Stair-Stepping metamaterial and the derived isolator for all-DOF vibrations with multi-payloads

Abstract

The vibrations usually come from various directions and the mass of the isolated object tends to vary in engineering. However, the existing low-frequency isolators with multi-loads are limited in a single DOF, while the multi-directional isolators mitigate vibrations for only a certain payload and cannot work well or even make the matters worse under other levels of load. Here, a novel mechanical metamaterial is specially designed to exhibit stair-stepping force-displacement curve with multiple plateaus, and based on which a six-DOF isolator is subsequently proposed. The six metamaterial struts are symmetrically connected to the platform by spherical hinges with universal movement characteristics, enabling the platform to move in orthogonal six DOFs (three translational and three rotational directions). A dynamic model is established to evaluate the isolator’s performance in each DOF and the frequency-response is solved by using the harmonic balance method. Both experiments and theories indicate that the metamaterial-based isolator (MBI) can achieve almost full-band vibration isolation in all DOFs under multi-levels of payload rather than a certain one, which has not been achieved previously. Moreover, the introduction of metamaterial makes the MBI compact in structure, efficient in assembly and flexibility in nonlinear adjustment, which opens a door for small-scale design of isolators. The proposed metamaterial and the derived isolator pave an avenue for isolating low-frequency vibrations in all DOFs under complex and variable vibration environments.