Lightweight Topology Structure Inertial Assembly Body Model Design Method

Abstract

The present invention provides a method for designing a lightweight topological structure inertial assembly body model, including the following steps arranged in sequence: a basic model for structural design; data analysis of the stress and strain of the original model; structural optimization based on the principles of additive and subtractive manufacturing; topological optimization design; judging whether the optimization goal is met; fairing treatment; finite element analysis; additive manufacturing; post-processing; subtractive manufacturing, test and detection, etc. Before the generative topological optimization step, the present invention performs structural optimization on the inertial assembly body that meets the requirements obtained from the basic structural design based on the principles of additive and subtractive manufacturing, can leave process allowances for various connection structures, precision docking surfaces, and fixed structures in the actual processing of the inertial assembly body, consider the optimization treatment of positions prone to deformation during processing and surfaces that do not require processing later, effectively ensures the requirements of high precision, high stability and lightweight design of the inertial assembly body, and avoids the requirement that the structure after topological optimization is not conducive to additive and subtractive manufacturing.

Description

Technical Field

[0001] The present invention relates to the technical fields of inertial measurement unit (IMU) housing design and metal processing and manufacturing, and particularly relates to a design method for a lightweight topological structure IMU housing model. Background Art

[0002] The IMU is an important instrument in an aircraft and plays a key role in the success or failure of the product. The IMU housing is the core component for installing gyroscopes and accelerometers, and its main function is to sense the flight attitude, speed, etc. of the aircraft in real time to help control the flight trajectory of the aircraft. IMU devices are key components in the guidance and control system, and their performance directly affects the performance of the entire aircraft.

[0003] Therefore, the IMU housing structure needs to meet the requirements of high stiffness and high precision. Traditional IMU housing structures mostly use metal subtractive manufacturing such as numerical control turning and milling. In order to meet the high stiffness requirements of the IMU housing, the weight of its structure is relatively large, which will increase the weight of the aircraft when used in the aircraft. When the total weight of the aircraft is fixed, it will affect the placement ability of the payload, and further affect the amount of tasks that can be executed. Reducing the weight of the aircraft by 1 kg can reduce 10 kg of fuel, and reducing the weight of the aircraft head by 1 kg can increase the flight range by 14 km. Therefore, reducing the weight of the inertial housing structure is of great significance.

[0004] Topology optimization technology takes the material distribution as the optimization object and can find the best material distribution scheme that meets the design goal in the specified design space, so as to realize the lightweight design of the target structure. Generative topology optimization technology can adjust the best distribution relationship of materials in the design space according to the design goals (such as target stress, target stiffness) and constraint parameters (such as material properties, working conditions, non-design space) provided by the designer, optimize the force distribution, and through multiple iterative calculations, while realizing the lightweight design of the target structure to the greatest extent, provide multiple alternative solutions that meet the design goals for the designer to refer to and select.

[0005] In the prior art, there are methods of applying topology optimization technology to optimize the structure of complex parts. Due to the limitations of the gyro installation platform and the two-axis rotary structure of the IMU housing, there are technical bottlenecks in aspects such as platform stability, mechanism precision, and space rationality. Moreover, since the IMU housing is used in an aircraft, its structure and processing accuracy requirements are high, and the traditional processing method has many processing procedures and a long processing cycle, resulting in too high costs, which is not conducive to the cost control of the aircraft and the improvement of production efficiency. Summary of the Invention

[0006] In view of this, the present invention aims to propose a design method for a lightweight topology inertial assembly body model, so as to be able to apply the topology optimization design method to the structural design of the inertial assembly body, and combine the design concepts of additive and subtractive manufacturing to optimize the structure of the inertial assembly body, perform lightweight design on the inertial assembly body, improve the machining accuracy of the inertial assembly body, and shorten the machining process route.

[0007] To achieve the above object, the technical solution of the present invention is realized as follows:

[0008] A design method for a lightweight topology inertial assembly body model includes the following steps:

[0009] S1. Structural design basic model;

[0010] S11. Perform original model design on the inertial assembly body, and optimize the part structure using modeling software according to requirements such as working conditions, part assembly dimensions, and subsequent additive and subtractive machining requirements.

[0011] S12. Material selection, select the required metal material with a lower density according to weight requirements and working conditions, and the metal material needs to meet the requirements of additive manufacturing process.

[0012] S2. Analyze the stress and strain data of the original model, determine the fixed structure and gyro precision docking surface of the original model, define the load and boundary constraint conditions according to the working conditions, apply pressure and gravitational acceleration to the gyro precision docking surface, and perform fixed constraint on the fixed structure, perform stress and deformation analysis, and check whether the selected material meets the design requirements. If it meets, execute step S3; if not, return to execute step S1.

[0013] S3. Optimize the structure of the original model that meets the design requirements in step S2 based on the principles of additive and subtractive manufacturing, specifically including the following steps:;

[0014] S31. Perform process allowances on the first connection structure and the second connection structure on the inertial assembly body. The first connection structure is used to install the gyroscope, and the second connection structure is used to install the accelerometer.

[0015] S32. Perform process allowances on the gyro precision docking surface, accelerometer precision docking surface, and fixed structure in step 2.

[0016] S33. Optimize the surfaces that are prone to deformation during additive manufacturing and do not require subtractive machining in the later stage.

[0017] S4. Perform topology optimization design on the optimized inertial assembly body in step S3.

[0018] S41. Endow the original model with the same material properties, loads, and boundary constraint conditions as in step S2, and set the optimization goal.

[0019] S42. Define the space for topology optimization of the original model as the design space, and define the machining process allowance and necessary existing structures as the entity requirements to be present after topology optimization, to obtain the structure of the inertial assembly body after topology optimization.

[0020] S43. Adjust the discreteness of the material distribution during the optimization process and adjust the material distribution rate.

[0021] S44. Import the structure of the original model after topology optimization obtained in step S42 into finite element analysis software, and perform a stress analysis according to whether the materials, stresses, and strains in step S3 meet the design requirements, to optimize the structure and boundary conditions of the inertial assembly body.

[0022] S5. Determine whether the inertial assembly body obtained in step 4 meets the optimization goal, as well as the requirements for additive and subtractive manufacturing. If it meets the requirements, execute step 6; if not, return to execute step 3.

[0023] S6. Smooth the inertial assembly body obtained in step 5 to avoid stress concentration.

[0024] S7. Define the loads and boundary constraint conditions according to the working conditions in step 2, and use finite element analysis software to perform a structural stress analysis on the inertial assembly body obtained in step 6.

[0025] S8. Import the external dimensions of the inertial assembly body obtained in step 7 into the additive manufacturing equipment, and after reserving the machining allowance for subtractive manufacturing, perform additive manufacturing.

[0026] S9. Perform post-processing on the solid model of the inertial assembly body obtained in step 8.

[0027] S10. Perform subtractive manufacturing on the solid model of the inertial assembly body obtained in step 9 to obtain the inertial assembly body that meets the lightweight requirements.

[0028] S11. Perform experimental testing on the solid model of the inertial assembly body obtained in step 10.

[0029] Furthermore, the material of the inertial assembly body model is AlSi10Mg.

[0030] Furthermore, select two fixed structures, three gyroscope precision docking surfaces, and three accelerometer precision docking surfaces in the original model in step 2. The fixed structures are used to fix the inertial assembly body during the subtractive manufacturing in step 10, and the gyroscope precision docking surfaces are used to install gyroscopes.

[0031] Further, the working conditions in step S11 are set to apply a force of 1000 N respectively to the three gyro precision docking surfaces and apply a gravitational acceleration of 30 G.

[0032] Further, the optimization objectives include mass requirements, strength requirements, stiffness requirements, and dimensional requirements. The self-supporting structure is adopted in the optimization process.

[0033] Further, the mass requirement of the inertial assembly body is: the total mass of the inertial assembly body ≤ 0.4 kg;

[0034] The strength requirement of the inertial assembly body is: the inertial assembly body shall not be damaged or fail during the working state, and the design safety factor is not less than 3;

[0035] The stiffness requirement of the inertial assembly body is: under accelerations in all directions, the deformation of the parts of the inertial assembly body is as small as possible;

[0036] The dimensional requirement of the inertial assembly body is: it shall not be larger than the original model, and the positions, dimensions, and tolerances of parts such as each gyro and clamping table installed on the inertial assembly body are consistent.

[0037] Further, the additive manufacturing is 3D printing. The technological processes sequentially set in the additive manufacturing process are additive manufacturing, fitter work, stress relief annealing, abrasive slag removal, flaw detection, semi-finishing, thermal cycling treatment, surface treatment (anodic oxidation treatment), and five-axis precision machining.

[0038] Further, the post-processing of the process includes mechanical strength treatment, dimensional tolerance treatment, and surface roughness treatment;

[0039] The mechanical strength treatment includes heat treatment and anodic oxidation treatment;

[0040] The dimensional tolerance treatment includes burr removal, grinding, lapping, and honing;

[0041] The surface roughness treatment includes sandblasting, coating, abrasive flow machining, and machining.

[0042] Further, the test and detection steps of the inertial assembly body in step 11 include:

[0043] Centrifugal test, vibration test, shock test, and clamping total test.

[0044] Compared with the prior art, the present invention has the following advantages:

[0045] The lightweight topology inertial assembly body model design method described in the present invention performs structural optimization on the qualified inertial assembly body obtained in the structural design basis based on the principles of additive and subtractive manufacturing before the generative topology optimization step, which can perform process allowances on the connection structures, precision docking surfaces, and fixed structures of the inertial assembly body during the actual machining process, and consider the optimization of the easily deformed positions during machining and the surfaces that do not require machining later. By fully considering the structural optimization during the machining of the inertial assembly body, the structural optimization effect of the inertial assembly body and the physical product yield after machining are improved, effectively ensuring the high-precision and high-stability requirements of the inertial assembly body model, and avoiding the requirement that the structure after topology optimization is not conducive to additive and subtractive machining.

[0046] In addition, in step one of the present invention, a preliminary structural design basis for the inertial assembly body is obtained according to the working condition requirements, part assembly, and machining requirements to obtain the original model, and material selection is carried out. Then, through the stress and strain data analysis of the original model in step two to check whether the obtained original model and material selection meet the design requirements, an initial check of the original model is performed. Through the structural optimization based on the principles of additive and subtractive manufacturing and the topology optimization structure using generative design, an optimization step of combining lightweight design for the inertial assembly body is carried out to obtain an optimized inertial assembly body that meets the optimization goal. Again, according to the working condition in step two, finite element analysis is used to perform structural stress analysis on the optimized inertial assembly body model, which not only meets the lightweight requirement and realizes effective weight reduction but also ensures the structural strength requirement of the inertial assembly body model.

[0047] With such a setting, two structural stress checks can be performed during the model design stage of the inertial assembly body to ensure the stability and structural strength of the optimized inertial assembly body model. And the check data of the original model can be compared and analyzed with the design of the optimized inertial assembly body model to obtain the strain and stress data before and after the structural optimization, so as to further adjust the parameter design during optimization to obtain a better inertial assembly body model.

[0048] The present invention uses software to simulate the original model, and optimizes it by inputting the original model data into the topology optimization design structure to obtain the module body model. By inputting the obtained inertial assembly body model data into the additive manufacturing software, the physical inertial assembly body is obtained in the processing modes of additive and subtractive manufacturing, and physical tests are carried out, so that more accurate real data of the inertial assembly body can be obtained, which is more accurate than the simulation evaluation of the data model after topology optimization in the prior art, and can achieve the purpose of subsequent mass production data collection through the actual machining process. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0050] Figure 1 Flow chart of the lightweight topology inertial assembly body model design method described in the embodiments of the present invention;

[0051] Figure 2 Load diagram of the working conditions that the original model described in the embodiments of the present invention needs to withstand;

[0052] Figure 3 Fixed structure of the original model under working conditions described in the embodiments of the present invention;

[0053] Figure 4 Stress distribution diagram of the original model described in the embodiments of the present invention;

[0054] Figure 5 Deformation diagram of the original model after being stressed described in the embodiments of the present invention;

[0055] Figure 6 Comparison diagram of the inertial assembly body after topology optimization and the original model described in the embodiments of the present invention;

[0056] Figure 7 Product analysis cloud map before and after topology optimization when the strain is the largest under the same working conditions described in the embodiments of the present invention;

[0057] Figure 8 Deformation diagram of the inertial assembly body after being stressed after topology optimization described in the embodiments of the present invention;

[0058] Figure 9 Stress distribution diagram of the inertial assembly body after topology optimization described in the embodiments of the present invention;

[0059] Figure 10 Centrifugal test image of the inertial assembly body under working conditions described in the embodiments of the present invention;

[0060] Figure 11 Test image and mechanical properties of the inertial assembly body under three - coordinate vibration working conditions described in the embodiments of the present invention;

[0061] Figure 12 Mechanical properties of the inertial assembly body under impact load satisfying the working conditions described in the embodiments of the present invention;

[0062] Figure 13 Schematic diagram of the structure with a 95% dispersion in the test in step 3 of the inertial assembly body described in the embodiments of the present invention. Detailed implementation manners

[0063] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0064] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "upper", "lower", "inner", "back", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. Additionally, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0065] Furthermore, in the description of the present invention, unless otherwise clearly defined, the terms "installed", "connected", "connected to", "connecting member" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in combination with specific circumstances.

[0066] The present invention will be described in detail below with reference to the drawings and in conjunction with embodiments.

[0067] The following describes this embodiment with reference to the drawings.

[0068] In order to solve the problems of the complex processing and many processing procedures of the inertial measurement unit (IMU) assembly body using the mechanical processing method in the prior art, and to provide a more accurate optimization scheme for the structure of the IMU assembly body in an aircraft, etc., this embodiment proposes a method for a lightweight topology-structured IMU assembly body model. On the basis of avoiding the processing defects of the existing IMU assembly body, it realizes a high-degree lightweight design of the original model based on the requirements of additive and subtractive manufacturing, and reduces the production and manufacturing cost and processing difficulty of the IMU assembly body.

[0069] In the original processing method of the process route, and in order to meet the strength requirements of the IMU assembly body in an aircraft, the IMU assembly body uses 7075-T651 super-hard aluminum alloy, and the overall mass after processing is nearly 1 kilogram. For the raw material of the unprocessed original model, due to the high precision requirements and many processing procedures of the IMU assembly body size, the raw material is about 5 kilograms, which greatly increases the input cost of the raw material.

[0070] This embodiment relates to a method for designing a lightweight topology-structured IMU assembly body model, including the following steps:

[0071] S1. Structural design of the basic model;

[0072] S11. Design the original model of the inertial assembly body. According to the working condition requirements, part assembly dimensions, subsequent additive and subtractive manufacturing requirements, etc., use modeling software to optimize the design of the part structure. According to the given working condition conditions and assembly dimension space, use CAD 3D modeling software such as UG or SolidWorks to initially construct an original design model that meets the use function, and save it in a common format of CAD software such as IGES.

[0073] S12. Material selection. Select the required low-density metal material according to the weight requirements and working condition requirements, and the metal material needs to meet the requirements of additive manufacturing technology. The material used for the inertial assembly body model in this embodiment is AlSi10Mg. This material has good strength, toughness and corrosion resistance, which is not only conducive to the needs of additive manufacturing, but also can meet the weight requirements of the optimized inertial assembly body model. The density, Young's modulus, Poisson's ratio and property information of this material are shown in the following table.

[0074]

[0075] S2. Analyze the stress and strain data of the original model, determine the fixed structure and gyro precision docking surface of the original model, define the load and boundary constraint conditions according to the working condition conditions, apply pressure and gravitational acceleration to the gyro precision docking surface, and perform fixed constraint on the fixed structure, and perform stress and deformation analysis to check whether the selected material meets the design requirements. If it meets, execute step S3; if not, return to execute step S1.

[0076] In the original model of this embodiment, two fixed structures and three gyro precision docking surfaces are selected. The fixed structure is used to fix the inertial assembly body during the following subtractive manufacturing, and the gyro precision docking surface is used to install the gyroscope. As Figure 3 shown, the two black surfaces are the fixed structures.

[0077] As Figure 2 and Figure 4As shown, the working conditions of this embodiment are to apply a vertical centripetal pressure of 1000 N to each of the three gyro precision docking surfaces, and each surface is subjected to a gravitational acceleration of 30 G to meet the maximum acceleration during the acceleration of the aircraft. Thus, a simulation boundary condition is formed in which the original model is stressed in the three directions of the coordinate system X, Y, and Z, and two fixed structures are constrained. Then, a finite element simulation analysis is performed on the fixed original model. Volume meshes are divided for the original design model. In areas where stress concentration is likely to occur and peak stresses appear, such as at cross-section mutations, high-order elements are used to increase the mesh density to improve the calculation accuracy. Submit the job to run the mechanical simulation, analyze the stress distribution and deformation data of the original design model under the corresponding working conditions, record the peak stress and the maximum deformation, and check whether the selected metal material meets the strength and stiffness requirements. If it meets the requirements, execute step S3; if it does not meet the requirements, execute step S1. The specific data of the material and the original model selected in this embodiment show that the maximum stress is 6.3 MPa and the maximum deformation is 0.001 mm, which can meet the strength and stiffness requirements.

[0078] S3. Based on the principles of additive and subtractive manufacturing, perform structural optimization on the original model that meets the design requirements in step S2;

[0079] S31. Perform process allowances on the first connection structure and the second connection structure on the inertial assembly body. The first connection structure is used to install the gyroscope, and the second connection structure is used to install the accelerometer. The process allowances of the first connection structure and the second connection structure are processed in step 10 below;

[0080] S32. Perform process allowances on the gyro precision docking surface, the accelerometer precision docking surface, and the fixed structure in step 2, and process them in step 10 below;

[0081] S33. Optimize the surfaces that are prone to deformation during the additive and subtractive processing in steps 8 and 10 below and do not require subtractive processing in the later stage.

[0082] In addition, in order to avoid manual removal of the support structure of the inertial assembly body after additive manufacturing, it needs to be set as a self-supporting structure, that is, manually set some supports to facilitate heat dissipation during the printing process and stabilize the printing structure to prevent deformation during the printing process.

[0083] S4. Perform topology optimization design on the optimized inertial assembly body in step S3; Based on the concept of removing inefficient materials from the structure, by identifying effective designs, the remaining materials are evolved towards the optimal state. By adopting structural topology optimization technology, the inertial component body can obtain an internal porous structure composed of materials with different densification degrees, and this structure can provide enhanced structural features where the parts actually need them.

[0084] In this embodiment, the software used is NX Topology Optimization. For the topology optimization of continua, the more commonly used optimization strategy is the variable density method, including the SIMPS (Solid Isotropic with penalizatiom) method and the RAMP (Rational Approximation of Material Properties) method. Element division is performed in the preprocessing stage of optimization, and the element shape remains unchanged during the optimization process. The variable density method transforms the topology optimization problem of the structure into the optimal distribution problem of the materials of each independent element. The mathematical model of topology optimization is:

[0085] X = [X1, X2, X3,..., X n T

[0086] min C = F T D

[0087]

[0088] 0 < X min ≤ X N ≤ X max

[0089] F = KD

[0090] In the formula,

[0091] C - compliance of the structure;

[0092] F - load vector;

[0093] K - stiffness matrix;

[0094] D - displacement vector;

[0095] V - volume of the structure filled with materials;

[0096] V0 - volume of the structure design domain;

[0097] V1 - volume of materials with element density less than X min ;

[0098] F - percentage of remaining materials;

[0099] X min - lower limit of the element relative to the density;

[0100] X max - upper limit of the element relative to the density;

[0101] ​In the variable density method, the SIMP method can achieve both stable and rapid convergence, and can find the optimal material layout within the design area, thereby obtaining the corresponding topological structure. Currently, the methods adopted by common topological software are all SIMP methods.

[0102] Assume that the elastic modulus of the material is the Poisson's ratio of isotropic μ which is a constant, and the elastic modulus E of the part will change with the change of the relative density of the element. Then the mathematical model of the SIMP method is:

[0103] E(ρ) = ρ P E0

[0104] ∫ρdΩ ≤ V

[0105] 0 ≤ ρ ≤ 1

[0106] E(ρ) — The equivalent elastic modulus of the material element

[0107] P — Penalty factor, greater than 1

[0108] E0 — The elastic modulus of the material

[0109] ρ — The density of the material

[0110] V — The volume of the material design area

[0111] As the penalty factor P increases, the topological optimization density value will approach 0 and 1. For a three-dimensional model, the determination of the P value is related to the Poisson's ratio μ of the material, and the relationship is:

[0112]

[0113] The optimization result of the variable density method is the density equal-value distribution cloud map. The optimization result contains parts that cannot be processed in engineering. For this part, manual post-processing or secondary design must be carried out to better meet the engineering requirements. Therefore, in actual engineering applications, it may be necessary to perform size optimization or shape optimization on the results of topological optimization, and the structural model also needs to be carried out in computer-aided design software.

[0114] S41. Assign the same material properties, loads, and boundary constraint conditions as in step S2 to the original model, and set the optimization goal; after determining the material and its properties, apply constraints to the inertial assembly body in the software, and fix the two large surfaces of the inertial assembly body and the threaded holes on them (such as Figure 3 the black surface in

[0115] Among them, the optimization goals of this embodiment include mass requirements, strength requirements, stiffness requirements, and dimension requirements, and the self-supporting structure is adopted in the optimization process.

[0116] The mass requirement for the inertial assembly body is: the total mass of the inertial assembly body ≤ 0.4 kg; by setting this goal, it is convenient to reduce the weight of the inertial assembly body by about 50% compared to the original model, and then facilitate the weight setting space for other components.

[0117] The strength requirement for the inertial assembly body is: the inertial assembly body shall not be damaged or fail during operation, and the design safety factor shall not be less than 3; setting the safety factor to 3 not only improves the safety of the inertial assembly body, but also prevents the insecurity of material density caused by the additive manufacturing method.

[0118] The stiffness requirement for the inertial assembly body is: under accelerations in all directions, the deformation of the inertial assembly body parts should be as small as possible;

[0119] The dimension requirement for the inertial assembly body is: it shall not be larger than the original model, and the positions, dimensions, and tolerances of parts such as each gyroscope and clamp table installed on the inertial assembly body shall be consistent.

[0120] S42. Define the space during the topology optimization of the original model as the design space, and define the process machining process allowance and the necessary existing structure as the entity requirements that need to exist after topology optimization, to obtain the structure of the inertial assembly body after topology optimization; in this embodiment, the necessary existing structure is also the structure of the inertial assembly body after optimization.

[0121] S43. Adjust the discrete degree of the material distribution during the optimization process to adjust the material distribution rate;

[0122] The material distribution rate of topology optimization is the degree of discrete control of the material distribution during the topology optimization process. By balancing the material distribution rate, the stability of the inertial assembly body structure can be improved, and high stability is one of the main indicators of the inertial assembly body structure.

[0123] An appropriate multi-porous structure can produce the function of shock absorption and energy absorption under extreme working conditions. During the adjustment of the material distribution rate of topology optimization, the discrete degree of the material distribution during the optimization process can be adjusted, and different degrees of pore structures can be obtained according to the size of the discrete degree. Based on this characteristic, during the topology optimization of the inertial assembly body, the material distribution rate was adjusted.

[0124] Specifically, when its distribution rate is too low, the generated structure will have smaller and fewer pores, and the function of shock absorption and energy absorption cannot be formed. When its distribution rate is too high, a branched structure will be generated, which will have a large number of pores in the structure. This structure requires a large number of support structures for printing, and it is difficult to remove the supports in the pores later.

[0125] Derived from the characteristic requirements of the inertial assembly body, when the generated pore size is not greater than about 5 mm in diameter, it is a self-supporting structure during printing, without the need to design printing supports, and it meets the function of multi-porous energy absorption and shock absorption.

[0126] Therefore, by adjusting the material distribution rate, after multiple calculations, when the material distribution rate reaches 68%, about 60% of the pore diameters of the optimized structure of the inertial assembly body are about 5 mm, and the supports at other positions during the later printing process are not difficult to remove.

[0127] S44. Import the structure after topological optimization of the original model obtained in step S42 into finite element analysis software, and perform a stress analysis according to whether the materials, stresses, and strains in step S3 meet the design requirements to optimize the structure and boundary conditions of the inertial assembly body; the model optimization and reconstruction mainly use CAD modeling software, and the model optimization and reconstruction can be directly carried out based on the topological optimization structure model. The optimized and reconstructed model is shown in Figure 6 (The left figure is the optimized inertial assembly body, and the transparent part in the right figure of the original model is the design space, and the opaque part is the optimized structure), and the stress and strain analysis diagram is shown in Figure 7 and Figure 8 .

[0128] The design variable for this optimization is the relative density of the element, the constraint is to determine the volume fraction (later converted to mass) according to the design goal, and the optimization goal is to minimize the strain (the stiffness of the inertial assembly body is the largest under the same conditions). The mathematical model of the SIMP interpolation method topological optimization of the inertial component body is:

[0129] find ρ = [ρ1, ρ2, ρ3, …, ρ i T

[0130] min C(ρ) = F T U = U T KU

[0131] s.t. KU = F

[0132]

[0133] 0 < ρ min ≤ ρ ≤ 1

[0134] In the formula

[0135] find ρ = [ρ1, ρ2, ρ3, …, ρ i T — Design variable, relative density of the element;

[0136] C(ρ) — Objective function, strain energy;

[0137] U — Model displacement matrix

[0138] K — Model stiffness matrix

[0139] V — Volume constraint ​​

[0140] v i — Unit volume

[0141] F — Force vector

[0142] ρ min — Minimum unit density of the model

[0143] Based on the SIMP interpolation method, the strain energy calculation formula is as follows:

[0144] In the formula

[0145] U i — Unit displacement matrix of the model

[0146] K i — Element stiffness matrix of the model

[0147] The relationship between the elastic modulus E and the relative density of the element is:

[0148]

[0149] ΔE = E - E min

[0150] To ensure the stability of the calculation, make

[0151]

[0152] 0 < E min < E(ρ i ) < E

[0153]

[0154]

[0155] k * — Unit stiffness matrix of the model element;

[0156] k0 — Element stiffness matrix with a density of 1.

[0157] The functional form of the strain of the model obtained is:

[0158]

[0159] The sensitivity calculation formula is:

[0160]

[0161] Based on the above formula, the OptiStruct software solver will be used for solution.

[0162] In addition, in this step, the sphericity and particle size of the printing material in additive manufacturing, as well as the influence of the printing process and parameters, etc., should also be considered. Since the density of the workpiece processed by additive manufacturing may be weaker than that of traditional processes (such as forging), there may be phenomena such as porosity and bubbles, which will weaken the structural strength. Therefore, by increasing the load on the force-bearing positions of the inertial assembly body structure, the distribution of materials in the main structure part is increased during topology optimization, and the structural safety factor is increased, so as to obtain the required topology optimization model. Compared with the original model, the topology optimization model of the multi-dimensional pore structure can adapt to the impact and vibration under complex working conditions and has good shock absorption and noise reduction performance.

[0163] S5. Judge whether the inertial assembly body obtained in step 4 meets the optimization goal and the requirements of additive and subtractive manufacturing. If it meets, execute step 6; if not, return to execute step 3.

[0164] S6. Smooth the inertial assembly body obtained in step 5 to avoid stress concentration. There are many irregular edges in the conceptual model after topology optimization, which will have a certain impact on the machinable form and the performance of the final part. In addition, there are some sharp transition edges in the optimized model, and these edges will cause stress concentration phenomena, reducing the service life of the part. Therefore, while strictly following the optimized structure to reconstruct the model, in order to avoid the adverse effects caused by these regions, these regions will be smoothed.

[0165] S7. Define the load and boundary constraint conditions according to the working condition conditions in step 2, and use finite element analysis software to perform structural force analysis on the inertial assembly body obtained in step 6. Specifically, the optimized structure obtained in step 6 is imported into the finite element analysis software and the structural force analysis is carried out according to the original working condition conditions. The finite element simulation data shows that the maximum stress is 3.4 MPa and the maximum deformation is 0.0107 mm; through software measurement and analysis, the weight of the optimized product is 0.36 kg. With such settings, the purpose of effectively reducing the weight of the inertial assembly body is achieved, providing space for setting the weights of other components of the entire aircraft, and thus improving the performance of the entire aircraft. As Figure 7 、 Figure 8 、 Figure 9 shown, under the same working conditions, when performing simulation force analysis, the position with the largest structural strain is on the original model.

[0166] S8. Import the outer dimensions of the inertial assembly body obtained in step 7 into the additive manufacturing equipment, and after reserving the machining allowance for subtractive manufacturing, perform additive manufacturing. Among them, the additive manufacturing in this embodiment is 3D printing, and the technological route of the additive manufacturing is sequentially set with processes of additive manufacturing, fitter work, stress relief annealing, abrasive slag removal, flaw detection, semi-finishing, thermal and cold cycle treatment, surface treatment, and five-axis precision machining.

[0167] It should be noted that although the structural model after topology optimization meets the structural requirements, there are some parts with unreasonable stress. Therefore, by changing the loads at the structural stress positions multiple times, and then changing the material distribution during topology optimization, the structure is made more reasonable.

[0168] S9. Perform post - processing on the solid model of the inertial assembly body obtained in step 8. Among them, the post - processing includes mechanical strength treatment, dimensional tolerance treatment, and surface roughness treatment; the mechanical strength treatment includes heat treatment, surface hardening, and anodic oxidation treatment. In this embodiment, the additive manufacturing technology used is SLM (Selective Laser Melting), which uses a high - power laser to completely melt each layer of metal powder. The high - temperature gradient that appears during the SLM manufacturing process will also cause internal stress in the final product, and in severe cases, it will damage the physical properties. Therefore, after printing, the optimized model of the inertial assembly body is subjected to heat treatment annealing to eliminate the internal stress existing during the printing process.

[0169] Among them, the dimensional tolerance treatment includes removing burrs, grinding, lapping, and honing. The surface roughness treatment includes sandblasting, coating, abrasive flow machining, and machining. Specifically, the above - mentioned processing is carried out according to the processing requirements and process route of the inertial assembly body.

[0170] S10. Perform subtractive machining on the solid model of the inertial assembly body obtained in step 9 to obtain the inertial assembly body that meets the lightweight requirements. The subtractive machining in this embodiment is machining, such as milling, turning, drilling, etc. In addition, after subtractive machining, the inertial assembly body also needs to be subjected to heat treatment, surface hardening, and anodic oxidation and other treatments to increase the mechanical properties and surface corrosion resistance of the inertial assembly body.

[0171] S11. Conduct experimental testing on the solid model of the inertial assembly body obtained in step 10.

[0172] Specifically, as Figures 10 to 12 shown, the experimental testing steps of the inertial assembly body include: centrifugal test, vibration test, shock test, and clamping total test.

[0173] The lightweight topology - structured body model design method in this embodiment mainly uses this design method to perform lightweight topology optimization design on one of the precision parts in the aircraft, that is, the inertial assembly body. During the design process, the connection structures and precision docking surfaces of the inertial assembly body are designed and adjusted, and the positions prone to deformation and the positions that do not need to be processed later are structurally optimized again during the printing process, avoiding processing defects in the inertial assembly body model after topology optimization during subsequent additive and subtractive machining, effectively ensuring the high - precision and high - stability requirements of the inertial assembly body. And through the topology - optimized structure, the inertial assembly body can be reduced by 50% in weight compared with the original model, meeting the lightweight requirements.

[0174] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for designing a lightweight topological structure inertial group platform model, characterized in that: The following steps are involved: S1, basic model of structural design; S11. Design the original model of the inertial platform, and optimize the part structure using modeling software according to the working conditions, part assembly dimensions, and post-processing requirements of material addition and subtraction; S12. Material selection: AlSi10Mg is selected based on weight requirements and working conditions, and AlSi10Mg meets the additive manufacturing process requirements; S2, analyzing the stress and strain data of the original model, determining the fixed structure, the gyro precision docking surface and the accelerometer precision docking surface of the original model, defining the load and boundary constraint conditions according to the working conditions, applying pressure and gravity acceleration to the gyro precision docking surface, and performing fixed constraints on the fixed structure, performing stress and deformation analysis, and checking whether the selected material meets the design requirements. If so, executing step S3, otherwise returning to executing step S1; S3, performing structural optimization on the original model that meets the design requirements in step S2 based on additive and subtractive manufacturing principles; S31, performing process processing on a first connection structure and a second connection structure on the inertial group platform, wherein the first connection structure is used for installing a gyroscope, and the second connection structure is used for installing an accelerometer; S32, making process allowances for the gyro precision docking surface, accelerometer precision docking surface and fixed structure in step 2; S33. Optimize the surfaces that are easily deformed during additive processing and those that do not require subtractive processing in the later stage; S4, performing topology optimization design on the inertial group platform optimized in step S3; S41, assigning the same material properties, loads and boundary constraints as those in step S2 to the original model, and setting an optimization target; S42, defining the space of the original model during topology optimization as a design space, defining the process processing allowance and the optimized inertial group platform structure as entity requirements that need to exist after topology optimization, and obtaining the structure of the inertial group platform after topology optimization; S43, adjusting the discrete degree of material distribution during the optimization process, and adjusting the material distribution rate; S44, importing the topologically optimized structure of the original model obtained in step S42 into finite element analysis software, performing force analysis according to whether the material, stress, and strain in step S3 meet the design requirements, and optimizing the structure and boundary conditions of the inertial group platform; S5, judging whether the inertial platform obtained in step 4 meets the optimization target and the additive and subtractive processing requirements, if it does, then executing step 6, if not, then returning to executing step 3; S6, performing a smoothing treatment on the inertial platform body obtained in step 5 to avoid stress concentration; S7, defining loads and boundary constraints according to the working conditions in step 2, and using finite element analysis software to perform structural stress analysis on the inertial group platform obtained in step 6; S8, importing the outer dimensions of the inertial platform obtained in step 7 into the additive equipment, retaining the processing allowance during subtractive processing, and then performing additive processing; S9, performing post-processing on the solid model of the inertial platform body obtained in step 8; S10, performing subtractive processing on the solid model of the inertial group platform obtained in step 9 to obtain the inertial group platform that meets the lightweight requirements; S11, testing and inspecting the physical model of the inertial platform body obtained in step 10.

2. The method for designing a lightweight topological structure inertial unit platform model according to claim 1, characterized in that: Select two fixed structures and three gyro precision docking surfaces and three accelerometer precision docking surfaces from the original model in step 2. The fixed structures are used to fix the inertial group platform in the subtractive processing in step 10, and the gyro precision docking surfaces are used to install the gyroscope.

3. The method for designing a lightweight topological structure inertial unit platform model according to claim 2, characterized in that: The working condition requirement in step S11 is set to apply a force of 1000N and a gravity acceleration of 30G respectively to the three gyro precision docking surfaces.

4. The method for designing a lightweight topological structure inertial unit platform model according to claim 2, characterized in that: The optimization objectives include quality requirements, strength requirements, stiffness requirements and size requirements, and the optimization process adopts a self-supporting structure.

5. The method for designing a lightweight topological structure inertial unit platform model according to claim 4, characterized in that: The mass requirement of the inertial group platform is: the total mass of the inertial group platform is ≤ 0.4 kg; The strength requirements of the inertial group platform are: the inertial group platform shall not fail in the working state, and the design safety factor shall not be less than 3; The rigidity requirement of the inertial group platform is: under acceleration in all directions, the deformation of the inertial group platform parts is no more than 0.001mm; The size requirements of the inertial group platform are: it must not be larger than the original model, and the position, size and tolerance of each gyroscope and clamp meter installed on the inertial group platform must be consistent.

6. The method for designing a lightweight topological structure inertial unit platform model according to claim 1, characterized in that: The additive processing is 3D printing processing, and the process route of the additive processing includes the following steps: additive manufacturing, benchwork, stress relief annealing, abrasive slag, flaw detection, semi-finishing, hot and cold cycle treatment, surface treatment, and five-axis precision machining.

7. The method for designing a lightweight topological structure inertial unit platform model according to claim 1, characterized in that: The post-processing includes mechanical strength processing, dimensional tolerance processing and surface roughness processing; The mechanical strength treatment includes heat treatment, surface hardening, and anodizing treatment; The dimensional tolerance treatment includes removing flash, grinding, lapping and honing; The surface roughening treatments include sandblasting, coating, abrasive flow machining and machining.

8. The method for designing a lightweight topological structure inertial unit platform model according to claim 1, characterized in that: The test and detection steps of the inertial group platform in step 11 include: Centrifugal test, vibration test, impact test, and total clamping test.

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