A multifunctional mechanical metamaterial structure cell and metamaterial structure capable of achieving casual balance and zero force state

Abstract

The present application relates to the technical field of metamaterials, and discloses a multifunctional mechanical metamaterial structure cell capable of realizing random equilibrium and zero force state and a metamaterial structure, wherein the metamaterial structure cell comprises a coupled neutral stable tensile whole structure and a control unit; the tensile whole structure provides random equilibrium and zero force state characteristics; when the tensile whole structure is deformed to a set threshold, the control unit autonomously abandons or maintains the neutral stability condition of the tensile whole structure, realizing switching between an elastomer and neutral stability. The metamaterial structure comprises a plurality of metamaterial structure cells, and the plurality of metamaterial structure cells are arranged in an array, and adjacent two metamaterial structure cells are connected through the ends of straight rods or support rods. The present application has the beneficial effect that it can exhibit properties similar to ideal rigid-plasticity, mechanisms and liquids at a certain stage of deformation, and can play a role in wave regulation, shape adaptation and retention and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metamaterials, and particularly relates to a multifunctional mechanical metamaterial structure cell capable of realizing random equilibrium and zero force state and a metamaterial structure. BACKGROUND

[0002] In the process of human social development, the level of productivity is closely related to the level of understanding and utilization of materials. Since the twentieth century, with the progress of science and technology, natural materials and traditional manufacturing and processing technologies have gradually been difficult to meet the demand for more powerful, richer and more intelligent material performance in the fields of architecture, automobiles, electronics, biological engineering and aerospace. Through reasonable design of the microstructure of traditional materials, unique and extraordinary superconventional mechanical properties are achieved, and mechanical metamaterials emerge as the times require.

[0003] Although the special mechanical behaviors of mechanical metamaterials such as negative Poisson's ratio, rigid-flexible coupling, lightweight high strength and toughness, negative compressibility, isotropy break many inherent recognitions of materials, the boundaries between elasticity and plasticity, elastomers and mechanisms, solids and liquids still exist. In recent years, many researchers have tried to break this boundary to further improve and explore the performance and design space of materials.

[0004] In the field of flexible metamaterial design, most of the deformations are based on the elastic connection of folding paper and other types of modules, so that zero deformation mode appears, which consumes very little or even no elastic energy and plays a key role in realizing reconfigurable elastic properties. For example, researchers have proposed a 3D metamaterial with an engineering zero mode, which can reversibly switch between all seven extreme modes from zero mode (solid state) to six modes (near gaseous state), and achieve tunable wave manipulation in 1D, 2D and 3D systems. Similar to zero deformation mode, some researchers pay more attention to the unloading characteristics of structures similar to plasticity, i.e. random equilibrium. By using a single-degree-of-freedom self-stressed hinged structure cell as a building block to create a deformable structural material, all deformation movements are energy equivalent, thus no force response is generated. However, unlike the moving mechanism, by making the hinge part transform between solid and liquid, or actively controlling the sensor and motor, the elastic-plastic mechanical properties can be quickly and controllably switched.

[0005] Although the current structural design of mechanical metamaterials can achieve a certain degree of ideal rigid-plasticity, mechanism and liquid properties in elastomers, the boundaries between them still exist. We need to reconfigure, phase change, actively control and other operations on the material to realize the random equilibrium and zero force state characteristics in different directions or states, and cannot make it exhibit multiple deformation modes in a continuous deformation to realize the real combination of elastomers and ideal rigid-plasticity, mechanism and liquid properties. SUMMARY

[0006] To address the shortcomings of existing technologies, this invention provides a multifunctional mechanical metamaterial structure capable of achieving both equilibrium and zero-force states. It is composed of a neutral and stable tensioned monolithic structure coupled with a control unit. The neutral and stable tensioned monolithic structure provides equilibrium and zero-force state characteristics, enabling it to exhibit properties similar to ideal rigid-plasticity, mechanisms, and liquids at a certain stage of deformation. This allows it to function in scenarios such as wave manipulation, shape adaptation, and shape retention.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] According to one aspect of the present invention, a multifunctional mechanical metamaterial structural cell capable of achieving both equilibrium and zero-force states is provided, comprising a coupled neutral and stable tensioned integral structure and a control unit; the tensioned integral structure provides equilibrium and zero-force state characteristics; the control unit autonomously discards or maintains the neutral and stable conditions of the tensioned integral structure when the tensioned integral structure deforms to a set threshold, thereby achieving a switch between an elastic body and neutral stability.

[0009] Furthermore, the tensioning integral structure includes a first straight rod, a second straight rod, and a support rod connected by a first hinge center. The angle between the first straight rod and the second straight rod is 180 degrees. The support rod is located between the first straight rod and the second straight rod. A first elastic body is provided between the end of the first straight rod and the end of the support rod, and a second elastic body is provided between the end of the second straight rod and the end of the support rod.

[0010] Furthermore, the control unit is a combination structure of a non-elastic rope and a pre-tensioned spring, and this combination structure is located between the end of the first straight rod and the center of the first hinge.

[0011] Furthermore, the control unit may consist of two constraint structures and a third elastic body connected by a second hinge center, with the ends of the two constraint structures respectively connected to the end of the first straight rod and the end of the support rod; the end of the third elastic body is connected to the first hinge center.

[0012] Furthermore, the constraint structure is a constraint bar.

[0013] According to another aspect of the present invention, a multifunctional mechanical metamaterial structure capable of achieving equilibrium and zero-force state is provided, comprising multiple metamaterial structural cells, the multiple metamaterial structural cells being arranged in an array, and adjacent two metamaterial structural cells being connected by the ends of a straight rod or a support rod.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] 1. The present invention is composed of a neutral and stable tensioned integral structure coupled with a control unit. The neutral and stable tensioned integral structure provides the characteristics of equilibrium and zero force state under any circumstances, so that it can exhibit properties similar to ideal rigid-plastic, mechanism and liquid at a certain stage of deformation, and can play a role in scenarios such as wave control, shape adaptation and maintenance.

[0016] 2. When the structure deforms to a set threshold, the control unit actively discards or maintains the neutral stability condition of the overall tensile structure, achieving automatic switching between elasticity and neutral stability. This allows the material to possess a certain degree of intelligence while retaining conventional mechanical properties such as load-bearing and energy absorption, better meeting the complex and ever-changing engineering application requirements. This solution truly combines the characteristics of elasticity, ideal rigidity and plasticity, mechanisms, and liquids, breaking their boundaries and enabling the material to autonomously switch between these properties during continuous deformation, without relying on reconstruction, phase change, or active control.

[0017] 3. This invention has potential application value in fields such as intelligent sensing, self-regulation, mechanical exoskeletons, wave modulation, vibration isolation, energy absorption, and reverse design of nonlinear behavior, and is conducive to deepening and expanding the understanding of the mechanical behavior of materials. Attached Figure Description

[0018] Appendix Figure 1 This is a schematic diagram of the cellular unit of the multifunctional mechanical metamaterial structure of the present invention, which can achieve both random equilibrium and zero-force states. Figure 1 ;

[0019] Appendix Figure 2 This is a schematic diagram of the cellular unit of the multifunctional mechanical metamaterial structure of the present invention, which can achieve both random equilibrium and zero-force states. Figure 2 ;

[0020] Appendix Figure 3 The above is a schematic diagram of a metamaterial array structure composed of metamaterial structural cells with the same elastic segment state energy lower than the random equilibrium state energy, as shown in Example 1.

[0021] Appendix Figure 4 This is a force diagram of Example 1;

[0022] Appendix Figure 5 This is the stress-strain relationship diagram for Example 1;

[0023] Appendix Figure 6 Example 2: A schematic diagram of a metamaterial array composed of metamaterial structural cells with different energy levels and switching direction sequences;

[0024] Appendix Figure 7 This is the stress-strain relationship diagram for Example 2;

[0025] Appendix Figure 8 This is a schematic diagram of the forces acting on Example 3 and a stress-strain relationship diagram;

[0026] The reference numerals in the attached diagram are as follows: 1. First hinge center; 2. First straight rod; 3. Second straight rod; 4. Support rod; 5. First elastic body; 6. Second elastic body; 7. Non-elastic rope; 8. Pre-tension spring; 9. Second hinge center; 10. Constraint structure; 11. Third elastic body. Detailed Implementation

[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

[0028] This invention proposes a multifunctional mechanical metamaterial design scheme that can achieve both unpredictable equilibrium and zero-force states. The designed structure consists of a neutral and stable tensioned monolithic structure coupled with a control unit. The neutral and stable tensioned monolithic structure provides unpredictable equilibrium and zero-force state characteristics, enabling it to exhibit properties similar to ideal rigid-plasticity, mechanisms, and liquids at a certain stage of deformation. This allows it to function in scenarios such as wave manipulation, shape adaptation, and shape retention. When the structure deforms to a set threshold, the control unit autonomously discards or maintains the neutral and stable conditions of the tensioned monolithic structure, achieving a switch between an elastic body and neutral stability. This allows the material to possess a certain degree of intelligence while retaining conventional mechanical properties such as load-bearing and energy absorption, better meeting the complex and ever-changing engineering application requirements.

[0029] This scheme truly combines the properties of elastomers with ideal rigid-plasticity, mechanisms, and fluids, breaking their boundaries and enabling materials to autonomously switch between these properties during continuous deformation, without relying on reconstruction, phase transitions, or active control. By designing metamaterial structures, the threshold and direction of deformation behavior changes can be precisely preset, achieving continuous and autonomous free switching between elastomer states and passive equilibrium and zero-force states. The structure exhibits strong designability in the elastic segment, achieving excellent linear elasticity and negative stiffness characteristics under quasi-static loading. It also possesses arrayable spatial characteristics, enabling arbitrary Poisson's ratios and Gaussian curvatures, and possesses extremely strong shape designability. Different array methods can cause the material to exhibit different unique mechanical properties, such as multi-energy plateau characteristics and stress-strain behavior varying with loading. It can be applied in multiple different scenarios, possessing potential application value in fields such as intelligent sensing, self-regulation, mechanical exoskeletons, wave manipulation, vibration isolation, energy absorption, and inverse design of nonlinear behavior. Furthermore, it is beneficial for deepening and expanding the understanding of material mechanical behavior. The specific structure of the metamaterial structure cell is as follows:

[0030] like Figures 1-2As shown, a multifunctional mechanical metamaterial structural cell capable of achieving both equilibrium and zero-force states is disclosed, comprising a coupled neutral and stable tensioned integral structure and a control unit; the tensioned integral structure provides equilibrium and zero-force state characteristics; when the tensioned integral structure deforms to a set threshold, the control unit autonomously discards or maintains the neutral and stable conditions of the tensioned integral structure, thereby achieving the switching between an elastic body and neutral stability.

[0031] Specifically, such as Figure 1 As shown, one structure of a metamaterial structural cell is disclosed. The tensioned integral structure includes a first straight rod 2, a second straight rod 3, and a support rod 4 connected by a first hinge center 1. The angle between the first straight rod 2 and the second straight rod 3 is 180 degrees. The support rod 4 is located between the first straight rod 2 and the second straight rod 3. A first elastic body 5 is disposed between the end of the first straight rod 2 and the end of the support rod 4, and a second elastic body 6 is disposed between the end of the second straight rod 3 and the end of the support rod 4. The control unit is a combination structure of a non-elastic rope 7 and a pre-tensioned spring 8, and this combination structure is located between the end of the first straight rod 2 and the first hinge center 1. The metamaterial structural cell can achieve different elastic segment mechanical properties, state switching thresholds, and directions, such as... Figure 1 As shown, in a neutral and stable tensioned monolithic structure and control unit, material parameters k1 and k2 determine the mechanical properties of the elastic segment; these material parameters, along with geometric parameters l0 and l2, jointly determine the state switching threshold; as the structure deforms, the geometric parameter θ changes accordingly, and together with the threshold, determines the current deformation mode. Depending on the loading direction, the direction and order of state switching also change.

[0032] like Figure 2 The disclosed metamaterial structural cell structure is another type of structure, the tensile integral structure and Figure 1 Similarly, the control unit consists of two constraint structures 10 and a third elastic body 11 connected by a second hinge center 9. The ends of the two constraint structures 10 are respectively connected to the end of the first straight rod 2 and the end of the support rod 4. The end of the third elastic body 11 is connected to the first hinge center 1. In this structure, its elastic segment has higher energy than the random equilibrium and zero force state. The combination of the two can meet the mechanical performance requirements of different scenarios.

[0033] A multifunctional mechanical metamaterial structure capable of achieving equilibrium and zero-force state under any circumstances includes multiple metamaterial structural cells arranged in an array. Adjacent metamaterial structural cells are connected by the ends of straight rods or support rods 4. The array structure can be configured as needed, as detailed in the embodiments.

[0034] Example 1:

[0035] Figures 3-5The diagram illustrates a preferred embodiment of the present invention, comprising a metamaterial array composed of metamaterial structural cells with identical elastic segment state energies lower than the energy of the passive equilibrium state. When the structure deforms, it first experiences an elastic segment with negative stiffness. If unloaded in this state, the structure will return to its initial state. After reaching a threshold, it enters a passive equilibrium and zero-force state, where the force response is zero. If unloaded in this state, the structure will maintain its current state. If loading is applied vertically, the switching sequence changes, and the elastic segment structure actively adapts to the deformation, similar to the negative force stage of a bistable state. The elastic segment state can satisfy conventional scenarios such as load bearing and energy absorption, while the passive equilibrium state after reaching the threshold can well adapt to certain special scenarios and tasks, such as wave manipulation and shape compliance adaptation.

[0036] Example 2:

[0037] Figures 6-7 The illustration shows another preferred embodiment of the present invention, which is a metamaterial array composed of metamaterial structural cells with different energy levels and switching direction sequences. When the structure deforms, it experiences elastic segments and random equilibrium and zero-force states in a specific sequence, which can well adapt to the force response requirements of complex tasks, such as for assisting mechanical exoskeletons. It can provide support for specific actions within a specific range, while not causing obstruction or influence in other specific activities. This is often achieved through active control in current research. At the same time, existing research has shown that tensioned integral structures can achieve arbitrary Gaussian curvature and Poisson's ratio, and the loading (strain) direction of the metamaterial array can also be customized as needed, possessing strong practicality and designability.

[0038] Example 3:

[0039] like Figure 8 The illustration shows another preferred embodiment of the present invention, comprising two metamaterial arrays composed of metamaterial structural cells with different elastic segments having energies lower than the energy of the random equilibrium state. The switching thresholds increase or decrease sequentially from the inside out. For the array with increasing stiffness, when the structure deforms, multiple elastic segments and random equilibrium segments alternate sequentially, exhibiting a stepped plateau characteristic in the energy curve. All elastic segments have negative stiffness, which is significant for reusable multi-segment low-rebound energy absorption and impact protection. For the array with decreasing stiffness, when the structure deforms, different segments of the inner metamaterial cells are activated to respond to force based on the current load, achieving a load-related force-deformation response. This is highly analogous to viscous fluids (where force response is related to shear strain rate). Existing research indicates that such adjustable stiffness typically requires external active control, such as phase transitions, and usually manifests at different stages of deformation, unable to change according to the load, lacking intelligence. This structure, in addition to autonomously adjusting its deformation behavior according to the load, can also quickly assess the current load based on the deformation, exhibiting a certain degree of intelligence.

Claims

1. A multifunctional mechanical metamaterial structural cell capable of achieving both random equilibrium and zero-force states, characterized in that: It includes a coupled, neutral, stable tensioned monolithic structure and a control unit; the tensioned monolithic structure provides inertial equilibrium and zero-force state characteristics; the control unit autonomously discards or maintains the neutral stability condition of the tensioned monolithic structure when the tensioned monolithic structure deforms to a set threshold, realizing the switching between the elastic body and neutral stability; The tensioning integral structure includes a first straight rod (2), a second straight rod (3) and a support rod (4) connected by a first hinge center (1). The angle between the first straight rod (2) and the second straight rod (3) is 180 degrees. The support rod (4) is located between the first straight rod (2) and the second straight rod (3). A first elastic body (5) is provided between the end of the first straight rod (2) and the end of the support rod (4). A second elastic body (6) is provided between the end of the second straight rod (3) and the end of the support rod (4). The control unit is a combination of an inelastic rope (7) and a pre-tensioned spring (8), and the combination is located between the end of the first straight rod (2) and the first hinge center (1).

2. A multifunctional mechanical metamaterial structural cell capable of achieving both random equilibrium and zero-force states, characterized in that: It includes a coupled, neutral, stable tensioned monolithic structure and a control unit; the tensioned monolithic structure provides inertial equilibrium and zero-force state characteristics; the control unit autonomously discards or maintains the neutral stability condition of the tensioned monolithic structure when the tensioned monolithic structure deforms to a set threshold, realizing the switching between the elastic body and neutral stability; The tensioning integral structure includes a first straight rod (2), a second straight rod (3) and a support rod (4) connected by a first hinge center (1). The angle between the first straight rod (2) and the second straight rod (3) is 180 degrees. The support rod (4) is located between the first straight rod (2) and the second straight rod (3). A first elastic body (5) is provided between the end of the first straight rod (2) and the end of the support rod (4). A second elastic body (6) is provided between the end of the second straight rod (3) and the end of the support rod (4). The control unit consists of two constraint structures (10) and a third elastic body (11) connected by a second hinge center (9). The ends of the two constraint structures (10) are respectively connected to the end of the first straight rod (2) and the end of the support rod (4); the end of the third elastic body (11) is connected to the first hinge center (1).

3. The multifunctional mechanical metamaterial structural cell capable of achieving both random equilibrium and zero-force state according to claim 2, characterized in that: The constraint structure (10) is a constraint rod.

4. A multifunctional mechanical metamaterial structure capable of achieving both random equilibrium and zero-force state, characterized in that: It includes multiple metamaterial structural cells as described in any one of claims 1-3, and multiple metamaterial structural cells are arranged in an array, with two adjacent metamaterial structural cells connected by the ends of a straight rod or a support rod (4).

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