The observable dispersion spectrum of waves with skewed power flux

Abstract

Guided waves in plates are often measured on a line away from the source. A spatio-temporal Fourier transform yields the dispersion spectrum in the frequency-wavenumber domain. For anisotropic plates it is possible to observe multiple contributions in the spectrum that are all due to the same mode. We explain this effect with the skewing angle, i.e., the angle between the wave vector and the power flux of the wave. By introducing the concept of „stationary phase points“, we are able to precisely model the observed spectrum, even when the skew angle covers 360°. Our findings are confirmed experimentally on a monocrystalline silicon wafer.

Daniel A. Kiefer

Researcher at Institut Langevin

Research in guided elastodynamic waves, fluid-structure interaction, simulation and signal processing for ultrasonic sensors and nondestructive testing.