Multi-acoustic black hole coupled periodic vibration reduction structure

Abstract

The application relates to the field of damping technology, and particularly discloses a multi-acoustic black hole coupling periodical damping structure which is formed by a main acoustic structure and an additional acoustic structure arranged in a periodical mode; the main acoustic structure has a first acoustic black hole area; the center of the first acoustic black hole area is coincident with the center of the main acoustic structure, and the thickness of the first acoustic black hole area changes in a power exponential mode from the periphery to the center; the additional acoustic structure is arranged at the center position of the first acoustic black hole area, and a gap is formed between the main acoustic structure and the additional acoustic structure; the thickness of the additional acoustic structure changes in a power exponential mode from the central axis to the outer edge; when used, the periodical number of the structure can be increased or decreased to control the reasonable size of the structure; in the case of ensuring the complete appearance of the structure, a small amount of structure can realize the high-efficiency damping and noise reduction effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vibration reduction, and in particular to a multi-acoustic black hole coupled periodic vibration reduction structure. BACKGROUND

[0002] Lightweight vibration reduction structures have wide application prospects in various engineering fields. However, it is difficult to control the structural wave because of its frequency dispersion and rapid dissipation to the surrounding structure and environment. Traditional vibration reduction methods usually require a very thick damping layer on the surface of the structure. The disadvantage of this method is that it is often difficult to achieve significant results at low frequencies. In addition, the additional mass and the lack of substantial improvement in structural strength make its application have great limitations, especially considering the economic effects of the transportation and aerospace industries.

[0003] Acoustic black holes use the propagation characteristics of waves in structures with gradually decreasing thickness. When the thickness of the structure is a certain power function h(x) = εx m , the wavelength, phase velocity and group velocity of the bending wave will also decrease to zero when the index approaches zero, and the amplitude tends to infinity. Limited by the strength and processing technology of the structure, the thickness of the structure cannot approach zero, resulting in a truncated thickness, so that the acoustic black hole structure cannot completely concentrate the bending wave at the center of the acoustic black hole. In addition, due to the small truncated thickness of the structure, the strength of the structure is also difficult to meet the engineering application standard, resulting in the fact that the acoustic black hole structure is difficult to be put into practical use. SUMMARY

[0004] The purpose of the present application is to alleviate the limitations of the reduction of structural strength and to achieve better vibration reduction effects. A multi-acoustic black hole coupled periodic vibration reduction structure is provided.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] The embodiment provides a multi-acoustic black hole coupled periodic vibration reduction structure, which comprises a main acoustic structure and an additional acoustic structure.

[0007] The main acoustic structure has a first uniform thickness region and a first acoustic black hole region.

[0008] The center of the first acoustic black hole region coincides with the center of the main acoustic structure. The thickness of the first acoustic black hole region changes in the form of a power index from the periphery to the center of the first acoustic black hole region.

[0009] The additional acoustic structure is arranged at the center position of the first acoustic black hole region. The maximum length of the additional acoustic structure is smaller than the maximum length of the first acoustic black hole region, and there is a gap between the main acoustic structure and the additional acoustic structure.

[0010] The additional acoustic structure has a second uniform region and a second acoustic black hole region, a thickness of the second acoustic black hole region changes in a power exponential form from a central axis of the additional acoustic structure to an outer edge direction, and a truncated thickness exists at an end of the additional acoustic structure.

[0011] In the multi-acoustic black hole coupled periodic damping structure provided by at least one embodiment of the present disclosure, a top surface of the additional acoustic structure and a surface of the first uniform thickness region are in the same horizontal plane.

[0012] In the multi-acoustic black hole coupled periodic damping structure provided by at least one embodiment of the present disclosure, a sound-absorbing and vibration-absorbing material is fixedly arranged on the first acoustic black hole region and / or the second acoustic black hole region.

[0013] In the multi-acoustic black hole coupled periodic damping structure provided by at least one embodiment of the present disclosure, a thickness of the first acoustic black hole region gradually decreases to a center x0 in an exponential function form h(x)=ε(x-x0) m +m from an outer periphery of the first acoustic black hole region to the center x0, a truncated thickness h0 is obtained at the center x0, and an index m is not less than 2.

[0014] In the multi-acoustic black hole coupled periodic damping structure provided by at least one embodiment of the present disclosure, a cross section of the additional acoustic structure is arranged in a horn shape.

[0015] In the multi-acoustic black hole coupled periodic damping structure provided by at least one embodiment of the present disclosure, a thickness of the additional acoustic structure changes in a power exponential function h(x)=εx m +m from a central axis of the additional acoustic structure to an outer edge direction, and an index m is not less than 2.

[0016] In the multi-acoustic black hole coupled periodic damping structure provided by at least one embodiment of the present disclosure, the main acoustic structure and the additional acoustic structure are arranged in a periodic manner.

[0017] In the multi-acoustic black hole coupled periodic damping structure provided by at least one embodiment of the present disclosure, two main acoustic structures are arranged, and the two main acoustic structures are symmetrically distributed in an up-down direction.

[0018] Two additional acoustic structures are arranged, and the two additional acoustic structures are symmetrically distributed in an up-down direction.

[0019] In the multi-acoustic black hole coupled periodic damping structure provided by at least one embodiment of the present disclosure, two first uniform thickness regions are arranged, and the additional acoustic structure is located between the two first uniform thickness regions.

[0020] The present application has the following beneficial effects:

[0021] Compared with the acoustic black hole structure of the same size, the multi-acoustic black hole coupling periodic damping structure has better flatness of the structure surface, the overall stiffness of the structure is improved, the overall vibration of the element occurs at a higher frequency, the frequency of local resonance is further separated, thereby reducing the coupling between the local resonance caused by the acoustic black hole and the overall vibration of the unit.

[0022] The additional acoustic structure is equivalent to a spring mass oscillator for the main acoustic structure, has a vibration absorber effect, can reduce the band gap frequency; at the same time, the additional acoustic structure also has the damping effect of the acoustic black hole, gathers the bending wave to the end of the structure, reduces the vibration of the main acoustic structure, and further widens the band gap.

[0023] A small amount of multi-acoustic black hole damping structure can achieve significant vibration attenuation and isolation effect, thereby making it possible to realize vibration control by using a structure of reasonable size.

[0024] By reducing the truncation thickness of the acoustic black hole profile or increasing the power law index, it is easy to realize the reduction of wide band gap frequency and the widening of the band width. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 The profile of a single damping structure in some embodiments.

[0027] Figure 2 The profile of a single damping structure in some embodiments.

[0028] Figure 3 The three-dimensional view of the damping structure after stretching based on the profile of a single damping structure in some embodiments.

[0029] Figure 4 The three-dimensional view of the damping structure after rotation based on the profile of a single damping structure in some embodiments.

[0030] Figure 5 The band contrast diagram of an infinite periodic structure.

[0031] Figure 6 The transmissibility contrast diagram of a finite periodic structure (5x1 unit).

[0032] Figure 7 The vibration displacement distribution diagram of a finite periodic structure (5x1 unit).

[0033] In the picture:

[0034] 10. Main acoustic structure; 11. First uniform thickness region; 12. First acoustic black hole region;

[0035] 20. Additional acoustic structure; 21. Second uniform region; 22. Second acoustic black hole region. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments, rather than all the embodiments.

[0037] Example

[0038] This embodiment provides a multi-acoustic black hole coupled periodic vibration reduction structure, which is composed of multiple vibration reduction structures arranged in a periodic pattern.

[0039] Reference Figure 1 As shown in the cross-sectional view of a single vibration damping structure, each vibration damping structure includes a main acoustic structure 10 and an additional acoustic structure 20.

[0040] The main acoustic structure 10 will be further described below with reference to the accompanying drawings.

[0041] In this embodiment, the main acoustic structure 10 has a first uniform thickness region 11 and a first acoustic black hole region 12. The center of the first acoustic black hole region coincides with the center of the main acoustic structure 10, and the thickness of the first acoustic black hole region changes in a power exponential form from the periphery of the first acoustic black hole region to the center.

[0042] Specifically, there are two first uniform thickness regions 11 , and the additional acoustic structure 20 is located between the two first uniform thickness regions 11 , thereby forming a vibration reduction structure.

[0043] Specifically, the thickness of the first acoustic black hole region increases from the periphery of the first acoustic black hole region to the center in the form of an exponential function h(x)=ε(x-x0) m +h0 gradually decreases to the center x0 and is truncated to obtain the truncation thickness h0, and the exponent m is not less than 2.

[0044] Where h(x) is the thickness of the structure and x-x0 is the distance at the cutoff.

[0045] The main acoustic structure 10 itself has an acoustic black hole structure, which has excellent vibration reduction and noise reduction effects.

[0046] The additional acoustic structure 20 will be further described below with reference to the accompanying drawings.

[0047] The additional acoustic structure 20 is equivalent to a spring-mass oscillator for the main acoustic structure 10, has a vibration absorber effect, and can reduce the band gap frequency; at the same time, the additional acoustic structure 20 also has the vibration reduction effect of an acoustic black hole, and can gather bending waves to the end of the structure to reduce the vibration of the main acoustic structure 10, thereby further widening the band gap.

[0048] The additional acoustic structure 20 is arranged at the center of the first acoustic black hole region 12, the maximum length of the additional acoustic structure 20 is less than the maximum length of the first acoustic black hole region 12, and there is a gap between the main acoustic structure 10 and the additional acoustic structure 20.

[0049] Specifically, the top surface of the additional acoustic structure 20 and the surface of the first uniform thickness region 11 are at the same level, have good structural integrity, so that the surface of the structure has better flatness, the overall stiffness of the structure is improved, so that the overall vibration of the element occurs at a higher frequency, and the frequency of local resonance is further separated from the frequency of local resonance, thereby reducing the coupling between the local resonance caused by the acoustic black hole and the overall vibration of the unit.

[0050] Specifically, the additional acoustic structure 20 is arranged in a horn shape in cross section, and there is a truncated thickness at the end of the additional acoustic structure 20. The additional acoustic structure 20 has a second uniform region 21 and a second acoustic black hole region 22. The thickness of the second acoustic black hole region 22 is a power function h(x) = εx m +h0, the index m is not less than 2.

[0051] Wherein, h(x) is the thickness of the structure, h0 is the truncated thickness, and x is the distance from the center of the second acoustic black hole region.

[0052] In some embodiments not shown, a sound-absorbing and vibration-absorbing material (not shown) is arranged on the first acoustic black hole region, further improving the overall sound-absorbing and vibration-absorbing performance.

[0053] In some embodiments not shown, a sound-absorbing and vibration-absorbing material (not shown) is fixedly arranged on the second acoustic black hole region, further improving the overall sound-absorbing and vibration-absorbing performance.

[0054] In some embodiments not shown, a sound-absorbing and vibration-absorbing material (not shown) is fixedly arranged on the first acoustic black hole region and the second acoustic black hole region. The sound-absorbing and vibration-absorbing material is added to the acoustic black hole region, further improving the overall sound-absorbing and vibration-absorbing performance.

[0055] Exemplarily, the sound-absorbing and vibration-absorbing material adopts a damping pad.

[0056] As Figure 2As shown, in some embodiments, each vibration reduction structure contains two main acoustic structures 10 and two additional acoustic structures 20. The two main acoustic structures 10 are symmetrically distributed up and down, and the two additional acoustic structures 20 are also symmetrically distributed up and down. Among them Figure 3 is based on Figure 2 An example of a vibration reduction structure formed after stretching, Figure 4 is based on Figure 2 Another example of a vibration reduction structure formed after rotation.

[0057] The effectiveness of the vibration reduction structure formed after stretching is verified by simulation as follows.

[0058] Calculation model:

[0059] The length of the unit cell is selected as a = 80 mm, the height is h = 6.4 mm, m = 2, and the thickness of the acoustic black hole center is 1 mm.

[0060] The material is steel, the mass density is 7800 kg / m 3 , the Young's modulus is 210 Gpa, and the Poisson's ratio is 0.3. Finite element analysis is performed using COMSOL Multiphysics 6.3. For an infinite plate, Floquet-Bloch periodic boundary conditions are applied to the element edges in the x direction, and the parameter is scanned for the simple wave vector kπ / a; for a finite periodic structure, a 5x1 element of finite free support structure is selected to evaluate the vibration reduction capability of the vibration reduction structure, and a transverse harmonic point excitation is applied to one end of the vibration reduction structure, while the receiver is located at the opposite corner. The transmittance is defined as and are the mean square displacement of the section where the receiver is located and the mean square displacement amplitude of the section where the excitation point is located, respectively.

[0061] Result analysis:

[0062] As shown in Figure 5 , the black solid line represents the vibration reduction structure in the embodiment, and the red dashed line represents the band curve of the infinite periodic structure of the acoustic black hole structure of the same size (i.e. the same as the main structure). As can be seen, compared with the band curve of the vibration reduction structure in the embodiment, the band curve is relatively flat, which is due to the increase in the overall structure mass caused by the introduction of the vibration reduction structure in the embodiment and the role of providing a resonator, which moves the bandgap to low frequency; on the other hand, the aggregation of waves in the vibration reduction structure makes the bandgap wider.

[0063] As shown in Figure 6As shown, the solid black line represents the vibration-damping structure of the embodiment, while the dashed red line represents the transmissibility curve for a finite-period structure (5x1 unit cells) with the same acoustic black hole structure dimensions (i.e., the same as the main structure). Across a wide frequency range, the amplitude is significantly reduced by over 100 dB, demonstrating the vibration isolation capability of the vibration-damping structure of the embodiment with a limited number of units. The weak transmission attenuation band corresponds well to the wide band gap calculated using simulations using infinite-period units.

[0064] like Figure 7 Figure 2 shows the displacement distribution of the vibration field at two typical frequencies, one within the attenuation band and one outside the attenuation band, with a being 355 Hz and b being 29,225 Hz. At 29,225 Hz within the attenuation band, the vibration is essentially confined to the center of the first acoustic black hole unit and the vibration-damping structure, and rapidly decays in subsequent units. The remaining vibration quickly disappears in subsequent units. This also confirms to a certain extent that this frequency band is attributed to the coupling effect of local resonance and Bragg scattering. In contrast, at 355 Hz outside the attenuation band, the vibration propagates throughout the structure, with no significant attenuation along the excitation-receiver path.

[0065] Although the embodiments of the present application have been shown and described above, the scope of protection of the present invention is not limited thereto, and any changes or substitutions that are not conceivable through creative work should be included in the scope of protection of the present invention; unless expressly stated, any elements, actions or instructions used in this document should not be interpreted as critical or necessary.

Claims

1. A multi-acoustic black hole coupled periodic vibration reduction structure, characterized in that: include: Main acoustic structure and additional acoustic structure; The main acoustic structure has a first uniform thickness region and a first acoustic black hole region; The center of the first acoustic black hole region coincides with the center of the main acoustic structure, and the thickness of the first acoustic black hole region changes in a power exponential form from the periphery to the center of the first acoustic black hole region; The additional acoustic structure is arranged at the center of the first acoustic black hole region, the maximum length of the additional acoustic structure is smaller than the maximum length of the first acoustic black hole region, and there is a gap between the main acoustic structure and the additional acoustic structure. The additional acoustic structure is used to gather bending waves to the end of the structure, reduce the vibration of the main acoustic structure, and further widen the band gap; The additional acoustic structure has a second uniform region and a second acoustic black hole region, the thickness of the second acoustic black hole region changes in a power exponential form from the central axis of the additional acoustic structure toward the outer edge, and there is a truncation thickness at the end of the additional acoustic structure; The top surface of the additional acoustic structure and the surface of the first uniform thickness area are on the same horizontal plane; The thickness of the first acoustic black hole region increases in the form of an exponential function from the periphery to the center of the first acoustic black hole region. Gradually decreases to the center Cut off at the point and get the cutoff thickness ,index Not less than 2; in, is the structure thickness, is the distance to the cutoff.

2. The multi-acoustic black hole coupled periodic vibration reduction structure according to claim 1, characterized in that: Sound and vibration absorbing materials are fixedly arranged on the first acoustic black hole region and / or the second acoustic black hole region.

3. The multi-acoustic black hole coupled periodic vibration reduction structure according to claim 1, characterized in that: The cross section of the additional acoustic structure is arranged in a trumpet shape.

4. The multi-acoustic black hole coupled periodic vibration reduction structure according to claim 1, characterized in that: The thickness of the additional acoustic structure increases from the central axis of the additional acoustic structure to the outer edge in a power exponential function. ,index Not less than 2; in, is the structure thickness, is the cut-off thickness.

5. The multi-acoustic black hole coupled periodic vibration reduction structure according to claim 1, characterized in that: The main acoustic structure and the additional acoustic structure are arranged in a periodic pattern.

6. The multi-acoustic black hole coupled periodic vibration reduction structure according to claim 1, characterized in that: There are two main acoustic structures, and the two main acoustic structures are symmetrically distributed up and down; There are two additional acoustic structures, and the two additional acoustic structures are symmetrically distributed up and down.

7. The multi-acoustic black hole coupled periodic vibration reduction structure according to claim 1, characterized in that: There are two first uniform thickness regions, and the additional acoustic structure is located between the two first uniform thickness regions.

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