Biomimetic cellular structure, lattice and method of manufacture

Abstract

The application relates to a kind of bionic cell structure, lattice and manufacturing method, applied in the field of additive manufacturing and structure design, including support unit, the support unit includes several support leg parts, several support leg parts meet at cell center, and the end of several support leg parts away from cell center is respectively provided with bionic hoof for being connected with lattice node.The application has the technical effect that: bionic hoof expands the contact area of cell structure at lattice node, replaces the traditional lattice structure rod end single point or small area contact, significantly improves the stability of node connection, limits the rotation and swing of support leg part end through bionic hoof surface contact form, reduces the local warping of rod, improves the integrity of cell structure and the stability of lattice structure, makes cell structure present stable deformation mode and significantly improves bearing capacity and energy absorption efficiency.

Description

Technical Field

[0001] This application relates to the fields of additive manufacturing and structural design technology, and in particular to a biomimetic unit cell structure, lattice, and manufacturing method. Background Technology

[0002] As a new generation of high-performance porous materials, lattice structures are composed of several unit cell structures connected together to form a lattice structure. With its high specific strength, high specific stiffness, excellent energy absorption and shock absorption properties, lattice structures have become the core configuration for lightweight load-bearing in aerospace, biomedical implantation, automotive buffer energy absorption and high-end protective structures.

[0003] In related technologies, unit cell structures are mostly cylindrical rod-shaped structures, and lattice nodes are mostly connected by rod-like point contacts. In the aforementioned lattices using rod-like point contacts, the load is transferred only through a single point or a small area at the node, resulting in significant stress peaks, severe stress concentration, and a tendency to fail first at the node under compressive loads. This leads to low overall load-bearing efficiency and poor overall integrity of the lattice structure. Summary of the Invention

[0004] To address the problems of lattices using rod-type point-contact connections where loads are transferred only through single points or small areas at nodes, resulting in significant stress peaks, severe stress concentration, and easy failure at nodes under compressive loads, leading to low overall load-bearing efficiency and poor lattice structure integrity, this application provides a biomimetic unit cell structure with the following technical solution: It includes a support unit comprising several support legs converging at the center of the unit cell, and each support leg having a biomimetic hoof-like part at one end away from the center of the unit cell for connection to lattice nodes.

[0005] In one specific implementation, the bionic hoof includes connecting blocks disposed on the support leg, and a plurality of the connecting blocks have contoured grooves on their end faces facing the central axis of the support unit.

[0006] In one specific implementation, the connecting block is provided with oppositely arranged transition arc surfaces, and the contoured groove is located between the two transition arc surfaces.

[0007] In one specific implementation, the number of supporting legs is four, and the four supporting legs are respectively centrally symmetrical about the center of the unit cell.

[0008] In one specific implementation, a transition section is provided between the supporting leg and the bionic hoof.

[0009] In one specific implementation, the distance from the end of the supporting leg away from the center of the unit cell to the center of the lattice is the first distance, and the distance from the center of the bionic hoof to the lattice vertex corresponding to the bionic hoof is the second distance, and the length ratio of the second distance to the first distance is 0.48~0.54.

[0010] In one specific implementation scheme, the relative density of the support unit is 14.8~15.7%.

[0011] In one specific implementation scheme, a lattice is characterized by comprising a biomimetic unit cell structure as described in any one of claims 1 to 7, wherein a plurality of the biomimetic unit cell structures are periodically arranged and connected in three-dimensional space to form a lattice.

[0012] In one specific implementation scheme, the end of the bionic hoof that is away from the center of the unit cell is a bottom surface design portion, and there is an overlapping portion between the bionic hoof of the bionic unit cell structure and the bionic hoof of the adjacent bionic unit cell structure. The ratio of the area of ​​the overlapping portion to the area of ​​the bottom surface design portion is 0.27~0.31.

[0013] In one specific feasible embodiment, a manufacturing method for producing the lattice according to any one of claims 8-9, characterized in that the method comprises:

[0014] Based on the design parameters, complete the single-cell modeling of the biomimetic unit cell structure, and form an overall lattice structure model in a three-dimensional spatial array. Import the overall lattice structure model of the 3D model into the additive manufacturing equipment, perform slicing, and set the printing process parameters. Using selective laser melting technology, metal powder is used as raw material and melted and printed layer by layer according to preset printing process parameters to obtain an integrated biomimetic lattice structure. The molded biomimetic lattice structure is then subjected to powder removal, heat treatment, and surface polishing. Mechanical tests were conducted on the prepared biomimetic lattice structure.

[0015] In summary, this application has the following beneficial technical effects: the bionic hoof expands the contact area of ​​the unit cell structure at the lattice node, replacing the single point or small area contact of the rod end of the traditional lattice structure, significantly improving the stability of the node connection; the bionic hoof surface contact form restricts the rotation and sway of the end of the supporting leg, reduces the local warping of the rod, improves the integrity of the unit cell structure and the stability of the lattice structure, enables the unit cell structure to exhibit a stable deformation mode and significantly improves the load-bearing capacity and energy absorption efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of this application.

[0017] Figure 2 This is a schematic diagram illustrating the structure of the supporting leg in Embodiment 1 of this application.

[0018] Figure 3 This is a schematic diagram of the structure used to illustrate the bionic hoof in Embodiment 1 of this application.

[0019] Figure 4 yes Figure 3 Enlarged diagram of point A in the middle.

[0020] Figure 5 This is a schematic diagram of the structure used to illustrate the bottom surface parameters of the bionic hoof in Embodiment 1 of this application.

[0021] Figure 6 This is a schematic diagram of the crystal structure in Embodiment 2 of this application.

[0022] Figure 7 This is a diagram showing the deformation process and stress distribution of the crystal lattice during quasi-static compression in Embodiment 3 of this application.

[0023] Reference numerals: 1. Supporting leg; 2. Bionic hoof; 3. Connecting block; 4. Contouring groove; 5. Transition arc surface. Detailed Implementation

[0024] The following is in conjunction with the appendix Figure 1-7 This application will be described in further detail.

[0025] Embodiment 1 of this application discloses a biomimetic unit cell structure.

[0026] Example 1 Reference Figure 1 and Figure 2 The biomimetic unit cell structure includes a support unit, which in turn includes several support legs 1. In this embodiment, the support legs 1 are cylindrical rods with a cross-sectional diameter d = 0.7 mm. The support legs 1 converge at the center of the unit cell to form the load-bearing skeleton of the BCC configuration. At the ends of the support legs 1 facing away from the center of the unit cell, biomimetic hoofs 2 are respectively provided for connection to lattice nodes. In this embodiment, there are four support legs 1, and the four support legs 1 are centrally symmetrical along the center of the unit cell, ensuring uniform and balanced load distribution in three-dimensional space. The unit cell structure experiences uniform and symmetrical stress, retaining the spatial topological advantages of the traditional BCC lattice. Simultaneously, the symmetrical arrangement allows the biomimetic hoofs 2 to be regularly arranged and stably connected at the nodes, facilitating conformal fusion of adjacent unit cell structures and improving the structural continuity of the overall lattice.

[0027] Therefore, the bionic hoof 2 expands the contact area of ​​the unit cell structure at the lattice node, replacing the single point or small area contact of the rod end of the traditional lattice structure, which significantly improves the stability of the node connection. The surface contact form of the bionic hoof 2 restricts the rotation and swing of the end of the support leg 1, reduces the local warping of the rod, improves the integrity of the unit cell structure and the stability of the lattice structure, and enables the unit cell structure to present a stable deformation mode and significantly improve the load-bearing capacity and energy absorption efficiency.

[0028] Reference Figure 2 , Figure 3 and Figure 4 The bionic hoof 2 includes connecting blocks 3 disposed on the support leg 1. Several connecting blocks 3 have contoured grooves 4 on their end faces facing the central axis of the support unit. The connecting blocks 3 have oppositely arranged transition arc surfaces 5. The contoured grooves 4 are located between two transition arc surfaces 5. The oppositely arranged transition arc surfaces 5 realize a smooth geometric transition between the connecting blocks 3 and adjacent connecting blocks 3. In this embodiment, the contoured grooves 4 and transition arc surfaces 5 of the connecting blocks 3 work together to form a bionic horseshoe structure. The contoured grooves 4 are opened along the direction of force, accurately replicating the mechanical characteristics of the bearing grooves at the bottom of the horseshoe. They can guide the load to be evenly transmitted along both sides of the contoured grooves 4, reduce the stress accumulation in the center of the connecting blocks 3, and form a local stiffness reinforcement zone, improving the node's resistance to compression and shear. Through bionic geometric reconstruction and parameter optimization, the structure presents a unique "H"-shaped deformation mode during compression.

[0029] Reference Figure 2 , Figure 3 and Figure 4 A transition section is provided between the supporting leg 1 and the bionic hoof 2. The cross-sectional shape of the transition section gradually changes from the non-circular outline on the upper surface of the bionic hoof 2 along the axial direction of the rod to the circular cross-section of the supporting leg 1, forming a smooth geometric transition. The transition section adopts a continuously changing cross-sectional shape without sharp corners or step-like abrupt changes in cross-section, reducing stress concentration and making the bionic hoof 2 and the supporting leg 1 form an integrated load-bearing structure, optimizing the load transmission path and improving the integrity of the unit cell structure.

[0030] Reference Figure 2 , Figure 3 and Figure 4 In this embodiment, the unit cell structure size L is preferably 4mm, that is, the unit cell size is 4mm×4mm×4mm. The ratio of the area occupied by the bottom surface of the bionic hoof 2 to the 4mm×4mm square of the bottom surface is 0.25. The relative density of the support unit is 14.8~15.7%, preferably 15.5%. This relative density range ensures that the elastic modulus, yield strength and platform stress reach the optimal ratio while achieving high lightweight, balancing lightweight and load-bearing capacity, and optimizing energy absorption efficiency.

[0031] Reference Figure 2 , Figure 3 and Figure 4 The key bottom surface parameters of the bionic hoof 2 mainly include: the leading edge arc chord length a is preferably 0.8 mm, the leading edge arc radius b is preferably 1.3 mm, the bottom length c is preferably 1.1 mm, the hoof height d is preferably 1.3 mm, the side arc radius j is preferably 1.0 mm, the groove top arc radius e is preferably 0.1 mm, the distance f from the center of the groove arc to the bottom is preferably 0.9 mm, the inner side arc radius g is preferably 2.0 mm, the bottom arc radius h is preferably 0.13 mm, and the distance i from the center of the bottom arc to the bottom is preferably 0.3 mm. The distance from the end of the supporting leg 1 away from the unit cell center to the lattice center is the first distance, and the distance from the center of the bionic hoof 2 to the corresponding lattice vertex is the second distance. The length ratio of the second distance to the first distance is 0.48~0.54, preferably 0.5, so that the rotational constraint of the bionic hoof 2 on the end of the supporting leg 1 is in a moderate state, ensuring smooth load transmission and deformation coordination.

[0032] The implementation principle of Embodiment 1 of this application is as follows: the bionic hoof 2 expands the contact area of ​​the unit cell structure at the lattice node, replacing the single point or small area contact of the rod end of the traditional lattice structure, which significantly improves the stability of the node connection. The surface contact form of the bionic hoof 2 restricts the rotation and swing of the end of the support leg 1, reduces the local warping of the rod, improves the integrity of the unit cell structure and the stability of the lattice structure, so that the unit cell structure presents a stable deformation mode and significantly improves the load-bearing capacity and energy absorption efficiency.

[0033] Example 2 Reference Figure 6 and Figure 7 Embodiment 2 of this application discloses a crystal lattice comprising the aforementioned biomimetic unit cell structure. Several biomimetic unit cell structures are periodically arranged and connected in three-dimensional space to form a crystal lattice. In this embodiment, the total unit cell arrangement of the crystal lattice structure is 5×5×5, with an overall external dimension of 20 mm×20 mm×20 mm and a theoretical relative density of 0.219. The end of the biomimetic hoof 2 away from the center of the unit cell is a bottom surface design portion. An overlapping portion is provided between the biomimetic hoof 2 of the biomimetic unit cell structure and the biomimetic hoof 2 of the adjacent biomimetic unit cell structure. The ratio of the area of ​​the overlapping portion to the area of ​​the bottom surface design portion is 0.27~0.31, preferably 0.29. It should be noted that this biomimetic crystal lattice structure can achieve control over porosity, stiffness, strength, toughness, and energy absorption characteristics by adjusting the structural geometric parameters, the relative area of ​​the biomimetic hoof 2, the transition structure type of the supporting leg 1, and the length ratio of the biomimetic hoof 2 to the supporting leg 1. Specific parameters are not limited here.

[0034] Therefore, by conformally fusing adjacent bionic hoof parts 2 together, a continuous transition without additional connecting components is formed, thus constituting an overall lattice structure. The lattice nodes are locally reinforced by the conformal hoof parts. The bionic hoof parts 2 of the adjacent bionic unit cell structure are seamlessly fused by overlapping conformally, eliminating additional connecting components and topologically eliminating lattice node gaps, which greatly improves the overall structure and combines lightweight, high load-bearing capacity and high energy absorption characteristics.

[0035] Example 3 Reference Figure 6 and Figure 7 Embodiment 3 of this application discloses a manufacturing method for producing the above-mentioned crystal lattice, the method comprising: Step 1: Complete the single-cell modeling of the biomimetic single-cell structure according to the design parameters, and form an overall lattice structure model in a three-dimensional spatial array.

[0036] Step 2: Import the overall lattice structure model of the 3D model into the additive manufacturing equipment, perform slicing, and set the printing process parameters.

[0037] Step 3 involves selective laser melting (SLM) using metal powder as the raw material. The powder is melted and printed layer by layer according to preset printing parameters to obtain a one-piece biomimetic lattice structure. Specifically, the matrix material is 316L stainless steel powder with a particle size distribution of 15–53 μm. The printing equipment is an EP-M260 metal 3D printer with the following process parameters: laser power 214W, scanning speed 928 mm / s, layer thickness 40 μm, and scanning spacing 0.10 mm. During the printing process, high-purity argon gas is introduced into the equipment chamber as a protective atmosphere, and the oxygen content is controlled below 0.1%.

[0038] Step 4: After the integrated biomimetic lattice structure is completed, the sample is cut off from the substrate and unmelted powder is removed using compressed air.

[0039] Step 5: Perform heat treatment on the molded sample to eliminate internal stress. Specifically, the heat treatment process involves heating to 1080℃ and holding for 2 hours, followed by rapid cooling with argon gas.

[0040] Step 6: Perform surface sandblasting and polishing on the heat-treated sample to obtain the final BHH lattice structure.

[0041] Step 7: Conduct mechanical tests on the prepared crystal structure. Specifically, a quasi-static compression test is used, which is carried out on a DDL100 electronic universal testing machine with a loading speed of 1 mm / min, compressing along the Z-axis to a strain ε = 0.6.

[0042] Experimental results show that the elastic modulus of this lattice structure (BHH) is 155.3 MPa, the yield strength is 7.3 MPa, and the plateau stress is 15.18 MPa. Compared with the traditional body-centered cubic (BCC) lattice structure of the same dimensions, the elastic modulus is increased by 42.2%, the yield strength by 49.0%, and the plateau stress by 110.1%. Observations during compression show that the stress distribution is uniform at ε = 0.2, with the stress peak region shifting from the nodes to the middle section of support leg 1. At ε = 0.4, the unit cell is compressed into a unique "H" shape, and support leg 1 exhibits obvious tensile stress distribution characteristics. This indicates that the lattice structure has achieved a transformation from a bending-dominated to a tension-dominated local deformation mechanism, and can be widely used in lightweight aerospace components, biomedical implants, automotive energy absorption devices, and protective structures.

[0043] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A biomimetic unit cell structure, characterized in that: The support unit includes a plurality of support legs (1), which converge at the center of the unit cell. Each of the support legs (1) has a biomimetic hoof (2) for connecting to a lattice node at one end away from the center of the unit cell.

2. The biomimetic unit cell structure according to claim 1, characterized in that: The bionic hoof (2) includes connecting blocks (3) disposed on the support leg (1), and a plurality of the connecting blocks (3) have contoured grooves (4) on their end faces facing the central axis of the support unit.

3. The biomimetic unit cell structure according to claim 2, characterized in that: The connecting block (3) is provided with oppositely arranged transition arc surfaces (5), and the contour groove (4) is located between the two transition arc surfaces (5).

4. The biomimetic unit cell structure according to claim 1, characterized in that: The number of the supporting legs (1) is four, and the four supporting legs (1) are centrally symmetrical along the center of the unit cell.

5. The biomimetic unit cell structure according to claim 1, characterized in that: A transition section is provided between the supporting leg (1) and the bionic hoof (2).

6. The biomimetic unit cell structure according to claim 1, characterized in that: The distance from the end of the supporting leg (1) away from the center of the unit cell to the center of the lattice is the first distance, and the distance from the center of the bionic hoof (2) to the lattice vertex corresponding to the bionic hoof (2) is the second distance. The length ratio of the second distance to the first distance is 0.48~0.

54.

7. The biomimetic unit cell structure according to claim 1, characterized in that: The relative density of the support unit is 14.8~15.7%.

8. A crystal lattice, characterized in that: It includes the biomimetic unit cell structure as described in any one of claims 1 to 7, wherein a plurality of the biomimetic unit cell structures are periodically arranged and connected in three-dimensional space to form a lattice.

9. The lattice according to claim 8, characterized in that: The end of the bionic hoof (2) away from the center of the unit cell is the bottom surface design part. There is an overlapping part between the bionic hoof (2) of the bionic unit cell structure and the bionic hoof (2) of the adjacent bionic unit cell structure. The ratio of the area of ​​the overlapping part to the area of ​​the bottom surface design part is 0.27~0.

31.

10. A manufacturing method for producing the crystal lattice according to any one of claims 8 to 9, characterized in that: The methods include: Based on the design parameters, complete the single-cell modeling of the biomimetic unit cell structure, and form an overall lattice structure model in a three-dimensional spatial array. Import the overall lattice structure model of the 3D model into the additive manufacturing equipment, perform slicing, and set the printing process parameters. Using selective laser melting technology, metal powder is used as raw material and melted and printed layer by layer according to preset printing process parameters to obtain an integrated biomimetic lattice structure. The molded biomimetic lattice structure is then subjected to powder removal, heat treatment, and surface polishing. Mechanical tests were conducted on the prepared biomimetic lattice structure.

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