چكيده به لاتين
Abstract
Metamaterials are artificial structures with unnatural properties. They can manipulate or control light, noise, and vibration. These structures are able to bend, absorb, and block the acoustic and elastic waves.
Many ways are available in order to damp vibrations. The more common one is adding absorber layer to the main structure which suppresses the propagating elastic wave. An acoustic metamaterial uses negative mass and negative stiffness to generate Stopband. For the frequencies in the stopband, there is no positive real amount for wave number, and accordingly, elastic wave with such frequency can not propagate in the metamaterial.
In this study, some metamaterial structures are investigated, and one of them is chosen in order to be studied more detailed and used for reducing the vibration transferred from trains to the adjacent buildings. The problem is solved by the Finite Element Method for a Euler-Bernoulli beam. The results showed a good effect of metamaterial beam on propagating elastic waves and work properly in three stopbands, which include three purpose vibration frequencies caused by moving a train.
Key words: Acoustic Metamaterials, Stopband, Negative mass, Negative stiffness, Vibration, Finite Element Method.
