Local resonance type acoustic meta-structure device with low-frequency vibration reduction characteristic

Abstract

The invention discloses a local resonance type acoustic meta-structure device with a low-frequency vibration reduction characteristic, which comprises an annular foundation frame plate, oscillator mass blocks, a first transition area, a second transition area, a middle cantilever beam and a side cantilever beam, and the middle cantilever beam and the side cantilever beam are connected to the inner wall of the annular foundation frame plate. And each oscillator mass block is connected with the middle cantilever beam through a second transition area and is connected with the side cantilever beam through a first transition area. Based on the local resonance principle, the band gap range can be adjusted by adjusting the geometric parameters of the mass block and the cantilever beam so as to adapt to different external excitation frequencies, the wide-frequency-domain vibration suppression effect can be achieved for low-frequency vibration of the equipment thin-wall plate, and the purpose that the large wavelength is controlled through the small size is achieved. The method is suitable for effectively protecting important equipment against low-frequency out-of-plane vibration under actual engineering constraint conditions such as weight and space, and has wide practical value.

Description

Technical Field

[0001] The present invention relates to the field of vibration reduction technology, and in particular to a local resonance type acoustic metastructure device with low-frequency vibration reduction characteristics. Background Art

[0002] In recent years, the independent research and development of various equipment represented by new energy vehicles, high-speed trains, large aircraft, aircraft carriers, submarines, etc. has been promoted to the level of national strategic development. These equipment are constantly moving towards high speed, long-distance and extreme service environments. The resulting vibration problems have a huge impact on the normal operation of the equipment and the quality of life of the people. Therefore, the demand for vibration control technology is very urgent.

[0003] The essence of vibration originates from the propagation of elastic waves in the structure and the interaction with the surrounding medium. Among them, low-frequency vibration has large energy and is difficult to be attenuated in a uniform medium. How to effectively control low-frequency vibration has been a technical problem that has long plagued people. Although traditional vibration reduction measures, such as dynamic vibration absorbers and vibration isolators, can achieve low-frequency vibration attenuation to a certain extent, their working principles determine that the effective working frequency of such methods is often single-frequency. Moreover, when the actual parameters of the system or vibration reduction components deviate from the design values, these vibration reduction methods not only fail to achieve the vibration reduction effect, but may also aggravate the vibration. At the same time, viscoelastic damping materials, which are widely used in the industrial field, do not have an ideal vibration attenuation effect in the low-frequency band. Although the vibration amplitude of these parts can be effectively reduced by adding reinforcing ribs or locally thickening the structure in the parts with severe vibration, this method often requires a large weight and size (thickness) price. Actual equipment has strict restrictions on the additional weight and installation space of vibration reduction measures. Therefore, under the actual engineering constraints such as weight and space, it is difficult for traditional vibration reduction measures to achieve low-frequency and efficient vibration reduction performance, which seriously restricts the improvement of equipment vibration quality and even affects the replacement of equipment.

[0004] In recent years, the introduction of acoustic metamaterials has provided a new path to achieve low-frequency and high-efficiency vibration reduction under lightweight and small-size conditions. By regulating and designing the microstructure units and their arrangement in acoustic metamaterials, it is possible to achieve efficient artificial manipulation of elastic waves, and produce a series of extraordinary effects such as low-frequency elastic wave band gaps, negative equivalent mass density, and negative elastic modulus. Among them, local resonance acoustic metamaterials can produce low-frequency band gaps under deep subwavelength conditions (lattice size is much smaller than the wavelength of the matrix elastic wave), that is, "small size controls large wavelength", which provides new inspiration for achieving low-frequency vibration and noise reduction under small-size conditions. Most of the existing studies on local resonance acoustic metamaterials reduce the vibration of plate-like structures by adhering or embedding multi-material local resonance units on the plate. Although this type of method can produce low-frequency band gaps, its processing difficulty and manufacturing cost will also increase accordingly.

[0005] Low-frequency elastic waves have a long wavelength and are difficult to attenuate in a uniform medium. Excitation within this frequency range can easily cause equipment resonance, thereby reducing equipment safety, stability and service life. Traditional vibration reduction measures generally use additional dynamic vibration absorbers, viscoelastic damping materials, reinforcing ribs or local thickening. These vibration reduction methods have problems such as a narrow vibration reduction frequency domain, poor low-frequency vibration attenuation, and a large weight and size cost. Most local resonant acoustic meta-devices reduce the low-frequency vibration of plate structures by adhering or embedding local resonators on thin-walled plates of equipment. These local resonators are mostly composed of two or more materials, which are difficult to process and have high manufacturing costs. Summary of the invention

[0006] Purpose of the invention: The present invention aims to provide a local resonance acoustic metastructure device which can meet the actual engineering constraints such as weight, space, manufacturing process, production cost, etc. and has a wide bandgap characteristic in the low frequency range.

[0007] Technical solution: The local resonance acoustic metastructure device with low-frequency vibration reduction characteristics described in the present invention includes an annular basic frame plate, a vibrator mass block, a first transition region, a second transition region, and a side cantilever beam and a middle cantilever beam connected to the inner wall of the annular basic frame plate. The middle cantilever beam is located on the center line of the annular basic frame plate, and vibrator mass blocks are symmetrically arranged on both sides of the middle cantilever beam. Each vibrator mass block is connected to the middle cantilever beam through the second transition region, and is connected to the side cantilever beam through the first transition region.

[0008] Preferably, the bottom surfaces of the vibrator mass block, the middle cantilever beam, the side cantilever beam, the first transition region and the second transition region are all on the same horizontal plane.

[0009] Preferably, the cross-section of the basic frame plate is an annular square frame plate structure, and the middle cantilever beam, side cantilever beams, first transition area and second transition area are all rectangular plate structures. The middle cantilever beam and side cantilever beams are respectively connected to the inner wall of the annular basic frame plate and the outer walls of the first transition area and the second transition area.

[0010] Preferably, the angle between the first transition zone and the side cantilever beam and the angle between the second transition zone and the middle cantilever beam are both 90°, and the axial heights of the annular base frame plate, the middle cantilever beam, the side cantilever beam, the first transition zone and the second transition zone are the same.

[0011] Preferably, the local resonance type acoustic metastructure device forms an axisymmetric structure along the center line.

[0012] Preferably, the middle cantilever beam and the side cantilever beam are equivalent spring parts in the local resonance system, and the vibrator mass block is the equivalent mass part in the local resonance system; the multi-cantilever beam design of the local resonance type acoustic meta-device can reduce stress concentration and avoid excessive amplitude of the vibrator mass block.

[0013] Preferably, all components are made of the same material and can be manufactured using an integrated molding process.

[0014] Preferably, the device is suitable for vibration reduction in the low frequency range of 1-200 Hz.

[0015] Working principle: The local resonance type acoustic meta-structure device is arranged in the x and y directions according to the Bloch-Floquet periodic boundary conditions. The local resonance type acoustic meta-structure device can be equivalent to a spring-mass block system. When the elastic wave excitation in the plate propagates in the local resonance type acoustic meta-structure device, it will be affected by the periodically arranged resonance units. When the excitation frequency is 0 or very low, the resonance unit of the local resonance type acoustic meta-structure device maintains rigid motion in the same direction as the plate; when the excitation frequency is close to the natural frequency of the resonance unit, the resonance unit and the plate move out of phase, and the structure has a negative mass effect. Its out-of-plane vibration modes are coupled with each other, absorbing and dissipating part of the energy of the plate, thereby opening the lower limit of the band gap; as the excitation frequency continues to increase, until the resonance unit and the plate move in the same direction again, the negative mass effect ends and reaches the upper limit of the band gap.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0017] (1) It has a wide bandgap characteristic for low-frequency out-of-plane vibration within 200Hz of thin-walled plates, produces a universal vibration attenuation effect within the bandgap range, and achieves the special effect of "small size controlling large wavelength", which has a wide range of practical value;

[0018] (2) At the same time, based on the principle of local resonance, the present invention can adjust the bandgap frequency domain by adjusting the axial height of the mass block and the cantilever beam, adapt to different external excitation frequencies, and optimize the vibration reduction effect under different working conditions;

[0019] (3) Design a small local resonance acoustic meta-device that can be integrated and molded using the same material to achieve local resonance under a single material;

[0020] (4) Compared with traditional metal local resonance plates, adhesive or embedded multi-material local resonance substructures of the same size, it is lighter in weight and has good processing and manufacturing advantages and low cost advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the present invention;

[0022] Figure 2 It is a physical diagram of the present invention;

[0023] Figure 3 is a schematic diagram of the energy band of the present invention;

[0024] Figure 4 is the influence of geometric parameters on the upper and lower bounds of the band gap of the present invention, wherein (a) the axial height of the annular base frame plate; (b) the axial height of the vibrator mass block;

[0025] Figure 5 It is a schematic diagram of the three-row and three-column combination arrangement of the present invention;

[0026] Figure 6 It is a schematic diagram of the transmission loss analysis under the three-row and three-column combination arrangement of the present invention;

[0027] Figure 7 It is a schematic diagram of simulated displacement under the three-row and three-column combination arrangement of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0029] Example

[0030] like Figure 1 and Figure 2 As shown, the local resonance type acoustic meta-structure device with low-frequency vibration reduction characteristics of the present invention comprises an annular basic frame plate 1, a vibrator mass block 2, a side cantilever beam 3, a middle cantilever beam 4, a first transition region 5 and a second transition region 6. The device uses nylon-66 material as the overall material of the local resonance type acoustic meta-structure device. The specific material properties are: density 1150kg / m 3 , Young's modulus 2GPa, Poisson's ratio 0.35, damping factor 0.05. Figure 2 As shown, the device can form a bandgap in the frequency domain of 38 to 49 Hz.

[0031] The cross section of the annular basic frame plate 1 is an annular square frame plate structure, the side cantilever beam 3, the middle cantilever beam 4, the first transition area 5, and the second transition area 6 are all rectangular plate structures, and the side cantilever beam 3 and the middle cantilever beam 4 are respectively connected to the inner wall of the annular basic frame plate 1 and the outer wall of the first transition area 5 and the second transition area 6. The bottom surfaces of the vibrator mass block 2, the side cantilever beam 3, the middle cantilever beam 4, the first transition area 5, and the second transition area 6 are all on the same horizontal plane.

[0032] The middle cantilever beam 4 is located on the center line of the annular foundation frame plate 1, the oscillator mass block 2 is composed of two rectangular mass blocks symmetrical along the middle cantilever beam 4, and the side surfaces of the square mass blocks are connected to the inner walls of the side cantilever beams 3 and the middle cantilever beam 4 through the first transition region 5 and the second transition region 6. The local resonance type acoustic meta-structure device forms an axisymmetric structure along the center line.

[0033] The annular base frame plate 1, the middle cantilever beam 3, the side cantilever beam 4, the first transition area 5 and the second transition area 6 have the same axial height.

[0034] The rectangular mass block 2 has a length of 45 mm, a width of 11.5 mm, and an axial height of 8.6 mm; the middle cantilever beam 4 has a length of 42.5 mm, a width of 3 mm, and an axial height of 1.6 mm; the side cantilever beam 3 has a length of 47.5 mm, a width of 3 mm, and an axial height of 1.6 mm; the cross-section of the annular base frame plate 1 is a square with a side length of 60 mm, a frame plate wall thickness of 5 mm, and an axial height of 1.6 mm; the first transition region 5 has a length of 3 mm, a width of 3 mm, and an axial height of 1.6 mm; the second transition region 6 has a length of 9 mm, a width of 5 mm, and an axial height of 1.6 mm, and the angles between the first transition region 5, the second transition region 6 and the side cantilever beams 3 and the middle cantilever beam 4 are 90°.

[0035] The unit model of the local resonance acoustic meta-structure device is constructed in COMSOL software, and Bloch-Floquet periodic boundary conditions are set in the x and y directions of the annular base frame 1, and free boundary conditions are set in the z direction. The wave vector k is set and parametrically scanned along the irreducible Brillouin zone of the structure to obtain the band curve of the local resonance acoustic meta-structure device. Figure 3 As shown, the structure forms a band gap in the frequency domain of 38-49 Hz. Within the band gap range, the vibration elastic wave is confined in the resonance unit and cannot continue to propagate forward, thereby achieving a vibration reduction effect.

[0036] The local resonance acoustic meta-device can be equivalent to a spring-mass system, and the two main parameters affecting the system are the concentrated mass and the stiffness of the equivalent spring. Figure 4 It can be seen that the concentrated mass and spring stiffness of the equivalent spring-mass system are closely related to the axial height of the vibrator mass block 2 and the cantilever beam, respectively. By using the method of controlling variables, increasing the axial height of the vibrator mass block 2 or the cantilever beam, the concentrated mass and equivalent spring stiffness in the spring-mass system increase, and the upper and lower limits of the band gap move upward and downward, respectively, as shown in Figure 2. Figure 4As shown in FIG. 1 , a wide bandgap is formed within 0-75 Hz. The local resonance type acoustic meta-structure device is arrayed in two mutually perpendicular directions parallel to the thin-walled plate 8 to obtain a three-row and three-column combination arrangement, and the annular base frame plate 1 of the local resonance type acoustic meta-structure device obtained by the array is adhered with adhesive asphalt 7 to be bonded and fixed to the thin-walled plate 8, as shown in FIG. Figure 5 As shown. Viscous asphalt 7 uses magnetic particle hot melt asphalt, and its material properties are: density 1200kg / m 3 , Young's modulus 1.2GPa, Poisson's ratio 0.3; thin-walled plate 8 uses 0.7mm steel plate, and its material properties are: density 7880kg / m 3 , Young's modulus 205.4GPa, Poisson's ratio 0.32.

[0037] In the finite element software COMSOL, according to Figure 5 A numerical calculation model is established. In the numerical model, the specified displacements in the x and y directions are set to 0 along the upper and lower boundaries of the x direction. A simple harmonic force with an amplitude of 1 and a frequency varying from 20 Hz to 100 Hz is applied to one end at 9, and the acceleration amplitude is monitored at 10 as a function of frequency. The transmission loss function of the structure can be obtained, such as Figure 6 shown.

[0038] like Figure 6 As shown, there is a region in the frequency domain of 39-48 Hz where the vibration attenuation is lower than 0 dB, which basically corresponds to the low-frequency band gap in the energy band structure. Figure 6 The frequency at point 11 corresponds to the natural frequency of the local resonance acoustic metadevice, and the transmission loss reaches -13.7dB.

[0039] Figure 7 correspond Figure 6 The simulated displacement diagram of the local resonance acoustic meta-device with three rows and three columns at the frequency 11 in the middle. When the elastic wave propagates in the local resonance acoustic meta-device with three rows and three columns, the displacement of the annular base frame plate 1 is small, and the vibrator has a large displacement. The vibration direction of the vibrator is opposite to that of the annular base frame plate 1, and the displacement of the vibrator gradually decreases along the propagation direction of the elastic wave, and the energy of the elastic wave is gradually absorbed.

Claims

1. A local resonance acoustic meta-device with low-frequency vibration reduction characteristics, characterized in that: The invention comprises an annular basic frame plate (1), a vibrator mass block (2), a first transition region (5), a second transition region (6), and a side cantilever beam (3) and a middle cantilever beam (4) connected to the inner wall of the annular basic frame plate (1); the middle cantilever beam (4) is located on the center line of the annular basic frame plate (1), and has vibrator mass blocks (2) symmetrically arranged on both sides thereof; each vibrator mass block (2) is connected to the middle cantilever beam (4) via the second transition region (6), and is connected to the side cantilever beam (3) via the first transition region (5).

2. The local resonance type acoustic meta-structure device with low-frequency vibration reduction characteristics according to claim 1, characterized in that: The bottom surfaces of the vibrator mass block (2), the side cantilever beam (3), the middle cantilever beam (4), the first transition area (5) and the second transition area (6) are all on the same horizontal plane.

3. The local resonance type acoustic meta-structure device with low-frequency vibration reduction characteristics according to claim 1, characterized in that: The annular basic frame plate (1), the middle cantilever beam (4), the side cantilever beam (3), the first transition area (5) and the second transition area (6) have the same axial height.

4. The local resonance type acoustic meta-structure device with low frequency vibration reduction characteristics according to claim 1, characterized in that: The angle between the first transition region (5) and the side cantilever beam (3) and the angle between the second transition region (6) and the middle cantilever beam (4) are both 90°.

5. The local resonance acoustic metastructure device with low-frequency vibration reduction characteristics according to claim 1, characterized in that: All parts are made of the same material and can be manufactured using an integrated molding process.

6. The local resonance acoustic meta-device with low-frequency vibration reduction characteristics according to claim 1, characterized in that: The device forms an axisymmetric structure along the center line of the annular basic frame plate (1).

7. The local resonance acoustic metastructure device with low-frequency vibration reduction characteristics according to claim 1, characterized in that: The side cantilever beam (3) and the middle cantilever beam (4) are equivalent spring parts in the local resonance type acoustic meta-structure device, and the oscillator mass block (2) is the equivalent mass part in the local resonance type acoustic meta-structure device.

8. The local resonance acoustic metastructure device with low-frequency vibration reduction characteristics according to claim 1, characterized in that: The multi-cantilever beam design of the device can reduce stress concentration and prevent the amplitude of the vibrator mass block (2) from being too large.

9. The local resonance acoustic metastructure device with low-frequency vibration reduction characteristics according to claim 1, characterized in that: The device is suitable for vibration reduction in the low frequency range of 1-200Hz.

10. The local resonance acoustic metastructure device with low-frequency vibration reduction characteristics according to claim 1, characterized in that: The cross section of the annular basic frame plate (1) is an annular square frame plate structure, and the side cantilever beams (3), the middle cantilever beams (4), the first transition area (5) and the second transition area (6) are all rectangular plate structures.

Images