Low-frequency load-bearing acoustic black hole damping element

Abstract

The invention relates to the field of vibration reduction devices, and particularly discloses a low-frequency bearing-resistant acoustic black hole vibration reduction element which comprises a plurality of acoustic black hole sheet bodies, elastic bodies and isolation pieces, the acoustic black hole sheet bodies are arranged at intervals in the thickness direction of the acoustic black hole sheet bodies, and each acoustic black hole sheet body comprises a sheet body and an acoustic black hole formed in the sheet body; the elastic bodies are fixedly connected between two adjacent sheet bodies, and the elastic bodies and the sheet bodies are made of different materials; and the separator is fixedly arranged on the sheet body and is used for reducing secondary noise formed by interference between the sheet body and the acoustic black hole. The acoustic black holes and the spiral lines are combined, the acoustic black hole sheet bodies and the elastic bodies are periodically arranged and assembled, the vibration absorption effect, the acoustic black hole effect and the band gap effect are integrated, and the low-frequency broadband vibration absorption effect can be achieved.

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] The low-frequency mechanical vibration of the ship's power plant is transmitted to the hull through the supporting base. The hull vibration radiation noise can be transmitted over long distances in the water, greatly limiting the ship's stealth. In order to match the ever-increasing overall sound radiation indicators of new ships and break through the key bottleneck of existing low-frequency acoustic control, more low-frequency vibration reduction and suppression technologies need to be incorporated.

[0003] The acoustic black hole (ABH) structure has excellent elastic wave control capabilities, which brings new inspiration to the low-frequency and broadband vibration reduction design of ships. However, the effective action frequency of acoustic black holes is often high, making it difficult to effectively control low-frequency vibrations. At present, the research hotspots of acoustic black holes generally focus on the study of mechanisms such as wave control and energy focusing and dissipation, and most of the test specimens used are small-sized and simple structures. The low-frequency and load-bearing problems of acoustic black hole vibration reduction are still the technical bottlenecks for the actual engineering application of acoustic black holes in the field of vibration reduction. Therefore, there is an urgent need for an acoustic black hole vibration reduction structure with the characteristics of low-frequency target frequency design, broadband vibration reduction, and small space size.

[0004] Traditional acoustic black holes generally have two vibration reduction application scenarios: one is to make grooves on the main structure to be reduced to form an embedded disc-shaped acoustic black hole. If the vibration reduction frequency is lower, the size of the acoustic black hole will be larger and the groove will be larger, which will weaken the strength of the main structure to be reduced. Traditional acoustic black hole structures are difficult to achieve low-frequency vibration reduction within the commonly used engineering size range, and usually only produce acoustic black hole effects in the medium and high frequency bands. The second is to make the acoustic black hole into a disc and fix it to the main structure to be reduced by bolts or glue, but it is often too large and occupies a large space, which is still far from practical engineering applications. 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: A low-frequency load-bearing acoustic black hole vibration reduction element, comprising: 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; 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.

[0007] 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.

[0008] If multiple acoustic black hole sheets are directly superimposed, the vibration energy is 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 sheets and elastomers of different materials are arranged periodically, and a band gap effect is formed based on the principles of Bragg scattering and local resonance. Within the band gap frequency band, the vibration reduction effect is better.

[0009] The application is small in size and can be used in floating raft vibration isolation systems, connected in series, parallel or as a substitute for commonly used rubber vibration dampers. Unlike conventional acoustic black holes that are pasted or embedded in the main structure of vibration reduction, the application will make the acoustic black hole act on the energy transfer path, greatly improving the vibration reduction effect.

[0010] 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 a vibration source.

[0011] Preferably, bolt holes are provided on the cover plate body.

[0012] When in use, one cover plate can be connected to the marine power machinery vibration source device by bolts, and the other cover plate can be connected to the ship base or the pad on the floating raft by bolts. The size and position of the bolt hole can be designed according to the actual working conditions to meet different installation requirements.

[0013] Furthermore, the thickness of the middle sheet is smaller than the thickness of the cover sheet.

[0014] As a bearing structure, the cover plate has a relatively large thickness to ensure the bearing strength of the vibration reduction element as a whole; since the elastic body between the plates can play a certain bearing role, the thickness of the middle plate can be less than that of the cover plate, so as to reduce the overall volume and weight of the present application. In addition, the thickness of the middle plate is as small as possible, which is conducive to achieving a lower frequency local resonance effect.

[0015] Furthermore, the number of the intermediate sheets is no less than 4.

[0016] A sufficient number of intermediate sheets are provided to ensure that a band gap effect can be produced.

[0017] 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 body.

[0018] The elastic pad helps to prevent the acoustic black hole from interfering with the sheet body under impact and generating secondary noise.

[0019] Furthermore, the acoustic black hole is a spiral acoustic black hole.

[0020] Furthermore, the spiral acoustic black hole includes a spiral body and a damping layer fixed to the end of the spiral body.

[0021] 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.

[0022] The spiral 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.

[0023] Furthermore, the cross-sectional thickness of the spiral h ( x ) and the helical radius x The following relations are satisfied:

[0024] 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 index, ε is the coefficient.

[0025] Preferably, h 0 ≥ 0.4 mm, x 0≤ 10mm, x 1≤ 250mm, h t ≥ 50mm, m ≥ 2, ε ≥ 0.001.

[0026] Through the acoustic black hole energy focusing effect, the 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, and 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 has a larger modal density after being compounded with the damping layer, and the modal damping ratio is more improved.

[0027] Furthermore, the elastomer is selected from one or more of rubber, plastic, and glass fiber.

[0028] In summary, the present application includes at least one of the following beneficial technical effects: 1. This application integrates the spiral line and the acoustic black hole cross section, expands the characteristic size of the acoustic black hole, makes the natural frequency of the acoustic black hole sheet lower than 50Hz, successfully breaks through the acoustic black hole effect to below 100Hz, and the spiral line acoustic black hole mode is very rich and dense in the low-frequency band, and the low-frequency broadband vibration absorption effect can be achieved through design; 2. This application makes full use of the energy focusing effect of the acoustic black hole, lays the energy-dissipating damping material at the tip of the acoustic black hole, improves the modal coupling loss factor, greatly improves the damping energy dissipation efficiency, and improves the damping vibration reduction efficiency; 3. This application constructs a periodic arrangement structure of "acoustic black hole sheet-elastic body", based on the principle of Bragg scattering and local resonance, to form a certain vibration reduction band gap, within the band gap frequency band, the vibration reduction effect is better; 4. Both the sheet and the elastic body have a certain bearing function. After being assembled into a vibration reduction element, the volume is small and can be used in the floating raft vibration isolation system, in series, parallel or as a substitute for the commonly used rubber vibration damper; unlike the conventional acoustic black hole pasted or embedded in the main structure of vibration reduction, this application will make the acoustic black hole act on the energy transfer path, greatly improving the vibration reduction effect; 5. The design parameters of a single sheet of the acoustic black hole plate are adjustable, such as spiral parameters, thickness, damping, etc., to meet the vibration reduction requirements of different target frequency bands; the parameters of the multi-layer acoustic black hole plate assembly are adjustable (sheet spacing, reserved distance between sheets, sheet bearing outer frame, etc.) to meet the vibration reduction requirements of different spaces, different frequency bands, and different loads in application scenarios such as different equipment and different rafts. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a front view of a low-frequency load-bearing acoustic black hole vibration reduction element according to an embodiment of the present application; Figure 2It is a top view of a low-frequency load-bearing acoustic black hole vibration reduction element according to an embodiment of the present application; Figure 3 is a schematic diagram of the acoustic black hole configuration in an embodiment of the present application; Figure 4 This is a comparison chart of the damping enhancement effect of spiral acoustic black holes with different structures.

[0030] Figure numerals: 1. cover plate body; 2. middle plate body; 3. elastic body; 4. spacer; 5. bolt hole; 6. spiral acoustic black hole; 7. damping layer. DETAILED DESCRIPTION

[0031] The following is combined with Figure 1-4 This application is described in further detail.

[0032] The present application embodiment 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 at 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 or the like.

[0033] Reference Figure 1 and Figure 2 The sheet body is square or other shapes, and can be made of metal materials such as steel, aluminum alloy, and titanium alloy. When selecting and designing materials, impedance matching with the equipment installation plate, floating raft, etc. in the engineering application scenario is required. The multiple sheets include cover sheet bodies 1 located at both ends and a plurality of intermediate sheets 2 arranged between the two cover sheet bodies 1.

[0034] Reference Figure 2 The cover plate body 1 is the main bearing structure, and its four edges are respectively provided with bolt holes 5 for connecting with the vibration source. When in use, one cover plate body 1 can be connected with the marine power machinery vibration source equipment by bolts, and the other cover plate body 1 can be connected with the ship base or the pad on the floating raft by bolts. The size and position of the bolt hole 5 can be designed according to the actual working conditions to meet different installation requirements.

[0035] In order to ensure the bearing strength, the thickness of the cover plate body 1 is not less than 10mm; the greater the load, the greater the thickness of the cover plate body 1. In order to achieve a lower frequency local resonance effect, the thickness of the middle plate body 2 should be as small as possible, usually not more than 3mm. In this embodiment, the cover plate body 1 is a steel plate with a length of 210mm, a width of 210mm, and a thickness of 20mm, which can bear a load of 400kg; the middle plate body 2 is a steel plate with a length of 210mm, a width of 210mm, and a thickness of 3mm.

[0036] 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, and can be made of metal materials such as steel and aluminum, or non-metal materials such as acrylic and resin. The damping layer 7 can be made of materials such as VHB, T54, butyl rubber, etc. 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.

[0037] Reference Figure 2 The radius of the spiral is ,in r 0 is the initial radius, s is the radius change rate, θ is the helical angle; in this embodiment, the helical angle θ π to 10π, the initial radius r 0=50mm, radius change rate s =0.008.

[0038] The spiral 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.

[0039] Further, refer to Figure 3 , the cross-sectional thickness of the spiral h ( x ) and the helical radius x The following relations are satisfied:

[0040] 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 index, 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, x1= 250mm.

[0041] The cross-sectional thickness of the spiral body of the present application is gradually varied, and has better damping enhancement characteristics compared to 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 additional acoustic black hole, that is, the spiral acoustic black hole in this application).

[0042] 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 is 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, and the alternating stress caused by the small deformation of the spiral is more likely to cause it to couple with the additional damping layer, and the shear and compression deformation of the damping layer material is the main way for the system to consume energy, which 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 larger improvement in the modal damping ratio, that is, the energy dissipation efficiency is higher and the vibration reduction effect is better.

[0043] Reference Figure 1 , an elastic body 3 is fixedly connected between two adjacent sheets, and the elastic body 3 is made of elastic material and the material is different from that of the sheet, and can be made of rubber, plastic or glass fiber. In this embodiment, the elastic body 3 is a rubber block with a thickness of 30 mm, and 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 respectively.

[0044] If multiple acoustic black hole sheets are directly superimposed, the vibration energy is 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 the 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 and elastomers 3 of different materials are arranged periodically, and a band gap effect is formed based on the principles of Bragg scattering and local resonance. Within the band gap frequency band, the vibration reduction effect is better. In order to produce a band gap effect, the number of intermediate sheets 2 is not less than 4.

[0045] Reference Figure 1 An isolation member 4 is fixedly provided on the side of each sheet body opposite to the acoustic black hole. The isolation member 4 is a 2 mm thick rubber pad, which is used to reduce the secondary noise generated by interference between the sheet body and the acoustic black hole under impact.

[0046] 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 substitute for commonly used rubber shock absorbers. For example, in a floating raft vibration isolation system, it is 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 allow the acoustic black hole to act on the energy transfer path, greatly improving the vibration reduction effect.

[0047] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A low-frequency load-bearing acoustic black hole vibration reduction element, characterized in that: 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 comprising a sheet and an acoustic black hole disposed on the sheet; 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. A low-frequency load-bearing acoustic black hole vibration reduction 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 reduction 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. A low-frequency load-bearing acoustic black hole vibration reduction element according to claim 2, 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 2, 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 isolating member is an elastic pad, and the isolating member and the acoustic black hole are respectively located on two opposite sides of the sheet body.

7. The low-frequency load-bearing acoustic black hole vibration reduction element according to claim 1, characterized in that: The acoustic black hole is a spiral acoustic black hole.

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

9. The low-frequency load-bearing acoustic black hole vibration reduction element according to claim 8, characterized in that: The cross-sectional thickness of the spiral h ( x ) and the helical radius x The following relations are 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 index, is the coefficient.

10. The low-frequency load-bearing acoustic black hole vibration reduction 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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