Abstract
A pulsed thermography system with laser beam homogenizing is developed to measure the thickness of thermal barrier coatings (TBCs) by numerical fitting. A simplified model is proposed to avoid the complexity of deriving an analytical solution of thermal diffusion in TBC systems that include a thin semi-transparent top coating. A characteristic parameter is identified that captures the system response to fast heating by a short laser pulse and to optothermal effects due to volume heating, bulk emission and multiple reflections in the thin coating. It is demonstrated that small thickness changes can be measured when the unpainted ultra-thin TBC is thermally excited using short laser pulses with flat-top spatial profile. Experimental results show that the proposed laser thermography reconstruction method is fast and reliable when using laser beam shaping with a homogenizer.
Published Version
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