Widening the Frequency Stop-Bandwidth of Metasurfaces for Controlling Lamb Wave Propagation

Open Access
- Author:
- Keirn, Jeremy
- Area of Honors:
- Engineering Science
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Parisa Shokouhi, Thesis Supervisor
Parisa Shokouhi, Thesis Honors Advisor
Clifford Jesse Lissenden, III, Faculty Reader - Keywords:
- Lamb waves
locally-resonant metasurfaces
resonator
transmission
bandgap - Abstract:
- ABSTRACT - Technical A locally-resonant metasurface is a specific type of metamaterial consisting of a thin plate and small resonating structures attached to the surface of the plate that can have different effects on plate waves. One of the most common functions of metasurfaces is the ability to block or attenuate incoming vibrations, which is often very desirable for applications such as vibration isolation. However, these metasurfaces are often only effective at controlling waves over a narrow frequency bandgap. Many vibrations are composed of a range of frequencies, and it is not always ideal to only be able to control some of those frequencies. Previous studies suggest that it may be possible to design a metasurface that can effectively control waves for a wider range of frequencies. One approach that shows promise for widening the bandgap of metasurfaces is the concept of resonator grading, which involves using resonators with varying resonant frequencies to create a metasurface that is effective across the range of frequencies that the resonators are designed for. This project investigates the use of resonator grading for a 4-arm resonator made from 6063-T83 aluminum that was previously designed to block the fundamental symmetric Lamb wave mode in thin plates made from the same aluminum alloy. The results show that increasing the number of resonators is a viable option for increasing the bandgap around a defined target frequency, but this approach is limited in how wide the bandgap can become. Alternatively, using resonator grading appears to be capable of wide bandgaps for a given number of resonators as long as the resonant frequencies of those resonators only differ by small intervals. ABSTRACT - Non-technical Locally-resonant metasurfaces are a type of structure consisting of a thin plate with small, vibrating parts called resonators. These metasurfaces can be designed to block incoming vibrations, which is desirable for applications such as vibration isolation. However, these metasurfaces are often only effective at controlling waves with specific frequencies. The range of frequencies that the metasurface can block is known as a bandgap. Vibrations are often composed of a range of frequencies, and it is not always ideal to control only some of those frequencies. One particular method that shows promise for widening the bandgap of metasurfaces is a concept known as resonator grading. This method involves using multiple resonators with slightly different sizes or other properties to change the way that they vibrate to create a metasurface with a wider bandgap. This project investigates the use of resonator grading for a metasurface with 4-arm resonators that were previously designed to block waves in a thin plate. The results confirm that it is possible to widen the bandgap for this particular metasurface design using concepts from resonator grading.