1 April 2015 Non-destructive evaluation of coating thickness using guided waves
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Abstract
Among existing strategies for non-destructive evaluation of coating thickness, ultrasonic methods based on the measurement of the Time-of-Flight (ToF) of high frequency bulk waves propagating through the thickness of a structure are widespread. However, these methods only provide a very localized measurement of the coating thickness and the precision on the results is largely affected by the surface roughness, porosity or multi-layered nature of the host structure. Moreover, since the measurement is very local, inspection of large surfaces can be time consuming. This article presents a robust methodology for coating thickness estimation based on the generation and measurement of guided waves. Guided waves have the advantage over ultrasonic bulk waves of being less sensitive to surface roughness, and of measuring an average thickness over a wider area, thus reducing the time required to inspect large surfaces. The approach is based on an analytical multi-layer model and intercorrelation of reference and measured signals. The method is first assessed numerically for an aluminum plate, where it is demonstrated that coating thickness can be measured within a precision of 5 micrometers using the S0 mode at frequencies below 500 kHz. Then, an experimental validation is conducted and results show that coating thicknesses in the range of 10 to 200 micrometers can be estimated within a precision of 10 micrometers of the exact coating thickness on this type of structure.
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Pierre-Claude Ostiguy, Pierre-Claude Ostiguy, Nicolas Quaegebeur, Nicolas Quaegebeur, Patrice Masson, Patrice Masson, } "Non-destructive evaluation of coating thickness using guided waves", Proc. SPIE 9437, Structural Health Monitoring and Inspection of Advanced Materials, Aerospace, and Civil Infrastructure 2015, 94371K (1 April 2015); doi: 10.1117/12.2084299; https://doi.org/10.1117/12.2084299
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