A topology optimization method for component weight reduction and local skeletal reinforcement

Abstract

The present invention provides a topology optimization method for component weight reduction and local skeleton-like reinforcement, which relates to the technical field of large complex components in aerospace. The method specifically comprises: constructing a blank model of the component to be optimized and performing finite element analysis; optimizing the blank model of the component to be optimized using a variable density method, obtaining the retained density distribution of the blank model and reducing the weight of the blank model to obtain a preliminary weight-reduced model of the component to be optimized; dividing the preliminary weight-reduced model into a stress concentration area and a matrix through finite element analysis; then extracting the geometric features of the stress concentration area to split the stress concentration area into several local structures, and performing a reinforced skeleton-like design on each of the local structures to generate an adaptive lattice structure for each local structure; performing Boolean summation on the adaptive lattice structures and matrices of all local structures to complete the topology optimization of the component to be optimized. This achieves the function-structure integrated manufacturing of complex components.

Description

Technical Field

[0001] The present invention relates to the technical field of large and complex aerospace components, and in particular to a topology optimization method for component weight reduction and local skeletal reinforcement. Background Art

[0002] To achieve long-range strike and a high thrust-to-weight ratio, aerospace components are developing towards integrated and holistic design. Using additive manufacturing technology to achieve lightweight design of complex components has become a major concern. Additive manufacturing, also known as 3D printing, is a process based on digital three-dimensional modeling that integrates computer-aided design, material processing, and forming technologies. It uses metal and non-metallic materials to rapidly fabricate complex workpieces from the bottom up, following the principle of discrete-accumulation layer-by-layer manufacturing. Topology optimization, a mathematical method that designs structural distribution within a given design area based on load conditions, constraints, and performance indicators, can effectively help designers achieve lightweight structures. Topology optimization computational methods include homogenization, variable density, evolutionary structural optimization (ESO), and level set methods. However, research has also found that weight reduction through topology optimization is often accompanied by load redistribution, resulting in sudden increases in local loads and reduced system stability and reliability, thus limiting its application in critical load-bearing structures.

[0003] Currently, traditional approaches to structural strengthening still focus on uniformly strengthening materials. These methods primarily include heat treatment strengthening, deformation processing strengthening, and composite material strengthening. Heat treatment processes can improve alloying element segregation and eliminate internal stresses, thereby achieving strengthening. However, due to the inverse strength-toughness relationship, the increase in strength during heat treatment is often accompanied by a decrease in ductility. Cold working deformation methods, such as rolling, extrusion, forging, and friction stir processing, manipulate microstructure uniformity and refine grains by introducing dislocations, thereby improving the mechanical properties of the structure. However, this approach is not suitable for topological components with numerous hollow structures. Composite material strengthening involves introducing a secondary phase into the material, distributing the reinforcing phase in a dispersed or agglomerated manner within the matrix, thereby enhancing strength while retaining the excellent properties of the matrix itself. However, these approaches all have limitations for large, complex, and load-bearing structures with specific load conditions. Summary of the Invention

[0004] In response to the above-mentioned shortcomings of the existing technology, the present invention is based on topological optimization theory and load distribution, and utilizes local skeleton-like reinforcement means to propose a topological optimization method for component weight reduction and local skeleton-like reinforcement, aiming to achieve simultaneous weight reduction and reinforcement, and ultimately realize the functional-structural integrated manufacturing of complex components.

[0005] The present invention proposes a topology optimization method for component weight reduction and local skeletal reinforcement, which includes the following steps:

[0006] Step 1: Construct a blank model of the component to be optimized and perform finite element analysis on the blank model to generate a stress distribution cloud map of the blank model;

[0007] Step 2: Based on the stress distribution cloud map of the blank model, the variable density method is used to optimize the blank model of the component to be optimized, the retained density distribution of the blank model is obtained, and the blank model is weighted to obtain a preliminary weight-reduced model of the component to be optimized;

[0008] Step 3: Perform finite element analysis on the preliminary weight reduction model of the component to be optimized, generate a stress distribution cloud map of the preliminary weight reduction model, and divide the preliminary weight reduction model into a stress concentration area and a matrix according to the generated stress distribution cloud map;

[0009] Step 4: Extract geometric features of the stress concentration area of ​​the preliminary weight reduction model, and split the stress concentration area into several local structures based on the extracted geometric features;

[0010] Step 5: Perform enhanced skeleton design on several local structures to generate adaptive lattice structures for each local structure;

[0011] Step 6: Perform Boolean summation on the adaptive lattice structures of all local structures and the matrix in the preliminary weight reduction model to complete the topology optimization of the component to be optimized;

[0012] The specific content of step 1 is: determining the component to be optimized, and constructing a blank model of the component to be optimized according to the design requirements of the component to be optimized;

[0013] The design requirements include: working environment requirements, workload requirements, dimensional accuracy requirements, motion law requirements and material selection requirements;

[0014] By meshing the blank model of the component to be optimized, the blank model is converted into a finite element model, and boundary constraints and load limits of the component to be optimized are applied to the obtained finite element model. The finite element analysis method is used to perform stress analysis on the finite element model to generate a stress distribution cloud map of the blank model;

[0015] The specific content of step 2 is: in the finite element model converted from the blank model, assigning an initial unit density to each mesh of the finite element model, defining an objective function and constraints, and constructing a density optimization model based on the objective function and constraints; wherein the objective function is to minimize component flexibility; and the constraints include: volume fraction constraint, strength constraint, and additive manufacturing constraint;

[0016] The density optimization model is expressed as:

[0017] Find:ρ i ,i=1,2,3,...,n;

[0018] Minimize: C(x)=F T u

[0019] stK(ρ i ,u)=F;

[0020] V fra ≤V0;

[0021] g s <ε,g v <ε;

[0022] 0≤ρ i ≤1

[0023] where ρ i represents the cell density of the i-th grid; n is the number of grids in the blank model; Minimize represents minimization; C(x) is the component flexibility; F is the static load; u is the displacement; T represents transposition; K is the global stiffness matrix; V fra is the volume fraction; V0 is the preset upper limit of the volume fraction; g s is the strength constraint; g v is the additive manufacturing constraint; ε is a constant, and ε is a positive number;

[0024] Applying boundary constraints and expected workloads to the finite element model, and iteratively optimizing the finite element model using a density optimization model, adjusting the cell density of each grid in each iteration to minimize the objective function and satisfy the constraints, thereby obtaining an optimized finite element model;

[0025] Set the retention density parameter. For any mesh in the optimized finite element model, if the cell density of the mesh is lower than the retention density parameter, the mesh is marked as a removed mesh; otherwise, the mesh is marked as a retained mesh. Use binarization to reassign values ​​to all removed and retained meshes, and generate the retention density distribution of the blank model based on the reassigned meshes.

[0026] In the optimized finite element model, all removed meshes are removed and replaced with holes. All retained meshes are solidified. All solidified parts are modeled based on the retained density distribution of the blank model to obtain a preliminary weight-reduced model of the component to be optimized.

[0027] The specific contents of step 3 are: meshing the preliminary weight reduction model of the component to be optimized, applying boundary constraints and load limits of the component to be optimized to the preliminary weight reduction model, and performing stress analysis on the preliminary weight reduction model using a finite element analysis method to generate a stress distribution cloud map of the preliminary weight reduction model;

[0028] Identifying a stress concentration portion of the preliminary weight reduction model based on a stress distribution cloud map of the preliminary weight reduction model, and locally partitioning the preliminary weight reduction model based on the identified stress concentration portion and the stress distribution cloud map of the preliminary weight reduction model, thereby dividing the preliminary weight reduction model into a stress concentration area and a matrix;

[0029] The method for locally partitioning the preliminary weight reduction model is as follows: obtaining the allowable stress intensity of the component to be optimized, and setting a high stress threshold σ according to the allowable stress intensity H and low stress threshold σ L , and σ H >σ L , all stress intensities in the preliminary weight reduction model higher than σ H The part is taken as the stress concentration area of ​​the preliminary weight reduction model; all stress intensities higher than σ in the preliminary weight reduction model are taken as the stress concentration area of ​​the preliminary weight reduction model; L and lower than σ H The part is taken as the coordinated deformation zone of the preliminary weight reduction model; all stress intensities in the preliminary weight reduction model below σ L The part is used as the stress stable area of ​​the preliminary weight reduction model; and the coordinated deformation area and the stress stable area of ​​the preliminary weight reduction model are used as the matrix of the preliminary weight reduction model;

[0030] The specific contents of step 4 are as follows: defining the length direction of the component to be optimized and obtaining the component length L, and extracting the geometric features of any cross section perpendicular to the defined length direction in the stress concentration area; wherein the geometric features include: cross section width W, cross section height H, and cross section great circle radius R;

[0031] Identify interfaces in the preliminary weight reduction model based on the stress distribution cloud map and the geometric features of each cross section in the preliminary weight reduction model, and use all identified interfaces to split the stress concentration area of ​​the preliminary weight reduction model into several local structures; and determine the structural type of each local structure based on the geometric features of the cross section in each local structure.

[0032] The structural types include: columnar structure, ring structure, plate structure, rod structure and beam structure; the columnar structure includes: solid cylinder and hollow cylinder;

[0033] When H>>R, the structure type of the structure where the cross section is located is defined as a columnar structure;

[0034] When H < R, define the structural type of the structure where the cross-section is located as a ring structure;

[0035] When L, W ≥ 3H, define the structural type of the structure where the cross-section is located as a plate structure;

[0036] When L / H > 5 and L / W > 5, define the structural type of the structure where the cross-section is located as a rod structure;

[0037] When the structure where the cross-section is located is composed of several rod structures, plate structures or column structures alone or in combination, define the structural type of the structure where the cross-section is located as a beam structure;

[0038] The specific content of step 5 is: For any local structure, select the enhanced skeletal design method for the local structure according to the structural type of the local structure. If the structural type of the local structure is a plate structure or a rod structure, use the enhanced skeletal design method based on the stepped load pattern to perform the enhanced skeletal design on the local structure; if the structural type of the local structure is a column structure or a ring structure, use the isotropic enhanced skeletal design method based on the stress nephogram and typical configuration to perform the enhanced skeletal design on the local structure; if the structural type of the local structure is a beam structure, use the enhanced skeletal design method based on the continuously varying load pattern to perform the enhanced skeletal design on the local structure;

[0039] Generate the adaptive lattice structure of each local structure according to the selected enhanced skeletal design method;

[0040] The process of using the enhanced skeletal design method based on the stepped load pattern to perform the enhanced skeletal design on the local structure is: For any local structure, extract the stress distribution data of the local structure from the stress distribution nephogram of the preliminary weight reduction model, and judge the stress type of the local structure as resisting tensile stress or bending stress; Select the lattice unit cell structure for the local structure according to the stress type of the local structure. Specifically: If the stress type of the local structure is resisting tensile stress, select the lattice unit cell structure dominated by tensile stress for the local structure; If the stress type of the local structure is bending stress, select the lattice unit cell structure dominated by bending stress for the local structure; Then generate the adaptive lattice structure of the local structure according to the selected lattice unit cell structure;

[0041] The lattice unit cell structure dominated by tensile stress refers to the lattice unit cell structure that satisfies b - 3j + 6 > 0; where b is the number of bars in the lattice unit cell structure; j is the number of nodes in the lattice unit cell structure;

[0042] The lattice unit cell structure dominated by bending stress refers to the lattice unit cell structure that satisfies b - 3j + 6 < 0;

[0043] The process of using the isotropic reinforcement skeleton design method based on stress cloud maps and typical configurations to perform reinforcement skeleton design on the local structure is as follows: for any local structure, the stress distribution form of the local structure is obtained according to the stress distribution cloud map of the preliminary weight reduction model, randomly distributed feature points are generated in the three-dimensional space inside the local structure, and different feature point densities are set according to the stress distribution form of the local structure, the feature point spacing at the maximum stress position is set to the minimum, and the feature point spacing increases as the stress decreases, and then an adaptive lattice structure of the local structure is generated according to the feature points in the three-dimensional space inside the local structure;

[0044] The process of the reinforced skeleton design based on the continuous gradient load mode is as follows: for any local structure, the stress distribution form of the local structure is obtained according to the stress distribution cloud map of the preliminary weight reduction model, and the length and diameter of the lattice beam arm are designed according to the stress distribution form of the local structure, so that the lattice beam arm length is the shortest and the diameter is the largest at the point of maximum stress. As the stress decreases, the lattice beam arm length gradually increases and the diameter gradually decreases, thereby generating an adaptive lattice structure with continuous gradient change for the local structure.

[0045] The beneficial effects of adopting the above technical solution are:

[0046] Based on the load distribution of components, the method of the present invention utilizes topology optimization technology to optimize the structure of complex models by reducing unnecessary materials in complex structures, thereby obtaining a lightweight model. Furthermore, the method of the present invention utilizes a lattice-based local skeletal reinforcement design based on stress distribution and geometric characteristics, which can make the designed structure more compatible with the stress conditions of the original component and more uniformly distribute the stress, thereby avoiding excessive local stress concentration in the lightweight model, which can lead to a decrease in the overall performance and stability of the structure. At the same time, through micro-area powder feeding technology, the local structural material is controlled to obtain a locally heterogeneous grid-based reinforcement structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a flow chart of a topology optimization method for component weight reduction and local skeletal reinforcement in this embodiment;

[0048] Figure 2 Schematic diagram of a rough model of an aircraft door rocker arm in this embodiment;

[0049] Figure 3 : is a stress distribution cloud diagram of the blank model of the hatch rocker arm in this embodiment;

[0050] Figure 4 Schematic diagram of the retained density distribution of the hatch rocker arm in this embodiment;

[0051] Figure 5Schematic diagram of a preliminary weight reduction model of the door rocker arm in this embodiment;

[0052] Figure 6 This is a stress distribution cloud diagram of the preliminary weight reduction model in this embodiment;

[0053] Figure 7 Schematic diagram of local partitioning based on stress distribution in this embodiment;

[0054] Figure 8 Schematic diagram of a partial partition of the hatch rocker arm in this embodiment;

[0055] Figure 9 Schematic diagram of five typical local structures based on geometric features in this embodiment;

[0056] Figure 10 This is a schematic diagram of a local structure separated from the stress concentration area of ​​the door rocker arm based on geometric features in this embodiment;

[0057] Figure 11 Schematic diagram of a typical stretching and bending-dominated lattice unit cell structure in this embodiment;

[0058] Figure 12 Schematic diagrams of adaptive lattice structures of different bone-enhancing designs in this embodiment; (a) is a schematic diagram of an adaptive lattice structure of a bone-enhancing design based on a stepped load mode; (b) is a schematic diagram of an adaptive lattice structure of an isotropic bone-enhancing design based on a stress cloud diagram and a typical configuration; (c) is a schematic diagram of an adaptive lattice structure of a bone-like design based on a continuous gradient load mode;

[0059] Figure 13 Schematic diagram of the structure of the reinforced skeleton-like design of the ear portion in this embodiment; (a) is a schematic diagram of the ear portion model; (b) is a stress distribution cloud diagram of the ear portion; (c) is a unit cell spatial distribution diagram of the ear portion; (d) is a schematic diagram of the gradient lattice structure of the ear portion;

[0060] Figure 14 Schematic diagram of the structure of the reinforced skeletal design of the ribs and flanges in this embodiment; (a) is a schematic diagram of the flange and rib model; (b) is a schematic diagram of the surface mesh reshaping of the flange and rib; (c) is a cloud diagram of the stress distribution of the flange and rib; (d) is a schematic diagram of the gradient rib structure of the flange and rib;

[0061] Figure 15Schematic diagram of the structure of the web portion with a reinforced skeleton-like design in this embodiment; (a) is a schematic diagram of the web portion model; (b) is a cloud diagram of the stress distribution of the web portion; (c) is a schematic diagram of the random distribution of spatial points in the web portion; and (d) is a schematic diagram of the three-dimensional gradient lattice structure of the web portion.

[0062] Figure 16 Schematic diagram of the local reinforced skeleton structure of the stress concentration area in the door rocker arm in this embodiment;

[0063] Figure 17 Schematic diagram of the principle of the LDM powder feeding system in this embodiment. DETAILED DESCRIPTION

[0064] For ease of understanding of the present application, the specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings and embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly and comprehensively understood.

[0065] For large and complex load-bearing components, structural properties, strength, stiffness, and reliability are all issues that must be considered. In actual service environments, it is rare for the load to be evenly distributed across the entire component. However, the uneven distribution of stress also provides designers with a window for topological optimization and weight reduction. At the same time, the demand for local high strength is also raised. Therefore, this embodiment proposes a topological optimization method for component weight reduction and local skeletal reinforcement. In order to ensure the mechanical reliability of the lightweight structure after topological optimization, the optimized stress concentration site is determined based on the stress distribution cloud map, and local skeletal reinforcement is proposed for the stress concentration site: different forms of lattice structures are designed for different structures, and the lattice structure is combined with the matrix to generate a composite skeletal-enhanced local structure. Finally, 3D printing technology is used to achieve integrated molding of the complex load-bearing structure.

[0066] This embodiment is a topology optimization method for component weight reduction and local skeletal reinforcement, such as Figure 1 As shown, the method includes the following steps:

[0067] Step 1: Construct a blank model of the component to be optimized and perform finite element analysis on the blank model to generate a stress distribution cloud map of the blank model.

[0068] The specific content of step 1 is: determining the component to be optimized, and constructing a blank model of the component to be optimized according to the design requirements of the component to be optimized.

[0069] The design requirements include: working environment requirements, workload requirements, dimensional accuracy requirements, motion law requirements and material selection requirements.

[0070] In this embodiment, for the component to be optimized, design requirements are proposed based on the actual service conditions of the component. Based on the actual working environment and load conditions of the component, that is, the environmental conditions of the component in actual use, such as temperature, humidity, corrosiveness, etc., are clarified, and the type and size of the load the component bears during service are determined, and lightweight materials that meet the strength requirements are selected. Based on the dimensional accuracy requirements and motion law requirements of the component, the initial structure and size design of the complex component is carried out by consulting the relevant component data to obtain the blank model of the component to be optimized; wherein the dimensional accuracy requirements are used to ensure the processing accuracy of the component, and the dimensional accuracy requirements include: dimensional tolerance, shape tolerance and parallelism tolerance. The motion law requirements refer to the kinematic requirements such as displacement, angular displacement and velocity of the specified point that the component needs to meet.

[0071] Take the aircraft door rocker arm as an example, which is a complex component. Figure 2 As shown, this embodiment consults relevant information based on the service conditions and working environment of the aircraft door rocker arm, obtains the door rocker arm lifting displacement range and load range, selects aluminum alloy as the rocker arm material, and uses 3D software to draw a blank model of the aircraft rocker arm that meets the size / tolerance based on the general tolerance HB5000-1999 for part processing.

[0072] By meshing the blank model of the component to be optimized, the blank model is converted into a finite element model, and boundary constraints and load limits of the component to be optimized are imposed on the obtained finite element model. The finite element analysis method is used to perform stress analysis on the finite element model to generate a stress distribution cloud map of the blank model.

[0073] In this embodiment, if Figure 3As shown in the figure, the resulting blank model is imported into mechanical simulation software, and the simulation software is used to perform targeted meshing of the blank model of the component to be optimized based on the loading position. Structural materials are defined. To simulate the various constraints to which the component is subject during actual operation, boundary constraints such as fixed constraints, support constraints, friction constraints, and contact constraints are applied to the boundaries of the blank model based on the component's actual operating conditions. This ensures that the model accurately reflects the actual operating conditions during the analysis. To ensure that the component still meets design requirements under the most unfavorable operating conditions, the load limit of the component during normal operation is applied based on a series of basic conditions that the component should meet under normal operation, such as the load environment, structural strength, stiffness, and deformability. The load limit is typically calculated by multiplying the applied load by a safety factor to ensure design conservatism and reliability. If the component's load environment is stable, the safety factor is selected between 1.1 and 1.2; if the component's load environment fluctuates violently, the safety factor is selected between 1.3 and 1.6. In this embodiment, according to the working conditions and corresponding working loads of the hatch rocker arm, hole A is fixed, and load limits are applied to holes B and C to generate a stress distribution cloud map of the blank model.

[0074] Step 2: Based on the stress distribution cloud map of the blank model, the variable density method is used to optimize the blank model of the component to be optimized, the retained density distribution of the blank model is obtained, and the blank model is weighted to obtain a preliminary weight-reduced model of the component to be optimized.

[0075] The specific content of step 2 is: in the finite element model converted from the blank model, an initial unit density is assigned to each grid of the finite element model, an objective function and constraints are defined, and a density optimization model is constructed based on the objective function and constraints; wherein the objective function is to minimize the flexibility of the component; and the constraints include: volume fraction constraint, strength constraint and additive manufacturing constraint.

[0076] In this embodiment, the initial density value of each grid unit is usually between 0 and 1. Figure 4 As shown in the figure, based on the variable density method and according to the flexibility principle of minimizing the objective function, additive manufacturing constraints are imposed with the upper limit of the structure volume fraction of 0.5 and the strength limit as constraints, that is, a minimum size constraint of 5mm, a symmetry constraint based on the YOZ plane, and a printing direction constraint along the positive direction of the Y axis are established.

[0077] The density optimization model is expressed as:

[0078]

[0079] where ρ irepresents the cell density of the i-th grid; n is the number of grids in the blank model; Minimize represents minimization; C(x) is the component flexibility; F is the static load; u is the displacement; T represents transposition; K is the global stiffness matrix; V fra is the volume fraction; V0 is the preset upper limit of the volume fraction; g s is the strength constraint; g v is the additive manufacturing constraint; ε is a constant and is a positive number.

[0080] Boundary constraints and expected workloads are applied to the finite element model, and the finite element model is iteratively optimized using a density optimization model. During each iteration, the cell density of each grid is adjusted to minimize the objective function and satisfy the constraints, thereby obtaining an optimized finite element model.

[0081] Set the retention density parameter. For any mesh in the optimized finite element model, if the cell density of the mesh is lower than the retention density parameter, the mesh is marked as a removed mesh; otherwise, the mesh is marked as a retained mesh. Binarization processing is used to reassign values ​​to all removed meshes and retained meshes respectively, and the retention density distribution of the blank model is generated based on the reassigned meshes.

[0082] In this embodiment, the retention density parameter is set to 0.7. For any grid in the optimized blank model, if the cell density of the grid is lower than the retention density parameter, the cell density of the grid is assigned to 0; otherwise, the cell density of the grid is assigned to 1; thereby obtaining a retention density distribution of the blank model that preliminarily meets the actual working conditions of the component, which serves as the basis for subsequent reconstruction of the weight reduction model.

[0083] In the optimized finite element model, all removed meshes are removed and all removed locations are replaced with holes. All retained meshes are solidified. All solidified parts are modeled based on the retained density distribution of the blank model to obtain a preliminary weight reduction model of the component to be optimized.

[0084] In this embodiment, if Figure 5 As shown in the figure, according to the retained density distribution of the blank model, the removed parts and the retained parts are clearly identified, the removed meshes are replaced with holes, the retained meshes are solidified, and then the solidified part of the door rocker model is modeled to obtain a preliminary weight-reduced model of the aircraft door rocker.

[0085] Step 3: Perform finite element analysis on the preliminary weight reduction model of the component to be optimized, generate a stress distribution cloud map of the preliminary weight reduction model, and divide the preliminary weight reduction model into a stress concentration area and a matrix according to the generated stress distribution cloud map.

[0086] The specific content of step 3 is: meshing the preliminary weight reduction model of the component to be optimized, applying boundary constraints and load limits of the component to be optimized to the preliminary weight reduction model, and using the finite element analysis method to perform stress analysis on the preliminary weight reduction model to generate a stress distribution cloud map of the preliminary weight reduction model.

[0087] In this embodiment, if Figure 6 As shown in the figure, to ensure the strength and reliability of the preliminary weight-reduced model and achieve local structural strengthening, the weight-reduced model was meshed based on the rocker arm's deadweight and working loads such as wind load. Based on the component's load environment and working conditions, boundary constraints and load limits during normal operation were imposed. Finite element analysis was then performed on the preliminary weight-reduced model to obtain a stress distribution cloud map of the preliminary weight-reduced model, clearly identifying the fixed end lug and its torsion point in the door rocker arm as stress concentration areas. It should be noted that the boundary constraints and load limits imposed during the stress analysis of the preliminary weight-reduced model of the component to be optimized are the same as those imposed during the stress analysis of the blank model of the component to be optimized.

[0088] According to the stress distribution cloud map of the preliminary weight reduction model, the stress concentration part of the preliminary weight reduction model is identified, and based on the identified stress concentration part and the stress distribution cloud map of the preliminary weight reduction model, the preliminary weight reduction model is locally partitioned and the preliminary weight reduction model is divided into a stress concentration area and a matrix.

[0089] The method for locally partitioning the preliminary weight reduction model is as follows: obtaining the allowable stress intensity of the component to be optimized, and setting a high stress threshold σ according to the allowable stress intensity H and low stress threshold σ L , and σ H >σ L , all stress intensities in the preliminary weight reduction model higher than σ H The part is taken as the stress concentration area of ​​the preliminary weight reduction model; all stress intensities higher than σ in the preliminary weight reduction model are taken as the stress concentration area of ​​the preliminary weight reduction model; L and lower than σ H The part is taken as the coordinated deformation zone of the preliminary weight reduction model; all stress intensities in the preliminary weight reduction model below σ L The part is used as the stress stable area of ​​the preliminary weight reduction model; and the coordinated deformation area and stress stable area of ​​the preliminary weight reduction model are used as the matrix of the preliminary weight reduction model.

[0090] In this embodiment, if Figure 7 As shown, the stress concentration zone, the coordinated deformation zone and the stress stability zone are divided according to the stress intensity. In this embodiment, the high stress threshold σ is set H For 40% of the allowable stress intensity, set the low stress threshold σ LThe allowable stress intensity is 20%, that is, the part where all stress intensities in the preliminary weight-reduced model are higher than 40% of the allowable stress intensity is regarded as the stress concentration area; the part where all stress intensities in the preliminary weight-reduced model are 20%-40% of the allowable stress intensity is regarded as the coordinated deformation area; the part where all stress intensities in the preliminary weight-reduced model are lower than 20% of the allowable stress intensity is regarded as the stress stable area. As Figure 8 shown, the structure of the hatch rocker arm is disassembled, and the hatch rocker arm is divided into a stress concentration area and a non-stress concentration area, that is, the matrix.

[0091] Step 4: Extract the geometric features of the stress concentration area of the preliminary weight-reduced model, and disassemble the stress concentration area into several local structures according to the extracted geometric features.

[0092] The specific content of the above step 4 is: Define the length direction of the component to be optimized and obtain the component length L. For any cross-section perpendicular to the defined length direction in the stress concentration area, extract the geometric features of this cross-section; where the geometric features include: cross-section width W, cross-section height H, and large circle radius R of the cross-section.

[0093] Identify the interface in the preliminary weight-reduced model according to the stress distribution nephogram of the preliminary weight-reduced model and the geometric features of each cross-section in the preliminary weight-reduced model, and use all the identified interfaces to disassemble the stress concentration area of the preliminary weight-reduced model into several local structures; at the same time, judge the structure type of each local structure according to the geometric features of the cross-sections in each local structure.

[0094] The structure types include: columnar structure, ring structure, plate structure, rod structure, and beam structure; the columnar structure includes: solid cylinder and hollow cylinder.

[0095] When H >> R, define the structure type of the structure where this cross-section is located as a columnar structure.

[0096] When H < R, define the structure type of the structure where this cross-section is located as a ring structure.

[0097] When L, W ≥ 3H, define the structure type of the structure where this cross-section is located as a plate structure.

[0098] When L / H > 5 and L / W > also 5, define the structure type of the structure where this cross-section is located as a rod structure.

[0099] When the structure where this cross-section is located is composed of several rod structures, plate structures or columnar structures alone or in combination, define the structure type of the structure where this cross-section is located as a beam structure.

[0100] In this embodiment, the beam structure is composed of multiple rod-shaped, plate-shaped or columnar structures alone or in combination, and is used to resist the bending deformation caused by lateral external forces, and is mostly I-shaped, L-shaped, etc.

[0101] In this embodiment, if Figure 9 As shown in Figure 1, the stress concentration area is divided into several local structures according to the geometric characteristics of five typical local structures. According to the mechanical requirements of different local structures, including strengthening, coordinated deformation, stable connection, etc., Figure 10 As shown in the figure, the stress concentration area separated from the door rocker arm structure can be roughly divided into three parts by geometric feature decomposition: the lug (annular structure), the web (plate structure) and the ribs and flanges (beam structure).

[0102] Step 5: Perform enhanced skeleton design on several local structures respectively to generate adaptive lattice structures for each local structure.

[0103] The specific content of step 5 is: for any local structure, the reinforcement skeleton design method of the local structure is selected according to the structural type of the local structure; if the structural type of the local structure is a plate structure or a rod structure, the reinforcement skeleton design method based on the step load mode is adopted to perform reinforcement skeleton design on the local structure; if the structural type of the local structure is a columnar structure or annular structure, the isotropic reinforcement skeleton design method based on the stress cloud map and the typical configuration is adopted to perform reinforcement skeleton design on the local structure; if the structural type of the local structure is a beam structure, the reinforcement skeleton design method based on the continuous gradient load mode is adopted to perform reinforcement skeleton design on the local structure.

[0104] An adaptive lattice structure of each local structure is generated according to the selected enhanced skeleton design method.

[0105] In this embodiment, a reinforced skeleton design is performed on the local structures separated from the stress concentration area. According to the configuration requirements and stress environment of different local structures, a distributed form of reinforced skeleton, namely an adaptive lattice structure, is selected and designed for each local structure. This embodiment mainly includes three types of distributed reinforced skeletons. For regular structures, such as plate structures or rod-shaped structures, a reinforced skeleton design based on step loads can be selected according to the form of resistance. For columnar structures or ring structures, a reinforced skeleton design based on continuous gradient loads can be selected. For irregular structures, an isotropic reinforced skeleton design based on stress distribution and typical configuration can be selected.

[0106] The process of using the reinforced skeleton design method based on the stepped load mode to perform reinforced skeleton design on the local structure is as follows: for any local structure, the stress distribution data of the local structure is extracted from the stress distribution cloud map of the preliminary weight reduction model, and the stress type of the local structure is determined to be resisting tensile stress or bending stress; a lattice unit cell structure is selected for the local structure according to the stress type of the local structure, specifically: if the stress type of the local structure is resisting tensile stress, a lattice unit cell structure dominated by tensile stress is selected for the local structure; if the stress type of the local structure is bending stress, a lattice unit cell structure dominated by bending stress is selected for the local structure; and then an adaptive lattice structure of the local structure is generated according to the selected lattice unit cell structure.

[0107] The tensile stress-dominated lattice unit cell structure refers to a lattice unit cell structure that satisfies b-3j+6>0; wherein b is the number of rods in the lattice unit cell structure; and j is the number of nodes in the lattice unit cell structure.

[0108] The bending stress-dominated lattice unit cell structure refers to a lattice unit cell structure satisfying b-3j+6<0.

[0109] In this embodiment, for different types of local typical components, depending on whether the local structure is to resist tensile stress or bending stress, a lattice unit cell structure dominated by tensile stress or bending stress is selected, such as Figure 11 As shown in the figure, the number of ordinary cube members is 12, the number of nodes is 8, and the bending stress is dominant. The number of octagonal truss structure (Octet) members is 36, the number of nodes is 12, and the tensile stress is dominant. Figure 12 As shown in (a), according to the different stress resistance forms in different regions, lattice unit cell structures with different stress dominant modes are designed and embedded in each region.

[0110] The process of using the isotropic reinforcement skeleton design method based on stress cloud map and typical configuration to perform reinforcement skeleton design on the local structure is as follows: for any local structure, the stress distribution form of the local structure is obtained according to the stress distribution cloud map of the preliminary weight reduction model, randomly distributed feature points are generated in the three-dimensional space inside the local structure, and different feature point densities are set according to the stress distribution form of the local structure, the feature point spacing at the maximum stress position is set to the minimum, and the feature point spacing increases as the stress decreases, and then an adaptive lattice structure of the local structure is generated according to the feature points in the three-dimensional space inside the local structure.

[0111] In this embodiment, if Figure 12As shown in (b), the isotropic reinforced skeleton design based on the stress cloud map and typical configuration is as follows: According to the stress distribution cloud map of the preliminary weight reduction model, the local typical structural stress distribution form is obtained, and a random lattice pattern is selected to generate randomly distributed feature points in the three-dimensional space inside the local component. Different feature point densities are set based on the local structural stress distribution, and the point spacing at the maximum stress position is set to the minimum. As the stress decreases, the point spacing gradually increases to obtain a reinforced skeleton lattice distributed according to the feature points.

[0112] The process of the reinforced skeleton design based on the continuous gradient load mode is as follows: for any local structure, the stress distribution form of the local structure is obtained according to the stress distribution cloud map of the preliminary weight reduction model, and the length and diameter of the lattice beam arm are designed according to the stress distribution form of the local structure, so that the lattice beam arm length is the shortest and the diameter is the largest at the point of maximum stress. As the stress decreases, the lattice beam arm length gradually increases and the diameter gradually decreases, thereby generating an adaptive lattice structure with continuous gradient change for the local structure.

[0113] In this embodiment, if Figure 12 As shown in (c), according to the stress distribution form of the local structure, the length and diameter of the lattice beam arm are adjusted based on the stress distribution to achieve a continuous gradient change in the strengthening effect. The lattice beam arm should be the shortest and the largest in diameter at the point where the stress is maximum to provide maximum support and strength; as the stress decreases, the length of the lattice beam arm gradually increases and the diameter gradually decreases; at the point where the stress is minimum, the lattice beam arm should be the longest and the smallest in diameter to reduce weight and reduce material usage.

[0114] In this embodiment, the ear portion is reinforced with a skeleton-like design, such as Figure 13 As shown in the figure, specifically: the lifting ear part is a ring-shaped structure, which is often matched with the rotating shaft during assembly. It is subjected to tensile stress along the radial direction during the opening and closing process of the hatch. According to the geometric characteristics of the ring part and the stress distribution, the beam arm along the annular direction and the strengthening beam arm along the radial direction are designed. The whole is filled in the form of a regular lattice truss, and the gradient change of the strengthening effect is achieved by changing the density of the lattice structure.

[0115] Strengthen the ribs and edges with a skeleton-like design, such as Figure 14 As shown, specifically: since the edge strips and ribs in the local structure of the door rocker arm are mainly used to resist bending, this embodiment selects built-in reinforcement ribs along the rib direction for reinforcement according to the rib directionality, and designs the reinforcement rib cross-sectional area according to the stress distribution.

[0116] Strengthen the skeletal design of the belly plate, such as Figure 15As shown in the figure, specifically: the reinforcement design of the internal plate structure can be completely based on the local stress distribution of the web, and a random lattice structure can be selected to generate randomly distributed feature points in the three-dimensional space inside the component. Different feature point densities are set based on the stress distribution of the web, and the reinforcement effect generated by the connection points fully meets the skeletal reinforcement structure of the stress cloud map.

[0117] Step 6: Perform Boolean summation on the adaptive lattice structures of all local structures and the matrix in the preliminary weight reduction model to complete the topology optimization of the component to be optimized.

[0118] In this embodiment, an integrated complex component with local skeletal lattice reinforcement is formed by performing a Boolean sum operation on the local structure and the matrix, wherein the Boolean operation refers to obtaining a new entity by adding two intersecting entities, such as Figure 16 As shown in the figure, a model of an aircraft door rocker arm that achieves both weight reduction and local reinforcement is obtained. After completing the topology optimization of the component, the topology-optimized component is printed using the additive manufacturing process. By planning the additive manufacturing process for the component, writing the printing program, and using the laser micro-area powder feeding additive manufacturing technology (Laser Deposition Manufacturing, LDM) for integrated printing, in order to achieve the local reinforcement effect, the printing system diagram is shown in the figure. Figure 17 As shown, the integrated printing of complex components is achieved. In addition to laser powder feeding additive manufacturing technology, component printing methods can also use additive manufacturing technologies such as arc fuse additive manufacturing and laser selective melting.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the claims of the present invention.

Claims

1. A topology optimization method for component weight reduction and local skeletal reinforcement, characterized in that: The method comprises the following steps: Step 1: Construct a blank model of the component to be optimized and perform finite element analysis on the blank model to generate a stress distribution cloud map of the blank model; Step 2: Based on the stress distribution cloud map of the blank model, the variable density method is used to optimize the blank model of the component to be optimized, the retained density distribution of the blank model is obtained, and the blank model is weighted to obtain a preliminary weight-reduced model of the component to be optimized; Step 3: Perform finite element analysis on the preliminary weight reduction model of the component to be optimized, generate a stress distribution cloud map of the preliminary weight reduction model, and divide the preliminary weight reduction model into a stress concentration area and a matrix according to the generated stress distribution cloud map; Step 4: Extract geometric features of the stress concentration area of ​​the preliminary weight reduction model, and split the stress concentration area into several local structures based on the extracted geometric features; Define the length direction of the component to be optimized and obtain the component length L. For any cross section perpendicular to the defined length direction in the stress concentration area, extract the geometric features of the cross section; The geometric features include: cross-sectional width W, cross-sectional height H and cross-sectional great circle radius R; Identify interfaces in the preliminary weight reduction model based on the stress distribution cloud map and the geometric features of each cross section in the preliminary weight reduction model, and use all identified interfaces to split the stress concentration area of ​​the preliminary weight reduction model into several local structures; and determine the structural type of each local structure based on the geometric features of the cross section in each local structure. Step 5: Perform enhanced skeleton design on several local structures to generate adaptive lattice structures for each local structure; Step 6: Perform Boolean summation on the adaptive lattice structures of all local structures and the matrix in the preliminary weight reduction model to complete the topology optimization of the component to be optimized.

2. A topology optimization method for component weight reduction and local skeletal reinforcement according to claim 1, characterized in that: The specific content of step 1 is: determining the component to be optimized, and constructing a blank model of the component to be optimized according to the design requirements of the component to be optimized; The design requirements include: working environment requirements, workload requirements, dimensional accuracy requirements, motion law requirements and material selection requirements; By meshing the blank model of the component to be optimized, the blank model is converted into a finite element model, and boundary constraints and load limits of the component to be optimized are imposed on the obtained finite element model. The finite element analysis method is used to perform stress analysis on the finite element model to generate a stress distribution cloud map of the blank model.

3. A topology optimization method for component weight reduction and local skeletal reinforcement according to claim 2, characterized in that: The specific content of step 2 is: in the finite element model converted from the blank model, assigning an initial unit density to each mesh of the finite element model, defining an objective function and constraints, and constructing a density optimization model based on the objective function and constraints; wherein the objective function is to minimize component flexibility; and the constraints include: volume fraction constraint, strength constraint, and additive manufacturing constraint; The density optimization model is expressed as: ； in Indicates the The cell density of the grid; is the number of grids in the blank model; It means minimization; is the component flexibility; is the static load; is displacement; T represents transposition; is the global stiffness matrix; is the volume fraction; is the preset upper limit of volume fraction; is the strength constraint; for additive manufacturing constraints; is a constant, and is a positive number; Applying boundary constraints and expected workloads to the finite element model, and iteratively optimizing the finite element model using a density optimization model, adjusting the cell density of each grid in each iteration to minimize the objective function and satisfy the constraints, thereby obtaining an optimized finite element model; Set the retention density parameter. For any mesh in the optimized finite element model, if the element density of the mesh is lower than the retention density parameter, mark the mesh as a removed mesh; otherwise, mark the mesh as a retained mesh. Perform binary processing to reassign values to all removed meshes and retained meshes respectively, and generate the retention density distribution of the blank model based on the reassigned meshes. In the optimized finite element model, remove all removed meshes and replace all removed positions with holes, solidify all retained meshes, and model all solidified parts based on the retention density distribution of the blank model to obtain the preliminary weight-reduced model of the component to be optimized.

4. A topology optimization method for component weight reduction and local skeletal reinforcement according to claim 3, characterized in that: The specific content of step 3 is as follows: Perform mesh division on the preliminary weight-reduced model of the component to be optimized, apply boundary constraint conditions and the load limit of the component to be optimized to the preliminary weight-reduced model, and use the finite element analysis method to perform stress analysis on the preliminary weight-reduced model to generate the stress distribution contour map of the preliminary weight-reduced model. Identify the stress concentration part of the preliminary weight-reduced model based on the generated stress distribution contour map of the preliminary weight-reduced model, and perform local zoning on the preliminary weight-reduced model based on the identified stress concentration part and the stress distribution contour map of the preliminary weight-reduced model, dividing the preliminary weight-reduced model into a stress concentration area and a matrix.

5. A topology optimization method for component weight reduction and local skeletal reinforcement according to claim 4, characterized in that: The method for locally partitioning the preliminary weight reduction model is as follows: obtaining the allowable stress intensity of the component to be optimized and setting a high stress threshold according to the allowable stress intensity. and low stress threshold ,and , all stress intensities in the preliminary weight reduction model are higher than As the stress concentration area of ​​the preliminary weight reduction model; all stress intensities higher than and lower than As the coordinated deformation zone of the preliminary weight reduction model; all stress intensities below The part is used as the stress stable area of ​​the preliminary weight reduction model; And use the coordinated deformation area and stress stable area of the preliminary weight-reduced model as the matrix of the preliminary weight-reduced model.

6. A topology optimization method for component weight reduction and local skeletal reinforcement according to claim 5, characterized in that: The specific content of step 4 is as follows: The structural types include: columnar structure, ring structure, plate structure, rod structure, and beam structure; the columnar structure includes: solid cylinder and hollow cylinder. Among them, when H When R, the structure type of the structure where the section is located is defined as a columnar structure; When H < R, define the structural type of the structure where the section is located as a ring structure. When L, W ≥ 3H, define the structural type of the structure where the section is located as a plate structure. When L / H > 5 and L / W > 5, define the structural type of the structure where the section is located as a rod structure. When the structure where the section is located is composed of several rod structures, plate structures, or columnar structures alone or in combination, define the structural type of the structure where the section is located as a beam structure.

7. A topology optimization method for component weight reduction and local skeletal reinforcement according to claim 6, characterized in that: The specific content of step 5 is as follows: For any local structure, select the reinforced skeletal design method for the local structure according to the structural type of the local structure. If the structural type of the local structure is a plate structure or a rod structure, use the reinforced skeletal design method based on the stepped load pattern to perform the reinforced skeletal design on the local structure; if the structural type of the local structure is a columnar structure or a ring structure, use the isotropic reinforced skeletal design method based on the stress contour map and typical configuration to perform the reinforced skeletal design on the local structure; if the structural type of the local structure is a beam structure, use the reinforced skeletal design method based on the continuously varying load pattern to perform the reinforced skeletal design on the local structure. Generate the adaptive lattice structure of each local structure according to the selected reinforced skeletal design method.

8. A topology optimization method for component weight reduction and local skeletal reinforcement according to claim 7, characterized in that: The process of using the reinforced skeleton design method based on the step load mode to perform reinforced skeleton design on the local structure is as follows: for any local structure, extract the stress distribution data of the local structure from the stress distribution cloud map of the preliminary weight reduction model, and determine whether the stress type of the local structure is resisting tensile stress or bending stress; select a lattice unit cell structure for the local structure according to the stress type of the local structure, specifically: if the stress type of the local structure is resisting tensile stress, select a lattice unit cell structure dominated by tensile stress for the local structure; if the stress type of the local structure is bending stress, select a lattice unit cell structure dominated by bending stress for the local structure; and then generate an adaptive lattice structure for the local structure according to the selected lattice unit cell structure; The tensile stress-dominated lattice unit cell structure refers to a lattice unit cell structure that satisfies b-3j+6>0; wherein b is the number of rods in the lattice unit cell structure; j is the number of nodes in the lattice unit cell structure; The bending stress-dominated lattice unit cell structure refers to a lattice unit cell structure satisfying b-3j+6<0.

9. A topology optimization method for component weight reduction and local skeletal reinforcement according to claim 8, characterized in that: The process of using the isotropic reinforcement skeleton design method based on stress cloud map and typical configuration to perform reinforcement skeleton design on the local structure is as follows: for any local structure, the stress distribution form of the local structure is obtained according to the stress distribution cloud map of the preliminary weight reduction model, randomly distributed feature points are generated in the three-dimensional space inside the local structure, and different feature point densities are set according to the stress distribution form of the local structure, the feature point spacing at the maximum stress position is set to the minimum, and the feature point spacing increases as the stress decreases, and then an adaptive lattice structure of the local structure is generated according to the feature points in the three-dimensional space inside the local structure.

10. A topology optimization method for component weight reduction and local skeletal reinforcement according to claim 9, characterized in that: The process of the reinforced skeleton design based on the continuous gradient load mode is as follows: for any local structure, the stress distribution form of the local structure is obtained according to the stress distribution cloud map of the preliminary weight reduction model, and the length and diameter of the lattice beam arm are designed according to the stress distribution form of the local structure, so that the lattice beam arm length is the shortest and the diameter is the largest at the point of maximum stress. As the stress decreases, the lattice beam arm length gradually increases and the diameter gradually decreases, thereby generating an adaptive lattice structure with continuous gradient change for the local structure.

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