CN113886988A

CN113886988A - Egg-box type unit cell with gradient stacking characteristic and egg-box type structure

Info

Publication number: CN113886988A
Application number: CN202111164160.6A
Authority: CN
Inventors: 管奔; 温海鹏; 白中豪; 郜志英; 臧勇
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2021-09-30
Filing date: 2021-09-30
Publication date: 2022-01-04

Abstract

The invention relates to the field of mechanical metamaterial structure design, in particular to an egg-box type unit cell with gradient stacking characteristics, which comprises an upper unit cell and a lower unit cell; the upper unit cell and the lower unit cell are arranged in a mirror symmetry mode; the upper unit cell and the lower unit cell have the same structure and comprise at least 4 layers of unit cells with the same period spacing, different forming heights and the same or different unit cell matrix thicknesses, and the unit cells form a gradient layer in a certain arrangement mode. The invention has the advantages that; by adopting the technical scheme, the egg-box type unit cell forms gradient change of mechanical characteristics along the thickness direction through symmetrical superposition of the unit cell units, has structural gradient change characteristics and out-of-plane negative Poisson's ratio characteristics, and improves the mechanical properties such as equivalent rigidity, compression characteristics, energy absorption characteristics, vibration characteristics and the like.

Description

Egg-box type unit cell with gradient stacking characteristic and egg-box type structure

Technical Field

The invention relates to the field of mechanical metamaterial structure design, in particular to an egg-box type unit cell with gradient stacking characteristics and an egg-box type structure.

Background

The light structure is a high-performance material structure with extremely high porosity, and the overall structural and functional requirements are met through reasonable design of periodic unit cells in the plane of the material. The lightweight structural material has the characteristics of high specific strength, high specific surface area, negative Poisson ratio and excellent buffering and energy absorption properties by analyzing from the aspect of mechanical properties. The excellent comprehensive mechanical property can be widely applied to the manufacture of structures with light weight, impact resistance and damage resistance, vibration reduction and noise reduction, strong heat and mass transfer and the like of high-end technical equipment. The egg-box type structure is a light structure which is simple to prepare and wide in application, can be efficiently manufactured by stamping and rolling a common metal plate, but is usually used by adopting an egg-box type structure single plate at present, so that the regulation and control capability of the comprehensive mechanical property of the egg-box type structure cannot be fully exerted. In fact, the egg-box type structure is very easy to obtain egg-box type structure single plates in various different geometric states through adjustment of manufacturing process parameters, and the single plates can obtain a structural form which has a gradient distribution of mechanical states in the thickness direction and has an out-of-plane negative poisson ratio characteristic through a reasonably designed stacking combination, so that the requirements of various use scenes of a light structure are met.

Disclosure of Invention

The invention discloses an egg-box type unit cell with gradient lamination characteristics and an egg-box type structure, which are used for solving any one of the technical problems and other potential problems in the prior art.

In order to solve the technical problems, the technical scheme of the invention is as follows: an egg-box-shaped unit cell with a gradient stacking characteristic, the egg-box-shaped unit cell comprising an upper unit cell and a lower unit cell; the upper unit cell and the lower unit cell are arranged in a mirror symmetry mode;

the upper unit cell and the lower unit cell have the same structure and comprise at least 4 layers of unit cell units, the unit cell units have the same period spacing, the unit cell unit matrixes have the same thickness and different forming heights, and the multi-layer unit cell units form a gradient layer in a certain connection mode.

The unit cell units have the same periodic interval, different thickness of the unit cell unit matrix and different forming height.

The projection of the unit cell unit on a two-dimensional plane where the unit cell unit is located in the first direction (along the X-axis direction) and the second direction (along the y-axis direction) is square, a peak is arranged at the symmetrical center of the square, a trough is arranged at each of the central points of the four side lines, and the peak and the trough are connected through a curved surface.

Further, the connection mode is as follows: the odd layers are formed by overlapping and connecting the lowest point of the unit cell unit between the nth layer and the (n + 1) th layer, wherein n is 1,3,5, 7;

the even layers are connected by overlapping the highest point of the unit cell unit between the mth layer and the (m + 1) th layer, wherein the highest point of the unit cell unit is m ═ 2,4,6,8 ·.

Further, the forming height of the unit cell unit of the nth layer is smaller than that of the unit cell unit of the (n + 1) th layer; the forming height of the unit cell unit of the mth layer is larger than that of the unit cell unit of the (m + 1) th layer.

The egg-box-shaped structure with the gradient stacking characteristic is formed by arranging the egg-box-shaped unit cells in a plane lattice mode.

The period intervals of the egg-box type unit cells are the same.

A gradient egg box type plate is provided with the egg box type structure.

In order to better exert the advantages of lightweight, impact resistance, energy absorption and vibration reduction of the egg-box-shaped structure and adjust the mechanical properties such as equivalent rigidity and the like of the egg-box-shaped structure by a certain means, the invention designs the laminated egg-box-shaped unit cell with the structural gradient change characteristic and the out-of-plane negative Poisson's ratio characteristic. On one hand, the egg-box unit cell can form a structure with mechanical properties changing along the thickness direction in a gradient manner by overlapping unit cell units with the same period spacing but different thicknesses and forming heights, and on the other hand, the egg-box unit cell can adjust the mechanical properties of the egg-box unit cell, such as equivalent rigidity, compression property, energy absorption property, vibration property and the like, by changing the gradient difference size and the gradient distribution manner.

The invention designs an egg-shaped box type unit cell with gradient lamination characteristics. The egg-box type unit cell is generally characterized in that a double-arrow-shaped laminated egg-box type periodic arrangement plate which is symmetrical along a bending neutral layer is formed to form a negative Poisson ratio structure which has a substrate thickness gradient or a forming height gradient and is similar to a double arrow in the thickness direction of the plate. Taking a unit cell as an example, the specific steps of stacking are described as follows:

the method comprises the following steps: outwards from the neutral layer of the plate (the layer 1 is closest to the neutral layer, the layer 2 is close to the layer 1 and far from the neutral layer, and the like), a wave trough (the lowest point of the single plate) is arranged between the nth layer and the (n + 1) th layer to carry out superposition connection on the wave trough (n is 1,3,5, 7).

Step two: the wave crest (the highest point of the veneer) is superposed and connected between the mth layer (close to the 1 st layer and separated from the neutral layer by the 1 st layer and regarded as the 2 nd layer) and the (m + 1) th layer of the plate from the neutral layer to the outside. (m ═ 2,4,6,8 ·).

Step three: and (4) symmetrically copying the structure formed by the first and second steps by taking the bottom plane of the lowest layer as a reference, and superposing to obtain a double-arrow structure symmetrical in the thickness direction.

The limiting conditions are as follows: the forming height of the unit cell unit on the nth layer is not higher than that of the (n + 1) th layer from the neutral layer of the plate to the outside (the layer 1 is closest to the neutral layer, the layer 2 is close to the layer 1 and is far away from the neutral layer, and the like); the forming height of the unit cell of the mth layer is not lower than that of the m +1 th layer.

In the above structure, the cycle pitch is a dimension in a length direction of the unit cell model, the forming height is a vertical distance from a peak at the highest point to a trough at the lowest point of the unit cell unit, and the thickness is a substrate thickness of the egg-box type unit cell unit.

In the above structure, the number of unit cells to be connected in a stacked manner can be selected according to the gradient requirement, for example, 4,6,8, 10, etc. can be selected. However, it should be noted that in order to ensure a symmetrical structure, an even number of layers is required.

The invention has the following outstanding beneficial effects: by adopting the technical scheme, the structure can form the characteristic that the plate surface presents the negative Poisson ratio along the thickness direction, and the gradient mechanical properties of the structural material, such as equivalent rigidity, the size of the negative Poisson ratio, vibration energy absorption characteristic and the like, can be conveniently adjusted by adjusting the superposition combination mode of the single plates. Meanwhile, the geometric form of the single plate can be flexibly adjusted according to design requirements, for example, the shape of the egg-box type single plate is changed by adjusting the sin cluster function, and the form of the egg-box type single plate is changed by adjusting the period interval or the thickness and the forming height. The design freedom is high, and the forming and manufacturing are convenient and stable.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention.

FIG. 1 is a schematic diagram of an egg-box unit cell with gradient stacking features according to the present invention.

FIG. 2 is a schematic diagram of a unit cell according to the present invention.

FIG. 3 is a schematic cross-sectional side view of a unit cell according to the present invention.

FIG. 4 is a schematic diagram of the stacking method of the multi-layer thickness gradient egg-box unit of the present invention (8 layers as an example).

Fig. 5 is a schematic diagram of an egg-box structure with gradient stacking features.

In the figure:

1. the cell unit comprises an egg-box type cell, a cell unit I, an upper cell, a cell unit II, a cell unit 2, a cell unit 3, a period interval of the cell unit 4, a forming height of the cell unit 5, a thickness of the cell unit 5, a cell unit 6, a thickness of the cell unit 0.5mm and a forming height of the cell unit 4mm, a cell unit 7, a thickness of the cell unit 8, a forming height of the cell unit 8, a thickness of the cell unit 0.3mm and a forming height of the cell unit 4mm, a cell unit 9, a thickness of the cell unit 0.3mm and a forming height of the cell unit 8mm, a cell unit 10, a unit 11 and a unit 12 of the cell unit in figure 3, a unit 13, a thickness of the cell unit 0.5mm and a forming height of the cell unit 2mm, a unit 14, a thickness of the cell unit 0.5mm and a forming height of the cell unit 15, a thickness of the cell unit 0.5mm and a forming height of the cell unit 16, a forming height of the cell unit 8 mm.

Detailed Description

The technical solution of the present invention is further explained with reference to the accompanying drawings and specific embodiments.

As shown in fig. 1, the present invention is an egg-box type unit cell having a gradient stack characteristic, wherein the egg-box type unit cell includes an upper unit cell and a lower unit cell; the upper unit cell and the lower unit cell are arranged in a mirror symmetry mode;

The connection mode is as follows: the odd layers are formed by overlapping and connecting the lowest point of the unit cell unit between the nth layer and the (n + 1) th layer, wherein n is 1,3,5, 7. cndot. i;

The forming height of the unit cell unit of the nth layer is smaller than that of the unit cell unit of the (n + 1) th layer; the forming height of the unit cell unit of the mth layer is larger than that of the unit cell unit of the (m + 1) th layer.

As shown in fig. 2 and 3, the unit cell unit is projected to be square in shape on a two-dimensional plane where the first direction and the second direction are located, a peak is located at the symmetrical center of the square, a trough is located at each of the center points of the four side lines, and the peak and the trough are connected through a curved surface.

The period interval of each egg-box type unit cell of the egg-box type structure is the same.

A gradient egg box type plate is provided with the egg box type structure.

Example (b):

one appearance of the egg-box type structure is shown in fig. 5. The egg-box structure is obtained from the egg-box unit cells 1 by means of an array. The side shape of the plate is sin function shape, and the plate is a single plate with the specification of 10 multiplied by 10 in the figure. It should be noted that the unit cell need not be complete, depending on the desired sheet size, and for example, a 11.3 × 12.6 gauge is also possible. The size of the egg-box type unit cell is marked as shown in figure 3 and is controlled by three sizes of a periodic interval 3, a forming height 4 and a thickness 5. The following takes two kinds of multi-layer gradient egg-box type unit cells as an example to introduce a specific structure.

Example 1:

the design of the 8-layer double-arrow thickness gradient egg box type structure with the period spacing of 30mm, the forming height of 8/4mm and the thickness of 0.5/0.3mm is as follows:

first, 2 kinds of single-layer egg-box-shaped unit cells 6 (cycle pitch 30mm, forming height 4mm, thickness 0.5mm), unit cells 7 (cycle pitch 30mm, forming height 8mm, thickness 0.5mm), unit cells 8 (cycle pitch 30mm, forming height 4mm, thickness 0.3mm), and unit cells 9 (cycle pitch 30mm, forming height 8mm, thickness 0.3mm) were prepared according to the above dimensions. Then, in the manner shown in fig. 1, 8 layers of unit cell units are stacked, where the unit cell unit 6 is a first layer (the layer closest to the neutral layer), the unit cell unit 7 is a second layer (immediately adjacent to the first layer and slightly distant from the neutral layer), the unit cell unit 8 is a third layer (immediately adjacent to the second layer), and the unit cell unit 9 is a fourth layer (immediately adjacent to the third layer and farthest from the neutral layer). Wherein, the connecting point 10 is that the wave trough of the first layer unit cell 6 is connected with the wave trough of the second layer unit cell 7; the connection point 11 is that the wave crest of the second layer of unit cell unit 7 is connected with the wave crest of the third layer of unit cell unit 8; the connection point 12 is the connection of the wave trough of the third layer unit cell 8 and the wave trough of the fourth layer unit cell 9. Note that the structure is mirror symmetric along the center plane.

Example 2:

the design of the 8-layer double-arrow-shaped forming height gradient egg box type structure with the period spacing of 30mm, the forming height of 8/4mm and 6/2mm and the thickness of 0.5mm is as follows:

first, 2 kinds of single-layer egg-box-shaped unit cells 13 (cycle pitch of 30mm, forming height of 2mm, thickness of 0.5mm), unit cells 14 (cycle pitch of 30mm, forming height of 6mm, thickness of 0.5mm), unit cells 15 (cycle pitch of 30mm, forming height of 4mm, thickness of 0.5mm), and unit cells 16 (cycle pitch of 30mm, forming height of 8mm, thickness of 0.5mm) were prepared according to the above dimensions. After that, the superimposition is performed in the manner shown in fig. 4. The unit cell unit 13 is the first layer (the layer closest to the neutral layer), the unit cell unit 14 is the second layer, the unit cell unit 15 is the third layer, and the unit cell unit 16 is the fourth layer. The connection of the overlapping joints was made in the same manner as in example 1. It should be noted that the height difference between each two layers (e.g. the first layer unit cell 13 and the second layer unit cell 14, the third layer unit cell 15 and the fourth layer unit cell 16) needs to be kept consistent to eliminate the influence of the overall height of the multi-layer unit cell model. Finally, the structures are arrayed 10 times in the length and width directions to obtain an 8-layer egg-box-shaped structural plate with the forming height gradient and the negative Poisson ratio characteristic, as shown in fig. 5.

The above description is only a specific embodiment of the present invention, and it is not intended to limit the scope of the present invention, so the design of unit cells in the egg-box structure of the present invention includes the shape, material, and size of the unit cells; and the design of the gradient, including the type of the gradient (thickness, forming height, etc.), the gradient difference, the distribution of the gradient (increasing or decreasing from inside to outside, or other gradient distribution rules); and the change of the stacking mode and the number of stacked layers; and a cell array approach; and equivalents and modifications to the structure disclosed herein are deemed to be within the scope of the present patent.

In summary, the multi-layer egg-box structure with the negative poisson ratio characteristic of the gradient characteristic designed by the invention is not seen before, and particularly, the free overlapping arrangement mode of the multi-layer unit cells with different gradients is extremely flexible and changeable, so that the egg-box structure can adapt to a considerable number of practical application occasions. By adjusting the thickness gradient or the forming height gradient, the gradient difference, the gradient distribution and the like, the mechanical properties of the structure, such as equivalent rigidity, energy absorption and vibration reduction performance, compression performance and the like, can be flexibly adjusted, and the structure has advancement and universality.

The above details are provided for the egg-box unit cell and the egg-box structure with the gradient stacking feature provided by the embodiments of the present application. The above description of the embodiments is only for the purpose of helping to understand the method of the present application and its core ideas; meanwhile, for a person skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.

As used in the specification and claims, certain terms are used to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. "substantially" means within an acceptable error range, and a person skilled in the art can solve the technical problem within a certain error range to substantially achieve the technical effect. The description which follows is a preferred embodiment of the present application, but is made for the purpose of illustrating the general principles of the application and not for the purpose of limiting the scope of the application. The protection scope of the present application shall be subject to the definitions of the appended claims.

It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a good or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such good or system. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a commodity or system that includes the element.

It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

The foregoing description shows and describes several preferred embodiments of the present application, but as aforementioned, it is to be understood that the application is not limited to the forms disclosed herein, but is not to be construed as excluding other embodiments and is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the application as described herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the application, which is to be protected by the claims appended hereto.

Claims

1. An egg-box cell with a gradient stacking characteristic, wherein the egg-box cell comprises an upper cell and a lower cell; the upper unit cell and the lower unit cell are arranged in a mirror symmetry mode;

2. The egg-box unit cell of claim 1, wherein the unit cell units have the same period spacing, different unit cell substrate thicknesses, and different forming heights.

3. The egg-box type unit cell of claim 1 or 2, wherein the unit cell is in a square shape projected on a two-dimensional plane where the first direction and the second direction are located, a peak is located at the symmetrical center of the square, a trough is located at each of the center points of four side lines, and the peak and the trough are connected through a curved surface.

4. The egg-box unit cell of claim 3, wherein the connection means is: the odd layers are formed by overlapping and connecting the lowest point of the unit cell unit between the nth layer and the (n + 1) th layer, wherein n is 1,3,5, 7;

the even layers are connected by overlapping the highest point of the unit cell unit, which is the highest point of the unit cell unit, between the mth layer and the (m + 1) th layer, wherein m is 2,4,6, 8.

5. The egg-box unit cell of claim 4, wherein the n-th layer unit cell unit has a formed height less than the formed height of the n + 1-th layer unit cell unit; the forming height of the unit cell of the mth layer is larger than that of the unit cell of the (m + 1) th layer.

6. An egg-box structure with gradient stacking characteristics, wherein the egg-box structure is formed by arranging the egg-box unit cells of any one of claims 1-5 in a planar lattice manner.

7. The egg-box structure according to claim 6, wherein the egg-box structure has the same period pitch for each egg-box unit cell.

8. A gradient egg carton template, characterized in that the gradient egg carton template has an egg carton structure according to claim 6.