Beating resonance patterns and extreme power flux skewing in anisotropic elastic plates

Abstract

Elastic waves in anisotropic media can exhibit a power flux that is not collinear with the wave vector. This has notable consequences for waves guided in a plate. Through laser-ultrasonic experiments, we evidence remarkable phenomena due to slow waves in a single crystal silicon wafer. Waves exhibiting power flux orthogonal to their wave vector are identified. A pulsed line source that excites these waves reveals a wave packet radiated parallel to the line. Furthermore, there exist precisely eight plane waves with zero power flux. These so-called zero-group-velocity modes are oriented along the crystal's principal axes. Time acts as a filter in the wave vector domain that selects these modes. Thus, a point source leads to beating resonance patterns with moving nodal curves on the surface of the infinite plate. We observe this pattern as it emerges naturally after a pulsed excitation.

11 pages, 8 figures

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Cited by in corpus (4)

• Extreme wave skewing and dispersion spectra of anisotropic elastic plates
• Adiabatic Lamb modes in 3D tapered waveguides: Cut-off effects and ZGV resonances
• Electroelastic guided wave dispersion in piezoelectric plates: spectral methods and laser-ultrasound experiments
• A Sylvester equation approach for the computation of zero-group-velocity points in waveguides