Lamb wave-based monitoring of shear failure of an adhesive lap joint

Magdalena Rucka,Jacek Lachowicz,Erwin Wojtczak

doi:10.29354/diag/95176

Abstract

The paper presents a study on the elastic wave propagation in adhesive joints of steel plates subjected to tensile loading. A single lap joint was chosen for analysis because of its simplicity and plurality of applications. Experimental investigations consisted of the uniaxial extension of prepared specimens. Force and displacement values were recorded by a testing machine. Simultaneously, guided Lamb waves were excited and signals of their propagation were collected in a number of points by piezoelectric transducers attached to the specimen surface. Further processing of signals allowed to determine some disturbances in gathered data. The continuous wavelet transform revealed discontinuities in force-displacement relations. The Fourier transform showed changes in frequency values of recorded signals. Large disturbances of the root mean square values was also observed. The results of all analyses allowed to conclude that the identification of partial degradation state before the sample destruction was possible.

Highlights

Structural adhesive joints are a specific kind of non-separable connections that can be applied in many fields of engineering
The failure generally had an adhesive mechanism for all specimens but each adhesive layer was different
The paper presents the research on the guided Lamb wave propagation in the single lap adhesive joint under tensile load

Summary

Introduction

Structural adhesive joints are a specific kind of non-separable connections that can be applied in many fields of engineering. There can be the cohesive mechanism that is the desirable one and it consists in the destruction of the internal structure of the adhesive layer (the glue remains on the whole surface of both adherend overlaps). Another mechanism is called the adhesive failure and it performs when the connection between the glue and adherend is poor but the adhesive layer is not destroyed itself. There can exist a third variant called the mixed failure mechanism that has features of both fundamental ones (delamination occurs partially in the adhesive layer and between the adhesive and the adherends)

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