Calibration of a constitutive model for diffusive moisture transport in wood using data from X-ray CT-scanning and digital speckle photography

An unsteady-state diffusion model is applied for studying wood drying below the fibre saturation point. The moisture diffusion coefficient in Fick\u27s law for Norway spruce under isothermal drying conditions is determined. Using X-ray CT-scanning and Digital Speckle Photography, the wood density and moisture content are obtained in the radial direction of the wood samples. An optimization scheme is used to minimize the difference between observed and computed moisture content in order to calibrate the values of a set of parameters describing the diffusion coefficient. In this study the values of the parameters for a parameterization of Arrhenius\u27 type are determined. The general idea discussed, however, is not limited to a specific model, butcan be used for a wide class of parameter identification problems. The results show a good agreement between observed and computed moisture content and it is concluded that the numerical realization of the optimization scheme works well. Nevertheless, the value of the diffusion coefficient is somewhat higher than expected. This is likely the consequence of a permeable coating of the samples