From guided waves to resonances

Abstract

Guided elastic waves find numerous applications in nondestructive testing, ultrasonic sensing and telecommunication electronics. My talk will be focused on the physical background of resonant testing of structures. This method is based on zero-group-velocity (ZGV) resonances, which are guided waves with vanishing power flux. In anisotropic plates we find a discrete set of ZGV points pertaining to a single mode. They explain the beautiful beating resonance pattern that emerges naturally close to the source after a short point-source excitation. Furthermore, we find waves propagating with transverse-group velocity (TGV), i.e., their power flux is orthogonal to the wave vector. I will comprehensively present both the theory and measurements of these effects. The discussed phenomena are particularly hard to predict computationally. To overcome this difficulty, I will sketch numerical methods based on multi-parameter eigenvalue problems to reliably locate all ZGV frequencies of generic waveguides. These are implemented in the ‘GEWtool’ software (https://github.com/dakiefer/GEWtool). I will show that this framework is also well-adapted to solve another important waveguide problem that has drawn much attention, namely, leaky waves in plates.

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.