A frame structure stiffening design method based on quadratic topology optimization

Abstract

The application belongs to the technical field of helicopter structure design, and discloses a frame structure stiffening design method based on secondary topology optimization, which comprises the following steps: firstly, determining the initial model of the frame structure according to the aerodynamic shape, and then determining the design region and the non-design region; defining the load condition of the topology optimization according to the dangerous working condition, and performing the primary topology optimization; reconstructing the optimization result, and reconstructing the structure of the topology optimization into a machineable structure form; determining the design region and the non-design region again, and then performing the second topology optimization on the reconstruction result of step four; reconstructing the second topology optimization result to obtain a machineable structure form, and finally determining the form of the frame structure. Compared with the frame structure obtained by the traditional reverse design, the application has lower requirements for the experience of the designers, and can greatly improve the design efficiency. The model obtained by the secondary topology optimization has higher feasibility in machining manufacturing, and effectively reduces the manufacturing cost on the basis of the optimized structure.

Description

Technical Field

[0001] This invention belongs to the field of helicopter structural design technology, and relates to a frame structure design method for helicopters, specifically a frame structure stiffening design method based on quadratic topology optimization. Background Technology

[0002] Panel-reinforced structures, in the form of support frames, are widely used in various aircraft. As the main load-bearing structure, they require high strength and reliability. With the improvement of machining capabilities, the production of helicopter structural frames often adopts integral machining processes, which places higher demands on the design of support frames in helicopter structures.

[0003] The traditional frame structure design approach involves first determining the frame structure's outline based on aerodynamic shape, then initially determining the wall panel thickness and stiffening positions based on experience. Finite element analysis is then performed on the initial structure, and adjustments are made to the local wall panel thickness and stiffening forms based on stress calculation results. The adjusted results are then subjected to strength calculation analysis again. This iterative process is repeated to ultimately determine the frame structure form. This traditional design method has two main problems: firstly, it requires designers to have extensive design experience to effectively place stiffening positions in the initial design; secondly, the iterative process leads to low efficiency and a conservative approach, which is detrimental to aircraft weight reduction design.

[0004] In the design of high-speed helicopters, unlike traditional frame structures, some frame structures need to withstand large outward thrust loads on the wall panels, resulting in complex stress patterns and load conditions, making traditional design methods difficult. Topology optimization theory can be used to directly design frame structures in a forward manner, but the structural forms obtained through topology optimization are difficult to apply directly to machining production. Summary of the Invention

[0005] The purpose of this invention is to solve the above problems by providing a frame structure reinforcement design method based on quadratic topology optimization, which can determine the reinforcement arrangement of wall panels and the cross-sectional shape of stiffeners, and quickly complete the design of frame structures.

[0006] The technical solution of the present invention:

[0007] A stiffening design method for frame structures based on quadratic topology optimization includes the following steps:

[0008] Step 1: Determine the initial model of the frame structure based on its aerodynamic shape, including the outer surface of the frame structure and the large opening area;

[0009] Step two: Determine the design area and the non-design area;

[0010] Step 3: Define the load conditions for topology optimization based on the hazardous operating conditions, and perform the initial topology optimization;

[0011] Step 4: Reconstruct the optimization results, converting the topology optimization structure into a machine-compatible structure.

[0012] Step 5: Determine the design area and non-design area again, and then perform a second topology optimization on the reconstruction results of Step 4;

[0013] Step six: Reconstruct the results of the second topology optimization to obtain a machinable structural form, and finally determine the form of the frame structure.

[0014] Furthermore, in step two, the non-design area includes a certain thickness of the frame structure's shape and a certain thickness of the large opening area, i.e., the boundary conditions extend to a certain thickness; the non-design area is the other areas of the frame structure.

[0015] Furthermore, in step three, the hazardous conditions include the hazardous condition of maximum thrust load and the hazardous condition of maximum vertical overload.

[0016] Furthermore, in step three, maximizing stiffness is selected as the optimization objective function, the mass objective is defined as the optimization constraint, thickness constraints are established based on the actual dimensions of the frame structure, and initial topology optimization is performed on the frame structure for multiple load conditions.

[0017] Furthermore, in step four, the width and arrangement of the ribs are determined based on the optimization results, and the thickness of the inner wall panels in different partitions formed by adjacent ribs is obtained, thereby reconstructing a preliminary frame structure digital model that can be machined.

[0018] Furthermore, in step five, the initial frame structure model is topology optimized again. The areas where loads and boundary conditions are applied, as well as the wall panel areas, are defined as non-design areas, while other structural parts are defined as design areas. The load cases, objective functions, optimization constraints, and geometric limitations are the same as those defined in the initial topology optimization.

[0019] Furthermore, in step six, the optimized rib cross-sectional shape is reconstructed again, and the curved rib cross-section is replaced by an intersecting plane that can provide similar load support, resulting in a final frame structure model that can be machined.

[0020] Furthermore, topology optimization was performed using Inspire software, and the digital model reconstruction was performed using 3D modeling software.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention performs lightweight design of the frame structure through two topology optimizations. The first topology optimization determines the stiffening position and wall thickness. The model is reconstructed using CAD software for a second topology optimization. The second topology optimization determines the cross-sectional form of the stiffeners. The final frame structure model is obtained by a second reconstruction.

[0023] 2. A lightweight frame structure that can be manufactured using integral machining processes is obtained through secondary topology optimization, which has great advantages for reducing the weight of helicopter structures, improving helicopter performance, and increasing design efficiency.

[0024] 3. Compared to traditional frame structures obtained through reverse engineering, the method of this invention requires less experience from designers, significantly improving design efficiency. Furthermore, the model obtained through secondary topology optimization is more feasible for machining than that obtained through single topology optimization, effectively reducing manufacturing costs based on the optimized structure. Attached Figure Description

[0025] Figure 1 This is a flowchart of the technical solution of the present invention;

[0026] Figure 2 This is a schematic diagram of the initial frame blank model according to an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the initial topology optimization results according to an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the reconstructed numerical model based on the initial topology optimization results of an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of the secondary topology optimization results in an embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram of the final frame structure in an embodiment of the present invention. Detailed Implementation

[0031] This section describes embodiments of the present invention, used to explain and illustrate the technical solutions of the present invention. Unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0032] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating directions or positional relationships, are given in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or device referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include more than one of those features. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integrated connection; they can refer to a mechanical connection or a point connection; they can refer to a direct connection or a connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] Topology optimization theory can be used to directly design frame structures in a forward manner. By performing two topology optimizations, the design of the wall panel stiffening structure can be completed efficiently and accurately. The structural form obtained from the first topology optimization is difficult to apply directly to machining production, but it can determine the arrangement of wall panel stiffenings and the selection of different frame wall panel thicknesses based on the optimization results. By reconstructing the results of the first topology optimization and performing a second topology optimization, the cross-sectional form of the stiffeners can be determined, further optimizing the structure and reducing weight.

[0035] Specifically, a stiffening design method for frame structures based on quadratic topology optimization includes the following steps:

[0036] Step 1: Determine the initial model of the frame structure based on its aerodynamic shape, including the outer surface of the frame structure and the large opening area;

[0037] Step two: Determine the design area and the non-design area;

[0038] Step 3: Define the load conditions for topology optimization based on the hazardous operating conditions, and perform the initial topology optimization;

[0039] Step 4: Reconstruct the optimization results, converting the topology optimization structure into a machine-compatible structure.

[0040] Step 5: Determine the design area and non-design area again, and then perform a second topology optimization on the reconstruction results of Step 4;

[0041] Step six: Reconstruct the results of the second topology optimization to obtain a machinable structural form, and finally determine the form of the frame structure.

[0042] In step two, the non-design area includes a certain thickness of the frame structure's shape and a certain thickness of the large opening area, i.e., the boundary conditions extend to a certain thickness; the non-design area is the other areas of the frame structure.

[0043] In step three, the dangerous operating conditions include the dangerous operating condition of maximum thrust load and the dangerous operating condition of maximum vertical overload.

[0044] In step three, the objective function is to maximize stiffness, the objective function is to define mass as the optimization constraint, the thickness constraint is to be established based on the actual dimensions of the frame structure, and the initial topology optimization of the frame structure is performed for multiple load conditions.

[0045] In step four, the width and arrangement of the ribs are determined based on the optimization results, and the thickness of the inner wall panels in different partitions formed by adjacent ribs is obtained, thereby reconstructing a preliminary frame structure digital model that can be machined.

[0046] In step five, the initial frame structure model is topology optimized again. The areas where loads and boundary conditions are applied, as well as the wall panel area, are defined as non-design areas, while other structural parts are defined as design areas. The load cases, objective functions, optimization constraints, and geometric limitations are the same as those defined in the initial topology optimization.

[0047] In step six, the optimized rib cross-sectional shape is reconstructed again, and the curved rib cross-section is replaced by intersecting planes that can provide similar load support, resulting in the final frame structure model that can be machined.

[0048] Topology optimization was performed using Inspire software, and the digital model reconstruction was performed using 3D modeling software.

[0049] Another example of the present invention will now be described with reference to the accompanying drawings.

[0050] The overall technical solution flow of this invention is as follows: Figure 1 As shown, the present invention will be further described below using a tail section frame structure of a certain type of aircraft as an example. The outer arc surface of this frame structure is defined as a fixed constraint, and the structure includes two hazardous operating conditions: the maximum thrust load hazardous condition and the maximum vertical overload hazardous condition. The technical solution is as follows:

[0051] The first step is to determine the outer contour and initial thickness of the frame structure based on its aerodynamic shape. For large openings requiring the passage of equipment such as drive shafts, pre-drill holes to obtain the initial frame blank model before optimization in CATIA software. Figure 2 As shown;

[0052] The second step is to import the initial frame model into the Inspire software, define multiple topology optimization load cases according to the hazardous working conditions, extend the structural surface with defined loads and boundary conditions by a certain thickness to define the non-design area, and define the other parts of the frame structure as the design area; the first topology optimization is to determine the position of the stiffeners, and change the other areas except the stiffener positions to the non-design area;

[0053] The third step involves selecting maximizing stiffness as the objective function, defining the mass objective as the optimization constraint, establishing thickness constraints based on the actual frame structure dimensions, and performing initial topology optimization on the frame structure for multiple load conditions. The results are as follows. Figure 3 As shown;

[0054] The fourth step is to import the initial optimization results into CATIA software, reconstruct the frame structure model based on the optimization results, determine the basic positions of the stiffeners, and obtain the thickness of the inner wall panels in different partitions by measurement. The initial reconstructed model results are as follows: Figure 4 As shown;

[0055] The fifth step involves re-importing the reconstructed numerical model into Inspire software for secondary topology optimization. The regions where loads and boundary conditions are applied, as well as the wall panel region, are defined as non-design regions. Other structural parts are defined as design regions. The load cases, objective functions, optimization constraints, and geometric limitations are the same as those defined in the initial topology optimization. The results of the secondary topology optimization are as follows: Figure 5 As shown; the second topology optimization is to optimize the ribs;

[0056] Step 6: Import the results of the secondary topology optimization back into CATIA software. Based on the optimized stiffener cross-sectional shape, reconstruct the model again to obtain the final frame structure digital model. The result is as follows: Figure 6 As shown.

[0057] The above description is merely a specific embodiment of the present invention, providing a detailed description of the invention. Parts not covered herein are conventional techniques. However, the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A stiffening design method for frame structures based on quadratic topology optimization, characterized in that, Includes the following steps: Step 1: Determine the initial model of the frame structure based on its aerodynamic shape, including the outer surface of the frame structure and the large opening area; Step two: Determine the design area and the non-design area; Step 3: Define the load conditions for topology optimization based on the hazardous operating conditions, and perform the initial topology optimization; Step 4: Reconstruct the optimization results, converting the topology optimization structure into a machine-compatible structure. Step 5: Determine the design area and non-design area again, and then perform a second topology optimization on the reconstruction results of Step 4; Step 6: Reconstruct the results of the second topology optimization to obtain a machinable structural form, and finally determine the form of the frame structure; In step two, the non-design area includes the frame structure with a certain thickness and a large opening area with a certain thickness, that is, the boundary conditions extend to a certain thickness; the design area is the other areas of the frame structure. In step four, the width and arrangement of the ribs are determined based on the optimization results, and the thickness of the inner wall panels in different partitions formed by adjacent ribs is obtained, thereby reconstructing a preliminary frame structure digital model that can be machined. In step five, the initial frame structure model is topology optimized again. The areas where loads and boundary conditions are applied, as well as the wall panel area, are defined as non-design areas, while other structural parts are defined as design areas. The load cases, objective functions, optimization constraints, and geometric limitations are the same as those defined in the initial topology optimization. In step six, the optimized rib cross-sectional shape is reconstructed again, and the curved rib cross-section is replaced by intersecting planes that can provide similar load support, resulting in the final frame structure model that can be machined.

2. The frame structure stiffening design method based on quadratic topology optimization according to claim 1, characterized in that, In step three, the dangerous operating conditions include the dangerous operating condition of maximum thrust load and the dangerous operating condition of maximum vertical overload.

3. The frame structure stiffening design method based on quadratic topology optimization according to claim 1, characterized in that, In step three, the objective function is to maximize stiffness, the objective function is to define mass as the optimization constraint, the thickness constraint is to be established based on the actual dimensions of the frame structure, and the initial topology optimization of the frame structure is performed for multiple load conditions.

4. The frame structure stiffening design method based on quadratic topology optimization according to claim 1, characterized in that, Topology optimization was performed using Inspire software, and the digital model reconstruction was performed using 3D modeling software.

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