Design method of variable-size variable-density lattice structure wing with optimized heat dissipation bearing

Abstract

The invention provides a design method of a variable-size variable-density lattice structure wing with optimized heat dissipation load, and relates to the technical field of aerospace engineering, and the design method comprises the following steps: S10: carrying out variable cross-section design on a D-type unit to obtain a variable cross-section D-type unit, taking the variable cross-section D-type unit as a lattice unit configuration, and filling the wing to form a skin lattice structure; the skin lattice structure of the wing comprises a skin and a lattice filling area; s20, cell element variable-size design is adopted for the dot matrix units, and variable-size dot matrix units are constructed; s30, according to the stress field of the wing, cell element variable-density design is adopted for the variable-size dot matrix units, and variable-size variable-density dot matrix units are constructed; and S40, establishing a wing configuration. The variable-cross-section D-type unit is used as a dot matrix unit configuration, deep coupling of integrated design of heat dissipation and bearing performance is achieved through variable-size and variable-density design, application scenes are flexibly adjusted, and complex working condition requirements are met.

Description

Technical Field

[0001] The present invention belongs to the field of aerospace engineering technology, and in particular relates to a design method for a variable-size and variable-density lattice structure wing with optimized heat dissipation load. Background Art

[0002] The complex thin-walled structural parts of high-speed UAV wings often adopt curved skin-lattice structures, which are widely used in aerospace products. Their design and manufacturing technology have a direct impact on the quality, load-bearing and heat dissipation performance of the products. When the high-speed UAV wing is flying at Mach 3, its surface temperature reaches 350℃. When the speed reaches Mach 5-6, its surface temperature will be higher. Even the wings made of titanium alloy can hardly withstand such high temperatures. In addition, during the flight, there are multiple loads of compression, bending and torsion. In order to improve the ability of high-speed UAV wings to cope with multiple environments during high-speed flight, so that they have light weight, high load-bearing and high heat dissipation performance, the complex curved skin-lattice structure generative design technology based on additive manufacturing is particularly important.

[0003] In the prior art, first, in the research on the force, thermal performance and optimization design of minimal surface lattice structures at Nanjing University of Science and Technology, the engine combustion chamber cooling wall panel was used as the research background, and a force and thermal performance optimization design method for the lattice sandwich panel structure based on minimal surfaces was given; however, this method only used equal-section lattice units, and in the variable size optimization process, the lattice unit length was set to a constant value, that is, only the width and height of the lattice unit were optimized. This method has the defects of stress concentration in the node area of ​​the lattice unit and structural damage defects. The research focus is limited to the performance of minimal surface structures, and has not been extended to more complex geometric shapes or non-homogeneous structural designs, and the design flexibility is limited; and the research only targets the engine combustion chamber lattice plate structure in terms of material, and does not involve the titanium alloy structure of the aircraft wing metal material, which has the defects of high temperature difference resistance, weak mechanical properties and inconvenient processing. Second, in the research on thermal performance analysis and optimization of composite material lattice sandwich structures under thermal loads at Harbin Institute of Technology, the distribution and geometric dimensions of the rods in the lattice core were optimized. This research mainly relies on the embedding of heat pipes. Although this method can improve the heat dissipation performance of composite materials, it lacks flexibility in complex multifunctional structures, especially the design requirements for simultaneous optimization of load bearing and heat dissipation are not perfect; and because the research object is a composite material structure, the design and embedding position of the heat pipe will limit the design freedom of the structure, especially under complex working conditions, the heat dissipation and load-bearing performance cannot be flexibly adjusted. Therefore, the design flexibility of this research is limited, and there are also defects such as low heat dissipation efficiency, poor continuous cooling and large structural impact. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention proposes a design method for a variable-size and variable-density lattice structure wing with optimized heat dissipation and load-bearing capacity, constructs a skin lattice structure wing with a variable-section D-type unit as the lattice unit configuration, and based on the high-strength titanium alloy TC4 wing material, adopts a variable-size and variable-density design to achieve deep coupling of the integrated design of heat dissipation and load-bearing performance, so that the lattice structure can be flexibly adjusted according to the actual application scenario to meet the needs of complex working conditions, and realize precise regulation of the heat dissipation and load-bearing performance of the wing, so that the wing has the performance of light weight, high heat dissipation and high load-bearing capacity, thereby ensuring the improvement of the comprehensive performance of the wing; and the present invention adopts cold flow heat dissipation, which has the advantages of high heat dissipation efficiency, continuous cooling and little impact on the structure.

[0005] To achieve the above object, a design method of a variable-size and variable-density lattice structure wing with optimized heat dissipation load of the present invention comprises the following steps: S10: performing variable cross-section design on the D-type unit to obtain a variable cross-section D-type unit, using the variable cross-section D-type unit as a lattice unit configuration to fill the wing to form a skin lattice structure; the skin lattice structure includes a skin and a lattice filling area; S20: adopting a cell variable size design for the lattice unit to construct a variable size lattice unit; S30: The wing is made of titanium alloy TC4. According to the stress field of the wing, the variable-size lattice unit is designed with variable cell density to construct a variable-size and variable-density lattice unit. S40: Filling the lattice filling area with the variable size and variable density lattice units to establish an overall wing configuration.

[0006] Preferably, the S10 includes S101, S102 and S103, wherein: S101: adding an auxiliary function based on the D-type implicit function of the TPMS, establishing a variable-section D-type unit parallel implicit function expression, and using the variable-section D-type unit parallel implicit function expression to model the D-type unit to obtain a variable-section D-type unit; S102: Parameter definition and analysis of the variable cross-section D-type unit to establish a cross-section control coefficient The relationship function with the cross-sectional radius of the strut of the variable cross-section D-type unit; S103: According to the design requirements, the cross-section control coefficient is adjusted The parametric variable cross-section design of the D-type unit is completed.

[0007] Preferably, in S101, the variable cross-section D-type unit parallel implicit function expression is: ; In the formula, is the parallel implicit function of the variable cross-section D-type unit, are the unit vectors of the three axes in the Cartesian coordinate system, ， ， ， , , is the coordinate in the Cartesian coordinate system, is the side length of the lattice unit, is the threshold value, is the section control coefficient.

[0008] Preferably, in S102, the cross-section control coefficient The relationship function with the cross-sectional radius of the support rod of the variable cross-section D-type unit is: ; In the formula, is the cross-sectional radius of the support rod of the variable cross-section D-type unit.

[0009] Preferably, in S20, the cell variable size design is to set the cell size to a gradient cell size.

[0010] Preferably, the S20 includes S201, S202 and S203, wherein: S201: Determine the skin and lattice filling area of ​​the wing, the skin is a non-design domain, and the lattice filling area is a design domain; S202: Filling the dot matrix filling area with a uniform cell size using a single dot matrix unit; S203: Determine the heating surface of the skin, and use the heating surface of the skin as a reference to perform a gradient design on the cell size of the lattice filling area.

[0011] Preferably, the S30 includes S301, S302 and S303, wherein: S301: Establishing the threshold value in the D-type implicit function of TPMS The equivalent elastic modulus of the D-type unit is calculated by a homogenization method according to the corresponding relationship with the volume fraction of the D-type unit; the equivalent elastic modulus is a polynomial interpolation model of the equivalent elastic matrix; S302: Utilizing a topology optimization method of SIMP combined with an optimization criterion method, and optimizing and acquiring grid unit density information of the lattice unit according to a stress field load of a corresponding wing; S303: constructing the variable-size and variable-density lattice unit according to the correspondence between the grid unit density information of the lattice unit obtained through optimization and the volume fraction of the lattice unit.

[0012] Preferably, the wing includes but is not limited to a drone wing.

[0013] The beneficial effects of the present invention are: The present invention uses a variable-section D-type unit as a lattice unit configuration to construct a wing skin lattice structure, improves the stress concentration phenomenon in the lattice unit node area, overcomes the defects of structural discontinuity and extremely small size of the skin lattice structure at an extremely small volume fraction, improves the mechanical properties of the structure, and achieves light weight, high heat dissipation and high load-bearing performance of the wing.

[0014] The present invention adopts a cell variable size wing design so that the wing surface temperature can be quickly transferred to the inside of the wing and carried away by the cold flow, thereby achieving high heat dissipation performance of the wing.

[0015] The present invention takes heat dissipation factors into consideration, is based on high-strength titanium alloy TC4 wing material, adopts a unit variable density wing design, and is designed according to the stress field to achieve high compression, high bending and high torsion load bearing of the wing.

[0016] The present invention takes cell size and cell density as two sets of design variables, thermal control and load-bearing performance as two sets of optimization design objectives, performs an optimization design of thermal control and load-bearing integration on the wing with a variable-section lattice structure, establishes an overall wing configuration with excellent heat dissipation and load-bearing performance, and realizes precise regulation of the wing's heat dissipation and load-bearing performance.

[0017] The present invention provides strong support for the generation and design of complex thin-walled structures of wings, improves the modeling and design quality of complex thin-walled structural parts, meets the design and manufacturing requirements of lightweight, high strength and high heat dissipation of complex thin-walled structural parts under additive manufacturing, and improves the thermal performance of complex thin-walled structural parts and their ability to cope with complex working conditions.

[0018] According to the design requirements, the present invention designs the D-type unit with a variable cross-section and configures it as a lattice unit according to the target design domain, boundary conditions, gradient size design conditions and volume fraction, fills the wing to form a skin lattice structure, improves the stress concentration phenomenon in the node area of ​​the original D-type unit with equal cross-section, overcomes the discontinuity and extremely small size of the skin lattice structure at an extremely small volume fraction, and improves the mechanical properties of the wing structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Process of designing a variable-size, variable-density lattice structure wing optimized for heat dissipation load of the present invention Figure 1 ; Figure 2 Process of designing a variable-size, variable-density lattice structure wing optimized for heat dissipation load of the present invention Figure 2 ; Figure 3is a schematic diagram of the xz plane of a variable cross-section D-type unit; where (a) is the front view of the variable cross-section D-type unit in the xz plane; (b) Schematic diagram of the support parameters of the variable cross-section D-type unit; (c) Figure 3 (b) Enlarged schematic diagram of the dotted box; Figure 4 Schematic diagram of the relationship between the value of K and r and R; Figure 5 Schematic diagram of the D-type unit shape and the cross-sectional shape of the strut under different values ​​of K; (a) Schematic diagram of the D-type unit shape and the cross-sectional shape of the strut when the value of K is 0.05; (b) Schematic diagram of the D-type unit shape and the cross-sectional shape of the strut when the value of K is 0.06; (c) Schematic diagram of the D-type unit shape and the cross-sectional shape of the strut when the value of K is 0.07; Figure 6 The schematic diagram of the wing lattice profile under different conditions of cell size and cell density design; (a) Schematic diagram of the wing lattice cross section designed with equal cell size and uniform cell density; (b) is a schematic diagram of the wing lattice cross section designed only with variable cell size; (c) is a schematic diagram of the wing lattice section designed only with variable cell density; (d) is a schematic cross-sectional view of a wing lattice constructed with variable size and density lattice units according to the present invention; Figure 7 A flow chart for designing a variable density lattice structure of the present invention; Figure 8 It is a schematic diagram of the load condition of the wing of the present invention in the flying state in the air; Fig. 9 It is a schematic diagram of the analysis of the wing under different static conditions; among them, (a) is a simplified schematic diagram of the wing loading static analysis; (b) is a schematic diagram of static analysis of wing equivalent stress; Fig.10 Schematic diagram of filling different lattice cell sizes of the wing; among them, (a) Schematic diagram of the uniform lattice cell size filling of the wing; (b) Schematic diagram of filling the wing gradient lattice with variable cell size; Fig.11 Fill in the schematic diagram for the different lattice units of the wing; (a) is a schematic diagram of the lattice unit density distribution analysis of the wing; (b) Schematic diagram of uniform lattice unit filling of the wing; (c) Schematic diagram of filling variable-size lattice units of the wing; (d) Schematic diagram of the variable size and density lattice unit filling of the wing; In the figure, q is the aerodynamic distributed load; Q is the mass force distributed load. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted again that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] Embodiment 1

[0022] like Figure 1 The method for designing a variable-size and variable-density lattice structure wing with optimized heat dissipation load of the present invention includes the following steps: S10: performing variable cross-section design on the D-type unit to obtain a variable cross-section D-type unit, using the variable cross-section D-type unit as a lattice unit configuration to fill the wing to form a skin lattice structure; the skin lattice structure includes a skin and a lattice filling area; S20: The lattice unit is designed with variable cell size to construct a variable size lattice unit; S30: Taking heat dissipation into consideration, based on the use of titanium alloy TC4 material for the wing and the stress field of the wing, a variable-size lattice unit is designed with variable cell density to construct a variable-size lattice unit; S40: Establish the overall wing configuration using variable size and density lattice elements.

[0023] In this embodiment, the wing includes but is not limited to the wing of a high-speed UAV. In S10, the D-type unit (Diamond) is a basic building unit of TPMS (Triply Periodic Minimal Surface) with good comprehensive heat dissipation and load-bearing performance. According to the design requirements, based on the target design domain, boundary conditions, gradient size design conditions and volume fraction, and on the basis of considering the heat dissipation factor, the D-type unit is designed with a variable cross-section and configured as a lattice unit to fill the wing to form a skin lattice structure, improve the stress concentration phenomenon in the node area of ​​the original equal-section D-type unit, and improve the discontinuity and extremely small size of the skin lattice structure at the extremely small volume fraction, thereby improving the mechanical properties of the wing structure.

[0024] S10 includes three steps: S101, S102 and S103: S101: adding an auxiliary function based on the D-type implicit function of the TPMS, establishing a parallel implicit function expression of a variable cross-section D-type unit, and modeling the D-type unit to obtain a variable cross-section D-type unit.

[0025] The D-type implicit function expression of the conventional TPMS is: (1) In the formula, are the unit vectors of the three axes in the Cartesian coordinate system, ， ， ， , , is the coordinate in the Cartesian coordinate system, is the side length of the lattice unit, is the threshold value.

[0026] Volume fraction of D-type implicit function With threshold The relationship is as follows: (2) in ,when When The minimum volume fraction to maintain unit continuity is 9.58% at this time. Such a volume fraction obviously does not meet the lightweight design requirements. In order to avoid the phenomenon of discontinuity and extremely small size of lattice units due to small volume fractions, auxiliary functions are added on the basis of the above-mentioned D-type implicit function of TPMS to establish a variable cross-section D-type unit parallel implicit function expression, so that without changing the geometric topological configuration of the D-type unit, the isosurface of the function in the same period range is further indented, thereby improving the lightweight design capability of the D-type implicit function of TPMS and effectively improving the mechanical properties of the lattice structure. Therefore, the above-mentioned variable cross-section D-type unit parallel implicit function expression is as follows: (3) In the formula, is a constant; in order to realize the function of variable cross-section of D-type unit, Set the value of the variable to define is the section control coefficient; is the parallel implicit function of the variable cross-section D-type unit; It is the D-type implicit function of TPMS; is an auxiliary function; is the unit vector of the three axes in the Cartesian coordinate system; is the threshold value.

[0027] Setting up helper functions for: (4) Substitute expressions (1) and (4) into expression (3). To reduce the complexity, let , the implicit function expression of the variable cross-section D-type unit in parallel is obtained as: (5) In the formula, is the parallel implicit function of the variable cross-section D-type unit, are the unit vectors of the three axes in the Cartesian coordinate system, ， ， ， , , is the coordinate in the Cartesian coordinate system, is the side length of the lattice unit, is the threshold value, is the section control coefficient.

[0028] S102: See Figure 3 (a) Figure 3 (b) and Figure 3 As shown in (c), the parameters of the variable cross-section D-type unit are defined and analyzed to establish the cross-section control coefficient. The relationship function between the cross-sectional radius of the variable cross-section D-type unit support rod. Specifically, Figure 3 (a) Figure 3 (b) and Figure 3 (c) is the main view of the variable cross-section D-type unit and its support parameters. Figure 3 (c) Figure 3 (b) Enlarged schematic diagram of the upper AOFM unit, where is the side length of the lattice unit, is the pore width, B is the midpoint of segment AC, E is the midpoint of segment GF, , is the length of the support rod, is the cross-sectional radius at the center of the variable cross-section D-type unit support rod, is the cross-sectional radius at the edge of the variable cross-sectional D-type unit support rod; Figure 3 (c) shows the enlarged view of the D-type unit support rod. xzThe angle between the plane strut and the horizontal plane is 45°. The cross-sectional radius of the variable cross-section D-type unit strut increases gradually from the center to the sides. The closer to the node, the larger the cross-sectional radius of the variable cross-section D-type unit strut. The transition at the node is also smoother, which will make the structure have better stress distribution at the node where stress concentration is prone to occur, thereby improving the bearing capacity of the skin lattice structure. Since the surface of the variable cross-section D-type lattice unit is generated by the isosurface of the implicit function, and the D-type unit strut is xz The angle between the plane support and the horizontal plane is 45°. z=x The distance between the two intersection points of the axis and the isosurface strut is the cross-sectional diameter of the variable cross-section D-type unit strut. , Section Control Coefficient With variable cross-section D-type unit support rod The cross-sectional radius satisfies the following relationship: (6) In the formula, It is a variable cross-section D-type unit support rod The cross-sectional radius, is the side length of the lattice unit, is the cross-section control coefficient, is the threshold value.

[0029] Now let the side length of the lattice unit be is dimensionless 10, and the volume fraction is 10%. The cross-sectional radius of the variable cross-section D-type unit support rod is is defined as the normalized cross-sectional radius, which The numerical value and and The relationship curve is as follows Figure 4 As shown, from Figure 4 As can be seen in The value of gradually increases from 0 to 0.14. The value of gradually increases, The value of gradually decreases, and The values ​​of are gradually approaching, so The larger the value of is, the closer the diameter change of the cross-section rod of the variable cross-section D-type lattice unit is to that of the uniform cross-section rod. The value of can realize the free adjustment of the cross-sectional dimensions of the support rod and realize the parametric design requirements of the variable cross-sectional D-type unit. Figure 4 The slope changes with As the value increases, the change range of the rod diameter is affected by The influence of the value change is getting smaller and smaller, and the cross-section diameter of the support rod The variation of size gradually decreases and approaches that of a rod with equal cross-section.

[0030] S103: Adjust the section control coefficient according to design requirements The parametric variable cross-section design of the D-type unit is completed. Specifically, in the design process, according to the comprehensive mechanical performance requirements of equivalent elastic modulus and equivalent yield strength, a reasonable The value of is used to adjust the effect of the D-type unit variable cross-section, thereby improving the discontinuity and small size of the structure at the minimum volume fraction, optimizing the distribution of the cross-sectional size of the D-type unit, and further optimizing its stress distribution and improving the mechanical properties of the structure. Figure 5 As shown, different The D-type unit shape and the cross-sectional shape of the support rod under the value of. According to the test, when The value of K is in the range of 0.05~0.07. The equivalent elastic modulus of the skin lattice structure gradually increases with the increase of K. This is because the cross-sectional radius at the center of the variable cross-sectional D-type unit strut increases. As the stress at the center gradually diffuses to the edge, the stress concentration at the center of the support gradually decreases. reaches its peak value when As the value of increases, the cross section of the variable cross-section D-type unit strut at the center increases further, which reduces the cross section at the edge node, and its stress gradually diffuses to the node of the strut. The value of decreased again in the stage of 0.07~0.09; while the yield strength is The value is 0.05~0.08. The value of The yield strength reaches its peak value when , and its change is not completely consistent with the change trend of the elastic modulus. This shows that the design of the variable cross-section D-type unit does not change the structural mechanical properties in the same way as the homogeneous material. The change in the cross-sectional radius of the support from the center to the edge can achieve a greater enhancement in the mechanical properties when the difference range is smaller.

[0031] In this embodiment, S20 is to adopt a variable cell size design for the above-mentioned lattice unit, so that the surface temperature of the wing is quickly transferred to the inside of the wing and carried away by the cold flow, thereby achieving high heat dissipation performance of the wing. Specifically, See also Figure 2 and Figure 6As shown, the cell variable size design is a cell gradient size design, which is an optimization design for the thermal control performance of the wing thin-walled structure. It is a wing structure with excellent heat dissipation performance obtained by establishing a skin lattice structure formed by filling the wing with lattice units with variable cross-sections and sizes. In this step, the cell variable size design is to set the cell size to a gradient cell size. The cell size at the center of the wing is the largest, and the cell gradually becomes smaller along the gradient direction of the wing airfoil. The closer to the wing wall, the smaller the cell. In other words, the upper and lower skins of the wing are the heating surfaces. The closer to the upper and lower skin walls, the smaller the cell size. Conversely, the farther away from the upper and lower skin walls, the larger the cell size. The cell size on the wing isogradient contour line is consistent. The cell size near the wing skin wall is small, and the cell density of the lattice structure is large, which is conducive to the rapid transfer of heat from the wing surface to the central area inside the wing; the cell size in the central area of ​​the wing is large, the cell density of the lattice structure is small, and the gaps are large, which is conducive to the circulation of cold flow, speeds up the cold flow velocity, and can take away heat faster.

[0032] like Figure 6 As shown in (a), the overall wing is filled with a uniform lattice structure of a single lattice unit configuration, as shown in Figure 6 (b) shows the whole wing filled only with variable-size lattice units. By comparing the two, it can be seen that the cell size near the wing skin wall is small, which makes the local convection heat transfer more intense. The internal lattice structure absorbs a large amount of heat, which is conducive to quickly transferring the heat from the wing surface to the inside of the wing; the cell size and gap in the central area of ​​the wing far away from the heated surface are large, so that the cooling medium has a smaller flow resistance when it flows into the lattice structure, which is conducive to the circulation of cold flow and accelerates the flow rate of cold flow, so that the inside of the wing can fully exchange heat with the cooling medium under high temperature environment, thereby taking heat away from the wing body and realizing the heat dissipation of the wing components. Therefore, the use of variable cell size design can better improve the heat dissipation performance of the wing.

[0033] S20 includes S201, S202 and S203, and the specific steps are as follows: S201: The skin lattice structure of the wing includes a skin and a lattice filling area, and the skin and the lattice filling area of ​​the wing are determined, wherein the skin is a non-design domain and the lattice filling area is a design domain; S202: Use a single lattice unit to fill the lattice filling area with uniform cell size. The cell size of the filled cell must ensure that the minimum cell size under the condition of small flow resistance is maintained after the coolant is passed into the skin lattice structure. The cell size is set to ; S203: Determine the heating surface of the skin, and take the heating surface of the skin as a reference to perform a gradient design on the cell size of the lattice filling area. That is, the cell size closer to the heating surface of the skin is closer to the set minimum cell size, and the cell size farther away from the heating surface of the wing skin is closer to the maximum cell size. The minimum cell size of the gradient is , the maximum cell size is ,in and Select the appropriate value according to the gradient direction size. In the heat dissipation gradient design, the cell size will gradually change in different areas of the structure and should maintain a smooth transition. and The appropriate value is 5%-15% of the cell size in the gradient direction.

[0034] In this embodiment, in S30, after the cell size is determined based on the consideration of heat dissipation factors, the cell variable density design is performed accordingly based on the use of high-strength titanium alloy TC4 material for the wing and the load field of the wing in the air flight state, so as to achieve high compression, high bending and high torsion load bearing of the wing. Figure 6 (d) with Figure 6 (b) In contrast, the density of the cell itself corresponds to the load field. The greater the load, the greater the cell density, and the smaller the load, the smaller the cell density. The greater the cell density, the better the load-bearing performance. Therefore, the wing structure has better load-bearing performance and can achieve lightweight.

[0035] S30 includes S301, S302 and S303, see Figure 7 As shown, the details are as follows: S301: establishing a corresponding relationship between a threshold value C in a D-type implicit function of the TPMS and a volume fraction of a D-type unit, calculating an equivalent elastic modulus of the D-type unit by a homogenization method, and establishing a polynomial interpolation model of an equivalent elastic matrix in order to avoid tedious homogenization calculations during the optimization process; S302: The SIMP (Solid Isotropic Material with Penalization) topology optimization method is combined with the OC (Optimality Criteria Method) to obtain the grid cell density information of the lattice unit according to the stress field load of the corresponding wing; specifically, the SIMP method is used to solve the variable density distribution problem of the material in the topology optimization, combined with sensitivity analysis, to optimize the distribution of design variables, and the OC optimization criterion method is used to iterate the new cell structure unit density.

[0036] S303: According to the correspondence between the grid unit density information of the lattice unit obtained by optimization and the volume fraction of the lattice unit, a variable size and variable density lattice unit is constructed. If the result converges, the cell structure of the average density size of the interval is output to construct a variable density lattice structure. If the result does not converge, the SIMP method is returned to solve the topology optimization process for re-analysis.

[0037] In this embodiment, in S40, the variable cell size design and the variable cell density design are used as two groups of design variables, and the thermal control and load-bearing performance are used as two groups of optimization design objectives. The lightweight point wing is optimized for integrated thermal control and load-bearing performance, and an overall wing configuration with excellent heat dissipation and load-bearing performance is established, thereby achieving precise regulation of the heat dissipation and load-bearing performance of the wing.

[0038] Embodiment 2 See also Figure 1-Figure 11 As shown, this embodiment takes the wing of a high-speed UAV as a design example, with the skin of the wing as the non-design domain, maintaining the original shape during the optimization process, and the lattice filling area as the design domain, and filling the lattice filling area with a variable cross-section D-type lattice as the lattice unit configuration. The purpose is to implement a variable-size and variable-density lattice structure wing design method for optimizing the heat dissipation load of the skin lattice structure of the wing of a high-speed UAV, and verify the effectiveness of its optimized design. In this embodiment, the high-speed UAV is mainly subjected to two types of distributed loads when in service, such as Figure 8 As shown in the figure, the sources of load are respectively from the mass force distributed load Q generated by the wing structure's own mass under the action of gravity, and the aerodynamic distributed load q that maintains lift during flight; and in order to maintain lift, the aerodynamic distributed load q is generally greater than the mass force distributed load Q, so the load condition of the wing is simplified as: the wing root is fixed, and the distributed load pressure acts on the lower surface of the wing.

[0039] Through a simplified wing load model, the wing model was statically analyzed using Abaqus / CAE2022 software, and its material was set to additively manufactured titanium alloy TC4 with a material density of 4.43g / cm 3 The elastic modulus of the material is 118 GPa, the Poisson's ratio is 0.3, the mesh size is set to 100 mm, and 72476 C3D10 tetrahedral meshes are divided. According to the simplified wing load model, the distributed load is set as follows Fig. 9 As shown in (a), the root of the wing is set to "completely fixed" and the lower wing surface is set to 1×10 -5 N / mm 2 The uniformly distributed load pressure is obtained as Fig. 9 (b) shows the wing equivalent stress cloud diagram. Fig. 9(b) shows that, viewed from the span direction, the closer the wing is to the wing root, the greater the stress value is, and the closer it is to the wing tip, the smaller the stress value is. The closer the wing root is to the center of the wing root, the greater the stress value is, and the closer it is to the edge of the wing root, the smaller the stress value is. Therefore, when filling the lattice units in the subsequent process, lattice units with a larger volume fraction should be arranged near the center of the wing root, and lattice units with a smaller volume fraction should be arranged in areas with smaller stress values ​​such as the wing tip.

[0040] During the flight of a wing, the leading edge of the wing is often the first to experience intense compression, friction, and viscous dissipation with the air when flying forward. Therefore, the closer to the leading edge, the greater the temperature load. As time goes by, the entire surface skin of the fuselage will be subject to high temperature loads. In order to reduce the complexity of the design, the temperature load of the wing is considered to be uniformly heated on the surface, and the temperature is higher near the surface skin. Since the surface heating condition of the wing is considered to be uniformly heated on the wing skin, the temperature is higher near the surface skin. Therefore, based on the skin as the benchmark, a cell-size gradient design is performed on the variable-section D-type unit that fills the wing. A variable-section D-type unit with a unit size of 300mm×300mm×300mm and a volume fraction of 15% is used for filling. The results of uniform filling of the variable-section D-type are shown as follows. Fig.10 (a) shows; the variable cell size design still uses the above-mentioned variable cross-section D-type lattice unit. Unlike uniform filling, the original 300mm lattice cell size is offset by 30mm up and down, that is, The minimum cell size is set to 270mm×270mm×270mm, and the maximum cell size is set to 330mm×330mm×330mm. When filling the lattice, the wing skin is used as the gradient design benchmark. The closer to the wing skin, the closer to the minimum cell size. Conversely, the farther away from the wing skin, the closer to the maximum cell size. According to this method, the wing is filled with gradient cell variable size, and the following is obtained. Fig.10 (b) is the filling result, in which only the cell size is gradient changed, and the volume fraction is still 15%, that is, the volume fraction remains unchanged.

[0041] After the cell size is designed with gradient cell size variation, its active cooling performance should be improved to a certain extent, and the load-bearing performance is further optimized according to the cell density variation design method based on topology optimization. The optimization model adopts the homogenization topology optimization theory for cell density variation design. The cell density variation design process of topology optimization is as follows: Step 1: Topology Optimization Design Area Divide the design domain into non-design domain.

[0042] Step 2: Constraints After setting the optimization, the percentage of the overall volume fraction retained is 15%. In terms of the cell volume fraction setting, when the setting is too small, it is not conducive to the load-bearing and additive manufacturing of the low stress area. When the cell volume fraction is too large, the coolant will not be able to pass smoothly into the lattice structure. Therefore, the constraint range of the defined cell volume fraction is: the minimum unit volume fraction is not less than 5%, the maximum unit volume fraction is not higher than 60%, and the other constraints are consistent with the constraints of the static analysis.

[0043] Step 3: Optimize your goals The optimization goal is set to maximize stiffness, that is, the flexibility is set to the minimum for solving.

[0044] Step 4: Solve the calculation After completing all settings, solve the calculation and get Fig.11 (a) shows the unit density distribution diagram, in which 9 density gradients are divided, and the maximum unit volume fraction is 52.66% and the minimum is 5%. The variable density lattice structure wing is modeled based on the density distribution information solved by the topology optimization algorithm. Fig.11 (b) Fig.11 (c) and Fig.11 (d) are the comparison pictures of the uniform lattice filled wing, the lattice filled wing after variable size design, and the lattice filled wing after variable size and density design. For the convenience of display, the wing skin is hidden. Fig.11 The uniform lattice filled wing shown in (b) is directly filled with a variable cross-section D-type lattice structure with a volume fraction of 15% and a cell size of 300mm×300mm×300mm; Fig.11 (c) The lattice structure wing with variable cell size design maintains the same volume fraction of cell lattice units to fill the lattice filling area. The cell size continues the result of cell size gradient design, that is, the minimum cell size is set to 270mm×270mm×270mm, and the maximum cell size is set to 330mm×330mm×330mm. Under the same overall volume fraction as uniform filling, lattice units of different sizes are used to fill the lattice filling area. When filling the lattice, the wing skin is used as the gradient design benchmark. The closer to the wing skin, the closer to the minimum cell size. Conversely, the farther away from the wing skin, the closer to the maximum cell size. Fig.11(d) The result of the variable size and variable density design is to fill the lattice filling area with lattice units of different volume fractions. Based on the result of the cell size gradient design, a variable density cell design with variable cell volume fraction is carried out on this basis. The lattice filling area is filled with lattice units of different volume fractions. According to the structural force transmission path calculated by topology optimization, lattice units with larger volume fractions are set in the area with greater load, while lattice units with smaller volume fractions are set in the area with less load. That is, the active cooling performance of the wing structure is optimized by optimizing the cell size, and the load-bearing performance of the wing structure is optimized by optimizing the unit density distribution in different areas, so as to realize the integrated design of thermal control and load-bearing.

[0045] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A design method for a variable-size, variable-density lattice structure wing with optimized heat dissipation load, characterized in that: The steps include: S10: performing variable cross-section design on the D-type unit to obtain a variable cross-section D-type unit, using the variable cross-section D-type unit as a lattice unit configuration to fill the wing to form a skin lattice structure; the skin lattice structure includes a skin and a lattice filling area; S20: adopting a cell variable size design for the lattice unit to construct a variable size lattice unit; S30: The wing is made of titanium alloy TC4. According to the stress field of the wing, the variable-size lattice unit is designed with variable cell density to construct a variable-size and variable-density lattice unit. S40: Filling the lattice filling area with the variable size and variable density lattice units to establish an overall wing configuration.

2. The design method of a variable-size and variable-density lattice structure wing with optimized heat dissipation load according to claim 1 is characterized in that: The S10 includes S101, S102 and S103, wherein: S101: adding an auxiliary function based on the D-type implicit function of the TPMS, establishing a variable-section D-type unit parallel implicit function expression, and using the variable-section D-type unit parallel implicit function expression to model the D-type unit to obtain a variable-section D-type unit; S102: Parameter definition and analysis of the variable cross-section D-type unit to establish a cross-section control coefficient The relationship function with the cross-sectional radius of the strut of the variable cross-section D-type unit; S103: According to the design requirements, the cross-section control coefficient is adjusted The parametric variable cross-section design of the D-type unit is completed.

3. The design method of a variable-size and variable-density lattice structure wing with optimized heat dissipation load according to claim 2 is characterized in that: In S101, the variable cross-section D-type unit parallel implicit function expression is: ; In the formula, is the parallel implicit function of the variable cross-section D-type unit, are the unit vectors of the three axes in the Cartesian coordinate system, ， ， ， , , is the coordinate in the Cartesian coordinate system, is the side length of the lattice unit, is the threshold value, is the section control coefficient.

4. The design method of a variable size and density lattice structure wing with optimized heat dissipation load according to claim 3 is characterized in that: In S102, the section control coefficient The relationship function with the cross-sectional radius of the support rod of the variable cross-section D-type unit is: ; In the formula, is the cross-sectional radius of the support rod of the variable cross-section D-type unit.

5. The design method of a variable-size and variable-density lattice structure wing with optimized heat dissipation load according to claim 1, characterized in that: In the S20, the cell variable size design is to set the cell size to a gradient cell size.

6. The design method of a variable-size and variable-density lattice structure wing with optimized heat dissipation load according to claim 5, characterized in that: The S20 includes S201, S202 and S203, wherein: S201: Determine a skin and a lattice filling area of ​​a wing, wherein the skin is a non-design domain and the lattice filling area is a design domain; S202: Filling the dot matrix filling area with a uniform cell size using a single dot matrix unit; S203: Determine the heating surface of the skin, and use the heating surface of the skin as a reference to perform a gradient design on the cell size of the lattice filling area.

7. The method for designing a variable-size and variable-density lattice structure wing with optimized heat dissipation load according to claim 1, characterized in that: The S30 includes S301, S302 and S303, wherein: S301: establishing a corresponding relationship between a threshold value C in a D-type implicit function of the TPMS and a volume fraction of a D-type unit, and calculating an equivalent elastic modulus of the D-type unit by a homogenization method; the equivalent elastic modulus is a polynomial interpolation model of an equivalent elastic matrix; S302: Utilizing a topology optimization method of SIMP combined with an optimization criterion method, and optimizing and acquiring grid unit density information of the lattice unit according to a stress field load of a corresponding wing; S303: constructing the variable-size and variable-density lattice unit according to the correspondence between the grid unit density information of the lattice unit obtained through optimization and the volume fraction of the lattice unit.

8. The method for designing a variable-size and variable-density lattice structure wing with optimized heat dissipation load according to claim 1, characterized in that: The wings include but are not limited to drone wings.

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