Session: 01-01-04: Phononics IV

Paper Number: 75318

Start Time: Friday, 11:35 AM

75318 - Negative Effective Mass in Nonlinear Metamaterial for Vibration Mitigation 

We propose a nonlinear metamaterial which shows tunable bandgap at extremely low frequency and investigate bandgap-tunability depending on nonlinear parameters. Over the last decades, metamaterial based design has been paid great attention due to its extraordinary phenomena which are difficulty to be observed in nature such as negative Poisson, negative stiffness, negative density and negative refraction. The main insight of the metamaterial based artificial design is that it can manifest many extraordinary phenomena depending on how their small unit-cells are structured and arranged. In particular, these unit cell based metamaterial also can exhibit bandgap phenomena where the traveling of wave is prohibited. Since harnessing the bandgap of the metamaterials allows wave-manipulation depending on the frequency, many applications have been approached based on the bandgap mechanism to overcome the existing limitation and to achieve the superior performance such as noise filtering, vibration-mitigation, shock-absorption, wave-guide, seismic cloaking, or energy harvesting, etc. Generally, to mitigate vibration, the locally resonant metamaterial is designed by tuning with the frequency of external actuation. However, for practical usages the resonance bandgap has a prominent limitation, ‘narrow bandwidth’. Recently, tunable metamaterial has emerged as a one way which breakthroughs this limitation. In the tunable metamaterial, bandgap shifts depending on the external condition to broaden or to fit. Among the tunable ways, nonlinear tunability is important since it is not only a kind of tool to tune the bandgap but also a precede to combine with other tunable mechanism. Nevertheless, the number of research on nonlinear metamaterial is quite lacking and nonlinear metamaterials with an effective parameter have been rarely reported. Especially, to the author's best knowledge, the previous research on the nonlinear tunable metamaterial has not covered the extremely low frequency including zero-frequency. Here, we propose a nonlinear metamaterial with negative effective mass which shows tunable bandgap at the extremely low frequency. Unit cell of the proposed nonlinear metamaterial has double elastic foundations which induce geometric nonlinearity with amplitude of incident wave and initial force of springs bounded to the foundations. Focusing on the enhancement of feasibility, the nonlinearity of the proposed metamaterial is achieved by the only linear springs. First, nonlinearity-dependent dispersion of the proposed metamaterial was derived based on perturbation approach. After that, we verified the existence of the nonlinear bandgap which exhibits tunability for the amplitude and the initial force at extremely low frequency with 3 steps - theoretical approach based on the theory of nonlinear effective mass, numerical simulations based on the commercial FEA software ABAQUS, and the experiment for a metamaterial with three degrees of freedom. Through the investigation of this research, nonlinear tunability for the whole frequency range is completed by covering extremely low frequency. Also, this research paves way to harness the nonlinear metamaterials for vibration mitigation by enriching the practical usability.

Presenting Author: Myung Hwan Bae Korea Research Institute of Standards and Science (KRISS)

Authors:

Myung Hwan Bae Korea Research Institute of Standards and Science (KRISS)
Joo Hwan Oh Ulsan National Institute of Science and Technology (UNIST)