Low frequency load bearing resistant acoustic black hole damping element

Abstract

The application relates to the field of damping devices, and particularly discloses a low-frequency load-resistant acoustic black hole damping element, which comprises a plurality of acoustic black hole pieces, an elastic body and a spacer, the acoustic black hole pieces are arranged at intervals along the thickness direction of the acoustic black hole pieces, each acoustic black hole piece comprises a piece body and an acoustic black hole arranged on the piece body, the elastic body is fixedly connected between two adjacent piece bodies, and the material of the elastic body is different from that of the piece body; and the spacer is fixedly arranged on the piece body and used for reducing secondary noise formed due to interference between the piece body and the acoustic black hole. The acoustic black hole and the spiral line are combined, the acoustic black hole pieces and the elastic body are periodically arranged and assembled, the vibration absorption effect, the acoustic black hole effect and the band gap effect are comprehensively utilized, and the broadband vibration absorption effect in the low-frequency range can be realized.

Description

Technical Field

[0001] The present application relates to the field of vibration reduction devices, and in particular to a low-frequency load-bearing acoustic black hole vibration reduction element. Background Art

[0002] Low-frequency mechanical vibrations from a ship's propulsion system are transmitted to the hull through the support base. The hull's radiated noise can travel long distances underwater, significantly limiting the ship's stealth capabilities. To meet the ever-increasing overall acoustic radiation requirements of new ships and overcome the current bottleneck in low-frequency acoustic control, more low-frequency vibration reduction and suppression technologies must be incorporated.

[0003] Acoustic black hole (ABH) structures possess superior elastic wave manipulation capabilities, offering new insights into the design of low-frequency, broadband vibration reduction systems for ships. However, the effective operating frequency of ABHs is often relatively high, making it difficult to effectively control low-frequency vibrations. Current research on ABHs focuses on mechanisms such as wave manipulation and energy focusing and dissipation, and the test specimens used are mostly small and simple. Low-frequency and load-bearing issues remain technical bottlenecks for the practical engineering application of ABHs in vibration reduction. Therefore, an ABH vibration reduction structure with programmable low-frequency targets, broadband vibration reduction, and compact footprint is urgently needed.

[0004] Traditional acoustic black holes generally have two vibration reduction application scenarios: one is to cut a slot in the main structure to be dampened, forming an embedded disc-shaped acoustic black hole. The lower the vibration reduction frequency, the larger the size of the acoustic black hole and the larger the slot, which will weaken the strength of the main structure to be dampened. Traditional acoustic black hole structures have difficulty achieving low-frequency vibration reduction within the range of common engineering dimensions, and the acoustic black hole effect usually only occurs in the medium and high frequency bands. The second method is to make the acoustic black hole into a disc and fix it to the main structure to be dampened with bolts or glue. However, this is often too large and takes up a lot of space, which is still a long way from practical engineering application. Summary of the Invention

[0005] In order to improve the problem that traditional acoustic black holes are large in size and difficult to achieve low-frequency vibration reduction, the present application provides a low-frequency load-bearing acoustic black hole vibration reduction element.

[0006] The low-frequency load-bearing acoustic black hole vibration reduction element provided in this application adopts the following technical solution:

[0007] A low-frequency load-bearing acoustic black hole vibration reduction element, comprising:

[0008] A plurality of acoustic black hole sheets are arranged at intervals along the thickness direction of the sheet, each of the acoustic black hole sheets comprising a sheet and an acoustic black hole disposed on the sheet;

[0009] an elastic body, fixedly connected between two adjacent sheets, wherein the material of the elastic body is different from that of the sheets;

[0010] The isolating member is fixedly arranged on the sheet body and is used to reduce the secondary noise generated by interference between the sheet body and the acoustic black hole.

[0011] Furthermore, the elastic body is located at the four corners of the sheet, and the acoustic black hole is located at the center of the sheet.

[0012] If multiple acoustic black hole sheets are directly superimposed, the vibration energy can be easily transmitted directly through the sheets, and the energy gathered in the acoustic black hole is less, which is not conducive to the dissipation of energy in the acoustic black hole. The present application adopts multiple acoustic black hole sheets arranged at intervals, and an elastomer is connected between adjacent acoustic black hole sheets; on the one hand, the elastomer has a vibration reduction effect, and on the other hand, the elastomer is conducive to more vibration energy gathering in the acoustic black hole, so that the vibration energy is efficiently dissipated and the vibration reduction effect is improved. In addition, the periodic arrangement of sheets and elastomers of different materials forms a band gap effect based on the principles of Bragg scattering and local resonance. Within the band gap frequency band, the vibration reduction effect is better.

[0013] This application is relatively small and can be used in floating raft vibration isolation systems, either in series, in parallel, or as a replacement for conventional rubber vibration dampers. Unlike conventional acoustic black holes that are glued or embedded into the main vibration damping structure, this application allows the acoustic black holes to act on the energy transfer path, significantly improving the vibration reduction effect.

[0014] Furthermore, the plurality of sheets include two cover sheet bodies and a plurality of intermediate sheets arranged between the two cover sheet bodies, and the cover sheet bodies are connected to the vibration source.

[0015] Preferably, bolt holes are provided on the cover plate body.

[0016] During use, one cover plate can be bolted to the marine power machinery vibration source, while the other cover plate can be bolted to the ship's foundation or raft pad. The size and position of the bolt holes can be designed according to actual working conditions to meet different installation requirements.

[0017] Furthermore, the thickness of the intermediate sheet is smaller than the thickness of the cover sheet.

[0018] The cover plate, as a load-bearing structure, has a relatively large thickness to ensure the overall load-bearing strength of the vibration damping element. Because the elastic members between the plates can provide a certain load-bearing function, the thickness of the intermediate plates can be smaller than that of the cover plates, reducing the overall volume and weight of the present application. Furthermore, minimizing the thickness of the intermediate plates facilitates achieving a lower-frequency localized resonance effect.

[0019] Furthermore, the number of the intermediate sheets is no less than 4.

[0020] A sufficient number of intermediate sheets are provided to ensure that a band gap effect can be generated.

[0021] Furthermore, the isolation member is an elastic pad, and the isolation member and the acoustic black hole are respectively located on two opposite sides of the sheet.

[0022] The elastic pad helps to prevent the acoustic black hole from interfering with the sheet body under impact and generating secondary noise.

[0023] Furthermore, the acoustic black hole is a spiral acoustic black hole.

[0024] Furthermore, the spiral acoustic black hole includes a spiral body and a damping layer fixed to the end of the spiral body.

[0025] Preferably, the radius of the helix is ,in r 0 is the initial radius, s is the radius change rate, θ is the spiral angle.

[0026] The helix increases the length of the acoustic black hole in a space of limited size, fully utilizes the curled space, realizes "small size controlling large wavelength", expands the effective frequency band of the acoustic black hole to low frequency, and breaks through the acoustic black hole effect to below 100 Hz. In the low-frequency band, the spiral acoustic black hole mode is very rich and dense.

[0027] Furthermore, the cross-sectional thickness of the spiral h ( x ) and the spiral radius x The following relationship is satisfied:

[0028]

[0029] in, h 0 is the residual thickness of the spiral, x 0 is the radius of the top cone, x 1 is the maximum radius of the helix, h t is the thickness of the non-acoustic black hole region, m is the power exponent, ε is the coefficient.

[0030] Preferably, h 0 ≥ 0.4 mm, x 0≤ 10mm, x 1≤ 250mm, h t ≥ 50mm, m ≥ 2, ε ≥ 0.001.

[0031] Through the acoustic black hole energy focusing effect, energy is gathered at the end of the spiral, and the vibration energy is efficiently dissipated through the damping layer, thereby improving the vibration reduction effect. The cross-sectional thickness of the spiral of the present application is gradually set. Compared with the spiral of uniform thickness, the variable thickness part of the spiral in the present application has more small local deformation modes. The alternating stress caused by the small deformation of the spiral is more likely to cause mutual coupling with the additional damping layer. The shear and compression deformation of the damping layer material is the main way for the system to consume energy. This makes the spiral of the present application have better damping enhancement characteristics, that is, the spiral and the damping layer have a greater modal density after being combined, and the modal damping ratio is further improved.

[0032] Furthermore, the elastomer is selected from one or more of rubber, plastic, and glass fiber.

[0033] In summary, this application includes at least one of the following beneficial technical effects:

[0034] 1. This application combines helical lines and acoustic black hole cross-sections to expand the characteristic size of the acoustic black hole, reducing the natural frequency of the acoustic black hole sheet to below 50 Hz. This successfully extends the acoustic black hole effect to below 100 Hz. Furthermore, the helical acoustic black hole modes are very rich and dense in the low-frequency range, enabling broadband vibration absorption at low frequencies through design.

[0035] 2. This application fully utilizes the energy focusing effect of the acoustic black hole and lays the energy-dissipating damping material at the tip of the acoustic black hole, thereby improving the modal coupling loss factor, greatly improving the damping energy dissipation efficiency, and improving the damping vibration reduction efficiency;

[0036] 3. This application constructs a periodic arrangement structure of "acoustic black hole sheet-elastic body", which forms a certain vibration reduction band gap based on the principles of Bragg scattering and local resonance. Within the band gap frequency band, the vibration reduction effect is better;

[0037] 4. Both the sheet and the elastic body have a certain load-bearing function. When assembled into a vibration-damping element, it is compact and can be used in floating raft vibration isolation systems, in series, parallel, or as a replacement for commonly used rubber vibration dampers. Unlike conventional acoustic black holes that are glued or embedded in the main vibration damping structure, this application will make the acoustic black hole act on the energy transfer path, greatly improving the vibration reduction effect.

[0038] 5. The design parameters of a single acoustic black hole panel are adjustable, such as helix parameters, thickness, and damping, to meet the vibration reduction requirements of different target frequency bands. The parameters of a multi-layer acoustic black hole panel assembly are adjustable (sheet spacing, reserved distance between sheets, sheet support frame, etc.) to meet the vibration reduction requirements of different spaces, different frequency bands, and different loads in different application scenarios such as different equipment and rafts. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1This is a front view of a low-frequency load-bearing acoustic black hole vibration reduction element according to an embodiment of the present application;

[0040] Figure 2 1. It is a top view of a low-frequency load-bearing acoustic black hole vibration reduction element according to an embodiment of the present application;

[0041] Figure 3 Schematic diagram of the acoustic black hole configuration in the embodiment of the present application;

[0042] Figure 4 This is a comparison chart of the damping enhancement effects of spiral acoustic black holes with different structures.

[0043] Figure numerals: 1. cover plate; 2. middle plate; 3. elastic body; 4. spacer; 5. bolt hole; 6. spiral acoustic black hole; 7. damping layer. DETAILED DESCRIPTION

[0044] The following is combined with Figure 1-4 This application is described in further detail.

[0045] The embodiment of the present application discloses a low-frequency load-bearing acoustic black hole vibration reduction element. Figure 1 and Figure 2 The low-frequency load-bearing acoustic black hole vibration reduction element includes a plurality of acoustic black hole sheets arranged at equal intervals along its own thickness direction. Each acoustic black hole sheet includes a sheet and a spiral acoustic black hole 6 arranged in the center of the sheet. The spiral acoustic black hole 6 and the sheet can be processed in an integral molding manner, or the spiral acoustic black hole 6 can be fixed to the sheet by bolts.

[0046] Reference Figure 1 and Figure 2 The plates are square, but other shapes are possible, and can be made of metal materials such as steel, aluminum alloy, and titanium alloy. Material selection and design require impedance matching with the equipment mounting plate, raft, and other components in the engineering application scenario. The multiple plates include cover plates 1 at both ends and several intermediate plates 2 positioned between the two cover plates 1.

[0047] Reference Figure 2 The cover plate 1 is the primary load-bearing structure, with bolt holes 5 located on each of its four edges for connecting to the vibration source. During use, one cover plate 1 can be bolted to the marine power machinery vibration source, while the other cover plate 1 can be bolted to the ship's foundation or raft pad. The size and location of the bolt holes 5 can be designed based on actual operating conditions to meet diverse installation requirements.

[0048] To ensure load-bearing strength, the thickness of the cover plate 1 should be no less than 10 mm; the greater the load, the thicker the cover plate 1 needs to be. To achieve lower-frequency local resonance, the thickness of the intermediate plate 2 should be minimized, typically no greater than 3 mm. In this embodiment, the cover plate 1 is a steel plate measuring 210 mm long, 210 mm wide, and 20 mm thick, capable of bearing a load of 400 kg; the intermediate plate 2 is a steel plate measuring 210 mm long, 210 mm wide, and 3 mm thick.

[0049] Reference Figure 2 The spiral acoustic black hole 6 includes a spiral body and a damping layer 7 fixed to the end of the spiral body. The spiral body can be formed by mechanical processing or 3D printing. It can be made of metal materials such as steel and aluminum, or non-metallic materials such as acrylic and resin. The damping layer 7 can be made of materials such as VHB, T54, and butyl rubber. The damping material with a larger damping loss factor is better. The damping layer 7 can be pasted or coated on the end of the spiral body; the thickness of the damping layer 7 is h d =5mm, damping layer length x d =120mm.

[0050] Reference Figure 2 The radius of the helix is ,in r 0 is the initial radius, s is the radius change rate, θ is the spiral angle; in this embodiment, the spiral angle θ π to 10π, the initial radius r 0=50mm, radius change rate s =0.008.

[0051] The helix increases the length of the acoustic black hole in a space of limited size, fully utilizes the curled space, realizes "small size controlling large wavelength", expands the effective frequency band of the acoustic black hole to low frequency, and breaks through the acoustic black hole effect to below 100 Hz. In the low-frequency band, the spiral acoustic black hole mode is very rich and dense.

[0052] Further, refer to Figure 3 , the cross-sectional thickness of the spiral h ( x ) and the spiral radius x The following relationship is satisfied:

[0053]

[0054] in, h 0 is the residual thickness of the spiral, h t is the thickness of the non-acoustic black hole region, x 0 is the radius of the top cone,x 1 is the maximum radius of the helix, m is the power exponent, ε is a coefficient. In this embodiment, h 0=0.5mm, h t =50mm, m =2.1, ε =0.003, x 0=0 or 10mm, x 1= 250mm.

[0055] The cross-sectional thickness of the spiral body of the present application is gradually changed, which has better damping enhancement characteristics compared with a spiral body with uniform thickness. Figure 4 The damping ratio test results of three different models are shown, among which (a) is the case where the cross-section of the spiral does not become thinner with the acoustic black hole, and the cross-section of the spiral is always of maximum thickness and constant thickness, on which an equal damping model is laid, that is, the design parameters of the damping layer remain consistent (damping material parameters, length, thickness, width); (b) is the case where the total weight of the acoustic black hole spiral is consistent, the cross-section of the spiral is of constant thickness, and an equal damping model is laid on it; (c) is the variable thickness spiral in this application, on which an equal damping model is laid (SABH stands for supplementary acoustic black hole, that is, the spiral acoustic black hole in this application).

[0056] Compared with the other two spiral structures, the present application has a larger modal density within the range of 500Hz, and the modal damping ratio has been greatly improved compared with the other two models. The damping ratio of some modes has been increased to around 0.1 or even higher, reflecting the damping enhancement effect of the present application. This is because there are more small local deformation modes in the variable thickness part of the spiral in the present application. The alternating stress caused by the small deformation of the spiral is more likely to cause it to couple with the additional damping layer. The shear and compression deformation of the damping layer material is the main way for the system to consume energy. This makes the spiral of the present application have better damping enhancement characteristics. After the spiral is compounded with the damping layer, it has a larger modal density and a greater improvement in the modal damping ratio, that is, the energy dissipation efficiency is higher and the vibration reduction effect is better.

[0057] Reference Figure 1 , an elastic body 3 is fixedly connected between two adjacent sheets. The elastic body 3 is made of elastic material and the material is different from that of the sheet. It can be made of rubber, plastic or glass fiber. In this embodiment, the elastic body 3 is a rubber block with a thickness of 30mm. The rubber block is connected to the steel sheet by hot vulcanization. Figure 1 and Figure 2 Between two adjacent sheets, four rubber blocks are located at the four corners of the sheets.

[0058] If multiple acoustic black hole sheets are directly superimposed, the vibration energy can be easily transmitted directly through the sheets, and the energy gathered in the acoustic black hole is less, which is not conducive to the dissipation of energy in the acoustic black hole. The present application adopts a plurality of acoustic black hole sheets arranged at intervals, and an elastomer 3 is connected between adjacent acoustic black hole sheets; on the one hand, the elastomer 3 has a vibration reduction effect, and on the other hand, the elastomer 3 is conducive to more vibration energy gathering in the acoustic black hole, so that the vibration energy is efficiently dissipated and the vibration reduction effect is improved. In addition, the sheets of different materials and the elastomer 3 are arranged periodically, and based on the principles of Bragg scattering and local resonance, a band gap effect is formed. Within the band gap frequency band, the vibration reduction effect is better. In order to produce the band gap effect, the number of intermediate sheets 2 is not less than 4.

[0059] Reference Figure 1 An isolation member 4 is fixedly provided on the side of each sheet opposite to the acoustic black hole. The isolation member 4 is a 2 mm thick rubber pad used to reduce the secondary noise generated by interference between the sheet and the acoustic black hole under impact.

[0060] The present application is relatively small in size and can be used in floating raft vibration isolation systems, in series, in parallel, or as a replacement for commonly used rubber vibration dampers. For example, in a floating raft vibration isolation system, it can be used in series with a 400kg, 2t airbag. The general installation frequency of the airbag vibration isolation system is 5Hz-15Hz. The vibration reduction element provided by the present application can be placed above the airbag in the vibration isolation system to weaken the vibration peak response at the installation frequency of the vibration isolation device. Unlike conventional acoustic black holes that are pasted or embedded in the main structure of the vibration reduction, the present application will enable the acoustic black hole to act on the energy transfer path, greatly improving the vibration reduction effect.

[0061] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A low-frequency load-bearing acoustic black hole vibration reduction element, characterized by: include: A plurality of acoustic black hole sheets are arranged at intervals along the thickness direction of the sheet, each of the acoustic black hole sheets comprises a sheet and an acoustic black hole disposed on the sheet, and the acoustic black hole is a spiral acoustic black hole; an elastic body, fixedly connected between two adjacent sheets, wherein the material of the elastic body is different from that of the sheets; The isolating member is fixedly arranged on the sheet body and is used to reduce the secondary noise generated by interference between the sheet body and the acoustic black hole.

2. The low-frequency load-bearing acoustic black hole vibration damping element according to claim 1, characterized in that: The elastic body is located at the four corners of the sheet, and the acoustic black hole is located at the center of the sheet.

3. The low-frequency load-bearing acoustic black hole vibration damping element according to claim 1, characterized in that: The plurality of sheets include two cover sheet bodies and a plurality of intermediate sheets arranged between the two cover sheet bodies, and the cover sheet bodies are connected to a vibration source.

4. The low-frequency load-bearing acoustic black hole vibration damping element according to claim 3, characterized in that: The thickness of the intermediate sheet is smaller than the thickness of the cover sheet.

5. The low-frequency load-bearing acoustic black hole vibration reduction element according to claim 3, characterized in that: The number of the intermediate sheets is no less than 4.

6. The low-frequency load-bearing acoustic black hole vibration reduction element according to claim 1, characterized in that: The isolation member is an elastic pad, and the isolation member and the acoustic black hole are respectively located on two opposite sides of the sheet.

7. The low-frequency load-bearing acoustic black hole vibration reduction element according to claim 1, characterized in that: The spiral acoustic black hole includes a spiral body and a damping layer fixed to the end of the spiral body.

8. The low-frequency load-bearing acoustic black hole vibration reduction element according to claim 7, characterized in that: The cross-sectional thickness of the spiral h ( x ) and the spiral radius x The following relationship is satisfied: in, is the residual thickness of the spiral, is the radius of the top cone, is the maximum radius of the helix, is the thickness of the non-acoustic black hole region, is the power exponent, is the coefficient.

9. The low-frequency load-bearing acoustic black hole vibration damping element according to claim 1, characterized in that: The elastomer is selected from one or more of rubber, plastic, and glass fiber.

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