Damper

Abstract

A damper provided at a bearing, comprising an inner sleeve and an outer sleeve, the inner sleeve and the outer sleeve being coaxially arranged and the inner sleeve being sleeved to the bearing wherein the damper further comprises: a damping ring which is elastically deformable, is provided between the inner sleeve and the outer sleeve and abuts against opposite surfaces of the inner sleeve and the outer sleeve simultaneously; the limit load force transmission ring and the damping ring are adjacently arranged between the inner sleeve and the outer sleeve; the damper comprises a damping state and a limit state, in the damping state, a gap exists between the limit load force transmission ring and one of the outer sleeve and the inner sleeve, and the damping ring is allowed to deform; in the limit state, the limit load force transmission ring abuts against the outer sleeve and the inner sleeve at the same time, and the damping ring is prevented from deforming. According to the damper, nonlinear response easily caused by oil film damping vibration attenuation is eliminated, and meanwhile the damping performance can be maintained under the great impact load.

Description

Technical Field

[0001] The present invention relates to the field of bearing vibration damping, and specifically, to a damper. Background Art

[0002] Aeroengines need to withstand vibration loads caused by factors such as rotor imbalance under normal operating conditions. In addition, during flight, aeroengines may also be subjected to transient impact loads such as bird strikes. The peak value of the transient impact load is much higher than the vibration load generated during the normal operation of aeroengines.

[0003] In order to protect other engine structures from the influence of vibration, aeroengines usually use damping and vibration reduction structures such as squeeze film dampers. A squeeze film damper fills a layer of lubricating oil outside the bearing of the rotating shaft to form an oil film, and uses the viscous damping of the oil film to convert the kinetic energy of vibration into internal energy, which can effectively damp and reduce vibration. This mechanism has a significant vibration reduction effect and occupies a small space, so it is widely used in aeroengines. Existing squeeze film dampers usually adopt a concentric structure with a centering spring (generally a squirrel-cage elastic support), so the gravity of the rotor can be assumed to be balanced by the initial restoring force of the elastic support, and in most cases, the steady-state response trajectory of the rotor can be assumed to be circular. However, due to the fluidity of the oil film, in the case of poor design or deterioration of the imbalance of the rotor system, the nonlinearity of the oil film force will increase significantly, which will lead to many harmful nonlinear responses, such as non-synchronous precession of the rotor, bistable jump, and the "locking" situation where the critical speed cannot be passed, etc.

[0004] In addition, when the engine is subjected to a large impact load, the lubricating oil in the oil film of the existing squeeze film damper is easily squeezed out instantaneously, resulting in the loss of damping performance of the squeeze film damper and the inability to reduce vibration.

[0005] Some dampers use metal rubber instead of the oil film as the damping component. As an elastic solid, metal rubber has stronger stability compared to the fluid lubricating oil, which is beneficial to preventing the rotor from generating nonlinear responses. However, since metal rubber is formed by stamping metal wires, its material properties are uncertain, that is, its Young's modulus, yield strength, and failure parameters are not definite values. Therefore, its elastic deformation limit is uncertain, that is to say, its crushing load is uncertain. This characteristic of metal rubber has a great negative impact when the engine is subjected to an impact load, and may cause the damping component to fail at an uncertain time point during compression, resulting in structural damage.

[0006] Therefore, it is necessary to propose an improved damper that can solve the problems and defects existing in the above-mentioned prior art. Summary of the Invention

[0007] The object of the present invention is to provide an improved damper, which is provided with a solid elastic damping ring and an ultimate load transfer ring to prevent non-linear response and ensure that the damper still retains its damping performance when the engine is subjected to a large impact load.

[0008] According to the present invention, there is provided a damper which is arranged at a bearing and includes an inner sleeve and an outer sleeve. The inner sleeve and the outer sleeve are coaxially arranged, and the inner sleeve is sleeved on the bearing. Wherein, the damper further includes: a damping ring which can elastically deform and is arranged between the inner sleeve and the outer sleeve and simultaneously abuts against the opposite surfaces of the inner sleeve and the outer sleeve; an ultimate load transfer ring which is arranged between the inner sleeve and the outer sleeve adjacent to the damping ring; and wherein the damper includes a damping state and an ultimate state. In the damping state, there is a gap between the ultimate load transfer ring and one of the outer sleeve and the inner sleeve, allowing the damping ring to deform; in the ultimate state, the ultimate load transfer ring abuts against both the outer sleeve and the inner sleeve simultaneously, preventing the damping ring from deforming. Since the present invention uses a solid damping ring instead of a fluid oil film, its structure is stable and will not cause non-linear response of the engine structure. In the normal working state, the damper is in the damping state and the damping ring is compressed under pressure; when subjected to an impact load exceeding the elastic deformation force limit of the damping ring, the damper is in the ultimate state, and the ultimate load transfer ring is used to transfer the load under pressure to protect the damping ring from damage. In this way, the damping ring can work normally in various situations and retain its damping performance.

[0009] According to another aspect of the present invention, the ultimate load transfer ring includes a pair of ultimate load transfer rings respectively arranged on the axial two sides of the damping ring. Wherein, each of the ultimate load transfer rings is in clearance fit with the damping ring and one of the outer sleeve and the inner sleeve. And the ultimate load transfer ring is fixed to the other of the inner sleeve and the outer sleeve, so as to ensure that the ultimate load transfer ring is firmly positioned in the damper to prevent structural damage or reduction of damping performance due to its accidental displacement. Specifically, the ultimate load transfer ring can be in screw fit, snap fit or interference fit with the other of the inner sleeve and the outer sleeve. The clearance fit allows the ultimate load transfer ring to allow relative movement between the outer sleeve and the inner sleeve in the damping state, thereby squeezing the damping ring to perform damping and vibration reduction.

[0010] In an embodiment of the present invention, the axial clearance between the ultimate load transfer ring and the damping ring is between 0.5 mm and 1 mm, and the radial clearance between the ultimate load transfer ring and one of the outer sleeve and the inner sleeve is between 2 mm and 3 mm. Generally, the clearances between the ultimate load transfer ring and the damping ring and the inner and outer sleeves are calculated according to the interval of the elastic change size of the damping ring, or other appropriate clearance sizes can be selected according to different materials of the damping ring.

[0011] According to another aspect of the present invention, the ultimate load transfer ring is made of a rigid material, which includes an alloy or a composite material, preferably the same as the material of the bearing. In addition, in order to ensure that the ultimate load transfer ring does not undergo irreversible yield deformation or structural damage under high-energy impact loads, the radial dimension of the ultimate load transfer ring needs to be calculated based on the strength of the ultimate load transfer ring under ultimate impact loads. In the embodiment of the present invention, the radial dimension of the ultimate load transfer ring is between 5 mm and 6 mm.

[0012] To solve the uncertainty problem of some existing solid damping members, the damping ring of the present invention includes an elastic porous structure. The elastic porous structure includes at least one of the following structures: a triply periodic minimal surface structure, and the unit cell structure construction formula of the triply periodic minimal surface structure is selected from one or more of the Schoen-Gyroid unit cell construction formula, the Schwarz Primitive unit cell construction formula, and the Neovius unit cell construction formula; a lattice structure; and a corrugated structure. Such an elastic porous structure itself has strong elasticity, and due to its porous characteristics, other damping materials can be filled in the structure to further improve the damping performance. The elastic porous structure is preferably made of a metal with strong plasticity such as a titanium alloy. This elastic porous structure, especially the triply periodic minimal surface structure, has three-dimensional anisotropy, but the strength in all directions in the Euclidean space is fixed, making it have high material stability and enabling the calculation of the crushing load that makes it reach the elastic deformation limit.

[0013] According to another aspect of the present invention, the damping ring includes an outer frame and an elastic porous structure, and a fillet is provided between the elastic porous structure and the outer frame, which can improve the connection stiffness between the two.

[0014] In the embodiment of the present invention, the range of each dimension of the unit cell structure of the triply periodic minimal surface structure in the plane is 2 mm to 3 mm. However, other suitable dimensions can also be envisaged in alternative embodiments.

[0015] According to another aspect of the present invention, the elastic porous structure can be filled with a damping material, and the damping material includes rubber or plastic. This can further improve the damping performance of the elastic porous structure, enabling it to withstand greater loads. Specifically, since the low-temperature end bearing with a working temperature lower than 200°C is subjected to greater loads, a damping ring filled with an additional damping material is used thereon.

[0016] The damper of the present invention uses an elastically deformable solid damping ring to replace the oil film of the traditional squeeze film damper, enabling the avoidance of the non-linear response that may occur when using an oil film and simplifying the structure. At the same time, the damper of the present invention is provided with a limit load transfer ring so that the damping ring can be allowed to deform to damp the bearing vibration in the damping state, and in the limit state where the damping ring reaches the limit of elastic deformation, it can simultaneously abut against and clamp the inner and outer sleeves that hold the damping ring to prevent the damping ring from deforming further, thereby protecting the damping ring from damage. In addition, the damper of the present invention uses an advanced elastic porous structure such as a triply periodic minimal surface structure to make the damping ring, which has the advantages of better elasticity, stable strength, and a wide working temperature range, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] To more fully understand the present disclosure, reference may be made to the following description of exemplary embodiments considered in conjunction with the accompanying drawings. The drawings are not intended to limit the present disclosure to the specific embodiments depicted and are not necessarily to scale. In the drawings:

[0018] Figure 1 is a cross-sectional view taken along the axial direction of the damper of the preferred embodiment of the present invention in the damping state;

[0019] Figure 2 is a cross-sectional view taken along the axial direction of the damper of the preferred embodiment of the present invention in the limit state;

[0020] Figure 3 is Figure 1 a partial enlarged view of the damping ring of the damper, which shows the first embodiment of the damping ring;

[0021] Figure 4 is Figure 3 a partial enlarged view of the damping ring;

[0022] Figures 5a to 5b is a plan view and a three-dimensional view of the unit cell structure of the first embodiment of the damping ring;

[0023] Figures 6a to 6b is a plan view and a three-dimensional view of the unit cell structure of the second embodiment of the damping ring; and

[0024] Figures 7a to 7b is a plan view and a three-dimensional view of the unit cell structure of the third embodiment of the damping ring.

[0025] LIST OF REFERENCE NUMERALS

[0026] 100 Damper

[0027] 1 Inner sleeve

[0028] 2 Outer sleeve

[0029] 21 Ring groove

[0030] 3 Damping ring

[0031] 31 Outer frame

[0032] 32 Elastic porous structure

[0033] 4 Ultimate load transfer ring

[0034] d1 Axial clearance between the ultimate load transfer ring and the damping ring

[0035] d2 Radial clearance between the ultimate load transfer ring and the outer sleeve

[0036] d3 Radial width of the ultimate load transfer ring

[0037] 200 Bearing

[0038] 300 Rotating shaft

[0039] 400 Support outer ring

[0040] A Axial direction

[0041] B Radial direction

[0042] F(t) Load

[0043] w Width of the ring groove Detailed implementation manners

[0044] The following elaboration of the specific implementation manners of the present invention refers to the accompanying drawings, which show specific embodiments in which the present invention can be practiced. The embodiments are intended to describe all aspects of the present invention in sufficient detail to enable those skilled in the art to implement the present invention. Other embodiments can be utilized and changes can be made without departing from the scope of the present invention. Therefore, the following elaboration of the specific implementation manners should not be considered restrictive. The scope of the present invention is defined only by the appended claims and the full scope of equivalents covered by the claims. The same reference numerals are used throughout all the drawings and the specific implementation manners to refer to the same or similar components.

[0045] In this article, orientation terms such as "upper", "lower", "top", "bottom", "radial", "axial", etc. are with reference to Figure 1 and Figure 2 the placement position of the damper 100 in

[0046] Figure 1 and Figure 2The damper 100 according to a preferred embodiment of the present invention is assembled with a rotating shaft 300 and a bearing 200. The damper 100 generally comprises an inner sleeve 1 sleeved on the bearing 200, an outer sleeve 2 arranged coaxially with the inner sleeve 1 and spaced a certain distance apart, a damping ring 3 arranged between the inner sleeve 1 and the outer sleeve 2, and a limit load transmission ring 4 arranged adjacent to the damping ring 3. The damper 100 has the following features: Figure 1 The damping state shown and Figure 2 Additionally, a supporting outer ring 400 is disposed externally of the outer sleeve 2 to fix the damper 100 in place.

[0047] Two limit load force transmission rings 4 are provided at both axial sides of the damping ring 3, and each of these limit load force transmission rings 4 has an axial gap d1 with the damping ring 3, and has a radial gap d2 with one of the inner sleeve 1 and the outer sleeve 2, and is fixedly matched with the other of the inner sleeve 1 and the outer sleeve 2. In this embodiment, the limit load force transmission ring 4 has a clearance fit with the outer sleeve 2 and is fixedly matched with the inner sleeve 1. Specifically, the limit load force transmission ring 4 has an interference fit with the inner sleeve 1. It is also conceivable that the limit load force transmission ring 4 is screw-fitted or snap-fitted with the inner sleeve 1, or is fixed to the inner sleeve 1 in other suitable matching ways. Of course, the present invention is not limited to this, and it is also conceivable in alternative embodiments that there is a radial gap d2 between the limit load force transmission ring 4 and the inner sleeve 1, and it is fixed to the outer sleeve 2 in an interference fit, screw-fitted, snap-fitted or other matching ways.

[0048] The sizes of the axial gap d1 and the radial gap d2 are calculated based on the elastic variation range of the size of the damping ring 3. In this embodiment, since the damping ring 3 is mainly composed of a three-period minimal surface structure made of plastic metal, the axial gap d1 is between 0.5 mm and 1 mm, and the radial gap d2 is between 2 mm and 3 mm. Of course, different suitable gaps can also be set according to the different materials of the damping ring 3. In order to ensure that the limit load force transmission ring 4 will not suffer structural damage when subjected to extremely large impact loads, the radial size d3 of the limit load force transmission ring 4 needs to be calculated based on the strength limit of the limit load force transmission ring under the action of the limit impact load. In this embodiment, the radial size d3 is between 5 mm and 6 mm.

[0049] The extreme load transmission ring 4 is made of a rigid material, such as an alloy or a composite material, preferably the same material as the bearing 200. In this way, the extreme load transmission ring 4 can avoid deformation when subjected to a large impact load, thereby effectively protecting the damping ring 3 with a lower elastic strength from damage.

[0050] Different from the clearance fit with the ultimate load transfer ring 4, the damping ring 3 abuts against both the inner sleeve 1 and the outer sleeve 2 simultaneously, so that the damping ring 3 can be compressed and deformed when the rotating shaft 300 is subjected to the load F(t), and damping and vibration reduction are carried out. Therefore, in this embodiment, the outer sleeve 2 can be designed to have a ring groove 21 at the position corresponding to the ultimate load transfer ring 4. The depth of the ring groove 21 is preferably equal to the radial clearance d2 between the ultimate load transfer ring 4 and the outer sleeve 2, and the width w of the ring groove 21 in the axial direction A is equal to the axial width of the ultimate load transfer ring 4. Of course, it is also conceivable to design the inner sleeve in this way in an alternative embodiment with a clearance fit between the ultimate load transfer ring 4 and the inner sleeve 1.

[0051] As Figure 1 shown, when the engine is in a rest state or a normal working state, the vibration amplitude of the rotating shaft 300 is small, that is, when the load F(t) is zero or less than the maximum elastic deformation force of the damping ring 3, the damper 100 is in a damping state. At this time, due to the existence of the radial clearance d2 between the outer sleeve 1 and the ultimate load damping ring 4, the inner sleeve 1 and the outer sleeve 2 can move relative to each other under the action of the load F(t), so that the damping ring 3 is compressed and deformed to carry out damping and vibration reduction.

[0052] As Figure 2 shown, when the engine is subjected to an impact load and the deformation caused by the impact load reaches the elastic deformation limit of the damping ring 3, the damper 100 is in an ultimate state. At this time, the radial clearance d2 between the ultimate load transfer ring 4 and the outer sleeve 2 is zero, and a part of the ultimate load transfer ring 4 abuts against both the inner sleeve 1 and the outer sleeve 2 simultaneously. Since the ultimate load transfer ring 4 is a rigid member, it can prevent the inner sleeve 1 and the outer sleeve 2 from approaching each other further and squeezing the damping ring 3, thereby protecting the damping ring 3 from irreversible yield deformation.

[0053] When the impact load F(t) that causes the damping ring 3 to reach the elastic deformation limit decays with time, the vibration amplitude of the rotating shaft 300 decreases, and the radial clearance d2 between the ultimate load transfer ring 4 and the outer sleeve 2 becomes non-zero again, allowing the damping ring 3 to be elastically deformed again for damping and vibration reduction.

[0054] The damping ring 3 is composed of an elastic porous structure, which includes one or more of a triply periodic minimal surface structure, a lattice structure, and a corrugated structure. Preferably, it is a triply periodic minimal surface structure, and the filled cell structure can adopt a walled TPMS (surface structure) unit cell with a hexahedron uniform array. Figures 5a to 7b The schematic diagrams of three different triply periodic minimal surface unit cell structures are shown, and their component formulas are as follows:

[0055] Figure 5a and Figure 5bThe plan view and the three-dimensional view of the unit cell of the Schoen-Gyroid structure (the first embodiment) are respectively shown, and its construction formula is sin X cos Y + sin Y cos Z + sin Z cos X = c;

[0056] Figure 6a and Figure 6b The plan view and the three-dimensional view of the unit cell of the Schwarz Primitive structure (the second embodiment) are respectively shown, and its construction formula is cos X + cos Y + cos Z = c;

[0057] Figure 7a and Figure 7b The plan view and the three-dimensional view of the unit cell of the Neovius structure (the third embodiment) are respectively shown, and its construction formula is 3(cos X + cos Y + cos Z) + 4(cos X cos Y cos Z) = c.

[0058] In the above formula, X = 2απX, Y = 2βπX, Z = 2γπX, where X, Y, and Z are independent variables and regarded as the coordinates of a certain point in the three-dimensional Euclidean space, and α, β, and γ are constants related to the unit cell size in the X, Y, and Z directions respectively. c is the calculated value of the level set equation. When it is equal to zero, the iso-surface divides the space into sub-domains with equal volumes.

[0059] Different unit cell sizes, wall thicknesses, and filling layers (filled along the axial direction A) can be selected to construct the required triply periodic minimal surface structure. In this embodiment, each unit cell has the same size, and the ranges of the dimensions of the unit cell in the plane, that is, its length, width, and height, are limited between 2 mm and 3 mm, preferably 2.5 mm. The wall thickness is a uniform wall thickness, preferably greater than 0.1 mm, and the filling layer is 4 to 5 layers, as Figure 3 shown. However, the present invention is not limited thereto, and a triply periodic minimal surface structure of the damping ring 3 can also be constructed by using variable wall thickness and variable unit cell size.

[0060] A metal with strong plasticity such as TC4 titanium alloy is used to manufacture the triply periodic minimal surface structure of the damping ring 3 to ensure that the damping ring 3 has an elastic deformation ability sufficient to resist impact loads. In addition, an additive manufacturing technology is preferably used to manufacture the damping ring 3. After the additive manufacturing is completed, the formed damping ring needs to be further polished and finely processed to trim it into the required shape. The finishing process will cause a certain amount of wear, so the wall thickness of the triply periodic minimal surface is set to be greater than 0.1 mm to ensure that after the trimming is completed, the wall thickness of the outer frame 31 of the damping ring 3 is about 0.1 mm.

[0061] As Figure 3 and Figure 4As shown, the damping ring 3 includes an outer frame 31 and an elastic porous structure 32 (a triply periodic minimal surface cell structure in this example), but it can also be envisioned in alternative embodiments that the damping ring 3 includes an outer frame 31 and other elastic porous structures 32 such as lattice structures and corrugated structures. Among them, as Figure 4 shown, a fillet is provided between the elastic porous structure 32 (a triply periodic minimal surface cell structure in this example) and the outer frame to improve the connection stiffness between the two.

[0062] In an aeroengine, there are multiple low-temperature end bearings with operating temperatures below 200°C and high-temperature end bearings with operating temperatures above 200°C. Among them, the low-temperature end bearings often need to bear greater loads. Therefore, it can be considered to additionally fill damping substances such as rubber and plastic inside the elastic porous structure 32 (a triply periodic minimal surface cell structure in this example) to further enhance the elastic deformation ability and damping performance of the damping ring 3. The damping substances are, for example, butyl, acrylate, polysulfide, nitrile, and silicone rubber, polyurethane, polyvinyl chloride, and epoxy resin. The operating temperature range of these damping substances is -50°C to 200°C, and they can be used in combination with the elastic porous structure to enable the damping ring to better meet the greater damping performance requirements of the low-temperature end bearings.

[0063] The damper according to the present invention is provided with a solid damping ring capable of elastic deformation and a limit load transfer ring for preventing the damping ring from deforming beyond the elastic deformation limit. The damping ring adopts an elastic porous structure such as a triply periodic minimal surface, and damping materials (such as rubber and plastic) can be optionally filled in the elastic porous structure to further improve the damping performance of the damping ring according to requirements. When the damping ring reaches the elastic deformation limit, the limit load transfer ring abuts against and clamps the inner and outer sleeves of the damping ring to prevent the damping ring from continuing to deform, achieving the purpose of protecting the damping ring from failing under excessive vibration. In this way, the problem of nonlinear response that easily occurs in the prior art when using an oil film damper is effectively solved, and the structure is simplified because components such as a squirrel cage are omitted. At the same time, the triply periodic minimal surface with higher material stability additionally solves the problem of uncertain elastic deformation limits caused by the instability of existing solid damping materials.

[0064] As used herein, the terms "comprising", "including", "having", or any other variant thereof are intended to cover non-exclusive inclusion. For example, a method, article, or device comprising a series of elements is not necessarily limited to those elements and may further include other elements not expressly listed or inherent to such method, article, or device.

[0065] The present invention is not limited to the above embodiments, which are merely illustrative rather than restrictive. Those skilled in the art can make any possible changes and modifications under the inspiration of the present invention without departing from the spirit of the present invention and the scope protected by the claims. Therefore, any modifications, equivalent changes and decorations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention all fall within the protection scope defined by the claims of the present invention.

Claims

1. A damper, the damper is arranged at a bearing, comprising an inner sleeve and an outer sleeve, the inner sleeve and the outer sleeve are coaxially arranged, and the inner sleeve is sleeved on the bearing, wherein, the damper further comprises: a damping ring, the damping ring can elastically deform, is arranged between the inner sleeve and the outer sleeve, and simultaneously abuts against the opposite surfaces of the inner sleeve and the outer sleeve; a limit load transfer ring, the limit load transfer ring is arranged between the inner sleeve and the outer sleeve adjacent to the damping ring; and wherein, the damper includes a damping state and a limit state, in the damping state, there is a gap between the limit load transfer ring and one of the outer sleeve and the inner sleeve, allowing the damping ring to deform; in the limit state, a part of the limit load transfer ring simultaneously abuts against the outer sleeve and the inner sleeve, preventing the damping ring from deforming.

2. The damper according to claim 1, wherein, the limit load transfer ring includes a pair of limit load transfer rings respectively arranged on the axial two sides of the damping ring, each of the limit load transfer rings is in clearance fit with the damping ring and one of the outer sleeve and the inner sleeve.

3. The damper according to claim 2, wherein, the axial clearance between the limit load transfer ring and the damping ring is between 0.5 mm and 1 mm, and the radial clearance between the limit load transfer ring and one of the outer sleeve and the inner sleeve is between 2 mm and 3 mm.

4. The damper according to claim 1, wherein, the limit load transfer ring is fixed to the other of the inner sleeve and the outer sleeve.

5. The damper according to claim 4, wherein, the limit load transfer ring is fixed to the other of the inner sleeve and the outer sleeve by screw fit, snap fit or interference fit.

6. The damper according to any one of claims 1 to 5, wherein, the limit load transfer ring is made of a rigid material, and the rigid material is the same as the material making the bearing.

7. The damper according to claim 1, wherein, the damping ring includes an elastic porous structure, and the elastic porous structure includes at least one of the following structures: a triply periodic minimal surface structure, and the unit cell structure construction formula of the triply periodic minimal surface structure is selected from one or more of Schoen-Gyroid unit cell construction formula, Schwarz Primitive unit cell construction formula and Neovius unit cell construction formula; a lattice structure; and a corrugated structure.

8. The damper according to claim 7, wherein, the damping ring includes an outer frame and the elastic porous structure, and a fillet is formed between the elastic porous structure and the outer frame.

9. The damper according to claim 8, wherein, the ranges of the sizes of the unit cell structure of the triply periodic minimal surface structure on a plane are from 2 mm to 3 mm.

10. The damper according to any one of claims 7 to 9, wherein, The elastic porous structure is filled with a damping material, and the damping material includes rubber or plastic.

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