A flexible mechanical metamaterial and a preparation method and application thereof

Abstract

The application discloses a kind of flexible mechanics metamaterial and preparation method and application thereof, belong to the technical field of metamaterial, the present application is combined with negative stiffness theory to carry out crystal structure beam design and insert thin-walled support structure in inside, the geometric model of the metamaterial constructed has excellent geometric nonlinear characteristics, is manufactured using silicone mold method, can guarantee that the metamaterial is in or close to low stiffness state under specific load condition, to realize the purpose of low-frequency vibration isolation. Compared with the traditional parallel vibration isolator through positive and negative stiffness unit, the structure is more simple, compact, more easily realizes low-frequency vibration isolation under specific load conditions in limited space by the method designed by the present application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metamaterials, and particularly relates to a flexible mechanical metamaterial and a preparation method and application thereof. BACKGROUND

[0002] Vibration isolation has a wide range of applications in precision mechanical engineering, on-orbit aerospace engineering, marine engineering, etc., and low-frequency vibration isolation has always been one of the recognized technical difficulties in the industry. For example, precision machining equipment is particularly sensitive to system stability, and various vibrations existing in the machining environment can have a great impact on the machining precision, so appropriate low-frequency vibration isolation technology needs to be used. In order to achieve the effect of low-frequency vibration isolation, existing vibration isolation technologies generally use passive vibration isolation (such as high-damping materials), active vibration isolation (such as quasi-zero stiffness vibration isolation systems with actively adjustable stiffness), etc. Although traditional damping vibration isolation systems can achieve good results in low-frequency vibration isolation, they face the demand for load bearing and cannot infinitely reduce their stiffness; the quasi-zero stiffness vibration isolation system has good vibration isolation effect in low-frequency vibration control due to its "high static and low dynamic" characteristics, but the traditional vibration isolation system design generally requires a complex control system and meets certain space requirements, so it is a very challenging technical problem to realize simple low-frequency vibration isolation in limited space.

[0003] Metamaterials refer to a class of artificial materials with special properties, and their unique properties are derived from their precise geometric structure design. Currently, metamaterial structures are mostly single or narrow frequency range high-frequency vibration isolation, and have poor applicability in the low-frequency vibration isolation field. Therefore, how to control elastic wave transmission in the low-frequency range and achieve low-frequency vibration isolation is a technical challenge that needs to be solved urgently. SUMMARY

[0004] The application provides a flexible mechanical metamaterial and a preparation method and application thereof. The metamaterial is in or close to a low stiffness state under specific loading conditions, thereby achieving the purpose of low-frequency vibration isolation. The structure is simpler and more compact, and it is easier to achieve low-frequency vibration isolation in limited space under specific loading conditions.

[0005] To achieve the above purpose, the application adopts the following technical solutions:

[0006] A flexible mechanical metamaterial comprises an elastic element and a thin-walled support structure. The elastic element is a half-imitated octahedral crystal structure periodic array, the interior of the half-imitated octahedral crystal structure is a hollow sphere, and the thin-walled support structure is located in the interior of the half-imitated octahedral crystal structure.

[0007] The material of the elastic element is a flexible material, preferably silicone.

[0008] A preparation method of a flexible mechanical metamaterial comprises the following steps:

[0009] Step 1: material structure design: according to the negative stiffness theory "deformation increases, load decreases", the "compression induced" mode is adopted to design the negative stiffness beam structure, first, the octahedral crystal structure is constructed and the edge is processed, then the node is curved and smoothed, secondly, the half anti-octahedral lattice structure is obtained by cutting the half anti-octahedral lattice structure and placing a thin-walled support structure in the interior, and finally the metamaterial geometric model is obtained by periodic array of the half anti-octahedral lattice structure;

[0010] Step 2: mold making: the mold includes a lower mold, a clamp and an upper mold, wherein the lower mold is obtained according to the Boolean calculation of the metamaterial geometric model obtained in step 1, and the upper mold and the clamp matched with the lower mold are designed; the lower end of the clamp is provided with a clamping ring matched with the lower mold, and the upper end is provided with six clamping grooves in the front and rear directions matched with the upper mold to ensure the matching precision of the upper mold and the lower mold, and the thickness can control the gap between the upper mold and the lower mold. The upper mold is composed of a plurality of discrete units, each unit includes a plurality of spherical structures at the lower end, and is connected to the upper end by a cylinder. The mold is made of photosensitive resin 3D printing;

[0011] Step 3: preparation of metamaterial: the upper mold, lower mold and clamp designed in step 2 are matched together, liquid silicone is used for casting, the gap between the upper mold and the lower mold is controlled by the clamp, and after 12h solidification, the mold is opened to obtain the silicone structure of the metamaterial.

[0012] The above-mentioned flexible mechanical metamaterial is applied to a vibration isolation system, the vibration isolation system comprising a device, an upper layer plate, a flexible mechanical metamaterial, and a lower layer plate; the flexible mechanical metamaterial is arranged between the upper layer plate and the lower layer plate, and the device is arranged on the upper layer plate, so that the vibration isolation system is in or close to a low stiffness state by the weight of the device.

[0013] Beneficial effects: the application provides a flexible mechanical metamaterial, a preparation method and application thereof, a crystal structure beam is designed according to the negative stiffness theory, and a thin-walled support structure is placed in the interior, the constructed metamaterial geometric model has excellent geometric nonlinear characteristics, the silicone mold method is used for processing and manufacturing, the flexible mechanical metamaterial realizes low stiffness characteristics by compression buckling, that is, the overall beam unit of the metamaterial buckles under compression under specific load conditions to be in a low stiffness state, so as to realize low-frequency vibration isolation, and the method can greatly simplify the complexity of the vibration isolator design. Compared with the traditional vibration isolator with parallel connection of positive and negative stiffness units, the vibration isolator designed in the application has a simpler and more compact structure, and is easier to realize low-frequency vibration isolation under specific load conditions in a limited space. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is a design process schematic diagram of the flexible mechanical metamaterial of the application;

[0015] Figure 2 It is a structure schematic diagram of the flexible mechanical metamaterial of the application;

[0016] Figure 3 This is a schematic diagram of the assembly of the flexible mechanical metamaterial mold of the present invention;

[0017] Figure 4 This is a schematic diagram of the lower mold structure of the flexible mechanical metamaterial of the present invention;

[0018] Figure 5 This is a schematic diagram of the flexible mechanical metamaterial clamp structure of the present invention;

[0019] Figure 6 This is a schematic diagram of the upper mold structure of the flexible mechanical metamaterial of the present invention;

[0020] Figure 7 This is a physical image of the mold for the flexible mechanical metamaterial of this invention;

[0021] Figure 8 This is a physical image of the mold for the flexible mechanical metamaterial of this invention;

[0022] Figure 9 This is a schematic diagram of the vibration isolation device of the present invention;

[0023] Figure 10 This is the static load-displacement curve of the integral beam unit of the flexible mechanical metamaterial of this invention;

[0024] Figure 11 This is the static load-displacement curve of the vibration isolation device of the present invention;

[0025] In the diagram, 1-lower mold, 2-clamp, 3-upper mold, 4-slot, 5-ring, 6-equipment, 7-upper plate, 8-flexible metamaterial, 9-lower plate. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments:

[0027] Example 1

[0028] A method for preparing a flexible mechanical metamaterial includes the following steps:

[0029] Step 1: Flexible Mechanics Metamaterial Design Method: Based on the negative stiffness theory that "deformation increases, load decreases," a "compression-induced" method is used to design negative stiffness beam structures, such as... Figure 1 As shown, an octahedral crystal structure is first constructed. Figure 1 (a) contains 6 atoms with a radius of r1 and 8 cylindrical rods with a length of l and a base radius of r2. The structural parameters of the atoms and the cylindrical rods satisfy r1 + r2 = l / 2. When the rod length l = 2a, the atomic coordinates can be determined as (a, a, 0), (-a, a, 0), (-a, -a, 0), and (a, -a, 0). and edge processing Figure 1 (b)), then surface fairing is performed on its nodes Figure 1 (c)), secondly, it is processed by half Figure 1 (d)), and a thin-walled support structure is placed inside to obtain a half anti-octahedral crystal structure Figure 1 (e)), and finally, a metamaterial geometric model is obtained by processing a half anti-octahedral crystal structure periodic array Figure 1 The pseudo-octahedral crystal structure is a whole beam element, which can provide negative stiffness characteristics under specific loads, and the internal thin-walled support structure can compensate for the negative stiffness characteristics, so that the metamaterial is in a low stiffness state under specific loads. Finally, the metamaterial can exhibit excellent geometric nonlinear properties under static load conditions and can be in or close to a low stiffness state under specific load conditions, thereby achieving low-frequency vibration isolation.

[0030] Step 2: Preparation process of flexible mechanical metamaterial: The designed flexible mechanical metamaterial is preferably prepared by a silicone casting method, and can also be prepared by integrated printing of "rubber-like" materials. This embodiment introduces the silicone casting method. First, a mold is designed, as shown in Figures 4-6 The mold mainly includes a lower mold, a clamp, and an upper mold. The lower mold is obtained based on the metamaterial geometric model according to Boolean calculation, that is, in the flexible mechanical metamaterial design method in step 1, the mechanical metamaterial geometric model is obtained, and a solid cuboid slightly larger than the model is subtracted to obtain the lower mold. A mold pulling plate is provided around the lower mold to facilitate mold opening. Then, the upper mold and the clamp are designed based on the lower mold. The lower end of the clamp is provided with a clamping ring for assembly with the lower mold, and the upper end is provided with six clamping grooves in the front and rear directions for assembly with the upper mold to ensure the assembly accuracy of the upper and lower molds. The thickness of the clamp can control the gap between the upper and lower molds. The upper mold is composed of multiple discrete units, each unit at the lower end includes multiple spherical structures connected to the upper end by a cylinder. The mold is made of photosensitive resin 3D printing. The upper mold, clamp, and lower mold are assembled together, and liquid silicone is poured to control the gap between the upper and lower molds through the clamp. After curing for 12 hours, the mold is opened to obtain the metamaterial silicone structure.

[0031] The flexible mechanical metamaterial obtained by the above method includes elastic elements and a thin-walled support structure. The elastic elements are a half pseudo-octahedral crystal structure periodic array, the anti-octahedral lattice structure is hollow, and the thin-walled support structure is located inside the half pseudo-octahedral lattice structure.

[0032] The aforementioned flexible metamaterial is applied to a vibration isolation system, which includes equipment, an upper plate, the flexible metamaterial, and a lower plate. The flexible metamaterial is placed between the upper and lower plates, and the lower plate has grooves to avoid the influence of pore gas inside the metamaterial on its stiffness. After a specific load mass of equipment is placed in the vibration isolation system, the flexible metamaterial buckles under compression, and the monolithic beam element exhibits negative stiffness characteristics. Figure 10 (Shaded area), while thin-walled support structures can balance the negative stiffness characteristics of the overall beam ( Figure 11 The shaded area makes the load-displacement curve of a specific section of the vibration isolation system tend to be horizontal, and the entire vibration isolation system is in a low stiffness state, thereby achieving low-frequency vibration isolation. This method can greatly simplify the complexity of vibration isolator design.

[0033] The above are merely preferred embodiments of the present invention and are only explanations of the present invention. They are not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to these embodiments without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a flexible mechanical metamaterial, characterized in that, The method comprises the following steps: Step 1: material structure design: according to the negative stiffness theory "deformation increases, load decreases", a "compression-induced" mode is adopted to design a negative stiffness beam structure model; first, an octahedral crystal structure is constructed and edge processing is performed, then the nodes are curved and smoothed, second, the structure is cut in half and a thin-walled support structure is placed inside to obtain a half anti-octahedral lattice structure, and finally, a metamaterial geometric model is obtained by periodic array of the half anti-octahedral lattice structure; Step 2: mold making: the mold includes a lower mold, a fixture, and an upper mold, wherein the lower mold is obtained according to the Boolean calculation of the metamaterial geometric model obtained in step 1, and the upper mold and the fixture are designed to cooperate with the lower mold; the fixture is provided with a clasp at the lower end, which is matched and assembled with the lower mold, and six clamping grooves are arranged in the front and back directions at the upper end, which are matched and assembled with the upper mold to ensure the matching precision of the upper and lower molds, and the thickness can control the gap between the upper and lower molds; the upper mold is composed of a plurality of discrete units, each unit contains a plurality of spherical structures at the lower end, and is connected to the upper end as a whole through a cylindrical structure; Step 3: preparation of metamaterial: the upper mold, lower mold and fixture designed in step 2 are matched together, liquid flexible material is used for pouring, the gap between the upper and lower molds is controlled by the fixture, and the mold is opened after solidification to obtain a metamaterial structure.

2. The method of claim 1, wherein the flexible metamaterial is prepared by a process comprising: The mold is manufactured by 3D printing of photosensitive resin.

3. The flexible metamaterial of any of claims 1-2, wherein, The elastic element is a half anti-octahedral crystal structure periodic array, the anti-octahedral lattice structure is hollow spherical, and the thin-walled support structure is located inside the half anti-octahedral crystal structure.

4. The flexible metamaterial of claim 3, wherein, The anti-octahedral crystal structure is an integral beam unit.

5. The flexible metamaterial of claim 3, wherein, The material of the elastic element is silica gel.

6. The flexible metamaterial of claim 3 or 4, wherein, The pseudo-octahedral crystal structure comprises 6 atoms and 8 cylindrical rods, the length of the cylindrical rods being , the base radius being , and the atom radius being .

7. Use of the flexible metamaterial of any one of claims 3 to 6 in a vibration isolation system, characterized in that, The vibration isolation system comprises a device, an upper layer plate, a flexible mechanical metamaterial, and a lower layer plate; the flexible mechanical metamaterial is placed between the upper layer plate and the lower layer plate, the device is placed on the upper layer plate, and the vibration isolation system is in or close to a low stiffness state by the weight of the device.

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