Simulation of drying stresses in wood -: Part I:: comparison between one- and two-dimensional models

A number of rheological models of drying wood have been presented during the last ten years. At the material point level, most models show high accuracy. The models in themselves, however, have no value unless used for improving wood drying, technique, quality, etc. To achieve this, they have to be implemented in applicable programs/methods. In this article, the implementation of a material model calibrated on small clear wood specimen is presented. The strain (cup-deformations) and the internal stresses (indicator of surface checks and internal collapse) of the boards cross-section are calculated for given moisture histories. Comparisons with test results concerning cupping show that the model can describe the deformation of a board cross-section. It is also shown that in many cases a simple analytical solution can be used to determine the cupping. Comparisons between two-dimensional and one-dimensional calculations show that the one-dimensional formulation in many cases is sufficient to describe the maximum internal stresses during drying as function of time.