A bionic cactus spine negative Poisson's ratio energy absorption structure and its design method

Abstract

The present invention relates to the technical field of biomimetic cactus thorn negative Poisson's ratio energy absorption structures, and discloses a biomimetic cactus thorn negative Poisson's ratio energy absorption structure, which includes a five-claw structure and a circular ring 6. The five-claw structure includes a vertical rod root cross-section, an outer rod, an outer rod head contact surface, a vertical rod, an inner rod, a vertical rod head, an inner rod head and a circular ring contact surface. There are 6 five-claw structures evenly distributed around the circular ring. One end of the inner rod is fixedly connected to the outer wall of the circular ring, and the end of the inner rod far from the circular ring is fixedly connected to the outer wall of the outer rod, which can exhibit the negative Poisson's ratio effect under loads in different directions. The five-claw structure has a design with a small head and heavy feet, so that the negative Poisson's ratio structure not only has a negative Poisson's ratio effect longitudinally, but also has a negative Poisson's ratio effect transversely. It should be noted that the transverse negative Poisson's ratio effect has a gradient property.

Description

Technical Field

[0001] The present invention relates to the technical field of bionic cactus spine negative Poisson's ratio energy absorption structures, and specifically to a bionic cactus spine negative Poisson's ratio energy absorption structure and its design method. Background Art

[0002] Negative Poisson's ratio metamaterials, as a typical mechanical metamaterial, are favored by scholars. To date, the application of energy absorption structures in the market still remains at the traditional square energy absorption box. For some lattice structures with relatively better energy absorption effects, only conceptual proposals have been made. For negative Poisson's ratio energy absorption structures with better energy absorption effects, they are only limited to traditional concave structures, simple four-handed structures, arrow-shaped structures, etc. For chiral negative Poisson's ratio structures with higher specific energy absorption, due to the difficulty in design, there are few conceptual proposals in the field of negative Poisson's ratio energy absorption. Existing gradient negative Poisson's ratio structures mostly focus on longitudinal gradients, and there is a lack of transverse gradient materials. Finally, the negative Poisson's ratio materials we often mention mostly have negative Poisson's ratio effects in one direction, that is, only when loaded and deformed in one direction can they have the advantages of negative Poisson's ratio performance, and they cannot achieve the excellent performance of showing negative Poisson's ratio under multi-directional loading. Summary of the Invention

[0003] The purpose of the present invention is to provide a bionic cactus spine negative Poisson's ratio energy absorption structure and its design method, which solves the problems mentioned in the above background art.

[0004] To achieve the above purpose, the present invention provides the following technical solution: A bionic cactus spine negative Poisson's ratio energy absorption structure, including a five-claw structure and a circular ring. The five-claw structure includes a cross-section of the root of the vertical rod, an outer rod, a contact surface at the head of the outer rod, a vertical rod, an inner rod, the head of the vertical rod, the head of the inner rod, and a contact surface with the circular ring. There are 6 five-claw structures evenly distributed around the circular ring. One end of the inner rod is fixedly connected to the outer wall of the circular ring, and the end of the inner rod away from the circular ring is fixedly connected to the outer wall of the outer rod. The end of the outer rod connected to the inner rod is fixedly connected to the bottom of the vertical rod. The cross-section of the root contact surface of the vertical rod is the cross-section of the part where the vertical rod is connected to the outer rod and the inner rod. The cross-section of the head contact surface of the outer rod is the cross-section of the part where the outer rods of two adjacent five-claw structures are connected. The head of the vertical rod is the end of the vertical rod away from the inner rod. The cross-section of the contact surface between the head of the inner rod and the circular ring is the cross-section of the part where the inner rod is connected to the circular ring.

[0005] Preferably, the length of the quadrilateral cross-section of the head of the vertical rod is c, the width is e, the side length of the square cross-section of the circular ring is f, the inner diameter of the circular ring is D, the outer angle between two adjacent outer rods is γ - 1, the inner angle between two adjacent outer rods is γ, the outer angle between an adjacent outer rod and an inner rod is β - 1, and the inner angle between an adjacent outer rod and an inner rod is β.

[0006] Preferably, the length of the outer rod is L1, the width of the contact surface at the head of the outer rod is a, the length of the vertical rod is L2, the width of the vertical rod is c, the angle between the outer rod and the vertical rod is θ, the lengths of the quadrilateral at the root cross-section of the vertical rod are f and g, one interior angle of the quadrilateral at the root cross-section of the vertical rod is φ, and the angle between one edge line of the outer rod and one edge line of the edge surface of the outer rod is δ.

[0007] Preferably, the value of β is 75.99°, the value of β - 1 is 72.24°, the value of γ is 135.58°, the value of γ - 1 is 130.93°, the value of c is 3.68 mm, the value of e is 3.28 mm, the value of f is 4.18 mm, the value of g is 4.14 mm, the value of D is 77.17 mm, the value of L1 is 52.36 mm, the value of L2 is 12.94 mm, the value of a is 2.83 mm, the value of θ is 90°, the value of φ is 90°, and the value of δ is 106.11°.

[0008] Preferably, the outer rod, the inner rod, and the vertical rod are all designed with a lightweight structure that is thick at the root and thin at the head. One end of the inner rod connected to the ring is thinner, so that this structure not only has a negative Poisson's ratio effect longitudinally, but also has a negative Poisson's ratio effect transversely. The transverse negative Poisson's ratio effect has a gradient property. The cross-section of the ring is square. The lengths of the outer rod, the inner rod, and the vertical rod in the axial direction of the pillar are less than the lengths in the tangential direction, reducing the interlayer distance, improving the stiffness after being impacted, and further improving the specific energy absorption of this structure.

[0009] Preferably, the root of the outer rod is thick and the head is thin, which is a design imitating the large thorns of the cactus. The vertical rod is cut from the outer rod with a certain length, and the root is thick and the head is thin, which is a design imitating the small thorns of the cactus.

[0010] A design method for a negative Poisson's ratio energy absorption structure imitating cactus thorns includes the following steps:

[0011] S1. Adopt the principle of thick head and thin foot of the cactus thorn to establish a five-claw structure;

[0012] S2. Design a ring in the center of the five-claw structure.

[0013] Preferably, in step S1, after cutting off a part of the connection roots of the inner rod, the outer rod, and the vertical rod in the five-claw structure at a specific angle, they are seamlessly spliced at a certain angle, and the connection between the inner rod and the outer rod is a cut-surface connection.

[0014] Preferably, in step S2, the connection between the circular ring and the five-claw structure adopts the principle of bionic cactus spines. The contact surface between the head of the inner rod of the five-claw structure and the circular ring is tangent to the circular ring, which is used as a transmission device during impact. The inward driving force of the five-claw structure is converted into the rotation of the circular ring, thereby driving the bionic cactus spine negative Poisson's ratio energy absorption structure to rotate, improving the stiffness and energy absorption effect of the bionic cactus spine negative Poisson's ratio energy absorption structure.

[0015] The present invention provides a bionic cactus spine negative Poisson's ratio energy absorption structure and its design method. The bionic cactus spine negative Poisson's ratio energy absorption structure has the following beneficial effects:

[0016] (1) The bionic cactus spine negative Poisson's ratio energy absorption structure can exhibit the negative Poisson's ratio effect under loading in different directions. The design of the five-claw structure with a small head and heavy feet enables the negative Poisson's ratio structure to have a negative Poisson's ratio effect not only longitudinally but also transversely. It should be noted that the transverse negative Poisson's ratio effect has a gradient property.

[0017] (2) By designing different sizes at both ends of the outer rod, inner rod, and vertical rod in the five-claw structure of the bionic cactus spine negative Poisson's ratio energy absorption structure, the design requirements of gradient rods are met, enabling the structure to achieve the best energy absorption effect during loading.

[0018] (3) By changing the ratio of the sizes at both ends of the outer rod, inner rod, and vertical rod in the five-claw structure of the bionic cactus spine negative Poisson's ratio energy absorption structure to adjust the stiffness of the structure, the advantage of variable stiffness can be realized, meeting the application requirements in various scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of the present invention;

[0020] Figure 2 It is a schematic diagram of the external shape and a partial enlarged view of the bionic cactus spine negative Poisson's ratio energy absorption structure of the present invention;

[0021] Figure 3 It is a schematic diagram of the dimension marking of the bionic cactus spine negative Poisson's ratio energy absorption structure of the present invention;

[0022] Figure 4 It is a schematic diagram of the partial dimension marking of the bionic cactus spine negative Poisson's ratio energy absorption structure of the present invention;

[0023] Figure 5 It is a schematic diagram of the partial dimension marking of the bionic cactus spine negative Poisson's ratio energy absorption structure of the present invention;

[0024] Figure 6 It is a schematic diagram of the lattice structure of the bionic cactus spine negative Poisson's ratio energy absorption structure of the present invention.

[0025] In the figure: 1 cross-section at the root of the vertical pole, 2 outer pole, 3 contact surface at the head of the outer pole, 4 vertical pole, 5 inner pole, 6 circular ring, 7 head of the vertical pole, 8 contact surface between the head of the inner pole and the circular ring, 9 contact surface between the root of the outer pole and the root of the vertical pole. Specific implementation mode

[0026] Such as Figures 1-5As shown in the figure, the present invention provides a technical solution: a bionic cactus thorn negative Poisson's ratio energy absorption structure, including a five-claw structure and a circular ring 6. The five-claw structure includes a vertical rod root cross-section 1, an outer rod 2, an outer rod head contact surface 3, a vertical rod 4, an inner rod 5, a vertical rod head 7, and an inner rod head and circular ring contact surface 8. There are 6 five-claw structures evenly distributed around the circular ring 6. One end of the inner rod 5 is fixedly connected to the outer wall of the circular ring 6, and the end of the inner rod 5 far from the circular ring 6 is fixedly connected to the outer wall of the outer rod 2. One end of the outer rod 2 connected to the inner rod 5 is fixedly connected to the bottom of the vertical rod 4. The vertical rod root contact surface is the cross-section of the part where the vertical rod 4 is connected to the outer rod 2 and the inner rod 5. The outer rod head contact surface 3 is the cross-section of the part where the outer rods 2 are connected in two adjacent five-claw structures. The vertical rod head 7 is the end of the vertical rod 4 far from the inner rod 5. The inner rod head and circular ring contact surface 8 is the cross-section of the part where the inner rod 5 is connected to the circular ring 6. The length of the quadrilateral of the cross-section of the vertical rod head 7 is c, and the width is e. The side length of the square cross-section of the circular ring 6 is f. The inner diameter of the circular ring 6 is D. The outer angle between two adjacent outer rods 2 is γ - 1, the inner angle between two adjacent outer rods 2 is γ, the outer angle between an adjacent outer rod 2 and the inner rod 5 is β - 1, and the inner angle between an adjacent outer rod 2 and the inner rod 5 is β. The length of the outer rod 2 is L1, the width of the outer rod head contact surface 3 is a, the length of the vertical rod 4 is L2, the width of the vertical rod 4 is c, the angle between the outer rod 2 and the vertical rod 4 is θ, the length of the quadrilateral of the vertical rod root cross-section 1 is f and the width is g, one inner angle of the quadrilateral of the vertical rod root cross-section 1 is φ, the angle between one edge line of the outer rod 2 and one edge line of the edge surface of the outer rod 2 is δ. The value of β is 75.99°, the value of β - 1 is 72.24°, the value of γ is 135.58°, the value of γ - 1 is 130.93°, the value of c is 3.68 mm, the value of e is 3.28 mm, the value of f is 4.18 mm, the value of g is 4.14 mm, the value of D is 77.17 mm, the value of L1 is 52.36 mm, the value of L2 is 12.94 mm, the value of a is 2.83 mm, the value of θ is 90°, the value of φ is 90°, the value of δ is 106.11°. The outer rod 2, the inner rod 5, and the vertical rod 4 are all designed with a lightweight design with a thick head and a thin foot, and one end of the inner rod 5 connected to the circular ring 6 is thinner, so that the structure not only has a negative Poisson's ratio effect in the longitudinal direction, but also has a negative Poisson's ratio effect in the transverse direction. The transverse negative Poisson's ratio effect has a gradient property. The cross-section of the circular ring 6 is a square. The axial length of the outer rod 2, the inner rod 5, and the vertical rod 4 is less than the tangential length, reducing the interlayer distance, improving the stiffness after being impacted, and further improving the specific energy absorption of the structure. The thick root and thin head of the outer rod 2 is the design of the large thorn in the bionic cactus thorn. The vertical rod 4 is intercepted from the outer rod 2 by a certain length, and the thick root and thin head is also the design of the small thorn in the bionic cactus;

[0027] A design method for a bionic cactus thorn negative Poisson's ratio energy absorption structure includes the following steps:

[0028] S1. Adopt the principle of the head of the bionic cactus thorn being small and the foot being heavy to establish a five-claw structure. After cutting off a part of the connecting roots of the inner rod 5, outer rod 2, and vertical rod 4 in the five-claw structure at a specific angle, they are seamlessly spliced at a certain angle. The connection between the inner rod 5 and the outer rod 2 adopts a sectional connection.

[0029] S2. Design a circular ring 6 at the center of the five-claw structure. The circular ring 6 and the five-claw structure are connected using the bionic cactus thorn principle. The contact surface 8 between the head of the inner rod of the five-claw structure and the circular ring is tangent to the circular ring 6, which is used as a transmission device during impact. The inward pushing force of the five-claw structure is converted into the rotation of the circular ring 6, thereby driving the bionic cactus thorn negative Poisson's ratio energy absorption structure to rotate, improving the stiffness and energy absorption effect of the bionic cactus thorn negative Poisson's ratio energy absorption structure.

[0030] When the bionic cactus thorn negative Poisson's ratio energy absorption structure is in use, the circular ring 6 in the middle of the bionic cactus thorn negative Poisson's ratio energy absorption structure is obtained by rotating and stretching a square cross-section around the center of the circle by a certain distance. The outer rod 2 is first formed by stretching a boss between a square cross-section at the vertex of a small regular hexagon at the root and a square cross-section at the vertex of a large regular hexagon at the head. Then, a straight line passing through the center of the circular ring 6 on the upper view reference plane is established on the square cross-section at the root of the outer rod 2. Two reference planes are established by rotating 45° around the straight line respectively, and the two reference planes are stretched and cut off outside the outer rod 2. Then, they are circularly arrayed 4 around the straight line and just seamlessly connected together to form a four-claw structure composed of two outer rods 2 and two vertical rods 4. Then, a normal plane of the previous straight line is used as a reference plane, and the root of the four-claw structure is stretched and cut off with this reference plane to obtain a cross-section that fits tightly with the root of the inner rod 5 and the four-claw structure. Then, a tangent line is made from the root of the inner rod 5 to the circular ring 6 to form the inner rod 5. The upper and lower two outer rods 2 in the four-claw structure are intercepted by a certain length in their extending directions to form the vertical rod 4, and finally a single five-claw structure is formed. The five-claw structure is then circularly arrayed 6 equidistantly around a straight line passing through the center of the circular ring 6 on the front view reference plane in the structure, and finally the bionic cactus thorn negative Poisson's ratio energy absorption structure is obtained.

[0031] It should be noted that in this article, the term "including", "comprising", or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article, or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or elements inherent to such process, method, article, or device. Without further limitations, an element defined by a statement "including a reference structure" does not exclude the existence of additional identical elements in the process, method, article, or device including the said element.

[0032] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

[0033] As described above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A bionic cactus thorn negative Poisson's ratio energy absorption structure, comprising a five-claw structure and a circular ring (6), characterized in that: The five-claw structure includes the cross-section of the root of the vertical rod (1), the outer rod (2), the contact surface of the head of the outer rod (3), the vertical rod (4), the inner rod (5), the head of the vertical rod (7), and the contact surface between the head of the inner rod and the ring (8). There are 6 such five-claw structures evenly distributed around the ring (6). One end of the inner rod (5) is fixedly connected to the outer wall of the ring (6), and the end of the inner rod (5) far from the ring (6) is fixedly connected to the outer wall of the outer rod (2). The end of the outer rod (2) connected to the inner rod (5) is fixedly connected to the bottom of the vertical rod (4). The contact surface at the root of the vertical rod is the cross-section of the part where the vertical rod (4) is connected to the outer rod (2) and the inner rod (5). The contact surface of the head of the outer rod (3) is the cross-section of the part where the outer rods (2) are connected in two adjacent five-claw structures. The head of the vertical rod (7) is the end of the vertical rod (4) far from the inner rod (5). The contact surface between the head of the inner rod and the ring (8) is the cross-section of the part where the inner rod (5) is connected to the ring (6). The outer rod (2), the inner rod (5), and the vertical rod (4) are all designed with a lightweight structure that is thick at the head and thin at the foot, and the end of the inner rod (5) connected to the ring (6) is thinner. The cross-section of the ring (6) is square, and the length of the five-claw structure in the axial direction is less than the length in the tangential direction.

2. The bio-inspired cactus thorn negative Poisson's ratio energy absorption structure according to claim 1, wherein: The length of the quadrilateral cross-section of the head of the vertical rod (7) is c, and the width is e. The side length of the square cross-section of the ring (6) is f. The inner diameter of the ring (6) is D. The outer angle between two adjacent outer rods (2) is γ - 1, and the inner angle between two adjacent outer rods (2) is γ. The outer angle between an adjacent outer rod (2) and the inner rod (5) is β - 1, and the inner angle between an adjacent outer rod (2) and the inner rod (5) is β.

3. The bio-inspired cactus thorn negative Poisson's ratio energy absorption structure according to claim 1, characterized in that: The length of the outer rod (2) is L1, the width of the contact surface of the head of the outer rod (3) is a, the length of the vertical rod (4) is L2, the width of the vertical rod (4) is c, the angle between the outer rod (2) and the vertical rod (4) is θ, the length of the quadrilateral of the cross-section of the root of the vertical rod (1) is f and the width is g, one interior angle of the quadrilateral of the cross-section of the root of the vertical rod (1) is φ, and the angle between one edge line of the outer rod (2) and one edge line of the edge surface of the outer rod (2) is δ.

4. The bio-inspired cactus spine negative Poisson's ratio energy absorption structure according to claim 2 or 3, characterized in that: The value of β is 75.99°, the value of β - 1 is 72.24°, the value of γ is 135.58°, the value of γ - 1 is 130.93°, the value of c is 3.68 mm, the value of e is 3.28 mm, the value of f is 4.18 mm, the value of g is 4.14 mm, the value of D is 77.17 mm, the value of L1 is 52.36 mm, the value of L2 is 12.94 mm, the value of a is 2.83 mm, the value of θ is 90°, the value of φ is 90°, and the value of δ is 106.11°.

5. The biomimetic cactus spine negative Poisson's ratio energy absorption structure according to claim 1, wherein: The root of the outer rod (2) is thick and the head is thin, which is a design imitating the large thorns of the cactus. The vertical rod (4) is cut from the outer rod (2) with a certain length, and its root is thick and the head is thin, which is a design imitating the small thorns of the cactus.

6. The design method of a bionic cactus spine negative Poisson's ratio energy absorption structure according to any one of claims 1 to 5, characterized in that: It includes the following steps: S1. Using the principle of thick head and thin foot of the cactus thorns, establish a five-claw structure; S2. Design a circular ring (6) at the center of the five-claw structure.

7. The design method of a bionic cactus thorn negative Poisson's ratio energy absorption structure according to claim 6, characterized in that: In the step S1, after cutting off a part of the connecting roots of the inner rod (5), the outer rod (2), and the vertical rod (4) in the five-claw structure at a specific angle, seamless splicing is carried out at a certain angle, and the inner rod (5) and the outer rod (2) are connected by a cut surface connection.

8. A design method of a bionic cactus thorn negative Poisson's ratio energy absorption structure according to claim 6, characterized in that: In the step S2, the circular ring (6) and the five-claw structure are connected by the principle of bionic cactus spines, and the contact surface (8) between the head of the inner rod of the five-claw structure and the circular ring is tangent to the circular ring (6).

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