Distributed shunted patches are utilized for the control of wave propagation in structures. Periodic positioning of the patches introduces sources of mismatch of the equivalent mechanical impedance, which is responsible for strong attenuation of elastic waves over broad frequency bands. The center frequency of the attenuation band is defined by the resonant frequency of the electrical circuit through which the patches are shunted. This results in a periodic structure which behaves as a tunable mechanical filter. The concept is illustrated on beam and plate structures, where the onset of vibrations over the tuning frequency band is impeded by the attenuation of propagating waves [1]. The effectiveness of the technique for both vibration and radiated noise control is illustrated by numerical and experimental results. Structures with periodically shunted patches can be also interpreted as a novel class of tunable acoustic metamaterials. The patches produce equivalent elastic moduli which are negative within the tuning frequency range of the shunting circuit as a result of its resonant behavior. This has the potential to lead to extraordinary wave properties such as total reflection, negative acoustic refraction and superlensing characteristics. The considered periodic configurations can be considered as a novel class of “locally resonant sonic materials”, which in contrast to configurations previously presented in the metamaterial literature [2,3], have the ability to be easily tuned through proper selection of the shunting circuit impedance.

References

1.      Spadoni, M. Ruzzene and K. Cunefare “Vibration and Wave Propagation Control of Plates with Periodic Arrays of Shunted Piezoelectric Patches”, Journal of Intelligent Material Systems and Structures 2009; 20; 979.

2.      Liu Z. et al. “Locally Resonant Sonic Materials” Science, Vol. 289, September 2000, pp. 1734-1736.

3.      N. Fang et al. “Ultrasonic Metamaterials with Negative Modulus”, Nature Materials, Vol. 5, June 2006, pp.452-456.