Negative Poisson's ratio vibration reduction structure

Abstract

The invention discloses a negative Poisson's ratio vibration reduction structure which comprises a plurality of unit cell structures, and each unit cell structure comprises a first horizontal beam, a second horizontal beam and an elastic oblique beam. The cross sections of the first horizontal beam and the second horizontal beam are triangular; the two first horizontal beams are arranged up and down, and the end parts on the same side are connected through an elastic oblique beam; the elastic oblique beam comprises two sections of straight beams which are connected with each other and form an included angle; one side, far away from the first horizontal beam, of each elastic oblique beam is connected with a second horizontal beam at the straight beam connecting part of the elastic oblique beam; the adjacent first horizontal beams of the adjacent unit cell structures are connected, the adjacent second horizontal beams of the adjacent unit cell structures are connected, and the adjacent elastic oblique beams are connected.

Description

Technical Field

[0001] The invention relates to the field of negative Poisson's ratio metamaterials, and in particular to a negative Poisson's ratio vibration reduction structure. Background Art

[0002] Metamaterials are man-made materials that are made up of carefully designed units arranged in a regular pattern. The careful design of the unit structure and arrangement can produce new properties that do not exist in nature. These new properties involve electromagnetic, optical, acoustic, mechanical, thermal and other properties, allowing metamaterials to be used in stealth, imaging, vibration reduction, sound absorption, load bearing and heat insulation.

[0003] Structural vibration reduction mainly relies on two mechanisms: Bragg scattering and local resonance. At present, there are relatively more studies on local resonance, which is formed by the local vibration of the structural unit around the resonant frequency, which allows the structural unit to have a sub-wavelength size. For local resonance, the current traditional vibration reduction structures such as Figure 1 As shown, the structure includes a plurality of unit cell structures connected in parallel, each unit cell structure is square, frame beams are arranged on its four sides, and connecting beams are arranged on the two diagonals, and each connecting beam is provided with an additional mass, which is achieved by increasing the cross-sectional radius of the middle part of the connecting beam. The connecting beam part and the additional mass part correspond to the mass element and the stiffness element of the spring-oscillator respectively. When the structure is subjected to external excitation, the structure exhibits local resonance, thereby achieving vibration suppression; however, due to the large stiffness of the connecting beam and the small density of the additional mass part, this structure is often used for vibration reduction in higher frequency bands; due to the large vibration reduction frequency of this structure, it is currently mostly used for vibration reduction in higher frequency bands above 1000 Hz, and cannot effectively suppress low-frequency vibrations and prevent the transmission of harmful elastic waves. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the negative Poisson's ratio vibration reduction structure provided by the present invention solves the problem that the existing vibration reduction structure cannot effectively suppress low-frequency vibration to prevent the transmission of harmful elastic waves.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0006] A negative Poisson's ratio vibration reduction structure is provided, which includes a plurality of unit cell structures, wherein the unit cell structure includes a first horizontal beam, a second horizontal beam and an elastic inclined beam; the cross sections of the first horizontal beam and the second horizontal beam are both triangular;

[0007] The two first horizontal beams are arranged up and down, and the ends on the same side are connected by an elastic inclined beam; the elastic inclined beam comprises two sections of straight beams connected to each other and forming an angle; each elastic inclined beam is connected to a second horizontal beam at the connection point of the straight beams and at a side away from the first horizontal beam;

[0008] Adjacent first horizontal beams of adjacent unit cell structures are connected, adjacent second horizontal beams are connected, and adjacent elastic inclined beams are connected.

[0009] Furthermore, in each unit cell structure, the two first horizontal beams are symmetrically arranged, and the surfaces of the two first horizontal beams away from each other are parallel to the horizontal plane; the two second horizontal beams are symmetrically arranged, and the surfaces of the two second horizontal beams away from each other are perpendicular to the horizontal plane.

[0010] Furthermore, the first horizontal beam and the second horizontal beam have the same mass.

[0011] Furthermore, in the unit cell structure, the two elastic inclined beams do not contact each other, and the two first horizontal beams do not contact each other.

[0012] Furthermore, the first horizontal beam and the second horizontal beam of the unit cell structure are provided with an arc-shaped cavity at the end face away from the elastic inclined beam, and a metal core with an end face flush with the end face of the arc-shaped cavity is arranged in the arc-shaped cavity, and an elastic layer is filled between the metal core and the arc-shaped cavity; the sum of the radius of the metal core and the thickness of the elastic layer is equal to the radius of the arc-shaped cavity.

[0013] Furthermore, the depth of the arc-shaped cavity is equal to its radius, and the cross-section of the metal core is semicircular.

[0014] Furthermore, in adjacent unit cell structures, two adjacent first horizontal beams are an integrated structure, two adjacent second horizontal beams are an integrated structure, two adjacent metal cores are an integrated structure, and two adjacent elastic layers are an integrated structure.

[0015] Furthermore, the angle θ between the two straight beams of the elastic inclined beam is 60°≤θ≤120°.

[0016] Furthermore, the first horizontal beam, the second horizontal beam and the elastic inclined beam of the unit cell structure are all made of epoxy resin.

[0017] Furthermore, the normalized equivalent mass density of the unit cell structure is:

[0018]

[0019]

[0020] Where ρ is the normalized equivalent mass density; M t is the mass of the unit cell structure; m is the mass of the metal core; k is the stiffness of the elastic layer; M is the difference between the mass of the unit cell structure and the mass of the metal core; is the external excitation frequency; a is the length of the first horizontal beam; c is the out-of-plane height of the vibration reduction structure; ρ1 is the density of the material used to prepare the unit cell structure; ρ2 is the density of the metal core; r1 is the radius of the metal core; r2 is the radius of the arc cavity.

[0021] The beneficial effects of the present invention are as follows: the structure formed by the adjacent first horizontal beams of the adjacent unit cell structures of the present scheme combined with the elastic inclined beams at both ends can constitute a shock absorber, and the structure formed by the adjacent second horizontal beams combined with the elastic inclined beams at both ends can also constitute a shock absorber, which can form multiple shock absorbers in the negative Poisson's ratio shock absorbing structure of the present scheme. When subjected to external force, the multiple shock absorbers resonate and cooperate with each other to absorb low-frequency vibrations, so as to buffer the external force and achieve the transmission of harmful elastic waves.

[0022] After the metal core and the elastic layer are set on the first horizontal beam and the second horizontal beam, the metal core can increase the mass of each shock absorber, which can further enable the elastic inclined beam and the two paired horizontal beams to absorb lower vibration damping frequencies; the two paired horizontal beams can also form a shock absorber after combining the metal core and the elastic layer, which is equivalent to doubling the number of shock absorbers in the negative Poisson's ratio vibration damping structure, thereby further improving the vibration damping effect and being able to adapt to lower vibration damping frequencies during the vibration damping process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of a traditional vibration reduction structure based on local resonance.

[0024] Figure 2 This is the three-dimensional effect diagram of the negative Poisson's ratio vibration reduction structure.

[0025] Figure 3 This is the three-dimensional rendering of the unit cell structure of the negative Poisson's ratio vibration damping structure.

[0026] Figure 4 Schematic diagram of the unit cell structure of the negative Poisson's ratio vibration damping structure.

[0027] Figure 5 It is the experimental model of the negative Poisson's ratio vibration reduction structure.

[0028] Figure 6 It is the equivalent mass density curve of the negative Poisson's ratio vibration reduction structure.

[0029] Among them, 1. unit cell structure; 11. first horizontal beam; 12. second horizontal beam; 13. elastic inclined beam; 14. elastic layer; 15. metal core. DETAILED DESCRIPTION

[0030] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0031] like Figure 2-5 As shown, the negative Poisson's ratio vibration reduction structure provided by the present solution includes a plurality of unit cell structures 1, wherein the unit cell structure 1 includes a first horizontal beam 11, a second horizontal beam 12 and an elastic inclined beam 13; wherein the first horizontal beam 11, the second horizontal beam 12 and the elastic inclined beam 13 of the unit cell structure 1 are all made of epoxy resin.

[0032] The cross-sections of the first horizontal beam 11 and the second horizontal beam 12 are both triangular; the triangular arrangement can generate multiple gaps inside the unit cell structure 1, which can reserve sufficient vibration space for the shock absorber formed by the matching horizontal beams to buffer and consume external forces.

[0033] like Figure 4 As shown, the two first horizontal beams 11 are arranged up and down, and the ends on the same side are connected by an elastic inclined beam 13; the elastic inclined beam 13 includes two straight beams that are connected to each other and form an angle; preferably, the angle θ between the two straight beams of the elastic inclined beam 13 is 60°≤θ≤120°.

[0034] The setting of the angle between the two straight beams of the elastic inclined beam 13 can firstly increase the size of the cavity inside each unit cell structure 1, providing a larger buffering space for the vibration of the shock absorber; secondly, an inflection point is formed at the connection, and when subjected to external force, the inflection point can be used as a support point to quickly respond to external vibrations and buffer the external force.

[0035] Each elastic inclined beam 13 is connected to a second horizontal beam 12 at its straight beam connection point and at a side away from the first horizontal beam 11; adjacent first horizontal beams 11 of adjacent unit cell structures 1 are connected, adjacent second horizontal beams 12 are connected, and adjacent elastic inclined beams 13 are connected.

[0036] In this solution, the structure formed by the interconnected first horizontal beams 11 combined with the elastic inclined beams 13 at both ends can form a shock absorber, and the structure formed by the adjacent second horizontal beams 12 combined with the elastic inclined beams 13 at both ends can also form a shock absorber.

[0037] Reference again Figure 2-5 In this scheme, the two first horizontal beams 11 of each unit cell structure 1 are symmetrically arranged, and the surfaces of the two first horizontal beams 11 away from each other are parallel to the horizontal plane; the two second horizontal beams 12 are symmetrically arranged, and the surfaces of the two second horizontal beams 12 away from each other are perpendicular to the horizontal plane.

[0038] During implementation, this solution preferably has adjacent unit cell structures 1 in which two adjacent first horizontal beams 11 are an integrated structure, two adjacent second horizontal beams 12 are an integrated structure, two adjacent metal cores 15 are an integrated structure, and two adjacent elastic layers 14 are an integrated structure.

[0039] The two horizontal beams adopt the above-mentioned structural arrangement, which can facilitate the integrated molding of multiple unit cell structures 1 of the negative Poisson's ratio vibration reduction structure, so as to facilitate rapid processing, thereby achieving the purpose of improving processing efficiency and reducing processing costs.

[0040] The masses of the first horizontal beam 11 and the second horizontal beam 12 are equal. After such arrangement, when vibration is generated by external force, the internal vibration can be made relatively uniform, so that the entire vibration reduction structure has a better vibration reduction effect.

[0041] like Figure 4 As shown, in this solution, the two elastic inclined beams 13 in the unit cell structure 1 preferably do not touch each other, and the two first horizontal beams 11 do not touch each other; this can avoid collision between adjacent shock absorbers and affect the shock absorption effect.

[0042] During implementation, this scheme preferably provides an arc-shaped cavity in the first horizontal beam 11 and the second horizontal beam 12 of the unit cell structure 1 at the end faces away from the elastic inclined beam 13 thereof, and a metal core 15 with an end face flush with the end face of the arc-shaped cavity is provided in the arc-shaped cavity, and an elastic layer 14 is filled between the metal core 15 and the arc-shaped cavity; the sum of the radius of the metal core 15 and the thickness of the elastic layer 14 is equal to the radius of the arc-shaped cavity.

[0043] The provision of the metal core 15 can increase the mass of each shock absorber, which can further enable the elastic inclined beam 13 and the two paired horizontal beams to absorb lower vibration damping frequencies; the two paired horizontal beams can also form a shock absorber after combining the metal core 15 and the elastic layer 14, which is equivalent to doubling the number of shock absorbers in the negative Poisson's ratio shock absorbing structure, thereby further improving the shock absorbing effect and being able to further absorb lower vibration damping frequencies during the shock absorbing process.

[0044] The depth of the arc cavity is equal to its radius, and the cross section of the metal core 15 is semicircular. After this arrangement, two adjacent arc cavities can form a complete circle, which is convenient for placing the circle formed by the two metal cores 15 and facilitating the processing of the vibration reduction structure.

[0045] During implementation, this scheme preferably sets the normalized equivalent mass density of the unit cell structure 1 to be:

[0046]

[0047]

[0048] Where ρ is the normalized equivalent mass density; M t is the mass of the unit cell structure 1; m is the mass of the metal core 15; k is the stiffness of the elastic layer 14; M is the difference between the mass of the unit cell structure 1 and the mass of the metal core 15; is the external excitation frequency; a is the length of the first horizontal beam 11; c is the out-of-plane height of the vibration reduction structure; ρ1 is the density of the material used to prepare the unit cell structure 1; ρ2 is the density of the metal core 15; r1 is the radius of the metal core 15; r2 is the radius of the arc cavity.

[0049] This embodiment provides a specific negative Poisson's ratio vibration reduction structure, whose structure thickness is 67.5 mm, and its geometric parameters (combined with the annotation of the parameters, please refer to Figure 4 ) includes the length of the horizontal cell wall (a = 45 mm), the length of the inclined cell wall (b = 22.5 mm), the width of the inclined cell wall (t = 1.5 mm), the angle between two adjacent inclined cell walls (θ = 120°), the height of the lattice (i.e., the unit cell structure 1) The width of the lattice (l = 67.5 mm), the inner angle that controls the size of the resonant cavity (α = 30°), the radius of the circular cross section of the metal core 15 (r1 = 7.5 mm), and the arc radius of the contact line between the elastic interlayer and the epoxy resin skeleton (r2 = 9 mm). The density of epoxy resin is: ρ1 = 477.5 kg / m 3 , the density of the metal core 15 is: ρ2 = 11000 kg / m 3 .

[0050] Based on the above parameters, the mass of epoxy resin (the difference between the mass of unit cell structure 1 and the mass of metal core 15) M and the mass of metal core 15 m are calculated to be 15.4 g and 134.8 g respectively. The stiffness k is measured experimentally and its value is 1.57*10 -6 N / m.

[0051] Substituting the material parameters into the normalized equivalent mass density, the frequency-normalized equivalent mass density curve can be plotted, such as Figure 6 As shown in the figure, the normalized equivalent mass density in the range of 471.4-1500Hz is less than zero. When the normalized equivalent mass density is less than zero, the structure resonates, which makes the vibration reduction structure of this scheme have vibration suppression properties.

[0052] Therefore, this solution can introduce multiple vibration absorbers through the unique setting of the vibration reduction structure, thereby effectively suppressing low-frequency vibrations and preventing the transmission of harmful elastic waves.

Claims

1. Negative Poisson's ratio vibration reduction structure, characterized in that: It comprises a plurality of unit cell structures, wherein the unit cell structures comprise a first horizontal beam, a second horizontal beam and an elastic inclined beam; the cross sections of the first horizontal beam and the second horizontal beam are both triangular; The two first horizontal beams are arranged up and down, and the ends on the same side are connected by an elastic inclined beam; the elastic inclined beam comprises two sections of straight beams connected to each other and forming an angle; each elastic inclined beam is connected to a second horizontal beam at the connection point of the straight beams and at a side away from the first horizontal beam; Adjacent first horizontal beams of adjacent unit cell structures are connected, adjacent second horizontal beams are connected, and adjacent elastic inclined beams are connected.

2. The negative Poisson's ratio vibration damping structure according to claim 1, characterized in that: In each unit cell structure, the two first horizontal beams are symmetrically arranged, and the surfaces of the two first horizontal beams away from each other are parallel to the horizontal plane; the two second horizontal beams are symmetrically arranged, and the surfaces of the two second horizontal beams away from each other are perpendicular to the horizontal plane.

3. The negative Poisson's ratio vibration damping structure according to claim 2, characterized in that: The first horizontal beam and the second horizontal beam have equal masses.

4. The negative Poisson's ratio vibration damping structure according to claim 2, characterized in that: In the unit cell structure, the two elastic inclined beams do not contact each other, and the two first horizontal beams do not contact each other.

5. The negative Poisson's ratio vibration damping structure according to any one of claims 2 to 4, characterized in that: The first horizontal beam and the second horizontal beam of the unit cell structure are provided with an arc-shaped cavity at the end face away from the elastic inclined beam, and a metal core with an end face flush with the end face of the arc-shaped cavity is arranged in the arc-shaped cavity, and an elastic layer is filled between the metal core and the arc-shaped cavity; the sum of the radius of the metal core and the thickness of the elastic layer is equal to the radius of the arc-shaped cavity.

6. The negative Poisson's ratio vibration damping structure according to claim 5, characterized in that: The depth of the arc-shaped cavity is equal to its radius, and the cross section of the metal core is semicircular.

7. The negative Poisson's ratio vibration damping structure according to claim 5, characterized in that: In adjacent unit cell structures, two adjacent first horizontal beams are an integrated structure, two adjacent second horizontal beams are an integrated structure, two adjacent metal cores are an integrated structure, and two adjacent elastic layers are an integrated structure.

8. The negative Poisson's ratio vibration damping structure according to any one of claims 1-4, 6-7, characterized in that: The angle θ between the two straight beam sections of the elastic inclined beam is 60°≤θ≤120°.

9. The negative Poisson's ratio vibration damping structure according to claim 8, characterized in that: The first horizontal beam, the second horizontal beam and the elastic inclined beam of the unit cell structure are all made of epoxy resin.

10. The negative Poisson's ratio vibration damping structure according to claim 5, characterized in that: The normalized equivalent mass density of the unit cell structure is: Mt=M+m Where ρ is the normalized equivalent mass density; M t is the mass of the unit cell structure; m is the mass of the metal core; k is the stiffness of the elastic layer; M is the difference between the mass of the unit cell structure and the mass of the metal core; is the external excitation frequency; a is the length of the first horizontal beam; c is the out-of-plane height of the vibration reduction structure; ρ1 is the density of the material used to prepare the unit cell structure; ρ2 is the density of the metal core; r1 is the radius of the metal core; r2 is the radius of the arc cavity.

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