CN108119588B - Low-frequency broadband vibration suppression structure based on double-period forbidden band characteristic - Google Patents

Abstract

The invention relates to a low-frequency broadband vibration suppression structure based on a double-period forbidden band characteristic, belonging to the field of mechanical vibration and noise control, in particular to the technical field of aviation, aerospace and ship vibration and noise control. The vibration-suppressing structure is composed of the same cell cycle, in which a single cell contains four-layer structure, which are homogeneous attachment layer, periodic sandwich layer, homogeneous confinement layer and homogeneous surface layer from bottom to top. The periodic sandwich layer of a single cell of the structure is composed of two materials, A and B, through holes are respectively provided in the center of the sandwich layers composed of A and B, and a local resonance is installed in each through hole. The unit and the local resonance unit are composed of two upper and lower spring elements connected with the middle mass element, wherein the two spring elements are respectively connected with the homogeneous attachment layer on the lower side and the homogeneous confinement layer on the upper side. The periodic vibration suppression structure provided by the present invention can produce a vibration suppression effect in a low frequency and wide frequency range, and is helpful to solve the problem that the existing vibration suppression technology has poor low frequency vibration suppression effect.

Description

A Low-frequency and Wide-frequency Vibration Suppression Structure Based on Double-period Bandgap Characteristics

technical field

The invention relates to a low-frequency broadband vibration suppression structure based on a double-period forbidden band characteristic, belonging to the field of mechanical vibration and noise control, in particular to the technical field of aviation, aerospace and ship vibration and noise control.

Background technique

Mechanical structures vibrate when excited, which is a common physical phenomenon. While vibration can be exploited and economically beneficial, in many cases it can cause serious harm. In the aviation field, reducing the vibration of the structure and thus reducing the noise in the cabin can improve the passenger comfort. In the aerospace field, the huge external load of a rocket or missile during launch or working state will cause strong vibration of the structure. Effectively reducing the structural vibration can improve the working safety of the rocket and the guidance accuracy of the missile. In addition, in the field of ship engineering, reducing the structural vibration of underwater vehicles, controlling the propagation of mechanical waves in the structure, and thus reducing the noise radiation of the vehicle, can reduce the probability of being detected by enemy sonar and achieve good stealth performance. Improving maritime defense capabilities can go a long way. Therefore, vibration control has already become a very important technical problem in various fields such as aviation, aerospace and shipbuilding.

In response to structural vibration problems in various engineering fields, some relatively mature traditional technologies and methods for vibration isolation, vibration absorption, damping and vibration reduction have gradually been formed, and good vibration suppression effects have been obtained at medium and high frequencies. However, the traditional vibration control technology is not effective at low frequency vibration suppression. Although active vibration suppression technology can solve the problem of low-frequency line-spectrum vibration control to a certain extent, it is currently powerless for low-frequency broadband vibration. Therefore, how to control the vibration of structures in the low frequency and wide frequency range has gradually become a key issue in the field of vibration control.

The periodic structure is composed of the same unit period, and its periodic distribution makes the structure exhibit band-gap filtering characteristics, that is, elastic waves outside the band-gap frequency range can propagate normally, while elastic waves within the band-gap frequency range cannot be free. spread, is inhibited. Therefore, the band gap characteristics of periodic structures can provide a new method and idea for vibration control. By rationally designing the cell parameters of the periodic structure, the band gap can be regulated in the low frequency range, and the periodic structure can be used to solve the problem of low frequency vibration control. The band gap mechanism of periodic structures can generally be divided into Bragg scattering type and local resonance type. The wavelength corresponding to the band gap frequency of the Bragg scattering type is in the same order of magnitude as the lattice constant, while the band gap frequency of the local resonance type is different. The corresponding wavelength may be greater than the lattice constant. Therefore, it is possible to design a dual-period structure that combines the two band gap mechanisms, and adjust the band gap frequency range of the Bragg scattering type periodic structure and the band gap frequency range of the local resonance type periodic structure in different frequency bands of low frequencies, and then we can obtain The low frequency and wide frequency band gap can control the vibration of the structure in the low frequency and wide frequency range, and solve the problem of low frequency and wide frequency vibration control.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a vibration suppression structure for reducing the vibration of elastic structures in the engineering field in the low frequency and wide frequency range. The purpose of vibration reduction and noise reduction.

To achieve the above object, the present invention adopts the following technical solutions:

A low-frequency broadband vibration suppression structure based on the double-period band gap characteristic is composed of the same cell period, wherein a single cell contains a four-layer structure, from bottom to top are a homogeneous attachment layer, a periodic sandwich layer, Homogeneous confinement layer and homogeneous surface layer. The periodic sandwich layer of a single cell of the structure is composed of two materials, A and B, and through holes are respectively provided in the center of the sandwich layers composed of materials A and B, and a local resonance is installed in each through hole. unit. The local resonance unit is composed of two upper and lower spring elements connected with the middle mass element, wherein the two spring elements are respectively connected with the homogeneous attachment layer on the lower side and the homogeneous confinement layer on the upper side.

In the low-frequency broadband vibration suppression structure based on the double-period band gap characteristic, the materials of the homogeneous attachment layer, the periodic core layer and the homogeneous surface layer are viscoelastic damping materials, and the materials of the homogeneous confinement layer are elastic metal materials.

In the low-frequency broadband vibration suppression structure based on the double-period band gap characteristic, the sandwich layer A and the sandwich layer B in the periodic sandwich layer select different lengths along the periodic direction, and are located in the sandwich layer A and the sandwich layer B respectively. The resonance frequencies of the two local resonance elements in the through hole are set to different frequencies.

In the low-frequency broadband vibration suppression structure based on the double-period band gap characteristic, the spring element in the local resonance unit is a structure composed of a spring or a homogeneous soft material that can provide elastic support.

Compared with the prior art, the present invention has the following main features and beneficial effects:

The vibration suppression structure proposed by the present invention exhibits the characteristic of periodic distribution, the periodic sandwich layer can generate the Bragg scattering band gap, and the periodic local resonance unit can generate the local resonance band gap. Within the band gap, the vibrational response of the structure can be effectively suppressed. By reasonably selecting the size and material parameters of the cells, the frequency of the band gap of the periodic vibration suppression structure in the present invention can be adjusted to a low frequency band, and the Bragg scattering band gap and the local resonance band gap can be in different frequency ranges, so as to achieve a low frequency and a wide frequency range. Vibration suppression effect. In addition, the homogeneous attachment layer, periodic core layer and homogeneous surface layer with damping, and the local resonance unit with damping are beneficial to further widen the frequency range of the vibration suppression bandgap. The invention helps to solve the problem that the existing vibration suppression technology has poor vibration suppression effect at low frequencies.

Description of drawings

Figure 1: Schematic diagram of a single cell of the periodic vibration suppression structure.

Figure 2: Schematic diagram of the section A–A of a single cell of the periodic vibration suppression structure.

Figure 3: Schematic diagram of the installation of the periodic vibration suppression structure (exploded view).

Figure 4: Comparison of the average vibration response of the base excitation area and the base vibration pickup area of the periodic vibration suppression structure.

In the figure: 1—homogeneous attachment layer; 2—periodic sandwich layer; 21—sandwich layer A; 22—sandwich layer B; 23—through hole A in sandwich layer A; 24—local resonance unit Spring element A of A; 25—mass element A of local resonance unit A; 26—through hole B in sandwich layer B; 27—spring element B of local resonance unit B; 28—local resonance unit B Quality element B. 3—homogeneous confinement layer; 4—homogeneous surface layer; 5—substrate structure to be vibration-suppressed; 51—excitation area of the vibration-suppressed substrate structure; 52—vibration pickup area of the vibration-suppressed substrate structure.

Detailed ways

The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

The periodic vibration suppression structure in the present invention is a multi-layer composite structure, which is used to adhere to the vibration-suppressed base structure (5) to reduce the vibration of the vibration-suppressed base structure (5). The vibration suppression structure can be regarded as being composed of a single cell as shown in Fig. 1 and Fig. 2 periodically compounded along two directions of the plane. The periodic vibration suppression structure as a whole is composed of a homogeneous attachment layer (1), a periodic sandwich layer (2), a homogeneous confinement layer (3) and a homogeneous surface layer (4). The homogeneous attachment layer (1) is directly connected to the vibration-suppressed base structure (5), so as to be attached to the vibration-suppressed base structure (5). The periodic sandwich layer (2) contains two different sandwich materials and two identical (or different) local resonance units, which are used to form the Bragg scattering band gap and the local resonance band gap respectively, so as to reduce the structural band gap. vibration in the gap. The homogeneous confinement layer (3) is made of metal materials (steel or aluminum, etc.), and its function is: on the one hand, it constrains the periodic sandwich layer to form a restrained damping structure, and on the other hand, it can improve the compressive capacity of the periodic vibration suppression structure. The homogeneous surface layer (4) is made of viscoelastic damping material, and its function is: on the one hand, it can increase the damping of the structure and thus reduce the vibration of the structure; The metal material is protected from rust. The layers of the vibration suppression structure are tightly bonded by solid glue or liquid glue to prevent interlayer slippage, wherein the homogeneous attachment layer (1) on the lowermost side is directly connected with the vibration-suppressed base structure, Also use solid glue or liquid glue to fasten and bond. Through holes (23, 26) are opened at the center positions of the periodic sandwich layer A (21) and the periodic sandwich layer B (22) for installing the periodic local resonance unit. By adjusting the mass (25, 28) of the local resonance unit or the spring stiffness of the elastic element (24, 27) of the local resonance unit, the band gap of the local resonance unit can be regulated in the low frequency range, and the two local resonances Cells can exhibit different band gap frequencies.

The vibration suppression mechanism of the periodic vibration suppression structure in the present invention mainly includes three aspects: Bragg scattering band gap vibration suppression, local resonance band gap vibration suppression and damping structure vibration suppression. Specific parameters of the vibration suppression structure are selected below to further illustrate the vibration suppression effect of the vibration suppression structure in the low frequency range. The size of the vibration-suppressed base structure (5) is 1600mm×300mm×4mm, and the material is steel. The periodic vibration suppression structure consists of 6 cells, of which the length of a single cell is 200mm and the width is 300mm, and the length of the sandwich layer A (21) and the sandwich layer B (22) are equal, both 100mm. The thickness of each layer is 1mm, 8mm, 1mm and 1mm from bottom to top as shown in Figure 1. The radii of the through holes A (23) and B (26) in the periodic sandwich layer are both 25mm, and the radii of the mass elements A (25) and B (28) and the spring elements A (24) and B (27) are both 25mm. is 20mm. The height of the mass elements (25, 28) is 4 mm and the height of the spring elements (24, 27) is 2 mm. The material of the mass elements (25, 28) is lead, and the total mass is 58.3g; the equivalent spring stiffnesses of the spring elements A (24) and B (27) are respectively set to 23065.1Pa and 70576.5Pa. The homogeneous attachment layer (1) and the homogeneous surface layer (4) in the periodic vibration suppression structure are selected in the same way, and are viscoelastic materials, wherein the elastic modulus is 10 ⁷ Pa, the density is 1100kg/m ³ , and the loss factor is 0.2 . The material of the homogeneous confinement layer (3) is aluminum. The core layer A (21) is a KT foam material, the elastic modulus is 2×10 ⁵ Pa, the density is 58 kg/m ³ , and the loss factor is 0.2. The core layer B ( 22 ) is made of nitrile rubber material, the elastic modulus is 3×10 ⁸ Pa, the density is 1780kg/m ³ , and the loss factor is 0.2.

Figure 3 is a schematic diagram of the overall structure explosion of the additional periodic vibration suppression structure, wherein the periodic vibration suppression structure is installed in the middle area (called the vibration suppression area) of the vibration suppression base structure (5), and the left and right sides of the vibration suppression area are not A vibration suppression structure is installed, wherein the left side is called the base body excitation area (51) and is excited by a unit linear force, and the right side is called the base body vibration pickup area (52). It can be seen from the corresponding comparison of the average vibration of the excitation area (51) of the base body and the vibration pickup area (52) of the base body in Fig. 4 that the elastic wave is transmitted from the excitation area (51) to the vibration pickup area (52) through the vibration suppression area at a frequency of 80 Hz to 285 Hz. A large attenuation is obtained within the range, that is, the vibration is effectively suppressed in the low frequency and broadband range, indicating that the periodic vibration suppression structure of the present invention exhibits good low frequency and broadband vibration suppression characteristics.

Claims (4)

1. A low frequency broadband vibration suppression structure based on a bicycle forbidden band characteristic is characterized in that: the structure is formed by periodically compounding the same cells, wherein each single cell comprises a four-layer structure which comprises a homogeneous attachment layer (1), a periodic sandwich layer (2), a homogeneous constraint layer (3) and a homogeneous surface layer (4) from bottom to top in sequence, the periodic sandwich layer of each single cell of the structure is formed by materials of A (21) and B (22), through holes (23 and 26) are respectively formed in the centers of the sandwich layers formed by the materials of A (21) and B (22), a local resonance unit is respectively arranged in each through hole and is formed by connecting an upper spring element (24) and a lower spring element (27) with a middle mass element (25 and 28), and the two spring elements (24 and 27) are respectively connected with the homogeneous attachment layer (1) on the lower side and the homogeneous constraint layer (3) on the upper side.

2. The dual-period forbidden band characteristic-based low-frequency broadband vibration suppression structure as claimed in claim 1, wherein the materials of the homogeneous attachment layer (1), the periodic sandwich layer (2) and the homogeneous surface layer (4) are viscoelastic damping materials, and the material of the homogeneous constraint layer (3) is an elastic metal material.

3. The dual-period-forbidden-band-characteristic-based low-frequency broadband vibration suppression structure according to claim 1 or 2, wherein the length dimensions of the sandwich layer A (21) and the sandwich layer B (22) in the periodic sandwich layer are different along the periodic direction, and the resonant frequencies of the two local resonance units respectively located in the through holes of the sandwich layer A (21) and the sandwich layer B (22) are set to be different frequencies.

4. The structure of claim 3, wherein the spring elements (24, 27) in the local resonance unit are springs or a structure made of soft material with homogeneous quality and capable of providing elastic support.

Images