SUBJECT: Ph.D. Proposal Presentation
BY: William Johnson
TIME: Tuesday, April 3, 2018, 3:00 p.m.
PLACE: Love Building, 295
TITLE: Challenges and constraints in the application of resonance-based metamaterials for vibration isolation
COMMITTEE: Dr. Massimo Ruzzene, Chair (AE, ME)
Dr. Michael Leamy (ME)
Dr. Karim Sabra (ME)
Dr. Claudio Di Leo (AE)
Dr. Aldo Ferri (ME)


This work applies elastic metamaterials to two different structures, a power generator, and a high voltage vacuum circuit breaker. Elastic metamaterials offer strong benefits for passive vibration control. However, the application of these concepts is difficult. This work pushes the use boundaries of elastic metamaterials.

Power generators convert mechanical energy into electrical energy. Mechanical energy causes the rotor of the generator to spin in a magnetic field, creating electricity. The spinning causes longitudinal vibration in the support at 100 Hz. The objective of this research is to mitigate this vibration, because it can result in detrimental sound and vibration.

This work proposes a grounded spring-mass-chain support. This concept is a retrofit to the support. The dispersion relationship for a grounded spring-mass chain shows that it creates a mechanical high pass filter. It also provides design relationships that allow for tuning the stop band, to attenuate low frequency excitation. The concept is realized on a model of the generator, and provides the desired filtering at 100 Hz.

Vacuum circuit breakers interrupt the flow of electricity. The vacuum prevents current flow when open. When closing a circuit breaker, arcing melts the surfaces of the electrodes. Upon impact the electrodes bounce, resulting in further arcing and melting. When resting, a weld is formed. If too much melting occurs this weld will be too strong, and the circuit breaker will fail. The objective of this research is to reduce the melting. If each bounce is less than 1 ms, then melting can be prevented during bouncing.

Previous models looked at the bouncing as a resonance phenomenon. In this research the bouncing of the electrodes is looked at as a wave phenomenon. Simplified models of the electrodes show how waves initiate upon impact and propagate. The models also reveal how the waves result in bouncing. This leads to a new concept to reduce bouncing. By adding grounding springs the electrodes are stiffened, resulting in faster waves and shorter bounces, which prevent arcing during bouncing.

Finally, this work outlines a design process for the application of elastic metamaterials. The design process says that to design metamaterials for a design problem, the simplest possible model should be used. Metamaterials should be developed on that model, and when verified the entire model can be scaled up.