Artificial disbonds for calibration of transient thermography inspection of thermal barrier coating systems

Grzegorz Ptaszek, Peter Cawley, Darryl Almond, Simon Pickering

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Transient thermography is commonly used for the detection of disbonds in thermal barrier coatings (TBC). As for other NDT techniques, reference test specimens are required for calibration, but unfortunately, real disbonds are very difficult to use because it is difficult to control their size, and large ones tend to spall. Flat bottomed holes are commonly used, but these over-estimate the thermal contrast obtained for a defect of a given diameter. This paper quantifies the differences in thermal response using finite element analysis validated by experiments, and proposes a form of artificial disbond that gives a better representation of the thermal responses seen with real defects. Real disbonds tend to have a non-uniform gap between the disbonded surfaces across the defect, and the effect of this on the thermal response is evaluated using finite element simulations. It is shown that the effect can be compensated for by adjusting the diameter of the calibration defect compared to the real defect.
Original languageEnglish
Pages (from-to)71-78
Number of pages8
JournalNDT and E International
Volume45
Issue number1
DOIs
Publication statusPublished - Jan 2012

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Keywords

  • thermal barrier coating
  • calibration
  • disbonds
  • transient thermography

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