A three-dimensional negative poisson's ratio and pressure-torsion coupling metamaterial and a preparation method thereof

Abstract

The application discloses a three-dimensional negative Poisson's ratio and pressure-torsion coupling metamaterial and a preparation method thereof. The metamaterial is composed of a plurality of same structure units periodically extended; each structure unit comprises a quadrilateral rod group and an eccentric rod group; the quadrilateral rod group is composed of two mutually perpendicular rhombuses or ellipses connected at two points; the two connecting points formed by the two rhombuses or ellipses are used for connecting adjacent structure units in the vertical direction; the eccentric rod group is composed of four nested eccentric rod pieces, one end point of each eccentric rod piece is connected with the rhombus or ellipse, and the other end point is used for connecting adjacent structure units. The metamaterial appears overall shrinkage (or expansion) when compressed (or stretched) in the z-axis direction, and rotates around the z-axis when compressed or stretched in the x-axis or y-axis direction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metamaterial preparation, and particularly to a three-dimensional negative Poisson's ratio and pressure-torsion coupled metamaterial and a preparation method thereof. BACKGROUND

[0002] A negative Poisson's ratio metamaterial refers to a material that shrinks (expands) in a direction perpendicular to a loading direction under uniaxial compression (tension), thereby achieving a performance opposite to that of a natural material. Due to the complexity of three-dimensional space, the design of a negative Poisson's ratio structure is currently mainly limited to two dimensions, which cannot fully meet application requirements. The design and manufacture of a structural unit (basic cell) of a three-dimensional mechanical metamaterial are extremely important.

[0003] Therefore, the prior art still needs to be further improved and promoted. SUMMARY

[0004] In view of the above problems of the prior art, the present application aims to provide a three-dimensional negative Poisson's ratio and pressure-torsion coupled metamaterial and a preparation method thereof, and aims to solve the problem that the existing metamaterials can only be used in a plane.

[0005] A three-dimensional negative Poisson's ratio and pressure-torsion coupled metamaterial, wherein the metamaterial is composed of a plurality of identical structural units periodically extended.

[0006] Each structural unit comprises an orthogonal rod group and an eccentric rod group; the orthogonal rod group is composed of two center-symmetric patterns of the same shape connected at two points perpendicular to each other; two connection points formed by the two center-symmetric patterns are used to connect with adjacent structural units in the vertical direction.

[0007] The eccentric rod group is composed of four nested eccentric rod members, one end point of each eccentric rod member is connected to an edge or a vertex of the center-symmetric pattern, and the other end point is used to connect with the eccentric rod member of an adjacent structural unit.

[0008] Optionally, the three-dimensional negative Poisson's ratio and pressure-torsion coupled metamaterial, wherein the eccentric rod member is a straight rod or a curved rod.

[0009] Optionally, the three-dimensional negative Poisson's ratio and pressure-torsion coupled metamaterial, wherein the four eccentric rod members are arranged in a counterclockwise or clockwise manner.

[0010] Optionally, the three-dimensional negative Poisson's ratio and pressure-torsion coupled metamaterial, wherein one end point of each eccentric rod member is fixedly connected to a part of the center-symmetric pattern different from the connection point.

[0011] Optionally, the three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial, wherein the metamaterial is stretched along the longitudinal z-axis, and the metamaterial expands along the transverse x-axis and y-axis.

[0012] Optionally, the three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial, wherein the metamaterial is compressed along the longitudinal z-axis, and the metamaterial contracts along the transverse x-axis and y-axis.

[0013] Optionally, the three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial, wherein the metamaterial is stretched along the transverse x-axis or y-axis, and the metamaterial twists around the z-axis.

[0014] A preparation method of the three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial, comprising the following steps:

[0015] Constructing a structural unit model and array extending the structural unit model;

[0016] Selecting corresponding materials, manufacturing according to the structural unit model and the array extension result, and obtaining the three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial.

[0017] Optionally, the preparation method of the three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial, wherein when the orthogonal rod group is composed of two rhombuses connected at two points, the three-dimensional negative Poisson's ratio is predicted by the following formula:

[0018]

[0019] E is the elastic modulus of the material used, A is the cross-sectional area of the orthogonal rod group, F p is the load size, l is the side length of the rhombus, and θ is the vertical angle of the orthogonal rod group;

[0020] The rotation angle is predicted by the following formula:

[0021]

[0022] Where e is the eccentricity of the eccentric rod, R is the radius, Δ1 is the movement distance of the curved rod end, and w is the deflection of the straight rod group in the horizontal plane.

[0023] Optionally, the preparation method of the three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial, wherein the constructing a structural unit model and array extending the structural unit model specifically comprises:

[0024] According to the requirements of the negative Poisson's ratio and the torsion angle ω, the relationship between the parameters is determined by the formulas (1) and (2);

[0025] Pre-given application working condition load F p , displacement constraint Vp and material parameter elastic modulus E, to determine part of the parameters in the formula;

[0026] Any two parameters of eccentric moment, radius, characteristic length and characteristic angle are determined, and the remaining parameters are solved according to the formula (1) and formula (2), and then the cell modeling and array extension are performed according to the geometric shapes of the orthogonal rod group and the eccentric rod group.

[0027] Beneficial effects: compared with the prior art, the three-dimensional negative Poisson's ratio and torsion-coupled metamaterial is obtained by constructing the structural unit with the orthogonal rod group and the eccentric rod group and performing array extension, the overall contraction (or expansion) occurs when the three-dimensional negative Poisson's ratio and torsion-coupled metamaterial is compressed (or stretched) in the z-axis direction; and the rotation around the z-axis occurs when the three-dimensional negative Poisson's ratio and torsion-coupled metamaterial is compressed or stretched in the x-axis or y-axis direction. Compared with the disadvantage that the two-dimensional metamaterial can only be used in the plane, the three-dimensional negative Poisson's ratio and torsion-coupled metamaterial can be applied to the transmission mechanism in the three-dimensional orthogonal direction, the multi-directional vibration absorption device and the like. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The three-dimensional negative Poisson's ratio and torsion-coupled metamaterial is provided for the embodiment of the application;

[0029] Figure 2 The left-handed and right-handed structure schematic diagram of the three-dimensional negative Poisson's ratio and torsion-coupled metamaterial;

[0030] Figure 3 The structural unit perspective view of the negative Poisson's ratio and torsion-coupled metamaterial with the rhombus as the orthogonal rod group;

[0031] Figure 4 The structural unit top view of the negative Poisson's ratio and torsion-coupled metamaterial with the rhombus as the orthogonal rod group;

[0032] Figure 5 The structural unit front view of the negative Poisson's ratio and torsion-coupled metamaterial with the rhombus as the orthogonal rod group;

[0033] Figure 6 The structural unit perspective view of the negative Poisson's ratio and torsion-coupled metamaterial with the ellipse as the orthogonal rod group;

[0034] Figure 7 The structural unit top view of the negative Poisson's ratio and torsion-coupled metamaterial with the ellipse as the orthogonal rod group;

[0035] Figure 8 The structural unit front view of the negative Poisson's ratio and torsion-coupled metamaterial with the ellipse as the orthogonal rod group. DETAILED DESCRIPTION

[0036] The application provides a three-dimensional negative Poisson's ratio and pressure-torsion coupling metamaterial and a preparation method thereof.

[0037] In order to solve the problem that the existing metamaterial can only be used in a two-dimensional plane, the embodiment provides a three-dimensional negative Poisson's ratio and pressure-torsion coupling metamaterial. Figures 1 to 8 As shown in the figure, the metamaterial is composed of a plurality of same structure units periodically extended; the structure unit can be formed by connecting a set of orthogonal central symmetric patterns such as a rhombic rod group and a set of eccentric curved rods according to certain rules. The structure is a central symmetric structure, and two rod groups each contain four rod members, and the rod members of each orthogonal rod group are connected with an eccentric curved rod. It is easy to understand that the structure unit can also be formed by connecting a set of orthogonal elliptical rod groups and an eccentric curved rod according to certain rules. The structure is a central symmetric structure, and the rod members of each orthogonal rod group are connected with an eccentric curved rod.

[0038] In the embodiment, as shown in the figure, Figure 3 The orthogonal rhombic rod group refers to two rhombuses perpendicular to each other, and one diagonal line of the two rhombuses coincides, forming a structure, wherein 101 is an orthogonal rod group, and 102 is an eccentric rod group. The connecting points of the two rhombuses are used to connect with adjacent structure units in the vertical direction. It is easy to understand that the orthogonal rhombic group rod is placed in a three-dimensional coordinate system, and the connecting points of the two rhombuses are arranged along the z-axis, and at this time, the upper and lower connecting points of each orthogonal rhombic group are connected with the connecting points of the adjacent structure group. The eccentric rod group refers to four rod members arranged on the orthogonal rod group, and the four rod members are nested, wherein the four rod members can be curved rods or straight rods. One end of the four rod members of the eccentric rod group is connected with the orthogonal rod group, that is, the four rod members of the eccentric rod group are fixed at the top points of the rhombuses on the x-axis and the y-axis. The other end is used to connect with the eccentric rod group on the adjacent structure unit, so as to be extended, and the metamaterial as shown in the figure can be obtained. Figure 1

[0039] In the embodiment, as shown in the figure, Figure 2 The structure unit can be a left-handed structure or a right-handed structure, and it is easy to understand that the left-handed structure refers to the direction of rotation of the orthogonal rhombic group when the eccentric rod group is subjected to force and the orthogonal rhombic group rotates in the clockwise direction, and the right-handed structure refers to the direction of rotation of the orthogonal rhombic group when the eccentric rod group is subjected to force and the orthogonal rhombic group rotates in the counterclockwise direction.

[0040] In the embodiment, as shown in the figures, Figure 4 and Figure 5 ​The vertical angle between the orthogonal rod group of the structure unit coupled with the torsion is θ, the rod length is l; the eccentricity of the eccentric curved rod group is e, the curved rod radius is R, and the cross section of the two rod groups can be a rectangle with a cross section of a x b or a circle with a radius of r, etc.

[0041] The negative Poisson's ratio of the structure should be:

[0042]

[0043] Wherein, E is the elastic modulus of the material used, A is the cross-sectional area of the orthogonal rod group, F p is the size of the load.

[0044] The size of the rotation angle of the structure is measured and predicted by the following formula:

[0045]

[0046] Wherein e is the eccentricity of the eccentric rod, R is the radius, Δ1 is the moving distance of the curved rod end, and w is the deflection of the straight rod group in the horizontal plane.

[0047] The above formula can be used to theoretically predict the negative Poisson's ratio of the designed metamaterial, improving the design efficiency of the metamaterial. By changing the geometric parameters in the formula, different negative Poisson's ratio and torsion angle of the metamaterial can be designed and prepared according to the needs.

[0048] Exemplarily, under the working condition of force load of 10N and displacement load of 5mm, the elastic modulus of the structural material is 1GMp, and the preparation process is illustrated by taking the Poisson's ratio of-0.4 and the rotation angle ratio of 2.3 as an example. According to the design process mentioned above, the radius R is first determined to be 15mm, the cross-sectional area is 1mm 2 The characteristic length l is 20mm, the characteristic angle is 76.5°, and the eccentricity is 3mm, which are obtained by using the above two formulas. After the design stage, a three-dimensional modeling software (such as solidworks) is used to establish a cell model and periodic extension, according to the determined structure material parameters, the material is selected, the established model is exported and sliced, and finally the 3D printing technology is used for preparation.

[0049] In the present embodiment, unlike the combination design of the conventional inner recessed polygon or origami base structure, the application adopts a unique space structure for displacement transformation, proposes a three-dimensional metamaterial structure unit (base unit) and its array extension, and obtains a three-dimensional negative Poisson's ratio and torsion coupling metamaterial. Under longitudinal load, the deformation of the orthogonal rod group drives the nested curved rod to transmit the deformation to the adjacent unit, realizing the special mechanical properties of tension and compression. Under lateral load, the deformation of the nested curved rod applies torque to the four points of the rhombic rod group on the middle plane, promoting the rotation of the rhombic rod group, and realizing the special mechanical properties of tension, compression and torsion. The structural material type of the metamaterial of the application can be selected according to the actual application scene (such as various metals, polymer materials, etc.), and it can also be a combination of multiple materials. Different manufacturing technologies can be used according to actual needs (such as base unit size, performance requirements, manufacturing cost, etc.). For example, if the metamaterial is required to have a micron-scale base unit, the metamaterial of the application can be realized by additive manufacturing technology.

[0050] Based on the same inventive concept, the application further provides a preparation method of a three-dimensional negative Poisson's ratio and torsion coupling metamaterial, the method comprising:

[0051] According to the requirements of the negative Poisson's ratio and the torsion angle ω, the relationship between the parameters is determined by using the above formulas (1) and (2); the load F p , displacement constraint V p and material parameter elastic modulus E are pre-defined for the application working condition, so as to determine part of the parameters in the formula; any two parameters of the eccentric moment, radius, characteristic length and characteristic angle are determined, and the remaining parameters are solved according to the above formulas (1) and (2), and then the cell modeling and array extension are performed according to the geometric shapes of the orthogonal rod group and the eccentric rod group. Select the material to produce, and obtain the three-dimensional negative Poisson's ratio and torsion coupling metamaterial.

[0052] In summary, the application provides a three-dimensional negative Poisson's ratio and torsion coupling metamaterial and a preparation method thereof, the metamaterial being composed of a plurality of same structure units periodically extended; each structure unit comprising an orthogonal rod group and an eccentric rod group; the orthogonal rod group being composed of two rhombic or elliptic shapes connected to each other at two points; the two connection points formed by the connection of the two rhombic or elliptic shapes being used to connect with adjacent structure units in the vertical direction; the eccentric rod group being composed of four nested eccentric rod members, one end point of each eccentric rod member being connected with the rhombic or elliptic shape, and the other end point being used to connect adjacent structure units. The metamaterial appears overall contraction (or expansion) when compressed (or stretched) in the z-axis direction; and rotates around the z-axis when compressed or stretched in the x-axis or y-axis direction. Compared with the two-dimensional metamaterial which can only be used in the plane.

[0053] It is to be understood that the application is not limited to the examples described above, which can be modified or adapted in several ways by those skilled in the art without departing from the scope of the present application, as defined by the appended claims.

Claims

1. A three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial, characterized in that: The metamaterial is composed of a number of identical structural units that are periodically extended; Each of the structural units includes an orthogonal rod group and an eccentric rod group; the orthogonal rod group is composed of two centrally symmetrical figures of the same shape connected perpendicularly at two points; the two connection points formed by the connection of the two centrally symmetrical figures are used to connect with the adjacent structural units in the vertical direction; The eccentric rod group consists of four nested eccentric rods, one end point of each eccentric rod is connected to an edge or a vertex of the central symmetrical figure, and the other end point is used to connect to the eccentric rod of the adjacent structural unit; When the metamaterial is stretched along the longitudinal z-axis, the metamaterial expands along the transverse x-axis and y-axis; when the metamaterial is compressed along the longitudinal z-axis, the metamaterial contracts along the transverse x-axis and y-axis; when the metamaterial is stretched along the transverse x-axis or y-axis, the metamaterial twists around the z-axis.

2. The three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial according to claim 1, characterized in that: The eccentric rod is a straight rod or a curved rod.

3. The three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial according to claim 1, characterized in that: The four eccentric rods are arranged counterclockwise or clockwise.

4. The three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial according to claim 1, characterized in that: One end point of each eccentric rod is fixedly connected to a portion of the central symmetrical figure that is different from the connection point.

5. A method for preparing the three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial according to claim 1, characterized in that: The steps include: Constructing a structural unit model and performing array extension on the structural unit model; The corresponding material is selected and manufactured according to the structural unit model and the array extension result to obtain the three-dimensional negative Poisson's ratio and compression-torsion coupled metamaterial.

6. The method for preparing a three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial according to claim 5, characterized in that: When the orthogonal rod group is composed of two rhombuses connected perpendicularly at two points, the three-dimensional negative Poisson's ratio is predicted using the following formula: （1） is the elastic modulus of the material used, is the cross-sectional area of ​​the orthogonal rod group, is the magnitude of the applied load, is the side length of the rhombus, is the vertical angle of the orthogonal rod group; The turning angle is predicted using the following formula: （2） in e is the eccentricity of the eccentric member, R is its radius, Δ1 is the distance the end of the crankshaft moves, w is the deflection of the straight rod group in the horizontal plane.

7. The method for preparing a three-dimensional negative Poisson's ratio and compression-torsion coupling metamaterial according to claim 6, characterized in that: The constructing of the structural unit model and performing array extension on the structural unit model specifically includes: Depending on the desired negative Poisson's ratio ν and the torsion angle ω, and use the formulas (1) and (2) to determine the relationship between the parameters; Predetermined load F under application conditions p , displacement constraint V p And the material parameter elastic modulus E , in order to determine the geometric parameters in the formula: radius R , eccentric moment e , side length l , cross-sectional area A , vertical angle For any two parameters in , according to the formula (1) and formula (2), after solving the remaining parameters, cell modeling and array extension are performed according to the geometric shapes of the orthogonal rod group and the eccentric rod group.

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