Gradient multi-vibrator vibration absorber based on periodic acoustic black holes

Abstract

The invention belongs to the technical field of vibration and noise reduction, and particularly relates to a gradual change multi-vibrator vibration absorber based on periodic acoustic black holes. The device comprises multiple layers of eccentric rectangular discs which are arranged from bottom to top and connected through connecting columns, the sizes of the eccentric rectangular discs are gradually reduced from bottom to top, and each eccentric rectangular disc structurally comprises a rectangular column at an internal eccentric position, an external lower rectangular ring and an acoustic black hole located between the rectangular column and the lower rectangular ring; the upper ends of the rectangular column, the lower rectangular ring and the acoustic black hole are coplanar, and the upper end of the lower rectangular ring is also provided with an upper rectangular ring with the same size in the plane direction; the thickness h (wi) of the acoustic black hole is gradually increased from each inner edge of the lower rectangular ring to the inside in an index form of h (wi) = awim, i = 1, 2, 3 and 4, the outer edge thickness of the acoustic black hole is consistent with the thickness of the lower rectangular ring, and the inner edge thickness of the acoustic black hole is consistent with the height of the rectangular column. Through the energy focusing effect and the dynamic vibration absorption effect of the acoustic black holes, the eccentric rectangular disc can act on more frequencies, and the broadband vibration reduction effect can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of vibration and noise reduction, and particularly relates to a gradient multi-oscillator vibration absorber based on a periodic acoustic black hole. Background Technique

[0002] Vibration is a standing wave generated by multiple reflections at the boundaries in a structure, and noise is the wave energy radiated from the structural vibration into the air. Therefore, interfering with the wave behavior in the structure is an effective means to achieve vibration and noise reduction of the structure.

[0003] Currently, the common wave manipulation methods are mainly divided into two types: active and passive. Active methods generally require external energy supply and the design of the system is very cumbersome, so they have not been widely promoted at present. For passive methods, the most basic form is to attach damping materials. Some viscoelastic materials can effectively absorb vibration energy. However, for some major equipment, a large amount of damping materials need to be pasted on the surface for vibration reduction. Although this can achieve the effect of vibration and noise reduction, it is not conducive to the lightweight of the structure, not only increasing the economic cost but also adding too much additional mass.

[0004] The proposal of the concept of the Acoustic Black Hole (ABH) effect has opened a new chapter in the research on realizing the artificial control of the propagation of flexural waves in elastic media and structures. As a new type of passive control method, the acoustic black hole controls the wave propagation through the design and optimization of the structure's own shape, with the advantages of simple and flexible implementation and small mass, and has great potential and broad application prospects in thin-walled structures.

[0005] Currently, the main way to change the structural impedance to achieve the acoustic black hole effect is to change the thickness of the structure. Utilizing the propagation characteristics of flexural waves in a variable-thickness structure, when the structure thickness decreases in the form of a certain exponential function, the phase velocity and group velocity of the flexural waves also decrease accordingly. Ideally, when the thickness decreases to zero, the wave velocity at the edge of the structure can be reduced to zero, achieving zero reflection of the wave, concentrating all the wave energy at the tip position of the structure, and achieving the purpose of energy absorption or vibration and noise reduction through the damping of the structure and the damping materials attached to the structure. However, the traditional acoustic black hole structure achieves the purpose of vibration and noise reduction by cutting the controlled object, which inevitably reduces the stiffness and strength of the structure, and such a design is not applicable in some key structure designs. In recent years, through the periodic research on the acoustic black hole structure, it has been found that by using the Bragg scattering effect caused by impedance mismatch and the local resonance effect of the acoustic black hole, a band gap can be generated at a lower frequency, further broadening the action range of the acoustic black hole and improving the vibration reduction effect. Summary of the Invention

[0006] The object of the present invention is to provide a gradient multi - oscillator vibration absorber based on a periodic acoustic black hole, which utilizes the bandgap generated by the Bragg scattering effect and the local resonance effect of the acoustic black hole, as well as the dynamic vibration absorption effect, to achieve broadband vibration reduction of the controlled structure and improve the vibration reduction effect.

[0007] The present invention proposes a gradient multi - oscillator vibration absorber based on a periodic acoustic black hole, which includes multiple layers of eccentric rectangular disks connected by connecting columns and arranged from bottom to top. The size of the eccentric rectangular disks gradually decreases from bottom to top. The structure of the eccentric rectangular disk includes a rectangular column at the internal eccentric position, a lower rectangular ring at the outside, and an acoustic black hole located between the rectangular column and the lower rectangular ring. The upper ends of the rectangular column, the lower rectangular ring, and the acoustic black hole are coplanar. An upper rectangular ring with the same size in the plane direction is also installed at the upper end of the lower rectangular ring; the thickness h(w i ) of the acoustic black hole exponentially increases as h(w i ) = aw i m , i = 1, 2, 3, 4 from each inner edge of the lower rectangular ring inwards, where w i represents the distance extended inwards from the i - th inner edge of the lower rectangular ring, a is a coefficient, m is greater than or equal to 2. The outer edge thickness of the acoustic black hole is the same as the thickness of the lower rectangular ring, and the inner edge thickness is the same as the height of the rectangular column.

[0008] Advantageously, the upper rectangular ring is made of a damping material.

[0009] Advantageously, the damping material of the upper rectangular ring is butyl rubber material.

[0010] Advantageously, the upper rectangular ring is adhered above the lower rectangular ring.

[0011] Advantageously, the material of the connecting column is rubber.

[0012] Advantageously, the thickness of the connecting column is 5 mm.

[0013] Advantageously, the material of the eccentric rectangular disk is aluminum.

[0014] Advantageously, the eccentric rectangular disk is connected to the connecting column by gluing or bolts.

[0015] Waves with a certain frequency emitted by the controlled structure are transmitted to the eccentric rectangular disk through the connecting column. Due to the exponentially decreasing thickness of the eccentric rectangular disk, the eccentric rectangular disk exerts an energy - gathering effect. The wave propagation speed decreases as the thickness decreases, the wavelength decreases, and the vibration amplitude of the wave increases, gathering towards the region with a smaller thickness; due to the different sizes of each eccentric rectangular disk, using the dynamic vibration absorption effect, it can be matched with more frequencies to achieve broadband vibration reduction and noise reduction for the passive structure.

[0016] The eccentric rectangular disks and connecting columns are arranged periodically. Due to the band gaps caused by the Bragg scattering effect and the local resonance effect of the acoustic black hole, waves are dissipated by the periodic structure when passing through the frequency range of the band gap, further broadening the vibration damping range and improving the vibration damping effect.

[0017] Advantageous effects: In the present invention, due to the Bragg scattering effect caused by the impedance mismatch between the rubber and the acoustic black hole and the local resonance effect of the acoustic black hole itself, the vibration damping structure can also achieve good vibration damping effects at low frequencies. Moreover, the size parameters of the eccentric rectangular disks follow the rule of increasing from the top to the bottom. Through the energy focusing effect and the dynamic vibration absorption effect of the acoustic black hole, the eccentric rectangular disks can act on more frequencies and achieve broadband vibration damping effects.

[0018] The features, functions, and advantages discussed above can be implemented independently in various examples or combined in other examples. Other details of the examples can be seen with reference to the following description and drawings. Description of the Drawings

[0019] When read in conjunction with the drawings, the examples, as well as the preferred mode of use, other objectives, and their descriptions, will be best understood by reference to the following detailed description of the examples of the present invention, in which:

[0020] Figure 1 is a schematic diagram of a gradient multi-oscillator vibration absorber based on a periodic acoustic black hole;

[0021] Figure 2 is a top view schematic diagram of the lowermost eccentric rectangular disk;

[0022] Figure 3 in which a and b are cross-sectional views of the lowermost eccentric rectangular disk along AA and BB, respectively;

[0023] Figure 4 is a schematic diagram of the propagation of elastic waves in the eccentric rectangular disk structure;

[0024] Figure 5 is a comparison diagram of the origin responses before and after installing the vibration absorber on a uniform plate.

[0025] 1 - Uniform plate; 2 - Rectangular column; 3 - Connecting column; 4 - Acoustic black hole; 5 - Upper rectangular ring; 6 - Lower rectangular ring Detailed Embodiments

[0026] The disclosed examples will be described more fully with reference to the drawings, in which some (but not all) of the disclosed examples are shown. In fact, many different examples can be described and these examples should not be construed as limited to the examples set forth herein. Rather, these examples are described so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art.

[0027] As shown Figure 1 The gradient multi-oscillator absorber based on the periodic acoustic black hole includes multiple layers of eccentric rectangular disks and multiple connecting columns 3. The structure of the eccentric rectangular disk includes a rectangular column 2 at the eccentric position, an acoustic black hole 4 coated on the side of the rectangular column 2, and a lower rectangular ring 6 extending outward from the edge of the acoustic black hole. An upper rectangular ring 5 is also arranged above the lower rectangular ring 6. The rectangular columns 2 of each eccentric rectangular disk are connected by connecting columns 3. The plane where the upper rectangular ring 5 is located is parallel to the upper and lower end faces of the rectangular column 2, and the connection line between the center of the upper rectangular ring 5 and the center of the lower end face of the rectangular column 2 is not perpendicular to the plane where the upper rectangular ring 5 is located.

[0028] See Figure 2 and Figure 3 the embodiment of the lowermost eccentric rectangular disk shown. The area between the rectangular column 2 and the lower rectangular ring 6 is the area of the acoustic black hole 4. The upper end face of the acoustic black hole 4 forms an inner rectangular ring, and the widths of the four sides of the inner rectangular ring are w ABH1 = 119.5 mm, w ABH2 = 80.25 mm, w ABH3 = 82.5 mm, w ABH4 = 50.75 mm.

[0029] The thickness h(w i ) of the acoustic black hole 4 decreases exponentially from each side of the rectangular column 2, that is, it increases exponentially from each inner edge of the lower rectangular ring 6 inward. The exponential expression for the increase is h(w i ) = aw i m , i = 1, 2, 3, 4, where w i , i = 1, 2, 3, 4 represents the distance extending inward from the 1st, 2nd, 3rd, and 4th inner edges of the lower rectangular ring 6, a represents the coefficient, and m is greater than or equal to 2.

[0030] Since the frequency of the eccentric rectangular disk is related to its size, the larger the size, the lower its first-order characteristic frequency. The size of the eccentric rectangular disk gradually decreases from bottom to top, and the frequencies matching the controlled structure increase from small to large, which can couple different frequencies. Therefore, the size of the eccentric rectangular disk can be specifically designed according to the characteristic frequency of the controlled structure. The upper rectangular ring 5 is made of a damping material. The upper rectangular ring 5 adheres above the lower rectangular ring 6, and the upper rectangular ring 5 and the lower rectangular ring 6 have the same size on the horizontal plane. The damping material of the upper rectangular ring 5 is butyl rubber material. The thickness of the lower rectangular ring 6 is equal to the minimum thickness of the acoustic black hole 4.

[0031] The material of the connecting column 3 is rubber, and the thickness is 5 mm. The material of the eccentric rectangular disk is aluminum. The eccentric rectangular disk structure can be connected to the connecting column 3 by various connection methods such as gluing or bolt connection.

[0032] To evaluate the vibration reduction level of the vibration absorber, it is installed on the uniform plate 1 in the simulation software. The boundary condition of the uniform plate 1 is the free boundary condition, and the original response before and after installation is measured. Figure 4 The schematic diagram of the propagation of elastic waves in the eccentric rectangular disk structure is shown in Figure 5 It can be seen from the origin response in that after installing the vibration absorber, all the resonance peaks within 500 Hz have decreased to varying degrees, and the dynamic vibration absorption phenomenon appears at the first resonance peak, reflecting the good vibration reduction performance of the vibration absorber for the controlled structure. This is because the eccentric rectangular disks with different size parameters have the acoustic black hole effect and the dynamic vibration absorption effect, and the eccentric design can generate richer modes, increasing the coupling between the controlled structure and the acoustic black hole structure. And due to the periodic arrangement of the connecting columns and the eccentric rectangular disks, the band gap caused by the Bragg scattering effect due to the impedance mismatch between them and the local resonance effect of the eccentric rectangular disk itself. When the wave passes through the frequency range of the band gap, it is dissipated by the periodic structure, improving the vibration reduction effect.

[0033] The description of the different advantageous arrangements has been presented for purposes of illustration and description, but the description is not intended to be exclusive or limited to the examples in the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. Additionally, the different advantageous examples may describe different advantages compared to other advantageous examples. The selection and description of the selected example or examples are made in order to best illustrate the principles, practical applications, and to enable those of ordinary skill in the art to understand the disclosure of various examples that have been made with various modifications suitable for the particular use contemplated.

Claims

1. A gradual multi-vibrator vibration absorber based on periodic acoustic black hole, characterized in that: The invention comprises a plurality of eccentric rectangular disks connected by connecting columns (3) arranged from bottom to top, wherein the size of the eccentric rectangular disks gradually decreases from bottom to top, and the structure of the eccentric rectangular disks comprises a rectangular column (2) at an internal eccentric position, an external lower rectangular ring (6), and an acoustic black hole (4) located between the rectangular column (2) and the lower rectangular ring (6), wherein the upper ends of the rectangular column (2), the lower rectangular ring (6) and the acoustic black hole (4) are coplanar, and an upper rectangular ring (5) having the same size in a plane direction is also installed on the upper end of the lower rectangular ring (6); the thickness h (w i ) from each inner edge of the lower rectangular ring (6) inward in the form of exponential h(w i ) = aw i m ,i=1,2,3,4 increasing, w i represents the distance extending inward from the i-th inner edge of the lower rectangular ring (6), a is a coefficient, m is greater than or equal to 2, the outer edge thickness of the acoustic black hole (4) is consistent with the thickness of the lower rectangular ring (6), and the inner edge thickness is consistent with the height of the rectangular column (2).

2. The gradient multi-vibrator vibration absorber according to claim 1, characterized in that: The upper rectangular ring (5) is made of damping material.

3. The gradient multi-vibrator vibration absorber according to claim 2, characterized in that: The damping material of the upper rectangular ring (5) is butyl rubber material.

4. The gradient multi-vibrator vibration absorber according to claim 3, characterized in that: The upper rectangular ring (5) is adhered to the upper part of the lower rectangular ring (6).

5. The gradient multi-vibrator vibration absorber according to claim 1, characterized in that: The material of the connecting column (3) is rubber.

6. The gradient multi-vibrator vibration absorber according to claim 1, characterized in that: The thickness of the connecting column (3) is 5 mm.

7. The gradient multi-vibrator vibration absorber according to claim 1, characterized in that: The material of the eccentric rectangular disk is aluminum.

8. The gradient multi-vibrator vibration absorber according to claim 1, characterized in that: The eccentric rectangular disk is connected to the connecting column (3) by gluing or bolts.

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