Absorption Coefficient Dispersion in Flash Thermography of Semitransparent Solids
- 58 Downloads
Pulse and flash thermography are experimental techniques which are widely used in the field of non-destructive testing for materials characterization and defect detection. We recently showed that it is possible to determine quantitatively the thickness of semitransparent polymeric solids by fitting of results of an analytical model to experimental flash thermography data, for both transmission and reflection configuration. However, depending on the chosen experimental configuration, different effective optical absorption coefficients had to be used in the model to properly fit the respective experimental data, although the material was always the same. Here, we show that this effect can be explained by the wavelength dependency of the absorption coefficient of the sample material if a polychromatic light source, such as a flash lamp, is used. We present an extension of the analytical model to describe the decay of the heating irradiance by two instead of only one effective absorption coefficient, greatly extending its applicability. We show that using this extended model, the experimental results from both measurement configurations and for different sample thicknesses can be fitted by a single set of parameters. Additionally, the deviations between experimental and modeled surface temperatures are reduced compared to a single optimized effective absorption coefficient.
KeywordsAbsorptance Dispersion Flash thermography Infrared thermography NDT Semitransparency
- 12.M. Goldammer, J. Baumann, in NDE For Health Monitoring and Diagnostics (San Diego, California, United States, 2002), pp. 211–218Google Scholar
- 14.S.J. Altenburg, R. Krankenhagen, H. Weber, in Conference QIRT 2016, Documents and sessions presented during the 13th conference QIRT (Gdańsk, Poland, 2016), pp. 71–78Google Scholar
- 16.Osram product brochure, XBO—theater lamps. Technology and application (Osram, 2017). http://web.mit.edu/jhawk/tmp/ENGR_BLTN11.pdf. Accessed 31 March 2017