A New‐Type Lightweight Helical Elastic Metamaterial with Ultra‐Low‐Frequency Bandgaps

The local resonance (LR) structure can effectively suppress the low‐frequency noise and vibration, but how to obtain a lightweight and small‐scale LR structure with broadbands to satisfy engineering requirements is still a great challenge. This article proposes an LR structure by designing a helical spring group, in which not only the stability and bearing capacity can be greatly improved by properly designing its number of helical spring wires, but also the dynamic equivalent stiffness of the system can be better adjusted. Based on the theory, the initial frequency of the broadband within the LR structure can be successfully adjusted from 93 to 67 Hz only by adjusting the number of helical spring wires from 3 to 6. Finally, there are two bandgaps obtained by the finite element method (FEM), the first is the ultra‐low‐frequency bandgap of 11–15 Hz, the second is the broadband of 67–315 Hz. Thus, the regulation mechanism of bandgaps by adjusting the number of the wires can overcome the big structures or heavy mass in traditional methods. Most importantly, the helical structure provides a new idea for lightweight and small‐scale LR structures with the low‐frequency broadband, which would have a potential application in the field of vibration isolation.