Inertial amplified topological metamaterial beams

What is it about?

Topological insulator (TI) has been a research hotspot in condensed matter physics in recent years due to its backscattering and imperfection immunity. Different from wave attenuation in band gaps, waves can localize at the interface between two domains with distinct topological properties, known as topologically protected interface modes (TPIMs). As one of the fundamental one-dimensional (1D) components, beams have been found extensive applications in civil and mechanical engineering. Therefore, the exploration of TPIMs in beams deserves further consideration. For example, the main frequency range of vibration in civil engineering is from 0.1Hz to 100 Hz. Therefore, the local resonance system is much more suitable due to its subwavelength characteristics. However, it should be noted that the realization of lower-frequency TPIM remains challenging. Specifically, the larger mass and softer spring are required to realize lower natural frequency of resonators. It is impractical in the cases requiring lightweight and high bearing capacity such as the defense and aerospace industries. Fortunately, the inertial amplification mechanism (IAM) can effectively tackle the problem. Specifically, the introduction of IAM can amplify the motion of small mass without sacrificing total stiffness or increasing total mass. Based on this assumption, Anchen Ni and Zhifei Shi at Beijing Jiaotong University conducted both theoretical and numerical studies on the TPIM in novel inertial amplified metamaterials beams.

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Photo by John McArthur on Unsplash

Photo by John McArthur on Unsplash

Why is it important?

The introduction of inertial amplification mechanism (IAM) will be beneficial for forming lower- frequency and high tunability TPIMs without sacrificing total stiffness or increasing total mass. Transmission simulation confirms the existence of TPIM between two domains with different topological properties. Moreover, with the increase in the arm length ratio, the TPIM is shifted to the lower frequency. It is worth noting that the quality factor of TPIM is also improved. Although the defect cannot affect the existence of TPIM, the frequency and transmission efficiency of TPIM will be slightly affected. To further enlarge the response area of TPIM, a sandwich structure is proposed. With the increase of the number of the sandwich layers, the response area is effectively enlarged. However, the peak displacement is reduced and the frequency of TPIM is shifted.

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