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Analysis of acoustic emission propagation in metal-to-metal adhesively-bonded joints.

Crawford, Alasdair; Droubi, Mohamad Ghazi; Faisal, Nadimul Haque


Alasdair Crawford


Acoustic emission (AE) monitoring shows promise as one of the most effective methods for condition monitoring of adhesively-bonded joints. Previous research has demonstrated its ability to detect, locate and classify adhesive joint failure, though in these studies little attention appears to have been paid to the differences in AE wave propagation through the bonded and un-bonded sections of the specimens tested, or to the effects of the wave modes excited or the propagation distances. This paper details an experimental study conducted on large aluminium sheet specimens to identify the effects of the presence of an adhesive layer on AE wave propagation. Three specimens are considered; a single aluminium sheet, two aluminium sheets placed together without adhesive, and an adhesively-bonded specimen. A pencil lead break (PLB) is used as a simulated AE source, and is applied to the three specimens at varying propagation distances and orientations. The acquired signals are processed using wavelet-transforms to explore time-frequency features, and compared with modified group-velocity curves based on the Rayleigh-Lamb equations to allow identification of wave-modes and edge-reflections. The effects of propagation distance and source orientation are investigated while comparison is made between the three specimens. It is concluded that while the wave propagation modes can be approximated as being constant throughout all three specimens, there is a significant change in the received waveforms due to the attenuation of high-frequency components exhibited by the bonded specimen. These findings may be utilised to provide a deeper understanding of acquired AE data, improving the current abilities to identify, locate and characterise damage mechanisms occurring within adhesive joints, ultimately improving safety in the use of adhesive bonding for critical applications.


CRAWFORD, A., DROUBI, M.G. and FAISAL, N.H. 2018. Analysis of acoustic emission propagation in metal-to-metal adhesively-bonded joints. Journal of nondestructive evaluation [online], 37(2), article number 33. Available from:

Journal Article Type Article
Acceptance Date Apr 20, 2018
Online Publication Date May 4, 2018
Publication Date Jun 30, 2018
Deposit Date May 11, 2018
Publicly Available Date May 11, 2018
Journal Journal of nondestructive evaluation
Print ISSN 0195-9298
Electronic ISSN 1573-4862
Publisher Springer
Peer Reviewed Peer Reviewed
Volume 37
Issue 2
Article Number 33
Keywords Adhesive joints; Acoustic emission; Wave propagation; Wavelet transform; Signal processing; Pencil lead break (PLB)test
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