method include: 1) determining the layup of the curved fiber layers and metal / alloy layers of the curved fiber metal cylindrical shell; 2) setting key design variables to describe the curved fiber trajectory; 3) generating initial samples using the Latin hypercube sampling method and calculating the critical buckling load of the curved fiber metal cylindrical shell under external loads using ANSYS finite element analysis software; 4) establishing a Kriging surrogate model using the DACE toolbox in MATLAB; and 5) determining the optimal design value of the fiber angle in the curved fiber trajectory using a two-layer optimization algorithm. Compared to traditional composite material shells and metal shells, the curved fiber metal cylindrical shell optimized by this invention exhibits superior buckling resistance.

Description

Technical Field

[0001] This invention relates to the field of composite material rotation modeling, design, and manufacturing technology. In particular, it relates to a curved fiber-reinforced metal cylindrical shell, its optimized design method, and model. Background Technology

[0002] In traditional composite material research, linear fiber composite structures have always been a focus. These materials are widely used in various engineering fields, including aerospace vehicles, marine engineering pipelines, industrial pressure vessels, and automobile manufacturing, due to their high specific strength, high specific stiffness, good thermal insulation and temperature regulation properties, good fatigue resistance, and excellent vibration damping performance. However, as load conditions and operating environments become increasingly complex, their limitations in practical applications are becoming more and more apparent. These structures are manufactured using uniformly spaced linear fibers, resulting in a constant overall structural stiffness, which fails to fully realize the material's potential.

[0003] To address this issue, there are currently two main approaches: the first is to utilize curved fibers to achieve variable stiffness design in the structure; the second is to use fiber-reinforced metal laminates, which are essentially straight fiber-reinforced metal structures composed of alternating layers of metal / alloy and straight fibers. While curved fiber composite structures can improve the mechanical properties of the structure to some extent, they still fall short in terms of impact resistance and material toughness. Furthermore, although existing fiber-reinforced metal laminate structures have certain advantages in damage tolerance and impact resistance, their fiber layup is mostly straight fibers, resulting in a relatively uniform overall stiffness distribution. This limits the applicability of the material and hinders the wider application of its high specific strength, high specific stiffness, thermal insulation and temperature regulation properties, fatigue resistance, and vibration damping performance in engineering fields.

[0004] Therefore, in view of the shortcomings of existing structures in coping with increasingly complex load conditions and working environments, there is an urgent need to develop and design a new structural form and its design and manufacturing method. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a curved fiber metal cylindrical shell, its optimized design method, and model. Compared with traditional composite material shells and metal shells, the curved fiber metal cylindrical shell obtained by the optimized design of this invention combines the advantages of curved fibers and metal laminates, and has superior mechanical properties.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: In its first aspect, the present invention provides a design method for a curved fiber metal cylindrical shell, wherein the curved fiber metal cylindrical shell is formed by alternating layers of curved fibers and metal layups, and the method includes the following steps: S1. Determine the laying pattern of the curved fiber layer and the metal layer of the curved fiber metal cylindrical shell; S2. Set design variables for describing the laying trajectory of the curved fibers in the curved fiber layer: S2-1. The laying trajectory of the curved fibers is simply referred to as the curved fiber trajectory. Define the fiber angle θ as follows: On the surface of the curved fiber metal cylindrical shell where the curved fiber trajectory is located, draw an axial straight line intersecting the curved fiber trajectory. At the intersection of the curved fiber trajectory and this straight line, draw a tangent to the curved fiber trajectory. The angle between this tangent and this straight line is the fiber angle θ at this intersection; S2-2. Divide the curved fiber metal cylindrical shell vertically in the middle into two semi-cylindrical shells. Divide each semi-cylindrical shell axially from top to bottom into four regions. The entire cylindrical shell is correspondingly divided into eight symmetrically left and right regions. Each region is further axially divided into M narrow strips, and it is set that the same narrow strip has the same fiber angle; Dividing a semi-cylindrical shell into four regions requires five circumferential angles {α1, α2, α3, α4, α5} = {0°, 45°, 90°, 135°, 180°}. Define the fiber angles θ(α) = {T1, T2, T3, T4, T5} at specific circumferential angles as design variables; S2-3. Calculate the fiber angle through the following formula: ; where, i represents the region, θ i,k is the fiber angle at the k-th narrow strip in the i-th region; T i+1 and T i are the fiber angles at the upper and lower boundaries of the i-th region; α i+1 and α i are the circumferential angles at the upper and lower boundaries of the i-th region; α i,k is the circumferential angle at the k-th narrow strip in the i-th region.

[0007] S3. According to the fiber angles determined as design variables in step S2, use the Latin hypercube sampling method to generate several groups of initial samples, and calculate the critical buckling load of the curved fiber metal cylindrical shell under external loads; S4. Establish a Kriging surrogate model; S5. Use the double-layer optimization algorithm to determine the optimal design values of the fiber angles in the curved fiber trajectory, and complete the design of the curved fiber metal cylindrical shell.

[0008] Preferably, in step S3, the number of generated initial samples is 50 - 200 groups.

[0009] Preferably, in step S3, the critical buckling load of the curved fiber metal cylindrical shell under external load is calculated using ANSYS finite element analysis software.

[0010] Preferably, step S4 specifically involves: establishing a Kriging proxy model using the DACE toolbox in MATLAB.

[0011] Preferably, the two-layer optimization algorithm in step S5 includes the following specific steps: S5-1, First Layer Optimization: S5-1-1. Use the Monte Carlo method to generate several sets of random samples; S5-1-2. Based on the current Kriging surrogate model, predict the response value and variance of the critical buckling load of the random sample generated in step S5-1-1, and select the sample with the largest response value and the largest variance. S5-1-3. Apply the particle swarm optimization algorithm to determine the optimal sample; S5-1-4. Take the sample with the largest response value, the sample with the largest variance obtained in step S5-1-2, and the optimal sample obtained in S5-1-3 as new samples. Use ANSYS finite element analysis software to calculate the true response value of the critical buckling load of the new samples and update the Kriging proxy model. S5-1-5. During the iteration process, if the difference between the true response values ​​of the optimal sample in two adjacent iterations is less than the set threshold ε, then proceed to step S5-1-6; otherwise, return to step S5-1-2. S5-2, Second Layer Optimization: S5-1-6, Set i=1; S5-1-7. Optimize the i-th design variable and fix the other four design variables. S5-1-8. Based on the current Kriging surrogate model, predict the response value and variance of the Monte Carlo sample, and select the sample with the largest response value and the largest variance. S5-1-9. Apply the particle swarm optimization algorithm to determine the optimal sample; S5-1-10. Take the sample with the largest response value, the sample with the largest variance obtained in step S5-1-8, and the optimal sample obtained in step S5-1-9 as new samples. Use ANSYS finite element analysis software to calculate the true response value of the critical buckling load of the new samples and update the Kriging proxy model. S5-1-11. During the iteration process, if the difference between the true response values ​​of the optimal sample in two adjacent iterations is less than the set threshold ε, then proceed to step S5-1-12; otherwise, return to step S5-1-8. S5-1-12, Set i = i + 1; S5-1-13. If i > 5, then proceed to step S5-1-14; otherwise, return to step S5-1-7. S5-1-14. Output the currently obtained optimal solution as the optimal design value for the fiber angle.

[0012] Preferably, the number of random samples in step S5-1-1 is 25,000-100,000 groups, and the threshold ε in steps S5-1 and S5-2 is 0.005-0.02.

[0013] Preferably, the number of initial samples generated in step S3 is 100, the number of random samples in step S5-1-1 is 50,000, and the threshold ε in steps S5-1 and S5-2 is 0.01.

[0014] Preferably, the raw material for the metal layup is a single metal or an alloy containing at least two metals.

[0015] In a second aspect, the present invention provides a design model for a curved fiber metal cylindrical shell, wherein the model employs the method described above for optimizing the design of the curved fiber metal cylindrical shell.

[0016] A third aspect of the present invention provides a curved fiber metal cylindrical shell, which is designed using the method described above.

[0017] The beneficial effects of this invention are: 1) This invention proposes a design method for a curved fiber metal cylindrical shell and a curved fiber metal cylindrical shell obtained by the optimized design method. The curved fiber metal cylindrical shell is composed of alternating layers of metal / alloy and curved fiber, exhibiting excellent buckling resistance.

[0018] 2) The design method of the present invention provides a single three-sample addition strategy for updating the Kriging surrogate model, which improves the update efficiency and prediction accuracy of the Kriging surrogate model.

[0019] 3) The design method of this invention provides a two-layer optimization algorithm. The first layer uses the traditional particle swarm optimization algorithm to obtain a coarse optimization solution; the second layer fixes the remaining design variables and optimizes each design variable sequentially until it approaches the global optimum. This two-layer optimization approach effectively avoids the optimization result from getting trapped in local optima. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a curved fiber-reinforced metal cylindrical shell; Figure 2a This is a schematic diagram of the curved fiber layer of a curved fiber metal cylindrical shell; Figure 2bIt is a diagram of the curved fiber trajectory of a curved fiber metal cylindrical shell; Figure 3 This is a diagram showing the circumferential node arrangement of a curved fiber-reinforced metal cylindrical shell. Figure 4 It is a coordinate diagram of the curved fiber trajectory of a curved fiber metal cylindrical shell; Figure 5 This is a flowchart of a two-layer optimization algorithm; Figure 6 It is a finite element model diagram of a cylindrical shell; Figure 7 This is a schematic diagram of the forces acting on a cylindrical shell under bending moment load; Figure 8a It is a buckling mode diagram of a quasi-isotropic cylindrical shell; Figure 8b It is a buckling mode diagram of a straight fiber cylindrical shell; Figure 8c It is a buckling mode diagram of a linear fiber metal cylindrical shell; Figure 8d It is a buckling mode diagram of a curved fiber cylindrical shell; Figure 8e It is a buckling mode diagram of a curved fiber-reinforced metal cylindrical shell; Figure 8f It is a buckling mode diagram of a metal / alloy cylindrical shell. Detailed Implementation

[0021] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0023] This invention provides a design method for a curved fiber metal cylindrical shell, which is formed by alternating layers of curved fibers and metal layups. The method includes the following steps: S1. Determine the stacking method of the curved fiber layer and metal layer of the curved fiber metal cylindrical shell; S2. Set design variables to describe the layup trajectory of curved fibers in the curved fiber layer: The key to the curved fiber layer lies in describing the curved fiber trajectory. Once a curved fiber trajectory is determined, translating this trajectory along the axial direction (x-direction) of the cylindrical shell generates the curved fiber layer. That is, the fiber angle θ of the curved fiber trajectory only varies along the circumferential direction (α-direction) and is independent of the axial direction (x-direction). If the surface of the cylindrical shell is divided into several narrow strips, then each strip has the same fiber angle θ, which is only related to the circumferential coordinate α. To accurately describe the curved fiber trajectory, half of the cylindrical shell is divided into four regions from top to bottom, resulting in eight regions for the entire cylindrical shell. Each region is further subdivided into M narrow strips, all of which have the same fiber angle. To simplify the problem, it is assumed that the cylindrical shell is symmetrical from left to right, and the fiber angles on both sides are symmetrical; therefore, only half of the cylindrical shell is analyzed. Specifically, the method used in this step is as follows: S2-1. The laying trajectory of this curved fiber is simply referred to as the curved fiber trajectory, and the fiber angle θ is defined as follows: Draw a straight line along the axial direction on the surface of the curved fiber metal cylindrical shell where the curved fiber trajectory is located. Draw a tangent line to the curved fiber trajectory through the intersection point of the curved fiber trajectory and the straight line. The angle between the tangent line and the straight line is the fiber angle θ at the intersection point. S2-2. The curved fiber metal cylindrical shell is vertically divided into two semi-cylindrical shells. The semi-cylindrical shells are divided into four regions along the axial direction from top to bottom. The entire cylindrical shell is divided into eight symmetrical regions. Each region is further divided into M narrow strips along the axial direction. The same narrow strip is set to have the same fiber angle. Dividing half of the cylindrical shell into four regions requires five circumferential angles {α1, α2, α3, α4, α5} = {0°, 45°, 90°, 135°, 180°}. The fiber angle θ(α) = {T1, T2, T3, T4, T5} at a specific circumferential angle is defined as a design variable. S2-3. Once the fiber angle at the node is determined, the fiber angle θ at the narrow strip between adjacent nodes is... i,k The fiber angle can be obtained through linear interpolation, specifically calculated using the following formula: ; Where i represents the region, θ i,k T represents the fiber angle at the k-th narrow strip in the i-th region; i+1 and T i α represents the fiber angle at the upper and lower boundaries of the i-th region. i+1 and α iLet α be the circumferential angle at the upper and lower boundaries of the i-th region; i,k Let be the circumferential angle at the k-th narrow strip in the i-th region.

[0024] S3. Based on step S2, determine the fiber angle as the design variable, generate several initial samples using the Latin hypercube sampling method, and calculate the critical buckling load of the curved fiber metal cylindrical shell under external load. S4. Establish the Kriging agent model; S5. Use a two-layer optimization algorithm to determine the optimal design value of the fiber angle in the curved fiber trajectory, and complete the design of the curved fiber metal cylindrical shell.

[0025] In a preferred embodiment, in step S3, the number of initial samples generated is 50-200 groups, such as 50, 100, 150, 200 groups, etc., more preferably 100 groups.

[0026] In a preferred embodiment, in step S3, the critical buckling load of the curved fiber metal cylindrical shell under external load is calculated using ANSYS finite element analysis software.

[0027] In a preferred embodiment, step S4 specifically involves: establishing a Kriging proxy model using the DACE toolbox in MATLAB.

[0028] In a preferred embodiment, the two-layer optimization algorithm in step S5 includes the following specific steps: S5-1, First Layer Optimization: S5-1-1. Use the Monte Carlo method to generate several sets of random samples; S5-1-2. Based on the current Kriging surrogate model, predict the response value and variance of the critical buckling load of the random sample generated in step S5-1-1, and select the sample with the largest response value and the largest variance. S5-1-3. Apply the particle swarm optimization algorithm to determine the optimal sample; S5-1-4. Take the sample with the largest response value, the sample with the largest variance obtained in step S5-1-2, and the optimal sample obtained in S5-1-3 as new samples. Use ANSYS finite element analysis software to calculate the true response value of the critical buckling load of the new samples and update the Kriging proxy model. S5-1-5. During the iteration process, if the difference between the true response values ​​of the optimal sample in two adjacent iterations is less than the set threshold ε, i.e., |F cr new -F cr old If |<ε, then proceed to step S5-1-6; otherwise, return to step S5-1-2. Among them, F crnew F represents the current critical buckling load. cr old This represents the critical buckling load of the adjacent previous iteration; S5-2, Second Layer Optimization: S5-1-6, Set i=1; S5-1-7. Optimize the i-th design variable and fix the other four design variables. S5-1-8. Based on the current Kriging surrogate model, predict the response value and variance of the Monte Carlo sample, and select the sample with the largest response value and the largest variance. S5-1-9. Apply the particle swarm optimization algorithm to determine the optimal sample; S5-1-10. Take the sample with the largest response value, the sample with the largest variance obtained in step S5-1-8, and the optimal sample obtained in step S5-1-9 as new samples. Use ANSYS finite element analysis software to calculate the true response value of the critical buckling load of the new samples and update the Kriging proxy model. S5-1-11. During the iteration process, if the difference between the true response values ​​of the optimal sample in two adjacent iterations is less than the set threshold ε, then proceed to step S5-1-12; otherwise, return to step S5-1-8. S5-1-12, Set i = i + 1; S5-1-13. If i > 5, then proceed to step S5-1-14; otherwise, return to step S5-1-7. S5-1-14. Output the currently obtained optimal solution as the optimal design value for the fiber angle.

[0029] In a preferred embodiment, the number of random samples in step S5-1-1 is 25,000-100,000 groups, such as 25,000, 50,000, 100,000, etc., and more preferably 50,000.

[0030] In a preferred embodiment, the threshold ε in steps S5-1 and S5-2 is 0.005-0.02, such as 0.005, 0.01, 0.015, 0.02, etc., and more preferably 0.01.

[0031] In a preferred embodiment, the raw material for the metal layup is a single metal or an alloy containing at least two metals, such as aluminum or an aluminum alloy.

[0032] The present invention also provides a design model for a curved fiber metal cylindrical shell, which uses the method described above to optimize the design of the curved fiber metal cylindrical shell.

[0033] In a preferred embodiment, the design model can be described as follows:

[0034] Among them, F cr The critical buckling load is represented by the fiber angle θ(α) = {T1, T2, T3, T4, T5} at the circumferential node of the curved fiber layer, which are five design variables.

[0035] Specifically, the design model is described as: maximizing the critical buckling load F cr The objective function is defined by the fiber angles θ(α) = {T1, T2, T3, T4, T5} at the circumferential nodes of the curved fiber layer, which are the five design variables. The values ​​of the five design variables range from 0° to 90°.

[0036] The present invention also provides a curved fiber metal cylindrical shell, which is designed using the method described above.

[0037] The above is the general concept of the present invention. Based on this, detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0038] Example 1: A curved fiber-reinforced metal cylindrical shell and its optimized design method In this embodiment, a balanced and symmetrical quasi-isotropic composite material structure is first considered, with the specific layup sequence as follows: The total number of layers is 16. This represents an 8-layer ply structure, where 's' indicates a symmetrical ply, which is... / β).

[0039] Among them, the ply angles β, θ and All values ​​are selected from [0°, ±45°, 90°], and 4 can be obtained through system combination. 3 =64 different ply layups. The buckling performance of these 64 ply layups was calculated using ANSYS finite element analysis software. The results show that the ply layup sequence [90° / 45° / 0° / -45° / -45° / 0° / 45° / 90°] is optimal. s The corresponding critical buckling load is the largest. β, θ, and The values ​​of are 90°, 45°, and 0°. Therefore, it is determined as the optimal layup scheme for the quasi-isotropic structure and used as a benchmark model for comparison with other structural forms.

[0040] In the ply layup design of this type of cylindrical shell, the ±45° ply angle is typically considered a key design variable. Therefore, only θ is retained as a design variable here. In straight fiber and curved fiber cylindrical shells, β and They are fixed at 90° and 0° respectively. In the cylindrical shells of straight fiber metal and curved fiber metal, β and All are made of metal Al. Six different cylindrical shell structures are shown in Table 1.

[0041] Table 1. Six different structural forms of cylindrical shells

[0042] Obviously, the key to this embodiment lies in finding the optimal ply angle θ under different structural forms, thereby obtaining the maximum critical buckling load. As shown in Table 1, straight fiber and straight fiber cylindrical metal shells have only one design variable θ, which ranges from 0° to 90°. For curved fiber and curved fiber cylindrical metal shells, the curved fiber trajectory only varies along the circumferential direction. To simplify the problem solution, only the fiber angles θ(α) = {T1, T2, T3, T4, T5} at five circumferential nodes are considered as design variables.

[0043] For straight fibers and straight fiber metal cylindrical shells, the following optimization model is proposed:

[0044] Among them, F cr The critical buckling load is represented by θ, which is the fiber angle of the straight fiber layer. This optimization problem contains only one design variable.

[0045] The optimization model is specifically described as: maximizing the critical buckling load F cr The objective function is defined by the fiber angle θ of the straight fiber layer, which is a design variable ranging from 0° to 90°. Similarly, for curved fibers and curved fiber metal cylindrical shells, the optimization model is as follows:

[0046] Among them, F cr The critical buckling load is represented by the fiber angle θ(α) = {T1, T2, T3, T4, T5} at the circumferential node of the curved fiber layer, which are five design variables.

[0047] The optimization model is specifically described as: maximizing the critical buckling load F cr The objective function is defined by the fiber angles θ(α) = {T1, T2, T3, T4, T5} at the circumferential nodes of the curved fiber layer, which are the five design variables. The values ​​of the five design variables range from 0° to 90°.

[0048] In this embodiment, all cylindrical shells have a diameter and length of 0.4572 m, a total of 16 layers, and a single layer thickness of 0.127 mm. The material properties of the different cylindrical shells are shown in Table 2, where the fiber material is AS4D / 9310 carbon fiber / epoxy resin composite material, and the metal material is Al / 6061 aluminum alloy.

[0049] Table 2. Main material properties of cylindrical shells

[0050] When calculating the critical buckling load of a cylindrical shell under external load using ANSYS finite element analysis software, the SHELL181 finite element was used. The entire cylindrical shell was divided into 138 narrow strips, and the corresponding finite element model is as follows: Figure 6 As shown.

[0051] The force diagram of a cylindrical shell under bending moment load is shown below. Figure 7 As shown in Table 3, the optimization designs of six different cylindrical shell structures were carried out using ANSYS finite element analysis software, the DACE toolbox in MATLAB, and a two-layer optimization algorithm. The optimization results are shown in Table 3 and 4. Figures 8a-8f As shown (where the percentage performance improvement specifically refers to the increase in critical buckling load relative to the "quasi-isotropic" structural form).

[0052] Table 3 Critical buckling loads of cylindrical shells with different structural forms

[0053] As shown in Table 3, the critical buckling loads of the quasi-isotropic and metal / alloy cylindrical shells are 97.42 kN·m and 139.91 kN·m, respectively. For the straight fiber cylindrical shell, the critical buckling load is the largest at θ = 46.04°, at 97.48 kN·m. Compared with the quasi-isotropic cylindrical shell, its maximum critical buckling load is slightly increased, with an increase of only 0.06%. When θ = 70.41°, the critical buckling load of the straight fiber metal cylindrical shell reaches its maximum, at 116.38 kN·m. That is to say, the maximum critical buckling load of the straight fiber metal cylindrical shell is significantly improved compared with the quasi-isotropic cylindrical shell, with a performance improvement of 19.46%. The main reason is that the straight fiber metal cylindrical shell combines the advantages of straight fiber composite materials and metal / alloy materials, which can significantly improve the mechanical properties of the structure.

[0054] For the curved fiber cylindrical shell, the fiber angles at the five circumferential nodes are θ(α) = {0°, 0.91°, 11.82°, 40.91°, 56.36°}, corresponding to a maximum critical buckling load of 120.37 kN·m. Compared with the quasi-isotropic cylindrical shell, the performance of the curved fiber cylindrical shell is improved by 23.56%. The results show that the fiber angle in the tension region is around 1°, which can effectively resist the tensile stress in this region. The fiber angle in the compression region is around 41°, which is used to resist the compressive stress in this region. The fiber angle at the point of maximum tensile stress is approximately 0°, while the fiber angle at the point of maximum compressive stress is approximately 56°.

[0055] For the curved fiber-reinforced metal cylindrical shell, when θ(α) = {0°, 0°, 0°, 44.55°, 75.45°}, the maximum critical buckling load of the structure is 152.63 kN·m. Compared with the quasi-isotropic cylindrical shell, its performance is improved by 56.67%. It can be seen that the fiber angles in the tension region are all 0°, which fully utilizes the axial tensile strength of the fiber composite material. In the compression region, the metal / alloy material can fully utilize its excellent compressive strength. The design of the curved fiber-reinforced metal cylindrical shell fully explores the potential of curved fiber composite materials and effectively combines the characteristics of metal / alloy materials, further improving the comprehensive mechanical properties of the structure. The results show that among the six structural forms compared, the curved fiber-reinforced metal cylindrical shell proposed in this invention performs the best.

[0056] from Figures 8a-8f It can be seen that buckling mainly occurs in the compression zone of cylindrical shells with different structural forms. The results show that the buckling distribution range of curved fiber and curved fiber-reinforced metal cylindrical shells is significantly larger than that of other structural forms, indicating that curved fiber design can make the structure more uniformly stressed, thereby improving its buckling resistance. Simultaneously, due to the excellent compressive strength of metal / alloy materials, the stress distribution of curved fiber-reinforced metal cylindrical shells is more uniform, further enhancing their buckling resistance. Therefore, curved fiber-reinforced metal cylindrical shells can effectively leverage the synergistic effect of curved fiber composite materials and metal / alloy materials, significantly improving the mechanical properties of thin-walled structures.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A design method for a curved fiber metal cylindrical shell, wherein the curved fiber metal cylindrical shell is formed by alternating layers of curved fibers and metal layups, characterized in that, The method includes the following steps: S1. Determine the stacking method of the curved fiber layer and metal layer of the curved fiber metal cylindrical shell; S2. Set design variables to describe the laying trajectory of curved fibers in the curved fiber layer; S3. Based on step S2, determine the fiber angle as the design variable, generate several initial samples using the Latin hypercube sampling method, and calculate the critical buckling load of the curved fiber metal cylindrical shell under external load. S4. Establish the Kriging agent model; S5. Use a two-layer optimization algorithm to determine the optimal design value of the fiber angle in the curved fiber trajectory, and complete the design of the curved fiber metal cylindrical shell.

2. The design method for the curved fiber metal cylindrical shell according to claim 1, characterized in that, Step S2 includes the following steps: S2-1. The laying trajectory of curved fibers is simply referred to as the curved fiber trajectory, and the fiber angle θ is defined as follows: Draw a straight line along the axial direction on the surface of the curved fiber metal cylindrical shell where the curved fiber trajectory is located. Draw a tangent line to the curved fiber trajectory through the intersection point of the curved fiber trajectory and the straight line. The angle between the tangent line and the straight line is the fiber angle θ at the intersection point. S2-2. The curved fiber metal cylindrical shell is vertically divided into two semi-cylindrical shells. The semi-cylindrical shells are divided into four regions along the axial direction from top to bottom. The entire cylindrical shell is divided into eight symmetrical regions. Each region is divided into M narrow strips along the axial direction. The same narrow strip is set to have the same fiber angle. Dividing half of the cylindrical shell into four regions requires five circumferential angles {α1, α2, α3, α4, α5} = {0°, 45°, 90°, 135°, 180°}. Define the fiber angle θ(α) = {T1, T2, T3, T4, T5} at the circumferential angles as design variables. S2-3. Calculate the fiber angle using the following formula: ； Where i represents the region, θ i,k T represents the fiber angle at the k-th narrow strip in the i-th region; i+1 and T i α represents the fiber angle at the upper and lower boundaries of the i-th region. i+1 and α i Let α be the circumferential angle at the upper and lower boundaries of the i-th region; i,k Let be the circumferential angle at the k-th narrow strip in the i-th region.

3. The design method for the curved fiber metal cylindrical shell according to claim 2, characterized in that, In step S3, the number of initial samples generated is 50-200 sets; the critical buckling load of the curved fiber-reinforced metal cylindrical shell under external load is calculated using ANSYS finite element analysis software.

4. The design method for the curved fiber metal cylindrical shell according to claim 1, characterized in that, In step S4, the Kriging surrogate model is established using the DACE toolbox in MATLAB.

5. The design method for the curved fiber metal cylindrical shell according to claim 3, characterized in that, The two-level optimization algorithm in step S5 includes the following steps: S5-1, First-level optimization: S5-1-1. Use the Monte Carlo method to generate several sets of random samples; S5-1-2. Based on the current Kriging surrogate model, predict the response value and variance of the critical buckling load of the random sample generated in step S5-1-1, and select the sample with the largest response value and the largest variance. S5-1-3. Apply the particle swarm optimization algorithm to determine the optimal sample; S5-1-4. Take the sample with the largest response value, the sample with the largest variance obtained in step S5-1-2, and the optimal sample obtained in S5-1-3 as new samples. Use ANSYS finite element analysis software to calculate the true response value of the critical buckling load of the new samples and update the Kriging proxy model. S5-1-5. During the iteration process, if the difference between the true response values ​​of the optimal sample in two adjacent iterations is less than the set threshold ε, then proceed to step S5-1-6; otherwise, return to step S5-1-2. S5-2, Second Layer Optimization: S5-1-6, Set i=1; S5-1-7. Optimize the i-th design variable and fix the other four design variables. S5-1-8. Based on the current Kriging surrogate model, predict the response value and variance of the Monte Carlo sample, and select the sample with the largest response value and the largest variance. S5-1-9. Apply the particle swarm optimization algorithm to determine the optimal sample; S5-1-10. Take the sample with the largest response value, the sample with the largest variance obtained in step S5-1-8, and the optimal sample obtained in step S5-1-9 as new samples. Use ANSYS finite element analysis software to calculate the true response value of the critical buckling load of the new samples and update the Kriging proxy model. S5-1-11. During the iteration process, if the difference between the true response values ​​of the optimal sample in two adjacent iterations is less than the set threshold ε, then proceed to step S5-1-12; otherwise, return to step S5-1-8. S5-1-12, Set i = i + 1; S5-1-13. If i > 5, then proceed to step S5-1-14; otherwise, return to step S5-1-7. S5-1-14. Output the currently obtained optimal solution as the optimal design value for the fiber angle.

6. The design method for the curved fiber metal cylindrical shell according to claim 5, characterized in that, The number of random samples in step S5-1-1 is 25,000-100,000 groups, and the threshold ε in steps S5-1 and S5-2 is 0.005-0.

02.

7. The design method for the curved fiber metal cylindrical shell according to claim 6, characterized in that, The initial sample size generated in step S3 is 100 groups, the random sample size in step S5-1-1 is 50,000 groups, and the threshold ε in steps S5-1 and S5-2 is 0.

01.

8. The design method for the curved fiber metal cylindrical shell according to claim 1, characterized in that, The raw material for the metal layup is a single metal or an alloy containing at least two metals.

9. A design model for a curved fiber-reinforced metal cylindrical shell, characterized in that, The model employs the method described in any one of claims 1-8 for the optimized design of curved fiber metal cylindrical shells.

10. A curved fiber metal cylindrical shell, characterized in that, It is designed using the method described in any one of claims 1-8.

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