Design and manufacturing method of mechanical programmable metamaterial

Abstract

The invention relates to a design and manufacturing method of a mechanical programmable metamaterial, and belongs to the technical field of metamaterials, and the construction method of a mechanical programmable metamaterial model specifically comprises the following steps: S1, dividing polygonal units of a substrate; s2, generating a secondary rotating polygon mesh; s3, embedding a negative Poisson's ratio honeycomb unit, namely embedding the negative Poisson's ratio honeycomb unit into the secondary rotating polygonal grid by changing the geometrical characteristics of part of side lines of the secondary rotating polygonal grid; s4, constructing a two-dimensional polygon-honeycomb mixed structure; s5, constructing a metamaterial model: modeling the two-dimensional polygon-honeycomb mixed structure by using three-dimensional modeling software or a programming means to form the metamaterial model; and S6, metamaterial additive manufacturing is carried out. The metamaterial with different mechanical properties can be designed and manufactured according to different requirements through the division mode of the polygonal units of the substrate, the configuration regulation and control of the secondary polygons and the embedded reconstruction of the negative Poisson's ratio honeycomb units and by using the additive manufacturing technology for forming.

Description

Technical Field

[0001] The present invention relates to the technical field of metamaterials, and particularly to a design and manufacturing method of a mechanically programmable metamaterial. Background Art

[0002] Metamaterials refer to artificial structures or composite materials with extraordinary physical properties not possessed by natural materials. According to their realized properties and application fields, they can be divided into mechanical metamaterials, thermal metamaterials, acoustic metamaterials, electromagnetic metamaterials, etc. Mechanically programmable metamaterials are a new type of mechanical metamaterials that provide the ability to intelligently program and control various mechanical properties such as stiffness, damping, thermal expansion, and shape memory behavior, thereby realizing the integration and customization of multiple properties and functions. However, traditional methods for regulating and programming mechanical properties such as elastic modulus, shear modulus, yield strength, and Poisson's ratio in each region of metamaterials are relatively complex and difficult to design, so further improvement is needed. Summary of the Invention

[0003] Based on this, it is necessary to provide a design and manufacturing method of a mechanically programmable metamaterial for the problem that traditional methods for regulating and programming mechanical properties such as elastic modulus, shear modulus, yield strength, and Poisson's ratio in each region of metamaterials are relatively complex and difficult to design.

[0004] A design and manufacturing method for a mechanically programmable metamaterial, the specific steps are as follows: S1. Divide the substrate polygon units: Divide multiple substrate polygon units in the planar space. The division of the substrate polygon units needs to comply with the anti-chirality division rule. Multiple substrate polygon units form a substrate polygon grid, and any one substrate polygon unit has multiple original vertices; S2. Form a secondary rotating polygon grid and complete the edge reconstruction: Determine the positions of multiple secondary vertices on any one substrate polygon unit according to the scaling factor, and determine the positions of the secondary vertices of multiple substrate polygon units based on the chirality characteristics of the substrate polygon unit and the anti-chirality propagation mode. Connect the secondary vertices of each substrate polygon unit in sequence to form a secondary rotating polygon grid. Divide the edges of the substrate polygon grid into two parts, and complete the edge reconstruction after deleting a part of the edges of the substrate polygon grid; S3. Embed the negative Poisson's ratio honeycomb unit: By changing the geometric characteristics of some edges of the secondary rotating polygon grid, embed the negative Poisson's ratio honeycomb unit into the secondary rotating polygon grid; S4. Construct a two-dimensional polygon-honeycomb hybrid structure: Further operate on the other part of the edges of the substrate polygon grid in step S2 to complete the construction of the two-dimensional polygon-honeycomb hybrid structure; S5. Construct a metamaterial model: Use 3D modeling software or programming means to model the two-dimensional polygon-honeycomb hybrid structure to form a metamaterial model; S6. Additive manufacturing of the metamaterial: Post-process the metamaterial model, and complete the additive manufacturing by configuring the processing environment and setting the processing parameters for the 3D printer.

[0005] The present application discloses a design and manufacturing method for a mechanically programmable metamaterial. The design in step S1 is a fundamental step in constructing the mechanically programmable metamaterial. The division of the base polygon units needs to be based on the structure of the metamaterial and the required mechanical properties / functions of each region. Based on the spatial division method of the base polygon mesh, it can effectively adapt to design regions with different geometric shapes and meet the requirements of different structural shapes of the metamaterial model. The design in step S2 is to reconstruct a secondary rotating polygon mesh for the subsequent shape design of the metamaterial model on the basis of the base polygon. By constructing the secondary rotating polygon mesh, intelligent programming of zero / negative Poisson's ratio deformation and precise regulation of normal stiffness and shear stiffness in each region can be achieved, adapting to various complex working environments. Through the designs of step S3 and step S4, the deformation of each position of the secondary polygon mesh can be programmatically regulated by embedding negative Poisson's ratio honeycombs with different configurations, and mechanical properties such as modulus and strength can be changed to meet various personalized requirements. The construction method of the mechanically programmable metamaterial model disclosed in the present application can adjust the structure generation method, design parameters, material properties, manufacturing process parameters, etc. according to different requirements and application environments to obtain the integration of multiple performances and functions and achieve the best application effect. Through the division method of the base polygon units, the configuration regulation of the secondary polygons, and the embedded reconstruction of the negative Poisson's ratio honeycomb units, it is easier to regulate and program the mechanical properties such as elastic modulus, shear modulus, yield strength, and Poisson's ratio of each region of the designed mechanical metamaterial, and metamaterial models with different mechanical properties can be designed according to different requirements. This design can achieve multifunctional customization integration such as energy absorption and vibration reduction, large-range deformable recovery, and zero / negative Poisson's ratio deformation through the reasonable selection of the mechanical metamaterial design. Using 3D printing technology, high-performance and customized structures can be manufactured, optimizing the mechanical properties and effectively obtaining the required products.

[0006] In one embodiment, the base polygon units are triangles and / or convex quadrilaterals. By using triangles or convex quadrilaterals as the base polygon units, it is possible to change the type of the base polygon units, the number of original vertices, the number of secondary vertices, and the position information, etc. to represent various complex shapes and models, which can increase the degree of freedom in regulating the mechanical properties of the final product and has extremely high flexibility and adaptability. This enables the mechanically programmable metamaterial to effectively adapt to design regions with different geometric shapes and meet the requirements of different structural shapes.

[0007] In one embodiment, the boundary of the planar space is represented by a polygon. By representing the boundary of the planar space with a polygon, various designs for the edges of the base polygon mesh are more convenient. Moreover, it can effectively regulate the size of the final metamaterial model to be within a suitable range.

[0008] In one embodiment, the number of the secondary vertices and the number of the original vertices of the base polygon unit are the same. Designing the same number of original vertices and secondary vertices is the basis for precisely programming the mechanical properties of the metamaterial, facilitating the design of the metamaterial model.

[0009] In one embodiment, the metamaterial model is a truss structure or a thin-walled structure. By selecting a truss structure or a thin-walled structure as the implementation form of the metamaterial model, it has the advantages of light weight, high design freedom, and compatibility with additive manufacturing.

[0010] In one embodiment, the anti-chiral segmentation rule in step S1 is as follows: The side line of any base polygon unit coincides with the boundary of the plane space or the side line of an adjacent base polygon unit, and any original vertex that does not coincide with the boundary of the plane space coincides with an even number of side lines of the adjacent base polygon unit. By forcing each side of the base polygon unit to coincide exactly with the adjacent unit or boundary, it ensures that the plane space is seamlessly segmented, thus providing a more comprehensive design area and enabling different designs to be implemented smoothly.

[0011] In one embodiment, the specific steps of "determining the positions of multiple secondary vertices on any base polygon unit according to the scale factor" in step S2 are as follows: Vectorization of the base polygon unit: Select one of the original vertices of the base polygon unit as the starting vertex, and sequentially set multiple vector side lines. The number of the vector side lines is the same as the number of the side lines of the base polygon unit, and the vector side lines coincide with the side lines of the base polygon unit one by one. One end of one of the multiple vector side lines coincides with the starting vertex, and one end of another of the multiple vector side lines coincides with the starting vertex. The multiple vector side lines are denoted as, where i = 1, 2, …, n, and n is the number of sides of the polygon, satisfying the following conditions: Setting the secondary vertices: For any original vertex A i and the vector side line starting from it, define the scale factor p and determine the position of the secondary vertex B i as follows: where i = 1, 2, …, n, and n is the number of sides of the polygon. Determining the positions of the secondary vertices in this way is more systematic and accurate, avoiding errors in determining the positions of the secondary vertices that may affect the mechanical properties of the metamaterial model. Moreover, the determination method is simpler and more convenient.

[0012] In one embodiment, the scaling factor p ∈ (0, 0.5]. With the scaling factor p ∈ (0, 0.5], different scaling factors can be selected according to design requirements to determine the secondary vertices, realizing the structural programming of the metamaterial model, increasing the degree of freedom to control the mechanical properties of the final product, and finally generating the required metamaterial model.

[0013] In one embodiment, the specific operation of "deleting a part of the side lines of the base polygon mesh" in the step S2 is to delete the side lines of the base polygon A i B i By deleting the side lines of the base polygon A i B i the unnecessary line segments can be reduced in the design process, making the finally formed two-dimensional metamaterial model more intuitive. Specifically, it is to delete the line segments A1B1, A2B2... A n B n This sets a design standard, making subsequent production and manufacturing more convenient.

[0014] In one embodiment, the specific operation of "deleting a part of the side lines of the base polygon mesh" in the step S2 is to delete the side lines of the base polygon A i+1 B i and A1B n By deleting the side lines of the base polygon A i+1 B i and A1B n the unnecessary line segments can be reduced in the design process, making the finally formed two-dimensional metamaterial model more intuitive and realizing the structural programming of the metamaterial model. Moreover, a design standard is set, making subsequent production and manufacturing more convenient.

[0015] In one embodiment, the specific process of "determining the positions of secondary vertices of multiple base polygon units based on the chiral characteristics of base polygon units and the anti-chiral propagation mode" in step S2 is as follows: Determine the chiral characteristics of base polygon units: With the top view of the planar space as a reference, if the vector side lines are connected end to end in a clockwise direction, the base polygon unit is defined as a left-handed base polygon; if the vector side lines are connected end to end in a counterclockwise direction, the base polygon unit is defined as a right-handed base polygon. Determine the anti-chiral propagation mode: Propagate from the base polygon unit with the determined chiral characteristics to adjacent base polygon units. Any base polygon unit sharing a side line with the left-handed base polygon is a right-handed base polygon, and any base polygon unit sharing a side line with the right-handed base polygon is a left-handed base polygon. Determine the secondary vertices of multiple base polygon units in sequence through the scale factor. Any base polygon unit sharing a side line with the left-handed base polygon is a right-handed base polygon, and any base polygon unit sharing a side line with the right-handed base polygon is a left-handed base polygon. Thus, the secondary vertices of each base polygon can be connected to each other to form a tight metamaterial structure, and the mechanical properties of the finally manufactured metamaterial model are better.

[0016] In one embodiment, the specific situation of "embedding negative Poisson's ratio honeycomb units into the secondary rotating polygon grid" in step S3 is as follows: When the base polygon is a triangle, it can be embedded into a double-V-shaped negative Poisson's ratio honeycomb structure or a triangular star honeycomb structure, and the derivation directions are 3 and 1 respectively; when the base polygon is a quadrilateral, it can be embedded into a re-entrant honeycomb structure or a star honeycomb structure, and the derivation directions are 2 and 1 respectively. According to the different performance / function requirements of each region, the embedding operation can be not performed. Embedding negative Poisson's ratio honeycombs based on the polygon-honeycomb structure embedding relationship can greatly improve the mechanical properties and the deformation ability regulation range of the mechanically programmable metamaterial, so as to expand the boundary of its function realization. Selecting whether to perform the embedding operation, as well as different derivation relationships and derivation directions provides a large number of and sufficient performance programming means for the mechanical metamaterial, can increase the freedom degree of regulating the mechanical properties of the final product, and helps to meet the different performance and function requirements of each region. The structures of the polygon-honeycomb structures formed by different derivation directions are different.

[0017] In one embodiment, the further operations in step S4 include one or more of buckling, replacing with an arc, replacing with a parabola, deleting, and retaining. Delete some of the side lines of the polygon grid, and for the other part of the side lines, any one of a variety of processing methods can be arbitrarily selected to reconstruct the side lines to achieve mechanical property programming, so that a metamaterial model with excellent mechanical properties required can be designed.

[0018] In one embodiment, the buckling treatment method is to modify the side line of the base polygon unit into two concave broken lines. The two broken lines and the original side line of the base polygon unit form an enclosed triangle, so that there is more design space for the side line of the base polygon unit to customize the mechanical properties.

[0019] In one embodiment, the additive manufacturing method includes powder bed fusion, stereolithography, directed energy deposition, material extrusion, binder jetting, material jetting, and sheet lamination. The additive manufacturing materials include one of metals, polymers, ceramics, or their composites. By reasonably selecting different additive manufacturing technologies and additive manufacturing materials, the degree of freedom of mechanical property regulation of the mechanically programmable metamaterial can be further improved, and it can respond to external stimuli such as heat and force, expanding the scope of its multifunctional realization.

[0020] In one embodiment, the specific steps of "post-processing the metamaterial model" are as follows: Model manufacturability optimization: Convert the metamaterial model into a mesh type file and perform filleting and chamfering on the regions of the metamaterial model; Polygonal mesh post-processing: Perform post-processing on the polygonal mesh of the metamaterial model. The post-processing includes mesh redrawing, interference shell repair, hole repair, bad edge repair, overlap repair, and cross triangular patch repair. By performing corresponding post-processing on the polygonal mesh of the metamaterial model, a product with better mechanical properties is formed. Brief Description of the Drawings

[0021] Figure 1 It is a schematic flow chart of a design and manufacturing method of a mechanically programmable metamaterial of the present invention;

[0022] Figure 2 It is a schematic diagram of determining secondary vertices within the base polygon unit of an embodiment of the present invention;

[0023] Figure 3 It is a schematic diagram of deleting part of the side line of the base polygon unit of an embodiment of the present invention;

[0024] Figure 4 It is a schematic diagram of embedding a star-shaped negative Poisson's ratio honeycomb structure of an embodiment of the present invention;

[0025] Figure 5 It is a schematic diagram of a two-dimensional polygon-honeycomb hybrid structure of an embodiment of the present invention;

[0026] Figure 6 It is a schematic diagram of a metamaterial model of an embodiment of the present invention;

[0027] Figure 7 It is a schematic diagram of determining secondary vertices within the base polygon unit of the second embodiment of the present invention;

[0028] Figure 8 Schematic diagram of deleting partial side lines of the base polygon unit in the second embodiment of the present invention;

[0029] Figure 9 Schematic diagram of embedding a star-shaped negative Poisson's ratio honeycomb structure in the second embodiment of the present invention;

[0030] Figure 10 Schematic diagram of a two-dimensional polygon-honeycomb hybrid structure in the second embodiment of the present invention;

[0031] Figure 11 Schematic diagram of a metamaterial model in the second embodiment of the present invention;

[0032] Figure 12 Schematic diagram of an embedded negative Poisson's ratio honeycomb structure related to the present invention. Detailed implementation manners

[0033] In order to more clearly understand the above objects, features and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0034] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0035] Embodiment 1

[0036] As Figure 1As shown, this embodiment discloses a design and manufacturing method of a mechanically programmable metamaterial, and the specific steps are as follows: S1. Divide the base polygon units: Divide a plurality of base polygon units in the plane space. The division of the base polygon units needs to conform to the anti-chirality segmentation rule. A plurality of base polygon units form a base polygon mesh, and any one of the base polygon units has a plurality of original vertices; S2. Form a secondary rotating polygon mesh and complete the edge reconstruction: Determine the positions of a plurality of secondary vertices on any one of the base polygon units according to the scaling factor, and determine the positions of the secondary vertices of a plurality of base polygon units based on the chirality characteristics of the base polygon unit and the anti-chirality propagation mode. Connect the secondary vertices of each base polygon unit in sequence to form a secondary rotating polygon mesh. Divide the edges of the base polygon mesh into two parts, and delete a part of the edges of the base polygon mesh to complete the edge reconstruction; S3. Embed the negative Poisson's ratio honeycomb unit: By changing the geometric characteristics of some edges of the secondary rotating polygon mesh, embed the negative Poisson's ratio honeycomb unit into the secondary rotating polygon mesh; S4. Construct a two-dimensional polygon-honeycomb hybrid structure: Further operate on the other part of the edges of the base polygon mesh in step S2 to complete the construction of the two-dimensional polygon-honeycomb hybrid structure; S5. Construct a metamaterial model: Use three-dimensional modeling software or programming means to model the two-dimensional polygon-honeycomb hybrid structure to form a metamaterial model; S6. Additive manufacturing of the metamaterial: Post-process the metamaterial model, and complete the additive manufacturing by configuring the processing environment and setting the processing parameters for the 3D printer.

[0037] The present application discloses a design and manufacturing method for a mechanically programmable metamaterial. The design in step S1 is a fundamental step in constructing the mechanically programmable metamaterial. The division of the base polygon units needs to be based on the metamaterial structure and the required mechanical properties / functions of each region. Based on the spatial division method of the base polygon mesh, it can effectively adapt to design regions with different geometric shapes and meet the requirements of different structural shapes of the metamaterial model. The design in step S2 is to reconstruct the secondary rotating polygon mesh for the subsequent shape design of the metamaterial model on the basis of the base polygon. By constructing the secondary rotating polygon mesh, intelligent programming of zero / negative Poisson's ratio deformation and precise regulation of normal stiffness and shear stiffness in each region can be achieved, adapting to various complex working environments. Through the designs of step S3 and step S4, the deformation of each position of the secondary polygon mesh can be programmed and regulated by embedding negative Poisson's ratio honeycombs with different configurations, changing mechanical properties such as modulus and strength to meet various personalized requirements. The construction method of the mechanically programmable metamaterial model disclosed in the present application can adjust the structure generation method, design parameters, material properties, manufacturing process parameters, etc. according to different requirements and application environments to obtain the integration of multiple performances and functions and achieve the best application effect. Through the division method of the base polygon units, the configuration regulation of the secondary polygons, and the embedded reconstruction of the negative Poisson's ratio honeycomb units, it is easier to regulate and program the mechanical properties such as elastic modulus, shear modulus, yield strength, and Poisson's ratio of each region of the designed mechanical metamaterial, and different mechanical property metamaterial models can be designed according to different requirements. This design can achieve multifunctional customization integration such as energy absorption and vibration reduction, large-range deformable recovery, and zero / negative Poisson's ratio deformation through the reasonable selection of the mechanical metamaterial design. Using 3D printing technology can realize the manufacture of high-performance and customized structures, optimize the mechanical properties, and effectively obtain the required products.

[0038] As Figure 2 and Figure 7 shown, in addition to the features of the above embodiments, this embodiment further defines that: the base polygon units are triangles and / or convex quadrilaterals. By using triangles or convex quadrilaterals as the base polygon units, it is possible to change the base polygon unit type, the number of original vertices, the number of secondary vertices, and the position information, etc. to represent various complex shapes and models, which can increase the degree of freedom in regulating the mechanical properties of the final product and has extremely high flexibility and adaptability. This enables the mechanically programmable metamaterial to effectively adapt to design regions with different geometric shapes and meet the requirements of different structural shapes.

[0039] As Figure 2 and Figure 7As shown, in addition to the features of the above embodiments, this embodiment further defines that the boundary of the planar space is represented by a polygon. By representing the boundary of the planar space using a polygon, various designs for the edges of the base polygon mesh are more convenient. Moreover, it can effectively standardize the size of the final metamaterial model within an appropriate range.

[0040] As Figure 2 and Figure 7 shown, in addition to the features of the above embodiments, this embodiment further defines that the number of the secondary vertices and the original vertices of the base polygon unit is the same. Designing the same number of original vertices and secondary vertices is the basis for precisely programming the mechanical properties of the metamaterial and facilitates the design of the metamaterial model.

[0041] As Figure 6 and Figure 11 shown, in addition to the features of the above embodiments, this embodiment further defines that the metamaterial model is a truss structure or a thin-walled structure. By selecting a truss structure or a thin-walled structure as the implementation form of the metamaterial model, it has advantages such as lightweight, high design freedom, and additive manufacturing compatibility.

[0042] As Figure 2 and Figure 7 shown, in addition to the features of the above embodiments, this embodiment further defines that the anti-chirality segmentation rule in step S1 is as follows: the edge of any base polygon unit coincides with the boundary of the planar space or the edge of an adjacent base polygon unit, and any original vertex that does not coincide with the boundary of the planar space coincides with an even number of edges of adjacent base polygon units. By forcibly requiring each edge of the base polygon unit to completely coincide with an adjacent unit or the boundary, it ensures that the planar space is seamlessly segmented, thereby providing a more comprehensive design area and enabling different designs to be smoothly implemented.

[0043] As Figure 2 and Figure 7 shown, in addition to the features of the above embodiments, this embodiment further defines that the specific steps of "determining the positions of multiple secondary vertices on any base polygon unit according to the scale factor" in step S2 are as follows: Vectorization of the base polygon unit: Select one of the original vertices of the base polygon unit as the starting vertex, and sequentially set multiple vector edges. The number of the vector edges is the same as the number of the edges of the base polygon unit and the vector edges coincide with the edges of the base polygon unit one by one. One end of one of the multiple vector edges coincides with the starting vertex, and one end of another of the multiple vector edges coincides with the starting vertex. The multiple vector edges are denoted as, where i = 1, 2,... n, and n is the number of polygon sides, satisfying the following conditions: Set secondary vertices: For any original vertex A i and the vector edge line starting from it, define the scaling factor p to determine the secondary vertex B i Location: where i = 1, 2, …, n, and n is the number of sides of the polygon. Determining the secondary vertex location in this way is more systematic and accurate, avoiding errors in determining the secondary vertex location that may affect the mechanical properties of the metamaterial model. Moreover, the determination method is simpler and more convenient.

[0044] As Figure 2 and Figure 7 shown, in addition to the features of the above embodiments, this embodiment further defines that: the scaling factor p ∈ (0, 0.5]. By setting the scaling factor p ∈ (0, 0.5], different scaling factors can be selected according to design needs to determine the secondary vertices, realizing the structural programming of the metamaterial model, increasing the degree of freedom in regulating the mechanical properties of the final product, and finally generating the required metamaterial model.

[0045] As Figure 3 and Figure 8 shown, in addition to the features of the above embodiments, this embodiment further defines that: in the step S2, the specific operation of "deleting a part of the edge lines of the base polygon mesh" is to delete the edge lines of the base polygon A i B i . By deleting the edge lines of the base polygon A i B i , unnecessary line segments are reduced in the design process, making the finally formed two-dimensional metamaterial model more intuitive. Moreover, specifically, it is to delete the line segments A1B1, A2B2... A n B n , formulating a design standard, making subsequent production and manufacturing more convenient.

[0046] As Figure 3 and Figure 8 shown, in addition to the features of the above embodiments, this embodiment further defines that: in the step S2, the specific operation of "deleting a part of the edge lines of the base polygon mesh" is to delete the edge lines of the base polygon A i+1 B i and A1B n . By deleting the edge lines of the base polygon A i+1 B i and A1B n , unnecessary line segments are reduced in the design process, making the finally formed two-dimensional metamaterial model more intuitive, realizing the structural programming of the metamaterial model. Moreover, a design standard is formulated, making subsequent production and manufacturing more convenient.

[0047] AsFigure 3 and Figure 8 As shown, in addition to the features of the above embodiments, this embodiment further defines that the specific process of "determining the positions of the secondary vertices of multiple base polygon units based on the chiral characteristics of the base polygon units and the anti-chiral propagation mode" in step S2 is as follows: Determine the chiral characteristics of the base polygon units: Based on the top view of the plane space, if the vector side lines are connected end to end in a clockwise direction, the base polygon unit is defined as a left-handed base polygon, and if the vector side lines are connected end to end in a counterclockwise direction, the base polygon unit is defined as a right-handed base polygon; Determine the anti-chiral propagation mode: Propagate from the base polygon unit with the determined chiral characteristics to the adjacent base polygon units. Any one sharing a side line with the left-handed base polygon is a right-handed base polygon, and any one sharing a side line with the right-handed base polygon is a left-handed base polygon; Determine the secondary vertices of multiple base polygon units through the scale factor in turn. Since any one sharing a side line with the left-handed base polygon is a right-handed base polygon, and any one sharing a side line with the right-handed base polygon is a left-handed base polygon, the secondary vertices of each base polygon can be connected to each other, forming a tight metamaterial structure, and the mechanical properties of the finally manufactured metamaterial model are better.

[0048] As Figure 4 and Figure 9 As shown, in addition to the features of the above embodiments, this embodiment further defines that the specific situation of "embedding the negative Poisson's ratio honeycomb unit into the secondary rotating polygon grid" in step S3 is as follows: When the base polygon is a triangle, it can be embedded into a double-V-shaped negative Poisson's ratio honeycomb structure or a triangular star honeycomb structure, and there are 3 and 1 derivative directions respectively; When the base polygon is a quadrilateral, it can be embedded into a re-entrant honeycomb structure or a star honeycomb structure, and there are 2 and 1 derivative directions respectively. According to the different required properties / functions of each region, the embedding operation can be not performed. Embedding the negative Poisson's ratio honeycomb based on the polygon-honeycomb structure embedding relationship can greatly improve the mechanical properties and the deformation ability regulation range of the mechanically programmable metamaterial, so as to expand the boundary of its function realization. Selecting whether to perform the embedding operation, as well as different derivative relationships and derivative directions provides a large number of and sufficient performance programming means for the mechanical metamaterial, can increase the freedom degree of regulating the mechanical properties of the final product, and helps to meet the different property and function requirements of each region. The structures of the polygon-honeycomb structures formed by different derivative directions are different.

[0049] In addition to the features of the above embodiments, this embodiment further defines that the further operations in step S4 include one or more of buckling, replacing with an arc, replacing with a parabola, deleting, and retaining. Perform a deletion operation on a part of the side lines of the polygon mesh, and for the other part of the side lines, any one of various processing methods can be arbitrarily selected to reconstruct the side lines, realizing mechanical property programming, so that a metamaterial model with excellent mechanical properties required can be designed.

[0050] In addition to the features of the above embodiments, this embodiment further defines that the processing method of buckling is to modify the side line of the base polygon unit into two concave broken lines. The two broken lines and the original side line of the base polygon unit form a closed triangle, so that the processing of the side line of the base polygon unit is more standardized, avoiding affecting the mechanical properties of the metamaterial model.

[0051] In addition to the features of the above embodiments, this embodiment further defines that the additive manufacturing method includes powder bed fusion, stereolithography, directed energy deposition, material extrusion, binder jetting, material jetting, and sheet lamination, and the additive manufacturing materials include one of metals, polymers, ceramics, or their composites. By reasonably selecting different additive manufacturing technologies and additive manufacturing materials, the degree of freedom of mechanical property programming of the metamaterial can be further improved, and it can respond to external stimuli such as heat and force, expanding the scope of its multifunctional realization.

[0052] In addition to the features of the above embodiments, this embodiment further defines that the specific steps of "performing post-processing on the metamaterial model" are as follows: Model manufacturability optimization: Convert the metamaterial model into a mesh type file, and perform rounding and chamfering on the areas of the metamaterial model; Polygon mesh post-processing: Perform post-processing on the polygon mesh of the metamaterial model, and the post-processing includes mesh redrawing, interfering shell repair, hole repair, bad edge repair, overlap repair, and cross triangular patch repair. By performing corresponding post-processing on the polygon mesh of the metamaterial model, a product with better mechanical properties is formed.

[0053] A two-dimensional polygon-honeycomb hybrid structure is formed by embedding negative Poisson's ratio honeycomb cells into a secondary rotating polygon mesh. Based on different modeling software or programming languages, the steps of manufacturing a supermaterial model of a rod system structure or a thin-walled structure include various different methods. Only the modeling ideas are listed here. If a rod system structure model is constructed, a sphere with a diameter of d moves along all the edges of the two-dimensional polygon-honeycomb hybrid structure once in space, and the outer contour of the space covered by it is the outer surface of the three-dimensional rod system model, and the rod diameter is d. If a thin-walled structure model is constructed, a circle with a diameter of d' moves along all the edges of the two-dimensional polygon-honeycomb hybrid structure once in the two-dimensional plane, and the outer contour of the covered area is the cross-sectional shape of the three-dimensional model; it is stretched along the normal direction of this plane by a certain height h to construct a three-dimensional thin-walled model, and its wall thickness is d'; according to the requirements of additive manufacturing, the model is saved as a mesh type file, specifically including.STL,.OBJ,.AMF formats. According to the geometric dimensions and manufacturing process requirements, filleting and chamfering are performed on some areas of the model; post-processing is performed on the model mesh for subsequent slicing and additive manufacturing processes, and the post-processing includes mesh redrawing, repairing of interfering shells, holes, bad edges, overlapping and intersecting triangular patches.

[0054] Embodiment 2

[0055] This application includes the following steps:

[0056] Step S1: Taking the realization of adjustable stiffness and strength of mechanical metamaterials and having functions such as zero Poisson's ratio, uniform large deformation, and recoverable deformation as an example, divide the base polygon unit: evenly divide a 40mm×40mm plane space into a base polygon mesh composed of 16 10mm×10mm regular quadrilateral base polygon units, and this division conforms to the anti-chiral segmentation rule.

[0057] Step S2: Reconstruct the secondary rotating polygon mesh. Based on the divided base polygon mesh, determine the secondary vertices inside the upper right base polygon unit, such as Figure 2 , specifically divided into the following steps: a. Vectorize the base polygon. After vectorization, this polygon unit is defined as a right-handed base polygon; b. Set the secondary vertices, and set the scale factor p = 0.37. As Figure 3 , starting from the upper right base polygon unit, determine the positions of the secondary vertices in the entire base polygon mesh based on the anti-chiral propagation mode, and connect the secondary vertices to generate a secondary rotating polygon mesh; delete the A i B i (i = 1, 2, 3, 4) part of the edges to complete the reconstruction of the secondary rotating polygon mesh;

[0058] Step S3: Such as Figure 4As shown in the figure, embed the negative Poisson's ratio honeycomb unit: According to the mechanical properties / functional requirements such as homogenized large deformation in each region and the embedding relationship between the polygon-honeycomb structure, through the buckling of the corresponding side lines. For a quadrilateral, select to embed the star-shaped negative Poisson's ratio honeycomb unit into the secondary rotating polygon unit. The two broken lines formed during the buckling operation and the side line of the original rotating polygon form a first closed triangle. All the first closed triangles contain two 30° base angles, and its longest side is the side line of the original rotating polygon;

[0059] Step S4, as Figure 5 As shown in the figure, reconstruct the geometric structure of the base polygon side line: According to the mechanical properties / functional requirements such as homogenized large deformation in each region, use the buckling reconstruction method for each side line of the base polygon that was not deleted in Step S2 one by one. The two broken lines formed during the buckling operation and the side line of the base polygon form a second closed triangle. All the second closed triangles contain two 30° base angles, and its longest side is the side line of the original base polygon that was not deleted. Thus, the construction of the two-dimensional polygon-honeycomb hybrid structure is completed;

[0060] Step S5, as Figure 6 As shown in the figure, construct a mechanically programmable metamaterial model: Use the solidworks 3D modeling software to model the designed two-dimensional polygon-honeycomb hybrid structure into a manufacturable thin-walled mechanically programmable metamaterial and store it as an.STL format file for pre-processing of additive manufacturing. It specifically includes the following steps: a. 3D modeling of the model: Based on different modeling software or programming languages, this step includes a variety of different methods. Only the modeling idea is listed here. To construct a thin-walled structure model, a circle with a diameter of d = 0.4 mm moves once along all the side lines of the two-dimensional polygon-honeycomb hybrid structure in the two-dimensional plane. The outer contour of the covered area is the cross-sectional shape of this 3D model; Stretch a certain height h = 4 mm along the normal direction of this plane to construct a 3D thin-walled model, and its wall thickness is 0.4 mm; b. Optimization of model manufacturability: According to the requirements of additive manufacturing, convert the model into an.STL format file of the mesh type. According to the geometric dimensions and manufacturing process requirements, to reduce the accumulation of thermal stress during the manufacturing process, the sharp corner parts of the model are rounded, and the rounding radius is 0.2 mm; c. Mesh post-processing: Perform post-processing on the model mesh for subsequent slicing and additive manufacturing processes. The post-processing includes mesh redrawing, repair of interfering shells, holes, bad edges, overlapping, and intersecting triangular patches;

[0061] S6. Additive manufacturing: Select selective laser melting (SLM) additive manufacturing technology and NiTi superelastic alloy as the base material to maximize its material properties such as shape memory and superelasticity, and achieve multi-functions such as programmable elastic modulus, recoverable large deformation, energy absorption and vibration damping; Configure an argon protection processing environment, set processing parameters including a spot diameter of 0.05 mm, a laser power of 135 W, a slice thickness of 0.03 mm, etc., and complete additive manufacturing.

[0062] Example 3

[0063] A design and manufacturing method of a mechanically programmable metamaterial according to the present invention includes the following steps:

[0064] S1. As Figure 7 (left), taking a mechanically metamaterial with programmable variable stiffness and functions such as large normal deformation and programmable deformation behavior as an example, divide the base polygon unit: evenly divide a hexagonal plane space with a side length of 20 mm into a base polygon grid composed of 24 equilateral triangle base polygon units with a side length of 10 mm, and this division conforms to the anti-chiral segmentation rule.

[0065] S2. Reconstruct the secondary rotating polygon grid: Based on the base polygon grid divided in S1, determine secondary vertices inside the central base polygon unit, as Figure 7 (right), which is specifically divided into the following steps: a. Vectorize the base polygon, and after vectorization, this polygon unit is defined as a right-handed base polygon; b. Set the secondary vertices, and set the scaling factor p = 0.30. As Figure 8 , starting from this base polygon unit, determine the positions of the secondary vertices in the entire base polygon grid based on the anti-chiral propagation mode, and connect the secondary vertices to generate a secondary rotating polygon grid; Delete the A i B i (i = 1, 2, 3) partial side lines to complete the reconstruction of the secondary rotating polygon grid;

[0066] S3. As Figure 9, Embedding negative Poisson's ratio honeycomb cells: According to the performance / function requirements such as variable stiffness programmability, large normal deformation, and programmable deformation behavior, as well as the derivation relationship between polygon-honeycomb structures, by buckling the corresponding side edges, two different negative Poisson's ratio honeycomb cells derived from triangles (double-V negative Poisson's ratio honeycomb structure and triangular star honeycomb structure) are respectively embedded into the secondary rotating polygons in the corresponding regions. Specifically: the double-V negative Poisson's ratio honeycomb structure is embedded into the 6 secondary rotating polygon cells at the center of the plane space, with the derivation direction towards the outside. All the triangles formed during the buckling operation contain two base angles of 21.5°, and its longest side is the side edge of the original rotating polygon; the triangular star honeycomb structure is embedded into the 18 secondary rotating polygon cells outside the plane space. All the triangles formed during the buckling operation contain two base angles of 11.3°, and its longest side is the side edge of the original rotating polygon. By embedding different derived types of negative Poisson's ratio honeycomb structures in different regions and adjusting the design parameters during the buckling operation, the purpose of variable stiffness programmability and normal deformation behavior design is achieved;

[0067] S4. As Figure 10 , Reconstructing the geometric structure of the base polygon side edges: According to the performance / function requirements such as variable stiffness programmability, large normal deformation, and programmable deformation behavior, the side edges that were not deleted in step S2 are respectively reconstructed using the methods of deletion or retention to achieve the programmable mechanical properties of large stiffness at the center and small stiffness at the edge. Specifically, 3 side edges in the most central region are retained, and the rest of the side edges are deleted. Thus, the construction of the two-dimensional polygon-honeycomb hybrid structure is completed;

[0068] S5. As Figure 11 , Constructing a mechanically programmable metamaterial model: Using the solidworks 3D modeling software, the designed two-dimensional polygon-honeycomb hybrid structure is modeled into a manufacturable thin-walled mechanically programmable metamaterial and stored as an.STL format file for pre-processing of additive manufacturing. It specifically includes the following steps: a. 3D modeling of the model: Based on different modeling software or programming languages, this step includes various different methods, and only the modeling idea is listed here. To construct a thin-walled structure model, a circle with a diameter of d = 0.4 mm moves along all the side edges of the two-dimensional polygon-honeycomb hybrid structure once in the two-dimensional plane, and the outer contour of the covered area is the cross-sectional shape of this 3D model; to achieve large normal deformation, a thin-layer mechanically programmable metamaterial needs to be constructed. Therefore, it is stretched a certain height h = 0.4 mm along the normal direction of this plane to construct a thin-walled model, and its wall thickness is 0.4 mm. b. Optimization of model manufacturability: According to the requirements of additive manufacturing, the model is transferred and stored as an.STL format file of the mesh type. c. Mesh post-processing: The mesh of the model is post-processed for subsequent slicing and additive manufacturing processes. The post-processing includes mesh redrawing, repair of interfering shells, holes, bad edges, overlapping, and intersecting triangular facets;

[0069] S6. Additive manufacturing: Select the SLM additive manufacturing technology and CuAlMn shape memory alloy as the base material to maximize its shape memory material characteristics and achieve multifunctions such as variable stiffness regulation, programmable normal deformation behavior, energy absorption and vibration damping, and response to thermal field excitation; Configure an inert gas protection processing environment, set processing parameters including a spot diameter of 0.05 mm, a laser power of 175 W, a slice thickness of 0.03 mm, etc., and complete the additive manufacturing.

[0070] The above embodiments only represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent shall be subject to the appended claims.

Claims

1. A design and manufacturing method of a mechanically programmable metamaterial, characterized in that, The specific steps are as follows: S1. Divide the base polygon units: Divide multiple base polygon units in the planar space. The division of the base polygon units needs to conform to the anti-chirality segmentation rule. The multiple base polygon units form a base polygon grid, and any one base polygon unit has multiple original vertices. S2. Form a secondary rotational polygon grid and complete the edge reconstruction: Determine the positions of multiple secondary vertices on any one base polygon unit according to the scale factor, determine the positions of the secondary vertices of multiple base polygon units based on the chirality characteristics of the base polygon unit and the anti-chirality propagation mode, connect the secondary vertices of each base polygon unit in sequence to form a secondary rotational polygon grid, divide the edges of the base polygon grid into two parts, and complete the edge reconstruction after deleting one part of the edges of the base polygon grid. S3. Embed the negative Poisson's ratio honeycomb units: Embed the negative Poisson's ratio honeycomb units into the secondary rotational polygon grid by changing the geometric characteristics of some edges of the secondary rotational polygon grid. S4. Construct a two-dimensional polygon-honeycomb hybrid structure: Further operate on the other part of the edges of the base polygon grid in step S2 to complete the construction of the two-dimensional polygon-honeycomb hybrid structure. S5. Construct a metamaterial model: Use 3D modeling software or programming means to model the two-dimensional polygon-honeycomb hybrid structure to form a metamaterial model. S6. Metamaterial additive manufacturing: Post-process the metamaterial model, and complete the additive manufacturing by configuring the processing environment and setting the processing parameters for the 3D printer.

2. The design and manufacturing method of the mechanically programmable metamaterial according to claim 1, wherein the base polygon unit is a triangle and / or a convex quadrilateral; and / or the boundary of the planar space is represented by a polygon; and / or the number of the secondary vertices and the original vertices of the base polygon unit is the same; and / or the metamaterial model is a truss structure or a thin-walled structure.

3. The design and manufacturing method of the mechanically programmable metamaterial according to claim 1, characterized in that The anti-chirality segmentation rule in step S1 is: The edges of any one base polygon unit coincide with the boundary of the planar space or the edges of adjacent base polygon units, and any original vertex that does not coincide with the boundary of the planar space coincides with an even number of edges of adjacent base polygon units.

4. The design and manufacturing method of the mechanically programmable metamaterial according to claim 1, characterized in that The specific steps of "determining the positions of multiple secondary vertices on any one base polygon unit according to the scale factor" in step S2 are as follows: Vectorization of the base polygon unit: Select one of the original vertices of the base polygon unit as the starting vertex, and sequentially set a plurality of vector edges. The number of the vector edges is the same as the number of the edges of the base polygon unit, and the vector edges coincide with the edges of the base polygon unit one by one. One end of one of the plurality of vector edges coincides with the starting vertex, and one end of another of the plurality of vector edges coincides with the starting vertex. The plurality of vector edges are denoted as where i = 1, 2, … n, and n is the number of sides of the polygon, satisfying the following conditions: Set secondary vertices: For any original vertex A i and the vector edge starting from it Define the scaling factor p to determine the position of the secondary vertex B i Location: where i = 1, 2,..., n, and n is the number of sides of the polygon.

5. The design and manufacturing method of the mechanically programmable metamaterial according to claim 4, characterized in that The scale factor p ∈ (0, 0.5].

6. The design and manufacturing method of the mechanically programmable metamaterial according to claim 4, wherein In the step S2, the specific operation of "deleting a part of the side lines of the base polygon mesh" is to delete the side lines of the base polygon A i B i ; And / or the specific operation of "deleting a part of the side lines of the base polygon mesh" in the step S2 is to delete the base polygon A i+1 B i and A1B n side lines.

7. The design and manufacturing method of the mechanically programmable metamaterial according to claim 1, characterized in that the specific process of "determining the positions of the secondary vertices of multiple base polygon units based on the chirality characteristics of the base polygon unit and the anti-chirality propagation mode" in step S2 is as follows: Determine the chirality characteristics of the base polygon unit: Based on the top view of the planar space as a reference, if the vector edges are connected end to end in a clockwise direction, the base polygon unit is defined as a left-handed base polygon; if the vector edges are connected end to end in a counterclockwise direction, the base polygon unit is defined as a right-handed base polygon. Determine the anti-chiral propagation mode: Propagate from the base polygon unit whose chiral characteristics have been determined to adjacent base polygon units. Any base polygon sharing a side with the left-handed base polygon is a right-handed base polygon, and any base polygon sharing a side with the right-handed base polygon is a left-handed base polygon; Determine the secondary vertices of multiple base polygon units successively through the scale factor.

8. The design and manufacturing method of the mechanically programmable metamaterial according to claim 1, characterized in that The further operations in step S4 include one or more of buckling, replacing with an arc, replacing with a parabola, deleting, and retaining.

9. The design and manufacturing method of the mechanically programmable metamaterial according to claim 8, characterized in that The buckling processing method is to modify the side of the base polygon unit into two concave broken lines.

10. The design and manufacturing method of the mechanically programmable metamaterial according to claim 1, characterized in that, The specific steps of "post-processing the metamaterial model" are as follows: Model manufacturability optimization: Save the metamaterial model as a mesh type file, and perform filleting and chamfering on the area of the metamaterial model; Polygon mesh post-processing: Perform post-processing on the polygon mesh of the metamaterial model. The post-processing includes mesh redrawing, interference shell repair, hole repair, bad edge repair, overlap repair, and cross triangular patch repair.

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