Theoretically, resonance-based metamaterials offer strong benefits in the realm of passive vibration control, given their potential to generate low-frequency band gaps. However, these concepts have seen little implementation in industrial applications due to a number of limitations. In vibration of heavy machinery, practical limitations are introduced by the combination of the low amount of space available, the high static stiffness of supports required for the mass, and low frequencies of operation. This makes the implementation of metamaterial concepts as a retrofit to existing support structures challenging. In analyzing elastic metamaterials, typically an infinitely repeating unit cell is assumed, but in practical implementation as few as two or three unit cells may be all that can be accommodated, significantly reducing their efficacy. Several different resonance based metamaterial concepts have been analyzed, using analytical models and finite element analysis, as candidates for retrofits or replacements to typical elastic supports for heavy machinery, specifically large generators, that avoid these problems. One concept, using grounded resonators, reduces vibration at the frequency of interest by creating a mechanical high pass filter. Another concept has been used to target a significantly contributing rotational mode of the generator, to reduce longitudinal vibration of the supports, instead of targeting the longitudinal vibration of the supports directly. Off-resonance operating frequencies of the generator have been targeted and successfully reduced using these concepts. Results from these simulations show that resonance-based metamaterial concepts can be used to reduce vibration transmission at operating frequencies of massive machinery.
William R. Johnson and Massimo Ruzzene, "Challenges and constraints in the application of resonance-based metamaterials for vibration isolation," Proc. SPIE 10600, Health Monitoring of Structural and Biological Systems XII, 1060024 (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 08, 2018; Published: 27 March 2018); https://doi.org/10.1117/12.2294919.
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