WO2021147209A1

WO2021147209A1 - Three-dimensional multi-cell material having local thermal-torsion coupling effect

Info

Publication number: WO2021147209A1
Application number: PCT/CN2020/089309
Authority: WO
Inventors: 富明慧; 龙丽榕; 胡玲玲
Original assignee: 中山大学
Priority date: 2020-01-20
Filing date: 2020-05-09
Publication date: 2021-07-29
Also published as: CN111379679A; CN111379679B

Abstract

A three-dimensional multi-cell material having a local thermal-torsion coupling effect, relating to the technical field of metamaterials, and formed by several unit cell three-dimensional structures by means of a spatial periodic array. Each unit cell three-dimensional structure comprises an upper layer of honeycomb grid units and a lower layer of honeycomb grid units, and inclined uniform-cross-section straight rods and vertical uniform-cross-section straight rods used for connecting the upper layer of honeycomb grid units and the lower layer of honeycomb grid units, wherein the upper layer of honeycomb grid units and the lower layer of honeycomb grid units are completely the same; adjacent upper and lower layers of honeycomb grid units are arranged in parallel at equal intervals and aligned along centroids; nodes of the adjacent upper and lower layers of honeycomb grid units are connected in a staggered manner by means of the inclined uniform-cross-section straight rods, and the nodes of the adjacent upper and lower layers of honeycomb grid units are vertically connected by means of the vertical uniform-cross-section straight rods. The three-dimensional multi-cell material is used as a sensor or an actuator in a micromachine capable of achieving reciprocating motion without an external force in a space environment with large temperature change or periodic temperature change.

Description

A three-dimensional multicellular material with local thermal torsion coupling effect

Technical field

The invention relates to the technical field of metamaterials, in particular to a three-dimensional multicellular material with local thermal torsion coupling effect.

Background technique

Metamaterials refer to man-made materials with extraordinary physical properties that traditional materials do not have. They have great advantages in energy absorption, acoustics, optics, and mechanical properties. Mechanical metamaterials are a large category of metamaterials. Typical mechanical metamaterials are materials with negative mechanical parameters, such as negative Poisson's ratio, negative thermal expansion, and negative stiffness. In addition, mechanical metamaterials also include superfluids, topological materials, and metamaterials with tensile-shear effects.

The thermal torsion coupling effect is a unique mechanical effect, which means that the material will cause torsional deformation in a certain direction due to the internal stress distribution under the action of temperature load. This peculiar property is expected to be applied in many aspects, such as sensing equipment and actuators in micromachines in an environment with alternating temperature changes. However, the prior art lacks a kind of transmission that can be used in micromachines. Thermal torsion coupling material for sensing equipment.

Summary of the invention

In view of the shortcomings in the prior art, the present invention provides a three-dimensional multicellular material with local thermal torsion coupling effect, which can realize reciprocating motion without external force in a space environment with large temperature changes or periodic temperature changes. The sensors and actuators in the micro-machines.

In order to achieve the above objective, the technical solution of the present invention is as follows:

A three-dimensional multi-cell material with local thermal torsion coupling effect, which is obtained by a spatial periodic array of a number of unit cell three-dimensional structures. The unit cell three-dimensional structure includes two layers of identical honeycomb grid units and is used to connect the two upper and lower layers. The inclined straight rods of uniform cross-section and the vertical straight rods of uniform cross-section of the honeycomb grid unit, the honeycomb grid units are connected to each other on their planes by connecting ligaments, and the two ends of the connecting ligaments are connected with the honeycomb grid unit to form nodes. The adjacent upper and lower layers of honeycomb grid units are arranged in parallel and equidistantly and aligned along the centroid. The nodes of the adjacent upper and lower layers of honeycomb grid units are connected by dislocations of the inclined straight rods. The adjacent upper and lower honeycomb grid units are The nodes are connected vertically by the vertical straight rods of constant cross section. The number of inclined straight rods of constant cross section and the number of vertical straight rods connected by the honeycomb grid unit of the upper and lower layers are the same as the number of nodes of a single honeycomb grid unit. The inclined straight rods of constant cross-section and the plane of the honeycomb grid unit are at the same inclination angle and form a consistent twisting direction. The honeycomb grid units, the inclined straight rods of constant cross section and the vertical straight rods of constant cross section have different thermal expansion coefficients. Of at least two materials.

As described above, the three-dimensional multi-cell material with local thermal torsion coupling effect, further, the honeycomb grid unit is a square ring, and the adjacent square rings are connected to each other at the nodes by two parallel connecting ligaments, and the inclined constant cross-section is straight. The number of rods and vertical equal cross-section straight rods are both 4. Inclined equal cross-section straight rods connect the nodes of two adjacent square rings staggeredly, and vertical equal cross-section straight rods connect the nodes of two adjacent square rings vertically and obliquely. The straight rod with constant cross section and the straight rod with vertical constant cross section are respectively composed of two materials with different thermal expansion coefficients, and the square ring and the connecting ligament are composed of one of the above two materials or the third material.

As described above, the three-dimensional multi-cell material with local thermal torsion coupling effect, further, the unit cell three-dimensional structure does not have vertical straight rods of constant cross section, and the inclined straight rods of constant cross section and the square ring are respectively composed of two materials with different thermal expansion coefficients. .

As mentioned above, the three-dimensional multi-cell material with local thermal torsion coupling effect, further, the honeycomb grid unit is a ring, three connecting ligaments are connected to the ring at equal angles along the circumferential direction of the ring, and straight rods and straight rods of inclined constant cross-section and The number of vertical uniform cross-section straight rods is 3. The inclined uniform cross-section straight rods connect the nodes of two adjacent layers of rings in a staggered manner. The vertical uniform cross-section straight rod connects the nodes of the adjacent two layers of circular rings vertically. The straight rod and the vertical straight rod with constant cross-section are respectively composed of two materials with different thermal expansion coefficients, and the ring and the connecting ligament are composed of one of the two materials mentioned above, or the third material.

As mentioned above, the three-dimensional multi-cell material with local thermal torsion coupling effect, further, the honeycomb grid unit is a square ring, four connecting ligaments are respectively connected to the four nodes of the square ring, straight rods and vertical oblique cross-sections, etc. The number of cross-section straight rods is 4. The inclined straight rods of equal cross-section connect the nodes of two adjacent layers of square rings staggeredly, and the vertical straight rods connect the nodes of two adjacent layers of square rings vertically. The inclined straight rods of equal cross section connect the nodes of two adjacent square rings vertically. The vertical straight rods with constant cross-section are respectively composed of two materials with different thermal expansion coefficients, and the square ring and the connecting ligament are composed of one of the two materials mentioned above, or the third material.

As described above, the three-dimensional multicellular material with local thermal torsion coupling effect, further, the honeycomb grid unit is a circular ring, the six connecting ligaments are connected to the circular ring at equal angles along the circumferential direction of the circular ring, and the inclined straight rods of equal cross-section and The number of vertical uniform cross-section straight rods is 6. The inclined uniform cross-section straight rods connect the nodes of the adjacent two layers of rings in a staggered manner, the vertical uniform cross-section straight rod connects the nodes of the adjacent two layers of circular rings vertically, and the inclined equal cross section The straight rod and the vertical straight rod with constant cross-section are respectively composed of two materials with different thermal expansion coefficients, and the ring and the connecting ligament are composed of one of the two materials mentioned above, or the third material.

The above-mentioned three-dimensional multi-cell material with local thermal torsion coupling effect, further, the material with different thermal expansion coefficients includes metal, polymer material, composite material or resin material.

As described above, the three-dimensional multicellular material with local thermal torsion coupling effect, further, the materials used for the vertical straight rods, honeycomb grid units, and connecting ligaments have large thermal expansion coefficients.

Compared with the prior art, the present invention has the beneficial effect that: the present invention provides straight rods with inclined constant cross section and straight rods with vertical constant cross section between the upper and lower layers of honeycomb grid units that are completely the same. The inclined straight rod and the vertical straight rod are composed of two materials with different thermal expansion coefficients. Therefore, when the temperature of the material changes, the honeycomb mesh will be driven by the thermal stress generated in the inclined straight rod and the vertical straight rod. The grid unit rotates, and the thermal torsion coupling effect is generated. The numerical simulation analysis shows that the present invention has a relatively significant thermal torsion coupling effect, which can be realized without external force in a space environment with large temperature changes or periodic temperature changes. Sensors, actuators, etc. in reciprocating micro-machines.

Description of the drawings

Fig. 1 is a schematic diagram of a three-dimensional thermal torsion structure of embodiment 1 of the present invention;

Fig. 2 is a schematic diagram of the unit cell three-dimensional structure of the three-dimensional thermal twist structure of Fig. 1;

Figure 3 is a schematic structural diagram of Embodiment 2 of the present invention;

Figure 4 is a schematic structural diagram of Embodiment 3 of the present invention;

Figure 5 is a schematic structural diagram of Embodiment 4 of the present invention;

Figure 6 is a schematic diagram of the structure of Embodiment 5 of the present invention;

Figure 7 is a numerical simulation analysis diagram of Example 1 of the present invention. Figure 7(a) shows the change of the torsion angle of the structure as the tilt angle increases, and Figure 7(b) shows the change in the number of transverse cells Increase, the change of the torsion angle of the structure.

Detailed ways

The content of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1

As shown in Figure 1, a three-dimensional multi-cell material with local thermal torsion coupling effect is obtained from a spatial array of unit cell three-dimensional structure, which is obtained by increasing the tilt between two identical square mesh cells. Obtained from equal cross-section straight rods (hereinafter referred to as inclined straight rods) and vertical equal cross-section straight rods (hereinafter referred to as vertical straight rods). The three-dimensional structure of the unit cell is shown in FIG. The units are arranged in parallel and equidistant, and the square rings are aligned along the centroid. The inclined straight rods and the vertical straight rods connect the aligned square ring nodes of the two adjacent layers, forming a three-dimensional space structure. Connect four identical inclined straight rods and four identical vertical straight rods. These four inclined straight rods form a group and form a twisting direction, and the twisting direction formed by each group of inclined straight rods is exactly the same. The inclined straight rod and the vertical straight rod are respectively composed of two materials with significantly different thermal expansion coefficients. The square ring and the ligament are composed of one of the above two materials, or the third material. When the temperature of this unit cell three-dimensional structure changes, due to the inconsistency of the thermal expansion and deformation of the two groups of materials, the vertical straight rods and the inclined straight rods inside the unit cell three-dimensional structure generate opposite axial forces, thereby pushing the two adjacent layers of square rings. There was a relative twist between them. Since the rotation direction of each group of inclined straight rods is the same, the twisting direction generated is also the same, so these twists will be superimposed and transmitted in the direction of the vertical square ring, and the whole unit cell three-dimensional structure will generate a thermal torsion coupling effect as a whole. If the three-dimensional structure of the unit cell is made of the same material, the thermal torsion coupling effect will not occur when the temperature changes. The most preferred situation is that the vertical straight rods use the same material as the honeycomb grid unit and the connecting ligaments, and the inclined straight rods use another material with a thermal expansion coefficient. At this time, the thermal torsion effect of the three-dimensional unit cell structure will be significantly improved. The principle is: if the thermal expansion coefficient of the inclined straight rod is large (small), when the temperature rises, a tensile force (pressure) is generated inside the vertical straight rod, which causes the entire structure to shrink (stretch) in the vertical direction. , This is equivalent to compression (tension), the unit cell three-dimensional structure produces a corner, this corner is the same as the thermal torsion direction when there is no vertical straight rod, so the combined action of the two factors will increase the torsion angle. If the material of the inclined straight rod and the honeycomb grid unit is the same, and the vertical straight rod uses another material, although it will also cause the thermal torsion effect, the only factor that causes the torsion is the pulling or pressing of the vertical straight rod, and the inclined straight rod It does not contribute to torsion due to temperature changes.

Numerical simulation analysis of a series of m×m×n multi-cell structures was carried out using ANSYS software, where m=1, 2, 枰, 5, 7, and n=8. The two materials used are high temperature resistant resin (HTL) and transparent resin (CR). The modulus of elasticity is E _{H L} ＝4.2 _{GPa, E CR} ＝1.5 GPa, and the coefficient of thermal expansion is α _{H L} ＝4.75×10 ^-5 K ^-1 , α _CR =9.56×10 ^-5 K ^-1 . The inclined straight rod is made of high temperature resistant resin, and the vertical straight rod is made of transparent resin. The geometric parameters of the structure are: the side length of the square ring a=4mm, the angle between the inclined straight rod and the square ring is θ=20°, 30°, 40°, 50°, 60°, 70°, 80°, the square ring and The cross section of the inclined straight rod and the vertical straight rod are both square, the side length of the cross section is b=0.5mm, and the distance between two adjacent layers of square mesh units is h=4*tanθ. The bottom surface of the structure is fixed, the top surface is axially displaced and torsion angle coupled, and the temperature rises from 20° to 50°. Numerical simulation analysis results can observe the thermal torsion coupling effect of this material. It can be seen from Figure 7(a) that as the tilt angle increases, the torsion angle of the structure increases. It can be seen from Figure 7(b) that as the number of transverse cells increases, the torsion angle of the structure decreases.

Example 2

Referring to Example 1, the difference is that only the inclined straight rods are connected between the upper and lower layers (as shown in Fig. 3). In the three-dimensional unit cell structure, two adjacent layers of identical square mesh units are arranged equidistantly, and the square rings are aligned along the centroid. The inclined straight rods connect the aligned square ring nodes of the two adjacent layers two by one, thereby forming A spatial three-dimensional structure, these four inclined straight rods form a group and form a torsion direction, and the rotation direction of each group of inclined straight rods is exactly the same.

The inclined straight rod, the square ring and the ligament are respectively composed of two materials with significantly different thermal expansion coefficients. When the temperature of this structure changes, due to the inconsistency of the thermal expansion and deformation of the two groups of materials, the inclined straight rods inside the structure generate axial force, which promotes relative torsion between the two adjacent layers of square mesh units, although there is no vertical straight rod. Thermal torsion effect will occur, but the torsion angle will be small. Adding vertical straight rods to the adjacent two layers of square mesh elements and the thermal expansion coefficients of the vertical straight rods and the inclined straight rods are different, the thermal torsion angle will increase significantly. The principle is: when the temperature rises, a tensile force is generated inside the vertical straight rod. This tensile force causes the entire three-dimensional structure of the unit cell to shrink (equivalent to compression), causing the three-dimensional structure of the unit cell to produce a corner. The thermal torsion direction of the vertical straight rod is the same, so the combined action of the two factors will increase the torsion angle. Since the rotation direction of each group of inclined straight rods is the same, the torsion direction generated is also the same, so these torsions will be superimposed and transmitted in the direction perpendicular to the honeycomb unit, thereby causing the thermal torsion coupling effect of the structure as a whole.

Example 3

Referring to Example 1, the difference is that the honeycomb grid unit is a circular ring (as shown in Figure 4), and it can also be replaced with a triangular ring or a hexagonal ring. The three connecting ligaments are connected at equal angles along the circumferential direction of the ring. On the ring and the connecting ligaments are tangent to the ring, the number of inclined straight rods and vertical straight rods connected between layers is replaced with three. In the unit cell three-dimensional structure, the honeycomb grid units of the two adjacent upper and lower layers are arranged in parallel and equidistant and aligned along the center of the ring. The inclined straight rods and the vertical straight rods align the ring nodes of the adjacent two layers in pairs. They are connected to form a three-dimensional structure in which each pair of rings are connected with three identical inclined straight rods with constant cross section and three identical vertical straight rods with constant cross section. The three inclined straight rods form a group and form a rotation direction, and the rotation direction of each group of inclined straight rods is exactly the same.

The vertical straight rod and the inclined straight rod are respectively composed of two materials with significantly different thermal expansion coefficients. The ring and the ligament are composed of one of the above two materials, or may be composed of the third material. When the temperature of this structure changes, due to the inconsistent thermal expansion and deformation of the two sets of materials, the vertical straight rods and the inclined straight rods inside the structure generate opposite axial forces, thereby pushing the relative torsion between the two adjacent layers of honeycomb units. Since the rotation direction of each group of inclined straight rods is the same, the twisting direction generated is also the same, so these torsions will be superimposed and transmitted in the direction perpendicular to the honeycomb unit, thereby causing the thermal torsion coupling effect of the structure as a whole.

Example 4

Referring to Example 1, the difference is that the honeycomb grid unit is a square ring (as shown in Fig. 5), the four connecting ligaments are respectively connected to the four nodes of the square ring and the connecting ligaments are perpendicular to the corresponding diagonal sides of the square ring. The four ligament chiral honeycomb units are formed, and the number of inclined straight rods and vertical straight rods connected between layers is 4 each. In the three-dimensional unit cell structure, the two adjacent layers of the quadrilateral ligament chiral honeycomb unit with the same four-ligament chiral honeycomb unit are added with inclined straight rods and vertical straight rods. In the three-dimensional unit cell structure, two adjacent layers are completely The same four ligament chiral honeycomb cells are arranged in parallel and equidistant, and the square rings of the chiral honeycomb cells are aligned along the centroid. The inclined straight rod and the vertical straight rod connect the corresponding square ring nodes of the two adjacent layers in two to form one Three-dimensional space structure, in which four identical inclined straight rods with constant cross section and four identical vertical straight rods with constant cross section are connected between each pair of rings. The four tilt rods form a group and form a rotation direction, and the rotation direction of each group of tilt rods is exactly the same.

The vertical straight rod and the inclined straight rod are respectively composed of two materials with significantly different thermal expansion coefficients. The four ligament chiral honeycomb unit is composed of one of the above two materials, or it can be composed of the third material. When the temperature of this structure changes, due to the inconsistency of the thermal expansion and deformation of the two groups of materials, the vertical straight rods and the inclined straight rods inside the structure generate opposite axial forces, which pushes the relative torsion between the two adjacent layers of honeycomb units. Since the rotation direction of each group of inclined straight rods is the same, the torsion direction generated is also the same, so these torsions will be superimposed and transmitted in the direction perpendicular to the honeycomb unit, thereby causing the thermal torsion coupling effect of the structure as a whole.

Example 5

Referring to Example 1, the difference is that the honeycomb grid unit is a circular ring (as shown in Figure 6) or a hexagonal ring. The six connecting ligaments are connected to the ring at equal angles along the circumference of the ring and connect the ligaments to the circle. The rings are tangent to form a six ligament chiral honeycomb unit, and the number of inclined straight rods and vertical straight rods connected between the layers is 6 each. In the three-dimensional unit cell structure, two adjacent layers of identical circular or hexagonal rings are arranged in parallel and equidistant, and the circular or hexagonal rings are aligned along the centroid, and the inclined straight rods and the vertical straight rods will be opposite to each other. The corresponding hexagonal ring nodes of the two adjacent layers are connected in pairs to form a spatial three-dimensional structure, in which the upper and lower layers of circular rings or hexagonal rings are connected with six identical inclined straight rods and six identical vertical bars. Sectional straight rod. The six tilt rods form a group and form a rotation direction, and the rotation direction formed by each group of tilt rods is exactly the same.

The inclined straight rod and the vertical straight rod are respectively composed of two materials with significant differences in thermal expansion coefficients. The six ligament chiral honeycomb unit is composed of one of the above two materials, and can also be composed of the third material. When the temperature of this structure changes, due to the inconsistency of the thermal expansion and deformation of the two groups of materials, the vertical straight rods and the inclined straight rods inside the structure generate opposite axial forces, which pushes the relative torsion between the two adjacent layers of honeycomb units. Since the rotation direction of each group of inclined straight rods is the same, the torsion direction generated is also the same, so these torsions will be superimposed and transmitted in the direction perpendicular to the honeycomb unit, thereby causing the thermal torsion coupling effect of the structure as a whole.

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and their purpose is to enable those of ordinary skill in the art to understand the content of the present invention and implement them accordingly, and should not limit the protection scope of the present invention. All equivalent changes or modifications made according to the essence of the present invention should be covered by the protection scope of the present invention.

Claims

A three-dimensional multi-cell material with local thermal torsion coupling effect, characterized in that it is obtained from a number of unit cell three-dimensional structures through a spatial periodic array. The unit cell three-dimensional structure includes two identical upper and lower layers of honeycomb grid units and Inclined straight rods of constant cross section and vertical straight rods of constant cross section connecting the upper and lower layers of honeycomb grid units, the honeycomb grid units are connected to each other on their planes by connecting ligaments, and both ends of the connecting ligaments are connected to the honeycomb grid unit A node is formed, and the adjacent upper and lower honeycomb grid units are arranged in parallel and equidistant and aligned along the centroid. The nodes of the adjacent upper and lower honeycomb grid units are connected by dislocations of the inclined straight rods, and the adjacent upper and lower honeycombs The nodes of the grid cells are connected vertically by the vertical straight rods of constant cross section, and the number of straight rods of inclined constant cross section and the number of straight rods of vertical constant cross section connected by the upper and lower honeycomb grid cells are both the same as the number of nodes of a single honeycomb grid cell. In the same way, a number of the straight rods of inclined constant cross-section are at the same inclination angle with the plane of the honeycomb grid unit and form a consistent twisting direction, and the honeycomb grid unit, connecting ligaments, straight rods of inclined constant cross section and vertical constant cross-section The straight rods are respectively composed of at least two materials with different thermal expansion coefficients.
The three-dimensional multicellular material with local thermal torsion coupling effect according to claim 1, wherein the honeycomb grid unit is a square ring, and adjacent square rings are connected to each other at the node by two parallel connecting ligaments, inclined The number of equal cross-section straight rods and vertical equal cross-section straight rods are both 4. Inclined equal cross-section straight rods connect the nodes of two adjacent layers of square rings staggeredly, and vertical equal cross-section straight rods perpendicularly connect the nodes of two adjacent layers of square rings. Connected, inclined straight rods with constant cross-section and vertical straight rods with constant cross-section are respectively composed of two materials with different coefficients of thermal expansion. The square ring and the connecting ligament are composed of one of the above two materials, or they can be composed of a third material. constitute.
The three-dimensional multi-cell material with local thermal torsion coupling effect according to claim 2, wherein the three-dimensional unit cell structure has no vertical straight rods of constant cross section, and the straight rods of inclined constant cross section and the square ring have different thermal expansion coefficients. It is composed of two materials.
The three-dimensional multicellular material with local thermal torsion coupling effect according to claim 1, wherein the honeycomb grid unit is a circular ring, and three connecting ligaments are connected to the circular ring at equal angles along the circumferential direction of the circular ring, inclined, etc. The number of straight rods and vertical straight rods is 3. The inclined straight rods connect the nodes of two adjacent rings in a staggered manner, and the vertical straight rods connect the nodes of two adjacent rings vertically. , The inclined straight rod with constant cross section and the straight rod with vertical constant cross section are respectively composed of two materials with different thermal expansion coefficients. The ring and the connecting ligament are composed of one of the above two materials, or the third material.
The three-dimensional multicellular material with local thermal torsion coupling effect according to claim 1, characterized in that the honeycomb grid unit is a square ring, four connecting ligaments are respectively connected to the four nodes of the square ring, and straight rods with inclined constant cross-section The number of straight rods with vertical equal cross section is 4. The straight rods with oblique equal cross section connect the nodes of two adjacent square rings staggeredly, and the straight rods with vertical equal cross section connect the nodes of two adjacent square rings vertically, obliquely, etc. The cross-section straight rod and the vertical constant-section straight rod are respectively composed of two materials with different thermal expansion coefficients, and the square ring and the connecting ligament are composed of one of the above two materials, or the third material.
The three-dimensional multicellular material with local thermal torsion coupling effect according to claim 1, wherein the honeycomb grid unit is a circular ring, and the six connecting ligaments are connected to the circular ring at equal angles along the circumferential direction of the circular ring, inclined, etc. The number of straight rods and vertical straight rods is 6. The inclined straight rods of constant cross section connect the nodes of two adjacent rings in a staggered manner, and the straight rods of vertical constant cross section connect the nodes of two adjacent rings vertically. , The inclined straight rod with constant cross section and the straight rod with vertical constant cross section are respectively composed of two materials with different thermal expansion coefficients. The ring and the connecting ligament are composed of one of the above two materials, or the third material.
The three-dimensional multicellular material with local thermal torsion coupling effect according to any one of claims 1 to 6, wherein the materials with different thermal expansion coefficients include metals, polymer materials, composite materials or resin materials.
The three-dimensional multicellular material with local thermal torsion coupling effect according to any one of claims 1 to 6, wherein the vertical straight rods, honeycomb grid cells, and connecting ligaments are made of the same material, inclined, etc. Another material is used for the cross-section straight rod.