Inerter-based Vibration Mitigation at Extremely Low Frequency
ORAL
Abstract
Mitigation of low-frequency vibrations has long been a major challenge. One promising research direction points to architected materials — widely referred to as acoustic or elastic metamaterials. They can exhibit a phononic band gap, i.e., a range of frequencies in which no vibration can propagate.
While many recent studies attempted to demonstrate low-frequency band gaps, there is no consensus on which frequency ranges should be called ‘‘low’’ or ‘‘ultra-low’’. The exact meaning of low frequency varies from a fraction of one Hz, to several Hz, and up to many kHz. The word ‘‘low’’ is a relative concept that depends on application-specific scenarios. To facilitate a generally meaningful discussion and a fair comparison among different systems and configurations, we advocate a universal and dimensionless frequency for all vibro-elastic metamaterials: f = a/λ, where a denotes the size of a metamaterial unit, and λ is the operating wavelength.
We demonstrate the unique capability of inerter-based metamaterials in forming band gaps at ultra-low dimensionless frequencies, where f = a/λ ∼ 10-4. The key component of this achievement is the inerter, a two-terminal mechanical device offering a frequency-independent inertia much larger than its own physical mass. This is possible because the inerter couples linear relative motions between its two ends to the rotation of a flywheel. The flywheel moment of inertia can be amplified to produce a large inertial effect. The metamaterial shows definite superiority in forming a band gap in the ultralow frequency - equivalently the ultra-long wavelength - regime, where the unit cell size can be 4 or more orders of magnitude smaller than the operating wavelength. In addition, our parametric studies in both one and two dimensions pave the way towards designing next-generation metamaterials for structural vibration mitigation. Like springs and dampers, the inerter is a passive device without the need for any active control. Hence, we envision that inerter-based metamaterials will be the next disruptive technological advancement emerging from the research community of extreme mechanics
While many recent studies attempted to demonstrate low-frequency band gaps, there is no consensus on which frequency ranges should be called ‘‘low’’ or ‘‘ultra-low’’. The exact meaning of low frequency varies from a fraction of one Hz, to several Hz, and up to many kHz. The word ‘‘low’’ is a relative concept that depends on application-specific scenarios. To facilitate a generally meaningful discussion and a fair comparison among different systems and configurations, we advocate a universal and dimensionless frequency for all vibro-elastic metamaterials: f = a/λ, where a denotes the size of a metamaterial unit, and λ is the operating wavelength.
We demonstrate the unique capability of inerter-based metamaterials in forming band gaps at ultra-low dimensionless frequencies, where f = a/λ ∼ 10-4. The key component of this achievement is the inerter, a two-terminal mechanical device offering a frequency-independent inertia much larger than its own physical mass. This is possible because the inerter couples linear relative motions between its two ends to the rotation of a flywheel. The flywheel moment of inertia can be amplified to produce a large inertial effect. The metamaterial shows definite superiority in forming a band gap in the ultralow frequency - equivalently the ultra-long wavelength - regime, where the unit cell size can be 4 or more orders of magnitude smaller than the operating wavelength. In addition, our parametric studies in both one and two dimensions pave the way towards designing next-generation metamaterials for structural vibration mitigation. Like springs and dampers, the inerter is a passive device without the need for any active control. Hence, we envision that inerter-based metamaterials will be the next disruptive technological advancement emerging from the research community of extreme mechanics
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Publication: Jamil, F., Chen, F., Deng, B., Parker, R. G., & Wang, P. (2022). Inerter-based elastic metamaterials for band gap at extremely low frequency. Extreme Mechanics Letters, 56, 101847.
Presenters
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Pai Wang
University of Utah
Authors
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Pai Wang
University of Utah
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Fei Chen
The University of Utah, University of Utah
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Bolei Deng
Massachusetts Institute of Technology