Edge and Notch Detection in a Plate Using Time Reversal Process of Leaky Lamb Waves

Jean-Christophe Vallée,Marie-Aude Ploix,François Baqué,Matthieu Cavaro,Jean-François Chaix

doi:10.3390/app12010228

Abstract

Leaky Lamb waves are proven effective to carry out nondestructive testing especially on parallel and immersed plates. To detect and localize defects in such a set, this work associates for the first time the topological energy method and leaky Lamb waves. This methodology is applied in a single immersed plate to validate its application. Firstly, Lamb mode A1 is generated in the plate, and the reflected waves on the defect are measured. A first case is examined where the edge is considered as a defect to be localized. Then, measurements are taken on a plate where a notch is machined. The measurements are time reversed and reinjected in a finite-element simulation. The results are then correlated with the direct problem of the topological energy method that is also simulated. In both cases, the defects are precisely localized on the energy images. This work is the preliminary step to an application of the topological energy method to a set of two parallel and immersed plates where the research defect is located in the second plate.

Highlights

Ultrasonic methods are proven to be relevant within the inspection and monitoring of sodium-cooled fast reactors (SFR) due to opacity and the oxidizing property of liquid sodium that prevents optical inspection and the immersion of conventional ultrasonic transducers
The results presented in this paper are in good agreement with the results of free anisotropic plate [29]
The theory of leaky Lamb waves was discussed in the first part

Summary

Introduction

Ultrasonic methods are proven to be relevant within the inspection and monitoring of sodium-cooled fast reactors (SFR) due to opacity and the oxidizing property of liquid sodium that prevents optical inspection and the immersion of conventional ultrasonic transducers. It has been shown previously that nondestructive testing from the outside of the main vessel allows generating and propagating guided waves in the internal structures, similar to a layered structure (parallel steel plates) immersed in liquid [1,2]. The context implies a main restriction: the only available access to position the transducers is the outside face of the first plate. These immersed guided waves, called leaky Lamb waves, have been widely studied in the literature [3,4,5,6] and applied to damage detection in plate-like structures [7,8]. The Lamb waves are called “leaky” because of the re-emission of bulk waves in the surrounding fluid

Methods

Discussion

Conclusion