A skin non-uniform-thickness beam-slab composite type lattice structure and a preparation process thereof

Abstract

The present application relates to beam-slab composite lattice structure, and particularly relates to a beam-slab composite lattice structure with non-uniform thickness of skin and a preparation process thereof, which solves the technical problems of insufficient lightweight degree and split design of skin and unit cell of the existing beam-slab composite lattice structure. The beam-slab composite lattice structure provided by the present application has non-uniform thickness of skin, and the thickness of the skin and the diameter of the support beam of the unit cell are related to the stress at the corresponding position of the skin, thereby improving the rigidity of the structure. By adjusting the thickness of the skin of the composite unit cell itself, the lightweight degree of the structure can be further improved. Meanwhile, a transition platform is arranged between the skins of two adjacent unit cells, so that the connectivity of the adjacent composite unit cells is enhanced, and the stress concentration effect is reduced while meeting the lightweight requirement of the structure. The present application further provides a preparation process of the beam-slab composite lattice structure with non-uniform thickness of skin, which can realize synchronous and integrated gradient design of the skin layer and the unit cell layer.

Description

Technical Field

[0001] This invention relates to beam-slab composite lattice structures, specifically to a beam-slab composite lattice structure with non-uniform skin thickness and its fabrication process. Background Technology

[0002] With the rapid development of deep space exploration, the demand for lightweight advanced optomechanical equipment is becoming increasingly urgent. Metal lattice structures, as lightweight porous materials, possess characteristics such as high porosity, high specific stiffness, high specific strength, and energy absorption and vibration reduction. With the development of metal additive manufacturing technology, metal lattice structures are being increasingly applied to aerospace precision optomechanical equipment.

[0003] Due to limitations in the payload capacity of optomechanical equipment, the application of metal lattice structures is often in the form of an outer skin plus a core lattice structure. This achieves a high degree of lightweighting while preventing external stray light from affecting optical imaging and effectively blocking foreign objects from entering the optomechanical equipment. Due to limitations in additive manufacturing processes and structural lightweighting targets, the core layer of optomechanical structures is generally only a single-layer lattice unit cell filled.

[0004] Currently, the most common metal thin-walled lattice sandwich structure involves filling the space between the outer skin layers with conventional lattice unit cells, such as body-centered cubic (BCC) or face-centered cubic (FCC) lattice cells. The skin thickness depends on the engineering experience of the technicians. This type of structure is called a beam-plate composite lattice structure. Since the skin thickness is uniform across all unit cells, it lacks gradient and differentiated design tailored to the specific stress conditions of the structure. This makes it difficult to simultaneously meet design requirements such as lightweighting, stiffness, and strength. Furthermore, the design of the unit cell layer and the skin layer is somewhat disconnected, lacking sufficient matching design.

[0005] Chinese patent CN112395700A discloses a surrogate model-driven optimization method for gradient lattice sandwich structures. When the core lattice is a single layer, this method can be used for the design of beam-slab composite lattice structures. However, although this method can simultaneously optimize the skin thickness and unit cell parameters of the beam-slab composite lattice structure, the skin thickness on one side remains the same, and the optimization of the skin and unit cell is also performed sequentially, failing to achieve simultaneous design of the skin layer and the core layer. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems of insufficient lightweighting and fragmented skin and unit cell design in existing beam-slab composite lattice structures, and to provide a beam-slab composite lattice structure with non-uniform skin thickness and its manufacturing process.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A beam-plate composite lattice structure with non-uniform skin thickness includes an upper skin, a lower skin, and a lattice unit cell disposed between the upper skin and the lower skin; wherein the upper skin is a load-bearing skin and the lower skin is a non-load-bearing skin.

[0009] Its special feature is that: the upper skin and the lower skin each include multiple interconnected unit cell skins that correspond one-to-one with the lattice unit cells; the unit cells and the corresponding unit cell skins on the upper and lower sides constitute a composite unit cell;

[0010] The unit cell includes a support beam that is connected to the corresponding unit cell skins on the upper and lower sides respectively. The diameter of the support beam is proportional to the average stress of the composite unit cell, and the thickness of the unit cell skin is proportional to the stress of the unit cell skin.

[0011] The average stress of the composite unit cell and the stress of the unit cell skin are obtained from the load force analysis of the upper skin.

[0012] Furthermore, it also includes a transition platform disposed between two adjacent unit cell skins;

[0013] The width of the transition platform is the sum of the thicknesses of two adjacent unit cell skins.

[0014] Furthermore, the end of the support beam is disposed on the side wall of the corresponding transition platform.

[0015] Furthermore, an arc transition is provided between the transition platform and the corresponding unit cell skin; the end of the support beam is located on the arc transition.

[0016] Furthermore, all transition platforms are at the same height.

[0017] Furthermore, the height of the arc transition is the difference between the height of the transition platform and the thickness of the corresponding unit cell skin.

[0018] Furthermore, the average stress of the composite unit cell and the stress of the unit cell skin are obtained by finite element analysis from the load force on the bearing skin.

[0019] Furthermore, the unit cell is a BCC-type unit cell and / or an FCC-type unit cell.

[0020] This invention also provides a fabrication process for the above-mentioned beam-plate composite lattice structure with non-uniform skin thickness, characterized by the following steps:

[0021] Step 1: Analyze the load force on the upper skin to obtain the stress at each position of the upper and lower skins;

[0022] Step 2: Based on the stress at each position of the upper and lower skin, obtain the stress of the corresponding unit cell skin and the average stress of the corresponding composite unit cell.

[0023] Step 3: Obtain the thickness of the unit cell skin based on the stress of the unit cell skin, and obtain the diameter of the supporting beam based on the average stress of the composite unit cell.

[0024] Step 4: Input the thickness of the unit cell skin and the diameter of the supporting beam into the additive manufacturing equipment to obtain a beam-plate composite lattice structure with non-uniform skin thickness.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] 1. The non-uniform thickness beam-plate composite lattice structure provided by the present invention has a skin thickness of non-uniform thickness and a supporting beam diameter that are related to the stress at the corresponding position of the composite unit cell. This can not only ensure the rigidity of the structure, but also further adjust the thickness of the corresponding unit cell skin according to the stress, thereby further improving the lightweighting of the structure.

[0027] 2. The beam-plate composite lattice structure with non-uniform skin thickness provided by the present invention has non-uniform skin thickness between the upper and lower skins and the skin thickness of the unit cells on both sides of the same composite unit cell is not forced to be equal, which can achieve greater design space and greater weight reduction.

[0028] 3. In the beam-plate composite lattice structure with non-uniform skin thickness provided by the present invention, a transition platform is provided between two adjacent skins, which can ensure the connection between adjacent composite unit cells while ensuring the structural stiffness and strength, and reduce stress concentration effect.

[0029] 4. In the beam-slab composite lattice structure with non-uniform skin thickness provided by the present invention, all transition platforms have the same height, which can ensure that the shape of the beam-slab composite lattice structure is consistent, so that the stress is distributed more evenly on it, thereby further reducing the stress concentration effect.

[0030] 5. The fabrication process of the beam-plate composite lattice structure with non-uniform thickness skin provided by the present invention parametrically designs the corresponding composite unit cell according to the stress at the corresponding position of the skin, and can simultaneously complete the design of single-layer lattice unit cell and skin, thereby enabling synchronous integrated gradient design of skin layer and unit cell layer for complex working conditions.

[0031] 6. In the fabrication process of the beam-plate composite lattice structure with non-uniform skin thickness provided by the present invention, only the thickness of the skin cell and the diameter of the supporting beam are needed to define a composite unit cell. The control parameters are few, which helps to parametrically design and optimize the composite unit cell. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention;

[0033] Figure 2 For along Figure 1 Partial sectional views of the mid-symmetry planes S3 and S4;

[0034] Figure 3 for Figure 2 A magnified view of region I, where B is the upper skin and A is the lower skin;

[0035] Figure 4 This is a schematic diagram of the structure of the composite unit cell in an embodiment of the present invention;

[0036] Figure 5 For along Figure 4 A quarter section view of the mid-symmetry planes S1 and S2;

[0037] Figure 6 This is a schematic diagram of the load force on the supporting skin in an embodiment of the present invention;

[0038] Figure 7 for Figure 6 Mises stress contour plot for medium load;

[0039] Figure 8 The following are schematic diagrams of the structures of different types of unit cells used in this embodiment, wherein (a) uses BCCz type unit cell and (b) uses FCC type unit cell;

[0040] The annotations in the attached figures are explained as follows:

[0041] 1-Upper skin, 2-Lower skin, 3-Single cell, 4-Composite single cell, 5-Single cell skin, 6-Support beam, 7-Transition platform. Detailed Implementation

[0042] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of the beam-slab composite lattice structure with non-uniform skin thickness proposed in this invention and its fabrication process. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of this invention and are not intended to limit the scope of protection of this invention.

[0043] A beam-slab composite lattice structure with non-uniform skin thickness, such as Figures 1-3 As shown, it includes an upper skin 1, a lower skin 2, and a lattice-type unit cell 3 disposed between the upper skin 1 and the lower skin 2. The upper skin 1 is the load-bearing skin, and the lower skin 2 is the non-load-bearing skin. The upper skin 1 and the lower skin 2 each include multiple interconnected unit cell skins 5, each corresponding one-to-one with a lattice-type unit cell 3, as shown... Figure 4 , Figure 5 As shown, unit cell 3 and corresponding unit cell skins 5 on the upper and lower sides constitute composite unit cell 4. A transition platform 7 is provided between two adjacent unit cell skins 5, and an arc transition is provided between the transition platform 7 and the corresponding unit cell skin 5. Unit cell 3 includes support beams 6 that are respectively connected to the corresponding unit cell skins 5 on the upper and lower sides. The ends of the support beams 6 are provided on the arc transition of the corresponding transition platform 7.

[0044] like Figure 5 As shown, the diameter D of the supporting beam 6 is directly proportional to the average stress of the composite unit cell 4. The thickness t of the skin 5 on both sides of the unit cell is... u and t d The stress is directly proportional to the stress of the unit cell skin 5. The average stress of the composite unit cell 4 and the stress of the unit cell skin 5 are obtained from the load force on the upper skin 1 through finite element analysis. The height t of all transition platforms 7 is... B The width of the transition platform 7 is equal to the sum of the thicknesses of the two adjacent unit cell skins 5. The height r of the arc transition between the transition platform 7 and the corresponding unit cell skin 5 is equal to the thickness of the transition platform 7. u The height t of transition platform 7 B The thickness t of the corresponding unit cell skin 5 u The difference, correspondingly, r d =t B -t d .

[0045] In this embodiment, if the thickness of the beam-slab composite lattice structure is 10mm, then the height t of the transition platform 7 is... B It can be taken as 20% of the thickness of the beam-slab composite lattice structure, i.e., 2mm. The thickness t of the upper skin 1 in the composite unit cell 4 can be set as follows: u The thickness t of the lower skin 2 at the corresponding position d Given that the diameters are 1.5mm and 0.5mm respectively, and the diameter D of the support beam 6 is 1.5mm, then the diameter r of the arc transition between the transition platform 7 and the corresponding unit cell skin 5 is... u and r d The thicknesses are 0.5mm and 1.5mm respectively.

[0046] like Figure 6 The diagram shows the load force on the upper skin 1, i.e., the load-bearing skin. Finite element analysis was performed on it, and the results are as follows: Figure 7 The Mises stress cloud diagram shown indicates that the stress is relatively large on both sides and in the middle of the upper skin 1 and lower skin 2 before the filling lattice. Based on the stress magnitude, the composite unit cell 4 at different positions of the beam-plate composite lattice structure is designed. Where the stress is large, the supporting beam 6 of the composite unit cell 4 has a larger diameter and the unit cell skin 5 is thicker. Where the stress is small, the supporting beam 6 of the composite unit cell 4 has a smaller diameter and the unit cell skin 5 is thinner.

[0047] In other embodiments, unit cell 3 can be adopted as follows: Figure 8 The BCCz type unit cell and / or FCC type unit cell are shown. The material of the composite unit cell 4 is a material that can be manufactured by metal additive manufacturing, such as aluminum alloy AlSi10Mg, titanium alloy Ti-6Al-4V, 316L stainless steel, etc.

[0048] like Figure 2 and Figure 3As shown, in this embodiment, the arrangement of composite unit cells 4 can achieve a consistent shape, while the thickness of the skin 5 is inconsistent. Furthermore, the composite unit cells 4 are smoothly transitioned through transition platforms 7, and there is no stress concentration effect between adjacent composite unit cells 4, allowing for greater design flexibility and a greater degree of weight reduction. The thickness of the upper skin 1 and lower skin 2 is non-uniform, directly proportional to the stress at corresponding positions on the skin. Moreover, the thickness of the upper skin 1 and lower skin 2 at corresponding positions is not forced to be consistent. The stress at corresponding positions of the upper skin 1 and lower skin 2 can be combined to perform parametric design of the corresponding composite unit cells 4, thereby enabling synchronous integrated gradient design of the skin layer and core layer for complex working conditions.

[0049] Compared to existing beam-slab composite lattice structures with uniform single-sided skin thickness, this embodiment exhibits a non-uniform skin thickness due to the correlation between skin thickness and stress at corresponding locations, thus further enhancing the lightweight nature of the beam-slab composite lattice structure. Simultaneously, the presence of the transition platform 7 reduces stress concentration effects between adjacent composite unit cells 4 while meeting structural lightweight requirements, ensuring structural stiffness and strength.

[0050] This embodiment also provides a fabrication process for the above-mentioned beam-plate composite lattice structure with non-uniform skin thickness, including the following steps:

[0051] Step 1: Analyze the load force on the load-bearing skin to obtain the stress at each position of the upper skin 1 and the lower skin 2;

[0052] Step 2: Based on the stress at each position of the upper skin 1 and the lower skin 2, obtain the stress of the unit cell skin 5 and the average stress of the corresponding composite unit cell 4.

[0053] Step 3: Obtain the thickness of the unit cell skin 5 based on the stress of the unit cell skin 5, and obtain the diameter of the support beam 6 based on the average stress on the composite unit cell 4.

[0054] Step 4: Input the thickness of the unit cell skin 5 and the diameter of the supporting beam 6 into the additive manufacturing equipment to obtain a beam-plate composite lattice structure with non-uniform skin thickness.

[0055] The fabrication process of the beam-slab composite lattice structure proposed in this embodiment can simultaneously complete the design of the lattice unit cell 3, upper skin 1, and lower skin 2 in the beam-slab composite structure. A composite unit cell 4 can be defined by the thickness of the unit cell skin 5 and the diameter of the supporting beam 6, requiring fewer control parameters and facilitating parametric design and optimization of the composite unit cell 4. The thickness of the unit cell skin 5 is related to the stress at the corresponding position, and uniform thickness is not required, nor is it mandatory for the thicknesses of the upper skin 1 and lower skin 2 at corresponding positions to be equal, providing greater freedom for structural design. Periodic boundary conditions can also be used to perform transversely isotropic force and thermal equivalent predictions of the composite unit cell 4, significantly improving simulation and optimization efficiency. Simultaneously, a series of composite unit cells 4 generated by changing relevant parameters can be used to fabricate the beam-slab composite lattice structure. Technicians can adjust the thickness of the unit cell skin 5 and the diameter of the supporting beam 6 of the composite unit cell 4 at different positions according to load input, specific equipment dimensions, and installation location requirements to achieve the optimal load-bearing effect of the beam-slab composite lattice structure.

Claims

1. A beam-plate composite lattice structure with non-uniform skin thickness, comprising an upper skin (1), a lower skin (2), and a lattice unit cell (3) disposed between the upper skin (1) and the lower skin (2); wherein, The upper skin (1) is a load-bearing skin, and the lower skin (2) is a non-load-bearing skin; The features are as follows: the upper skin (1) and the lower skin (2) each include a plurality of interconnected single-cell skins (5) that correspond one-to-one with the dot matrix single cells (3); the single cells (3) and the corresponding single-cell skins (5) on the upper and lower sides constitute a composite single cell (4); The unit cell (3) includes a support beam (6) that is connected to the corresponding unit cell skins (5) on the upper and lower sides respectively. The diameter of the support beam (6) is proportional to the average stress of the composite unit cell (4), and the thickness of the unit cell skin (5) is proportional to the stress of the unit cell skin (5). It also includes a transition platform (7) disposed between two adjacent unit cell skins (5); the width of the transition platform (7) is the sum of the thicknesses of the two adjacent unit cell skins (5), and all transition platforms (7) have the same height; The average stress of the composite unit cell (4) and the stress of the unit cell skin (5) are obtained by analyzing the load force on the upper skin (1), thereby enabling the simultaneous design of the diameter of the support beam (6), the thickness of the unit cell skin (5), and the width and height of the transition platform (7).

2. The beam-slab composite lattice structure with non-uniform skin thickness according to claim 1, characterized in that: The end of the support beam (6) is set on the side wall of the corresponding transition platform (7).

3. The beam-slab composite lattice structure with non-uniform skin thickness according to claim 2, characterized in that: A circular arc transition is provided between the transition platform (7) and the corresponding unit cell skin (5); the end of the support beam (6) is provided on the circular arc transition.

4. The beam-slab composite lattice structure with non-uniform skin thickness according to claim 3, characterized in that: The height of the arc transition is the difference between the height of the transition platform (7) and the thickness of the corresponding unit cell skin (5).

5. A beam-slab composite lattice structure with non-uniform skin thickness according to any one of claims 1-4, characterized in that: The average stress of the composite unit cell (4) and the stress of the upper and lower unit cell skins (5) are obtained by finite element analysis from the load force on the upper skin (1).

6. The beam-slab composite lattice structure with non-uniform skin thickness according to claim 1, characterized in that: The unit cell (3) adopts BCC class unit cell and / or FCC class unit cell.

7. A fabrication process for a beam-plate composite lattice structure with non-uniform skin thickness as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Analyze the load force on the upper skin (1) to obtain the stress at each position of the upper skin (1) and the lower skin (2); Step 2: Based on the stress at each position of the upper skin (1) and the lower skin (2), obtain the stress of the corresponding unit cell skin (5) and the average stress of the corresponding composite unit cell (4); Step 3: Obtain the thickness of the unit cell skin (5) based on the stress of the unit cell skin (5), and obtain the diameter of the support beam (6) based on the average stress of the composite unit cell (4); Step 4: Input the thickness of the unit cell skin (5) and the diameter of the supporting beam (6) into the additive manufacturing equipment to obtain a beam-plate composite lattice structure with non-uniform skin thickness.

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