Elastic metamaterial high-efficiency wide-frequency high-load isolation base

Abstract

The present application belongs to the technical field of shock absorption, and particularly relates to a structural device which can block vibration in a wide range of low frequency bands and has high bearing capacity. The device is almost completely rigid on the outside, and the sinking under load is not more than 3 mm, no matter how low the working frequency is. The device overcomes the shortcomings of the prior art, such as the strong resonance of the vibration isolation base with the working principle equivalent to a spring, the serious sinking of the low-frequency vibration isolation equipment, and the high correlation between the vibration isolation performance and the load weight.

Description

Technical Field

[0001] This invention belongs to the field of vibration reduction technology, specifically relating to structural devices that isolate vibrations in a wide range of low-frequency bands while having high load-bearing capacity. Background Technology

[0002] A seismic isolation base is a device used to reduce vibration. It is typically installed at the base of industrial equipment, electronic equipment, buildings, etc., or between the base and the ground. It reduces the transmission of vibration and noise during machine operation, protecting the stability and lifespan of the machine and its accessories. The importance of vibration damping technology lies in its ability to effectively reduce the impact of vibration on equipment and the environment. Some special-purpose machines and equipment, such as precision instruments, laboratory equipment, and heavy machinery, require even higher vibration damping effects and specially designed seismic isolation bases. The design of a seismic isolation base usually considers multiple factors, such as the weight of the machine, its operating frequency, amplitude, and noise level, among which the selection of the vibration damper is crucial.

[0003] (A) Existing technology

[0004] Currently widely used shock absorbers include spring shock absorbers, pneumatic shock absorbers, hydraulic shock absorbers, and rubber pad shock absorbers. The working principle of these shock absorbers is equivalent to... Figure 1 The spring damper shown.

[0005] consider Figure 1 The mass in M Device 101 with vibration amplitude A、 Vibration at angular frequency ω, through a force constant of K Spring 102 is connected to ground 103. If device 101 is placed directly on ground 103, the force exerted by the machine on the ground is... If a spring 102 is installed between the machine 101 and the ground 103, then through simple mechanical calculations, the force exerted on the ground can be obtained as follows: ,in , Let be the system's natural frequency or inherent frequency. Therefore, the vibration transmissibility is defined as . (1).

[0006] Representative transmission coefficients in Figure 2 The figure shows that the transfer coefficient at the driving frequency... With the system's natural frequency When the frequencies are equal, the vibration of the equipment is amplified dramatically, severely impacting the surrounding environment and other equipment. The natural frequency of the transfer coefficient curve 201 is lower than that of the transfer coefficient curve 202. At any driving frequency higher than their natural frequencies, the transfer coefficient curve 201 is lower than that of the transfer coefficient curve 202. Furthermore, since real springs have a certain mass, the transfer coefficient of the actual system is as shown in curve 203. In most frequency ranges, its transfer coefficient is much higher than that of an ideal spring with negligible mass, causing the actual vibration isolation effect of the base to deviate significantly from the design, greatly increasing the design difficulty. In practical applications, the force constant or stiffness of the spring must be selected according to the weight of the equipment; therefore, many different specifications of springs are needed to ensure that the natural frequency of the system is far lower than the actual vibration frequency.

[0007] If the natural frequency of the system is Then in the gravitational field on the Earth's surface Under the action of the load, the spring is compressed and sinks a distance of . Therefore, the system's natural frequency can be obtained. The spring sinks 25 centimeters. The spring sinks by 0.25 cm. The lower the natural frequency (the vibration isolation operating frequency), the more severe the sinking.

[0008] (B) Metamaterial individual seismic base

[0009] The performance of existing vibration damping products depends on the performance of the core materials. Unfortunately, the damping mechanisms of various core materials all follow the same physical laws, resulting in highly consistent product functions. Their performance in each frequency range is limited by an upper limit that is locked by physical principles and cannot be surpassed by any core material.

[0010] Technological progress has played a decisive role in the history of human development, and this development is often marked by the discovery and widespread application of new materials. From the ancient Pottery Age, Bronze Age, and Iron Age to the present era based on semiconductor materials and numerous other advanced materials, the advancement of materials has been inextricably linked to this progress. The properties of materials are primarily determined by their chemical composition and manufacturing process, but their performance and functionality still fall far short of meeting human needs and our curiosity about nature. Therefore, more than 20 years ago, humanity embarked on a new path, beginning the fruitful research into metamaterials. Metamaterials utilize structural design to achieve functional leaps and significantly reduce dependence on the types and properties of materials, making them an important branch of advanced materials science.

[0011] Mass is one of the most familiar concepts in physics, playing a particularly important role in classical mechanics. ,in It acts on a mass of M The resultant force on the object, It is the acceleration of an object. It is the mass that quantifies the inertia of an object. For centuries, people have taken it for granted that gravitational mass is equivalent to inertial mass. However, even our everyday experiences can be quite different from this simple consensus. The sloshing of a half-full bottle of water has a noticeable inertial effect, making the bottle feel lighter and heavier at times. If we didn't know the internal structure of this container, its inertial mass would certainly deviate from its static weight reading, becoming a dynamic quantity related to the external driving force. Recent studies on the propagation of vibrational waves in metamaterials have shown that this "dynamic inertial mass" has important consequences.

[0012] To illustrate this, let's first consider Figure 3A A simple yet inspiring one-dimensional mass block-spring-rigid box model with no dissipation. A mass of... The rigid box 301 contains a force constant of K The spring 302 and the mass are The mass block 303 is connected to the spring 302 at one end, and the other end is anchored to the rigid box 301. The driving force can be obtained through simple mechanical analysis. acceleration of rigid box 301 The relationship is (2).

[0013] For simplicity, we define the effective inertial mass of the entire mass block-spring-rigid box system as: (3).

[0014] It is obvious that As driving frequency The function in It reaches its maximum. From this simple example, we can clearly see that when the dynamics of a system involve the relative motion between its internal components, its inertial mass can be very different from its gravitational mass. The properties of the acoustic metamaterial isolation base depend entirely on the dynamic characteristics of its internal "hidden objects" (spring 302 and mass block 303 in Figure 3). Using the concept of effective mass, we can easily understand and describe the force transmission effect of a rigid outer shell box system ('black box') containing an elastic structure. When the effective mass of the 'black box' reaches its maximum, the acceleration of the 'black box' reaches its minimum, and the 'black box' can effectively block the driving force on the left side of the 'black box' from affecting the object on the right side. This is the basic working principle of the acoustic metamaterial isolation base. As can be seen from this example, the outer shell of the base is rigid. Its isolation effect depends entirely on its internal spring oscillator structure, meaning it contains a localized resonant structure.

[0015] If the mass of the rigid box is negligible, then the transfer coefficient can be expressed as: (4).

[0016] This formula has the same form as formula-1, where It is the driving frequency. The 'black box' is the system's natural frequency or inherent frequency, but it is only related to its internal structure. The 'black box' is completely rigid on the outside, which solves the problems of insufficient stiffness of low-frequency damping base and the significant change of transmission coefficient with the weight of the load-bearing equipment.

[0017] Figure 3B shows an acoustic metamaterial with a localized resonant structure as its basic unit (Reference-1, Science , 289(5485): 1734-1736 (2000) ). This acoustic metamaterial is a three-component composite material equivalent to a spring oscillator, in which a rigid heavy metal ball 304 is a mass block, wrapped with a soft silicone layer 305 equivalent to a spring, and then these coated mass blocks are embedded in a rigid epoxy resin background material 306 to form a local resonant structure. Its dynamic performance is equivalent to the mass block 304 being anchored to the outer shell 306 of a rigid black box by the spring 305. This structure can block vibration waves from various excitation sources. If the vibration wave is excited by the incident sound wave, the local resonant structure can block the sound wave in the frequency band near its resonant frequency with an efficiency that breaks the mass density law (Reference-1). If the vibration wave is excited by the vibration of an object, this structure can be used as a vibration isolation base for the object, having a rigid outer body but effectively blocking the vibration waves excited by the object from being transmitted to various places through the base. Summary of the Invention

[0018] The metamaterial seismic isolation base described in this invention has an almost rigid outer body, with a maximum load capacity of several tons per square meter and a maximum subsidence compression of no more than three millimeters, independent of the seismic isolation operating frequency. Internally, it comprises numerous vibrating element structures and a rigid support structure. The rigid support structure gives the base a high degree of rigidity. Within the inherent resonant frequency range of these vibrating elements, the base exhibits highly efficient seismic isolation performance. The combination of the vibrating structures and the rigid support structure constitutes an almost rigid, low-frequency, high-efficiency, broadband seismic isolation base whose seismic isolation characteristics are not significantly correlated with load capacity. Attached Figure Description

[0019] Figure 1. Schematic diagram of the principle of a conventional spring shock absorber.

[0020] Figure 2 shows the representative vibration transmission coefficient versus vibration frequency curves for three conventional spring dampers.

[0021] Figure 3(A) One-dimensional motion mass block-spring-rigid box model.

[0022] Figure 3(B) Schematic diagram of the world's first locally resonant acoustic metamaterial (Reference-1) Science , 289(5485): 1734-1736 (2000) ).

[0023] Figure 4 shows the usage method of the metamaterial seismic isolation base - 1. The vibration source is installed above the metamaterial seismic isolation base, and the ground is below the base.

[0024] Figure 5 Method of using metamaterial seismic isolation base - 2: The vibration source is installed on the side of the metamaterial seismic isolation base, and the other side of the base is fixed to the wall.

[0025] Figure 6 Method 3 for using metamaterial vibration isolation base: The vibration source is installed below the metamaterial vibration isolation base, and the base is fixed to the ceiling.

[0026] Figure 7(A) shows the structure of a purely local, uncoupled, locally resonant metamaterial based on dynamic principles.

[0027] Figure 7(B) shows the dynamic principle structure of a localized resonant metamaterial where localized vibration and vibration coupling coexist.

[0028] Figure 7(C) shows the dynamic principle structure of a fully coupled local resonant metamaterial.

[0029] Figure 8 Structural cross-section of a three-dimensional array seismic isolation base of a purely local, uncoupled, locally resonant metamaterial.

[0030] Figure 9 Structural cross-section of a three-dimensional array seismic isolation base of a purely coupled local resonant metamaterial.

[0031] Figure 10(A) is a three-dimensional diagram of a simple and regular rigid support structure.

[0032] Figure 10(B) Side view of a simple and regular rigid support structure.

[0033] Figure 10(C) is a schematic diagram of a fully coupled local resonant metamaterial seismic isolation base structure containing a rigid support structure.

[0034] Figure 11 A fully coupled local resonant metamaterial seismic isolation base containing an irregular rigid support structure.

[0035] Figure 12(A) is a three-dimensional structural diagram of a seismic isolation base composed of a rigid support structure made of irregular brackets and a soft elastic medium. The cover plate is not shown in the figure for clarity.

[0036] Figure 12(B) is a three-dimensional structural diagram of a seismic isolation base composed of a rigid support structure consisting of an irregular bracket without mass blocks and a soft elastic medium. The cover plate is not shown in the figure for clarity.

[0037] Figure 13(A) is a three-dimensional structural diagram of the rigid support structure of the local resonant metamaterial seismic isolation base with local vibration and vibration coupling coexisting.

[0038] Figure 13(B) is a top view of the rigid support structure of the local resonant metamaterial seismic isolation base with local vibration and vibration coupling coexisting.

[0039] Figure 13(C) is a side view of a local resonant metamaterial seismic isolation base structure containing a rigid support structure, where local vibration and vibration coupling coexist.

[0040] Figure 13(D) is a three-dimensional schematic diagram of a local resonant metamaterial seismic isolation base structure containing a rigid support structure, where local vibration and vibration coupling coexist.

[0041] Figure 13(E) is a schematic diagram of a local resonant metamaterial isolation base structure with local vibration and vibration coupling coexisting, containing a rigid support structure and a massless block. The cover plate is not shown in the figure for clarity.

[0042] Figure 14(A) Black and white photograph of a real metamaterial seismic isolation base sample.

[0043] Figure 14(B) Black and white photograph of the experimental setup for measuring the vibration transmission coefficient of the isolation base sample.

[0044] Figure 14(C) shows the experimental vibration transmission coefficient versus vibration frequency curves of the metamaterial isolation base sample under loads of 120 kg / m² and 800 kg / m². Detailed Implementation

[0045] Overview

[0046] The method of using the metamaterial seismic isolation base described in this invention is the same as that of existing spring seismic isolation bases. For example... Figure 4 As shown, the mass is M The vibrating body 401 is fixed to the upper surface of the metamaterial vibration isolation base 402. The lower surface of the metamaterial vibration isolation base 402 is fixed to the ground 403. Similarly, the vibrating body can be fixed to the wall surface using the metamaterial vibration isolation base. Figure 5 In the middle, the mass is M The vibrating body 501 is fixed to the right surface of the metamaterial isolation base 502. The left surface of the metamaterial isolation base 502 is fixed to the wall 503. Figure 6 Another application scenario shown is that the vibrator is fixed to the ceiling using a metamaterial vibration isolation base.

[0047] As shown in Figure 7, based on the coupling strength between the local resonant units inside the local resonant metamaterial, it can be divided into three types: pure local uncoupled, coexistence of local vibration and vibration coupling, and full vibration coupling. Figure 7A A schematic diagram of a purely localized, uncoupled structure is shown. The resonant structure, consisting of the mass block 701 and the spring 702 of the resonant unit, is anchored to rigid walls 703 that surround the resonant unit from all sides. The completely rigid walls 703 completely isolate the vibrations of each resonant unit, meaning that the vibration of one unit will not induce the vibration of other units. Figure 3 shows two examples. This structure has only one or a few resonant modes and frequencies, so it can only block vibrations in certain narrow frequency bands. Figure 7B The diagram illustrates the structural principle of the coexistence of local vibration and vibration coupling. The partition wall 704 between each resonant unit has a certain degree of flexibility. The vibration of one resonant unit will cause the vibration of other resonant units, but the vibration coupling between units will be weakened but not completely blocked by the partition wall 704. Figure 7C The structural principle diagram of a fully coupled resonant unit assembly is shown. The resonant units are interconnected, and the vibrations of each unit can be coupled without obstruction. By selecting partitions with different rigidity / flexibility contrasts, local resonant metamaterials with varying degrees of coupling can be obtained. This type of resonant unit assembly with a certain degree of coupling possesses rich resonant modes, and its resonant frequencies form a quasi-continuous frequency band, which can isolate vibrations over a fairly wide frequency range, meeting our requirements for broadband seismic isolation bases. By purposefully selecting and stacking isolation bases with different resonant modes, a full-frequency combined seismic isolation base can be obtained.

[0048] example

[0049] Bundle Figure 3B The resonant units on display are arranged in a three-dimensional array like bricks, which can form a cuboid seismic isolation base. Figure 8 A structural cross-sectional view of this purely localized, uncoupled seismic isolation base is shown. The rigid epoxy resin background material 803 effectively blocks the coupling between the resonant units composed of the mass block 801 and the flexible elastic medium layer 802. This seismic isolation base is completely rigid, but its vibration damping frequency band is narrow.

[0050] Figure 9 A side section of a seismic isolation base with fully coupled resonant unit vibration is shown. Figure 8 Compared to the previously rigid epoxy resin-filled base, the space now occupied by the flexible elastic medium 902 is filled with this new seismic isolation base, resulting in dynamic performance equivalent to... Figure 7C The structure shown. This type of seismic isolation base has poor stiffness and sinks severely under high loads, making it unsuitable as a high-load-bearing seismic isolation base.

[0051] Figure 10 shows a seismic isolation base with added rigid support structures to enhance load-bearing stiffness. Figure 10A A 3D diagram of a simple yet regular rigid support structure is shown. The rigid support structure consists of a rigid bracket 1001 and rigid upper and lower cover plates 1002 and 1003. The bracket and cover plates can be made of composite materials such as metal, carbon fiber, and fiberglass. Figure 10B The image shows Figure 10A The side view of the rigid support structure shown in the image. Figure 10C A seismic isolation base with a rigid support structure is demonstrated. Both the mass block 1004 and the rigid support structure are encased in a flexible elastic medium 1005. The flexible elastic medium 1005 completely covers the cover plate of the rigid support structure. The thickness of the gap between the cover plate and the adjacent surface of the flexible elastic medium determines the maximum settlement of the composite seismic isolation base. The flexible elastic medium within the seismic isolation base remains a continuous whole; the strip-shaped supports have minimal impact on the coupling between resonant elements, ensuring that the seismic isolation base still possesses a rich resonant range of modes. By using mass blocks of varying weights, the frequencies of each resonant mode of the seismic isolation base can be adjusted.

[0052] Figure 11 A rigid support structure consisting of irregular brackets 1101 is shown. The endpoints of some brackets are on the upper and lower cover plates 1102 and 1103, while the endpoints of the remaining brackets are on other brackets. Figure 12A A perspective view shows a seismic isolation base composed of a rigid support structure made of irregular bracket 1101 and a soft elastic medium. Cover plates 1102 and 1103 are not shown for clarity.

[0053] Figure 12B The text describes a seismic isolation base without mass blocks. The soft, elastic medium itself has a certain mass density, forming a continuously distributed elastic mass body, which also possesses rich resonant modes, but the frequency bands differ compared to seismic isolation bases containing mass blocks.

[0054] Figure 13 illustrates a seismic isolation base exhibiting both localized vibration and vibration coupling. The rigid support structure comprises rigid support components 1301 and rigid upper and lower cover plates 1303 and 1304. Support component 1301 in the figure is a hexagonal honeycomb thin-walled grid structure, but a similar effect can be achieved using square or other shaped thin-walled grid structures. Mass blocks 1302 are distributed throughout the grid units. Some grid units have multiple mass blocks 1302, while others do not. Figure 13B A top view of the combined structure of thin-walled grid structure and mass block is shown. Figure 13CThis demonstrates a composite structure where a flexible elastic medium (1305) fills the space surrounding a rigid support structure and a mass block, completely burying them within the medium. The flexible elastic medium (1304) completely covers the cover plate of the rigid support structure. The thickness of the gap between the cover plate and the adjacent surface of the flexible elastic medium determines the maximum settlement of the composite isolation base. In this isolation base, the flexible elastic medium is no longer a continuous whole. The thin-walled grid structure allows vibrations to be semi-locally coupled in a plane parallel to the cover plate, and fully coupled in a direction perpendicular to the cover plate. This isolation base also exhibits a rich resonant mode distribution, but the frequency distribution of the modes differs from that of a fully coupled isolation base.

[0055] By rationally designing and using vibration-coupled coexistence structures and fully coupled structures, and adjusting the spatial distribution of the mass blocks, the resonant modes of the seismic isolation base can cover a large frequency range and reach any low-frequency band, thus forming a seismic isolation base with efficient seismic isolation effect in the entire frequency domain.

[0056] Figure 14A A photograph of a real metamaterial seismic isolation base sample is shown. The metamaterial sample has a planar dimension of 15 × 25 cm, a thickness of 4 cm, and weighs approximately 1.5 kg. Figure 14B The photograph shows the experimental setup for measuring the vibration transmission coefficient. Sample 1401 is placed on a horizontal table 1402, and a metal plate load 1403 is placed on the upper surface of the sample. Vibration sensor 1404 is mounted on the table, and vibration sensor 1405 is mounted on the upper surface of the metal plate. By gently tapping the metal plate with a small hammer, the vibration of the upper and lower surfaces of the sample can be measured, thus obtaining the vibration transmission coefficient of the sample. Figure 14C The figure shows the functional relationship curves of the vibration transmission coefficient of the sample under different loads as a function of frequency (referred to as the transmission coefficient curves). The solid line 1406 represents the transmission coefficient curve of the sample under a load of 120 kg / m², and the dashed line 1407 represents the transmission coefficient curve of the sample under a load of 800 kg / m². As can be seen from the figure, the vibration transmission coefficient curve of the metamaterial sample differs significantly from that of the existing vibration isolation base, which is equivalent to a spring. First, the vibration transmission coefficient curve of the metamaterial sample has no resonance peak, and its maximum value is significantly less than 1 above 50 Hz, demonstrating significant vibration damping function. Second, the transmission coefficient of the metamaterial sample does not decrease monotonically with increasing frequency. Third, the transmission coefficient of the metamaterial sample does not change significantly with changes in load. This is because the structure of the metamaterial determines that the load has a limited impact on the resonant mode, therefore the transmission coefficient will not change significantly. Finally, it should be noted that the metamaterial vibration isolation base sample still exhibits excellent vibration isolation performance from the lowest frequency band above 50 Hz under a high load of 800 kg / m², with a subsidence of less than 1 mm. Due to limitations in experimental conditions, the load used in the experiment of the metamaterial vibration isolation base sample was far from reaching its load limit.

[0057] It is anticipated that, within the spirit of this invention and within the scope of protection defined by the appended claims, those skilled in the art may make many other changes to the details, materials, steps, and arrangements described herein for explaining the characteristics of this subject matter.

Claims

1. A high-load-bearing-capacity seismic isolation metamaterial polyhedron structure, comprising a polyhedron, wherein a skeleton structure contained within the polyhedron connects two or more surfaces of the polyhedron; The space within the polyhedron not occupied by the skeleton is filled with a soft, elastic material, and the soft, elastic material protrudes from the outer surface of the polyhedron. The outer surface boundary of the soft, elastic material constitutes the polyhedron of the high-load-bearing, vibration-isolation metamaterial, wherein, The skeleton is composed of strip or sheet metal, carbon fiber, artificial resin or glass fiber with Young's modulus on the same order of magnitude. The number and spatial distribution of the skeleton are sufficient to ensure that at least two surfaces of the polyhedron have the ability to bear a weight similar in size to that surface. The total volume of the skeleton does not exceed 30% of the volume of the polyhedron; The soft, elastic material inside the polyhedron is silicone or rubber, whose Young's modulus is 3 to 4 orders of magnitude lower than that of the skeleton material. Among them, the two parallel planes of the polyhedron used to support the weight are covered by a flat cover plate; The flat cover plate is made of metal, carbon fiber, artificial resin or glass fiber with a Young's modulus on the same order of magnitude. The polyhedron contains one or more mass blocks.

2. The seismic isolation metamaterial polyhedral structure according to claim 1, wherein: The geometric dimensions and spatial positions of the skeleton structure are selected to adjust the intrinsic vibration frequencies of the metamaterial polyhedron.

3. The seismic isolation metamaterial polyhedral structure according to claim 1, wherein: The vibration amplitude of one face of the metamaterial polyhedron that is excited by an external force is greater than that of the other faces that are not in direct contact with an external force.

4. The seismic isolation metamaterial polyhedral structure according to claim 3, wherein: The frequency of the external force is greater than the lowest eigenstate vibration frequency of the isolation metamaterial polyhedron structure.

5. The seismic isolation metamaterial polyhedral structure according to claim 1, wherein: The geometric dimensions, mass density, elastic properties, and spatial position of the skeleton structure and the mass block are selected to adjust the intrinsic vibration frequencies of the metamaterial polyhedron.

6. The seismic isolation metamaterial polyhedral structure according to claim 5, wherein: The vibration amplitude of one face of the metamaterial polyhedron that is excited by an external force is greater than that of the other faces that are not in direct contact with an external force.

7. The seismic isolation metamaterial polyhedral structure according to claim 6, wherein: The frequency of the external force is greater than the lowest eigenstate vibration frequency of the isolation metamaterial polyhedron structure.

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