Enhancement of Guided Wave Detection and Measurement in Buried Layers of Multilayered Structures Using a New Design of V(z) Acoustic Transducers

Abstract

This paper presents the possibility of enhancement of the generation and detection of poorly energetic acoustic-guided waves in multilayered structures using a new design for a V(z) transducer. By defining a modified V(z) transducer composed of segmented piezoelectric elements, the acoustical energy can be directed towards specific angles in such a way as to generate guided waves that are poorly energetic. By comparing the results using this new design to those obtained with a classical V(z) transducer, it is shown that the generation and detection of such waves is greatly improved, especially for poorly energetic waves that belong to a buried layer in a multilayered structure. This is especially seen on the components of the spectra of V(z). The modeling of the modified V(z) signature for a multi-element focused transducer is widely detailed first. Then, in order to illustrate the advantages of our proposed method, a three-layer structure (aluminum/epoxy/steel) is discussed. The interest of this method for the characterization of elastic properties of “buried” layers through specific guided waves that are detected with great difficulty—or even not at all—with a classical V(z) transducer is demonstrated, especially for the A0 and S0 modes corresponding to the steel layer inside the three-layer structure. In this study, we also develop a specific tracking method for particular guided waves possessing large phase velocity variations over the considered frequency range, as is the case for the S0 mode of the steel sub-layer.

Elastic Waves Excitation and Focusing by a Piezoelectric Transducer with Intermediate Layered Elastic Metamaterials with and without Periodic Arrays of Interfacial Voids

“…For the routine nondestructive inspection of metallic and composite structures, ultrasonic methods relying on elastic waves as a physical basis are widely adopted [ 1 , 2 , 3 , 4 , 5 ]. A common way for the excitation of wave motion in the examined construction is to use piezoelectric transducers of different types.…”