An assembled tubular metamaterial with adjustable stiffness

Abstract

The application discloses an assembled tubular metamaterial with adjustable rigidity, and a core is composed of a buffer body and a reinforcing body through thread assembly, both of which are processed into a shape through a circumferential and horizontal array based on a thin shell cell as a basic unit. The assembled thread adopts a multi-line rectangular thread, the buffer body is a cylindrical thin-walled pipe provided with threads on inner and outer surfaces (thread pitch L1=100 mm, wall thickness t1=1 mm), and the reinforcing body is a thin-walled pipe provided with threads on an outer surface (thread pitch L2=40 mm, wall thickness t2=1.5 mm), and a M20 hexagonal nut in line with the GB / T6191-1986 standard is assembled on the top and bottom of the reinforcing body to assist in completing the assembly. Performance tests show that the metamaterial can accurately control the turning point of the structural rigidity increase by adjusting the assembly position of the reinforcing body and the buffer body; the coupling effect can be generated under different thread numbers to absorb additional energy when being compressed, and the metamaterial has excellent energy absorption performance. The structure realizes the combination of adjustable rigidity and high-efficiency energy absorption, and effectively widens the application scenarios of the mechanical metamaterial.

Description

Technical Field

[0001] This invention relates to the field of mechanical metamaterials technology, and discloses an assembled tubular metamaterial with adjustable stiffness. Background Technology

[0002] With the rapid development of industry, natural materials and structures can no longer meet the needs of engineering. As a new type of artificial material, metamaterials can provide customizable and unprecedented superior physical properties, which are usually dependent on their structural composition rather than the substrate material. Metamaterials have been extensively studied in many fields. For example, electromagnetic metamaterials for electromagnetic shielding, metamaterials with negative refractive index properties, acoustic metamaterials with acoustic transformation properties, thermal metamaterials for heat dissipation and heat conduction, and the mechanical metamaterials involved in this invention.

[0003] Mechanical metamaterials are man-made materials with complex structures that, through careful design, exhibit extraordinary mechanical properties. With proper design, they can possess characteristics such as vibration damping, isolation, negative Poisson's ratio, and negative stiffness. Furthermore, various configurations and highly customizable mechanical properties have been investigated, such as compression-torsion coupled metamaterials, multistable metamaterials, and programmable metamaterials. Compression-torsion coupled metamaterials exhibit torsional deformation under compressive loads, while multistable mechanical metamaterials utilize buckling phenomena to possess two or more stable states. Programmable metamaterials achieve desired mechanical properties and deformation characteristics through the design and configuration of unit cells, which are permanently programmed into the material. Mechanical metamaterials are gradually developing towards multifunctionality, assemblability, and reprogrammability.

[0004] Existing research on multi-steady-state mechanical metamaterials often involves permanently embedding unit structures into the structure itself. This results in a lack of adaptability and reconfigurability in the structure's configuration and mechanical properties. This invention proposes an assemblable, adjustable-stiffness tubular metamaterial. Through its assemblable design and the ability to change the installation position of the reinforcements, the time it takes for the structure to reach a second steady state can be altered. These characteristics broaden the application scenarios of this invention. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an assembled tubular metamaterial with adjustable stiffness, which improves the design freedom and energy absorption capacity of the structure.

[0006] The technical solution adopted in this invention is as follows: An assembled, adjustable stiffness tubular metamaterial is formed by threaded assembly of a buffer body and a reinforcement body. Both the buffer body and the reinforcement body are obtained by circumferential and horizontal arraying of thin-shell unit cells. The buffer body is formed solely by the arraying of thin-shell unit cells, and the reinforcement body is formed by the arraying of thin-shell unit cells, with hexagonal nuts at the top and bottom. The reinforcement body can be screwed into the buffer body using a hexagonal screwdriver to complete the assembly. The thread is a multi-start thread with a rectangular tooth profile and n threads.

[0007] More preferably, the thin-shell unit cell is a thin plate structure, with threads on both its outer and inner surfaces; the threads on the outer and inner surfaces of the thin-shell unit cell have the same pitch and opposite directions, forming a complete helix after being arrayed; the bending angle of the thin-shell unit cell is θ=40°; the horizontal spacing between the threads is half k=5mm; and the thread pitch is b=10mm.

[0008] More preferably, the direction of the thread on the outer surface of the buffer body is counterclockwise when viewed from top to bottom, and the direction of the thread on the inner surface is clockwise when viewed from top to bottom.

[0009] More preferably, the pitch of both the outer and inner surface threads of the buffer body is L1 = 100 mm. The wall thickness of the buffer body is t1 = 1 mm, and the wall thickness of the reinforcement body is t2 = 1.5 mm.

[0010] More preferably, the pitch of the reinforcing outer surface thread is L2=40mm; the direction of the reinforcing outer surface thread is clockwise when viewed from top to bottom.

[0011] Further preferred, the hexagonal nut is model M20 as specified in GB / T6191-1986.

[0012] The beneficial effects of this invention are as follows: This invention improves upon the design strategy for mechanical metamaterials capable of achieving adjustable stiffness. Existing research on multi-steady-state mechanical metamaterials often involves permanently embedding unit structures into the structure itself, leading to a lack of adaptability and reconfigurability in the structure's configuration and mechanical properties. This invention proposes an assemblable, adjustable-stiffness tubular metamaterial. Through its assemblable design and the ability to change the installation position of the reinforcement, the time it takes for the structure to reach a second steady state can be altered. Furthermore, when in the installed state, the adjustable-stiffness mechanical metamaterial absorbs additional energy under pressure through the buffer and reinforcement components. These characteristics broaden the application scenarios of this invention.

[0013] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0014] Figure 1This is a schematic diagram of an assembled adjustable stiffness thin-shell unit cell design provided in an embodiment of the present invention.

[0015] Figure 2 This is a schematic diagram of an assembled, adjustable stiffness tubular metamaterial provided in an embodiment of the present invention.

[0016] Figure 3 This is a schematic cross-sectional view of an assembled adjustable stiffness tubular metamaterial provided in an embodiment of the present invention.

[0017] Figure 4 A top view of an assembled, adjustable stiffness tubular metamaterial provided in an embodiment of the present invention.

[0018] Figure 5 This is a diagram of the deformation mode of a tubular metamaterial with adjustable stiffness in an assembly configuration.

[0019] Figure 6 Force-displacement curves of a modular, adjustable stiffness tubular metamaterial under three different assembly conditions.

[0020] Figure 7 This is to absorb additional energy generated by the coupling effect of assembled adjustable stiffness tubular metamaterials under different numbers of threads. Detailed Implementation

[0021] The specific embodiments of the present invention are described below with reference to the accompanying drawings: The following is in conjunction with the appendix Figures 1-7 The specific embodiments of the present invention will be described in detail below. This embodiment is only used to explain the present invention and is not intended to limit the scope of protection of the present invention.

[0022] I. Overall Structural Composition The assembled adjustable stiffness tubular metamaterial of this embodiment consists of a core composed of a buffer body 2 and a reinforcing body 3 assembled by threads. Both the buffer body 2 and the reinforcing body 3 are based on a thin-shell unit cell 1 and are formed by circumferential and horizontal array processing (e.g., Figure 1 (As shown).

[0023] II. Core Component Structure and Parameters Thread design: All threads used in assembly are multi-start threads with a rectangular tooth profile, and the number of threads is set to n; among them, buffer body 2 is a cylindrical thin-walled tube structure with threads on both its outer and inner surfaces, and reinforcement body 3 is a thin-walled tube structure with threads only on its outer surface. Furthermore, the threads on the outer surface of buffer body 2 and reinforcement body 3 have the same pitch and opposite directions of rotation (e.g., ...). Figure 2 (As shown).

[0024] Key dimensional parameters: The thread pitch of buffer body 2 is L1=100mm, and the wall thickness is t1=1mm; the thread pitch of reinforcement body 3 is L2=40mm, and the wall thickness is t2=1.5mm (e.g., ...).Figure 2 , Figure 3 (As shown).

[0025] Assembly auxiliary structure: Hex nuts 5 are installed at both the top and bottom of the reinforcement 3. These nuts conform to the M20 specification in GB / T6191-1986 standard. Using a hex screwdriver, the reinforcement 3 can be screwed into the buffer body 2 to complete the overall assembly (e.g., Figure 4 (Assembly action shown in mark 4).

[0026] III. Performance Testing and Result Analysis Test conditions: All tests were conducted using a quasi-static compression method with a compression speed of 2 mm / min and a total compression distance of 80 mm. The focus was on observing the deformation mode, stiffness change, and energy absorption characteristics of the structure under axial load.

[0027] Deformation mode and steady-state switching: When the reinforcement 3 is assembled at a position 30mm from the bottom of the buffer 2 (e.g. Figure 5 As shown in the figure, when the deformation is 10% and 30%, only the buffer body 2 deforms and wrinkles, achieving initial energy absorption; when the deformation reaches 45%, the reinforcement body 3 begins to deform synchronously, the overall stiffness of the structure is significantly improved, and the deformation mode enters the second stable state; until the deformation reaches 80%, the reinforcement body 3 continues to absorb energy through wrinkle deformation.

[0028] Influence of Assembly Position on Stiffness: Three test models with different assembly positions were set up. Model 1 had the reinforcement 3 10mm from the bottom of the buffer 2, Model 2 had a distance of 20mm, and Model 3 had a distance of 30mm (e.g., ...). Figure 6 As shown). Test results show that as the compression process progresses, all three models experience a secondary increase in stiffness due to the deformation of reinforcement 3, and the lower the assembly position of reinforcement 3, the greater the inflection point of stiffness increase (e.g., Figure 6 (As shown in mark 6) The earlier it appears, the sooner the structure enters the second stable state.

[0029] The effect of the number of threads on energy absorption: such as Figure 7 As shown, in tests with different numbers of threads n (n=4, 6, 9, 12), the tubular metamaterial will generate a thread coupling effect when it is subjected to pressure and absorbs energy. This effect allows the structure to absorb additional energy, and different numbers of threads correspond to different additional energy absorption effects, which fully demonstrates the excellent energy absorption performance of this structure.

[0030] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A modular, adjustable-stiffness tubular metamaterial, characterized in that, It is formed by threaded assembly of a buffer body and a reinforcing body; both the buffer body and the reinforcing body are obtained by circumferential and horizontal arraying of thin-shell unit cells. The buffer body is formed only by thin-shell unit cell array. After the reinforcement body is formed by thin-shell unit cell array, hexagonal nuts are set at the top and bottom. The reinforcement body can be screwed into the buffer body to complete the assembly by using a hexagonal screwdriver. The thread is a multi-start thread with a rectangular tooth profile. The number of such thread structures is n=9.

2. The assembled adjustable stiffness tubular metamaterial according to claim 1, characterized in that, The thin-shell unit cell is a thin plate structure with threads on both its outer and inner surfaces; the threads on the outer and inner surfaces of the thin-shell unit cell have the same pitch and opposite directions, forming a complete helix when arrayed; the bending angle θ of the thin-shell unit cell is 40°; the horizontal spacing between the threads is half k = 5 mm; the thread spacing b of the thin-shell unit cell is 10 mm.

3. The assembled adjustable stiffness tubular metamaterial according to claim 1, characterized in that, The outer surface thread of the buffer is counterclockwise when viewed from top to bottom, while the inner surface thread is clockwise when viewed from top to bottom.

4. The assembled adjustable stiffness tubular metamaterial according to claim 3, characterized in that, The pitch of the threads on both the outer and inner surfaces of the buffer body is L1 = 100 mm. The wall thickness of the buffer body is t1 = 1 mm, and the wall thickness of the reinforcement body is t2 = 1.5 mm.

5. The assembled adjustable stiffness tubular metamaterial according to claim 1, characterized in that, The pitch of the thread on the outer surface of the reinforcing body is L2=40mm; the direction of the thread on the outer surface of the reinforcing body is clockwise when viewed from top to bottom.

6. The assembled adjustable stiffness tubular metamaterial according to claim 1, characterized in that, The hexagonal nut is model M20 according to GB / T6191-1986.

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