A buffer structure with negative stiffness and negative Poisson's ratio characteristics

Abstract

This invention discloses a buffer structure with negative stiffness and negative Poisson bit characteristics, which is composed of single-cell units arranged in a two-dimensional array. Each single-cell unit includes a first connecting beam, a second connecting beam, a crossbeam, a first side beam, a second side beam, and a bottom beam. The bottom beam is V-shaped, with one end fixed to one end of the first side beam and the other end fixed to one end of the second side beam. The other end of the first side beam is also fixed to the other end of the second side beam. The bottom beam is positioned between the first and second side beams, with one end fixed to the first side beam and the other end fixed to the second side beam, forming an isosceles triangle S with the first and second side beams. The lengths of the first and second connecting beams are half the length of the bottom beam, symmetrically positioned on both sides of the isosceles triangle S, with one end of the first connecting beam fixed to the first side beam and one end of the second connecting beam fixed to the second side beam. This invention exhibits two-stage compression characteristics, and its energy absorption performance is far superior to that of a single-configuration structure.

Description

Technical Field

[0001] This invention relates, and more particularly, to a buffer structure having negative stiffness and negative Poisson bit properties. Background Technology

[0002] In recent years, metamaterials have emerged rapidly and have been widely used in fields such as medicine, architecture, automobiles, and aerospace. Most metamaterials are materials that do not exist in nature and whose microstructures are artificially designed to give them special acoustic, optical, thermal, and mechanical properties. Some materials are used as buffer and vibration isolation media in the automotive or aerospace fields due to their special structure and mechanical properties. Negative stiffness materials and negative Poisson's ratio materials are typical examples.

[0003] The greater the displacement of a structure, the greater the force required. Therefore, the slope of the force-displacement curve is positive, which is called positive stiffness. Negative stiffness can be achieved through special design of the internal structure of the material, so that when the structure undergoes displacement under load, the greater the displacement, the smaller the force required. Negative stiffness materials are essentially arrays of multiple unit structures with negative stiffness characteristics, so negative stiffness is actually a structural property. Negative stiffness structures are often called multistable structures. When a structure is loaded, it undergoes elastic deformation. After the load is removed, the structure maintains its current shape. Applying a load again causes the structure to deform further, and removing the load again allows it to maintain its current shape. This is a multistable structure. Applying a reverse load can restore a multistable structure to its initial state, indicating that multistable structures can absorb and store energy, and under certain conditions, can even be reused.

[0004] A few materials with negative Poisson's ratio exist in nature, but most existing negative Poisson's ratio materials are artificially manufactured and are mostly porous materials. Essentially, they are cellular materials composed of arrays of multiple unit structures with negative Poisson's ratio properties; however, at the microscopic level, they exhibit a positive Poisson's ratio. When subjected to axial tension (or compression), negative Poisson's ratio materials exhibit expansion (or contraction) in the vertical direction, also known as tensile expansion materials. Therefore, when subjected to impact loads and compression, negative Poisson's ratio materials will undergo lateral contraction on both sides, increasing their overall stiffness and significantly improving their load-bearing capacity. They possess excellent impact resistance, fracture resistance, and energy absorption and vibration isolation capabilities, thus being widely used in buffer and vibration damping devices in aerospace, shipbuilding, and automotive fields. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a buffer structure with negative stiffness and negative Poisson bit properties, addressing the deficiencies mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A buffer structure with negative stiffness and negative Poisson bit properties, wherein the buffer structure is plate-shaped and is composed of single-cell units arranged in a two-dimensional array.

[0008] The single cell unit includes a first connecting beam, a second connecting beam, a crossbeam, a first side beam, a second side beam, and a bottom beam;

[0009] The first connecting beam and the second connecting beam have the same structure, and the first side beam and the second side beam have the same structure.

[0010] The bottom beam is V-shaped, with one end fixedly connected to one end of the first side beam and the other end fixedly connected to one end of the second side beam; the other end of the first side beam is fixedly connected to the other end of the second side beam.

[0011] Let L be the straight line containing both ends of the bottom beam;

[0012] The crossbeam is parallel to the straight line L and is located between the first side beam and the second side beam. One end is fixed to the first side beam and the other end is fixed to the second side beam, forming an isosceles triangle S with the first side beam and the second side beam.

[0013] The lengths of the first connecting beam and the second connecting beam are half the length of the crossbeam. They are symmetrically arranged on both sides of the isosceles triangle S. One end of the first connecting beam is fixed to the first side beam, and one end of the second connecting beam is fixed to the second side beam. The first connecting beam and the second connecting beam are collinear on the straight line M.

[0014] The turning point of the bottom beam and the crossbeam are located on both sides of the straight line L, and the distance from the end of the first side beam away from the bottom beam to the straight line M is equal to the distance between the turning point of the bottom beam and the straight line L.

[0015] In a single-cell unit, the end of the first side beam furthest from the bottom beam is positioned at the top, the first connecting beam is positioned on the left, the second connecting beam is positioned on the right, and the bottom beam is positioned at the bottom. When the single-cell units are arrayed in a two-dimensional array, the end of the first side beam furthest from the bottom beam of the single-cell unit is fixedly connected to the turning point of the bottom beam of the adjacent single-cell unit above it, the first connecting beam of the single-cell unit is fixedly connected to the second connecting beam of the adjacent single-cell unit to its left, the second connecting beam of the single-cell unit is fixedly connected to the first connecting beam of the adjacent single-cell unit to its right, and the turning point of the bottom beam of the single-cell unit is fixedly connected to the end of the first side beam furthest from the bottom beam of the adjacent single-cell unit below it.

[0016] As a further optimization of the buffer structure with negative stiffness and negative Poisson bit characteristics of the present invention, the bottom beam includes a first sine curve segment and a second sine curve segment;

[0017] The first sine curve segment and the second sine curve segment have the same structure and are symmetrically arranged, with one end of the first sine curve segment and one end of the second sine curve segment fixedly connected.

[0018] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0019] This invention features two stages of compression: the first stage is the buckling of the base edge of the sine curve of the cell triangle, which can be called the negative stiffness compression stage; the second stage is the compression of the upper triangular region, which can be called the negative Poisson's ratio compression stage. Macroscopically, the two stages can occur simultaneously, making the energy absorption characteristics of this invention far superior to those of a single-configuration structure. Attached Figure Description

[0020] Figure 1 This is a three-dimensional schematic diagram of the present invention;

[0021] Figure 2 This is a schematic diagram of the structure of the monomer cell in this invention;

[0022] Figure 3 This is a two-dimensional schematic diagram of the structure of the present invention;

[0023] Figure 4 This is a schematic diagram of the buffer operation of the present invention;

[0024] Figure 5 This is a diagram showing the experimental and simulation relationship between the buffer force and displacement of the present invention.

[0025] In the diagram, 1-first side beam, 2-second side beam, 3-first connecting beam, 4-second connecting beam, 5-crossbeam, 6-bottom beam. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings:

[0027] This invention can be implemented in many different forms and should not be considered limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully express the scope of the invention to those skilled in the art. In the drawings, components are enlarged for clarity.

[0028] It should be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, and / or parts, these elements, components, and / or parts are not limited by these terms. These terms are merely used to distinguish elements, components, and / or parts from one another. Therefore, the first element, component, and / or part discussed below may be a second element, component, or part without departing from the teachings of this invention.

[0029] like Figure 1 As shown, the present invention discloses a buffer structure with negative stiffness and negative Poisson bit properties. The buffer structure is plate-shaped and is formed by arranging single-cell units in a two-dimensional array.

[0030] like Figure 2 As shown, the single-cell unit includes a first connecting beam, a second connecting beam, a crossbeam, a first side beam, a second side beam, and a bottom beam;

[0031] The first connecting beam and the second connecting beam have the same structure, and the first side beam and the second side beam have the same structure.

[0032] The bottom beam is V-shaped, with one end fixedly connected to one end of the first side beam and the other end fixedly connected to one end of the second side beam; the other end of the first side beam is fixedly connected to the other end of the second side beam.

[0033] Let L be the straight line containing both ends of the bottom beam;

[0034] The crossbeam is parallel to the straight line L and is located between the first side beam and the second side beam. One end is fixed to the first side beam and the other end is fixed to the second side beam, forming an isosceles triangle S with the first side beam and the second side beam.

[0035] The lengths of the first connecting beam and the second connecting beam are half the length of the crossbeam. They are symmetrically arranged on both sides of the isosceles triangle S. One end of the first connecting beam is fixed to the first side beam, and one end of the second connecting beam is fixed to the second side beam. The first connecting beam and the second connecting beam are collinear on the straight line M.

[0036] The turning point of the bottom beam and the crossbeam are located on both sides of the straight line L, and the distance from the end of the first side beam away from the bottom beam to the straight line M is equal to the distance between the turning point of the bottom beam and the straight line L.

[0037] In a single-cell unit, the end of the first side beam furthest from the bottom beam is positioned at the top, the first connecting beam is positioned on the left, the second connecting beam is positioned on the right, and the bottom beam is positioned at the bottom. When the single-cell units are arrayed in a two-dimensional array, the end of the first side beam furthest from the bottom beam of the single-cell unit is fixedly connected to the turning point of the bottom beam of the adjacent single-cell unit above it, the first connecting beam of the single-cell unit is fixedly connected to the second connecting beam of the adjacent single-cell unit to its left, the second connecting beam of the single-cell unit is fixedly connected to the first connecting beam of the adjacent single-cell unit to its right, and the turning point of the bottom beam of the single-cell unit is fixedly connected to the end of the first side beam furthest from the bottom beam of the adjacent single-cell unit below it.

[0038] like Figure 3 As shown, during array formation, the present invention creates inverted new single-cell units between adjacent single-cell units. The present invention can be freely extended in the thickness direction according to specific requirements.

[0039] Both sides of the V-shaped bottom beam can be sinusoidal curves, namely the first sinusoidal curve segment and the second sinusoidal curve segment;

[0040] The first sine curve segment and the second sine curve segment have the same structure and are symmetrically arranged, with one end of the first sine curve segment and one end of the second sine curve segment fixedly connected.

[0041] like Figure 4 As shown, this invention exhibits negative stiffness characteristics in the early stage of compression. However, due to the constraint of the triangular crossbeam in the cell, the negative Poisson's ratio effect decreases in the later stage, but it still exhibits certain negative Poisson's ratio characteristics. In the early stage of compression, the stiffness of the base edge of the triangular sine curve is less than that of the upper triangular region, and buckling occurs first. Due to the effect of the triangular crossbeam, the stiffness of the arch structure formed by the base edge of the triangular sine curve and the crossbeam increases after buckling, exceeding that of the upper triangular region. At this point, the triangular region begins to compress. Therefore, this invention has the characteristic of two-stage compression: the first stage is the buckling of the base edge of the triangular sine curve, which can be called the negative stiffness compression stage; the second stage is the compression of the upper triangular region, which can be called the negative Poisson's ratio compression stage. Macroscopically, the two stages can occur simultaneously, making the energy absorption characteristics of this invention far superior to those of a single-configuration structure. Figure 5 The experimental and simulation relationship diagrams of the buffer force-displacement of the present invention clearly demonstrate the superior performance of the present invention.

[0042] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0043] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A buffer structure with negative stiffness and negative Poisson bit properties, characterized in that, The buffer structure is flat and is composed of single-cell units arranged in a two-dimensional array. The single cell unit includes a first connecting beam, a second connecting beam, a crossbeam, a first side beam, a second side beam, and a bottom beam; The first connecting beam and the second connecting beam have the same structure, and the first side beam and the second side beam have the same structure. The bottom beam is V-shaped, with one end fixedly connected to one end of the first side beam and the other end fixedly connected to one end of the second side beam; the other end of the first side beam is fixedly connected to the other end of the second side beam. Let L be the straight line containing both ends of the bottom beam; The crossbeam is parallel to the straight line L and is located between the first side beam and the second side beam. One end is fixed to the first side beam and the other end is fixed to the second side beam, forming an isosceles triangle S with the first side beam and the second side beam. The lengths of the first connecting beam and the second connecting beam are half the length of the crossbeam. They are symmetrically arranged on both sides of the isosceles triangle S. One end of the first connecting beam is fixed to the first side beam, and one end of the second connecting beam is fixed to the second side beam. The first connecting beam and the second connecting beam are collinear on the straight line M. The turning point of the bottom beam and the crossbeam are located on both sides of the straight line L, and the distance from the end of the first side beam away from the bottom beam to the straight line M is equal to the distance between the turning point of the bottom beam and the straight line L. In a single-cell unit, the end of the first side beam furthest from the bottom beam is positioned at the top, the first connecting beam is positioned on the left, the second connecting beam is positioned on the right, and the bottom beam is positioned at the bottom. When the single-cell units are arrayed in a two-dimensional array, the end of the first side beam furthest from the bottom beam of the single-cell unit is fixedly connected to the turning point of the bottom beam of the adjacent single-cell unit above it, the first connecting beam of the single-cell unit is fixedly connected to the second connecting beam of the adjacent single-cell unit to its left, the second connecting beam of the single-cell unit is fixedly connected to the first connecting beam of the adjacent single-cell unit to its right, and the turning point of the bottom beam of the single-cell unit is fixedly connected to the end of the first side beam furthest from the bottom beam of the adjacent single-cell unit below it.

2. The buffer structure with negative stiffness and negative Poisson bit properties according to claim 1, characterized in that, The bottom beam includes a first sine curve segment and a second sine curve segment; The first sine curve segment and the second sine curve segment have the same structure and are symmetrically arranged, with one end of the first sine curve segment and one end of the second sine curve segment fixedly connected.

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