Guided waves (GWs) have characteristic dispersive time-frequency representations (TFRs). Unfortunately, any TFR is subjected to the time-frequency uncertainty principle. This limits the capability of the TFR to distinguish multiple, closely spaced guided modes over a wide frequency range. To this aim we implemented a new time-frequency signal processing tool, that we call Warped Frequency Trans...

In the application of guided waves NDT, the selection of exciting frequency is not only related with the setup of sensor, but also with the characteristics of pipe’s structure and material. In this paper, the characteristic of guided waves propagation in pipes that L(0,1) and L(0,2) have a cutoff frequency are respectively discussed, and the calculation formulas of their cutoff frequency are gi...

[1] In a magnetized plasma with two ion species, shear Alfvén waves (or guided electromagnetic ion cyclotron waves) have zero parallel group velocity and experience a cut‐off near the ion‐ion hybrid frequency. Since the ion‐ion hybrid frequency is proportional to the magnetic field, it is possible, in principle, for a magnetic well configuration to behave as an Alfvén wave resonator in a two‐io...

This paper examines the propagation of guided circumferential waves in a hollow isotropic cylinder that contains a crack, with the goal of using these guided waves to both locate and size the crack. The crack is sized using a modified Auld's formula, which relates the crack's length to a reflected energy coefficient. The crack is then located by operating on the backscattered signal with a time...

This paper presents a theoretical modeling of power and energy transduction of structurally-bonded piezoelectric wafer active sensors (PWAS) for structural health monitoring (SHM). After a literature review of the state of the art, we developed a model of power and energy transduction between the PWAS and a structure containing multimodal ultrasonic guided waves. The use of exact Lamb waves mod...

Motivated by their functional conformity, micro-cantilever-based MEMS oscillators are investigated in this study as structure-integrable transducers for the acquisition of guided ultrasonic waves fiber–metal laminates. While acceleration-sensitive limited maximum frequency, presented displacement-sensitive oscillator is operated quasi-free fashion a seismometer, making it particularly sensitive...