Multi-acoustic black hole coupling periodic vibration reduction structure

Abstract

The invention relates to the technical field of vibration reduction, and particularly discloses a multi-acoustic black hole coupling periodic vibration reduction structure which is formed by periodically and regularly arranging a main body acoustic structure and an additional acoustic structure. The main body acoustic structure is provided with a first acoustic black hole area; the center of the first acoustic black hole area coincides with the center of the main body acoustic structure, and the thickness of the first acoustic black hole area changes from the periphery of the first acoustic black hole area to the center direction in a power exponent mode; the additional acoustic structure is arranged in the center 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 from the central axis of the additional acoustic structure to the outer edge direction in a power exponent form; during application, the reasonable size of the structure can be controlled by increasing or decreasing the period number of the structure, and the efficient vibration and noise reduction effect can be achieved through a small number of structures under the condition that it is guaranteed that the structure has the complete appearance.

Description

Technical Field

[0001] The invention relates to the field of vibration reduction technology, and in particular to a multi-acoustic black hole coupled periodic vibration reduction structure. Background Art

[0002] Lightweight vibration-damping structures have broad application prospects in various engineering fields. However, structural waves are difficult to control due to their dispersion and rapid dissipation to surrounding structures and the environment. Traditional vibration reduction methods usually require a thick damping layer to be covered on the surface of the structure. The disadvantage is that this method often has difficulty in achieving significant results at low frequencies, and the additional mass and lack of substantial improvement in structural strength make its application very limited, 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 When the exponential decreases to zero, the wavelength, phase velocity and group velocity of the bending wave will also decrease to zero accordingly, and the amplitude will tend to infinity. Limited by the structural strength and processing technology, the thickness of the structure cannot approach zero, resulting in the existence of a truncation thickness, which makes it impossible for the acoustic black hole structure to completely gather the bending waves at the center of the acoustic black hole. In addition, due to the relatively small truncation thickness of the structure, the strength of the structure is difficult to meet the engineering application standards, making it difficult for the acoustic black hole structure to be put into practical use. Summary of the invention

[0004] The purpose of the present invention is to alleviate the limitation of reduced structural strength and achieve better vibration reduction effect, and to provide a multi-acoustic black hole coupled periodic vibration reduction structure.

[0005] To achieve the above object, the present invention adopts the following technical solution:

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

[0007] The bulk 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 a power exponential form from the periphery to the center of the first acoustic black hole region.

[0009] 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.

[0010] The additional acoustic structure has a second uniform area and a second acoustic black hole area, the thickness of the second acoustic black hole area changes in a power exponential form from the central axis of the additional acoustic structure toward the outer edge, and there is a truncated thickness at the end of the additional acoustic structure.

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

[0012] In the multi-acoustic black hole coupled periodic vibration reduction structure provided in at least one embodiment of the present disclosure, sound-absorbing and vibration-absorbing materials are 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 vibration reduction structure provided in at least one embodiment of the present disclosure, the thickness of the first acoustic black hole region increases from the periphery to the center of the first acoustic black hole region in the form of an exponential function h(x)=ε(x-x0) m +h0 gradually decreases and is truncated at the center x0 to obtain the truncation thickness h0, and the exponent m is not less than 2.

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

[0015] In the multi-acoustic black hole coupled periodic vibration reduction structure provided in at least one embodiment of the present disclosure, the thickness of the additional acoustic structure increases from the central axis of the additional acoustic structure to the outer edge in the direction of the power exponential function h(x)=εx m +h0, exponent m is not less than 2.

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

[0017] In the multi-acoustic black hole coupled periodic vibration reduction structure provided in at least one embodiment of the present disclosure, two main acoustic structures are provided, and the two main acoustic structures are symmetrically distributed up and down;

[0018] There are two additional acoustic structures, and the two additional acoustic structures are symmetrically distributed up and down.

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

[0020] The beneficial effects of the present invention are:

[0021] Compared with the acoustic black hole structure of the same size, the multi-acoustic black hole coupled periodic vibration reduction structure of the present invention has better flatness on the structural surface and improved overall stiffness, so that the overall vibration of the element occurs at a higher frequency and is further separated from the frequency of the local resonance, 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, and has a vibration absorber effect, which can reduce the band gap frequency; at the same time, the additional acoustic structure also has the vibration reduction effect of an acoustic black hole, which gathers the bending waves to the end of the structure, reduces the vibration of the main acoustic structure, and further widens the band gap.

[0023] A small number of multi-acoustic black hole vibration reduction structures can achieve significant vibration attenuation and vibration isolation effects, thus making it possible to achieve vibration control using structures of reasonable size.

[0024] By reducing the cutoff thickness of the acoustic black hole profile or increasing its power-law index, it is easy to achieve a reduction in the wide bandgap frequency and a widening of the bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 2 is a cross-sectional view of a single vibration-damping structure in some embodiments.

[0027] Figure 2 2 is a cross-sectional view of a single vibration-damping structure in some embodiments.

[0028] Figure 3 It is a three-dimensional diagram of a vibration-damping structure after stretching the cross-sectional diagram of a single vibration-damping structure in some embodiments.

[0029] Figure 4 It is a three-dimensional view of a vibration-damping structure after rotating a cross-sectional view of a single vibration-damping structure in some embodiments.

[0030] Figure 5 This is a comparison diagram of the energy bands of infinite periodic structures.

[0031] Figure 6 Comparison of transmissibility of finite period structures (5x1 units).

[0032] Figure 7 This is the vibration displacement distribution diagram of a finite period structure (5x1 unit).

[0033] In the figure:

[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 in conjunction with the drawings in the embodiments. 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 and is truncated at the center x0 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 a vibration reduction and noise reduction effect.

[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, and has a vibration absorber effect, which 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, which gathers the bending waves to the end of the structure, reduces the vibration of the main acoustic structure 10, and thus further widens 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 smaller 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 on the same horizontal plane and have good structural integrity, so that the surface of the structure has better flatness and the overall stiffness of the structure is improved, so that the overall vibration of the element occurs at a higher frequency and is further separated from the frequency of the 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 has a trumpet-shaped 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 increases from the central axis of the additional acoustic structure 20 to the outer edge in a power exponential function h(x)=εx m +h0, exponent m is not less than 2.

[0051] Where h(x) is the structure thickness, h0 is the cutoff thickness, and x is the distance to the center of the second acoustic black hole region.

[0052] In some embodiments not shown, sound-absorbing and vibration-absorbing materials (not shown) are provided on the first acoustic black hole region to further improve the overall sound-absorbing and vibration-absorbing performance.

[0053] In some embodiments not shown, sound-absorbing and vibration-absorbing materials (not shown) are fixedly disposed on the second acoustic black hole region to further improve the overall sound-absorbing and vibration-absorbing performance.

[0054] In some embodiments not shown, sound-absorbing and vibration-absorbing materials (not shown) are fixedly arranged on the first acoustic black hole region and the second acoustic black hole region. Adding sound-absorbing and vibration-absorbing materials to the acoustic black hole region further improves the overall sound-absorbing and vibration-absorbing performance.

[0055] Exemplarily, the sound and vibration absorbing material is a damping gasket.

[0056] like Figure 2As shown, in some embodiments, each vibration reduction structure includes 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. Figure 3 is based on Figure 2 An example of a vibration-damping structure formed after stretching, Figure 4 is based on Figure 2 Another example of a vibration-damping structure formed after rotation.

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

[0058] Computational model:

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

[0060] The material is steel, with a mass density of 7800kg / m 3 , Young's modulus is 210 GPa, and Poisson's ratio is 0.3. Finite element analysis was performed using COMSOL Multiphysics 6.3. For infinite plates, Floquet-Bloch periodic boundary conditions were applied to the edge of the unit in the x direction, and the simplified wave vector kπ / a was parametrically scanned; for finite periodic structures, a 5×1 unit finite free support structure was selected to evaluate the vibration reduction capacity of the vibration reduction structure, and a transverse harmonic point excitation was applied at one end of the vibration reduction structure, while the receiver was located at the opposite corner. The transmittance is defined as and are the mean square displacement of the section where the receiving point is located and the mean square displacement amplitude of the section where the excitation point is located.

[0061] Result analysis:

[0062] like Figure 5 As shown, the black solid line represents the vibration reduction structure in the embodiment, and the red dotted line represents the energy band curve of the infinite period structure of the acoustic black hole structure of the same size (i.e., the same as the main structure). It can be seen that the energy band curve of the vibration reduction structure in the embodiment is relatively flat in comparison. On the one hand, the introduction of the vibration reduction structure in the embodiment causes the overall structure mass to increase and provides a resonator, so that the band gap moves to a low frequency; on the other hand, the gathering of waves in the vibration reduction structure widens its band gap.

[0063] like Figure 6As shown, the solid black line represents the vibration reduction structure in the embodiment, and the dashed red line represents the transmissibility curve of the finite period structure (5x1 unit) of the acoustic black hole structure of the same size (i.e., the same as the main structure). In a wide frequency range, the amplitude is significantly reduced by more than 100dB, and the vibration isolation capability of the vibration reduction structure in the embodiment is demonstrated with a limited number of units. The attenuation band of weak transmission can correspond well to the wide band gap simulated and calculated with infinite period units.

[0064] like Figure 7 As shown, the displacement distribution of the vibration field at two typical frequencies inside and outside the attenuation band is provided, a is 355Hz, and b is 29225Hz. For 29225Hz within the attenuation band, the vibration is basically confined to the center of the first acoustic black hole unit and the vibration-damping structure, and decays rapidly in the subsequent units, and the remaining vibration disappears rapidly in the 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 355Hz outside the attenuation band, the vibration propagates throughout the structure, and there is no obvious 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 explicitly 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 has a second uniform area and a second acoustic black hole area, the thickness of the second acoustic black hole area changes in a power exponential form from the central axis of the additional acoustic structure toward the outer edge, and there is a truncated thickness at the end of the additional acoustic structure.

2. The multi-acoustic black hole coupled periodic vibration reduction structure according to claim 1, characterized in that: The top surface of the additional acoustic structure and the surface of the first uniform thickness area are at the same level.

3. 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.

4. The multi-acoustic black hole coupled periodic vibration reduction structure according to claim 1, characterized in that: The thickness of the first acoustic black hole region increases from the periphery to the center of the first acoustic black hole region in the form of an exponential function h(x)=ε(x-x0) m +h0 gradually decreases to the center x0 and is cut off to obtain the cutoff thickness h0, and the index m is not less than 2; Where h(x) is the thickness of the structure and x-x0 is the distance at the cutoff.

5. 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.

6. The multi-acoustic black hole coupled periodic vibration reduction structure according to claim 1, characterized in that: The thickness of the additional acoustic structure is expressed as a power exponential function h(x)=εx from the central axis of the additional acoustic structure to the outer edge. m +h0, exponent m is not less than 2; Where h(x) is the structure thickness and h0 is the cutoff thickness.

7. 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.

8. The multi-acoustic black hole coupled periodic vibration reduction structure according to claim 1, characterized in that: The main body acoustic structure is provided with two, and the two main body 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.

9. 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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