Experimental Study of Phononic Structures With Dda Enhanced Unit-Cells

Abstract

Phononic structures with periodic unit-cells that exhibit Bragg scattering, have been investigated during the latest years by various researchers due to their extraordinary wave manipulation and filtering properties. One major feature of these metamaterials is their ability to generate stopbands or bandgaps in the frequency domain, hence presenting significant vibration attenuation properties. However, this mechanism presents certain design constraints in generating broadband bandgaps, especially in the low-frequency range, where large masses are required. To this end, a novel dynamic directional amplifier, namely the DDA, is introduced as a means to artificially increase the inertia of an oscillating mass. The DDA is realized by imposing kinematic constraints to the degrees of freedom (DoFs) of the oscillator, hence inertia is increased by coupling the horizontal and vertical motion. In this study, the DDA is implemented in an experimental scaled phononic set-up that is constructed using LEGO® Technic components. Experimental testing is undertaken as a feasibility assessment of the concept and results indicate the low-frequency wave attenuation properties of the structure.