Topological optimization method for component weight reduction and local skeleton type enhancement

Abstract

The invention provides a topological optimization method for component weight reduction and local skeleton type enhancement, and relates to the technical field of aerospace large complex components. The method specifically comprises the following steps: constructing a blank model of a to-be-optimized component and performing finite element analysis; optimizing the blank model of the to-be-optimized component by adopting a variable density method to obtain reserved density distribution of the blank model, and reducing the weight of the blank model to obtain a preliminary weight reduction model of the to-be-optimized component; dividing the preliminary weight reduction model into a stress concentration area and a matrix through finite element analysis; secondly, the stress concentration area is split into a plurality of local structures by extracting geometric features of the stress concentration area, reinforced skeleton type design is conducted on the local structures, and adaptive dot matrix structures of the local structures are generated; and Boolean summation is carried out on the adaptive lattice structures of all the local structures and the base bodies, and topological optimization of the to-be-optimized component is completed. Therefore, function-structure integrated manufacturing of complex components is achieved.

Description

Technical Field

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

[0002] In order to achieve long-range strike and high thrust-to-weight ratio, aerospace components are developing towards integration. Using additive manufacturing technology to achieve lightweight design of complex components has become one of the currently concerned issues. Additive manufacturing, also known as 3D printing, is a forming technology based on digital three-dimensional modeling, integrating computer-aided design, material processing, and material forming technologies. Using metal materials and non-metal materials, according to the discrete-accumulation principle of layer-by-layer stacking and layer-by-layer manufacturing, a complex-shaped workpiece can be rapidly prepared from bottom to top. Topology optimization, as a mathematical method for designing the structure distribution within a given design area according to load conditions, constraint conditions, and performance indicators, can effectively help designers achieve lightweight structures. The calculation methods of topology optimization include the homogenization method, the variable density method, the evolutionary structural optimization method (ESO), the level set method, etc. At the same time, research has also found that during the process of achieving weight reduction through topology optimization, load redistribution usually occurs, resulting in a sudden increase in local loads, reducing the system stability and reliability, thus limiting the application of this technology in important load-bearing structural components.

[0003] Currently, for structural strengthening, traditional means still focus on uniform strengthening of materials. The main methods include: heat treatment strengthening, deformation processing strengthening, and composite material strengthening, etc. Among them, the heat treatment process can improve alloy element segregation, eliminate internal stress, etc., so as to achieve the strengthening purpose. However, due to the inverse relationship between strength and toughness, the increase in strength during the heat treatment process is often accompanied by a decrease in ductility. Means of cold working deformation processing, such as rolling, extrusion, forging, friction stir processing, etc., regulate the uniformity of the structure and refine grains by introducing dislocations, thereby improving the mechanical properties of the structure. However, this method is not applicable to topological components with a large number of hollow structures. Composite material strengthening refers to introducing a second phase into the material, distributing the reinforcing phase in the matrix in a dispersed or agglomerated manner, and improving the strength while retaining the excellent properties of the matrix itself. However, for large and complex load-bearing structures with specific load conditions, the above methods all have certain limitations. Summary of the Invention

[0004] Aiming at the deficiencies of the above-mentioned prior art, based on the topology optimization theory and load distribution, the present invention uses local skeletal reinforcement means to propose a topology optimization method for component weight reduction and local skeletal reinforcement, aiming to achieve weight reduction and enhancement simultaneously, and ultimately achieve functional-structure integrated manufacturing of complex components.

[0005] A topology optimization method for component weight reduction and local skeletal enhancement proposed by the present invention 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 contour map of the blank model;

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

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

[0009] Step 4: Extract geometric features of the stress concentration area of the preliminary weight-reduced model, and split the stress concentration area into several local structures according to the extracted geometric features;

[0010] Step 5: Perform strengthened skeletal design on several local structures respectively to generate an adaptive lattice structure 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-reduced model to complete the topology optimization of the component to be optimized;

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

[0013] Wherein the design requirements include: working environment requirements, working load requirements, dimensional accuracy requirements, motion law requirements, and material selection requirements;

[0014] By performing mesh division on the blank model of the component to be optimized, convert the blank model into a finite element model, apply boundary constraint conditions and the load limit of the component to be optimized to the obtained finite element model, and use the finite element analysis method to perform stress analysis on the finite element model to generate a stress distribution contour map of the blank model;

[0015] The specific content of Step 2 is: In the finite element model converted from the blank model, assign an initial element density to each grid of the finite element model, define the objective function and constraint conditions, and construct a density optimization model based on the objective function and constraint conditions; wherein the objective function is to minimize the compliance of the component; the constraint conditions 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] s.t. K(ρ i , u) = F;

[0020] V fra ≤ V 0 ;

[0021] g s <ε, g v <ε;

[0022] 0 ≤ ρ i ≤ 1

[0023] where ρ i represents the element density of the i-th grid; n is the number of grids in the blank model; Minimize represents minimization; C(x) is the component compliance; F is the static load; u is the displacement; T represents transpose; K is the global stiffness matrix; V fra is the volume fraction; V 0 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] Apply boundary constraint conditions and expected working loads to the finite element model, and use the density optimization model to perform iterative optimization on the finite element model. In each iteration, adjust the element density of each grid to minimize the objective function and satisfy the constraint conditions, so as to obtain an optimized finite element model;

[0025] Set the retention density parameter. For any grid in the optimized finite element model, if the element density of the grid is lower than the retention density parameter, mark the grid as a removed grid; otherwise, mark the grid as a retained grid; use binary processing to reassign values to all removed grids and retained grids respectively, and generate the retention density distribution of the blank model according to the re-assigned grids;

[0026] In the optimized finite element model, remove all removed grids and replace all removed positions with holes, solidify all retained grids, and model all solidified parts based on the retention density distribution of the blank model to obtain a preliminary weight-reduced model of the component to be optimized;

[0027] The specific content of step 3 is as follows: Perform mesh division on the preliminary weight reduction 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 reduction model, and use the finite element analysis method to perform stress analysis on the preliminary weight reduction model to generate a stress distribution nephogram of the preliminary weight reduction model;

[0028] Identify the stress concentration part of the preliminary weight reduction model according to the generated stress distribution nephogram of the preliminary weight reduction model, and perform local zoning on the preliminary weight reduction model based on the identified stress concentration part and the stress distribution nephogram of the preliminary weight reduction model, and divide the preliminary weight reduction model into a stress concentration area and a matrix;

[0029] The method for performing local zoning on the preliminary weight reduction model is as follows: Obtain the allowable stress intensity of the component to be optimized, and set a high stress threshold σ H and a low stress threshold σ L , and σ H >σ L . Take the part of the preliminary weight reduction model with all stress intensities higher than σ H as the stress concentration area of the preliminary weight reduction model; Take the part of the preliminary weight reduction model with all stress intensities higher than σ L and lower than σ H as the coordinated deformation area of the preliminary weight reduction model; Take the part of the preliminary weight reduction model with all stress intensities lower than σ L as the stress stable area of the preliminary weight reduction model; And take the coordinated deformation area and the stress stable area of the preliminary weight reduction model as the matrix of the preliminary weight reduction model;

[0030] The specific content of step 4 is as follows: 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; where the geometric features include: cross-section width W, cross-section height H, and cross-sectional large circle radius R;

[0031] Identify the interfaces in the preliminary weight reduction model according to the stress distribution nephogram of the preliminary weight reduction model and the geometric features of each cross-section in the preliminary weight reduction model, and use all the identified interfaces to split the stress concentration area of the preliminary weight reduction model into several local structures; At the same time, judge the structural types of each local structure according to the geometric features of the cross-sections 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, define the structural type of the structure where the cross-section is located as a columnar structure;

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

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

[0037] When the structure where the cross-section is located is composed of several rod-like structures, plate-like structures or columnar 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 as follows: 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-like structure or a rod-like 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 columnar structure or an annular structure, use the isotropic enhanced skeletal design method based on the stress nephogram and the 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 as follows: 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 strengthening skeletal design method based on stress nephogram and typical configuration to perform the strengthening skeletal design on this local structure is as follows: For any local structure, obtain the stress distribution form of this local structure according to the stress distribution nephogram of the preliminary weight reduction model. Generate randomly distributed feature points in the three-dimensional space inside this local structure, and set different feature point densities according to the stress distribution form of the local structure. Set the minimum distance between feature points at the position with the maximum stress, and the distance between feature points increases as the stress decreases. Then, generate the adaptive lattice structure of this local structure according to the feature points in the three-dimensional space inside this local structure;

[0044] The process of the strengthening skeletal design based on the continuous gradient load mode is as follows: For any local structure, obtain the stress distribution form of this local structure according to the stress distribution nephogram of the preliminary weight reduction model, and design the length and diameter of the lattice beam arms according to the stress distribution form of the local structure, so that the length of the lattice beam arms at the position with the maximum stress is the shortest and the diameter is the largest. As the stress decreases, the length of the lattice beam arms gradually increases and the diameter gradually decreases, thereby generating an adaptive lattice structure with continuous gradient change for this local structure.

[0045] The beneficial effects produced by adopting the above technical solutions are as follows:

[0046] Based on the component load distribution, the method of the present invention uses topology optimization technology to optimize the structure of a complex model by reducing unnecessary materials of the complex structure, thereby obtaining a lightweight model. At the same time, in the method of the present invention, the lattice local skeletal strengthening design based on stress distribution and geometric features can make the designed structure more matched with the force-bearing situation of the original component and the force more uniform, thereby avoiding the decline of the overall performance and stability of the structure caused by excessive local stress concentration in the lightweight model. At the same time, through the micro-area powder feeding technology, the local structure materials are controlled to obtain a locally heterogeneous grid strengthening structure. Description of the Drawings

[0047] Figure 1 It is a flowchart of a topology optimization method for component weight reduction and local skeletal enhancement in this embodiment;

[0048] Figure 2 It is a schematic diagram of the blank model of the aircraft cabin door rocker arm in this embodiment;

[0049] Figure 3 It is a stress distribution nephogram of the blank model of the cabin door rocker arm in this embodiment;

[0050] Figure 4 It is a schematic diagram of the retained density distribution of the cabin door rocker arm in this embodiment;

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

[0052] Figure 6 Schematic diagram of the stress distribution nephogram of the preliminary weight reduction model in this embodiment;

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

[0054] Figure 8 Schematic diagram of the local zoning of the hatch rocker arm in this embodiment;

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

[0056] Figure 10 Schematic diagram of the local structure split from the stress concentration area of the hatch rocker arm based on geometric features in this embodiment;

[0057] Figure 11 Schematic diagram of the lattice unit cell structure dominated by typical tension and bending in this embodiment;

[0058] Figure 12 Schematic diagram of the adaptive lattice structure with different reinforced bone designs in this embodiment; among them, (a) is the schematic diagram of the adaptive lattice structure with the reinforced bone design based on the stepped load pattern; (b) is the schematic diagram of the adaptive lattice structure with the isotropic reinforced bone design based on the stress nephogram and typical configuration; (c) is the schematic diagram of the adaptive lattice structure with the bone-like design under the continuous gradient load pattern;

[0059] Figure 13 Schematic diagram of the structure with the reinforced bone-like design for the lug part in this embodiment; among them, (a) is the model schematic diagram of the lug part; (b) is the stress distribution nephogram of the lug part; Figure (c) is the crystal cell space distribution diagram of the lug part; (d) is the schematic diagram of the gradient change lattice structure of the lug part;

[0060] Figure 14 Schematic diagram of the structure with the reinforced bone-like design for the rib and flange parts in this embodiment; among them, (a) is the model schematic diagram of the rib and flange parts; (b) is the surface mesh remodeling schematic diagram of the rib and flange parts; (c) is the stress distribution nephogram of the rib and flange parts; (d) is the schematic diagram of the gradient change rib structure of the rib and flange parts;

[0061] Figure 15Schematic diagram of the structure with a strengthened skeletal design for the web part in this embodiment; among them, (a) is the model diagram of the web part; (b) is the stress distribution nephogram of the web part; (c) is the schematic diagram of the random distribution of spatial points of the web part; (d) is the schematic diagram of the three-dimensional gradient lattice structure of the web part;

[0062] Figure 16 Schematic diagram of the local strengthened skeletal structure of the stress concentration area in the hatch rocker arm in this embodiment;

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

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

[0065] For large and complex structural load-bearing components, structure, strength, stiffness, and reliability are all issues that must be considered. In the actual service environment, it is very rare for the load to be evenly distributed over the entire component, but the uneven distribution of stress also provides a topological optimization weight reduction window for designers. At the same time, the need for local high strength is also put forward. Therefore, this embodiment proposes a topological optimization method for component weight reduction and local skeletal strengthening. In order to ensure the mechanical reliability of the lightweight structure after topological optimization, the stress concentration areas after optimization are determined according to the stress distribution nephogram, and local skeletal strengthening is proposed for the stress concentration areas: different forms of lattice structures are designed for different structures, and the lattice structure is combined with the matrix to generate a local structure with composite skeletal strengthening. Finally, the 3D printing technology is used to realize the integrated molding of complex load-bearing structures.

[0066] A topological optimization method for component weight reduction and local skeletal strengthening in this embodiment, as Figure 1 shown, this method includes the following steps:

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

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

[0069] Among them, the design requirements include: working environment requirements, working load requirements, dimensional accuracy requirements, motion law requirements, and material selection requirements.

[0070] In this embodiment, for the component to be optimized, design requirements are put forward according to the actual service conditions of the component. According to the actual working environment and loading conditions of the component, that is, the environmental conditions in actual use of the component are clarified, such as temperature, humidity, corrosiveness, etc., and the type and magnitude of the loads borne by the component during service are determined. A lightweight material that meets the strength requirements is selected. Based on the dimensional accuracy requirements and motion law requirements of the component, the first structural and dimensional design of the complex component is carried out by referring to relevant materials of the component to obtain the blank model of the component to be optimized; wherein the dimensional accuracy requirements are used to ensure the machining 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 that the component needs to meet at specified points.

[0071] Take the complex component of the aircraft cabin door rocker arm as an example for introduction, as Figure 2 shown. In this embodiment, according to the service conditions and working environment of the aircraft cabin door rocker arm, relevant materials are consulted to obtain the lifting displacement range and load range of the cabin door rocker arm. Aluminum alloy is selected as the rocker arm material, and according to the general tolerance HB5000 - 1999 for parts processing, the blank model of the aircraft rocker arm that meets the dimensions / tolerances is drawn using 3D software.

[0072] By meshing the blank model of the component to be optimized, the blank model is converted into a finite element model, and boundary constraint conditions and the load limit 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, and a stress distribution nephogram of the blank model is generated.

[0073] In this embodiment, as Figure 3As shown in the figure, the obtained blank model is imported into the mechanical simulation software, and the blank model of the component to be optimized is meshed using the simulation software according to the loading position. Define the structural material. In order to simulate various limiting conditions that the component is subjected to during actual operation, boundary constraint conditions such as fixed constraints, support constraints, friction constraints, and contact constraints are applied at the boundaries of the blank model according to the actual working conditions of the component to ensure that the model can correctly reflect the actual working conditions during the analysis process. In order to ensure that the component can still meet the design requirements under the most unfavorable working conditions, a series of basic conditions such as load environment, structural strength, stiffness, and deformability that the component should meet during normal operation are applied, and the load limit that the component is subjected to during normal operation is applied. The load limit is usually obtained by multiplying the applied load by a safety factor, which is used to ensure the conservativeness and reliability of the design. If the load environment of the component is stable, the safety factor is selected from 1.1 to 1.2; if the load environment of the component is severely fluctuating, the safety factor is selected from 1.3 to 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 the stress distribution contour map of the blank model.

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

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

[0076] In this embodiment, the initial density value of each grid cell is usually between 0 and 1. As Figure 4 shown, based on the variable density method, according to the flexibility principle of minimizing the objective function, with the upper limit of the structural volume fraction of 0.5 and the strength limit as the constraint conditions, the additive manufacturing constraint is applied, that is, the minimum size constraint of 5 mm, the symmetry constraint based on the YOZ plane, and the printing direction constraint along the positive 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; V 0 is the preset upper limit of 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.

[0080] Boundary constraints and expected workloads are imposed on the finite element model, and the finite element model is iteratively optimized using a density optimization model. In 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 according to the reassigned meshes.

[0082] In this embodiment, the retention density parameter is set to 0.7. For any mesh in the optimized blank model, if the cell density of the mesh is lower than the retention density parameter, the cell density of the mesh is assigned to 0; otherwise, the cell density of the mesh is assigned to 1; thereby obtaining the 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 positions are replaced with holes, all retained meshes are solidified, and 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, 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 by holes, the retained meshes are solidified, and then the solidified part of the door rocker model is modeled to obtain a preliminary weight reduction 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 as follows: Mesh the preliminary weight reduction model of the component to be optimized, apply boundary constraint conditions and the load limit of the component to be optimized to this preliminary weight reduction model, and use the finite element analysis method to perform stress analysis on this preliminary weight reduction model to generate a stress distribution nephogram of the preliminary weight reduction model.

[0087] In this embodiment, as Figure 6 shown, to ensure the strength and reliability of the preliminary weight reduction model and achieve local structural strengthening, based on the self-weight of the rocker arm and working condition loads such as wind load, mesh the weight reduction model. Based on the load environment and working conditions of the component, apply boundary constraints and the load limit during normal operation, so as to perform finite element analysis on the preliminary weight reduction model, obtain the stress distribution nephogram of the preliminary weight reduction model, and clarify that the fixed-end lug and its torsion part in the hatch rocker arm are stress concentration parts. It should be noted that the boundary constraint conditions and load limits applied during the stress analysis of the preliminary weight reduction model of the component to be optimized are the same as those applied during the stress analysis of the blank model of the component to be optimized.

[0088] Identify the stress concentration part of the preliminary weight reduction model according to the generated stress distribution nephogram of the preliminary weight reduction model, and based on the identified stress concentration part and the stress distribution nephogram of the preliminary weight reduction model, perform local zoning on this preliminary weight reduction model, and divide this preliminary weight reduction model into a stress concentration area and a matrix.

[0089] The method for performing local zoning on this preliminary weight reduction model is as follows: Obtain the allowable stress intensity of the component to be optimized, and set a high stress threshold σ H and a low stress threshold σ L , and σ H >σ L . Take the part of this preliminary weight reduction model with all stress intensities higher than σ H as the stress concentration area of the preliminary weight reduction model; take the part of this preliminary weight reduction model with all stress intensities higher than σ L and lower than σ H as the coordinated deformation area of the preliminary weight reduction model; take the part of this preliminary weight reduction model with all stress intensities lower than σ L as the stress stable area of the preliminary weight reduction model; and take the coordinated deformation area and the stress stable area of the preliminary weight reduction model as the matrix of the preliminary weight reduction model.

[0090] In this embodiment, as Figure 7 shown, divide the stress concentration area, the coordinated deformation area and the stress stable area according to the stress intensity. In this embodiment, the high stress threshold σ H is set as 40% of the allowable stress intensity, and the low stress threshold σ LThe allowable stress intensity is 20%, that is, the part where the stress intensity in the preliminary weight-reduced model is higher than 40% of the allowable stress intensity is taken as the stress concentration area; the part where the stress intensity in the preliminary weight-reduced model is 20%-40% of the allowable stress intensity is taken as the coordinated deformation area; the part where the stress intensity in the preliminary weight-reduced model is lower than 20% of the allowable stress intensity is taken as the stress stable area. As Figure 8 shown, the structure of the cabin door rocker arm is disassembled, and the cabin door 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 split the stress concentration area into several local structures according to the extracted geometric features.

[0092] The specific content of the said 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 the 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 split 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-section in each local structure.

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

[0095] Among them, 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 > 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 rods, plates or columns 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, as Figure 9 shown, according to the geometric characteristics of five categories of typical local structures, the stress concentration area is split into several local structures. According to the mechanical requirements of different local structures, including: strengthening, coordinating deformation, firm connection, etc., as Figure 10 shown, the geometric characteristics of the stress concentration area split from the hatch rocker arm structure can be roughly divided into three parts: lugs (ring structures), webs (plate structures), and ribs and flanges (beam structures).

[0102] Step 5: Perform a strengthened skeletal design on several local structures respectively to generate an adaptive lattice structure for each local structure.

[0103] The specific content of the above Step 5 is: for any local structure, select the strengthened skeletal design method for this local structure according to the structural type of this local structure. If the structural type of this local structure is a plate structure or a rod structure, then use the strengthened skeletal design method based on the stepped load pattern to perform a strengthened skeletal design on this local structure; if the structural type of this local structure is a columnar structure or a ring structure, then use the isotropic strengthened skeletal design method based on the stress nephogram and typical configurations to perform a strengthened skeletal design on this local structure; if the structural type of this local structure is a beam structure, then use the strengthened skeletal design method based on the continuously varying load pattern to perform a strengthened skeletal design on this local structure.

[0104] Generate an adaptive lattice structure for each local structure according to the selected strengthened skeletal design method.

[0105] In this embodiment, a strengthened skeletal design is performed on the local structures split from the stress concentration area. According to the configuration requirements and stress environment of different local structures, a strengthened bone of a distribution form is selected and designed for each local structure respectively, that is, an adaptive lattice structure. There are mainly 3 distribution forms of strengthened bones in this embodiment. For regular structures, such as plate structures or rod structures, the strengthened skeletal design based on the stepped load can be selected according to the form of resistance to force, and for columnar structures or ring structures, the strengthened skeletal design based on the continuously varying load can be selected; for irregular structures, the isotropic strengthened skeletal design based on the stress distribution and typical configurations can be selected.

[0106] The process of using the enhanced skeletal design method based on the stepped load pattern to perform enhanced skeletal 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 contour map of the preliminary weight reduction model, and determine the stress type of the local structure as 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 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; then generate an adaptive lattice structure for the local structure according to the selected lattice unit cell structure.

[0107] 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.

[0108] The lattice unit cell structure dominated by bending stress refers to the lattice unit cell structure that satisfies b - 3j + 6 < 0.

[0109] In this embodiment, for different types of local typical components, according to whether the local structure is resistant to tensile stress or bending stress, select a lattice unit cell structure dominated by tensile stress or bending stress, as Figure 11 shown. For a regular cube, the number of bars is 12 and the number of nodes is 8, which is dominated by bending stress. For an octet truss structure, the number of bars is 36 and the number of nodes is 12, which is dominated by tensile stress. As Figure 12 (a) shows, and then according to the different stress resistance forms in different regions, design and embed lattice unit cell structures with different stress-dominant methods in different regions.

[0110] The process of using the isotropic enhanced skeletal design method based on stress contour map and typical configuration to perform enhanced skeletal design on the local structure is as follows: For any local structure, obtain the stress distribution form of the local structure according to the stress distribution contour map of the preliminary weight reduction model, generate randomly distributed feature points in the three-dimensional space inside the local structure, and set different feature point densities according to the stress distribution form of the local structure. Set the feature point spacing at the position with the maximum stress to be the smallest, and the spacing of the feature points increases as the stress decreases. Then generate an adaptive lattice structure for the local structure according to the feature points in the three-dimensional space inside the local structure.

[0111] In this embodiment, as Figure 12(b) Based on the stress nephogram and the isotropic strengthening skeletal design of the typical configuration: According to the stress distribution nephogram of the preliminary weight reduction model, obtain the stress distribution form of the local typical structure, select a random lattice pattern, generate randomly distributed feature points in the three-dimensional space inside the local component, set different feature point densities based on the local structure stress distribution, set the minimum distance between the points at the position with the maximum stress, and as the stress decreases, the point distance gradually increases, obtaining a strengthened skeletal lattice distributed according to the feature points.

[0112] The process of the strengthened skeletal design under the continuous gradient load mode is as follows: For any local structure, obtain the stress distribution form of the local structure according to the stress distribution nephogram of the preliminary weight reduction model, and according to the stress distribution form of the local structure, design the length and diameter of the lattice beam arms, so that the lattice beam arms at the position with the maximum stress are the shortest and the diameter is the largest. As the stress decreases, the length of the lattice beam arms gradually increases and the diameter gradually decreases, thereby generating an adaptive lattice structure with continuous gradient changes for the local structure.

[0113] In this embodiment, as Figure 12 (c) shown, according to the stress distribution form of the local structure, adjust the length and diameter of the lattice beam arms based on the stress distribution to achieve continuous gradient changes in the strengthening effect. The lattice beam arms at the position with the maximum stress should be the shortest in length and the largest in diameter to provide the maximum support and strength; as the stress decreases, the length of the lattice beam arms gradually increases and the diameter gradually decreases; the lattice beam arms at the position with the minimum stress should be the longest in length and the smallest in diameter to reduce weight and material usage.

[0114] In this embodiment, perform a strengthened skeletal design on the lug part, as Figure 13 shown. Specifically: The lug part is a ring structure, which is often matched with a rotating shaft during assembly and is subjected to tensile stress in 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, design the beam arms along the ring surface direction and the strengthening beam arms along the radial direction, and the whole is filled in the form of a regular lattice truss, and the gradient change of the strengthening effect is realized by changing the density of the lattice structure.

[0115] Perform a strengthened skeletal design on the rib and flange parts, as Figure 14 shown. Specifically: Since the ribs and flanges in the local structure of the hatch rocker mainly resist bending, in this embodiment, according to the rib directionality, select the built-in stiffeners along the rib direction for strengthening, and at the same time design the cross-sectional area of the stiffeners according to the stress distribution.

[0116] Perform a strengthened skeletal design on the web part, as Figure 15As shown, specifically: for the enhanced design of the internal plate structure, a random lattice structure can be selected according to the local stress distribution of the web. Characteristic points randomly distributed in the three-dimensional space inside the component are generated, and different characteristic point densities are set based on the stress distribution of the web. The reinforcement structure formed by connecting the points fully meets the skeletal reinforcement structure of the stress nephogram.

[0117] Step 6: Perform a Boolean sum on the adaptive lattice structures of all local structures and the matrix in this 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. The Boolean operation refers to obtaining a new entity by adding two intersecting entities, as Figure 16 shown, and an aircraft cabin door rocker arm model that simultaneously achieves weight reduction and local reinforcement is obtained. After completing the topology optimization of the component, the topologically optimized component is printed using additive manufacturing technology. By planning the additive manufacturing process for the component, writing a printing program, and using the laser micro-area powder feeding additive manufacturing technology (Laser Deposition Manufcturing, LDM) for integrated printing, in order to achieve the local enhancement effect, the schematic diagram of the printing system is as Figure 17 shown, to achieve the integrated printing of complex components. In addition, in addition to the laser powder feeding additive manufacturing technology, the printing method of the component can also use additive manufacturing technologies such as arc wire additive manufacturing and selective laser melting forming.

[0119] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions 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 blank model of the component to be optimized is optimized using the variable density method to obtain the retained density distribution of the blank model and reduce the weight of the blank model to obtain a preliminary weight reduction 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 according to the extracted geometric features; Step 5: Perform enhanced skeleton design on several local structures respectively to generate adaptive lattice structures of 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, working load requirements, dimensional accuracy requirements, motion law requirements and material selection requirements; The blank model of the component to be optimized is meshed and converted into a finite element model. 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.

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, an initial unit density is assigned to each grid of the finite element model, an objective function and constraint conditions are defined, and a density optimization model is constructed based on the objective function and constraint conditions; wherein the objective function is to minimize the flexibility of the component; and the constraint conditions include: volume fraction constraint, strength constraint and additive manufacturing constraint; The density optimization model is expressed as: Find:ρ i ,i=1,2,3,...,n; Minimize:C(x)=F T u s.t.K(ρ i ,u)=F; In fra ≤V0; g s <e,g v <e; 0≤ρ i ≤1 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; Apply boundary constraints and expected working loads to the finite element model, and iteratively optimize the finite element model using a density optimization model. In 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. 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 re-assign values ​​to all removed meshes and retained meshes, and generate the retention density distribution of the blank model based on the re-assigned meshes; In the optimized finite element model, all removed meshes are eliminated and all removed positions are replaced with holes. All remaining meshes are solidified, and the solidified parts are modeled based on the remaining density distribution of the blank model to obtain a 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: Mesh 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 this preliminary weight-reduced model, and use the finite element analysis method to perform stress analysis on this preliminary weight-reduced model to generate a stress distribution contour map of the preliminary weight-reduced model. Identify the stress concentration parts of the preliminary weight-reduced model according to the generated stress distribution contour map of the preliminary weight-reduced model, and perform local zoning on this preliminary weight-reduced model based on the identified stress concentration parts 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: obtaining the allowable stress intensity of the component to be optimized, and setting the 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 the stress intensities in the preliminary weight reduction model lower than 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.

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: 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 this stress concentration area, extract the geometric features of this cross-section. The geometric features include: cross-section width W, cross-section height H, and cross-sectional large circle radius R. Identify the interface surfaces in the preliminary weight-reduced model according to the stress distribution contour map 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 interface surfaces to split the stress concentration area of the preliminary weight-reduced model into several local structures; at the same time, judge the structural types of each local structure according to the geometric features of the cross-sections in each local structure. The structural types include: columnar structure, ring structure, plate structure, rod structure, and beam structure; the columnar structure includes: solid cylinder and hollow cylinder. When H >> R, define the structural type of the structure where this cross-section is located as a columnar structure. When H < R, define the structural type of the structure where this cross-section is located as a ring structure. When L, W ≥ 3H, define the structural type of the structure where this cross-section is located as a plate structure. When L / H > 5 and L / W > 5, define the structural type of the structure where this cross-section is located as a rod structure. 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 structural type of the structure where this cross-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 this local structure according to the structural type of this local structure. If the structural type of this local structure is a plate structure or a rod structure, use the reinforced skeletal design method based on the stepped load mode to perform reinforced skeletal design on this local structure; if the structural type of this 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 configurations to perform reinforced skeletal design on this local structure; if the structural type of this local structure is a beam structure, use the reinforced skeletal design method based on the continuously varying load mode to perform reinforced skeletal design on this local structure. Generate the adaptive lattice structures 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 enhanced skeleton design method based on the step load mode to perform enhanced 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 judge 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 of 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 strengthen the skeleton design of 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 the 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 length of the lattice beam arm at the maximum stress point is the shortest and the diameter is the largest. As the stress decreases, the length of the lattice beam arm gradually increases and the diameter gradually decreases, thereby generating an adaptive lattice structure with continuous gradient changes for the local structure.

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