CN118441822B - Curved honeycomb structure and curved structure with negative Poisson's ratio effect - Google Patents

Abstract

The invention discloses a curved honeycomb structure and a curved structure with a negative Poisson's ratio effect, and relates to the field of curved structures with a negative Poisson's ratio effect. The curved honeycomb structure includes a curved unit, and the curved unit includes an upper horizontal ligament, two intermediate horizontal ligaments and a lower horizontal ligament. Two symmetrically arranged Z-shaped long connecting ligaments are connected between the upper horizontal ligament and one of the intermediate horizontal ligaments, and two symmetrically arranged Z-shaped short connecting ligaments are connected between the lower horizontal ligament and the other intermediate horizontal ligament; the two intermediate horizontal ligaments are symmetrical about the symmetry axis of the two Z-shaped long connecting ligaments; the curved unit is an outward convex curved structure, and the upper horizontal ligament and the lower horizontal ligament are both arc-shaped curved panels. The structure has the characteristics of light weight and high strength, and can show excellent performance when subjected to impact loads, allowing large plastic deformation.

Description

Curved honeycomb structure and curved structure with negative Poisson's ratio effect

Technical Field

The invention relates to the field of curved surface structures with negative Poisson's ratio effect, in particular to a curved surface honeycomb structure and a curved surface structure with negative Poisson's ratio effect.

Background Art

Engineering accidents include but are not limited to explosions, falling rocks, and collisions caused by loss of vehicle control. These accidents not only endanger the lives and property of citizens, but are also easily accompanied by various secondary disasters caused by structural damage. Compared with single engineering accidents, the consequences of these secondary disasters are often more serious.

Therefore, there is an urgent need for a structure or material with good seismic resistance that can be used as energy absorption protection.

Auxetic metamaterials are artificially designed materials with unique mechanical properties that natural materials in nature do not have. Auxetic metamaterials exhibit mechanical properties that are superior to traditional materials, such as shear resistance, indentation resistance, seismic resistance, sound absorption, and energy absorption. Benefiting from these excellent mechanical properties, auxetic metamaterials are widely used in aerospace, biomedicine, civil engineering and other fields.

There are many related studies on auxetic metamaterials, but there are relatively few studies on the structure and mechanical properties of curved structures. In addition, the existing research on the auxetic effect of curved auxetic metamaterials is mainly the performance when it is bent out of plane, such as the vascular stents successfully used in the medical field. The auxetic effect of curved auxetic metamaterials is that when it is bent out of plane, the existing structure will show obvious warping when used, and the energy absorption effect is not good.

Summary of the invention

One object of the present invention is to provide a curved honeycomb structure and a curved structure with a negative Poisson's ratio effect, and to achieve the effects of earthquake resistance and energy absorption protection through the negative Poisson's ratio effect of the curved units of the structure; on the other hand, the curved honeycomb structure composed of the curved units is applied to the curved structure, and has the advantages of low cost, simple assembly, and high engineering responsiveness.

This purpose is achieved by adopting the following technical solutions:

The curved honeycomb structure with negative Poisson's ratio effect of the present invention comprises a curved unit, the curved unit comprises an upper horizontal ligament, two intermediate horizontal ligaments and a lower horizontal ligament, two symmetrically arranged long Z-shaped connecting ligaments are connected between the upper horizontal ligament and one of the intermediate horizontal ligaments, and two symmetrically arranged short Z-shaped connecting ligaments are connected between the lower horizontal ligament and the other intermediate horizontal ligament; the two intermediate horizontal ligaments are symmetrical about the symmetry axis of the two long Z-shaped connecting ligaments; the curved unit is an outwardly convex curved structure, and the upper horizontal ligament and the lower horizontal ligament are both arc-shaped curved panels.

Furthermore, when a negative Poisson's ratio structure is subjected to an external force, the material around the force-bearing area gathers toward the force-bearing area, thereby increasing the local density of the material, so that the strength and stiffness of the structure are greatly improved. Therefore, the force enhancement effect of the negative Poisson's ratio structure can always be maintained in nonlinear large deformations.

The negative Poisson's ratio structure reacts differently under different external forces. When the negative Poisson's ratio structure is subjected to force, the material concentrates at the force point, and when the distributed force acts, it has the effect of protruding toward the surface of the structure. Therefore, this structure has good impact resistance and energy absorption effect.

Furthermore, the curved honeycomb structure includes a plurality of curved units, and two adjacent curved units in the same layer are connected by an intermediate horizontal ligament. Two adjacent curved units in adjacent layers are connected by an upper horizontal ligament and a lower horizontal ligament. In actual use, the wrapping angle of the combined structure, the number of curved units in each layer, and the number of layers of curved units can be freely adjusted according to the actual situation of the energy of the impact object and the protected curved structure, with high flexibility and adjustability.

Furthermore, the curved honeycomb structure is wrapped around the outer side of the curved structure, the curved honeycomb structure includes a plurality of curved units, and the plurality of curved units form a semicircular or circular structure. The ratio of the thickness of the curved honeycomb structure to the radius of the curved structure is 1:2-3.5.

Compared with the positive Poisson's ratio structure, the curved surface unit of this structure has a negative Poisson's ratio effect. Even during the impact process, the structure itself can maintain a good fit with the protected curved structure, thereby greatly enhancing its reliability in impact protection.

The symmetry axes of the two Z-shaped long connecting ligaments are collinear with the symmetry axes of the two Z-shaped short connecting ligaments. The centers of the upper horizontal ligament, the middle horizontal ligament and the lower horizontal ligament are the same.

The radial widths of the upper horizontal ligament, lower horizontal ligament, Z-shaped long connecting ligament and Z-shaped short connecting ligament are the same, and the radial width of the middle horizontal ligament is twice that of the upper horizontal ligament. The radial widths of the upper horizontal ligament, lower horizontal ligament, Z-shaped long connecting ligament and Z-shaped short connecting ligament are 0.5-1mm.

Preferably, the Z-shaped short connecting ligament includes a first connecting segment, an arcuate short connecting segment and a second connecting segment, the arcuate short connecting segment is connected between the first connecting segment and the second connecting segment, the length of the arcuate short connecting segment is S4, and the length of the upper horizontal ligament is S1, wherein 0＜S4≤0.4S1.

Preferably, the center angle of the upper horizontal ligament is θ2, the center angle of the middle horizontal ligament is θ1, and the center angle of the arc-shaped short connecting segment is θ4, wherein θ2=0.75*θ1.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

The invention provides a curved honeycomb structure and a curved structure with a negative Poisson's ratio effect. The structure has a good energy absorption and protection effect. At the same time, the structure is a curved convex structure and is more suitable for the protection of curved structures.

The structure includes a plurality of curved surface units. During use, the number and position of the curved surface units of the structure can be adjusted according to the energy of the impact object and the actual situation of the protected curved surface structure, and the structure has high flexibility and adjustability.

The curved honeycomb structure of this structure can not only effectively protect curved structures, but also respond quickly when a disaster occurs, thereby minimizing the loss of life and property of citizens.

Secondly, since the structure itself has the characteristics of negative Poisson's ratio and porous structure, it has the characteristics of light weight and high strength, and can show excellent performance when subjected to impact loads, allowing large plastic deformation.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

FIG1 is a schematic diagram of the front structure of the curved surface unit in Example 1;

FIG2 is a schematic diagram of the three-dimensional structure of the curved surface unit in Example 1;

FIG3 is a schematic diagram of the structure of connecting multiple curved surface units on the same layer in Example 2;

FIG4 is a schematic diagram of the structure of connecting multiple curved surface units in different layers in Example 2;

FIG5 is a schematic diagram of a structure when a plurality of curved surface units form a semicircular structure;

FIG6 is a schematic diagram of the deformation cross section of the composite structure when the compression ratio of the radially distributed load is 0.35 in the numerical simulation;

FIG7 is a schematic diagram of a deformed cross section of a composite structure subjected to a radially distributed load with a compression ratio of 0.7 in a numerical simulation;

FIG8 is an energy-displacement graph.

Marks and corresponding parts names in the attached drawings:

1-upper horizontal ligament, 2-arc-shaped long connecting segment, 3-third connecting segment, 4-first connecting segment, 5-arc-shaped short connecting segment, 6-second connecting segment, 7-lower horizontal ligament, 8-middle horizontal ligament, 9-fourth connecting segment.

DETAILED DESCRIPTION

In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary implementation modes of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

In the description of the present invention, it should be understood that the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the scope of protection of the present invention.

Example 1

As shown in FIGS. 1 and 2 , the curved honeycomb structure includes a curved unit, and the curved unit includes an upper horizontal ligament 1, two intermediate horizontal ligaments 8, and a lower horizontal ligament 7. Two symmetrically arranged Z-shaped long connecting ligaments are connected between the upper horizontal ligament 1 and one of the intermediate horizontal ligaments 8, and two symmetrically arranged Z-shaped short connecting ligaments are connected between the lower horizontal ligament 7 and the other intermediate horizontal ligament 8; the two intermediate horizontal ligaments 8 are symmetrical about the symmetry axis of the two Z-shaped long connecting ligaments.

Among them, the Z-shaped long connecting ligament includes a third connecting segment 3, an arc-shaped long connecting segment 2 and a fourth connecting segment 9, and the arc-shaped long connecting segment 2 is connected between the third connecting segment 3 and the fourth connecting segment 9; the Z-shaped short connecting ligament includes a first connecting segment 4, an arc-shaped short connecting segment 5 and a second connecting segment 6, and the arc-shaped short connecting segment 5 is connected between the first connecting segment 4 and the second connecting segment 6; the symmetry axes of the two Z-shaped long connecting ligaments are collinear with the symmetry axes of the two Z-shaped short connecting ligaments.

The curved surface unit is an outwardly convex curved surface structure, and the upper horizontal ligament 1 and the lower horizontal ligament 7 are both arc-shaped curved panels.

In some embodiments, the radial widths of the upper horizontal ligament 1 , the lower horizontal ligament 7 , the Z-shaped long connecting ligament and the Z-shaped short connecting ligament are the same, and the radial width of the middle horizontal ligament 8 is twice that of the upper horizontal ligament 1 .

In some embodiments, the centers of the upper horizontal ligament 1, the middle horizontal ligament 8 and the lower horizontal ligament 7 are the same.

In some embodiments, the upper horizontal ligament 1 , the middle horizontal ligament 8 , the lower horizontal ligament 7 , the Z-shaped long connecting ligament and the Z-shaped short connecting ligament in the curved surface unit are all metal plates.

Example 2

On the basis of the above-mentioned embodiment, the curved honeycomb structure includes a plurality of curved units.

In some embodiments, for multiple curved surface units in the same layer, as shown in FIG. 3 , two adjacent curved surface units are connected by an intermediate horizontal ligament 8 .

In some embodiments, for multiple curved surface units in different layers, as shown in FIG. 4 , two adjacent curved surface units are connected by an upper horizontal ligament 1 and a lower horizontal ligament 7 .

In some embodiments, the curved structure with negative Poisson's ratio effect includes a curved structure and a curved honeycomb structure, the curved honeycomb structure is wrapped around the outside of the curved structure, and the curved honeycomb structure includes a plurality of curved units, and the plurality of curved units form a semicircular or circular structure. When the plurality of curved units form a semicircular structure, as shown in FIG5 . The ratio of the thickness of the curved honeycomb structure to the radius of the curved structure is 1:2-3.5. Among them, the thickness of the curved honeycomb structure is the radial distance from the lower horizontal ligament 7 of the innermost curved unit to the upper horizontal ligament 1 of the outermost layer, and the radial direction in this application refers to the direction of the straight line along the radius of the center of the curved unit.

In some embodiments, the number of layers of the curved honeycomb structure is not less than 3 layers.

In some embodiments, the curved honeycomb structure has 4 layers, the height of each curved unit is 20 mm, the radius of the curved structure is 200 mm, and the ratio of the thickness of the curved honeycomb structure to the radius of the curved structure is 80:200=1:2.5.

Example 3

Based on the above embodiments, this embodiment provides a curved honeycomb structure.

The length of the upper horizontal ligament 1 is S1, the length of the lower horizontal ligament 7 is S2, the length of the arc-shaped long connecting segment 2 is S3, the length of the arc-shaped short connecting segment 5 is S4, and the length of the middle horizontal ligament 8 is S5.

The upper horizontal ligament 1, the lower horizontal ligament 7, the arc-shaped long connecting section 2, the arc-shaped short connecting section 5, and the middle horizontal ligament 8 are all outwardly convex arc-shaped curved panels. In this embodiment, the outwardly convex refers to convex in a direction away from the curved surface structure.

The radial widths of the upper horizontal ligament 1, the lower horizontal ligament 7, the Z-shaped long connecting ligament and the Z-shaped short connecting ligament are t, t=0.5-1 mm. The radial width of the intermediate horizontal ligament 8 is 2t. The distance between the upper horizontal ligament 1 and the lower horizontal ligament 7 is H. The length of the third connecting segment 3 is h1, the length of the second connecting segment 6 is h2, and the sum of the lengths of the first connecting segment 4 and the fourth connecting segment 9 is L. The radius of the coated curved structure is r.

In some embodiments, 0＜S4≤0.4S1. The center angle of the upper horizontal ligament 1 is θ2, the center angle of the middle horizontal ligament 8 is θ1, and the center angle of the arc-shaped short connecting section 5 is θ4, wherein θ2＝0.75*θ1.

In some embodiments, H=19.5, t=0.5, S1=14.5, S2=13.5, S3=4.135, S4=3.475, h1=5.125, h2=5.125, L=9.25, and r=200.

In some embodiments, L = 0.5*H-t, h1 = h2 = 0.25*H+0.5t, S5 = 0.5*S1, L is a straight line segment, and its position should be above the radius of the complete embodiment. Therefore, the negative Poisson's ratio effect of the structure can be controlled by limiting the S4 length, h1 height and the position of the L segment.

Example 4

On the basis of the above embodiments, the radial load-bearing energy absorption effect of the curved honeycomb structure with negative Poisson's ratio effect in Embodiment 3 was simulated and calculated by ABAQUS/Explict. According to V=36km/h and the mass of the impactor m=140kg, the force-displacement curve was obtained to obtain F _max =138.44KN within the effective stroke. According to the force-displacement curve, the energy-displacement curve shown in Figure 8 can be further obtained, and the total energy absorption is EA=1650J, and the energy absorption efficiency is η=28.6%.

Among them, all the intermediate horizontal ligaments 8, Z-shaped long connecting ligaments and Z-shaped short connecting ligaments produce a large deformation in the impact direction during the impact process, which helps to improve the local stiffness and strength of the structure, and also ensures that the structure still has a negative Poisson's ratio effect under large deformation. The size of all ligaments can be adjusted proportionally as a whole, the number of layers of curved surface units can be adjusted, and the number of curved surface unit groups in each layer can be adjusted, so that the cross-sectional size of the annular structure can be changed. Any two curved surface units are symmetrically distributed, and the symmetrical distribution form helps to improve the tensile expansion effect of the present structure.

Secondly, in the numerical simulation, the schematic diagram of the cross-section of the combined structure before deformation by the radially distributed load is shown in Figure 5; in the numerical simulation, the schematic diagram of the deformed cross-section of the combined structure when the compression ratio of the radially distributed load is 0.35 is shown in Figure 6; in the numerical simulation, the schematic diagram of the deformed cross-section of the combined structure when the compression ratio of the radially distributed load is 0.7 is shown in Figure 7.

It can be concluded from Figures 5-7 that the negative Poisson's ratio effect of the structure of this embodiment means that when the compression ratio reaches 0.7, the internal circular arc surface of the structure still maintains the original circular arc surface, and no deformation such as warping occurs. During the entire deformation process, the deformation along the impact direction converges toward the impact point, which has a good effect of enhancing stiffness.

The terms "first", "second", "third", etc. used herein are only used to distinguish the corresponding components for the sake of clarity of description, and are not intended to limit any order or emphasize importance, etc. In addition, the term "connected" used herein, unless otherwise specified, may refer to direct connection or indirect connection via other components.

The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims (9)

1. A curved honeycomb structure with a negative Poisson's ratio effect, characterized in that the curved honeycomb structure comprises a curved unit, the curved unit comprising an upper horizontal ligament (1), two intermediate horizontal ligaments (8) and a lower horizontal ligament (7), two symmetrically arranged Z-shaped long connecting ligaments are connected between the upper horizontal ligament (1) and one of the intermediate horizontal ligaments (8), and two symmetrically arranged Z-shaped short connecting ligaments are connected between the lower horizontal ligament (7) and the other intermediate horizontal ligament (8); the two intermediate horizontal ligaments (8) are symmetrical about the symmetry axis of the two Z-shaped long connecting ligaments; the curved unit is an outwardly convex curved structure, and the upper horizontal ligament (1) and the lower horizontal ligament (7) are both arc-shaped curved panels; the radial widths of the upper horizontal ligament (1), the lower horizontal ligament (7), the Z-shaped long connecting ligament and the Z-shaped short connecting ligament are the same, and the radial width of the intermediate horizontal ligament (8) is twice that of the upper horizontal ligament (1). 2. The curved honeycomb structure with negative Poisson's ratio effect according to claim 1, characterized in that the curved honeycomb structure comprises a plurality of curved units, and two adjacent curved units are connected by an intermediate horizontal ligament (8), or by an upper horizontal ligament (1) and a lower horizontal ligament (7). 3. The curved honeycomb structure with negative Poisson's ratio effect according to claim 1, characterized in that the symmetry axes of the two Z-shaped long connecting ligaments are collinear with the symmetry axes of the two Z-shaped short connecting ligaments. 4. The curved honeycomb structure with negative Poisson's ratio effect according to claim 1, characterized in that the centers of the upper horizontal ligament (1), the middle horizontal ligament (8) and the lower horizontal ligament (7) are the same. 5. The curved honeycomb structure with negative Poisson's ratio effect according to claim 1, characterized in that the radial widths of the upper horizontal ligament (1), the lower horizontal ligament (7), the Z-shaped long connecting ligament and the Z-shaped short connecting ligament are 0.5-1 mm. 6. The curved honeycomb structure with negative Poisson's ratio effect according to claim 1, characterized in that the Z-shaped short connecting ligament comprises a first connecting segment (4), an arcuate short connecting segment (5) and a second connecting segment (6), the arcuate short connecting segment (5) is connected between the first connecting segment (4) and the second connecting segment (6), the length of the arcuate short connecting segment (5) is S4, the length of the upper horizontal ligament (1) is S1, wherein 0＜S4≤0.4S1. 7. The curved honeycomb structure with negative Poisson's ratio effect according to claim 6, characterized in that the center angle of the upper horizontal ligament (1) is θ2, and the center angle of the middle horizontal ligament (8) is θ1, wherein θ2=0.75*θ1. 8. A curved structure with a negative Poisson's ratio effect, characterized in that it comprises a curved structure and a curved honeycomb structure as described in any one of claims 1 to 7, wherein the curved honeycomb structure is wrapped around the outer side of the curved structure, and the curved honeycomb structure comprises a plurality of curved units, and the plurality of curved units form a semicircular or circular structure. 9. The curved structure with negative Poisson's ratio effect according to claim 8, characterized in that the ratio of the thickness of the curved honeycomb structure to the radius of the curved structure is 1:2-3.5.