A lightweight multi-directional low-frequency broadband honeycomb sandwich vibration reduction structure

Abstract

The present invention relates to a lightweight, multi-directional, low-frequency, broadband honeycomb sandwich vibration damping structure, which uses a lattice sandwich structure as a matrix, and integrates a local resonance unit in its internal cavity. Through the independent design and regulation of the matrix and the local resonance unit performance, the lightweight and ultra-strong characteristics and the vibration suppression function can be achieved simultaneously. The structure of the present invention includes an upper panel, a lower panel and a vibration isolation functional structure. The vibration isolation functional structure is composed of a honeycomb core layer and a local resonance unit. The main body of the local resonance unit is a three-group spring sheet-mass block resonance system. The modal frequency and direction of the resonance system can be changed by adjusting the installation method of the spring sheet. The structure of the present invention has both lightweight and ultra-strong properties and low-frequency broadband vibration damping performance, and is easy to adjust the vibration damping frequency band and direction. It is suitable for multi-directional, low-frequency broadband and multi-line spectrum vibration control scenarios under lightweight requirements.

Description

Technical Field

[0001] The invention relates to the field of vibration reduction structures, in particular to a lightweight multi-directional low-frequency broadband honeycomb sandwich vibration reduction structure. Background Art

[0002] Lightweight sandwich structures have advantages such as high specific stiffness and specific strength. However, due to the constraints of the mass law, the low-frequency acoustic vibration performance of lightweight materials is generally poor. Metamaterials / structures are achieved by finely designing artificial microstructures of subwavelength size, so that the overall structure has excellent dynamic performance, thereby producing a good suppression effect on low-frequency vibrations. By combining lightweight sandwich structures with artificial microstructures, a multifunctional integrated superstructure can be constructed, which has important application prospects in the field of lightweight and efficient vibration reduction and noise reduction.

[0003] After searching, the following relevant Chinese patent documents were found.

[0004] Patent document A: A phononic crystal negative Poisson's ratio honeycomb vibration isolation and impact resistance device, application number 201710042535.9, publication number CN106907418A.

[0005] The patent document is aimed at a negative Poisson's ratio honeycomb structure. First, a lead block is embedded in a rubber block to form a whole, and then the rubber block is matched and embedded in the cell structure of the negative Poisson's ratio honeycomb core, thereby constructing a phononic crystal negative Poisson's ratio honeycomb structure, while achieving multiple use and design indicators such as vibration reduction, impact resistance, and load-bearing. The processing and assembly of the negative Poisson's ratio honeycomb core in this technology is difficult, and there are problems such as inconvenient installation and insufficient stability.

[0006] Patent document B: A honeycomb structure panel integrating vibration suppression, light weight and high strength and a preparation method thereof, application number 202110024815.3, publication number CN112874066A.

[0007] This patent document targets the grid sandwich structure, and prepares a local resonance type intermediate oscillator layer containing several "racket" shaped unit structures by laser cutting aluminum alloy plates, and then assembles the double-layer grid structure, the intermediate oscillator layer, and the upper and lower panels by gluing, thereby obtaining a multifunctional quadrilateral honeycomb structure, which achieves both vibration suppression and lightweight and super-strong performance. This technology only targets vibrations in the main bearing direction, but in real environments, there are often multiple vibration directions coexisting. Therefore, the function of this design method will be seriously affected when facing multi-polarized vibrations.

[0008] In addition, after the above two structures are designed and prepared, it is difficult to actively adjust the vibration reduction frequency band and direction according to the actual working conditions and environment. At the same time, the internal space of the sandwich structure is not fully utilized by the local resonance unit, and there are problems such as insufficient space utilization and too low proportion of vibration absorption mass. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a lightweight multi-directional low-frequency broadband honeycomb sandwich vibration reduction structure in view of the above shortcomings.

[0010] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0011] A lightweight multi-directional low-frequency broadband honeycomb sandwich vibration reduction structure, comprising an upper panel, a lower panel and a vibration isolation functional structure, wherein the upper panel and the lower panel are parallel to each other and are respectively fixed on the upper and lower surfaces of the vibration isolation functional structure;

[0012] The vibration isolation functional structure includes a honeycomb core layer and a local resonance unit, the honeycomb core layer is composed of a honeycomb core body arranged periodically, and the honeycomb core body is a hollow regular hexagonal prism structure surrounded by a plurality of rectangular plates;

[0013] A local resonance unit is detachably arranged in each honeycomb core, and the local resonance unit consists of a base, a bracket, a mass block and a spring sheet. The base is fixed on the lower panel, the bracket is fixed on the base and coincides with the axis of the base and the honeycomb core, and a plurality of vertically arranged detachable spring sheets are arranged on the bracket from top to bottom, and a mass block is fixed at the other end of the spring sheet, and each group of spring sheets and mass blocks forms a spring sheet-mass block resonance system.

[0014] Furthermore, the upper panel and the honeycomb core layer are detachably connected via bolts.

[0015] Furthermore, the lower panel and the honeycomb core layer are integrally formed and manufactured in one step by milling with a high-speed precision engraving machine.

[0016] Furthermore, the bracket is in the shape of a rectangular column and is provided with cross-shaped square grooves at different heights on the four sides. The spring sheet can be inserted into the horizontal groove or the vertical groove of the square groove by rotating around the axis. The direction of the bending vibration of the spring sheet can be adjusted by changing the mounting surface and embedding method of the spring sheet, thereby realizing independent regulation and combination of the modal directions of the three groups of spring sheet-mass block resonance systems.

[0017] Furthermore, the mass block is in a cubic shape, and the spring sheet passes through the center of gravity of the mass block.

[0018] Furthermore, the bracket is interference-fitted with the circular hole on the base, and the base is glued to the lower panel, so as to integrate the local resonance unit into the internal cavity of the honeycomb core layer.

[0019] Furthermore, the square groove and the spring sheet are interference fit and the depth of the spring sheet inserted into the square groove is adjustable, and the frequency of the bending vibration of the spring sheet can be adjusted by changing the embedding depth of the spring sheet.

[0020] Furthermore, the base is a regular hexagonal prism structure and its size is smaller than the size of the inner cavity of the honeycomb core.

[0021] Furthermore, the spring sheet of the local resonance unit is obtained by wire cutting a manganese steel plate.

[0022] After adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0023] 1. The present invention uses a lightweight sandwich structure as a matrix, integrates a local resonance unit in its internal cavity, and constructs a low-frequency broadband vibration reduction structure. Through the independent design and regulation of the matrix and the local resonance unit performance, the lightweight and ultra-strong characteristics and the vibration suppression function can be achieved simultaneously.

[0024] 2. The present invention uses wire cutting to process manganese steel plate to prepare ultra-thin spring sheets, which significantly reduces the bending stiffness of the spring sheets. In addition, manganese steel material has good elasticity and strength. Combining one end of the spring sheet with a high-density mass block can construct a low-frequency resonance system, which is easy to achieve low-frequency vibration reduction.

[0025] 3. In the present invention, a total of three sets of spring-mass resonance systems can be configured on the bracket of the local resonance unit, which significantly increases the vibration absorption mass ratio and space utilization, and effectively broadens the vibration absorption frequency band.

[0026] 4. The present invention adjusts the vibration reduction direction by changing the installation surface of the spring sheet and embedding it into the square groove of the bracket. It is easy to operate and can achieve vibration suppression in multiple directions at the same time.

[0027] 5. In the present invention, the spring sheet and the bracket square groove adopt an interference fit, and the stiffness characteristics are changed by adjusting the depth of the spring sheet embedded in the square groove, which makes it easy to adjust the modal frequency of the spring sheet-mass block resonance system without configuring additional parts.

[0028] In summary, the lightweight, multi-directional, low-frequency, broadband honeycomb sandwich vibration damping structure designed in the present invention has a compact structure, a large vibration-absorbing mass ratio, low-frequency, broadband vibration damping performance, and is easy to adjust the vibration damping frequency band and direction, providing a design scheme for a multifunctional vibration damping structure.

[0029] The present invention is described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the honeycomb sandwich vibration reduction structure of the present invention;

[0031] Figure 2 An exploded view of the honeycomb sandwich vibration damping structure of the present invention;

[0032] Figure 3 It is a schematic diagram of the structure of the local resonance unit of the present invention;

[0033] Figure 4 An exploded view of the local resonance unit structure of the present invention;

[0034] Figure 5 Schematic diagram of a typical application scenario of the honeycomb sandwich vibration reduction structure of the present invention;

[0035] Figure 6 This is a vertical vibration absorption effect diagram of the honeycomb sandwich vibration reduction structure of the present invention;

[0036] Figure 7 This is a diagram showing the lateral vibration absorption effect of the honeycomb sandwich vibration damping structure of the present invention;

[0037] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0038] 1. Upper panel; 2. Through hole; 3. Vibration isolation functional structure; 4. Lower panel; 5. Local resonance unit; 6. Honeycomb core layer; 7. Threaded hole; 8. Bracket; 9. Mass block; 10. Square hole; 11. Square groove; 12. Spring sheet; 13. Base; 14. Round hole. DETAILED DESCRIPTION

[0039] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0040] The lightweight multi-directional low-frequency broadband honeycomb sandwich vibration reduction structure of the present invention comprises an upper panel 1, a lower panel 4 and a vibration isolation functional structure 3, wherein the upper panel 1 and the lower panel 2 are parallel to each other and are fixed on the upper and lower surfaces of the vibration isolation functional structure 3 respectively;

[0041] The vibration isolation functional structure 3 includes a honeycomb core layer 6 and a local resonance unit 5. The honeycomb core layer 6 is composed of a periodic arrangement of honeycomb core bodies. The honeycomb core body is a hollow regular hexagonal prism structure surrounded by a plurality of rectangular plates.

[0042] Each honeycomb core is detachably provided with a local resonance unit 5, which is composed of a base 13, a bracket 8, a mass block 9 and a spring sheet 12. The base 13 is fixed on the lower panel 4, the bracket 8 is fixed on the base 13 and coincides with the axis of the base 13 and the honeycomb core, and a plurality of vertically arranged detachable spring sheets 12 are provided on the bracket 8 from top to bottom, and a mass block 9 is fixed at the other end of the spring sheet 12, and each group of spring sheets 12 and mass block 9 forms a spring sheet-mass block resonance system.

[0043] As an implementation mode, a plurality of through holes 2 are formed on the upper panel 1, and the position of each through hole 2 corresponds to the position of a threaded hole 7 in the honeycomb core layer 6, and the upper panel 1 is connected and fixed to the honeycomb core layer 6 by bolts.

[0044] As an embodiment, the lower panel 4 and the honeycomb core layer 6 are integrally formed in one step by milling with a high-speed precision engraving machine.

[0045] As an embodiment, the main structure of the local resonance unit 5 is a three-group spring sheet-mass block resonance system, in which the three groups of spring sheets 12 are respectively interference fit with the three-layer square grooves 11 on the bracket 8, the bracket 8 is interference fit with the circular hole 14 on the base 13, and the base 13 is glued to the lower panel 4, thereby integrating the local resonance unit 5 into the internal cavity of the honeycomb core layer 6.

[0046] As an implementation mode, the square groove 11 of the local resonance unit is interference fit with the spring sheet 12, and the frequency of the bending vibration of the spring sheet 12 is adjusted by changing the embedding depth of the spring sheet 12, thereby realizing independent regulation and combination of the modal frequencies of the three groups of resonance systems.

[0047] As an implementation mode, the square groove 11 of the local resonance unit is a cross-shaped square groove. On each side of the bracket 8, the spring sheet 12 has two embedding modes, horizontal and vertical. By changing the mounting surface and embedding mode of the spring sheet 12, the direction of the bending vibration of the spring sheet 12 can be adjusted, thereby realizing independent regulation and combination of the modal directions of the three groups of resonance systems.

[0048] As an implementation mode, the size of the base 13 in the local resonance unit is slightly smaller than the size of the internal cavity of the honeycomb core, in order to ensure that the base 13 can smoothly enter and exit the cavity, thereby facilitating the installation and removal of the local resonance unit 5 .

[0049] As an implementation manner, the spring piece 12 of the local resonance unit is obtained by wire cutting a manganese steel plate.

[0050] Typical application scenarios of the lightweight multi-directional low-frequency broadband honeycomb sandwich vibration damping structure of the present invention:

[0051] Figure 5 The figure shows a typical application scenario of the honeycomb sandwich vibration reduction structure in the field of ship vibration isolation engineering, including the hull, base, vibration isolator and raft, wherein the honeycomb sandwich vibration reduction structure of the present invention can be stacked in multiple layers as needed and arranged between the base and the raft, and regarded as a part of the base. At present, the floating raft vibration isolation technology is mainly used in the ship field to isolate broadband mechanical vibrations, and the line spectrum active control technology is used to reduce the vibration line spectrum, wherein the raft mainly acts as an intermediate mass and a common platform, and the main function of the base is to provide support and stability, without considering the vibration isolation potential of the raft and the base. Figure 5 The vibration isolation system design based on the honeycomb sandwich vibration damping structure shown in the text provides a new vibration isolation solution. The low-frequency broadband vibration damping performance and rich control characteristics of the honeycomb sandwich vibration damping structure can significantly improve the vibration attenuation capacity of the raft and the base, further increasing the effectiveness of the vibration isolation system.

[0052] The working principle of the lightweight multi-directional low-frequency broadband honeycomb sandwich vibration reduction structure described in the present invention is:

[0053] The lightweight multi-directional low-frequency broadband honeycomb sandwich vibration damping structure mainly relies on the resonance characteristics of the local resonance unit integrated in the internal cavity of the honeycomb core layer to open the elastic wave band gap and realize the suppression of vibration transmission within the band gap. When the frequency of the elastic wave propagating in the structure is near a certain natural frequency of the internal local resonance unit, the local resonance mode with the same polarization direction as the elastic wave will be excited. At this time, the vibration of the local resonance unit is opposite to the elastic wave in the structure. When the filling rate of the local resonance unit in the structure is high enough, the response characteristics of the entire structure are dominated by the response of the local resonance unit, so that the movement of the entire structure is opposite to the excited elastic wave, resulting in a negative dynamic mass density. Since the relationship between the speed of sound, mass density and elastic modulus in the elastic medium is , the negative mass density means that the wave velocity and wave vector have an imaginary part. At this time, the elastic wave propagating in the medium will decay rapidly in an exponential form and cannot propagate, thus forming an elastic wave band gap.

[0054] The specific method of use of the present invention is as follows:

[0055] Test the excitation characteristics of the main vibration source equipment in the application scenario, and determine the characteristic line spectrum and broadband continuous spectrum that need to be controlled in each direction. According to the vibration reduction requirements in different directions, reasonably allocate the number of resonant systems in each direction, and determine the design criteria for the vibration absorption frequency of the resonant system.

[0056] The design formula of the first-order resonant frequency of the spring sheet-mass block resonant system is: , ,

[0057] In the formula E represents the Young's modulus of the spring leaf, b Represents the width of the spring leaf, h m represents the thickness of the spring sheet, l s represents the cantilever beam length, m s Represents the mass of the mass block.

[0058] The design criteria for the characteristic line spectrum are as follows: when designing the parameters, the first-order resonance frequency of the spring sheet-mass block resonance system of each layer in the local resonance unit should be aligned with the characteristic line spectrum. When the frequency and direction of the resonance system in the local resonance unit are consistent, the band gap width can be calculated as follows: , ,

[0059] In the formula m irepresents the mass of the mass block, represents the effective mass proportion of the local resonance unit, N represents the number of parametric resonant systems in the vibration-damping material, m h Indicates the mass of the matrix.

[0060] The design criteria for broadband continuous spectrum are as follows: For simplicity, broadband continuous spectrum is described as ,in f c is the center frequency of the continuous spectrum, is the frequency range covered by the continuous spectrum. The following two cases are considered:

[0061] (1) Situation 1: When When , the band gap width generated by the local resonance unit with the same impedance characteristics is sufficient to cover the entire frequency range of the continuous spectrum. At this time, the center frequency of the band gap can be equal to the center frequency of the continuous spectrum, and the design frequency of the local resonance unit can be further obtained as follows: (1)

[0062] (2) Case 2: When When the spring stiffness is changed in sequence, a series of resonant systems with frequency gradients can be established. To expand the vibration reduction bandwidth, the construction scheme of the gradient resonance system is as follows:

[0063] (2)

[0064] in, represents the first-order resonance frequency of the spring-mass resonant system, represents the resonant frequency of the resonant system located in the middle of the gradient, Indicates the first and S The frequency interval between the resonant frequencies of a resonant system.

[0065] Similar to case 1, the center of the vibration reduction bandwidth can be located at the center frequency of the continuous spectrum. At the same time, since there will be redundant attenuation areas when the vibration reduction bandwidth is larger than the frequency band covered by the continuous spectrum, the vibration reduction bandwidth is further made equal to the frequency band covered by the continuous spectrum, so:

[0066] (3)

[0067] (4)

[0068] Substituting equations (3)-(4) into equation (2), we can obtain the resonant frequency design formula for each resonant system.

[0069] The processing technology difficulties of the present invention are:

[0070] Difficulty: The present invention involves many types of materials, ultra-small parts, and high precision requirements. The technical difficulties are concentrated in the processing and manufacturing, especially the processing and manufacturing of spring leaves.

[0071] The specific difficulty is: in order to achieve low-frequency vibration control, the cross-sectional size of the spring sheet needs to be designed to be small enough, and at the same time, the clearance between the spring sheet and the bracket square slot needs to be moderate, so as to facilitate the subsequent regulation of the vibration absorption frequency. This requirement for small size and high precision poses a challenge to the machining method.

[0072] Solution: The present invention first customizes manganese steel plates of similar thickness, uses a medium-speed wire cutting machine to cut and shape them, and then uses a precision grinding method to achieve the size requirements, thereby solving the problem of spring leaf processing and manufacturing.

[0073] The vibration reduction effect of the lightweight multi-directional low-frequency broadband honeycomb sandwich vibration reduction structure of this embodiment is verified:

[0074] The main size parameters of the lightweight multi-directional low-frequency broadband honeycomb sandwich vibration reduction structure are as follows: length L = 690mm, width = 160mm, height = 41mm, lattice constant = 40mm, upper and lower panel thickness = 3mm, honeycomb wall thickness = 1mm, spring sheet thickness = 0.25mm, spring sheet width = 1mm, square mass block side length d = 6mm, bracket height 30mm, base thickness 5mm. The upper and lower panels and honeycomb core of the local resonance unit vibration reduction material are made of aluminum alloy, the base and bracket of the local resonance unit are made of polytetrafluoroethylene, the spring sheet is made of 65Mn spring steel, and the mass block is made of lead.

[0075] The vibration reduction structure is a two-point elastic support boundary condition. During the test, a PBE-120 rubber vibration isolator is used at each end to support it. A hammer is used to apply vertical and lateral excitations to one end of the vibration reduction material, and the acceleration response of the other end of the vibration reduction material is extracted. The vibration reduction performance is evaluated based on the calculated frequency response function. In order to better observe the vibration reduction performance of the present invention, the direction of the resonant mode group of the spring sheet-mass block resonant system is adjusted accordingly according to the direction of the excitation application, so as to maximize the number of parametric resonance systems under excitation in different directions.

[0076] Figure 6 , Figure 7 The vertical and lateral vibration absorption effects of the lightweight multi-directional low-frequency broadband honeycomb sandwich vibration reduction structure are shown, with the effective mass percentage of the local resonance unit. In order to intuitively see the vibration reduction efficiency generated by the resonance characteristics of the local resonance unit, a mass control group was added during the analysis, and the added mass was equal to the mass of the local resonance unit. Figure 6It can be seen that under vertical excitation, the mass control group has two prominent frequency response peaks in the 45-80Hz frequency range. After applying vibration reduction materials and rationally adjusting the modal frequency of the internal local resonance unit, the peak at 51Hz is reduced from 128dB to 120dB, and the peak at 73Hz is reduced from 131dB to 124dB compared to the control group. Figure 7 It can be seen that under lateral excitation, the mass control group has a prominent broadband continuous spectrum in the frequency range of 75-120Hz. After applying vibration-damping materials and reasonably adjusting the modal frequency of the internal local resonance unit, the vibration level of the broadband continuous spectrum is significantly reduced compared with the control group, and the effective vibration reduction bandwidth is about 35dB.

[0077] The above is an example of the best implementation of the present invention, and the parts not described in detail are common knowledge of ordinary technicians in the field. The protection scope of the present invention shall be based on the content of the claims, and any equivalent transformation based on the technical enlightenment of the present invention is also within the protection scope of the present invention.

Claims

1. A lightweight multi-directional low-frequency broadband honeycomb sandwich vibration reduction structure, characterized in that: It includes an upper panel, a lower panel and a vibration isolation function structure, wherein the upper panel and the lower panel are parallel to each other and are respectively fixed on the upper and lower surfaces of the vibration isolation function structure; The vibration isolation functional structure includes a honeycomb core layer and a local resonance unit, the honeycomb core layer is composed of a honeycomb core body arranged periodically, and the honeycomb core body is a hollow regular hexagonal prism structure surrounded by a plurality of rectangular plates; A local resonance unit is detachably provided in each honeycomb core, and the local resonance unit includes a base, a bracket, a mass block and a spring sheet, wherein the base is fixed on the lower panel, the bracket is fixed on the base and coincides with the axis of the base and the honeycomb core, and a plurality of spring sheets are detachably and vertically provided on the bracket from top to bottom, and a mass block is fixed at the other end of the spring sheet, and each group of spring sheets and mass blocks forms a spring sheet-mass block resonance system; The bracket is in the shape of a rectangular column and has cross-shaped square grooves at different heights on the four sides. The spring sheet can be inserted into the horizontal groove or the vertical groove of the square groove by rotating around the axis. The direction of the bending vibration of the spring sheet can be adjusted by changing the installation surface and the embedding method of the spring sheet, thereby realizing independent regulation and combination of the modal directions of the three groups of spring sheet-mass block resonance systems.

2. The lightweight multi-directional low-frequency broadband honeycomb sandwich vibration damping structure according to claim 1 is characterized in that: The upper panel and the honeycomb core layer are detachably connected via bolts.

3. The lightweight multi-directional low-frequency broadband honeycomb sandwich vibration damping structure according to claim 1 is characterized in that: The lower panel and the honeycomb core layer are integrally formed and manufactured by one-step milling of a high-speed precision engraving machine.

4. The lightweight multi-directional low-frequency broadband honeycomb sandwich vibration damping structure according to claim 1 is characterized in that: The mass block is in a cubic shape, and the spring sheet passes through the center of gravity of the mass block.

5. The lightweight multi-directional low-frequency broadband honeycomb sandwich vibration damping structure according to claim 1 is characterized in that: The bracket is interference-fitted with the circular hole on the base, and the base is glued to the lower panel, so as to integrate the local resonance unit into the internal cavity of the honeycomb core layer.

6. The lightweight multi-directional low-frequency broadband honeycomb sandwich vibration damping structure according to claim 1 is characterized in that: The square groove and the spring sheet are interference-fitted, and the depth of the spring sheet inserted into the square groove is adjustable. The frequency of the bending vibration of the spring sheet can be adjusted by changing the embedding depth of the spring sheet.

7. The lightweight multi-directional low-frequency broadband honeycomb sandwich vibration damping structure according to claim 1 is characterized in that: The base is a regular hexagonal prism structure and its size is smaller than the size of the inner cavity of the honeycomb core.

8. The lightweight multi-directional low-frequency broadband honeycomb sandwich vibration damping structure according to claim 1 is characterized in that: The spring sheet of the local resonance unit is obtained by wire cutting a manganese steel plate.

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