TY - JOUR A1 - Altenburg, Simon A1 - Bernegger, Raphael A1 - Krankenhagen, Rainer T1 - Absorption coefficient dispersion in flash thermography of semitransparent solids JF - International Journal of Thermophysics N2 - 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. T2 - 19th International Conference on Photoacoustic and Photothermal Phenomena CY - Bilbao, Spain KW - Absorptance KW - Dispersion KW - Flash thermography KW - Infrared thermography KW - NDT KW - Semitransparency PY - 2018 DO - https://doi.org/10.1007/s10765-018-2474-0 SN - 0195-928X SN - 1572-9567 VL - 40 IS - 1 SP - 13, 1 EP - 13 PB - Springer Nature AN - OPUS4-47105 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Altenburg, Simon A1 - Weber, H. A1 - Krankenhagen, Rainer T1 - Thickness determination of semitransparent solids using flash thermography and an analytical model JF - Quantitative InfraRed Thermography Journal N2 - As groundwork for thickness determination of polymeric surface protection systems for concrete, we present a method for measuring the thickness of isolated semitransparent solids using flash thermography both in transmission and reflection configuration. Since standard models do not capture semitransparency, an advanced analytical model by Salazar et al. is applied. Physical material parameters are deduced by fitting experimental data from samples of well-known thickness. Using those, the thickness of samples of the material can be obtained by fitting, as demonstrated for different semitransparent polymer materials. KW - Analytical model KW - Concrete KW - Semitransparency KW - Surface protection KW - Thermography KW - Thickness PY - 2017 DO - https://doi.org/10.1080/17686733.2017.1331655 SN - 1768-6733 SN - 2116-7176 VL - 15 IS - 1 SP - 95 EP - 105 PB - Taylor and Francis CY - Abingdon, UK AN - OPUS4-40468 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -