Acoustic emission (AE) is used to monitor conditions of various structures across many industrial sectors, including containment vessels or storage tanks of nuclear materials. Periodic monitoring, inspection and analysis of structure conditions can help prevent failure and accidents. Understanding the transient elastic waves in multi-layered structures (planar or rounded types) has long been of great interest. This paper experimentally investigates changes in AE wave propagation patterns in multilayer planar structures - detecting and assessing the effect of coating layers, and assumed surrogate of deposits or protective layer. Epoxy phenolic-coated two mild steel plates were assembled without any adhesion and two piezoelectric AE sensors were placed on the coating layer. The pencil lead break (PLB) test was used to initiate the AE waves from the surface and cross-section of different layers. From wavelet transforms (WT) analysis, significant energy zone changes were observed up to the 450 kHz frequency level with PLB on the surface and cross-section of different layers. Love wave propagation on the coated plate structure resulted in wave pattern changes with PLB locations and layers. Wave duration, energy, energy ratio and peak amplitude levels were also analysed to characterise the AE wave pattern relationship with defect location in a multilayer plate-like (planar) structure. The approaches used in this work could potentially be useful in providing a greater understanding of defects within multilayer nuclear containment structures and also offering an alternative way to monitor corrosion related degradation of structures with insulations.
RAJENDRAN, V., PRATHURU, A., FERNANDEZ, C. and FAISAL, N.H. 2023. Investigation of wave propagation pattern in a multilayer planar structure. e-Journal of nondestructive testing [online], Special Issue NDE-Nuclear-2023: proceedings of the 2nd Non-destructive examination in nuclear international conference (NDE in Nuclear 2023), 27-29 June 2023, Sheffield, UK, article number 28270. Available from: https://www.ndt.net/search/docs.php3?id=28270