A negative Poisson's ratio structure based on rotating rod unit

Abstract

The present invention discloses a negative Poisson's ratio structure based on a rotating rod unit, including a plurality of rotating rod units, which are periodically arranged and combined in a plane, wherein the rotating rod unit includes two compliant curved beam units, four bent rods and two straight rods, wherein the two compliant curved beam units are connected between the two straight rods and are symmetrically distributed, wherein the four bent rods are connected to the two compliant curved beam units and are symmetrically distributed, wherein the left and right adjacent rotating rod units are directly connected via symmetrical bent rod ends, and the upper and lower adjacent rotating rod units are directly connected via symmetrical straight rod ends. The negative Poisson's ratio structure based on the rotating rod unit provided by the present invention is simple, effective, and easy to manufacture, and has the advantages of small stress concentration and convenient energy storage and conversion.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical metamaterial structure design, and in particular to a negative Poisson's ratio structure based on a rotating rod unit. Background Art

[0002] Compared with traditional materials, negative Poisson's ratio materials have unique mechanical properties, such as expansion when stretched and contraction when compressed. They also have advantages in shear bearing capacity, fracture resistance, energy absorption and indentation resistance. Negative Poisson's ratio materials have physical properties such as light weight, high damping, sound absorption and heat insulation, and play an important role in functional materials. They have been applied in the medical and aerospace fields, such as smart medical bandages, esophageal stents and negative Poisson's ratio honeycomb chord side protection structures.

[0003] However, the types of existing negative Poisson's ratio materials are limited, and there is little choice in application. In addition, the unit structure is becoming more and more complex, and the difficulty of preparation is increasing, which limits its practical application. Therefore, designing a new type of negative Poisson's ratio structure with a simple structure has important theoretical significance and application value. Summary of the invention

[0004] The purpose of the present invention is to provide a negative Poisson's ratio structure based on a rotating rod unit to address the problems existing in the prior art, and to achieve negative Poisson's ratio characteristics using a simpler microstructure.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A negative Poisson's ratio structure based on a rotating rod unit comprises a plurality of rotating rod units, wherein the rotating rod unit comprises two compliant curved beam units, four bent rods and two straight rods, wherein the two compliant curved beam units are connected between the two straight rods and are symmetrically distributed, and the four bent rods are connected to the two compliant curved beam units and are symmetrically distributed; the rotating rod units adjacent to each other on the left and right are directly connected via symmetrical bent rod ends, and the rotating rod units adjacent to each other on the top and bottom are directly connected via symmetrical straight rod ends.

[0007] Furthermore, the plurality of rotating rod units are periodically arranged and combined in a plane.

[0008] Furthermore, the ratio of the width of the straight rod to the width of the compliant curved beam unit is 3:1.

[0009] Furthermore, the ratio of the width of the compliant curved beam unit to the width of the curved rod is 1:1.

[0010] Furthermore, the ratio of the length of the compliant curved beam unit to the length of the bending rod is 1:1.

[0011] Furthermore, the curved rod has a straight portion, and the angle between the straight portion of the curved rod and the x-axis is 27°.

[0012] Compared with the prior art, the present invention has the following beneficial technical effects:

[0013] The negative Poisson's ratio structure based on the rotating rod unit provided by the present invention has the characteristics of expanding perpendicular to the direction of tension when stretched and contracting perpendicular to the direction of pressure when compressed. The negative Poisson's ratio structure based on the rotating rod unit provided by the present invention realizes the negative Poisson's ratio effect through the bending moment at the connection between the flexible curved beam unit and the curved rod. The flexible curved beam unit has the advantages of small stress concentration and convenient energy storage and conversion. This negative Poisson's ratio mechanism is novel, and its structure is simple, effective, and easy to prepare, which increases the room for choice in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic structural diagram of a compliant curved beam unit in a rotating rod unit of the present invention;

[0015] Figure 2 It is a structural schematic diagram of the rotating rod unit of the present invention;

[0016] Figure 3 It is a structural schematic diagram of a negative Poisson's ratio structure based on a rotating rod unit of the present invention;

[0017] Figure 4 This is a displacement cloud diagram of a material in the X direction when a negative Poisson's ratio structure based on a rotating rod unit is pulled in the Y direction according to the present invention;

[0018] In the figure, 1-straight rod, 2-bent rod, 3-compliant curved beam element. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0020] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0021] like Figure 1-3As shown, a negative Poisson's ratio structure based on a rotating rod unit in this embodiment includes multiple rotating rod units, and the rotating rod unit includes two straight rods 1, four curved rods 2 and two flexible curved beam units 3. The two flexible curved beam units 3 are connected between the two straight rods 1 and are symmetrically distributed. The four curved rods 2 are connected to the two flexible curved beam units 3 and are symmetrically distributed. The left and right adjacent rotating rod units are directly connected through the symmetrical ends of the curved rods 2, and the upper and lower adjacent rotating rod units are directly connected through the symmetrical ends of the straight rods 1. Multiple rotating rod units are periodically arranged and combined in a plane to form a negative Poisson's ratio structure.

[0022] The ratio of the width of the straight rod 1 to the width of the compliant curved beam unit 3 is 3: 1. This can avoid forming a sharp angle when the two ends of the two curved beam units are close together, thereby avoiding stress concentration.

[0023] The ratio of the width of the flexible curved beam unit 3 to the width of the bent rod 2 is 1:1, the ratio of the length of the bent rod 2 to the length of the flexible curved beam unit 3 is 1:1, the length of the bent rod is the vertical distance between the two farthest points on the bent rod, the length of the flexible curved beam unit is the distance between the two end faces, and the straight part of the bent rod 2 is at an angle of 27° with the x-axis.

[0024] When a negative Poisson's ratio structure based on rotating rod units is subjected to tension in the y-axis direction, the flexible curved beam unit of each rotating rod unit will be straightened. At the same time, since each flexible curved beam unit is also connected to a bent rod, the flexible curved beam unit will give the bent rod a bending moment, so that the flexible curved beam unit will drive the bent rod to rotate in the plane; the difference in deformation caused by the bending moment will cause the two-dimensional negative Poisson's ratio structure to have a negative Poisson's ratio effect on a macroscopic scale.

[0025] Finite element analysis software was used to simulate and verify the negative Poisson's ratio effect of the negative Poisson's ratio structure designed in the present invention. After the solid model was established in Solidworks software, it was imported into ANSYS software for finite element analysis. The elastic modulus in the linear elastic material properties was set to 3Gpa, the Poisson's ratio was set to 0.38, and the C3D10 tetrahedron unit was used. Some simulation results are shown in Figure 2. Figure 4 As shown in the figure, it can be seen from the schematic diagram of the structure under stress and deformation that when a tensile displacement load is applied in the y-axis direction, an obvious expansion occurs in the x-direction, showing a significant negative Poisson's ratio effect.

[0026] Although the specific embodiments of the present invention are described above, it should be understood by those skilled in the art that this is only for illustration and the protection scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A negative Poisson's ratio structure based on a rotating rod unit, characterized in that: It comprises a plurality of rotating rod units, wherein the rotating rod units comprise two compliant curved beam units, four bent rods and two straight rods; the two compliant curved beam units are connected between the two straight rods and are symmetrically distributed; the four bent rods are connected to the two compliant curved beam units and are symmetrically distributed; the rotating rod units adjacent to each other on the left and right are directly connected via symmetrical bent rod ends, and the rotating rod units adjacent to each other on the top and bottom are directly connected via symmetrical straight rod ends.

2. A negative Poisson's ratio structure based on a rotating rod unit according to claim 1, characterized in that: The plurality of rotating rod units are periodically arranged and combined in a plane.

3. A negative Poisson's ratio structure based on a rotating rod unit according to claim 1, characterized in that: The ratio of the width of the straight rod to the width of the compliant curved beam unit is 3:

1.

4. A negative Poisson's ratio structure based on a rotating rod unit according to claim 1, characterized in that: The ratio of the width of the compliant curved beam unit to the width of the curved rod is 1:

1.

5. A negative Poisson's ratio structure based on a rotating rod unit according to claim 1, characterized in that: The ratio of the length of the compliant curved beam unit to the length of the curved rod is 1:

1.

6. A negative Poisson's ratio structure based on a rotating rod unit according to claim 1, characterized in that: The bent rod has a straight portion, and the angle between the straight portion of the bent rod and the x-axis is 27°.

Images