Elastic metamaterial unit and vibration reduction method using elastic metamaterial unit

Abstract

The present application relates to a kind of elastic metamaterial unit and the damping method using elastic metamaterial unit, wherein, elastic metamaterial unit includes: outer shell, multiple different resonant frequency vibrator units are arranged in the outer shell;Multiple vibrator units are sequentially arranged in the outer shell along vertical direction, and the vibrator units between upper and lower adjacent are arranged with interval;The vibrator unit includes: rigid three-dimensional mass and flexible side connecting piece;The side connecting piece is respectively arranged in the opposite side of three-dimensional mass, and the side connecting piece is connected with the outer shell.Elastic metamaterial unit of the present application, using the shear strain of side connecting piece, can utilize its damping effect to a large extent, and the damping frequency band of metamaterial unit is widened by damping structure piece, and then excellent vibration control effect is obtained.

Description

Technical Field

[0001] This invention relates to the field of vibration and noise control, and more particularly to an elastic metamaterial unit and a vibration reduction method using the elastic metamaterial unit. Background Technology

[0002] Structural vibration and noise are widespread in the field of mechanical engineering. Vibration and noise not only directly affect the performance of mechanical devices but can also lead to serious accidents such as runaway, structural fatigue failure, fracture, and explosive disintegration. Designing materials and structures with vibration suppression properties and applying them to the structural design of mechanical equipment is of great significance for improving the overall performance of equipment, enhancing its safety, and extending its service life. However, traditional dynamic vibration absorption and damping technologies are still insufficient to effectively address the widespread low-frequency, broadband vibration problems encountered in equipment.

[0003] Both vibrations and sound waves propagate in the form of elastic waves. Elastic metamaterials are artificial metamaterials / structures with subwavelength modulation properties of elastic waves, and are usually periodic structures. The properties of metamaterials often depend not on the properties of the constituent materials, but on the coupling characteristics between the artificial microstructure units (i.e., cells) and the elastic waves.

[0004] Research over the past decade has shown that the bandgap of elastic metamaterials designed based on local resonance mechanisms can efficiently suppress elastic wave propagation, providing a new technical approach to overcome the bottlenecks of traditional vibration reduction technologies. However, the design theory of elastic metamaterials cannot reconcile the contradiction between lightweight, low-frequency, and broadband elastic wave suppression. Moreover, the spectral passband of metamaterials with finite size is composed of dense resonance peaks; the more cells there are, the more resonance peaks there are within the passband. That is, while the narrow bandgap of elastic metamaterials can attenuate structural vibrations, the response within their wider passband is resonantly amplified.

[0005] Damping can effectively reduce structural vibration and is therefore widely used in vibration control. However, the damping coefficient is highly dependent on the material itself. Most metallic materials have limited damping coefficients, while materials with higher damping coefficients, such as rubber, often do not meet the stiffness requirements of mechanical devices. Traditional damping vibration reduction technologies, such as dampers, have a vibration reduction effect that depends on the vibration frequency. The lower the vibration frequency, the worse the vibration reduction effect. Therefore, dampers and other methods are still unable to effectively cope with low-frequency vibrations of structures.

[0006] Applying damping effects to metamaterial cell design can effectively suppress vibrations within the passband of elastic metamaterials. Designing oscillators with different resonant frequencies within the metamaterial cell and coupling them with highly damped materials can broaden the vibration reduction bandwidth of the metamaterial. Furthermore, appropriate structural design can maximize the utilization of the material's damping effect. This design method can also effectively suppress vibrations in mechanical structures.

[0007] For large floating structures, vibration reduction methods based on elastic metamaterials often face the following constraints:

[0008] (1) It is lightweight and cannot be fully distributed in large quantities.

[0009] (2) The space layout is limited, making it impossible to achieve an ideal periodic arrangement.

[0010] (3) The mode is difficult to predict accurately, and it is impossible to determine the peak point of the mode.

[0011] Therefore, a reasonable metamaterial unit layout is needed to address the above problems. By comprehensively considering the vibration energy pathways, the layout of elastic metamaterials can be optimized, thereby achieving the best vibration control effect under the condition of a small added mass ratio. Summary of the Invention

[0012] The purpose of this invention is to provide an elastic metamaterial unit and a vibration reduction method using the elastic metamaterial unit.

[0013] To achieve the above-mentioned objectives, the present invention provides an elastic metamaterial unit, comprising: an outer shell, and a plurality of oscillator units with different resonant frequencies disposed within the outer shell;

[0014] In the outer casing, a plurality of the oscillator units are arranged sequentially along the vertical direction, and there is a gap between the vertically adjacent oscillator units;

[0015] The oscillator unit includes: a rigid three-dimensional mass block and a flexible side connector;

[0016] The side connectors are respectively provided on opposite sides of the three-dimensional mass block, and the side connectors are connected to the outer shell.

[0017] According to one aspect of the invention, the vertically adjacent oscillator units can be optionally connected by a damping structure; wherein the upper and lower ends of the damping structure are respectively connected to the three-dimensional mass block of the oscillator unit.

[0018] According to one aspect of the invention, the three-dimensional mass block of each of the said oscillator units has a different resonant frequency in the vertical direction.

[0019] According to one aspect of the invention, the resonant frequency of the oscillator unit is adjusted by changing the characteristic parameters of the side connector, and multiple low-frequency resonant modes are generated in the three-dimensional direction by the three-dimensional mass block in the oscillator unit; wherein the characteristic parameters are at least one of hardness, shape, and material.

[0020] According to one aspect of the invention, the oscillator unit further includes: a frequency modulation structure;

[0021] The frequency modulation structure is detachably connected to the three-dimensional mass block, and the connection position between the frequency modulation structure and the three-dimensional mass block is different from the side of the three-dimensional mass block that is connected to the side connector.

[0022] According to one aspect of the invention, the three-dimensional mass block in the oscillator unit may be configured as a cylinder, a cuboid, or a prism;

[0023] The damping structure can be configured as a cylinder, sphere, cuboid, or prism.

[0024] According to one aspect of the invention, the side connector is made of an elastic material with a damping coefficient higher than 0.15;

[0025] The damping structure is made of an elastic material with a damping coefficient higher than 0.15.

[0026] According to one aspect of the present invention, the housing includes: a base, a load-bearing side plate disposed on the base, a top plate supported on the load-bearing side plate, and an encapsulation side plate connected to the load-bearing side plate and the top plate;

[0027] The load-bearing side plate is detachably connected to the base, and there are two load-bearing side plates arranged symmetrically to each other;

[0028] The top plate and the load-bearing side plate are detachably connected;

[0029] The encapsulation side plates are arranged symmetrically to each other;

[0030] The side connector of the vibrator unit is connected to the side of the load-bearing side plate.

[0031] According to one aspect of the invention, the spacing between the two opposing load-bearing side plates is adjustable for pressing or releasing the side connector.

[0032] To achieve the above-mentioned objective, the present invention provides a vibration reduction method using the aforementioned elastic metamaterial unit, comprising:

[0033] The target structure is determined, and a simulation model of the target structure is established; wherein the target structure is a floating structure, which includes: a floating base and a flexible support for supporting the floating base;

[0034] Vibration response is added based on the simulation model, and the elastic metamaterial unit is arranged on the simulation model and simulation is performed; wherein, the anti-resonance force of the elastic metamaterial unit acts on the matrix resonance of the floating matrix, and the damping formed by the coupled resonance acts on the broadband vibration.

[0035] The vibration response of the simulation model before and after adding the elastic metamaterial unit was compared, and the layout of the elastic metamaterial was optimized based on the comparison results. The optimal vibration control effect was obtained under the condition of small added mass ratio. In this case, multiple elastic metamaterial units were respectively set on the key energy path nodes when the floating matrix vibrates, and the key energy path nodes are located above the flexible support.

[0036] According to one aspect of the present invention, the elastic metamaterial unit designed in this invention comprises a three-dimensional mass block connected to a load-bearing side plate via flexible side connectors to form a local resonant oscillator; by controlling the shape and hardness of the side connectors, oscillators with different resonant frequencies can be obtained, and these two oscillators are coupled together by a damping structure; a frequency tuning plate can be installed on the mass block of the oscillator, and the resonant frequency of the oscillator can be adjusted by increasing or decreasing the number of frequency tuning structures, which greatly improves the flexibility of use of the present invention.

[0037] According to one aspect of the present invention, elastic metamaterial units are periodically arranged and installed on a substrate structure requiring vibration reduction to construct an elastic metamaterial structure for controlling the vibration of the substrate structure. For large floating structures, by comprehensively considering the pathways of vibration energy, the layout of the elastic metamaterials can be optimized, thereby achieving the best vibration control effect under the condition of a small added mass ratio.

[0038] According to one aspect of the present invention, the elastic metamaterial unit provided by the present invention can utilize the shear strain of the side connectors to a large extent to leverage their damping effect, and broaden the vibration reduction frequency band of the metamaterial unit through damping structural components. For large floating structures, considering the limitations of their installation conditions, the path of vibration energy can be comprehensively considered, and the layout of the elastic metamaterial can be optimized, thereby achieving the best vibration control effect under the condition of a small added mass ratio. Attached Figure Description

[0039] Figure 1 This is a perspective view schematically representing an elastic metamaterial unit according to an embodiment of the present invention;

[0040] Figure 2 This is an exploded view schematically representing an elastic metamaterial unit according to an embodiment of the present invention;

[0041] Figure 3 This is a perspective view schematically illustrating another embodiment of the elastic metamaterial unit of the present invention;

[0042] Figure 4 This is a schematic diagram illustrating the vibration conditions of a simplified large floating structure in Example 1;

[0043] Figure 5This is a schematic diagram illustrating the placement of the elastic metamaterial units on a large floating structure in Example 1;

[0044] Figure 6 This is a schematic representation of the vibration response of the large floating structure in three cases in Example 1;

[0045] Figure 7 This schematically represents the modes of the upper oscillator unit in the elastic metamaterial unit ① of Example 1 at different vibration frequencies;

[0046] Figures 8(a), 8(b), and 8(c) schematically illustrate the modes of the floating structure with added elastic metamaterial units in Example 1 at vibration frequencies of 50Hz, 112Hz, and 147Hz.

[0047] Figure 9 This schematically represents the vertical (Z) displacement of each oscillator of the metamaterial unit in Example 1 and its total displacement (Total);

[0048] Figure 10 This is a schematic diagram illustrating the placement of the optimized elastic metamaterial units in a large floating structure according to Example 1.

[0049] Figure 11 This is a schematic representation of the vibration response of the large floating structure before and after optimization in Example 1. Detailed Implementation

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0051] In describing embodiments of the present invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" express orientations or positional relationships based on the orientations or positional relationships shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limitations on the present invention.

[0052] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described in detail here, but the embodiments of the present invention are not limited to the following embodiments.

[0053] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, an elastic metamaterial unit includes: an outer shell 1, and a plurality of oscillator units 2 disposed within the outer shell 1. In this embodiment, the resonant frequencies of the plurality of oscillator units 2 are different. In this embodiment, the outer shell 1 has a rectangular hollow structure, and the plurality of oscillator units 2 are all installed within the outer shell 1; wherein, the plurality of oscillator units 2 are arranged sequentially along the vertical direction, and adjacent oscillator units 2 are spaced apart. In this embodiment, the oscillator unit 2 includes: a rigid three-dimensional mass block 21 and a flexible side connector 22; wherein, the side connector 22 is respectively disposed on opposite sides of the three-dimensional mass block 21, and the side connector 22 is connected to the outer shell 1.

[0054] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the side connector 22 is connected to the three-dimensional mass block 21 and the outer shell 1 by means of gluing, vulcanization, etc. In this embodiment, if the side connector 22 is connected by gluing, the side surfaces of the side connector 22 on both sides are coated with adhesive, thereby achieving full-surface gluing of the side connector 22 to the three-dimensional mass block 21 and the outer shell 1 on both sides respectively.

[0055] The above-mentioned configuration effectively ensures the connection strength and stability between the components, while also effectively avoiding the influence on the internal shear strain of the side connector 22, which is beneficial to ensuring the vibration reduction effect of the present invention.

[0056] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the side of the side connector 22 connected to the three-dimensional mass block 21 is smaller than or equal to the side of the three-dimensional mass block 21 to which it is connected.

[0057] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the vertically adjacent oscillator units 2 can be connected by a damping structure 3; wherein, the upper and lower ends of the damping structure 3 are respectively connected to the three-dimensional mass block 21 of the oscillator unit 2.

[0058] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the three-dimensional mass block 21 of each oscillator unit 2 has a different resonant frequency in the vertical direction.

[0059] Combination Figure 1 and Figure 2As shown, according to one embodiment of the present invention, the resonant frequency of the oscillator unit 2 is adjusted by changing the characteristic parameters of the side connector 22, and multiple low-frequency resonant modes are generated in different directions (e.g., three-dimensional XYZ directions) by the three-dimensional mass block 21 in the oscillator unit 2; wherein the characteristic parameters are at least one of hardness, shape, and material. For example, when two oscillator units 2 are provided, the hardness, shape, and material of the side connectors 22 in the upper and lower oscillator units 2 are different from each other, thereby making the resonant frequencies of the upper and lower oscillator units 2 different. When more oscillator units 2 are provided, the hardness, shape, and material of the corresponding side connectors 22 are different.

[0060] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the oscillator unit 2 further includes a frequency modulation structure 23. In this embodiment, the frequency modulation structure 23 is plate-shaped and is used to adjust the overall mass of the oscillator unit 2, thereby adjusting the resonant frequency of the oscillator unit 2. Furthermore, the frequency modulation structure 23 is detachably connected to the three-dimensional mass block 21 to facilitate corresponding replacement and adjustment according to different needs. In this embodiment, the connection position of the frequency modulation structure 23 to the three-dimensional mass block 21 is different from the side where the three-dimensional mass block 21 is connected to the side connector 22. For example, when the side connector 22 is provided on the left and right sides of the three-dimensional mass block 21, the frequency modulation structure 23 is provided on either the front or rear sides of the three-dimensional mass block 21 or on both sides. In this embodiment, to facilitate the detachable installation of the frequency modulation structure 23, it can be fixed by using a threaded connector, which not only ensures stable and reliable installation but also does not occupy extra space.

[0061] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the three-dimensional mass block 21 in the oscillator unit 2 can be configured as a cuboid ( Figure 1 ), cylinder ( Figure 3 Or a prism. In this embodiment, when multiple oscillator units 2 are provided, the three-dimensional mass blocks 21 in the multiple oscillator units 2 have different resonant frequencies, and therefore at least one characteristic parameter such as their shape, volume, and material is different. By adjusting the arrangement of the three-dimensional mass blocks 21 (such as shape, volume, material, etc.), the three-dimensional mass blocks 21 can be made to have different resonant frequencies, thereby directly affecting the resonant frequency of the oscillator unit 2, thus realizing flexible adjustment of the mode shape and the coupling state between different oscillators in this scheme, thereby producing different vibration reduction effects.

[0062] In this embodiment, the damping structure 3 can be configured as a cylinder, sphere, cuboid, or prism. The configuration of the damping structure 3 can be adjusted according to the configuration of the three-dimensional mass block 21; for example, the shape of the damping structure 3 can be consistent with the shape of the three-dimensional mass block 21. Of course, the shape of the damping structure 3 can also be different from the shape of the three-dimensional mass block 21.

[0063] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the side connector 22 is made of an elastic material with a damping coefficient higher than 0.15; for example, the side connector 22 may be configured as a rubber block.

[0064] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the damping structure 3 is made of an elastic material with a damping coefficient higher than 0.15; for example, the damping structure 3 is made of rubber.

[0065] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the outer casing 1 includes: a base 11, a load-bearing side plate 12 disposed on the base 11, a top plate 13 supported on the load-bearing side plate 12, and an encapsulation side plate 14 connected to the load-bearing side plate 12 and the top plate 13. In this embodiment, the base 11 has a plate-like structure and serves as the foundation for connecting the entire outer casing 1 to other structures. In this embodiment, the load-bearing side plate 12 is supported on the base 11 and is the main structure for connecting the oscillator unit 2. In this embodiment, the load-bearing side plate 12 is detachably connected to the base 11, and two load-bearing side plates 12 are symmetrically arranged; wherein, the load-bearing side plate 12 includes: a load-bearing plate body, a bottom connecting portion and a top connecting portion respectively disposed at the upper and lower ends of the load-bearing plate body; the bottom connecting portion and the top connecting portion are respectively disposed perpendicular to the load-bearing plate body and extend in opposite directions for connection to the base 11 and the top plate 13 respectively. In this embodiment, the load-bearing side plate 12 is connected to the base 11 using a threaded connector, and corresponding holes can be provided at the bottom connection part to achieve the connection function.

[0066] In this embodiment, the top plate 13 rests on the top connecting portion of the load-bearing side plate 12; wherein, the top plate 13 and the load-bearing side plate 12 are detachably connected; specifically, the top plate 13 and the load-bearing side plate 12 are connected by threaded connectors, wherein the connection is achieved by providing corresponding holes on the top connecting portion of the load-bearing side plate 12.

[0067] In this embodiment, the top plate 13 is a rectangular plate, and a through hole is provided at the position where it connects with the load-bearing side plate 12 to allow threaded connectors to pass through.

[0068] In this embodiment, there are two symmetrically arranged encapsulation side plates 14. The encapsulation side plate 14 is generally rectangular. In order to connect with the top plate 13 and the load-bearing side plate 12, through holes are provided at the corresponding edge positions of the encapsulation side plate 14, so that threaded connectors can pass through and connect with the threaded holes on the corresponding structures.

[0069] In this embodiment, the side connector 22 of the vibrator unit 2 is connected to the side of the load-bearing side plate 12.

[0070] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the interval between the two opposing load-bearing side plates 12 is adjustable for pressing or releasing the side connector 22. In this embodiment, the relative position is adjusted by setting the through hole at the threaded connection position as an elongated oval hole. Specifically, the load-bearing side plate 12 is connected to the base 11 via a bottom connecting portion. The base 11 has a threaded hole, and the bottom connecting portion has a through hole for the threaded connector to pass through. To adjust the position of the load-bearing side plate 12, the through hole at the bottom connecting portion can be set as an elongated oval hole, allowing adjustment when the load-bearing side plate 12 is fixed on the base 11. Correspondingly, a threaded hole for connecting the threaded connector is provided at the top connecting portion of the load-bearing side plate 12, and a through hole for the threaded connector to pass through is provided on the top plate 13. This through hole is correspondingly set as an elongated oval hole to facilitate adjustment of the connection position between the load-bearing connecting plate 12 and the top plate 13.

[0071] According to one embodiment of the present invention, a vibration reduction method using the aforementioned elastic metamaterial unit includes:

[0072] The target structure is determined, and a simulation model of the target structure is established; wherein, the target structure is a floating structure, which includes: a floating base and a flexible support for supporting the floating base;

[0073] Vibration response is added based on the simulation model, and elastic metamaterial elements are arranged on the simulation model and simulation is performed; wherein, the anti-resonance force of the elastic metamaterial elements acts on the matrix resonance of the floating matrix, and the damping formed by the coupled resonance acts on the broadband vibration.

[0074] The vibration response of the simulation model before and after adding elastic metamaterial units was compared, and the layout of the elastic metamaterial was optimized based on the comparison results. The optimal vibration control effect was obtained under the condition of small added mass ratio. Multiple elastic metamaterial units were respectively set on the key energy path nodes when the floating matrix vibrates, and the key energy path nodes are located above the flexible support.

[0075] To further illustrate this plan, examples are provided in conjunction with the accompanying drawings.

[0076] Example 1

[0077] In this embodiment, the example of setting two oscillator units 2 in an elastic metamaterial unit is described. The side connectors 22 in the oscillator unit 2 are made of rubber. The elastic metamaterial unit is obtained through the following steps:

[0078] Step 1: Determine the shape and hardness of the side connector 22

[0079] First, the dimensions of the three-dimensional mass block 21 are determined based on the additional mass requirements. Then, the resonant frequency of the oscillator of the elastic metamaterial unit is determined based on the vibration damping frequency band. Finally, the hardness, material, dimensions, and shape of the side connector 22 are determined based on the oscillator resonant frequency. In this embodiment, the side connector 22 can be adjusted and verified using finite element software.

[0080] Step 2: Determine the overall dimensions and manufacturing of the elastic metamaterial unit.

[0081] Based on the parameters determined in step one, the dimensions of each structure in the outer shell 1 of the elastic metamaterial unit are determined, and after obtaining the processing drawings, the unit is manufactured and assembled.

[0082] Step 3: Adjust and determine the resonant frequency of oscillator element 2

[0083] A damping structure 3 is set between the two oscillator units 2. After the oscillator unit 2 is assembled with the outer shell 1, a vibration test is performed on the assembled metamaterial unit to obtain the oscillator resonance frequency of the actually manufactured elastic metamaterial unit. The resonance frequency of the oscillator is adjusted by adding or removing the number of frequency tuning structure 23 on the oscillator unit 2 to obtain the ideal resonance frequency.

[0084] Step 4: Determine the layout of the elastic metamaterial units

[0085] For the actual vibration conditions of the structure requiring vibration reduction, finite element software is used to model and simulate its vibration response. Taking into account the path of vibration energy, the layout of the elastic metamaterial elements is optimized to obtain the optimal vibration reduction scheme for the large floating raft structure.

[0086] Based on the above design steps, various specific oscillator unit structures can be designed. Therefore, the advantages of this invention will be detailed in conjunction with the specific setup process.

[0087] In this embodiment, when the two oscillator units 2 are installed in the outer shell 1, the side connectors 22 are respectively connected to the load-bearing side plates 12, so that the three-dimensional mass block 21 mainly forms a local resonance structure through the shear strain of the side connectors 22. Compared with the compressive strain of the side connectors 22, the shear strain can more effectively utilize the damping effect of the material (rubber) of the side connectors 22, thereby more effectively achieving the purpose of vibration suppression.

[0088] In this embodiment, due to the resonant frequency of the upper and lower oscillator units 2, by further setting a damping structure 3 made of rubber material between the two oscillator units 2, the vibration in the middle frequency band of the resonant frequency of the upper and lower oscillator units 2 can be effectively suppressed by the damping effect of the damping structure 3, thereby achieving the purpose of broadband vibration reduction.

[0089] In this embodiment, the three-dimensional mass block 21 is made of steel and is configured as a cuboid structure. The outer shell 1 is made of aluminum alloy.

[0090] In this embodiment, the resonant frequency of the upper oscillator unit 2 is lower than the resonant frequency of the lower oscillator unit 2.

[0091] In this embodiment, the side connector 22 and the damping structure 3 are both made of nitrile rubber.

[0092] To illustrate the vibration suppression effect of the elastic metamaterial unit of the present invention, based on the above-described configuration of the elastic metamaterial unit, and using finite element analysis software, simulations were conducted to demonstrate its vibration reduction effect on a large floating structure. The vibration responses of the large floating structure before and after adding the elastic metamaterial unit of the present invention, as well as the vibration responses of the large floating structure after replacing the rubber material of the elastic metamaterial unit with steel material, were compared, verifying the effectiveness of the elastic metamaterial unit of the present invention. Furthermore, considering the characteristics of the working conditions of large floating structures, the layout of the elastic metamaterial was optimized by comprehensively considering the vibration energy pathways, thereby achieving optimal vibration control under a small added mass ratio. Comparison of the vibration responses of the structures before and after optimization verified the effectiveness of the vibration reduction design scheme.

[0093] Specifically, taking the low-frequency vibration reduction of a large floating structure in the 50Hz-200Hz range as an example, the large floating structure is a cuboid, 5m long and wide, and 0.4m high, made of steel. The lower surface of the large floating structure has 14 smaller cuboids (0.3m × 0.3m × 0.1m, i.e., flexible supports), made of rubber with a Young's modulus of 11.2MPa, used to simulate airbags, forming the large floating structure. See [link to documentation]. Figure 4 As shown.

[0094] For the aforementioned large floating structures, vibration reduction methods based on elastic metamaterials often face the following constraints:

[0095] (1) It is lightweight and cannot be fully distributed in large quantities.

[0096] (2) The space layout is limited, making it impossible to achieve an ideal periodic arrangement.

[0097] (3) The mode is difficult to predict accurately, and it is impossible to determine the peak point of the mode.

[0098] Therefore, based on the aforementioned large floating structure, and combined with the preceding steps, the elastic metamaterial units used are structurally designed. In this embodiment, two types of elastic metamaterial units are designed: elastic metamaterial unit ① and elastic metamaterial unit ②. Considering weight limitations, there are eight of each type of elastic metamaterial unit. In this embodiment, the shape and hardness of the rubber-made side connectors 22 differ between the two types of elastic metamaterial units, while the rest of the structure is the same. Specifically, in elastic metamaterial unit ① and elastic metamaterial unit ②, the upper three-dimensional mass block 21 is a 0.287m × 0.2m × 0.244m rectangular steel mass block, and the lower three-dimensional mass block 21 is also a 0.287m × 0.2m × 0.2m rectangular steel mass block. In this embodiment, each three-dimensional mass block 21 is provided with a frequency modulation structure 23. This frequency modulation structure 23 is a rectangular plate with the same surface dimensions as the three-dimensional mass block 21 to be installed, and a thickness of 1mm. The material used is steel.

[0099] In this embodiment, in the elastic metamaterial unit ①, the side connector 22 connected to the upper three-dimensional mass block 21 is a cuboid of 0.134m × 0.09m × 0.008m with a Young's modulus of 10MPa (hardness of 50 degrees), and the side connector 22 connected to the lower three-dimensional mass block 21 is a cuboid of 0.2m × 0.18m × 0.008m with a Young's modulus of 25.5MPa (hardness of 70 degrees), thereby making the resonant frequency of the upper oscillator unit 2 50Hz and the resonant frequency of the lower oscillator unit 2 150Hz.

[0100] In the elastic metamaterial unit ②, the side connector 22 connected to the upper three-dimensional mass block 21 is a cuboid of 0.244m×0.2m×0.008m with a Young's modulus of 10MPa (hardness of 50 degrees). The side connector 22 connected to the lower three-dimensional mass block 21 is also a cuboid of 0.2m×0.2m×0.008m with a Young's modulus of 40MPa (hardness of 85 degrees). This results in the upper oscillator unit 2 having a resonant frequency of 100Hz and the lower oscillator unit 2 having a resonant frequency of 200Hz.

[0101] In this embodiment, in the elastic metamaterial unit ① and the elastic metamaterial unit ②, the damping structure 3 made of rubber is a cuboid with a size of 0.287m × 0.2m × 0.01m and a Young's modulus of 3.6MPa (hardness of 30 degrees).

[0102] Here, the operating state of the large floating structure is set, wherein, for the large floating structure, the excitation position is as follows: Figure 4 As shown, the excitation displacement is 1 mm, and the excitation direction is vertically downward. The vibration response of this large floating structure is obtained by calculating the displacement of the upper surface of the airbag at different excitation frequencies, which is used to analyze the vibration reduction effect of the elastic metamaterial unit.

[0103] Based on the above-mentioned large floating structure's operating state, three scenarios are considered for comparative verification:

[0104] (1) No elastic metamaterial unit installed (no elastic metamaterial unit);

[0105] (2) Install elastic metamaterial units (normal elastic metamaterial units);

[0106] (3) Install the elastic metamaterial unit and replace all the rubber material of the elastic metamaterial unit with steel material (all-steel elastic metamaterial unit).

[0107] Elastic metamaterial unit ① and elastic metamaterial unit ② were all placed around the floating structure, and then... Figure 5 The initial layout was performed, and the vibration response of the floating structure under three different conditions was simulated. The results are as follows: Figure 6 As shown.

[0108] Comparing the vibration responses before and after installing elastic metamaterial unit ① and elastic metamaterial unit ②, it can be seen that the vibration of the floating structure in the 50-200Hz range is effectively suppressed after installing the metamaterial unit. Furthermore, by comparing the vibration response with that of the metamaterial unit installed with an all-steel structure, it can be seen that the metamaterial unit installed with an all-steel structure cannot effectively suppress vibration. On the contrary, it will increase the vibration modes of the floating structure, proving that the vibration suppression effect of the elastic metamaterial unit is not caused by the increase in weight.

[0109] For an elastic metamaterial unit, each oscillator unit 2 can generate multiple vibration modes at different frequencies. Taking the upper oscillator unit 2 in the elastic metamaterial unit ① as an example, its modes at different vibration frequencies are as follows: Figure 7 As shown. From Figure 7 As can be seen, the oscillator element 2 of the metamaterial unit possesses a dominant mode in the vertical direction and modes in other directions. For the dominant mode in the vertical direction, strong coupling can be formed between the two resonant elements using coupling rubber (i.e., damping structure 3), thereby enhancing the energy dissipation effect of damping, as shown in Figure 8(a). Simultaneously, the torsional modes of the two oscillators can also form coupled vibrations through the coupling rubber, increasing the resonant modes of the elastic metamaterial unit, as shown in Figure 8(b). Furthermore, the torsional modes of the two resonant elements can also drive the shell to vibrate, similarly providing a vibration reduction effect for the floating structure, as shown in Figure 8(c). Figure 9 As shown, the vertical displacement (Z-direction) of each oscillator in the metamaterial unit is not equal to its total displacement, and there are even significant differences. This indicates that not only is the main resonant mode of the oscillator excited, but resonant modes at other frequencies are also excited. Different resonant modes can function within the pass frequency range, achieving a wideband and high-efficiency effect.

[0110] Figure 9 Legend: 50Hz, Total—total displacement of oscillator 2 above elastic metamaterial unit ①; 50Hz, Z—vertical displacement of oscillator 2 above elastic metamaterial unit ①; 100Hz, Total—total displacement of oscillator 2 below elastic metamaterial unit ①; 100Hz, Z—vertical displacement of oscillator 2 below elastic metamaterial unit ①; 150Hz, Total—total displacement of oscillator 2 above elastic metamaterial unit ②; 50Hz, Z—vertical displacement of oscillator 2 above elastic metamaterial unit ②.

[0111] The above results preliminarily verify the vibration reduction effect of the elastic metamaterial unit. Next, considering the path of vibration energy in the floating structure, we will optimize the layout of the elastic metamaterial to obtain a more complete vibration reduction scheme.

[0112] For this large floating structure, the energy input point is the vibration source, and the energy output point is the vibration isolator. Therefore, metamaterial units are placed at key energy path nodes. In this case, the key energy path nodes are the vibration isolator mounting points of the floating structure (i.e., above the flexible supports of the floating matrix). At the path nodes, the damping effect formed by coupled resonance acts over a wide frequency range, while the anti-resonance force acts on the matrix resonance, thereby maximizing the utilization of the limited number of metamaterial units. The optimized distribution of elastic metamaterial units is as follows: Figure 10 As shown. A comparison of the vibration response of the large floating structure before and after optimization is presented, such as... Figure 11 As shown in the figure. The results indicate that optimizing the distribution of elastic metamaterial elements on large floating structures can further enhance the vibration suppression effect, verifying the effectiveness of the vibration reduction design scheme.

[0113] The simulations above show that the elastic metamaterial constructed from the elastic metamaterial cells (i.e., oscillator units 2) designed according to the present invention can achieve low-frequency broadband structural vibration suppression; optimizing the distribution of the elastic metamaterial units on large floating structures can further enhance the vibration suppression effect.

[0114] The above description is merely an example of a specific solution of the present invention. For any devices and structures not described in detail herein, it should be understood that they are implemented using common devices and methods already available in the art.

[0115] The above description is merely one embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An elastic metamaterial unit, characterized in that, include: The outer shell (1) contains multiple oscillator units (2) with different resonant frequencies disposed within the outer shell (1). In the outer shell (1), a plurality of the oscillator units (2) are arranged sequentially in the vertical direction, and there is a gap between the upper and lower adjacent oscillator units (2); The oscillator unit (2) includes: a rigid three-dimensional mass block (21) and a flexible side connector (22). The side connectors (22) are respectively provided on opposite sides of the three-dimensional mass block (21), and the side connectors (22) are connected to the outer shell (1); The three-dimensional mass block (21) of each of the oscillator units (2) has a different resonant frequency in the vertical direction; The resonant frequency of the oscillator unit (2) is adjusted by changing the characteristic parameters of the side connector (22), and the three-dimensional mass block (21) in the oscillator unit (2) generates multiple low-frequency resonant modes in three dimensions; wherein the characteristic parameters are at least one of hardness, shape, and material; The side connector (22) is made of an elastic material with a damping coefficient higher than 0.15; The three-dimensional mass block (21) forms a local resonance structure through the shear strain of the side connector (22).

2. The elastic metamaterial unit according to claim 1, characterized in that, Along the vertical direction, the upper and lower adjacent oscillator units (2) can be connected by a damping structure (3); wherein the upper and lower ends of the damping structure (3) are respectively connected to the three-dimensional mass block (21) of the oscillator unit (2); The damping structure (3) is made of an elastic material with a damping coefficient higher than 0.

15.

3. The elastic metamaterial unit according to claim 2, characterized in that, The oscillator unit (2) also includes: a frequency modulation structure (23); The frequency modulation structure (23) is detachably connected to the three-dimensional mass block (21), and the connection position of the frequency modulation structure (23) and the three-dimensional mass block (21) is different from the side of the three-dimensional mass block (21) connected to the side connector (22); The frequency modulation structure (23) is plate-shaped and is used to adjust the overall mass of the oscillator unit (2) to adjust the resonance frequency of the oscillator unit (2).

4. The elastic metamaterial unit according to claim 3, characterized in that, The three-dimensional mass block (21) in the oscillator unit (2) can be set as a cylinder, cuboid or prism; The damping structure (3) can be configured as a cylinder, sphere, cuboid or prism.

5. The elastic metamaterial unit according to claim 4, characterized in that, The outer casing (1) includes: a base (11), a load-bearing side plate (12) disposed on the base (11), a top plate (13) supported on the load-bearing side plate (12), and an encapsulation side plate (14) connected to the load-bearing side plate (12) and the top plate (13). The load-bearing side plate (12) is detachably connected to the base (11), and there are two load-bearing side plates (12) arranged symmetrically to each other; The top plate (13) and the load-bearing side plate (12) are detachably connected; The encapsulation side plates (14) are arranged symmetrically in two places; The side connector (22) of the vibrator unit (2) is connected to the side of the load-bearing side plate (12).

6. The elastic metamaterial unit according to claim 5, characterized in that, The spacing between the two opposing load-bearing side plates (12) is adjustable for pressing or releasing the side connector (22).

7. A vibration reduction method using the elastic metamaterial unit according to any one of claims 1 to 6, characterized in that, include: The target structure is determined, and a simulation model of the target structure is established; wherein the target structure is a floating structure, which includes: a floating base and a flexible support for supporting the floating base; Vibration response is added based on the simulation model, and the elastic metamaterial unit is arranged on the simulation model and simulation is performed; wherein, the anti-resonance force of the elastic metamaterial unit acts on the matrix resonance of the floating matrix, and the damping formed by the coupled resonance acts on the broadband vibration. The vibration response of the simulation model before and after adding the elastic metamaterial unit was compared, and the layout of the elastic metamaterial was optimized based on the comparison results. The optimal vibration control effect was obtained under the condition of small added mass ratio. In this case, multiple elastic metamaterial units were respectively set on the key energy path nodes when the floating matrix vibrates, and the key energy path nodes are located above the flexible support.

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