Lamb waves monitoring of the thermomechanical aging effects in ceramic coatings

Ceramic coatings are mainly used to protect underlying alloy structures, and cover a wide range of thermomechanical and electrochemical applications, especially in the energy management and related industries. The work described in this paper focuses on the use of the Acoustic Emission (AE) technique to produce a permanent Structural Health Monitoring (SHM) of various coating systems subject to thermal cycling conditions. SHM generally refers to those methods that provide the ability to detect and interpret adverse changes in a structure in order to improve their reliability. The AE consists of elastic wave that propagates in the material carrying the information of occurred and latent defects. Since the challenge in designing such a method is knowing what changes to look for and how to identify them, the emphasis in this particular paper is placed on the cumulative frequency analysis of such AE waves and their potential for determining damage to coatings prior to their final breakdown.