Negative Poisson's ratio mechanical metamaterial anti-collision energy-absorbing device

Abstract

The utility model relates to the field of metamaterials, in particular to a negative Poisson's ratio mechanical metamaterial anti-collision energy-absorbing device which comprises a plurality of cell element structures, each cell element structure comprises a first pressure-torsion unit and a second pressure-torsion unit, and each first pressure-torsion unit and each second pressure-torsion unit are each of a cube hollow structure formed by connecting six chiral structures. The chiral structure is a structure that the periphery of a circular ring is connected with an extending ligament along the tangential direction, the ligament of the chiral structure in the first pressing and twisting unit extends clockwise along the tangential direction of the circular ring, and the ligament of the chiral structure in the second pressing and twisting unit extends anticlockwise along the tangential direction of the circular ring; the two first pressing and twisting units and the two second pressing and twisting units are arranged at intervals according to the mode of rotating the square structure to form a cell element structure. The mechanical metamaterial has two types of deformations of compression torsion and rotation in the compression process, and the two types of deformations both have energy absorption performance, so that the mechanical metamaterial has better energy absorption and vibration reduction performance.

Description

Technical Field

[0001] The utility model relates to the field of metamaterials, in particular to a negative Poisson's ratio mechanical metamaterial anti-collision energy absorption device. Background Art

[0002] Metamaterials are artificial materials with extraordinary physical properties not found in natural materials. Their most significant characteristic is that their properties are derived from their artificially designed internal structures. After years of development, metamaterials have been widely applied in fields such as electromagnetism, optics, acoustics, thermodynamics, and mechanics.

[0003] In the research of mechanical metamaterials, a class of metamaterials exhibits the mechanical phenomenon of negative Poisson's ratio. Due to their excellent shear resistance, indentation resistance, fracture resistance, surface isotropy, permeability variability, and energy absorption, they are widely used in aerospace, semiconductors, optical components, precision instruments, and architecture. Poisson's ratio describes the phenomenon in which a material undergoes simultaneous longitudinal deformation when subjected to an external force. While generally, a material undergoes longitudinal contraction when stretched transversely, negative Poisson's ratio materials exhibit the opposite deformation. The fundamental reason for the anomalous mechanical properties of negative Poisson's ratio metamaterials lies unrelated to the material itself, but rather stems from the fundamental cellular structure of its constituent materials. Based on the deformation mechanism, negative Poisson's ratio metamaterial structures can be categorized as concave, rotated polygonal, chiral, perforated, sheet-like, corrugated, node-fiber, and interlocking polygonal. Rotated polygonal structures are typically composed of rigid polygons connected by vertices. Rotation of the rigid body results in changes in the internal voids within the structure, producing a negative Poisson's ratio effect. Chiral structure refers to a structural property that has mirror symmetry but cannot be completely overlapped. Depending on the number of tangential connecting ligaments in each ring, there are five main types: three-ligament chirality / counter-chirality, four-ligament chirality / counter-chirality and six-ligament chiral superstructures.

[0004] Mechanical metamaterials exhibit the mechanical phenomenon of negative Poisson's ratio. Due to their excellent shear resistance, indentation resistance, fracture resistance, surface isotropy, permeability variability, and energy absorption, they are widely used in fields such as marine ships, aerospace, precision instruments, and engineering construction. However, the cellular structure of metamaterials is complex, and traditional manufacturing processes are unable to meet the requirements of trial production of their prototypes, thus limiting the research work on new metamaterials. With the rise of micro-nano manufacturing technology and 3D printing technology, the manufacture of ultra-complex structural parts has become possible, which has also brought opportunities for the development of metamaterials. With the increasing application of negative Poisson's ratio metamaterials in various industries, the existing negative Poisson's ratio metamaterial structures can no longer meet market demand. How to design more negative Poisson's ratio metamaterial structures has become an urgent problem that needs to be solved. Summary of the Invention

[0005] This utility model designs a new type of negative Poisson's ratio metamaterial structure by combining a compression-torsion module composed of chiral units and a rotating polygonal structure, and produces samples through 3D printing technology for performance testing. The verification results show that the structure can achieve diverse expressions of material deformation characteristics by changing the cell connection method and setting different initial configurations.

[0006] The technical solutions adopted in this utility model are as follows:

[0007] A negative Poisson's ratio mechanical metamaterial anti-collision energy absorption device includes multiple cellular structures, wherein the cellular structure includes a first compression-torsion unit and a second compression-torsion unit. The first compression-torsion unit and the second compression-torsion unit are both cubic hollow structures composed of six connected chiral structures. The chiral structure is a structure with extended ligaments connected along the tangential direction of the ring. The ligaments of the chiral structure in the first compression-torsion unit extend clockwise along the tangential direction of the ring, and the ligaments of the chiral structure in the second compression-torsion unit extend counterclockwise along the tangential direction of the ring. The ligaments of the chiral structures on two adjacent faces of the cubic hollow structure are connected to each other, and the center points of the rings on the two opposite faces are on the same straight line; the two first compression-torsion units and the two second compression-torsion units are arranged at intervals in the manner of a rotated square structure to form a cellular structure.

[0008] Furthermore, the inner diameter of the ring in the chiral structure is 5-8 mm, the outer diameter is 6-9 mm, and the width is 1 mm; the width of the ligament is 1-2 mm.

[0009] Furthermore, the height of the cube hollow structure is 10 mm.

[0010] Furthermore, two adjacent compression-torsion units on the same plane are connected at the edges of the cube by means of rotational connection, and the compression-torsion units on two adjacent upper and lower planes are connected by means of surface-to-surface fixing.

[0011] Furthermore, in the cell structures on the upper and lower planes, the first compression-torsion units and the second compression-torsion units are staggered and distributed.

[0012] Furthermore, the chiral structure is a four-ligament chiral structure, and the ligaments are evenly distributed around the ring.

[0013] The compression-torsion unit of this utility model is a cubic structure composed of six chiral structures. When compressed, it twists in the direction of the pressure, causing the upper and lower surfaces to shift without changing their shapes. By replacing the square rigid body in the two-dimensional rotating square structure with the compression-torsion unit, a new three-dimensional negative Poisson's ratio metamaterial structure can be developed. This metamaterial structure possesses diverse deformation capabilities, exhibiting different deformation behaviors when subjected to external forces in different directions, and altering its initial position can also change the deformation characteristics of the material structure.

[0014] Compared with the existing technology, the mechanical metamaterial anti-collision energy absorption device of the utility model has the following advantages:

[0015] During the compression process, there are two types of deformation: compression-torsion and rotation. Both types of deformation are energy-absorbing and have better energy absorption and vibration reduction performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the structure of the first compression-torsion unit and the second compression-torsion unit of the mechanical metamaterial anti-collision energy absorption device in an embodiment.

[0017] Figure 2 Schematic diagram of the structure of the mechanical metamaterial anti-collision energy absorption device in Example 1.

[0018] Figure 3 Schematic diagram of the structure of the cell structure of the mechanical metamaterial anti-collision energy absorption device in Example 2.

[0019] Figure 4 This is a simulation analysis model diagram of negative Poisson's ratio mechanical metamaterial.

[0020] Figure 5 This is the simulation analysis result of the negative Poisson's ratio mechanical metamaterial structure.

[0021] Figure 6 This is a curve diagram of the angle change data of the simulation analysis of the negative Poisson's ratio mechanical metamaterial structure.

[0022] Figure 7 State change diagram of the model sample for the performance test of negative Poisson's ratio mechanical metamaterial.

[0023] Figure 8 A graph showing the angle variation data of a model sample from the performance test of a negative Poisson's ratio mechanical metamaterial. DETAILED DESCRIPTION

[0024] In order to more clearly understand the above-mentioned purposes, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0025] Example 1

[0026] like Figures 1 and 2The negative Poisson's ratio mechanical metamaterial anti-collision energy absorption device shown is composed of a plurality of cell structures. The cell structure includes a first compression-torsion unit and a second compression-torsion unit. The first compression-torsion unit and the second compression-torsion unit are both cube hollow structures composed of six chiral structures connected together. The chiral structure is a structure with extended ligaments connected along the tangential direction of the ring. In this embodiment, the chiral structure is a four-ligament chiral structure, and the ligaments are evenly spaced around the ring. Among them, the ligaments of the chiral structure in the first compression-torsion unit extend clockwise along the tangential direction of the ring, as shown in FIG. Figure 1 As shown in (a); the ligament of the chiral structure in the second compression-torsion unit extends counterclockwise along the tangent direction of the ring, as shown in Figure 1 As shown in (b) of the figure, the chiral ligaments of two adjacent faces of the hollowed-out cube structure of the compression-torsion unit are connected to each other, and the center points of the rings on the two opposite faces are on the same straight line; two first compression-torsion units and two second compression-torsion units are arranged in a rotated square structure with intervals between them to form a cell structure.

[0027] In this embodiment, the inner diameter of the ring in the chiral structure is 5-8 mm, the outer diameter is 6-9 mm, and the width is 1 mm; the width of the ligament is 1-2 mm. In this embodiment, the height of the cube hollow structure is 10 mm.

[0028] In this embodiment, two adjacent compression-torsion units on the same plane are connected at the edges of the cube by means of a rotational connection.

[0029] Example 2

[0030] like Figure 3 As shown in Figure 1, based on Example 1, the negative Poisson's ratio mechanical metamaterial anti-collision and energy absorption device in this embodiment has the first and second compression-torsion units arranged in a staggered arrangement within the cell structures on the upper and lower planes. This design increases the torsional deformation direction of the mechanical metamaterial, enhancing the shock absorption and collision absorption capabilities of the negative Poisson's ratio mechanical metamaterial anti-collision and energy absorption device.

[0031] In this embodiment, the inner diameter of the ring in the chiral structure is 5-8 mm, the outer diameter is 6-9 mm, and the width is 1 mm; the width of the ligament is 1-2 mm. In this embodiment, the height of the cube hollow structure is 10 mm.

[0032] The cell structure of the negative Poisson's ratio mechanical metamaterial anti-collision energy absorption device of the present invention involves two types of compression-torsion units, namely the first compression-torsion unit and the second compression-torsion unit. The first compression-torsion unit and the second compression-torsion unit are both cubes made of six chiral structures, and are a hollow structure. The first compression-torsion unit is a cube that produces clockwise twisting after being compressed, and the second compression-torsion unit is a cube that produces counterclockwise twisting after being compressed. The two compression-torsion units are arranged and combined in a rotating square manner to form a new negative Poisson's ratio cell structure, such as Figure 3 As shown in (a) in the figure. This kind of negative Poisson's ratio mechanical metamaterial composed of cellular structure has two deformation modes when subjected to external force in the initial configuration. One is the compression-torsion deformation of the compression-torsion unit in the cellular structure, as shown in Figure 3 As shown in (b); the other is the deformation of the square connection of the cell structure, as shown in Figure 3 (c) in the figure. This also illustrates the diverse deformation modes of the cell structure constructed in this manner. Therefore, this negative Poisson's ratio mechanical metamaterial has superior energy absorption and vibration reduction capabilities. Furthermore, the negative Poisson's ratio mechanical metamaterial of the present invention can produce different deformation modes under different external forces, thus having a wider range of applications.

[0033] (1) Simulation analysis of negative Poisson's ratio mechanical metamaterials

[0034] To verify the performance of this cellular metamaterial, a prototype metamaterial constructed from the cellular structure described in Example 2 was fabricated using 3D printing technology. Performance simulations and experimental analysis were then conducted. An equivalent analysis model was constructed using the metamaterial's smallest unit structure (i.e., the cellular structure) as the analysis object. The deformation patterns of the unit structure were then determined through simulation analysis.

[0035] General finite element analysis software was used to simulate and analyze the negative Poisson's ratio metamaterial designed in this utility model. With the development of computer technology, the simulation capabilities of virtual simulation software have continued to improve. Performing simulation analysis before product sample trial production can effectively improve the product's success rate. Virtual simulation has become a key step in the product development cycle. Since the metamaterial designed in this utility model is composed of multiple groups of units, selecting a minimum unit (a cell structure composed of four compression-torsion unit intervals) for simulation analysis can verify its feasibility. The specific simulation process is carried out as follows:

[0036] (1.1) A 3D structural model of the negative Poisson's ratio metamaterial was constructed using the 3D modeling software SolidWorks. Considering that the deformation of the metamaterial is related to its cellular structure rather than the material itself, and to facilitate the subsequent 3D printing of metamaterial prototypes and their performance characterization, nylon was selected as the material for finite element analysis. The material parameters of nylon PA6 are shown in Table 1.

[0037] Table 1 Parameters of nylon PA6 material:

[0038] name Elastic modulus GPa Poisson's ratio <![CDATA[Density kg / m 3 > Yield stress MPa value 8.3 0.28 1400 139

[0039] (1.2) Finite element analysis was performed using the Simulation analysis module in Solidworks software. Static loading was applied to the model, constraints and loads were added, a vertical downward force of 1000N was applied to the top of the model, a fixed constraint was added to the bottom of the model, and a 2×10 6 N / ㎡ pressure, the direction is vertically upward. The simulation parameter settings are shown in Table 2, and the finite element analysis model is as follows Figure 4 shown.

[0040] Table 2 Finite element analysis parameter settings:

[0041] External loads Force N Pressure N / ㎡ value 1000 <![CDATA[2×10 6 ]]>

[0042] (1.3) After analysis and calculation by the software, the analysis results are exported. Figure 5 The figure shows the simulation analysis results of the negative Poisson's ratio mechanical metamaterial structure. The image clearly and intuitively shows the material structure and its deformation under a given force. Figure 5 (a) is the initial state of compression, Figure 5 (b) and Figure 5 (c) in the figure is the state during compression. Figure 5 (d) in the figure is the end state of compression. Figure 5 (e) in FIG. 5 represents the superposition state of the initial compression state and the final compression state.

[0043] In order to obtain the specific situation of the simulated structural deformation, the two adjacent angles α and θ of the cube compression and torsion unit in the cell structure are defined. Figure 5 From (a) to (d) in the figure, it can be clearly seen that the angle α increases from 90° to 170° during the simulation. The angle θ decreases from 90° to 30°, and the compression-torsion unit as a whole also produces a 35° twist. The angle change data curve is shown in the figure. Figure 6 The results of finite element simulation analysis show that the structure composed of the designed compression-torsion units can achieve torsional motion under compression.

[0044] (2) Preparation of negative Poisson's ratio metamaterial samples using additive manufacturing technology

[0045] Because the new negative Poisson's ratio metamaterial designed in this utility model has a hollow structure, samples were produced using a 3D photocuring method using resin materials. 3D printing is a well-established rapid prototyping technology. Based on a digital model file, it utilizes adhesive materials such as powdered metal and plastic to create an object layer by layer. The 3D printer used in this utility model is an industrial-grade SLA600 photocuring machine manufactured by Guangzhou Stereo Easy.

[0046] According to the principles of 3D printing, SolidWorks software was first used to construct a 3D model of the metamaterial. The 3D model in Part format was then exported to STL format. The STL data file was then imported into Magics software for slicing. Parameters such as layer thickness, number of bottom layers, exposure time, bottom layer exposure time, and scraper speed were set. Considering the complex cellular structure of the metamaterial sample, the travel speed of the stereolithography machine's work platform was set to 5 mm / s, and the scraper speed was set to 20 mm / s (the scraper speed is typically set to 50 mm / s for model printing).

[0047] (3) Performance test of negative Poisson's ratio mechanical metamaterials

[0048] The printed samples were tested and verified using a Zwick-010 universal material testing machine produced by the German Zwick Roell Group. During the compression test, a high-speed camera was used to capture the entire compression process frame by frame, mainly capturing the deformation process of each marked unit on the test piece, so that the pixel length and frame time can be used for data processing to calculate the Poisson's ratio.

[0049] The compression test is carried out by position control. Figure 7 As shown, Figure 7 (a) is the initial state of compression, Figure 7 (b) is the state during compression. Figure 7 (c) in the figure is the state at the end of compression. Figure 7 It can be clearly seen that the angle of the cell structure is constantly changing. In order to show the deformation of the material, two adjacent angles α and θ of a square unit are defined as observation objects. The measured angle change data curve is shown in Figure 8 As shown. Figure 8 The test results show that the angle α increases from 90° to 160° during the compression test, the angle θ decreases from 90° to 20°, and the compression-torsion unit as a whole also produces a 34° torsion.

[0050] The experimental results are basically consistent with the results of finite element simulation analysis, indicating that the structure composed of the designed compression-torsion units is a three-dimensional mechanical metamaterial that can generate torsional motion under pressure.

[0051] Through virtual simulation and model sample test analysis, it was concluded that the three-dimensional negative Poisson's ratio mechanical metamaterial designed in this utility model will produce different types of deformation when subjected to pressure in different directions. The upper and lower surfaces of the compression-torsion unit that produces torsional deformation under pressure remain square and rotate in opposite directions. By alternating and stacking cubes that produce clockwise torsions under pressure and cubes that produce counterclockwise torsions under pressure and arranging them in the manner of rotating squares (a method of constructing negative Poisson's ratio metamaterial structures), a new type of negative Poisson's ratio metamaterial can be formed. A Cartesian coordinate system is established with the geometric center of the new metamaterial sample as the origin to analyze the diversity of its force deformation. Deformation 1: When the material is subjected to pressure in the Z-axis direction, it produces contraction deformation in both the X-axis and Y-axis directions; Deformation 2: When the material is subjected to pressure in the X-axis direction, it produces contraction deformation in the Y-axis direction, and the length in the Z-axis direction remains unchanged; Deformation 3: When the material is subjected to pressure in the Y-axis direction, it produces contraction deformation in the X-axis direction, and the length in the Z-axis direction remains unchanged. During the compression process, there are two types of deformation: compression-torsion and rotation, and both types of deformation have energy absorption properties. Therefore, the new negative Poisson's ratio metamaterial designed in the present invention has better energy absorption and vibration reduction performance and has a wider range of applications.

Claims

1. A negative Poisson's ratio mechanical metamaterial anti-collision energy absorption device, characterized in that: The invention comprises a plurality of cell structures, wherein the cell structure comprises a first compression-twist unit and a second compression-twist unit, wherein the first compression-twist unit and the second compression-twist unit are both cubic hollow structures composed of six chiral structures connected to each other, wherein the chiral structure is a structure with extended ligaments connected along the tangential direction around the ring, wherein the ligaments of the chiral structures in the first compression-twist unit extend clockwise along the tangential direction of the ring, and the ligaments of the chiral structures in the second compression-twist unit extend counterclockwise along the tangential direction of the ring; the two first compression-twist units and the two second compression-twist units are arranged at intervals in the manner of a rotated square structure to form a cell structure.

2. The negative Poisson's ratio mechanical metamaterial anti-collision energy absorption device according to claim 1, characterized in that: The inner diameter of the ring in the chiral structure is 5-8 mm, the outer diameter is 6-9 mm, and the width is 1 mm; the width of the ligament is 1-2 mm.

3. The negative Poisson's ratio mechanical metamaterial anti-collision energy absorption device according to claim 1, characterized in that: The height of the cube hollow structure is 10 mm.

4. The negative Poisson's ratio mechanical metamaterial anti-collision energy absorption device according to claim 1, characterized in that: Two adjacent compression-torsion units on the same plane are connected at the edges of the cube by a rotational connection, and the compression-torsion units on two adjacent upper and lower planes are connected by a surface-to-surface fixed connection.

5. The negative Poisson's ratio mechanical metamaterial anti-collision energy absorption device according to claim 1, characterized in that: In the cell structures on the upper and lower planes, the first compression-torsion unit and the second compression-torsion unit are staggered and distributed.

6. The negative Poisson's ratio mechanical metamaterial anti-collision energy absorption device according to claim 1, characterized in that: The chiral structure is a four-ligament chiral structure, and the ligaments are evenly distributed around the ring.

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