Comparative Study of Coupling Techniques in Lamb Wave Testing of Metallic and Cementitious Plates.

Santiago Vázquez,Alicia Carrión,Jordi Payá,Jorge Gosálbez,Ignacio Bosch,Carles Gallardo

doi:10.3390/s19194068

Santiago Vázquez, Alicia Carrión + Show 4 more

Open Access

https://doi.org/10.3390/s19194068

Copy DOI

Abstract

Lamb waves have emerged as a valuable tool to examine long plate-like structures in a faster way compared to conventional bulk wave techniques, which make them attractive in non-destructive testing. However, they present a multimodal and dispersive nature, which hinders signal identification. Oblique incidence is one of the most known methods to generate and receive Lamb waves and it is applied in different experimental arrangements with different types of sensors. In this work, several setups were conducted and compared to determine the optimal ones to launch and detect ultrasonic Lamb waves, especially in non-homogeneous specimens. The chosen arrangements were contact with angle beam transducers, immersion in a water tank, localised water coupling using conical containers and air coupling. Plates of two different materials were used, stainless steel and Portland cement mortar. Theoretical and experimental dispersion curves were compared to verify the existence of Lamb modes and good correspondence was achieved.

Highlights

Conventional ultrasonic inspection techniques used in non-destructive testing (NDT) are based on bulk waves
The particle motion of longitudinal waves is parallel to the direction of wave propagation while the particle motion of transverse waves is perpendicular to the direction of wave propagation
A pair of angle beam probes (MUBW 2N, Krautkramer, Huerth, Germany) with a 2 MHz central frequency were employed for Lamb wave excitation and detection

Summary

Introduction

Conventional ultrasonic inspection techniques used in non-destructive testing (NDT) are based on bulk waves ( called body or volume waves). Bulk waves consist of longitudinal ( known as P-waves/primary waves, pressure waves or compressional waves) and transverse waves ( known as S-waves/secondary waves or shear waves) Both kinds of waves occur in solids with dimensions greater than a wavelength in the three dimensions [2,3]. Lamb waves propagate in a linear, homogeneous and isotropic elastic plate with stress-free upper and lower surfaces if the plate placed in vacuumand [36,62]). Theyinare created by theand constructive upper andfar lower surfaces if thickness the plate was placed vacuum with lateralinterference dimensionsof (length and width) far greater than thewaves thickness created by the reflections of longitudinal and transverse with[39].

Objectives

Results

Conclusion