Mixed star-shaped mechanical metamaterial unit and metamaterial structure

Abstract

The invention discloses a mixed star-shaped mechanical metamaterial unit and a metamaterial structure, and relates to the technical field of metamaterial structures, the mixed star-shaped mechanical metamaterial unit comprises a concave polygonal honeycomb structure which is of a central symmetry structure and is provided with a long edge and short edges which are bent inwards, and two ends of the long edge are respectively connected with one ends of the two short edges to form a closed structure; the two concave polygonal honeycomb structures are respectively arranged along an X axis and a Y axis and have the same symmetric center, and the long sides of the two concave polygonal honeycomb structures define a star-shaped structure by taking the symmetric center as a base point; the short edge is bent inwards to form a mounting part matched with the vibration reduction assembly in shape, and the vibration reduction assembly is arranged on the mounting part; the straight line where the two ends of the short edge are located is a base line. The outer edge of the damping assembly is located outside the base line. Each mixed star-shaped mechanical metamaterial unit is composed of two inwards-concave polygonal honeycomb structures and a vibration reduction assembly, and has the large-load bearing capacity and the vibration isolation function.

Description

Technical Field

[0001] The present invention relates to the technical field of metamaterial structures, and in particular to a hybrid star-shaped mechanical metamaterial unit and a metamaterial structure. Background Art

[0002] Mechanical metamaterial structures are artificially designed structures that exhibit extraordinary physical properties that natural materials do not have. They break through the limitations of certain apparent natural laws through the design of various physical structures, thereby obtaining extraordinary material properties. They are widely used in aerospace, automobile manufacturing, ocean, and medical fields. At present, all fields require mechanical metamaterial structures to have high rigidity to carry large loads, and also require effective isolation of vibration during equipment operation, especially vibration isolation in low-frequency vibration environments. Existing mechanical metamaterial structures cannot meet the above requirements.

[0003] Honeycomb structure is a common form of metamaterial structure, which has excellent static properties such as light weight, high stiffness, high strength and potential vibration isolation performance. In view of this, how to provide a honeycomb mechanical metamaterial structure with large load bearing capacity and vibration isolation function is an urgent problem to be solved by technicians in this field. Summary of the invention

[0004] The purpose of the present invention is to provide a hybrid star-shaped mechanical metamaterial unit and a metamaterial structure to solve the problems existing in the prior art.

[0005] To achieve the above object, the present invention provides a hybrid star-shaped mechanical metamaterial unit, comprising:

[0006] The inward-concave polygonal honeycomb structure is a centrally symmetrical structure and has long sides and short sides that are bent inwardly, and the two ends of the long sides are respectively connected with one end of the two short sides to form a closed structure; the two inward-concave polygonal honeycomb structures are respectively arranged along the X-axis and the Y-axis and have the same symmetry center, and the long sides of the two inward-concave polygonal honeycomb structures are surrounded by a star-shaped structure with the symmetry center as the base point;

[0007] A vibration damping component, wherein the short side is bent inwardly to form a mounting portion adapted to the shape of the vibration damping component, and the vibration damping component is arranged on the mounting portion; the straight line where the two ends of the short side are located is the baseline, and the outer edge of the vibration damping component is located outside the baseline.

[0008] Furthermore, the inwardly concave polygonal honeycomb structure is an inwardly concave quadrangular honeycomb structure, and the star-shaped structure is a regular quadrangular star-shaped structure.

[0009] Furthermore, the vibration reduction assembly comprises:

[0010] A semicircular ring structure, adapted to the shape of the mounting portion and arranged on the mounting portion, and a mounting cavity is formed on the outer side of the semicircular ring structure;

[0011] A semicircular mass column is arranged in the installation cavity, and the outer edge of the semicircular mass column is located outside the baseline.

[0012] Furthermore, the center of the semicircular mass column and the straight line where the symmetry center is located are perpendicular to the baseline.

[0013] Furthermore, the long sides, short sides of the inwardly concave polygonal honeycomb structure and the semicircular ring structure have the same thickness.

[0014] Furthermore, the concave polygonal honeycomb structure and the semicircular ring structure are made of metal or plastic by 3D printing.

[0015] Furthermore, the cross-section of the short side is T-shaped, I-shaped, groove-shaped, box-shaped, polygonal, circular or elliptical.

[0016] The present invention also provides a hybrid star-shaped mechanical metamaterial structure, which is composed of a plurality of the hybrid star-shaped mechanical metamaterial units arranged in a matrix, and the semicircular mass columns of adjacent hybrid star-shaped mechanical metamaterial units are connected.

[0017] The present invention discloses the following technical effects:

[0018] The hybrid star-shaped mechanical metamaterial unit consists of two concave polygonal honeycomb structures and a vibration reduction component, which has a large load-bearing capacity and vibration isolation function.

[0019] For large load bearing, the present application adopts a method of cross-setting two concave polygonal honeycomb structures in the horizontal and vertical directions, and forming a star-shaped structure at the center. When the structure is loaded, the star-shaped structure can reduce the bending deformation of the long sides of the two concave polygonal honeycomb structures, thereby improving the load capacity. The short sides of the concave polygonal honeycomb structure are bent inward to form a mounting portion that matches the shape of the vibration reduction component. The vibration reduction component is arranged in the mounting portion to increase local stiffness and avoid stress concentration, further increasing the load capacity of the structure.

[0020] For vibration isolation, the vibration reduction component is set on the outside of the concave polygonal honeycomb structure, which can significantly change the overall mass distribution, thereby producing a local resonance effect in the low-frequency band. In addition, the vibration reduction component itself can also absorb the vibrating mass, flatten the dispersion curve, generate a band gap, and significantly improve the vibration reduction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 Schematic diagram of hybrid star-shaped mechanical metamaterial;

[0023] Figure 2 It is a schematic diagram of the hybrid star mechanical superstructure;

[0024] Figure 3 The band structure of the hybrid star-shaped mechanical metamaterial structure;

[0025] Figure 4 A graph showing the change in the first full bandgap frequency for structures with different ligament widths;

[0026] Figure 5 A graph showing the change in the first full bandgap frequency for structures with different baseline offset distances;

[0027] Figure 6 The curve diagram of the change of the first complete bandgap frequency for adjusting the structure with different horizontal fold angles;

[0028] Figure 7 The curve diagram of the change of the first complete bandgap frequency for adjusting different vertical fold angles;

[0029] Figure 8 A stress-strain curve comparison diagram of the hybrid star-shaped mechanical metamaterial structure of the embodiment of the present invention and a single concave quadrangular honeycomb structure of the same size under quasi-static compression is shown;

[0030] Fig. 9 is a deformation mode of an embodiment of the present invention under quasi-static compression simulation;

[0031] Fig.10 Comparison of stress-strain curves of structures with different ligament widths under quasi-static compression;

[0032] Fig.11 Comparison of stress-strain curves of structures with different baseline offset distances under quasi-static compression;

[0033] Fig.12 Comparison of stress-strain curves of structures with different horizontal angles under quasi-static compression;

[0034] Fig.13 Comparison of stress-strain curves of structures with different vertical bending angles under quasi-static compression;

[0035] Among them, 1. Hybrid star-shaped mechanical metamaterial unit; 2. Long side; 3. Short side; 4. Semicircular ring structure; 5. Semicircular mass column; 6. Star-shaped structure. DETAILED DESCRIPTION

[0036] The mechanical metamaterial structures for improving bearing capacity and vibration reduction in the prior art are as follows:

[0037] In terms of low-frequency vibration isolation, the main technical means at this stage include: (1) Constructing local resonance modes to obtain low-frequency broadband: The local resonance band gap boundary frequency of the mechanical metamaterial structure is determined by the eigenmode frequency corresponding to the lattice. By analyzing the relationship between structural parameters and band gap boundary frequency, the key structural parameters are adjusted to adjust the band gap range, thereby obtaining a low-frequency wide band gap. (2) Constructing a mass amplification mechanism to obtain a low-frequency band gap: The mass amplification effect can generate a band gap at low frequency through a small additional mass. The emergence of mass amplification structures is expected to solve the problems of large additional mass and narrow bandwidth faced by low-frequency vibration and noise reduction. (3) Obtaining a low-frequency band gap through structural design: By increasing the number of ligaments or mixing multiple structural designs, a low-frequency band gap can be achieved using only a single-phase material. Patents related to the above-mentioned technical means include: a star-shaped structure acoustic lining for an aero-engine proposed by Shenyang Aerospace University (application number: 202410390664.7); a negative Poisson's ratio honeycomb metamaterial proposed by Northwestern Polytechnical University (application number: 202310997961.3); an X-shaped negative Poisson's ratio local resonance module and its supporting metamaterial disk structure proposed by the National University of Defense Technology of the People's Liberation Army of China (application number: 202410860999.0); a chiral-diamond mechanical metamaterial based on mass amplification proposed by Shanghai University of Engineering Science (application number: 202410761932.1), etc.

[0038] In terms of improving bearing capacity, the main technical means at this stage include: (1) Hybrid design: Hybrid design refers to connecting the topological features of the existing cell configuration to form a new configuration. Improving the mechanical properties of honeycomb structures is a typical micro-scale design strategy. The new hybrid honeycomb retains the characteristics of the original honeycomb to a large extent and achieves better performance, and even new characteristics that cannot be achieved by the classical configuration. (2) Curved design: There are many curved structures in nature, such as shells of shells, woodpecker beaks, turtle shells and beetle forewings. They have high stiffness / strength and energy absorption to protect themselves. Due to their excellent mechanical properties, these curved structures have gradually developed in natural biology. In recent years, with the help of curved structures and bionic methods, lightweight honeycombs with curved ligaments have been proposed. (3) Reinforcement pillar design: Reinforcement pillars are strengthened by adjusting the thickness of the cell wall, changing the topological structure or matrix material of the key nodes and inserting additional ligaments to strengthen the key parts of the microstructure. Patents related to the above-mentioned technical means include: a new type of negative Poisson's ratio vehicle seat belt proposed by Hebei University of Technology (application number: 201910937637.6); a star-shaped diamond-shaped negative Poisson's ratio structure proposed by Chang'an University (application number: 202111153005.4); a negative Poisson's ratio metamaterial structure and design method proposed by the 719th Institute of China Shipbuilding Industry Corporation (application number: 202410181312.0); a metamaterial structure and its manufacturing method proposed by Yangzhou University (application number: 20231114369 0.1); a tile-shaped negative Poisson's ratio honeycomb metamaterial proposed by Wuhan University of Science and Technology (application number: 202311833257.0); a three-dimensional star-shaped negative Poisson's ratio structure proposed by Beijing University of Technology (application number: 202410086930.7); a three-dimensional zero Poisson's ratio mesostructure and its macrostructure based on star structure proposed by Wuyi University (application number 201910922838.9); an inward-concave negative Poisson's ratio metamaterial cell and honeycomb structure proposed by Southeast University (application number: 202111316592.4), etc. The main technologies that can simultaneously meet the requirements of load-bearing and vibration isolation are hierarchical structures and sandwich structures. The relevant patents include: a lightweight sandwich metamaterial plate with high load-bearing and low-frequency vibration isolation characteristics proposed by Shandong University of Science and Technology (application number: 202410806193.3); an ultra-low frequency and ultra-wideband omnidirectional metamaterial structure and wave-damping vibration isolator proposed by the National University of Defense Technology of the People's Liberation Army of China (application number: 202410056988.7), etc.

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] Example 1

[0042] An embodiment of the present invention provides a hybrid star-shaped mechanical metamaterial unit, comprising an inwardly concave polygonal honeycomb structure and a vibration reduction component.

[0043] The concave polygonal honeycomb structure is specifically a concave quadrangular honeycomb structure, which is a centrally symmetrical structure and has long sides 2 and short sides 3 that are bent inwards, and four bottom angles (acute angles) are formed at the junction of the long sides 2 and the short sides 3, and the overall shape is close to an elongated quadrangular star structure 6. The two ends of the long side 2 are connected to one end of the two short sides 3 to form a closed structure; the two concave polygonal honeycomb structures are arranged along the X-axis and the Y-axis respectively and have the same symmetry center (one of the concave polygonal honeycomb structures can be completely overlapped with the other concave polygonal honeycomb structure by rotating it 90°), the long sides 2 of the two concave polygonal honeycomb structures intersect and partially overlap, and the overlapping area is surrounded by a regular quadrangular star structure 6 with the symmetry center as the base point (the regular quadrangular star structure 6 is also a centrally symmetrical structure, and its symmetry center coincides with the symmetry center of the concave polygonal honeycomb structure). The short sides 3 of the two concave polygonal honeycomb structures are located on the outside of the star structure 6 in four directions: up, down, left, and right.

[0044] The short sides 3 of the two concave polygonal honeycomb structures are bent inward to form a mounting portion that matches the shape of the vibration damping component, and the vibration damping component is arranged on the mounting portion; the straight line where the two end ends of the short sides 3 are located is the baseline (virtual line), and the outer edge of the vibration damping component is located outside the baseline.

[0045] In this embodiment, the vibration reduction assembly includes: a semicircular ring structure 4, the short side 3 is bent inward to form an arc-shaped mounting portion that is compatible with the semicircular ring structure 4, the semicircular ring structure 4 is fixed on the mounting portion, and the outer side of the semicircular ring structure 4 forms a semicircular mounting cavity; a semicircular mass column 5 is arranged in the mounting cavity, the outer edge of the semicircular mass column 5 is located outside the baseline, the center of the semicircular mass column 5 and the straight line where the center of symmetry is located are perpendicular to the baseline, and when the structure is loaded, the load is transmitted by the semicircular mass column 5.

[0046] In the above arrangement, the semicircular ring structure 4 is fixed to the outer side of the short side 3 in a tangential posture. When the structure is loaded, the semicircular ring structure 4 can effectively avoid stress concentration and greatly improve the structural rigidity.

[0047] The concave polygonal honeycomb structure and the semicircular ring structure 4 are made of metal or plastic 3D printing. The semicircular mass column 5 is made of high-density materials such as metal, which significantly changes the mass distribution of the entire structure, thereby generating a local resonance mode in the low-frequency band. At the same time, the semicircular mass column 5 has enough mass to absorb vibration energy, which can flatten the dispersion curve and generate a band gap. This highlights the significant impact of local mass on the vibration performance of the metamaterial.

[0048] When the structure generates load in the X-axis direction or the Y-axis direction, the semicircular mass column 5 compresses different long sides 2 to cause them to bend and deform. No matter which direction the load is generated, the star-shaped structure 6 located in the center can reduce the bending deformation of the long sides 2 of the concave polygonal honeycomb structure, thereby improving the load capacity.

[0049] On the whole, this embodiment can effectively obtain a low-frequency band gap in a wider frequency range and have a certain bearing capacity. The band gap and bearing capacity within the target range can be obtained by modifying the parameters of the structure, which is convenient for practical application.

[0050] In this embodiment, the long side 2, the short side 3 and the semicircular ring structure 4 of the concave polygonal honeycomb structure have the same thickness (ligament width), which is convenient for integrated manufacturing through 3D printing and can avoid stress concentration.

[0051] In this embodiment, the cross section of the short side 3 is T-shaped, I-shaped, groove-shaped, box-shaped, polygonal, circular or elliptical. The polygonal shape may be rectangular, triangular, rhombus or trapezoidal.

[0052] Example 2

[0053] This embodiment provides a hybrid star-shaped mechanical metamaterial structure, which is composed of a plurality of hybrid star-shaped mechanical metamaterial units 1 arranged in a matrix with a lattice constant as the array spacing, the semicircular mass columns 5 of adjacent hybrid star-shaped mechanical metamaterial units 1 are connected to form a circular mass column, and the semicircular ring structures 4 of adjacent hybrid star-shaped mechanical metamaterial units 1 are connected to wrap the circular mass column inside. There is a certain gap between the short sides 3 of adjacent hybrid star-shaped mechanical metamaterial units 1.

[0054] In the above-mentioned hybrid star-shaped mechanical metamaterial structure, the circular mass columns are distributed in a lattice pattern, which can improve the stability and rigidity of the overall structure. The structure is composed of multiple hybrid star-shaped mechanical metamaterial units 1, so it also has high load capacity and vibration reduction characteristics. On this basis, when a hybrid star-shaped mechanical metamaterial unit 1 generates load or local vibration, the load and vibration can be transmitted and distributed to more hybrid star-shaped mechanical metamaterial units 1 through the circular mass columns, further improving the load capacity of the structure; the overall structure can form a resonance effect, so that the vibration energy is greatly attenuated during the transmission process, thereby achieving a vibration isolation effect.

[0055] Experimental example

[0056] like Figure 3 As shown, the band structure simulation of the hybrid star-shaped mechanical metamaterial structure disclosed in Example 2 is performed. On the end face in the direction of the unit cell array, the Floquet periodic boundary condition is applied, and the wave vector of the Brillouin zone Γ-XM-Γ in the periodic direction is swept to obtain the band structure to determine the frequency range where the band gap is located. It can be seen that the structure of the present invention has four obvious complete band gaps below 1000Hz. Considering that the characteristics of the band gap are related to the lattice constant, structural characteristics and shear wave velocity, in order to eliminate their influence, the band gap normalized frequency is quoted to evaluate the band gap characteristics of the metamaterial. The band gap normalized frequency is defined as:

[0057]

[0058] In the formula, ω is the frequency, a is the lattice constant, c t =1465.1m / s, which is the shear wave velocity of the constituent material. The initial normalized frequency of the first complete band gap is 0.01360.

[0059] The frequency band in which the band gap is located can be changed to meet actual needs by adjusting the thickness of the long side 2, short side 3 and semicircular ring structure 4 of the hybrid star-shaped mechanical metamaterial unit 1 (referred to as the ligament width in the figure), the angle of the bottom angle (the bottom angle of the hybrid star-shaped mechanical metamaterial unit 1 arranged along the Y-axis is a vertical angle, and the bottom angle of the hybrid star-shaped mechanical metamaterial unit 1 arranged along the X-axis is a horizontal angle), and the offset distance of the baseline (the vertical distance between the baseline and the center of symmetry).

[0060] like Figure 4-Figure 7 As shown in the figure, as the offset distance of the baseline increases, the starting frequency of the first complete band gap gradually decreases, and the toughness width gradually increases. It can be seen that the offset distance of the baseline is an important factor affecting the low-frequency broadband. When adjusting the thickness of the long side 2, short side 3 and semicircular ring structure 4 of the hybrid star-shaped mechanical metamaterial unit 1, the angle of the bottom angle, and the offset distance of the baseline, the corresponding frequency can be changed, and then the purpose of adjusting the band gap width and range can be achieved by modifying the above parameters.

[0061] like Figure 8 and Fig. 9 As shown in the figure, when the structure is subjected to in-plane quasi-static compression, the hybrid star-shaped mechanical metamaterial structure can withstand greater stress under the same strain conditions, indicating that the hybrid star-shaped mechanical metamaterial structure has better bearing capacity than the existing concave quadrangular honeycomb structure of the same size. When the hybrid star-shaped mechanical metamaterial structure is subjected to in-plane quasi-static compression, the long side 2, the short side 3 and the star-shaped structure 6 are slightly bent and deformed.

[0062] When the in-plane quasi-static compression simulation calculation of the hybrid star-shaped mechanical metamaterial structure is performed, the equivalent Young's modulus of the hybrid star-shaped mechanical metamaterial structure is obtained to be 7.1x10 5 Pa. Figure 10-13 As shown, by adjusting the thickness of the long side 2, the short side 3 and the semicircular ring structure 4 of the hybrid star-shaped mechanical metamaterial unit 1, the angle of the bottom angle, and the offset distance of the baseline, the corresponding Young's modulus can be changed, and the equivalent Young's modulus of the metamaterial structure of the present invention can be adjusted by modifying the above parameters.

[0063] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0064] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A hybrid star-shaped mechanical metamaterial unit, characterized in that: include: The inwardly concave polygonal honeycomb structure is a centrally symmetrical structure and has a long side (2) and a short side (3) that are bent inwardly, and the two ends of the long side (2) are respectively connected to one end of the two short sides (3) to form a closed structure; The two inwardly concave polygonal honeycomb structures are arranged along the X-axis and the Y-axis respectively and have the same symmetry center, and the long sides (2) of the two inwardly concave polygonal honeycomb structures are surrounded by a star-shaped structure (6) with the symmetry center as a base point; A vibration damping component, wherein the short side (3) is bent inwardly to form a mounting portion that matches the shape of the vibration damping component, and the vibration damping component is arranged on the mounting portion; the straight line where the two ends of the short side (3) are located is the baseline, and the outer edge of the vibration damping component is located outside the baseline.

2. A hybrid star-shaped mechanical metamaterial unit according to claim 1, characterized in that: The inwardly concave polygonal honeycomb structure is an inwardly concave quadrangular honeycomb structure, and the star-shaped structure (6) is a regular quadrangular star-shaped structure (6).

3. A hybrid star-shaped mechanical metamaterial unit according to claim 2, characterized in that: The vibration reduction assembly comprises: A semicircular ring structure (4) adapted to the shape of the mounting portion and arranged on the mounting portion, wherein the outer side of the semicircular ring structure (4) forms a mounting cavity; A semicircular mass column (5) is arranged in the installation cavity, and the outer edge of the semicircular mass column (5) is located outside the baseline.

4. A hybrid star-shaped mechanical metamaterial unit according to claim 3, characterized in that: The center of the semicircular mass column (5) and the straight line where the symmetry center is located are perpendicular to the baseline.

5. A hybrid star-shaped mechanical metamaterial unit according to claim 4, characterized in that: The long sides (2), short sides (3) and the semicircular ring structure (4) of the inwardly concave polygonal honeycomb structure have the same thickness.

6. A hybrid star-shaped mechanical metamaterial unit according to claim 4, characterized in that: The inwardly concave polygonal honeycomb structure and the semicircular ring structure (4) are made by 3D printing of metal or plastic.

7. A hybrid star-shaped mechanical metamaterial unit according to claim 4, characterized in that: The cross section of the short side (3) is T-shaped, I-shaped, groove-shaped, box-shaped, polygonal, circular or elliptical.

8. A hybrid star-shaped mechanical metamaterial structure, characterized in that: The hybrid star-shaped mechanical metamaterial unit (1) is composed of a plurality of hybrid star-shaped mechanical metamaterial units (1) as described in any one of claims 4 to 7 arranged in a matrix, and the semicircular mass columns (5) of adjacent hybrid star-shaped mechanical metamaterial units (1) are connected.

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