Acoustic emission analysis on tensile failure of air plasma-sprayed thermal barrier coatings

Abstract

An acoustic emission technique was used to monitor the cracking behavior and fracture process of thermal barrier coatings subjected to tensile loading. Acoustic emission signals were extracted and preformed by fast Fourier transform, and their characteristic frequency spectrums and dominant bands were obtained to reveal fracture modes. Three different characteristic frequency bands were confirmed, corresponding to substrate deformation, surface vertical cracking and interface delamination, with the aid of scanning electronic microscopy observations. A map of the tensile failure mechanism of air plasma-sprayed thermal barrier coatings was HighlightsWe established several good correlations between AE data and fracture modes.The correlations can be utilized to reveal cracking profile and coating failure.A tensile failure mechanism of coating system was established.Fracture strength of thermal barrier coating has been obtained by this method.The method has a large advantage to study the failure of coating/film materials.

Acoustic emission monitoring and damage mode discrimination of APS thermal barrier coatings under high temperature CMAS corrosion

“…This method transforms the AE signals from time domain to frequency domain, and extracts the message reflecting the AE source [28]. The frequency spectrum of AE signals are strongly dependent on the failure modes of materials, but are almost independent of the failure size and operating pressure [23,28].…”

“…This method transforms the AE signals from time domain to frequency domain, and extracts the message reflecting the AE source [28]. The frequency spectrum of AE signals are strongly dependent on the failure modes of materials, but are almost independent of the failure size and operating pressure [23,28]. Previous studies indicated that the surface vertical cracks, sliding interface cracks, and opening interface cracks correspond to the characteristic frequency bands of 0.20-0.25 MHz, 0.25-0.32 MHz, and 0.4-0.45 MHz, respectively [16,23,28,29].…”

“…The frequency spectrum of AE signals are strongly dependent on the failure modes of materials, but are almost independent of the failure size and operating pressure [23,28]. Previous studies indicated that the surface vertical cracks, sliding interface cracks, and opening interface cracks correspond to the characteristic frequency bands of 0.20-0.25 MHz, 0.25-0.32 MHz, and 0.4-0.45 MHz, respectively [16,23,28,29]. After the statistical analysis on the characteristic peak frequency of AE signals, we also found three similar frequency bands for surface vertical cracks, sliding interface cracks, and opening interface cracks (Fig.…”

Study of mechanical properties and cracking extension resistance behavior of C/SiC composites by single edge notched beam and digital image correlation techniques

“…The sampling rate of the camera was set as one image per second. The detailed information was described in our previous works [27,[33][34][35][36]. In order to observe the crack nucleation and propagation patterns clearer，a telephoto lens with an optical enlargement factor of 200X was equipped in front of the camera, as shown in Fig.…”

Fracture characteristics of freestanding 8wt% Y2O3–ZrO2 coatings by single edge notched beam and Vickers indentation tests

“…Therefore, the evolution of mechanical, physical and chemical properties of 8YSZ coatings during thermal cycling plays an important role in predicting their durability and reliability. In recent years, various experimental methods such as tension [7][8][9][10][11], indentation [12][13][14][15][16], compression [17], shear [18], double cantilever beam [19] and bending tests [20][21][22][23] have been developed to measure the fracture strength and toughness of 8YSZ coatings as well as the interface adhesion strength of a TBC system. Due to the influence of bond coat, substrate and components with complicated structures, however, it is difficult to thoroughly study the mechanical properties of deposited 8YSZ top coatings.…”