In-situ and real-time tests on the damage evolution and fracture of thermal barrier coatings under tension: A coupled acoustic emission and digital image correlation method

By using a coupled acoustic emission (AE) and digital image correlation (DIC) technique, the failure behavior of air plasma sprayed thermal barrier coatings (TBCs) was investigated. The in-situ DIC observations show that the characteristics of AE signals, extracted from the fast Fourier transform, are closely related to the failure modes of a TBC system, which was applied to real-time reveal its damage evolution during tension. It is shown that there is a typical power-law relationship between the vertical crack density in coating and strain in substrate. A damage variable defined as a function of the cumulative AE events can be used to characterize the different fracture stages of a TBC system. With the increase of strain in substrate, the AE-b value estimated by the Gutenberg–Richter law varies from 2.0 at the initial regime to a plateau value of 1.2. •Tensile failure of APS TBCs system has been in-situ monitored by two techniques.•We further clarified several good correlations between AE data and fracture modes.•Evolution of crack density and damage was analyzed by AE and strain test results.•Relationship of AE-b change and failure modes was successfully established.