TPMS Lamellar and Rod Mixed Lattice Structure and Its Generation Method

Abstract

The present invention discloses a TPMS sheet and rod hybrid lattice structure and a method for generating the same, which relates to the field of material structure design. The method includes: S1, selecting the types of TPMS sheet structures and rod structures to be connected; S2, selecting the type of TPMS skeleton structure according to the selected type of rod structure; S3, generating a TPMS sheet structure and a TPMS skeleton structure according to the selected types of TPMS sheet structure and TPMS skeleton structure, generating a transition structure between the two structures by using the functions of the TPMS sheet structure and the TPMS skeleton structure, and obtaining an intermediate structure by bridging the two structures with the transition structure; S4, generating a rod structure according to the selected type of rod structure to replace the non-transition region of the intermediate structure, and obtaining a TPMS sheet and rod hybrid lattice structure including a TPMS sheet structure, a transition structure, and a rod structure connected in sequence. The present invention realizes the continuous compliant connection between the TPMS sheet and the rod structure by identifying the boundary distribution similarity between the TPMS skeleton structure and the rod structure and generating a transition structure.

Description

Technical Field

[0001] The present invention relates to the field of material structure design, and particularly to a TPMS sheet and rod hybrid lattice structure and a method for generating the same. Background Art

[0002] Engineering lattice structures have extensive application potential in fields such as biomedical engineering and the automotive industry. The core challenge lies in achieving specific mechanical and functional properties through microstructure optimization. Traditional designs rely on the rational configuration of microstructures. Traditional single-topology lattice structures have great limitations (for example, the literature "Plate-nanolattices at the theoretical limit of stiffness and strength" mentions the theoretical limit of plate nanolattices in stiffness and strength). To make more full use of the design space provided by additive manufacturing, it is necessary to break through the limitations of single-form structures: Rod-like lattices (such as BCC, FCC) have clear bending / tensile-dominated mechanical behaviors, but abrupt changes at the interfaces are prone to causing stress concentration; Surface-type structures (such as TPMS), based on triply periodic minimal surfaces, have continuous self-supporting characteristics and excellent mechanical properties, but lack structural adaptability. Hybrid lattice structures can achieve the collaborative optimization of multi-physical field performance by integrating the advantageous mechanical characteristics of different structure types. However, due to differences in geometric morphology, characteristic dimensions, and spatial distribution laws between rod-like and surface-type lattices, there are often geometric discontinuities and characteristic dimension differences at their connection interfaces. This incompatibility not only causes significant stress concentration effects but also increases the process complexity during additive manufacturing, easily leading to structural defects or mechanical property degradation at the interfaces.

[0003] Existing solutions mainly improve the integrity of hybrid structures through functional gradient strategies (such as gradual change of rod diameter, scaling of unit cells) (such as the research in the literature "Functionally graded lattice structures for energy absorption: Numerical analysis and experimental validation"), but the change of porosity within a single topology will lead to limited mass transfer or manufacturing defects. Although the multi-structure hybrid design expands the design freedom through a spatially heterogeneous architecture, the problem of geometric incompatibility at the interfaces of different lattices is prominent. For example, although the mathematical surface definition of TPMS supports smooth transitions, rod-like structures lack continuous mathematical representations, resulting in stress concentration and manufacturing difficulties at the connection regions. Traditional interpolation or transitional unit cell methods have high computational costs and limited effects, and are difficult to meet the requirements of complex applications. Summary of the Invention

[0004] In view of the above problems, the present invention proposes a TPMS sheet and rod hybrid lattice structure and its generation method. The generation method of the TPMS sheet and rod hybrid lattice structure designs a transition structure of the TPMS sheet and rod hybrid lattice structure by identifying the node similarity between the TPMS skeleton and the rod structure, realizes the continuous compliant connection between the TPMS sheet and the rod structure, avoids the limitations of simple array design, and solves the geometric and mechanical compatibility problems between heterogeneous structures.

[0005] On the one hand, the generation method of the TPMS sheet and rod hybrid lattice structure is as follows:

[0006] S1. Select the types of the TPMS sheet structure and the rod structure to be connected; each transition connection node on the transition boundary of the unit cell of the rod structure type satisfies the vertex condition, the edge condition or the face-centered condition; the vertex condition means that the transition connection node is located at the vertex position of the unit cell cube; the edge condition means that the transition connection node is located at the midpoint position of the edge of the unit cell cube; the face-centered condition means that the transition connection node is located at the center point position of the face of the unit cell cube; the unit cell cube is a cube shape formed by all the boundaries of the unit cell of the rod structure and its adjacent unit cells; the transition boundary is the boundary of the unit cell cube facing the TPMS sheet structure to be connected; the transition connection node is the intersection point of the unit cell of the rod structure and the transition boundary.

[0007] S2. Select the TPMS skeleton structure type according to the selected type of the rod structure; the TPMS skeleton structure types include the I-Wrapped Package structure, the Neovius structure and the Primitive structure; if all the transition connection nodes of the rod structure type satisfy the vertex condition, the I-Wrapped Package structure is selected for the TPMS skeleton structure; if all the transition connection nodes of the rod structure type satisfy the edge condition, the Neovius structure is selected for the TPMS skeleton structure; if all the transition connection nodes of the rod structure type satisfy the face-centered condition, the Primitive structure is selected for the TPMS skeleton structure; if each transition connection node satisfies different conditions, select the condition satisfied by one transition connection node as the condition satisfied by all the transition connection nodes, and select the corresponding TPMS skeleton structure type.

[0008] S3. Generate the TPMS sheet structure and the TPMS skeleton structure according to the selected types of the TPMS sheet structure and the TPMS skeleton structure, generate the transition structure of the two structures by using the functions of the TPMS sheet structure and the TPMS skeleton structure, and bridge the TPMS sheet structure type and the TPMS skeleton structure by using the transition structure to obtain an intermediate structure; the intermediate structure includes a TPMS sheet structure, a transition structure with a unit cell thickness, and a TPMS skeleton structure as a non-transition area connected in sequence.

[0009] S4. Generate a rod structure to replace the non-transition region of the intermediate structure according to the selected rod structure type, obtaining a TPMS sheet and rod hybrid lattice structure including a TPMS sheet structure, a transition structure with a unit cell thickness, and a rod structure connected in sequence.

[0010] Preferably, the rod structure types include SC, BCC, SC-BCC hybrid, NP1, Iso truss, Rhombicdodecahedron, Auxetic, Truncated cube, OCT, and CC; among them, SC, BCC, SC-BCC hybrid, NP1, Isotruss, and Rhombicdodecahedron satisfy the vertex condition, Auxetic and Truncated cube satisfy the edge condition, and OCT and CC satisfy the face-centered condition.

[0011] Preferably, the TPMS sheet structure types include TPMS P sheet lattice structure, TPMS G sheet lattice structure, TPMS D sheet lattice structure, and TPMS I-WP sheet lattice structure.

[0012] Preferably, the function of the transition structure is expressed as:

[0013] ;

[0014] Wherein, represents the function of the transition structure; is the function of the th TPMS sheet structure or TPMS skeleton structure, , represents the number of superposed functions, n = 2; represents weight parameters of the TPMS sheet structure or TPMS skeleton structure, controlling the continuous transition between structures.

[0015] Preferably, is expressed as:

[0016] ;

[0017] ;

[0018] Wherein, k represents a constant for controlling the length of the transition interval; represents the distance function between the point and the th TPMS sheet structure or TPMS skeleton structure, represents the point represents the distance function from the th TPMS sheet structure or TPMS framework structure, used to control the boundary of the function; represents the coordinates of the point cloud formed by the boundary of the jth TPMS sheet structure or TPMS framework structure; represents the coordinates of a point in space in the Cartesian coordinate system.

[0019] Preferably, the mathematical expressions of each type of TPMS framework structure are as follows:

[0020] ;

[0021] ;

[0022] ;

[0023] where represents the function of the I-Wrapped Package TPMS framework structure; represents the function of the Neoviuse TPMS framework structure; represents the function of the Primitive TPMS framework structure; represents the coordinates of a point in space in the Cartesian coordinate system; , and respectively represent the constant parameters controlling the periods of the I-Wrapped Package, Neovius, and Primitive TPMS framework structures.

[0024] Preferably, after S4, the following steps are further included:

[0025] S5, using additive manufacturing technology to generate a physical object of the TPMS sheet and rod hybrid lattice structure.

[0026] On the other hand, for the TPMS sheet and rod hybrid lattice structure generated by the above TPMS sheet and rod hybrid lattice structure generation method, the types of rod structures used in the TPMS sheet and rod hybrid lattice structure include SC, BCC, SC-BCC hybrid, NP1, Iso truss, Rhombic dodecahedron, Auxetic, Truncated cube, OCT, and CC, and the types of TPMS sheet structures used include TPMS P sheet lattice structure, TPMS G sheet lattice structure, TPMS D sheet lattice structure, and TPMS I-WP sheet lattice structure; 40 types of TPMS sheet and rod hybrid lattice structures are generated through the combination of the rod structure type and the TPMS sheet structure type.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) By introducing a transition structure through matching the boundary distribution characteristics of the TPMS skeleton and the rod-like structure, the present invention realizes the geometric compatibility of two types of heterogeneous lattices, eliminates the mutations and discontinuities at the interface of traditional hybrid structures, ensures a smooth transition from the TPMS sheet to the support structure, effectively avoids stress concentration, improves the structural integrity, and is particularly suitable for complex geometric adaptation scenarios such as the bone-tendon interface;

[0029] (2) The hybrid lattice structure generated by the present invention integrates the high specific surface area of the TPMS and the adjustable stiffness characteristics of the rod-like structure, realizing the collaborative optimization of multiple physical properties; it can be used in bionic bone-tendon structures to meet the dual requirements of mechanics and mass transfer in tissue regeneration; it can also be extended to lightweight structures in aerospace or stress buffer components in precision machinery;

[0030] (3) Through the gradient design from the TPMS (bone-like) to the rod-like structure (tendon-like), the present invention can mimic the construction of the natural bone-fibrocartilage-tendon structure, solve the problem of large geometric differences between bones and tendons, and achieve good adaptation; it has strong load-bearing capacity, can effectively disperse mechanical loads, improve the structural integrity; the strain distribution is uniform, the strain concentration at the interface is small, and the structural stability is high; moreover, the modulus gradient of the structure is consistent with the natural bone-tendon transition range, and the tensile stiffness is enhanced, which has great potential in the field of biomedicine, especially in the application of tendon-bone repair implants, and is expected to improve the treatment effect.

[0031] (4)The present invention directly generates a physical model of the TPMS sheet and the rod-like hybrid lattice structure through additive manufacturing technology (such as 3D printing), providing a multifunctional lattice design solution with high strength and high adaptability for fields such as biomedical implants (such as bone-tendon interfaces) and structural engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The following further describes the present invention in detail with reference to the drawings;

[0033] Figure 1 It is a flowchart of the method for generating the TPMS sheet and the rod-like hybrid lattice structure;

[0034] Figure 2 It is a schematic diagram of the unit cell structure of the TPMS sheet lattice of the TPMS sheet and the rod-like hybrid lattice structure and its generation method; among them, (a) is a schematic diagram of the unit cell structure of the TPMS P sheet lattice; (b) is a schematic diagram of the unit cell structure of the TPMS G sheet lattice; (c) is a schematic diagram of the unit cell structure of the TPMS D sheet lattice; (d) is a schematic diagram of the unit cell structure of the TPMS I-WP sheet lattice;

[0035] Figure 3 Schematic diagram of the rod structure for the generation method of the TPMS sheet and rod hybrid lattice structure; among them, (a) is the schematic diagram of the rod structure with similar nodes to the I-Wrapped Package TPMS skeleton unit cell structure in the prior art; (b) is the schematic diagram of the rod structure with similar nodes to the Neovius TPMS skeleton unit cell structure in the prior art; (c) is the schematic diagram of the rod structure with similar nodes to the Primitive TPMS skeleton unit cell structure in the prior art;

[0036] Figure 4 Schematic diagram of the TPMS skeleton unit cell structure for the generation method of the TPMS sheet and rod hybrid lattice structure; among them, (a) is the schematic diagram of the I-Wrapped Package TPMS skeleton unit cell structure; (b) is the schematic diagram of the Neovius TPMS skeleton unit cell structure; (c) is the schematic diagram of the Primitive TPMS skeleton unit cell structure;

[0037] Figure 5 Schematic diagram of the transition structure generated by the TPMS G sheet structure and the I-Wrapped Package TPMS skeleton lattice structure in Example 1;

[0038] Figure 6 Schematic diagram of the TPMS sheet and rod hybrid lattice structure generated by the TPMS G sheet lattice structure and the BCC rod lattice structure in Example 1;

[0039] Figure 7 Hybrid lattice structure where the TPMS G sheet lattice structure and the CC rod lattice structure are connected in Example 2;

[0040] Figure 8 Schematic diagram of the hybrid lattice structure where the TPMS G sheet lattice structure and the Truncated cube rod lattice structure are connected in Example 3. Detailed implementation manners

[0041] The present invention will be further described below through specific implementation manners.

[0042] As Figure 1 shown, a method for generating a TPMS sheet and rod hybrid lattice structure comprises the following specific steps:

[0043] S1, select the type of TPMS sheet structure and the type of rod structure to be connected.

[0044] As Figure 2As shown, the unit cell types of the TPMS sheet structure in this embodiment include the TPMS P sheet lattice unit cell structure shown in (a), the TPMS G sheet lattice unit cell structure shown in (b), the TPMS D sheet lattice unit cell structure shown in (c), and the TPMS I-WP sheet lattice unit cell structure shown in (d).

[0045] As Figure 3 shown, the unit cell types of the rod-like structure include SC (Simple Cubic) shown in (a)-1, BCC (Body-Centered Cubic) shown in (a)-2, SC-BCC hybrid shown in (a)-3, NP1 shown in (a)-4, Iso truss (fiber-wound lattice beam) shown in (a)-5, Rhombicdodecahedron shown in (a)-6, Auxetic (negative Poisson's ratio material) shown in (b)-1, Truncated cube shown in (b)-2, OCT (Octahedron) shown in (c)-1, and CC structure shown in (c)-2.

[0046] It should be noted that the unit cell types of the TPMS sheet structure can be other TPMS sheet structure unit cell types, and the unit cell types of the rod-like structure can be other types that meet the connection conditions, which are specifically set according to needs and are not limited in this embodiment.

[0047] S2. Select the TPMS skeleton structure type according to the selected type of the rod-like structure.

[0048] Select the TPMS skeleton structure type with similar node distribution characteristics at the structural boundary of the rod-like structure as the twin unit. The so-called TPMS skeleton structure with similar node distribution characteristics refers to a structure with similar node distribution characteristics at the structural boundary. The node distribution characteristics of most structures are summarized into the following three categories: nodes are distributed at the eight vertices, the midpoints of the edges, and the center points of the faces of the cube. The so-called cube is composed of the structural boundaries of the unit cell and adjacent unit cells, and the so-called structural boundary refers to the boundary of the cube facing the TPMS sheet structure to be connected.

[0049] As Figure 4 shown, these three types correspond to the I-Wrapped Package, Neovius, and Primitive TPMS skeleton structures respectively. Therefore, these three TPMS skeleton structures are used as twin units, and their mathematical expressions are respectively:

[0050] ;

[0051] ;

[0052] ;

[0053] Among them, is a function representing the skeletal structure of I-Wrapped Package TPMS; is a function representing the skeletal structure of Neoviuse TPMS; is a function representing the skeletal structure of Primitive TPMS; x, y, and z are the coordinates of a point in space in the Cartesian coordinate system, , and are the constant parameters that control the periods of the skeletal structures of I-Wrapped Package, Neovius, and Primitive TPMS, respectively.

[0054] Specifically, Figure 3 in (a) represents the unit cell structures of rod-like structures in the prior art that have similar nodes to the unit cell structure of the I-Wrapped Package TPMS skeletal structure, which are SC, BCC, SC-BCC hybrid, NP1, Iso truss, and Rhombic dodecahedron, respectively. Figure 3 in (b) represents the unit cell structures of rod-like structures in the prior art that have similar nodes to the unit cell structure of the Neovius TPMS skeletal structure, which are Auxetic and Truncated cube, respectively. Figure 3 in (c) represents the unit cell structures of rod-like structures in the prior art that have similar nodes to the unit cell structure of the Primitive TPMS skeletal structure, which are OCT and CC, respectively.

[0055] If all the nodes at the boundaries of the connection structure of the selected rod-like structure are located at the vertex positions of the cube, the TPMS skeletal structure selects the I-Wrapped Package structure; if all the nodes at the boundaries of all the connection structures of the rod-like structure are distributed at the center points of the edges of the cube, the TPMS skeletal structure selects the Neovius structure; if all the nodes at the boundaries of all the connection structures of the rod-like structure type are distributed at the face center positions of the cube, the TPMS skeletal structure selects the Primitive structure; if the nodes at the boundaries of the connection structure are distributed at different positions of the cube, select the TPMS skeletal structure corresponding to the distribution position of any one of the nodes at the boundaries of the connection structure of the rod-like structure.

[0056] S3. Generate the TPMS sheet structure and the TPMS skeleton structure according to the selected TPMS sheet structure type and TPMS skeleton structure type. Generate the transition structure between the two structures using the functions of the TPMS sheet structure and the TPMS skeleton structure, and bridge the TPMS sheet structure type and the TPMS skeleton structure with the transition structure to obtain the intermediate structure.

[0057] The intermediate structure includes a TPMS sheet structure, a transition structure with a unit cell thickness, and a TPMS skeleton structure as the non-transition region, which are connected in sequence.

[0058] The functional expression of the transition structure is as follows:

[0059] ;

[0060] Among them, is the function of the th TPMS skeleton structure, , represents the number of superimposed TPMS skeleton structures; is the spatial correlation weight parameter, which defines the continuous transition between structures. In this embodiment, n = 2.

[0061] The weight parameter is determined by the Sigmoid transition function and is expressed as:

[0062] ;

[0063] Among them, k represents a constant used to control the length of the transition interval; represents represents the point represents the distance function from the th lattice structure, which is used to control the boundary of the function and is determined by the point cloud Pj(xj, yj, zj) formed by the structure boundary, and is expressed as:

[0064] ;

[0065] Among them, represents the coordinates of the point cloud .

[0066] S4. Generate a rod structure according to the selected rod structure type and replace the non-transition region of the intermediate structure to obtain a TPMS sheet and rod hybrid lattice structure including a TPMS sheet structure, a transition structure with a unit cell thickness, and a rod structure connected in sequence.

[0067] Forty kinds of TPMS sheet and rod hybrid lattice structures can be generated through the combination of 10 kinds of rod structure types and 4 kinds of TPMS sheet structure types.

[0068] Embodiment 1:

[0069] The proposed hybrid structure connection scheme in this embodiment is not obtained from a simple array of unit structures. Therefore, it is necessary to design and model each unit in the design domain one by one. It will be a complex and time-consuming task to achieve this manually with general commercial modeling software. Therefore, in this embodiment, MATLAB code is written (codes with similar programming logics are within the scope of the application's protection) to automatically distribute the design space structure instead of manual work to meet the manufacturing of this integrated design, so as to realize the design of the hybrid lattice structure and establish manufacturing files that can be directly 3D printed and INP files for simulation. The steps are as follows:

[0070] 1) Define the design domain;

[0071] 2) Define the structures of different regions, including rod-like structures and TPMS sheet structures;

[0072] 3) Generate the voxel matrix of the hybrid structure;

[0073] 4) Convert the voxel matrix into.INP and.STL files.

[0074] Specifically, the size of the hybrid structure is defined by its design domain. The design domain contains two sub-regions, which respectively represent the two rod-like structures and TPMS sheet structures to be hybridized. The spaces occupied by two three-dimensional models in.stl format are used to describe these two design domains. These two design domains are described in the same coordinate system. When generating the structure, an extended cuboid (assuming the length, width, and height are L D , B D and H D ) is constructed according to the maximum dimension of the design domain in the coordinate axis directions. Subsequently, according to the given accuracy (the number of voxels n u contained in the side length L u of each unit cell), the entire design domain is converted into a matrix (containing N elements, N = L D B D H D / (L u / n u )) for description. Different values are assigned to the design domains corresponding to different structure types as "identity tags" for computer recognition and processing (such as integers 1, 2, and 3. All voxel units within the design domain of the rod-like structure are assigned "1", all voxel units within the design domain of the TPMS sheet structure are assigned "2"; the subsequent identified transition region (connection boundary) is assigned "3"). Starting from the origin of the coordinate system with n u 3The unit matrix composed of elements is used as the step size to search the global design domain, and the connection boundaries of the two types of structures are identified (the boundary identification is achieved through the spatial intersection operation of the numerical matrix, that is, when the numerical marks of the two structures exist in a unit at the same time, it is determined as the boundary area). The n u 3 elements containing the boundary are extracted as the design domain of the transition unit cell, and new values are assigned as the "identity tags" of the transition area. Then, the corresponding structures are generated according to the "identity tag" values of the elements in different areas of the matrix within the design domain. Among them, the rod diameter or wall thickness of the transition unit cell takes the same value as that of the adjacent connected rod-shaped or TPMS sheet structure at that position, so as to ensure the flexibility of the connection and at the same time control the relative density within a range similar to that of the adjacent structure. Finally, the generated cuboid structure is subjected to a Boolean intersection operation with the geometric shape of the initial design domain, so as to finally obtain the hybrid structure that meets the given geometric shape.

[0075] The generation of the transition structure is achieved in the following way: Use the weight parameter to superimpose two different TPMS skeleton structure functions (the skeleton structure corresponding to the target TPMS sheet structure topology, and the TPMS skeleton structure as the twin unit), and then remove the material in the design domain where the target TPMS sheet structure is located through Boolean subtraction, that is, perform a Boolean subtraction with a TPMS skeleton structure of the same topology with a relatively small relative density and convert it into a sheet structure.

[0076] The "voxel" in this embodiment is a concept, and the voxel is expressed by the element value in the matrix. One voxel corresponds to one element value. In computer processing, the structure in space is expressed by a matrix. For example, if the value at a certain position in the matrix is 1, it means that the voxel at this position is a solid, and if it is 0, it is empty. In this way, the three-dimensional structure can be mathematically expressed by the matrix. When generating the structure model, the STL file will be converted into a voxelized image, and the design domain will be discretized into voxels.

[0077] In this embodiment, select Figure 3 the lattice structure formed by the array of rod-shaped unit cell structures (i.e., BCC) shown in (a)-2 in Figure 2 and the lattice structure formed by the TPMS sheet unit cell (i.e., TPMS G) shown in (b) in

[0078] Select the TPMS skeleton structure with similar nodes to BCC, that is, the I-Wrapped Package TPMS skeleton unit cell structure. The transition unit cell is generated by the mathematical function expression of the I-Wrapped Package TPMS skeleton unit cell structure and the TPMS sheet structure generated by TPMS G. Finally, generate as shown in Figure 5The intermediate structure 1 between the TPMS G lattice and the I-Wrapped Package lattice shown includes a TPMS G lattice 11, a transition structure 12 between the TPMS G lattice and the BCC lattice, and a non-transition region 13 of the I-Wrapped Package TPMS skeleton connected in sequence.

[0079] The non-transition region 13 of the I-Wrapped Package TPMS skeleton is replaced with the selected BCC lattice 21, and the final complete hybrid structure obtained is as Figure 6 shown, resulting in a hybrid structure 2 of the TPMS G lattice and the BCC lattice, including a TPMS G lattice 11, a transition structure 12 between the TPMS G lattice and the BCC lattice, and a BCC lattice 21 connected in sequence.

[0080] The twin cell design in this method realizes the geometric compatibility of two types of heterogeneous lattices by matching the node features of the TPMS skeleton and the support structure. For example, the introduction of the transition unit eliminates the mutations and discontinuities at the interface of the traditional hybrid structure, ensuring a smooth transition from the TPMS sheet to the support structure. This design effectively avoids stress concentration and improves structural integrity, and is particularly suitable for complex geometric adaptation scenarios such as the bone-tendon interface.

[0081] This method realizes the collaborative optimization of multiple physical properties by integrating the high specific surface area of the TPMS and the adjustable stiffness of the rod-like structure. For example, in the bionic bone-tendon structure, the gradient design enables the stiffness to vary by 84 times while maintaining the specific surface area gradient, meeting the dual requirements of mechanics and mass transfer in tissue regeneration. In addition, this strategy can also be extended to aerospace lightweight structures or stress buffer components in precision machinery.

[0082] This method aims at the mechanical gradient problem of the natural tissue interface. Through the gradient design from the TPMS (bone-like) to the rod-like structure (tendon-like), this strategy can mimic and construct the natural bone-fibrocartilage-tendon structure, solve the problem of the large geometric difference between the bone and the tendon, and achieve good adaptation. It has strong load-bearing capacity, can effectively disperse mechanical loads, and improve structural integrity. The strain distribution is uniform, the strain concentration at the interface is small, and the structural stability is high. Moreover, the modulus gradient of the structure is consistent with the natural bone-tendon transition range, and the tensile stiffness is enhanced, which has great potential in the biomedical field, especially in the application of tendon-bone repair implants, and is expected to improve the treatment effect.

[0083] This method designs a twin cell as a transition unit by identifying the node similarity between the TPMS skeleton and the rod-like structure; combines the voxel principle with compensation optimization to achieve continuous compliant connection between the TPMS sheet and the rod-like structure, avoiding the limitations of simple array design. This novel hybrid connection strategy not only solves the geometric and mechanical compatibility problems between heterogeneous structures, but also directly generates models through 3D printing, providing a multifunctional lattice design solution with high strength and high adaptability for fields such as biomedical implants (such as bone-tendon interfaces) and structural engineering.

[0084] Example 2:

[0085] The main steps of this example are the same as those of Example 1, except that: the TPMS G sheet lattice structure and the CC rod lattice structure are selected for connection to obtain a hybrid structure in which the TPMS G sheet lattice structure and the CC rod lattice structure are connected, that is, the TPMS G and CC hybrid lattice structure 3, as shown in Figure 7 shown, including the TPMS G lattice 11, the transition region 31 between the TPMS G lattice and the CC lattice, and the CC lattice 32.

[0086] Example 3:

[0087] The main steps of this example are the same as those of Example 1, except that: the TPMS G sheet lattice structure and the Truncated cube rod lattice structure are selected for connection to obtain a hybrid structure in which the TPMS G sheet lattice structure and the Truncated cube rod lattice structure are connected, that is, the TPMS G and Truncated cube hybrid lattice structure 4, as shown in Figure 8 shown, including the TPMS G lattice 11, the transition region 41 between the TPMS G lattice and the Truncated cube lattice, and the Truncated cube lattice 42.

[0088] The above are only the specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantive modification made to the present invention using this concept shall fall within the scope of infringement of the protection scope of the present invention.

Claims

1. A method for generating a TPMS sheet and rod-shaped hybrid lattice structure, characterized in that, It includes the following steps: S1. Select the type of the TPMS sheet structure and the type of the rod structure to be connected; the type of the rod structure meets the vertex condition, the edge condition or the face-centered condition; each transition connection node on the transition boundary of the unit cell of the type of the rod structure meets the vertex condition, the edge condition or the face-centered condition; the vertex condition means that the transition connection node is located at the vertex position of the unit cell cube; the edge condition means that the transition connection node is located at the midpoint position of the edge of the unit cell cube; the face-centered condition means that the transition connection node is located at the center point position of the face of the unit cell cube; the unit cell cube is a cube shape formed by all the boundaries of the unit cell of the rod structure and the adjacent unit cells; the transition boundary is the boundary of the unit cell cube facing the TPMS sheet structure to be connected; the transition connection node is the intersection point of the unit cell of the rod structure and the transition boundary; S2. Select the type of the TPMS skeleton structure according to the selected type of the rod structure; the type of the TPMS skeleton structure includes the I-Wrapped Package structure, the Neovius structure and the Primitive structure; if all the transition connection nodes of the type of the rod structure meet the vertex condition, the I-Wrapped Package structure is selected for the TPMS skeleton structure; if all the transition connection nodes of the type of the rod structure meet the edge condition, the Neovius structure is selected for the TPMS skeleton structure; if all the transition connection nodes of the type of the rod structure meet the face-centered condition, the Primitive structure is selected for the TPMS skeleton structure; if each transition connection node meets different conditions, select the condition met by one transition connection node as the condition met by all the transition connection nodes, and select the corresponding type of the TPMS skeleton structure; S3. Generate the TPMS sheet structure and the TPMS skeleton structure according to the selected type of the TPMS sheet structure and the type of the TPMS skeleton structure, generate the transition structure of the two structures by using the functions of the TPMS sheet structure and the TPMS skeleton structure, and bridge the TPMS sheet structure type and the TPMS skeleton structure by using the transition structure to obtain the intermediate structure; the intermediate structure includes the TPMS sheet structure, the transition structure with the unit cell thickness and the TPMS skeleton structure as the non-transition area connected in sequence; S4. Generate the rod structure according to the selected type of the rod structure to replace the non-transition area of the intermediate structure, and obtain the TPMS sheet and rod hybrid lattice structure including the TPMS sheet structure, the transition structure with the unit cell thickness and the rod structure connected in sequence.

2. The method for generating the TPMS sheet and rod hybrid lattice structure according to claim 1, wherein The types of rod-like structures include SC, BCC, SC-BCC hybrid, NP1, Iso truss, Rhombic dodecahedron, Auxetic, Truncated cube, OCT, and CC; among them, SC, BCC, SC-BCC hybrid, NP1, Iso truss, and Rhombic dodecahedron satisfy the vertex condition, Auxetic and Truncated cube satisfy the edge condition, and OCT and CC satisfy the face-centered condition.

3. The method for generating the TPMS sheet and rod hybrid lattice structure according to claim 1, wherein The types of TPMS sheet structures include TPMS P sheet lattice structure, TPMS G sheet lattice structure, TPMS D sheet lattice structure, and TPMS I-WP sheet lattice structure.

4. The method for generating the TPMS sheet and rod hybrid lattice structure according to claim 1, wherein The function of the transition structure is expressed as: ； Among them, a function representing a transition structure; is the function of the th TPMS sheet structure or TPMS skeleton structure, , indicating the number of functions to be superimposed, n = 2; indicating weight parameters of the TPMS sheet structure or TPMS skeleton structure, controlling the continuous transition between structures.

5. The method for generating a TPMS sheet and rod hybrid lattice structure according to claim 4, wherein Expressed as: ； ； Where k is a constant used to control the length of the transition interval; Indicates a point With the The distance function of a TPMS layer structure or a TPMS skeleton structure, Indicates a point Indicates the A distance function of a TPMS layer structure or a TPMS skeleton structure is used to control the boundary of the function; The coordinates of the point cloud formed by the boundary of the j-th TPMS layer structure or TPMS skeleton structure; Represents the coordinates of a point in space in the Cartesian coordinate system.

6. The method for generating the TPMS sheet and rod hybrid lattice structure according to claim 1, characterized in that The mathematical expressions of each type of TPMS skeleton structure are as follows: ； ； ； Among them, A function representing the skeleton structure of I-Wrapped Package TPMS; A function representing the skeleton structure of NeoviuseTPMS; A function representing the skeleton structure of Primitive TPMS; Represents the coordinates of a point in space in the Cartesian coordinate system; 、 and Respectively represent the constant parameters controlling the periods of the skeleton structures of I-Wrapped Package, Neovius, and Primitive TPMS.

7. The method for generating a TPMS sheet and rod hybrid lattice structure according to claim 1, wherein After S4, the following steps are further included: S5, using additive manufacturing technology to generate a physical object of the TPMS sheet and rod-like hybrid lattice structure.

8. A TPMS sheet and rod-like hybrid lattice structure, comprising a TPMS sheet structure, a transition structure with a unit cell thickness, and a rod-like structure connected in sequence; the TPMS sheet structure, the transition structure with a unit cell thickness, and the rod-like structure are generated based on the TPMS sheet and rod-like hybrid lattice structure generation method according to any one of claims 1 to 7.

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