A multifunctional mechanical metamaterial unit and structure with both energy absorption and vibration reduction

Abstract

The present invention discloses a multifunctional mechanical metamaterial unit and structure that has both energy absorption and vibration reduction capabilities, specifically relating to the fields of vibration reduction and energy absorption protection. The unit comprises a substructure and a base structure of identical shape, each of which comprises four transverse rods and eight V-shaped concave rods. The four transverse rods are symmetrically arranged in parallel, and the eight concave rods are respectively arranged at the ends of two adjacent transverse rods on the same side. The concave portions of all the concave rods are located between the transverse rods. Two V-shaped convex rods are connected between the concave portions of the four concave rods on the same side. The base structure is embedded in the interior of the outer structure, and a first connecting rod is connected between the convex rods of the base structure and the substructure. The technical solution of the present invention solves the problem that existing metamaterial structures cannot simultaneously meet the requirements of buffering energy absorption and low- and medium-frequency vibration reduction, thereby enhancing the performance of the metamaterial.

Description

Technical Field

[0001] The present invention relates to the field of vibration reduction and energy absorption protection, and in particular to a multifunctional mechanical metamaterial unit and structure with both energy absorption and vibration reduction capabilities. Background Art

[0002] Major national equipment, such as aerospace and high-speed trains, is increasingly becoming larger, heavier-loaded, and more precise. These applications often face complex challenges such as energy absorption and low-frequency, broadband operation. The resulting multi-physics challenge is becoming increasingly prominent, but traditional protective structures cannot simultaneously achieve the multifunctional effects of buffering energy absorption and wide-band vibration reduction. Therefore, there is an urgent need to develop a new high-performance, multi-physics technology to address the challenges of buffering energy absorption and low-frequency, broadband vibration isolation within a compact footprint.

[0003] Currently, metamaterial research focuses on designing novel structural materials with multifunctional properties. For example, porous structures with negative Poisson's ratios are typical mechanical metamaterials. Due to their unusual deformation modes, negative Poisson's ratio structures possess excellent mechanical and physical properties, such as resistance to indentation and shearing, and energy absorption efficiency, making them promising for use as protective structures. However, achieving buffering, energy absorption, and low- to medium-frequency vibration reduction presents significant challenges for metamaterials. Summary of the Invention

[0004] The present invention aims to provide a multifunctional mechanical metamaterial unit and structure with both energy absorption and vibration reduction, which solves the problem that existing metamaterial structures cannot simultaneously meet the requirements of buffering energy absorption and medium and low frequency vibration reduction.

[0005] In order to achieve the above-mentioned purpose, the technical solution of the present invention is as follows: a multifunctional mechanical metamaterial unit with both energy absorption and vibration reduction, comprising a substructure and a base structure of the same shape, wherein the substructure and the base structure both comprise four transverse rods and eight V-shaped concave rods, the four transverse rods are symmetrically arranged in parallel, the eight concave rods are respectively arranged at the ends on the same side of two adjacent transverse rods, the concave portions of all the concave rods are located between the transverse rods, two V-shaped convex rods are connected between the concave portions of the four concave rods on the same side, the base structure is embedded in the interior of the outer layer structure, and a first connecting rod is connected between the convex rods of the base structure and the substructure.

[0006] Furthermore, the size ratio of the base structure to the substructure is 0.6.

[0007] Through the above settings, it can be ensured that the negative Poisson's ratio structures have seamless contact during the assembly process, and stress waves can propagate continuously in the structure, thereby improving the energy absorption performance of the metamaterial.

[0008] Furthermore, the angle between each of the transverse rods and the end of the concave rod is 63°.

[0009] Another technical solution provided by the present invention is: a multifunctional mechanical metamaterial structure with both energy absorption and vibration reduction, which is composed of a plurality of any of the above-mentioned mechanical metamaterial units, a second connecting rod is connected between two adjacent inner recesses on two adjacent mechanical metamaterial units, and the two adjacent mechanical metamaterial units share a transverse rod or a second connecting rod.

[0010] Compared with the existing technology, this solution has the following beneficial effects:

[0011] 1. This solution provides a multifunctional mechanical metamaterial unit and structure with both energy absorption and vibration reduction, which can solve the problem that existing metamaterial structures cannot simultaneously meet the requirements of buffering energy absorption and low- and medium-frequency vibration reduction.

[0012] 2. This solution has excellent cushioning and energy absorption properties. Compared with the three-dimensional reentrant hexagonal structure based on the 3D truss, the multifunctional mechanical metamaterial can significantly improve the energy absorption characteristics under the premise of the same mass. Under quasi-static compression, the energy absorption characteristics of the structure can be improved by 30% and the cushioning characteristics can be improved by 80%.

[0013] 3. Vibration test experiments show that the transmission curve of this scheme shows obvious vibration attenuation in the frequency ranges of 1375Hz~2135Hz and 4715Hz~9965Hz. Band gaps are formed in these two frequency ranges, while longitudinal waves propagate in other frequency ranges. This shows that multifunctional mechanical metamaterials can achieve broadband isolation of elastic waves in the low-frequency range with low mass density.

[0014] 4. The mechanical metamaterials of this scheme can be customized to meet the requirements of different working conditions at the initial design stage. They have the characteristics of highly controllable materials and geometric dimensions, and can be adjusted according to actual application conditions, with good engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 An axonometric view of a multifunctional mechanical metamaterial unit with both energy absorption and vibration reduction capabilities according to Example 1;

[0016] Figure 2 A front view of a multifunctional mechanical metamaterial unit with both energy absorption and vibration reduction capabilities according to Example 1;

[0017] Figure 3 An axonometric view of a multifunctional mechanical metamaterial unit with both energy absorption and vibration reduction capabilities in Example 2;

[0018] Figure 4 A front view of a multifunctional mechanical metamaterial unit with both energy absorption and vibration reduction capabilities according to Example 2;

[0019] Figure 5An axonometric view of a multifunctional mechanical metamaterial structure with both energy absorption and vibration reduction capabilities according to Example 2;

[0020] Figure 6 is a schematic diagram of the beam structure in Example 2;

[0021] Figure 7 This is an axonometric view of a three-dimensional reentrant hexagonal structure based on a 3D truss;

[0022] Figure 8 2. This is a comparison diagram of the quasi-static compressive stress and strain of the multifunctional mechanical metamaterial unit and the three-dimensional reentrant hexagonal structure based on the 3D truss under the same equivalent density in Example 2 by experiment and finite element analysis;

[0023] Figure 9 It is the transmission curve of the vibration signal of the beam structure in Example 2 at a frequency of 0-10000 Hz. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below through specific embodiments:

[0025] The reference numerals in the drawings of the specification include: substructure 1 , base structure 2 , transverse rod 3 , inner concave rod 4 , outer convex rod 5 , first connecting rod 6 , and second connecting rod 7 .

[0026] Example 1

[0027] like Figure 1 and 2 As shown, a multifunctional mechanical metamaterial unit with both energy absorption and vibration reduction properties is shown. A single mechanical metamaterial unit comprises a substructure 1 and a base structure 2 of identical shape. Both the substructure 1 and base structure 2 include four transverse rods 3 and eight V-shaped concave rods 4. The four transverse rods 3 are symmetrically arranged in parallel, with each transverse rod 3 forming a 63° angle with the end of the concave rod 4. The eight concave rods 4 are located on the left and right sides of the substructure 1, with four concave rods 4 on each side. The eight concave rods 4 are connected to the ends of two adjacent transverse rods 3 on the same side. The concave portions of all concave rods 4 are located between two adjacent transverse rods 3. Two V-shaped convex rods 5 are connected between the concave portions of the four concave rods 4 on the same side. The base structure 2 is embedded within the outer structure. In this embodiment, the size ratio of the base structure 2 to the substructure 1 is 0.6. This ensures seamless contact between the negative Poisson's ratio structures during assembly. Stress waves can propagate continuously through the substructure 1 and base structure 2, thereby improving the metamaterial's energy absorption performance. A first connecting rod 6 connects adjacent external protrusions 5 on the base structure 2 and substructure 1.

[0028] Principle and effect of the technical solution: This technical solution can significantly enhance the mechanical properties of the structure while maintaining the unit / structure mass and volume to meet application requirements, and can also bring unexpected results in vibration suppression. Compared with the traditional three-dimensional reentrant hexagonal structure based on 3D trusses, it can significantly improve the energy absorption characteristics of the unit / structure while maintaining the same mass, and can significantly improve the vibration suppression characteristics of the structure while maintaining the same unit / structure size, and has good engineering application prospects.

[0029] Example 2

[0030] like Figures 3 to 5 As shown, a multifunctional mechanical metamaterial structure with both energy absorption and vibration reduction capabilities is constructed from an array of multiple mechanical metamaterial units according to Example 1. A second connecting rod 7 connects two adjacent inner recesses of two adjacent mechanical metamaterial units, and the two adjacent mechanical metamaterial units share a transverse rod 3 or a second connecting rod 7. The presence of the matrix structure 2 significantly enhances the buffering energy absorption and vibration suppression properties of the entire metamaterial structure. The mechanical metamaterial structure was found to exhibit excellent mechanical properties under quasi-static compression conditions and good wide-range low-frequency vibration reduction performance in vibration testing experiments.

[0031] The mechanical metamaterial structure of this embodiment is used to produce protective structures such as sandwich beams and sandwich panels with engineering application value, which have good buffering, energy absorption and vibration reduction characteristics, and effectively improve the relevant performance of the protected structure.

[0032] Case Study:

[0033] like Figure 6 As shown, the mechanical metamaterial structure of Example 2 was arrayed in a 5×1 array to obtain the beam structure used in the vibration test experiment. A simulation model was established in ABAQUS / Explicit finite element software based on the designed beam structure. The material of the beam structure was stainless steel 316L, and the material parameters were: density 7900 kg / cm 3 , Poisson's ratio of 0.3, elastic modulus of 180 GPa, tangent modulus of 800 GPa, yield modulus of 421 MGa, and yield strain of 0.23. The length of the transverse rod 3 is 20 mm, the length of a single hypotenuse on the concave rod 4 is 11.18 mm, the angle between the ends of the transverse rod 3 and the concave rod 4 (i.e., the concave angle) is 63°, and the size ratio of the base structure 2 to the substructure 1 is 0.6.

[0034] In order to prove the excellent performance of the multifunctional mechanical metamaterial cell structure proposed in this embodiment, Figure 7As shown, a three-dimensional reentrant hexagonal structure based on a 3D truss (i.e., a structure in which the matrix structure 2 is not added to the multifunctional mechanical metamaterial structure of this embodiment) is compared with the mechanical metamaterial structure of this embodiment. To ensure that the two structures have the same equivalent density, the wall thicknesses of the substructure 1 and the matrix structure 2 in the mechanical metamaterial structure of this embodiment are 1.2 mm and 2 mm, respectively. In order to demonstrate the vibration damping properties of the mechanical metamaterial structure of this embodiment, a beam structure was made using stainless steel 316L material and 3D printing technology, and then a mechanical wave transmission experiment was conducted. This experiment used a Polytec laser testing system (this system is an existing technology and has not been improved in this embodiment) to conduct a vibration test. One end of the beam structure was clamped with a fixture to test the vibration response under the cantilever boundary conditions. The stress-strain curves of the two structures under quasi-static compression and different impact velocities were extracted, as shown in FIG. Figure 8 To evaluate the energy absorption characteristics of the structure, the energy absorption characteristics of the structure are calculated based on the stress-strain curve of the beam structure under compression and impact.

[0035] In the linear elastic range, the formula for calculating the structural elastic modulus is:

[0036]

[0037] Where ε1 and ε2 are both less than the yield strain ε y , yield strain ε y The corresponding stress is the yield strength σ y .

[0038] The average stress in the platform area is the average stress from the time the structure enters the yield stage to before densification, and the calculation formula is:

[0039]

[0040] Where, ε D is the densification strain. The densification strain can be calculated from the energy absorption efficiency, which is the ratio of the area enclosed by the stress-strain curve and the horizontal axis to the stress. When the beam structure enters the densification range, the stress level rises rapidly within a very small strain, resulting in a decrease in energy absorption efficiency. Therefore, the calculation of the densification strain can be determined by the peak energy absorption efficiency:

[0041]

[0042] Where η is the energy absorption efficiency.

[0043] The energy absorption characteristic index of a structure refers to the energy absorbed when the structure is completely compressed and destroyed. The calculation formula is:

[0044]

[0045] Where F is the compression force and δ is the compression distance.

[0046] Specific energy absorption is the absorbed energy within the mass of a structural unit and is an important indicator for evaluating the energy absorption characteristics of a structure. The calculation formula is:

[0047]

[0048] Based on the simulated stress-strain curve, the densification strain, initial peak stress, energy absorption characteristics, and average plateau stress of the beam structure are extracted to evaluate its performance. The densification strain is the distance required for the beam structure to be compressed to the incompressible stage, the initial peak stress is the compressive force required for the beam structure to enter the yield stage, the average plateau stress is the average stress from the yield stage to densification, and the energy absorption characteristic is the energy required to compress the beam structure from its initial state to densification.

[0049] Table 1

[0050]

[0051] Table 1 shows the relevant data for the three-dimensional reentrant hexagonal structure based on a 3D truss and the mechanical metamaterial structure of this embodiment under quasi-static compression. As can be seen from Table 1, under quasi-static compression, the mechanical metamaterial structure of this embodiment exhibits superior cushioning and energy absorption properties. Given the same mass and volume, the mechanical metamaterial structure of this embodiment exhibits an 80% improvement in cushioning properties and a 30% improvement in energy absorption properties compared to the three-dimensional reentrant hexagonal structure based on a 3D truss.

[0052] Figure 9 The transmission curves of vibration signals for the array beam structure of this embodiment at frequencies between 0 and 10,000 Hz are shown. As can be seen from the figure, the vibration transmissibility curve exhibits significant vibration attenuation in the ranges of 1238 Hz to 1990 Hz and 4244 Hz to 9550 Hz, indicating that the band gap characteristics of the mechanical metamaterial unit of this embodiment have a significant impact on the attenuation of low-frequency and medium- and high-frequency vibration signals.

[0053] The above are only embodiments of the present invention, and common knowledge such as the specific structure and / or characteristics of the scheme are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A multifunctional mechanical metamaterial unit with both energy absorption and vibration reduction capabilities, characterized by: It includes a substructure and a base structure of the same shape, and the substructure and the base structure both include four transverse rods and eight V-shaped concave rods. The four transverse rods are symmetrically arranged in parallel, and the eight concave rods are respectively arranged at the ends on the same side of two adjacent transverse rods. The concave parts of all the concave rods are located between the transverse rods, and two V-shaped convex rods are connected between the concave parts of the four concave rods on the same side. The base structure is embedded in the interior of the substructure, and a first connecting rod is connected between the convex rods of the base structure and the substructure.

2. The multifunctional mechanical metamaterial unit with both energy absorption and vibration reduction capabilities according to claim 1, characterized in that: The size ratio of the base structure to the substructure is 0.

6.

3. The multifunctional mechanical metamaterial unit with both energy absorption and vibration reduction capabilities according to claim 1, characterized in that: The included angle between each of the transverse rods and the end of the concave rod is 63°.

4. A multifunctional mechanical metamaterial structure with both energy absorption and vibration reduction capabilities, characterized by: The invention is composed of a plurality of mechanical metamaterial units according to any one of claims 1 to 3, wherein a second connecting rod is connected between two adjacent inner recesses of two adjacent mechanical metamaterial units, and the two adjacent mechanical metamaterial units share a transverse rod or a second connecting rod.

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