Low-frequency Locally Resonant Band Gap of the Two-dimensional Quasi-zero-stiffness Metamaterials

Flexural wave attenuation by metamaterial beam with compliant quasi-zero-stiffness resonators

Design and testing of a parabolic cam-roller quasi-zero-stiffness vibration isolator

Abstract Metamaterials are an emerging type of man-made material capable of obtaining some extraordinary properties that cannot be realized by naturally occurring materials. Due to tremendous application foregrounds in wave manipulations, metamaterials have gained more and more attraction. Especially, developing research interest of low-frequency vibration attenuation using metamaterials has emerged in the past decades. To better understand the fundamental principle of opening low-frequency (below 100 Hz) band gaps, a general view on the existing literature related to low-frequency band gaps is presented. In this review, some methods for fulfilling low-frequency band gaps are firstly categorized and detailed, and then several strategies for tuning the low-frequency band gaps are summarized. Finally, the potential applications of this type of metamaterial are briefly listed. This review is expected to provide some inspirations for realizing and tuning the low-frequency band gaps by means of summarizing the related literature. 

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A brief review of metamaterials for opening low-frequency band gaps

This study presented a novel negative-stiffness based metamaterial with the characteristics of buffering, energy absorption, and state recovery in two loading directions. The unit cell of the metamaterial is composed of cross-curve-beams (CCBs), supporting frames, and supporting beams. Through snap-through of the stable states of the curved beams, buffering, energy absorption and recovery of the initial state are fulfilled. The theoretical model of the negative stiffness (NS) unit cell is developed to quantify the mechanical feature and validated by finite element (FE) simulation. FE analysis has been done on the properties of the NS metamaterial structures composed of 1  × 1 × 1, 2  × 2 × 2 and 3  × 3 × 3 metamaterial unit cells under compression and tensile loads. Furthermore, quasi-static compression and tensile experiments are carried out on the three designed NS structures to verify the effectiveness of the simulation method and results. Meanwhile, the experimental and the simulation results demonstrate that the designed NS structures exhibit snap-through behavior and NS effect in both loading directions, so the structure can be used for bidirectional buffering and energy absorption. Repeated experiments also verify the designed NS structure has good state-recoverability and shock-resistance.

A negative-stiffness based 1D metamaterial for bidirectional buffering and energy absorption with state recoverable characteristic

Metamaterials are artificially structured materials that enable wave attenuation in band gaps. However, opening an ultralow-frequency band gap is still a challenge, since it is hard to realize near-zero stiffness in a traditional way. In this paper, a one-dimensional tunable quasi-zero-stiffness (QZS) metamaterial is engineered for ultralow-frequency (about a few tens Hertz) wave attenuation. Design optimization on the configuration of this new metamaterial is conducted to achieve quasi-zero stiffness. The dispersion relation is derived theoretically based on a lumped diatomic chain model, and then the band structure is revealed. The characteristics of longitudinal wave propagation in the metamaterial are studied by both numerical analyses and FE simulations, which are also validated by experimental tests. The results indicate that the stiffness is deformation-related, and the band gap can be tuned substantially by just changing the pre-compression. Therefore, the quasi-zero stiffness and then the ultralow-frequency band gap can be fulfilled by pre-compressing the metamaterial properly.

Tunable ultralow frequency wave attenuations in one-dimensional quasi-zero-stiffness metamaterial

Numerical and Experimental Investigations on Tunable Low-frequency Locally Resonant Metamaterials

The invention relates to an adjustable ultra-low-frequency quasi-zero-stiffness vibration isolator, and belongs to the field of vibration isolators. The adjustable ultra-low-frequency quasi-zero-stiffness vibration isolator includes a shell, a first cylinder is arranged in the shell, the first cylinder is in a cylindrical shape with the closed upper end and the opened lower end, the upper end of the first cylinder is arranged horizontally, the first cylinder is used for bearing vibration isolated equipment, and more than two negative stiffness mechanisms are evenly arranged on the outer side of the first cylinder; and one end of each of the negative stiffness mechanisms is fixedly connected with the inner wall of the shell, the other end of each of the negative stiffness mechanisms is mounted on a second connecting rod horizontally and fixedly arranged on the inner wall of the shell, the second connecting rod faces the center shaft of the first cylinder, the other end of each of the negative stiffness mechanisms is connected to the first cylinder through a first connecting rod, the two ends of the first connecting rod are hinged to the first cylinder and the negative stiffness mechanisms respectively, a positive spring is arranged in the first cylinder, the upper end of the positive spring is fixedly connected to the upper end of the first cylinder, and the lower end of the positive spring is connected to the bottom of the shell through a lifting device. The invention has the wider zero-stiffness range.

Hongbin Pan

Papers

Tunable ultralow frequency wave attenuations in one-dimensional quasi-zero-stiffness metamaterial

Flexural wave attenuation by metamaterial beam with compliant quasi-zero-stiffness resonators

Numerical and Experimental Investigations on Tunable Low-frequency Locally Resonant Metamaterials

Adjustable ultra-low-frequency quasi-zero-stiffness vibration isolator