Abstract
Precise control of elastic waves is a challenge for many applications in the field of mechanical vibrations, ultrasonic inspection, and energy harvesting. Graded arrays of resonators on elastic substrates recently revealed superior performances for broadband wave trapping and mode conversion. In this study we present elastic waveguides able to govern waves at different scales exploiting rainbow reflection, trapping and mode conversion. We investigate whether these mechanisms, and the associated control, can be used for energy harvesting or signal conversion devices.
Highlights
In the last two decades, metamaterials are receiving increasing popularity for wave control across much of physics and engineering in the field of electromagnetism [1,2], acoustics [3,4], and elasticity [5]
In this study we present elastic waveguides able to govern waves at different scales exploiting rainbow reflection, trapping and mode conversion
While the momentum initially focused on Bragg scattering [6,7] and subwavelength bandgaps generated by the resonance [4,8,9,10], the research has delivered new forms of control, encompassing tailored designs to obtain a variety of wave manipulation phenomena [11,12] including focusing and lensing [13,14,15,16], localization [17] and topological edge states [18,19] amongst others
Summary
In the last two decades, metamaterials are receiving increasing popularity for wave control across much of physics and engineering in the field of electromagnetism [1,2], acoustics [3,4], and elasticity [5]. The term graded refers to the smooth variation of a particular parameter of the resonators along space, allowing to control the propagation of waves in a broadband regime. This modulation strategy promotes a wavenumber transformation that, in turn, activates a spatial decrease of the wave velocity when the wave enters inside the array. In the setting of elasticity, particular advances have been recently reported in elastic devices made of arrays of resonant rods for deep elastic substrates [27,28] to mode convert Rayleigh (R) into Shear (S) or Pressure (P) waves. We show that rainbow trapping is intrinsically related to mode conversion and strongly dependent on the adiabaticity of the graded design
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