Multi-scale topological optimization lightweight design method and system for space propulsion system support

Abstract

The invention provides a multi-scale topological optimization lightweight design method and system for a space propulsion system support, and the method comprises the steps: building a topological optimization initial model based on original design, load and installation conditions, and distinguishing a design domain from a non-design domain; a design domain is optimized through finite element analysis, then local adjustment and grid smoothing are carried out on a macroscopic optimization result, and a model is reconstructed; further shelling to form a skin structure, and adopting dot matrix filling to form a skin-dot matrix structure; dot matrix geometric parameters are adjusted according to stress field distribution of finite element analysis, and multi-scale topological optimization and variable-density dot matrix filling are achieved; and finally, carrying out mechanical property equivalence on the lattice structure, and verifying the design margin through multi-wheel dynamic school verification. If the requirements are met, outputting a final model; otherwise, the optimization process is repeated. The invention aims to quickly develop the space propulsion system bracket integrating light weight, high strength, high reliability and high machinability, and accelerates the product research and development process in the aerospace field.

Description

Technical Field

[0001] The present invention relates to the technical field of aerospace structure design, and in particular, to a multi-scale topology optimization lightweight design method and system for a space propulsion system bracket. Background Art

[0002] In the fields of deep space exploration, satellite communication, etc., the lightweight design of various components in a space propulsion system plays a crucial role in improving the payload, reducing costs, and enhancing the performance of the space propulsion system. As a key load-bearing component in the structure of the space propulsion system, the design of the bracket structure must take into account the two requirements of high strength and lightweight. However, traditional design methods mainly rely on engineers' experience and finite element analysis technology, and these methods often make it difficult to achieve the optimal distribution of materials, easily leading to material waste or an increase in structural weight.

[0003] With the increasing demand for reducing the weight of spacecraft, traditional design methods can no longer meet the dual requirements of lightweight and strength for modern spacecraft. Therefore, developing new design concepts and methods to achieve the optimal balance between structural lightweight and strength has become a research hotspot in the field of aerospace structure design.

[0004] As an advanced structural design method, topology optimization technology realizes the optimal distribution of materials by simulating the distribution of materials during the force-bearing process and removing those material regions that contribute less to the structural load-bearing capacity. This method can effectively reduce the structural weight while ensuring the load-bearing capacity and stiffness requirements of the structure. However, traditional topology optimization often focuses on macro-scale design and ignores the interaction and coupling effect between the macro and micro scales. To solve this problem, a lattice structure is introduced into the structural lightweight design. This periodic lattice structure can meet the processability constraints of additive manufacturing while further reducing the weight of the bracket.

[0005] Regarding the design research of spacecraft bracket products, some related invention patents have proposed different solutions. For example, the Chinese invention patent with the application publication number CN109948255B proposes an additive manufacturing metal skin lattice structure for tank installation and its design method. The structure includes a skin and a space lattice structure, and the space lattice structure is filled inside the skin, so that the mass of the entire load-bearing structure is reduced and the overall stiffness is improved. However, this method uses a single type of cubic rod unit connected along the diagonal of the cube, and the design parameters of the rods composed of each cubic unit are also the same, and a multi-scale topology optimization configuration cannot be achieved.

[0006] The Chinese invention patent with the application publication number CN109766656B proposes a design method for gradient lattice structures based on topology optimization. This method obtains the stress field distribution of the initial structure based on the topology optimization method and replaces the solid design domain with a variable-density lattice structure. However, this method also fails to achieve multi-scale topology optimization configurations, and there is no skin envelope outside the lattice structure, which is not suitable for the stringent requirements of manned spaceflight for strength and reliability.

[0007] The Chinese invention patent with the application publication number CN117708978A proposes a lightweight design method for spacecraft brackets based on skin-lattice structures. This method combines macroscopic topology optimization with lattice structures to obtain a skin-lattice structure that meets the maximum stress design requirements of the structure. However, this method does not consider the stress distribution state of the entire structure and fills the lattice according to the stress distribution, so the optimal lightweight design of the structure cannot be achieved.

[0008] In summary, there are still many problems in the existing methods in practical use, such as failure to achieve multi-scale topology optimization, failure to fully consider stress distribution for lattice structure filling, and failure to balance lightweight and high-strength requirements. Therefore, it is necessary to propose a more advanced and comprehensive lightweight design method for brackets used in space propulsion systems to meet the dual requirements of lightweight and strength for modern spacecraft. Summary of the Invention

[0009] Aiming at the defects in the prior art, the purpose of the present invention is to provide a multi-scale topology optimization lightweight design method and system for brackets of a space propulsion system.

[0010] According to a multi-scale topology optimization lightweight design method for brackets of a space propulsion system provided by the present invention, the method includes the following steps:

[0011] Step S1: For the bracket used in the space propulsion system, determine the design domain and non-design domain according to the available layout space and installation requirements, and establish an initial model before optimization;

[0012] Step S2: Establish a finite element analysis model, set material properties, divide the mesh, select acceleration, natural frequency, static mechanics, and modal conditions for load application, set boundary conditions, set structural constraints and manufacturability constraints, and use the flexible weighted method to transform the solution of the multi-objective topology optimization problem into the solution of a single-objective optimization problem, and perform macroscopic topology optimization design on the design domain;

[0013] Step S3: Smooth the model after macroscopic topology optimization, re-model it, and set the skin thickness to perform shelling to obtain a cavity model;

[0014] Step S4: Select lattice units to fill the cavity model with a lattice structure of uniform size, and obtain the skin-lattice structure through Boolean operations;

[0015] Step S5: Conduct simulation verification on the bracket optimization model of macroscopic topology optimization and progressive lattice structure filling. Use a mechanical equivalent model to process the lattice structure, and determine whether the dynamic response performance, maximum stress, and displacement data of the optimized bracket model meet the design margin through modal, impact, and vibration finite element analyses;

[0016] Step S6: Conduct simulation verification on the optimized model. If the design margin is met, output the final model; otherwise, repeat the above steps until it is satisfied.

[0017] Preferably, the multi-objective topology optimization method with compliance weighting performed in step S2 is as follows:

[0018]

[0019]

[0020] s.t. KU e = F e

[0021]

[0022] x min ≤ x i ≤ x max

[0023] wherein, is the design variable vector, corresponding to the relative density of each unit in the design domain of the bracket for the space propulsion system. n is the total number of bracket load conditions; W e is the weight factor for the e-th condition; c e (x) is the compliance for the e-th condition; K is the global stiffness matrix; F e and U e are the load and displacement matrices corresponding to the e-th condition respectively; v i is the optimized unit volume; V 0 is the total volume of the bracket structure before optimization; f is the volume fraction; x min is the lower limit of the design variable; x max is the upper limit of the design variable. Based on the above finite element model and topology optimization model, set topology optimization parameters to solve the multi-condition topology optimization.

[0024] Preferably, the manufacturability constraints in step S2 consider the minimum feature size of the topology optimization structure and the maximum inclination angle of the overhanging surface in the design domain:

[0025]

[0026] In the formula, t is the cross-sectional dimension of the topology-optimized structure, and t min is the lower limit of the value of the cross-sectional dimension; θ is the inclination angle of the overhanging surface, and θ max is the maximum value of the inclination angle.

[0027] Preferably, in step S5, the stress levels at different positions inside the combined bracket and the wall thickness of the lattice unit are combined to automatically cluster and partition the lattice structure, and multiple homogeneous solid materials are used to equivalently replace the lattice unit.

[0028] Preferably, in step S5, the mechanical properties of the reconstructed structure are evaluated as follows:

[0029]

[0030] In the formula, MS is the safety margin, indicating the safety of the structure design; [σ] is the allowable stress, indicating the maximum stress that the material can withstand during long-term operation, which is the yield strength of the material; σ max is the maximum stress value under the actual load condition; f is the safety factor, and its value is greater than 1.

[0031] The present invention also provides a multi-scale topology optimization and lightweight design system for a space propulsion system bracket, and the system includes the following modules:

[0032] Module M1: For the bracket used in the space propulsion system, determine the design domain and non-design domain according to the available layout space and installation requirements, and establish an initial model before optimization;

[0033] Module M2: Establish a finite element analysis model, set the material properties, divide the mesh, select the acceleration, natural frequency, static mechanics, and modal conditions for load application, set the boundary conditions, set the structural constraints and manufacturability constraints, and use the flexible weighted method to transform the solution of the multi-objective topology optimization problem into the solution of a single-objective optimization problem, and conduct macroscopic topology optimization design on the design domain;

[0034] Module M3: Smooth the model after macroscopic topology optimization, re-model it, and set the skin thickness to perform shelling to obtain a cavity model;

[0035] Module M4: Select lattice units to fill the cavity model with a lattice structure of uniform size, and obtain a skin-lattice structure through Boolean operation;

[0036] Module M5: Simulate and verify the optimized bracket model of macroscopic topology optimization and progressive lattice structure filling, use a mechanical equivalent model to process the lattice structure, and determine whether the dynamic response performance, maximum stress, and displacement data of the optimized bracket model meet the design margin through modal, impact, and vibration finite element analysis;

[0037] Module M6: Simulate and verify the optimized model. If the design margin is met, output the final model; otherwise, repeat the above modules until it is satisfied.

[0038] Preferably, the flexibility-weighted multi-objective topology optimization system performed in the module M2 is as follows:

[0039]

[0040]

[0041] s.t. KU e = F e

[0042]

[0043] x min ≤ x i ≤ x max

[0044] In the formula, is the design variable vector, corresponding to the relative density of each element in the design domain of the bracket for the space propulsion system. n is the total number of bracket load conditions; W e is the weight factor for the e-th condition; c e (x) is the flexibility for the e-th condition; K is the global stiffness matrix; F e and U e are the load and displacement matrices corresponding to the e-th condition respectively; v i is the optimized element volume; V 0 is the total volume of the bracket structure before optimization; f is the volume fraction; x min is the lower limit of the design variable; x max is the upper limit of the design variable. Based on the above finite element model and topology optimization model, set the topology optimization parameters to solve the multi-condition topology optimization.

[0045] Preferably, the manufacturability constraints in the module M2 consider the minimum feature size of the topology optimization structure and the maximum inclination angle of the overhanging surface of the design domain:

[0046]

[0047] In the formula, t is the cross-sectional dimension of the topology optimization structure, t min is the lower limit of the cross-sectional dimension value; θ is the inclination angle of the overhanging surface, θ max is the maximum value of the inclination angle.

[0048] Preferably, the module M5 automatically partitions the lattice structure into clusters based on the stress levels at different positions inside the stent and the wall thickness of the lattice units, and uses a variety of homogeneous solid materials to perform equivalent replacement of the lattice units.

[0049] Preferably, in module M5, the mechanical properties of the reconstructed structure are evaluated as follows:

[0050]

[0051] In the formula, MS is the safety margin, which indicates the safety of the structural design; [σ] is the allowable stress, which indicates the maximum stress that the material can withstand in long-term operation, and is the yield strength of the material; σ max is the maximum stress value under the actual load condition; f is the safety factor, and its value is greater than 1.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. The present invention realizes for the first time a lightweight design method of multi-scale topological optimization and variable-density lattice structure filling of a support structure for a space propulsion system, which can reduce the weight of the support to the greatest extent while meeting the design margin requirements, or achieve maximum rigidity of the structure when the support weight is constant, which can not only reduce the cost of space launch, but also improve the safety of the structure under extreme conditions, and provide more reliable structural support for the space propulsion system;

[0054] 2. The present invention performs multiple rounds of modal, impact, vibration and other checks on the skin-lattice bracket after topology optimization and lattice filling to ensure that the dynamic response performance and maximum stress, displacement and other data of the optimized bracket model meet the design margin, thereby enhancing the reliability and stability of the bracket and enabling it to adapt to the complex space environment;

[0055] 3. The present invention proposes for the first time a multi-scale topological optimization method that takes into account the variable-density lattice structure filling along the force transmission path of the structure and the process constraints of additive manufacturing. While achieving lightweight design, it minimizes the overhang characteristics of the structure as much as possible, improves the machinability and production efficiency of the bracket, thereby reducing production costs. It fully considers the advantages of additive manufacturing technology in the precise manufacturing of complex structures, making the designed bracket model more in line with actual manufacturing needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0057] Figure 1 A step diagram of a lightweight design method for multi-scale topological optimization of a bracket for a space propulsion system according to an embodiment of the present invention;

[0058] Figure 2 It is the assembly drawing of the storage tank module in an embodiment of the present invention;

[0059] Figure 3 It is the schematic diagram of the initial structure model in an embodiment of the present invention;

[0060] Figure 4 It is the axonometric drawing of the design domain before the macroscopic topology optimization in an embodiment of the present invention;

[0061] Figure 5 It is the bottom view of the design domain before the macroscopic topology optimization in an embodiment of the present invention;

[0062] Figure 6 It is the axonometric drawing of the macroscopic topology optimization configuration in an embodiment of the present invention;

[0063] Figure 7 It is the bottom view of the macroscopic topology optimization configuration in an embodiment of the present invention;

[0064] Figure 8 It is the schematic diagram of the internal variable density lattice structure configuration in an embodiment of the present invention. Detailed implementation manners

[0065] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all belong to the protection scope of the present invention.

[0066] Example 1:

[0067] Refer to Figure 1 , according to a multi-scale topology optimization and lightweight design method for a space propulsion system bracket provided by the present invention, the method includes the following steps:

[0068] Step S1: For the bracket used in the space propulsion system, determine the design domain and non-design domain according to the available layout space and installation requirements, and establish an initial model before optimization;

[0069] Step S2: Establish a finite element analysis model, set the material properties, divide the mesh, select the acceleration, natural frequency, static and modal working conditions for load application, set the boundary conditions, set the structural constraints and manufacturability constraints, and use the flexible weighted method to transform the solution of the multi-objective topology optimization problem into the solution of a single-objective optimization problem, and perform macroscopic topology optimization design on the design domain;

[0070] The multi-objective topology optimization method with flexibility weighting is as follows:

[0071]

[0072]

[0073] such that \(KU\) e = \(F\) e

[0074]

[0075] \(x\) min \(\leq x\) i \(\leq x\) max

[0076] wherein, is the design variable vector, corresponding to the relative density of each unit in the design domain of the bracket for the space propulsion system, \(n\) is the total number of bracket load conditions; \(W\) e is the weight factor for the \(e\)-th condition; \(c\) e \((x)\) is the compliance for the \(e\)-th condition; \(K\) is the global stiffness matrix; \(F\) e and \(U\) e are the load and displacement matrices corresponding to the \(e\)-th condition respectively; \(v\) i is the optimized unit volume; \(V\) 0 is the total volume of the bracket structure before optimization; \(f\) is the volume fraction; \(x\) min is the lower limit of the design variable; \(x\) max is the upper limit of the design variable; Based on the above finite element model and topology optimization model, set the topology optimization parameters to solve the multi-condition topology optimization.

[0077] Manufacturability constraints consider the minimum feature size of the topology optimization structure and the maximum inclination angle of the overhanging surface in the design domain:

[0078]

[0079] wherein, \(t\) is the cross-sectional dimension of the topology optimization structure, \(t\) min is the lower limit of the cross-sectional dimension value; \(\theta\) is the inclination angle of the overhanging surface, \(\theta\) max is the maximum value of the inclination angle.

[0080] Step S3: Smooth the model after macroscopic topology optimization, re-model it, and set the skin thickness to perform shelling to obtain a cavity model;

[0081] Step S4: Select lattice units to fill the cavity model with a lattice structure of uniform size, and obtain a skin-lattice structure through Boolean operations;

[0082] Step S5: Perform simulation verification on the optimized model of the stent with macro-topology optimization and progressive lattice structure filling. Use a mechanical equivalent model to process the lattice structure, and determine whether the dynamic response performance, maximum stress, and displacement data of the optimized stent model meet the design margin through modal, shock, and vibration finite element analyses;

[0083] Combine the stress levels at different positions inside the stent and the wall thickness of the lattice cells to automatically cluster and partition the lattice structure, and use a variety of homogeneous solid materials to equivalently replace the lattice cells.

[0084] Evaluate the mechanical properties of the reconstructed structure as follows:

[0085]

[0086] In the formula, MS is the safety margin, indicating the safety of the structure design; [σ] is the allowable stress, representing the maximum stress that the material can withstand during long-term operation, which is the yield strength of the material; σ max is the maximum stress value under the actual load condition; f is the safety factor, and its value is greater than 1.

[0087] Step S6: Perform simulation verification on the optimized model. If the design margin is met, output the final model; otherwise, repeat the above steps until it is met.

[0088] The present invention also provides a multi-scale topology optimization and lightweight design system for a space propulsion system stent. The multi-scale topology optimization and lightweight design system for the space propulsion system stent can be implemented by executing the process steps of the multi-scale topology optimization and lightweight design method for the space propulsion system stent. That is, those skilled in the art can understand the multi-scale topology optimization and lightweight design method for the space propulsion system stent as a preferred implementation manner of the multi-scale topology optimization and lightweight design system for the space propulsion system stent.

[0089] Example 2:

[0090] The present invention also provides a multi-scale topology optimization and lightweight design system for a space propulsion system stent. The system includes the following modules:

[0091] Module M1: For the stent used in the space propulsion system, determine the design domain and non-design domain according to the available layout space and installation requirements, and establish an initial model before optimization;

[0092] Module M2: Establish a finite element analysis model, set material properties, divide the mesh, select acceleration, natural frequency, static mechanics, and modal conditions for load application, set boundary conditions, set structural constraints and manufacturability constraints, and use the flexible weighted method to transform the solution of the multi-objective topology optimization problem into the solution of a single-objective optimization problem, and perform macro-topology optimization design on the design domain;

[0093] The flexibility-weighted multi-objective topology optimization system carried out is as follows:

[0094]

[0095] s.t. KU e = F e

[0096]

[0097] x min ≤ x i ≤ x max

[0098] In the formula, is the design variable vector, corresponding to the relative density of each element in the design domain of the bracket for the space propulsion system, and n is the total number of bracket load conditions; W e is the weight factor for the e-th condition; c e (x) is the flexibility of the e-th condition; K is the global stiffness matrix; F e and U e are the load and displacement matrices corresponding to the e-th condition respectively; v i is the optimized element volume; V 0 is the total volume of the bracket structure before optimization; f is the volume fraction; x min is the lower limit of the design variable; x max is the upper limit of the design variable; Based on the above finite element model and topology optimization model, topology optimization parameters are set to solve the multi-condition topology optimization.

[0099] Manufacturability constraints consider the minimum feature size of the topology optimization structure and the maximum inclination angle of the overhanging surface in the design domain:

[0100]

[0101] In the formula, t is the cross-sectional dimension of the topology optimization structure, t min is the lower limit of the cross-sectional dimension value; θ is the inclination angle of the overhanging surface, and θ max is the maximum value of the inclination angle.

[0102] Module M3: Smooth the model after macroscopic topology optimization, re-model it, and set the skin thickness to perform shelling to obtain a cavity model;

[0103] Module M4: Select lattice units to fill the cavity model with a lattice structure of uniform size, and obtain a skin-lattice structure through Boolean operations;

[0104] Module M5: Simulate and verify the bracket optimization model for macro-topological optimization and progressive lattice structure filling. Use a mechanical equivalent model to handle the lattice structure, and determine whether the dynamic response performance, maximum stress, and displacement data of the optimized bracket model meet the design margin through modal, shock, and vibration finite element analyses. Combine the stress levels at different positions inside the bracket and the wall thickness of the lattice cells to automatically cluster and partition the lattice structure, and use multiple homogeneous solid materials to equivalently replace the lattice cells.

[0105] The mechanical properties evaluation of the reconstructed structure is as follows:

[0106]

[0107] In the formula, MS is the safety margin, indicating the safety of the structure design; [σ] is the allowable stress, representing the maximum stress that the material can withstand during long-term operation, which is the yield strength of the material; σ max is the maximum stress value under the actual load condition; f is the safety factor, and its value is greater than 1.

[0108] Module M6: Simulate and verify the optimization model. If the design margin is met, output the final model; otherwise, repeat the above modules until it is satisfied.

[0109] Example 3:

[0110] As Figure 1 shown is the flowchart of the lightweight design method for multi-scale topological optimization of a bracket for a space propulsion system according to the present invention. Figure 2 It is a model of a tank module for a certain space propulsion system. The tank is connected to the cabin through front and rear titanium alloy brackets, and the mounting holes of the brackets are all threaded holes. Figure 3 The rear bracket shown is the research object of this embodiment. This embodiment includes the following steps:

[0111] S1: According to the 3D model of the rear bracket, establish an initial topological optimization model based on the payload type, bracket position layout constraints, and installation requirements. This model includes a design domain and a non-design domain. A thickness of 4 mm needs to be left as the non-design domain around the mounting holes and in the depth direction to ensure the subsequent machining allowance, as Figure 4 shown; Connect the mounting holes on the bottom surface with solid non-design domains, as Figure 5 shown;

[0112] S2: Establish a finite element analysis model: Perform finite element mesh division on the initial model established in step S1 to obtain a finite element model, and set the material parameters, boundary conditions, and loads of the finite element model according to the actual working conditions; The following is this embodiment:

[0113] Simplify the loads on the storage tank model. Simplify the tank body on the upper part and the structure on the side of the storage tank model into mass points and load them onto their respective brackets.

[0114] Perform finite element mesh division on the initial model. The mass point element uses the MASS21 element. MASS21 is a point element with six degrees of freedom, namely translation in the x, y, and z directions and rotation about the x, y, and z axes. Each direction has different masses and moments of inertia. The bracket is simulated using solid elements and mass point elements. Among them, the solid element selects the solid186 element. solid186 is a high-order 3D 20-node solid structure element, and each node has 3 degrees of freedom for translation along the xyz directions. The element supports plasticity, hyperelasticity, creep, stress stiffening, large deformation, and large strain capabilities, and is more insensitive to mesh density and size. The number of solid186 elements obtained by meshing is 2,175,270.

[0115] Assign the material properties of TC4 titanium alloy to the model. The material properties refer to GB / T 2965-2007. Specifically, the density is 4430 kg / m3, the Young's modulus is 1.2×105 MPa, the Poisson's ratio is 0.3, the bulk modulus is 1×105 MPa, and the shear modulus is 46154 MPa.

[0116] S3: Use the ANSYS Mechnical 2023R1 simulation tool to perform macroscopic topology optimization on the design domain according to the load conditions when the storage tank is full. Perform static and modal simulations on the finite element model in six directions respectively. The overall acceleration applied in the six directions is 10316543.2 mm / s2. Use the flexible weighted method to transform the problem of solving multi-objective topology optimization into solving a single-objective optimization problem. Before optimization, set the retained mass to 25%, set the symmetry of the bracket in the YZ plane, adjust the minimum characteristic size of the generated structure to 2 mm, determine conditions such as the printing overhang angle of the bracket, and perform macroscopic topology optimization design on the design domain.

[0117] S4: The initial optimized model obtained from macroscopic topology optimization has some complex geometric features, such as slender connecting rods, cavities, and irregular boundaries. These features will cause problems in subsequent finite element analysis or manufacturing. Evaluate the initial optimized model, determine the areas that can be modified or removed, delete or merge local small features, use a smoothing tool to smooth the model, adjust the size and distribution of the mesh, ensure that there are sufficiently fine meshes in key areas (such as stress concentration areas) to reduce sharp edges and irregular surfaces and capture details. The smoothed model is as Figure 6 ;

[0118] S5: Use nTopology software to perform shelling on the obtained macroscopic topology optimization model to obtain a cavity model, and set the shell wall thickness to 2 mm;

[0119] S6: Select Primitive cells from the lattice cell library of nTopology to fill the topology-optimized cavity model with a lattice structure of uniform size. The unit cell size is 6×6×6 mm, and the cell wall thickness is 0.45 mm, meeting the weight requirement of the final optimized model of 1.76 kg. Combine the skin and the lattice structure through Boolean operation to obtain the skin-lattice structure;

[0120] S7: Use nTopology software to perform a static finite element analysis of the skin-lattice structure under load again, and solve to obtain the corresponding force transmission path and stress field distribution;

[0121] S8: Optimize the geometric parameters of the lattice structure based on the stress distribution field. Fill the lattice structure with a relatively low relative density in the region with relatively low stress to reduce the structural weight, and fill the lattice structure with a relatively high relative density in the region with relatively high local stress to increase the structural stiffness. Here, the relative density is changed by adjusting the wall thickness of the Primitive cells, and the cell wall thickness gradually changes within the range of 0.35 - 0.60 mm. The weight of the final multi-scale topology optimization model is 1.70 kg;

[0122] S9: Use the ANSYS Material Designer module to approximately equivalent the lattice structure in the wall thickness range of 0.35 - 0.60 mm with 5 homogeneous solid materials, and perform a static analysis on these 5 lattice structures to obtain the mechanical properties of the solid materials; then divide the lattice structure inside the bracket skin into regions according to the wall thickness and assign the properties of homogeneous solid materials; finally, use ANSYS Workbench to re-mesh and perform a finite element analysis check on the solid bracket topology optimization model, and establish modal simulation-based simulations of impact, sinusoidal vibration, escape random vibration, and non-escape random vibration in three axial directions;

[0123] S10: Obtain the frequency and vibration mode results of the first 10 orders of the modal analysis, and find that the first 10 natural frequencies have a large increase compared to the initial design frequency, and the maximum displacement decreases. Determine that the mechanical properties of the optimized bracket model meet the design margin through the finite element analysis of impact, sinusoidal vibration, non-escape random vibration, and escape random vibration of the bracket / tank module. Re-model the final optimized model, add process powder cleaning holes after additive manufacturing, and set a total of 14 powder cleaning holes with a diameter of 2 mm at the top and bottom of the model according to the bracket size and internal cavity structure. These powder cleaning holes need to be plugged by means such as welding after the additive manufacturing powder is removed.

[0124] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1 and Embodiment 2.

[0125] Those skilled in the art know that, in addition to implementing the system and its various devices, modules, and units provided by the present invention in the form of pure computer-readable program code, the method steps can be logically programmed to enable the system and its various devices, modules, and units provided by the present invention to be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers, etc., to achieve the same functions. Therefore, the system and its various devices, modules, and units provided by the present invention can be regarded as a kind of hardware component, and the devices, modules, and units included therein for implementing various functions can also be regarded as the structures within the hardware component; the devices, modules, and units for implementing various functions can also be regarded as software modules for implementing the method and the structures within the hardware component.

[0126] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A multi-scale topological optimization lightweight design method for a space propulsion system bracket, characterized in that: The method comprises the following steps: Step S1: for the bracket for the space propulsion system, the design domain and the non-design domain are determined according to the available space and installation requirements, and an initial model before optimization is established; Step S2: Establish a finite element analysis model, set material properties, divide the mesh, select acceleration, natural frequency statics and modal conditions for load application, set boundary conditions, set structural constraints and manufacturing constraints, use a flexible weighted method to transform the solution of a multi-objective topology optimization problem into a solution of a single-objective optimization problem, and perform macroscopic topology optimization design on the design domain; Step S3: smoothing the model after macro topology optimization, remodeling, and setting the skin thickness to extract the shell to obtain a cavity model; Step S4: Select lattice units to fill the cavity model with a lattice structure of uniform size, and obtain a skin-lattice structure through Boolean operation; Step S5: Simulate and check the optimized model of the bracket filled with macro-topology optimization and progressive lattice structure, use a mechanical equivalent model to process the lattice structure, and determine whether the dynamic response performance and maximum stress and displacement data of the optimized bracket model meet the design margin through modal, impact, and vibration finite element analysis; Step S6: Perform simulation verification on the optimized model. If the design margin is met, the final model is output. Otherwise, the above steps are repeated until it is met.

2. The multi-scale topological optimization lightweight design method for a space propulsion system bracket according to claim 1 is characterized in that: The flexibility weighted multi-objective topology optimization method performed in step S2 is as follows: findx={x1,x2,...,x i } T ,i=1,2,...,n stKU e =F e x min ≤x i ≤x max Where x = {x1, x2, ..., x i } T is the design variable vector, corresponding to the relative density of each unit in the design domain of the support for the space propulsion system, n is the total number of support load conditions; W e is the weight factor of the e-th working condition; c e (x) is the flexibility of the e-th working condition; K is the overall stiffness matrix; F e with U e are the load and displacement matrices corresponding to the e-th working condition; v i is the optimized unit volume; V0 is the total volume of the support structure before optimization; f is the volume fraction; x min is the lower limit of the design variable; x max is the upper limit of the design variable; Based on the above-mentioned finite element model and topology optimization model, the topology optimization parameters are set to perform multi-condition topology optimization solutions.

3. The multi-scale topological optimization lightweight design method for a space propulsion system bracket according to claim 1 is characterized in that: The manufacturing constraints in step S2 consider the minimum feature size of the topology optimization structure and the maximum inclination angle of the overhang surface of the design domain: Where t is the cross-sectional size of the topologically optimized structure, t min is the lower limit of the cross-sectional size; θ is the inclination angle of the overhanging surface, θ max is the maximum value of the tilt angle.

4. The multi-scale topological optimization lightweight design method for a space propulsion system bracket according to claim 1 is characterized in that: In step S5, the lattice structure is automatically partitioned into clusters based on the stress levels at different positions inside the stent and the wall thickness of the lattice unit, and the lattice units are equivalently replaced using a variety of homogeneous solid materials.

5. The multi-scale topological optimization lightweight design method for a space propulsion system bracket according to claim 1 is characterized in that: In step S5, the mechanical properties of the reconstructed structure are evaluated as follows: In the formula, MS is the safety margin, which indicates the safety of the structural design; [σ] is the allowable stress, which indicates the maximum stress that the material can withstand in long-term operation, and is the yield strength of the material; σ max is the maximum stress value under the actual load condition; f is the safety factor, and its value is greater than 1.

6. A multi-scale topological optimization lightweight design system for a space propulsion system bracket, characterized in that: The system includes the following modules: Module M1: For the bracket used in space propulsion system, the design domain and non-design domain are determined according to the available space and installation requirements, and the initial model before optimization is established; Module M2: Establish a finite element analysis model, set material properties, divide the mesh, select acceleration, natural frequency statics and modal conditions for load application, set boundary conditions, set structural constraints and manufacturing constraints, use flexible weighted method to transform the solution of multi-objective topology optimization problem into the solution of single-objective optimization problem, and perform macroscopic topology optimization design on the design domain; Module M3: Smoothing the model after macro-topology optimization, remodeling, and setting the skin thickness to extract the shell to obtain a cavity model; Module M4: Select lattice units to fill the cavity model with a lattice structure of uniform size, and obtain the skin-lattice structure through Boolean operation; Module M5: Simulate and verify the bracket optimization model of macro-topology optimization and progressive lattice structure filling, use the mechanical equivalent model to process the lattice structure, and determine whether the dynamic response performance and maximum stress and displacement data of the optimized bracket model meet the design margin through modal, impact and vibration finite element analysis; Module M6: Simulate and check the optimized model. If the design margin is met, the final model is output. Otherwise, the above modules are repeated until it is met.

7. The multi-scale topological optimization lightweight design system for a space propulsion system bracket according to claim 6 is characterized in that: The flexibility-weighted multi-objective topology optimization system performed in the module M2 is as follows: findx={x1,x2,...,x i } T ,i=1,2,...,n stKU e =F e x min ≤x i ≤x max Where x = {x1, x2, ..., x i } T is the design variable vector, corresponding to the relative density of each unit in the design domain of the support for the space propulsion system, n is the total number of support load conditions; W e is the weight factor of the e-th working condition; c e (x) is the flexibility of the e-th working condition; K is the overall stiffness matrix; F e with U e are the load and displacement matrices corresponding to the e-th working condition; v i is the optimized unit volume; V0 is the total volume of the support structure before optimization; f is the volume fraction; x min is the lower limit of the design variable; x max is the upper limit of the design variable; Based on the above-mentioned finite element model and topology optimization model, the topology optimization parameters are set to perform multi-condition topology optimization solutions.

8. The multi-scale topological optimization lightweight design system for a space propulsion system support according to claim 6 is characterized in that: The manufacturability constraints in module M2 consider the minimum feature size of the topology optimization structure and the maximum tilt angle of the overhang surface in the design domain: Where t is the cross-sectional size of the topologically optimized structure, t min is the lower limit of the cross-sectional size; θ is the inclination angle of the overhanging surface, θ max is the maximum value of the tilt angle.

9. The multi-scale topological optimization lightweight design system for a space propulsion system bracket according to claim 6, characterized in that: In the module M5, the stress levels at different positions inside the bracket and the wall thickness of the lattice unit are combined to automatically partition the lattice structure into clusters, and the lattice units are equivalently replaced with a variety of homogeneous solid materials.

10. The multi-scale topological optimization lightweight design system for a space propulsion system bracket according to claim 6, characterized in that: In module M5, the mechanical properties of the reconstructed structure are evaluated as follows: In the formula, MS is the safety margin, which indicates the safety of the structural design; [σ] is the allowable stress, which indicates the maximum stress that the material can withstand in long-term operation, and is the yield strength of the material; σ max is the maximum stress value under the actual load condition; f is the safety factor, and its value is greater than 1.

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